Figure 1.

As-received coal fly ash and synthesised CNFs. Images of as-received coal fly ash (a) and CNFs synthesized at (b) 400°C, (c) 500°C, (d) 600°C and (e, f) 700°C. In (a), the as-received coal fly ash was observed to be glassy, smooth and spherical in nature. The glassy, smooth-shaped fly ash became covered with regularly and irregularly shaped CNFs. In (c) and (d), large CNFs were intertwined with smaller ones. In (e), well-defined CNFs, apparently formed by tip growth, were clearly visible as seen by the red-coloured circles.