Glass sintering with concurrent crystallisation. Part 2. Nonisothermal sintering of jagged polydispersed particles
We propose a model, translated into an algorithm, to simulate nonisothermal sintering of polydispersed glass undergoing concurrent crystallisation. The model is based on the two classical sintering stages proposed by Frenkel and Mackenzie-Shuttleworth. The input parameters are green density, particle size distribution, surface tension, viscosity, number of surface nucleation sites (N s) and crystal growth velocity. We test the model using physical parameters and densification rates for two distinct glasses: a (devitrifying) cordierite glass having a narrow distribution of jagged particles and an alumino-borosilicate glass, ABS (which is stable against crystallisation) having widely polydispersed jagged particles. The experimental densities of the compacts saturate at slightly different values than predicted. Entrapped gases or glass degassing explains the residual porosity in ABS while partial surface crystallisation accounts for density saturation in cordierite glass. The algorithm provides a powerful simulation tool to design the densification of (devitrifying or stable) glass compacts having any particle size distribution, subjected to any heating rate, thus minimising the number of time consuming laboratory experiments.
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