Strength of sillimanite sand reinforced porcelain subjected to thermal shock

An attempt has been made to eliminate quartz and gradually replace felspar by sillimanite sand to improve the thermomechanical properties of porcelains. It has been observed that the quenching temperature difference (Delta T) required to initiate thermal stress fracture in the porcelain increased greatly, when compared to classical compositions, with gradual replacement of felspar by sillimanite sand. Similar behaviour has also been observed in linear thermal expansion measurements. It was concluded that improvement in thermal shock resistance of the material was due to the absence of quartz and the presence of sillimanite-a volume-stable mineral-in addition to the decreased amount of glassy phase. (C) 1997 Elsevier Science Limited.