Special Issue "Nanoporous Metals"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 May 2019).

Special Issue Editor

Prof. Dr. Takeshi Fujita
E-Mail Website
Guest Editor
School of Environmental Science and Engineering, Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami City, Kochi 782-8502, Japan
Interests: nanoporous metal; catalysis; 2D materials; transmission electron microscopy

Special Issue Information

Dear Colleagues,

Nanoporous metals prepared by the dealloying (selective leaching) of a solid-solution alloy or compound represent an emerging class of materials. Nanoporous metal has a three-dimensional structure of randomly interpenetrating ligaments/nanopores, of which sizes can be tuned, from 5 nm to several tens of microns, by altering conditions (dealloying time, temperature and subsequent thermal coarsening). Nanoporous metals have several merits for application compared with other nanostructured materials; bicontinuous structure, tunable pore size, bulk form, good conductivity, and high structural stability. Therefore, nanoporous metal is an ideal 3D material to meet various applications, and the attractive versatile functionality such as catalysis, optical sensing, actuation or energy storage and conversion has been emerged. The understanding of the atomistic description of surface roughening and nanopore formation is also important to maximize the functionality.

This Special Issue focuses on recent advances of nanoporous metals by alloy corrosion from fundamental aspects to various applications. We welcome contributions from experimentalists, theorists, and computational scientists in this research field.

Prof. Takeshi Fujita
Guest Editor

Manuscript Submission Information

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Keywords

  • Nanoporous metal
  • Dealloy
  • Catalysis
  • Energy storage and conversion
  • Pore formation
  • Optical sensing
  • Actuation
  • Mechanical property

Published Papers (9 papers)

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Editorial

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Open AccessEditorial
Diversity of Nanoporous Metals
Metals 2019, 9(9), 996; https://doi.org/10.3390/met9090996 - 10 Sep 2019
Abstract
Nanoporous metals have been attracting considerable research and industrial attention because of the structural uniqueness of their bicontinuous metallic structure [...] Full article
(This article belongs to the Special Issue Nanoporous Metals)

Research

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Open AccessArticle
Nanoporous Quasi-High-Entropy Alloy Microspheres
Metals 2019, 9(3), 345; https://doi.org/10.3390/met9030345 - 19 Mar 2019
Cited by 1
Abstract
High-entropy alloys (HEAs) present excellent mechanical properties. However, the exploitation of chemical properties of HEAs is far less than that of mechanical properties, which is mainly limited by the low specific surface area of HEAs synthesized by traditional methods. Thus, it is vital [...] Read more.
High-entropy alloys (HEAs) present excellent mechanical properties. However, the exploitation of chemical properties of HEAs is far less than that of mechanical properties, which is mainly limited by the low specific surface area of HEAs synthesized by traditional methods. Thus, it is vital to develop new routes to fabricate HEAs with novel three-dimensional structures and a high specific surface area. Herein, we develop a facile approach to fabricate nanoporous noble metal quasi-HEA microspheres by melt-spinning and dealloying. The as-obtained nanoporous Cu30Au23Pt22Pd25 quasi-HEA microspheres present a hierarchical porous structure with a high specific surface area of 69.5 m2/g and a multiphase approximatively componential solid solution characteristic with a broad single-group face-centered cubic XRD pattern, which is different from the traditional single-phase or two-phase solid solution HEAs. To differentiate, these are named quasi-HEAs. The synthetic strategy proposed in this paper opens the door for the synthesis of porous quasi-HEAs related materials, and is expected to promote further applications of quasi-HEAs in various chemical fields. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessArticle
Dealloying of Cu-Mg-Ca Alloys
Metals 2018, 8(11), 919; https://doi.org/10.3390/met8110919 - 08 Nov 2018
Cited by 1
Abstract
The chemical dealloying of Cu-Mg-Ca alloys in free corrosion conditions was investigated for different alloy compositions and different leaching solutions. For some of the precursor alloys, a continuous, pure fcc copper with nanoporous structure can be obtained by dealloying in 0.04 M H [...] Read more.
The chemical dealloying of Cu-Mg-Ca alloys in free corrosion conditions was investigated for different alloy compositions and different leaching solutions. For some of the precursor alloys, a continuous, pure fcc copper with nanoporous structure can be obtained by dealloying in 0.04 M H2SO4 solution. Superficial nanoporous copper structures with extremely fine porous size were also obtained by dealloying in pure water and 0.1 M NaOH solutions. The dealloying of both amorphous and partially crystalline alloys was investigated obtaining bi-phase nanoporous/crystal composites with microstructures depending on the precursor alloy state. The fast dissolution of Mg and Ca makes the Cu-Mg-Ca system an ideal candidate for obtaining nanoporous copper structures with different properties as a function of different factors such as the alloy composition, the quenching process, and leaching conditions. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessArticle
Fabrication of a Porous Metal via Selective Phase Dissolution in Al-Cu Alloys
Metals 2018, 8(6), 378; https://doi.org/10.3390/met8060378 - 24 May 2018
Cited by 1
Abstract
Through free corrosion, a new low cost porous material was successfully fabricated by removing a single phase of a binary aluminum-copper alloy. This selective phase dissolution was carried out an Al-Al2Cu eutectic alloy of the Al-Cu binary system and additionally for [...] Read more.
Through free corrosion, a new low cost porous material was successfully fabricated by removing a single phase of a binary aluminum-copper alloy. This selective phase dissolution was carried out an Al-Al2Cu eutectic alloy of the Al-Cu binary system and additionally for two hypereutectic compositions. The porosity of the material depends on the microstructure formed upon solidification. For this reason, several solidification methods were studied to define the most convenient in terms of uniformity and refinement of the average pore and ligament sizes. The samples were corroded in a 10% v/v NaOH aqueous solution, which demonstrated to be the most convenient in terms of time involved and resulting porosity conditions after the corrosion process. The porosity was measured through analysis of secondary electron images. The effectiveness of the process was verified using X-ray diffraction, which showed that, under the proposed methodology, there was complete removal of one of the phases, namely the aluminum one. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessArticle
Skeletonization, Geometrical Analysis, and Finite Element Modeling of Nanoporous Gold Based on 3D Tomography Data
Metals 2018, 8(4), 282; https://doi.org/10.3390/met8040282 - 19 Apr 2018
Cited by 5
Abstract
Various modeling approaches simplify and parametrize the complex network structure of nanoporous gold (NPG) for studying the structure–property relationship based on artificially generated structures. This paper presents a computational efficient and versatile finite element method (FEM) beam model that is based on skeletonization [...] Read more.
Various modeling approaches simplify and parametrize the complex network structure of nanoporous gold (NPG) for studying the structure–property relationship based on artificially generated structures. This paper presents a computational efficient and versatile finite element method (FEM) beam model that is based on skeletonization and diameter information derived from the original 3D focused ion beam-scanning electron microscope (FIB-SEM) tomography data of NPG. The geometrical skeleton network is thoroughly examined for a better understanding of the NPG structure. A skeleton FEM beam model is derived that can predict the macroscopic mechanical behavior of the material. Comparisons between the mechanical response of this skeleton beam model and a solid FEM model are conducted. Results showed that the biggest-sphere diameter algorithm implemented in the open-source software FIJI, commonly used for geometrical analysis of microstructural data, overestimates the diameter of the curved NPG ligaments. The larger diameters lead to a significant overestimation of macroscopic stiffness and strength by the skeleton FEM beam model. For a parabolic shaped ligament with only 20% variation in its diameter, a factor of more than two was found in stiffness. It is concluded that improved algorithms for image processing are needed that provide accurate diameter information along the ligament axis. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessArticle
Chemical Dealloying Synthesis of CuS Nanowire-on-Nanoplate Network as Anode Materials for Li-Ion Batteries
Metals 2018, 8(4), 252; https://doi.org/10.3390/met8040252 - 09 Apr 2018
Cited by 5
Abstract
CuS is a metal sulfide anode material used in constructing lithium ion batteries (LIBs) with great promise. However, its practical application is limited by rapid capacity decline, poor cycling, and rate performance. In this work, the CuS nanowire-on-nanoplate network is synthesized through an [...] Read more.
CuS is a metal sulfide anode material used in constructing lithium ion batteries (LIBs) with great promise. However, its practical application is limited by rapid capacity decline, poor cycling, and rate performance. In this work, the CuS nanowire-on-nanoplate network is synthesized through an improved dealloying method under two contrasting reaction temperatures. When used as an LIB anode, the as-obtained CuS network exhibits superior cycling performance (420 mAh·g−1 retained after 100 cycles at 0.2 C). When at 3 C, it still delivers a capacity of around 350 mAh·g−1. The improved electrochemical performances of the CuS anode should be attributed to the well-designed nanowire-on-nanoplate network structure in which the introduction of nanowires improves Li storage sites, shortens Li-ion diffusion distance, enhances the conductivity of active materials, and offers multiscale spaces for buffering the volume variation. The fabrication route adopted in this paper has an important significance for developing the dealloying technique and designing more suitable anode structures for LIBs. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessFeature PaperCommunication
Bottom-up Synthesis of Porous NiMo Alloy for Hydrogen Evolution Reaction
Metals 2018, 8(2), 83; https://doi.org/10.3390/met8020083 - 23 Jan 2018
Cited by 8
Abstract
Bottom-up synthesis of porous NiMo alloy reduced by NiMoO4 nanofibers was systematically investigated to fabricate non-noble metal porous electrodes for hydrogen production. The different annealing temperatures of NiMoO4 nanofibers under hydrogen atmosphere reveal that the 950 °C annealing temperature is key [...] Read more.
Bottom-up synthesis of porous NiMo alloy reduced by NiMoO4 nanofibers was systematically investigated to fabricate non-noble metal porous electrodes for hydrogen production. The different annealing temperatures of NiMoO4 nanofibers under hydrogen atmosphere reveal that the 950 °C annealing temperature is key for producing bicontinuous porous NiMo alloy without oxide phases. The porous NiMo alloy acts as a cathode in electrical water splitting, which demonstrates not only almost identical catalytic activity with commercial Pt/C in 1.0 M KOH solution, but also superb stability for 12 days at an electrode potential of −200 mV vs. reversible hydrogen electrode (RHE). Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessCommunication
Synthesis of Metastable Au-Fe Alloy Using Ordered Nanoporous Silica as a Hard Template
Metals 2018, 8(1), 17; https://doi.org/10.3390/met8010017 - 30 Dec 2017
Cited by 2
Abstract
Nanoporous Au-Fe alloy was synthesized via a wet chemistry route using ordered nanoporous silica as a hard template. The nanoporous Au-Fe consisted of aligned arrays of nanopores that were uniform in composition and ordered in hexagonal lattice, whereas Au-Fe nanoparticles synthesized without templates [...] Read more.
Nanoporous Au-Fe alloy was synthesized via a wet chemistry route using ordered nanoporous silica as a hard template. The nanoporous Au-Fe consisted of aligned arrays of nanopores that were uniform in composition and ordered in hexagonal lattice, whereas Au-Fe nanoparticles synthesized without templates exhibited broad dispersions in the chemical composition and/or particle size. Nanoporous Au-Fe has potential for applications as catalysts and/or adsorbents because of the large specific surface area of 81.2 m2·g−1 and high pore volume of 0.56 cm3·g−1. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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Open AccessFeature PaperCommunication
In-Situ TEM Study of a Nanoporous Ni–Co Catalyst Used for the Dry Reforming of Methane
Metals 2017, 7(10), 406; https://doi.org/10.3390/met7100406 - 01 Oct 2017
Cited by 5
Abstract
We performed in-situ transmission electron microscopy (TEM) on a dealloyed nanoporous NiCo catalyst used for the dry reforming of methane (DRM) to investigate the origin of the catalytic activity and structural durability. The in-situ observations and local chemical analysis indicated that the DRM [...] Read more.
We performed in-situ transmission electron microscopy (TEM) on a dealloyed nanoporous NiCo catalyst used for the dry reforming of methane (DRM) to investigate the origin of the catalytic activity and structural durability. The in-situ observations and local chemical analysis indicated that the DRM induced chemical demixing of Ni and Co accompanied by grain refinement, implying possible “synergic effects” in a general bimetallic NiCo catalyst when used for the DRM. Full article
(This article belongs to the Special Issue Nanoporous Metals)
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