The Experts below are selected from a list of 3015 Experts worldwide ranked by ideXlab platform
Zhonghua Zhang - One of the best experts on this subject based on the ideXlab platform.
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Dealloying strategy to fabricate ultrafine nanoporous gold based alloys with high structural stability and tunable magnetic properties
CrystEngComm, 2012Co-Authors: Zhonghua Zhang, Chi Zhang, Jan Frenzel, G EggelerAbstract:In the present work, the Dealloying of Al–Au-based precursors and formation of nanoporous Au-based alloys have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and energy dispersive X-ray (EDX) analysis. The results show that the addition of Ni and/or Co has no influence on phase constitution of rapidly solidified Al–Au–M (M = Ni, Co, or Ni/Co) alloys and a single-phase Al2(Au,M) intermetallic compound can be identified in these ternary and quarternary precursor alloys. The Al–Au-based precursors can be fully dealloyed in an alkaline solution under free corrosion conditions, and the Dealloying results in the formation of novel ultrafine nanoporous Au-based alloys (Au(Ni), Au(Co) and Au(Ni,Co)) with ligaments/channels of ∼5 nm. The ultrafine nanoporous Au-based alloys possess extraordinarily high structural stability against thermal annealing. Moreover, due to the intrinsic magnetism of Ni and Co, the addition of Ni and/or Co leads to the formation of novel magnetic nanoporous alloys. The Dealloying mechanism of these Al–Au-based precursors has been discussed based upon surface diffusion of Au adatoms and interaction between Au and additional elements. The present findings provide a new Dealloying route to fabricate ultrafine nanoporous Au-based alloys with high stability and magnetic properties through alloy design of precursors.
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influence of anion species on electrochemical Dealloying of single phase al2au alloy in sodium halide solutions
RSC Advances, 2012Co-Authors: Zhonghua Zhang, Chi Zhang, Junzhe Sun, Tianyi KouAbstract:The electrochemical Dealloying of single-phase Al2Au alloy in 1 M sodium halide (NaF, NaCl, NaBr and NaI) aqueous solutions at 270, 290 and 340 K has been systematically investigated in this work. The effects of halide ions and temperature on the Dealloying behavior have been studied with electrochemical methods like open-circuit potential measurements and dynamic polarization tests. Nanoporous gold (NPG) with a typical three-dimensional, bicontinuous, interpenetrating ligament-channel structure can be obtained from the single-phase Al2Au alloy by electrochemical Dealloying in the NaCl, NaBr, and NaI solutions. In addition, the dealloyed NPG samples and the samples after coarsening at ambient conditions were characterized using field-emission scanning electron microscopy (FESEM). Morphological features like cracks and ligament sizes in NPG have been discussed. Furthermore, NPG samples that were almost free of cracks have been successfully prepared in the NaI solution at 340 K. Besides, based on the surface diffusion controlled coarsening mechanism, the surface diffusivities of gold adatoms along the alloy–electrolyte interfaces during Dealloying have been evaluated in this work, as well as the activation enthalpy and activation entropy.
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formation and microstructure of nanoporous silver by Dealloying rapidly solidified zn ag alloys
Electrochimica Acta, 2012Co-Authors: Chi Zhang, Xiaoguang Wang, Changchun Zhao, Junling Xu, Hong Ji, Zhonghua ZhangAbstract:a b s t r a c t The electrochemical Dealloying of rapidly solidified (RS) Zn–Ag alloys in a 5 wt.% HCl solution and 1 M NaCl solution has been investigated using electrochemical measurements and microstructural analysis. The results show that the electrochemical properties of the RS Zn–Ag alloys are associated not only with the alloy composition, but with the phase constitution of the alloys. Nanoporous silver (NPS) ribbons can be fabricated through potentiostatically Dealloying the RS Zn–Ag alloys in both solutions. Moreover, a minor difference in the applied potential has a significant influence on the Dealloying process and formation of NPS. The critical potential and polarization behavior of the Zn–Ag alloys have also been discussed, as well as surface diffusion of Ag adatoms.
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potential and concentration dependent electrochemical Dealloying of al2au in sodium chloride solutions
Journal of Physical Chemistry C, 2012Co-Authors: Yan Wang, Zhonghua ZhangAbstract:Electrochemical Dealloying of a single-phase Al2Au alloy in sodium chloride solutions has been investigated considering influence of potential and electrolyte concentration. Both open-circuit potentials and corrosion potentials of Al2Au decrease with increasing electrolyte concentration and temperature. The overpotential and electrolyte concentration have a significant influence on Dealloying behaviors of Al2Au, such as steady-state current density and Dealloying duration. Nanoporous gold (NPG) can be fabricated by potentiostatic Dealloying of Al2Au in the NaCl solutions. Moreover, surface diffusion evaluation demonstrates that there exist good linear relationships between the logarithm of surface diffusivities of Au adatoms (Auad) and overpotential, and between the surface diffusivities of Auad and electrolyte concentration. In addition, the activation energy decreases with increasing overpotential or chloride ion concentration.
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Dealloying Ag-Al alloy to prepare nanoporous silver as a substrate for surface-enhanced Raman scattering: effects of structural evolution and surface modification.
ChemPhysChem, 2011Co-Authors: Zhonghua Zhang, Xirong Huang, Yinbo QuAbstract:Sensitive detection of molecules by using the surface-enhanced Raman scattering (SERS) technique depends on the nanostructured metallic substrate and many efforts have been devoted to the preparation of SERS substrates with high sensitivity, stability, and reproducibility. Herein, we report on the fabrication of stable monolithic nanoporous silver (NPS) by chemical Dealloying of Ag-Al precursor alloys with an emphasis on the effect of structural evolution on SERS signals. It was found that the Dealloying conditions had great influence on the morphology (the ligament/pore size) and the crystallization status, which determined the SERS signal of rhodamine 6G on the NPS. NPS with small pores, low residual Al, and perfect crystallization gave high SERS signals. A high enhancement factor of 7.5 x 10(5) was observed on bare NPS obtained by Dealloying Ag(30)Al(70) in 2.5 wt% HCl at room temperature followed by 15 min aging at around 85 degrees C. After coating Ag nanoparticles on the NPS surface, the enhancement factor increased to 1.6 x 10(8) owing to strong near-field coupling between the ligaments and nanoparticles.
Mingwei Chen - One of the best experts on this subject based on the ideXlab platform.
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Vapor phase Dealloying: A versatile approach for fabricating 3D porous materials
Acta Materialia, 2019Co-Authors: Cheng Li, Kentaro Watanabe, Zhili Wang, Zhen Lu, Hao Wang, Mingwei ChenAbstract:Abstract Three-dimensional porous materials with bicontinuous open porosity represent a new class of functional materials for various applications. Top-down Dealloying has been demonstrated to be one of the most effective ways to fabricate 3D porous materials. Vapor phase Dealloying, which makes use of the saturated vapor pressure difference between the constituent components in an alloy for selectively removing a less stable element or phase, is a promising versatile method for fabricating porous materials from active metals to inorganic elements. Here, using nickel-zinc and germanium-zinc alloys as the prototypes of single-phase and two-phase precursors, respectively, we report the fabrication of 3D bicontinuous porous Ni and Ge by vapor phase Dealloying on the basis of selective element or selective phase evaporations. We also show the incorporation of vapor phase Dealloying with chemical vapor deposition for the one-pot growth of 3D nanoporous graphene and the functional applications of vapor phase dealloyed porous Ge as Li ion battery electrodes. This study shines lights on the versatility of vapor phase Dealloying for the fabrication of bicontinuous porous materials for a wide range of functional applications.
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engineering the internal surfaces of three dimensional nanoporous catalysts by surfactant modified Dealloying
Nature Communications, 2017Co-Authors: Zhili Wang, Takeshi Fujita, Akihiko Hirata, Pan Liu, Jiuhui Han, Chun Cheng, Shoucong Ning, Mingwei ChenAbstract:Tuning surface structures by bottom-up synthesis has been demonstrated as an effective strategy to improve the catalytic performances of nanoparticle catalysts. Nevertheless, the surface modification of three-dimensional nanoporous metals, fabricated by a top-down Dealloying approach, has not been achieved despite great efforts devoted to improving the catalytic performance of three-dimensional nanoporous catalysts. Here we report a surfactant-modified Dealloying method to tailor the surface structure of nanoporous gold for amplified electrocatalysis toward methanol oxidation and oxygen reduction reactions. With the assistance of surfactants, {111} or {100} faceted internal surfaces of nanoporous gold can be realized in a controllable manner by optimizing Dealloying conditions. The surface modified nanoporous gold exhibits significantly enhanced electrocatalytic activities in comparison with conventional nanoporous gold. This study paves the way to develop high-performance three-dimensional nanoporous catalysts with a tunable surface structure by top-down Dealloying for efficient chemical and electrochemical reactions.
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hierarchical nanoporous metal metal oxide composite by Dealloying metallic glass for high performance energy storage
Corrosion Science, 2015Co-Authors: H J Qiu, Pan Liu, Junqiang Wang, Y Wang, Mingwei ChenAbstract:Abstract A free-standing nanoporous YNiCo metal/metal-oxide composite with hierarchical porosity is fabricated by chemically Dealloying Al 85 Y 6 Ni 6 Co 3 metallic glass in alkaline solutions. The mixed core–shell-like metal/metal-oxide structure formed during Dealloying due to the active properties of these metals. Time-dependent etching experiments suggest that the formation of large and small pores occur simultaneously, which may be related to the different dissolution rate of Al at different sites. The nanoporous composite with a highly conductive metal core exhibits a high areal capacitance. Moreover, this strategy can be extended to fabricate other nanoporous composites considering that the composition of metallic glass can be easily tuned.
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fabrication of large scale nanoporous nickel with a tunable pore size for energy storage
Journal of Power Sources, 2014Co-Authors: H J Qiu, Takeshi Fujita, Mingwei Chen, Akihiko Hirata, Pan Liu, Jianli KangAbstract:Nanoporous Ni with a tunable nanopore size and chemical compositions was fabricated by Dealloying a Ni30Mn70 precursor alloy at various temperatures. The influence of electrochemical parameters on the formation of large-scale nanoporous Ni was systematically investigated. Different from the fabrication of nanoporous noble metals (Au, Pt and Pd), the Dealloying of Ni30Mn70 includes three kinetically competitive processes: dissolution of Mn, interface diffusion of Ni and dissolution of Ni. The nanopore size and residual Mn can be tailored by controlling the Dealloying time, temperature and applied potential. The as-dealloyed nanoporous Ni with a large internal surface area, excellent conductivity and naturally formed oxide surface can be directly used as a free-standing electrode for electrochemical supercapacitors with a high capacitance and excellent cycling stability.
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nanoporous pdni bimetallic catalyst with enhanced electrocatalytic performances for electro oxidation and oxygen reduction reactions
Advanced Functional Materials, 2011Co-Authors: Luyang Chen, Takeshi Fujita, Akihiko Hirata, Akihisa Inoue, Wei Zhang, Mingwei ChenAbstract:A nanoporous PdNi (np-PdNi) bimetallic catalyst fabricated by electrochemically Dealloying a Pd20Ni80 alloy in an acid solution is reported. Residual Ni in the nanoporous alloy can be controlled by tuning Dealloying potentials and the electrocatalysis of the np-PdNi shows evident dependence on Ni concentrations. With ∼9 at.% Ni, the np-PdNi bimetallic catalyst presents superior electrocatalytic performances in methanol and formic acid electro-oxidation as well as oxygen reduction in comparison with commercial Pd/C and nanoporous Pd (np-Pd). The excellent electrocatalytic properties of the dealloyed np-PdNi bimetallic catalyst appear to arise from the combined effect of unique bicontinuous nanoporosity and bimetallic synergistic action.
Jonah Erlebacher - One of the best experts on this subject based on the ideXlab platform.
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self assembled porous metal intermetallic nanocomposites via liquid metal Dealloying
Acta Materialia, 2019Co-Authors: Bernard Gaskey, Ian Mccue, Alyssa Chuang, Jonah ErlebacherAbstract:Abstract A major challenge in the synthesis of high surface area metals via subtractive processes such as Dealloying is maintaining the mechanical integrity of the resulting porous materials. This problem is especially apparent in liquid metal Dealloying, in which high-temperature selective dissolution in a molten metal bath leads to bicontinuous porosity formation. In liquid metal Dealloying of polycrystalline alloys, grain boundary separation leads to the detachment of individual grains. In this work, we show that addition of small amounts of silicon to Nb Ti or Ta Ti parent alloys leads to the generation of self-assembled arrays of intermetallic (niobium silicide or tantalum silicide) plates that are structurally merged with the usual bicontinuous porosity seen in Dealloying. These silicide plates pass through grain boundaries and hold the niobium or tantalum network intact without strongly affecting the microstructural evolution during Dealloying. Our approach yields a mechanically robust porous metal-intermetallic composite, which can be further processed to form tertiary materials via re-impregnation by a new third phase. The materials design strategy introduced here can be generalized to serve as a platform to form dense multiphase nanocomposites.
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pattern formation during electrochemical and liquid metal Dealloying
Mrs Bulletin, 2018Co-Authors: Ian Mccue, Alain Karma, Jonah ErlebacherAbstract:Dealloying has evolved from a problematic corrosion process to a versatile tool for scalable fabrication of nanostructured metals. While the original, and majority of, work in the area has focused on electrochemical Dealloying, a powerful variation of Dealloying—liquid metal Dealloying—has recently gained popularity. This process relies on a melt to carry out selective dissolution, replacing the traditional electrolyte solution. While electrolytes and molten metals are both suitable Dealloying media, they can lead to very different morphologies. In this article, we compare and contrast what is known about the microscale physics and chemistry controlling microstructural evolution in electrochemical and liquid metal Dealloying. We conclude that the core phenomenology of porosity evolution—a competition between dissolution and interface diffusion—is similar in both Dealloying processes, but that the relative magnitudes of these two processes control interfacial pattern formation.
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kinetics and morphological evolution of liquid metal Dealloying
Acta Materialia, 2016Co-Authors: Ian Mccue, Alain Karma, Bernard Gaskey, Pierreantoine Geslin, Jonah ErlebacherAbstract:Abstract Liquid metal Dealloying (LMD) has recently emerged as a novel technique to fabricate bulk nanostructures using a bottom-up self-organization method, but the literature lacks fundamental studies of this kinetic process. In this work, we conduct an in-depth study of the kinetics and fundamental microstructure evolution mechanisms during LMD using Ti Ta alloys immersed in molten Cu as a model system. We develop a model of LMD kinetics based on a quantitative characterization of the effects of key parameters in our system including alloy composition, Dealloying duration, and Dealloying temperature. This work demonstrates that the Dealloying interface is at or near equilibrium during LMD, and that the rate-limiting step is the liquid-state diffusion of dissolving atoms away from the Dealloying interface (diffusion-limited kinetics). The quantitative comparison between theoretically predicted and measured Dealloying rates further reveals that convective transport and rejection of the dissolving element during coarsening of the structure also influence the Dealloying kinetics.
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Dealloying and dealloyed materials
Annual Review of Materials Research, 2016Co-Authors: Ian Mccue, Bernard Gaskey, Ellen Benn, Jonah ErlebacherAbstract:A successful working model for nanoporosity evolution during Dealloying was introduced 15 years ago. Since that time, the field has rapidly expanded, with research groups from across the world studying Dealloying and dealloyed materials. Dealloying has grown into a rich field, with some groups focusing on fundamentals and mechanisms of Dealloying, other groups creating new porous metals and alloys, and even more groups studying their properties. Dealloying was originally considered only in the context of corrosion, but now it is considered a facile self-organization technique to fabricate high-surface-area, bicontinuous nanoporous materials. Owing to their high interfacial area and the versatility of metallic materials, nanoporous metals have found application in catalysis, sensing, actuation, electrolytic and ultracapacitor materials, high-temperature templates/scaffolds, battery anodes, and radiation damage–tolerant materials. In this review, we discuss the fundamental materials principles underlying th...
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Topology-generating interfacial pattern formation during liquid metal Dealloying
Nature Communications, 2015Co-Authors: Pierreantoine Geslin, Ian Mccue, Jonah Erlebacher, Bernard Gaskey, Alain KarmaAbstract:Liquid metal Dealloying has emerged as a novel technique to produce topologically complex nanoporous and nanocomposite structures with ultra-high interfacial area and other unique properties relevant for diverse material applications. This process is empirically known to require the selective dissolution of one element of a multicomponent solid alloy into a liquid metal to obtain desirable structures. However, how structures form is not known. Here we demonstrate, using mesoscale phase-field modelling and experiments, that nano/ microstructural pattern formation during Dealloying results from the interplay of (i) interfacial spinodal decomposition, forming compositional domain structures enriched in the immiscible element, and (ii) diffusion-coupled growth of the enriched solid phase and the liquid phase into the alloy. We highlight how those two basic mechanisms interact to yield a rich variety of topologically disconnected and connected structures. Moreover, we deduce scaling laws governing microstructural length scales and Dealloying kinetics.
Hidemi Kato - One of the best experts on this subject based on the ideXlab platform.
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open porous Dealloying based biomaterials as a novel biomaterial platform
Materials Science and Engineering: C, 2018Co-Authors: I V Okulov, Hidemi Kato, Takeshi Wada, A V Okulov, Ivan Soldatov, Berengere J C Luthringer, Regine Willumeitromer, J Weissmuller, Jurgen MarkmannAbstract:Abstract The close match of stiffness between implant material and bone is critically important to avoid stress-shielding effect and ensure a fast healing of injured tissues. Here, we introduce liquid metal Dealloying method for synthesis of robust open porous biomaterials possessing low Young's modulus. The remarkable advantage of the liquid metal Dealloying method is a large flexibility in selecting chemical composition of a desired porous biomaterial together with unique tunable microstructure. To demonstrate the versatility of the method, a number of open porous TixZr100-x alloys with different chemical compositions and microstructural characteristics was developed by Dealloying precursor (TixZr100-x)yCu100-y alloys in liquid magnesium. The effects of the processing conditions and the precursors' chemical composition on the microstructure of the porous TixZr100-x as well as their mechanical behavior were discussed in detail. In particular, the porous TixZr100-x distinguish themselves due to a low and tunable stiffness ranging from 3.2 to 15.1 GPa and a rather high strength reaching up to 480 MPa. This unique combination of mechanical properties of the new open porous TixZr100-x alloys becomes even more interesting in view of preliminary biological tests highlighting their excellent cytocompatibility. Overall, the liquid metal Dealloying provides an opportunity for designing a new biomaterials platform with flexible tunable functionality.
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Fabrication and mechanical properties of bulk metallic glass matrix composites by in-situ Dealloying method
Journal of Alloys and Compounds, 2017Co-Authors: Hidemi Kato, Rui Yamada, Junji SaidaAbstract:Abstract In-situ Ti-reinforced Mg-based (MT-D) and in-situ Ta-reinforced Zr-based (ZT-D) bulk metallic glass matrix composites (BMGMCs) were prepared by a novel Dealloying method, which contains an element-selective leaching process in a metallic melt. The BMGMCs exhibit better mechanical properties, including higher fracture strength and larger plastic strain, than their monolithic glassy counterparts or similar BMGMCs by ex-situ dispersing or conventional arc-melting methods. The differences of Young's modulus between the dispersoids and the glassy matrix for these BMGMCs generate stress concentration at the interface, which is considered to suppress the propagation of the single main shear band and initiate multiple shear bands to accommodate the plastic deformation. Furthermore, the fine size of dispersoids for these BMGMCs, caused by low reaction temperature during Dealloying in the metallic melt, results in more interfaces with the matrix for further improvement of mechanical properties. In addition, the low reaction temperature can also contribute to less composition fluctuation of the matrix to maintain the glass-forming ability of itself, which can introduce no undesired phases to degrade the mechanical properties. This novel in-situ Dealloying method is believed to make a breakthrough in designing ductile BMGMCs with fine-sized secondary particles.
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optimizing niobium Dealloying with metallic melt to fabricate porous structure for electrolytic capacitors
Acta Materialia, 2015Co-Authors: Joung Wook Kim, Kunio Yubuta, Takeshi Wada, Masashi Tsuda, Sung Gyoo Kim, Hidemi KatoAbstract:Abstract The transition behavior from a Nb–Ni precursor to porous Nb and the coarsening of ligaments by a Dealloying reaction in a Mg melt are investigated. Based on these results, the kinetics of the reaction are discussed. When a Nb 25 Ni 75 (at.%) disk was immersed in a Mg melt, the Ni content decreased the most at the surface of the disk and less so towards the interior of the disk. In this disk, it was found that transition layers of body-centered cubic-Nb and Ni 6 Nb 7 formed. These transition layers grew, following a parabolic law, and the activation energy of such growth was close to values reported for the diffusion of solute atoms in liquids, suggesting that diffusion of Ni in the Mg melt was the rate-controlling process of the Dealloying reaction. The ligament size depended on time and temperature, following a power law with an exponent of 4, suggesting that surface diffusion was a key part of coarsening. These results agree well with those reported for conventional Dealloying in an aqueous solution. Based on the kinetics analyses, the Dealloying conditions were optimized to maximize the specific surface area, allowing a Nb electrolytic capacitor to be produced with a maximum mass-specific capacitance of 650,000 μFV g −1 , about three times larger than the highest value previously reported.
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zrcu based metallic glass matrix composites with ta dispersoid by in situ Dealloying method
Materials Transactions, 2013Co-Authors: Kunio Yubuta, Hidemi KatoAbstract:Zr48Cu36Al8Ag8-based bulk metallic glass matrix composites (BMGCs) with in situ dispersed Ta-rich particles surrounded by microcrystalline phases were fabricated successfully by both the conventional arc melting and a new Dealloying methods followed by copper mold casting. The microstructures and uniaxial compressive mechanical properties of as-cast ¤3-mm rods fabricated by the two different methods were compared. The size and dispersion of the Ta-rich particles and the mechanical properties of the as-cast BMGC rods obtained using the new Dealloying method were smaller, finer and better than those of the rods obtained using the conventional arc-melting method. Both the compressive and tensile plastic strain increased from almost 0% for monolithic Zr48Cu36Al8Ag8 bulk metallic glass to about 7 and 1%, respectively, for as-cast BMGC rods with 5at% Ta formed by the in situ Dealloying method. These in situ Ta-rich particles are considered as obstacles that restrict shear band propagation. An obvious work-hardening phenomenon can be observed in compression tests considerably due to work hardening of the Ta-rich particles restricted by the surrounding microcrystals. [doi:10.2320/matertrans.M2013102]
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nano to submicro porous β ti alloy prepared from Dealloying in a metallic melt
Scripta Materialia, 2011Co-Authors: Takeshi Wada, Kunio Yubuta, A D Setyawan, Hidemi KatoAbstract:Dealloying in metallic melts has been used to prepare pure base metals with an open-cell porous structure, an example of which is Ti. In this study, previously suggested strategies have been extended to prepare a porous multicomponent Ti alloy of non-equilibrium body-centered cubic phase at room temperature. Dealloying in metallic melts is a promising method for preparing functional nano- to submicro-porous alloys which cannot be prepared by conventional methods.
Akihisa Inoue - One of the best experts on this subject based on the ideXlab platform.
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Dealloying of Cu–Zr–Ti bulk metallic glass in hydrofluoric acid solution
2020Co-Authors: Hiroya Abe, Kazuyoshi Sato, Hiroshi Nishikawa, Tadashi Takemoto, Mikio Fukuhara, Akihisa InoueAbstract:The Dealloying behavior of Cu 60 Zr 30 Ti 10 metallic glass was investigated under free corrosion conditions using hydrofluoric acid (HF) solutions at room temperature. After immersing in HF solutions with various concentrations (0.05, 0.1, 0.5 and 1 M) for 300 s, color of all samples changed to be pinkish or peachy, which was ascribed to Cu based on the XRD patterns. According to the SEM-EDS study, HF immersion selectively leached the Zr and Ti elements, leaving Cu behind. Increasing the HF concentration increased the Dealloying rate. Moreover, the HF concentration strongly influenced the surface morphology of the resulting Cu
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formation of nano porous pd ni structure produced by Dealloying zr al ni pd base glassy alloys and their electrochemical properties
Journal of Non-crystalline Solids, 2019Co-Authors: E Shalaan, Akihisa Inoue, F Almarzouki, S Alheniti, A Y Obaid, S AlhashimiAbstract:Abstract In this work bulk metallic glasses of Zr55Al10Ni10Pd25, Zr50Al10Ni15Pd25 and Zr40Al10Ni25Pd25 in rod form s were prepared by copper mold casting technique. The glass-forming ability, thermal stability and corrosion behavior were examined with the aim to investigate the possibility of synthesizing nanoporous Pd(Ni) alloy structure which are exhibiting good electrochemical characteristics by the Dealloying treatment of Zr-Al-Ni-Pd bulk metallic glasses in acid solution. After chemical treatments, the glassy rods exhibit open, three-dimensional, and separated nanopore s structure. The size of nanopores (NP) is increased with increasing Zr content due to the enhanced Dealloying kinetics.
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nanoporous pdni bimetallic catalyst with enhanced electrocatalytic performances for electro oxidation and oxygen reduction reactions
Advanced Functional Materials, 2011Co-Authors: Luyang Chen, Takeshi Fujita, Akihiko Hirata, Akihisa Inoue, Wei Zhang, Mingwei ChenAbstract:A nanoporous PdNi (np-PdNi) bimetallic catalyst fabricated by electrochemically Dealloying a Pd20Ni80 alloy in an acid solution is reported. Residual Ni in the nanoporous alloy can be controlled by tuning Dealloying potentials and the electrocatalysis of the np-PdNi shows evident dependence on Ni concentrations. With ∼9 at.% Ni, the np-PdNi bimetallic catalyst presents superior electrocatalytic performances in methanol and formic acid electro-oxidation as well as oxygen reduction in comparison with commercial Pd/C and nanoporous Pd (np-Pd). The excellent electrocatalytic properties of the dealloyed np-PdNi bimetallic catalyst appear to arise from the combined effect of unique bicontinuous nanoporosity and bimetallic synergistic action.
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Dealloying by metallic melt
Materials Letters, 2011Co-Authors: Takeshi Wada, Kunio Yubuta, Akihisa Inoue, Hidemi KatoAbstract:Abstract Dealloying, which commonly involves corrosion processes in aqueous solutions, is a promising technique for preparing functional nanoporous metals. While this technique is ideal for preparing nanoporous noble metals such as of Au, it is not readily applicable to less-noble metals. Here, we propose a novel Dealloying method employing a metallic melt, instead of an aqueous solution, as the Dealloying liquid for a preparing of nanoporous metals. An atomic interaction among alloy components and metallic melt causes specific component to dissolve out from the alloy solid into the melt with self-organizing nanoporous structure by the remaining component. The Dealloying method can be applied for preparation of nanoporous less-noble metal such as of Ti for the development of functional materials such as fluid filters, gas absorption media, and biomaterials.
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Dealloying of cu zr ti bulk metallic glass in hydrofluoric acid solution
Materials Transactions, 2009Co-Authors: Hiroya Abe, Kazuyoshi Sato, Hiroshi Nishikawa, Tadashi Takemoto, Mikio Fukuhara, Akihisa InoueAbstract:metallic glass was investigated under free corrosion conditions using hydrofluoric acid (HF)solutions at room temperature. After immersing in HF solutions with various concentrations (0.05, 0.1, 0.5 and 1M) for 300s, color of allsamples changed to be pinkish or peachy, which was ascribed to Cu based on the XRD patterns. According to the SEM-EDS study, HFimmersion selectively leached the Zr and Ti elements, leaving Cu behind. Increasing the HF concentration increased the Dealloying rate.Moreover, the HF concentration strongly influenced the surface morphology of the resulting Cu. [doi:10.2320/matertrans.ME200823](Received December 15, 2008; Accepted March 18, 2009; Published May 13, 2009)Keywords: Dealloying, bulk metallic glass, Cu
