镍包覆碳纳米管复合薄膜的制备及电磁防护性能研究

This project mainly focus on observation of the electroless nickel growth process (i.e., generation of nickel nucleus, formation of island-like nickel particles and growth of nickel film) on carbon nanotubes (CNTs) as well as investigation of relevant growth mechanism by using an in situ solution-related TEM technology. Limited by the deficiency in lacking of real-time and in situ-related data, it is impossible to explore the intrinsic growth mechanism of nickel on CNTs fully by merely using the traditional observation methods (i.e., using static samples for observations). In general, the deposition rates of nickel are difficult to control in the early electroless deposition (ELP) stage, which results in an obscure boundary between Ni loading contents and the surface morphologies of the composite films. By the judicious control of the concentrations of various main components in ELP solution, the loading contents of Ni on CNTs can be precisely determined based on the equilibrium constant of the ELP reaction, which guarantees an exact definition of the relationship between Ni loading contents and the corresponding surface morphologies. Regarding the current exploitation mode of nickel-coated CNTs (Ni/CNT) composite film with high electromagnetic shielding efficiency, “Experience-guided Experiment” mode is the commonly used as there is no theoretical guidelines except for experiences. Based on the connotation of Materials Genome Initiative (MGI), the exploitation mode of Ni/CNT composite film will shift from traditional “Experience-guided Experiment” mode to innovative “Theoretically Prediction, Experimentally Validation” mode by integrating the high-throughput preparation and measurement, response surface analysis, establishment of reasonable theoretical models.

本项目针对化学镀工艺中镍在碳纳米管上的生长机制研究不完善，缺乏实时、原位观测证据的问题，利用原位溶液相关TEM技术，观察化学镀液中碳纳米管表面“镍核生成-镍核生长-镍岛形成-薄膜生长”的过程，揭示镍包覆碳纳米管生长机制。针对化学镀初始阶段的镀镍速率不易控制，导致复合薄膜形貌与镍包覆量依赖关系难以界定的问题，基于化学镀反应平衡常数，利用喷墨打印与化学镀联用技术，通过调节喷墨（镀液各组分）量来实现镍包覆量的精准控制，构建更准确的复合薄膜形貌与镍包覆量依赖关系理论。针对镍包覆碳纳米管复合薄膜的电磁屏蔽效能提升缺乏理论指导的问题，基于材料基因组工程，利用高通量制备及测试数据，以响应面分析方法，建立显著程度和精准性指标符合要求的理论模型，以理论指导实践，提升复合薄膜屏蔽效能及开发效率，实现镍包覆碳纳米管复合薄膜研发由“经验指导实验”的传统模式向“理论预测、实验验证”的新模式转变。

本项目研究镍包覆碳纳米管复合薄膜的制备及电磁防护性能，包括四个方面：（1）镍包覆碳纳米管生长机理；以丝胶粉调节碳纳米管界面之间的相互作用，将碳纳米管均匀的分散在水中，碳纳米管的高分散性提高了传统化学镀镍中Ni2+离子与碳纳米管的接触面积。在 含Ni2+ 离子的水溶液浸渍过程中，Ni2+ 离子能够更容易地吸附在碳纳米管表面。然后，Ni2+ 离子被还原剂原位还原成小的 Ni0 颗粒，这些Ni0 颗粒将作为化学镀镍的催化活性位点，催化化学镀镍。（2）简单、高效的复合薄膜制备工艺技术；采用真空蒸镀法，先在PET基板上涂布有机硅橡胶，再用扬尘法将碳纳米管颗粒吹起，悬浮密闭箱的空气中，然后自然沉降在有机硅橡胶上，加热固化，得碳纳米管薄膜。将碳纳米管薄膜置于真空镀膜机中蒸镀镍，利用蒸发粒子的平均自由程必须远远大于蒸距，蒸发粒子在向基片迁移过程中与残余气体分子发生碰撞，从而使得镍在碳纳米管薄膜不同区域的包覆量不同，实现镍包覆碳纳米管复合薄膜的高通量制备。（3）复合薄膜形貌与镍包覆量依赖关系：通过电镜观察及EDX元素分析，Ni元素原子百分含量很低，为1.60%，聚集成簇的球形结节状颗粒，Ni元素原子百分含量大幅上升，达到了55.62%，Ni的球形结节状颗粒密集均匀地分布在CNT基底表面，Ni元素原子百分含量进一步提高，达到了84.26%，Ni的颗粒亦完全包覆在CNT基底表面，Ni元素原子百分含量在所有条件下达到了最大值，高达98.01%，不再是球形的结节状颗粒，而出现了层状鳞片形的晶粒组织。（4）不同镍包覆量对复合薄膜的电导、介电和磁导率的影响及复合材料电磁屏蔽特性：通过矢量网络分析仪测试了不同镍包覆样品在X波段的电磁屏蔽效能（包括吸波损耗和反射损耗），发现随着镍包覆量的增加，电磁屏蔽效能提升，最高可达60dB以上，在低镍包覆量下，以吸波损耗为主，在高镍包覆量下，以反射损耗为主。总之，本项目基本完成了基金计划书的主要内容，镍包覆碳纳米管在5G基站屏蔽涂料以及6G太赫兹吸波材料中有应用前景。