Investigation on Elementary Process of Fracture in Ceramic Materials based on Measurement of Fracto-emission

研究了多晶陶瓷及其单晶断裂过程中的光子发射和电子发射，讨论了陶瓷材料断裂的基本过程。得出以下结论。(1)缺口试样通过三点弯曲试验断裂，并同时检测发射的光子和电子。(2)光子峰值计数|发射强烈地依赖于材料，然而，峰计数的顺序不能由材料特性来解释。(3)晶粒尺寸对MgO和Al_（23）多晶的光子发射总量有很大的影响，因为光子发射受晶粒尺寸变化引起的裂纹扩展过程的控制。(4)MgO和Al_2_3单晶断裂后的光子发射具有晶体取向依赖性。(5)光子发射的波长分布测量表明，在断裂处发射紫外光或紫色光（在某些情况下还发射黄光或橙子光），随后发射红光或红外光约200 ms。根据实验结果，提出了光子发射机制。(6)在断裂时，电子发射也显示出对应于光子发射的峰计数。然而，从加载开始观察到明显的预发射电子，这表明微裂纹发生在断裂之前。

Photon emission and electron emission were investigated during fracture of polycrystalline ceramics and their single crystals, and elementary processes of fracture in ceramics materials were discussed. The following conclusions were obtained.(1) A notched specimen was fractured by 3-point bending test, and emitted photons and electrons were simultaneously detected.(2) The peak count of photon | emission strongly depended on material, however, the order in the peak count could not be explained by the material characteristics.(3) The grain size largely influenced the total count of photon emission of polycrystalline MgO and Al_2_3, because the photon emission was controlled by the crack extension process on grain size change.(4) The photon emission showed crystal orientation dependence when MgO and Al_2_3 single crystals were fractured.(5) The wavelength distribution measurements of the photon emission indicated that ultraviolet or purple light (and also yellow or orange light in some cases) was emitted at fracture and subsequently red or infrared light was emitted for about 200ms. From the result, the photon emission mechanism was proposed.(6) At fracture, electron emission also showed the peak count corresponding to the photon emission. However, the distinct pre-emission of electrons was observed from the beginning of loading, which suggested that micro cracking occurred before fracture.