P. Mogilersky, 4. Zanguil Materials Science and Engineering 4354(2003)58-66 Volume fraction, f 0.5 0 0.08 -------- →==-- ●-1375°C -■--1575°C (1f Volume fraction, f 0.5 0.1 1500°C 所 Fig 3. Dependence of the parabolic growth constant Kp on the volume fraction of the reinforcement in the studies [8](a)and [6](b). The parameter f s was calculated assuming k=2.2 for the transformation of Sic into amorphous silica. p~(po0y-6)≈(p2 0.146 (36) indicate for the aluminosilicate glass the value of n in the range 4.2-3.3, respectively Luthra and Park [8] studied the oxidation kinetics in flowing oxygen and Ar-1%O2 mixture. The exact effect of the partial oxygen pressure in this study is not 4. Conclusions possible to predict, since the parameter n for the aluminosilicate liquid, which apparently was the main a quantitative model for the oxidation mode I of path for oxygen diffusion in that study, is unknown oxide CMCs was developed, which allows an analysis of Without the reaction between alumina and silica, Eq. the oxidation kinetics, depending on the oxygen perme- 6) would predict the ratio of the parabolic constants ability values, external oxygen pressure, and structural for these two atmospheres close to 2. Experimentally, characteristics such as phase composition of the oxida- however, the parabolic constant ratio about 3-4 ticle eported, which, according to the present model, would size and volume fraction. For systems where such dataKp(pO2 ) (1(5=6) b6 ) :(pO2 ) 0:146 (36) Luthra and Park [8] studied the oxidation kinetics in flowing oxygen and Ar
/1% O2 mixture. The exact effect of the partial oxygen pressure in this study is not possible to predict, since the parameter n for the aluminosilicate liquid, which apparently was the main path for oxygen diffusion in that study, is unknown. Without the reaction between alumina and silica, Eq. (36) would predict the ratio of the parabolic constants for these two atmospheres close to 2. Experimentally, however, the parabolic constant ratio about 3
/4 was reported, which, according to the present model, would indicate for the aluminosilicate glass the value of n in the range 4.2
/3.3, respectively. 4. Conclusions A quantitative model for the oxidation mode I of oxide CMCs was developed, which allows an analysis of the oxidation kinetics, depending on the oxygen perme￾ability values, external oxygen pressure, and structural characteristics such as phase composition of the oxida￾tion product, phase distribution, reinforcement particle size and volume fraction. For systems where such data Fig. 3. Dependence of the parabolic growth constant Kp on the volume fraction of the reinforcement in the studies [8] (a) and [6] (b). The parameter fs was calculated assuming k/2.2 for the transformation of SiC into amorphous silica. 64 P. Mogilevsky, A. Zangvil / Materials Science and Engineering A354 (2003) 58
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