Study On The Preparation And Forming Process Of Solid Electrolyte Tube As Hydrogen Sensors For Application In Molten Aluminum

Aluminum and its alloys is lightweight, corrosion resistance, excellent mechanical properties and high electrical conductivity, etc. It has got relatively extensive application in the recent years. In the preparation and forming process of aluminum alloy material, effective control of hydrogen content in aluminum alloy melt was an important factor to ensure high performance parts. The hydrogen was the only soluble gas in liquid aluminum. Therefore, the detection of the hydrogen content in liquid aluminum was extremely important. The concentration cell can detect hydrogen content online continuously, so it has a wide range of applications. The concentration cell hydrogen sensor has already began been developed with Ca Zr O3 and Ba Zr O3 based proton conductor for solid electrolyte hydrogen sensor in domestic. Currently used in the experiments of Ca Zr O3 and Ba Zr O3 based electrolyte tube can't achieve continuous measurement under variable temperature environment, and many did not realize the transition, so it's a urgent need to optimize the preparation of solid electrolyte tube materials, as well as the electrolyte material forming as the parts used in the manufacture of sensors. This paper aims to study a solid electrolyte material for the hydrogen sensor to measure in variable temperature environments, and mainly on the preparation and forming method, and preliminary study on hydrogen sensor structure design.The experiments apply Ca CO3, Zr O2, In2O3 as raw materials. With calcination at different temperatures between 1000°C and 1550°C, the solid-state reaction synthesizing process of Ca Zr0.9In0.1O3-? was investigated by means of thermos gravimetric-differential thermal analysis and X-ray diffracttometer analysis. The results show Ca Zr O3 matrix phase can be synthesized directly by Ca O and Zr O2 at 1000°C or stepwise by intermediate oxide Ca Zr2O4 at higher temperatures. Doping of indium into Ca Zr O3 occurs in the temperature range of 1200 °C to 1400 °C. If calcination temperature exceeds 1400°C, no significant improvement of doping occurrs. Even a sharp deterioration of doping effect happened with a calcination temperature of 1550°C. So sintering process for Ca Zr0.9In0.1O3-? is determined at 1400°C calcined for 10 h.The tube forming and discharging wax processes with Ca Zr0.9In0.1O3-? solid electrolyte were investigated. Hot pressure casting method was used to form the calcined synthtic Ca Zr0.9In0.1O3-? into a U-shaped tube. The forming process parameters were: casting pressure at 0.4MPa, the mold and wax slurry temperature at 32°C and 73°C, grouting mouth temperature set at 42°C. After the forming process, the tube discharging wax and sintering process was: 120°C holding for 5h to soften the wax; 360°C holding for 4h to ensure the wax volatilize to absorbent; 460°C holding for 3h to volatilize further; 500°C holding for 2h to volatilize complete; 1000°C holding for 2h to pre-sintered the solid electrolyte tube, finally, in 1550°C sintering 10 h to obtain a solid electrolyte tube, and it's relative density was 93.7%.Using Ca Zr0.9In0.1O3-? solid electrolyte as proton conductor, platinum as electrode, platinum wire as the lead, with H2-Ar gas mixture containing 10% hydrogen as a reference, a gas hydrogen sensor was assembled. Using the method of H2-Ar mixture gas as a reference electrode for concentration cell hydrogen sensor testing, it's verified that the solid electrolyte is able to meet the Nernst Law.