Thermal shock tests of β-SiC pellets prepared from laser synthesized nanoscale SiC powders

Nanoscale SiC powders, produced by laser synthesis from gaseous precursors, have been successfully used to prepare sintered pellets. All the sintered samples showed the low temperature β-SiC structures and presented an enhanced thermal conductivity (>20%) with respect to materials prepared from commercial powders. Samples hardness and toughness, comparable with commercial products, confirmed the good samples quality. The thermal shock tests have been performed by irradiating the pellets with a Nd-YAG pulsed laser (pulse duration and energy: 0.25 μs and 0.18 J or 0.4 ms and 0.65 J). The laser fluence (power density) was increased by reducing the spot size, up to the appearance of a visible surface damage. The threshold values for the structural damage were quantified using a heat flux parameter φabs√(t)p. The measured threshold value rose from ca. 20 MW/m2√(s) for the best materials prepared from commercial SiC powders to ca. 24 MW/m2√(s) for the newly developed β-SiC. (orig.)