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Silicon nitride is one of the leading candidate materials for next generation gasifiers because of its exceptional high temperature properties, which include strength, wear and oxidation resistance and thermal shock resistance. It does, however, have a tendency to form gaseous products, namely SiS and SiO, during corrosion in sulphur-containing environments of low oxygen potential at high temperatures. This paper reports the results of exposing two commercially available silicon nitride grades, densified with the aid of yttrium oxide and aluminium oxide, to gas mixtures containing both oxygen and sulphur as corrosion species. The effects of the material composition, temperature and the water content of the gas mixtures on the reaction rates were investigated. A volatility diffusion map, showing partial pressures of P(SiO) and P(SiS) in equilibrium with both Si and SiO(2) as a function of both the water and hydrogen sulphide partial pressures, was constructed for 1300 C at a fixed hydrogen partial pressure of 0.15 MPa. This takes into account thermodynamic criteria, as well as mass transfer phenomena, and predicts rapid material loss in areas where P(SiS) is high and SiO(2) is unstable.

Additional information

Authors: COSTA OLIVEIRA F A, JRC Petten (NL);FORDHAM R J, JRC Petten (NL);EDWARDS R A H, JRC Ispra (IT);DE WIT J H W, TU-Delft, Faculty of Chemical Engineering and Materials Engineering (NL)
Bibliographic Reference: Paper presented: Corrosion of Advanced Ceramics : Measurement and Modelling, Tübingen (DE), August 30 - September 3, 1993
Availability: Available from (1) as Paper EN 37827 ORA
Record Number: 199311284 / Last updated on: 1994-11-29
Original language: en
Available languages: en