Kinetics of Silicon Monoxide Ammonolysis for Nanophase Silicon Nitride Synthesis

Abstract

Silicon monoxide vapor generated from Si/SiO2 mixed‐powder compacts was used with NH3 to synthesize silicon nitride in a tubular flow reactor operated at temperatures in the range of 1300°‐1400°C. The ammonolysis of SiO with excess NH3 was very rapid, yielding three different types of silicon nitride at different longitudinal locations in the reactor: amorphous nanophase powder of an average size of about 20 nm, amorphous whiskers of a few micrometers in diameter, and α‐polycrystals. The amorphous products were heat‐treated for crystallization at temperatures between 1300° and 1560°C in a stream of dissociated NH3, N2, or N2/H2 mixture gas. When dissociated NH3 was used, nanophase powder was crystallized at 1300°C. The yield of nanophase silicon nitride from SiO varied from 13% to 43%, depending on operating conditions.