Compaction of submicron and nanocrystalline Al(sub 2)O(sub 3)-ZrO(sub 2) ceramics

摘要

The eutectic in the Al(sub 2)O(sub 3)-ZrO(sub 2) system was rapidly solidified by heating with an 0(sub 2)-H(sub 2) torch and then quenching the melt with a twin roller device. The as-quenched material, which was amorphous or nanocrystalline, was milled with B(sub 4)C or Al(sub 2)0(sub 3) media and pressed into pellets which were sintered conventionally or with microwaves. Samples contaminated with boron carbideresulted in compacts with substantially reduced porosity and a lower fraction of tetragonal ZrO(sub 2). Conventional sintering at low temperatures resulted in the formation of ''rods'' of an Al(sub 2)0(sub 3) rich phase which grew from the presence of a low melting B(sub 2)0(sub 3)-rich liquid. Conventional and microwave sintering at temperatures up to 1600(degrees)C resulted in a microstructure where 100--200 nm ZrO(sub 2) grains were present intragranularly in the (alpha)-Al(sub 2)0(sub 3) grains. Larger ZrO(sub 2) grains ((approximately)1 (mu)m) were found intergranularly. As-quenched lamellar microstructures were preserved at low temperatures but spheroidized at sintering temperatures > 1600(degrees)C.