Production of Carbon Nanotubes for Gas Sensor Application

Gas sensors have a wide application in everyday life, whether in industry, medical, agriculture and environmental monitoring. A good sensor should be selective, sensitive, responsive, reliable and cost effective. Currently available gas sensors are lacking in one or more of these criteria. Therefore, there is a need to develop new sensing materials and technologies. Carbon nanotubes have a potential to be developed as a new gas sensing material due to their inherent properties such as small, high strength, high electrical and thermal conductivity, and high specific surface area. As a result, it is possible to create a miniaturized sensor, which can lead to low power consumption, lighter and low cost. This research was carried out to investigate the absorption effect of the following selected gases namely, carbon dioxide, ammonia, acetylene, natural gas and hydrogen towards the change of resistance of CNTs pellet as sensor signal. CNTs used in this research were synthesized by means of Floating Catalyst Chemical Vapor Deposition (FC-CVD) method. Benzene was used as a hydrocarbon source while ferrocene as a source of catalyst with Hydrogen and Argon as carrier and purge gas respectively. From the research, it can be concluded that FC-CVD method produced high quality CNTs at temperature range of 750˚C-850˚C. CNTs show high sensitivity towards ammonia, acetylene and carbon dioxide at room temperature. Maximum increment in CNTs pellets’ resistance upon exposure to ammonia, acetylene and carbon dioxide are 21.75, 26.53 and 18.91 respectively. However, for natural gas and hydrogen no detection was observed at room temperature. It is predicted that sensor activity can be enhanced by doping the CNTs and/or increasing the temperature of the sensing activity. It is expected that many applications of CNT-based sensors will be explored in future as the interest of the nanotechnology research community in this field increases. However, CNTs have yet to overcome many technological barriers in order to fulfill their potential as the preferred material for sensor applications.

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