Preparation Of Staged Porous Tin Oxide And Its Gas - Sensing Properties

Metal oxide semiconductor gas sensitive material has the advantages of simple structure, low cost, fast response reply, high sensitivity and mature craft. Recently, it has been widely used in environmental pollution control, industrial gas monitoring, combustible gas, toxic gas leakage alarm, and other fields.Present study showed that a hierarchical porous structure is ideal for building high sensitivity and fast response of metal oxide gas sensitive material. However, at this stage for hierarchical porous structure of gas sensitive materials research is still faced with numerous difficulties and challenges, such as synthesizing difficultly, simple structure, monotonous species, etc. These difficulties and challenges greatly restricted the development and application of the hierarchical porous structure of gas sensitive materials. In view of this, this thesis starting from the PS nanometer microsphere templates, through methods of the introduction of precursors, PS microspheres self-assembly, heat treatment to the template, exploring the method of synthesis of hierarchical porous SnO2 material. At the same time, for the hierarchical porous SnO2 doped with rare earth, and analyze the hierarchical structure and effect on the properties and rare earth doping of gas sensitive material, provide ideas and basis for the hierarchical porous gas sensitive material research and development. In this paper the research content is as follows:Using PS microspheres template, through the adhesive gel precursor impregnation self-assembly (gravity sedimentation) and heat treatment after removal of the template method, successfully prepare porous SnO2 open graded materials, on the analysis and characterization of XRD, SEM and BET, coupled with exploring the precursor solution concentration, self-assembly temperature and time on the impact of hierarchical porous structure. Ultimately, confirmed the optimum condition for synthesis of SnO2 open hierarchical porous structure. Because of its open three-dimensional porous and the surface of gas molecules into the open structure and transmission, internal hierarchical porous structure can provide a lot of area of reaction. Open hierarchical porous structure effectively improves the SnO2 gas-sensing properties of materials. At 200 PPM for ethanol gas sensor test, for example, the optimum working temperature of open hierarchical porous SnO2 material reduced from 370℃ to 310℃, gas sensitive response values are about 3 times of the reference samples,4-6 s response recovery time shortened.By adding rare earth element precursor liquid impregnation of hierarchical porous structure SnO2 doped with rare earth elements(Ce, La), studied the gas-sensing properties before and after doping, it can be found that doping significantly improved the gas-sensing properties of SnO2 material, improve effect with doping elements and concentration, the gas species, such as working temperature varies embodied in:1) the best doping effect was got when Ce/Sn atoms mole ratio for 3% of the precursor solution of hierarchical porous SnO2, its sensitivity of acetone had significantly increased, about 2 times to 500 PPM acetone response values in 53.6. At the same time, the doping of Ce is helpful to of gases such as ethanol, methanol, formaldehyde gas sensitive response to ascend. Compared with best working temperature changes before and after the found of the Ce doping leads to the best working temperature has a tendency to rise or increase.2) La/Sn atoms mole ratio for 5% of the precursor solution doping effect is good, its gas sensitive response to ethanol and methanol has been improved significantly, to 500 ppm methanol response values increase from 46.7 to 82.3, about 1 times. Results showed that the doped La also is advantageous to reduce the best working temperature and shorten response recovery time.