Materials, Volume 16, Issue 18 (September-2 2023) – 273 articles

Vacuum on-load tap-changers (OLTC) for converter transformers have a much higher number of breakings than conventional circuit breakers. Contact ablation after several breakings will affect the stability and life of the device. This paper establishes the electromagnetic thermal multi-physical field coupling model of the vacuum interrupter for OLTC based on the finite element analysis method. The thermal field distribution of normal and ablative contact materials during the breaking process was analyzed. The key parameters affecting the contact temperature under the cumulative number of breakings are analyzed and the optimized design is completed. The simulation results show that the contact surface reaches a maximum temperature of 1390 K at 8 ms. There is a significant increase in the area of the high-temperature area on the contact surface. The possibility of re-ignition of the interrupter is increased. Based on the judgment matrix method, the key influencing parameters of the contact temperature rise are analyzed. The final parameters are selected as follows: contact material—CuCr8 alloy, contact seat thickness—2 mm, contact thickness—10 mm, and contact diameter—40 mm. Full article

The science related to biomaterials and tissue engineering accounts for a growing part of our knowledge. Surface modifications of biomaterials, their performance in vitro, and the interaction between them and surrounding tissues are gaining more and more attention. It is because we are interested in finding sophisticated materials that help us to treat or mitigate different disorders. Therefore, efficient methods for surface analysis are needed. Several methods are routinely applied to characterize the physical and chemical properties of the biomaterial surface. Mass Spectrometry Imaging (MSI) techniques are able to measure the information about molecular composition simultaneously from biomaterial and adjacent tissue. That is why it can answer the questions connected with biomaterial characteristics and their biological influence. Moreover, this kind of analysis does not demand any antibodies or dyes that may influence the studied items. It means that we can correlate surface chemistry with a biological response without any modification that could distort the image. In our review, we presented examples of biomaterials analyzed by MSI techniques to indicate the utility of SIMS, MALDI, and DESI—three major ones in the field of biomaterials applications. Examples include biomaterials used to treat vascular system diseases, bone implants with the effects of implanted material on adjacent tissues, nanofibers and membranes monitored by mass spectrometry-related techniques, analyses of drug-eluting long-acting parenteral (LAPs) implants and microspheres where MSI serves as a quality control system. Full article

Polymer materials and composites play a pivotal role in modern industry, prized for their durability, light weight, and resistance to corrosion. This study delves into the effects of mineral engine oil exposure on the mechanical parameters of 3D-printed materials created through fused deposition modeling (FDM). The research scrutinizes prototype materials under diverse environmental conditions, with a particular focus on the tensile parameters. The primary aim is to analyze and compare how mineral engine oil affects the mechanical parameters of four commonly used FDM 3D-printed materials: PLA, PLA+CF composites, PETG, and PETG+CF composites. In the case of the PLA specimens, the tensile strength decreased by approximately 36%, which, considering the 30% infill, remained acceptable. Simultaneously, the nominal strain at the point of breaking increased by 60.92% after 7 days and 47.49% after 30 days, indicating enhanced ductility. Interestingly, the PLA’s Young’s modulus remained unaffected by the oil. The 3D-printed PLA+CF materials exposed to 30 days of mineral engine oil displayed a substantial Young’s modulus increase of over 49.93%. The PETG specimens exhibited intriguing behavior, with a tensile strength decrease of 16.66% after 7 days and 16.85% after 30 days, together with a notable increase in the nominal strain at breaking by 21.34% for 7 days and 14.51% for 30 days, signifying enhanced ductility. In PETG material specimens, the Young’s modulus increased by 55.08% after 7 days and 66.27% after 30 days. The PETG+CF samples initially exhibited increases in tensile strength (1.78%) and nominal strain at breaking (6.08%) after 7 days, but later experienced an 11.75% reduction in the tensile strength after 30 days. This research underscores the critical role of material selection in oil-exposed environments and suggests avenues for future exploration, encompassing microstructural analysis, the long-term impact of oil exposure, and broader considerations related to environmental and oil-specific factors. It contributes to a deeper understanding of the intricate interactions between polymer materials and mineral engine oil, offering valuable insights that can enhance industrial applications. Full article

Building thermal insulation and energy conservation have become urgent problems in the field of civil engineering because they are important for achieving the goal of carbon neutralization. Thermal conductivity is an important index for evaluating the thermal insulation of materials. To study the influence of different porosity levels on the thermal conductivity of materials, this paper established a random distribution model using MATLAB and conducted a comparative analysis using COMSOL finite element software and classical theoretical numerical calculation formulas. The thermal conductivity of composite materials was determined based on a theoretical calculation formula and COMSOL software simulations, and the theoretical calculation results and simulation results were compared with the measured thermal conductivity of the composites. Furthermore, the influence of the width of the gaps between the materials on the heat transfer process was simulated in the fabricated roof structure. The results showed the following: (1) The thermal conductivity values calculated using the Zimmerman model were quite different from those calculated using the Campbell-Allen model and those calculated using the COMSOL software; (2) The thermal conductivity values calculated using the theoretical calculation formula were lower than the measured data, and the maximum relative error was more than 29%. The COMSOL simulation results were in good agreement with the measured data, and the relative error was less than 5%; (3) When the gap width was less than 60 mm, it increased linearly with the heat transfer coefficient. The heat transfer coefficient increased slowly when the gap width was greater than 60 mm. This was mainly due to the thermal bridge effect inside the insulation system. Based on these research results, a thermal insulation system was prepared in a factory. Full article

Semiconducting nanomaterials based heterogeneous photocatalysis represent a low-cost, versatile technique for environmental remediation, including pollution mitigation, energy management and other environmental aspects. Herein, we demonstrate the syntheses of various heterogeneous photocatalysts based on highly reduced graphene oxide (HRG) and vanadium oxide (VO_x)-based nanocomposites (HRG–VO_x). Different shapes (rod, sheet and urchin forms) of VO_x nanoparticles were successfully fabricated on the surface of HRG under solvo-/hydrothermal conditions by varying the amount of water and ethanol. The high concentration of water in the mixture resulted in the formation of rod-shaped VO_x nanoparticles, whereas increasing the amount of ethanol led to the production of VO_x sheets. The solvothermal condition using pure ethanol as solvent produced VO_x nano-urchins on the surface of HRG. The as-prepared hybrid materials were characterized using various spectroscopic and microscopic techniques, including X-ray diffraction, UV–vis, FTIR, SEM and TEM analyses. The photocatalytic activities of different HRG–VO_x nanocomposites were investigated for the photodegradation of methylene blue (MB) and methyl orange (MO). The experimental data revealed that all HRG–VO_x composite-based photocatalysts demonstrated excellent performance toward the photocatalytic degradation of the organic dyes. Among all photocatalysts studied, the HRG–VO_x nanocomposite consisting of urchin-shaped VO_x nanoparticles (HRG–VO_x-U) demonstrated superior photocatalytic properties towards the degradation of dyes. Full article

The susceptibility of reinforced concrete (RC) slabs to punching shear failure is heightened when subjected to close-in explosion loads, leading to a wider range of damage caused by the resultant leakage shock wave through the punching hole. Consequently, it is crucial to analyze the conditions for punching shear failure and the size of the punching hole in RC slabs. This study investigates the punching shear failure of RC slabs under close-in explosions through numerical simulation and theoretical analysis. Initially, a finite element model is developed to examine the distribution of the explosion load on the slab’s surface. Subsequently, the critical explosion load for punching shear failure is determined using a damage criterion specific to RC slabs. Additionally, a calculation model based on the twin shear stress yield criterion is established to predict the punching hole’s radius. To validate the accuracy of this method, a comparison is conducted with existing test results. Full article

Thermal damage to diamonds is a major limitation in laser powder bed fusion (LPBF) processing of metal matrix diamond composites. In this paper, a numerical simulation model was established to describe the thermal effect of the Diamond-CuSn10 composite on the LPBF process. The simulation results show that the temperature of the diamond presents a double-peak structure, and the double-peak temperature curve shape can be modulated by modifying the laser scanning offset and the size of the diamond powder. And it suggests that the heat of the diamond mainly comes from the transfer of the molten pool. Then, combined with the experimental phenomenon, the mechanism of diamond graphitization in the LPBF process is analyzed. It indicates that since the surface defects of the diamond inhibit the heat conduction of the diamond, the temperature accumulates on the surface, leading to the graphitization of the diamond. Finally, based on this model, the potential of Ti-coated diamonds to prevent and reduce thermal damage in the LPBF process has been extensively studied. It is found that a Ti coating with low thermal conductivity can effectively reduce diamond temperature and improve diamond graphitization resistance. This study can provide a good method and basis for the preliminary selection of LPBF process parameters and the understanding of the graphitization mechanism of diamond tools. Full article

This paper presents a numerical investigation on the residual stresses and co-existent equivalent plastic strains in cold-formed high-strength steel (CFHSS) circular hollow sections (CHS) by using an advanced finite element (FE)-based method. In this method, the entire manufacturing process of the CFHSS CHS was modeled numerically. The accuracy of the numerical predictions of equivalent plastic strains and residual stresses in the CFHSS CHS was verified by comparing the predictions with the existing test results of both the residual stress measurement and load-end shortening response of the stub column. By using the FE-based method, the effects of high-frequency electric resistance welding on the residual stresses and the stub column response were investigated. The through-thickness variations of both the equivalent plastic strains and residual stresses in CFHSS CHS, which are difficult to measure in the laboratory, were explored numerically. Finally, the effect of cold work (which is quantified by the equivalent plastic strains and residual stresses) on the stub column response of CFHSS CHS tubes was evaluated. It can be found that the equivalent plastic strains and longitudinal residual stresses are generally uniform around the cross-section of CFHSS CHS. The transverse and longitudinal residual stresses are generally uniform across each half-thickness, with the inner half-thickness under compression and the outer half-thickness under tension. The results also demonstrate that both the plastic strains and residual stresses may significantly affect the cross-section capacities of CFHSS CHS. Full article

Dapsone is an effective antibacterial drug used to treat a variety of conditions. However, the aqueous solubility of this drug is limited, as is its permeability. This study expands the available solubility data pool for dapsone by measuring its solubility in several pure organic solvents: N-methyl-2-pyrrolidone (CAS: 872-50-4), dimethyl sulfoxide (CAS: 67-68-5), 4-formylmorpholine (CAS: 4394-85-8), tetraethylene pentamine (CAS: 112-57-2), and diethylene glycol bis(3-aminopropyl) ether (CAS: 4246-51-9). Furthermore, the study proposes the use of intermolecular interactions as molecular descriptors to predict the solubility of dapsone in neat solvents and binary mixtures using machine learning models. An ensemble of regressors was used, including support vector machines, random forests, gradient boosting, and neural networks. Affinities of dapsone to solvent molecules were calculated using COSMO-RS and used as input for model training. Due to the polymorphic nature of dapsone, fusion data are not available, which prohibits the direct use of COSMO-RS for solubility calculations. Therefore, a consonance solvent approach was tested, which allows an indirect estimation of the fusion properties. Unfortunately, the resulting accuracy is unsatisfactory. In contrast, the developed regressors showed high predictive potential. This work documents that intermolecular interactions characterized by solute–solvent contacts can be considered valuable molecular descriptors for solubility modeling and that the wealth of encoded information is sufficient for solubility predictions for new systems, including those for which experimental measurements of thermodynamic properties are unavailable. Full article

Polymers mixed with conductive fillers hold significant potential for use in stretchable and wearable sensor devices. Enhancing the piezoresistive effect and mechanical stability is critical for these devices. To explore the changes in the electrical resistance under high strains, typically unachievable in single-layer composites, bi-layer structures were fabricated from carbon nanotubes (CNTs) and EcoFlex composites to see unobservable strain regions. Spherical types of non-conductive fillers composed of polystyrene and conductive filler, coated with Ni and Au on non-conductive fillers, were used as secondary fillers to improve the piezoresistive sensitivity of composites, and their respective impact on the conductive network was compared. The electrical and mechanical properties were examined in the static state to understand the impact of these secondary fillers. The changes in the electrical resistance under 100% and 300% tensile strain, and their dependence on the inherent electrical properties of the secondary fillers, were also investigated. Single-layer CNT composites proved incapable of withstanding 300% strain, whereas the bi-layer structures proved resilient. By implementing cyclic stretching tests, contrary to non-conductive fillers, reduced piezoresistive influence of the conductive secondary filler under extreme strain conditions could be observed. Full article

Selective laser melting is a form of additive manufacturing in which a high-power density laser is used to melt and fuse metallic powders to form the final specimen. By performing fatigue and tensile tests under various loading conditions, the study sought to establish the impact of internal defects on the specimens’ fatigue life. Scanning electron microscopy and finite element simulation were conducted to determine the defect characteristics and the stress intensity factor of the specimens. Four different methods were used to determine the intrinsic defect length of the specimen, using data such as grain size, yield strength, and hardness value, among others. Kitagawa–Takahashi and El-Haddad diagrams were developed using the results. A correction factor hypothesis was established based on the deviation of measured data. Using Paris law, fatigue life was determined and compared to the experimental results later. The study aims to select one or more approaches that resemble experimental values and comprehend how internal defects and loading situations affect fatigue life. This study’s findings shed light on how internal defects affect the fatigue life of selective laser-melted AlSi10Mg specimens and can aid in improving the fatigue life prediction method of additively manufactured components, provided an appropriate intrinsic crack criterion is selected. Full article

Methods for the remote detection of warfare agents and explosives have been in high demand in recent times. Among the several detection methods, fluorescence methods appear to be more convenient due to their low cost, simple operation, fast response time, and naked-eye-visible sensory response. For fluorescence methods, a large variety of fluorescent materials, such as small-molecule-based fluorophores, aggregation-induced emission fluorophores/materials, and supramolecular systems, have been reported in the literature. Among them, fluorescent (bio)polymers/(bio)polymer-based materials have gained wide attention due to their excellent mechanical properties and sensory performance, their ability to recognize explosives via different sensing mechanisms and their combinations, and, finally, the so-called amplification of the sensory response. This review provides the most up-to-date data on the utilization of polymers and polymer-based materials for the detection of nitroaromatic compounds (NACs)/nitro-explosives (NEs) in the last decade. The literature data have been arranged depending on the polymer type and/or sensory mechanism. Full article

Durable concrete significantly reduces the spalling caused by chemical damage. The objective of current research is to substitute cement with supplementary such as fly ash (FA), ground granulated blast furnace slag (GGBS), and alccofine (AF). Additionally, the impact of nano-silica (NS) and silica fumes (SF) on the GPC durability when cured at various temperatures has been attempted. In order to perform this, GPC samples were produced by combining NS and SF at proportions of 0.5% NS + 5% SF, 1% NS + 10% SF, and 1.5% NS + 15% SF, and then cured at temperatures of 27 °C, 60 °C, 90 °C, and 120 °C, respectively. In this research, all concrete specimens were continuously immersed for twelve weeks under four different chemicals, i.e., HCl (2%), H₂SO₄ (2%), NaCl (6%), and Na₂SO₄ (6%). The influence of chemical attack on the qualities of concrete was examined by evaluating the water absorption, sorptivity, loss of mass, and loss of GPC strength. The durability aspect is also studied by visual appearance and mass loss under harmful chemical attack. The combination of GPC with integrated NS and SF affords great resistance against chemical attacks. The percentages of these two components are 1.5% and 15%. For GPC specimens, when cured at 90 °C, the resultant strength is found at its maximum. Full article

Corrosion affecting reinforced concrete (RC) structures generates safety and economical problems. This paper is focused on the simulation of corrosion-induced fractures in concrete, whereby non-uniform corrosion growth is taken into account. In particular, the volumetric expansion of rust accumulated around reinforcement bars causes cracking of the surrounding concrete. This phenomenon is simulated using the finite element (FE) method. In the analyses, concrete is described as a fracturing material by using a damage–plasticity model, steel is assumed to be elastic–plastic and rust is modeled as an interface between concrete and steel. The behavior of corrosion products is simulated as interface opening. Two-dimensional FE models of RC cross-sections with 2, 4 or 6 reinforcing bars are considered. Crack formation and propagation is examined. Moreover, interactions between cracks and patterns of possible failure are predicted. The most developed and complex crack pattern occurs around the side reinforcing bar. Conclusions concerning the comparison of results for uniform and non-uniform corrosion distribution as well as the prediction of concrete spalling are formulated. Full article

For the sake of solving sustainability issues and analyzing the complicated service force states, eccentric compression experiments on self-compacting concrete-filled thin-walled medium-length steel tube columns with a circular cross-section were carried out in the present study. Thereafter, the influence of the eccentric ratios and the wall thickness factors on the mechanical behavior and failure characteristics of both the eccentrically loaded and axially loaded columns was comprehensively analyzed. Finally, prediction formulas for the ultimate load of the columns under eccentric compression were proposed, and a comprehensive comparison of the ultimate loads between the predicted values and experimental values was also conducted. The results indicated that the typical failure characteristics of the eccentrically loaded columns presented lateral deflection together with buckling, while the axially compressed columns displayed expansion and rupture at local positions. Moreover, the ultimate loads of the eccentrically loaded columns decreased by 43.0% and 34.5% in comparison to the columns under axial compression, with the wall thickness factor decreasing from 116.7 to 46.7, respectively. Meanwhile, the ratios of the ultimate loads calculated using design codes to the tested values were in the range of 0.70~0.90, which demonstrated that the design codes could predict the ultimate loads conservatively. Additionally, the ratios of the ultimate loads calculated using the proposed formulas to the tested values were within the range of 0.99~1.08, implying that the proposed formulas were more accurate than the design codes. At the same time, the initial stiffness of the columns under eccentric compression was correspondingly lower than that of the columns undergoing axial compression. The lateral deflections along the height of the columns were almost symmetrical at different loading levels. This study could provide a meaningful approach for designing columns and facilitate their application in civil industry. Full article

In this study, the phase field method has been used to study the effect of second phase particles with different shapes and different orientations on the grain growth of AZ31 magnesium alloy, after annealing at 350 °C for 100 min. The results show that the shape of the second phase particles would have an effect on the grain growth; the refinement effect of elliptical particles and rod-shaped particles was similar, and better than the spherical particles; the spatial arrangement direction of the second phase particles had no significant effect on the grain growth. On the other hand, when the microstructure of AZ31 magnesium alloy contained second phase particles with different shapes, the effect of mixing different shapes of second phase particles on the grain refinement was enhanced gradually with the decrease im the volume fraction of spherical particles. Full article

The objective of this study was to evaluate different delaying times after bleaching and the use of different sodium ascorbate (SA) concentrations (10% and 35%) in the bond strength of adhesive cementation to enamel. This study used 54 sound bovine incisors, which were randomly assigned to the following groups: G1 (unbleached/control+ adhesive cementation (AC)); G2 (bleached + AC after 7 days); G3 (bleached + 10% SA + AC after 24 h); G4 (bleached + 10% SA + AC after 7 days); G5 (bleached + 35% SA + AC after 24 h); and G6 (bleached + 35% SA + AC after 7 days). After bleaching, G3, G4, G5, and G6 received an application of SA before the cylinders build up with RelyX Veneer cement. The samples were subjected to microshear test, and the results were analyzed by two-way ANOVA with Tukey’s post hoc test. Group one presented the highest mean bond strength (19.1 MPa) and G3 the lowest (16.96 MPa). There was no statistical difference between the groups tested (p ˃ 0.05). The fracture pattern observed was predominantly mixed. The adhesive cementation may be performed 24 h after bleaching when SA (10% or 35%) is used or after 7 days, without compromising bond strength. Full article

To reduce the environmental impacts from sodium silicate synthesis, a ceramic method was suggested, with sugarcane bagasse ash (SCBA) as the source of silicon dioxide and sodium carbonate. Although the production of sodium silicate is carried out on a large scale, it should be noted that its process requires temperatures above 1000 °C; it also requires the use of highly corrosive agents such as sodium hydroxide and chlorine gas to neutralize the remaining sodium hydroxide. In the present study, the synthesis temperatures were reduced to 800 °C with a reaction time of 3 h by pressing equimolar mixtures of previously purified SCBA and sodium carbonate; then, heat treatment was carried out under the indicated conditions. The resulting materials were analyzed with Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Among the crystalline phases, calcium disodium silicate was identified, in addition to sodium silicate; thus, it was inferred that the other components of the ash can interfere with the synthesis of silicate. Therefore, in order to obtain the highest composition of sodium silicate, a leaching treatment of the SCBA is required. Full article

To study the fatigue failure and microstructure evolution behavior of SS304, low-cycle fatigue tests are conducted at room temperature (RT), 300 °C, and 650 °C. The results indicate that, because of the influence of the dislocation walls, carbon-containing precipitates, and deformation twins, the cyclic hardening behavior is presented at RT. However, different from the cyclic hardening behavior at RT, the cyclic softening behavior of SS304 can be observed due to the dynamic recovery and recrystallization containing dislocation rearrangement and annihilation at 300 °C and 650 °C. In addition, two fatigue crack initiation modes are observed. At RT, the single fatigue crack initiation mode is observed. At high temperatures, multiple crack initiation modes are presented, resulting from the degradation of material properties. Furthermore, a new fatigue life prediction model considering the temperature is conducted as a reference for industrial applications. Full article

Objective: Testing the influence of various restorative materials (conventional or bulkfill composites) and filling techniques (single- or multi-layered techniques) on the in vitro marginal adaptation of large class II direct composites with supra and sub-gingival margins subjected to thermomechanical loading (TML). Methods: A total of 40 prepared teeth were attributed randomly to five experimental groups. In Group 1, restorations were made of multi-layered high-viscosity conventional composite (Tetric EvoCeram); in Groups 2 and 3, restorations were made of a high viscosity bulkfill composite (Tetric EvoCeram Bulk Fill) applied in one (Group 2) or three layers (Group 3); in Groups 4 and 5, restorations were made of a flowable bulkfill composite (SDR flow) applied in one (Group 4) or two layers (Group 5), covered with a layer of high-viscosity conventional composite (Ceram-X Universal). A single adhesive (OptiBond FL) was used in all groups. All specimens were submitted to a staged TML comprising three phases (2 × 500,000 and 1,000,000 cycles) at 50 N with 3350 thermal cycles (5 to 55 °C) every 500,000 cycles. The tooth–restoration interfaces on proximal surfaces were evaluated quantitatively by scanning electron microscopy, before and after each TML phase, hence at three timepoints (T0, T1, T2 and T3). The following segments were considered for evaluation: proximal, vertical enamel margins (assessed individually on both restoration sides), cervical enamel (restoration side above CEJ) and cervical dentin margin (restoration side below the CEJ). Results: TML induced a significant reduction in continuous adaptation at both enamel and dentin margins in all groups, with percentages of continuous margins ranging from 75.2 to 91.8% at T0, and decreasing to values ranging from 21.3 to 73.9% at T3. Both composite systems and layering protocols had a significant influence on marginal adaptation of the restorations, with statistical associations depending on the restoration group and the timepoint considered. Defective margins in enamel were all of a cohesive nature with micro-fractures, while in dentin, interfacial gaps were the main defect observed. Conclusions/Clinical significance: The present results highlighted significant degradation of marginal adaption after long-term in vitro fatigue test using materials even with high-viscosity conventional resin composites, applied with a proper layering approach in medium–large sub-gingival cavities. While no significant differences were observed at the dentin cervical margins, there was a tendency for better adaptation at the enamel margin when using a higher modulus material with a multi-layered technique. Full article

Chip seals are widely used for asphalt pavement maintenance, yet the understanding of the interaction between asphalt and aggregates embedded in the asphalt layer remains limited. This paper aims to quantify the interaction between asphalt and aggregate at the microscope level to better understand their adhesion performance in chip seals. Rubber-modified and neat asphalt models are established and verified based on various parameters, including density, viscosity, solubility, glass-transition temperature (Tg), and cohesive energy density (CED). Subsequently, nanoindentation simulation is employed to analyze the adhesion force and interface stress between aggregates and asphalt, considering different embedded depths and pull-off speeds. The adhesion energy between asphalt and silica is also calculated. The results indicate that rubber-modified asphalt exhibits lower density, CED, solubility parameters, and Tg while having higher viscosity than neat asphalt. The adhesion force and interface stress display a quadratic relationship with embedded depths and pull-off speeds. Furthermore, the bond between rubber-modified asphalt and silica is stronger than that between neat asphalt and silica. These findings advance the comprehension of asphalt–aggregate adhesion in chip seals and offer insights for optimizing chip seal design through molecular simulation, thereby potentially enhancing asphalt pavement performance. Full article

Tire–road characteristics are a critical focus of research in the automotive and transportation industries. On the one hand, the research can help optimize tires’ structural design; on the other hand, it can analyze the mechanical response of the pavement structure under the vehicle load. In addition, the non-uniformity distribution of the tire ground stress will also have a direct impact on the skid resistance, which determines the driving safety. Due to the limitation of testing technology, the measurement of tire ground pressure was mainly carried out on a flat test platform, ignoring the roughness of the actual pavement surface texture. The tire–road contact characteristics research on the macro-texture and micro-texture of asphalt pavement needs to be broken through. A high-precision pressure-sensitive film measurement system is utilized to examine the actual contact characteristics between two types of automobile tires and three types of asphalt pavement in this paper. The influence law of pavement texture and patterned tires on the contact area and stress was explored, and the concentration effect of tire–road contact stress was evaluated. The results indicate that the contact area of grounding tires exhibits a nearly linear relationship with tire inflation pressure and load. Notably, the change in load has a more significant influence on the contact area than tire inflation pressure. On asphalt pavement, the contact reduction rate decreases by approximately 5–10% for block pattern tires and 10–15% for longitudinal pattern tires. Furthermore, as the texture depth of the pavement increases, the contact area between tires and the pavement texture decreases. The actual tire–road interface experiences significant stress concentration due to the embedding and meshing effects between the tire and road surface. Even on a flat steel surface, the peak stress at the edge of the tread block exceeds the 0.7 MPa design load, which is about 2.5–3 times higher than the design uniform load. The peak stress between the tire and asphalt pavement reaches 4–10 times the design uniform load, with a rising trend as the pavement texture depth increases. This study can provide relevant experimental technical support for tire design and functional design of asphalt pavement. Full article

This study aimed to reveal the effects of the hydration products AH₃ and AFt phases on the hydration and hardening properties of calcium sulfoaluminate (CSA) cement. In addition, the effects of anhydrite ($\mathrm{C}\overline{\mathrm{S}}$) and gypsum ($\mathrm{C}\overline{\mathrm{S}}{\mathrm{H}}_2$) on the properties of CSA cement were compared. Calcium sulfoaluminate (${\mathrm{C}}_4{\mathrm{A}}_3\overline{\mathrm{S}})$ was synthesized with analytical reagents, and the ${\mathrm{C}}_4{\mathrm{A}}_3\overline{\mathrm{S}}$-$\mathrm{C}\overline{\mathrm{S}}$-H₂O system with different molar ratios of $\mathrm{C}\overline{\mathrm{S}}$ and ${\mathrm{C}}_4{\mathrm{A}}_3\overline{\mathrm{S}}$ was established. The phase compositions and contents of AFt and AH₃ were determined by X-ray diffraction (XRD), Rietveld quantitative phase analysis, and thermogravimetric analysis (TG). The effects of pore structure and hydration product morphology on mechanical properties were analyzed by mercury intrusion porosity (MIP) and scanning electron microscopy (SEM). The results showed that the compressive strength exhibited a correlation with the AH₃ content. In the case of relatively sufficient anhydrite or gypsum, ${\mathrm{C}}_4{\mathrm{A}}_3\overline{\mathrm{S}}$ has a high degree of hydration, and the AH₃ content can be considered to contribute more to the strength of the hardened cement paste. When anhydrite was selected, the combined and interlocked AFt crystals were covered or wrapped by a large amount of AH₃. The mechanical properties of the hardened cement paste mixed with anhydrite were better than those of that mixed with gypsum. Full article

In this study, the research aim is to enhance the activity index of activated coal gangue and study its activation mechanism. The activation process of coal gangue was optimized through orthogonal tests, and the Back-Propagation (BP) neural network model was improved using a genetic algorithm. With the effects of grinding duration, calcination temperature, and calcination duration, the morphological changes and phase transformation processes of coal gangue were studied at the micro and meso levels to clarify the activation mechanism. The results indicated that the effect of calcination temperature on the strength activity index of coal gangue was most significant, followed by grinding duration and calcination duration. The potential activity of coal gangue can be effectively stimulated through mechanical and thermal activation, and the content of potential active minerals in coal gangue powders was also increased. The activation process of coal gangue for the optimal scheme was obtained as grinding at 76 min first and thermal treatment at 54 min at 749 °C. As the thermal activation under 950 °C, some unstable external hydroxyls, and internal hydroxyls in kaolinite from coal gangue were removed, the Al^Ⅵ-O octahedron was destroyed, and kaolinite was transformed into spatially disordered metakaolinite with very high activity. Full article

Oil spills and chemical leakages are a serious source of pollution in oceans and rivers, and have attracted worldwide attention. Many scientists are currently engaged in the development of oil–water separation technology. In this study, the umbrella skirt of a discarded silicone rubber insulator was utilized as feedstock, and polydimethylsiloxane (PDMS) was employed to immobilize the prepared powder (FXBW) onto a polyurethane (PU) sponge skeleton. Without any modifications using chemical reagents, a novel oil–water separation material, FXBW-PU, was developed, with a water contact angle of 155.3°. The FXBW-PU sponge exhibited an absorption capacity ranging from 11.79 to 26.59 g/g for various oils and organic solvents, while maintaining an excellent selective adsorption performance, even after undergoing ten compression cycles, due to its exceptional chemical and mechanical stability. With the assistance of a vacuum pump, the FXBW-PU sponge was utilized in a continuous separation apparatus, resulting in a separation efficiency exceeding 98.6% for various oils and organic solvents. The separation efficiency of n-hexane remains as high as 99.2% even after 10 consecutive separation cycles. Notably, the FXBW-PU sponge also separated the dichloromethane-in-water emulsions, which achieved the effect of purifying water. In summary, FXBW-PU sponge has great potential in the field of cleaning up oil/organic solvent contamination due to its low preparation cost, environmental friendliness and excellent performance. Full article

Proton exchange membrane water electrolysis (PEMWE) represents promising technology for the generation of high-purity hydrogen using electricity generated from renewable energy sources (solar and wind). Currently, benchmark catalysts for hydrogen evolution reactions in PEMWE are highly dispersed carbon-supported Pt-based materials. In order for this technology to be used on a large scale and be market competitive, it is highly desirable to better understand its performance and reduce the production costs associated with the use of expensive noble metal cathodes. The development of non-noble metal cathodes poses a major challenge for scientists, as their electrocatalytic activity still does not exceed the performance of the benchmark carbon-supported Pt. Therefore, many published works deal with the use of platinum group materials, but in reduced quantities (below 0.5 mg cm⁻²). These Pd-, Ru-, and Rh-based electrodes are highly efficient in hydrogen production and have the potential for large-scale application. Nevertheless, great progress is needed in the field of water electrolysis to improve the activity and stability of the developed catalysts, especially in the context of industrial applications. Therefore, the aim of this review is to present all the process features related to the hydrogen evolution mechanism in water electrolysis, with a focus on PEMWE, and to provide an outlook on recently developed novel electrocatalysts that could be used as cathode materials in PEMWE in the future. Non-noble metal options consisting of transition metal sulfides, phosphides, and carbides, as well as alternatives with reduced noble metals content, will be presented in detail. In addition, the paper provides a brief overview of the application of PEMWE systems at the European level and related initiatives that promote green hydrogen production. Full article

The growing awareness of the environment and sustainable development has prompted the search for solutions involving the development of bio-based composite materials for insulating applications, offering an alternative to traditional synthetic materials such as glass- and carbon-reinforced composites. In this study, we investigate the thermal and microstructural properties of new biocomposite insulating materials derived from flaxseed-gum-filled epoxy, with and without the inclusion of reinforced flax fibers. A theoretical approach is proposed to estimate the thermal conductivity, while the composite’s microstructure is characterized using X-ray Computed Tomography and image analysis. The local thermal conductivity of the flax fibers and the flaxseed gum matrix is identified by using effective thermal conductivity measurements and analytical models. This study provides valuable insight into the thermal behavior of these biocomposites with varying compositions of flaxseed gum and epoxy resin. The results obtained could not only contribute to a better understanding the thermal properties of these materials but are also of significant interest for advanced numerical modeling applications. Full article

Lead-based halide perovskite nanocrystals (PeNCs) have demonstrated remarkable potential for use in light-emitting diodes (LEDs). This is because of their high photoluminescence quantum yield, defect tolerance, tunable emission wavelength, color purity, and high device efficiency. However, the environmental toxicity of Pb has impeded their commercial viability owing to the restriction of hazardous substances directive. Therefore, Pb-free PeNCs have emerged as a promising solution for the development of eco-friendly LEDs. This review article presents a detailed analysis of the various compositions of Pb-free PeNCs, including tin-, bismuth-, antimony-, and copper-based perovskites and double perovskites, focusing on their stability, optoelectronic properties, and device performance in LEDs. Furthermore, we address the challenges encountered in using Pb-free PeNC-LEDs and discuss the prospects and potential of these Pb-free PeNCs as sustainable alternatives to lead-based PeLEDs. In this review, we aim to shed light on the current state of Pb-free PeNC LEDs and highlight their significance in driving the development of eco-friendly LED technologies. Full article

Lead-free Ba_1−xSr_xTiO₃ (BST) (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.45) ceramics were successfully prepared via the solid-state reaction route. A pure perovskite crystalline structure was identified for all compositions by X-ray diffraction analysis. The basic phase transition temperatures in these ceramics were studied over a wide temperature range. A change in symmetry from a tetragonal to cubic phase was detected, which was further proven by phonon anomalies in composition/temperature-dependent Raman spectra. The incorporation of Sr²⁺ into BaTiO₃ (BT) lead to a shift in the phase transitions to lower temperatures, suppressing the ferroelectric properties and inducing relaxor-like behavior. Therefore, it was reasonable to suppose that the materials progressively lack long-range ordering. The initial second-harmonic generation (SHG) measurements demonstrated that the cubic phase of BST ceramics is not purely centrosymmetric over a wide temperature interval. We discussed the possible origin of the observed effects, and showed that electric field poling seems to reconstruct the structural ordering destroyed by the introduction of Sr²⁺ to BT. In the first approximation, substitution of Sr for larger Ba simply reduced the space for the off-central shift in Ti in the lattice and hence the domain polarization. A-site cation ordering in BST and its influence on the density of electronic states were also explored. The effect of doping with strontium ions in the BST compound on the density of electronic states was investigated using ab initio methods. As the calculations showed, doping BT with Sr²⁺ atoms led to an increase in the bandgap. The proposed calculations will also be used in the subsequent search for materials optimal for applications in photovoltaics. Full article

This paper aims to reduce power loss in electrical steel by improving its surface resistivity. The proposed approach involves introducing additional alloying elements through diffusion once the steel sheet reaches the desired thickness. Various effective techniques have been suggested and tested to enhance the resistivity of the strip. The method entails creating a paste by combining powdered diffusing elements with specific solutions, which are then applied to the steel’s surface. After firing the sample, a successful transfer of certain elements to the steel surface is achieved. The amount and distribution of these elements can be controlled by adjusting the paste composition, modifying the firing parameters, and employing subsequent annealing procedures. This study specifically investigates the effectiveness of incorporating cobalt oxide (II, III) into non-oriented silicon iron to mitigate power loss. The experimental samples consist of non-oriented electrical steels with a composition of 2.4 wt% Si-Fe and dimensions of 0.305 mm × 300 mm × 30 mm. Power loss and permeability measurements are conducted using a single strip tester (SST) within a magnetic field range of 0.5 T to 1.7 T. These measurements are performed using an AC magnetic properties measurement system under controlled sinusoidal conditions at various frequencies. The research explores the impact of cobalt oxide (II, III) addition, observing successful diffusion into the steel through the utilization of a paste based on sodium silicate solution. This treatment results in a significant reduction in power loss in the non-oriented material, with power loss reductions of 14% at 400 Hz and 23% at 1 kHz attributed to the elimination of a porous layer containing a high concentration of the diffusing element. The formation of porosity in the cobalt addition was found to be particularly sensitive to firing temperature near the melting point. The diffusion process was examined through scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDS). The results demonstrate improved power losses in the coated samples compared with the uncoated ones. In conclusion, this study establishes that the properties of non-oriented electrical steels can be enhanced through a safer process compared with the methods employed by previous researchers. Full article