fig7
Figure 7. Schematic illustrations of porous metal preparation via chemical etching method. (A) Schematic illustration of porous Si nanowires. Reproduced with permission[75] (Copyright 2012, American Chemical Society). (B) Schematic illustration of the formation process of porous Si wafer. Reproduced with permission[76] (Copyright 2015, Wiley-VCH Verlag).
