Development of Microscale Air Ionizer -- Generation of Negative air Ions by Carbon-nanotube Electric Discharging

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.