Low-energy mechanochemistry formation of silver and copper metals from hemioxides

A number of oxides and mixtures of oxides with or without carbon were ball-milled in homemade stainless steel vessels and the resulting compounds examined by X-ray powder diffraction. The expected trend to amorphization was systematically observed. Moreover, chemical action developed in most cases. Copper oxides tend to be reduced from CuO to Cu2O and metallic copper forms at the surface of the balls and diffuses a few micrometers within the ball steel as revealed by energy-dispersive X-ray spectroscopy. Mixtures of Ag2O with carbon lead to small nuggets and square platelets of metallic silver, and YBCO superconductor is decomposed into Y2O3, Cu2O, and some unidentified compounds, The behavior of the balls was observed visually: in the powder, an overall rotating motion takes place, revealing a crushing process instead of the expected smashing one. (C) 1998 Academic Press.