Diffusion of Silver in Structural Graphite

Diffusion kinetics of silver (Ag) in nuclear grade graphites, IG-110 and ZXF-5Q were investigated from 500 to 900 °C by the thin film diffusion technique. Dynamic secondary ion mass spectroscopy was utilized for depth profiling of concentrations and diffusion coefficients were calculated utilizing solutions to Fick’s second law. Ag was found to diffuse through the bulk of both graphite grades with diffusivities on the order of 10 −20 to 10 −22 m 2 /s. For IG-110 graphite, temperature-dependence of Ag diffusion coefficients yielded activation energy and pre-exponential factor of 66.7 kJ/mol and 2.11 x 10 −17 m 2 /s, respectively. For ZXF-5Q graphite, activation energy and pre-exponential factor were determined to be 66.6 kJ/mol and 2.04 x 10 −17 m 2 /s, respectively. These diffusion coefficients were very consistent despite the difference grain size, porosity and filler presence for the two types of graphite.