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

Abstract

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 °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 CrC 1− x and Cr 2O 3. These Cr-species were transferred into stable chromium carbide (Cr 3C 2 and Cr 7C 3) 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.