The Molecular Sieve And Oxygen Permeation Membrane Studies--The Fundamental Studies On Oxygen Diffusion Characteristics, Application, Substitution And Doping Of YBa₂Cu₃O_7-x

The review of the research developments of high temperature superconductor material YBa2Cu3O7-x (YBCO in short) since its discovery was given firstly in the paper. The application situation of superconductors was introduced briefly. We focus our study on the oxygen characteristics of YBCO. We explore the Explication of YBCO to a new field, the non-superconducting field - air separation and gas purification as well as mixed-conductor oxygen permeating membrane, by utilizing its oxygen in-diffusion and out-diffusion characteristics.The variation of oxygen content in YBCO is the basis of its applications in the non-superconducting field. Therefore, the importance of oxygen content occurs through this paper. The relationship among the structure of YBCO, superconducting electrical properties and normal state properties and oxygen content was presented in the paper. Especially, we studied the resistivity variation of YBCO with surrounding atmosphere at high temperature by experiment. At a constant temperature, the resistivity increases rapidly when switching from oxygen environment to nitrogen, since the oxygen content in YBCO sample decreases speedily, which is caused by oxygen partial pressure decreasing abruptly. When switching to oxygen environment again, the oxygen partial pressure increases abruptly, and the exterior oxygen diffuses into the material. The rapid increase of oxygen content results in the swift decrease of resistivity of the sample. Therefore, the resistivity of YBCO decreases with its oxygen content increase.It is important to make YBCO deoxidant molecular sieve in the process of applying YBCO to air separation and gas purification. The process of preparing YBCO molecular sieve by means of solid-state reaction is optimized. The variation of oxygen content in YBCO at different temperature and at different oxygen partial pressure is studied by thermogravimetry and by static oxygen absorption device. The oxygen desorption of the YBCO sample begins to take place obviously at about 400C in air environment. The weight loss arrives at 1.2% of its original weight when temperature rising to 800C. However, the oxygen lost can completely come back to the sample when temperature lowering to 400C. The mass variation exhibits a very good repetition. This means that the homeostasis oxygen content of the sample decreases with temperature increase. The results of static oxygen absorption experiments show that when temperature kept at a constant the oxygen amount of saturation absorption increases with oxygen partial pressure, and below about 20 kPa, the rising rate of the oxygen amount of saturation absorption is fast versus oxygen partialpressure. The rising rate becomes gradually slow when oxygen partial pressure above the value. The results of these experiments confirm that YBCO molecular sieve have the function of air separation and gas purification. The effect of naphthaline as an additive on the oxygen adsorption performance of YBCO molecular sieve is also studied. The result of the research shows that adding naphthaline in the YBCO raw material can enhance the capacity of oxygen respiration of YBCO molecular sieve. The appropriate proportion of the additive is between 5-10%.The small-scale experiment devices have been designed and fabricated. And experiments for air separation and gas purification are done. The results indicate that as long as the dry air flux is smaller than 2.5 1/min and the beginning air separation temperature lower than 550C, 1 kg YBCO molecular sieve can produce 17-litre high purification nitrogen in one cycle. One can obtain immediately high purification nitrogen in the purification experiments as long as the beginning purification temperature is between 450~550C, and it have nothing to do with the oxygen concentration of gas source. The oxygen concentration of gas source determines the output of high purification nitrogen. The pilot-scale purification experiment with total 40 kg YBCO molecular sieve can produce 15m3 high purification nitrogen (oxygen concentration-lppm) at s...