Studies On Surface Coating Of Nano-Titania And Its Properties

The nanometer-sized titania is an important high performance fine inorganic materials. It has a very high additional value. Its size is between l-100nm. Because of its physical properties are quite different from those of the bulk nano-titania is now being studied intensively.lt has a lot of special physics and chemistry properties, such as good resistance to weathering , chemical resistance, good transparency and uniform distribution of particle size, etc. But, because of its surface strong polarity and easy aggregation limit its practical use. So surface modification of nanometer TiOz is a hotspot in nanometer materials science.Although many people are engaged in researching on modification of TiOa powder, the effect factors of modification and properties of products have been less studied systematically, much less on mechanism of coating and structure analysis. In this paper, the simultaneous neutralization method is proposed for the process of silicon dioxide film coating on different size TiOz particles. The main experimental conditions including neutralization speed, temperature and pH on film formation, concentration and joined way of sodium silicate etc are researched systematically. Surface characterization and properties of coated powders were researched by using UV-Vis, IR, XRD, TEM, etc. The mechanism of coating and the effect factors are proposed.The main research shows as follows:(l)The preparation of different size anatase nano-titaniaDifferent size anatase nano-titania were synthesized by boiling reflux from TiCL?aqueous solution. Transmission electron microscopy(TEM), X-ray diffraction(XRD), particle size distribution were used to characterize it.(2)Study on dispersion behavior of nano-titania powder in aqueous solutionIt's important to improve dispersion of nano-titania in aqueous solution, because its dispersion can decide directly the effect of modification. So the effects of experimental conditions (such as, dispersant, pH, etc.) on dispersion behavior of nano-titania in aqueous solution were studied by spectrophotometry for the first time. Experimental results show that satisfactory and stable dispersion TiO2 in aqueous solution is obtained under the condition of using the Na2SiO3 as dispersant which is 0.8% of TiOa in mass, pH between 8 to 10 and ultrasonic dispersing time about 10 minutes. Particle size distribution and zeta potential confirm the above result. This method is with such outstanding characteristics as simple equipment, fast rate, high accuracy etc.(3)Research on the coating process of silica on nano-titania and mechanism of coatingIn this part, the simultaneous neutralization method is proposed for the process of silicon dioxide film coating on different size TiCh particles. The main experimental conditions are researched systematically, including neutralization speed, temperature and pH on film formation, concentration and joined way of sodium silicate etc. The mechanism of coating and the effect factors are proposed.(4)Characterization and properties of SiOj-coated nanometer TiO2SiO2-coated nanometer-sized TiOi was characterized by TEM, XRD, andrvX-ray energy spectrometry(XES). The result shows that the surface of TiOj is coated with amorphous membrane of SiC^. The properties of nano-titania and SiCVcoated nano-titania were compared by using Ultraviolet absorption spectrometry(UV) and particle size distribution. All data of UV shielding capability, average size and size distribution show that the properties of modified nano-titania have had improvement in dispersion, stability and solubility in acid, etc.