芳纶纤维复合银镀层的结构设计及其宽频电磁屏蔽性能的研究

Silver-plated aramid fibers possess outstanding advantages such as excellent conductivity, lightweight, high strength, flame retardancy, flexibility, and etc., which are the first choice of electromagnetic shielding materials in the special fields such as aerospace, military affairs, and communications. It is widely known that electroless silver plating has poor stability, low efficiency and high waste. Electroless Ni and Ni alloy plated aramid fibers have been successfully prepared in our lab. On this basis, silver electroplating on different Ni and Ni alloy substrates will be investigated in this project. By observing the growth morphology and the crystalline structure of the silver coating, the deposition mechanism of silver will be proposed and the mathematical model of silver coating will be built. Taking deposition kinetics as a reference, the influence of substrate roughness, crystalline structure, electrical and magnetic conductivity on the nucleation and the growth of silver plating layer will be clearly demonstrated. The metallic interfacial bonding performance will be explored, and the interfacial bonding mechanism will be discussed. The effects of different constructions, microstructures, morphologies and properties of metal layers on the overall broadband electromagnetic shielding effectiveness will be studied, and the electromagnetic shielding mechanism will be elucidated. The project has important academic significance for developing the application of electroplated aramid in electromagnetic shielding materials.

镀银芳纶兼具导电性好、质轻、高强、阻燃、柔软等诸多优势，是航空航天、军工通讯等特殊部门首选的电磁屏蔽材料。针对化学镀银稳定性差、效率低下、浪费严重等现象，申请者率先成功制备了化学镀镍及镍合金芳纶纤维，拟继续深入开展其上的电镀银研究。通过观察银镀层的生长形貌和晶体结构变化，提出银镀层的沉积生长机理，建立银镀层数学模型；以沉积动力学作为参考，阐明基底粗糙度、晶体结构、导电性、导磁性对电镀银层形核和生长的影响；考察层间界面结合性能，探讨界面结合形成机理；研究金属层不同的复合、结构、形貌和性能对整体宽频电磁屏蔽效能的影响，分析其电磁屏蔽机理。本项目的开展为开拓电镀芳纶在电磁屏蔽材料中的应用具有重要的学术意义。

镀银芳纶兼具导电性好、质轻、高强、阻燃、柔软等诸多优势，是航空航天、军工通讯等特殊部门首选的电磁屏蔽材料。针对化学镀银稳定性差、效率低下、浪费严重等现象，本项目率先成功制备了可以稳定沉积的化学镀镍、镍-磷-硼、镍-铁芳纶纤维，研究了其沉积形貌、沉积机理、及电磁屏蔽等性能。发现在相同增重下，镀镍芳纶的导电性及电磁屏蔽性能（30MHz-18GHz）优于镀镍-磷-硼芳纶；镀镍芳纶的导电性优于镀镍-铁芳纶，电磁屏蔽性能（30MHz-18GHz）优于大部分镀镍-铁芳纶（次于镍铁比例为8:2的镍铁芳纶）。铁的适量沉积会提高镍-铁合金镀层在低频区的电磁屏蔽性能，过量添加则由于电导率的持续下降导致电磁屏蔽性能的下降。而后在镍及镍磷硼基底上深入开展电镀银研究，先在两种基底上，使用不同的电流密度进行沉积，通过观察银镀层的生长形貌和晶体结构变化，确定最佳的沉积电流密度。阐明基底粗糙度、晶体结构、导电性、导磁性对电镀银层形核和生长的影响；考察层间界面结合性能，探讨界面结合形成机理；研究金属层不同的复合、结构、形貌和性能对整体电磁屏蔽性能的影响，分析其电磁屏蔽机理。研究结果发现，非晶的镍-磷-硼芳纶上更容易开展电镀银的工作，其非晶的衬底结构不具有银原子沉积时需要进行晶格匹配的阻力，在其上开展电镀银，有着更为广阔的电流密度沉积区间，同时由于沉积形貌及结构更为完善，镍磷硼@银复合结构的电磁屏蔽性能（30MHz-18GHz）比镍@银的复合结构更高。本项目的开展为全面研究芳纶化学镀镍和电镀银提供基础理论依据和部分参考数据，也对开拓电镀芳纶在电磁屏蔽材料中的应用具有重要的学术意义。本项目也借助目前宏观层状复合屏蔽结构的设计理念，并应用在导电芳纶结构中，为国内宽频高效电磁屏蔽芳纶的研制成功奠定基础。