| Summary: | 碩士 === 南臺科技大學 === 機械工程系 === 107 === Gas sensors have been widely used to monitor leakage and control concentrations of various gases during production and fabrication processes. Graphene nanosheets and carbon nanotubes (CNTs) strong ability to sense gas, Gas sensors have been widely used to monitor leakage and control concentrations of various gases during production and fabrication processes. Graphene nanosheets and carbon nanotubes (CNTs) perform strong ability to sense gas. Mass producible electrochemically-exfoliated graphene and multi-walled CNT is used in order to ensure detection capabilities. They are uniformly dispersed in a solvent of THF (tetrahydrofuran) to prepare a carbon nanocomposite. A simple spraying process is utilized to coat the different concentrations of carbon nanocomposite ink, 0.1,0.2,0.3 wt% (ECG 0.1,0.2,0.3 and CNT 0.1,0.2,0.3) on different substrates: glass and flexible substrate (polyethylene terephthalate, PET). The carbon nanocomposite ink is sprayed into a H shape with a mask. The electrical resistance change of sensing alcohol is measured by the four-point probe method. In order to ensure detection capabilities, Tin dioxide nanoparticles (SnO2) are added to increase their selectivity. In addition, the different concentrations of carbon nanocomposite ink (Graphene/ THF and CNT /THF) is sprayed on the flexible substrate, PET bent with different radii of curvature of R22.5 mm and R23.1 mm for alcoholic sensing. The result shows that the sensing behavior is also functional for the bent sensor. The data collection is a plot of electrical resistance difference with respect to time. The amount of 95% alcohol per test is 3 grams and each sample is tested for three times. First, for PET and glass substrate, CNT0.1 has a relatively obvious resistance change compared with other concentrations. After the alcoholic gas is introduced, the resistance difference is up to 10KΩ, and 0.3wt% of ECG0.3 has the highest difference that is about 6000 times higher than that of CNT. Almost all concentrations of CNTs have resistance retention; however, graphene doesn’t perform good resistance retention. Therefore, the best sensing effect of CNT0.1 and ECG0.3 are mixed; however, the effect is not as expected. In order to increase the sensitivity and repeatability, a fixed amount of SnO2 is added, prepare a carbon nanocomposite ink(ECG 0.1,0.2,0.3/ SnO2 and CNT 0.1,0.2,0.3/ SnO2). CNT 0.1/ SnO2 provides highly sensitive sensing effect for both glass and PET substrates. The resistance difference can reach 30MΩ and it is highly reusable after drying the alcohol.
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