多壁奈米碳管強化環氧樹脂複合材料的熱傳導性質

Thermal Conductivities of MWCNT-Reinforced Epoxy Composites

唐伯偉(Po-Wei Tang)

指導教授 ： 江右君

元智大學/工程學院/機械工程學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00227

摘要

由於奈米碳管具有高熱傳導性能，它可被視為最佳的複合材料的補強材。本研究使用環氧樹脂為基材，並且加入不同直徑的多壁奈米碳管作為補強材。探討多壁奈米碳管的添加重量百分比(0.1 – 5 wt. %)、碳管直徑(20 – 40 or 40 – 60 nm)以及試片厚度(1 or 3 mm)對於複合材料熱傳導性能的影響。結果顯示以厚度為1 mm的試片而言，在試片上下表面的平均溫度為50 ℃的測試環境下，純環氧樹脂的熱傳導係數為0.204 W/m K。多壁奈米碳管重量百分比的增加在複合材料上反應出較高的熱傳導係數；在添加0.9 wt. %以下的多壁奈米碳管時，會使複合材料的熱傳導係數呈現趨近線性成長的趨勢。但含量繼續增加時，則提升速率出現緩和的現象。添加0.9 wt. %且直徑介於20 – 40 nm或介於40 – 60 nm的多壁奈米碳管/環氧樹脂複合材料，其熱傳導係數分別為0.289 W/m K或0.281 W/m K，相較於純環氧樹脂則分別成長了42 或38 %。添加5 wt. %且直徑介於20 – 40 nm或介於40 – 60 nm的多壁奈米碳管/環氧樹脂複合材料，其熱傳導係數分別為0.404 W/m K或0.423 W/m K，相較於純環氧樹脂則分別成長了98 或107 %。而厚度3 mm的試片所量測出來的結果低於厚度1 mm的量測值，這是由於3 mm的試片有較大的側面積直接與空氣接觸，使得熱損失較明顯。此外，本研究亦利用Eshelby的微觀力學模型結合Nemat-Nasser和Hori之理論，推導多壁奈米碳管/環氧樹脂複合材料之熱傳導方程式，用來預測多壁奈米碳管/環氧樹脂複合材料的熱傳導係數。與實驗結果比較後發現，厚度為1 mm的試片在添加小於0.9 wt. %的多壁奈米碳管時，不論碳管直徑介於20 – 40 nm或介於40 – 60 nm，實驗結果與此模型的預測值相近，而添加高重量百分比多壁奈米碳管的實驗結果則由於出現非線性的成長，故略低於模型推導的結果。

關鍵字

多壁奈米碳管 ； 環氧樹脂 ； 複合材料 ； 熱傳導係數

並列摘要

Due to its excellent thermal conductivity, carbon nanotubes (CNTs) are considered as candidates for heat management materials. In the present works, the epoxy resin is used as the matrix, and the multi-walled carbon nanotubes (MWCNTs) with different diameters are as the reinforcement. The objectives of this study are to understand the effects of MWCNT weight percent (0.1 – 5 wt. %), MWCNT diameter (20 – 40 or 40 – 60 nm), and the thickness of the specimens (1 or 3 mm) on the effective thermal conductivities of the composite. The results show that under 50 and the specimen with thickness = 1 mm, the thermal conductivity of the pure epoxy is 0.204 W/m K. The thermal conductivity of the composite increases with the increase in the MWCNTs weight percent. By adding of the MWCNTs under 0.9 wt. %, the thermal conductivity of the MWCNT/epoxy composite increases linearly, but the increasing rate decreases once the MWCNTs weight percent is over 0.9 wt. %. The thermal conductivities of 0.9 wt. % MWCNT/epoxy composites with a MWCNT diameter D = 20 - 40 nm or D = 40 - 60 nm are 0.289 or 0.281 W/m K, respectively. Compare with the pure epoxy, the thermal conductivities increase 42 or 38 %, respectively. The thermal conductivities of 5 wt. % MWCNT/epoxy composites with a MWCNT diameter D = 20 - 40 nm or D = 40 - 60 nm are 0.404 or 0.423 W/m K, respectively, with the increments of 98 or 107 %. The experimental results of the composite specimens with thickness = 3 mm is lower than that with thickness = 1 mm. This is attributed to the fact that there is a larger lateral area exposing to the external environment in the specimens with thickness = 3 mm, which results in a large heat loss. The micromechanics model, Eshelby, is developed to predict the thermal conductivity of MWCNT-reinforced composites. Compared with the experimental data, the predictions are fitted well with the experimental data of the composite specimens with thickness = 1 mm by adding MWCNTs under 0.9 wt. %, no matter the diameters of the MWCNTs are between 20 - 40 nm or 40 - 60 nm. However, at high wt. % of MWCNTs (> 0.9 wt. %), there are large discrepancies between the predictions and the experimental data because the trend of the increase by adding high wt. % MWCNTs are nonlinear.

並列關鍵字

multi-walled carbon nanotube ； epoxy ； composite ； thermal conductivity

參考文獻

Bagchi, A., and Nomura, S. (2006) “On the effective thermal conductivity of carbon nanotube reinforced polymer composites,” Composites Science and Technology, 66, pp 1703-1712.

Berber, S., Kwon, Y. K., and Tomanek, D. (2000) ”Unusually high thermal conductivity of carbon nanotubes,” Physical Review Letters, 84 (20), 4613.

Che, J., Cagin, T., and Goddard, W.A., III. (2000) “Thermal conductivity of carbon nanotubes,” Nanotechnology, 11 (2), 65-69.

Choi, S. U. S., Zhang, Z. G., Yu, W., Lockwood, F. E., and Grulke, E. A. (2001) “Anomalous thermal conductivity enhancement in nanotube suspensions,” Applied Physics Letters, 79 (14), 2252-2254.

Choi, T. Y., Poulikakos, D., Tharian, J., and Sennhauser, U. (2005) “Measurement of thermal conductivity of individual multiwalled carbon nanotubes by the 3-ω method,” Applied physics letters, 87, 013108-1-3.