Strengthening of alumina by a low thermal expansion glass at surface

A low thermal expansion glass was melted on the sintered alumina. The molten glass penetrated into the surface region of the alumina along the grain boundaries. Thermal and elastic properties mismatch between the glass-penetrated surface region and the interior of alumina produced residual compression in the surface region during cooling. The glass penetration improved the strength by about 53% and also there was a significantly improvement in the thermal shock resistance of the alumina. The observed enhancement in the strength was found to be almost equal to the residual stress generated as a result of thermal and elastic properties mismatch.