非水溶液体系下贫铀表面阴极等离子体电沉积陶瓷涂层的沉积机制研究

Improving the corrosion resistance of Depleted Uranium (DU) has become a key problem for its application. In this project, composite ceramic coatings will be prepared on DU surface by cathode plasma electrolytic deposition (CPED) method in non-aqueous electrolyte to improve its corrosion resistance. However, the key problem for using CPED method to prepare ceramic coatings on the surface of metals is the porous structure of the CPED coating, which leads to a poor corrosion resistance of the CPED coating. Therefore, to solve such problem, nano-particles with different conductivities and surfactants with different chemical polarities are added in the electrolyte. Then, the current density-voltage curve, high-speed video analysis, plasma optical emission spectroscopy, analogue simulation and some other analysis technologies are used to investigate the influence of the electrolyte composition on the coating structure and properties. The concrete content of this project includes: (1) Investigating the plasma discharge ignition mechanism of the gaseous film and the ethanol gaseous film/ceramic coating double-dielectric-layer in non-aqueous electrolyte; (2) Investigating the influence of additives mentioned above on the electrolyte conductivity, solute structure, surface reaction, the transportation of gaseous bubbles, the adsorption of sediments, and the homogeneousness of plasma discharges on DU surface during the CPED process; (3) Investigating the influence of the nano-particles with different conductivities in coatings on the breakdown mechanism of the ceramic coating with Maxwell-Wagner model and electron avalanche model. Through such researches, a further understanding of the CPED basic law will be gained, the way of improving the CPED ceramic coating compactness will be obtained. Finally, a novel method for the protection of DU and some other activated materials will be proposed. Therefore, this project can be considered as one with an important scientific and engineering application value.

贫铀耐蚀性能差是其工程应用中面临的关键难题，本项目提出在非水溶液体系中采用阴极等离子体电沉积技术在其表面制备陶瓷涂层以提高其耐蚀性能。针对非水溶液体系下该技术沉积陶瓷涂层致密性较差影响耐蚀性能的问题，拟在电解液中添加不同导电性能的纳米颗粒和不同极性的表面活性剂，利用电流密度-电压曲线、高速摄像、等离子体放弧光信号检测及模拟计算等研究手段，对该技术基础规律进行研究：（1）研究非水溶液体系下气膜以及气膜/陶瓷膜双介电层的放弧机理；（2）研究不同导电性能的纳米颗粒和不同极性的有机表面活性剂对溶液电导率、溶质存在形式、试样表面反应过程、气泡传输过程、沉积物吸附状态及等离子体放弧均匀性的影响；（3）研究添加不同导电性能的纳米颗粒对涂层成分和放电击穿行为的影响。项目实验结果有望加深对非水溶液体系下该技术沉积基础规律的认识，掌握控制陶瓷涂层致密度的方法，最终为贫铀等特殊材料表面防护提供新的技术途径。

贫铀等活性材料被广泛的应用于航空航天、电子及核能等领域。但由于其化学性质较为活泼易发生腐蚀，这不仅会影响材料的服役寿命，还有可能对环境造成污染。上述缺点严重限制了其应用，因此提高其耐蚀性能是解决其应用的关键问题之一。针对上述关键问题，采用阴极等离子体电沉积技术，以提高贫铀等活性材料的耐蚀性能为目标，对贫铀表面阴极等离子体电沉积陶瓷涂层的沉积机制进行了研究。.（1）通过在硝酸铝乙醇电解液中添加纳米SiC、TiO2颗粒，在贫铀表面制备Al2O3-Y2O3-SiC、Al2O3-TiO2陶瓷耐蚀涂层。制备的涂层由内层致密层和外层多孔层组成，与贫铀基体结合紧密。电化学极化曲线测试和盐雾腐蚀测试的结果表明，所制备的陶瓷耐蚀涂层能有效提高贫铀基体的耐蚀性能，且随着涂层中纳米颗粒含量的的增加，涂层耐蚀性得到明显提高。.（2）通过测试电流密度-电压曲线对阴极体电沉积技术的动力学过程进行了研究。根据对动力学过程的分析，我们发现在电解液中添加一定量的非极性离子表面活性剂（聚乙二醇）或阴离子表面活性剂（三乙醇胺）后，阴极等离子电沉积过程的电流密度降低了一个数量级，临界起弧电流密度明显降低，样品表面由气泡形成的气膜层厚度减小且更加均匀，样品表面各处等离子体放弧均匀，涂层孔隙率减小，获得更加均匀致密的Al2O3涂层。.（3）通过在硝酸铝乙醇电解液中添加不同浓度的硝酸钇，在贫铀表面制备Al2O3-Y2O3陶瓷耐蚀涂层。通过增加电解液中硝酸钇含量，涂层耐蚀性得到明显提高。在硝酸铝电解液中添加不同浓度的硝酸钇主要从以下两个方面对沉积过程以及涂层结构产生影响：一方面在Al2O3陶瓷涂层中掺杂第二相Y2O3，另一方面又通过改变电解液电导率从而调节阴极试样表面电场强度，使得阴极试样表面等离子体放弧更加均匀，进而降低了剧烈等离子体微弧对涂层表面轰击破坏的作用，涂层的表面孔隙率和粗糙度。