Study on Laser Reaction Sintering of Silicon Carbide From Slurry-Coated Silicon and Carbon
Liquid silicon infiltration of porous carbon preform has been commonly used to produce silicon carbide materials without additional sintering aids. This process starts with molten silicon encasing solid carbon followed by reactive wetting to form silicon carbide. Reaction sintering of silicon carbide from a mixture of silicon and carbon powder in slurry form was conducted using high-frequency, pulsed laser as heat source. Slurry coating was able to provide much more coherent and compact, micron-size layers compared to conventional powder coating. Since this reaction is a slow process, low scanning speed with proper power intensity allows sufficient time for silicon to melt and encase adjacent carbon particles to form β-phase silicon carbide in vacuum environment, producing a very thin layer of Si-SiC-C matrix. This encasing process causes moving and combining of particles resulting in loose bonding and high porosity of the sintered region. High laser power intensity causes bulk crystallization of silicon carbide, which results in high porosity and surface roughness. In addition, prolonged time of laser heating may cause the development of silicon-filled cracks within the continuous matrix. Future works include laser sintering of multiple layers, development of slurry coating system, post-sintering in furnace for complete conversion into full-density, alpha-phase silicon carbide.
Authors: Nanzhu Zhao, and Joseph Beaman
Conference: SAMPE Seattle 2017