Microwave Sinter High-purity Alumina Ceramic And Toughening Improvement Research

Al₂O₃ ceramic with the properties of high strength, high hardness, low-expansion, high corrosion resistance and quality light which other metals are unmatchable to it, it is widely used in various fields. And high-purity Al₂O₃ ceramic substitute for the purity of the low more and more obvious, but due to the high-purity ceramic difficult to sinter restrict to application. The development of microwave heat technology provides a condition of high-purity Al₂O₃ ceramics to widely use.This paper use of laboratory made microwave sinter equipment for the purity in 99.8% or more to Al₂O₃ ceramic sinter and toughening improvement research. Respectively experiment by pure Al₂O₃, Al₂O₃/MgO and Al₂O₃/MgO/Y₂O₃ powders mixed sintering in a new type of multi-mode cylindrical microwave sintering resonant cavity, obtain the best additives ratio, by holding time analyzes the ingredients for Al₂O₃ crystals grow grain. By adding nano-Al₂O₃ to increase and enhance the effectiveness of a strong and the mechanism provided analysis and discussion.The experiment results show that the specimen of microscopic structure can be improved by additives, with different set of points and amounts of support was an added, the sample of microscopic structure is different, and get the best results :the sample M5Y5(0.05% MgO+0.05% Y₂O₃) under 1700℃of the density is 3.94/cm³, relative density is 98.7%. The hardness value is 22. 7HV/GPa. MgO low level in a sketchy, crystalline grain sizes will vary according to holding time for larger and larger, also in hardness;MgO contents of the ingredients from the unit continues to grow grain Al₂O₃, the increase of the unit of a certain extent reduce the hardness of the samples. The composite add MgO and Y₂O₃ serve in a holding time, the unit within the scope of the size unchanged basically, more evenly spread and kinichi to the crystals of size and type of material degree of hardness.For high-purity Al₂O₃ ceramic best environment and nano-Al₂O₃ different add to explore the crystals granularity Al₂O₃ ceramic microscope allows for the performance effects of structural and mechanics. The results show that, adding that the sample of microscopic particles Al₂O₃ after the crystal structure has the"in crystal " and "between crystal ", two type of situation. in 1700℃sinter temperature of the particles that Al₂O₃ content reaches 30wt%, the sample density, the hardness and fracture toughness to the highest value 3.92/cm³,23.2 HV/GPa and 4.21 Pa·m^1/2. nano-Al₂O₃ grains add a feature of ceramic is no single crystals break down. the unit began to break, rupture, and small changes in the mode of the unit led to the expansion of the way to expand and cost of energy and increasing Al₂O₃ ceramic of fracture toughness.Using microwave sinter high-purity Al₂O₃ ceramic can acquire good microscopic structure and excellent mechanical properties, at the condition of do not add a second phase of improves Al₂O₃ ceramic of fracture toughness. Speed up the industrialization process of high-purity Al₂O₃ ceramic.