EFFECT OF TEMPERATURE-GRADIENT ON CONCENTRATION PROFILE OF HYDROGEN IN A PALLADIUM LATTICE

A thermodynamic calculation is conducted to determine the distribution of hydrogen atoms absorbed in a one-dimensional palladium rod, along which a temperature gradient is imposed. The rod is assumed to be completely sealed, so that the total number of the hydrogen atoms is conserved regardless of its thermal conditions. A model calculation based on a zeroth-order interaction model predicts that upon the imposition of the gradient, the hydrogen distribution will significantly change from its initial uniformity. The profile of the redistributed hydrogen can be discontinuous at one point on the rod. The concentration gap developed at this point of temperature T implies that the two-phase region in the palladium hydride phase under the thermal equilibrium is nonexistent under the nonequilibrium condition. Similar to the disappearance of the two-phase region above the critical temperature, the concentration gap is reduced with an increase of the temperature gradient.