深共熔點溶劑輔助之快速陽極處理法成長二氧化鈦奈米管與其場發性質探討

Field Emission of Titania Nanotube Arrays Prepared with a Fast Anodization Process Enabled by Use of a Deep Eutectic Solvent

陳君怡(Chun-Yi Chen)

指導教授 ： 呂世源

國立清華大學/工學院/化學工程學系/碩士(2007年)

摘要

在製備奈米孔洞結構的各種製程中，陽極處理不但製程簡易，且成本低廉，易於量產，所製備出的奈米孔洞結構，可藉由參數調整得到孔洞大小均勻，排列整齊且規則堆積的奈米多孔結構。十餘年來，陽極氧化鋁模版(AAO)的製備與應用已經發展得相當成熟與多樣化，而近五年來亦開始發展二氧化鈦奈米管的製備。由初期的二氧化鈦奈米管的製備與改良，到後期的應用價值探討與機制研究，已漸漸吸引許多學者的高度興趣。由於二氧化鈦奈米管具有優良的光催化(photocatalysis)性質，是廣為人知的光觸媒材料，具有自清潔(selfcleaning)環境汙染物的特性；二氧化鈦奈米管的卓越的電催化性質(electrocatalysis)可以將其組裝為光電極參與水的分解反應，或是應用於染料敏化太陽能電池(dye-sensitized solar cell)；亦可作為氫氣的檢測器(H2 sensor)與生化測器(biosensor)。
關於鈦的陽極處理，本研究成果有：(1)添加深共熔點溶劑成功製備出孔洞在20~30奈米左右的孔洞結構，並成功改善二氧化鈦奈米管成長速率至每分鐘9.79微米；將深共熔點溶劑與甘油系統結合，可將原本孔洞50奈米的二氧化鈦奈米管擴張至80~100奈米。(2)藉由電解液成份的控制與機制的掌握，可以成功製備出非管狀結構的奈米結構。以琥珀酸為電解液製備出30奈米的奈米棒陣列，其高度約為20~100奈米。(3)製備出管徑為50與100奈米的二氧化鈦奈米管，作為相對的實驗對照組，探討反應機制與相關應用。(4)添加深共熔點溶劑之反應機制探討，修改文獻所提出之反應模型。(5)將快速成長與孔洞約為20~30奈二氧化碳奈米管，歷經不同鍛燒條件控制，應用於場發射 (field emission)，在兩極間距(vacuum gap)為300μm時，可得到相當低的導通電場1.5V/μm (電流密度定義在1μA/cm2)，並且在低電壓2.2 V/μm，就可到達大電流值1m A/cm2。(6)在不同的距離量測場發射，探討β值與距離關係，可得到僅與材料特性相關的特徵值β0值，為11,111，與奈米碳管場發射性質相近。

關鍵字

陽極處理 ； 二氧化鈦 ； 奈米管 ； 場發射 ； 深共熔點溶劑

並列摘要

Preparation of long, straight nanopore structures using the anodization process is relatively simple, low cost, and easy to mass-produce as compared to other processes. In addition, application properties of the nanopore structures such as size and uniformity can be easily adjusted by varying relevant operating parameters.
The most popular and well-known application of the anodization process is the preparation of aluminum oxide membranes. For the past five years, researchers began to study the preparation of titanium dioxide nanotubes through Ti anodization. Titanium dioxide nanotubes have excellent photocatlytic and self-cleaning properties. They can be applied to water degradation processes because of their excellent electrocatalytic property. Such property allows them to be used in methanol oxidation process. Titanium dioxide nanotubes can also be used in a wide range of areas such as dye-sensitized solar cell and hydrogen sensing.
Experimental results obtained from this research include the following. (1) Nanoporous structures with pore size of 20~30nm were successfully prepared with addition of a deep eutectic solvent (DES), and the growth rate of the titianium dioxide nanotubes can be as high as 9.79μm/min. Pore size of the nanostructure prepared can be increased from 50nm to 80~100nm by combining DES and glycerol as the solvent system. (2) Non-tubular nanostructures were successfully prepared through control of the composition of the electrolyte and reaction mechanism. Electrolyte composed mainly of succinic acid was used to prepare nanorod arrays with heights of 20~100nm. (3) Reaction mechanisms and applications of the titanium nanotubes prepared were studied. Comparison was made for titanium dioxide nanotubes of two different lengths, 50 and 100nm. (4) A modified nanotube growth mechanism was proposed to explain the high growth rate achieved in this work made possible by addition of the DES. (5) Field emission characteristics of the titania nanotubes of 20-30 nm with various heat treatment were studied. The turn-on field was 1.5V/μm (defined at current density of 1μA/cm2) when the vacuum gap was 300μm. The current density reached 1 mA/cm2 at the applied field of 2.2V/μm. (6) The relationship between the field enhancement factor (β) and vacuum gap was studied. The resulting absolute field enhancement factor, β0, was determined for the titanium dioxide nanotube arrays to be 11,111, which is larger than that of the carbon nanotubes grown on silicaon wafers.

並列關鍵字

anodization ； TiO2 ； nanotube ； field emission ； deep eutectic solvent