Study On High-performance Alumina-based Composites

Though Al2O3 ceramics has many excellent properties such ashigh-temperature-resistance, good wear and excellent corrosion resistance, thebrittleness of Al2O3 ceramics has a great effect on its exploitation and application.Lately, the study of toughening Al2O3 ceramics is an important field of ceramicsresearch. The main intention of this study is to use Al2O3 fibers and nano-ZrO2 toimprove toughness of Al2O3 ceramics. In this thesis, the research of Al2O3 ceramics athome and abroad and various toughening methods are introduced, especially making asummary of toughening actuality of Al2O3 fibers and nano-ZrO2. In this thesis, the composites are prepared by using nano-ZrO2 powders, Al2O3fibers and commercial Al2O3 powders. Ball-grinding and sedimentation are used inorder to control the original particle size of powders and the length-diameter ratio ofAl2O3 fibers. The influence of process routing on the sintering behavior, mechanicalproperties and microstructure is studied, with the purpose of preparing thealumina-based composites with high performance and low costs. In the preparation of ZrO2 - Al2O3 composites and the study of theirmicrostructure and mechanical properties, it has been demonstrated that thealumina-based composites with high performance and low costs could be preparedthrough the optimization of the content of ZrO2, the processing of ball-grinding andsintering and the control of microstructure. The results showed that ZTA compositeswith high bulk density and good mechanical properties could be obtained at thesintering temperature of 1600℃, soaking time of 2 hours by introducing 30wt% ZrO2.And the bending strength and fracture toughness of the composites were 604MPa and6.87MPa·m1/2, respectively. By analyzing the relation between the microstructureand mechanical properties, the toughening mechanism of ZrO2-Al2O3 composites isthat the mechanical properties are improved by the intragranular formation and thephase transformation toughening of zircoina. IIEffect of different Al2O3 fibers, various content and the processing of sintering onAl2O3 ceramics is studied, and the reason of Al2O3 fibers improving mechanicalproperties of Al2O3 ceramics is discussed. The results indicate that composites withhigh bulk density and good mechanical properties could be obtained at the sinteringtemperature of 1600℃, soaking time of 2 hours by introducing 5wt% Al2O3 fibers.And the bending strength and fracture toughness of the composites were 368MPa and4.5MPa·m1/2, respectively. By analyzing the relation between the microstructure andmechanical properties, Al2O3 fibers didn't exist in the sintered bodies, the tougheningmechanism of composites probably is that high activated Al2O3 fibers could promotethe sintering and some Al2O3 fibers become liquid phase, which also could promotethe sintering.