In situ measurements of reactions in a glass‐forming batch by X‐ray and neutron diffraction

Abstract

The batch materials used in glass production are often too coarse to allow phase evolution measurements by in situ high‐temperature x‐ray diffraction (HTXRD). Reducing the particle sizes to accommodate these measurements changes the reaction kinetics and can alter the reaction pathway. Unlike conventional laboratory XRD, which operates in reflection mode and analyzes the surface region of finely ground powder, neutron diffraction can be used to characterize as‐received batch materials by means of an intense beam which penetrates through a bulk sample. In this study, the phase evolution in a glass‐forming batch made with fine batch materials was probed in situ by both HTXRD and time‐of‐flight neutron diffraction to determine the similarities and differences between measurements by the two techniques. Then, the same composition, prepared using the coarser, as‐received size distributions of the same batch materials, was studied by both techniques, demonstrating the unique capability of neutron diffraction to analyze material which is too coarse for the HTXRD, and to reveal the effect of the particle size distribution on the reaction kinetics.

Model for batch-to-glass conversion: coupling the heat transfer with conversion kinetics

“…Silica particles initially react with molten carbonates, producing silicates, intermediate crystalline compounds, and carbon dioxide [35][36][37][38]. At higher temperatures, silica grains dissolve in the silicate melt.…”

“…The material properties, c p;e and λ ¼ ac p ρ, where a is the thermal conductivity, c p is the true heat capacity, and is the density, are functions of temperature and the temperature history [30,57,58] the batch had experienced before reaching a spatial point x. The experimental methods used to obtain their values include thermal analysis, evolved gas analysis, differential scanning calorimetry, batch expansion test, insitu high-temperature neutron diffraction [36], and laser flash method [59]. Figure 6 displays the thermal diffusivity and effective heat capacity versus temperature as reported by Doi et al [60] for a soda-lime glass.…”

Modeling batch melting: Roles of heat transfer and reaction kinetics

“…The dissolution of refractory particles during melting is often regarded as a measure of the conversion progress . In most batches, this usually means dissolution of silica sand, but in some more complex batches, such as those for vitrification of nuclear waste, the dissolution of other solid particles, such as spinel crystals, can serve as markers for the batch conversion.…”

Conversion kinetics of container glass batch melting

“…The processes occurring in the batch (Figure 1) are numerous and complex: (a) batch reactions leading to the production of early glass-forming melt 14,15,16 ; (b) evolution of foam when glass-forming melt connects, the foam growth and decay 17,18,19,20 ; and (c) dissolution of residual solids, mainly silica. 21,22 For a thorough overview, the reader is directed to an early paper, 23 which summarizes the different batch melting stages and reviews the early published literature. The paper also highlights the role of batch history in determining the conversion kinetics, a phenomenon which has not been systematically studied.…”