| Semiconductor gas sensors, which have simple structure, low cost, high sensitivity and mature fabricating technique, are now widely employed in detection of toxic and inflammable gases and metering of atmospheric gases.Since 1960, the conventional semiconductor gas-sensing materials ( SnO2, Fe2O3, ZnO, and so on,) have been extensively studied by many researchers, and the application of SnO2-based gas sensors has been developed in domestic and industrial fields. But the semiconductor gas sensors have some disadvantages such as poor sensitivity, high power consumption and large dependence of environmental temperature and humidity, and the sensing mechanism is not very clear, thus the development and application of semiconductor gas sensor are limited. In order to upgrade the gas-sensing properties of semiconductor gas sensor, the preparation, gas-sensing properties, and sensing mechanism of a new gas-sensing material nanosized In2O3 have been investigated systemically in this thesis. The contents are listed below:In this thesis, the phase behaviors of nonionic surfactant Triton X-100 were studied by a laser method, and the influence of oil(hydrocarbon), cosurfactant, temperature, and saline on the W/O( water in oil) microemulsion region was observed, a microemulsion system has been selected, which had wide W/O microemulsion region, high water solubilization, and was less sensitive to various pHs and the present of reactants in the water pool, so it was favorable reaction media for preparing the inorganic nanomaterial.A optimized preparation procedure has been developed by a reverse microemulsion method, and the factors affecting the particle size have been discussed. The In2O3 particles prepared by optimized microemulsion method had a spherical form and narrow size distribution, the diameter of the In2O3 particles could be controlled in some extent, the minimum average diameter of In2O3 particle was 6.44nm, and the maximal one was 42.00nm.At the same time, the gas-sensing properties of nano-In2O3 have been investigated, the results showed that the In2O3-based gas sensor had high sensitivity to H2,i-C4H10 and C2H5OH, and a low electronic resistivity and high catalytic oxidation activity, so In2O3 is a satisfactory material for fabricating low power consumption gas sensor.In this thesis, the novel low power consumption gas sensors were developed byutilizing the low electronic resistivity and high catalytic activity of In2O3. A new type hot-wire inflammable gas sensor and a hot-wire C2H5OH gas sensor were developed. They both had high sensitivity, short response-recovery time and excellent stability, and had lower power consumption and minor temperature and humidity dependence than conventional indirect-heating gas sensor,A hot-wire H2 gas sensor and a new LPG gas sensor which had low power consumption have been developed by the surface modification techniques. The H2 gas sensor had very high sensitivity, good stability, remarkable selectivity, and minor temperature humidity dependence. The power consumption of the LPG gas sensor was much lower(75mW) than that of indirect-heating gas sensor, the LPG gas sensor had quick recovery-response rate and good stability, so it will be the basic to fabricating portable detector.The new hot-wire type gas sensors have only been investigated recently, until now the sensing mechanism of hot-wire gas sensor is unseen in literature, in this thesis, the sensing mechanism of hot-wire gas sensor was discussed, and the factors affecting the sensitivity were also analyzed. The results demonstrated the basic sensing mechanism was the same as that of conventional indirect-heating gas sensor, the semiconductor gas sensor utilized the change of resistance of gas-sensing material to detect target gas when the gas reacted with oxygen adsorbates (O- ,O2- et al.) on the surface of materials, and the quantity of the oxygen adsorbates was decreased, but their mechanisms have some different, the factors affecting sensitivity of hot-wire gas sensor were discussed, and the calculation...
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