The thermal expansion curves are reported for ''as-quenched'' and ''heat-treated'' glasses obtained by adding MgO (8-16%) and TiO2, (4%) to porphyric sands of composition: SiO2=72.40%; Al2O3=13.85%; K2O=4.60%; Na2O=3.00%; Fe2O3=2.15%; CaO= 1.30%; MgO=0.84%; TiO2=0.20%; loss on calcination = 2.06%. The variations in the glass transition temperature T-g, the thermal expansion coefficient alpha, and the dialatometric softening temperature M(g), are discussed. The experimental results can be explained by assuming that Na2O, K2O and CaO (all or a part of them) segregate preferentially with respect to MgO into the titania-rich phase. Diffusion appears to fall as the MgO content is increased.
Thermal-expansion Behavior of Glass-ceramics Derived From Prophyric Sands / Branda, Francesco; Costantini, Aniello; P., Scardi; A., Tomasi. - In: THERMOCHIMICA ACTA. - ISSN 0040-6031. - ELETTRONICO. - 227:(1993), pp. 43-48. [10.1016/0040-6031(93)80247-8]
Thermal-expansion Behavior of Glass-ceramics Derived From Prophyric Sands
BRANDA, FRANCESCO;COSTANTINI, ANIELLO;
1993
Abstract
The thermal expansion curves are reported for ''as-quenched'' and ''heat-treated'' glasses obtained by adding MgO (8-16%) and TiO2, (4%) to porphyric sands of composition: SiO2=72.40%; Al2O3=13.85%; K2O=4.60%; Na2O=3.00%; Fe2O3=2.15%; CaO= 1.30%; MgO=0.84%; TiO2=0.20%; loss on calcination = 2.06%. The variations in the glass transition temperature T-g, the thermal expansion coefficient alpha, and the dialatometric softening temperature M(g), are discussed. The experimental results can be explained by assuming that Na2O, K2O and CaO (all or a part of them) segregate preferentially with respect to MgO into the titania-rich phase. Diffusion appears to fall as the MgO content is increased.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
