ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Active-to-passive oxidation transition in chemical vapour deposited β-SiC was investigated in the temperature range 1300≤T≤1700°C under low total pressures (100≤Ptot≤800 Pa) and relatively high linear gas flow rates (10≤Vgas≤60 m s1) by thermogravimetric analysis. For given T, Ptot and Vgas, the oxygen partial pressure at the transition, PtO2, corresponds to the value where the mass-loss rate per unit area of the oxidized sample, R, is maximum. Logarithms of PtO2 are linear functions of reciprocal temperature for given Ptot, and Vgas. Vgas has a significant influence on the position of the transition log(PtO2)–T-1 line. PtO2 is also slightly affected by an increase of Ptot from 100 Pa to 800 Pa. In passive oxidation at high temperatures (〉1500°C), large bubbles form in the silica film which is then disrupted leading to a loss of material. In active oxidation, R significantly depends on Vgas: the kinetics is diffusion or mass transfer controlled under the conditions investigated in the present study. In both active and passive oxidation regimes, a mass loss of the test specimen is always observed; an explanation is proposed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1004313022769
