| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 102 === The purpose of this study is to produce a portable negative air ion (NAI) generator. NAI generated by corona discharge. In order to be portable, voltage which produces air ions needed should be reduced. This study attempts to replace the different electrode to reduce the voltage required to produce NAI. In this study chose carbon nanotubes directly (CNTs) grown on carbon cloth as the discharge electrode. It has lower resistance than the CNTs stick to the substrate. In this study, CNT have six terms, they are doped nitrogen (CNT-N) or not (CNT), growing time that is 5min, 10min, 15min. In this study measures starting voltage, stability of discharging and steady concentration of NAI in RH=0%, 20%, 40%, 60%, 80%,.
The result of experiment reveal CNT-N is easier gathering than CNT. Growing time of CNT in 5min, 10min, 15min that their starting voltage is 2.3kV、1.93kV、2.06kV; Growing time of CNT-N in 5min, 10min, 15min that their starting voltage is 3.23 kV、1.86 kV、2.33 kV. It revels CNT have lower staring voltage in 5min and 15min. CNT-N in 10min have lower starting voltage. Measuring six different CNTs in relative humidity is 0%, 20%, 40%, 60%, 80%, the average value of starting voltage is 2.22±0.43kV、1.67±0.38kV、1.63±0.38kV、1.63±0.36kV、1.67±0.37kV, showing in 20%~60% has lower starting voltage. Testing in stability with humidity 40% and 2.5kV, growing time of CNTs-blank in 5min, 10min, 15min their coefficient of variation is 5.50%、64.98%、10.75%, growing time of CNT-N 5min, 10min, 15min their coefficient of variation is 20.78%、63.26%、8.84%, they reveal growing in 5min and 15min have better stability. Four electrode with higher stability : growing time of CNTs-N in 5min, 15min and growing time of CNTs-blank in 5min, 15min. Chose the steady concentration of NAI is higher than 200×103ions/cm3 and growing time of CNT in 15min (CNT-15) which starting voltage is the lowest electrode as the best electrode. Observing the relation of distance, humidity and concentration of NAI which generated by CNT-15. The result reveal when the longer distance between detector and generator the lower concentration of NAI. And continuous discharging electricity in 30 min, detecting concentration of ozone is 1.5ppb、2.1ppb、0.8ppb、1.8ppb、2.4ppb、1.6ppb, lower 0.06ppm in air quality law, in the course, producing ozone is not enough to endanger human body.
Starting voltage of CNT-15 between 1.9~2.0kV. Coefficient of variation is 10.75%, average of concentration of NAI is around 773×103ions/cm3 , while CNT-15 discharge at -2.5kV and R.H.=40%. CNT 15 is most suitable CNTs to producing NAI in this study. Compare CNT-15 with research of 林(2009) stick carbon nanotubes on iron substrate (Fe-CNT), Fe-CNT has lower starting voltage(0.5kV). Fe-CNT can produce NAI only for 3 min. Consider the produce time of NAI, CNT-15 is better than Fe-CNT.
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