無機物包覆奈米碳管/乙烯酯樹脂複合材料之製備及其性質之研究

Preparation and Properties of Inorganic Material Coated Carbon Nanotube /Vinyl Ester Composites

黃彥瑋(Yen-Wei Huang)

指導教授 ： 馬振基

國立清華大學/工學院/化學工程學系/碩士(2009年)

摘要

近年來，半導體製程技術與微電子工業的蓬勃發展，電子元件朝著輕、薄、短、小與高密度發展，然而電子元件在工作時會產生熱，當熱無法排除時會降低元件效能或使電子訊號失真，更會導致電子元件損壞，因此，元件在運作時，系統散熱速度的快慢對電子元件的壽命及性質具有極大的影響。利用奈米碳管具有高的長徑比與高熱傳導的特性，以提高材料的熱傳導性質，製備出高導熱奈米複合材料， 但是奈米碳管具有的導電性會造成電子元件發生短路的現象。
本研究旨在建立奈米碳管界面絕緣包覆技術，以三步驟化學反應程序，利用無機物的絕緣性包覆奈米碳管以阻止其導電通路。第一，利用酸改質奈米碳管以增加奈米碳管分散性與提供反應官能基，第二，利用無機烷氧化物進一步改質奈米碳管以增進奈米碳管與無機物間的作用力，第三，以溶膠凝膠法製備奈米級無機物包覆奈米碳管。藉由拉曼光譜 (Raman Spectrum)、高解析電子能譜儀 (XPS)、紅外線光譜儀(FT-IR) 和熱重分析儀(TGA)分析鑑定，並以TEM觀察其型態。
研究結果證實已成功製備無機物包覆奈米碳管，由量測其電性與熱性質可知，利用無機物包覆奈米碳管可以成功阻止奈米碳管間的導電通路，使得奈米碳管的電阻值上升，電阻值皆可提高6 orders以上，增進其電絕緣性。三氧化二鋁包覆奈米碳管可以提升奈米碳管與三氧化二鋁的作用力，因此降低奈米碳管與三氧化二鋁的界面熱阻，使得奈米碳管的熱傳導值由6.44 W/mK上升到8.19 W/mK，增進27%的熱傳導性質。
本研究選用具有優異的耐化性、耐腐蝕性、快速含浸能力與良好的接著強度的乙烯酯樹脂，並利用奈米碳管的高導熱性加上界面絕緣包覆技術，以製備出無機物包覆奈米碳管/乙烯酯樹脂絕緣導熱奈米複合材料。以SEM觀察奈米複合材料橫截面可知無機物包覆奈米碳管可增進在基材的分散性，量測添加奈米碳管對複合材料電阻值、熱傳導值、玻璃轉移溫度(Tg)和熱膨脹係數(CTE)的影響。研究結果發現添加無機物包覆奈米碳管可增進複合材料的尺寸安定性、增加其Tg、維持複合材料的絕緣性並且提升熱傳導值。
當添加高含量(10phr)之純奈米碳管時，複合材料的電阻值會由7.83x1015 (Ωxcm)減少到48 (Ωxcm)，降低14個數量級(orders)，而添加添加氧化鋁包覆奈米碳管(Al2O3@SA-MWCNT)會由7.83x1015 Ωxcm減少到5.07x1012Ωxcm，只降低3 orders，並且維持複合材料的電絕緣性，添加三氧化二鋁包覆奈米碳管的複合材料熱傳導值會由0.131 (W/mK) 上升到1.123(W/mK)，提升7.57倍，同時複合材料的Tg會由125.8℃上升到138.9℃，增加10.4%，而CTE會由79.6(10-6/K)下降到56.2(10-6/K)，減少29.4%，提升複合材料的尺寸安定性。

關鍵字

奈米碳管 ； 乙烯酯樹脂 ； 複合材料

並列摘要

Recent advances in nanofabrication have enabled the continuing reduction in size of electronic devices. Smaller sizes have led to higher device density at the expense of increased power demand and the resultant heat generation. Electronic devices were damaged by much heat accumulation. The thermal management strategies are thus critically important to continue high performance, reliability and lifetime of devices. Carbon nanotubes possess low density, large aspect ratio and unique thermal properties that make carbon nanotubes be utilized as filler to fabricate nanocomposites. High thermal conductivity nanocomposites based on carbon nanotubes can be developed to assist heat conduction，however, high electrical conductivity of carbon nanotube provides the conductive path causing short circuit of the device at the same time.
For solving this problem the technologies of coating inorganic materials on the carbon nanotube is proposed to hinder the electrical conducting channel. There are three chemical processes were proposed for fabricating multi-walled carbon nanotube (MWCNT) coated with inorganic materials. The carboxylic groups were first introduced on the MWCNTs using acid oxidation method for dispersing individual MWCNTs. In order to provide the interfacial interactions between the MWCNTs and the inorganic materials for self-assembly of the nanoinorganic layer, acid oxidized MWCNTs were reacted with a silane coupling agent. Finally, the molecular interaction between the silane functionalized MWCNTs and inorganic materials via sol-gel process was utilized to form the structure of inorganic layer coated on MWCNTs. MWCNTs coated with inorganic materials was analyzed by Raman spectrometer, X-ray photoelectron (XPS), Fourier transform infrared spectrometer (FT-IR) and thermogravimetric analysis (TGA). The morphology of MWCNTs coated with inorganic materials were observed by Transmission electron microscope (TEM).The effect of inorganic materials on the electrical resistivity and thermal conductivity of MWCNTs were investigated.
The electrical resistivity of modified MWCNTs was increased 6 orders of magnitude than pristine MWCNTs by coating with inorganic materials .This result exhibits that inorganic layers successfully hinder the electrical conducting channel. The thermal conductivity of MWCNTs was increased from 6.44 W/mK to 8.19 W/mK.The enhancement is 27%.
Vinyl ester resin possesses excellent adhesion, mechanical properties and resistance to chemicals, such as acids, alkalies, oxidizing chemicals and salt solutions, etc. However, the thermal conductivity of vinyl ester is too low to be utilized in thermal applications. In this study, MWCNTs coated with inorganic materials were added in vinyl ester to fabricate high thermal conductivtiy and electrical insulation nanocomposite. Inorganic materials coated on MWCNT/vinyl ester nanocomposites were also prepared to investigate the electrical resistivity, the thermal conductivity, glass transition temperature (Tg) and coefficient of thermal expansion (CTE).Results show that inorganic materials coated on MWCNTs can reduce the CTE of nanocomposites and increase Tg, the thermal conductivity of nanocomposites while retain electrical insulation at same time.
SEM microphotographs show that the inorganic materials coated on MWCNT / Vinyl ester nanocomposites possess better compatibility and disperity. The volume electrical resistivity decreased 14 orders of magnitude from 7.8 x1015 (ohm*cm) to 4.8 x101 (ohm*cm) with 10phr(parts per hundred parts of resin) of MWCNT. On the other hand, the volume electrical resistivity of Al2O3@SA-MWCNT/vinyl ester nanocomposites decreased slightly from 7.8 x1015 (ohm*cm) to ~5x1012 (ohm*cm).The volume electrical resistivity of nanocomposites decreased only 3 orders of magnitude and maintained electrical insulation . Because the electrical networks of Al2O3@SA-MWCNT in the nanocomposites were hindered by the alumina coating layer. The thermal conductivity of the Al2O3@SA-MWCNT/vinyl ester nanocomposites increased from 0.13 W/mK to 1.12 W/mK when the content of the MWCNTs was increased from 0 to 10 phr. The enhancement is 757% .Tg of the Al2O3@SA- MWCNT/vinyl ester nanocomposites increased from 125. 8oC to 138.9oC when the content of the MWCNT was increased from 0 to 10 phr. The enhancement is 10.4 %.CTE of the Al2O3@SA-MWCNT/vinyl ester nanocomposites decreased from 79. 6 (10-6/K) to 56.2(10-6/K) when the content of MWCNT was increased from 0 to 10 phr.

並列關鍵字

Carbon Nanotube ； Vinyl Ester ； Composites

參考文獻

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