Bimetallic Structures Research Articles

Design of ultra-thin nanosheet bimetallic NiCo MOF with binary ligand via solvent-assisted ligand exchange (SALE) reaction for high performance supercapacitors

Metal-organic frameworks (MOFs) are attractive active materials for pseudocapacitor electrodes owing to their high porosities, large specific surface areas, and unique morphologies. MOFs comprising various metal ions have been studied to improve the electrochemical performance of pseudocapacitor electrodes. Bimetallic MOFs form more abundant redox sites owing to the synergetic effect of metal ions. In this work, we fabricated a NiCo-BDC ligand based bimetallic MOF (NiCo-BDC) directly on a Ni-foam substrate via a facile hydrothermal process. After the in-situ growth of NiCo-BDC, some of the 1,4-benzenedicarboxylic acid (BDC) ligands combined with metal ions on the surface and were exchanged to form a new ligand, 2-methylimidazole (MIM), through a solvent-assisted ligand exchange (SALE) reaction. Although the chemical composition of the MOF changed during the SALE reaction, the original nanosheet morphology and high specific surface area were maintained. The chemical state of the metal ions as well as the elemental composition were changed during the SALE reaction, resulting in an increase in the number of electrochemically active sites. Furthermore, this unique binary ligand system decreased the charge transfer resistance and facilitated redox reactions. The NiCo-BDC@MIM binary ligand based bimetallic MOF with a Ni/Co molar ratio of 2:3 (NiCo-23-BDC@MIM) exhibited a specific capacitance of 2252 F g−1 at 1 A g−1, which was considerably improved compared to that before the SALE reaction (1047 F g−1). Moreover, it not only showed a high energy density of 40.2 Wh kg−1 at a power density of 972 W kg−1, but maintained 73.2% of its initial capacitance and 100% Coulombic efficiency after 2000 cycles. These results demonstrate the potential of MOFs with binary ligand systems as well as bimetallic structures for application as energy storage materials.

Robust microwave absorption in silver-cobalt hollow microspheres with heterointerfaces and electric-magnetic synergism: Towards achieving lightweight and absorption-type microwave shielding composites

• Silver-cobalt hollow microspheres are successfully prepared. • Silver-cobalt hollow microspheres show excellent microwave absorption. • An effective absorption bandwidth of 8.40 GHz is achieved. • Silver-cobalt hollow microspheres endow absorption-type shielding materials. • Silver-cobalt hollow microspheres give the composites a low density. Lightweight and high-efficiency microwave shielding materials based on high absorption loss are the hotspot of current research. Herein, the silver-cobalt bimetallic hollow microspheres (Ag-Co-HM) with low reflection loss and broadband absorption efficiency were fabricated and then used to construct bimetallic hollow structures in polydimethylsiloxane/carbon nanotube composites (PDMS/CNT) to obtain the lightweight and absorption-type microwave shielding composites. The microwave absorption of Ag-Co-HM and the microwave shielding effectiveness (SE T ) of the PDMS/CNT/Ag-Co-HM composites was evaluated and discussed. The Ag-Co-HM with a molar ratio (Co/Ag) of 2.07 exhibited a low reflection loss as –46.6 dB at a thickness of 2.6 mm, and an effective absorption bandwidth of 8.40 GHz. The SE T of the PDMS/CNT composites was greatly enhanced by the incorporation of the Ag-Co-HM. Furthermore, the absorption coefficient ( A ) was also improved by adding the Ag-Co-HM and was much higher than the reflection coefficient. The composites exhibited absorption-type microwave shielding composites. For example, the average microwave SE T of 59.4 dB and A value of 0.78 are achieved in the PDMS/CNT/Ag-Co-HM composites containing 5 wt% CNTs and 10 wt% Ag-Co-HMs, which are much higher than the corresponding values of 33.7 dB and 0.63 in the PDMS/CNT composites with only 5 wt% CNTs. In addition, the hollow structure of Ag-Co-HM endows the PDMS/CNT/Ag-Co-HM composites to have a low density.

Aero-manufacture of nanobulges for an in-place anticoronaviral on air filters.

The interest in removing contagious viruses from indoor air using ventilation and filtration systems is increasing rapidly because people spend most of the day indoors. The development of an effective platform to regenerate the antiviral function of air filters during use and safe abrogation of used filters containing infectious viruses is a challenging task, because an on-demand safe-by-design manufacture system is essential for in-place antiviral coatings, but it has been rarely investigated. With these considerations, an electrically operable dispenser was prepared for decorating continuous ultrafine Fe-Zn, Fe-Ag, or Fe-Cu particles (<5nm) onto SiO2 nanobeads (ca. 130nm) to form nanobulges (i.e., nanoroughness for engaging coronavirus spikes) in the aerosol state for 3min direct deposition on the air filter surfaces. The resulting nanobulges were exposed to human coronaviruses (HCoV; surrogates of SARS-CoV-2) to assess antiviral function. The results were compared with similar-sized individual Zn, Ag, and Cu particles. The nanobulges exhibited comparable antiviral activity to Zn, Ag, and Cu particles while retaining biosafety in both in vitro and in vivo models because of the significantly smaller metallic fractions. This suggests that the bimetallic bulge structures generate reactive oxygen species and Fenton-mediated hydroxyl radicals for inactivating HCoV.

Bimetallic Structure of Ti6Al4V/IN718 with CuSi Interlayer for Wire-Arc Directed Energy Deposition Process

Bimetallic Structure of Ti6Al4V/IN718 with CuSi Interlayer for Wire-Arc Directed Energy Deposition Process

Microstructure and Mechanical Properties of Ti6Al4V/Inconel625 Bimetallic Structures Fabricated by Laser Melting Deposition

Microstructure and Mechanical Properties of Ti6Al4V/Inconel625 Bimetallic Structures Fabricated by Laser Melting Deposition

Electrocatalytic hydrogen evolution on metallic and bimetallic Pd–Co alloy nanoparticles

Increasing world energy demands and crises led to alternative energy production methods, such as fuel cells using hydrogen gas which is the half electrochemical reaction of water splitting process. Herein, we synthesize polyvinylpyrrolidone coated Pd, Co and PdxCo1-x (x: 0.5, 0.12, 0.23, 0.49, 0.55, 0.62) metallic and bimetallic nanoparticles (NPs) via polyol process alternative to Pt-based catalysts for hydrogen evolution reaction (HER). Detailed structural analyses of Pd, Co and PdxCo1-x NPs revealed that fcc-Pd, fcc/hcp-Co and fcc-PdCo NPs crystal structures, and the lattice parameters were calculated as 3.5358 Å for Co NPs and 3.9777 Å for Pd NPs. The average size confirmed below 9 nm via TEM imaging and XPS data confirmed the formation of a bimetallic PdCo structure. Although Pd catalyst is mostly responsible for HER process, Pd62Co38 catalysts reduced the onset potential to about 197 mV and provided greater current density. Although Ea values were slightly higher against the Pt/C (20 wt %) benchmark which is reported as 16 kJ mol−1, PdCo NPs provided considerably reduced activation energy (Ea) values compared to Pd/C catalyst of 31 kJ mol−1. The best onset potential was recorded for Pd62Co38 catalysts for HER activity which is 16 mV higher compared to commercially available Pt/C catalyst.

Highly stable nanoscale amorphous microstructure at steel-aluminum interface enabled by a new solid-state additive manufacturing method

In contrast to the established understanding that the interfacial microstructure of the bonded steel-aluminum (Fe-Al) structures coarsens significantly at elevated temperatures, this study shows that the special nanoscale interfacial layer of the Fe-Al bimetallic structures fabricated by a newly developed modified friction stir additive manufacturing (M-FSAM) exhibited extraordinary stability up to 500 °C. In tensile tests, the heat-treated Fe-Al samples failed within the aluminum alloys rather than along the Fe-Al interface. The heat treatment at 500 °C did not cause any observable microstructure change in the special nanoscale interfacial layer, which still consisted of a noncontinuous layer of Al-Fe-Si particles and a continuous Mg and O rich layer. The noncontinuous Al-Fe-Si particles were made of an amorphous-like microstructure and the Mg and O rich layer was comprised of an amorphous matrix interspersed with nanocrystalilne particles.

Large-Scale Preparation of Ultrathin Bimetallic Nickel Iron Sulfides Branch Nanoflake Arrays for Enhanced Hydrogen Evolution Reaction

Developing the large-scale preparation of non-noble metal catalysts with high performance is crucial for promoting the electrochemical production of hydrogen from water. In this work, a novel TiO2@FeNi2S4 (TiO2@FNS) branch nanoflake array on Ni foam can be prepared at a large scale (50 cm2) by combining an atomic-layer-deposited (ALD) TiO2 skeleton with one-step facile low-temperature (&lt;100 °C) sulfurization method. As-prepared TiO2@FNS arrays exhibit excellent hydrogen evolution reaction (HER) performance with an overpotential of 97 mV at 10 mA cm−2, superior to the FNS counterpart (without TiO2 coating) and other reported catalysts. The enhanced HER catalytic performance of TiO2@FNS is attributed to the increased specific surface area and improved structural stability due to the introduction of TiO2 coating. Moreover, theoretical calculations also show that the bimetallic NFS structure is more favorable to the dissociation of water molecule and the desorption of H than the monometallic Ni3S2 counterpart. With the combination of experimental results and theoretical calculations, this work has enlightened a new way of exploring high-efficient catalysts for HER.

Effect of Functionally Graded Material (FGM) Interlayer in Metal Additive Manufacturing of Inconel-Stainless Bimetallic Structure by Laser Melting Deposition (LMD) and Wire Arc Additive Manufacturing (WAAM).

Bimetallic structures manufactured by direct deposition have a defect due to the sudden change in the microstructure and properties of dissimilar metals. The laser metal deposition (LMD)-wire arc additive manufacturing (WAAM) process can alleviate the defect between two different materials by depositing the functionally graded material (FGM) layer, such as a thin intermediate layer using LMD and can be used to fabricate bimetallic structures at high deposition rates with relatively low costs using WAAM. In this study, the LMD-WAAM process was performed, and the microstructure of the fabricated bimetallic structure of IN625-SUS304L was investigated. The microstructure of the FGM zone of the LMD-WAAM sample was mainly fine equiaxed dendrite morphologies. In contrast, coarse columnar dendrite morphologies constituted the WAAM zone. The composition of the major alloying elements of the LMD-WAAM sample gradually changed with the height of the deposited layer. The microhardness of the LMD-WAAM sample tended to increase with an increasing Inconel content. In the case of the LMD-WAAM sample, the fracture occurred near the interface between 25% IN625 and 0% IN625; in the WAAM sample, the final fracture occurred in SUS304L near the interface. The tensile strength of the LMD-WAAM samples was inversely proportional to the laser power. The results showed that the LMD-WAAM samples had 8% higher tensile strength than the samples fabricated using only WAAM.

MXene-reinforced octahedral PtCu nanocages with boosted electrocatalytic performance towards endocrine disrupting pollutants sensing.

Rational tailoring of hollow and porous bimetallic structures with excellent electrocatalytic performance is appealing yet challenging. Further, combining independent bimetallic nanoparticles with flexible two-dimensional substrate by forming stable heterocomplex is still highly desired for electrocatalysis. Herein, hierarchical PtCu alloy octahedrons with hollow interiors and nanosheet-assembled nanoshells were synthesized by a facile and efficient chemical transformation strategy using Cu2O as sacrificial templates. Such octahedral PtCu nanocages displayed significantly enhanced electrocatalytic activity owing to their unique hollow and porous architectures which provided easy access for analytes to the catalyst surface. Thereafter, introduction of Ti3C2Tx MXene was realized via simple incubation of Ti3C2Tx in solution containing the 3-aminopropyltriethoxysilane-capped PtCu, and their electrostatic interaction guaranteed the firm adsorption of PtCu nanocages on Ti3C2Tx nanosheets. It turned out that the sensitivity of the hybrid sensor was remarkably improved for electrochemical monitoring of endocrine disrupting pollutants in water, exhibiting ultrawide linear ranges and sub-nanomole detection limits. The eminent electrode performance is attributed to the high specific area, fast electrochemical kinetics, decent electrical catalytic ability, and the synergistic effect between Pt, Cu, and MXene.

Structure-performance correlation on bimetallic catalysts for selective CO2 hydrogenation

The NiRu bimetallic structures act like a “H-atom valve” controlling the H2 spillover effect for highly selective CO2 hydrogenation.

Laser Additive Manufacturing of TC4/AlSi12 Bimetallic Structure via Nb Interlayer.

The TC4/AlSi12 bimetallic structures (BS) with Nb interlayer transition were fabricated by laser additive manufacturing (LAM). The results showed that the TC4/AlSi12 BS with Nb interlayer prepared with optimized process parameters can be divided into three regions (the TC4 region, Nb region and the AlSi12 region) and two interfaces (the TC4/Nb interface and the Nb/AlSi12 interface). The high melting point (Ti, Nb) solid solution formed in the Nb region acted as a diffusion barrier between the TC4 alloy and the AlSi12 alloy, thereby effectively inhibiting the formation of Ti-Al intermetallic compounds (IMCs). With the decrease of the laser output power for AlSi12 deposition, the NbAl3 IMC changed from layered to dispersed distribution, while γ-TiAl and Ti5Si3 IMC disappeared, thus significantly reducing the crack susceptibility of the BS deposited layer. The tensile strength of TC4/AlSi12 BS with Nb interlayer was about 128MPa, and the fracture was located near the Nb/AlSi12 interface.

Rationally Designed Bimetallic Co-Ni Sulfide Microspheres as High-Performance Battery-Type Electrode for Hybrid Supercapacitors.

Rational designing of electrode materials is of great interest for improving the performance of battery-type supercapacitors. The bimetallic NiCo2S4 (NCS) and CoNi2S4 (CNS) electrode materials have received much attention for supercapacitors due to their rich electrochemical characteristics. However, the comparative electrochemical performances of NCS and CNS electrodes were never studied for supercapacitor application. In this work, microsphere-like bimetallic NCS and CNS structures were synthesized via a facile one-step hydrothermal method by controlling the molar ratio of Ni and Co precursors. The physico-chemical results confirmed that microsphere-like structures with cubic spinel-type NCS and CNS materials were successfully fabricated by this method. When tested as the supercapacitor electrode materials, both NCS and CNS electrodes exhibited battery-type behavior in a three-electrode configuration with outstanding electrochemical performances such as specific capacity, rate performance and cycle stability. Impressively, the CNS electrode delivered a high specific capacity of 430.1 C g-1 at 1 A g-1, which is higher than 345.9 C g-1 of the NCS electrode. Furthermore, the NCS and CNS electrodes showed a decent cycling stability with 75.70 and 84.70% capacity retention after 10,000 cycles. Benefiting from the electrochemical advantage of CNS microspheres, we fabricated a hybrid supercapacitor (HSC) device based on CNS microspheres (positive electrode) and activated carbon (AC, negative electrode), which is named as CNS//AC. The assembled CNS//AC HSC device showed a large energy density of 41.98 Wh kg-1 at a power density of 800.04 W kg-1 and displayed a remarkable cycling stability with a capacity retention of 91.79% after 15,000 cycles. These excellent electrochemical performances demonstrate that both bimetallic NCS and CNS microspheres may provide potential electrode materials for high performance battery-type supercapacitors.

Highly Ordered and Thermally Stable FeRh Cluster Superlattice on Graphene for Low-Temperature Catalytic CO Oxidation.

We report on bimetallic FeRh clusters with a narrow size-distribution grown on graphene on Ir(111) as a carbon-supported model catalyst to promote low-temperature catalytic CO oxidation. By combining scanning tunneling microscopy with catalytic performance measurements, we reveal that Fe-Rh interfaces are active sites for oxygen activation and CO oxidation, especially at low temperatures. Rh core Fe shell clusters not only provide the active sites for the reaction, but also thermally stabilize surface Fe atoms towards coarsening compared with pure Fe clusters. Alternate isotope-labelled CO/O2 pulse experiments show opposite trends on preferential oxidation (PROX) performance because of surface hydroxyl species formation and competitive adsorption between CO and O2 . The present results introduce a general strategy to stabilize metallic clusters and to reveal the reaction mechanisms on bimetallic structures for low-temperature catalytic CO oxidation as well as preferential oxidation.

The elastic deformation process of bimetallic objects

In industrial problems linear elasticity simulation has been known to be successfully solved by the Finite Element Methods (FEMs). However, a mathematical model as well as a numerical solution program that can be applied to the deformation simulation of bimetallic materials are still the challenges in this research area. In this paper, we investigate a mathematical model for the linear elastic deformation of bimetallic structures. By reducing the linear elasticity problem to its weak form, we apply the continuous Galerkin approximation to obtain the discrete problem. The existence and the uniqueness of the solution of the weak problem are clearly demonstrated, ensuring the well-posedness of the problem. In addition, the numerical simulations with bimetallic materials have been built on Freefem[Formula: see text] software that illustrate the efficiency and reliability of the numerical method.

Interface Characterization of Bimetallic Ti-6Al-4V/Ti2AlNb Structures Prepared by Selective Laser Melting.

Additive Manufacturing (AM) of multimaterial components is a promising way of fabricating parts with improved functional properties. It allows for the combination of materials with different properties into a single component. The Ti2AlNb-based intermetallic alloy provides high temperature strength, while the Ti-6Al-4V (Ti64) alloy has good fracture toughness, ductility, and a relatively low cost. A combination of these alloys into a single component can be used to produce advanced multimaterial parts. In this work, Ti2AlNb/Ti-6Al-4V bimetallic structures were fabricated from pre-alloyed powders using the Selective Laser Melting (SLM) process. The effects of high-temperature substrate preheating, post-processing by annealing, and hot isostatic pressing on defect formation, the microstructural evolution of the interface area, and the mechanical properties of the bimetallic samples were investigated. High-temperature substrate preheating during the SLM process was necessary to prevent reheat cracking of the Ti2AlNb part, while annealing and hot isostatic pressing post-processing improved the chemical and microstructural homogeneity of the transition zone and enhanced the tensile properties of the bimetallic structure.

Near-Unity Electrochemical CO2 to CO Conversion over Sn-Doped Copper Oxide Nanoparticles.

Bimetallic electrocatalysts have emerged as a viable strategy to tune the electrocatalytic CO2 reduction reaction (eCO2RR) for the selective production of valuable base chemicals and fuels. However, obtaining high product selectivity and catalyst stability remain challenging, which hinders the practical application of eCO2RR. In this work, it was found that a small doping concentration of tin (Sn) in copper oxide (CuO) has profound influence on the catalytic performance, boosting the Faradaic efficiency (FE) up to 98% for carbon monoxide (CO) at -0.75 V versus RHE, with prolonged stable performance (FE > 90%) for up to 15 h. Through a combination of ex situ and in situ characterization techniques, the in situ activation and reaction mechanism of the electrocatalyst at work was elucidated. In situ Raman spectroscopy measurements revealed that the binding energy of the crucial adsorbed *CO intermediate was lowered through Sn doping, thereby favoring gaseous CO desorption. This observation was confirmed by density functional theory, which further indicated that hydrogen adsorption and subsequent hydrogen evolution were hampered on the Sn-doped electrocatalysts, resulting in boosted CO formation. It was found that the pristine electrocatalysts consisted of CuO nanoparticles decorated with SnO2 domains, as characterized by ex situ high-resolution scanning transmission electron microscopy and X-ray photoelectron spectroscopy measurements. These pristine nanoparticles were subsequently in situ converted into a catalytically active bimetallic Sn-doped Cu phase. Our work sheds light on the intimate relationship between the bimetallic structure and catalytic behavior, resulting in stable and selective oxide-derived Sn-doped Cu electrocatalysts.

Ta/Cu transition region in TC4/Inconel718 bimetallic structure fabricated by laser deposition manufacturing

The bimetallic structure formed by TC4 and Inconel718 has broad potential applications in aerospace. Based on the laser deposition manufacturing technique, a TC4/Inconel718 bimetallic structure was fabricated via the Ta/Cu transition layer. The test results indicated that a Ta/Cu transition region with a width of 475.0 μm was formed. The microstructure of the transition region changed from a reticular to a rod structure, and the corresponding phase compositions were β-Ta + Ti2Cu + TiCu and TiCu+γ-Cu + Cr2Ta. Owing to the formation of Ti–Cu and Cr–Ta phases in the transition region, the Vickers hardness reached 444.0 HV. The ultimate tensile strength was 280 MPa, and the fracture morphology presented a quasi-cleavage fracture, which occurred in the Ta/Cu transition region where Ti–Cu brittle phases exist.

Nonhydrolytic sol-gel in-situ synthesis of high performance MgAl2O4/C adsorbent materials

MgAl2O4/C composite was prepared via a facile low-temperature non-hydrolytic sol-gel (NHSG) route, using Mg powder, Al wire and isopropanol as raw materials. The influence of types of magnesium source and heat treatment temperature on the synthesis and adsorption properties were investigated, and the adsorption mechanism was also studied. The results showed that the amorphous MgAl2O4 formed at < 600 °C, and it crystallized at 700 °C. No impurity phase appeared in the samples calcined at 700–1300 °C, which was attributed to MgAl2O4 crystallized directly from Mg(Al(OiPr)4)2. The uniform-doped carbon in MgAl2O4/C composites came in-situ from the organic groups in Mg(Al(OiPr)4)2. MgAl2O4/C showed a superior adsorption capacity for Congo red (CR). The bimetallic alkoxides structure was favorable for high adsorption property, and the adsorption property of amorphous MgAl2O4/C was significantly superior to that of its crystalline counterpart. The adsorption kinetics data was fitted with the pseudo-second-order model, while the Langmuir isotherm model could well descript the adsorption isotherm behavior, and the maximum adsorption capacity for CR was 5690 mg/g. The high adsorption capacity was attributed to the Lewis acid-base reaction and the electrostatic interactions between the anionic dye CR and MgAl2O4/C surface as well as the in-situ carbon, and amorphous state.

W7Ni3Fe-Ti6Al4V bimetallic layered structures via directed energy deposition

ABSTRACT Bimetallic structures of Ti6Al4V-W7Ni3Fe were fabricated via directed energy deposition (DED)-based additive manufacturing (AM). Our research demonstrates the ability of DED-based AM to control Ti6Al4V-W7Ni3Fe bimetallic structures with tailorable mechanical and thermal performance. The thermal conductivity of the bimetallic structures was three times higher than Ti6Al4V at 300°C. Uniaxial compression along the transverse direction showed a failure strain of 63% compared to pure Ti6Al4V, while the longitudinal direction showed a failure strain of only 37% of Ti6Al4V. Variable hardness was observed throughout the sample due to diffusion of elements and intermetallic phase formations. Scanning electron microscopy revealed that the interfaces in the as-printed samples were crack-free with elemental gradients.