The compositional dependence and influence of relaxation state on the deformation behavior of a Pt–Pd-based bulk metallic glasses model system was investigated, where platinum is systematically replaced by topologically equivalent palladium atoms. The hardness and modulus increased with rising Pd content as well as by annealing below the glass transition temperature. Decreasing strain-rate sensitivity and increasing serration length are observed in nano indentation with increase in Pd content as well as thermal relaxation. Micro-pillar compression for alloys with different Pt/Pd ratios validated the greater tendency for shear localization and brittle behavior of the Pd-rich alloys. Based on total scattering experiments with synchrotron X-ray radiation, a correlation between the increase in stiffer 3-atom cluster connections and reduction in strain-rate sensitivity, as a measure of ductility, with Pd content and thermal history is suggested.
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Abstract -
Ni–P coatings have attracted wide attention due to their good tribological properties, corrosion resistance, and high catalytic activity. The surface properties impact the overall catalytic performance of Ni–P as electrocatalysts. In this study, highly catalytic amorphous Ni–P electrodeposits are synthesized using pulsed electrodeposition technique. Pulse parameters show a significant effect on the morphology, crystallinity, and electro‐catalytic activity of the deposits. The Ni–P deposits are found to be amorphous up to the duty cycle of 50%, whereas higher duty cycles (toward direct current deposition) result in a transition to nanocrystalline structure. This is attributed to an indirect reduction process involving intermediate phosphine leading to co‐deposition of phosphorus and nickel. Change in pulse frequency results in significant variations in surface morphology. Methanol electro‐oxidation in alkaline environment is studied as a function of surface morphology for the amorphous Ni–P catalysts. Up to four‐fold increase in oxidation peak current is observed for nano‐morphologies with large electrochemical surface area synthesized at pulse frequency of 50 Hz. This demonstrates the potential of pulsed electrodeposition as a versatile toolbox for obtaining highly catalytic amorphous Ni–P as a potential substitute for expensive noble‐metals used in direct alcohol fuel cells.