Mullite Based Oxidation Protection for SiC-C/C Composites in Air at Temperatures up to 1900 K
Mullite Based Oxidation Protection for SiC-C/C Composites in Air at Temperatures up to 1900 K
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DOI：
10.1016/s0955-2219(98)00242-8
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发表时间：
1997-04
期刊：
影响因子：
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通讯作者：
H. Fritze;J. Jojic;T. Witke;C. Rüscher;S. Weber;S. Scherrer;B. Schultrich;G. Borchardt
中科院分区：
文献类型：
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作者：
H. Fritze;J. Jojic;T. Witke;C. Rüscher;S. Weber;S. Scherrer;B. Schultrich;G. Borchardt
对于工业硅-碳化硅涂层C/C材料(标准物质)，在773<；T<；1973K温度范围内解释了线质量损失率与温度的关系。热重法测得的氧化速率的Arrhenius图显示了四个典型的区域。只有在1323<；T<；1823K的温度范围内，氧化速率才接近或低于长期使用的极限。脉冲激光沉积(PLD)可以烧蚀非导电性和高熔点的靶材，并可以制备成分复杂的薄膜。高能CO2激光脉冲(j=3·107W cm−2)一步熔化蒸发靶材。因此，金属部件的通量是化学计量的。沉积的绿色层没有出现典型的莫来石红外吸收峰。经短时氧化处理(1673K下15min)后，涂层中莫来石的形成完全完成，红外光谱和X射线衍射分析证实了这一点。薄的PLD-莫来石薄膜(900 Nm)在1473<；T<；1973K的高温范围内没有显著提高标准物质的抗氧化性。然而，对衬底材料和厚度为2.5μm的莫来石涂层进行预氧化处理，显著改善了氧化性能。由于在莫来石-碳化硅界面生成了二氧化硅，所有样品的氧化质量都有所增加。根据~(18)O在PLD莫来石层中的扩散系数测量，氧在外部含莫来石层中的向内扩散控制了反应动力学。由二氧化硅和莫来石中的扩散参数计算的氧化速率与热重数据接近。当氧化时间为3天时，莫来石-碳化硅界面上只形成无定形的二氧化硅。
For an industrial Si–SiC coated C/C material (reference material) the temperature dependence of the linear rate of mass loss is interpreted in the temperature range 773<T<1973K. The Arrhenius plot of the thermogravimetrically determined oxidation rate shows four typical regimes. Only in the temperature range 1323<T<1823K is the oxidation rate close to or lower than the limit for long-term application. Pulsed Laser Deposition (PLD) allows the ablation of nonconductive and high melting targets and the preparation of films with complex composition. High energy impact CO2laser pulses (j=3·107W cm−2) lead to melting and evaporation of the target material in a single step. Therefore the flux of the metal components is stoichiometric. Deposited green layers did not show IR peaks typical for mullite. After a short oxidation treatment (15min at 1673K) the formation of mullite in the coating was completed as was confirmed by IR spectroscopy and XRD investigations. Thin PLD-mullite layers (900nm) did not markedly improve the oxidation resistance of the reference material in the high temperature range 1473<T<1973K. However, a preoxidation treatment of the substrate material and mullite coatings with a thickness of 2·5μm improved the oxidation behaviour significantly. Because of SiO2formation at the mullite–SiC interface all samples exhibited a mass increase on oxidation. The inward diffusion of oxygen across the outer mullite-containing layer controlled the kinetics of the reaction as was deduced from18O diffusivity measurements in PLD mullite layers. The calculated oxidation rates resulting from the diffusion parameters in SiO2and mullite are close to the thermogravimetric data. For oxidation durations of three days only amorphous SiO2is formed at the mullite–SiC interface.