Preparation And Surface Modification Of Nanosized ZnO

Nanosized ZnO is a new type of functional material,is widely used in many industrial fields,such as metallic automotive coating,sunscreen cosmetics,dye sensitized solar cell,photocatalyst and so on.The application of nanosized ZnO is depended upon its microstructure,surface polarity and agglomeration.In this thesis,the research results was reported,including the synthesis of nano-particles ZnO with different particle sizes and morphologies,surface modification of nanosized ZnO.The main content was concluded as follows:1 The nano-ZnO was obtained at low temperature using an improved method. The nanosized zinc oxide with different particle size could be obtained by controlling calcination temperature, reaction temperature and reactant concentration. Kinetic rule of grain growth of zinc oxide nanocrystalline was given.The results indicate that the precursor prepared with the feeding methodⅠis Zn4(OH)6CO3 ,and that prepared with the feeding methodⅡis the mixture of Zn4(OH)6CO3 and Zn5(OH)6(CO3)2. The crystal size of nanosized zinc oxide prepared with the feeding methodⅠis much small and possess good dispersibility.The suitable conditions for the preparation were given: reactant concentration was 1mol·L-1, the reaction temperature was 60℃and the calination temperature was 500℃.2 The ZnO with different morphologies was prepared by hydrothermal method,and reaction mechanism was discussed. The results showed that the microstructure of ZnO powder was depended on hydrothermal conditions. It was found that the morphology of ZnO powder was changed in presence of glycol.When the solvent was distilled water, the precursor of ZnO could not decompose under hydrothermal conditions,while the solvent was glycol,the morphology of ZnO powder under hydrothermal conditions was spherical.When V(glycol):V(water)=1:1, the precursor of ZnO could not decompose wholly,while V(glycol):V(water)≥3:1, the morphology of ZnO powder was rod.3 The nanosized ZnO was coated with amorphous silica in ultrasonic field using sodium silicate as raw materia1.The prepared samples were characterized by FT-IR, XRD and HRTEM techniques.The photostability of nanosized ZnO was also evaluated. Acording to the spectra of FT-IR,it was inferred that the Zn-O-Si bond was formed at the interface of the coating layer and the surface of nanosized ZnO particles.The HRTEM images and photostability experiment showed that the homogeneity and densificatlon of coating layer was improved from ultrasonic field and suitable heat treatment.The UV shielding capability of nanosized ZnO was enhanced due to the dense coating of silica.The increase of m(SiO2):m(ZnO)promoted the photostability of nanosized ZnO.But while the m(SiO2):m(ZnO)=1:5,the photostability and heatstability were nearly unchanged,and the growth of the crystal grains was efflectively suppressed in the process of heat treatment. 4 The surface organic modification of nanosized ZnO with silane coupling reagent LM-N308 was prepared in distilled water.The particles were studied by means of FT-IR,TG-DTA and HRTEM.Both FT-IR and HRTEM results confirmed that LM-N308 was found on the surface of nanosized ZnO Particles and an organic coating layer was formed.The weting and dispersivity experiment showed that the surface property of nanosized ZnO modified with LM-N308 was changed from hydrophilicity to lipophilicity.