Preparation And Characterization Of α-Fe₂O₃-Based Nanomaterials Via Microemulsion Processing Route And Their Gas Sensitivity

Ferric oxides have used as the third series of gas-sensing maerials following SnO2 and ZnO, especiallyα-Fe2O3 nanomaterials with high chemical stability and selectivity. So far, in most reports the systematic research on preparation methods of the nano-powders with some ions as dopant ions, and certain achievements have been obtained in some aspects.The dissertation reports the preparations of the Fe2O3 powders prepared via the chemical reaction between Fe(NO3)3 and NH3·H2O using the nanodroplets in the water-in-oil microemulsion containing aqueous solution, TX100,n-hexanol and cyclohexane as microscale reactors.According to the comprehensive analysis of the above some Fe2O3 gas sensing materials with some ions doped were prepared. In this dissertation,on the basis of measurements and characterizations of nano-powders, Some correlation between the synthesis process,structure of powers and property of sensors were analyzed preliminarily, and the mechanism for C2H5OH,CO,H2,CH4 selectivity is tried to be discussed. The main results are as follows:(1) The effects of synthesis parameters on particle diameters were discussed using PCS. The results show that all the synthesis parameters have remarlable effects on the particle diameters. when the ratio of water is 7%, surfactant vs cosurfactant is 2, surfactant vs oil is 0.5, the concentration of metal ions is 0.2M, concentration of NH3.H2O is 3M, It benefit for the growing of particle diameters.(2) Nanoscale Fe2O3 powders doping with Sn4+,Au3+,Zr4+ ions were prepared using Fe(NO3).9H2O as source matter by two microemulsion. The corundum structure Fe2O3 was obtained at lower sintering temperature(400℃,1h). TG-DTA,XRD,UV-Vis,IR,BET, ESEM were used to character the powders. It has been found that the 0.5mol%Sn4+,Au3+ and Zr4+ incorporated Fe2O3 shows the better sensitivity to CO, shorter response time, good selectivity and...