Optimizing niobium dealloying with metallic melt to fabricate porous structure for electrolytic capacitors

Joung Wook Kim, Masashi Tsuda, Takeshi Wada, Kunio Yubuta, Sung Gyoo Kim, Hidemi Kato

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)

Abstract

The transition behavior from a Nb-Ni precursor to porous Nb and the coarsening of ligaments by a dealloying reaction in a Mg melt are investigated. Based on these results, the kinetics of the reaction are discussed. When a Nb25Ni75 (at.%) disk was immersed in a Mg melt, the Ni content decreased the most at the surface of the disk and less so towards the interior of the disk. In this disk, it was found that transition layers of body-centered cubic-Nb and Ni6Nb7 formed. These transition layers grew, following a parabolic law, and the activation energy of such growth was close to values reported for the diffusion of solute atoms in liquids, suggesting that diffusion of Ni in the Mg melt was the rate-controlling process of the dealloying reaction. The ligament size depended on time and temperature, following a power law with an exponent of 4, suggesting that surface diffusion was a key part of coarsening. These results agree well with those reported for conventional dealloying in an aqueous solution. Based on the kinetics analyses, the dealloying conditions were optimized to maximize the specific surface area, allowing a Nb electrolytic capacitor to be produced with a maximum mass-specific capacitance of 650,000 μFV g-1, about three times larger than the highest value previously reported.

Original languageEnglish
Pages (from-to)497-505
Number of pages9
JournalActa Materialia
Volume84
DOIs
Publication statusPublished - 2015 Feb 1

Keywords

  • Dealloying
  • Nanostructure
  • Nb electrolytic capacitor
  • Porous material

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Fingerprint Dive into the research topics of 'Optimizing niobium dealloying with metallic melt to fabricate porous structure for electrolytic capacitors'. Together they form a unique fingerprint.

Cite this