佐治 他三郎 富士電波工業(株), 研究開発部, 部長
TASHIMA Syunzo School Education, HIROSHIMA UNIVERSITY Assistant Professor, 学校教育学部, 助教授 (40136130)
SAJI Tasaburo Ddempa Kogyo Co., Ltd., Tsulkuba Laboratoty, Section Chier
|Budget Amount *help
¥12,800,000 (Direct Cost : ¥12,800,000)
Fiscal Year 1996 : ¥12,800,000 (Direct Cost : ¥12,800,000)
A high purity alumina made by high speed centrifugal compacion (AC) invented by Tashima et al. has many superiority over the conventional compacton, including low sintering temperature, fine and homogeneous microstructute, and high mechanical properties. In the study, we applied new method of sintering on the AC,a 28MHz microwave sintering proposed by Saji et al., in order to improve mechanical properties.
The reslts were following.
1.Appropriate setting position of the specimen in the furnace and appropriate heating program were determined. Using the determined condition, it was enable to sinter the green compacts in greater heating rate compared to the conventional sintering (ten times higher) without inhomogeneity of microstructure.
2.It was found that the microwave sintering in vacuum is suitable for the AC,because of the direct reaction of the microwave on the specimen. The specimen sintered by this method showed superio properties.
3.Applying microwave sintering in vacuum, the green compacts were enable to sinter at about 50K lower temperature than the conventional sintering. Furthermore, those compacts showed finer grain size distribution comparing to conventionally sintered compacts which had the same density.
4.The compacts made by microwave sintering in bacuum shows 4-point bending strength of 1140MPa (converted to 3-point vending strength of 1360MPa). This is the best record of the alumina ceramics ever reported. Besides, the specimens showed a vickers hardness of about 50MPa higher than the conventionally sintered specimens.
5.As for the fracture toughness, there was not an obvious difference in the value between differently sintered specimens.
6.By the results, we concluded that the processing of the processing of super high strength alumina ceramics were established, using both the centrifugal compaction and the microwave sintering in vacuum.