Explosive Compaction of Si₃N₄, SiC Ceramic Powders and Whiskers

Abstract

Explosive compaction of ceramic powders (α-Si₃N₄, SiC) and whiskers (β-Si₃N₄, SiC) were performed by using cylindrically axi-symmetric direct method. The mandrel was inserted into the center of container to increase the compacting pressure, and the momentum trap was adopted for avoiding the development of cracks in a compact. Sintering was treated to the explosively compacted ceramics under the various temperature and appropriate atmosphere. The effects of mandrel, momentumtrap and sintering conditions on the compact characteristics has been investigated by means of microhardness test, optical and scanning electron microscopy and density measurement. The obtained reslts are as follows:
It was found that the mandrel was very efficient in increasing the compacting pressure. In such a case, the mandrel made of Cu was more effective than that made of Al. In the explosively compacted Si3N4 whisker with Cu mandrel, maximum hardness reached 1400Hv. By adoption of the momentum trap, the cracks in a compact was gradually decreased as the weight of momentum trap increased. The density of the explosively compacted ceramics was incresed by even lower sintering temeparature as compared to conventional temparature. This seemed to be due to the activated condition of compacts by the through of shock waves which moved ceramic particles at high velocity and caused the particle refining and the cleaning of the particle surface.