The Mullite presence in ceramic materials is always regarded as a favourable advantageous property because it improves the product properties by its great hardness and low coefficient of expansion. The Mullite generation takes place between 1000oC and 1200oC after the producion of a glassy melt in the biscuit and it increases further between 1200oC and 1500oC.
According to Budnikov it is possible to produce a mullite brick suitable for blast furnaces by adding 2% MnO to a mixture of clay and Calcined Alumina. The presence of MnO discourages the formation of Carbonaceous deposits in the brick. Growth of crystals is favoured by prolonged heating.
Mullite produced from clays incorporated in normal ceramic products appears in the form of delicate apparently disconnected needles.
… to be contd.
