Atmospheric ageing of nanosized silicon nitride powders

Ambient oxidation of nanosized silicon nitride powder produced by the vapou r phase reaction of silicon tetrachloride and ammonia has been studied in t his work. Aliquots of the powder were stored in argon gas, in dry air and i n air of 80% humidity, and changes in the bulk and surface properties were investigated against the ageing time. The powder samples were characterised by wet chemical analysis, XPS, TG-MS, FTIR, XRD and TEM methods. No signif icant changes were detected on storage in argon gas for 90 days. However, i n samples stored in dry air and humid air, remarkable oxidation and formati on of N-H species were found. The particulate powder tends to agglomerate i n both dry and humid air, and this results in changes in the particle size and morphology. The nanosized silicon nitride powders therefore should be p rocessed by excluding their contact with the oxygen and moisture containing ambient atmosphere.