Abstract
Pitting corrosion is a common localized corrosion phenomenon, which can lead to cracks and mechanical failure in structural metal materials. On the contrary, pitting corrosion could be a beneficial tool for generating large-area porous structures, which holds a great premise in a number of functional services, such as catalysis, sensing, storage, imprint lithography, and membranes. Herein we presents an electrochemical approach for creating a large-area honeycomb-like porous structure in Zr-based metallic glasses. A pitting process followed by subsurface tunnel etching in NaCl solution elicits to characteristic micrometer scale channels and nanometer size amorphous sidewalls decorated by Cu nanoparticles on the metallic glass substrate. A root-shape growing mechanism of tunnels initiated from pits and penetrating into alloy matrix is postulated. In addition, the effect of alloy composition on the microstructure of honeycomb-like porous metallic glasses is also investigated in detail.
Highlights
After 24 h drying in air at room temperature, the grids were detached from the layer and thinned using Precision Ion Polishing System (PIPS) using argon ions at 3 keV
Electrochemical tests were conducted to identify the suitability for creating porous structure in Zr68Cu16Ni8Al8 metallic glass through galvanostatic etching
The slight increase of current density between Ecorr and Ep is still related to the passive film behavior the sudden increase suggests the pit initiation and propagation, which is common in a number of Zr-based metallic glasses [33,34,35]
Summary
The present study aims to develop a feasible approach, i.e. galvanostatic (GS) etching, differing from selective corrosion by the above mentioned electrochemical etching, to prepare large-area honeycomb-like porous structure on single-phase Zr-based metallic glasses. Results indicate that the employment of electrochemical etching method enriches the diversity of available metal precursors to yield honeycomb-like porous structure with large surface area. Such a GS etching offers new possibilities for fabrication of ordered porous surfaces in stiff glassy state or bulk porous metallic glass with high surface area, which holds a great promise for applications in energy, biomedical and environmental industries
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