Determination of the Nucleation and Crystallization Parameters for Making Nanoporous Titanium Phosphate Glass-ceramics

Nanoporous glass-ceramics were prepared with composition 45CaO-25TiO2-35P2O5 (mol%). Two molar percent of Na2O was added as a flux to the composition. With the aforementioned composition, glass melted and crystallized into glass-ceramics containing β-Ca3(PO4)2 and CaTi4(PO4)6 as the main phases. The differential thermal analysis (DTA) was conducted to determine the suitable temperatures for nucleation and crystallization. Various times were examined for nucleation and the best nucleation time was chosen. The microstructure of final nucleated sample was observed by Scanning Electron Microscopy (SEM). Then, the glasses were crystallized and identified by X-ray Diffraction (XRD).The microstructures of crystallized specimens were studied by SEM.The glass-ceramics were leached in HCl, resulting β-Ca3(PO4)2 was dissolved out leaving a porous structure as CaTi4(PO4)6. It was found that specific surface area and average pore size diameter of the nanoporous glass-ceramics were controlled by the correct choice of heat treatment parameters. Using the optimal conditions for the production of nanoporous glass-ceramics with minimum pore size, 26 m2 and 12.3 were obtained for the specific surface area and pore diameter, respectively.