金属氧化物中空球的构建及机理的研究

发布时间：2018-05-08 18:47

本文选题：空心球 + 氧化铁　；参考：《大连交通大学》2015年硕士论文

【摘要】：模板法已成为合成纳米空心材料的一种有效且有发展前景的方法。目前,利用模板法已经成功制备多种零维、一维、二维、三维结构的纳米材料,并且提出了各种关于模板法制备空心材料的反应机理。本文采用以碳球为硬模板的方法,通过水解作用机理,制备氧化铁、氧化钴、氧化镍中空球形貌的纳米材料。系统的研究了反应工艺参数对产物形貌的影响。通过实验结果,分析了碳球以及这三种金属氧化物的形成机理,并且建立了晶体的生长模型。本文的主要内容概括如下:在制备碳球的过程中,本实验以葡萄糖为碳源,水热法合成碳球,并且进行反复水醇清洗,得到产物采用一系列手段进行表征,考察了不同反应时间、反应温度、乙醇添加量等因素对碳球的影响。在上述实验的基础上推断出碳球的生长机理,在整个生长过程中核聚力与表面能的相互协同作用机理起到了关键的作用。水热反应是以开始生成的碳微粒为核,使碳元素逐渐吸引生长到一起,这种吸引力为核聚力,随着压力的适度增加,反应内分子聚集成核的几率更大,粉体的晶格畸变主要是由于样品受表面能和表面张力的作用而引起的,通过纳米晶体的热力学基本特征定性解释了碳球的形成过程,并运用此机理解释了各种反应因素对产物形貌的影响。在水溶液体系中,以碳球为模板,氯化铁水解特性,采用氯化铁直接水解法将铁的氢氧化物包覆在碳球表面,经过高温煅烧形成空心球状氧化铁材料。采用一系列手段进行表征,考察了反应温度、反应时间、氯化铁摩尔浓度等因素对氧化铁形貌的影响。在实验的基础上,推断了前驱体包覆碳球的形成机理,并且通过机理阐述了反应因素对产物的影响。在体系的包覆过程中,溶液pH值变化与颗粒的带电性起到了关键作用,通过此机理,溶液中形成的球核吸附到碳球的表面,随着反应时间的延长,碳球表面颗粒逐渐增多,最终完成包覆过程。以尿素与钴盐、镍盐作为反应物,采用以碳球为模板的方法,分别制备氧化钴空心球和氧化镍空心球。通过尿素水解所产生的氢氧化物沉淀包覆在碳球表面形成前驱体,再通过煅烧处理得到产物,采用一系列手段对产物进行表征,考察了盐与尿素的摩尔比、反应时间、反应温度等因素的影响,在体系的生长过程中,离子强度以及离子的带电变化决定了产物的形貌,早期阶段为聚集生长方式占主要优势,随后为溶质分子的连续方式为主要方式。所以,在整个均匀沉淀过程中,溶液粒子都经历了:成核-聚集生长-连续生长过程。
[Abstract]:Template method has become an effective and promising method for the synthesis of nano-hollow materials. At present, many kinds of nanomaterials with zero dimension, one dimension, two dimension and three dimensional structure have been successfully prepared by template method, and various reaction mechanisms of hollow materials prepared by template method have been put forward. In this paper, the morphology of iron oxide, cobalt oxide and nickel oxide hollow spheres was prepared by using carbon ball as hard template and hydrolysis mechanism. The effect of reaction parameters on the morphology of the product was studied systematically. Based on the experimental results, the formation mechanism of the carbon sphere and the three metal oxides were analyzed, and the crystal growth model was established. The main contents of this paper are summarized as follows: in the process of preparing carbon spheres, the carbon spheres were synthesized by hydrothermal method using glucose as carbon source, and the product was characterized by a series of methods. The effects of different reaction time, reaction temperature and the amount of ethanol on the carbon spheres were investigated. On the basis of the above experiments, the growth mechanism of carbon spheres is inferred. The synergistic mechanism between nuclear cohesion and surface energy plays a key role in the whole growth process. Hydrothermal reactions take the starting carbon particles as the nucleus, allowing the carbon element to gradually attract and grow together. This attraction is nuclear cohesion, and with a moderate increase in pressure, the probability of molecules gathering to nucleate in the reaction is greater. The lattice distortion of powders is mainly caused by the surface energy and surface tension. The formation process of carbon spheres is explained qualitatively by the thermodynamic characteristics of nanocrystalline. The influence of various reaction factors on the morphology of the product was explained by this mechanism. In aqueous solution system, the hydroxide of iron was coated on the surface of carbon ball by direct hydrolysis of ferric chloride with carbon ball as template, and the hollow spherical iron oxide was formed by calcination at high temperature. The effects of reaction temperature, reaction time and the molar concentration of ferric chloride on the morphology of ferric oxide were investigated by a series of methods. On the basis of the experiments, the formation mechanism of the precursor coated carbon spheres was inferred, and the influence of reaction factors on the products was explained through the mechanism. In the process of coating, the change of pH value of solution and the charge property of particles play a key role. Through this mechanism, the spherical nuclei formed in the solution adsorb to the surface of the carbon sphere, and with the increase of reaction time, the particles on the surface of the carbon sphere gradually increase. Finally, the coating process is completed. Cobalt oxide hollow spheres and nickel oxide hollow spheres were prepared using urea cobalt salt and nickel salt as reactants and carbon spheres as template respectively. The hydroxide precipitated by urea hydrolysis formed the precursor on the surface of the carbon sphere, and then calcined to obtain the product. The product was characterized by a series of methods. The molar ratio of salt to urea and the reaction time were investigated. Under the influence of reaction temperature and other factors, the morphology of the product was determined by the changes of ionic strength and ion charge during the growth process of the system, and the early stage was dominated by the aggregation growth mode. Then the continuous mode of solute molecule is the main way. Therefore, in the whole homogeneous precipitation process, the solution particles undergo a process of nucleation, aggregation growth and continuous growth.
【学位授予单位】：大连交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ123.4

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