Bulletin of Materials Science最新文献

The multiferroic RMnO₃ (R= Rare earth) are extensively investigated because of their critically important physical properties, as well as their potential applications in spintronics. Due to their magnetocaloric properties, they are also adequate for magnetic refrigeration in the low temperature regime. Most importantly, as refrigerants, they provide an electrical insulation combined with high chemical and mechanical stability. Such critical properties at the basis of the applications mainly depend on the local structure and chemistry. Therefore, the mechanical properties of manganite perovskites RMnO₃ (R=Tb, Dy, Ho and Er) have been studied by atomic simulation using the density-functional theory (DFT) as interatomic potential implemented in the Quantum Espresso code. For each perovskite RMnO₃, the hexagonal (h-RMO) and orthorhombic (o-RMO) crystal structures have been considered, and the bulk modulus (B), the elastic constants (C_ij), the shear’s modulus (G), Young’s modulus (E), the Poisson’s ratio (ν), the Pugh’s ratio (B/G), the universal anisotropy index (A^U), and the Debye temperature (θ_D), have been calculated. As a result, a relation between the plastic behaviour and the crystal structures has been established. The perovskites RMnO₃ tend to be brittle in the hexagonal phase (1.35 ≤ B/G ≤ 1.39) and ductile in the orthorhombic phase (1.85 ≤ B/G ≤ 2.00). The high values of the Young’s modulus, 281 GPa ≤ E ≤ 300 GPa for h-RMO and 237 GPa ≤ E ≤ 251 GPa for o-RMO, indicate that the investigated systems are solid materials. The values of the Poisson’s ratio found between 0.21 and 0.28 reflect their ionic character. The values of the universal anisotropy index, 0.47 ≤ A^U ≤ 0.74 for h-RMO and 0.09 ≤ A^U ≤ 0.15 for o-RMO, indicate that their mechanical anisotropy is higher for h-RMO than o-RMO, and the elastic anisotropy is better for o-RMO than h-RMO.

H atoms in strong O–H...O hydrogen bonds having double-well potential energy contours exhibit interesting dynamic behaviour that depends primarily on the shape of the double-well potential. Effective barrier height and asymmetry between the two wells of the potential are two important criteria determining the shape of double-well potential. The Diabatic state model for hydrogen bonds is utilized here to generate the double-well hydrogen bond potential for the O–H...O hydrogen bonds of some of the well-studied hydrogen-bonded crystalline solids, namely potassium dihydrogen phosphate (KDP), tris-potassium hydrogen bisulphate (TKHS) and urea phosphoric acid (UPA). Change in crystal temperature affects the H atom dynamics uniquely in each of these chosen examples, KDP undergoes a structural phase transition at 122 K with freezing of H atom disorder in its O–H...O bonds, whereas TKHS having O–H...O bonds very similar to that in KDP exhibits no structural phase transition, and H atom disorder in TKHS continues even at very low temperatures up to 5 K, while H atom in O–H...O bonds of UPA exhibits temperature-induced mobile proton behaviour. We attempt here to understand the unique H atom dynamics in each of these crystals on the basis of temperature-induced changes in the shapes of their double-well O–H...O hydrogen bond potentials.

High-temperature vulcanized silicone rubber (HTV-SiR) insulators degrade outdoors due to their biodegradable nature. To enhance their performance, various fillers are added. This study prepared four HTV-SiR composites using micro/nano-sized silicon dioxide (SiO₂) and micro alumina tri-hydrate (ATH) fillers. The samples were tested for 5000 h in a chamber subjected to electrical and environmental stresses. Post-ageing, the integrity of the composites was assessed through different diagnostic measurements. Results showed tensile strength reductions under positive DC voltage of 32.3, 25.32, 23.56 and 20.12% for samples H₁, H₂, H₃ and H₄, respectively. Sample H₄ exhibited the lowest leakage currents, with values of 5.05 and 5.78 μA for negative and positive DC voltages, respectively. Sample H₄ was hydrophobic attaining HC2 class, while sample H₁ was the least hydrophobic, showing HC4 and HC5 classes under positive and negative DC voltages. Thermogravimetric analysis showed H₄ had the least yield loss, decreasing from 50.1% to 49.2 and 48.9% under positive and negative DC voltages, respectively. FTIR spectroscopy revealed that H₄ maintained the highest integrity in its siloxane backbone (Si–O–Si) connections, with peak reductions of 28% under positive DC stress and 10.1% under negative DC stress. SEM inspection reveals that H₁ and H₂ have significantly degraded, including white powder, cracks, fissures and a blocky structure. After 5000 h of exposure to electrical and environmental stresses, co-filled sample H₄ demonstrated superior anti-ageing performance compared to the other composites. This study underscores the importance of filler selection in enhancing the durability and performance of HTV-SiR insulators in outdoor applications.

Graphene-based materials have garnered significant attention owing to their unique physicochemical properties, exceptionally high surface area, electron mobility, thermal conductivityand mechanical strength. However, graphene has certain limitations viz., irreversible self-agglomeration, low colloidal stability, limited repeatability and non-specificity, which restricts its overall utility. Addressing these issues, functionalization of graphene has been considered as a key strategy that provides augmented properties such as water solubility, biocompatibility, catalytic activity, high surface area, electrical conductivity, and the prevention of agglomeration etc. Thus, various functional groups such as amine, carboxyl and thiol groups have been employed in the fabrication of graphene-based materials for various applications. The present review highlights the synthesis of thiol-functionalized graphene-based materials and their applications in water remediation viz., removal of heavy metal ions and dyes. Additionally, biomedical applications have been addressed in the fields of drug delivery, tumour therapy and biomedical sensors. The present article would help the investigators to develop and explore graphene-based advanced functional materials for addressing real-world issues.

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Manufacturing optimal dressings for chronic wound treatment presents a significant challenge, requiring innovative and precise application techniques tailored to specific treatment needs. This review explores the difficulties associated with chronic wound care and the benefits of hydrogel technology. Ulcers, the most prevalent type of chronic wound, are particularly challenging due to the prolonged healing times. Recent research endeavors have delineated the requisite features of ideal dressings, spurred by advancements in technology, particularly in the realm of hydrogel-based dressings and their integration with promising therapeutic elements for chronic wound care. The study leverages the unique characteristics of hydrogels that emerges as the preeminent dressing choice for fostering the healing of chronic wounds, surpassing alternative dressing options. The potential synergy between hydrogel technology and diverse therapeutic agents holds promise for developing superior hydrogel dressings, exhibiting heightened efficacy in expediting the healing process of chronic wounds.

This study hypothesizes that the separation of the three layers of polypropylene (PP) material of the medical facemasks increases the electrostatic charge (ESC) generated from their triboelectrification by air flow. The ESC increases and enlarges the electric field in front of the facemask to repel viruses. This study examined the effect of the separation of the PP layers by polymeric and metallic spacers on the magnitude of the ESC. The separation by polyurethane (PU) particles showed the highest magnitude of ESC, where PU particles made an air gap between the PP layers. Besides, the negative ESC significantly increased with increasing the air gap between the PP layers. The negative ESC was significantly amplified with the increase in the air gap between the PP layers up to 8 mm at different distances from the outer layer of the tested facemask. Therefore, we suggest that the electric field repels negatively charged viruses. Also, the presence of polyethylene (PE) would generate extra ESC on the sliding surfaces due to its electrostatic property. Using metallic spacers showed lower values of ESC than those generated for PU and PE spacers, as the metallic spacers can conduct ESC generated on the PP layers, and therefore, the total magnitude of ESC decreased. In conclusion, we recommend using PU particles as a spacer in facemasks due to their lighter weight and lower resistance to air flow.

As the use of natural biomaterials has gained more attention, many natural resources—including the tea polyphenol (TP)—have come into focus. Green tea contains a type of natural plant polyphenol, TP, which has excellent properties. These include hydrophobicity, antibacterial, antioxidant, anti-ultraviolet, antiviral, antidiabetic, anti-ageing, anticancer, antitumor and anti-inflammatory properties that others lack. In this review, we first discuss the structure and properties of TP. Furthermore, we examine recently developed TP-based advanced composite materials that incorporate polymers such as polyacrylonitrile, polyaniline, polylactic acid and polyvinyl alcohol, as well as natural materials like chitosan, starch, pomelo peel gelatin and reduced graphene oxide. This review focuses on their structure, properties, and various applications in fields such as food packaging, cosmetics, medicine, health products, and flexible strain sensors, among others.

Crop straw is a kind of renewable resource with great application potential, which has the characteristics of a wide source, abundant reserves and low price. Using straw as a raw material and a hydrothermal process to prepare high-function carbon-based material, it is an economic and green way to promote straw resource utilization. In this article, the influencing factors in the preparation process of straw hydrothermal carbon were reviewed. The influences of process parameters such as straw carbon source, hydrothermal time, hydrothermal temperature and solid–liquid ratio on the structural properties of hydrothermal carbon were emphasized. The regulation of the morphology and structure of carbon by activators such as KOH and KMnO₄ were analysed. At the same time, the application of straw-based hydrothermal carbon in the field of environmental pollution control, catalysis and electrochemistry is summarized. Finally, it is pointed out that the future research should focus on the structure control method, green activation technology of straw-based hydrothermal carbon and the preparation of hydrothermal carbon from mixed straw, and further improve the stability of the porous structure of the hydrothermal carbon and the interference-free in the practical application environment, so as to realize the commercial application of straw-based hydrothermal carbon.

Tungsten oxide (WO₃) has recently gained attention as an electrochromic material for dynamic display technologies, particularly advertising, due to its tunable optical and electrochemical properties. In this study, we compared WO₃ with titanium dioxide (TiO₂) coatings and commercial display films. WO₃ layers with thicknesses of 2, 4, and 6 nm were fabricated using a surfactant-assisted spray pyrolytic method to ensure uniformity and adhesion. TiO₂ coatings served as controls. To confirm the monoclinic phase of WO₃, X-ray diffraction was performed. Optical performance was assessed through UV–Vis–NIR transmission and reflection spectra, while electrochemical behaviour was measured using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Durability testing included monitoring transmission and charge insertion/extraction over cycling, alongside environmental stability assessments. An economic evaluation compared Material and operational costs. At 6 nm, TiO₂ films achieved a sharpness score of 70, 75% contrast and 80% colour purity, with transmittance of 55% and colouration efficiency of 0.65 cm²/C. Their switching time was 15 s, and performance degraded significantly after extended cycling, including delamination beyond 50,000 cycles. By contrast, WO₃ films showed higher transmittance (70%), faster switching (12 s), and better colouration efficiency (0.75 cm²/C). They also exhibited more stable charge density retention, improved ion mobility, and stronger current responses in voltammetry. Overall, WO₃ films demonstrated superior optical clarity, faster response, and better durability compared to TiO₂. These findings suggests that WO₃ is a promising, cost-effective material for next-generation electrochromic displays in advertising applications.

This study explores the effect of zinc oxide (ZnO) nanomaterial doping on the electro-optical properties of 5CB-coded nematic liquid crystals and predicts these properties using machine learning algorithms. We produced seven composite structures with varying ZnO doping ratios and measured their electro-optical transmittance. Furthermore, a prediction model using four different machine learning algorithms (k-Nearest Neighbors, Decision Tree, Random Forest, and Extra Trees) was developed, which predicts optical transmittance as a function of voltage and doping ratio. The Extra Trees algorithm demonstrated the best prediction accuracy, achieving an R² value of 91% on the experimental dataset. Subsequently, a new composite with a different doping ratio was then experimentally prepared and measured to validate the model, which was trained on the experimental dataset. This study highlights the utility of machine learning for predicting the electro-optical characteristics of doped liquid crystal structures, resulting in considerable time and resource savings in experimental procedures.