Vacuum heat treatment of MgO-densified pressureless sintered silicon nitride ceramics

Demir V., Thompson D. P.

5th International Symposium on Nitrides, Eskişehir, Türkiye, 3 - 05 Nisan 2006, cilt.554, ss.107-109 identifier identifier


Silicon nitride samples were pressureless sintered with up to 5 w/o MgO to give densities in the range 98-99% of theoretical. After pressureless sintering, selected samples were placed in a vacuum heat treatment furnace surrounded by a carbon bed in a carbon crucible at a pressure of less than 4x10(-4) mbar, and vacuum heat treated at different temperatures and times to remove grain-boundary glass. The results showed that this was substantially achieved at 1575 degrees C for 3h and that increasing the time to 5 hours gave still further improvement. SEM images, EDX analysis and oxidation tests provided additional evidence for the removal of Mg from the samples.