A Study On The Refractory Structure Ceramic With Baddeleyit And Corundum Eutectoid Fine Crystallization

This project is based on the technological project of Shanxi Province, the industrial project of Xi'an City and the technological project of Zhengzhou City. Lots of detailed literature review was done concerning preparation nanometer and sub-micron grade fine powder of Al2O3, ZrO2 and composite ceramic; The technique and application of the fixed-diameter nozzle without interruption of flow in the tundish in home and abroad were analyzed. According to the conclusion of the seventh "five-year plan" science and technology project that the anti-corrosion properties of the baddeleyit and corundum eutectoid is much better than that of the singe phase of corundum or baddeleyit. Preparation of baddeleyit and corundum eutectoid composite fixed-diameter nozzle was firstly put forward in home and abroad.By adding dispersant's co-precipitation and gel method, Al2O3-ZrO2 nanometer or sub-micron grade usher composite powders with even composition was produced. After debonding, preheating, oppressive molding, high temperature sintering, the usher composite powders were conducted to produce the high temperature struture ceramic with baddeleyit and corundum eutectoid fine crystallizationIt was found that accumulation can be effectively prevented under the following condition:1. The concentration of composite salt concentration was 0.5~0.7mol/L.2. Ammonia was added by positive drop mode.3. The pH value is between 9.5 and 9.7.4. Ageing time is in the range of 16 to 23h.5. PEG(600+2000) mixture about 1.25wt% was added in the usher solution and before desiccation and water-free alcohol was used during the alcohol water interchange.After the gel was bathed, degumed, milled, fine powder was analyzed by XRD andDTA. It was found that composite powder was amorphous after heat treatment at 400℃ and zirconia crystaly appeared which was identified as tetragonal phase at 1200℃, after heat treatment at 1600℃ the volume fraction of ZrO2monoclinic phase increased and Al2O3 has a crystal structure of corundum phase. The size of the powder was about 3~4μm by laser grain size analyzer. The selection of the dispersant needs further study. By SEM it was found that the higher the sintering temperature and the longer the holding time, the larger the grain size. For the first time the oxyacetylene flame delaminating fusion and fast cooling techniques can be used to obtain Al2O3-ZrO2 nanometer composite ceramics.