The Synthesising Of Zircon Powder By The Hydrothermal Method

Zirconium silicate whose chemical formula is ZrSiO₄ and which belongs to the tetragonal crystal system is of the island structure of silicate minerals.Because ZrSiO₄ has so many excellent properties,for example high melting point,low thermal conductivity,low expansion coefficient,wonderful chemical and phase stability and so on,so it is widely used in refractory materials and pigment of zirconium based.Meanwhile sintered zirconium silicate is provided with superb thermal shock resistance,therefore,it becomes an important candidate material for high-temperature structural ceramics.The widespread use of zirconium silicate in ceramic industries is for its features such as nice chemical stability,good resistance to acids and alkali and organic solvents,great mechanical strength,strong ability of antimicrobial resistance and resistant to high temperature.In addition,it is also used in surface protection of metallic materials in corrosive environment.Zirconium silicate existing in the nature includes impurities like alumina,ferric oxide and titanium oxide,etc.which lead to the low purity.So the application of zirconium silicate is limited.It is well known that the synthesis temperature for the high-purity of zirconium silicate reaches up to 1500 degrees.In consequence,it is significant to study process research of zirconium silicate powders in low temperature.In this paper,zirconium silicate powders were prepared by hydrothermal method using zirconium oxychloride and tetraethoxysilane?TEOS?as raw materials,deionized water and as dissolvant,LiF as a mineralizer to promote crystallization of zirconium silicate.In the preparation process,the effect of zirconium silicon molar ratio,hydrothermal reaction temperature,hydrothermal reaction time,pH value of the precursor,sintering temperature and other factors on the zirconium silicate powder was studied.With the aid of XRD,SEM and other testing means to characterize the powder,so as to obtain the optimum synthesis process parameters.The results show that the ratio of Zr/Si in the former body affects the synthesis rate of zirconium silicate powder,the best molar ratio is 1.2:1.Hydrothermal synthesis of zirconium silicate powder,its synthesis rate increases with the increase of the temperature of the hydrothermal reaction,the best hydrothermal temperature is 200?.Hydrothermal reaction time also affects the synthesis of zirconium silicate powder,which can improve the synthesis of zirconium silicate powder.p H values have important influence in ZrSiO₄.pH values are 9 being propitious to compose ZrSiO₄.Without heat treatment using hydrothermal method can direct synthesis performance better zirconium silicate powder.But,hydrothermal time is long,zirconium silicate powders of hydrothermal synthesis at low temperature not only reduce hydrothermal temperature,hydrothermal time but also can increase the rate of synthesis of zirconium silicate.At the same time,speeding up the experimental progress,improve efficiency.The best synthesis parameters of not sintered zirconium silicate powder : Zr/Si mole ratio is 1.2:1,Zr/LiF mole ratio is 1.25:1,hydrothermal temperature is 200?,hydrothermal time is 48 h.Zirconium silicate powder synthesis rate of hydrothermal temperature 180?,hydrothermal time 24 h and sintering in 1000? is as high as 96%.