Elaboration of nanoporous copper by modifying surface diffusivity by the minor addition of gold

The basic concept of alloying was combined with modifications of the surface diffusivity through the addition of trace metals with low surface diffusivity in order to elaborate the dealloyed nanoporous metals. Nanoporous Cu with a pore size less than 10 nm was able to be elaborated. This nanoporous Cu was fabricated through dealloying from amorphous Ti60Cu40–xAux (x = 0, 1, 2 at.%) ribbon alloys under free immersion conditions. A bicontinuous nanoporous Cu structure formed on Ti60Cu40, Ti60Cu39Au1, and Ti60Cu38Au2 ribbon alloys with pore sizes of 140, 19, and 9 nm, respectively, in 0.13 M HF solution. The pore size of the nanoporous Cu dealloyed from Au-added alloys was more than one order smaller than that of the Ti–Cu alloy. The pore size depended not only on the treatment solutions and treatment time but also on the alloy compositions. The uniform distribution of an Au additive on Cu in effect modified the surface diffusivity, resulting in the formation of an ultrafine nanoporous structure. The surface diffusivity was estimated to decrease from 2.49 × 10−17 to 5.88 × 10−22 m2 s−1 by adding 2 at.% Au to Ti60Cu40 ribbons.

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► Nanoporous copper with a pore size of less than 10 nm was fabricated.
► Gold addition was effective for refining nanoporous copper.
► The elaboration was due to the drastic decrease in surface diffusivity.