| The nano-titania has high surface area and its size is between l-100nm. The surface atom number, surface ability and surface tension of nano-titania are sharply increased along with the degression of the diameter. Because of its physical and chemical properties such as good resistance to weathering , chemical resistance, good transparency and uniform distribution of particle size ,it is intensively applied in the environment, information, materials, sources of energy ,medical treatment and hygiene, etc. But in practice, its strong polarity and easy aggregation limit its excellent function. So surface modification of nano-titania is a hotspot in nanometer science.Presently, there are many methods of surface modification on nano-titania. But in the practical application, because of the limit in different conditions, we usually modify the surface of TiO2 by the methods of physical absorption and esterification. Although many people do such research, few people study the influence of surface modification systemically and disciplinarily. Fewer people study the modification mechanism and character of products perfectly. Based on the shortcoming of these researches, we selected TiCl4 as precursor, prepared nano-titania by boiling reflux method. And we modified the TiO2 surface with anion and cation surfactant. We studied the influences on surface modification of different conditions and the absorption mechanism of surfactant in the process of modification. At the same time, in order to get small size and well effect modified TiO2, we modified the titania surface with stearic acid by sol-gel method. Speculating the reaction mechanism by different character of products, this paper gave the theoretic base for industrial production of TiO2 in the surface modification field.The major work includes the following aspects:(l)The study on preparation of nano-anatase and its surface propertiesIn order to compare different conditions of modification and the properties of products, Firstly, we carry through literature search and analyze the former work , TiCl4 was selected as raw materials, the enough and different sized spherical nano-titania were prepared by boiling reflux method, as raw materials to study surface modification. All of the samples have been characterized by granularity distribution, XRD, TEM, at the same time we tested the contact angle, dispersion capability and surface electrics of the nano-titania. All of the above are prepared for next work.(2)The preparation and characterization of nano-titania modified by stearic acidIn order to get high effect modified nano-titania, we tried to make carboxyl react with hydroxyl, so that the surface of nano-titania was coated by stearic acid. However we found that stearic acid can not be satisfying dissolution in water, and at the same time nano-titania cant be effectively dispersed in organic dissolvent. For these factors, it is difficult to acquire small sized and high properties modified nano-titania. We added stearic acid in the process of preparation of nano-titania by sol-gel method. We successfully prepared nano-titania modified by stearic acid which size less than 30nm.All of the above samples have been characterized by contact angle, TG-DTA, FTIR, XPS,XRD etc. The results show that after modified by stearic acid ,nano-titania get fine surface effect. At the same time, we studied the mechanism of surface modification and put forward competition mechanism.(3) The study on nano-titania was modified by cetyl three methyl amine bromide and absorption mechanismIn order to acquire nano-titania which surface modified by organic, we selected cetyl three methyl amine bromide which has double relative structure as raw material. It not only has good solubility but also can keep good dispersion of nano-titania in the process of modification. By controlling factors of concentration, temperature, pH etc, we get small sized but high effective modified samples. By testing contact angle , TG-DTA,FTIR, absorption isotherm and TEM, we found that the surface of nano-tita... |
