The influence of green processing on the sintering and mechanical properties of ß-sialon.

The strength and structure of -sialon ceramics prepared by slip casting with a different degree of flocculation was investigated. Commercial -sialon (z=0.5) powder with 7 wt.% Y2O3 as sintering additive powder was used. Four different suspensions were prepared ranging from completely deflocculated to strongly flocculated. The degree of flocculation was checked with zeta potential and rheology investigations. The mechanical properties and microstructure of the green material reflected the varying degree of flocculation. After sintering, the various sintered materials showed similar mechanical properties for all ceramics. The strength was about 850 MPa, the toughness 4.4 MPa m1/2 and hardness about 15.8 GPa. Accordingly the different green products were homogenised during sintering. This occurred even for samples with very low green density thanks to the favourable powder characteristics (shape, distribution, chemical composition) and liquid phase sintering with sufficient amount of sintering additive

Ca-alpha/beta-sialon ceramics synthesised from fly ash : preparation, characterization and properties

Fly ashes from various sources were used to synthesise - and -sialon's by carbothermal reduction and nitridation. Both -sialon as well as / -sialon composites can be obtained depending on the overall composition of the fly ash. The / ratio is not only influenced by the overall composition of the fly ash but also by the time and temperature of the carbothermal conversion. The sialon powders obtained by carbothermal synthesis were used for preparation of compacts using either pressing or slip casting. After sintering, both methods yield similar final densities and mechanical properties. Sialon ceramics with mechanical properties similar to sialon's made of clay can be obtained from fly ashes

Preparation, characterization and properties of MgSiN2 ceramics

MgSiN2 ceramics with and without sintering additives were prepared by hot uni-axial pressing. For the sintered samples the lattice parameters, secondary phases, density, oxygen and nitrogen content, microstructure, oxidation resistance, hardness, elastic constants, linear thermal expansion coefficient and thermal diffusivity were determined. By suitable processing, fully dense MgSiN2 ceramics with an oxygen conten