Preparation And Properties Of Transparent Zn_1-xCo_xO Nano-Dispersion And Zn_1-xCo_xO/PVB Composite Films

Some inorganic materials have good UV-shielding property,such as TiO2, ZnO, CeO2, SiO2, et al. The transparent organic-inorganic nanocomposites with UV-shielding ability can be fabricated via the introduction of these inorganic nanoparticles into organic polymers, which can be widely used in the fields of optical devices and packaging. In order to prepare the highly transparent nanocomposites,the inorganic particles should be small enough and have good dispersibility in polymer matrices. However, the absorption edge of the nanoparticles would blue shift to shorter wavelength due to the quantum size effect, resulting in the transmission of part of UV light which is harmful to the optical devices. One solution is to dop metal oxide, which enable to modify the band gap structure of the matal oxide, thus lead shift of the absorption edge.In this research, the preparation of Co doped ZnO(Zn1-xCoxO) nano-dispersion and its application in Polyvinyl butyral(PVB) resin were studied, the influences of preparation conditions on Ultraviolet absorption edge of materials were also discussed, and nano-dispersion and composite films which could shield all UV light as well as keeping the transparency in visible light region were obtained. The main results are as follows:1. Zn1-xCoxO nanoparticles were prepared by solvothermal technique. The influences of preparation conditions on the optical properties of the Zn1-xCoxO nanoparticles were studied, and it proved that the doping of Co is an effective method of the absorption edge shifting to longer wavelength, and the appropriate preparation process conditions were as follows:solvothermal temperature140℃, solvothermal time10h, pH=9; The crystal structure and morphology of Zn1-xCoxO nanoparticles were investigated, proving that the doping of Co did not change the wurzite hexagonal structure of ZnO, but led to smaller particle size than undoped nanoparticles.2. Transparent Zn1-xCoxO dispersions were synthesized by one step solvothermal technique. The effect of molar percentage of Co, solvothermal temperature, solvothermal time, the amount of modifier, modifying time, et al to the dispersibility were investigated, and the appropriate preparation process conditions were as follows:solvothermal temperature140℃, solvothermal time10h, the amount of modifier30wt%, modifying time4h; the influence of Co molar percentage and concentration of Zn1-xCoxO nanoparticles on the optical properties of the dispersions were studied, and the results showed that the increase of molar percentage or concentration would lead to the red shift of absorption edge. The surface structure and morphology were characterized by XRD, XPS, TEM, FT-IR. The results showed that:the modified samples remained wurzite hexagonal structure and the surfactant interacted with the-OH on the surface of nanoparticles, making the nanoparticles dispersed uniformly in ethanol.3. Transparent Zn1-xCoxO/PVB composite films were obtained through the simple blending method. The influences of Co molar percentage and additive amount of Zn1-xCoxO nanoparticles on the optical properties of composite films were studied, and the results showed that increase of molar percentage or additive amount of Zn1-xCoxO nanoparticles would lead to the red shift of absorption edge. For example, with the same additive amount of Zn1-xCoxO nanoparticles, when the UV-shielding rate was95%, the wavelength of ZnO/PVB was350nm while the wavelength of Zn1-xCoxO(x=0.125)/PVB was380nm, indicating that the absorption edge red shifted30nm.