均匀沉淀法制备纳米Co₃O₄的研究

【作者】 张明月；

【导师】 廖列文；

【作者基本信息】 广东工业大学 ， 化学工艺， 2003， 硕士

【摘要】 本文采用均匀沉淀法制备纳米Co₃O₄粉体材料，研究了制备工艺条件、沉淀反应和前驱体热分解过程的动力学，主要研究内容及结果如下： 以硝酸钴为原料，尿素为沉淀剂，采用均匀沉淀法制备纳米Co₃O₄，考察了硝酸钴浓度、反应物摩尔比、反应温度和时间、干燥温度和时间、煅烧温度和时间等条件对产物粒径的影响。结果表明，在优化的制备条件下可得到分散性较好、平均粒径为20nm左右的立方相纳米Co₃O₄粒子。 以产物的平均粒径（nm）为优化指标，选择硝酸钴浓度、反应物摩尔比、反应温度和反应时间四个因素，运用均匀试验设计技术进行3⁵×1³因素优化试验，发现反应温度对产物的粒径影响最大，其次分别为反应物摩尔比、硝酸钴浓度以及反应时间，并确定最佳反应条件为：硝酸钴浓度0.35mol／L，反应物摩尔比为3.53：1，反应温度94℃，反应时间3.53h，预报值粒径Y₁=19.57nm，在此优化条件下制得的纳米Co₃O₄平均粒径为22nm。 研究了聚合物分散剂在纳米Co₃O₄制备过程中的作用。TG-DTA、XRD、TEM以及IR分析结果表明，加入分散剂后，其表面保护作用可很好地防止团聚的产生，控制粒子的形状和大小。其中，利用PEG制备的纳米Co₃O₄粒子分散性稍差，当PEG的用量为40mg／mL时，可以获得平均粒径为20nm左右的球形纳米Co₃O₄微粉；以聚丙烯酸钠作为分散剂可更好地控制纳米粒子的形状和大小，其用量为15mg／mL左右时，可得到平均粒径为10nm、长为0.2μm的球链状纳米Co₃O₄微粉。 研究了均匀沉淀反应动力学。经稳定态假设处理后，得到沉淀反应的表观活化能为100.19kJ／mol，硝酸钴的反应级数为1.42。 采用热重和差热分析方法对沉淀产物的热分解过程进行研究。利用Phadnis法则，推断碱式碳酸钴的热分解反应机理符合反应级数法则，得到非等温条件下碱式碳酸钴的热分解动力学方程为： 并利用Kissinger法计算碱式碳酸钻热分解反应的表观活化能为162.41kJ／mol，热分解反应级数为1.30。更多还原

【Abstract】 In this paper, Co3O4 nano-particles were prepared by homogeneous precipitation method, technical conditions and kinetics were studied, The main contents and results are as follows:Co(NO3)2 6H2O was used as raw materials, and CO(NH2)2 was used as precipitator, Co3O4 nano-particles were prepared by homogeneous precipitation. The influences of concentration, molar ratio of reactants, reaction temperature and time, dryness temperature and time, and calcining temperature and time on particle size were investigated. The results showed that cubic, dispersed Co3O4 nano-particles with average diameter of 20nm were obtained under optimize conditions.To determine influence of technical conditions on product diameter, the influences of concentrations, molar ratio, reaction temperature and time on average size were investigated by means of uniform design. The results of experiments indicated that product diameter was mostly influenced by reaction temperature, followed by molar ratio of reactant, concentration of reactants, and reaction time. The optimum conditions were C(Co(NO3)2 6H2O)=0.35mol/L, n(CO(NH2)2):n(Co(NO3)2 6H2O)=3.53 : 1, reaction temperature 94 and reaction time 3.53h. Under these conditions Co3O4 nano-particles with average diameter of 22nm were obtained.Influences of disperants on preparing Co3O4 nano-particles were studied, and TG-DTA, XRD, TEM and IR absorption spectra were used to characterize the samples.The results showed that shapes and sizes of Co3O4 nano-particles could be controlled and modified by dispersants. The diameter was about 20nm when PEG(40mg/mL) was used as dispersants, while the diameter was 10nm and the length is 0.2um for PAANa(15mg/mL).The kinetics of homogeneous precipitation was studied, the activation energy was about 100.19kJ/mol, and reaction index was 1.42.The TG and DTA techniques were used to research the decomposition kinetics of depositions. The decomposition mechanism and kinetics-equation were investigated according to Phadnis methods, and the equation can be depict as follow:The kinetics parameter of decomposition were obtained by using Kissinger methods. The activation energy was 162.41kJ/mol and reaction index was 1.30.更多还原