Preparation of Glass-Ceramics in the R2O-Bi2O3-B2O3-SiO2 System Applied in Automobile Glass Enamel

Abstract

Environmental deterioration has put higher requirements on the acid resistance of automotive glass enamel. The present paper aims to prepare acid-resistant glass-ceramics used in automobile glass enamel. Base glasses with the compositions 15R2O-xBi2O3-10B2O3-(75-x) SiO2 (R2O is a mixture of Li2O, Na2O, and K2O (1:1:1, molar ratio), where x = 10, 15, 20, 25, and 30, respectively) was prepared by the melt-quenching method, and glass-ceramics were prepared by their controlling crystallization heat treatment. Crystallization behavior and crystallization ability of base glasses were investigated using the thermal stability parameter (S), the crystallization kinetics calculation results of base glasses, as well as the phase identification results of the heat-treated samples. The effects of the heat treatment temperature on the micromorphology and acid resistance of the heat-treated glasses were also investigated. Then, the optimized glass ceramic was used to prepare automotive glass enamel. The results indicate that: (I) with the increase of Bi2O3/SiO2 ratio, the characteristic temperature of the base glass decreases, the coefficient of thermal expansion (CTE) and crystallization ability increases significantly, the crystallization temperature range becomes wider; (II) the crystallization activation energy of base glasses are in the range of 169~264 kJ/mol; (III) Bi2SiO5 and Bi2O2SiO3 metastable phases are mainly precipitated when the crystallization temperature is between 530 °C and 650 °C, while only Bi4Si3O12 phase is precipitated when the crystallization temperature is above 650 °C; (IV) crystallinity of base glass increases significantly with increasing heat treatment temperature, which is beneficial to improve the acid resistance of heat treated products; (V) automotive glass enamel was prepared by mixing 15R2O-25Bi2O3-10B2O3-50SiO2 glass-ceramic powder with copper-chrome black and varnish, and then printed on the automobile glass substrate. All the properties of the sintered enamel can meet the market requirements, and the acid resistance of our product is better than that of market products.