Effect of carbon content on mechanoreduction of copper oxide

The reduction of CuO with different amount of carbon (CuO:C = 2:1, 2:1.5, a nd 2:2, in molar ratio) induced by ball milling is examined by x-ray diffra ction and transmission electron microscopy. It is found that reduction proc ess is closely related to the carbon content. CuO can be completely convert ed into Cu if an excessive C is used (i.e., C = 1.5 or 2.0 mol). However, t he reduction of CuO follows a two-step process, CuO --> Cu --> Cu2O, if the mixture only contains a nominal C content (i.e., C = 1 mol). A tentative m odel in terms of solid state reaction at the interfaces is proposed to expl ain the effect of carbon content on the mechanoreduction of CuO.