纳米ZnO的制备

【作者】 王赛；

【导师】 石西昌； 秦毅红；

【作者基本信息】 中南大学 ， 冶金物理化学， 2003， 硕士

【摘要】 本文分别对均匀沉淀法和在超声振荡下用直接沉淀法合成纳米氧化锌进行了详细地研究，并研究了表面活性剂对氧化锌粒径的影响以及纳米氧化锌对紫外光的吸收。 首先对纳米氧化锌的制备方法进行探索，研究表明：均匀沉淀法以及在超声振荡下用直接沉淀法在液相制备纳米氧化锌中有明显的优势。 均匀沉淀法制备纳米氧化锌过程中原料的起始浓度、反应温度、反应时间、终点pH值、搅拌速度、洗涤方式以及焙烧温度和时间对纳米氧化锌的粒径有较大的影响。研究表明最佳工艺条件控制为：硝酸锌的浓度0.6～0.9mol／L，尿素的浓度2.6～2.8mol／L，反应温度95℃，反应时间2～3小时，反应过程伴随机械搅拌，且搅拌速度300r．min^-1，过滤时用低浓度的氨水洗涤数次，在60～80℃的干燥箱中干燥3～4h，然后放入500～550℃的马弗炉中焙烧3小时，能得到大部分颗粒粒径分布在60～150nm之间的纳米氧化锌。 不同的表面活性剂对纳米氧化锌的粒径影响差别较大，表面活性剂的浓度也是影响纳米氧化锌粒径的关键因素。研究表明：在液相法制备纳米氧化锌时，复合型表面活性剂以及阴离子型表面活性剂的分散性能优于非离子表面活性剂。添加浓度为3.2×10^-3mol／L的表面活性剂十二烷基苯磺酸钠时，沉淀物的分散活性好，能够较好的控制氧化锌的粒度；油酸钠和聚乙二醇1000复合型表面活性剂浓度分别为1.0×10^-4mol／L和1.6×10^-3mol／L时分散效果最好，能制得粒径为40-70nm的纳米ZnO。 直接沉淀法中用氨水为沉淀剂，氨水易和锌生成络合物，根据同时平衡原理和质量平衡原理对Zn-NH₃-H₂O体系进行了详细的热力学分析和计算，并在此基础上绘制了Zn-NH₃-H₂O在25℃下的锌的平衡总浓度对数—pH图，研究了沉淀物的稳定存在区，为超声振荡直接沉淀法提供了重要的理论依据。 在超声振荡下直接沉淀法制备纳米氧化锌的关键是控制硝酸锌的浓度、氨水的浓度以及滴加速度、表面活性剂加入时间。实验结果表明：用超声振荡直接沉淀法制备纳米氧化锌，当硝酸锌的初始浓度在0.7～1.0 mol／L，氨水和硝酸锌的摩尔比为1.0～1.2，在反应10分钟后加入油酸钠，15分钟后加入聚乙二醇1000能得到30～60nm的纳米氧化锌。 将制得的纳米氧化锌制成浓度为0.01％～0.05％的水溶胶，在可见光区的透光率能达到90％以上，而在紫外区的吸光度能达到1.0～2.0，纳米氧化锌在可见光区优良的透光性以及紫外光区强的吸光率能用于制备防晒化妆品。更多还原

【Abstract】 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.更多还原