Thermodynamic Model of Glass Ceramics Crystallization

Abstract

The increase in the economic efficiency in many industries (energy, mineral resources, metallurgy, chemical coal, construction) is associated with new materials with unusual combination of physical, mechanical and chemical properties. Glass-ceramic materials obtained by directional glass crystallization rank first among others. Compared to crystalline substances, glass has increased internal energy (latent energy of crystallization). Therefore, the substance in the glassy state is metastable (thermodynamically unstable). Ordinary glass under certain conditions begins to crystallize, sometimes, spontaneously. This process is called drying or devitrification. A thermodynamic model is proposed based on the concept of dynamic equilibrium of energy and matter flows during phase transitions in non-equilibrium open systems. The model considers thermal force of the metasilicate crystal growth. Some of the main dependencies of kinetic parameters on thermodynamic properties are suggested for М₂М₁[Si₂O₆] metasilicate composition. The crystallization temperature growth occurs as the overall basicity ∆Ζ^о₂₉₈ increases against relative increase in the basicity of ions in the cationic sublattice M₂ and, especially, in the octahedral sublattice M₁.