Reduction of hygroscopicity in zinc-calcium-phosphate glass via iron-oxide incorporation

Abstract

Despite several advantages of phosphate glass systems, their hygroscopic tendency (absorbing or attracting moisture from the atmosphere) remain a major limiting factor for widespread industrial applications. Dedicated efforts are made to improve the hygroscopic nature of such glasses for making them chemically durable and greatly resistant towards moisture attack. Guided by this requirement, we prepared five phosphate glass samples of composition (70-x) P2O5- xFe2O3-25ZnO-5CaO with controlled manipulation of iron-oxide contents (Fe2O3: x = 0 to 20 mol %) using melt-quenching method. The influence of Fe2O3 (as modifier) contents variation on the improvement of structural and chemical strength is determined. As-synthesized glass samples are immersed in acidic solutions for corrosion test. In this test, glass samples are engrossed in the aqueous hydrochloric acid (HCl) media at 90 °C and soaked for a period of 4 h. The corrosion rate (CR) was calculated from the weight loss obtained after the test. The least number of CR indicates that the inclusion of Fe2O3 in the glass network improved the network rigidity and made the glass much stronger as well as more water resistant. However, it is also established that there is an optimum limit of Fe2O3 content beyond which the durability cannot be further improved. The AFM analysis of pre- and post- chemically treated glass samples informed the surface roughness and 3D topography. Present observation must be validated with other supporting experiments and model calculation which is underway. In this study, it revealed that the lowest corrosion rate was sample S3 (10% of Fe2O3) which have CR value of 1.02±0.12x10-3gcm-2h-1.