Functionally mullite materials obtained from composite particles

We have performed experiments of composites sintering from mullite-ZrO2 by using composite particles α-Al2O3/SiO2 am. or substrates obtained by sol-gel method with varied components of ZrO2. The method of sintering composite particles causes so called transient viscous sintering (TVS) and the increase of temperature of synthesis the mullite up to above 1300 oC. We have observed another mechanism of the mullit-ZrO2 composites formation as well. The mullite-ZrO2 sinters with functional gradient have been prepared by using special method of formation from composite particles. Thin samples (∼ 3 mm high and 20 mm in diameter) with continuous variation of ZrO2 contents from 0 to 20 wt. % were preparing by special method of forming and sintering. In thin samples fracture toughness - K1c differ from 2.5 MPa0.5 (on the top layer with 0 ZrO2 contents) to 4.5 MPa0.5 (on the bottom layer with 20 wt. % ZrO2 contents). (author)