Volume nucleation of crystals in glass based on blast-furnace slag

The nucleation of crystals in glass obtained by blending metallurgical slag with silicon dioxide has been studied. The type of crystallization (homogeneous or heterogeneous, volume or surface) is revealed for each of nine compositions of synthesized glass. It is shown that the first crystalline phase in a volume-crystallizing glass is perovskite (CaO center dot SiO2); in this phase a nucleation of the main phase occurs: melilite (solid solution of gehlinite 2CaO center dot Al2O3 center dot SiO2 in akermanite 2CaO center dot MgO center dot 2SiO(2)). The fundamental characteristics of homogeneous (for a catalizing phase, perovskite) and heterogeneous (for a catalyzed phase, melilite) of crystallization are determined: the steady-state nucleation rate I (st), time of unsteady-state nucleation tau, crystal growth rate U, and activation energy of frictional flow. The temperature dependences of I (st), tau, and U are obtained. Practical recommendations are presented for the use of blast-furnace slag as a raw material for the synthesis of glass and their further utilization.