Study On The Preparation Of Three Dimensional Al₂O₃/Al Interpenetrating Composites

In recent years, due to its good overall performance, the 3-3 ceramic / metal interpenetrating composites attracts more and more researchers. Because of the ceramic phase and metal phase showing double continuous interlocking and mutually reinforcing in three-dimensional space, the wear resistance, high temperature strength of the composite properties have been greatly improved. wide raw materials, low cost, simple preparation and broad applications make 3-3 Al₂O₃/Al interpenetrating composites more imperative. But the poor wettability between alumina phase and aluminum phase weakens their interfacial bonding. In this experiment, depending on the reaction between silicon oxide and aluminum, two methods for preparing 3-3 Al₂O₃/Al interpenetrating composites are proposed. First, SiO₂ coating is prepared on the Al₂O₃ matrix by sol-gel method. Then, after immersing the matrix with coating in the Al liquid, the Al₂O₃/Al composites is down. In this way, the wettability between alumina phase and aluminum phase will be improved though the reaction wetting. Similarly, 3-3 Al₂O₃/Al interpenetrating composites can be prepared like that; Second, putting SiO₂ ceramic network in the Al liquid, and the 3-3 Al₂O₃/Al interpenetrating composites will be prepared through the situ reaction between SiO₂ and Al. In other words, the Al₂O₃ skeleton is formed on position of original SiO₂ skeleton.After testing, the conclusions is as follows:（1） SiO₂ coating began showing a trend of crystallization at 900℃. Higher heat treatment temperature lead more continuous coating. The thickness of SiO₂ coating can be controlled by adjusting the H₂O:TEOS molar ratio and the number of immersion.（2） SiO₂ coating can improve the wettability between Al₂O₃ and Al and makes the interfacial bonding more stable.（3） The mullite of 75 alumina can react with aluminum to form alumina, and the reaction can improve the wetting. The capillary force makes aluminum liquid move to the internal ceramic more quickly. The volume shrinkage caused by reaction and the inner holes of ceramic provide aluminum liquid channel into ceramic.（4） The density and the bending strength of the ceramic be enhanced by the adjunction of H₃BO₃. And with the increase of H₃BO₃ content, the density and the bending strength is increased.（5） 3-3 Al₂O₃/Al composites with good interfacial bonding was prepared by the reaction of SiO₂ ceramic skeleton and molten Al.（6） Al₂O₃ is formed on position of original SiO₂. The Al₂O₃ is composed of the granular Al₂O₃ and the reticular Al₂O₃. The newborn Al₂O₃ ceramic monolith maintains holds the original structure of SiO₂ skeleton. Silicon enters to aluminum matrix through the gap between the two kinds of alumina and forms the Al-Si alloy with aluminum.