Pump Oxygen Electrode Conductivity And Electrolytic Process

In view of the suspended inert anode technology and based on the character of oxygen ion migration in yttrium-stabilized zirconia solid electrolyte,the principal goal of the thesis is to establish a novel cryolite-alumina melt reduction cell with pumping oxygen electrode as anode and to investigate the conductivity of pumping oxygen electrode. The main conclusions and results are summarized as follows:1. The padding method of La_1-xSr_xMnO₃ nanometer powders was determined to carry out the leading-out of pumping oxygen electrode. The results show that the conductive leading-out mode with nickel chrome wire and La_0.7Sr_0.3MnO₃ nanometer powders is reasonable. La_0.7Sr_0.3MnO₃ powders were prevented from being corroded by fluoride vapor by sealing solid electrolyte tubes. Uniform electric field was used to advance the electric current of electrolysis system.2. La_1-xSr_xMnO₃ nanometer powders were prepared by sol-gel auto-combustion method with ethylene glycol as solvent and citric acid as complexing agent. The optimum experimental condition was investigated. X-ray diffraction was used to analyze the crystal structure of the powders with different doped-Sr concentration. The electronic conductivity of the powders was determined by digital electric bridge. The process of powder formation was studied by TG-DTG analysis and FTIR. The results show that the optimum preparation conditions are: the temperature of sol and gel formation 65℃, the pH of solution. 1.5, the calcining temperature 800℃. It is also found that the electronic conductivity is increased with the increase of doped-Sr concentration and the maximum value appears at x=0.3. Perovskite structure of La_1-xSr_xMnO₃ is obtained after auto-combustion process. It remains the same with strontium doped into the powders, but the unit cell parameters are changed.3. By compared with various formulation of silicate binder and phosphate binder, the reasonal formulation of high temperature binder and solidifying form were finalized. The formulation of the binder is 5gSiO₂-5gZnO-3gMgO-4ml industrial water glass. It is baked directly at 960℃after air-drying at room temperature for five hours.4. The operation state of pumping oxygen aluminium electrolytic cell was observed. The open-circuit voltage and decomposition voltage of electrolytic system were measured. The results indicated that the open-circuit voltage of the electrolysis system decreases with time. The actual decomposition voltage is smaller than the theoretical decomposition voltage because the electrochemical eaction of pumping oxygen electrode occurs at double interface where complex reaction mechanism may exist. It was also found that the component of solid electrolyte has an important effect on the decomposition voltage of Al₂O₃.