Fig. 4. SEM images of the hydrogen reduced nanoparticles. (a) Low and (b) high magnification images of a sample reduced at 390 °C (100 bar). (c–f) High magnification SEM images of samples reduced at 310 °C (100 bar), 270 °C (100 bar), 230 °C (300 bar) and 210 °C (530 bar) respectively.