Effect of K2O/ZnO+CaO Ratio on Density, Glass Forming Ability, Crystallization of SiO2- Al2O3- ZnO- K2O- CaO Frites

The frites by mole fraction of 2.5 SiO 2 , 0.20 Al 2 O 3 , 0.15 B 2 O 3 , 0.15ZnO, 0.17K 2 O, 0.67CaO systems in three ratios of S including 0.37(denoted by F1frites ),0.31(F2), 0.24(F3) (S=K 2 O/CaO+ZnO) were studied. ZnO powder with 500 nm (N series) and >1μm sizes (F series) opted from the recycled Zn ingots dusts and commercially ZnO respectively, were used as the raw materials. By decreasing the S ratio, the Molar Volumes of frites were decreased, The glass transition ΔT g (=-154ºC), and the crystallization temperatures ΔT p (=+17ºC) values were decreased and increased respectively. It was shown that the GS (glass stability) values are independent of the Zinc Oxide's powder size, while the Molar Volumes of N series were lower than the F ones. The Zinc Silicate (Willemite) beside Anorthite and Parawollastonite phases were crystallized in the resulted glazes. The hardness values were in 700-850 Hv range, the transparency and whiteness were higher than 80 and 60 respectively.