Fabrication and properties of cobalt-reinforced alumina-matrix composites

The Al2O3/Co powder with different metal contents was fabricated in the In-situ selected reduction method by controlling the process of wet chemical route, and the Al2O3/CO bulk composite was prepared by hot pressure sintering. The final microstructure can be controlled properly adopting the process. At first, cobalt-nitrate was dissolved into alcohol and mixed with alumina powder by milling. Next, the powder mixtures were calcinated. The calcinated temperature was determined by thermogravimetry and differential thermal analysis (TG-DTA). Calcinated in air, the powder mixtures of cobalt oxide and alumina were reduced in hydrogen atmosphere., Finally, the reduced powder were sintered by hot pressing in Ar atmosphere at 1 450degreesC in 30MPa and then dense alumina/cobalt composites were obtained (rho>97.7%). The bending strength and fracture roughness, were enhanced by 52% and 37% respectively compared with monolithic alumina. The powder micrograph was observed by TEM. Phase analysis of the synthesized powders and sintered composites was carried out by X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) was used to observe the microstructure of crack propagation and rupture micrographs. The reinforced mechanism was also discussed.