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Single-crystalline-like stainless steel 316L with different geometries fabricated by laser powder bed fusion
摘要： In this study, we explored the feasibility of fabricating single-crystalline or single-crystalline-like stainless steel 316L (SS316L) with different geometries (thin struts, cubes, walls and a simulated pump impeller) using laser powder bed fusion (LPBF). The LPBF-fabricated SS316L thin struts possessed a single-crystalline core featuring a ?110? ∥ building direction (BD) crystallographic texture. The cubes, walls and the pump impeller preserved this ?110? ∥ BD texture and also exhibited a well-defined single-crystalline-like {110}?001? Goss texture. Cellular sub-grain structures with their primary dendrite arm spacing (PDAS) values smaller than 1 μm were discovered in all the samples with their growth directions showing a 45° angular deviation from the BD. Nanoscale precipitates and dislocations were also found in the cellular sub-grain structures of the thin struts. The mechanical properties of different geometries (the thin struts, the walls, and the simulated pump impeller) were studied and compared. The anisotropic mechanical responses of the walls and the simulated pump impeller were correlated with their crystallographic textures.
关键词： Single crystal,Geometries,Crystallographic texture,Laser powder bed fusion,Mechanical properties,Stainless steel 316L
更新于2025-09-23 15:19:57
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Microstructure and mechanical properties of a MoSi2-Mo5Si3 eutectic composite processed by laser surface melting
摘要： Laser surface melting (LSM) of a single-crystal substrate of a MoSi2-Mo5Si3 eutectic composite has been performed to check the feasibility of mechanical property improvement through microstructure re?nement and seeded growth of the eutectic composite on top of the seed composite single crystal by additive manufacturing processes using scanned laser beam. LSM is proved to be capable of obtaining a eutectic composite maintaining the eutectic script-lamellar microstructure as well as crystallographic orientations of the substrate single crystal. The eutectic script-lamellar microstructure is considerably re?ned from several micrometers (the substrate) to several tenths nanometers (43 ± 7 nm) after LSM processing while maintaining the orientation relationship. Due to the microstructure re?nement, the hardness increases by about 38% from 11.60 ± 0.04 GPa (substrate) to 15.96 ± 0.42 GPa (LSMed region) and the fracture toughness increases by about 34% from 3.8 ± 0.3 MPa m1/2 (substrate) to 5.1 ± 1.5 MPa m1/2 (LSMed region).
关键词： Mechanical properties,Microstructure,Molybdenum silicides,Laser processing,Eutectic composites
更新于2025-09-23 15:19:57
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Photoinduced Regulation of the Heat Resistance in Polymer Networks with Diarylethene-Conjugated Reversible Covalent Cross-Links
摘要： A cross-linker with a diarylethene-conjugated Diels?Alder adduct (DAE/DA) was synthesized and applied in a radical polymerization system to afford polymer networks whose dynamic nature can be changed reversibly by photo-irradiation. Free-radical polymerization of hexyl methacrylate and the DAE/DA-based cross-linker furnished an insoluble and transparent poly(hexyl methacrylate) network with DAE/DA moieties at their cross-linking points, which undergo de-cross-linking via a thermally induced retro-DA reaction upon heating. The photoregulation of such a thermal de-cross-linking reaction in DAE/DA-based polymer networks was demonstrated by swelling experiments and tensile tests, revealing drastic changes in the heat resistance and mechanical properties upon exposure to UV?vis irradiation.
关键词： heat resistance,mechanical properties,polymer networks,diarylethene,photo-irradiation,Diels?Alder adduct
更新于2025-09-23 15:19:57
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DFT study of SmXO <sub/>3</sub> (X = Al and Co) for elastic, mechanical and optical properties
摘要： The first-principles study of cubic perovskites SmXO3 (X=Al and Co) for elastic, mechanical and optical properties is done in the framework of density functional theory (DFT). Optimized structural parameters are obtained first to find mechanical and optical properties of the materials. These obtained structural parameters are in accordance with the published data. The cubic elastic parameters C11, C12 and C44 are then calculated by using generalized gradient approximation (GGA) as an exchange correlation functional in Kohn–Sham equations. Poisson’s ratio, shear modulus, Young’s modulus and anisotropic factor are deduced from these elastic parameters. These compounds are found to be elastically anisotropic and SmAlO3 is brittle while SmCoO3 is ductile. Their covalent nature is also discussed by using Poisson’s ratio. In addition, optical properties like absorption coefficient, extinction coefficient, energy loss function, dielectric function, refractive index, reflectivity and optical conductivity are studied. This study predicts that SmAlO3 and SmCoO3 are suitable for optoelectronic devices.
关键词： mechanical properties,optical properties,perovskites.,elastic constants,DFT,optical constants
更新于2025-09-19 17:15:36
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Efficiency Improvement of Cellulose Derivative Nanocomposite Using Titanium Dioxide Nanoparticles
摘要： TiO2 nanoparticles were incorporated into hydroxypropyl methylcellulose (HPMC) nanocomposites films. The nanocomposites were investigated in relation to their structural, mechanical, and surface properties using scanning electron microscopy (SEM). The water solubility of the films showed a small decrease with respect to the nanocomposites films' content of the TiO2 nanoparticles. Incorporation of TiO2 nanoparticles in the films improved their mechanical and barrier properties significantly. SEM images showed that the lower concentration of nanoparticles were better dispersed in the nanocomposite matrix. The disk diffusion studies revealed a great bactericidal effectiveness for nanocomposite films containing smaller concentration of particles. In general, it was observed that the incorporation of the nanoparticles positively affected the structural properties and enhanced the antibacterial applications of the nanocomposites.
关键词： Biomaterial,Nano-Structures,Polymer-Matrix Composites,Mechanical Properties
更新于2025-09-19 17:15:36
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Influence of Heat Treatments on Microstructure and Mechanical Properties of Ti–26Nb Alloy Elaborated In Situ by Laser Additive Manufacturing with Ti and Nb Mixed Powder
摘要： In the present work, a Ti–26Nb alloy was elaborated in situ by laser additive manufacturing (LAM) with Ti and Nb mixed powders. The alloys were annealed at temperatures ranging from 650 °C to 925 °C, and the effects of the annealing temperature on the microstructure and mechanical properties were investigated. It has been found that the microstructure of the as-deposited alloy obtained in the present conditions is characterized by columnar prior β grains with a relatively strong <001> fiber texture in the build direction. The as-deposited alloy exhibits extremely high strength, and its ultimate tensile strength and yield strength are about 799 MPa and 768 MPa, respectively. The annealing temperature has significant effects on the microstructure and mechanical properties of the alloys. Annealing treatment can promote the dissolution of unmelted Nb particles and eliminate the micro-segregation of Nb at the elliptical-shaped grain boundaries, while increasing the grain size of the alloy. With an increase in annealing temperature, the strength of the alloy decreases but the ductility increases. The alloy annealed at 850 °C exhibits a balance of strength and ductility.
关键词： microstructure,Ti–Nb alloy,mechanical properties,in situ alloying,laser additive manufacturing,heat treatment
更新于2025-09-19 17:15:36
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Thermal Stability of WB2 and W–B–N Films Deposited by Magnetron Sputtering
摘要： The work is mainly to study the thermal stability including the phase stability, microstructure and tribo-mechanical properties of the AlB2-type WB2 and W–B–N (5.6 at.% N) films annealed in vacuum at various temperatures, which are deposited on Si and GY8 substrates by magnetron sputtering. For the WB2 and W–B–N films deposited on Si wafers, as the annealing temperature increases from 700 to 1000 °C, a-WB (700 °C) and Mo2B5-type WB2 (1000 °C) are successively observed in the AlB2-type WB2 films, which show many cracks at the temperature ≥ 800 °C resulting in the performance failure; by contrast, only slight α-WB is observed at 1000 °C in the W–B–N films due to the stabilization effect of a-BN phase, and the hardness increases to 34.1 GPa first due to the improved crystallinity and then decreases to 31.5 GPa ascribed to the formation of α-WB. For the WB2 and the W–B–N films deposited on WC–Co substrates, both the WB2 and W–B–N films react with the YG8 (WC–Co) substrates leading to the formation of CoWB, CoW2B2 and CoW3B3 with the annealing temperature increasing to 900 °C; a large number of linear cracks occur on the surface of these two films annealed at ≥ 800 °C leading to the film failure; after vacuum annealing at 700 °C, the friction performance of the W–B–N films is higher than that of the deposited W–B–N films, while the wear resistance of the WB2 films shows a slight decrease compared with that of the deposited WB2 films.
关键词： AlB2-type WB2 films,Thermal stability,W–B–N films,Magnetron sputtering,Mechanical properties
更新于2025-09-19 17:15:36
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Novel conducting PVA/Carbon quantum dots (CQDs) nanocomposite for high anti-electromagnetic wave performance
摘要： Novel conductive PVA/CQDs nanocomposite films were synthesized through the casting technique for the electromagnetic (EM) wave protection at microwave band. The surface morphology, thermal and mechanical properties were briefly studied. The SEM micrograph showed an excellent distribution, dispersion and a high adhesion property of the CQDs in the PVA chains. Also, DSC analysis showed an increase in the glass temperature (Tglass) from 83.2 °C for fresh PVA to 95.4 °C for 8 wt% of CQD and the increase in melting temperature from 215 °C for fresh PVA to 227.7 °C for the same CQDs concentration. It was found that Young's modulus is directly proportional to CQD nano-particles concentration in the nano-composites from 0.14 GPa for fresh PVA to 4.48 GPa for 8 wt% of CQDs. It was found that the strength at break increases, but the elongation declines with the increase of CQDs nano-particles. The EM shielding effectiveness (SE) of (PVA/CQDs) nanocomposite is measured in the microwave frequency range, and it is found around 36.8 dB with the CQDs concentration (8 wt%). Finally, the PVA/CQDs nano-composite is of promising potential applications in electronics and microwave devices at an affordable cost.
关键词： PVA,Mechanical properties,Electromagnetic shielding,Thermal properties,CQDs nano-particles
更新于2025-09-19 17:13:59
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Crystal Growth and Structure-Property Optimization of Thermally Annealed Nanocrystalline Ga2O3 Films
摘要： The effects of thermal annealing on the crystal chemistry, crystallization process, index of refraction, mechanical properties, and electrical characteristics of nanocrystalline Ga2O3 films was evaluated. Ga2O3 thin films were sputtered onto Si(100) substrates at 500 oC utilizing a Ga2O3 ceramic target, while post-deposition thermal annealing was performed between a range of 500-900 oC. Both structural quality and packing density of the Ga2O3 films was improved by the thermal annealing as indicated by the X-ray diffraction and ellipsometry studies. The atomic force microscopy analysis indicates that the annealing temperature has a dramatic effect on surface roughness, especially when the annealing temperature exceeds 700 oC. Corroborating with structure and morphology changes, the high values of hardness and elastic modulus are noted for Ga2O3 films annealed at higher temperatures (800-900 oC). Index of refraction (n) and extinction coefficient (k) results, and their dispersion profiles indicate that the annealing temperature strongly influences the optical properties. The refractive index values vary in the range of 1.78–1.84 (632 nm) due to gradual improvement of structural quality, texturing and packing density upon thermal annealing. A correlation between annealing temperature, optical and electrical characteristics in Ga2O3 films is established.
关键词： Mechanical Properties,Sputter-deposition,Annealing,Electrical Properties,β-Ga2O3 Films,Crystal Chemistry
更新于2025-09-19 17:13:59
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Low power direct laser-assisted machining of carbon fibre-reinforced polymer
摘要： The direct laser-assisted machining (DLAM) technique is introduced to improve the CFRP machining process. The DLAM technique applies focused laser at the tool edge through a sapphire tool. A fibre laser with 4.3 W power was used to have the desired temperature, estimated from the finite element model. Experimental orthogonal cutting tests were performed to compare the DLAM technique to the conventional dry cutting of the woven CFRP. We have observed reduced cutting forces in both in-plane and side cutting orientations. Observations with 3D surface profilometer also showed a decrease in defects and improved surface roughness when DLAM was applied.
关键词： CFRP machining,thermo-mechanical properties,Laser assisted machining
更新于2025-09-19 17:13:59