Nano-sized Zno

In this thesis, the methods of homogeneous precipitation and ultrasonic surge precipitation in preparation of nanoparticle ZnO and the influence of surfactants on the sizes of ZnO were studied in detail.Exploratory experiments for nano-ZnO preparation indicated the homogeneous precipitation and ultrasonic surge precipitation have obvious preponderance in preparation of nanometer ZnO.In the process of preparation of nano-ZnO by the homogeneous precipitation method, the average size of ZnO is mainly influenced by concentration of reactants, temperature, time, pH, stirring speed in the reaction process. Washing mode, calcining temperature and calcining time have effect to the average size of ZnO.The optimum conditions were obtained by experiments as follows: Zn(NO)2 0.6-0.8 mol/L, CO(NH2)2 2.6-2.8 mol/L, reaction temperature 95 C, reaction time 2-3 hours and stirring speed about 300 r.min-1. Zn(OH)2 was washed with low concentration ammonia, then dried for 3-4 hour at 60-80癈, and finally calcined for 3 hours at 500~550'C. ZnO with a size of 60 - 140 nm was obtained.Different surfactants and their concentrations have different influence on the size of ZnO prepared. The experiments with the optimum conditions showed that: compound surfactants and anion surfactants were better than non-ion surfactant for nanoparticle ZnO preparation by liquid precipitation method. Precipitate of good decentralization and nanoparticle ZnO of narrow distribution were obtained by controlling the sodium dodecyl benzene sulfonate 3.2 10-3 mol/L or sodium oleate 1.0 10-4 mol/L and PEG-1000 1.6 10-3 mol/L.Used as precipitator at ultrasonic surge precipitation, aqueous ammonia can increase the dissolvability of Zn(OH)2 in the form of complex. The concentration equilibrium and mass equilibrium were applied to thermodynamics analysis and calculation of the system of Zn-NH3-H2O. The diagrams of the logarithm of equilibrium concentration of the Zn-NH3-H2O system were drawn at 25 C, and the stable existing regions were studied,which provided and important theory basis for the process of the preparation nanoparticle ZnO by ultrasonic surge precipitation.The key factors of ultrasonic surge precipitation for nanoparticle ZnO preparation were the concentration of Zn(NO3)2, the concentration and dropping time of aqueous ammonia, the adding time of surfactants. The results showed that: Zn(NO3)20.7~1.0 mol/L, the mole rate of ammonia to Zn(NO3)2 is 1.0-1.2 to 1, by adding sodium oleate after reacting 10 minutes and adding PEG 1000 after 15 minutes, ZnO with a size of 30~60nm was obtained.0.01%~0.05% nano-ZnO was dispensed in water and its properties of ultraviolet and visible light absorbing were studied. The transmittance of nano-ZnO in visible zone was more than 90% and its absorbance in ultraviolet zone was 1.0-2.0. The nano-ZnO can be used to screen ultraviolet in cosmetic because the excellent properties of transmittance in visible zone and absorbance in ultraviolet zone.