Development of AE monitoring system for optimal sintering conditions of ceramics

陶瓷及陶瓷基复合材料在热压成型过程中，由于基体与颗粒之间的热膨胀系数不同，在冷却过程中产生的应力会使材料产生大量的微裂纹，这是一个严重的问题。烧结条件的处理或冷却速度是通过尝试和错误来确定，以避免这些微裂纹。然而，这些过程效率不高，并且存在大量的能量损失。烧结过程的无损监测有望避免这一问题。声发射（AE）是一种由裂纹引起的弹性波的发射，它已被用于材料微断裂的研究和构件完整性的监测。颗粒弥散陶瓷和玻璃基复合材料的制备研究已有很多报道。然而，关于微断裂机制的详细报道却很少。这类材料的研制还需要更多的微观断裂实验分析和定量评价。本研究制备了几种颗粒弥散陶瓷玻璃复合材料，并对弯曲试验和断裂韧性试验中的声发射信号进行了分析。通过对声发射波形的反分析，对材料的微观断裂进行了评价。最后定量地评价了材料的微观断裂过程和力学性能，并对材料的强韧化机理进行了定量的探讨。这些结果将引导这些材料的改进。

It becomes a severe problem that many microcracking occur due to the stress induced by the different of thermal coefficients between matrix and particles during cooling period of processing of ceramics and ceramics matrix composites by hot-press. The sintering conditions of processing or cooling rate are determined by try and error to avoid these microcracks. However, these processies are not efficient and there are a lot of loss in energy. Non-destructive monitoring of sintering is promising to avoid this problem. Acoustic emission (AE) is an emission of elastic wave due to cracking and it has been used for the research of microfracture of materials and the monitoring of integrity of components. Many research have been reported on the processing of particle dispersed ceramic and glass matrix compoxites. However, there were a few reports on the detail of microfracture mechanism. More experimental analysis of microfracture and quantitative eveluation are needed to develop these materials. In this research, several types of particle dispersed ceramic and glass composites were fabricated and AE signals during bending test and fracture toughness test were analyzed. Micrlfracture of these materials were eveluated by inverse analysis of AE waveform. Finally microfracture process and mechanical properties of these materials were quantitatively evaluated and the mechanism of strenthening and thoghening were quantitatively discussed. These results will lead the improvement of these materials.