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

Elongated β-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 β-Si3N4 crystals. In the silicone composites, elongated β-Si3N4 powders were proven to be a better filler than equiaxed ones by the investigations on the resultant thermal conductivities.

► Elongated β-Si3N4 crystals were prepared by gel-cast-foam-assisted combustion synthesis.
► Gel-casting-foam method was used to prepare porous green body composed of silicon powders.
► The save of diluents can increase the yield rate significantly.
► The pores also provide more room for crystal growth and more elongated particles are obtained.
► As-made elongated β-Si3N4 powder can help enhance the thermal conductivity of the silicone composites by over 30%.