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Atomic-scale simulations of ideal strength and deformation mechanism in β-SiC under H/He irradiation
摘要： We ?rstly investigated the mechanical responses of β-SiC to the tensile and shear strains under H/He irradiation using density functional theory, with a speci?c focus on the atomistic mechanism of deformation and fracture. The results revealed that the e?ect of introducing H/He on ideal strengths of tension and shear is limited, due to the strong sp3 bonds of Si-C. However, somehow large disparity in failure was discovered after introducing H/He. Under the tension, all Si-C bonds along the tensile direction are synchronously broken, causing cubic-to-graphitic transformation in the perfect β-SiC, in contrast to the asynchronous breakage of Si-C bonds in the H/He-doping systems. Under the shear, H- and He-doping systems display individual cleavage-like modes of lattice instability, respectively, whereas structural transformation by re-bonding new Si-C bonds is responsible for the failure in the perfect β-SiC. The cleavage-like modes were discussed, combining a detailed analysis of electronic structure. The mechanical response to H/He irradiation distinguishes β-SiC from conventional metals presently applied in nuclear industry. The study may provide a clue for new design strategy of irradiation-tolerant materials for energy applications.
关键词： Ideal strength,H/He irradiation,Deformation mechanism,β-SiC ceramic
更新于2025-09-23 15:23:52
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Effects of Microsphere Size on the Mechanical Properties of Photonic Crystals
摘要： Photonic crystal (PC) thin films that are self-assembled from different-sized silica microspheres were prepared for studying mechanical properties via nanoindentation at the submicron scale. We found that the silica photonic crystals (PCs) possessed a face-centered cubic (FCC) microstructure and their elastic modulus and hardness were in the range of ~1.81–4.92 GPa and 0.008–0.033 GPa, respectively. The calculated results proved that there were size-dependent properties in the silica PCs, in that the elastic modulus and hardness increased as the diameter decreased from 538 nm to 326 nm. After studying the total work and plastic work in the progressive deformation of silica PCs during the nanoindentation tests, we developed a two-stage deformation model to explain how the microsphere size affects the mechanical properties of PC thin films. The phenomenon of 'smaller is stronger' is mainly due to the energy consumption, which combines the effects of microstructure collapse, microsphere slide, and reduced porosity during the whole loading and unloading process. In addition, the results of numerical simulation matched the experimental data and reflected the energy change rules of PCs during the indentation process. Furthermore, the study affords useful guidance for constructing high-performance films with proper design and potential application in next-generation PC materials.
关键词： photonic crystals,deformation mechanism,nanoindentation,size-dependent
更新于2025-09-23 15:22:29
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Manufacturing profile-free copper foil using laser shock flattening
摘要： Copper foil is a key material of printed circuit boards and plays an important role in the conductance of electric circuits and interconnection of electronic components. When high-frequency signals were transmitted in rough copper foil wires, the conductor resistance, wire loss, and signal loss increased because of the skin effect. To reduce the negative influence of the skin effect and improve the quality of the copper foil, a laser shock flattening (LSF) method was proposed to manufacture profile-free copper foil with high performance. It was concluded that the better flattening effect for large-area profile-free copper foil could be achieved at a pulse energy of 0.25 J and an overlap rate of 25%, and its surface roughness decreased by 67.0% from 52.1 nm to 17.2 nm. Subsequently, to determine the mechanism for the flattened deformation of copper foil induced by LSF, the microstructures of the copper foil before and after flattening were characterised using transmission electron microscopy. A higher dislocation density and a few deformation twins were found in the profile-free copper foil. Ultimately, nano-indentation, micro-tensile, and electrochemical corrosion tests indicated that the mechanical properties and corrosion resistance of the copper foil were significantly improved by LSF. This technique would enable the successful fabrication of large-area profile-free copper foil with high performance for the emerging applications of ultra-high-frequency signal communication and printed circuit board manufacture.
关键词： Corrosion resistance,Mechanical properties,Flattened deformation mechanism,Microstructures,Laser shock flattening,Profile-free copper foil
更新于2025-09-23 15:21:01