Designing
materials with multiscale, hierarchical structure is critical to drive
the advancement of new technology. Specifically, porous metals with
multiscale porosity from nanometer to micrometer sizes would lead
to enhanced physical and chemical propertiesthe micron-sized
pores can increase the effective diffusivity of ion transport within
the porous media, and the nano-sized pores provide high specific surface
area, enabling functionalities that are unique to nanoporous metals.
A new ternary precursor alloy selection concept utilizing the different
mixing enthalpies is demonstrated in this work for the design of multiscale,
bimodal porous copper from a simple, one-step dealloying of Cu–Fe–Al
ternary alloy. The nanoporosity in the bimodal porous structure is
formed from dealloying of the Cu-rich phase, whereas the microporosity
is controlled by dissolving the Fe-rich phase, determined by both
the initial Fe particle size and sintering profile. In addition to
advancing the materials design method, the multiscale pore formation
during dealloying was directly visualized and quantified via an interrupted
in situ synchrotron X-ray nano-tomography. The 3D morphological analysis
on tortuosity showed that the presence of the microporosity can compensate
the increase of the diffusion path length due to nanoporosity, which
facilitates diffusion within the porous structure. Overall the focus
of the work is to introduce a new strategy to design multiscale porous
metals with enhanced transport properties, and sheds light on the
fundamental mechanisms on the 3D morphological evolution of the system
using advanced synchrotron X-ray nano-tomography for future materials
development and applications.
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