Preparation of low-shrinkage mullite based ceramics from polysiloxane as apreceramic polymer

Monolithic mullite was synthesized from polymer (cross-linked polysiloxane) /filler (alumina) blends, By virtue of a chemical oxidation reaction of ZrS i2, intentionally added in increasing fractions, a nearly zero-shrinkage mu llite based composite could be obtained by conventional sintering. The comp osites specimen after sintering were composed of mullite and monoclinic ZrO 2, according to the ZrSi2 fraction added to the starting mixture. Low-shrin kage mullite based ceramics could be obtained when the content of ZrSi2 Was between 30 and 50 mol%. In the case of ZrSi2 50 mol%, the shrinkage was as low as 4.5%, although some specimen was found cracked after sintering. The upper limit for ZrSi2 addition was considered to be approximate to 50 mol% because of inhomogeneity related to mixing a low fraction of siloxane poly mer (liquid) with the filler (solid).