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Synthesis of high-strength ceramics by centrifugal casting and microwave sinterieng and evaluation of mechanical properties

离心铸造和微波烧结高强度陶瓷的合成及力学性能评价

基本信息

批准号：
09555204
负责人：
KOIKE Jun-ichi
金额：
$ 6.66万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09555204/
关键词：
microwave sintering Al_2O_3 Si_3N_4 遠心成形アルミナ強度機械的性質

项目摘要

A12O3 and Si_3 N_4 were synthesized by microwave sintering. Its properties were investigated and advantages and disadvantages of microwave sintering were evaluated. Major obtained results were the following. In both ceramics, relative density was higher with microwave sintering than with conventional sintering. It was also found that by microwave sintering, the onset temperature for sintering was lowered by 50ﾟC and the sintering rate was increased. Since microwave sintering could decrease the activation energy for diffusion by 40%, these improvemens were due to the enhanced diffusion under microwave conditions.We also found that there was no direct correlation between the sintered density and the green density. This was contradictory to the results in the case of conventional sintereing. Observation of microwave-sintered Al2O3 and Si_3N_4 by a scanning electron microscope revealed the absence of pores having a diameter of less than 2 mum. This indicated that small pores of less than 2 mum were vanished during microwave sintering. Therefore, the final density was found to be determined not by the green density but by the amount of the small pores. A possible reason for the disappearance of the small pores is that the surface energy is increased under the microwave and that the small pores having a large surface/volume ratio would shrink and disappear. The reduction of the small pores during performing becomes a key to further improve the final density and associated mechanical properties

采用微波烧结法合成了Al_2O_3和Si_3N_4。研究了其性能，并对微波烧结的优缺点进行了评价。获得的主要结果如下。在这两种陶瓷中，微波烧结的相对密度高于常规烧结。研究还发现，通过微波烧结，烧结的起始温度降低了50 ℃，烧结速率提高。由于微波烧结使扩散活化能降低了40%，这些改善是由于在微波条件下增强了扩散，我们还发现烧结密度与绿色密度之间没有直接的相关性。这与常规烧结的结果相矛盾。通过扫描电子显微镜观察微波烧结的Al 2 O3和Si_3N_4，发现没有直径小于2 μ m的孔。这表明小于2 μ m的小孔在微波烧结过程中消失。因此，发现最终密度不是由绿色密度决定的，而是由小孔的量决定的。小孔消失的可能原因是在微波下表面能增加，并且具有大的表面/体积比的小孔将收缩并消失。减少预成型过程中的细小孔隙是进一步提高最终致密度和力学性能的关键