Study on crack-healing behavior of structural ceramics -Crack-healing behavior at service temperature and resultant strength at temperature of healing-

本研究的目的是探讨以下四个主题。(1)研究了莫来石/SiC复合材料在使用温度下的裂纹愈合行为和愈合温度下的合成强度。(2)烧结Si_3N_4/SiC复合材料在使用温度下的裂纹愈合行为和愈合温度下的合成强度。(3)具有较高裂纹愈合能力的氧化铝（Al_2O_3）的研制。(4)开发具有较高裂纹愈合能力的碳化硅（SiC）。结果表明：(A)莫来石/碳化硅材料具有较高的原位裂纹愈合能力，即材料在使用温度下仍能愈合裂纹，且在愈合温度下裂纹愈合区具有较高的强度。在1273K至1473K之间的温度下，即使在相当高的静应力和循环弯曲应力下，相当长的预裂纹也可以完全愈合，使抗弯强度降低了70%。裂纹愈合后试件的抗弯强度与光滑试件相近。(B)发现Si_3N_4/SiC具有较高的原位裂纹愈合能力。在1173K至1473K之间的温度下，即使在相当高的静应力和循环弯曲应力下，相当长的预裂纹也可以完全愈合，从而使抗弯强度降低50%。裂纹愈合后试件的抗弯强度与光滑试件相近。(C)制备了一种具有较高裂纹愈合能力和高温强度的氧化铝。研究了氧化铝的基本裂纹愈合行为。(D) SiC陶瓷裂纹愈合区的极限温度由873K提高到1473K。

The object of this study is to investigate the following four topics. (1) Crack-healing behavior at service temperature and resultant strength at temperature of healing of mullite/SiC composite sintered by the authors. (2) Crack-healing behavior at service temperature and resultant strength at temperature of healing of Si_3N_4/SiC composite sintered by the authors. (3) Development of alumina (Al_2O_3) having quite high crack-healing ability. (4) Development of silicon carbide (SiC) having quite high crack-healing ability. The results obtained for each object are as follows :(A) It was found that the mullite/SiC has quite high in-situ crack-healing ability, that is, the material can heal a crack even at service temperature and, moreover, crack-healed zone had quite high strength at the temperate of healing. A pre-crack of considerable length, which reduced the bending strength by 70%, can be healed completely at temperatures between 1273K and 1473K even under quite high static and cyclic bending stress. The bending strength of the crack-healed specimens is similar to that of the smooth specimens.(B) It was found that the Si_3N_4/SiC has quite high in-situ crack-healing ability. A pre-crack of considerable length, which reduced the bending strength by 50%, can be healed completely at temperatures between 1173K and 1473K even under quite high static and cyclic bending stress. The bending strength of the crack-healed specimens is similar to that of the smooth specimens.(C) An alumina having quite high crack-healing ability and high temperature strength has been developed. The basic crack-healing behavior of the alumina was investigated.(D) The limit temperature of the crack-healed zone of SiC ceramics was increased from 873K to 1473K.