奈米碳管放電產生空氣負離子微型裝置之研究

Abstract

本研究探討以負極放電產生空氣負離子的各項操作因子與空氣負離子之基礎特性。利用奈米碳管的特性與奈米等級的尖端於低電壓下在空氣中進行放電產生空氣負離子，進而設計微型空氣清淨裝置。實驗主要探討針尖曲率、電極直徑、電極材質、奈米碳管對起始放電電壓之影響；空氣負離子的有效距離、空氣負離子產生裝置之穩定度。使用負極放電方式產生空氣負離子，放電電極的針尖曲率愈大起始放電電壓就愈低；在相同的電極針尖曲率下，當電極直徑愈小時，其起始放電電壓亦愈低。對於不同材質的電極而言，在相同的電極直徑與針尖曲率情況下，銅有最低的起始放電電壓，其次為銀、石墨、鉛、鐵、鎢、鋁。使用奈米碳管作為負極放電產生空氣負離子之放電電極，其起始放電電壓可在0.2 kV以下，遠低於一般金屬電極。在溼度40%下，空氣負離子濃度在6.3*105 ion/cm3左右時，會有0.5 ppb的臭氧產生；在溼度70%下，空氣負離子濃度在9*105 ion/cm3左右時，開始有0.5 ppb的臭氧產生。研究顯示空氣負離子濃度會隨距離的增加呈現對數線性遞減之趨勢(logarithmic linear tendency)，在特定的對數線性距離後空氣負離子濃度隨著距離之增加呈現固定濃度。使用奈米碳管作為放電電極產生空氣負離子，在增加電壓時可以較穩定的產生空氣負離子。

This study investigated the operational factor and the base property of the negative air ions (NAIs) which were generated by negative electric discharge. This study also investigated the characteristics of carbon nanotubes which was used to generate negative air ions to develop a microscale air cleaner (MAC). First, this research investigated the influence of the initial discharging voltage about needle-point curvature, electrode diameter, electrode material, and the characteristics of carbon nanotubes. Second, it studied the effective distance of NAIs, stability of NAIs generator. NAIs were generated by the negative electric discharge method. The results show that the initial discharging voltage gets lower when the electrode needle-point curvature gets bigger. At the same needle-point curvature, the initial discharging voltage is lower when the electrode diameter is shorter. For different electrode material, when needle-point curvature and diameter are constant, copper had the lowest initial discharging voltage and followed by silver, graphite, lead, iron, tungsten, aluminum. The initial discharging voltage of carbon nanotubes which was used as the negative electrode to generate NAIs can be under 0.2 kV that was much lower than the initial discharging voltage of the experimental metal electrode. At relative humidity 40%, ozone was generated at 0.5 ppb when NAI concentration was about 6.3*105 ion/cm3. At relative humidity 70%, ozone was generated at 0.5 ppb when NAI concentration was about 9*105 ion/cm3. The NAI concentration decreased with the distance. The regression analysis of NAI concentration and distances from the discharge electrode indicated a logarithmic linear relationship. Additionally, more stable NAIs were generated by carbon nanotubes than other by metal electrodes when voltage was increased.