Preparation And Characterization Of α-Al 2 O₃ Composite Powders

The tritium permeation property of the Material in nuclear fusion environment is one of the most important research subjects in the nuclear fusion industry. Alumina functionally gradient coating based on aluminum metal compounds has been identified as a most promising material in tritium permeation barriers. However, crystalline alumina suffers from the disadvantages of ceramics, which results in poor effect. As the development of the composite technology and the surface modification technology, coated particles have become the focus of the nano composite particles research and by introducing some additives into the alumina could improve its effectiveness and avoid its shortcoming.Nanoα-Al₂O₃ composite powders with component evenly distributed are the foundation for the preparetion of Al₂O₃ tritium permeation barriers. In the present work, synthesizing ofα-Al₂O₃/SiC,α-Al₂O₃/TiC,α-Al₂O₃/Cr₃C₂ and Cr₃C₂/α-Al₂O₃ composite powders by heterogeneous precipitation and normal pressure sintering are the main subjects.During the preparation of coated powders, it's important to ensure the dispersibility of core material. In the paper, the dispersing technology was studied.In this paper, nanoα-Al₂O₃ and Cr₃C₂ powders were prepared by the sol-gel method to study the toughening affect of the second phase in theα-Al₂O₃/SiC,α-Al₂O₃/TiC,α-Al₂O₃/Cr₃C₂ and Cr₃C₂/α-Al₂O₃ composite powders. The results showed that Al(OH)3 could transformα- Al₂O₃ after calcined at 1200℃. Cr(OH)3 could transform to Cr2O3 after calcined at 850℃and Cr2O3 could transform to Cr₃C₂ after calcined at 1200℃with the method of carbon thermal reduction under the normal pressure.α-Al₂O₃/SiC composite particles were synthesized by calcining the dry gel prepared by heterogeneous precipitation method. The microstructure of the composite particles was tested. A series of factors which influenced the properties of coated powders had been studied, including the solvent of the reaction system, pH value of reaction system, calcinations temperature, the addition amount of SiC, et al. The average grain size of the composite particles was about 100nm and the thickness of theα-A12O3 shell was about 40 nm according to the results.α-Al₂O₃/TiC andα-Al₂O₃/Cr₃C₂ composite particles were synthesized by heterogeneous precipitation method and carbon-bed method. The results showed that Al(OH)3/Cr₃C₂ could transform toα-Al₂O₃/Cr₃C₂ after calcined at 1050℃and Al(OH)3/TiC could transform toα-Al₂O₃/TiC after calcined at 1050℃.Cr₃C₂/α-Al₂O₃ composite particles were synthesized by heterogeneous precipitation method and carbon thermal reduction. Cr2O3/α-Al₂O₃ could be obtained by calcined at 950℃, and could transform to Cr₃C₂/α-Al₂O₃ composite particles at 1200℃when calcined in oxidation oven mixed with carbon at the ratio of 4:9.