INFLUENCE OF PRESSURE AND SHEAR-FLOW ON THE CRYSTALLIZATION BEHAVIOR OF A GLASS MELT BASED ON THE LI2SI2O5-COMPOSITION

Extrusion experiments of a glass melt, based on lithiumdisilicate, sho w a different crystallization behaviour in comparison with experiments , where the same glass is heat treated identically, but without the pr essure and the shear flow. Therefore, the effect of pressure and shear flow on the nucleation and crystal growth are discussed. It is shown theoretically and practically that at least for the lithiumdisilicate the pressure used is not sufficient to reach significant differences i n crystallization. The shear flow is supposed to cause the crystalliza tion catalysis due to the non-Newtonian flow behaviour of the glass me lt used.