奈米碳管放電產生空氣負離子微型裝置之特性 與控制懸浮微粒之研究

Abstract

本研究為探討不同製備方式製成之奈米碳管(Carbon Nanotube, CNT)放電所產生空氣負離子(Negative air ion, NAI)之特性，其中探討項目包含起始電壓以及穩定度，並將此部分結果進一步應用於CNT產生NAI之微型裝置的研發，探討NAI在空間中有效範圍內移除室內懸浮微粒之增進效率。特性研究部份，選用電弧放電法(Arc-discharge)以及電漿輔助化學氣相沉積法(Plasma-enhanced Chemical vapor deposition, PE-CVD)製程之奈米碳管，藉由調整不同電壓來觀察空氣負離子之特性。空間中有效範圍實驗，則是選用電弧放電法製成之奈米碳管放電，將裝置配戴於模型鼻下20公分處，於特定電壓1kv下進行實驗，觀察空間中不同位置，空氣負離子對於懸浮微粒移除之增進效率。 特性研究部份，電弧法以及PE-CVD法製備之CNT皆可有效將起始電壓降至0.4kv，所產生之NAI濃度別為209.73×103 ions/cm3以及1236.00×103 ions/cm3，並且在電壓0.9~1.0kv下放電所產生之NAI皆有不錯穩定度。但PE-CVD製備之CNT於電壓0.8kv下放電，NAI濃度開始出現衰退現象，電弧法製備之CNT則於電壓0.5kv才出現衰退現象。此外，電弧法製備之CNT在0.6kv下放電，對於微粒仍有移除作用，增進效率為17.6％，但此時使用PECVD製備之CNT放電所產生之NAI，對於懸浮微粒之移除已無明顯貢獻，其增進效率僅為5.1％。故以電弧法製備之CNT放電所產生的NAI，可在較低電壓下對於懸浮微粒的移除達穩定操作。 有效範圍實驗部分，NAI作用於鼻下3公分處面部前方之範圍內，對於懸浮微粒之移除有最好的效果，增進效率平均可達17.9％；而於鼻子處面部前方範圍NAI對於微粒仍有作用，平均增進效率可達13.8％；但於鼻上3公分處面部前方之範圍內，NAI對於懸浮微粒移除之平均增進效率僅為7.1％，即空氣負離子在此處貢獻已降至非常低。此外，本研究結果顯示垂直方向上距離的改變，對於NAI增進效率的影響較水平方向上距離的改變還要來的顯著。

The air ionizer had become increasingly popular for removing suspended particulates. In this study, we utilized the Carbon nanotubes(CNTs) as a microscale air ionizer worn 20cm below the nose and established the best operational system. In this study, we investigated the characteristic of negative air ions(NAIs) generated by negative electric discharge using Carbon nanotubes(CNTs) needle of different growth methods. According to the unique efficient field emission property of the CNTs, the results were shown that used the CNTs produced by arc-discharge method and Plasma-enhanced Chemical vapor deposition method could decrease the threshold voltage strongly, reaching voltage value at 0.4kv, and the maximum NAIs concentration were 209.73×103 ions/cm3 and 1236.00×103 ions/cm3 respectively. At the voltage 0.9kv and 1.0kv, both CNTs could generate NAIs stably. But at the voltage 0.8kv, the NAIs generated by CNTs of PECVD method decayed evidently, and the NAI enhancement removal efficiency of particulates was only 5.1%. Compared to the PECVD method, the CNT produced by arc-discharge method could generate the NAIs stably at the lower voltage of 0.6kv, and the NAIs concentration decayed evidently until the voltage decreased at 0.5kv. Besides, at the voltage 0.6kv, the NAI still had the effect of removing the particulates, the NAI enhancement removal efficiency was 17.6%. It was obvious that apply the CNT produced by arc-discharge method to ionize the air could make the experiment system more steady and had the better operation. In this study, we also established the NAI enhancement removal efficiencies of particulates in the breathing zone. We used the CNT produced by arc-discharge method and set the discharge voltage at 1.0kv. It was shown that the NAIs had the best average enhanced efficiency among the breathing area 3cm below the nose.(17.9%). The NAIs still had the obvious effect among the breathing area at the nose, and the average enhanced efficiency was 13.8%. But among the breathing zone 3cm above the nose, NAIs had no evident enhancement removal efficiency of particulates(7.08%). It was also shown that the vertical distance played a more important role for the NAI enhancement removal efficiency than horizontal distance.