Analysis, Manufactureand characteristics improvement of gas sensor by carbon nanotube

According to this study, ZnO nanoparticles, mono and multi-layer carbon nanotube powder were deposited by using electrophoretic deposition under alternate field in low frequencies. Depositions were conducted on comb electrode with groove gap of 150 nm. The best frequency for deposition was 0.01Hz for ZnO and MWCNT and 1 Hz for SWCNT. Other parameters for deposition such as voltage and period for MWCNT and ZnO included 20 V and 10 min respectively while such rates were 15V and 5 min for SWCNT. For sensory properties of zinc oxide powder, there was indicated that for beginning its work, sensor requires high operational temperature; however due to limitation in increasing the temperature, it was impossible practically to use this kind of sensor. Sensors made by mono and multi-layered powders, while having low resistance, but due to reduced semi-conductive trait of powders could not be used for deposition. Therefore, there was used of simultaneously depositing two powders to make a sensor; it indicated that the resistance of sensor layer made by SWCNT-ZnO was equal to 300-400 ohms and MWCNT-ZnO layer was equal to 120 KOhms. The reason for such difference according to Electron Microscope observations was due to the amount of setting ZnO powder in the groove. Finally, the manufactured sensors were exposed to propane and Knox gas; it indicated that the resistance of sensor is reduced when exposed to reducing gas, propane and increased when exposed to oxidizing gas, Knox. Using the combination of nanotubes in this study caused reduction in the initial thermal rate of sensor due to reduced initial resistance.

کلیدواژه ها:

Electrophoretic deposition ، Comb electrodes ، Reducing gas