Investigation of chromium carbide/alumina nano-composite prepared via MOCVD in fluidized bed and densification process

Nano-sized Cr-species particles with a size about 20-40 nm, uniformly coated on alumina particles, has been prepared by metal organic chemical vapor deposition (MOCVD) in the fluidized chamber, using the pyrolysis of Cr(CO)6 precursor. The Carbothermal reactions of Cr-species in an Ar atmosphere in a graphite furnace at 1250 deg. C for 2 h and the microstructure of high pressure sintering specimen are reported. The crystalline phase of the powder deposited in fluidized bed was characterized by an X-ray diffractometer, and transmission electron microscopy. The analysis indicates that the deposited powders were metastable CrC1-x and Cr2O3. These Cr-species were transferred into stable chromium carbide (Cr3C2 and Cr7C3) after the thermal treatment as well as high pressure sintering. Microstructure of sintering specimen shows that the cluster of coating nano-particles were formed in the fluidized bed which coarsen during densification and generally located on the grain boundary to inhibit the alumina grain growth. Further, the independent coating nano-particle was also incorporated into the alumina grains