Research On The Densification Of AIN Caramic

Aluminium nitride (AlN) powder was synthesized by carbothermal reduction methodwith the raw materials of alumina powder and carbon powder made by phenolic resin.Then AlN ceramic was prepared by pressureless sintering with the AlN powder which wesynthesized. The influence of sintering temperature on the synthesis of aluminum nitridepowder was investigated. And the influence of sintering temperature, the kind and dosageof additives, soaking time on the relative density of AlN ceramic and the relationshipbetween relative density and rockwell hardness were studied in this paper.The results showed that:1) During the AlN powder was synthesized at1600~1800℃, higher temperature wasbenifit to synthesis of AlN and its crystallization. The AlN powder which synthesized at1800℃with4hours soaking time got the highest purity and crystallization, the lowestcontent of oxygen impurity was0.968wt%. The grain size was small and disperseduniformly. Its average diameter was4.22μm. So it can be used as the raw powder to sinterAlN ceramic.2) Higher temperature can promote the sintering of AlN ceramic and the growth ofgrains. When the temperature was1850℃, the AlN ceramic obtained the highest relativedensity. And the best soaking time was4h. The additive of CaF2, Y2O3and HfO2canimprove the densification of AlN ceramic. However,3wt%CaF2-3wt%Y2O3was the bestadditive for the densification of AlN ceramic.3) Rockwell hardness and relative density of AlN ceramic were positively related.The higher the relative density was, the greater the rockwell hardness obtained. The sampleadded3wt%CaF2-3wt%Y2O3sintered at1850℃with4h got the highest relative densityof99.3%, and its rockwell hardness was80.1.