General synthesis of sponge-like ultrafine nanoporous metals by dealloying in citric acid

Abstract

A general method is proposed to synthesize ultrafine nanoporous Cu, Ag, and Ni with novel sponge-like morphologies, high porosities, and large surface areas. The materials are produced by dealloying Mg 65 M 25 Y 10 (M = Cu, Ag, and Ni) metallic glasses in citric acid. Citric acid played a key role due to its capping effect, which reduced the surface diffusion of metals. A structural model consistent with the sponge-like morphology was constructed to calculate the porosity and the surface area. The mechanism of the dealloying process in citric acid, involving ligament formation and coarsening, was illustrated. The mechanism was capable of explaining the experimental trends of dealloying, especially the morphology. A glucose sensor, which can be further developed into a high-precision real-time glucose monitor for medical use, was constructed using sponge-like nanoporous copper. Our findings are not only relevant to understanding the dealloying mechanism of metallic glasses, but also provide promising materials for multiple applications.

Fabrication of Nanoporous Al by Vapor-Phase Dealloying: Morphology Features, Mechanical Properties and Model Predictions

“…The NP Al specific surface area, as obtained by BET analysis, is nearly 73 m 2 g −1 , a remarkably large value that compares well with the highest literature values for NP metals [35,36]. Although limitations associated to surface area determination by physisorption routes have been reported, the correlation with the structural features has been pointed out [35][36][37]. For instance, NP Au can have a specific surface area as large as 85 m 2 g −1 when its ligaments are about 7 nm in size [35].…”

“…The shape of the N 2 physisorption isotherms shown in Figure 3b is associated with the occurrence of a hysteresis loop and does not strictly match with a specific classification, supporting the NP Al structure's inhomogeneity [34]. The NP Al specific surface area, as obtained by BET analysis, is nearly 73 m 2 g −1 , a remarkably large value that compares well with the highest literature values for NP metals [35,36]. Although limitations associated to surface area determination by physisorption routes have been reported, the correlation with the structural features has been pointed out [35][36][37].…”

Ultra-rapid synthesis of the MgCu2 and Mg2Cu Laves phases and their facile conversion to nanostructured copper with controllable porosity; an energy-efficient, reversible process

“…[18][19][20][21][22] Nanoporous Cu (NP-Cu) materials have universally demonstrated a particularly impressive performance in the context of the above applications. 7,18,[23][24][25][26] A variety of synthesis methods have been proposed for NP metals, including thermal decomposition and reduction of metal salts/oxides (e.g. by H 2 gas), 27,28 electrochemical reduction of metal oxides (which are typically pre-synthesised in solution), 23 organo-lithium reduction of metal/lithium halide nano-composites in nonpolar solvents, 2 and chemical de-alloying of alloys by corrosive liquids (typically acidic or basic solutions).…”

Quantitative microstructure study of melt-spun Mg65Cu25Y10

“…These investigations were conducted on amorphous Mg 65 Cu 25 Y 10 obtained by different casting processes, namely, pressure die-casting [1,2,4], injection into a copper mold [6][7][8][9][10][11][12][13], injection into a water-cooled Cu mold [14], melt spinning [15][16][17][18][19][20], rapid quenching without listing the exact process [21,22] and permanent mold without stating anything about the mold [23]. The characterization techniques used in order to determine the amorphous structure of the Mg 65 Cu 25 Y 10 alloy included X-ray diffraction (XRD) [1,4,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], differential scanning calorimetry (DSC) [1, 2, 4, 6-8, 10-18, 22, 23] and transmission electron microscopy (TEM) [1,6,8,9,…”

“…All the studies that examined the microstructure of Mg 65 Cu 25 Y 10 seem to agree that sufficiently rapid cooling rates during the casting process of this composition yield a fully amorphous structure. It should be noticed that only two references [19,20] include high-resolution transmission electron microscopy (HRTEM) of Mg 65 Cu 25 Y 10 ; however, these HRTEM studies deal with the characterization of nanoporous structures obtained by selective dissolution of amorphous Mg 65 Cu 25 Y 10 and not with the degree of amorphization of the alloy.…”