Systematic Control Of Size, Shape, And Structure Of TiO₂ Nanoparticles

Nano-titania is an important fine inorganic material with high performance. Because of its advantages,such as big specific surface area,high surface activity, good resistance to weathering,outstanding chemical stabilization and good uviorsistant properties,nanosized TiO₂ can be applied in painting,cosmetic, photosensitive materials,photo catalyst,protection of environment,peeking material of food and medicine field and so on.All kinds of these applications are connected with crystal structure and shape of nanopowders,therefore the preparation of nano-titania has become a research hot spot in nano-material science and technology.Rutile TiO₂ has many advantages such as high refractive index,good heat resistance and stable chemical properties.But nowadays,little research has been done on preparation of rutile TiO₂ powders.Most of methods for preparing ruitle TiO₂ need high temperature calcination,which will cause agglomeration of the powders and then limit its application.Based on the above reasons,the preparation of rutile TiO₂ nanopowders with different size and shape is necessary and important.Titanium isopropoxide and titanium tetrachloride were selected as precursors to get the products by hydrothermal method.This method is of outstanding characteristics such as simple process,high rate of reaction and low reaction temperature etc.Very importantly,all of these characteristics may offer the theoretical and practical bases for industrial production.The main research aspects are follows:(1) Preparation of high aspect ratio rutile TiO₂ nanoparticlesRutile TiO₂ nanoparticles were prepared by hydrothermal method at low temperature.The influences of acid concentration,aging time and additives (polyethylene glycol 4000(PEG 4000),cetyl trimetylammonium bromide(CTAB), and sodium laury sulfate(SDS)) on the size and morphology of TiO₂ crystalline were investigated.The results showed that higher concentration of acid would be favorable to the preparation of large rutile TiO₂ nanoparticles with high aspect ratio. Concentration of acid can also affect the yield of TiO₂ nanoparticles.Smaller rutile TiO₂ nanoparticles were prepared in presence of the above additives.The size of TiO₂ nanoparticles reduced with increasing concentration of additives.The high aspect ratio rutile TiO₂ nanoparticles were obtained in high concentrated acid probably due to reduction of growing rate on special crystal planes caused by the adsorption of H⁺ ions.(2) Preparation of rutile TiO₂ nanospheresSpheric rutile TiO₂ nanoparticles were successfully synthesized using titanium tetrachloride in ethanol solution via hydrothermal method at 160℃.In the experiment, the size of TiO₂ nanoparticles could be controlled by the content of ethanol.(3) Influence of seeds on size and phase of TiO₂ nanoparticlesThe experiment that seeds with different phase structures were added during preparation of rutile or anatase TiO₂ nanoparticles,showed that seeding could not affect the phase structure of TiO₂ nanoparticle,but as the content of seeds increased, the reaction was accelerated and the particle size was decreased.The seeding technique is undoubtly useful for the systematic control of the final particle size and the growth model.