【作者】 王睿；

【导师】 万怡灶；

【作者基本信息】 天津大学 ， 材料学， 2012， 博士

【摘要】 随着电子设备的高频化、数字化,干扰信号的能量密度极度增大,有限空间的电磁环境发生前所未有的恶化,严重影响社会进程与人类生存和生态环境的协调、可持续发展。因此,电磁屏蔽材料的研究与发展成为人们日益关注的重要课题。随着科技的发展,新型电磁屏蔽材料的研究向着高屏蔽效率、低密度的方向发展。碳纤维具有强度高、质量轻,并且导电性良好的特点,可直接用于轻质屏蔽材料的制备,本课题采用连续电镀和化学镀的方法对碳纤维进行表面金属化,并将其填充于低密度的高分子材料基体,制备出新兴电磁屏蔽复合材料,该材料具有高效、质轻等突出优点,有望在电磁屏蔽材料领域发挥重要作用。本课题研究了连续碳纤维表面金属化改性的化学镀工艺和电镀工艺,理论分析和实验结果均证实对于碳纤维这样的小直径束状连续材料,采用电镀工艺可比化学镀工艺获得更好的表面金属化效果。因此本课题开发出我国第一条碳纤维表面连续电镀镍工艺的生产设备。由该设备制备的镀镍碳纤维镀层均匀致密,镀层厚度可调。采用镀镍碳纤维制备的三维编织镀镍碳纤维/环氧树脂(Ni-CF_3D/EP)复合材料比三维编织碳纤维/环氧树脂(CF_3D/EP)复合材料具有更高和更平稳的电磁屏蔽性能。在30¹50 MHz频率范围内,镀镍碳纤维的屏蔽优势尤为突出,Ni-CF_3D/EP复合材料的屏蔽效能比CF_3D/EP复合材料高约40 dB。当在Ni-CF_3D/EP复合材料中加入5%的导电介质（镍包石墨）时,复合材料具备更加优异的电磁屏蔽性能,屏蔽值比之前提高10 dB。通过对莎皮罗丝网材料电磁屏蔽效能计算模型的修正,得到适用于编织材料的电磁屏蔽效能计算理论模型。以镀镍碳纤维为屏蔽填料制备的镀镍碳纤维/硅橡胶（Ni-CF/VMQ）屏蔽复合材料同样具有优异的电磁屏蔽性能。当纤维含量为80 phr时,复合材料达到最佳的综合性能,在30¹200 MHz频率范围内Ni-CF/VMQ复合材料的电磁屏蔽效能均在80 dB以上,此时材料的拉伸强度为3.23 MPa,密度1.37 g/cm³,性能优于前人研究以粉末状填料制备的电磁屏蔽橡胶（拉伸强度1.5 MPa,密度3 g/cm³）。根据Schelkunoff电磁屏蔽理论的指导,本课题还研究制备了兼具高导电和高导磁性能的表面沉积镍/四氧化三铁纳米颗粒（Ni/Fe₃O₄-NPs）复合镀层的碳纤维,并对复合镀层的沉积机理进行了研究,将实验数据带入两步吸附理论模型发现,实验结果与模型完全吻合,说明Ni/Fe₃O₄-NPs复合镀层的沉积过程适用于两步吸附理论模型。课题还制备了Ni/Fe₃O₄-NPs复合镀层碳纤维的复合材料。测试结果表明,镀层中含有Fe₃O₄-NP的复合材料比没有Fe₃O₄-NP的复合材料屏蔽性能可高10 dB。总之,本课题采用表面金属化改性的碳纤维为导电填料制备的填充复合型电磁屏蔽材料具备高效、质轻的特点。将高导电性与高导磁性材料相结合可制备性能优异的电磁屏蔽复合材料的理论得到充分验证,为新型电磁屏蔽复合材料的设计和研究提供新的思路和研究基础。更多还原

【Abstract】 With rapid development of electronic devices with high frequency and digitization, the unprecedent deterioration of the electromagnetic environment in the limited space seriously impacts on social process and human survival, and harmonious environment and sustainable development of ecological environment. Therefore, the research and development of the electromagnetic shielding material have attracted extensive attention. With the development of technology, the research of electromagnetic shielding materials focus on the high shielding efficiency and low density direction. Due to high strength, light weight and good conductivity properties of carbon fiber, it can be directly used for preparation of light shielding material. In this work, metalized carbon fiber was filled in low density polymer matrix materials and used to fabricate novel high efficiency and low weight electromagnetic shielding composites, and is expected to play an important role in the electromagnetic shielding material field.In this work, the surface modification process of electroless and elecdeposition of carbon fiber was investigated. Especially, the manufactured equipment to synthesis of the long carbon fiber prepared by the continuous nickel electrodeposition was developed for the first time, which was applied for the fabrication of as-prepard carbon fiber with the dense and uniformly coatings with the adjustable thickness.The electromagnetic shielding effectiveness of three-dimensional braided nickel-plated carbon fiber/epoxy (Ni-CF_3D/EP) composite is about 40 dB higher than that of three-dimensional braided carbon fiber/epoxy (CF_3D/EP) composite in the frequency of 30¹50 MHz. By correction of calculation model of electromagnetic shielding efficiency of Shapi Luo screen materials, we get a suitable calculation model of electromagnetic shielding efficiency to woven materialsThe silicone rubber filled with nickel-plated carbon fiber （Ni-CF/VMQ） composite, when the fiber content is 80 phr, the composite achieves the best overall performance. The electromagnetic shielding effectiveness is more than 80 dB in the frequency of 30¹200 MHz. The tensile strength is 3.23 MPa, and the density is 1.37 g/cm³.According to Schelkunoff electromagnetic shielding theory, we studied the high conductivity and high permeability composite coatings of nickel/Fe₃O₄ nanoparticles （Ni/Fe₃O₄-NPs） on the surface of carbon fiber, and the deposition mechanism of composite coating. It was founded that the experimental data were fully consistent with the model of two-step adsorption theory. It demonstrates that the deposition process of Ni/Fe₃O₄-NPs composite coating is suitable for model of the two-step adsorption theory. We also prepared the composite of Ni/Fe₃O₄-NPs carbon fiber. The test results show that the electromagnetic shielding effectiveness of the composite of carbon fiber with Ni/Fe₃O₄-NPs coatings is 10 dB higher than that without Fe₃O₄-NPs.In conclusion, the filling electromagnetic shielding composite material filled with metalized carbon fiber have excellent electromagnetic shielding performance. It was confirmed in this work that the theory of material with both high conductivity and high permeability could obtain high electromagnetic shielding performance, providing the new train of thought and research foundation for the design and research of novel electromagnetic shielding materials.更多还原