| Perovskite ceramic materials have good catalytic properties, electrochemical properties and so on. They have a good view of application prospect in the areas of production of pure oxygen、electrode materials of solid oxide cell and the area of chemical catalysis. To realize the practical application of the oxygen separation membrane materials, it is necessary to improve the oxygen permeability of the membrane materials and to improve thestability of the membrane in low oxygen partial pressure atmosphere. Many factors affect the properties of the ceramic membrane, such as the raw materials,the microstructure and the surface modification of membrane materials and so on. Herein, the Ba0.5Sr0.5Co0.8Fe0.2O3-δ ceramic membrane’s preparation technology, the microsturue and the properties of ceramic membrane were investigated in this dissertation and the effect of surface modification on the oxygen separation performance of Ba0.5Sr0.5Co0.8Fe0.2O3-δ membrane materials were studied. A new type of oxygen separation membrane material was also developed, BaFeO3 were usedthe substrates, and the influence of different amount of Sc and Cr ion doping on the electrical properties and oxygen separation performance of BaFeO3-δ materials is studyed. The mail conductions are obtained as followings:Ba0.5Sr0.5Co0.8Fe0.2O3-δ materials with perovskite structure can be obtained by calcining the precursors at temperature above 900℃. The powder compacts were sintered at different temperature to prepare sintered samples. Measured the oxygen permeability of samples at 900℃ were sintered at 1000℃,1050℃ and 1100℃ are 0.81ml·cm-2·min-1,1.13 ml·cm-2·min-1 and 1.56 ml·cm-2·min-1, respectively. And the average thermal expansion coefficient of Ba0.5Sr0.5Co0.8Fe0.2O3-δ at 400-800℃ which sintered at 1000℃,1050℃ and 1100℃ are 14.34×10-6K-1, 15.46×10-6K-1 and 15.34×10-6K-1, respectively.The surface of Ba0.5Sr0.5Co0.8Fe0.2O3-δ oxygen membrane is modified by nitric acid etching treatment. The results show that the surface of the membrane will be changed from its’ original density state to rough state, thus increasing the surface area of the membrane, which is advantageous to oxygen exchange reaction in the surface. We find that the reaction of acid corrosion is enhanced when the time for nitric acid treatment is extended. And after that, the surface of membrane will become more rough. Oxygen permeability tests of membrane that after surface modification show oxygen permeability increased 1.6 to 4.5 times after nitric acid etching for 20 min and oxygen permeability increased 1.4 to 3.8 times after nitric acid etching for 10 min.BaFe1-yNyO3-δ (N=Sc、Cr, y=0、0.05、0.1、0.15) powder is prepared by glycine- nitrate process. And the corresponding oxygen separation membrane material is prepared. XRD results show that BaFeO3-δ is hexagonal structure at room temperature. But after doping with small content of Sc, the structure of BaFeO3-δ is transformed into tocubic structure, and a small content of Cr doping also promote BaFeO3-δ oxide into cubic phase at room temperature.Conductivity and oxygen permeability tests show that doping with a small amount of Sc and Cr will improve the conductivity and oxygen permeability of BaFeO3. The maximum conductivity value of BaFe0.95Sc0.0503-δ at 450℃ is 7.2s·cm-1, which is about 60 times of that of BaFeO3-δ. And the maximum conductivity value of BaFe0.95Cr0.05O3-δ at 450℃ is 4.8s·cm-1, which is about 40 times of that of BaFeO3-δ. Whats more, BaFe0.95Sc0.05O3-δ owns a maximum oxygen permeability, it can reach 0.66 ml·cm-2·min-1 at 900℃. |
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