Enhanced Reactivity and Primary Liquid-Phase Forming in Mechanochemically Activated Soda–Lime–Silica Glass Batches

Abstract

Glass manufacturing is a high-temperature, energyintensive, and highly inefficient process, with a significant global environmental impact. Therefore, given the high-scaled nature of the glass-making sector, the design of more energy-efficient manufacturing protocols is an economic and environmental imperative. In this context, this work presents a comprehensive study about the milling effect in the heat-driven chemistry and phase evolution, of a typical soda−lime−silica (Na 2 O:CaO:SiO 2 ) flat glass batch. Our findings show that, with the experimental settings imposed in this work, mechanochemical reactions leading to in situ formation of alkali/alkaline-earth silicate compounds in the vial, are most likely absent. However, all carbonated raw materials of the formula (soda ash, calcite, and dolomite), undergo severe structural damage during milling and even become amorphous to XRD after milling for 360 min, with their decomposition reactions shifting markedly toward lower temperatures as the milling time increases (e.g., the volatile fraction of the formula activated for 360 min, is completely removed almost 200 °C below than of a nonactivated reference sample). Furthermore, milling has also a profound effect in the evolution of the silicon local coordination environment, with temperature, and in the formation temperature and stoichiometry of silicate species observed on heating. Moreover, events related to the depolymerization of the fully linked Q 4 units characteristic of crystalline SiO 2 (i.e., formation of metal silicates), are observed in activated batches at temperatures well below those of the reference sample (e.g., 600 °C when activated for 360 min vs 900 °C of a nonactivated sample). These changes are not only a consequence of particle size reduction, because the particle size distribution of the batch does not change much after 30 min; milling-induced amorphization of the carbonated fraction of the formula and the corresponding reduced activation energy for their decomposition reactions and improved reactivity toward SiO 2 are the driving forces behind the significant reduction in the formation temperature of the first liquid phases with increasing milling time.