抄録
Porous AlN ceramics were fabricated from the porous AlN polytypoid ceramics by elimination of Si and O through carbonthermal reduction-nitiridation at high temperature. The powder compacts of AlN and SiO2 were fired at 1900°C for 6h in a Si3N4 crucible and then the sintered bodies were heat-treated at 1800 and 1900°C for 0 to 3h in a carbon crucible.As-sintered specimens were mainly composed of 27R or 21R AlN polytypoids. After heat treatment, plate-like grain structure of AlN polytypoids was mostly maintained after heat treatment. The maintenance of morphology probably resulted from structural similarity between AlN polytypoids and AlN, such as psuedomorph in several kinds of minerals. The porosity of the porous AlN ceramics was about 50% and its pore size distribution was narrow. It has low dielectric constant and high thermal conductivity.
