Study On The Preparation And Surface Modification Of Nano-sized Barium Sulfate

Nano-sized barium sulfate is a kind of white amorphous inorganic nano powder.It can be used for painting,printing,papermaking,plasticmaking,rubbermaking,pharmaceutical,ceramics industry and other industries as filling-agent.Compared with traditional barium sulfate,nano-sized barium sulfate has many excellent properties,such as good optical performance,good adsorption,strong anti-aging force and good stability.But as its particle size is small,big specific surface area and high cohesive energy,nano-sized barium sulfate is easy to get together hard in the process of drying,and its caking phenomenon is serious.So nano-sized barium sulfate losts the nanoscaleand advantage and its application is limited.The markets of domestic and foreign require for the fine and uniform nano-sized barium sulfate,therefore the market price of nano-sized barium sulfate is higher than the ordinary barium sulfate.So the domestic and foreign scholars pay much attention to study on how to produce nano-sized barium sulfate which is small particle size,and narrow distribution.Morever,how to improve the dispersion of powder products and the stability of the wet fluid products in later modified treatment is also important.The anthor firstly used industrial barium chloride and sodium sulfate as raw materials in this thesis.By different feeding cross-sectional area of the impinging stream reactor,nano-sized barium sulfate had been prepared in rapid precipitation.On the basis of the early research of the team,instead of impinging stream microreactor(impact angle was60°,feed cross-sectional area was 0.32mm~2),the feasibility of amplification experimental had been verificated.In order to got a small particle size,narrow distribution of nano-sized barium sulfate,the preparation conditions had been further optimizated.The experimental results showed that at room temperature using smaller than1.56mm~2 of feed sectional area of impinging stream reactor as the reactor was no amplification effect;When the feed sectional area of impinging stream reactor was 1.56mm~2,reactant concentration was 1.2 mol/L,feed velocity of reactant was 10.42 m/s,collision angle of two reactant is 60°,25.17 nm nano-sized barium sulfate still had been acquired.Using high speed mixer insteading of ordinary mixer,nano-sized barium sulfate had been modified by means of wet reaction to solve the problem of hard together of nano-sized barium sulfate in the process of drying so as to improve the dispersion of the powder product.Modified condition had been optimized.The cladding situation and the morphology of the modified nano-sized barium sulfate havd been characterized and the modified mechanism had been analyzed.The experimental results showed that using high speed mixer,the problem that common stirrer can't solve had been solved in the wet modifying.When the particle size of nano-sized barium sulfate was 25.17 nm,the modified speed was 3500 rpm,the modification time was 15 min,the modification temperature was 65?,the dosage of modifier was 5%,the activation degree of 99.88%powdered hydrophobic nano-sized barium sulfate had been acquired.In view of the small particle size,the large specific surface area,the easy agglomeration of nano-sized barium sulfate,by adding dispersant and the ultrasonic method,the stability of wet fluid products had been studied.Stability conditions of wet fluid product had been optimized.The experimental results showed that when the water and dimethyl sulfoxide were using as liquid medium respectively,the pH were 10 and 7respectively,the dispersant were polyacrylic acid sodium and none respectively,the ultrasonic time was 15 min,the precipitation height of nano-sized barium sulfate were 8.9cm and 9.7 cm respectively and diameter were 61.79 nm and 89.4 nm respectively and the potential were 38.6 mv and 22.3 mv respectively.A good stability effect was achieved.