Unconventional synthesis of Mg x C y Ni3: Synergic combination of mechanical alloying, SHS and isothermal heating

Several methods have been tested in order to prepare the perovskite type compound Mg _x C _y Ni₃ applying the mechanical alloying (MA), the self-propagating high-temperature synthesis (SHS) and the isothermal heating techniques in the different steps of preparation. These methods may be summarized as follows: method MCN-1) synthesis of the Mg _x C _y Ni₃ phase through MA of Mg₂Ni (previously synthesised by isothermal heating) and selected amounts of graphite and Ni, followed by isothermal treatment; method MCN-2) synthesis of the Mg _x C _y Ni₃ phase applying the SHS technique using powder compacts; method MCN-3) synthesis of an eutectic sample composed of Ni and MgNi₂ by means of isothermal heating, subsequent MA with graphite and final synthesis of Mg _x C _y Ni₃ by means of SHS. The methods MCN-2 and MCN-3 proved their validity to the synthesis of the desired compound with two main important results: complete conversion of the reactants into Mg _x C _y Ni₃ and control of the stoichiometry in the final product. For instance method MCN-1 shows instead a very low degree of conversion of the reactants. All the phases obtained after each preparation step (MA, SHS, isothermal heating) have been characterized by means of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS).