| Summary: | 碩士 === 長庚大學 === 化工與材料工程研究所 === 97 === In this work, zinc oxide (ZnO) nanoparticles was synthesized by calcining zinc hydroxide (Zn(OH)2) powders produced from precipitation reaction of zinc salts and sodium hydroxide (NaOH) in a rotating packed bed. ZnCl2, Zn(CH3COO)2, Zn(NO3)2, and ZnSO4 were the model zinc salts herein. This study was conducted to examine how the types of zinc salts and the mole ratio and concentration of reactants affect particles size, morphology and size distribution of Zn(OH)2.
Based on the experimental results, the different zinc salts could offer different morphologies of Zn(OH)2 powders under the appropriate conditions, including spheroidal, rod-like, flower-like, flake-like, spindle and random shapes. Furthermore, the condition for the superior performance of Zn(OH)2 powders was dependent on types of zinc salts. When zinc chloride was used, concentrations of ZnCl2 and NaOH were 0.8M and 1.6M, respectively.When zinc acetate was used, concentrations of Zn(CH3COO)2 and NaOH were 0.4M and 0.8M, respectively. When zinc nitrate was used, concentrations of Zn(NO3)2 and NaOH were 0.2M and 0.2M, respectively. When zinc sulfate was used, concentrations of ZnSO4 and NaOH were 0.1M and 0.2M, respectively.
Using ZnCl2 as zinc salt, spherical ZnO nanoparticles having the smallest mean size of about 85nm, narrower size distribution and better dispersion were produced. Moreover, the highest solid content of about 28 g/L in the product solution of Zn(OH)2 was obtained by using ZnCl2 as zinc salt. Based on UV absorption analysis, ZnO nanoparticles by ZnCl2 had a maximum absorption at the wavelength of 370 nm. Consequently, ZnCl2 was suggested to be used as zinc salt for production of ZnO nanoparticles.
The analytical result of ZnO powders was synthesizd by high-gravity reactive precipitation method and direct precipitation method indicated that the synthesizd ZnO powders by high-gravity reactive precipitation method had the advantage of smaller size, uniform morphology, narrow size distribution and higher UV absorption.
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