| Oxygen sensors are widely used to intelligent instruments and the secondary parts of other instruments. Currently, these products play a very important role in people's social life. They are applied in many kinds of fields, such as national defense scientific research, medical environmental, transportation, metallurgy, food and brewing and home appliances. Oxygen sensor technology is one of the rapid developments of high-tech in the world today. Oxygen sensor technology, communication technology and computer technology are as the three pillars of the information industry. And oxygen sensor industry gets the world's attention, for its high technological content, good economic returns, strong penetration ability, large scope of application, broad market prospects and so on.ZrO2 is a new type of ceramic material, and is one of the solid electrolyte materials which are used at the earliest. In order to overcome various deficiencies of pure ZrO2, the stable crystalline pHases of zirconia powder is prepared through a method that ZrO2 are doped with one or several kinds of chemicals which includes MgO, CaO, Y2O3, Al2O3, CeO2 and Sc2O3. Sintering this kind of stabilized zirconia powders, we can get the sintered body with good mechanical properties and ionic conductivity, which is better than that of the pure ZrO2. In recent years, with the depth of research about ZrO2 solid electrolyte structure and ionic conductivity properties, the application of zirconia solid electrolyte develops very quickly. Using various features of ZrO2 solid electrolyte, people has successfully developed many new functional devices and new uses, such as oxygen sensors, high temperature fuel cell temperature sensor, high temperature and humidity sensors as well as applications in national defense scientific research, transportation, metallurgy, medical environmental, food and brewing, home appliances and other fields.Research and application of oxygen sensors are showing a very active trend. And oxygen sensors are used for all aspects of daily life.The sensor of quick setting steel (?)xygen is a detection technology which developped with steel refining technology. Because oxygen is harmful elements in the steel, the oxygen and other elements combine to form oxide inclusions in the steel, directly affecting the quality of steel. Therefore, rapid detection of the oxygen content in steel is one of the important tasks of refining molten steel. Rapidly measuring the oxygen content in steel by electrochemical method cannot be replaced by other technology in any way. Early 80s of last century, many research institutes in China researched the detection technology about the oxygen content of molten steel. This work is conditioned by the quality of zirconia which is the key component, is always standing still.Magnesia partially stabilized zirconia is as solid electrolyte (MgO-PSZ), which has good high temperature mechanical properties, thermal shock resistance and high oxygen ion conductivity under high temperature. So MgO-PSZ is as a commodity to be development and utilization, which is high-temperature oxygen sensor of solid electrolyte materials. In the MgO-ZrO2 system, the stable cubic solid solution exists at temperature above 1400℃. After firing of the solid electrolyte, the cubic pHase stable still exists at room temperature. ZrO2 which is partially stabilized by MgO has better thermal shock resistance and lower n-type electronic conductivity under high temperature and low partial pressure of oxygen than pure ZrO2. Therefore, during rapidly setting the oxygen content in molten steel, MgO-PSZ tubes are widely used.The first chapter reviews the oxygen sensor, in particular the research progress of zirconia oxygen sensor, and give a detailed description of the preparation of the sensor about setting the oxygen content in the molten steel.The fellow chapters mainly studies that prepared the powder and ceramic block by co-precipitation which meet the sensor's requirement about setting the oxygen content in the molten steel. In order to adapt to industrial production, we employed the inverse titration method (It is that a certain concentration of mixed solution drops to a certain concentration of dilute ammonia to form a precipitation mixture) to prepare powders of magnesia partially stabilized zirconia. In the precipitation process, we must ensure that the pH value of precipitation agent is between 9 and 11 so that co-precipitation mixture can be precipitated in the maximum extent. We want to reduce the loss of magnesium hydroxide and the agglomeration of powders in the washing process. Firstly, we wash the precipitation with dilute ammonia solution to except Cl-. Then the precipitate was washed by ethanol to reduce the agglomeration. After MgO-PSZ powders were calcined at 650℃, small particles agglomerated together. Serious reunion impacts the pHase composition of powders. In order to ensure the pHase meeting the requirement of steel measuring oxygen probe, the powders which has been calcined at 650℃must be treated by the way of the milling or sanding to crush serious agglomeration of the powder. Then we can get MgO-PSZ powder which is relatively small particles and meet the special requirements.8mol% MgO-ZrO2 ceramics block is calcined at 1550℃for 2h. This MgO-ZrO2 ceramics block is relatively dense. And its X-ray diffraction pattern shows that zirconia is partially stabilized at this time. The scanning electron microscope pattern indicates that the crystal grows well. Ceramics block is also relatively dense that 12mol% MgO-ZrO2 Ceramics block is Calcined at 1500℃for 2h. And its X-ray diffraction pattern point out which is partially stabilized zirconia at this time. The scanning electron microscope pattern shows the crystal grows well too. This ceramics block basically satisfies the special needs of Oxygen sensor setting oxygen content in the molten steel.Another parter research work of the thesis is the preparation of zirconia powder being partially stabilized by MgO and ceramic block by the hydrothermal method, which is used in the oxygen sensor setting oxygen content in the molten steel. We can get the 8mol% and 12mol% MgO-PSZ powders through hydrothermal method at 180℃for 48h, which is monodisperse, have complete crystal as well as large surface area. And its particle size is about 0.15 um. Ceramics block by sintering at 1500℃has integrity crystal and high density. Its crystal pHase satisfies the special requirements of the sensor setting the oxygen content in molten steel. |
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