NiO-SnO2 composite nanofibers were synthesized via electrospinning techniques and characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy.Three types of sensor were applied to investigate the sensing properties of these nanofibers.Sensors A were fabricated by mixing the nanofibers with deionized water,and then grinding and coating them on ceramic tubes to form indirect heated gas sensors.Microsensors B(with an area of 600 μm×200 μm) were formed by spinning nanofibers on Si substrates with Pt signal electrodes and Pt heaters.Sensors C were fabricated by spinning nanofibers on plane ceramic substrates(with a large area of 13.4 mm×7 mm) with Ag-Pd signal electrodes only.The operating temperatures of sensors A and B were controlled by adjusting heater currents,and the operating temperatures of sensors C were controlled by adjusting an external temperature control device.Experimental results show that sensors C possess the highest sensing properties,such as high response values(about 42 to 100 μL/L ethanol),quick response/recovery speeds(the response and recovery times were 4 and 7 s,respectively),and excellent consistencies.These phenomena were explained by the retained fiber morphology and suitable sensor area.The presented results can provide some useful information for the design and optimization of one-dimensional nanomaterial-based gas sensors.
