Preparation And Characterization Of Nano-alumina Powder And Alumina / Metal Composite Ceramic

In most structural applications, the primary disadvantage of alumina ceramics is their inherent lack of toughness. Ceramic matrix composites are receiving much attention in recent times. The second ductile phase introduced in Al₂O₃ ceramic matrix is an effective method to improve the brittleness of the monolithic Al₂O₃ ceramic. However, the traditional processing used to prepare the Al₂O₃ composites can't meet the various requirements of the engineering field. Therefore, the fabrication processing of the ceramic composites is needed to be enhanced and improved. How to improve the preparation techniques to obtain Al₂O₃ powders and Al₂O₃ composite ceramics with a good microstructure and properties is becoming a primary issue of the research fields of ceramic. In the present work, synthesizing of nanocrystalline a- Al₂O₃ powder by adding seeds was developed and a novel coating processing was employed to introduce the second phase into Al₂O₃ ceramic matrix. Then, hot-processing was used to sinter the Al₂O₃ ceramic. The structure and mechanical properties of the composite ceramics were also studied in this paper.In this paper, DSC/TG, XRD, SEM,TEM and XPS were used to characterize the thermo-reaction properties of nanometer aluminum powders and micro-aluminum under air, Ar and O₂. The different oxidation condition of these two kind of powders were studied. The experimental results confirm the different thermo-reaction properties between nanometer aluminum powders and micrometer aluminum.A new process for synthesize ultra-fine a- Al₂O₃ particles by adding nanometer aluminum powders as seeds was proposed firstly. The effect of solution concentration, different adding rate of ammonia, pH value of reaction system, and sintering temperature on the properties of Al₂O₃ powders were studied, and the action of aluminium seeds was analysed. When pH value of the reaction system was about 8-9 it will be propitious to the dispersing of the Al(0H)3 sol. The transformation temperature of a- Al₂O₃ decreased to below 1050℃ due to the adding of 5mol.% nanometre aluminium particles. This synthesis method is simple, cheap and easy for...