HEAT OF SOLUTION AND DIFFUSIVITY OF NITROGEN IN MOLYBDENUM

A study has been made of the solubility and diffusivity of nitrogen in high purity zone refined molybdenum (resistivity ratio ~6000) making use of liquid helium resistivity measurements to monitor the presence of the gas. The nitrogen was retained in supersaturated solution in the molybdenum by quenching specimens into mercury after heating at high temperatures in a nitrogen atmosphere. The heat of solution was then found by measuring the quenehed-in resistivity as a function of quench temperature in the range 1400-2200°C. The value over this range was calculated to be 0.80 ± 0.01 eV. By varying the nitrogen pressure it was confirmed that Sieverts' p 1 2 law is obeyed. The diffusivity was determined at temperatures in the range 1500-2000°C from evolution curves representing the rate of loss of nitrogen from the specimens when heated in vacuum. The results show that the diffusivity of nitrogen in molybdenum obeys the equation D = 3.0 · 10-3 exp (- 1.2 eV/kT) cm2/sec. © 1969.