Study On The Preparation Of Nanometer TiO₂ By Hydrolysis

In view of the cheap and easily available titanium materials in Yunnan as the research object,the research on the preparation of nano titanium dioxide is carried out.The key technology of the easy reunion in the preparation of nanometer titanium dioxide by liquid phase method is broken through,and the best process parameters of the related process are obtained.In the study,anatase nano-titanium dioxide was prepared by direct hydrolysis,which is mainly used in lithium titanate cathode materials.The thermodynamic analysis of the preparation and hydrolysis process of TiCl₄ acid hydrolysate was focused on.The experimental conditions for the preparation of anatase nano-titanium dioxide with TiCl₄ and TiOSO₄ as raw materials were investigated,and get the best preparation conditions.During the preparation and hydrolysis of TiCl₄ acid hydrolysate,due to the extreme instability of TiCl₄,hydrolysis occurs vigorously with water,and the hydrolysis reaction is a step-wise reaction.So it can be dissolved in a higher concentration of hydrochloric acid solution to inhibit its hydrolysis.Because this is an exothermic reaction,the preparation must take place in an ice bath.The stability of the reaction solution increases with the increase of TiCl₄ concentration and decreases with the increase of the solution temperature.Lowering the concentration of TiCl₄ or increasing the temperature will promote the hydrolysis of TiCl₄.In the experiment,using TiCl₄ as raw material,studied that TiCl₄ concentration,NaOH concentration,NH₃·H₂O concentration,NH₄HCO₃ concentration,dispersant dosage,ultrasonic conditions,calcining temperature,calcination time and other experimental conditions affect the particle size and dispersibility of the product.The results showed that when the concentration of TiCl₄ was 100 g/L,the pH of the reaction solution was controlled by ammonia titration,the pH maintain at 6-7,the stirring speed was 450 r/min,and used the polyethylene glycol 2000 as the dispersant,ultrasonic aging for 60 min,the aging temperature was 40°C,and the calcination temperature was 400°C,then an anatase nano-titanium dioxide with a d50 of 30.00 nm,a specific surface area of 60-80 m²/g,and a purity of 99.1%was prepared.At the same time,ultrasonic dispersion can effectively solve the problem of product reunion,but the time should not be too long.Low-power long-time ultrasonic dispersion and high-power short-time ultrasonic dispersion can inhibit particle agglomeration.The experiment was conducted using TiOSO₄ as a raw material.The effects of surfactant dosage,TiOSO₄ concentration,reaction temperature,reaction system pH,ultrasonic dispersion,and calcination temperature on the formation and properties of nano-TiO₂ were studied.The results showed that the best calcining temperature of the product was 450°C.Too low a calcination temperature will result in the incomplete conversion of the product to anatase TiO₂;an excessively high calcining temperature will gradually transform into rutile TiO₂,and an excessively high calcination temperature will lead to further sintering of the particles,and can form hard agglomeration,resulting in difficult late grinding.Therefore,under the premise of guaranteeing the crystal phase transformation,the heat treatment temperature should be reduced as much as possible,and short the heat treatment time,or several short-time heat treatments also can contribute to the reduction of hard agglomeration.