摘要相对于传统单一金属电镀工艺，纳米复合电沉积技术则能满足人类更多的应用需 要，将纳米颗粒复合添加到电镀液中，使复合镀层具有更好的物理应用范围。

鉴于此，本文采用超声辅助脉冲电沉积工艺分别制备纳米晶纯镍和 Ni-CeO2 复合 镀层。通过对比实验来研究，在前期优化实验参数的基础上制备纳米晶镀层。采用 FE-SEM、XRD 及 TEM 等测试手段对比研究添加稀土 CeO2 纳米颗粒前后对纳米晶 Ni 镀层组织结构的影响。研究发现，在机械搅拌与超声冲击波和微射流共同作用下， 纳米 CeO2 颗粒吸附在晶界微孔等高能缺陷区，不仅改变了 Ni 晶生长的表面能，还起 到弥散强化与微合金化等作用，能显著提高镀层的致密度；Ni 晶粒尺寸由未添加纳 米 CeO2 颗粒前的~190 nm（纯镍）细化至~125 nm（Ni-CeO2 复合镀层），Ni 结晶取 向也由择优性向随机多方向性生长转变。这主要归功于稀土纳米颗粒或其微量离子能 优先吸附于择优生长的 Ni 晶尖端并可演变成 Ni 晶催化形核的中心（异质形核点）， 可促使 Ni 晶的形核率提高，临界形核半径降低，起到晶粒细化，组织结构致密。81107

采用 TG-DSC 热力学测试来绘制 Kissinger 图，拟合测算添加 CeO2 纳米颗粒对镍 基镀层中 Ni 晶粒长大表观激活能的影响，测出纯镍和 Ni-CeO2 纳米镀层中 Ni 晶粒长 大的表观激活能分别为 138。3 和 188。6 kJ/mol，特征峰分别是 520 和 690 ℃。同时， 将纯镍和 Ni-CeO2 复合镀层试样，在空气气氛中进行 500℃和 800℃抗氧化性能测试， 根据氧化膜的 XRD 和 XPS 对氧化膜的物相分析，推断出弥散析出的稀土化合物或其 Ce 溶质原子可吸附聚集在晶界等高能缺陷区，通过热愈合和黏性钉扎微裂纹等作用 来提高氧化膜的塑性和抗剥落能力，由此减缓热应力释放和降低 Ni/NiO 间的热膨胀 系数差异。在此基础上，建立稀土 Ce-rich 弥散相对纳米晶材料中晶界等缺陷的吸附 钉扎机理模型。

毕业论文关键词：CeO2 纳米颗粒；双脉冲电沉积；Ni-CeO2 复合镀层；高温抗氧化

Abstract Compared to conventional plating processes, composite plating technology can be applied into more applications。 With nano-particles introduced into the composite coating, the composite plating technology will be on a higher level。

In this paper, an effective method of ultrasonic-assisted double pulse  electro deposition was used to prepare nanocrystalline nickel coatings incorporated with CeO2 nanoparticels。 According to a great amount of our comparative tests, the optimization of processing parameters were therefore obtained to display a fully denser microstructure and superior properties for measured speciemns。 In order to evaluate beneficial effect of CeO2 addition on managing textural develoment of Ni grains, FE-SEM, XRD and TEM observations were carried out。 Results indicated that nano-sized CeO2 particles where adsorbed along high-energy grain boundaries or defective interfaces was likely to make inpidual contributions to both of dispersion strengthening and micro alloying for significant improvements of vacancies condensation。 As a result, the crystal size of Ni grains was refined from ~190 nm (pure nickel) into ~125 nm (Ni-CeO2 coatings), also appearing the persified directions instead of exclusively preferential growth for Ni growth。 This is mainly due to the existence of CeO2 nanoparticles or its small amount of Ce3+/4+ ions that could be acted as an increasing catalytic site of nucleation and growth for thereby achieving the effects of grain refinement。

For determination of the effect of CeO2 addition on modifications of activation energy for grain growth, a classical Kissinger plot based on TG-DSC thermodynamic tests was emplyed。 It turns out that the activation energy for grain growth of pure Ni and Ni-CeO2