Fabrication and physical characteristics of new glasses from wastes of limestone and phosphorite rocks

In this work, new glasses were synthesized from wastes of limestone and phosphate rocks besides commercial borax. The glasses were characterized by FTIR, DTA, ultrasonic techniques and UV spectroscopy. It was found that the concentration of both CaO and P2O5 increases and the concentrations of B2O3 and Na2O decrease as the content of phosphate rocks increases. Variation of the contents of the different oxides affects the concentration of the structural units constituting the glass, which was indicated by the behaviour of the fraction N4 of BO4 units in the borate matrix. The density and the refractive index of the glasses decrease as the CaO and P2O5 contents increase, which was attributed to the increase of [BO3] structural units. On the other hand, the physical parameters such as the ultrasonic velocity, the elastic moduli, the optical bandgap and the optical polarizability increased, which was attributed to the higher coordination number of CaO6 compared with the coordination of borate structural units and to the former effect of P2O5. As a result, a polymerization of the total co-ordination number of the glass, crosslink density and connectivity within the glass network will occur.