| In this thesis, ZnO, TiO2 and ZrO2 porous nanosolids have been prepared by a unique solvothermal hot-press method, using several kinds of nanoparticles and solvents as the starting materials. Furthermore, ZnO porous nanosolid thick film gas sensors have also been fabricated from a novel ZnO nanosolid using conventional thick films preparation method, and the gas sensing properties of the ZnO sensors are tested. In order to improve the gas sensing performance of the sensors, five kinds of composite porous nanosolids thick film gas sensors (ZnO-TiO2, ZnO-SnO2, ZnO-ZrO2, ZnO-Ga2O3 and ZnO-Co3O4) have been prepared and their gas sensing properties are tested and analyzed. For exploiting a new route of improving the gas sensing performance of sensors, the effect of hydrothermal pre-treatment on the gas sensing properties has also been studied.Firstly, ZnO, TiO2 and ZrO2 porous nanosolids have been prepared by a unique solvothermal hot-press method, and the properties of these nanosolids are systematically investigated. The results show that, the pore diameter, pore volume and specific surface area of the porous nanosolids can be adjusted by changing either the kind of solvent, the content of solvent or experimental hot-press pressure. Among these factors, the kind of solvent is an important one that dominating the above properties. For example, the primary pore diameter, pore volume and specific surface area is smaller when deionized water is used as the solvent, while those is larger when anhydrous ethanol is used, compared with that of the sample prepared by using other solvents in our experiments. Besides, the results of thermal analysis of the samples show that, the thermal stabilities of ZnO, TiO2 and ZrO2 porous nanosolids are all very high.In order to prepare composite porous nanosolid thick film gas sensors, ZnO-TiO2 composite porous nanosolids have been prepared. It is found that the pore diameter, pore volume and specific surface area of ZnO-TiO2 composite porous nanosolids...
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