Narrow Results

The effects of mechanical alloying on the microstructure of binary and ternary powder mixtures with stoichiometric compositions of Mg₂Ni and Mg₂Ni_0.75Nb_0.25 were studied, respectively. Also, the electrode properties of the milled products were investigated in 6M KOH solution. X-ray diffraction and scanning electron microscopy of the milled products showed the formation of Mg₂Ni-based nanocrystallites after 15 and 10h of milling using the initial binary and ternary mixtures, respectively. It was found that partial substitution of Nb for Ni has beneficial effect on the formation kinetic of nanocrystalline Mg₂Ni. Longer milling times resulted in the formation of an amorphous phase. A relatively high discharge capacity of 350mAhg^-1 was measured for the electrode made up of the ternary milled product after 20h. Also, the ternary milled product showed longer discharge life. This ternary electrode showed a microstructure consisting of Mg₂Ni nanocrystallites and an amorphous phase. Nb substitution for Ni was found to be beneficial to electrode properties of the milled products.

In the present work, high energy ball milling of binary (Mg₂Ni) and ternary powder mixtures (Mg_1.75Nb_0.25Ni and Mg₂Ni_0.75Nb_0.25, i.e., substitution of Nb for Mg and Ni, respectively) was carried out. The effects of milling process parameters on the microstructure of binary and ternary milled products were studied. Also, electrochemical properties of the nano-structured electrodes made from the milled products were measured. It was found that Nb substitution for Mg (Mg_1.75Nb_0.25Ni) has beneficial effect on the formation kinetic of Mg₂Ni-based nano-crystallites. Electrode made from the 20h milled product using initial composition of Mg_1.75Nb_0.25Ni exhibited a high discharge capacity of ~600mAhg-1 and relatively longer discharge life. Such electrode showed a microstructure consisting of an amorphous core surrounded by nano-crystallites.