Bulletin of Materials Science最新文献

A low-cost and efficient method should be developed to synthesize the stable nickel ferrites NiFe₂O₄ with the inverse spinel crystal structure, which is beneficial for improving product performance and broadening product application prospects. In the primary oxidation roasting process, nickel ferrite NiFe₂O₄ with a magnetization saturation (M_s) of 31.96 emu g^–1 and a coercive force (H_c) of 91.96 Oe was synthesized in an air atmosphere. In the secondary oxidation roasting technology, the synthesized NiFe₂O₄ with a M_s of 40.93 emu g^–1 and a H_c of 149.4 Oe had a BET surface area of 10.58 m² g^–1. The formation mechanism of nickel ferrites could be categorized in the synthesis process of NiFe₂O₄. The nickel ferrite NiFe₂O₄ was classified as an inverse spinel crustal structure. The secondary oxidation roasting process could facilitate the transformation from disordered to ordered structure and normal spinel to inverse spinel in the crystal structure of nickel ferrite NiFe₂O₄.

In this paper, we design a gradient metamaterial with a double resonance mode and measure the near-field radiative heat transfer (NFRHT) properties in 5–40 THz. The metamaterial sample achieves two NFRHT peaks based on the surface plasmon polarization (SPP) and the local surface plasmons (LSP) modes. The amplitudes and resonance positions of these NFRHT peaks are modulated by changing the gradient nanoparticles. We propose a sensing scheme based on this gradient metamaterial samples to reveal the thermal characteristics in the fabric field. The measured results verify the feasibility for expanding the applications of the metamaterials and developing new photoelectric devices.

Surface frictional drag developed by marine vessels utilizes a considerable percentage of fuel for propulsion. Superhydrophobic (SH) surface normally traps a layer of air at the interface and significantly reduces the surface frictional drag. Herein, the efficacy of the SH coating towards the surface drag reduction of the sailing boat is recognized by conducting a facile experiment where the bottom of the model boat is coated with SH additives. AlNiCo nanoparticles and nickel stearate prepared by ball-milling and co-precipitation methods, respectively, are drop-casted layer by layer over the surface of the model boat to impart SH. The fuel efficiency of the SH boat is improved by 51.49% substantiating the reduction in surface drag of the vessel. Further, the trapped air provides extra buoyancy force, enhancing the load-bearing capability of the SH boat by 5.77%.

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.