Gel-cast-foam-assisted combustion synthesis of elongated β-Si3N4 crystals and their effects on improving the thermal conductivity of silicone composites

Elongated beta-Si3N4 crystals were prepared by gel-cast-foam-assisted combustion synthesis, a combination method of gel-casting-foam method and combustion synthesis. Gel-casting-foam method was used to prepare porous green body composed of silicon powders and combustion reaction was ignited on the as-made green body. The impacts of porosity and pore structure on the phase purity and morphology of the resulting crystals are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Compared to ordinary combustion synthesis, gel-cast-foam-assisted combustion synthesis can enhance the conversion rate of silicon powder and the aspect ratio of resultant beta-Si3N4 crystals. In the silicone composites, elongated beta-Si3N4 powders were proven to be a better filler than equiaxed ones by the investigations on the resultant thermal conductivities. (C) 2012 Elsevier B. V. All rights reserved.