【作者】 赵娜；

【导师】 吴建锋；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2008， 硕士

【摘要】 本文分别对高分子网络法、溶胶-凝胶法和均匀沉淀法合成纳米氧化锌粉体进行了详细地研究,并研究了离子掺杂对纳米氧化锌粒径、形貌及其光催化性能的影响,分别采用X射线衍射仪、透射电镜、和紫外分光光度计进行了表征。实验结果明,采用高分子网络凝胶法、溶胶-凝胶法、均匀沉淀法均能获得结晶良好、纯度高的六方晶系红锌矿型纳米ZnO粉体。但由于工艺条件的限制,这些方法各有其优缺点,高分子网络法制备纳米ZnO的周期比较短（时间为15h左右）,但是该方法所用的有机试剂较多,成本较高,而且对反应设备的要求非常严格,实验可重复性差,不易实现工业化。溶胶-凝胶法制备纳米ZnO,虽然原料的成本的低,但是凝胶干燥困难,制备周期很长（时间为38h左右）,而且凝胶很容易粘在器壁上难于取出,给后续的处理带来很多不便,亦不易实现工业化生产。均匀沉淀法制备纳米ZnO,工艺相对比较简单,制备周期也比较短（时间为11h左右）,但是所制备的粉体粒径分布较宽,团聚比较严重。采用高分子网络凝胶法制备的纳米ZnO粒子平均晶粒尺寸在20～60nm范围内。综合衍射峰形态、半高宽、晶粒度、节能考虑,高分子网络法制备纳米ZnO过程中的优化工艺条件为:单体和网络剂比例为5:1、Zn²⁺浓度为0.35mol/L、引发剂与单体双键的比例为1:20（摩尔比）、溶液pH值的范围在5～6、反应温度80℃、反应时间2h、干燥温度100℃、干燥时间4h、热处理度为650℃。采用溶胶-凝胶法在热处理温度为550℃热处理1h时制备的纯纳米ZnO的平均晶粒度最小为28.33nm。随热处理温度的升高,纳米ZnO的平均晶粒尺寸呈现出先减小后增大的趋势,而平均结晶度则呈现出相反的趋势。La³⁺的掺入可抑制ZnO晶核的生长,当La³⁺掺入量为0.2%时,纳米ZnO粒子的晶粒尺寸达到最小,为21.27nm。随着La³⁺掺入量继续增加,晶粒尺寸长大。采用均匀沉淀法制备的纯相纳米ZnO粉体和Bi³⁺掺杂纳米ZnO粉体均为六方晶系红锌矿结构,掺杂并未改变ZnO的晶系结构,但对其晶粒形貌产生了影响,除了球状形貌外,还产生了大量棒状结构,长度在30～200nm不等。纳米ZnO的光催化性能研究结果表明:La³⁺离子的掺杂对纳米ZnO粉末的光催化效果有明显的改善,随着La³⁺离子掺入量的增加,纳米ZnO的光催化活性呈现先升后降的趋势。当La³⁺掺杂摩尔比为0.2%时,降解率最高,光照时间15min降解率可达68.31%。而Bi³⁺离子的掺杂降低了纳米ZnO的光催化活性,光照80minMB的降解率已由68.26%降低到10.02%,但随着Bi³⁺掺杂量的增加,其光催化活性有所改善,当掺杂量达到3%时,光催化降解率又升高到46.98%。更多还原

【Abstract】 In this article,the methods of polyacrylamide-gel,sol-gel and homogeneous precipitation in preparation of nanometer ZnO powder were studied in detail.The influence of ion implantation on particle size,appearance and photocatalysis performance of nanometer zinc oxide was researched,which have been separately characterized by X-ray powder diffractometer,transmission electron microscope and ultraviolet spectrophotometer.The experimental result was listed as follows.Well-crystallized and high-purity nanometer ZnO powders were all obtained by polyacrylamide-gel method,sol-gel method and homogeneous precipitation method, and the patterns of nano-ZnO particles all belonged to hexagonal system in type of zincite structure.But every method has its advantage and disadvantage respectively as the limit of technological conditions.The production cycle of polymer network method is quite short（it is about 15h）,but the cost is much higher due to the using of excessive organic reagents,moreover it is extraordinarily strict to the request of equipment.So polymer network method is difficult to realize industrialization on accout of bad repeatability.Although the cost of raw material is lower in sol-gel method,drying gelatin is quitely hard.The producetion cycle is very long（it is about 38h）,and the gelatin is much easy to stick on the vessel wall to bring for a lot of inconvenience in the follwing processing.So sol-gel method is also hard to realize industrialization.The craft of homogenous precipitation is relatively simple,the production cycle is short（it is about 11h）,but the grain-size distribution of nanpmeter ZnO powders is quite wide,and the reunion is quite serious.Nanometer zinc oxide was synthesized by polyacrylamide-gel method,and the mean particle size of zinc oxide powders was range from 20nm to 60nm.Overall considering the diffraction peak shape,half peak width,mean particle size,average crystallinity and energy conservation,the optimum technological conditions preparing nanometer ZnO by polyacylamide-gel method were that the ratio of monomer and lattice reagent was 5:1,the starting concentration of Zn²⁺ions was 0.35 mol/L,the ratio of reaction initiator content and the monomer double-bond was 1:20（mol ratio）,the range of pH value was 5～6,the reaction temperature was at 80℃,reaction time was for 2h,the dry temperature was at 100℃,the drying time was for 4h,the heat treatment temperature was at 650℃.The pure nanometer zinc oxide of smallest grain size was synthesized by sol-gel method,when the heat treatment was for 550℃.The heat treatment temperature had a directly influence on the crystallization and grain size.With the increasing of heat treatment temperature,the mean particle size of nanometer zinc oxide decreased firstly and increased afterwards,while the average crystallininty presented opposite trend.La³⁺ion dopant would immediately influence the grain size of nanometer zinc oxde.When the La³⁺ion dopant was 0.2%,the smallest mean particle size of nano-ZnO was acquired,the size of which is 21.27nm.But when the content of La³⁺ ion dopant surpassed the fixed quantity,the grain size of nanometer zinc oxide would increase again.The pure nanometer ZnO powder and Bi³⁺-doped nanometer ZnO powder were synthesized by homogeneous precipitation method.The pattems of them all belonged to hexagonal system in type of zincite structure.Bi³⁺-doping has not changed the crystal system structure,but had an influence on the grain appearance. Besides spherical appearance,massive clavate strunctrure was arised,the length of which was range from 30nm to 200nm.The result of photocatalysis performance of nanometer zinc oxide indicated that La³⁺ion dopant has a distinct improvement to the photocatalysis performance of nanometer zinc oxide,compared with pure nanometer zinc oxide.With the increasing of La³⁺ion dopant,the photocatalysis performance of nanometer zinc oxide increased firstly and decreased afterwards.When the La³⁺ion dopant was 0.2%, light application time was 15min,the degradation ratio of methylene blue reached the highest 68.31%.while Bi³⁺ion dopant presented opposite trendency,which reduced the photocatalysis performance of nanometer zinc oxide.When the light application time was 80min,the degradation ration of MB decreased from 68.26%to 10.02%.But the photocatalsis activity improved with increasing of Bi³⁺ion dopant. When the Bi³⁺ion dopant reached to 3%,photocatalysis degradation ratio rasied to 46.98%again.更多还原