【作者】 徐彬；

【导师】 魏雨； 宋秀芹；

【作者基本信息】 河北师范大学 ， 物理化学， 2004， 硕士

【摘要】 纳米TiO₂微粒尺寸约在1～100nm之间，它具有大的比表面积，其表面原子数、表面能和表面张力随粒径的下降急剧增加。由于其尺寸的细微化，表现出来的小尺寸效应、表面效应、量子尺寸效应及宏观量子隧道效应等特性导致纳米TiO₂微粒具备了良好的耐候性、耐化学腐蚀性，且抗紫外线能力强、透明性优异，从而使得它在环境、信息材料、能源、医疗与卫生领域有着广阔的前景，但在实际应用中，由于其极性强、易团聚，致使纳米TiO₂优异的性能得不到充分的发挥，严重影响了纳米TiO₂的应用，因此纳米TiO₂粉体的表面修饰是纳米材料科学的一个研究热点。 目前，对纳米TiO₂进行表面修饰的方法很多。但在实际应用中，由于各种条件的限制，我们通常采用物理吸附法及酯化法对TiO₂进行表面有机修饰。虽然这样做的人很多，但系统地、规律性地的研究表面修饰的影响因素很少，对其修饰机理的研究则更少，修饰后的产品的表征也不完善。鉴于现有对纳米TiO₂表面修饰存在的某些不足，本论文在以TiCl₄为原料采用沸腾回流法制备纳米TiO₂的基础上，采用了阴离子表面活性剂、阳离子表面活性剂分别对纳米TiO₂进行了表面修饰，详细地研究了各种条件对表面修饰效果的影响及原因，并探索了修饰过程中表面活性剂在纳米TiO₂表面上的吸附机理。同时为了获得修饰后粒度小、效果稳定的纳米TiO₂，本论文又在溶胶-凝胶法制备纳米TiO₂的过程中利用硬脂酸对纳米TiO₂进行了表面有机修饰，通过对产物的各种表征，推测了反应的机理。为表面有机修饰纳米TiO₂的工业化生产提供了理论依据。 论文的主要工作如下： （1） 锐钛型纳米级TiO₂粉体的制备及表面性质的研究 为了使各种修饰条件和修饰前后性能具有可比性，我们首先在分析前人工作和文献的基础上，选取TiCl₄为原料，采用沸腾回流法成功制备了足量的、不同粒径的锐钛型球形纳米TiO₂作为表面修饰研究的原料，同时对该原料进行了粒度分布测定、透射电子显微镜检测和X射线衍射表征，以及润湿性能、分散性能、表面电性等测定，为下一步表面的修饰做好了前期的准备。 （2） 硬脂酸表面修饰TiO₂的合成及表征 为了得到修饰后效果良好的TiO₂，我们试图让硬脂酸中的羧基和二氧化钛表面的羟基发生缩合反应，使TiO₂的表面上包覆上一层硬脂酸，但在实验中我们注意到，由于硬脂酸在水中不能很好的溶解而二氧化钛又不能在有机介质中很好的分散，所以对制各好的二氧化钛进行表面修饰无法得到粒度小、性能好的样品，因此我们在溶胶-凝胶法制备TiO₂的过程中加入硬脂酸，利用该法成功的制备出了30nm以下的经过硬脂酸修饰的锐钦型的TIOZ。通过对制备的样品进行接触角、差热分析、红外谱图、电子能谱、X射线衍射等测试，表明修饰后的样品确实得到了优异的修饰效果，与此同时探讨了表面修饰的机理，提出了竞争反应的机制。 （3）澳代十六烷基三甲胺对二氧化钦的表面修饰及吸附机理的探讨 为了使制备出的Tio:得到表面有机修饰，我们选择了具有双亲结构的阳离子表面活性剂澳代十六烷基三甲胺，这样既能解决表面修饰剂的溶解问题，又能使TIOZ在修饰过程中保持良好的分散性。通过控制表面活性剂溶液的浓度、温度、pH值等因素得到了粒径较小、修饰效果较好的样品。此外，通过对样品进行了接触角、差热分析、红外光谱、吸附量的测量和透射电镜的观察，确实证明了表面活性剂在Ti仇表面的存在并且使得Ti02得到了良好的有机改性。同时，根据对表面活性剂的浓度、表面活性剂的吸附量及样品的修饰效果等因素的对照，详细讨论了表面活性剂在TIO:表面上的吸附机理，提出了四种模型的吸附过程。 （4）十二烷基磺酸钠对二氧化钦的表面修饰及吸附机理的探讨 利用阴离子表面活性剂十二烷基磺酸钠分别对Ti02及包覆有A12O3的TIOZ（铝太白）进行表面修饰，通过同时对TIO:及铝太白进行有机修饰，发现先经过无机修饰的Ti02再进行有机修饰结果会更好。除此之外，通过对修饰后样品进行接触角、差热分析、红外光谱、吸附量以及TIO:和铝太白两种修饰后样品的比较，对阴离子表面活性剂十二烷基磺酸钠在TIOZ表面上的吸附机理做了详细的讨论。更多还原

【Abstract】 The nano-titania has high surface area and its size is between l-100nm. The surface atom number, surface ability and surface tension of nano-titania are sharply increased along with the degression of the diameter. Because of its physical and chemical properties such as good resistance to weathering , chemical resistance, good transparency and uniform distribution of particle size ,it is intensively applied in the environment, information, materials, sources of energy ,medical treatment and hygiene, etc. But in practice, its strong polarity and easy aggregation limit its excellent function. So surface modification of nano-titania is a hotspot in nanometer science.Presently, there are many methods of surface modification on nano-titania. But in the practical application, because of the limit in different conditions, we usually modify the surface of TiO2 by the methods of physical absorption and esterification. Although many people do such research, few people study the influence of surface modification systemically and disciplinarily. Fewer people study the modification mechanism and character of products perfectly. Based on the shortcoming of these researches, we selected TiCl4 as precursor, prepared nano-titania by boiling reflux method. And we modified the TiO2 surface with anion and cation surfactant. We studied the influences on surface modification of different conditions and the absorption mechanism of surfactant in the process of modification. At the same time, in order to get small size and well effect modified TiO2, we modified the titania surface with stearic acid by sol-gel method. Speculating the reaction mechanism by different character of products, this paper gave the theoretic base for industrial production of TiO2 in the surface modification field.The major work includes the following aspects:(l)The study on preparation of nano-anatase and its surface propertiesIn order to compare different conditions of modification and the properties of products, Firstly, we carry through literature search and analyze the former work , TiCl4 was selected as raw materials, the enough and different sized spherical nano-titania were prepared by boiling reflux method, as raw materials to study surface modification. All of the samples have been characterized by granularity distribution, XRD, TEM, at the same time we tested the contact angle, dispersion capability and surface electrics of the nano-titania. All of the above are prepared for next work.(2)The preparation and characterization of nano-titania modified by stearic acidIn order to get high effect modified nano-titania, we tried to make carboxyl react with hydroxyl, so that the surface of nano-titania was coated by stearic acid. However we found that stearic acid can not be satisfying dissolution in water, and at the same time nano-titania cant be effectively dispersed in organic dissolvent. For these factors, it is difficult to acquire small sized and high properties modified nano-titania. We added stearic acid in the process of preparation of nano-titania by sol-gel method. We successfully prepared nano-titania modified by stearic acid which size less than 30nm.All of the above samples have been characterized by contact angle, TG-DTA, FTIR, XPS,XRD etc. The results show that after modified by stearic acid ,nano-titania get fine surface effect. At the same time, we studied the mechanism of surface modification and put forward competition mechanism.(3) The study on nano-titania was modified by cetyl three methyl amine bromide and absorption mechanismIn order to acquire nano-titania which surface modified by organic, we selected cetyl three methyl amine bromide which has double relative structure as raw material. It not only has good solubility but also can keep good dispersion of nano-titania in the process of modification. By controlling factors of concentration, temperature, pH etc, we get small sized but high effective modified samples. By testing contact angle , TG-DTA,FTIR, absorption isotherm and TEM, we found that the surface of nano-tita更多还原