Editorial

2 pages, 160 KiB

Open AccessEditorial

by Takeshi Fujita

Metals 2019, 9(9), 996; https://doi.org/10.3390/met9090996 - 10 Sep 2019

Cited by 2 | Viewed by 1740

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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10 pages, 2603 KiB

Open AccessArticle

Nanoporous Quasi-High-Entropy Alloy Microspheres

by Lianzan Yang, Yongyan Li, Zhifeng Wang, Weimin Zhao and Chunling Qin

Metals 2019, 9(3), 345; https://doi.org/10.3390/met9030345 - 19 Mar 2019

Cited by 11 | Viewed by 3674

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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13 pages, 7410 KiB

Open AccessArticle

Dealloying of Cu-Mg-Ca Alloys

by Wael Ben Mbarek, Eloi Pineda, Lluïsa Escoda, Joan Josep Suñol and Mohamed Khitouni

Metals 2018, 8(11), 919; https://doi.org/10.3390/met8110919 - 08 Nov 2018

Cited by 7 | Viewed by 3916

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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17 pages, 18784 KiB

Open AccessArticle

Fabrication of a Porous Metal via Selective Phase Dissolution in Al-Cu Alloys

by Juan Vargas-Martínez, John E. Estela-García, Oscar Marcelo Suárez and Carmen A. Vega

Metals 2018, 8(6), 378; https://doi.org/10.3390/met8060378 - 24 May 2018

Cited by 8 | Viewed by 4504

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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20 pages, 6195 KiB

Open AccessArticle

Skeletonization, Geometrical Analysis, and Finite Element Modeling of Nanoporous Gold Based on 3D Tomography Data

by Claudia Richert and Norbert Huber

Metals 2018, 8(4), 282; https://doi.org/10.3390/met8040282 - 19 Apr 2018

Cited by 26 | Viewed by 5798

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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10 pages, 10634 KiB

Open AccessArticle

Chemical Dealloying Synthesis of CuS Nanowire-on-Nanoplate Network as Anode Materials for Li-Ion Batteries

by Zhifeng Wang, Xiaomin Zhang, Yongguang Zhang, Man Li, Chunling Qin and Zhumabay Bakenov

Metals 2018, 8(4), 252; https://doi.org/10.3390/met8040252 - 09 Apr 2018

Cited by 32 | Viewed by 5450

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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9 pages, 3175 KiB

Open AccessFeature PaperCommunication

Bottom-up Synthesis of Porous NiMo Alloy for Hydrogen Evolution Reaction

by Kailong Hu, Samuel Jeong, Mitsuru Wakisaka, Jun-ichi Fujita and Yoshikazu Ito

Metals 2018, 8(2), 83; https://doi.org/10.3390/met8020083 - 23 Jan 2018

Cited by 30 | Viewed by 8484

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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1959 KiB

Open AccessCommunication

Synthesis of Metastable Au-Fe Alloy Using Ordered Nanoporous Silica as a Hard Template

by Paskalis Sahaya Murphin Kumar, Thiripuranthagan Sivakumar, Takeshi Fujita, Ramasamy Jayavel and Hideki Abe

Metals 2018, 8(1), 17; https://doi.org/10.3390/met8010017 - 30 Dec 2017

Cited by 7 | Viewed by 4453

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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12173 KiB

Open AccessFeature PaperCommunication

In-Situ TEM Study of a Nanoporous Ni–Co Catalyst Used for the Dry Reforming of Methane

by Takeshi Fujita, Kimitaka Higuchi, Yuta Yamamoto, Tomoharu Tokunaga, Shigeo Arai and Hideki Abe

Metals 2017, 7(10), 406; https://doi.org/10.3390/met7100406 - 01 Oct 2017

Cited by 15 | Viewed by 5427

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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