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

采用常规烧结技术，在Al_2O_3/SiC、MgO/SiC、Si_3N_4/SiC、Sialon/SiC等复合体系中制备出纳米级第二相分散在基体晶粒内和晶界处的纳米复合材料。对这些纳米复合材料的 /SEM 观察和机械性能测试得出以下结论： 1) 包括断裂强度在内的机械性能提高了 2 至 4 倍。 2)纳米颗粒分散体显着提高了高温力学性能和抗热震断裂性能，特别是晶间纳米分散体使Al_2O_3和Si_3N_4的抗蠕变性能提高了1000至10000倍。 3）这些异常性能的改善归因于晶粒内纳米尺寸分散体对基体晶粒的强化以及原子尺度结构的控制。 4) 最后，成功开发了用这些纳米复合材料制造复杂形状机器零件的低压烧结工艺。然而，很明显，只有纳米复合材料技术无法突破纳米复合材料的脆性。因此，应用了微纳米混合概念，即通过用微米尺寸的第二相进一步增强纳米复合材料的断裂韧性的概念。选用长碳纤维作为微米级增强体，结果如下： 5) 1500°C 强度超过 1000 MPa，韧性达到 1000 MPa 以上。通过用碳长纤维增强Sialon/3vol% SiC纳米复合材料开发了20至25 MPam^<1/2> 6)某些部分的气体。除了这些结果之外，还获得了以下实验结果：Si_3N_4/SiC 和 Al_2O_3/SiC 纳米复合材料表现出比整体材料更好的性能。 8）对于超过十个复合体系，晶内/晶间纳米分散体的增韧强化机制已明确。