Fig. 4

Morphology of reaction products by SEM analysis at (a) 2 bar, (b) 4 bar, (d) 8 bar and (e) 12 bar and structure of reaction products by TEM analysis at c 2 bar (similar at 4 bar) and (f) 8 bar (similar at 12 bar) when the chamber is full of argon. The same results were obtained when the chamber is full of nitrogen