多壁奈米碳管-高分子複合材料之電磁波遮蔽研究

The Electromagnetic interference of Multi-Walled Carbon Nanotubes-Polymer Composite

洪前福

指導教授 ： 徐文光

國立清華大學/工學院/材料科學工程學系/碩士(2006年)

摘要

奈米碳管(Carbon Nanotubes, CNTs)是一種新的碳材料，從奈米碳管被發現到現今為止，它的各項特性一直都令人好奇與驚訝，因此有許多學者廣泛研究與討論。奈米碳管的導熱性佳，機械強度、韌性均遠超過於一般鋼鐵材料[1,2]，而碳管本身的長度和徑長比 (aspect ratio) 具有較低之功函數(4.5-5 eV,work function) 因 此 具 良好的場發射效應 (Field Emission)[3,4,5]。此外，電子元件三極體[6,7]、電鏡探針[8]、氣體偵測[9,10] 等等的各項應用也都逐漸被開發出來，奈米碳管儼然是當今最重要奈米材料材料之一！
由於近年來電磁波的影響越來越大[11-12]，傳統 防備電磁波干擾的方法通常是用具有金屬特性的材料，這是因為具有好的導電性或使用好的導磁性材料或以添加碳或鎳等導電纖維與高分子混合製成複合材料的方法將電磁波反射或以吸收的方式來達成電磁波遮蔽(electromagnetic interference shielding, EMI)。 奈米碳管因具有一定的導電性質並且含有高的aspect ratio，所以可視之為一種遮蔽材料。同時，由於碳管的各種特殊性質使得以奈米碳管為EMI的研究對象而言的研究也日漸著重。本實驗主要目的是研究與測試奈米碳管與高分子所形成的複合材料在電性上以及一般未被常討論到的影響遮蔽效果的因素上做出分析與假設，同時為了改變電磁波的遮蔽效應，於是也嘗試濺鍍鎳金屬於奈米碳管上以期望能有不同的遮蔽效果並與理論的公式相比較。

關鍵字

碳管 ； 環氧樹酯 ； 電磁遮蔽

並列摘要

These year, the effect of EM(Electromagnetic) wave in our daily life is more and more important. Besides the effects on the electrical products . It is also important to the effects on our human body. We want to stop the EM wave to pass through our bodies and reduce the effect of the electrical products. Therefore , there are many researches studied in this direction. For many kinds of shielding of EM wave[1][2] ,the mixing of metal fibers with the polymer is a good method to form the shape we need. By these researches, we know the fiber in the matrix can connect together to form a conductive network , and as the aspect ratio is higher, the conductivity of composite increases so as to the shielding of EM wave.
According to the electrical property of carbon nanotubes , we know it has some degree of conductivity by its special structure[3][4], and it has high aspect ratio for its length and width [5].therefore, we can take it as a kind of replacement of metal fiber to fill in polymer as filler to enhance the conductivity for the EMI effect. By the literatures reported [6][7], we can know the change of conductivity in the composite. And other literatures[8][9] which reported the shielding effect on the mixing of polymer and carbon nanotubes agree to the previous research[10] for that increase of the quantity of metal fiber ,increase the conductivity of composites so as to the shielding of EM wave.
this experiment is stressed on the pure multiwalled carbon tube and addition of some metal to change its shielding effects by adding methylbenzene to polymer and hoping to have a good distribution of MWCNT in the epoxy matrix.