奈米碳管特性對放電產生空氣負離子影響之研究

The traits of carbon-nanotubes affect generation of negative air ions by electric discharging

徐孟琮(Meng-Tsung Hsu)

指導教授 ： 李慧梅

國立臺灣大學/工學院/環境工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00915

摘要

本研究探討奈米碳管特性對利用負極放電電極產生空氣負離子的影響，並且探討發展微型空氣清淨裝置的可行性。實驗主要探討:奈米碳管在一維與二維金屬基體上、奈米碳管長徑比、奈米碳管排列、多壁與單壁奈米碳管、金屬材質、金屬長徑比、金屬針尖曲率對放電電壓之影響、產生空氣負離子之穩定度和有效作用距離、偵測臭氧濃度。奈米碳管在一維比在二維金屬基體上具有較低的放電，因為電子能夠聚集於一維基體尖端，使電子激發較容易。奈米碳管長徑比愈大，場增強效應(enhanced field emission)愈大，所以放電電壓亦愈低。奈米碳管陣列因規則排列能降低屏蔽效應(screening effect)，可以有效地降低放電電壓。單壁奈米碳管比多壁奈米碳管具有較大的長徑比、較好的導電性，所以具有較低的放電電壓。在相同電壓下，奈米碳管長徑比愈大，負極放電產生空氣負離子濃度之穩定度愈好。空氣負離子濃度會隨著距離的增加而遞減，呈現對數線性遞減的關係，並在反應器內距離超過60cm後，空氣負離子濃度皆為背景值。奈米碳管在銅或銀電極上，分別在電壓1.6kV與1.4kV即可產生空氣負離子濃度達極限偵測範圍，並且無臭氧的產生，皆在電壓3.0kV時，開始分別產生臭氧濃度0.6ppb與0.5ppb，且臭氧濃度隨著放電電壓的增加而迅速增加。

關鍵字

空氣負離子 ； 奈米碳管陣列 ； 長徑比 ； 場增強效應 ； 屏蔽效應

並列摘要

This study investigated the traits of carbon-nanotubes (CNTs) affect generation of negative air ions (NAIs) by negative electric discharging, and investigated the feasibility of developing a microscale air cleaner. The research investigated the effect of the discharging voltage about CNTs on the one and two dimension metal substrate, the aspect ratio of CNTs, aligned CNTs, single-walled and multi-walled CNTs, metal material, metal aspect ratio, metal needle-point curvature, the stability and the effective distance of NAIs which were generated by negative electric discharging, dectecting ozone concentration. Because electrons can gather on need-point of one dimension substrate to make electrons excite easilier, the discharging voltage of CNTs on the one dimension metal substrate gets lower than other on the two dimension metal substrate. The enhanced field emission gets bigger and the discharging voltage gets lower when the aspect ratio of CNTs gets bigger. Beacause CNTs array align regularly, it can reduce screening effect and the discharging voltage effectively. Because of bigger aspect ratio and better conductivity the discharging voltage of Single-walled CNTs gets lower than the one of multi-walled CNTs. At the same discharging voltage, the stability of NAIs which were generated by negative electric discharging gets better when the aspect ratio of CNTs gets bigger. The NAIs concentration decreased when the distance increased, and The NAIs concentration and the distance indicated logarithmic linear relationship. The NAIs concentration of CNTs on copper and silver electrode which was used as the negative electrode to generate NAIs can reach detecting limit range when the discharging voltage was about 1.6 kV and 1.4 kV, and there was no generation of ozone. When the discharging voltage was about 3.0 kV, ozone concentration which was generated by CNTs on copper and silver electrode was about 0.5 ppb and 0.6 ppb, and ozone concentration increased fast when the discharging voltage increased.

並列關鍵字

negative air ions (NAIs) ； carbon-nanotubes (CNTs) array ； aspect ratio ； enhanced field emission ； screening effect

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