Fabrication of nanoporous manganese by laser cladding and selective electrochemical de-alloying

Fabrication of nanoporous Cu–Mn alloy coatings was investigated by a two-step process involving high power laser cladding of a homogeneous Cu40Mn60 alloy coatings followed by selectively electrochemical de-alloying. Auger mapping results indicate that nanoporous manganese was obtained by selective electrochemical etching of the less active Cu component owing to the passivation of the more active manganese in potassium nitrate solution. The surface morphology of the porous Mn was a ribbon-like structure, different from interconnected bicontinuous nanopores that are usually obtained by de-alloying. The influence of de-alloying time, electric potential and temperature on the formation of nanoprosity is systematically investigated. Nanopore sizes can be tailored to be less than 100 nm. Under optimal etching conditions the nanopore size was below 25 nm. The surface area of the nanoporous manganese layer was enhanced by up to 990 times compared with that of a polished sample.