Processing of Super High Strength Neat Ner Shape Ceramics, Using High-speed Centrifugal Compaction and Micro Wave Sintering.

田岛（Tashima）等人发明的高速离心压实（AC）法制得的高纯氧化铝与常规压实相比具有烧结温度低、显微组织精细均匀、力学性能高等优点。在本研究中，我们将Saji等人提出的28MHz微波烧结新方法应用于AC上，以提高其力学性能。结果如下：确定了试样在炉内的适当设置位置和适当的加热程序。利用所确定的条件，与常规烧结相比（加热速率高10倍），可以在更大的加热速率下烧结绿色坯体，而不会出现微观结构的不均匀性。由于微波对试样的直接反应，真空微波烧结是一种适用于交流材料的烧结方法。用这种方法烧结的试样表现出优异的性能。采用微波真空烧结技术，制备的绿色坯坯比常规烧结温度低50K左右。此外，与具有相同密度的常规烧结压块相比，这些压块的晶粒尺寸分布更细。真空微波烧结压坯的4点抗弯强度为1140MPa（换算成3点抗弯强度为1360MPa）。这是迄今为止报道的氧化铝陶瓷的最好记录。试样的维氏硬度比常规烧结试样高约50MPa。断裂韧性在不同烧结试样间无明显差异。结果表明，采用离心压实法和真空微波烧结法制备超高强度氧化铝陶瓷的工艺条件已经建立。

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.