Continuously Preparation Of Nano-ZnO With Size And Morphology Controlled Using Supercritical (Subsupercritical) Water Method And The Research Of Its Photocatalytic Activity

Nano-ZnO is an important nano-material with wide direct energyband gap of3.37eV and a large exciton binding energy of60meV. It hasgreat potential to be used in a wide range of applications such as solar cells,photocatalytics, photoelectric materials and cosmetics. Now thepreparation of nano-ZnO with different sizes and morphologies is a hotresearch topic, however a variety of traditional methods havedisadvantages of high cost, size and morphology uncontrolled andenvironment pollutant. This dissertation used supercritical（subsupercritical） water method to produce ZnO nano materials which cancontinuously prepare nano ZnO with size and morphology controlledrapidly and nano ZnO was obtained in the pilot project. Meanwhile, thisdissertation researched the photocatalytic activity of the ZnO nanoparticles prepared regarding its morphology. Chapter2introduces the supercritical （subsupercritical） watermethod of preparing nanoparticles and discusses how to control the sizesand morphologies of the as-synthesized ZnO nanoparticles by studyingprocessing parameters. The processing parameters mainly used in theexperiment are: temperature, pressure, Zn²⁺/OH^-molar ratio, time, andprecursor concentration.1) star-like, spherical, needle-like and rod-likeZnO particles was obtained by controlling temperature;2) ZnOnanoparticles aggregate in low pressure and disperse well in high pressure;3) ZnO nanorod with the shortest length is obtained when the molar rationof Zn²⁺/OH^-is kept1:2;4) Short reaction time;5) The size of ZnOnanoparticles decrease to a certain size when the precursor concentrationincreased. This indicates output can be increased by increasing precursorconcentration.Chapter3researched the effect of surfactant on the size andmorphology of nano-ZnO and the scale-up of project. The morphology ofZnO is effected by the types and quantities of surfactants; nano-ZnO wasobtained in pilot project.Chapter4describes the photocatalytic properties of ZnOnanomaterials. Nano-ZnO has a better photocatalytic ability comparedwith normal ZnO, its photocatalytic activity was effected by pretreatment,concentration and morphology of ZnO.