Strengthening in porcelain reinforced with alumina particles

Abstract

Alumina has long been known to enhance the strength of porcelain; however, the strengthening mechanism is not sufficiently understood. The strengthening in alumina-strengthened porcelain is examined on the basis of the change in thermal shrinkage of a porcelain matrix upon addition of various amounts of calcined talc. The improvement in flexural strength of the porcelain as a result of the alumina addition is enhanced with increasing difference in the thermal shrinkage between the alumina particle and the matrix. The rate of increase of the flexural strength as a function of the difference in thermal shrinkage is described by the extent to which the compressive prestress on the matrix increases the nominal tensile stress required for the fracture of the porcelain. However, the strengthening due to the internal stress is not sufficient to describe the actual strength of the porcelain. Further strengthening is achieved by the relatively large thermal shrinkage of alumina particles suppressing the formation and extension of microcracks around quartz grains in the glass phase of the porcelain.