The role of magnesia and alumina in promoting the nitridation of magnesium and aluminium

Abstract The nitridation of magnesium, aluminium and their alloys is promoted by the addition of the oxides MgO or Al 2 O 3 . Non-isothermal kinetic measurements (TG and DTA) show that nitride formation proceeds to completion more rapidly in the presence of these oxides than when metal and gas only are present. The mechanisms of these reactions are discussed with reference to electron micrographs obtained for the magnesium/nitrogen reactions in the presence and absence of MgO, the only system where melting was absent. It is concluded that MgO provides an active surface across which there may be transport of reactants and products. MgO also accommodates the product Mg 3 N 2 where it does not represent an adherent layer on the metal constituting the barrier to solid (Mg)/gas (N 2 ) interaction that opposes the uncatalyzed reaction.