Measurements were made of the transient and steady-state permeation rates of D through a membrane. Use of the time-lag technique then yielded diffusion data (tables 137 and 138). Substantial deviations from ideal behavior were observed in the diffusion coefficients, so that the permeability could not be represented as being a simple function of pressure. When the diffusion coefficients were corrected for chemical non-ideality, an additional increase of a factor of 2 remained in the concentration dependence of the diffusivity. This was attributed to the expanded state of the lattice when the D/metal ratio was high.
R.G.Hickman: Journal of the Less-Common Metals, 1969, 19[4], 369-83
Table 137
Diffusivity of D in Pd-25%Ag as a Function of Pressure
[D (cm2/s) = a+ ßP + γP2]
Temperature (C) | a | ß | γ | P (psia) |
300 | 1.23 x 10-5 | 6.37 x 10-8 | 8.90 x 10-12 | 7.6-882 |
400 | 2.64 x 10-5 | 4.05 x 10-8 | 1.92 x 10-11 | 7.7-894 |
500 | 4.80 x 10-5 | 3.66 x 10-8 | -3.80 x 10-12 | 7.5-855 |
Table 138
Diffusivity of D in Pd-25%Ag as a Function of Concentration
[D (cm2/s) = a+ ßC + γC2 + dC3]
T (C) | a | ß | γ | d | C ([H]/[M]) |
300 | 9.52 x 10-6 | 1.91 x 10-4 | -1.98 x 10-3 | 7.07 x 10-3 | 0.037-0.290 |
400 | 2.35 x 10-5 | 1.47 x 10-4 | -1.26 x 10-3 | 7.49 x 10-3 | 0.023-0.224 |
500 | 4.85 x 10-5 | -2.04 x l0-6 | 1.17 x 10-3 | 0 | 0.014-0.156 |