Materials doi: 10.3390/ma17061392
Authors: Junxiang Zhang Shangjun Gu Jie Wang Fulong Wei Zhiying Li Zeyun Zeng Bin Shen Changrong Li
High-carbon hardline steels are primarily used for the manufacture of tire beads for both automobiles and aircraft, and vanadium (V) microalloying is an important means of adjusting the microstructure of high-carbon hardline steels. Using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM), the microstructure and precipitation phases of continuous cooled high-carbon steels were characterized, and the vanadium content, carbon diffusion coefficient, and critical precipitation temperature were calculated. The results showed that as the V content increased to 0.06 wt.%, the interlamellar spacing (ILS) of the pearlite in the experimental steel decreased to 0.110 μm, and the carbon diffusion coefficient in the experimental steel decreased to 0.98 × 10−3 cm2·s−1. The pearlite content in the experimental steel with 0.02 wt.% V reached its maximum at a cooling rate of 5 °C·s−1, and a small amount of bainite was observed in the experimental steel at a cooling rate of 10 °C·s−1. The precipitated phase was VC with a diameter of ~24.73 nm, and the misfit between ferrite and VC was 5.02%, forming a semi-coherent interface between the two. Atoms gradually adjust their positions to allow the growth of VC along the ferrite direction. As the V content increased to 0.06 wt.%, the precipitation-temperature-time curve (PTT) shifted to the left, and the critical nucleation temperature for homogeneous nucleation, grain boundary nucleation, and dislocation line nucleation increased from 570.6, 676.9, and 692.4 °C to 634.6, 748.5, and 755.5 °C, respectively.
]]>Materials doi: 10.3390/ma17061391
Authors: Luchechko Vasyltsiv Kushlyk Hreb Slobodzyan Vasylechko Zhydachevskyy
Undoped and Mg2+-doped β−Ga2O3-20% In2O3 solid solution microcrystalline samples were synthesized using the high-temperature solid-state chemical reaction method to investigate the influence of native defects on structural, luminescent, and electrical properties. The synthesis process involved varying the oxygen partial pressure by synthesizing samples in either an oxygen or argon atmosphere. X-ray diffraction (XRD) analysis confirmed the monoclinic structure of the samples with the lattice parameters and unit cell volume fitting well to the general trends of the (Ga1−xInx)2O3 solid solution series. Broad emission spectra ranging from 1.5 to 3.5 eV were registered for all samples. Luminescence spectra showed violet, blue, and green emission elementary bands. The luminescence intensity was found to vary depending on the synthesis atmosphere. An argon synthesis atmosphere leads to increasing violet luminescence and decreasing green luminescence. Intense bands at about 4.5 and 5.0 eV and a low-intensity band at 3.3 eV are presented in the excitation spectra. The electrical conductivity of the samples was also determined depending on the synthesis atmosphere. The high-resistance samples obtained in an oxygen atmosphere exhibited activation energy of around 0.98 eV. Samples synthesized in an argon atmosphere demonstrated several orders of magnitude higher conductivity with an activation energy of 0.15 eV. The results suggest that the synthesis atmosphere is crucial in determining the luminescent and electrical properties of undoped β−Ga2O3In2O3 solid solution samples, offering the potential for various optoelectronic applications.
]]>Materials doi: 10.3390/ma17061390
Authors: Nenad Kostić Nenad Petrović Vesna Marjanović Ružica R. Nikolić Janusz Szmidla Nenad Marjanović Robert Ulewicz
This research aims to show the effects of adding cardinality constraints to limit the number of different cross-sections used in simultaneous sizing and shape optimization of truss structures. The optimal solutions for sizing and shape optimized trusses result in a generally high, and impractical, number of different cross-sections being used. This paper presents the influence of constraining the number of different cross-sections used on the optimal results to bring the scientific results closer to the applicable results. The savings achieved using the cardinality constraint are expected to manifest in more than just the minimization of weight but in all the other aspects of truss construction, such as labor, assembly time, total weld length, surface area to be treated, transport, logistics, and so on. It is expected that the optimal weight of the structures would be greater than when not using this constraint; however, it would still be below conventionally sized structures and have the added benefits derived from the simplicity and elegance of the solution. The results of standard test examples for each different cardinality constraint value are shown and compared to the same examples using only a single cross-section on all bars and the overall optimal solution, which does not have the cardinality constraint. An additional comparison is made with results of just the sizing optimization from previously published research where authors first used the same cardinality constraint.
]]>Materials doi: 10.3390/ma17061389
Authors: Xu Wang Shao-Cong Li Duo-Wen Xiang Min Gao Hong-Mei Zuo Dian-Sen Li
Recently, short-fiber-reinforced thermoplastic composites (SFRTPCs) have been playing a more and more crucial role in the application of automotive interior materials due to their advantages of low density and environmental resistance properties. However, their relevant mechanical properties need to be optimized. Previous investigations revealed that the surface modification of fibers is useful to improve their mechanical properties. In this work, carbon fiber (CF)-reinforced polylactic acid (PLA) composites modified with MXene and graphene oxide (GO) were prepared by twin-screw extrusion and injection molding methods. Short CF was firstly modified with polyetherimide (PEI), then different weight ratios of MXene-GO (1:1) were subsequently modified on PEI-CF. Finally, the flexural properties and failure mechanisms were analyzed. The results showed that MXene-GO was successfully coated on CF surface, and the flexural strength and modulus of CF-PEI-MXene-GO-reinforced PLA (CF-PEI-MG/PLA) composite were improved compared to that of CF/PLA composite. In addition, the fracture sections of the composites were flat and white, and the fibers bonded well with PLA for CF-PEI-0.1MG/PLA composite compared to CF/PLA composite. The present study could provide a reference for further improving the mechanical performance of PLA-related composites.
]]>Materials doi: 10.3390/ma17061388
Authors: Mingjia Qu Zhengwei Gu Xin Li Jianbo Wang Ge Yu Lingling Yi
Titanium alloy hot stamping technology has a wide range of application prospects in the field of titanium alloy part processing due to its high production efficiency and low manufacturing cost. However, the challenges of forming titanium alloy parts with large depths and deformations have restricted its development. In this study, the hot stamping process of a Ti6Al4V alloy box-shaped part was investigated using ABAQUS 2020 software. The thermodynamic properties of a Ti6Al4V alloy sheet were explored at different temperatures (400 °C, 500 °C, 600 °C, 700 °C, 800 °C) and different strain rates (0.1 s−1, 0.05 s−1, 0.01 s−1). In addition, the influence law of hot stamping process parameters on the minimum thickness of the formed part was revealed through the analysis of response surface methodology (RSM), ultimately obtaining the optimal combination of process parameters for Ti6Al4V alloy hot stamping. The experimental results of the hot stamping process exhibited a favorable correlation with the simulated outcomes, confirming the accuracy of the numerical simulation. The study on the microstructure evolution of the formed parts showed that grain refinement strengthening occurred in the part with large deformation, and the formed box-shaped parts exhibited a uniform and fine microstructure overall, demonstrating high forming quality. The achievements of the work provide important guidance for the fabrication of titanium alloy parts with large depths and deformations used in heavy industrial production.
]]>Materials doi: 10.3390/ma17061387
Authors: Kosuke Sanai Sho Nakasaki Mikiyasu Hashimoto Arnaud Macadre Koichi Goda
In order to clarify the fracture behavior of a unidirectional CFRP under proportional loading along the fiber (0°) and fiber vertical (90°) directions, a biaxial tensile test was carried out using a cruciform specimen with two symmetric flat indentations in the thickness direction. Three fracture modes were observed in the specimens after the test. The first mode was a transverse crack (TC), and the second was fiber breakage (FB). The third mode was a mixture mode of TC and FB (TC&FB). According to the measured fracture strains, regardless of the magnitude of the normal strain in the 0° direction, TC and TC&FB modes occurred when the normal strain in the 90° direction, εy, ranged from 0.08% to 1.26% (positive values), and the FB mode occurred when εy ranged from −0.19% to −0.79% (negative values). The TC&FB mode is a unique mode that does not appear as a failure mode under uniaxial tension; it only occurs under biaxial tensile loading. Biaxial tensile tests were also conducted under non-proportional loading. The result showed three fracture modes similarly to the proportional loading case, each of which was also determined by the positive or negative value of εy. Thus, this study reveals that the occurrence of each fracture mode in a unidirectional CFRP is characterized by only one parameter, namely εy.
]]>Materials doi: 10.3390/ma17061386
Authors: Shaik Hussain Sudhir Amritphale John Matthews Niloy Paul Elizabeth Matthews Richard Edwards
Cement, as a construction material, has low thermal resistance, inherent fire resistance, and is incombustible up to a certain degree. However, the loss of its mechanical performance and spalling are its primary issues, and it thus cannot retain its performance in refractory applications. The present study explores the performance of geopolymer formulations that have excellent fire resistance properties for potential refractory applications. This study is unique, as it investigates advanced solid geopolymer formulations that need only water to activate and bind. Various solid geopolymer formulations with fly ash as a precursor; potassium hydroxide and potassium silicate as activators; and mullite and alumina as refractory aggregates were studied for their compressive strength at up to 1100 °C and compared with their two-part conventional liquid alkaline geopolymer counterparts. Advanced solid geopolymer formulations with mullite and alumina as refractory aggregates had mechanical strength values of 84 MPa and 64 MPa post-1100 °C exposure and were further exposed to ten thermal cycles of 1100 °C to study their fatigue resistance and post-exposure compressive strengths. The geopolymer sample with mullite as a refractory aggregate yielded 115.2 MPa compressive strength after the fourth cycle of exposure. This sample was also studied for its temperature distribution upon direct flame exposure. All the geopolymer formulations displayed a drop in compressive strength at 600 °C due to viscous sintering and then a rise in strength at 1100 °C due to phase transformation. X-ray diffraction studies revealed that the formation of crystalline phases such as leucite, sanidine, and annite were responsible for the superior strengths at 1100 °C for the alumina- and mullite-based geopolymer formulations.
]]>Materials doi: 10.3390/ma17061385
Authors: Farnoush Salehtash Adriana Annušová Anastasiia Stepura Yaryna Soyka Yuriy Halahovets Monika Hofbauerová Matej Mičušík Mário Kotlár Peter Nádaždy Paweł Albrycht Peter Šiffalovič Matej Jergel Mária Omastová Eva Majková
The surface-enhanced Raman scattering (SERS) properties of low-dimensional semiconducting MXene nanoflakes have been investigated over the last decade. Despite this fact, the relationship between the surface characteristics and SERSing performance of a MXene layer has yet to be comprehensively investigated and elucidated. This work shows the importance of surface morphology on the overall SERS effect by studying few-layer Ti3C2Tx MXene-based SERS substrates fabricated by vacuum-assisted filtration (VAF) and spray coating on filter paper. The VAF deposition results in a dense MXene layer suitable for SERS with high spot-to-spot and substrate-to-substrate reproducibility, with a significant limit of detection (LoD) of 20 nM for Rhodamine B analyte. The spray-coated MXenes film revealed lower uniformity, with a LoD of 50 nM for drop-casted analytes. Moreover, we concluded that the distribution of the analyte deposited onto the MXene layer is affected by the presence of MXene aggregates created during the deposition of the MXene layer. Accumulation of the analyte molecules in the vicinity of MXene aggregates was observed for drop-casted deposition of the analyte, which affects the resulting SERS enhancement. Ti3C2Tx MXene layers deposited on filter paper by VAF offer great potential as a cost-effective, easy-to-manufacture, yet robust, platform for sensing applications.
]]>Materials doi: 10.3390/ma17061384
Authors: Szymon Smykala Barbara Liszka Anna E. Tomiczek Miroslawa Pawlyta
Proton-exchange membrane fuel cells are one of the most promising energy conversion technologies for both automotive and stationary applications. Scientists are testing a number of solutions to increase the durability of cells, especially catalysts, which are the most expensive component. These solutions include, among others, the modification of the composition and morphology of supported nanoparticles, the platinum–support interface, and the support itself. A detailed understanding of the mechanism of platinum degradation and the subsequent improvement of the durability of the entire cell requires the development of methods for effectively monitoring the behavior of catalytic nanoparticles under various cell operating conditions. The Identical-Location Transmission Electron Microscopy (IL-TEM) method makes it possible to visually track structural and morphological changes in the catalyst directly. Because the tests are performed with a liquid electrolyte imitating a membrane, they provide better control of the degradation conditions and, consequently, facilitate the understanding of nanoparticle degradation processes in various operating conditions. This review is primarily intended to disseminate knowledge about this technique to scientists using electron microscopy in the study of energy materials and to draw attention to issues related to the characterization of the structure of carbon supports.
]]>Materials doi: 10.3390/ma17061383
Authors: Mariusz Walczak Aleksander Świetlicki Mirosław Szala Marcin Turek Dariusz Chocyk
The growing demand for modern steels showing corrosion and tribological resistance has led to their increased use in the production of medical devices. This study analyzed the effect of shot peening on wear resistance in 0.9% NaCl solution of 17-4PH steel produced by direct laser metal sintering (DMLS) technology. The study’s novelty relies on revealing the effect of shot peening (SP) surface treatment on the wet sliding wear resistance of 17-4PH steel produced with DMLS. Moreover, in the context of 17-4PH steel application for medical devices, the 0.9% NaCl tribological environment were selected, and SP processes were conducted using steel CrNi shot and ceramic (ZrO2) beads. The up-to-date scientific literature has not identified these gaps in the research. DMLS technology makes it possible to obtain products with complex architectures, but it also faces various challenges, including imperfections in the surface layer of products due to the use of 3D printing technology itself. The chemical and phase composition of the materials obtained, Vickers hardness, surface roughness, and microscopic and SEM imaging were investigated. Tribological tests were carried out using the ball-on-disc method, and the surfaces that showed traces of abrasion to identify wear mechanisms were subjected to SEM analysis. The XRD phase analysis indicates that austenite and martensite were found in the post-production state, while a higher martensitic phase content was found in peened samples due to phase transformations. The surface hardness of the peened samples increased by more than double, and the post-treatment roughness increased by 12.8% after peening CrNi steels and decreased by 7.8% after peening ZrO2 relative to the reference surfaces. Roughness has an identifiable effect on sliding wear resistance. Higher roughness promotes material loss. After the SP process, the coefficient of friction increased by 15.5% and 20.7%, while the wear factor (K) decreased by 25.9% and 32.7% for the samples peened with CrNi steels and ZrO2, respectively. Abrasive and adhesive mechanisms were dominant, featured with slight fatigue. The investigation showed a positive effect of SP on the tribological properties of DMSL 17-4PH.
]]>Materials doi: 10.3390/ma17061382
Authors: Xuming Zha Zhi Yuan Hao Qin Linqing Xi Yunwu Guo Zhilong Xu Xing Dai Feng Jiang
The demand for titanium alloy has been increasing in various industries, including aerospace, marine, and biomedical fields, as they fulfilled the need for lightweight, high-strength, and corrosion-resistant material for modern manufacturing. However, titanium alloy has relatively low hardness, poor wear performance, and fatigue properties, which limits its popularization and application. These disadvantages could be efficiently overcome by surface strengthening technology, such as the ultrasonic surface rolling process (USRP). In this study, the true thermo-mechanical deformation behavior of Ti-6Al-4V was obtained by dynamic mechanical experiment using a Hopkinson pressure bar. Moreover, USRP was applied on the Ti-6Al-4V workpiece with different parameters of static forces to investigate the evolution in surface morphology, surface roughness, microstructure, hardness, residual stress, and fatigue performance. The strain rate and temperature during the USRP of Ti-6Al-4V under the corresponding conditions were about 3000 s−1 and 200 °C, respectively, which were derived from the numerical simulation. The correlation between the true thermo-mechanical behavior of Ti-6Al-4V alloy and the USRP parameters of the Ti-6Al-4V workpiece was established, which could provide a theoretical contribution to the optimization of the USRP parameters. After USRP, the cross-sectional hardness distribution of the workpiece was shown to initially rise, followed by a subsequent decrease, ultimately to matrix hardness. The cross-sectional residual compressive stress distribution of the workpiece showed a tendency to initially reduce, then increase, and finally decrease to zero. The fatigue performance of the workpiece was greatly enhanced after USRP due to the effect of grain refinement, work hardening, and beneficial residual compressive stress, thereby inhibiting the propagation of the fatigue crack. However, it could be noted that the excessive static force parameter of USRP could induce the decline in surface finish and compressive residual stress of the workpiece, which eliminated the beneficial effect of the USRP treatment. This indicated that the choice of the optimal USRP parameters was highly crucial. This work would be conducive to achieving high-efficiency and low-damage USRP machining, which could be used to effectively guide the development of high-end equipment manufacturing.
]]>Materials doi: 10.3390/ma17061381
Authors: Chenlong Ji Zhongliang Zheng Ziming Qin Hao Xue
The corrosion process under the complex safe-end feedwater line conditions was investigated via experimental lab testing and numerical simulation. The corrosion of safe-end feedwater lines was controlled through the combination of galvanic corrosion, residual stress, and flow velocity. Firstly, galvanic corrosion occurred once the 20 steel was welded with 316L stainless steel. The pitting corrosion could be observed on the 20 steel side of the weld joint. Secondly, a vortex flow was detected around the welding bump and within the pits. The growth of the pits was accelerated in both the vertical and horizontal directions. Finally, under the residual stress condition, the stress intensity factor (K) at the bottom of the pits was easier to reach than the critical stress intensity factor (KISCC). Then, pitting was transformed into stress corrosion cracking which then propagated along the weld line. Therefore, the critical factor inducing the failure of safe-end feedwater lines was the combined action of galvanic corrosion, residual stress, and flow velocity.
]]>Materials doi: 10.3390/ma17061380
Authors: Dario Balestra Morgan Lowther Cecilia Goracci Mauro Mandurino Silvia Cortili Gaetano Paolone Chris Louca Alessandro Vichi
The objective of this study was to review the scientific evidence currently available on 3D printable materials and 3D printing technologies used for the fabrication of permanent restorations, focusing on material properties that are clinically relevant. A literature search was performed on four databases (MEDLINE/PubMed, Scopus, Cochrane Library, Web of Science) for articles published from January 2013 until November 2023, using a combination of free words: (restorative dentistry OR prosthetic dentistry) AND (3D printing OR additive manufacturing OR rapid prototyping) AND materials. Two reviewers screened titles and/or abstracts of 2.468 unique studies. In total, 83 studies were selected for full-text reading, from which 36 were included in the review. The assessed variables were mechanical properties, reporting in most of the cases positive results, dimensional accuracy and fit, reporting conflicting results with a predominance of positive, aesthetic properties, with positive reports but scarcely addressed, and biological properties, almost unexplored in independent studies. Despite numerous studies with positive results in favor, papers with negative outcomes were also retrieved. Aesthetic and biological properties are conversely still mostly unexplored. There remains a lack of conclusive evidence for viable 3D printable restorative and prosthodontic materials for permanent restorations. Research should be strengthened by defining international standards for laboratory testing and, where pre-clinical data are promising, conducting clinical trials.
]]>Materials doi: 10.3390/ma17061379
Authors: Ziming Wang Luo Liu Hui Cao
The thermal storage performance, cost, and stability of phase-change materials (PCMs) are critical factors influencing their application in the field of thermal energy storage. Porous carbon, with its excellent support, thermal conductivity, and energy storage properties, is considered one of the most promising support matrix materials. However, the simple and efficient synthesis of high-performance and highly active bio-based materials under mild conditions still faces challenges. In our work, a novel method for preparing new functional composite phase-change materials based on enzyme treatment technology and using waste walnut green husk biomass and polyethylene glycol as raw materials was developed. The enzymatic treatment method exposes the internal structure of the walnut green husk, followed by the adjustment of the calcination temperature to increase the adsorption sites of the biochar, thereby stabilizing polyethylene glycol (PEG). The porous properties of walnut green husk biochar effectively regulate the phase-change behavior of polyethylene glycol. In the biochar carbonized at 600 °C, the PEG loading reached 72.09%, and the absorption heat of the solid–solid phase-change material (SSPCM) reached 194.76 J g−1. This work not only enriches the application of biomass in heat storage but also demonstrates the broad prospects of SSPCMs in solar thermal utilization.
]]>Materials doi: 10.3390/ma17061378
Authors: Florina Branzoi Adriana Băran Marius Alexandru Mihai Mohamed Yassine Zaki
The corrosion protection property of three Brij-type surfactants, namely, Brij 35, Brij 56 and Brij 58P, was considered on OLC 45 carbon steel in a 0.5 M H2SO4 medium. The efficacy for these organic compounds was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods, scanning electron microscopy (SEM) procedures, and Fourier transform infrared (FT-IR) spectroscopy. We hypothesized that these surfactants hinder the corrosion for OLC 45 samples through a protecting mechanism owing to the adsorption of organic molecules that form an inhibitive film or through the formation of complex oxides. These surfactants exhibited an appreciable protective effect against OLC 45 corrosion, operating as mixed inhibitors, as could be demonstrated by their influence on the electrochemical characteristics of the metallic substrates. The adsorption of surfactants over the substrates zone conformed to the representation of the Langmuir isotherm. The effect of temperature on the electrochemical comportment of the OLC 45 specimens in H2SO4 without and with Brij at 800 ppm was examined in the temperature interval of 293 to 333 K. The negative estimate of thermodynamic attributed as Gibbs free energy of adsorption presented the spontaneity of the adsorption activity. The investigation with FT-IR and SEM established the adsorption of Brij and the constitution of the corrosive components on the OLC 45 surface. Electrochemical determinations of these surfactants indicated its anticorrosion inhibition performance and the highest inhibition of 96% was reached when the Brij 35 concentration was at 800 or 1000 ppm, while for Brij 56 and Brij 58P, the highest inhibition was obtained when their concentrations were 500, 800, or 1000 ppm.
]]>Materials doi: 10.3390/ma17061376
Authors: Younghun Jeong Dongwoon Han Seongtak Kim Chan Bin Mo
Not only can perovskite solar cells be exposed to high temperatures, up to 80 °C, depending on the operating environment, but absorbed energy is lost as heat, so it is important to have thermal stability for commercialization. However, in the case of the recently reported p-i-n structure solar cell, most of the electron and hole transport layers are composed of organic materials vulnerable to heat transfer, so the light absorption layer may be continuously exposed to high temperatures when the solar cell is operated. In this study, we attempted to improve the thermal conductivity of the electron transport layer using phenyl-C61-butyric acid methyl ester (PCBM) containing zinc oxide (ZnO). As a result, the thermal conductivity was improved by more than 7.4% and 23.5% by adding 6.57vol% and 22.38vol% of ZnO to PCBM, respectively. In addition, the insertion of ZnO resulted in changes in the electron transport behavior and energy level of the electron transport layer. As a result, it was confirmed that not only could the temperature stability of the perovskite thin film be improved, but the efficiency of the solar cell could also be improved from 14.12% to 17.97%.
]]>Materials doi: 10.3390/ma17061377
Authors: Chang-Da Yao Yong Li Zhi-Wei Zang Xin-Yang Li Shun Han
In order to examine the mechanical properties and rotational bending fatigue performance of 40CrNi2MoE steel subsequent to tempering at varying temperatures, the steel specimen was subjected to tempering within the range of 400~460 °C. SEM, EBSD, and TEM were used to analyze the microstructure as well as precipitates. The strain hardening law was studied using the modified Crussard–Jaoult method. Investigations were undertaken to reveal the rotational bending fatigue life with respect to the tempering temperature. The findings indicate that the strength and fatigue life of the examined steels exhibit a decline as the tempering temperature increases, with the primary factor affecting this trend being the alteration in dislocation density. No notable impact on the fatigue fracture morphology exerted by tempering temperature was found within the range of the experiment. The C–J model analysis reveals that the work-hardening behavior of the trial steels is influenced by dislocations and the second phase.
]]>Materials doi: 10.3390/ma17061374
Authors: Malgorzata Zienkiewicz-Strzalka Magdalena Blachnio Anna Derylo-Marczewska Szymon Winter Malgorzata Maciejewska
This study presents the results of applying the methods of synthesizing mesoporous carbon and mesoporous polymer materials with an extended porous mesostructure as adsorbents for cationic dye molecules. Both types of adsorbents are synthetic materials. The aim of the presented research was the preparation, characterisation, and utilisation of obtained mesoporous adsorbents. The physicochemical properties, morphology, and porous structure characteristics of the obtained materials were determined using low-temperature nitrogen sorption isotherms, X-ray diffraction (XRD), small angle X-ray scattering (SAXS), and potentiometric titration measurements. The morphology and microstructure were imaged using scanning electron microscopy (SEM). The chemical characterisation of the surface chemistry of the adsorbents, which provides information about the surface-active groups, the elemental composition, and the electronic state of the elements, was carried out using X-ray photoelectron spectroscopy (XPS). The adsorption properties of the mesoporous materials were determined using equilibrium and kinetic adsorption experiments for three selected cationic dyes (derivatives of thiazine (methylene blue) and triarylmethane (malachite green and crystal violet)). The adsorption capacity was analysed to the nanostructural and surface properties of used materials. The Generalized Langmuir equation was applied for the analysis of adsorption isotherm data. The adsorption study showed that the carbon materials have a higher sorption capacity for both methylene blue and crystal violet, e.g., 0.88–1.01 mmol/g and 0.33–0.44 mmol/g, respectively, compared to the polymer materials (e.g., 0.038–0.044 mmol/g and 0.038–0.050 mmol/g, respectively). The kinetics of dyes adsorption was closely correlated with the structural properties of the adsorbents. The kinetic data were analysed using various equations: first-order (FOE), second-order (SOE), mixed 1,2-order (MOE), multi-exponential (m-exp), and fractal-like MOE (f-MOE).
]]>Materials doi: 10.3390/ma17061375
Authors: Yunhao Jiao Yujin Yao Heping Qiu Huaxin Chen Yongchang Wu
The quasi-liquid layer (QLL), a microstructure located between ice and an adhering substrate, is critical in generating capillary pressure, which in turn influences ice adhesion behavior. This study employed molecular dynamics (MD) methods to obtain QLL thickness and utilized these measurements to estimate the adhesive strength between ice and asphalt. The research involved constructing an ice–QLL–asphalt MD model, encompassing four asphalt types and five temperature ranges from 250 K to 270 K. The QLL thickness was determined for various asphalts and temperatures using the tetrahedral order parameter gradient. Additionally, capillary pressure was calculated based on the QLL thickness and other geometric parameters obtained from the MD analysis. These findings were then compared with ice adhesion strength data acquired from pull-off tests. The results indicate that QLL thickness varies with different asphalt types and increases with temperature. At a constant temperature, the QLL thickness decreases in the order of the basal plane, primary prism plane, and secondary prism plane. Furthermore, the adhesion strength of the QLL diminishes as the temperature rises, attributed to the disruption of hydrogen bonds at lower temperatures. The greater the polarity of the asphalt’s interface molecules, the stronger the adhesion strength and binding free energy. The MD simulations of the asphalt–ice interface offer insights into the atomic-scale adhesive properties of this interface, contributing to the enhancement in QLL property prediction and calibration at larger scales.
]]>Materials doi: 10.3390/ma17061373
Authors: Jiaming Li Xiaoxun Zhang Fang Ma Shuxian Wang Yuanyou Huang
Internal pore defects are inevitable during laser powder bed fusion (LPBF), which have a significant impact on the mechanical properties of the parts. Therefore, detecting pores and obtaining their morphology will contribute to the quality of LPBF parts. Currently, supervised models are used for defect image detection, which requires a large amount of LPBF sample data, image labeling, and computing power equipment during the training process, resulting in high detection costs. This study extensively collected LPBF sample data and proposed a method for pore defect classification by obtaining its morphological features while detecting pore defects in optical microscopy (OM) images under various conditions. Compared with other advanced models, the proposed method achieves better detection accuracy on pore defect datasets with limited data. In addition, quickly detecting pore defects in a large number of labeling ground truth images will also contribute to the development of deep learning. In terms of image segmentation, the average accuracy scores of this method in the test images exceed 85%. The research results indicate that the algorithm proposed in this paper is suitable for quickly and accurately identifying pore defects from optical microscopy images.
]]>Materials doi: 10.3390/ma17061372
Authors: Magdalena Maciejewska Elżbieta Łastawiecka Marta Grochowicz
This paper presents the thermal behavior of polymer microspheres based on glycidyl methacrylate (GMA) and crosslinking agents benzene-1,4-diylbis(2-methylprop-2-enoate) (1,4DMB) and trimethylolpropane trimethacrylate (TRIM) before and after functionalization with thioglycolic acid (TGA). The thermal stability of the polymers was determined using thermogravimetric analysis and differential scanning calorimetry under non-oxidizing conditions. The evolved gases were detected by FTIR and NMR spectroscopy, and the chemical structure of solid residues after preheating was assessed by FTIR/ATR spectroscopy. The post-functionalized microspheres showed higher thermal stability (within 270–290 °C) than the initial copolymers (within 240–250 °C). In this paper, examples of decomposition patterns of polymer microspheres before and after functionalization are presented. The decomposition of the initial microspheres starts with the emission of GMA monomers, acrolein, carbon dioxide, and the formation of unsaturated bonds in the solid residue. In the case of functionalized microspheres, degradation involves the transesterification of ester groups with the -SH groups, resulting in the emission of carbonyl sulfide, acrolein and carbon dioxide. Furthermore, lactone groups are created in the solid residue. The degradation of the functionalized copolymers is a complex process due to their crosslinked structure, rendering the identification of all the degradation products unattainable.
]]>Materials doi: 10.3390/ma17061371
Authors: Xiangzhou Fu Hailong Yang Hanzhang Wang Chifu Huang Yongbin Chen Qiangang Huang Anmin Li Liwen Pan
This paper mainly investigated the effect of the Mn/Ag ratio on the microstructure and room temperature and high-temperature (350 °C) tensile mechanical properties of the as-cast and heat-treated Al-6Cu-xMn-yAg (x + y = 0.8, wt.%) alloys. The as-cast alloy has α-Al, Al2Cu, and a small amount of Al7Cu2 (Fe, Mn) and Al20Cu2 (Mn, Fe)3 phases. After T6 heat treatment, a massive dispersive and fine θ′-Al2Cu phase (100~400 nm) is precipitated from the matrix. The Mn/Ag ratio influences the quantity and size of the precipitates; when the Mn/Ag ratio is 1:1, the θ′-Al2Cu precipitation quantity reaches the highest and smallest. Compared with the as-cast alloy, the tensile strength of the heat-treated alloy at room temperature and high temperature is greatly improved. The strengthening effect of the alloy is mainly attributed to the nanoparticles precipitated from the matrix. The Mn/Ag ratio also affects the high-temperature tensile mechanical properties of the alloy. The high-temperature tensile strength of the alloy with a 1:1 Mn/Ag ratio is the highest, reaching 135.89 MPa, 42.95% higher than that of the as-cast alloy. The analysis shows that a synergistic effect between Mn and Ag elements can promote the precipitation and refinement of the θ′-Al2Cu phase, and there is an optimal ratio (1:1) that obtains the lowest interfacial energy for co-segregation of Mn and Ag at the θ′/Al interface that makes θ′-Al2Cu have the best resistance to coarsening.
]]>Materials doi: 10.3390/ma17061368
Authors: Xiangyu Gao Zheng Zhang Liyu Liu Chunhu Tao
This study investigates how deviation angles close to the [001] orientation affect the tensile properties and deformation behavior of a nickel-based single-crystal superalloy at room temperature. The research focuses on samples with deviation angles of 3°, 8°, and 13° from the [001] orientation and examines their strength and ductility. We employed scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) to explore the deformation micro-mechanisms at varying angles. Findings reveal that strength decreases and ductility increases as the deviation angle widens within the [001] vicinity. The study emphasizes that <110> octahedral slip-driven crystal slip and rotation are crucial for understanding tensile deformation. The deformation differences in samples at varying angles are attributed to the differential engagement of mechanisms. Specifically, at lower angles, reduced ductility and increased strength are due to short lattice rotation paths and work hardening causing superlattice stacking faults (SSFs) to slip in two directions on the {111} plane within the γ′ phase. As the angles increase, the lattice rotation paths extend, and Shockley partial dislocations (a/6<112>) accumulate in γ channels. This process, involving SSFs moving in a single direction within the γ′ phase, results in higher ductility and reduced strength.
]]>Materials doi: 10.3390/ma17061370
Authors: Ying Zhi Yao Jiang Diwen Ke Xianlei Hu Xianghua Liu
The cellular automata (CA) method has played an important role in the research and development of metallic materials. CA can interpret the microstructure changes of materials and obtain more abundant, accurate and intuitive information of microstructure evolution than conventional methods. CA can visually represent the process of grain formation, growth, development and change to us in a graphical way, which can assist us in analysis, thinking and solving problems. In the last five years, the application of CA in materials research has been rapidly developed, and CA has begun to occupy an increasingly important position in the simulation research of metallic materials. After introducing the advantages and limitations of CA compared to other widely used simulation methods, the purpose of this paper is to review the recent application progress on the microstructure simulation of metallic materials using CA, such as solidification, recrystallization, phase transformation and carbide precipitation occurring during forming and heat treatment. Specifically, recent research advances on microstructure simulation by CA in the fields of additive manufacturing, welding, asymmetrical rolling, corrosion prevention, etc., are also elaborated in this paper. Furthermore, this paper points out the future work direction of CA simulation in the research of metallic materials, especially in the simulation of the crystal structure, the prediction of mechanical properties, CA simulation software and rule systems, etc. These are expected to attract wide attention of researchers in the field of metallic materials and promote the development of CA in materials research.
]]>Materials doi: 10.3390/ma17061369
Authors: Nataša Tot Vesna Despotović Sanja Panić Branko Kordić Nina Finčur Jovana Prekodravac Dimitar Jakimov Predrag Putnik Biljana Abramović Daniela Šojić Merkulov
This study aimed to compare the effectiveness of adsorption and photocatalysis techniques at removing the herbicide clomazone (CLO) and the antidepressant known as amitriptyline (AMI) from water. This study employed kinetic models to analyze the removal processes and assess the potential toxicity of the treated water. The structure and morphology of the prepared multi-walled carbon nanotubes were characterized as adsorbents by transmission electron microscopy, X-ray diffraction, Fourier transform infrared techniques, and Raman spectroscopy. The adsorption kinetics of CLO and AMI were studied on the pristine and functionalized multi-walled carbon nanotubes. Kinetic studies were performed by modeling the obtained experimental data using three kinetic models: pseudo-first-order, pseudo-second-order, and Elovich kinetic models. On the other hand, the efficiency of CLO and AMI photodegradation was examined as a function of the type of irradiation (UV and simulated solar irradiation) and type of TiO2 photocatalyst (Aeroxide and Kronos). Under the experimental conditions employed, the reaction followed pseudo-first-order kinetics. Additionally, in order to assess the toxicity of water containing CLO, AMI, and their intermediates, toxicity assessments were conducted using human fetal lung fibroblast cells. The results obtained indicate the effectiveness of both methods and provide valuable insights into their removal mechanisms, contributing to the advancement of sustainable water treatment strategies.
]]>Materials doi: 10.3390/ma17061366
Authors: Qianying Zeng Feng Wang Zhengxi Li Maohua Rong Jiang Wang Zhongmin Wang
Due to the poor activation performance and kinetics of Ti50V25Cr25 alloys, the element Zr was added to improve the phase structure of the alloy and achieve a high-performance hydrogen storage alloy. The Ti50−xV25Cr25Zrx (x = 0, 5, 7, and 9) system alloys were prepared by arc melting. The alloys were analyzed using an X-ray diffractometer (XRD), scanning electron microscope (SEM), and differential scanning calorimeter (DSC). The hydrogen storage capabilities of the alloys were also obtained by the Sievert volumetric method. The results indicated that the alloy with Zr added had a combination of the C15 Laves phase and the BCC phase, whereas the Zr-free alloy had a BCC single phase. The partial replacement of Zr with Ti resulted in an increase in the lattice parameters of the main phase. The hydrogen storage kinetic performance and activation of the alloys both significantly improved with an increasing Zr concentration. The time to reach 90% of the maximum hydrogen storage capacity decreased to 2946 s, 230 s, and 120 s, respectively, with the increases in Zr concentration. The initial hydrogen absorption content of the alloys increased and then decreased after the addition of the element Zr. The second phase expanded with an increasing Zr concentration, which in turn decreased the abundance of the BCC main phase. The Ti43V25Cr25Zr7 alloy showed good cycle stability and hydrogen-desorption performance, and it could absorb 90% of the maximum hydrogen storage capacity in around 230 s. The maximum hydrogen-absorption capacity of the alloy was 2.7 wt%. The diffusion activation energy of hydrogen desorption dropped from 102.67 kJ/mol to 92.62 kJ/mol.
]]>Materials doi: 10.3390/ma17061367
Authors: Jakub Kowalczyk Dariusz Ulbrich
Adhesive joints are non-separable connections that are used in numerous ways in vehicle construction, particularly in buses. The widespread use of adhesive joints makes it necessary to assess their quality, especially under production conditions. The main goal of this study was to develop a mathematical model to estimate the width of the adhesive path in a plywood-adhesive-closed-profile joint based on selected parameters of the ultrasonic surface wave. A digital ultrasonic flaw detector and Rayleigh wave probes were applied. The test involved evaluating different widths of hybrid adhesive and two-component epoxy adhesive. The tests were conducted on a steel profile from a bus construction. The attenuation of the ultrasonic waves on the steel profile (0.026 db/mm) and the adhesive (0.264 dB/mm) was determined. A one-size-fits-all model for estimating adhesive path width for specific conditions is proposed.
]]>Materials doi: 10.3390/ma17061365
Authors: Wei Chen Mengmeng Wu Yue Liang
Ground Granulated Blast-Furnace Slag (GGBS) and silica fume (SF) are frequently utilized in gel materials to produce environmentally sustainable concrete. The blend of the two components contributes to an enhancement in the pore structure, which, in turn, increases the mechanical strength of the material and the compactness of the pore structure and decreases the permeability, thereby improving the durability of the concrete. In this study, the pore structures of GGBS and SF blends are assessed using Nuclear Magnetic Resonance (NMR) and Mercury Intrusion Porosimetry (MIP) tests. These methodologies provide a comprehensive evaluation of the effect of GGBS and SF on the pore structure of cementitious materials. Results showed that the addition of SF and GGBS reduces the amount of micro-capillary pores (10 < d < 100 nm) and the total pore volume. The results indicate that the transport properties are related to the pore structure. The incorporation of SF reduced the permeability of the concrete by an order of magnitude. The pore distribution and pore composition had a significant effect on the gas permeability. The difference in porosity obtained using the MIP and NMR tests was large due to differences in testing techniques.
]]>Materials doi: 10.3390/ma17061364
Authors: Xin Deng Xiao Zhang Xiaochuan Long Xiaopeng Liu
The Co3O4 is a typical p-type metal oxide semiconductor (MOS) that attracted great attention for hydrogen detection. In this work, porous, urchin-like Co3O4 was synthesized using a hydrothermal method with the assistance of glucose and a subsequent calcination process. Urchin-like Co3O4 has a large specific surface area of 81.4 m2/g. The response value of urchin-like Co3O4 to 200 ppm hydrogen at 200 °C is 36.5 (Rg/Ra), while the low-detection limit is as low as 100 ppb. The obtained Co3O4 also exhibited good reproducibility, long-term stability, and selectivity towards various gases (e.g., ammonia, hydrogen, carbon monoxide, and methane). Porous, urchin-like Co3O4 is expected to become a potential candidate for low-concentration hydrogen-sensing materials with the above advantages.
]]>Materials doi: 10.3390/ma17061363
Authors: Zhong-Lin Hou Hai-Quan Guo Jia-Ji Wang Zeng-Yang Huang Ze-An Wang Di-Sheng Fang Jun Qiao
Ultra-thick offshore steel, known for its high strength, high toughness, and corrosion resistance, is commonly used in marine platforms and ship components. However, when offshore steel is in service for an extended period under conditions of high pressure, extreme cold, and high-frequency impact loads, the weld joints are prone to fatigue failure or even fractures. Addressing these issues, this study designed a narrow-gap laser wire filling welding process and successfully welded a 100-mm new type of ultra-thick offshore steel. Using finite element simulation, EBSD testing, SEM analysis, and impact experiments, this study investigates the weld’s microstructure, impact toughness, and fracture mechanisms. The research found that at −80 °C, the welded joint exhibited good impact toughness (>80 J), with the impact absorption energy on the surface of the weld being 217.7 J, similar to that of the base material (225.3 J), and the fracture mechanism was primarily a ductile fracture. The impact absorption energy in the core of the weld was 103.7 J, with the fracture mechanism mainly being a brittle fracture. The EBSD results indicated that due to the influence of the welding thermal cycle and the cooling effect of the narrow-gap process, the grains gradually coarsened from the surface of the welded plate to the core of the weld, which was the main reason for the decreased impact toughness at the joint core. This study demonstrates the feasibility of using narrow-gap laser wire filling welding for 100-mm new type ultra-thick offshore steel and provides a new approach for the joining of ultra-thick steel plates.
]]>Materials doi: 10.3390/ma17061362
Authors: Daniel Gajda Michał Babij Andrzej Zaleski Doğan Avci Fırat Karaboga Hakan Yetis Ibrahim Belenli Tomasz Czujko
Currently, MgB2 wires made by the powder-in-tube (PIT) method are most often used in the construction and design of superconducting devices. In this work, we investigated the impact of heat treatment under both low and high isostatic pressures on the formation of a layered structure in PIT MgB2 wires manufactured using the Mg coating method. The microstructure, chemical composition, and density of the obtained superconductive wires were investigated using scanning electron microscopy (SEM) with an energy-dispersive X-ray spectroscopy (EDS) analyzer and optical microscopy with Kameram CMOS software (version 2.11.5.6). Transport measurements of critical parameters were made by using the Physical Property Measurement System (PPMS) for 100 mA and 19 Hz in a perpendicular magnetic field. We observed that the Mg coating method can significantly reduce the reactions of B with the Fe sheath. Moreover, the shape, uniformity, and continuity of the layered structure (cracks, gaps) depend on the homogeneity of the B layer before the synthesis reaction. Additionally, the formation of a layered structure depends on the annealing temperature (for Mg in the liquid or solid-state), isostatic pressure, type of boron, and density of layer B before the synthesis reaction.
]]>Materials doi: 10.3390/ma17061361
Authors: Min Li Gonggang Liu Chongqing Wang Shanshan Chang Jinbo Hu
Plastic pollution, particularly microplastic (MP) and nanoplastic (NP) pollution, has become a significant concern. This study explores the use of porous wood for filtration to remove MPs and NPs and investigates their removal mechanisms. Undecorated fir wood with a thickness of 4 mm achieves a 91% removal rate for model polystyrene (PS) MPs (2.6 μm) at a water flux of 198 L/m2h. However, its separation performance for NPs (255.8 and 50.9 nm) is poor. It also shows that fir wood (coniferous wood) has a higher PS removal rate than poplar wood (hard wood). With poly dimethyl diallyl ammonium chloride (PDDA) modification, both MPs and NPs are effectively removed, with NPs’ removal rate increasing from <10% to 90% for PDDA/wood. Characterization results reveal that size-exclusive interception dominates for micron-sized particles, and electrostatic interaction is crucial for nanosized particles. Additionally, intercepted NPs have been used as a strong binder for hot-pressed wood to remarkably enhance the mechanical properties of wood, suggesting a novel recycle utilization of discarded wood filters. Overall, this renewable wood material offers a simple solution for tackling MP/NP pollution.
]]>Materials doi: 10.3390/ma17061360
Authors: Juan Carlos Rodríguez Fernández Francisco Pastor José María Barrera Mora Elena Demiquels Eduardo Espinar Javier Gil
Invisible orthodontic aligners are having a great impact on tooth movement in an aesthetic and effective way. Different techniques, models, and clinical aspects have been studied for their proper use. However, the aim of this research has been to determine the effect of the shaping process on mechanical properties and their bacterial behavior. For this study, 40 original polyurethane plates and 40 identical models, obtained by hot forming the original plates, were used. The static tensile mechanical properties were studied with a Zwick testing machine using testing speeds of 5 mm/min at a temperature of 37 °C. The original plate and the aligner have been studied with a creep test by subjecting the samples to a constant tension of 30 N, and determining the elongation using a long-distance, high-resolution microscope at different time periods between 1 and 720 h. Studies of water absorption has been realized with artificial saliva for 5 h. Bacterial cultures of Streptococcus oralis and Actinomyces viscosus strains were grown on the original plates and on new and used models, to determine the proliferation of each bacterium through metabolic activity, colony-forming units, and LIVE/DEAD assays. The mechanical results showed an increase in the strength of the inserts with respect to the models obtained from 3.44 to 3.95 MPa in the elastic limit and a lower deformation capacity. It has been proven that the transition zone in the creep curves lasts longer in the original plate, producing the rapid increase in deformation at a shorter time (400 h) in the aligner. Therefore, the shaping process reduces the time of dental correction exerted by the aligner. The results of the bacterial culture assays show an increase in the number of bacterial colonies when the aligners have been used and when the polyurethane is conformed due to the internal energy of the model, with respect to the original polyurethane. It has been observed that between the original plate and the aligner there are no statistically significant differences in water absorption and therefore the forming process does not affect water absorption. A slight increase in water absorption can be observed, but after five hours of exposure, the increase is very small.
]]>Materials doi: 10.3390/ma17061359
Authors: Marat R. Agliullin Dmitry V. Serebrennikov Boris I. Kutepov
A study has been conducted to investigate the formation of intermediate phases during the crystallization of SAPO-11 molecular sieves from reaction mixtures with a varying template (di-n-propylamine) DPA/Al2O3 ratio. It was found that changing the DPA/Al2O3 ratio from 1.0 to 1.8 in the initial reaction gels leads to the formation of different intermediate phases during crystallization into a SAPO-11 molecular sieve. It is shown that at the ratio template/Al2O3 = 1.0, an intermediate amorphous silicoaluminophosphate is formed; at 1.4, a mixture consisting of amorphous and layered phases forms; and at 1.8, a layered phase is present. A simple and innovative approach for controlling the morphology, size, and characteristics of primary crystals and the secondary porous structure in hierarchical SAPO-11 is proposed. The method is based on regulating the DPA/Al2O3 ratio in the reaction gel. The synthesized SAPO-11 molecular sieves with a hierarchical porous structure exhibited high selectivity in the hydroisomerization of n-hexadecane.
]]>Materials doi: 10.3390/ma17061358
Authors: Yong-Hong Wang Ping Du Jiang Diao Bing Xie Ming-Hua Zhu
Coke plays a key role as the skeleton of the charge column in BF. The gas path formed by the coke layer in the BF has a decisive influence on gas permeability. At high temperatures, the interface between coke and ore undergoes a melting reaction of coke and a reduction reaction of ore. The better the reducibility of the ore, the more conducive it is to the coupling reaction of ore and coke. The melting loss reaction of coke becomes more intense, and the corresponding strength of coke will decrease, which will affect the permeability of the blast furnace and is not conducive to the smooth operation of the blast furnace. Especially with a deterioration in iron ore quality, BF operation faces severe challenges, which makes it necessary to find an effective way to strengthen BF operation. In this study, a melting-dropping furnace was used to develop and clarify the high-temperature interaction between coke and iron ores with different layer thicknesses. The influencing factors were studied by establishing a gas permeability mathematical model and observing the metallographic microscope images of samples after the coke solution loss reaction. The relationships between coke layer thickness, distribution of gas flow, and pressure drop were obtained. The results showed that, under certain conditions, the gas permeability property of a furnace burden has been improved after the coke layer thickness increased. Upon observing the size of coke particles at the interface reaction site, the degree of melting loss reaction can be determined. A smaller particle size indicates more melting loss reaction. A dripping eigenvalue for molten metal was introduced to evaluate the dynamic changes in the comprehensive dripping properties of molten metal of furnace burden, which showed that the dripping eigenvalue for the molten metal could deteriorate because of the unruly thickness and the coke layer thickness should be limited through considering the operational indicators of the blast furnace.
]]>Materials doi: 10.3390/ma17061357
Authors: Hryhorii Starykov Oleksandr Bezvikonnyi Karolis Leitonas Jurate Simokaitiene Dmytro Volyniuk Eigirdas Skuodis Rasa Keruckiene Juozas Vidas Grazulevicius
Two derivatives of phenyl pyrimidine as acceptor unit and triphenylamino or 4,4′-dimethoxytriphenylamino donor groups were designed and synthesized as emitters for organic light-emitting diodes (OLEDs) aiming to utilize triplet excitons in the electroluminescence. Thermogravimetric analysis revealed high thermal stability of the compounds with 5% weight loss temperatures of 397 and 438 °C. The theoretical estimations and photophysical data show the contributions of local excited and charge transfer states into emission. The addition of the methoxy groups led to the significant improvement of hole-transporting properties and the bathochromic shift of the emission from blue to green-blue spectral diapason. It is shown that mixing of the compounds with the organic host results in facilitation of the delayed emission. The singlet–triplet energy splitting was found to be too big for the thermally activated delayed fluorescence. No thermal activation of the long-lived emission was detected. No experimental evidence for triplet–triplet annihilation and room temperature phosphorescence were detected making the hot exciton mechanism the most probable one. The OLEDs based on the compounds reached the maximum external quantum efficiency of up to 10.6%.
]]>Materials doi: 10.3390/ma17061356
Authors: Shuang Yi Shichao Zhang Denghui Wang Jianxing Mao Zheng Zhang Dianyin Hu
Thermally induced pores (TIPs) are generally the source of fatigue crack initiation in the powder metallurgy (PM) Ni-based FGH96 superalloy. The effect of TIPs on fatigue crack initiation on the surface of the FGH96 superalloy was detected using scanning electron microscopy (SEM). The cause of fatigue crack deflection was studied using electron backscatter diffraction (EBSD) analysis. The results indicated that there are two states of TIPs including isolated TIPs and clustered TIPs located at the grain boundary. The investigation of crack initiation and propagation around TIPs was conducted in detail through the comprehensive integration of experimental findings and computational results. For cracks initiated by isolated TIPs, the maximum equivalent size and the ratio of the vertical–parallel axis to the loading direction of the TIPs reveal a linear relationship, and both of them determine crack initiation. Regarding clustered TIPs, the constituent pores of the clustered TIPs will compete to initiate cracks based on the experimental results, and the largest pore will be more likely to initiate cracking. Moreover, the results showed that fatigue crack propagation can be hindered by hard-orientation grains and twins with a low Schmid factor (SF). Large-angle crack deflection due to twins with a low SF can significantly increase crack length and resistance to crack propagation.
]]>Materials doi: 10.3390/ma17061355
Authors: Anetta Walawska Magdalena Olak-Kucharczyk Anna Kaczmarek Marcin H. Kudzin
The paper presents the new eco-friendly method of bleaching process of the cellulose fibre materials. Cellulose materials were bleached using hydrogen peroxide (both in aqueous solution, vapours, ozone and by the combined action of gaseous hydrogen peroxide and ozone. The method using hydrogen peroxide in aqueous solution presents the standard procedure and was used as the comparison technique. The bleaching processes using gaseous oxidants were carried out in a prototype device for dry, low-temperature treatment of fibrous materials with the use of oxidising agents in the gas phase. The influence of the innovative gas-phase bleaching method on the cotton samples’ properties was analysed by Scanning Electron Microscopy (SEM), evaluation of the colour and whiteness, assessment of the polymerisation degree (DP), analysis of the mechanical properties and sorption capacity as well as microbiological assessment against colonies of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The comparison of the obtained results led to the conclusion that the bleaching processes using gas-phase agents—vaporised hydrogen peroxide, ozone or their combination—are non-invasive. The applied bleaching processes resulted in a slightly lower whiteness parameters than standard bath bleaching. After the bleaching processes with ozone and vaporised hydrogen peroxide separately, the decrease in the DP and tensile strength was similar to that observed after the bleaching with aqueous H2O2. When both processes were used together, a higher reduction in DP and tensile strength was noticed. Both oxidising agents showed a strong biocidal effect against bacteria. Gas-phase bleaching procedures, due to the lower temperature (35 °C vs. 98 °C) and minimal water consumption, have economic and environmental advantages, which allows their use in semi-industrial applications. It has been shown that the treatment of cotton fabrics using ozone and hydrogen peroxide in the gas phase allows to simultaneously obtain the bleaching and disinfection effect.
]]>Materials doi: 10.3390/ma17061354
Authors: Salih Veziroglu
Noble metal/semiconductor nanocomposites have been synthesized using various methods, including precipitation and hydrothermal and electrochemical processes. Among these, the photodeposition method stands out for its simplicity, without the need for high temperatures, redox agents, or complex steps. This method facilitates the control over noble metal nanoparticle size by adjusting parameters such as metal precursor concentration, irradiation time, and power. However, understanding the interaction between solid and liquid interfaces, particularly the role of solution viscosity in the growth process, remains a challenge. This knowledge is crucial for precise control over nanoparticle size and distribution. Our study highlights the influence of viscosity, manipulated through different alcohols, on the formation of Ag nanostructures on TiO2 thin films via photodeposition, offering insights into optimizing nanocomposite synthesis.
]]>Materials doi: 10.3390/ma17061353
Authors: Amin Jamshidi Luís Sousa
One of the methods used to discover the development of deterioration in bricks used as a construction material in a building is the monitoring of the bricks’ strength characteristics over time. However, measuring the strength characteristics of bricks used in a building requires sampling for performing laboratory tests, which is not possible in some cases. As an alternative, ultrasonic wave velocity can be a useful, nondestructive tool for the indirect assessment of the strength characteristics of the bricks. In the present study, six different samples of clay bricks before utilization as construction materials in buildings located in Khorramabad City (Lorestan Province, western Iran) were collected. The mineralogical composition of the samples was studied using X-ray diffraction (XRD) analysis. As one common physical characteristic of the construction materials, the porosity (n) of the samples was measured. Next, the strength characteristics, including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and P-wave velocity (Vp), of the samples under dry and saturated conditions were determined. It was found that after the saturation of the samples, considerable decreases in the UCS and BTS and increases in the Vp occurred, respectively. By comparing the values of the UCS, BTS, and Vp of the samples under dry and saturated conditions, we found that the integrity loss for the UCS and BTS was higher than for the Vp. Results showed that the integrity loss of the UCS, BTS, and Vp was significantly affected by the n and clay mineral (CM) content of the samples. Considering the dry or saturated condition of the samples, there are good correlations with acceptable accuracy levels between the Vp and the UCS and BTS, with coefficients of determination (R2) varying from 0.95 to 0.98. Consequently, our findings showed that establishing UCS and BTS predictive equations for bricks before their use as a construction material can be a worthy, practical tool for monitoring the deterioration of bricks over time after their utilization in a building.
]]>Materials doi: 10.3390/ma17061352
Authors: Zbigniew Szklarz Karolina Kołczyk-Siedlecka Elizaveta Vereshchagina Aina Herbjørnrød Paul Wittendorp Shruti Jain Pawel Jerzy Wójcik
This paper discusses the electrochemical properties of thin-film, planar, titanium–platinum (Ti-Pt) microelectrodes fabricated using glass or silicon substrates and compares their performance to the classic platinum (Pt) microelectrodes embedded in glass. To analyze the possible differences coming both from the size of the tested electrodes as well as from the substrate, short- and long-term electrochemical tests were performed on selected water electrolytes (KCl, HCl, KOH). To study the electrochemical response of the electrodes, the cyclic voltammetry (CV) measurements were carried out at different scanning rates (from 5 to 200 mV/s). Long-term tests were also conducted, including one thousand cycles with a 100 mV/s scan rate to investigate the stability of the tested electrodes. Before and after electrochemical measurements, the film morphology was analyzed using a scanning electron microscope (SEM). The good quality of the thin-film Pt electrodes and the high repeatability in electrochemical response have been shown. There are minor differences in standard deviation values taken from electrochemical measurements, comparing thin-film and wire-based electrodes. Damages or any changes on the electrodes’ surfaces were revealed by SEM observations after long-term electrochemical tests.
]]>Materials doi: 10.3390/ma17061351
Authors: Saulius Drukteinis Goda Bilvinaite Simas Sakirzanovas
Hydraulic calcium silicate-based (HCS) sealers have recently gained tremendous popularity due to their unique properties. However, their removal during endodontic retreatment is challenging. The solvent, which could chemically deteriorate the material, would be highly desirable for endodontic retreatment procedures. This preliminary study assessed the interplay and dissolving capability of 10% and 20% citric acid, compared to 17% EDTA, on commonly used HCS sealers (AH Plus Bioceramic Sealer, Bio-C Sealer, BioRoot RCS, TotalFill BC Sealer), and evaluated the potential impact of these solutions on root dentin structure. The interaction between tested sealers and irrigating solutions was photographed, and solubility-related mass changes were determined. The surface morphology of treated filling materials and dentin was evaluated using a scanning electron microscope (SEM). One-way analysis of variance (ANOVA) along with Tukey’s test were used to detect the statistically significant differences among groups at the confidence level of 0.95. Intense gas release was observed during the interaction of HCS materials and citric acid, with no evidently visible “bubbling” after the immersion in EDTA. The mass loss of HCS sealers equally confirmed the significantly higher dissolving characteristics of 10% and 20% citric acid solutions compared to EDTA. The surface structural changes, associated with pore and crack formation, were mainly seen for HCS sealers exposed to citric acid. Meanwhile, no severe erosion was detected for dentin after root canal preparation with 10% and 20% citric acid solutions. These findings demonstrate that citric acid has the potential to dissolve HCS sealers with minimal or no negative impact on root dentin, suggesting citric acid as a solvent for HCS sealers in endodontic retreatment procedures.
]]>Materials doi: 10.3390/ma17061350
Authors: Saadman Abedin Vladislav Kurtash Sobin Mathew Sebastian Thiele Heiko O. Jacobs Jörg Pezoldt
Molybdenum disulfide, a two-dimensional material extensively explored for potential applications in non-von Neumann computing technologies, has garnered significant attention owing to the observed hysteresis phenomena in MoS2 FETs. The dominant sources of hysteresis reported include charge trapping at the channel–dielectric interface and the adsorption/desorption of molecules. However, in MoS2 FETs with different channel thicknesses, the specific nature and density of defects contributing to hysteresis remain an intriguing aspect requiring further investigation. This study delves into memristive devices with back-gate modulated channel layers based on CVD-deposited flake-based and thin-film-based MoS2 FETs, with a few-layer (FL) and thin-film (TF) channel thickness. Analysis of current–voltage (I−V) and conductance–frequency (Gp/ω−f) measurements led to the conclusion that the elevated hysteresis observed in TF MoS2 devices, as opposed to FL devices, stems from a substantial contribution from intrinsic defects within the channel volume, surpassing that of interface defects. This study underscores the significance of considering both intrinsic defects within the bulk and the interface defects of the channel when analyzing hysteresis in MoS2 FETs, particularly in TF FETs. The selection between FL and TF MoS2 devices depends on the requirements for memristive applications, considering factors such as hysteresis tolerance and scaling capabilities.
]]>Materials doi: 10.3390/ma17061349
Authors: Yuanzhan Wang Jing Liao Baohua Zhang
The application of recycled coarse aggregate (RA) in structural concrete can save non-renewable resources and reduce land occupation. Developing comprehensive knowledge of chloride penetration and service life modeling of recycled coarse aggregate concrete (RAC) is a prerequisite for practice. However, compared with the natural aggregate concrete (NAC), the inferior durability performance, especially chloride penetration resistance, of RAC hinders its application in structural concrete. Therefore, many RAC performance enhancement methods have been proposed. This paper presents a holistic review focused on the chloride penetration of RAC with/without enhancement methods and service life prediction. The current RAC performance enhancement methods are introduced. The improvement effect of the corresponding enhancement methods on the chloride penetration resistance of RAC are discussed and analyzed in turn. Based on the reviewed data on the chloride diffusion coefficient, the modification efficiencies of assorted enhancement methods are summarized. With the hope of promoting RAC application in structural concrete, the current literature on chloride-ingress-based service life prediction for RAC is also overviewed. In addition, the typical influencing factors on chloride transport properties are also discussed, i.e., RA quality. It can be concluded that enhancement techniques can effectively improve the chloride penetration resistance of RAC. The old mortar enhancement or removal methods can improve the chloride penetration resistance by 15–30%, depending on the specific treatment measures. The modification efficiency of the modifier material depends on the specific type and content of the incorporated substance, which ranges from approximately 5% to 95%. The estimated service life of RAC structures decreases with the increasing RA replacement ratio. Finally, concluding remarks are provided concerning future research on the chloride transport behavior of RAC.
]]>Materials doi: 10.3390/ma17061348
Authors: Shinichi Tashiro
The Keyhole Plasma Arc Welding (KPAW) process utilizes arc plasma highly constricted by a water-cooled cupper nozzle to produce great arc pressure for opening a keyhole in the weld pool, achieving full penetration to the thick plate. However, advanced control of welding is known to still be difficult due to the complexity of the process mechanism, in which thermal and dynamic interactions among the arc, keyhole, and weld pool are critically important. In KPAW, two large eddies are generally formed in the weld pool behind the keyhole by plasma shear force as the dominant driving force. These govern the heat transport process in the weld pool and have a strong influence on the weld pool formation process. The weld pool flow velocity is much faster than those of other welding processes such as Tungsten Inert Gas (TIG) welding and Gas Metal Arc (GMA) welding, enhancing the heat transport to lower the weld pool surface temperature. Since the strength and direction of this shear force strongly depend on the keyhole shape, it is possible to control the weld pool formation process by changing the keyhole shape by adjusting the torch design and operating parameters. If the lower eddy is relatively stronger, the heat transport to the bottom side increases and the penetration increases. However, burn-through is more likely to occur, and heat transport to the top side decreases, causing undercut. In order to realize further sophistication of KPAW, a deep theoretical understanding of the process mechanism is essential. In this article, the recent progress in studies regarding the interaction mechanism of arc, keyhole, and weld pool in KPAW is reviewed.
]]>Materials doi: 10.3390/ma17061347
Authors: Qiang Ma Pangkun Zheng Junjie Chen Xuesong Lu
The treatment of chromium-contaminated soil in seasonal frozen soil areas has been the subject of recent interest. Polyurethane (PU), as a polymer material with excellent freeze–thaw resistance and abrasion resistance, has the potential to solidify Chromium-Contaminated soil in seasonal frozen soil areas. However, there is a lack of research on the mechanism of PU involved in solidifying/stabilizing chromium-contaminated soil in seasonal frozen regions from the perspective of pore structure and functional group coordination bonds. In this study, the leaching behavior of PU with different contents under different freeze–thaw cycles was analyzed, and the mechanism of PU in seasonal frozen regions was explored from the perspective of pores and functional groups by combining various microscopic characterization methods. The results show that PU can effectively resist the deterioration of chromium-contaminated soil after freeze–thaw cycles and can better prevent the harm of secondary leaching. The leaching concentration of chromium ion is only 1.09 mg/L, which is below China’s regulatory limits. PU is beneficial for inhibiting the expansion of ice crystals in chromium-contaminated soil in seasonal frozen soil areas. PU solidifies chromium by physical encapsulation and complexation reactions. The amide functional groups, methyl-CH3 and isocyanate groups in PU play a leading role in the complexation with chromium. Although the freeze–thaw cycle will destroy the coordination bond between the PU functional group and chromium, chromium cannot break through the bond of PU film. This study confirmed the feasibility of using PU to solidify Chromium-Contaminated soil in seasonal frozen soil areas, which can provide research support and reference for in situ engineering in the future.
]]>Materials doi: 10.3390/ma17061345
Authors: Gheorghe Paltanea Veronica Manescu (Paltanea) Aurora Antoniac Iosif Vasile Nemoianu Horia Gavrila
The problem of energy consumption reduction establishes important challenges for electric motor producers in the framework of new international regulations regarding the conditions that must be accomplished by motors in the near future. One of the most important topics is related to the core loss decrease directly linked to the effect of electrical steel degradation induced by the cutting technology. Understanding exactly how this phenomenon occurs by analyzing the chemical, mechanical, crystallographic, magnetic domain, and magnetic properties is of utmost importance when manufacturing processes must be changed and adapted to a new market characterized by high-efficiency motors. Today, mechanical and laser cutting technologies are the most used because of their reduced price and high-speed process. Still, unfortunately, these methods are not the best due to the fact that they lead, in most cases, to a high value of magnetic core losses, low electromagnetic torque, and hence reduced efficiency. This review paper shows that non-conventional technologies such as water jetting and electroerosion could be applied if proper modifications are added. This paper’s main idea is to present a comprehensive study regarding the impact of cutting technologies on microhardness and residual stresses, crystallographic texture, magnetic domain structure, and magnetic properties of some non-oriented electrical steels used in motor production. It provides a detailed analysis of the abovementioned aspects by including the authors’ research and findings in the wider context of other research group contributions. It also offers a general idea of the mechanisms present at the macro- and microscopic levels. The readers can find some of the most used analytical models, including the cutting process’s damaged effect on the magnetic properties’ variation based on a simple mathematical approach and examples of finite element modeling performed on real motor designs implemented in various programs. Last but not least, some practical implementations of the cutting procedure’s influence on motor working conditions are presented in the last section of the paper. It provides an up-to-date analysis regarding how the cutting method should be included in high-efficiency motor production by emphasizing the importance of the topic and identifying where supplementary research must be undertaken. From the investigated literature, by analyzing specific sample geometries associated with different characterization methods, it can be concluded that all the cutting technologies have an important contribution to the mechanical and magnetic quantities. When the magnetic core of an electric motor is produced through non-conventional methods, the overall influence of the cutting procedure has a low percentage in the motor efficiency, as presented in this paper.
]]>Materials doi: 10.3390/ma17061346
Authors: Shuang Dong Yi-Ting Huang Xin Zhang Shan-Shan Cheng Xian-Wei Cheng Jin-Ping Guan
The use of biobased flame-retardant (FR) agents for reducing the flammability of polyester/cotton (T/C) blend fabrics is highly desirable. In this study, a novel and sustainable phosphorus/nitrogen-containing FR, namely, phytic acid–urea (PA-UR) salt, was synthesized. The PA-UR salt was further used to enhance the FR performance of T/C fabric through surface modification. We further explored the potential chemical structure of PA-UR and the surface morphology, thermal stability, heat release capacity, FR properties, and mode of action of the coated fabric. The coated fabric achieved self-extinguishing and exhibited an increased limiting oxygen index of 31.8%. Moreover, the coated T/C blend fabric demonstrated a significantly reduced heat release capacity, indicating a decreased fire hazard. Thermogravimetric analysis revealed the anticipated decomposition of the coated T/C blend fabric and a subsequent increase in thermal stability. The burned char residues also maintained their fiber shape structures, suggesting the presence of condensed FR actions in the PA-UR-coated T/C blend fabric.
]]>Materials doi: 10.3390/ma17061344
Authors: Yi Zhao Yanning Zhang Yilin Yan Zunyao Huang Yuting Zhang Xiaoli Wang Nandi Zhou
Nanotechnology-enabled pesticide delivery systems have been widely studied and show great prospects in modern agriculture. Nanodelivery systems not only achieve the controlled release of agrochemicals but also possess many unique characteristics. This study presents the development of a pH-responsive pesticide nanoformulation utilizing hollow mesoporous silica nanoparticles (HMSNs) as a nanocarrier. The nanocarrier was loaded with the photosensitive pesticide prochloraz (Pro) and then combined with ZnO quantum dots (ZnO QDs) through electrostatic interactions. ZnO QDs serve as both the pH-responsive gatekeeper and the enhancer of the pesticide. The results demonstrate that the prepared nanopesticide exhibits high loading efficiency (24.96%) for Pro. Compared with Pro technical, the degradation rate of Pro loaded in HMSNs@Pro@ZnO QDs was reduced by 26.4% after 24 h ultraviolet (UV) exposure, indicating clearly improved photostability. In a weak acidic environment (pH 5.0), the accumulated release of the nanopesticide after 48 h was 2.67-fold higher than that in a neutral environment. This indicates the excellent pH-responsive characteristic of the nanopesticide. The tracking experiments revealed that HMSNs can be absorbed by rice leaves and subsequently transported to other tissues, indicating their potential for effective systemic distribution and targeted delivery. Furthermore, the bioactivity assays confirmed the fungicidal efficacy of the nanopesticide against rice blast disease. Therefore, the constructed nanopesticide holds great prospect in nanoenabled agriculture, offering a novel strategy to enhance pesticide utilization.
]]>Materials doi: 10.3390/ma17061343
Authors: Seung-Mo Hong Oh Young Kim Seok-Ho Hwang
Thiols can react with readily available organic substrates under benign conditions, making them suitable for use in chemical, biological, physical, and materials and engineering research areas. In particular, the highly efficient thiol-based click reaction includes the reaction of radicals with electron-rich enes, Michael addition with electron-poor enes, carbonyl addition with isocyanate SN2 ring opening with epoxies, and SN2 nucleophilic substitution with halogens. This mini review provides insights into emerging venues for their industrial applications, especially for the applications of thiol-ene, thiol–isocyanate, and thiol–epoxy reactions, highlighting a brief chemistry of thiols as well as various approaches to polythiol synthesis.
]]>Materials doi: 10.3390/ma17061342
Authors: Yongqiang Zhang Peng Zhao Yiqi Tong Honggang Dong Jun Zhou Feng Qin Yanping Bi Peng Li
In recent years, for the structural characteristics and design requirements of the integral rotor and disc shaft of the integrated engine, the welding quality and mechanical properties of superalloy weldments have received increasing attention. In this paper, inertia friction welding (IFW) of FGH96 alloy was carried out using different welding parameters, and the homogeneous connection of FGH96 alloy hollow bars was successfully realized. The microstructure evolution, mechanical properties and fracture failure of the welded joints at room and high temperatures were investigated. The FGH96 alloy IFW joints were divided into the weld nugget zone (WNZ), the thermo-mechanically affected zone (TMAZ), the heat-affected zone (HAZ) and the base metal (BM), and there were significant differences in grain structure and distribution of the γ′ phase in each of the characteristic zones. The microhardness and tensile properties of the IFW joints were investigated, and the results showed an “M”-shaped curve in the microhardness distribution, with the lowest point of hardness observed in the HAZ. The tensile test results indicated that the fracture position moved from the BM to the WNZ with the increase in temperature, the microstructure at the fracture changed significantly and the tensile strength decreased from 1512.0 MPa at room temperature to 1201.3 MPa at 750 °C. The difference in the mechanical properties of the joints was mainly attributed to the changes in the dissolution and precipitation of the γ′ phase.
]]>Materials doi: 10.3390/ma17061341
Authors: Sung-Jun Lee Chang-Lae Kim
The study examined the correlation between collagen coating damage and self-healing under various tribological conditions. It confirmed that the friction coefficient and degree of damage on the collagen coating varied based on contact and sliding conditions. The friction coefficient, measured at 0.56 for a single sliding cycle under a 350 mN normal load, demonstrated a notable decrease to 0.46 for 2295 cycles under 30 mN, further reducing to 0.15 for 90 cycles under a 20 mN normal load. As the normal load increased, the friction coefficient decreased, and with repeated sliding cycles under the same load, the coefficient also decreased. Water droplets induced a self-healing effect on collagen coating, causing wear tracks to vanish as fibers absorbed water. Severe wear tracks, with broken fibers and peeled coating, showed limited self-healing. In contrast, mild wear tracks, with compressed yet connected fibers, exhibited the self-healing phenomenon, making the wear tracks disappear. Real-time observations during 90 cycles under a 20 mN normal load highlighted the formation of mild wear tracks with intact collagen fibers, providing quantitative insights into self-healing characteristics. To preserve the self-healing effect of the collagen coating, it is essential to ensure tribological conditions during contact and sliding that prevent the disconnection of collagen fibers.
]]>Materials doi: 10.3390/ma17061340
Authors: Blessing O. Adeleke John M. Kinuthia Jonathan Oti Duncan Pirrie Mathew Power
The effective use of waste materials is one of the key drivers in ensuring sustainability within the construction industry. This paper investigates the viability and efficacy of sustainably incorporating a polylactic acid-type plastic (WP) as a 10 mm natural coarse aggregate (NA) replacement in geopolymer concrete. Two types of concrete (ordinary Portland cement—OPC and geopolymer) were produced for completeness using a concrete formulation ratio of 1:2:3. The ordinary concrete binder control was prepared using 100% OPC at a water/binder ratio of 0.55, while the geopolymer concrete control used an optimum alkaline activator/precursor—A/P ratio (0.5) and sodium silicate to sodium hydroxide—SS/SH volume ratio (1.2/0.8). Using the same binder quantity as the control, four concrete batches were developed by replacing 10 mm NA with WP at 30 and 70 wt% for ordinary and geopolymer concrete. The mechanical performance of the developed concrete was assessed according to their appropriate standards, while a microstructural investigation was employed after 28 days of curing to identify any morphological changes and hydrated phases. The results illustrate the viability of incorporating WP in geopolymer concrete production at up to 70 wt% replacement despite some negative impacts on concrete performance. From a mechanical perspective, geopolymer concrete indicated a 46.7–58.3% strength development superiority over ordinary concrete with or without WP. The sample composition and texture quantified using automated scanning electron microscopy indicated that adding WP reduced the presence of pores within the microstructure of both concrete types. However, this was detrimental to the ordinary concrete due to the low interfacial zone (ITZ) between calcium silicate hydrate (CSH) gel and WP, resulting in the formation of cracks.
]]>Materials doi: 10.3390/ma17061339
Authors: Antanas Zinovicius Inga Morkvenaite-Vilkonciene Arunas Ramanavicius
This research is focused on enhancing the capabilities of scanning electrochemical impedance microscopy (SEIM) for detecting gold nanoparticle-labelled antibodies using electrochemically modified platinum ultramicroelectrode. The primary objective was to address the high resistance issue encountered in previous measurements with SEIM via the utilization of SEIM probes based on micro-electrodes modified by platinum microstructures, which improved the sensitivity and precision of the detection of targeted biomolecules. The modified probe resulted in a lowered charge transfer resistance by over ten times and a decrease in detection to around 100 fg/mL. We suggest potential applications in various biotechnological and biomedical fields, with future research expected to further refine this technique.
]]>Materials doi: 10.3390/ma17061338
Authors: Chen Liu Yu Zhan Hongjian Zhao Shuo Shang Changsheng Liu
Additive manufacturing (AM) technology has the advantages of designability, short process times, high flexibility, etc., making it especially suitable for manufacturing complex high-performance components for high-end industrial systems. However, the intensive temperature gradients caused by the rapid heating and cooling processes of AM can generate high levels of residual stresses, which directly affect the precision and serviceability of the components. Taking Inconel 690 alloy, which is widely used in nuclear power plants, as the research object, a thermo-coupled mechanical model of temperature field and residual stress field of directed energy deposition (DED) of Inconel 690 was established based on ABAQUS 2019 finite element software to study the influence of process parameters on the temperature history and the distribution of residual stresses in the DED process. The experimental results show that the peak temperature of each layer in the fabrication process increases with the increase in laser power and preheating temperature, and decreases with the increase in scanning speed and interlayer dwell time. Substrate preheating only has a large effect on the peak temperature of the first four layers. Residual stresses are mainly concentrated in the upper and middle parts, the bottom of the substrate, and the sides combined with the substrate, and the residual stresses increase with the increasing laser power and decrease with the increasing interlayer dwell time. Decreasing laser power, longer dwell time, higher preheating temperature, and appropriate scanning speed are beneficial for the reduction in residual stresses in Inconel 690 components. This research has important significance for the process design and residual stress modulation in the additive manufacturing of Inconel 690 alloy.
]]>Materials doi: 10.3390/ma17061336
Authors: R. K. Singh Raman W. H. Siew
Prompted by the unexpected observation of the pitting of the weldments of a highly corrosion- and pitting-resistant duplex stainless steel, SAF2507, in chloride solutions with nitride addition, the pitting and corrosion resistance of SAF2507 and its weldments were investigated in chloride solutions with and without different levels of nitrite. The Incoloy 825 and 316L austenitic stainless steels were included for the purpose of developing a comparative appreciation. The microstructures of the weldments were characterised, and 316L showed a profound influence of nitrite addition in inhibiting pitting, while ‘meta-stable’ pitting transients that were clearly visible in the chloride solution without nitrite were absent when nitrite was added. Both the parent metal and the weldment of SAF2507 had similar pitting potential (Ep) in 0.1 M NaCl without nitrite, which was the highest Ep among the three alloys tested. Additions of nitrite at low concentrations had an inhibitive effect on pitting, whereas higher nitrite contents had a deleterious effect on pitting resistance. On the other hand, Incoloy 825 showed a trend of Ep ennoblement with an increasing nitrite content of 0.1 M NaCl, and the weldment underwent greater ennoblement. Moreover, 316L showed a trend similar to Incoloy 825; however, the Ep ennoblements were significantly more pronounced for both the weldment and the base metal of 316L.
]]>Materials doi: 10.3390/ma17061337
Authors: Bang Liu Jun Lan Hongqiang Liu Xinya Chen Xin Zhang Zhengyi Jiang Jian Han
Wire arc additive manufacturing (WAAM) excels in producing medium to large components with a high deposition rate. Process optimization is crucial for uniform, defect-free components. This research employs orthogonal experimental design and response surface methodology (RSM) to control TIG WAAM-ed 308L stainless steel components. Varied parameters, including tungsten electrode angle, welding current, and speed, target weld bead attributes. Analysis of variance (ANOVA) evaluates multi-processing parameter influence on weld bead formation. Comparison with experimental results confirms accurate modeling of the relationship between parameters and bead attributes. The study optimizes process parameters and swing to enhance dimensional accuracy in single-layer and multi-layer components, improving precision, quality, and accuracy in thin-walled structures.
]]>Materials doi: 10.3390/ma17061335
Authors: Anna E. Tsai Kyriakos Komvopoulos
The complex dynamics of tribofilm formation on boundary-lubricated steel surfaces were investigated in real time by combining in situ measurements of the temporal variation of the coefficient of friction and contact voltage. Sliding experiments were performed with various blends consisting of base oil, zinc dialkyl dithiophosphate (ZDDP) additive, and two different dispersants at an elevated oil temperature for a wide range of normal load and fixed sliding speed. The evolution of the transient and steady-state coefficient of friction, contact voltage, and critical sliding distance (time) for stable tribofilm formation were used to evaluate the tribological performance of the tribofilms. The blend composition affected the load dependence of the critical sliding distance for stable tribofilm formation. Tribofilm friction was influenced by competing effects between the additive and the dispersants. Among various formulations examined, the tribofilm with the best friction characteristics was found to be the blend consisting of base oil, a small amount of ZDDP, and a bis-succinimide dispersant treated with ethylene carbonate. The results of this study demonstrate the effectiveness of the present experimental approach to track the formation and removal of protective tribofilms under boundary lubrication conditions in real time.
]]>Materials doi: 10.3390/ma17061334
Authors: Mostafa Katouzian Sorin Vlase Calin Itu Maria Luminita Scutaru
Determining the mechanical properties of a composite material represents an important stage in its design and is generally a complicated operation. These values are influenced by the topology and geometry of the resulting composite and the values of the elastic constants of the components. Due to the importance of this subject and the increasing use of composite materials, different calculation methods have been developed over the last fifty years. Some of the methods are theoretical, with results that are difficult to apply in practice due to difficulties related to numerical calculation. In the current paper, using theoretical results offered by the homogenization theory, values of engineering elastic constants are obtained. The finite element method (FEM) is used to determine the stress and strain field required in these calculations; this is an extremely powerful and verified calculation tool for the case of a material with any type of structure and geometry. In order to minimize errors, the paper proposes the method of least squares, a mathematical method that provides the best estimate for the set of values obtained by calculating FEM. It is useful to consider as many load cases as possible to obtain the best estimates. The elastic constants for a transversely isotropic material (composite reinforced with cylindrical fibers) are thus determined for a real case.
]]>Materials doi: 10.3390/ma17061333
Authors: Rachel Boillat-Newport Sriram Praneeth Isanaka Jonathan Kelley Frank Liou
Scalmalloy® is an Al-Mg-Sc-Zr-based alloy specifically developed for additive manufacturing (AM). This alloy is designed for use with a direct aging treatment, as recommended by the manufacturer, rather than with a multistep treatment, as often seen in conventional manufacturing. Most work with Scalmalloy® is conducted using powder bed rather than powder-fed processes. This investigation seeks to fill this knowledge gap and expand beyond single-step aging to promote an overall balanced AM-fabricated component. For this study, directed energy deposition (DED)-fabricated Scalmalloy® components were subjected to low-temperature treatments to minimize residual stresses inherent in the material due to the layer-by-layer build process. X-ray diffraction (XRD) indicated the possibility of stress minimization while reducing the detriment to mechanical strength through lower temperature treatments. Microstructural analyses consisting of energy dispersion spectroscopy (EDS) and electron backscatter diffraction (EBSD) revealed the presence of grain growth detrimentally affecting the strength and elongation made possible by very small grains inherent to AM and rapid solidification. Tensile testing determined that treatment at 175 °C for 1 h provides the best relief from the existing residual stresses; however, this is accompanied by a diminishment in the yield and tensile strength of 19 and 9.5%, respectively. It is noted that treatment at 175 °C for 2 h did not provide as great of a decrease in residual stresses, theorized to be the result of grain growth and other strengthening mechanisms further stressing the structure; however, the residual stresses are still significantly diminished compared with the as-built condition. Furthermore, a minimal reduction of the tensile strengths indicates the possibility of finding a balance between property diminishment and stress state through the work proposed here.
]]>Materials doi: 10.3390/ma17061332
Authors: Cristiano Albonetti Riva Alkarsifi Virginie El Qacemi Benjamin Dhuiege Giampiero Ruani Mirko Seri
Among solution-processable metal oxides, zinc oxide (ZnO) nanoparticle inks are widely used in inverted organic solar cells for the preparation, at relatively low temperatures (<120 °C), of highly efficient electron-transporting layers. There is, however, a recent interest to develop more sustainable and less impacting methods/strategies for the preparation of ZnO NPs with controlled properties and improved performance. To this end, we report here the synthesis and characterization of ZnO NPs obtained using alternative reaction solvents derived from renewable or recycled sources. In detail, we use (i) recycled methanol (r-MeOH) to close the loop and minimize wastes or (ii) bioethanol (b-EtOH) to prove the effectiveness of a bio-based solvent. The effect of r-MeOH and b-EtOH on the optical, morphological, and electronic properties of the resulting ZnO NPs, both in solution and thin-films, is investigated, discussed, and compared to an analogous reference material. Moreover, to validate the properties of the resulting materials, we have prepared PTB7:PC71BM-based solar cells containing the different ZnO NPs as a cathode interlayer. Power conversion efficiencies comparable to the reference system (≈7%) were obtained, validating the proposed alternative and more sustainable approach.
]]>Materials doi: 10.3390/ma17061330
Authors: Yinxun Tan Haofeng Xie Xue Feng Shuhui Huang Wenjing Zhang Lijun Peng Wanyu Wang Yizhi Zhao
To study the effect of aluminum and nickel elements on the microstructures and properties of the nickel–aluminum bronze (NAB) alloy, four kinds of alloys with different compositions, ZCuAl7–7–4–2, ZCuAl8-6-4-2, ZCuAl9-5-4-2, and ZCuAl10-4-4-2, are prepared by vacuum-melting technology. The effects of different Al/Ni ratios on the microstructures of NAB are investigated using a metalloscope, scanning electron microscopy, transmission electron microscopy, and XPS analysis. The mechanical property is evaluated with microhardness testing and tensile mechanical testing. The corrosion resistance is evaluated using mass-loss testing, electrochemical testing, and corrosion-product characterization. The results show that with the increase of the Al/Ni ratio, the content of precipitated phases increases, while β′ and hard κ, which have a different morphology, appear. As the Al/Ni ratio rises from 1 to 2.5, the hardness increases from 104 HV to 202 HV, and the tensile strength increases by 394 MPa from 356 MPa to 751 MPa, but the elongation decreases substantially from 50.50% to 11.00%. The best corrosion resistance is shown on ZCuAl7-7-4-2, with a corrosion rate of 0.00267 mm/a after 30 d of static immersion corrosion in 3.5 wt.% NaCl solution. Through electrochemical testing and corrosion-product characterization, it is found that ZCuAl7-7-4-2 has the largest polarization resistance Rp, and the selective corrosion of the surface is mild.
]]>Materials doi: 10.3390/ma17061331
Authors: Zhengquan Su Jun Liu Pengfei Li Changhao Liang
In this work, we focus on the degradation of membrane electrode assemblies (MEAs) in proton-exchange membrane water electrolysis (PEMWE) induced by different accelerated stress tests (ASTs), including constant-current mode, square-wave mode, and solar photovoltaic mode. In constant-current mode, at continuous testing for 600 h at 80 °C, a degradation of operating voltage increased by the enhanced current density from 22 µV/h (1 A/cm2) to 50 µV/h (3 A/cm2). In square-wave mode, we found that in the narrow fluctuation range (1–2 A/cm2), the shorter step time (2 s) generates a higher degradation rate of operating voltage, but in the wide fluctuation range (1–3 A/cm2), the longer step time (22 s) induces a faster operating voltage rise. In the solar photovoltaic mode, we used a simulation of 11 h sunshine duration containing multiple constant-current and square-wave modes, which is closest to the actual application environment. Over 1400 h ASTs, the solar photovoltaic mode lead to the most serious voltage rise of 87.7 µV/h. These results are beneficial to understanding the durability of the PEM electrolyzer and optimizing the components of MEAs, such as catalysts, membranes, and gas diffusion layers.
]]>Materials doi: 10.3390/ma17061329
Authors: Shuai Guo Yuwei Ma Peng Liu Yang Chen
In this study, a new structure is proposed based on the body-centered cubic (BCC) lattice structure by adding a cubic truss in the center of the BCC structure and denoting it TLC (truss–lattice–cube). The different dimensions of the central cube can notably affect the mechanical properties of the lattice structure. With a fixed length (15 mm) of a unit cell, the optimal size for the central cube is determined to be 5 mm. Quasi-static compressive tests are performed on specimens made of polylactic acid (PLA) using additive manufacturing technology. The deformation characteristics of the new structure are analyzed in detail by experiments and numerical simulations. Compared to the BCC structure, the mechanical properties of the TLC structure were significantly improved. The initial flow stress of the TLC increased by 122% at a strain of 0.1; the specific strength enhanced by 293% at a strain of 0.5; and the specific energy absorption improved by 312% at a strain of 0.6. Printing defects in the lattice structure may remarkably damage its mechanical properties. In this work, incorporation of microcracks into the finite element model allows the simulation to capture the influence of printing defects and significantly improve the predictive accuracy of the simulation.
]]>Materials doi: 10.3390/ma17061328
Authors: Massimiliano Annoni
This review paper aimed to draw the red line passing through almost 25 years of research on waterjet cutting carried out at WJ_Lab, the waterjet laboratory of the Department of Mechanical Engineering of Politecnico di Milano. The purpose was not to just historically analyse the obtained scientific results by themselves but to make them even more useful by introducing the concept of the waterjet digital twin passing through the accuracy improvements due to microAWJ. This strategy effectively creates synergy among the topics and gives the opportunity to researchers in this field to both have an example of how research in industrial manufacturing processes can be guided by scientific and industrial needs, at least from the author’s point of view, and to appreciate how it can be made useful for further improvements by introducing a powerful concept as the digital twin.
]]>Materials doi: 10.3390/ma17061327
Authors: Mingtao Chen Jinhao Hu Yunya Xiao Junwei Liang Zhiwei Ye Hongchao Wu Feng Zhou Guisheng Mao Hui Long Wei Tang Xiaoting Xiao
In hydroforming of parallel double-branch tubes, the material entering the branch zone is obstructed by material accumulation in the main tubes and corners, which decreases the branch height. A tube hydroforming approach is combined with pre-forming and crushing (THPC) to mitigate this problem. A larger diameter tube blank is flattened for pre-forming and then subjected to radial compression for crushing. In the next step, hydroforming forms the parallel double-branch tubes. Experiments and numerical simulations are then carried out to analyze the effect of traditional tube hydroforming (TTH) and the proposed THPC process on the formability of parallel double-branch tubes. The results show that for tubes obtained via THPC, the tube burst pressure increases by 27.5% and the branch height increases 2.37-fold compared to TTH. Additionally, the flattening, pre-forming, and crushing stages cause work hardening of the tube when using the TPHC process. Flattened tubes undergo radial compression to improve the material flowing into the branch tube. The formability of parallel double-branched tubes can be improved by using the TPHC process. Consequently, tube hydroforming, combined with pre-forming and crushing, has been confirmed as a feasible forming process for fabricating parallel double-branch tubes.
]]>Materials doi: 10.3390/ma17061326
Authors: Oriana Palma Calabokis Yamid Nuñez de la Rosa Paulo César Borges Tiago Cousseau
Aftermarket additives are used to enhance the performance of internal combustion engines in specific aspects such as reducing wear, increasing power, and improving fuel economy. Despite their advantages, they can sometimes cause corrosion-related problems. This research evaluated the corrosiveness of four aftermarket additives on the corrosion of a high-leaded tin bronze alloy over 28 days at 80 °C in immersion tests. Among the evaluated products, three showed corrosive effects ranging from intermediate to severe. Notably, the visual appearance of the surfaces often did not indicate the underlying corrosive damage. Therefore, the assessment of corrosiveness was based on chemical characterizations conducted on both the drained oils and the bronze surfaces. The study found minimal oil degradation under the testing conditions, indicating that the primary cause of corrosion was the interaction between the specific additives and the metal elements of the alloy, rather than oil degradation itself. A direct correlation was observed between the dissolution of lead and copper and the adsorption of S and Cl-containing additives on the surfaces, respectively. The corrosive impact of Cl-containing additives in aftermarket formulations was significantly reduced when mixed with engine oil SAE 10W-30 (at a 25:1 ratio), suggesting a mitigated effect in combined formulations, which is the recommended usage for engines.
]]>Materials doi: 10.3390/ma17061325
Authors: Shengnian Zhao Dehong Lu Fengbin Wang Jiaxing Zhong Yehua Jiang
TiCp/steel composites are conventionally produced via powder metallurgy. In this paper, a liquid pressure infiltration method was developed to prepare a kind of spherical hierarchical architectured composite, in which spherical TiCp-rich hard phase regions were uniformly dispersed in TiCp-free soft phase region. The microstructure and mechanical properties of the architectured composites were carefully studied and compared with the common composite, as well as the effect of TiCp fraction on the properties. The results show that architecturual design can effectively improve both the toughness and strength of the composites. With TiCp content increasing from 30% to 50%, both the bending strength and the impact toughness of the architectured composites first increase, then decrease, and reach the highest at 40% TiCp. The highest impact toughness reaches 21.2 J/cm2, being 6.2 times that of the common composite and the highest strength being 67% higher. The pressure infiltration method possesses adaptability to varying shapes and sizes of the products, allowing for large-scale preparation. Therefore, for the first time, the combination of pressure infiltration preparation and architectural design was applied to TiCp/steel composites.
]]>Materials doi: 10.3390/ma17061324
Authors: Grzegorz Świderski Ewelina Gołębiewska Natalia Kowalczyk Monika Kalinowska Renata Świsłocka Elżbieta Wołejko Urszula Wydro Piotr Malinowski Anna Pietryczuk Adam Cudowski Waldemar Priebe Włodzimierz Lewandowski
This paper presents the results of a study of the effects of the lanthanide ions Ce3+, Pr3+, Nd3+ and Sm3+ on the electronic structure and antioxidant and biological (antimicrobial and cytotoxic) properties of p-coumaric acid (p-CAH2). Structural studies were conducted via spectroscopic methods (FTIR, ATR, UV). Thermal degradation studies of the complexes were performed. The results are presented in the form of TG, DTG and DSC curves. Antioxidant properties were determined via activity tests against DPPH, ABTS and OH radicals. The reducing ability was tested via CUPRAC assays. Minimum inhibitory concentrations (MICs) of the ligand and lanthanide complexes were determined on E. coli, B. subtilis and C. albicans microorganisms. The antimicrobial activity was also determined using the MTT assay. The results were presented as the relative cell viability of C. albicans, P. aeruginosa, E. coli and S. aureus compared to controls and expressed as percentages. In the obtained complexes in the solid phase, lanthanide ions coordinate three ligands in a bidentate chelating coordination mode through the carboxyl group of the acid. Spectroscopic analysis showed that lanthanide ions increase the aromaticity of the pi electron system of the ligand. Thermal analysis showed that the complexes are hydrated and have a higher thermal stability than the ligand. The products of thermal decomposition of the complexes are lanthanide oxides. In the aqueous phase, the metal combines with the ligand in a 1:1 molar ratio. Antioxidant activity tests showed that the complexes have a similar ability to remove free radicals. ABTS and DPPH tests showed that the complexes have twice the ability to neutralise radicals than the ligand, and a much higher ability to remove the hydroxyl radical. The abilities of the complexes and the free ligand to reduce Cu2+ ions in the CUPRAC test are at a similar level. Lanthanide complexes of p-coumaric acid are characterised by a higher antimicrobial capacity than the free ligand against Escherichia coli bacteria, Bacillus subtilis and Candida albicans fungi.
]]>Materials doi: 10.3390/ma17061323
Authors: Hansong Liu Jinsong Sun Lianwang Zhang Zhaobo Liu Chengyu Huang Mingchen Sun Ziqi Duan Wenge Wang Xiangyu Zhong Jianwen Bao
The toughening modification of epoxy resin has received widespread attention. The addition of the second-phase resin has a good toughening effect on epoxy resin. In order to investigate the effect of the second-phase resin on the interphase of composites, in this work the interfacial properties of carbon fiber (CF)/epoxy resin with the second-phase resin structure were investigated. Methodologies including surface structure observation, chemical characteristics, surface energy of the CF, and micro-phase structure characterization of resin were tested, followed by the micro-interfacial performance of CF/epoxy composites before and after hygrothermal treatment. The results revealed that the sizing process has the positive effect of increasing the interfacial bonding properties of CF/epoxy. From the interfacial shear strength (IFSS) test, the introduction of the second phase in the resin reduced the interfacial bonding performance between the CF and epoxy. After the hygrothermal treatment, water molecules diffused along the interfacial paths between the two resins, which in turn created defects and consequently brought about a reduction in the IFSS.
]]>Materials doi: 10.3390/ma17061322
Authors: Xiaoshuang Du Nan Qu Xuexi Zhang Jiaying Chen Puchang Cui Jingtao Huang Yong Liu Jingchuan Zhu
SiCp/Al composites offer the advantages of lightweight construction, high strength, and corrosion resistance, rendering them extensively applicable across various domains such as aerospace and precision instrumentation. Nonetheless, the interfacial reaction between SiC and Al under high temperatures leads to degradation in material properties. In this study, the interface segregation energy and interface binding energy subsequent to the inclusion of alloying elements were computed through a first-principle methodology, serving as a dataset for machine learning. Feature descriptors for machine learning undergo refinement via feature engineering. Leveraging the theory of machine-learning-accelerated first-principle computation, six machine learning models—RBF, SVM, BPNN, ENS, ANN, and RF—were developed to train the dataset, with the ANN model selected based on R2 and MSE metrics. Through this model, the accelerated computation of interface segregation energy and interface binding energy was achieved for 89 elements. The results indicate that elements including B, Si, Fe, Co, Ni, Cu, Zn, Ga, and Ge exhibit dual functionality, inhibiting interfacial reactions while bolstering interfacial binding. Furthermore, the atomic-scale mechanism elucidates the interfacial modulation of these elements. This investigation furnishes a theoretical framework for the compositional design of SiCp/Al composites.
]]>Materials doi: 10.3390/ma17061321
Authors: Jana Biermann Charlyn Elise Bień Clemens Lechte Philipp Kanzow Annette Wiegand
This study analyzed the dentin shear bond strength (SBS) of an etch-and-rinse (ER) or a self-etch (SE) adhesive incorporated with multifunctional polyhedral oligomeric silsesquioxanes (MA-POSS-8). An ER adhesive (Solobond Plus, VOCO GmbH, Cuxhaven, Germany) and a universal adhesive applied in SE mode (Scotchbond Universal, 3M, St. Paul, MN, USA) were infiltrated with MA-POSS-8 (Hybrid Plastics Inc., Hattiesburg, MS, USA) at 5 wt.% or 10 wt.%. Pure adhesives served as controls. Bovine dentin specimens were conditioned with one of the adhesives prior to the application of a nano-hybrid composite (Venus Diamond A3, Kulzer, Hanau, Germany). SBS and failure modes were determined after water storage for 24 h, 6 months, 12 months, or 24 months (each subgroup n = 20). Statistical analysis was performed using ANOVAs, Weibull statistics, and χ2 tests (p < 0.05). SBSs for the control groups after 24 h were 17.4 ± 4.9 MPa for the ER adhesive and 19.1 ± 5.2 MPa for the universal adhesive. After 24 months, the SBS of the ER adhesive was significantly higher for 5 wt.% MA-POSS-8 (17.9 ± 5.1 MPa) than for the control group (14.6 ± 3.6 MPa) and 10 wt.% MA-POSS-8 (12.8 ± 4.1 MPa), and more cohesive failures were observed. The SBS of the universal adhesive increased during aging, irrespective of the MA-POSS-8 concentration. 5 wt.% MA-POSS-8 improves the SBS of the ER adhesive and does not impair the SBS of the SE adhesive.
]]>Materials doi: 10.3390/ma17061320
Authors: Tatiana Pyatina Toshifumi Sugama Al Moghadam Marcel Naumann Ragnhild Skorpa Blandine Feneuil Vincent Soustelle Rune Godøy
High-temperature (HT) geothermal wells can provide green power 24 hours a day, 7 days a week. Under harsh environmental and operational conditions, the long-term durability requirements of such wells require special cementitious composites for well construction. This paper reports a comprehensive assessment of geothermal cement composites in cyclic pressure function laboratory tests and field exposures in an HT geothermal well (300–350 °C), as well as a numerical model to complement the experimental results. Performances of calcium–aluminate cement (CAC)-based composites and calcium-free cement were compared against the reference ordinary Portland cement (OPC)/silica blend. The stability and degradation of the tested materials were characterized by crystalline composition, thermo-gravimetric and elemental analyses, morphological studies, water-fillable porosity, and mechanical property measurements. All CAC-based formulations outperformed the reference blend both in the function and exposure tests. The reference OPC/silica lost its mechanical properties during the 9-month well exposure through extensive HT carbonation, while the properties of the CAC-based blends improved over that period. The Modified Cam-Clay (MCC) plasticity parameters of several HT cement formulations were extracted from triaxial and Brazilian tests and verified against the experimental results of function cyclic tests. These parameters can be used in well integrity models to predict the field-scale behavior of the cement sheath under geothermal well conditions.
]]>Materials doi: 10.3390/ma17061319
Authors: Wei Huang Zhenhui Fan Kang Liu Gaoxing Hu Xinwei Miao Yujiao Sun Gang Liu
To reduce the damage to reinforced concrete shear walls in earthquakes and repair costs, a self-centering wall with sloped plane friction dampers (SPFDs) is proposed. In addition to the SPFDs, the proposed wall includes a precast composite wall, steel wall toes, and post-tensioned (PT) tendons. The steel wall toes embedded in the base of the precast wall were used to improve its strength, and the SPFDs installed in the steel toes were used to increase its energy dissipation capacity. To investigate the effect of the initial PT force and prestressing clamping force of the friction bolt on the seismic performance of the wall, quasistatic cyclic loading tests were carried out on three precast wall specimens. The damage to the self-centering walls was slight, the residual drift was small, and the energy dissipation met the specification requirements. The wall with the greater initial PT force showed higher self-centering and bearing capacity, and the wall with higher prestressing clamping forces showed greater energy dissipation capacity. Additionally, a calculation method for the bearing capacity of the precast wall, which was verified by comparison with the test results, is suggested.
]]>Materials doi: 10.3390/ma17061318
Authors: Barbara Hajduk Paweł Jarka Henryk Bednarski Henryk Janeczek Pallavi Kumari Aurica Farcas
Herein, we report the thermal transitions and structural properties of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) pseudopolyrotaxane (PEDOT∙CB7-PS) and polyrotaxane (PEDOT∙CB7-PR) thin films compared with those of pristine PEDOT. The structural characteristics were investigated by using variable-temperature spectroscopic ellipsometry (VTSE), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and atomic force microscopy (AFM). VTSE and DSC results indicated the presence of an endothermic process and glass transition in the PEDOT∙CB7-PS and PEDOT∙CB7-PR thin films. X-ray diffraction of PEDOT∙CB7-PS and PEDOT∙CB7-PR powders displayed the presence of interchain π-π stacking revealing a characteristic arrangement of aromatic rings in the internal structure of the crystallites. AFM imaging of PEDOT∙CB7-PS and PEDOT∙CB7-PR thin films exhibited significant differences in the surface topographies compared with those of PEDOT. A high degree of crystallization was clearly visible on the surface of the PEDOT layer, whereas the PEDOT∙CB7-PS and PEDOT∙CB7-PR thin films exhibited more favorable surface parameters. Such significant differences identified in the surface morphology of the investigated layers can, therefore, be clearly associated with the presence of surrounding CB7 on PEDOT skeletons.
]]>Materials doi: 10.3390/ma17061317
Authors: Chiara Bedon Filipe A. Santos Marco Fasan
The mechanical analysis of photovoltaics and building integrated photovoltaics is a key step for their optimal design and certification, and requires careful consideration, alongside solar power, durability and functionality issues. The solar cells are encapsulated in thin interlayers that are usually composed of a viscoelastic Ethylene–Vinyl Acetate compound, and protected by thin glass and/or plastic layers. This paper investigates the out-of-plane bending response of a full-scale commercial PV module and focuses attention on the shear bonding efficiency of the thin encapsulant for quasi-static and dynamic mechanical considerations. The parametric analytical analysis, carried out in this study for a laminated glass plate, highlights the possible consequences of the viscoelastic shear coupling on the cross-section load-bearing demand in the covers. As a direct effect of severe operational conditions (i.e., ageing, non-uniform/cyclic thermal gradients, humidity, extreme mechanical/thermal loads, etc.) the shear rigidity and adhesion of these films can suffer from repeated/progressive modification and even degradation, and thus induce major stress and deflection effects in the out-of-plane mechanical response of the PV module components. The minimum shear bond efficiency required to prevent mechanical issues is calculated for various configurations of technical interest. Accordingly, it is shown how the quasi-static and dynamic mechanical performance of the system modifies as a function of a more rigid or weak shear coupling.
]]>Materials doi: 10.3390/ma17061316
Authors: Ruzhao Chen Bin Fu Jie Han Hu Zhang Ping Wang Hongxia Yin
The microstructure, corrosion resistance, and phase-transition process of micro-arc oxidation (MAO) coatings prepared on LaFe11.6Si1.4 alloy surfaces in different electrolyte systems were systematically investigated. Research has demonstrated that various electrolyte systems do not alter the main components of the coatings. However, the synergistic action of Na2CO3 and Na2B4O7 more effectively modulated the ionization and chemical reactions of the MAO process and accelerated the formation of α-Al2O3. Moreover, the addition of Na2CO3 and Na2B4O7 improved the micromorphology of the coating, resulting in a uniform coating thickness and good bonding with the LaFe11.6Si1.4 substrate. The dynamic potential polarization analysis was performed in a three-electrode system consisting of a LaFe11.6Si1.4 working electrode, a saturated calomel reference electrode, and a platinum auxiliary electrode. The results showed that the self-corrosion potential of the LaFe11.6Si1.4 alloy without surface treatment was −0.68 V, with a current density of 8.96 × 10−6 A/cm2. In contrast, the presence of a micro-arc electrolytic oxidation coating significantly improved the corrosion resistance of the LaFe11.6Si1.4 substrate, where the minimum corrosion current density was 1.32 × 10−7 A/cm2 and the corrosion potential was −0.50 V. Similarly, after optimizing the MAO electrolyte with Na2CO3 and Na2B4O7, the corrosion resistance of the material further improved. Simultaneously, the effect of the coatings on the order of the phase transition, latent heat, and temperature is negligible. Therefore, micro-arc oxidation technology based on the in situ growth coating of the material surface effectively improves the working life and stability of La(Fe, Si)13 materials in the refrigeration cycle, which is an excellent alternative as a protection technology to promote the practical process of magnetic refrigeration technology.
]]>Materials doi: 10.3390/ma17061315
Authors: Paweł Sulik Bożena Kukfisz Adriana Dowbysz Agata Oszczak-Nowińska
Lightweight concrete exhibits many advantages over traditional concrete such as lower density and thermal conductivity and an easier, cheaper, less energy-consuming manufacturing process. In order to extend its applications, there is a need to study its behavior in fire situations. Due to that, the aim of this study was to assess the fire resistance of foam concrete, depending on its thickness and the foaming process applied. Fire resistance was assessed according to EN 1363-1. The results indicate the usefulness of foam concrete in terms of isolating fire temperatures for discontinuous partition filling that are consequently a real alternative to dedicated solutions in the field of passive fire protection. The density of foam concrete was shown to have a large effect on the ability to insulate fire temperatures with a standard material preparation process. It was also noted that changing the method to continuous foam feeding may result in the achievement of similar values while maintaining foam concrete low density.
]]>Materials doi: 10.3390/ma17061314
Authors: Tianheng Luo Lizhe Wang Fuyuan Liu Min Chen Ji Li
Lattice materials are widely used in industries due to their designable capabilities of specific stiffness and energy absorption. However, evaluating the mechanical response of macroscopic lattice structures can be computationally expensive. Homogenization-based multi-scale analysis offers an efficient approach to address this issue. To achieve a simpler, while precise, homogenization, the authors proposed an equidistant segmentation (ES) method for the measurement of the effective shear modulus. In this method, the periodic boundary conditions (PBCs) are approximated by constraining the lateral displacement of nodes between parallel layers of periodic cells. The validations were applied to three typical lattice topologies: body-centered cubic (BCC) lattices, gyroid-, and primitive-triply periodic minimal surface (TPMS) lattices, to predict and compare their anti-vibration capacities. The results demonstrated the rationality and the promising precision of the multi-scale-based equivalent modal analysis through the proposed method and that it eliminated the geometric limitation of lattices with diverse frameworks. Overall, a higher anti-vibration capacity of TPMS was observed. In the study, the authors examined the influence of the relative densities on the balance between the anti-vibration capacity and loading capacity (per unit mass) of the TPMS topologies. Specifically, the unit mass of the TPMS with lower relative densities was able to resist higher frequencies, and the structures were dominated by the anti-vibration capacity. In contrast, a higher relative density is better when emphasizing the loading capacity. These findings may provide notable references to the designers and inform the selection of lattice materials for various industrial applications.
]]>Materials doi: 10.3390/ma17061313
Authors: Marcus Ricker Sebastian Kuhn Tânia Feiri Katrin Zecherle Jan Binde Jana Winkelmann
In recent years, the use of natural flax fibres as a reinforcement in composite building structures has witnessed a growing interest amongst research communities due to their green, economical, and capable mechanical properties. Most of the previous investigations on the load-bearing behaviour of concrete components reinforced with natural flax fibres include inorganic impregnations (or even no impregnation) and exclude the use of textile fabrics. Also, the mechanical behaviour of textiles made of natural flax fibres produced as leno fabrics remains to be investigated. In this paper, the results of tensile tests on concrete components reinforced with bio-based impregnated leno fabrics are presented. For comparison, multilayer non-impregnated and impregnated textiles were considered. The results demonstrated that reinforced textiles yielded an increase in the failure loads compared to the concrete cross-sections without reinforcement. The stress-strain diagrams showed that the curves can be divided into three sections, which are typical for reinforced tensile test specimens. For the impregnated textiles, a narrowly distributed crack pattern was observed. The results showed that impregnated textiles tend to support higher failure stresses with less strains than non-impregnated textiles. Moreover, an increase in the reinforcement ratio alongside larger opening widths of the warp yarns enables higher failure loads.
]]>Materials doi: 10.3390/ma17061312
Authors: Yanqiu Feng Henghui Qu Yanxiang Wang Lanzhong Wang Yongbo Wang Deli Yang Bohan Ding Yue Sun Jinghe Guo Shichao Dai
Based on MnO2/carbon cloth (CC) composite materials, an Ag-doped MnO2 nanowire, self-assembled, urchin-like structure was synthesized in situ on the surface of CC using a simple method, and a novel and efficient flexible electrode material for supercapacitors was developed. The morphology, structure, elemental distribution, and pore distribution of the material were analyzed using SEM, TEM, XRD, XPS, and BET. The electrochemical performance was tested using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). In the three-electrode system, GCD testing showed that the specific capacitance of the material reached 520.8 F/g at 0.5 A/g. After 2000 cycles at a current density of 1 A/g, the capacitance retention rate was 90.6%, demonstrating its enormous potential in the application of supercapacitor electrode materials.
]]>Materials doi: 10.3390/ma17061311
Authors: Ying Ren Wei Lv Xiaogang Li Haoyong Dong Nicolas Wöhrl Xun Yang Zhengxin Li Tao Wang
Concurrently achieving high growth rate and high quality in single-crystal diamonds (SCDs) is significantly challenging. The growth rate of SCDs synthesized by microwave plasma chemical vapor deposition (MPCVD) was enhanced by introducing N2 into the typical CH4-H2 gas mixtures. The impact of nitrogen vacancy (NV) center concentration on growth rate, surface morphology, and lattice binding structure was investigated. The SCDs were characterized through Raman spectroscopy, photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy. It was found that the saturation growth rate was increased up to 45 μm/h by incorporating 0.8–1.2% N2 into the gas atmosphere, which is 4.5 times higher than the case without nitrogen addition. Nitrogen addition altered the growth mode from step–flow to bidimensional nucleation, leading to clustered steps and a rough surface morphology, followed by macroscopically pyramidal hillock formation. The elevation of nitrogen content results in a simultaneous escalation of internal stress and defects. XPS analysis confirmed chemical bonding between nitrogen and carbon, as well as non-diamond carbon phase formation at 0.8% of nitrogen doping. Furthermore, the emission intensity of NV-related defects from PL spectra changed synchronously with N2 concentrations (0–1.5%) during diamond growth, indicating that the formation of NV centers activated the diamond lattice and facilitated nitrogen incorporation into it, thereby accelerating chemical reaction rates for achieving high-growth-rate SCDs.
]]>Materials doi: 10.3390/ma17061309
Authors: Junguo Li Qiwang Cai Guoqiang Luo Xinyu Zhong Qiang Shen Rong Tu Xiaoping Guo Renchi Ding
The distribution of second phase particles in the microstructure of composite ceramics affects the mechanical properties, and the intragranular structures often result in better properties compared to the intergranular structures. However, it is difficult to obtain composite ceramics with intragranular structure by conventional route. To produce composite ceramics with an intragranular structure in a simpler route. In this work, starting powders with different phase compositions were obtained by the co-precipitation method, and zirconia toughened alumina (ZTA) composite ceramics were prepared with these starting powders by spark plasma sintering (SPS). The results show that it is easier to fabricate ZTA composite ceramics with an intragranular structure by using composite powders containing amorphous or transition phase Al2O3 as starting materials. The phase composition of the powder prepared by the co-precipitation method after calcination at 1100 °C is θ-Al2O3 and t-ZrO2, and the average grain size after sintering at 1500 °C is 1.04 ± 0.28 µm, and the maximum Vickers hardness and fracture toughness of the specimens reach 19.37 ± 0.43 GPa and 6.18 ± 0.06 MPa·m1/2, respectively. The ZrO2 particles were the core of crystallization and grow together with the Al2O3 matrix, forming the intragranular structure of ZTA ceramics. This work may provide a new idea for preparing composite ceramics with intragranular structure.
]]>Materials doi: 10.3390/ma17061310
Authors: Tianci Huang Xinjiao Cui Xiaoyu Zhou Xiaolong He Min Guo Junsheng Li
To facilitate the integration of a fragrance encapsulation system into different products to achieve effective releases, a dual-responsive release system with pH and thermal trigger control is designed in this work. A series of ZIF-8 (M) and bilayer ZIF-8-on-ZIF-8 (MM) materials are synthesized by a solvent method at room temperature. The fragrance is encapsulated into the ZIFs by dynamic adsorption or in situ encapsulation combined dynamic adsorption. The fragrance loading contributed by dynamic adsorption was as high as 80%. The fragrance loaded in the double-layer MM host was almost twice that of the monolayer host M due to the stronger electrostatic interaction between MM and vanillin. In the pH and thermal trigger response release experiments, the second MOF layer in the MM host, as a controlled entity, greatly improved the load and kinetic equilibrium time of vanillin, and realized the controlled release of guest molecules. The developed dual-responsive release system in this work exhibits great potential in daily chemical products.
]]>Materials doi: 10.3390/ma17061308
Authors: Jakub Smoleń Piotr Olesik Krzysztof Stępień Marta Mikuśkiewicz Hanna Myalska-Głowacka Mateusz Kozioł Anna Gawron Marcin Godzierz
In this work, epoxy composites filled with flake graphite of various size (less than 10 μm and less than 45 μm) were produced. The aim of the research was to develop a self-lubricating material with favorable tribological properties, i.e., reduced friction coefficient compared to unfilled epoxy resin and limited abrasive wear. The research material was produced using technical epoxy resins based on bisphenol A. The detailed process of composite production was described, and typical technological problems were considered. The addition of graphite led to an increase in dynamic viscosity, which positively limits the phenomenon of sedimentation, but an increase in the filler content also led to an increase in the porosity of the material. A series of tests have shown that the addition of graphite above 5% by weight allows for a reduction in the friction coefficient from 0.6 to 0.4 and significantly reduces the material’s tendency to abrasive wear.
]]>Materials doi: 10.3390/ma17061307
Authors: Alma Dauletbekova Sergey Zvonarev Sergey Nikiforov Abdirash Akilbekov Tatiana Shtang Natalia Karavannova Aiman Akylbekova Alexey Ishchenko Gulzhanat Akhmetova-Abdik Zein Baymukhanov Gulnara Aralbayeva Guldar Baubekova Anatoli I. Popov
Samples of ZrO2 ceramics with different concentrations of impurity titanium ions were synthesized by mixing zirconium and titanium oxide powders in different mass ratios. The X-ray diffraction analysis was used to determine the phase composition, lattice parameters, and crystallite size of the ceramics with varying dopant concentrations. Upon irradiation of the samples with 220 MeV Xe ions to a fluence of 1010 ions/cm2, a decrease in the intensity of the pulsed cathodoluminescence band at 2.5 eV was observed. Additionally, ion irradiation resulted in the emergence of a new thermoluminescence peak at 450–650 K attributed to radiation-induced traps of charge carriers. Further analysis revealed that the thermoluminescence curves of samples irradiated with electrons and ions comprise a superposition of several elementary peaks. Notably, a complex non-monotonic dependence of cathodo- and thermoluminescence intensity on titanium concentration was observed, suggesting the influence of concentration quenching and the presence of tunneling transitions.
]]>Materials doi: 10.3390/ma17061306
Authors: Jelena Pavlović Jasna Hrenović Dragan Povrenović Nevenka Rajić
Adsorptive, catalytic, and antibacterial properties of clinoptilolite-rich tuffs (ZT) are presented here. ZT transformed into Fe-containing ZT (Fe-ZT) removes various organic and inorganic anions from water. Fe-ZT, which contains selenium, is beneficial for growing Pleurotus ostreatus mushrooms. The fungi convert inorganic Se from Fe-ZT into a more useful organically bonded form. ZT and Fe-ZT as supplements retain nitrogen and potassium in sandy, silty loam and silty clay soils. ZT shows an affinity toward toxic metal cations, which are essential for cleaning contaminated water. The adsorption of atenolol, acetylsalicylic, and salicylic acid onto M-ZT (M–Cu2+, Mn2+, Ni2+, or Zn2+) from water solutions suggests that both the natures of M and pharmaceuticals have a significant impact on the adsorption mechanism and determine the adsorption capability of the ZT. ZT is an excellent carrier for ultrafine (2–5 nm) nano oxide particles, which have been shown to have catalytic activity in different chemical processes and photodegradation reactions of organic pollutants. ZT can also be transformed into SO4-SnO2-ZT, which is catalytically active as a solid acid. M-ZT is an effective carrier of valuable bacteria. Ag-ZT possesses beneficial bactericidal activity in disinfecting water and soil remediation.
]]>Materials doi: 10.3390/ma17061305
Authors: Mohamed Elgharib Gomah Guichen Li Ahmed A. Omar Mahmoud L. Abdel Latif Changlun Sun Jiahui Xu
Mineral transformations often induce microstructural deteriorations during temperature variations. Hence, it is crucial to understand why and how this microstructure weakens due to mineral alteration with temperature and the correlated physical and mechanical responses. Therefore, in this study, physical, chemical, thermal, petrographic, and mechanical analyses were carried out to comprehend better the thermal behaviors of Egyptian granodiorite exposed to temperatures as high as 800 °C. The experimental results indicate that the examined attributes change in three distinct temperature phases. Strength zone (up to 200 °C): During this phase, the temperature only slightly impacts the granodiorite mass loss and porosity, and the P-wave velocity and E slightly decrease. However, the rock structure was densified, which resulted in a minor increase in strength. After that, the transition zone (200–400 °C) was distinguished by the stability of most studied parameters. For instance, mass and porosity did not significantly alter, and the uniaxial compressive strength steadily increased with an axial failure mode. When the temperature rises, transgranular cracks cause the P-wave velocity and elastic modulus to decrease moderately. The decay zone started after 400 °C and continued to 800 °C. This zone is characterized by complicated factors that worsen the granodiorite properties, lead to color shift, and produce a shear failure mode. The properties of granodiorite became worse because of chemical reactions, structural and crystal water evaporation, rising thermal expansion coefficient variation, and quartz inversion at 575 °C (α to β, according to the differential thermal analysis). Thermal damage greatly affected granodiorite’s physical and mechanical properties and microstructure at 800 °C. As a result, UCS measurements were extremely small with a complex failure pattern, making Vp and E unattainable.
]]>Materials doi: 10.3390/ma17061304
Authors: Yue Xiao Tianlei Wang Zongwu Chen Chao Li Feng Wang
Water damage is one of the major distresses of asphalt pavements. Existing methods for investigating the water stability of asphalt mixtures rely primarily on static water test methods, the tensile strength ratio (TSR) test, and the retained Marshall stability (RMS) test, which evaluate the strength and stability loss after freeze-thaw damage or hot water immersion, respectively. However, these methods do not accurately replicate the actual dynamic water damage conditions to pavement. Therefore, in this study, a variety of damage conditions, including static water conditions and dynamic water pressure conditions, were used to investigate the effects of lignin fibers (LFs), polyester fibers (PFs), and polypropylene fibers (PPFs) on the water stability of asphalt mixtures. First, three fibers-enhanced SMA gap-gradation asphalt mixtures were designed. Then, TSR and RMS were measured under traditional static water damage conditions and new dynamic water pressure damage conditions to evaluate the effect of fiber types on the water stability of asphalt mixtures. Finally, the void rate of asphalt mixtures and its changes under dynamic water damage conditions were further revealed with the help of CT scanning technique. Results showed that, among these three types of fibers, PFs-enhanced asphalt mixture exhibited excellent stability under both static and dynamic water conditions, and the CT scanning test also indicated that the PFs can significantly reduce the increase rate of voids in asphalt mixtures after dynamic water pressure damage. This study identified the potential of incorporating suitable type of fiber to enhance the performance of asphalt mixture under dynamic water pressure damage.
]]>Materials doi: 10.3390/ma17061303
Authors: Chenguang Wang Yaowen Wu Yuanhai Zhang Shiying Tang Weiwen Li Peng Wang Walid Mansour
Distortion deformation usually imposes a potential threat to bridge safety. In order to comprehensively understand the distortion effect on thin-walled ultra-high performance concrete (UHPC) box girders, an innovative approach encompassing the governing distortion differential equation is introduced in this study based on the general definition of distortion angle within the cross-section plane. The analytical results obtained from the proposed method are in accordance with those obtained from the energy method, and exhibit favorable agreement with experimental findings documented in the existing literature. Furthermore, a finite element model is developed on the ANSYS 2021 R1 software platform with the employment of a Shell 63 element. Numerical outcomes are also in good agreement with the experimental data, affirming the validity and reliability of the findings. In addition, parameter analysis results indicate that the distortion angle remains approximately constant at a location approximately 1/10 of the span from the mid-span cross-section of the box girder, regardless of changes in the span-to-depth ratio. Increasing the web thickness yields a notable reduction in the distortion effects, and decreasing the wall thickness can effectively mitigate the distortion-induced transverse bending moment. Compared with normal-strength concrete box girders, UHPC box girders can reduce the distortion angle within the span range, which is beneficial for maintaining the overall stability of the box girders. The outcomes obtained from this study yield engineers an enhanced understanding of distortion effect on the UHPC girder performance.
]]>Materials doi: 10.3390/ma17061302
Authors: Azam Rasouli Artur Kudyba Grzegorz Bruzda Jafar Safarian Gabriella Tranell
High-temperature wetting of natural, high-purity quartz (SiO2) and liquid magnesium (Mg) was investigated at temperatures between 973 and 1273 K. Sessile drop experiments using the capillary purification (CP) procedure were carried out under an Ar gas atmosphere (N6.0), eliminating the native oxide layer on the surface of Mg melt. The results showed that the wetting behavior was strongly dependent on temperature. At 973 and 1073 K, the wetting system displayed relatively large contact angles of 90° and 65°, respectively, demonstrating modest wetting. The wetting increased to some extent by increasing the temperature to 1123 K with a wetting angle of 22°. However, the SiO2/Mg system demonstrated complete wetting at temperatures of 1173 K and above. Furthermore, interface microstructure examination showed different reaction product phases/microstructures, depending on the wetting experiment temperature.
]]>Materials doi: 10.3390/ma17061301
Authors: M. Y. Hacisalihoglu L. Tortora G. Tomassucci L. Simonelli N. L. Saini
We have investigated the effect of the Ni substitution on the local structure and the valence electronic states of the SrFe2−xNixAs2 (x = 0.00, 0.16, and 0.23) superconductor with a multi-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopy. The As K-edge and Fe K-edge EXAFS measurements in the two polarizations (E‖ab and E‖c) show a clear change in the local structure with Ni concentration. The near-neighbor bondlengths and the related mean-square relative displacements (MSRDs) decrease as the Ni content increases. The polarized XANES spectra at the As, Fe and Ni K edges reveal a systematic change in the anisotropy of the valence electronic structure. The results suggest that the quasi 2D electronic structure of this system tends to become more isotropic as the Ni content increases. The local structure and the valence electronic states are discussed in the frame of the evolving electronic transport of the SrFe2−xNixAs2 system.
]]>Materials doi: 10.3390/ma17061300
Authors: Leonid Dvorkin Vadim Zhitkovsky Ruslan Makarenko Yuri Ribakov
Thermal power plant slag is a waste that is presently obtained from many power stations all over the world. A possible method for its utilization is using it to produce concrete. This paper analyses the effect of thermal power plant slag on the technological properties of concrete mixtures and the mechanical properties of concrete subjected to heat–moisture processing. Quantitative estimates of the investigated factors’ influence on the concrete mixture’s water demand and the strength of steamed concrete were obtained. The influences of TPP slag content and its water demand on concrete composition features as well as concrete strength are shown. The novelty of the work lies in the use of an experimental–statistical model to optimize the composition of steamed concrete using slag from the viewpoint of maximum strength per kilogram of cement. It has been demonstrated that the optimal part of slag in aggregate, which provides maximum strength at 4 h and 28 days after steaming, is 0.5–0.55 and 0.45–0.55, respectively. A method for the design of concrete composition using slag from thermal power plants is proposed.
]]>Materials doi: 10.3390/ma17061299
Authors: Xiukun Jiang Yan Xin Bijiao He Fang Zhang Huajun Tian
Lithium iron phosphate (LiFePO4, LFP), an olivine–type cathode material, represents a highly suitable cathode option for lithium–ion batteries that is widely applied in electric vehicles and renewable energy storage systems. This work employed the ball milling technique to synthesize LiFePO4/carbon (LFP/C) composites and investigated the effects of various doping elements, including F, Mn, Nb, and Mg, on the electrochemical behavior of LFP/C composite cathodes. Our comprehensive work indicates that optimized F doping could improve the discharge capacity of the LFP/C composites at high rates, achieving 113.7 mAh g−1 at 10 C. Rational Nb doping boosted the cycling stability and improved the capacity retention rate (above 96.1% after 100 cycles at 0.2 C). The designed Mn doping escalated the discharge capacity of the LFP/C composite under a low temperature of −15 °C (101.2 mAh g−1 at 0.2 C). By optimizing the doping elements and levels, the role of doping as a modification method on the diverse properties of LFP/C cathode materials was effectively explored.
]]>Materials doi: 10.3390/ma17061298
Authors: Mohd Na’im Abdullah Faizal Mustapha Nurul ‘Izzati Yusof Tabrej Khan Tamer A. Sebaey
This study aims to develop suitable formulations of geopolymer concrete (GPC) by varying the percentages of the geopolymer with aggregates and evaluating the performances in thermal and mechanical properties of palm kernel shell ash (PKSA)-GPC compared to rice husk ash (RHA)-GPC and ordinary Portland cement concrete (OPCC). Preliminary tests were conducted to select the best mix design ratios before casting the specimens. Then, the performance of the PKSA-GPC, RHA-GPC and OPCC specimens was evaluated based on their thermal performance and drying shrinkage. The mix designs of PKSA-GPC 70:30, PKSA-GPC 60:40, PKSA-GPC 50:50 and PKSA-GPC 66.6:33.3 were found to produce an acceptable consistency, rheological and thixotropic behaviour for the development of the GPC. PKSA-GPC showed a better thermal performance than the RHA-GPC and OPCC due to their strong and dense intumescent layers and slow temperature increment upon exposure to a high flame temperature from ambient temperature to 169 °C. The low molar ratio of the Si/Al present in the PKSA-GPC created a thermally stable intumescent layer. In the drying shrinkage test, PKSA-GPC 60:40 and RHA-GPC 60:40 shared an equal drying shrinkage performance (5.040%) compared to the OPCC (8.996%). It was observed that microcrack formation could significantly contribute to the high shrinkage in the PKSA-GPC 50:50 and RHA-GPC 70:30 specimens. The findings of this study show that PKSA could be incorporated into GPC as a fire-retardant material due to its capability of prolonging the spread of fire upon ignition and acting as an alternative to the conventional OPCC.
]]>Materials doi: 10.3390/ma17061297
Authors: Tao Huang Lijing Yang Chunxiang Xu Cheng Xu Qingke Zhang Jinshan Zhang Zhenlun Song
The effect of extrusion on the microstructure, mechanical property, corrosion behavior, and in vitro biocompatibility of as-cast Mg-1.5Zn-1.2Y-0.1Sr (wt.%) alloy was investigated via tensile tests, electrochemical methods, immersion tests, methylthiazolyl diphenyltetrazolium bromide (MTT), and analytical techniques. Results showed that the as-cast and as-extruded Mg-1.5Zn-1.2Y-0.1Sr alloys comprised an α-Mg matrix and Mg3Y2Zn3 phase (W-phase). In the as-cast alloy, the W-phase was mainly distributed at the grain boundaries, with a small amount of W-phase in the grains. After hot extrusion, the W-phase was broken down into small particles that were dispersed in the alloy, and the grains were refined considerably. The as-extruded alloy exhibited appropriate mechanical properties that were attributed to refinement strengthening, dispersion strengthening, dislocation strengthening, and precipitation strengthening. The as-cast and as-extruded alloys exhibited galvanic corrosion between the W-phase and α-Mg matrix as the main corrosion mechanism. The coarse W-phase directly caused the poor corrosion resistance of the as-cast alloy. The as-extruded alloy obtained via hydrogen evolution and mass loss had corrosion rates of less than 0.5 mm/year. MTT, high-content screening (HCS) analysis, and cell adhesion tests revealed that the as-extruded alloy can improve L929 cell viability and has great potential in the field of biomedical biodegradable implant materials.
]]>Materials doi: 10.3390/ma17061294
Authors: Tatsuhiko Aizawa
The low-temperature plasma nitriding was utilized to describe the microscopic solid-phase separation in the austenitic stainless-steel type AISI316, induced by the nitrogen supersaturation. This nitrogen supersaturated layer with the thickness of 60 μm had a two-phase nanostructure where the nitrogen-poor and nitrogen-rich clusters separated from each other. Due to this microscopic solid-phase separation, iron and nickel atoms decomposed themselves from chromium atoms and nitrogen solutes in this nitrogen supersaturated AISI316 layer. These microscopic cluster separation and chemical decomposition among the constituent elements in AISI316 were induced in the multi-dimensional scale by the plastic straining along the slip lines in the (111)-orientation from the surface to the depth of matrix. The nitrogen solute diffused through the cluster boundaries into the depth. With the aid of masking technique, this nitrogen supersaturation and nanostructuring was controlled to take place only in the unmasked AISI316 matrix. The nanostructures with two separated clusters were mesoscopically embedded into AISI316 matrix after the masking micro-textures. This microscopic and mesoscopic structure control was available in surface treatment of multi-host metals such as superalloys and high entropy alloys.
]]>Materials doi: 10.3390/ma17061295
Authors: Igor Lapiro Rami Eid Konstantin Kovler
Coastal regions, home to a significant portion of the world’s population, confront a formidable challenge: the corrosive impact of chloride-rich environments on vital infrastructure. These areas often host essential transportation systems, such as trains and metros, reliant on pre-existing electrical infrastructure. Unfortunately, complete isolation of this infrastructure is rarely feasible, resulting in the emergence of stray currents and electrical potentials that expedite corrosion processes. When coupled with conducive mediums facilitating chemical electrocell formation, the corrosion of reinforced concrete elements accelerates significantly. To combat this issue, international standards have been established, primarily focusing on augmenting the thickness of reinforcement bar covers and restricting stray voltage between rails and the ground. Nevertheless, these measures only provide partial solutions. When subjected to service loads, these elements develop cracks, especially when exposed to stray currents and chlorides, dramatically increasing corrosion rates. Corrosion products, which expand in volume compared to steel, exert internal forces that widen cracks, hastening the deterioration of structural elements. The study deals with the degradation of reinforced concrete columns under the combined action of loads, chloride-rich environments, and electrical voltage-simulating stray currents. In these conditions, degradation and reduction of load-bearing capacity accelerate compared to unloaded conditions, significantly amplifying the corrosion rate. Astonishingly, even in the absence of mechanical loads, stray currents alone induce tensile stresses in elements due to corrosion product formation, leading to longitudinal cracks parallel to the reinforcement bars.
]]>Materials doi: 10.3390/ma17061296
Authors: Dongying Liu Junxiang Su Li Zhao Xudong Shen
This paper focuses on the size-dependent free vibration and buckling behaviors of the axially functionally graded (AFG) graphene platelets (GPLs) reinforced nanocomposite microbeams subjected to axially varying loads (AVLs). With various axial grading patterns, the GPL nano-reinforcements are distributed throughout the polymer matrix against microbeam length, and the improved Halpin–Tsai micromechanics model and the rule of mixture are adopted to evaluate the effective material properties. Eigenvalue equations of the microbeams governing the static stability and vibration are derived based on the modified couple stress Euler–Bernoulli beam theory via the state-space method, and are analytically solved with the discrete equilong segment model. The effects of axial distribution patterns, weight fraction, and geometric parameters of GPLs, as well as different types of AVLs, on the size-dependent buckling load and natural frequency are scrutinized in detail. The results show that the synchronized axial distributions of GPLs and AVLs could improve the buckling resistance and natural frequency more powerfully.
]]>Materials doi: 10.3390/ma17061292
Authors: Milena P. Dojčinović Ivana Stojković Simatović Maria Vesna Nikolić
Ni foam is an extensively used current collector and substrate in investigations of electrochemically active materials such as supercapacitors and electrocatalysts for oxygen and hydrogen evolution reactions. This material is relatively cheap, porous, and conductive and has a large specific surface area, all of which make it a good substrate. We investigated Ni-Mg ferrites and NiMn2O4 as active materials for electrochemical energy storage. These materials, when loaded on Ni foam, gave promising capacitance values: 172 F/g (at 2 mV/s) for NiMn2O4 in 6 M KOH and 242 F/g (at 2 mV/s) for MgFe2O4 in 3 M KOH. Nevertheless, during the authors’ work, many experimental problems occurred. Inconsistencies in the results directed further investigation towards measuring the capacitance of the active materials using GCE and platinum electrodes as substrates to discover if Ni foam was the culprit of the inconsistencies. When non-nickel substrates were used, both NiMn2O4 and MgFe2O4 showed reduced capacitance. Experimental problems associated with the utilization of Ni foam as a substrate for active materials in supercapacitor electrodes are discussed here, combined with other problems already addressed in the scientific literature.
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