Preparation And Properties Of Opaque Enstatite Glass-ceramic Glazes

White opaque glazes are very popular in the field of interior decoration and have broad market prospects.At present,the most widely used white opaque glaze on the market is the zirconium silicate opaque glaze.However,due to the increasing use of zirconium silicate year by year,high quality mineral storage is gradually depleted,leading to its high market price.Zirconium silicate contains radioactive isotopes and poses a potential threat to human safety.Therefore,it is of profound significance to prepare a kind of zirconium free glaze with good opacification effect,low price and safe usage.Besides the effect of adornment,glazes should develop toward the direction of function and the photocatalytic function of the surface is the direction that has actual use value.The purpose of this project is to prepare enstatite glass-ceramic opaque glaze,compare the performance difference between enstatite glass-ceramic opaque glaze and zirconium silicate glaze,and specifically study the crystallization process of enstatite glaze.The influences of the content of Al₂O₃ or TiO₂ on the properties of the glaze were explored.At the same time,a layer of photocatalytic film was coated on the glaze to study the influences of sintering temperature and atmosphere on the film.The main experiments and conclusions of this thesis are as follows:Firstly,enstatite glass-ceramic opaque glaze was successfully prepared by frit method.The glaze has a strong crystallization tendency,and only enstatite crystals precipitate on the glaze during the heating process.The calculated crystallization activation energy of enstatite is about300 k J/mol and the exothermic factor n is 0.35.When the sample was fired at 1200°C and held for 10 min,the enamel surface was uniformly distributed with the tetragonal and rod-shaped entensite crystals.The increase of holding time can promote the growth of enstatite along the long axis,up to 4μm.The intensity of the diffraction peak of enstatite increases with the increase of firing temperature and holding time,which reflects the tendency of high temperature crystallization and high temperature stability of enstatite.The L*value of the glaze is 91.93,the a*value is-0.89,the b*value is 0.25,and the Vickers hardness was 6.5±0.1 GPa.The internal and external illumination indexes of the samples are only 0.04 and 0.16,respectively.The comprehensive properties of the glaze are better than those of commercial zirconium silicate opaque glaze,and it has a good application prospect.Secondly,the increase of Al₂O₃ content usually improves the crystallization temperature of the glaze,reduces the thermal expansion coefficient of the glaze,promotes the growth of the crystal,and makes the glaze from enstatite crystal to spinel and cordierite mixed crystal transformation.Al₂O₃ was involved in the formation of glass network and crystal construction.The L*value of glaze is 95.52 when the addition amount of Al₂O₃ is 15 wt%.When 20 wt%Al₂O₃ is added,the microhardness of the glaze is 7.5±0.1 GPa.The increase of TiO₂ content will reduce the crystallization temperature of the glaze,improve the thermal expansion coefficient of the glaze,promote the growth of the crystal and make the glaze from enstatite to karrooite and enstatite mixed crystal transformation.When the content of TiO₂ is 8 wt%,the L*value of the glazed surface is 93.57,and the microhardness is 7.7±0.1 GPa.TiO₂ can depolymerize the glass network and destroy the integrity of the network structure.The TiO₂ photocatalytic thin film which was prepared by sol-gel method and heated at550°C under the oxidizing atmosphere contained anatase and rutile,resulting in mixed crystal effect,and the photocatalytic rate is 0.2368h^-1.When heated at 550°C under the reducing atmosphere,the film contains anatase and Ti³⁺,and the photocatalytic rate is 0.2590 h^-1.