Formation of metastable phases during spark plasma sintering of Fe@Au core–shell particles

ABSTRACT

The present work reports the formation of Fe-Au metastable alloys by galvanic replacement, pressureless spark plasma sintering (SPS) and acid treatment. The reaction of partial galvanic replacement between micrometer-sized iron particles and HAuCl₄ solution allowed synthesising core–shell Fe@Au particles. When the Fe@Au particles were treated in HCl solution, iron was selectively dissolved and hollow Au particles were formed. Pressureless SPS of the Fe@Au core–shell particles led to the formation of a metastable intermetallic phase, FeAu₃, and a supersaturated solid solution, Au(Fe). The latter was resistant to HCl solution; at the same time, the FeAu₃ phase decomposed during HCl treatment to form a porous gold structure. This work shows that a combination of galvanic replacement, SPS and acid treatment can be used for the preparation of metastable Fe-Au alloys with different phase compositions and particle morphologies.

KEYWORDS:

• Fe-Au alloys
• metastable phase
• galvanic replacement reaction
• selective dissolution
• spark plasma sintering
• morphology

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Ministry of Science and Higher Education of the Russian Federation, project #121121600298-7 (LIH SB RAS).