Nonstoichiometric Niobium Carbide Research Articles

Effect of atomic ordering on the heat-capacity of non-stoichiometric niobium carbide

Effect of atomic ordering on the heat-capacity of non-stoichiometric niobium carbide

A Study of the Atomic Ordering in the Niobium Carbide Using the Magnetic Susceptibility Method

The magnetic susceptibility of a nonstoichiometric niobium carbide in the ordered and disordered state in the region of homogeneity of the Nb6, C5, phase is measured. It is for the first time that the magnetic susceptibility method is employed to analyse the atomic distribution in the crystal and to determine the short-range order parameters. In terms of the cluster approach proposed, a short-range parameter calculation is carried out which shows that the variation of the magnetic susceptibility due to ordering in the niobium carbide is associated with, chiefly, the formation of short- range order rather than with the formation of long-range order. A considerable increase in the diamagnetism of an ordered niobium carbide compared to that of a disordered one is noted. [Russian Text Ignored].

The Vickers micro-hardness of non-stoichiometric niobium carbide and vanadium carbide single crystals up to 1500� C

The Vickers micro-hardness of non-stoichiometric niobium carbide and vanadium carbide single crystals up to 1500� C

Simple shell model for phonon dispersion of nonstoichiometric Niobium Carbide

A simple shell model for the acoustic dispersion curves of ideal and nonstoichiometric Niobium Carbide (measured by neutron scattering) is presented. The main emphasis is put on a qualitative understanding of the rather sharp dips, observed in some of the branches, and their extreme sensitivity to C-vancancies. The one phonon cross section of the defect crystal is calculated in various approximations. Large phonon shifts and broadenings are obtained in the dip regions in good agreement with experimental results.

Temperature dependence of the grain size of NbC0.80

A study was made of the effects of temperature in the range 1600–3300°K on the grain size of the nonstoichiometric niobium carbide NbC0.80. The energy of activation of the grain growth process was found to be 65.5 kcal/mole; this value leads to the conclusion that the grain growth process is controlled by boundary and surface diffusions.