Preparation Of Nanocrystalline Zinc Titanate Powders Via Precipitation Process And Their Performance

Zinc titanates are of great potentials to be applied in the material fields of sorbents for the desulfurization of hot coal gases, catalysts for dehydrogenation of alkanes, microwave dielectrics, and phosphors. Therefore current materials studies are much concerned with them. According to a great number of literatures, this paper summarizes that there exist three compounds of different structure in ZnO-TiO₂ system: zinc orthotitanate (Zn₂TiO₄), hexagonal zinc metatitanate (ZnTiO₃) and cubic zinc metatitanate (ZnTiO₃). As the most thermodynamically stable phase, Zn₂TiO₄ is easy to be prepared, but pure ZnTiO₃ phase is very difficult to be synthesized and the preparation method reported is mainly the sol-gel technique. This paper reveals that industry grade titanic hydroxide and ZnSO₄ are used as reactants to prepare nanocrystalline zinc titanate powders by a precipitation process and their application performance is studied.This paper first reports the remarkable broad-spectrum UV-shielding characteristic of Zn₂TiO₄ nano-powders. Ultraviolet spectrophotometric analysis was employed to investigate the UV-shielding performance of Zn₂TiO₄ nano-powders. The effect of Zn to Ti mole ratio, calcinations temperature and particle size on the UV-shielding performance of Zn₂TiO₄ nano-powders were discussed and the mechanism of UV-shielding was further analyzed. The optimum processing conditions for preparing nanocrystalline Zn₂TiO₄ powders via the precipitation process are as follows: Zn₂TiO₄ powders can be obtained with Zn to Ti mole ratios of 2:1, 3:1 or 5:1 at a temperature range of 600～900℃for 2h; when Zn:Ti=5:l, the sample powders obtained at a calcination temperature of 800℃develop completely in crystalline form and have a median particle size of 78nm, which can attenuate more than 97% UV radiation in both UVA and UVB region. As a broad band and strong absorption UV-shielding agent, nanocrystalline Zn₂TiO₄ powders have a well perspective in application areas such as cosmetic and dope et al.Cubic Zn₂TiO₄ nano-powders were prepared by a precipitation process. DSC, XRD, SEM, TEM and FTIR were employed to characterize the powders and study the formation and transformation of Zn₂TiO₄ phase. The results reveal that, when Zn:Ti=l:l, and Na₂CO₃ is used as the precipitant, pure cubic phase of ZnTiO₃ nano-powders can be synthesized, with a particle size of about 60-130nm, after three hours' calcination at a temperature of 600℃. If the temperature is much higher, cubic phase of ZnTiO₃ would be transformed into hexagonal ZnTiO₃ and further decomposed into Zn₂TiO₄ and rutile TiO₂ finally. The preparation process is not complex with low cost and can be easily applied in industrial production.In order to solve the severe environment pollution problems caused by dye waste water, this paper also conducts a preliminary study on the photocatalytic degradation and absorption performance of nanocrystalline zinc titanate powders. The results show that, under ultraviolet irradiation for a long time, both ZnTiO₃ and Zn₂TiO₄ have exhibited photocatalytic degradation effect; when the illumination time extends or the calcination temperature is lower, the degradation rate of methyl orange solution rises; after ultraviolet irradiation for 10h, the photocatalytic degradation rate of cubic ZnTiO₃ to methyl orange solution was 61.2%. Cubic ZnTiO₃ possess well absorption performance to different kinds of dye solution; with the increasing of the ZnTiO₃ dosage, the adsorption activity increases accordingly, when the dosage exceed 800mg; the adsorption rate was as high as 90%; in the strong acidity condition, the adsorption activity is enhanced dramatically. Due to their photocatalytic degradation and absorption performance, nanocrystalline zinc titanate powders are of some application value in solving the environment pollution problems caused by dye waste water.