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標題: | 以平衡分子動力學研究石墨烯與石墨烯奈米網格之熱傳性質 An Investigation of Thermal Conductivity of Graphene and Graphene Nanomesh in use of the Equilibrium Molecular Dynamics Simulation |
作者: | 廖浩羽 Hao-Yu Liao |
指導教授: | 黃美嬌 Mei-Jiau Huang |
關鍵字: | 平衡分子動力學,晶格熱傳導係數,石墨烯,石墨烯奈米網格,熱整流現象, Equilibrium Molecular Dynamics,Thermal Conductivity,Graphene,Graphene NanoMesh,Thermal Rectification, |
出版年 : | 2023 |
學位: | 碩士 |
摘要: | 本論文以平衡分子動力學模擬方法,研究單層石墨烯與石墨烯奈米網格的熱傳性質。一方面探討系統尺寸與溫度對石墨烯熱傳導係數之影響,也研究孔隙相關幾何參數對石墨烯奈米網格(GNM)熱傳導係數之影響,另一方面探索熱整流效應是否存在於石墨烯與石墨烯奈米網格兩種材料組合而成的系統。模擬採用最佳化特索夫(Opt. Tersoff)勢能函數來描述原子之間的作用力。
本文首先以平衡分子動力學模擬單層石墨烯的色散關係與態密度,並與實驗、模擬之文獻結果比較,確認設置的正確性。接著搭配 Green-Kubo 理論計算單層石墨烯的熱傳導係數,進行尺寸效應與溫度相性的分析。尺寸效應模擬於300K下進行,模擬結果顯示當單層石墨烯的尺寸變大的時候,熱傳導係數大約呈指數下降,並且觀察到在系統尺寸16.0nm × 16.2nm以上時達到收斂。溫度相依性模擬則是在16.0nm × 16.2nm的尺寸下,計算溫度在 100K 到 400K 間的熱傳導係數,發現隨著溫度的提升,熱傳導係數劇烈下降。在石墨烯奈米網格模擬中,觀察六個不同孔隙設定之熱傳導係數與諸幾何參數的關係,發現與石墨烯奈米網格之熱傳導係數最相關的參數為孔隙之頸寬,且兩者呈現線性正相關。另外,當頸寬越小,熱傳導係數對溫度的敏感性越弱,在頸寬為 2nm 時,熱傳導係數幾乎不隨溫度改變。 最後,在得到石墨烯與石墨烯奈米網格熱傳導係數的溫度相依性之後,進一步透過熱擴散方程式探討由石墨烯與石墨烯奈米網格組成之系統的熱整流效應,討論平均溫度、溫差、長度比、熱傳導係數的溫度相依性等因素對熱整流效應之影響。根據結果,歸納可能提升熱整流係數的方向。 In this study, we investigated the thermal conductivity of graphene and graphene nanomesh (GNM) in use of equilibrium molecular dynamic (EMD) simulations with optimized Tersoff potential. The effect size and temperature dependence were inspected. Besides, the correlations of the thermal conductivity with the geometric parameters of nanoholes on GNM were also explored. Finally, we examined if the thermal rectification exists in the system composed of Graphene and GNM. We first validated our simulation setup by comparing the calculated phonon dispersion relation and density of states with those in the literature, including experimental and MD measurements. Then, we investigated the size effect on the graphene thermal conductivity at 300K. The thermal conductivity decreases exponentially with increasing system size and converges as the system size is about 16.0nm × 16.2nm. By fixing the film size at 16.0nm x 16.2nm, we found the thermal conductivity of graphene decreases rapidly with increasing temperature while that of GNMs is much less sensitive to temperature. Among the geometric parameters of nanoholes, the neck width affects mostly. The GNM thermal conductivity decreases approximately linearly with decreasing neck width. Moreover, the smaller the neck width, the weaker the temperature dependence becomes. For those GNMs with neck width of 2nm, the temperature dependence almost completely disappears. Based on the obtained temperature-dependent thermal conductivities of graphene films and GNMs, we finally investigated the thermal rectification phenomenon in nanoribbons composed of Graphene and GNM by solving the heat diffusion equation. The effects of the mean temperature, temperature difference, length ratio and temperature dependence of GNMs on the intensity of thermal rectification were studied. According to the results, we summary some possible directions useful for promoting thermal rectification. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/87270 |
DOI: | 10.6342/NTU202300623 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 機械工程學系 |
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