Atmospheric ageing of nanosized silicon nitride powders

• Published in: Journal of materials chemistry 2001-01, Vol.11 (3), p.859-863
• Main Authors: SZEPVÖLGYI, Janos, MOHAI, Ilona, GUBICZA, Jenö
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Powders
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/b008429h

Silicon nitride powders produced in high temperature thermal plasmas by vapor phase reaction have many interesting properties, including high purity, mainly amorphous microstructure, and a mean particle size in the nanometer range. No hard agglomerates are formed in these powders. With high sintering activity, these powders are attractive precursors for advanced silicon nitride ceramics with good mechanical properties. Ambient oxidation of nanosized silicon nitride powder produced by the vapour phase reaction of silicon tetrachloride and ammonia has been studied in this work. Aliquots of the powder were stored in argon gas, in dry air and in 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 significant changes were detected on storage in argon gas for 90 days. However, in samples stored in dry air and humid air, remarkable oxidation and formation of N-H species were found. The particulate powder tends to agglomerate in both dry and humid air, and this results in changes in the particle size and morphology. The nanosized silicon nitride powders therefore should be processed by excluding their contact with the oxygen and moisture containing ambient atmosphere.