Preparation Of High-purity High-density Alumina Ceramics With Low Temperature Sintering

High purity alumina can be applied in many industries owing to its fine performances and low manufacture costs. With the development of science and technology, especially with the development of some industries such as electronic, energy, space and automobile etc., the demand for high quality materials is increased, so the demand for alumina ceramics especially for high-purity high-density alumina ceramics is much more higher than that it can supply.The preparation of high purity alumina ceramics (Al₂O₃>99.8wt%) is conducted in this thesis, which includes pretreatment of raw powder, selection of assistants, and optimization of formation process. The preparation of high purity high density alumina ceramics are conducted in normal atmosphere and low temperature. The tests show that the samples are with good microstructure and mechanical properties.The pretreatment of raw materials in this thesis is a new method of disaggregating alumina powder, which is simple, low cost and effective. This research can provide reference to the technology of powder disaggregating.In this thesis, MgO, Y₂O₃, La₂O₃, Nd₂O₃ and nano Al₂O₃ are selected as composite assistants, and MgO as basis assistant, and the sintering temperatures reach 1450℃ ,1550℃ and 1650℃, the effect of assistants on the densities of sintered simples is investigated. The results can provide others important reference to preparation of high purity high density alumina ceramics (Al₂O₃>99.8wt%).Optimization of the gel-casting process is also done in this thesis, the results show that high quality gel-casting samples can be got in this process.The analysis on vacuum sintering parameter and the testing on the sintering process are also done in this thesis and the results show that high purity high density alumina ceramics can be got at the temperature of 1500℃, that meanings the low temperature high density sintering can be reached. The mean density of alumina ceramics reaches 3.97g/cm³, the mean size of sintered samples is 3-4 um, the bending strength (3-Point) can reach 500Mpa and Vickers hardness is over 18.5GPa.