چكيده به لاتين
Since the molten fluoride opal glass due to severe volatilization of fluorine, causes corrosion and destruction of kiln refractories and serious environmental problems, therefore this study investigates the effects of adding P2O5 and fabricating fluorophosphate opal glasses, because these kind of glasses have less corrosive effect on refractories.The American Corelle®which is a kind of high quality dinnerware, was chosen as the basis composition and the effect of adding P2O5 and Na2O (for reducing viscosity) was investigated.
Density of glass samples was in the 2.39-2.52 g/cm3range. Chemical resistance of samples were very different with each other so that the amount of corrosion was various between 363 µg/cm2for sample D (4.8% P2O5 – 2.95% Na2O) and 3568 µg/cm2for sample G, this variety shows the effects of Na2O and P2O5. Tests of Colorimety, XRD, SEM, EDX, Vickers micro hardness, and DTA were performed. Sample D (4.8% P2O5 – 2.95% Na2O) with was the whitest one due to the high amount of P2O5. On the other hand sample D could not be selected as the optimum one, because of its excessively high viscosity that prevent forming.
Finally the hardest sample (950.58 microvickers) with best amount of viscosity in forming process and superior properties was selected as the optimum one, which contained 2.60% fluorine, 1.2% P2O5 and 3.95% Na2O. As a result it was concluded that adding P2O5 increases whiteness, viscosity, melting point and hardness of the glass and if the amount of P2O5 reaches more than 4.5 wt. % the opalescence mechanism will alter from liquid-liquid phase separation (spinodal decomposition) to nucleation and growth mechanism. Also adding 6.7% Na2O intensely decreased whiteness of the samples and the surface of glasses remained transparent. The optimum amount of Na2O in this study was 3.93%.
