CO sensing mechanism with WO3 based gas sensors (original) (raw)
Sensors and Actuators B: Chemical, 2018
WO3-based semiconductor-type gas sensors were fabricated, and their sensing properties to methylmercaptan (CH3SH) were examined in this study. The Ru loading on WO3 was an effective way of an increase in the CH3SH response. In addition, the CH3SH response increased with a decrease in the operating temperature as well as with an increase in the thickness of the Ru-loaded WO3 sensing layer. The increase in the porosity of the Ru-loaded WO3 sensors, which were fabricated by utilizing polymethylmethacrylate microspheres as a template, was also effective in improving the CH3SH response, especially at a low temperature of 150°C. In addition, the lamination of the Ru-loaded WO3 sensor with an α-Al2O3 film improved the CH3SH response at 200°C. Moreover, the Ru loading on the WO3 powder increased the catalytic activities of CH3SH oxidation, and CH3SH was partially oxidized to CH3SSCH3 at temperatures less than 330°C. It was suggested that the increase in the positively charged adsorption of the partially oxidized products onto the bottom part of the sensing layer is effective for enhancing the CH3SH response, especially at lower operating temperatures.
MoO3, WO3 Single and Binary Oxide Prepared by Sol-Gel Method for Gas Sensing Applications
2003
MoO 3 , WO 3 single and Mo/W binary compounds at different Mo/W atomic percentages were deposited by sol-gel spin coating technique on Si/Si 3 N 4 substrates provided with Pt interdigital electrodes and annealed at 450 • C for 1 h. Films were characterized by SEM, grazing incidence XRD and XPS techniques. Electrical responses to different gases were obtained by exposing the films to 30 ppm CO and 1 ppm NO 2. Increasing the Mo/W content the selectivity to NO 2 is enhanced. Gas responses resulted to be influenced by the Mo/W weight ratio, films morphology and amount of crystalline phases.
SO2 Gas Sensors based on WO3 Nanostructures with Different Morphologies
Procedia Engineering, 2012
Sulfur dioxide (SO 2 ) gas sensors based on WO 3 thick films were studied. WO 3 was synthesized following different procedures, yielding different morphologies. The obtained nanostructures were characterized by means of HRTEM and X-ray diffraction (XRD). The WO 3 inks were prepared by dispersing the different WO 3 nanopowders into terpineol with dispersion additives. The sensors were prepared by screen-printing of WO 3 inks on alumina substrates fitted with gold electrodes and a platinum heater. The sensors were then annealed in air at 400°C. The results of the exposure to 1-10 ppm SO 2 at different operating temperatures (200-300°C) at 50% relative humidity are shown. The sensors exhibit good responses to 1-10 ppm SO 2 at 200-300°C which is strongly dependent on the morphology of the WO 3 . The response of the sensors, response and recovery times are reported and discussed.
Ultrasensitive WO 3 gas sensors for NO 2 detection in air and low oxygen environment
Sensors and Actuators B: Chemical, 2017
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Development of Nano- \hbox {WO}_{3}$$ WO 3 Doped with NiO for Wireless Gas Sensors
Arabian Journal for Science and Engineering, 2018
WO 3 doped with NiO nanopowders with different NiO concentrations were prepared by sol-gel technique. The fabrication of the thin films for gas sensors applications was utilized using thermal vacuum evaporation technique. The morphological structure, crystallinity and optical properties of WO 3 and NiO-doped WO 3 nanopowders were characterized using scanning electron microscopy, X-ray diffraction and UV-Vis spectrophotometer, respectively. The electrical behaviors of the sensors were determined and measured by the two platinum electrodes sensor's resistance with different gases at various temperatures. The results show that a great response to CO 2 gas was 164% at 5% doping ratio which is applicable for all environmental and industrial fields. GSM module by MAX circuit was applied on gas sensor devices to send a wireless message telling that there is a leakage in the area which the sensor installed. Keywords WO 3 • WO 3 −NiO • Thin films • Sputtering • CO 2 gas sensor • Wireless 1 Introduction Wireless gas sensor is an excellent technique to monitor and control the environment remotely that makes it easy to detect any emissions of different toxic gases such as CO 2 , O 2 , NO, CO, C 6 H 4 , NH 3 , CH 4 and LPG from different sources in industry which has been polluting our air without any intensive observation. Moreover it is used for the explosives detection, environmental monitoring, industrial process control and automotive applications. As a result, it is an urgent
Gas sensors based on anodic tungsten oxide
Sensors and Actuators B: Chemical, 2011
Nanostructured porous tungsten oxide materials were synthesized by the means of electrochemical etching (anodization) of tungsten foils in aqueous NaF electrolyte. Formation of the sub-micrometer size mesoporous particles has been achieved by infiltrating the pores with water. The obtained colloidal anodic tungsten oxide dispersions have been used to fabricate resistive WO 3 gas sensors by drop casting the sub-micrometer size mesoporous particles between Pt electrodes on Si/SiO 2 substrate followed by calcination at 400 • C in air for 2 h. The synthesized WO 3 films show slightly nonlinear current-voltage characteristics with strong thermally activated carrier transport behavior measured at temperatures between −20 • C and 280 • C. Gas response measurements carried out in CO, H 2 , NO and O 2 analytes (concentration from 1 to 640 ppm) in air as well as in Ar buffers (O 2 only in Ar) exhibited a rapid change of sensor conductance for each gas and showed pronounced response towards H 2 and NO in Ar and air, respectively. The response of the sensors was dependent on temperature and yielded highest values between 170 • C and 220 • C.
Semiconductor gas sensors based on nanostructured tungsten oxide
Thin Solid Films, 2001
Semiconductor gas sensors based on nanocrystallline WO films were produced by two different methods. Advanced reactive 3 Ž . gas evaporation was used in both cases either for a direct deposition of films deposited films or to produce ultra fine WO 3 powder which was used for screen printing of thick films. The deposited films sintered at 480ЊC and the screen-printed films sintered at 500ЊC displayed a mixture of monoclinic and tetragonal phases and had a mean grain size of approximately 10 and 45 nm, respectively. We studied the influence of the sintering temperature T of the films on their gas sensitivity. Unique and s excellent sensing properties were found upon exposure to low concentrations of H S in air at room temperature for both 2 deposited and screen-printed films sintered at T s 480ЊC and at T s 500ЊC, respectively. ᮊ 2001 Elsevier Science B.V. All rights s s reserved.