Preparation And Characterization Of Zr (Zr/ZrO₂)

In order to investigate the hydrothermal vents in the Middle Ocean Ridge, scientists need a high temperature-pressure chemical sensor, which is able to realize the in-situ measurement of the chemical properties, such as pH, H2, H2S, of hydrothermal fluids at high temperatures up to 400°C and pressures to 40 MPa. Electrode film material of excellent electro-chemical properties is the key to such chemical sensors. Recent study indicates that transition metal/metal oxides are suitable electrode film materials, which may partially replace for YSZ sensors used in deep-sea hydrothermal vents, geothermal environments and in laboratory, to measure the pH, H2, H2S of hydrothermal fluids at high temperatures and pressures. So that Zr/ZrO2 oxidation/reduction electrode has been made and to construct high temperature-pressure chemical sensors, which have been successfully utilized to do the deep-sea investigation in Southern China Sea in July and December in 2004. This thesis deals with the preparation, electro-chemical properties, composition and structure of Zr/ZrO2 oxidation/reduction electrode film material. Zr/ZrO2 films were prepared by melt oxidation process, in which Zr was oxidized with a NaCO3 melt to form a thin film of ZrO2 on the surface of Zr, i.e.Zr/ZrO2 electrode. The electro-chemical properties of the prepared Zr/ZrO2 electrodes have been tested from room temperature to high temperatures and high pressures. Two kinds of electrodes, good electrodes and bad electrodes, were distinguished based on the measurements. Authors studied factors such as melting temperature and melting time, which affect the electro-chemical properties of Zr/ZrO2 electrode. The best process is that Zr is oxidized in a NaCO3 melt for half and an hour. SEM,EPMA,XAFS,XPS,HRTEM were adapted to investigate the topography, chemical composition, interface structure, oxidation state of Zr of Zr/ZrO2 electrode. Results show that the prepared electrodes are composed of five zones differing in topography and composition. From the outmost zone to the center, the content of oxygen decrease and the content of zirconium increase. And the interface of Zr/ZrO2 are divided into five zones: oxygen-rich ZrO2, ZrO2, oxygen-rich Zr,...