Journal of Materials Research最新文献

A thermally induced phase separation method was successfully developed to prepare spherical composite nylon 12 (PA12)/Nano-silica (Nano-SiO₂) powder. By comparing the performance of pure PA12 and composite PA12 powders, it was found that the introduction of Nano-SiO₂ can improve the sphericity of the composite PA12 powder, with a median particle size of 54–70 μm. Moreover, the presence of Nano-SiO₂ can induce the formation of more α-phase during the crystallization of PA12, and most of Nano-SiO₂ was coated by PA12 molecular chains during the solidification crystallization process, which improved the crystallization temperature and crystallinity of the composite PA12 powder. When the amount of Nano-SiO₂ was 0.3 wt%, the composite PA12 powder had the highest crystallinity, and the powder spreading performance was the best.

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Mechanism diagram of the reaction between PA12 and Nano-SiO₂. In this figure, it was found that Nano-SiO₂ was treated with silane coupling agent can form siloxane, so that amino groups were grafted to the surface of Nano-SiO₂. The amino groups can react with carboxyl groups in PA12 to form amide bonds, thereby improving the interfacial adhesion between nano silica and PA12 matrix and enhancing their compatibility. Meanwhile, by comparing the microstructure before and after addition, it was found that the addition of Nano-SiO₂ increased the sphericity of the powder, and the powder particle size increased from 55.2 to 68.71 μm.

Bioactive glass 58S (BG58S) is widely recognised for its bioactivity and antibacterial properties, making it a promising material for orthopaedic implant applications. This study investigates the effects of incorporating silver (BG58S-2.5Ag) and cerium oxide (BG58S-5C) into BG58S on early-stage bacterial adhesion and subsequent bacterial growth inhibition. Using a high-intensity ball milling approach, BG58S was modified with 5% cerium oxide (CeO₂) and 2.5% silver (Ag) nanoparticles to create homogeneous BG58S-2.5Ag and BG58S-5C nanocomposites. Custom-made biomineral probes were employed to measure the bacterial adhesion within one second of contact with Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, using Atomic Force Microscopy (AFM). The results demonstrated that BG58S-2.5Ag showed significantly stronger transient adhesion to bacteria compared to BG58S, leading to a more effective long-term antibacterial response. Additionally, it was observed that the antibacterial effect of Ag commenced within one second of contact. These findings indicate a potential correlation between the rate of bond strengthening and cell wall penetration. This study highlights the potential for enhancing the effectiveness of antibacterial implant surfaces for various biomaterial applications.

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Due to their excellent mechanical properties and biodegradability, biodegradable magnesium alloy vascular stents have become a hot topic in current research on vascular stent material. However, the further application of magnesium alloy is limited by its rapid degradation rate and insufficient ability to promote surface endothelialization. This study proposed a strategy of co-depositing a PDA-LYS coating on the surface of magnesium alloy treated with an alkaline pre-heating process. Experimental results demonstrated that the PDA-LYS composite coating significantly improved the corrosion resistance of the magnesium alloy. Furthermore, with the increase in LYS content in the samples, the coating facilitated the adhesion and proliferation of endothelial cells and effectively inhibited the excessive proliferation of pathological smooth muscle cells. In summary, the PDA-LYS composite coating had a positive impact on the biocompatibility of magnesium alloy, which has offered a new approach for surface modification of magnesium alloy vascular materials.

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This perspective—which arose from the “Distinguished Invited Speaker” series at the Materials Research Society Spring 2024 meeting—highlights five recent papers about ionogels. The title “Five-for-Five” refers to the dedication of a figure for each of the five papers. Ionogels are crosslinked polymer networks swollen with ionic liquids. Ionic liquids are interesting because they have ionic conductivity, negligible vapor pressure, high thermal and electrochemical stability. There are also many different ionic liquids to chose from. Thus, as we highlight here, it is possible to vary the concentration and composition of ionogels to make materials that are: (1) hydrophobic, (2) highly adhesive, (3) tough, (4) glassy, or (5) 3D printable. We hope this article will clearly illustrate several unique and tunable properties that are possible with ionogels while inspiring future research and applications of these remarkable materials.

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In present work polycrystalline Bi_1−xNd_xFeO₃ (X = 0.05 to 0.20 at step of 0.05) is synthesized by solid-state reaction method. Present study focuses on effect of temperature, frequency and concentration of Neodymium on BiFeO₃ structural, dielectric, magnetic and ferroelectric properties. Crystalline nature of samples confirmed by XRD. Rietveld refinement of XRD data for Bi_1−xNd_xFeO₃ shows structural transition for X = 0.20. Dielectric study shows very high value of dielectric constant i.e. (10⁵) and shows improvement in values of dielectric constant with increasing Nd amount and observed very low value (less than 20) for dielectric loss for all the samples. Magnetic study shows low value for Retentivity and maximum for X = 0.15 (0.0386emu/gm). Performed ferroelectric analysis shows that P_r has declining nature with increasing Nd concentration for all frequencies and minimum value of P_r is obtained for X = 0.15. All the properties like dielectric, magnetic and ferroelectric shows a transition in regular trend for X = 0.20.

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Multi-cycle micro-indentation tests were conducted on three polymers: Poly-ether-ether-ketone (PEEK), Poly (methyl methacrylate) (PMMA), and Poly (tetra-fluoroethylene) (PTFE). The load–displacement curve obtained from the indentation technique was used to evaluate the mechanical properties of these polymers. This study employed multi-cyclic indentation to establish a polymer fatigue model utilizing the indentation load–displacement curve. Currently, researchers are investigating fatigue life studies using stress- and energy-based approaches. Two empirical models for each approach were developed using the least-square curve-fitting method in this study. A simulation model based on finite element analysis has been utilized to verify the accuracy of these fatigue models for Vickers indentation. During the validation process, both models had a maximum error value of 2% compared to the experimental data, indicating a strong agreement with the simulation results. The generated models can evaluate polymer fatigue using non-destructive methodology.

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Magnetic particle testing is one of the popular methods to detect very small surface or near-surface defects in engineering parts. Successful defect detection depends on the physical properties of the particles. This work aims to synthesize cobalt ferrite-fluorescent polymer particles to detect finer defects located in deeper places. For this purpose, cobalt ferrite (CoFe₂O₄) nanoparticles were synthesized and the next step, fluorescence pigment was incorporated into CoFe₂O₄ nanoparticles. X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration magnetometer (VSM), and Fourier transform infrared spectroscope (FTIR) were used to examine the effects of various parameters. CoFe₂O₄ nanoparticles with a size of about 55 nm and suitable magnetic properties were chosen. The presence of pigment reduced the saturation magnetization to 25.17 emu/g, although this value is still within the suitable range. Finally, the stability of the pigment on CoFe₂O₄ nanoparticles in water was investigated, and synthesized nanocomposite was successfully used to reveal defects.

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Highly stable and bright emitting CsBr-Cs₄PbBr₆-CsPbBr₃ perovskite nanocrystals were synthesized using chemical route. For nanocrystals formed at higher Cs:Pb (10:1) ratios, multiple peak emission was observed in the UV–visible region (325–550 nm), while at lower Cs:Pb ratios (5:1 to 2.5:1), narrow high-intensity peak (at 522 nm, the signature peak of CsPbBr₃) along with a diminished broad multi-peak emission (325–500 nm) is observed. Blue-emitting nanocrystals were observed at higher Cs:Pb precursor (Pb deficient conditions) ratios. As concentration of Pb increases (Cs:Pb ratio decreases), contribution from broad emission decreases while green emitting 522 nm peak dominates. This broad emission is unique at room temperature for CsBr-Cs₄PbBr₆-CsPbBr₃ mixture of nanocrystals, unlike the single peak narrow emission reported in literature so far for inorganic lead halide perovskites. It is worth mentioning that the CsBr-Cs₄PbBr₆-CsPbBr₃ mixture of nanocrystals is highly stable and hence can be used for various optoelectronic applications.

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The hot workability of Ni–25Cr–14W alloy is studied through isothermal hot compression tests in the temperature (T) range of 1000–1200 °C and in the strain rates(ε̇) of 0.001–10 s⁻¹ in a thermomechanical simulator. Flow stress data show stable flow curves at T > 1050 °C and ε̇ < 0.1 s⁻¹. The values of flow stress decrease with increase in T or decrease in ε̇. Based on processing map, safe region for hot workability has been identified in the temperature range of 1000–1200 °C and ε̇ of 0.001–0.1 s⁻¹ with maximum efficiency(η) of ~ 44% at 1175 °C and 0.001 s⁻¹. Dynamic recrystallization has been identified as the softening mechanism operating in the material at high temperature and lower ε̇. Incomplete recrystallization of the microstructures was noted during multi-step forging by varying T or ε̇, indicating the importance of maintaining the same during industrial processing.

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Diamond/graphene (carbon sp³-sp²) interfaces exhibit various interesting and potentially useful electronic phenomena. The present work demonstrates the possibility of obtaining novel neuromorphic photodevices using such junctions. Junctions were found to show different photoconductivity relaxation behavior depending on their growth conditions such that various optoelectronic properties were observed. In particular, interfaces exhibiting shorter relaxation times could be used to construct image recognition devices mimicking short-term memory functions of the human brain. Using these devices, images of the hand-written numerals 0 through 9 could be optoelectronically recognized with an accuracy on the order of 80%, demonstrating both photo-detection and processing functions in a single device. These results suggest that novel image processing devices could be produced using graphene/diamond heterojunctions.

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