製備三維複合碳材料及其特性研究

Synthesis and Characterization of Three-Dimensional Carbon Fabrics

陳威宇(Wei-Yu Chen)

指導教授 ： 謝建德

元智大學/工程學院/化學工程與材料科學學系/碩士(2008年)

https://doi.org/10.6838/YZU.2008.00268

摘要

本研究提供一種製備三維複合碳材之技術，將此新穎材料應用於電化學儲能及超疏水行為。製程主要以聚丙烯氰(polyacrylonitrile)活性碳纖維為基體，利用觸媒催化化學氣相沉積法(catalytic chemical vapor deposition, CCVD)，將奈米碳管裝飾於活性碳纖維表面，形成擁有兩階層粗糙表面(奈米碳管與微米級活性碳纖)之三維複合碳結構。特性研究以Nitrogen adsorption/desorption isotherms analyser、Scanning Electron Microscope (SEM)進行分析。電化學特性則以電化學測試系統分析。關於表面親疏水特性以接觸角分析儀判斷其表面親疏水性質，研究奈米碳管植入對表面沾溼性之影響。
由孔徑分佈分析觀察出，植入奈米碳管使整體孔徑分佈往中孔方向移動。較大的孔徑，能提供酸性電解質中，質子移動所需空間，有效減少靜電吸脫附之阻抗。本研究第一部分進行電化學特性測試，循環伏安法與定電流充放電分析奈米碳管植入前後電化學特性之改變。因為奈米碳管擁有中孔級孔徑與高導電性，能降低活性碳纖作為電極之阻抗，同時提供有效電雙層靜電吸附活位，提升整體電容且改善高速率之充放電行為。在充放電測試結果印證，植入奈米碳管提升整體電容達264 %，並提供穩定的電容。
第二部份進行複合碳材表面親疏水特性研究。此複合碳材表面擁有兩階層之粗糙結構，一是連接在活性碳纖維呈放射狀之奈米碳管，二為規則排列微米級活性碳纖維網狀結構。以此不同層級粗糙面為基底，搭配表面氟化處理，成功改善碳材親疏水特性。接觸角從純活性碳纖維的148.2±2.1°增加到169.7±2.2°，証實植入奈米碳管改變表面結構，增加複合碳材表面粗糙度，提升三相接觸面之不連續性，減少水滴與基材接觸面積，將原本疏水介面轉換為超疏水介面。

關鍵字

活性碳纖維、奈米碳管、電雙層電容、高效率充放電能力、表面水滴接觸角、超疏水行為

並列摘要

Electrochemical behavior of polyacrylonitrile (PAN)-based carbon fabric decorated with carbon nanotubes (CNTs) was examined using cyclic voltammetry and charge-discharge cycling. A chemical vapor deposition was employed for decorating the CNTs onto PAN-based carbon fabrics, using acetylene and Ni nanoparticle as carbon precursor and catalyst, respectively. N2 physisorption indicated that the introduction of nanotubes affect the type of isotherm and improves the mesopore fraction of carbon fabrics. The electrochemical behavior of the carbon electrodes in H2SO4 indicated that the presence of nanotubes not only decreases the distributed capacitance effect and IR drop but also induces double-layer formation and high-rate capability. Charge-discharge cycling test showed that there is ca. 264 % capacitance increase and stable capacitance achieved through the introduction of CNTs.
The contact angle of water significantly increases from 148.2 ± 2.1° to 169.7 ± 2.2° through the introduction of CNTs. This confirms that the wettability of carbon fabric has changed from hydrophobicity to superhydrophobicity due to the structural transformation. This finding would shed one light on how the two-tier roughness surface would induce the superhydrophobicity of rough surfaces, and the presence of CNTs would reduce the area fraction of a water droplet in contact with the carbon surface with two-tier roughness.

並列關鍵字

activated carbon fabrics, carbon nanotubes, electric double-layer capacitance, high rate capability, contact angle, super hydrophibic

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