Figure 10.

Selected examples for additional microstructural signatures. (A) Cyclic voltammogram of current I versus electrode potential E for NPG in deaerated 0.1 mol L^–1 NaOH. Dark blue: scan to the switching potential at the Burshtein minimum (indicated by label). The shaded area under the surface oxide reduction peak scales with the surface area and can be used to measure that quantity. Light blue: scan to larger positive switching potential; note the larger reduction charge. (B) Grain size of NPG from electron backscatter diffraction in a scanning electron microscope.¹¹⁵ Color codes crystallographic orientation, identifying individual crystal grains as regions of uniform color. Note up to 100 μm grain size, more than thousandfold larger than the ligament size, L_SEM = 18 nm here. (C) Solid fraction, φ, of NPG versus initial Au fraction, x_Au⁰, in the starting alloy.¹¹⁸ Strong deviation at low x_Au shows that the starting alloy composition does not provide a good indicator of NPG solid fraction. Note also the dependency on the preparation protocol, free versus electrochemical corrosion. (B) Reproduced with permission from ref (115). Copyright 2021 from Elsevier. (C) Reproduced with permission from ref (118). Copyright 2021 The Authors.