分类: 材料科学 >> 材料科学(综合) 提交时间: 2022-10-06
摘要: A novel hybrid laser additive manufacturing process based on laser shock modulation of molten pool was proposed in this work. The flow behavior residual stress, and microstructure of the molten pool were comprehensively characterized by a combination of experiments and simulations. The relationship between the convection behavior, evolution of microstructure, and enhancement of residual stress induced by laser shock modulation was established. Laser shock modulation assisted additive manufacturing process exhibits high efficiency in residual stress control. The hidden mechanism in microstructure evolution and residual stress enhancement was expected to be related to intensified molten pool convection, uniform solute distribution and improved cooling rate induced by shock wave. The hybrid additive manufacturing process strategy based on laser shock modulation provides a new approach for heat and mass modulation in hybrid manufacturing.
分类: 物理学 >> 凝聚态:电子结构、电、磁和光学性质 提交时间: 2022-04-30
摘要: Strain engineeringof 2D materials is capable of tuning the electrical and optical properties of the materialswithout introducing additional atoms. However, there are still great challenges in realizing strainingof 2D materials with CMOS compatibility. Here, a method for large-scale ultrafast strain engineering of CVD-grown 2D materials is proposed. We introduce locally non-uniform strains through the cooperative deformation of materials and metal/metal oxide core/shell nanoparticles through cold laser shock. Raman and PL spectrareveal that the tensile strain of MoS2changes and the band gap decreases after laser shock. MD simulations are used to investigate the mechanism of the ultrafast straining of CVD-grown 2D materials. Field effect transistors of CVD MoS2were fabricated, and the performances before and after straining of the same devices are compared. By adjusting the strain level of MoS2, the field effect mobility can be increased from 1.9 cm2V-1s-1 to 44.1 cm2V-1s-1. This is the maximum value of MoS2FETs grown by CVDwith SiO2as dielectric. As an environment-friendly, large-scale and ultra-fast manufacturing method, laser shock provides a universal strategy for large-scale adjustment of 2D materials strain, which will help to promote the manufacturing of 2D nano electronic devices and optoelectronic devices.