6604

6604

بررسي اثر تغيير تركيب بر رفتار تبلور و خوا

كارشناسي ارشد

مهندسي مواد-سراميك

83

83

دكتر واهاك مارقوسيان- دكتر حسين سرپولكي

Abstract The aim of this project is the evaluation of compositional changes on crystallization and properties of low expansion opal glasses. In order to achieve this, glass samples with the general composition 71SiO2.2Al2O3.12B2O3.2P2O5. (13-X)Na2O.XRO(X = 0, 1.5, 3, 4.5, 6, 7.5; R= Mg, Ba, Ca, Zn) were prepared. After heat treatment of glasses at temperatures corresponding to Differential Thermal Analysis (DTA) curves, opal glasses were studied by XRD analysis and scanning electron microscopy (SEM). After that opacity and chemical resistivity (to water and alkaline solutions) tests were done. Results of XRD and SEM of compositions with CaO, BaO, and ZnO revealed more crystallization. Studies showed that crystallization and phase separation of glasses are effective factors on opacity and chemical durability. Improved opacity and chemical durability were related to crystallization of desired phases in glasses. Suitable conditions of heat treatment obtained at 850 C and 1 hour. Loss of chemical durability for longer periods was related to the formation of cristobalite in some glasses. Results also showed that CaO and MgO were more effective in opacity and BaO and ZnO were more effective in chemical durability.