奈米碳管氧化反應動力學研究

Kinetic Study of Carbon Nanotube Oxidation Reaction

劉亞蟬(Ya-Chan Liu)

指導教授 ： 李世琛

中原大學/理學院/奈米科技碩士學位學程/碩士(2011年)

https://doi.org/10.6840/cycu201100614

摘要

本實驗主要是利用低壓水電漿產生羥基(OH)自由基，對多壁奈米碳管進行不同溫度、時間之處理。透過顯微鏡式拉曼光譜儀及滴定方法，分析經OH電漿處理後之多壁奈米碳管表面官能基化程度。我們利用簡單的動力學方程式，來解釋拉曼強度比(ID/IG)的趨勢；在相同溫度下，隨著處理時間的不同，ID/IG呈非線性變化，透過此趨勢分析，在OH電漿處理的過程中，有兩種情形同時發生：一為形成新的缺陷，另一為清除原有的缺陷；我們根據所求得的反應速率及活化能發現，OH電漿比起破壞奈米碳管，更易清除非晶相碳和奈米碳管上的缺陷。最後，我們使用滴定的方法，對電漿處理前後之奈米碳管進行分析。主要是利用碳酸氫鈉(NaHCO3)及鹽酸(HCl) 與奈米碳管進行反應，再添加氫氧化鈉(NaOH)進行反滴定至pH值為7。藉由計算滴定溶液體積，即可求出每單位奈米碳管表面官能基的含量。我們發現表面官能基含量有週期性的變化且變化頻率隨著溫度的增加而增加。也就是說，當溫度越高，多壁奈米碳管的剝層速率增加。

關鍵字

多壁奈米碳管 ； 拉曼 ； 氫氧電漿

並列摘要

Multiwalled carbon nanotubes (MWCNTs) have been treated in different temperatures and different treatment times with a low pressure water plasma. Plasma-induced damage on MWCNT surface was monitored by micro-Raman spectroscopy and titration analysis. A simple kinetic model is adopted to interpret the observed intensity ratio (ID/IG) trends in plasma-treated MWCNTs. The change of ID/IG with respect to plasma treatment time was measured with different temperature settings. From the nonlinear time-dependent trends of ID/IG, it is found that there are two competing processes during plasma treatment. One is a defect formation process and the other one is a defect-scavenging process induced by OH plasma, with the reaction rate and activation energy of the former process slightly higher than the latter one. This indicates that OH is more effective in reacting with defective carbon impurities than purifying CNTs. In titration method, carbon nanotubes were mixed with NaHCO3 and HCl, and then NaOH for reverse-titration until pH equals 7. From the consumed solution volume, we can find out the number density of surface functional group in carbon nanotubes. We have found that the numbe density varies periodically and the variation frequency increases with increasing temperature. It implies that the unzipping rate of MWCNT shells increases with increasing temperature.

並列關鍵字

Raman ； OH plasma ； Multiwalled carbon nanotubes

參考文獻

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