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MAX phases are an advanced class of ceramics based on ternary carbides or nitrides that combine some of the ceramic and metallic properties, which make them potential candidate materials for many engineering applications under severe conditions. The present work reports the successful synthesis of nearly single bulk Ti2AlN MAX phase (>98% purity) through solid-state reaction and from a Ti and AlN powder mixture in a molar ratio of 2:1 as starting materials. The mixture of Ti and AlN powders was subjected to reactive spark plasma sintering (SPS) under 30 MPa at 1200 °C and 1300 °C for 10 min in a vacuum atmosphere. It was found that the massive formation of Al2O3 particles at the grain boundaries during sintering inhibits the development of the Ti2AlN MAX phase in the outer zone of the samples. The effect of sintering temperature on the microstructure and mechanical properties of the Ti2AlN MAX phase was investigated and discussed.

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Electrodeposited lead (Pb)-cobalt (Co) coatings are an effective electrocatalyst in the oxygen-evolution reaction. We studied the effect of an electrolytic bath pH on the electrodeposition of Pb-Co coatings, and the coating properties were analyzed. The pH was varied from 1 to 6 for a solution without and with ascorbic acid as complexing agent. Cathodic polarization curves show that the deposition conditions have a greater effect on the reduction potential of Co 2+ than the reduction potential of Pb 2+ . Energy-dispersive X-ray spectrometer analysis shows that a pH higher than 4 promotes Co deposition and yields a [Pb]/[Co] film ratio lower than 1. Scanning electron micrographs showed that samples grown at a pH higher than 2 were covered with Co dendrites, and that the sample grown with ascorbic acid at pH 1 exhibited a compact morphology. Anodic polarization curves showed that Pb-Co-coated anodes grown at pH 1 with a complexing agent evolved oxygen at c.a. 1.6 V vs. normal hydrogen electrode, which lead to a 40% reduction in the required overpotential (η) for the oxygen-evolution reaction compared with conventional Pb-Ca-Sn anodes.