Fig. 9.

Scanning electron microscopy of a corn cob, reprinted with permission from Shariff et al. (2016), b calcined corn cob ash obtained at 650 ˚C for 2 h, c nanosilica from corn cob, reprinted with permission from Mohanraj et al. (2012), d nano-structured silica from corn cob with an average diameter of 55 nm, reprinted with permission from Okoronkwo et al. (2016)