Study On Process And Mechanism Of Microwave Synthesis SiC Powers By Flaky Carbon Source

Microwave heating has the advantages of fast,environmental protection and energy saving.The synthesis of silicon carbide（SiC）by microwave heating technology has been the focus of research at home and abroad.However,current microwave-synthesized SiC carbon sources are granular.During the heating process,Granular carbon source absorbs microwave and generates diffuse heat.Limited and unconcentrated heat conduction leads to a longer synthesis cycle of SiC.In this study,graphite paper was used as a flake carbon source.A sol-gel method was carried out to coat SiO₂ on SiC seed by hydrolysis of tetraethoxysilane（TEOS）as silicon source.Two kinds of powder forming methods were designed to prepare pre-sintered samples and SiC were synthesized by microwave heating.The effects of heating temperature,graphite paper layer number,seed content and holding time on the synthesis of SiC by microwave heating were studied.The heating mechanism of microwave synthesis of SiC from Flaky carbon sources is described.The results demonstrate that the heating temperature affects the synthesis of SiC.Needle-like SiC whiskers were synthesized at 1300°C and rod-hammer-shaped SiC whiskers were synthesized at 1400°C.At a heating temperature of 1500°C,SiC whiskers were oxidatively decomposed into SiC particles.The number of graphite paper layers involves the synthesis of SiC.SiC particles and Si nanowires were formed under5 layers of graphite paper.At 30 layers of graphite paper,SiC whiskers with a length of10¹5μm and a width of 0.8¹μm were synthesized.Seed content influences the synthesis of SiC.At 0 wt%seed contents,the morphology of SiC was flower cluster.SiC nanowires were synthesized with 2 wt%seed contents.The holding time touches the synthesis of SiC.The rod-like SiC was synthesized under 30 min holding time.A long incubation time of 120 min result in oxidative decomposition of the SiC.In the microwave heating process,both the thermal effect and the non-thermal effect contribute to the microwave heating synthesis of the SiC crystal.Compared with the restricted heat conduction mode,the SiC growth is relatively intact in the unrestricted heat conduction mode.