【作者】 文瑾；

【导师】 李洁； 兴户正纯；

【作者基本信息】 中南大学 ， 应用化学， 2011， 博士

【摘要】 近年来,纳米铜由于其不同于块状材料的特殊性能,已经在各个领域呈现出了极其重要的应用价值。作为重要的工业原料,纳米铜可以代替贵金属降低工业成本,有着广阔的应用前景。因此,对纳米铜的研究已经引起了国内外的广泛关注。本论文通过电化学方法对还原剂的电化学性能进行了对比研究；选择价格低廉、对环境友好的葡萄糖和次亚磷酸钠作为还原剂成功制备了各种形貌的纳米铜并对其生长机理进行了研究；考察了球状纳米铜作为润滑油添加剂的摩擦磨损性能。主要内容如下：1.利用Zennium电化学工作站对各种还原剂的电化学性能进行了研究。通过对不同实验条件下还原剂的循环伏安曲线进行分析对比,得到各还原剂的电化学性能与体系pH值、电解质浓度以及电势扫描速率之间的关系,从而出在液相体系中还原剂还原性能处于最佳状态时的实验条件。2.选择价格低廉、对环境友好的次亚磷酸钠作为还原剂,以五水硫酸铜为原料,油酸作为萃取剂和表面活性剂,通过研究不同反应条件对产物形貌、粒径及分散性的影响,最终制备得到了具有结晶度高、粒度均匀,分散性好、抗氧化的纳米铜。采用XRD、FTIR、TG/DTA、SEM、TEM等方法对产物进行了表征并对其生长机理进行了探讨。3.通过改变实验条件,对液相体系中树枝状、空心球状、棒状和花状纳米铜的生长机理进行了研究。结果表明：1)球状纳米铜的形成主要是油酸吸附保护及位阻效应和奥斯特瓦德熟化过程共同作用的结果。2)油酸的结构导向作用和奥斯特瓦尔德熟化对产物晶体的影响是树枝状纳米铜生成的主要原因。在反应过程中,油酸引导着晶核沿着某些晶面方向优先生长；随着陈化时间的延长,奥斯特瓦尔德熟化过程继续进行使小晶核不断溶解,并在大晶核的特定晶面上沉积生长,最终导致了树枝状纳米铜的形成。3)空心球状纳米铜的形成是油酸的模板作用和奥斯特瓦尔德熟化共同作用的结果。油酸在体系中形成的球状胶束有利于空心结构的生成；而奥斯特瓦尔德熟化促使晶体内部的小晶核不断溶解,进一步促进了晶体中空结构的形成。4)奥斯特瓦尔德熟化和油酸的导向作用是棒状纳米铜的生成的主要原因。首先油酸分子的导向作用使晶体各个晶面上的生长速度产生差别,使晶体朝着某些晶面方向优先生长；其次,奥斯特瓦尔德熟化也有利于初级纳米铜颗粒逐步组装形成一维棒状纳米铜。5)花状纳米铜的形成主要是奥斯特瓦尔德熟化和螺旋位错生长共同作用的结果。产物通过奥斯特瓦尔德熟化过程的不断生长,经历了从细小颗粒到片状的变化过程；随着纳米片浓度的不断增大,体系中小晶核绕着晶面上的螺旋错位进行逐层生长；由于温度对片状结构的形成有一定的影响,因此对于花状结构产物的生成也存在一定的影响。4.通过对润滑油的摩擦系数和磨斑直径随纳米铜含量、摩擦时间、载荷及转速的变化规律进行研究,分析了各种形貌纳米铜作为润滑油添加剂的摩擦磨损性能。在摩擦过程中,添加剂与摩擦面相结合,形成均匀光滑的润滑膜,从而减小了摩擦系数,降低了磨损量,同时对摩擦表面原有的磨痕进行了填塞,显著地提高了150N基础油的减摩抗磨能力及承载能力。负磨损现象的存在以及摩擦表面纳米铜颗粒的沉积都证明了当球状和空心球状纳米铜作润滑油添加剂时,磨损表面存在着一种沉积自修复机制。当树枝状、棒状和花状纳米铜作为添加剂时,基础油的黏度及添加剂不规则的形貌特征都不利于改善基础油的抗磨性能；2)当树枝状、棒状和花状纳米铜作为添加剂时,其在磨损面的沉积修复作用弱于不规则结构对磨擦面的进一步磨损,因此对基础油抗磨性能的改善不大。此外黏度的增加也不利于改善基础油的抗磨性能。更多还原

【Abstract】 In recent years, the copper nano-particles have played an important role because of their properties different from bulk material. As a vital industrial raw material, copper nanoparticles are more economic when they take the place of the noble metal nanoparticles. Therefore, the researches on copper nanoparticles have attracted extensive attention in the world.In this dissertation, the electrochemical performances of reductants were detected by cyclic voltammetry. Sodium hypophosphite is chosen as reductant due to their price and environmentally friendly. Various morphologies of copper nanoparticles were prepared via a two-step reduction method, and their growth mechanisms were reviewed. The tribology performances of copper nanoparticles when they used as lubricant additive were also studied. The main contents are the following:1. The electrochemical performances of various reductants were studied by the Zennium electrochemical workstation. The relationships between electrochemical performances of reductants and the pH value of the system, electrolyte concentration and photodynamic scanning rate were studied by the cyclic voltammetric curves which obtained from different experiment conditions. The optimum conditions of reductibility in liquild system can be obtained.2. The influences of various reaction conditions on particles’morphology, size and dispersibility were studied. Copper nanoparticles with well dispersibility and uniform morphology were finally obtained. The products were characteristic by XRD, FTIR, SEM and TEM, and the growth mechanisms of spherical nanoparticles were discussed.3. The growth mechanisms of various morphology copper nanoparticles were studied in liquid system by changing the experiment conditions. The results showed that 1) the combined action of steric effects of oleic acid and Ostwald ripening process were the reasons of the formation of spherical copper nanoparticles; 2) the structure-directing effect of oleic acid and ageing time were the main reasons of the formation of dentritic nano-copper crystals. As a structure-director, oleic acid could guide crystal nucles grow successively along some orientations direction in the growth process. With the extension of ageing time, Ostwald ripening process took place continuously which caused small nuclei constantly dissolved, deposited and grew in the surface of big nuclei, finally dentritic copper nanoparticles obtained; 3) the growth mechanism of hollow spherical copper nanoparticles was studied in liquid system. In the formation process of hollow spherical copper nanoparticles, oleic acid was used as a soft template. The molecules of oleic acid could form to globularmicelles which were availed to the formation of hollow structure. Ostwald ripening process caused small nuclei constantly dissolved, which further promoted the formation of hollow structure; 4) Ostwald ripening and the structure directing effect of oleic acid were the main reasons of rodlike copper nanoparticles. Firstly, the structure directing effect of oleic acid could make the growth rate of various crystal faces are different. Crystals grew successively towards to some orientations. Secondly, Ostwald ripening was in favour of the formation of one-dimensional rodlike crystals from primary nanoparticles; 5) the formation of flowerlike copper nanoparticles could be considered as the results of the Ostwald ripening and screw dislocation growth process. Due to ripening process continuously, the products underwent a proess from fine particles to flake. With the increasing concentration of nanoflakes, they layer-grew around screw dislocation, and then flowerlike copper nanoparticles obtained. And since the temperature of system had some influence on the formation of nanoflakes, it could also affect the formation of flowerlike crystals.4. The friction coefficient and wear scar width were studied if copper nanoparticles were used as lubricant additive, when the concentration of copper nanoparticles, fiction time, load and rotational speed were changed. In the friction process, copper nanoparticles combined with the wear surface, evenly and smooth lubrication film formed. Thus the friction coefficient and the amount of wear reduced. At the same time, copper nanoparticles filled the grinding mark on the wear surfaces, the anti-wear ability and carrying capacity of 15 ON base oil were improved significantly. Negative wear and the deposition of copper nanoparticles on wear surface proved that a self-repairing mechanism existed on the wear surface when spherical and hollow spherical copper nanoparticles used as lubricant additives. When dentritic, rodlike and flowerlike copper nanoparticles were used as lubricant additives, the irregular morphology would make the wear surface further wearing, so they are not good at improving the anti-wear properties of base oil. In addition, the viscosity of lubricant was also made the tribological performance of lubrication less favorable.更多还原