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Development of Ceramic Based Nanocomposites with High Toughness and Strength at High Temperatures

高温高韧性、高强度陶瓷基纳米复合材料的开发

基本信息

批准号：
03555157
负责人：
NIIHARA Koichi
金额：
$ 10.37万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

项目摘要

The nanocomposites, in which nano-sized second phases were dispersed within matrix grains and at grain boundaries, were developed in the composite systems such as Al_2O_3/SiC,MgO/SiC,Si_3N_4/SiC and Sialon/SiC by usual sintering techniques. The TEM/SEM observations and mechanical properties tests on these nanocomposites gave the following conclusions. 1) Mechanicalproperties including fracture strength was 2 to 4 times improved by this nanocomposite technology. 2) High-temperature mechanical properties as well as thermal shock fracture resistance was significantly improved by nano-sized particle dispersions. In special, the creep resistance of Al_2O_3 and Si_3N_4 was 1000 to 10000 times improved mainly by intergranular nano-sized dispersions. 3) These abnormal properties improvement was attributed to the strengthening of matrix grains by intragranular nano-sized dispersions and the atomic scale structure control by intergranular nano-sized dispersions. 4) Finally, the low pressure less … More sintering proccess to make complex-shaped machine parts from these nanocomposite materials were successfully developed.It was clear, however, that only nanocomposite technology could not break thorugh the brittleness of ceramics. Thus, the micro-nano hybrid concept, that is, the concept to improve the fracture toughness of nanocomposites by further-reinforcing them with micro-sized second phases, was applied to the Sialon/SiC nanocomposite system. The long carbon fiber was selected as the micro-sized reinforcement. The results are as follows : 5) The super tough and strong ceramics with the strength of over 1000 MPa at 1500ﾟC and the toughness of 20 to 25 MPam^<1/2> were developed by reinforcing the Sialon/3vol% SiC nanocomposites with the carbonlong fiber. 6) Some parts of gas turbine engine could be successfully fabricated from this super-ceramic material. In adition to these results, following experimental results were also obtained. 7) The Si_3N_4/SiC and Al_2O_3/SiC nanocomposites exhibited essentiallyt much better properties for cutting tools than the monolithic materials. 8) The toughening strenghening mechanisms by intra/intergranular nano-sized dispersions were made clear for the over-tens composite systems. Less

在Al_2O_3/SiC、MgO/SiC、Si_3N_4/SiC和Sialon/SiC等复合体系中，通过常规烧结工艺制备出了纳米第二相弥散分布在基体晶粒和晶界的纳米复合材料。通过TEM/SEM观察和力学性能测试，得出以下结论。1)通过这种纳米复合技术，包括断裂强度在内的力学性能提高了2 ~ 4倍。2)纳米粒子分散体显著提高了复合材料的高温力学性能和抗热震断裂性能。特别是Al_2O_3和Si_3N_4的抗蠕变性能提高了1000 ~ 10000倍，这主要是由于晶粒间的纳米分散。3)这些反常的性能改善归因于晶内纳米分散体对基体晶粒的强化和晶间纳米分散体对原子尺度结构的控制。4)最后，低压少 ...更多信息然而，很明显，只有纳米复合技术不能突破陶瓷的脆性。因此，微纳米杂化的概念，即，通过进一步增强它们与微米尺寸的第二相，以提高纳米复合材料的断裂韧性的概念，被应用到Sialon/SiC纳米复合材料系统。选用长碳纤维作为微尺寸增强体。5）采用碳长纤维增强Sialon/3vol%SiC纳米复合材料，制备出1500 ℃强度超过1000 MPa、韧性为20 ~ 25 MPam^<1/2>的超坚韧高强陶瓷。6)用这种超级陶瓷材料可以成功地制造燃气涡轮机的某些零件。除了这些结果之外，还获得了以下实验结果。7)Si_3N_4/SiC和Al_2O_3/SiC纳米复合材料的刀具性能明显优于整体材料。8)对数十种复合体系的晶内/晶间纳米分散体增韧增强机理进行了研究。少