Dissolution and growth of spinel crystals in a borosilicate glass

The rate of dissolution and growth of settling crystals of spinel was measured optically in a borosilicate melt that was pre-heated at a temperature above liquidus to erase the effects of previous history. The Hixson-Crowell equation, which is based on Fick's first law, was used to determine mass-transfer coefficients (k_H) for dissolution and growth; both were found to fit the same Arrhenius function of temperature (T). An attempt was made to estimate the diffusion coefficient (D) and the concentration-boundary-layer thickness (δ). The calculated values of δ compared well with experimental results and observations. The D vs. T function was similar to a literature function obtained for the dissolution of magnetite in sodium disilicate glass.