Morphology, ligament strength, and energy absorption of nanoporous copper via vapor phase dealloying

Abstract

Nanoporous coppers (NPCs) with ligament size down to 800 nm and relative densities ranging from 15.7% to 47.5% were synthesized by vapor phase dealloying (VPD) Cu33Zn67, Cu16Zn84, and Cu6Zn94 precursor alloys. The ligament size of NPCs could be adjusted by applying different VPD temperatures under high vacuum, while the change in the mechanical properties of NPCs were monitored by compression tests. Although NPCs possessed a random ligament structure, the energy absorption capability of NPCs was up to 183.3 MJ/m3, which is an order higher than that of other Cu foam structures fabricated by different methods such as 3D printing, electron beam melting, electro-deposition, chemical dealloying and friction powder compaction. High apparent relative density and ligament connectivity could effectively transmit the compression energy in the form of stress waves, and therefore had higher densification strain and better energy absorption capacity. With the use of corrected Gibson and Ashby scaling equation, the ligament strength of NPC was up to 3456 MPa, which was ten times higher than that of bulk Cu and comparable to that of other ordered or periodic copper foams.