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Kinetics of MoSi2 pest during low-temperature oxidation

Published online by Cambridge University Press:  31 January 2011

T.C. Chou  and
T.G. Nieh
T.C. Chou
Affiliation:
Lockhead Research and Development Division, 0/93-10, B/204, 3251 Hanover Street, Palo Alto, California 94304-1191
T.G. Nieh
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-350, Livermore, California 94550
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Abstract

The kinetics of MoSi2 pest, caused by oxidation in air, has been studied. Experimental results indicated that pest disintegration occurred at temperatures between 375 and 500 °C. The volumes of test samples increased with oxidation duration. Analysis of change in sample volume versus oxidation duration revealed that the pest disintegration consisted of two stages, namely nucleation (or incubation) and growth. The onset of the growth stage depended on the test temperature. More importantly, changes in sample volume were found to obey a linear relationship with time during the growth stage. Equations were formulated to demonstrate that the growth kinetics of pest disintegration was proportional to the rates of change in sample volume. The rates of volume change during MoSi2 pest were calculated to be 4.9 × 10−6, 2.8 × 10−5, 3.7 × 10−5, and 5.4 × 10−5 cm3/s at 375, 400, 425, and 450 °C, respectively; the growth kinetics increased with oxidation temperature. The activation energy for the growth stage of pest disintegration was determined to be 27.6 kcal/mole, which agrees well with the activation energy for the low-temperature oxidation of MoSi2.

Type
Articles
Information
Journal of Materials Research , Volume 8 , Issue 7 , July 1993 , pp. 1605 - 1610
Copyright
Copyright © Materials Research Society 1993

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