Journal of Materials Research最新文献

In this study, glass transition and crystallization of Ce₆₈Al₁₀Cu₂₀Co₂ bulk metallic glass at heating rates ranging from 0.083 to 14,000 K/s, covering six orders of magnitude, are investigated. For the glass transition, two linear regions with different apparent activation energies (E_a,g) are distinguished by a critical heating rate of 2000 K/s: E_a,g decreases from 208.7 to 67.3 kJ/mol with the increase of heating rate. During the crystallization, the nucleation rate and crystal growth rate between T_g and T_m are calculated. According to their dependence on temperature, the contact angle for the nucleation of Ce crystals is estimated at 11–14 degrees. For the crystal growth, a maximum crystal growth rate of 0.03 m/s is found at 0.97 T_m. Moreover, the breakdown of the Stokes–Einstein equation in the deeply undercooled melt is observed, where the diffusivity is related to viscosity by D ∝ η^−0.865.

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Expanded polystyrene spheres (EPS) were coated by SiO₂–TiO₂ or TiO₂ for application as a fluidized bed in the photocatalytic reactor. Silica coating was realized by the sol–gel process carried out in a vacuum evaporator at 60–70 °C. The most uniform and thin layer of silica coating was obtained by the Stöber method based on the hydrolysis of tetraethyl orthosilicate (TEOS) catalysed by an ammonia solution. Effective TiO₂ coating was obtained by the immersion of EPS in the titania aqueous suspension and evaporation of water in a vacuum evaporator. Heating of EPS spheres coated by SiO₂, TiO₂ or SiO₂–TiO₂ at the temperatures of 120–140 °C resulted in a shrinkage of their volume. For the thick layer coating, a strong corrugation of EPS surface was observed. The photocatalytic tests showed, that highly corrugated surface of coated EPS slowed down ethylene decomposition, whereas a thin layer coating of both, SiO₂ and TiO₂ was advantageous.

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The present study investigated drug-loaded, titanium alloy (Ti6Al4V) graded porous structure with desired mechanical properties for implant-based local drug delivery application. The fabricated graded porous metallic structures displayed compressive yield strength in a range of 110.8–283.8 MPa, open porosity 30.2–69.4% and Young’s modulus 2.2–12.1 GPa. These characteristics resemble the range for human bone tissue. The electrochemical corrosion behaviour of the fabricated structures was found satisfactory even though comparatively higher corrosion rate was observed in porous samples. The analysis showed the formation of protective passive layer on the exposed surface of the porous samples. The micrographs confirmed the presence of well-distributed interconnected pores in the peripheral region of the samples which were used to load drug (simvastatin) using different dispersion media. It was found that by varying the later, the in vitro release of loaded drug can be prolonged to as long as 14 days.

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A novel pH-responsive drug carrier for the delivery of specific Docetaxel (DTX) administration is developed based on a zeolitic imidazolate framework (ZIF-8). Aminating the surface of ZIF-8 is allowed for the conjugation of folic acid (FA). Several spectroscopic studies characterized the newly fabricated DTX-encapsulated folic acid-embedded ethylene diamine (ED) ZIF-8 nanocomposites (DTX/FA@ED-ZIF-8). It has excellent chemical stability and high drug-loading efficiency. DTX from the folic acid-embedded aminated ZIF-8 (FA@ED-ZIF-8) is three-fold more efficient under acidic pH (5.0) than in physiological settings (pH 7.4), according to in vitro drug release tests. DTX/FA@ED-ZIF-8 exhibited cytotoxicity of 76.8% in an MTT experiment conducted in A549 and H1299 cells. Cell morphological and nuclear staining were investigated in the fabricated samples to support the MTT experiments. Further, the apoptosis mode of cell death was examined using Annexin V-FITC and PI by flow cytometry. These findings indicate that FA@ED-ZIF-8 holds great potential as a drug carrier for precise dosing.

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The cage-like CdS/MgFe₂O₄ Step-scheme heterojunctions (S-scheme heterojunction) material was synthesized by loading CdS onto the surface of magnetic MgFe₂O₄. The crystal structure, morphology and properties of the catalyst were fully characterized, and the photocatalytic performance of the catalyst was investigated by photodegradation of tetracycline hydrochloride (TCH). The crystalline structure of CdS/MgFe₂O₄ is dominated by the cubic spinel structure of MgFe₂O₄ with a hollow cage morphology. CdS and MgFe₂O₄ form a tight-binding S-scheme heterostructure, which can accelerate the recombination of ineffective charge carriers and promote the separation of the effective charge carriers via the internal electric field, enabling CdS/MgFe₂O₄ to maintain an optimal redox potential. Compared with pure CdS and MgFe₂O₄, CdS/MgFe₂O₄ is more effective on degradation of TCH. Moreover, magnetic separation, recovery, and recycling of the composite catalyst can be achieved without secondary contamination by using the magnetic properties of the CdS/MgFe₂O₄.

Abstract

Pt-based intermetallics exhibit distinctive physicochemical properties for electrocatalytic and thermocatalytic applications. It has been recognized that their catalytic performance is determined by their composition, configuration and surface structure. In this review, we summarize the advancements in the structural optimization of Pt-based intermetallic catalysts. We first introduce the crystal structures of Pt-based intermetallics, followed by a recapitulation of the thermodynamic and kinetic theory used to achieve these structures. Then, the optimization strategies, including ordering approaches and crystal regulation methods, are summarized. Furthermore, we delve into a discussion on the enhanced catalytic functions of Pt-based intermetallics in electrocatalysis and thermocatalysis. Finally, we outline future research directions focused on the practical industrial applications. We believe this review can inspire further exploration of materials for catalytic applications.

In this work, ultrafine grained commercially pure titanium (Cp-Ti) was developed using repetitive corrugation and straightening (RCS) process. The optical micrographs revealed a 90% grain refinement of processed sample to 5 µm from initial size of 50 µm. The microhardness value revealed a 44.70% increase in hardness from 170 to 246 HV. The ultimate tensile strength was found to be 589 MPa which is 37% more than the as-received sample. The contact angle (45.3°) of processed sample exhibits the hydrophilic behavior of processed sample. This further facilitated the enhanced protein adsorption and cell attachment in the samples which was instantiated by the biocompatibility studies. The in-vitro bioactivity study was conducted on the immersed samples in simulated body fluid and a dense apatite growth with a Ca/P ratio of 1.66 was observed. Hence, RCS processed Cp-Ti is suggested as a potential candidate for load bearing applications.

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Finding eco-friendly solvents that can replace conventional toxic ones (N-methyl-2-pyrrolidone and dimethylacetamide) in the production of polymeric membranes is of great interest. In this study, membranes were produced using the phase inversion technique using polysulfone, polyvinylpyrrolidone, and Cyrene—a recently developed solvent, whose physicochemical profile is comparable to conventional ones, but is biodegradable, non-toxic, and eco-friendly. The resulting membranes were characterized regarding their morphological and structural properties, permeation performance, rejection of reference solutes and an emerging contaminant, and antifouling performance. Scanning electron microscopy, contact angle determination, Fourier transform infrared spectroscopy, and filtration tests were accomplished for that. It was possible to use Cyrene to produce polysulfone-based membranes, in which the one with 5% polyvinylpyrrolidone was the membrane with the highest permeability. Conversely, the membrane without polyvinylpyrrolidone and with a 30-min heat treatment achieved 73% rejection of the emerging contaminant evaluated.

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Inspired by the internal spiral structure of the mantis shrimp claw rod, a new type of beam-shaped composite materials with spiral-layered arrangement were designed, and the corresponding strengthening and toughening mechanisms with different spiral arrangement modes were explored. It is found that, unlike the existing shells or plates with spiral structures, a smaller spiral angle is of great significance to coordinate the contradiction between strength and toughness of beam materials. As the angle changes (small spiral angle), the full-field distribution of each stress component will undergo significant changes, leading to a transformation of the key stress components that dominate the damage and failure behavior. By adjusting the spiral angle, certain normal stress components inside can be reduced to improve the strength, and certain shear stress components can be increased to improve the toughness. These results will provide optimization strategies for the mechanical design of beam.

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The beam with an internal structure of spiral laminated fiber has been designed. Its strength and toughness can be regulated and optimized by the stress distribution and the deformations and failure behavior controlled by the spiral angle.

This study focuses on synthesizing and characterizing Mg-doped SnO₂ nanoparticles as a safe substitute for lead-based X-ray shielding aprons. Various molar weight percentages of Mg dopant were utilized during synthesis, and the resulting samples were analyzed using multiple techniques, such as X-ray diffraction, UV–visible, Photoluminescence, Raman spectroscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission and scanning electron microscopes. The nanoparticles were then combined with a nano-epoxy polymer composite and coated onto rexine cloth through drop casting. To assess the X-ray shielding performance, the percentage of attenuation, attenuation coefficient, and half-value layer studies were conducted. Comparative analysis with traditional lead oxide (PbO) aprons revealed that the 3% Mg-doped SnO₂ nanocomposite aprons exhibited superior X-ray attenuation properties. In summary, this study highlights the potential of Mg-doped SnO₂ nanoparticles as an effective, hydrophobic, and lightweight alternative to commercial aprons that are made of toxic, hydrophilic, and heavy lead-based materials.

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