Materials

17 pages, 7468 KiB

Open AccessArticle

Microstructure and Hardness Properties of Additively Manufactured AISI 316L Welded by Tungsten Inert Gas and Laser Welding Techniques

by Mohamed Elsayed, Mahmoud Khedr, Antti Järvenpää, A. M. Gaafer and Atef Hamada

Materials 2024, 17(18), 4489; https://doi.org/10.3390/ma17184489 - 12 Sep 2024

Abstract

In this study, 316L austenitic stainless-steel (ASS) plates fabricated using an additive manufacturing (AM) process were joined using tungsten inert gas (TIG) and laser welding techniques. The 316L ASS plates were manufactured using a laser powder bed fusion (LPBF) technique, with building orientations [...] Read more.

In this study, 316L austenitic stainless-steel (ASS) plates fabricated using an additive manufacturing (AM) process were joined using tungsten inert gas (TIG) and laser welding techniques. The 316L ASS plates were manufactured using a laser powder bed fusion (LPBF) technique, with building orientations (BOs) of 0° and 90°, designated as BO-0 and BO-90, respectively. The study examined the relationship between indentation resistance and microstructure evolution within the fusion zone (FZ) of the welded joints considering the effects of different BOs. Microstructural analysis of the weldments was conducted using optical and laser confocal scanning microscopes, while hardness measurements were obtained using a micro-indentation hardness (H_IT) technique via the Berkovich approach. The welded joints produced with the TIG technique exhibited FZs with a greater width than those created by laser welding. The microstructure of the FZs in TIG-welded joints was characterized by dendritic austenite and 1–4 wt.% δ-ferrite phases, while the corresponding microstructure in laser-welded joints consisted of a single austenite phase with cellular structures. Additionally, the grain size values of FZs produced using the laser welding technique were lower than those produced using the TIG technique. Therefore, TIG-welded joints showcased hardness values lower than those welded by laser welding. Furthermore, welded joints with the BO-90 orientation displayed the greatest cooling rates following welding processing, leading to FZs with hardness values greater than BO-0. For instance, the FZs of TIG-welded joints with BO-0 and BO-90 had H_IT values of 1.75 ± 0.22 and 2.1 ± 0.09 GPa, whereas the corresponding FZs produced by laser welding had values of 1.9 ± 0.16 and 2.35 ± 0.11 GPa, respectively. The results have practical implications for the design and production of high-performance welded components, providing insights that can be applied to improve the efficiency and quality of additive manufacturing and welding processes. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Second Edition))

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13 pages, 1187 KiB

Open AccessArticle

Miniband and Gap Evolution in Gauss Chains

by D. S. Citrin

Materials 2024, 17(18), 4488; https://doi.org/10.3390/ma17184488 - 12 Sep 2024

Abstract

The Gauss chain is a one-dimensional quasiperiodic lattice with sites at

z_{j} = j^{n} d

, where

j \in {0, 1, 2, \dots, N - 1}

, [...] Read more.

The Gauss chain is a one-dimensional quasiperiodic lattice with sites at

z_{j} = j^{n} d

, where

j \in {0, 1, 2, \dots, N - 1}

,

n \in {2, 3, 4, \dots}

, and d is the underlying lattice constant. We numerically study the formation of a hierarchy of minibands and gaps as N increases using a Kronig–Penney model. Increasing n empirically results in a more fragmented miniband and gap structure due to the rapid increase in the number of minibands and gaps as n increases, in agreement with previous studies. We show that the Gauss chain

z_{j} = j^{2} d

and a specific generalized Gauss chain,

z_{j} = (j^{2} \pm \frac{1}{2} j) d

, are treatable by a real-space renormalization group approach. These appear to be the only Gauss chains treatable by this approach, suggesting a hidden symmetry for the quadratic cases. Full article

14 pages, 4816 KiB

Open AccessArticle

Influence of the Metallic Sublayer on Corrosion Resistance in Hanks’ Solution of 316L Stainless Steel Coated with Diamond-like Carbon

by Ewa Dobruchowska, Justyna Schulz, Viktor Zavaleyev, Jan Walkowicz, Tomasz Suszko and Bogdan Warcholinski

Materials 2024, 17(18), 4487; https://doi.org/10.3390/ma17184487 - 12 Sep 2024

Abstract

The purpose of the study was to ascertain the corrosion resistance in Hanks’ solution of Cr-Ni-Mo stainless steel (AISI 316L) coated with diamond-like carbon (DLC) coatings to establish its suitability for biomedical applications, e.g., as temporary implants. The influence of the carbon coating [...] Read more.

The purpose of the study was to ascertain the corrosion resistance in Hanks’ solution of Cr-Ni-Mo stainless steel (AISI 316L) coated with diamond-like carbon (DLC) coatings to establish its suitability for biomedical applications, e.g., as temporary implants. The influence of the carbon coating thickness as well as the correlated effect of the metallic sublayer type and defects present in DLC films on corrosion propagation were discussed. The results obtained were compared with findings on the adhesion of DLC to the steel substrate. The synthesis of carbon thin films with Cr and Ti adhesive sublayers was performed using a combined DC and a high-power-impulse vacuum-arc process. Evaluation of the corrosion resistance was carried out by means of potentiodynamic polarisation tests and scanning electron microscopy. Adhesive properties of the sublayer/DLC coating systems were measured using a scratch tester. It was found that systems with Ti sublayers were less susceptible to the corrosion processes, particularly to pitting. The best anti-corrosion properties were obtained by merging Ti with a DLC coating with a thickness equal to 0.5 μm. The protective properties of the Cr/DLC systems were independent of the carbon coating thickness. On the other hand, the DLC coatings with the Cr sublayer showed better adhesion to the substrate. Full article

(This article belongs to the Collection Microstructure and Corrosion Behavior of Advanced Alloys)

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15 pages, 7673 KiB

Open AccessArticle

Tensile Deformation Mechanism of an In Situ Formed Ti-Based Bulk Metallic Glass Composites

by Haiyun Wang, Na Chen, Huanwu Cheng, Yangwei Wang and Denghui Zhao

Materials 2024, 17(18), 4486; https://doi.org/10.3390/ma17184486 - 12 Sep 2024

Abstract

Ti-based bulk metallic glass composites (BMGMCs) containing an in situ formed metastable β phase normally exhibit enhanced plasticity attributed to induced phase transformation or twinning. However, the underlying deformation micromechanism remains controversial. This study investigates a novel deformation mechanism of Ti-based BMGMCs with [...] Read more.

Ti-based bulk metallic glass composites (BMGMCs) containing an in situ formed metastable β phase normally exhibit enhanced plasticity attributed to induced phase transformation or twinning. However, the underlying deformation micromechanism remains controversial. This study investigates a novel deformation mechanism of Ti-based BMGMCs with a composition of Ti_42.3Zr₂₈Cu_8.3Nb_4.7Ni_1.7Be₁₅ (at%). The microstructures after tension were analyzed using advanced electron microscopy. The dendrites were homogeneously distributed in the glassy matrix with a volume fraction of 55 ± 2% and a size of 1~5 μm. The BMGMCs deformed in a serrated manner with a fracture strength (σ_f) of ~1710 MPa and a fracture strain of ~7.1%, accompanying strain hardening. The plastic deformation beyond yielding was achieved by a synergistic action, which includes shear banding, localized amorphization and a localized BCC (β-Ti) to HCP (α-Ti) structural transition. The localized amorphization was caused by high local strain rates during shear band extension from the amorphous matrix to the crystalline reinforcements. The localized structural transition from BCC to HCP resulted from accumulating concentrated stress during deformation. The synergistic action enriches our understanding of the deformation mechanism of Ti-based BMGMCs and also sheds light on material design and performance improvement. Full article

(This article belongs to the Special Issue Synthesis, Sintering, and Characterization of Composites)

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14 pages, 5781 KiB

Open AccessArticle

One-Step Air Spraying of Structural Coating on Cu Alloy as Superhydrophobic Surface for Enhanced Corrosion Resistance and Anti-Icing Performance

by Ben Li and Xuewu Li

Materials 2024, 17(18), 4485; https://doi.org/10.3390/ma17184485 - 12 Sep 2024

Abstract

With the development of modern technology, the construction industry, and navigation technology, the metal Cu alloy has become an important metal material in mainstream industrial applications. As an indispensable basic metal material in the field of science and technology, its problem with corrosion [...] Read more.

With the development of modern technology, the construction industry, and navigation technology, the metal Cu alloy has become an important metal material in mainstream industrial applications. As an indispensable basic metal material in the field of science and technology, its problem with corrosion is still a long-term problem that scientists have been working to solve. In this paper, air spraying technology is used to prepare an Al₂O₃-PDMS composite coating. By adjusting the content of Al₂O₃, the surface of the Cu alloy can reach different wetting states. The results show that the corrosion potential of the as-prepared superhydrophobic Al₂O₃-PDMS coating increases by 70 mV compared with the substrate, the corrosion current density decreases by one order of magnitude, and the impedance modulus increases from 2000 to 12,000 Ω⋅cm², indicating a significantly enhanced corrosion resistance. It also possesses excellent anti-pollution and anti-icing behaviors, thereby allowing them to work in harsh industrial conditions. Full article

(This article belongs to the Section Metals and Alloys)

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18 pages, 5125 KiB

Open AccessArticle

Short Fatigue-Crack Growth from Crack-like Defects under Completely Reversed Loading Predicted Based on Cyclic R-Curve

by Keisuke Tanaka and Yoshiaki Akiniwa

Materials 2024, 17(18), 4484; https://doi.org/10.3390/ma17184484 - 12 Sep 2024

Abstract

Understanding short fatigue-crack propagation behavior is inevitable in the defect-tolerant design of structures. Short cracks propagate differently from long cracks, and the amount of crack closure plays a key role in the propagation behavior of short cracks. In the present paper, the buildup [...] Read more.

Understanding short fatigue-crack propagation behavior is inevitable in the defect-tolerant design of structures. Short cracks propagate differently from long cracks, and the amount of crack closure plays a key role in the propagation behavior of short cracks. In the present paper, the buildup of fatigue-crack closure due to plasticity with crack extension from crack-like defects is simulated with a modified strip yield model, which leaves plastic stretch in the wake of the advancing crack. Crack-like defects are assumed to be closure-free and do not close even under compression. The effect of the size of crack-like defects on the growth and arrest of short cracks was systematically investigated and the cyclic R-curve derived. The cyclic R-curve determined under constant amplitude loading of multiple specimens is confirmed to be independent of the initial defect length. Load-shedding and ΔK-constant loading tests are employed to extend the cyclic R-curve beyond the fatigue limit determined under constant amplitude loading. The initiation stage of cracks is taken into account in R-curves when applied to smooth specimens. Full article

(This article belongs to the Special Issue Advances in High Cycle Fatigue and Fracture Failure of Metallic Materials and Components)

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23 pages, 6257 KiB

Open AccessArticle

Physicochemical Characterization of Ca- and Cu-Decorated TiO₂ Microparticles and Investigation of Their Antimicrobial Properties

by Andreea Neacsu, Viorel Chihaia, Razvan Bucuresteanu, Anton Ficai, Roxana Doina Trusca, Vasile-Adrian Surdu, Adela Nicolaev, Bogdan Cojocaru, Monica Ionita, Ioan Calinescu, Viorica Parvulescu and Lia-Mara Ditu

Materials 2024, 17(18), 4483; https://doi.org/10.3390/ma17184483 - 12 Sep 2024

Abstract

Ca- and Cu-decorated TiO₂ microparticles are titanium dioxide nanoparticles that have been decorated with calcium and copper ions. TiO₂, CaO, and CuO are low-cost, non-toxic, and non-hazardous materials. The aim of the present study was the physicochemical characterization of Ca- [...] Read more.

Ca- and Cu-decorated TiO₂ microparticles are titanium dioxide nanoparticles that have been decorated with calcium and copper ions. TiO₂, CaO, and CuO are low-cost, non-toxic, and non-hazardous materials. The aim of the present study was the physicochemical characterization of Ca- and Cu-decorated TiO₂ microparticles and the evaluation of their antimicrobial activity. Thus, Ca²⁺ and Cu²⁺ species were incorporated onto TiO₂ surfaces by a two-step wet method. The obtained TiO₂-CaO-CuO composites were characterized by several experimental techniques. The electronic structure and charge properties of the composites were investigated by density functional theory calculations. Furthermore, the composites were successfully tested for inhibitory effects on Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans standard strains. The zeta potential data indicate that the physiological condition of investigated microbial strains was strongly affected in presence of a dispersion of 10 μg/L of composites in a saline phosphate buffer also, the recorded SEM images show a damaged microbial cell surface in the presence of composites. Full article

(This article belongs to the Special Issue Emerging Technologies for Development of Novel Materials Systems and Coatings (Volume 2))

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12 pages, 3446 KiB

Open AccessArticle

Dynamic Response of Fiber–Metal Laminates Sandwich Beams under Uniform Blast Loading

by Jianan Yang, Yafei Guo, Yafei Wu and Jianxun Zhang

Materials 2024, 17(18), 4482; https://doi.org/10.3390/ma17184482 - 12 Sep 2024

Abstract

In this work, theoretical and numerical studies of the dynamic response of a fiber–metal laminate (FML) sandwich beam under uniform blast loading are conducted. On the basis of a modified rigid-plastic material model, the analytical solutions for the maximum deflection and the structural [...] Read more.

In this work, theoretical and numerical studies of the dynamic response of a fiber–metal laminate (FML) sandwich beam under uniform blast loading are conducted. On the basis of a modified rigid-plastic material model, the analytical solutions for the maximum deflection and the structural response time of FML sandwich beams with metal foam core are obtained. Finite element analysis is carried out by using ABAQUS software, and the numerical simulations corroborate the analytical predictions effectively. The study further examines the impact of the metal volume fraction, the metal strength factor between the metal layer and the composite material layer, the foam strength factor of the metal foam core to the composite material layer, and the foam density factor on the structural response. Findings reveal that these parameters influence the dynamic response of fiber–metal laminate (FML) sandwich beams to varying degrees. The developed analytical model demonstrates its capability to accurately forecast the dynamic behavior of fiber–metal laminate (FML) sandwich beams under uniform blast loading. The theoretical model in this article is a simplified model and cannot consider details such as damage, debonding, and the influence of layer angles in experiments. It is necessary to establish a refined theoretical model that can consider the microstructure and failure of composite materials in the future. Full article

(This article belongs to the Special Issue Impact Behaviour of Materials and Structures)

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12 pages, 5913 KiB

Open AccessArticle

Fabrication and Characterization of Ce³⁺-Doped Lithium Alumino-Silicate Scintillating Glass–Ceramic and Fiber

by Yongya Wang, Fanbo Meng, Huiyu Chen, Wenqin Luo, Shunjian Xu and Chunyan Lv

Materials 2024, 17(18), 4481; https://doi.org/10.3390/ma17184481 - 12 Sep 2024

Abstract

Ce³⁺-doped lithium alumino-silicate (Li-Al-Si) scintillating glass was prepared using a melting method and crystallized via heat treatment. X-ray diffraction and transmission electron microscopy confirmed the presence of nanocrystals in the materials. Radioluminescence spectra, obtained by X-ray excitation, and luminescence spectra, obtained [...] Read more.

Ce³⁺-doped lithium alumino-silicate (Li-Al-Si) scintillating glass was prepared using a melting method and crystallized via heat treatment. X-ray diffraction and transmission electron microscopy confirmed the presence of nanocrystals in the materials. Radioluminescence spectra, obtained by X-ray excitation, and luminescence spectra, obtained by 338 nm excitation, showed that the luminescence intensity increased after crystallization. The glass was combined with pure silica as the inner cladding to fabricate a hybrid fiber core using a melt-in-tube technique. The composition of the fiber core was examined using an electron probe microanalyzer. The glass fiber produced strong blue luminescence under UV excitation. After a micro-crystallizing heat treatment of the hybrid fiber at 850 °C in a reducing atmosphere, a Ce³⁺-doped lithium alumino-silicate glass–ceramic scintillating hybrid fiber was obtained. The nanocrystal structure of the fiber core was examined using micro-Raman spectroscopy. Excitation and luminescence spectra of the hybrid fiber before and after micro-crystallization were measured using microspectrofluorimetry. The results demonstrated that the fiber remained luminous after micro-crystallization. Hence, this work provides a new way to prepare scintillating glass–ceramic hybrid fibers for neutron detection. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

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16 pages, 3707 KiB

Open AccessArticle

Fast, Simple, and Sensitive Voltammetric Measurements of Acyclovir in Real Samples via Boron-Doped Diamond Electrode

by Damian Gorylewski, Katarzyna Tyszczuk-Rotko, Magdalena Wójciak and Ireneusz Sowa

Materials 2024, 17(18), 4480; https://doi.org/10.3390/ma17184480 - 12 Sep 2024

Abstract

The voltammetric acyclovir (ACV) trace-level determination procedure has been introduced. This is the first time that a commercially available boron-doped diamond electrode (BDDE) coupled with differential-pulse voltammetry (DPV) has been used for this purpose. The commercially available BDDE is characterized by a short [...] Read more.

The voltammetric acyclovir (ACV) trace-level determination procedure has been introduced. This is the first time that a commercially available boron-doped diamond electrode (BDDE) coupled with differential-pulse voltammetry (DPV) has been used for this purpose. The commercially available BDDE is characterized by a short response time, low background current, and very good analytical parameters of ACV determination. Ultimately, DPV measurements using the BDDE in 0.075 mol L⁻¹ PBS with a pH of 7.2 under optimized conditions achieved the lowest detection limit (LOD = 0.0299 nmol L⁻¹) reported in the literature for voltammetric procedures. Moreover, it is highly resistant to the presence of various interfering agents and has been used to analyze pharmaceutical and municipal wastewater samples. The obtained results are consistent with measurements made using chromatographic reference methods. Full article

(This article belongs to the Special Issue Advances in Electrochemical Technologies for Environmental Applications)

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14 pages, 11441 KiB

Open AccessArticle

Effect of Different Welding Modes on Morphology and Property of SS316L Stainless Steel Deposition by Robotic Metal-Inert Gas Welding

by Wei Wu, Chunjie Wen, Jisheng He, Yanfeng Li, Wei Xu, Ping Yao and Xiangkun Zeng

Materials 2024, 17(18), 4479; https://doi.org/10.3390/ma17184479 - 12 Sep 2024

Abstract

The widespread adoption of arc additive manufacturing techniques across various industries has advanced the field of SS316L stainless steel manufacturing. It is crucial to acknowledge that different welding modes exert distinct influences on the forming and mechanical performance. This study analyzed the thermal [...] Read more.

The widespread adoption of arc additive manufacturing techniques across various industries has advanced the field of SS316L stainless steel manufacturing. It is crucial to acknowledge that different welding modes exert distinct influences on the forming and mechanical performance. This study analyzed the thermal input associated with four specific welding modes in LORCH MIG welding, clarifying the transition dynamics of molten droplets through waveform analysis and examining the resultant effects on microstructure and performance characteristics. The Pulse, Speed-Pulse-XT, and Twin-Pulse modes were found to induce spatter during the manufacturing process, consequently reducing molding efficiency in comparison to the SA-XT mode. Notably, the Twin-Pulse mode, characterized by double-pulse agitation, generated fish scale patterns along the lateral surfaces of the fabricated parts, promoting anisotropic grain growth. This microstructural refinement, compared to single-pulse samples with equivalent thermal input, resulted in enhanced mechanical properties. Nevertheless, the horizontal tensile strength of the three pulse modes was lower than the industrial standard for SA-XT mode and forging. In contrast, the SA-XT mode with an average hardness of 168.1 ± 6.9 HV and a tensile strength of 443.58 ± 5.7 MPa. Therefore, while three pulse modes offer certain microstructural advantages, the SA-XT mode demonstrates superior overall performance. Full article

(This article belongs to the Special Issue 3D Printing Technology with Metal Materials)

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16 pages, 6004 KiB

Open AccessArticle

Natural and Artificial Aging Effects on the Deformation Behaviors of Al–Mg–Zn Alloy Sheets

by Kwangmin Choi, Sangjun Lee and Donghyun Bae

Materials 2024, 17(18), 4478; https://doi.org/10.3390/ma17184478 - 12 Sep 2024

Abstract

This study investigated the effects of aging profiles on the precipitate formation and the corresponding strengthening and deformation behaviors of Al–Mg–Zn alloys. The alloys subjected to natural aging (NA) demonstrated significantly enhanced ductility at equivalent stress levels compared to those subjected to artificial [...] Read more.

This study investigated the effects of aging profiles on the precipitate formation and the corresponding strengthening and deformation behaviors of Al–Mg–Zn alloys. The alloys subjected to natural aging (NA) demonstrated significantly enhanced ductility at equivalent stress levels compared to those subjected to artificial aging (AA). In AA-treated alloys, η′ and η-phases with incoherent interfaces were formed, while GP zones and solute clusters were dominantly exhibited in the NA-treated alloy with a coherent interface with the matrix. Due to the change in interface bonding, the dislocation movement and pinning behavior after deformation are varied depending on the aging conditions of Al–Mg–Zn alloy sheet. Thus, the elongation to fracture of the NA alloy sheet was improved compared to that of the AA alloy sheet because of the enhanced work-hardening capacity and the thin precipitate-free zone (PFZ). Deformation textures and dislocation densities varied between NA and AA treatments, as revealed by electron backscatter diffraction (EBSD) and kernel average misorientation (KAM) analysis. The interactions between the precipitates, dislocations, and the PFZ in the AA- and NA-treated alloys were analyzed via transmission electron microscopy (TEM). The insights gained from this research provide a valuable foundation for industrial applications, particularly in sectors demanding lightweight, high-strength materials, where optimizing the aging process can lead to significant performance improvement and cost savings. Full article

(This article belongs to the Special Issue Alloy Strengthening Mechanisms, Microstructural Control, and Performance Optimization)

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21 pages, 6750 KiB

Open AccessArticle

Distribution of Rare Earth Elements in Ash from Lignite Combustion in Polish Power Plants

by Zdzisław Adamczyk, Joanna Komorek, Magdalena Kokowska-Pawłowska and Jacek Nowak

Materials 2024, 17(18), 4477; https://doi.org/10.3390/ma17184477 - 12 Sep 2024

Abstract

Rare earth elements are an essential critical raw material in the development of modern technologies and are highly sensitive to both supply chain disruptions and market turbulence. The presented study examines the characteristics of fuel, fly ash, and bottom ash from lignite combustion [...] Read more.

Rare earth elements are an essential critical raw material in the development of modern technologies and are highly sensitive to both supply chain disruptions and market turbulence. The presented study examines the characteristics of fuel, fly ash, and bottom ash from lignite combustion in power plant units. Also, we attempted to determine the amount of amorphous glass in the ashes and whether and to what extent the glass from the ash samples is bound to REY. The suitability of the ash was assessed as an alternative source of REY. The fuel and ash samples were acquired from power plants in Poland. The tests determined the fuel quality parameters, including the chemical and phase composition, of amorphous glass using ICP-MS and XRD methods, respectively. The study showed that all ash samples dissolved in 4% HF were enriched in REY. The efficiency of REY enrichment varied, and its presence in the residue samples was found to be in similar proportions compared to the raw sample. All ash residue samples were enriched in critical elements. The obtained values of the C_outl prospective coefficient allowed for the classification of some of the analyzed ashes and their residues after dissolution in 4% HF as prospective REY raw materials. Full article

(This article belongs to the Special Issue Current and Future Trends in Mineral Processing and Extractive Metallurgy)

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9 pages, 329 KiB

Open AccessArticle

Theoretical Study of the Multiferroic Properties of Pure and Ion-Doped Pb₅M₃F₁₉, M = Fe, Cr, Al

by Iliana N. Apostolova, Angel T. Apostolov and Julia M. Wesselinowa

Materials 2024, 17(18), 4476; https://doi.org/10.3390/ma17184476 - 12 Sep 2024

Abstract

In a first theoretical investigation of the multiferroic properties of

{Pb}_{5}

{Fe}_{3}

F_{19}

(PFF) and

{Pb}_{5}

{Cr}_{3}

F_{19}

(PCF), we analyze their magnetic, ferroelectric, and dielectric characteristics as functions of temperature, magnetic field, and ion doping concentration [...] Read more.

In a first theoretical investigation of the multiferroic properties of

{Pb}_{5}

{Fe}_{3}

F_{19}

(PFF) and

{Pb}_{5}

{Cr}_{3}

F_{19}

(PCF), we analyze their magnetic, ferroelectric, and dielectric characteristics as functions of temperature, magnetic field, and ion doping concentration using a microscopic model and Green’s function theory. The temperature-dependent polarization in PFF and PCF shows a distinctive kink at the magnetic Neel temperature

T_{N}

, which vanishes when an external magnetic field is applied, indicating the multiferroic behavior of these two compounds. Ion doping effectively tunes the properties of PFF and PCF. In PFF, Cr ion doping leads to a decrease in the Neel temperature

T_{N}

, while Cr and Al ion doping lowers the ferroelectric Curie temperature

T_{C}

. In the case of PCF, we observe the enhancement of

T_{C}

by Fe ion doping and the reduction by Al ion doping. The last result coincides well quantitatively with the experimental data. Additionally, the magnetodielectric coefficient of PFF is enhanced with the increasing magnetic field. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques (Second Edition))

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17 pages, 4315 KiB

Open AccessArticle

Low-Frequency Sound-Insulation Performance of Labyrinth-Type Helmholtz and Thin-Film Compound Acoustic Metamaterial

by Peizhou Hu, Jingbo Zhao, Hong Liu, Xiaosheng Zhang, Guangjun Zhang and Hong Yao

Materials 2024, 17(18), 4475; https://doi.org/10.3390/ma17184475 - 12 Sep 2024

Abstract

This paper presents a type of acoustic metamaterial that combines a labyrinth channel with a Helmholtz cavity and a thin film. The labyrinth-opening design and thin-film combination contribute to the metamaterial’s exceptional sound-insulation performance. After comprehensive research, it is observed that in the [...] Read more.

This paper presents a type of acoustic metamaterial that combines a labyrinth channel with a Helmholtz cavity and a thin film. The labyrinth-opening design and thin-film combination contribute to the metamaterial’s exceptional sound-insulation performance. After comprehensive research, it is observed that in the frequency range of 20–1200 Hz, this acoustic metamaterial exhibits multiple sound-insulation peaks, showing a high overall sound-insulation quality. Specifically, the first sound-insulation peak is 26.3 Hz, with a bandwidth of 13 Hz and giving a transmission loss of 56.5 dB, showing excellent low-frequency sound-insulation performance. To further understand the low-frequency sound-insulation mechanism, this paper uses the equivalent model method to conduct an acoustic–electrical analogy, construct an equivalent model of the acoustic metamaterial, and delve into the sound-insulation mechanism at the first sound-insulation peak. To confirm the validity of the theoretical calculations, physical experiments are carried out by 3D printing experimental samples. The analysis of the experimental data has yielded results that are consistent with the simulation data, providing empirical evidence for the accuracy of the theoretical model. The material has significant practical application value. Finally, various factors are studied in depth based on the established equivalent model, which can provide valuable insights for the design and practical engineering application of acoustic metamaterials. Full article

(This article belongs to the Section Materials Physics)

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13 pages, 5169 KiB

Open AccessArticle

Influence of Zinc Chloride Exposure on Microstructure and Mechanical Behavior of Age-Hardened AZ91 Magnesium Alloy

by Pavel Konopík, Tomasz Bucki, Sylwia Rzepa, Daniel Melzer, Dana Bolibruchová, Ying Li and Jan Džugan

Materials 2024, 17(18), 4474; https://doi.org/10.3390/ma17184474 - 12 Sep 2024

Abstract

The AZ91 magnesium alloy was subjected to a complex treatment involving age hardening (supersaturation and artificial aging) and simultaneous surface layer modification. The specimens were supersaturated in contact with a mixture containing varying concentrations of zinc chloride, followed by cooling either in air [...] Read more.

The AZ91 magnesium alloy was subjected to a complex treatment involving age hardening (supersaturation and artificial aging) and simultaneous surface layer modification. The specimens were supersaturated in contact with a mixture containing varying concentrations of zinc chloride, followed by cooling either in air or water. After supersaturation, the specimens were subjected to artificial aging and then air-cooled. This process resulted in the formation of a surface layer made of zinc-rich phases. The thickness and microstructure of the surface layer were influenced by the process parameters, namely, the zinc chloride content in the mixture and the cooling rate during supersaturation. The treated specimens exhibited favorable tensile strength and greater elongation compared to the as-cast AZ91 alloy, with values comparable to those of the alloy subjected to standard T6 tempering. No cracking of the layer was observed under moderate deformation, though greater deformation resulted in the formation of cracks, primarily in the areas containing the Mg₅Al₂Zn₂ intermetallic phase. The produced layer demonstrated strong metallurgical bonding to the AZ91 substrate. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties Relationship for Metallic Materials (2nd Edition))

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16 pages, 5784 KiB

Open AccessArticle

Diatom-Based Artificial Anode—Uniform Coating of Intrinsic Carbon to Enhance Lithium Storage

by Junlong Luo, Jun Cai, De Gong, Aoping Guo, Jaw-Kai Wang and Jiangtao Zhang

Materials 2024, 17(18), 4473; https://doi.org/10.3390/ma17184473 - 12 Sep 2024

Abstract

Pursuing improved electrode materials is essential for addressing the challenges associated with large-scale Li-ion battery applications. Specifically, silicon oxide (SiO_x) has emerged as a promising alternative to graphite anodes, despite issues related to volume expansion and rapid capacity degradation. In this [...] Read more.

Pursuing improved electrode materials is essential for addressing the challenges associated with large-scale Li-ion battery applications. Specifically, silicon oxide (SiO_x) has emerged as a promising alternative to graphite anodes, despite issues related to volume expansion and rapid capacity degradation. In this study, we synthesized carbon-coated SiO_x using diatom biomass derived from artificially cultured diatoms. However, the inherent carbon content from diatoms poses a significant challenge for the electrochemical performance of diatom-based anodes in large-scale applications. Subsequently, we conducted further research and demonstrated excellent performance with a carbon content of 33 wt.% as anodes. Additionally, real-time characterization of the carbonization process was achieved using thermogravimetry coupled with infrared spectroscopy and gas chromatography mass spectrometry (TG-FTIR-GCMS), revealing the emission of CO and C₃O₂ during carbonization. Furthermore, electrochemical tests of the processed diatom and carbon (PD@C) anode exhibited outstanding rate capability (~500 mAh g⁻¹ at 2 A g⁻¹), high initial Coulomb efficiency (76.95%), and a D_Li⁺ diffusion rate of 1.03 × 10⁻¹² cm² s⁻¹. Moreover, structural characterization techniques such as HRTEM-SAED were employed, along with DFT calculations, to demonstrate that the lithium storage process involves not only reversible transport in Li₂Si₂O₅ and Li₂₂Si₅, but also physical adsorption between the PD and C layers. Exploring the integration of diatom frustules with the intrinsic carbon content in the fabrication of battery anodes may contribute to a deeper understanding of the mechanisms behind their successful application. Full article

(This article belongs to the Special Issue Artificial Biomimetic Materials)

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24 pages, 18105 KiB

Open AccessArticle

Diverse Strategies to Develop Poly(ethylene glycol)–Polyester Thermogels for Modulating the Release of Antibodies

by Daria Lipowska-Kur, Łukasz Otulakowski, Urszula Szeluga, Katarzyna Jelonek and Alicja Utrata-Wesołek

Materials 2024, 17(18), 4472; https://doi.org/10.3390/ma17184472 - 12 Sep 2024

Abstract

In this work, we present basic research on developing thermogel carriers containing high amounts of model antibody immunoglobulin G (IgG) with potential use as injectable molecules. The quantities of IgG loaded into the gel were varied to evaluate the possibility of tuning the [...] Read more.

In this work, we present basic research on developing thermogel carriers containing high amounts of model antibody immunoglobulin G (IgG) with potential use as injectable molecules. The quantities of IgG loaded into the gel were varied to evaluate the possibility of tuning the dose release. The gel materials were based on blends of thermoresponsive and degradable ABA-type block copolymers composed of poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA–PEG–PLGA) or poly(lactide-co-caprolactone)-b-poly(ethylene glycol)-b-(lactide-co-caprolactone) (PLCL–PEG–PLCL). Primarily, the gels with various amounts of IgG were obtained via thermogelation, where the only factor inducing gel formation was the change in temperature. Next, to control the gels’ mechanical properties, degradation rate, and the extent of antibody release, we have tested two approaches. The first one involved the synergistic physical and chemical crosslinking of the copolymers. To achieve this, the hydroxyl groups located at the ends of the PLGA–PEG–PLGA chain were modified into acrylate groups. In this case, the thermogelation was accompanied by chemical crosslinking through the Michael addition reaction. Such an approach increased the dynamic mechanical properties of the gels and simultaneously prolonged their decomposition time. An alternative solution was to suspend crosslinked PEG–polyester nanoparticles loaded with IgG in a PLGA–PEG–PLGA gelling copolymer. We observed that loading IgG into thermogels lowered the gelation temperature (T_GEL) value and increased the storage modulus of the gels, as compared with gels without IgG. The prepared gel materials were able to release the IgG from 8 up to 80 days, depending on the gel formulation and on the amount of loaded IgG. The results revealed that additional, chemical crosslinking of the thermogels and also suspension of particles in the polymer matrix substantially extended the duration of IgG release. With proper matching of the gel composition, environmental conditions, and the type and amount of active substances, antibody-containing thermogels can serve as effective IgG delivery materials. Full article

(This article belongs to the Special Issue Applied Stimuli-Responsive Polymer Based Materials)

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11 pages, 11934 KiB

Open AccessArticle

Effect of Alloying on Microstructure and Mechanical Properties of AlCoCrFeNi_2.1 Eutectic High-Entropy Alloy

by Xue-Yao Tian, Hong-Liang Zhang, Zhi-Sheng Nong, Xue Cui, Ze-Hao Gu, Teng Liu, Hong-Mei Li and Eshkuvat Arzikulov

Materials 2024, 17(18), 4471; https://doi.org/10.3390/ma17184471 - 12 Sep 2024

Abstract

In order to explore the effect of alloying on the microstructures and mechanical properties of AlCoCrFeNi_2.1 eutectic high-entropy alloys (EHEAs), 0.1, 0.2, and 0.3 at.% V, Mo, and B were added to the AlCoCrFeNi_2.1 alloy in this work. The effects of [...] Read more.

In order to explore the effect of alloying on the microstructures and mechanical properties of AlCoCrFeNi_2.1 eutectic high-entropy alloys (EHEAs), 0.1, 0.2, and 0.3 at.% V, Mo, and B were added to the AlCoCrFeNi_2.1 alloy in this work. The effects of the elements and contents on the phase composition, microstructures, mechanical properties, and fracture mechanism were investigated. The results showed that the crystal structures of the AlCoCrFeNi_2.1 EHEAs remained unchanged, and the alloys were still composed of FCC and BCC structures, whose content varied with the addition of alloying elements. After alloying, the aggregation of Co, Cr, Al, and Ni elements remained unchanged, and the V and Mo were distributed in both dendritic and interdendritic phases. The tensile strengths of the alloys all exceeded 1000 MPa when the V and Mo elements were added, and the Mo0.2 alloy had the highest tensile strength, of 1346.3 MPa, and fracture elongation, of 24.6%. The alloys with the addition of V and Mo elements showed a mixed ductile and brittle fracture, while the B-containing alloy presented a cleavage fracture. The fracture mechanism of Mo0.2 alloy is mainly crack propagation in the BCC lamellae, and the FCC dendritic lamellae exhibit the characteristics of plastic deformation. Full article

(This article belongs to the Special Issue Advanced Science and Technology of High Entropy Materials)

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14 pages, 2685 KiB

Open AccessArticle

A New Mechanism for the Inhibition of SA106 Gr.B Carbon Steel Corrosion by Nitrite in Alkaline Water

by Do-Haeng Hur, Jeoh Han, Joung-Hae Lee, Soon-Hyeok Jeon and Hee-Sang Shim

Materials 2024, 17(18), 4470; https://doi.org/10.3390/ma17184470 - 12 Sep 2024

Abstract

The purpose of this study was to investigate the composition of oxide films formed on SA106 Gr.B carbon steel in nitrite solutions at 35 °C for 1000 h. The product of the reduction of nitrite during the corrosion inhibition process was also examined. [...] Read more.

The purpose of this study was to investigate the composition of oxide films formed on SA106 Gr.B carbon steel in nitrite solutions at 35 °C for 1000 h. The product of the reduction of nitrite during the corrosion inhibition process was also examined. The X-ray photoelectron spectroscopy results revealed that a thin Fe₃O₄ film was formed and ammonium ions were adsorbed on the outermost surface of the oxide film. The presence of ammonium ions was also demonstrated by ion chromatography. These results indicate that nitrites are reduced to ammonium ions, which in turn promotes the formation of the protective Fe₃O₄ film. Full article

(This article belongs to the Special Issue Corrosion, Fatigue and Corrosion Protection of Metals and Their Alloys in Various Environments)

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33 pages, 10261 KiB

Open AccessReview

Theory and Measurement of Heat Transport in Solids: How Rigidity and Spectral Properties Govern Behavior

by Anne M. Hofmeister

Materials 2024, 17(18), 4469; https://doi.org/10.3390/ma17184469 - 11 Sep 2024

Viewed by 341

Abstract

Models of heat transport in solids, being based on idealized elastic collisions of gas molecules, are flawed because heat and mass diffuse independently in solids but together in gas. To better understand heat transfer, an analytical, theoretical approach is combined with data from [...] Read more.

Models of heat transport in solids, being based on idealized elastic collisions of gas molecules, are flawed because heat and mass diffuse independently in solids but together in gas. To better understand heat transfer, an analytical, theoretical approach is combined with data from laser flash analysis, which is the most accurate method available. Dimensional analysis of Fourier’s heat equation shows that thermal diffusivity (D) depends on length-scale, which has been confirmed experimentally for metallic, semiconducting, and electrically insulating solids. A radiative diffusion model reproduces measured thermal conductivity (K = Dρc_P = D × density × specific heat) for thick solids from ~0 to >1200 K using idealized spectra represented by 2–4 parameters. Heat diffusion at laboratory temperatures (conduction) proceeds by absorption and re-emission of infrared light, which explains why heat flows into, through, and out of a material. Because heat added to matter performs work, thermal expansivity is proportional to ρc_P/Young’s modulus (i.e., rigidity or strength), which is confirmed experimentally over wide temperature ranges. Greater uptake of applied heat (e.g., c_P generally increasing with T or at certain phase transitions) reduces the amount of heat that can flow through the solid, but because K = Dρc_P, the rate (D) must decrease to compensate. Laser flash analysis data confirm this proposal. Transport properties thus depend on heat uptake, which is controlled by the interaction of light with the material under the conditions of interest. This new finding supports a radiative diffusion mechanism for heat transport and explains behavior from ~0 K to above melting. Full article

(This article belongs to the Special Issue Advances in Materials Science and Engineering—in Celebration of 55th Anniversary of the Faculty of Technical Sciences, Warmia and Mazury University in Olsztyn, Poland)

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25 pages, 12892 KiB

Open AccessArticle

Mechanism of Rock Mass Detachment Using Undercutting Anchors: A Numerical Finite Element Method (FEM) Analysis

by Andrzej Wójcik, Kamil Jonak, Robert Karpiński, Józef Jonak, Marek Kalita and Dariusz Prostański

Materials 2024, 17(18), 4468; https://doi.org/10.3390/ma17184468 - 11 Sep 2024

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Abstract

Undercutting anchors are structural elements used in construction and geotechnics to stabilize both structures and soils. Their main applications include stabilizing slopes and embankments, reinforcing foundations, and providing support during tunnel construction and other underground works. The authors propose the use of these [...] Read more.

Undercutting anchors are structural elements used in construction and geotechnics to stabilize both structures and soils. Their main applications include stabilizing slopes and embankments, reinforcing foundations, and providing support during tunnel construction and other underground works. The authors propose the use of these anchors in rock mass detachment technology. This article presents a comprehensive analysis of the mechanism behind rock mass detachment using an undercutting anchor. Particular attention is given to the influence of parameters such as the fracture energy of the medium and the coefficient of friction between the medium and the anchor head on the detachment process of rock elements during anchor expansion in the drilled hole. Numerical FEM analysis was employed to model the effect of changes in the shape and size of failure cones under varying simulation conditions. The discussed problem is crucial for evaluating the effectiveness of this anchor design under non-standard conditions, particularly in the unconventional destruction of rock media. Full article

(This article belongs to the Special Issue Advances in Materials Science and Engineering—in Celebration of 55th Anniversary of the Faculty of Technical Sciences, Warmia and Mazury University in Olsztyn, Poland)

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18 pages, 9269 KiB

Open AccessArticle

Revealing the Corrosion Resistance Mechanism of Plain Carbon Steel Micro-Alloyed by La in Simulated Industrial Atmosphere

by Sha Sha, Feng Yang, Jianzhong He, Zhi Liu, Tianle Fu, Bing Wang, Xiaoping Chen, Shujun Jia and Qingyou Liu

Materials 2024, 17(18), 4467; https://doi.org/10.3390/ma17184467 - 11 Sep 2024

Viewed by 191

Abstract

Plain carbon steel is the most widely applied steel in current engineering construction. With the increased application property needs, the service life of plain carbon steel has been severely tested. As one of the most destructive failure modes, corrosion resistance of carbon steel [...] Read more.

Plain carbon steel is the most widely applied steel in current engineering construction. With the increased application property needs, the service life of plain carbon steel has been severely tested. As one of the most destructive failure modes, corrosion resistance of carbon steel has attracted wide attention. Rare earth La, as the microalloying element, was employed in plain carbon steel, Q355, to improve its corrosion resistance. As the content of La increased, the microstructure was refined. The fraction of pearlite decreased, while the content of acicular increased. Within the La addition of 230 ppm, the tensile strength and impact energy were jointly improved. Furthermore, the microalloying element of La modified the inclusion types and refined the inclusion size. The modified microstructure and inclusions by La co-improved the corrosion resistance. The formula of effective La content was proposed to estimate the effect of La on corrosion. As the effective content of La increased, the relative corrosion rate decreased. La³⁺ promoted the protective rust layer to increase corrosion resistance. Full article

(This article belongs to the Section Corrosion)

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40 pages, 3816 KiB

Open AccessArticle

Multiscale Analysis of Sandwich Beams with Polyurethane Foam Core: A Comparative Study of Finite Element Methods and Radial Point Interpolation Method

by Jorge Belinha

Materials 2024, 17(18), 4466; https://doi.org/10.3390/ma17184466 - 11 Sep 2024

Viewed by 169

Abstract

This study presents a comprehensive multiscale analysis of sandwich beams with a polyurethane foam (PUF) core, delivering a numerical comparison between finite element methods (FEMs) and a meshless method: the radial point interpolation method (RPIM). This work aims to combine RPIM with homogenisation [...] Read more.

This study presents a comprehensive multiscale analysis of sandwich beams with a polyurethane foam (PUF) core, delivering a numerical comparison between finite element methods (FEMs) and a meshless method: the radial point interpolation method (RPIM). This work aims to combine RPIM with homogenisation techniques for multiscale analysis, being divided in two phases. In the first phase, bulk PUF material was modified by incorporating circular holes to create PUFs with varying volume fractions. Then, using a homogenisation technique coupled with FEM and four versions of RPIM, the homogenised mechanical properties of distinct PUF with different volume fractions were determined. It was observed that RPIM formulations, with higher-order integration schemes, are capable of approximating the solution and field smoothness of high-order FEM formulations. However, seeking a comparable field smoothness represents prohibitive computational costs for RPIM formulations. In a second phase, the obtained homogenised mechanical properties were applied to large-scale sandwich beam problems with homogeneous and approximately functionally graded cores, showing RPIM’s capability to closely approximate FEM results. The analysis of stress distributions along the thickness of the beam highlighted RPIM’s tendency to yield lower stress values near domain edges, albeit with convergence towards agreement among different formulations. It was found that RPIM formulations with lower nodal connectivity are very efficient, balancing computational cost and accuracy. Overall, this study shows RPIM’s viability as an alternative to FEM for addressing practical elasticity applications. Full article

(This article belongs to the Special Issue Experimental Testing, Manufacturing and Numerical Modelling of Composite and Sandwich Structures (Second Edition))

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30 pages, 4383 KiB

Open AccessArticle

Evaluation of the Influence of the Tool Set Overhang on the Tool Wear and Surface Quality in the Process of Finish Turning of the Inconel 718 Alloy

by Krzysztof Smak, Piotr Szablewski, Stanisław Legutko, Jana Petru, Jiri Kratochwil and Sylwia Wencel

Materials 2024, 17(18), 4465; https://doi.org/10.3390/ma17184465 - 11 Sep 2024

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Abstract

The work deals with the influence of the reach of the applied tool holder on the edge wear, dimensional accuracy and surface quality defined by the topography as well as the roughness of the machined surface. The research has been conducted on specimens [...] Read more.

The work deals with the influence of the reach of the applied tool holder on the edge wear, dimensional accuracy and surface quality defined by the topography as well as the roughness of the machined surface. The research has been conducted on specimens made of Inconel 718 in the configuration of sleeves, within the scope of finish turning with constant cutting parameters, v_c = 85 m/min; f = 0.14 mm/rev; a_p = 0.2 mm. The material under machining has undergone heat treatment procedures such as solution treatment and precipitation hardening, resulting in a hardness of 45 ± 2 HRC. Two kinds of turning holders have been used with the reaches of 120 mm and 700 mm. The tools are intended for turning external and internal surfaces, respectively. The tests have been conducted using V-shaped cutting inserts manufactured by different producers, made of fine-grained carbide with coatings applied by the PVD (Physical Vapour Deposition) and CVD (Chemical Vapour Deposition) methods. The edge wear has been evaluated. The value of the achieved diameter dimensions has also been assessed in relation to the set ones, as well as the recorded values of surface roughness and the surface topography parameters have also been assessed. It has been determined that the quality of the manufactured surface evaluated by the 2D and 3D roughness parameters, as well as the dimensional quality are influenced by the kind of the applied tool holder. The influence is also visible considering the edge wear. The smallest values of the deviations from the nominal dimensions have been obtained for the coated inserts of the range of higher abrasion resistance (taking into account information from the producers). The obtained results show that in predicting the dimensional accuracy in the process of turning Inconel 718 alloy with long-overhang tools, one should consider the necessity of correction of the tool path. Taking into account the achieved surface roughness, it should be pointed out that not only the kind of the tool coating but also the character of its wear has a great influence, particularly, when a long cutting distance is required. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

17 pages, 12952 KiB

Open AccessArticle

Assessment of Changes in Selected Features of Pine and Birch Wood after Impregnation with Graphene Oxide

by Izabela Betlej, Sławomir Borysiak, Katarzyna Rybak, Barbara Nasiłowska, Aneta Bombalska, Zygmunt Mierczyk, Karolina Lipska, Piotr Borysiuk, Bogusław Andres, Małgorzata Nowacka and Piotr Boruszewski

Materials 2024, 17(18), 4464; https://doi.org/10.3390/ma17184464 - 11 Sep 2024

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Abstract

In this work, pine and birch wood were modified by graphene oxide using a single vacuum impregnation method. The research results indicate that the impregnation of wood with graphene oxide increases the crystallinity of cellulose in both pine and birch wood, and the [...] Read more.

In this work, pine and birch wood were modified by graphene oxide using a single vacuum impregnation method. The research results indicate that the impregnation of wood with graphene oxide increases the crystallinity of cellulose in both pine and birch wood, and the increase in crystallinity observed in the case of birch was more significant than in the case of pine. FT-IR analyses of pine samples impregnated with graphene oxide showed changes in intensity in the absorption bands of 400–600, 700–1500 cm⁻¹, and 3200–3500 cm⁻¹ and a peak separation of 1102 cm⁻¹, which may indicate new C-O-C connections. In the case of birch, only some differences were noticed related to the vibrations of the OH group. The proposed modification also affects changes in the color of the wood surface, with earlywood containing more graphene oxide than latewood. Analysis of scanning electron microscope images revealed that graphene oxide adheres flat to the cell wall. Considering the differences in the anatomical structure of both wood species, the research showed a statistically significant difference in water absorption and retention of graphene oxide in wood cells. Graphene oxide does not block the flow of water in the wood, as evidenced by the absorbability of the working liquid at the level of 580–602 kg/m³, which corresponds to the value of pure water absorption by wood in the impregnation method using a single negative pressure. In this case, higher graphene oxide retention values were obtained for pine wood. Full article

(This article belongs to the Section Advanced Materials Characterization)

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16 pages, 21816 KiB

Open AccessArticle

The High-Cycle Tensile–Shear Fatigue Properties and Failure Mechanism of Resistance Spot-Welded Advanced High-Strength Steel with a Zn Coating

by Yu Sun, Jiayi Zhou, Rongxun Hu, Hua Pan, Kai Ding, Ming Lei and Yulai Gao

Materials 2024, 17(18), 4463; https://doi.org/10.3390/ma17184463 - 11 Sep 2024

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Abstract

Advanced high-strength steels (AHSSs) with Zn coatings are commonly joined by the resistance spot welding (RSW) technique. However, Zn coatings could possibly cause the formation of liquid metal embrittlement (LME) cracks during the RSW process. The role of a Zn coating in the [...] Read more.

Advanced high-strength steels (AHSSs) with Zn coatings are commonly joined by the resistance spot welding (RSW) technique. However, Zn coatings could possibly cause the formation of liquid metal embrittlement (LME) cracks during the RSW process. The role of a Zn coating in the tensile–shear fatigue properties of a welding joint has not been systematically explored. In this study, the fatigue properties of tensile–shear RSW joints for bare and Zn-coated advanced high-strength steel (AHSS) specimens were comparatively studied. In particular, more severe LME cracks were triggered by employing a tilted welding electrode because much more stress was caused in the joint. LME cracks had clearly occurred in the Zn-coated steel RSW joints, as observed via optical microscopy. On the contrary, no LME cracks could be found in the RSW joints prepared with the bare steel sheets. The fatigue test results showed that the tensile–shear fatigue properties remained nearly unchanged, regardless of whether bare or Zn-coated steel was used for the RSW joints. Furthermore, Zn mapping adjacent to the crack initiation source was obtained by an electron probe micro-analyzer (EPMA), and it showed no segregation of the Zn element. Thus, the failure of the RSW joints with the Zn coating had not initiated from the LME cracks. It was concluded that the fatigue cracks were initiated by the stress concentration in the notch position between the two bonded steel sheets. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study (3rd Edition))

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12 pages, 5647 KiB

Open AccessArticle

Investigation of Microstructure and Interfacial Reactions of Diffusion Bonding of Ni-Ti6Al4V Materials Joined by Using Ag Interlayer

by Şükrü Çetinkaya and Haluk Kejanli

Materials 2024, 17(18), 4462; https://doi.org/10.3390/ma17184462 - 11 Sep 2024

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Abstract

Due to its super plasticity, low weight, and high mechanical resistance properties, generally, Ti6Al4V is used for aeronautical applications. However, it has low resistance to plastic shearing. In addition, it has poor wear resistance. For these reasons, a lot of techniques have been [...] Read more.

Due to its super plasticity, low weight, and high mechanical resistance properties, generally, Ti6Al4V is used for aeronautical applications. However, it has low resistance to plastic shearing. In addition, it has poor wear resistance. For these reasons, a lot of techniques have been developed to improve its wear resistance. Investigations of microstructure and interfacial reactions of diffusion bonding of Ni and Ti6Al4V materials have been performed experimentally. Ni samples were prepared with 50 ± 5 µm Ni powders in cylindrical shape. For diffusion bonding, Ag foil was used for improving the interlayer and connection quality. Nickel and its alloys can be joined by using some different processes, and the use of an interlayer can further facilitate the joining process and improve the joint quality. The experiments were carried out under the protected atmosphere. Argon gas was used for protection. The experiments were performed under 5 MPa pressure for 60 min duration at 850 °C, 900 °C, and 950 °C thermal conditions. Investigations of metallurgical structure occurring in the interface areas were examined by optic analysis of EDS, SEM, and X-ray. The strength of the joints was tested by lap-shear tests. From observations, the best quality of the coalescence at interfaces was indicated at elevated temperatures. Full article

(This article belongs to the Special Issue Mechanical and Metallurgical Behaviour of Welded Materials)

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20 pages, 5830 KiB

Open AccessArticle

Influence of Accelerated Carbonation on the Physico-Mechanical Properties of Natural Fiber-Reinforced Lime Mortars

by Fotini Kesikidou, Ioanna Matamadiotou and Maria Stefanidou

Materials 2024, 17(18), 4461; https://doi.org/10.3390/ma17184461 - 11 Sep 2024

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Abstract

Lime mortars are considered the most compatible material for monuments and historic buildings, and they are widely used in restoration works. A key factor determining the mechanical and physical properties of lime mortars is carbonation, which provides strength and hardness. This paper indicates [...] Read more.

Lime mortars are considered the most compatible material for monuments and historic buildings, and they are widely used in restoration works. A key factor determining the mechanical and physical properties of lime mortars is carbonation, which provides strength and hardness. This paper indicates the properties gained in lime mortars produced by Ca(OH)₂ and CaO reinforced with different bio-fibers (hemp and lavender) when exposed to the natural environment and in accelerated carbonation. At 90 and 180 days of manufacture, the mechanical and physical properties of the produced composites have been tested. The results show that the carbonation reaction works faster in the case of hot lime mortars, increasing their compressive strength by up to 3.5 times. Hemp-reinforced mortars led to an enhancement in strength by up to 30%, highlighting the significance of bio-fibers in facilitating CO₂ diffusion. This was also verified by the thermogravimetric analysis and the determination of the carbon content of the samples. Optimal mechanical properties were observed in mixtures containing quicklime and hemp fibers when conditioned with 3% CO₂ at the tested ages. Full article

(This article belongs to the Section Construction and Building Materials)

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22 pages, 14976 KiB

Open AccessArticle

Effect of Chlorine Salt Content on the Microstructural Development of C-S-H Gels and Ca(OH)₂ at Different Curing Temperatures

by Wenjie Qi, Zhisheng Fang, Shiyi Zhang, Yingfang Fan, Surendra P. Shah and Junjie Zheng

Materials 2024, 17(18), 4460; https://doi.org/10.3390/ma17184460 - 11 Sep 2024

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Abstract

Freshwater resources are scarce in coastal areas, and using seawater as mixing water can alleviate the scarcity of freshwater resources. However, the presence of chloride ions in seawater affects the generation of hydration products and the durability of concrete structures. In order to [...] Read more.

Freshwater resources are scarce in coastal areas, and using seawater as mixing water can alleviate the scarcity of freshwater resources. However, the presence of chloride ions in seawater affects the generation of hydration products and the durability of concrete structures. In order to investigate the effect of hydrated calcium silicate (C-S-H) gel and calcium hydroxide (CH) generation in seawater-mixed cement pastes under 50 °C curing, their microscopic morphology was investigated using differential scanning calorimetry analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The relationship between the amount of C-S-H gel and CH production and the amount of chloride ion dosing, fly ash dosing, and the age of curing were investigated. The degree of influence between hydration products and influencing factors was analyzed using the grey correlation analysis. It was shown that 50 °C curing promoted the hydration reaction and generated more hydration products compared with ASTM standard. The content of C-S-H gel and CH increased with chloride dosage. The content of C-S-H gel increased by 13.5% under 50 °C curing compared with the control group at a chloride dosage of 1.3%. Fly ash is rich in active SiO₂ and AI₂O₃, and other components, which can react with Ca(OH)₂ generated by cement hydration and then generate C-S-H gel. With the increase of fly ash, the content of C-S-H gel also increases, but the CH content decreases. When 25% of fly ash was doped under 50 °C curing, the C-S-H gel content increased by 5.02% compared to the control group. The CH content decreased by 31.8% compared to the control group. With the growth of the maintenance age, the hydration reaction continues, the generation of C-S-H gel and CH will continue to increase, and their microstructures will become denser. C-S-H gel and CH content increased the most by raising the curing temperature at 7 days of curing, increasing by 10.11% and 22.62%, respectively. C-S-H gel and CH content had the highest gray relation with fly ash dosing. Chloride dosage and age of maintenance had the highest correlation with CH content at room temperature maintenance of 0.788 and 0.753, respectively. Full article

(This article belongs to the Special Issue Application and Modification of Clay Minerals)

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Materials, Volume 17, Issue 18 (September-2 2024) – 51 articles

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