奈米碳管強化聚甲基丙烯酸甲酯之奈米複合材料的熱傳性質研究

Investigations on the thermal conductivity of composites reinforced with carbon nanotubes

洪文泰(Wen-Tai Hong)

指導教授 ： 戴念華

國立清華大學/工學院/材料科學工程學系/碩士(2007年)

摘要

在本研究以共沉澱法製備奈米碳管複合材料並以暫態平面法測量複合材料的熱導係數。另外，也利用過濾碳管溶液製作奈米碳管薄膜，並利用雷射閃光法測量其熱擴散係數進而計算其熱導係數，如此可以得知奈米碳管薄膜及其所強化的奈米複合材料之熱傳係數，此實驗值將與理論值作比較。除此，純化過程、量測溫度與碳管的異向性大幅影響複合材料的熱導係數，本研究中將加以探討影響的機制。
純化對於碳管熱導性質的影響是利用掃描式電子顯微鏡、熱重分析儀與拉曼等儀器來分析。掃描式電子顯微鏡分析奈米碳管純化前後的差異，發現純化後的碳管存在的金屬粒子變少。熱重的結果顯示純化的確改善了碳管的熱穩定性質；由拉曼分析得知碳管在純化過程會造成表面結構的破壞。在室溫下，單壁奈米碳管薄膜的熱導係數為2.24 W/m K，多壁奈米碳管薄膜為0.36 W/m K。另一方面，單壁與多壁奈米碳管薄膜的熱導係數並未隨著溫度的增加而上升，而是逐漸下降的。本研究對奈米複合材料的熱傳導係數進行研究，結果顯示添加4.0 wt%未純化的多壁奈米碳管對於複合材料熱導性質的提升量最高，可達到基材熱導係數的十倍以上。大致說來，奈米碳管複合材料的熱導係數皆隨著碳管含量與溫度的增加而上升。

關鍵字

奈米複合材料 ； 奈米碳管 ； 聚甲基丙烯酸甲酯 ； 熱傳導係數

並列摘要

In this work, we prepared carbon nanotubes/polymethyl methacrylate(CNTs/PMMA) composites and measured its thermal conductivity by the Transient Plane Source (TPS) method. Moreover, we prepared CNTs buckypapers from CNTs suspension and measured its thermal diffusivity by the laser flash method for calculating the thermal conductivity of the buckypapers. The thermal conductivity of the composites fabricated from buckypapers was also investigated, the results were compared with the theoretical predictions. The effects of purification, test temperature and anisotropy of CNTs on thermal conductivity of the composites were investigated.
The influences of the purification process on CNTs was analyzed by Thermogravimetry Analyzer (TGA)、Raman Scattering Spectrometer (Raman) and Field Emission Scanning Electron Microscopy (FESEM). FESEM images showed that the catalysts metals in CNTs were reduced after the purification process. The TGA results showed that thermal stability of CNTs was improved after purification, but the structure of carbon nanotubes was also damaged. The thermal conductivities at room temperature of SWNT and MWNT films were 2.24 W/m K, and 0.36 W/m K, respectively. The thermal conductivities of CNT films increased with decreased of temperature. In this study, the highest thermal conductivity of W/m K was attained when the unpurified MWNTs loadings reaches 4.0 wt %, which is over 10 times higher than the thermal conductivity of PMMA. The thermal conductivity of composites increases with CNT loadings and temperature was also detected.

並列關鍵字

Nanocomposites ； carbon nanotube ； PMMA ； thermal conductivity

參考文獻

1.S. K. Amin, M. Mohammad, B. Reza and F. Brian,“Temperature effects on Kevlar/hybrid and carbon fiber composite sandwiches under impact loading”, Composite Structures 78, 197–206 (2007)

2.E. T. Thostenson, W. Z. Li, D. Z. Wang, Z. F. Ren and T. W. Chou,“Carbon nanotube/carbon fiber hybrid multiscale composites”, Journal of Applied Physics 91, 6034-6037(2002)

3.M. M. J. Treacy, T. W. Ebbesen and J. M. Gibson,“Exceptionally high Young’s Modulus observed for individual carbon nanotubes”, Nature 381, 678-680 (1997)

4.S. Iijima, “Helical Microtubules of Graphitic Carbon” , Nature 354, 56-58 (1991)

6.N. Mingo and D. A. Broido, “Carbon Nanotube Ballistic Thermal Conductance and its Limits ”, Physical Review Letters 95, 096105 (2005)