An in Situ Small Angle Neutron Scattering Investigation of AgO.7Au0.3 Dealloying

Abstract

ABSTRACTIn situ small angle neutron scattering (SANS) was used to characterize the formation of the random 3-dimensional porous structure created during the free corrosion of a Ag0.7Au0.3 alloy in concentrated HNO3. The evolution of the porosity was followed in situ for a period of 21 hours. The average ligament width evolved from a size of approximately 6 nm following only 7 minutes of dealloying to approximately 22.5 nm after 21 hours of de-alloying. Using a model developed by N.F. Berk (Phys. Rev. Lett., 58 (1987) 2718) for the scattering properties of random porous media, we were able to characterize the average ligament width distribution as a function of time. Our results represent the first in situ nanoscale characterization of the formation of 3-dimensional porosity in a corrosion system.