Lime-alumina-silica vitreous ceramic processing incorporating wollastonite

Improvements m mechanical and physical properties of advanced ceramics have been undermined by high processing costs and the reputation of unpredictable reliability. One potential technique to address this situation is to use a naturally occurring mineral to develop new ceramic microstructures using a simple processing technique. The system chosen for potential development was an alumina ceramic modified using 20wt-% wollastonite (CaSiO3). Green body production was carried out by wet processing optimised by rheological measurements. The best conditions were found to be a pH of 3 using 1500 ppm BETZ (dispersant) processed at ~0.35 volume fraction of solids in a water based suspension. Thermal analysis revealed that the optimum sintering procedure involved vitreous composite sintering for 15 min at 1500° C followed by an air quench. This glass ceramic was then devitrified using a heat treatment at 1032° C (4 h) followed by 4 hat 1200°C. The final material of 68 wt% alumina, with anorthite and gehlenite, had a high indentation toughness (6-2 MPa m1/2 ) and an improved thermal expansion coefficient. Thus, the new material should be attractive as a low cost material for antiabrasion applications at elevated temperatures. BCT/326