THE SELF-DIFFUSION OF NIOBIUM--I. First Annual Progress Report, January 1, 1956 to June 30, 1957

The measurement of the self-diffusion coefficient of niobium as a function of temperature has been undertaken. It is planned to prepare the diffusion couples by the deposition of Nb/sup 95/ onto the surfaces of niobium discs from the Nb/sup 95/Cl/sub 5/ vapor phase and to anneal the couples in the temperature range 1600 deg to 2000 deg K. Details are given of the construction of the vapor deposition apparatus and of the preparation of Nb/sup 95/Cl/sub 5/ from the oxalate form in which the isotope is received. Preliminary measurements of the diffusion coefficient in a Nb-8 wt.% Ti alloy and In a Nb-1.4 wt.% V alloy indicate that the diffusion coefficient in the former is approximately 10/sup -9/ cm/sup 2//sec at 1600 deg C and is approximately 8 x 10/sup -11/ cm/sup 2//sec in the latter at 1400 deg C. (auth