Interface phenomena accompanying the early stages of glass batch reactions - A model study

Abstract

Interface phenomena accompanying the early stages of reactions in the batch compacted by pressing are considered. The interactions between slowly reacting components of batch, i.e. quartz, potash feldspar and AI₂O₃ (corundum), and alkali carbonates, below the melting temperature of the carbonates, were investigated. The investigations were carried out on quartz, potash feldspar and corundum monocrystals pressed into compacted Na₂CO₃ and K₂CO₃ tablets. The study of the interface reactions on monocrystals was supplemented with the investigation of mixtures of fme-grained (0.1 to 0.3 mm) minerals and alkalies carbonates. The corrosion of the mineral surface takes place due to the interface chemical reaction with alkalies as well as the transportation of free SiO₂ and AI₂O₃ inside the carbonate layer above 580 C for quartz and potash feldspar and above 600 °C for corundum. The mechanism of interaction of quartz and corundum with solid carbonates resembles simple dissolution. In the case of potash feldspar a deep migration of Na⁺ ions to the inside of the mineral structure occurs and its melting begins already above 800 °C. The interface processes determine, to a considerable degree, the effectiveness of the process of prereacting by heat treatment of the compacted glass batches.