中文论文文摘

    随着社会电气化的飞速发展，电子产品的种类、数量和电子元件的精密程度不断提高，电子元件所造成的电磁辐射、元件本身受外界电磁波干扰及电磁辐射人体危害等问题变得日益严峻。电磁辐射不仅直接影响电子产品的性能以及信息产业的健康有序发展，对人类及其它生物体造成严重伤害，而且还对国家政治、军事以及经济信息的安全带来极大的危害。因此，开发电磁屏蔽材料（特别是轻量化产品）具有十分重要的意义。
    碳纤维具有导电性能好、质量轻、价格比金属纤维低、易加工、耐氧化性能好等优点，因此是很有发展前景的电磁波屏蔽材料。本课题以碳纤维为原料来开发碳纤维导电屏蔽纸，以拓宽电磁屏蔽材料的研究领域和应用范围，并为研制高性能电磁屏蔽材料提供依据。
    本课题对碳纤维制备导电屏蔽纸的关键技术——分散工艺及抄造工艺进行了探讨，对纸页的力学性能、导电性能、屏蔽性能及其影响因素进行了系统研究，并对制造高性能导电屏蔽纸的可行性及方式进行了初步探讨。
碳纤维的红外光谱、扫描电镜观察及化学滴定测定结果表明，碳纤维表面的活性基团数量少，纤维亲水性低，在水中的分散性很差，必须加入分散剂才能改善其分散性；经过浓硝酸氧化后，碳纤维表面产生更多的活性基团，表面产生刻蚀，表面积增大，纤维亲水性增加，因此碳纤维在水中的分散性及稳定性得到改善。
在一定范围内增加碳纤维含量能够提高纸页的抗张强度、耐破度、撕裂度；超过这个范围会使这些力学性能急剧下降。碳纤维含量越高纸页的导电性越好；碳纤维含量一定，纸页体积电阻率一定，但阻值随定量的增加而减小，其变化规律符合物理导电模型。
    导电网络通路的搭接及接触电阻的大小对纸页的导电性有重要影响。在碳纤维含量较低时，适当增加碳纤维的长度能够提高纸页的导电性；碳纤维间接触得越紧密，接触电阻就越低，体积电阻率也越低。通过打浆、加强湿压榨作用和适当提高植物纤维用量等方法均可降低碳纤维间的接触电阻。
    碳纤维导电屏蔽纸具有较好的屏蔽性能，其屏蔽原理为反射损耗与吸收损耗，屏蔽效能随纸页导电性的升高而提高，并对不同频率的电磁波产生不同的屏蔽效能。增加碳纤维含量或者增加纸页厚度均能提高其屏蔽效能。
    银包铜粉加填碳纤维导电屏蔽纸对纸页导电性的提高效果不明显。但是将其制备成涂料后涂布于碳纤维导电屏蔽纸时，能够明显提高纸页的屏蔽效能。碳纤维导电屏蔽纸具有较好的屏蔽效能，能够代替厚重的金属板和容易氧化、脱落的金属涂层，应用于需要对电磁波进行屏蔽、防护及信息保密的军工、政治、商业、民用等场合，具有非常广阔的前景。

外文论文文摘

    
    As the structures of high performance electronic equipments and devices become increasingly more complex, electromagnetic interference (EMI), electromagnetic radiation hazards and compatibility (EMC) have emerged as key issues. Therefore, Electromagnetic materials play a very important role in preventing electromagnetic radiation(EMR), EMI and guaranteeing information safety on such occasions of commerce, polity, national security, and so on.
    Carbon fiber will be a promised material for electromagnetic shielding because of its predominant characters, for example, good conductivity, light weight, low price (compared with metal fiber) and oxidation resistance. In this study, carbon fiber electromagnetic shielding paper was developed for reducing or preventing EMI, electromagnetic hazards and information leakage. The dispersion properties, papermaking process, mechanic properties, shielding properties and the influential factors of this paper were investigated; and the possibility and approach for manufacturing a higher-SE material were also presented in this paper.
    The analysises of FT-IR, SEM and titration indicated that there were a few oxygen-containing groups on the carbon fiber surface, and its dispersion was poor, but it could be improved by dispersants and surface treatment. After being nitric acid oxidized, the oxygen-containing groups and the specific surface area increased visibly, and the dispersion of carbon fiber was modified further.
    The carbon fiber could enhance the tensile index, burst index and tear index of the sheets to some degree within certain content; the conductance of the sheets rested heavily on the carbon fiber content, the more the carbon fiber content was, the higher the conductance the sheets had. The resistance decreased with the basic weight of the sheets increase, and well fited the physics conductive theory and model.
    The conductive network and the contact resistance had very important effects on the conductance of the conductive shielding paper. Increasing the carbon fibers length could enhance its conductance. Wet pressing, wood fiber beating and its dosage affected the contact resistance greatly. By adjusting the carbon fibers length, wood fiber dosage and papermaking process, conductive network could be optimized, and conductivity could be enhanced.
    The conductance shielding paper had good shielding effectness（SE）, which result from reflection loss and absorption loss. The SE of the sheet increased visibly with the increase of carbon fiber content and the paper thickness. The SE also varied according to different electromagnetic wave frequency. In the frequency range of 600MHz～1.2GHz, the shielding paper had higher SE than that of other frequency. The conductive shielding paper with various SE (30dB～50dB) could be obtained by changing the carbon fiber content and the paper thickness.
    The effects of adding silver covered copper powder to the carbon fiber paper on the conductance and the SE were not so much as that of coating, and that presented us the possibility and approach for manufacturing a higher-SE paper could be used in different occasions for preventing or reducing EMI, electromagnetic hazards or information leakage.