Abstract
Explosion alarm in atmospheric condition requires detection of hydrocarbons at the level of volume percent concentration range. This is best achieved by the combustion type detection, contrary to the available sensitive conductive type sensors, which would be driven to saturation by concentration close to LEL. Therefore, for catalytic gas sensing a micro-heater system was prepared with an integrated thin film porous Anodic Aluminium Oxide (porous AAO) on the heated area which offers simultaneously large surface support material and better thermal control. Uniformly distributed Pt catalyst was selectively deposited in the porous AAO by atomic layer deposition (ALD). The device was tested and characterized by detection of methane and propane concentrations between 20 and 100% of their Lower Explosion Limit (LEL), and provided readings of >30mV for 20% LEL (>5vol%) of both methane and propane. The combination of porous alumina with ALD deposited Pt exhibited catalytic activity for both gases. As the temperature of the micro-heater is limited to ca. 700°C, during methane detection the sensor can be operated in the reaction kinetic controlled regime, whereas for propane measurement the temperature range of the ideal mass transport control can be set. The sensitivity loss was analysed in terms of possible ways for optimization.
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