Laser synthesis of nano powders of Si-based nitrides and carbides

摘要

Amorphous Si{sub}3N{sub}4, Si/N/C and crystalline SiC nano-powders, 5-50 nm in mean diameter, with yields of 250 g/h were synthesized via laser induced gas phase reactions flow cost hexamethyldisilazane (HMDS)and NH{sub}3(or H{sub}2).Reactionflame temperatures, which were controlled by the total gas flow rate, greatly influenced powder composition and crystallinity. Amorphous Si{sub}3N{sub}4 powders (96wt%) were obtained at l000°C flow HMDS+NH{sub}3; β-SiC (93wt%) was formed at 1600°C withH{sub}2. Amorphous Si/N/C powders with various N/C ratios (0.1-6) were synthesized at various temperatures. The main impurities in the powders were the organo-ligands such as NH{sub}x and CH{sub}x (X= 1-3) whose existence also resulted in a strong surface absorption of oxygen. Commercial production technologies of above mentioned powders were also stated.