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针对高温含水条件下非氧化物材料经常面临的性能失效问题,以六方BN粉体(平均粒度为1.2μm)为研究对象,利用高温热重分析、X射线衍射以及扫描电镜等手段,考察了BN粉体在不同温度(1273~1373 K)含水条件下(水和空气的体积比为3:7)的反应行为,并与其在干燥空气下的反应行为进行对比.BN粉体在含水条件下的反应有如下特点:在反应初期,试样质量增加率快速增加;在反应后期,试样质量增加率变缓.结合热力学分析探讨了BN材料在高温含水条件下的反应机理:质量快速增加阶段主要发生BN与O2之间的氧化反应,试样质量增加率变缓阶段主要是由于氧化产物B2O3与H2O反应生成了挥发性产物.随着温度的升高,两反应阶段试样的质量增加率均有所提高.利用周模型对BN材料在高温含水条件下的反应动力学进行了较为精确且定量的拟合,结果与实验数据吻合良好.
Aiming at the performance failure of non-oxide materials under high temperature and moisture condition, the hexagonal BN powder (average particle size 1.2 μm) was used as the research object. By means of TG-TG, X-ray diffraction and scanning electron microscopy, The reaction behavior of the powders at different temperatures (1273 ~ 1373 K) in water (the volume ratio of water to air is 3: 7) was compared with that under dry air. The reaction has the following characteristics: In the early stage of the reaction, the rate of increase of the sample mass increases rapidly, and the rate of increase of the mass of the sample slows down in the late stage of the reaction. The reaction mechanism of the BN material under high temperature and water content is discussed based on the thermodynamic analysis: The oxidation reaction between BN and O2 occurred and the increasing rate of sample quality was mainly due to the reaction of the oxidation product B2O3 with H2O to generate volatile products.With the increase of temperature, the mass increase rate of both reaction stages Has been improved.The reaction kinetics of BN material under high temperature and water containing conditions has been fitted with a more accurate and quantitative method by the weekly model.The results are in good agreement with the experimental data.