利用分子動力學模擬探討單寧酸吸附於單壁奈米碳管之分子結構與機械性質之研究

Abstract

奈米碳管為二十一世紀被眾人廣泛討論的新興材料，隨著近幾年人們對於此性質的研究與討論，其優點也隨之應用在各個領域與生活當中，然而在製造加工領域與奈米碳管分解的環保議題上，可以看到單寧酸(TA)在與奈米碳材應用上扮演著不同的角色。故本篇論文希望藉由分子動力學(Molecular Dynamics)模擬計算並觀察微觀尺度下單寧酸吸附於單壁奈米碳管上的構型與力學關係，本文採用CVFF(Consistent Valence Forcefield)勢能來表示原子之間的交互作用， 利用LAMMPS(Large-scale Atomic/Molecular Massively Parallel Simulator)來進行SMD(Steered Molecular Dynamics)與拔出試驗並收集原子的運動軌跡來進行機械性質與吸附構型的分析。 本文中採用去質子化 單寧酸的方式來模擬不同pH濃度的單寧酸，設計了單、多顆不同帶電量之單寧酸吸附於單壁奈米碳管、雙平行排列之碳管與單寧酸吸附於奈米碳管束總共四種模型，並量測不同帶電數的單寧酸吸附於單壁奈米碳管之構型，發現不同電子數下的單寧酸吸附於單壁奈米碳管之構型是有所差異性的，並藉由分析雙平行排列之碳管相互滑移的力學行為，發現單寧酸與單壁奈米碳管的交互作用力是優於相鄰兩裸碳管間的作用力，最後藉由單寧酸吸附於奈米碳管束之拔出試驗的力學分析與過往文獻的力學行為做比較，可以發現在鹼性環境下的單寧酸吸附於奈米碳管束時力學表現較佳。藉由本研究中分子動力模擬，可以協助了解微觀尺度下在不同pH環境中單寧酸吸附於單壁奈米碳管上的構型與力學關係。

Carbon nanotube is a new material is widely discussed in the twenty-first century. Recently, people have studied and discussed the properties of carbon nanotube, and its advantages have also been applied in various fields. However, in the field of manufacturing, processing, the environmental protection issues of carbon nanotube decomposition, it can be seen that tannic acid (TA) plays a different role from the application of carbon nanotube. In this thesis, we hope to simulate and observe the configuration and mechanical relationship of tannic acid adsorbed on single-walled carbon nanotubes at the micro scale by molecular dynamics. In this thesis, CVFF (Consistent Valence Forcefield) potential energy is used to represent the interaction between atoms. LAMMPS (Large-scale Atomic / Molecular Massively Parallel Simulator) was used to perform SMD (Steered Molecular Dynamics) and pull-out tests, atomic trajectories were collected to analyze mechanical properties and adsorption configurations. In this thesis, deprotonated tannic acid was used to simulate tannic acid with different pH concentrations. Four models were designed, namely, single and multiple tannic acids with different charges were adsorbed on single-walled carbon nanotubes, double parallel arranged carbon nanotubes and tannic acid adsorbed on carbon nanotubes. The configuration of tannic acid adsorbed on single-walled carbon nanotubes with different charges was measured. It was found that the configuration of tannic acid adsorbed on single-walled carbon nanotubes with different charges was different. By analyzing the mechanical behavior of double parallel arranged carbon nanotubes, it was found that the interaction force between tannic acid and single-walled carbon nanotubes was better than that between adjacent bare carbon nanotubes. Finally, by comparing the mechanical analysis of the pull-out test of tannic acid adsorbed on the carbon nanotube bundles with the mechanical behavior, it can be found that tannic acid adsorbed on the carbon nanotube bundles in alkaline environment has better mechanical performance. In this thesis, molecular dynamics simulation can help to understand the configuration and mechanical relationship of tannic acid adsorbed on single-walled carbon nanotubes at micro-scale in different pH environments.