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Some ternary ferrites having composition CoxNi1.5-xFe1.5O4 (0.0 ≤ x ≤ 1.25) have been synthesized by NH4OH co-precipitation method at 11.5 pH. Materials, so obtained, were tested for their electrocatalytic properties towards oxygen evolution reaction (OER) in the form film on Ni-support in alkaline solution. The study showed that the electrocatalytic properties the material increased with partial substitution of Co for Ni in the base oxide (Ni1.5Fe1.5O4). The value being highest with 0.5 mol Co-substitution. At E = 850 mV vs Hg/HgO in 1M KOH at 25 ºC, the electrode showed apparent current density 206.2 mA cm-2, which is about 3 times higher than the base oxide. The Tafel slope values were ranged between 46-82 mV decade-1. A pair of redox peak, an anodic (EPa = 522±28 mV) and corresponding cathodic (EPc= 356±9 mV), was observed in the cyclic voltammetry (CV) study of the material. The thermodynamic parameters namely, standard apparent electrochemical enthalpy of activation ( ), standard enthalpy of activation ( ) and standard entropy of activation ( ) for the oxygen evolution reaction (OER) have also been determined by recording anodic polarization curve in 1M KOH. The value of was observed to be almost similar with each oxide electrode. The values were highly negative and ranged between ~ -165 and ~ -207 J deg-1 mol-1. Phase and morphology of materials have been investigated by using physical techniques X-ray diffraction, infrared spectroscopy (IR) and scanning electron microscope (SEM), respectively.

Perovskite-type oxides of lanthanum and cobalt with composition La 1-x Sr x CoO 3 (x = 0.0, 0.2, 0.4, 0.6 and 0.8) have been prepared by a low temperature sol-gel route. Electrodes of the material were formed on pretreated Ni-support by oxide slurry painting technique and studied their electrochemical behavior with regards to oxygen evolution reaction (OER) in aqueous KOH solution. The electrochemical characterization was done in three electrode single compartment glass cell using Gamry (Reference 600) Electrochemical Work Station. Techniques used for electrochemical studies were cyclic voltammetry and Tafel polarization. The data showed that the substitution of Sr (0.2 -0.8 mol) increased the electrocatalytic activity of the oxide. The value was found to be highest with 0.8 mol Sr. The Tafel slopes and reaction order with respect to OH -concentration for oxygen evolution reaction were found to be 65-77 mVdecade -1 and unity, respectively. The cyclic voltammogram recorded between 0.0 -0.7 V in 1M KOH at 25 0 C exhibited a pair of redox peaks prior to oxygen evolution reaction. The thermodynamic parameters for oxygen evolution reaction such as, standard electrochemical enthalpy of activation , standard enthalpy of activation , and standard entropy of activation have also been calculated by recording the Tafel polarization curve in 1 M KOH at different temperatures. Oxide samples were characterized physicochemically by scanning electron microscope (SEM) powder X-ray diffraction (XRD) techniques.

This study discusses the dissimilar joining between AA6063 aluminium and AISI304L stainless steel of flat faying surfaces through a rotary friction welding process at different welding conditions as per L9 orthogonal array and the characterization of bimetal joints. The effect of welding parameters on the mechanical properties and the minimum level of welding conditions required for the metals joining were discussed. Bonding between the metals and the narrow heat-affected zone were observed from microscopy study. Energy dispersive x-ray analysis revealed the elements present at the weld interface and molybdenum formation. Fractography result on the tested specimens showed the dimple rupture during the fracture. The tensile test showed the plastic deformation near the weld joint for friction pressure 15 MPa and above. The maximum peak load and elongation of joint were around 12 kN and 12% respectively. 18 MPa friction pressure, 24 MPa upset pressure and 5 sec. friction time showed good bond strength and the maximum tensile strength of 189 MPa with 92 % of joint efficiency. Axial shortening was obtained in the range of 13-27 mm and a maximum of 26.9 mm during experiments. In joints, microhardness was decreasing towards AISI304L base metal from weld interface and conversely increasing towards AA6063 base metal. Impact tests showed the conversion of brittle into ductile fractures when increasing friction pressure and maximum impact energy observed was 38 Joule.