Correlation between the Pycnometric Density and Specific Surface Area of Nanocrystalline VCy Powders

Abstract

Nanocrystalline cubic VC_y nonstoichiometric vanadium carbide powders differing in nonstoichiometry (0.69 ≤ y ≤ 0.76) and ranging in average particle size from 20 to 60 nm have been prepared by solid-state reactions followed by high-energy milling. Milling of the VC_y powders has been shown to be accompanied by changes in their chemical composition, lattice parameter, specific surface area, average particle size, lattice strain, and density. We have derived a relation between the pycnometric density and specific surface area of the VC_y powders, which has been used to determine the percentage of oxygen in carbide powder particles and their true density. Oxygen adsorption on the surface of the carbide particles has been shown to be the main cause of the decrease in the pycnometric density of the powders with increasing specific surface area.