EFFECTS OF COMPOSITION ON SELECTED PHYSICAL-PROPERTIES OF SIO2-K2O-NA2O GLASSES

Physical properties were used to characterize a range of five, three-component glass formulations (SiO2-K2O-Na2O) synthesized from spray-dried precursor powders in terms of their final bulk chemical compositions. Five specimens per composition were produced by mixing dry glass powder with methyl alcohol to form a slurry, then shaping the slurry in a cylindrical mould, using conventional methods. Specimens were fired under vacuum. Optimum firing conditions for each glass were determined by selecting holding times which produced the maximum Young's modulus. Fracture toughness, K(IC), values ranged from 0.92-0.99 M Pa m1/2 and Young's modulus, E, values ranged from 45.09-58.06 GPa. Linear regression analyses showed significant correlations between chemical composition and fusion temperature (n = 5; P < 0.001), opacity (n = 5; P < 0.01), specific gravity (n = 5; P < 0.02), dynamic Young's modulus (n = 5; P < 0.01) and fracture toughness (n = 30; P < 0.001 ). The selected physical properties were found to be very sensitive to small variations in chemical composition.