Bimetallic Structures Research Articles

Large area friction stir additive manufacturing of intermetallic-free aluminum-steel bimetallic components through interfacial amorphization

Dissimilar metal additive manufacturing of aluminum-steel (AlFe) components offers many opportunities for achieving effective structural lightweighting and multi-functionalities. However, just like direct welding of aluminum alloys to steels, the formation of detrimental intermetallic compounds (IMCs) at the AlFe bimetallic interface has been seen as the major challenge. One recent development in understanding nanoscale shear localization induced alloy amorphization at the AlFe interface has provided a physical basis for developing a modified friction stir additive manufacturing (FSAM) process. This study shows that the modified FSAM is an effective solution for mitigating detrimental IMCs through the development of the nanoscale amorphous phase between the deposited aluminum alloy and steel substrate. The results show that the formation of the nanoscale amorphous metal at the AlFe bimetallic interface leads to the development of ductile fracture features within the aluminum layer in the mechanical tests. Compared to the existing FSAM, the modified FSAM enables a more robust and cost-effective manufacture of AlFe bimetallic structures without introducing detrimental IMCs.

Characterization of copper & stainless steel interface produced by electron beam powder bed fusion

Unalloyed copper (Cu) powder was deposited and melted onto a pre-existing stainless steel substrate using electron beam powder bed fusion (EB-PBF) additive manufacturing (AM) to form dense, bimetallic structures. The AM fabricated Cu was fully dense, and with strength properties consistent with recent reports on EB-PBF of Cu. The overall bimetallic structures exhibited total elongation of 25–35%, and was dominated by plastic deformation in the Cu region. Tensile failures were typically observed in the Cu portion of the bimetallic bodies demonstrating that the interface was not the source of mechanical failure. The interface region of the bimetallics contained areas of liquid phase separated Cu and Iron (Fe) + Chromium (Cr) rich regions resulting from a metastable miscibility gap in the Cu and Fe phase diagram. Metallurgical and mechanical examinations of the bimetallic structures showed the interface region transitions from an Fe rich mixture to a Cu rich mixture within a few AM layers.

Shell thickness-controlled synthesis of Au@Ag core–shell nanorods structure for contaminants sensing by SERS

The accessibility of contaminants detection methods is urgently required for environmental and food safety control. In this report, we developed the Au@Ag core–shell nanorod structures for contaminants sensing by surface-enhanced Raman spectroscopy (SERS). The silver shell thickness and the corresponding plasmon wavelength of Au@Ag core–shell nanorods were tuned by changing the coating time and the silver precursor amount. Moreover, these structures exhibit ultra-sensitive detection ability for Nile blue A dye and Fenobucarb pesticide sensing by SERS. Interestingly, the highest Raman enhancement factor is obtained for the Au@Ag core–shell sample with a minimal silver shell thickness leaded by the optimal enhancement of the electromagnetic field of bimetallic structures. Hence, our report demonstrates that the combination of unique features of two plasmonic metals into core–shell structures promises potential applicability in SERS-based analysis.

Incorporating Sulfur Atoms into Palladium Catalysts by Reactive Metal–Support Interaction for Selective Hydrogenation

Incorporating Sulfur Atoms into Palladium Catalysts by Reactive Metal–Support Interaction for Selective Hydrogenation

Electrocatalytic Reaction Driven Flow: Role of pH in Flow Reversal.

Immobilized bimetallic structures generate fluid flow during electrocatalytic reactions with hydrogen peroxide, which is typically driven from the anodic metal to the cathodic metal similar to an electroosmotic flow. However, under low reactive regimes, the generated flow becomes fully reversed, which cannot be explained by the classical electroosmotic theory. This work aims at unraveling the origin and dynamics of this flow hysteresis through a combined experimental and numerical approach. The key electrocatalytic parameters that contribute to flow reversal are analyzed experimentally and numerically under low reactive regimes induced by bulk pH variations. The proton gradient that initiates chemomechanical actuation is probed with the use of fluorescence lifetime imaging. The fluid flow dynamics under reactive regimes are visualized by the use of particle tracking. Our numerical simulations elucidate the role of pH variations and additional ionic species (counterions) toward flow reversal. The combination of these techniques highlights the interplay between electrocatalytic and electrokinetic phenomena on the occurrence of flow reversal.

Effect of ultrasonic peening treatment on microstructure and properties of CMT additive-manufactured Ti6Al4V/Al6.21Cu dissimilar alloys with Nb interlayer

The layer-by-layer ultrasonic peening treatment (UPT) was utilized to refine the coarse microstructure and decrease the pore number and size in the Al alloy of the Ti6Al4V/Al6.21Cu bimetallic structure with Nb interlayer manufactured by cold metal transfer additive manufacturing. After UPT, the pore in the deposited Al layer was compressed. Grains were compressed and refined significantly in the transition layer under the effect of UPT. The Nb interlayer still acted as the diffusion barrier and impeded the formation of harmful Ti-Al intermetallic compounds after UPT. The mean ultimate tensile strength of the bimetallic structure with Nb interlayer after UPT was 164.5 MPa, and increased by 36.1% compared to that of the bimetallic structure without UPT. The fracture occurred at brittle Al3Nb reaction layer for all samples.

Nickel-gold bimetallic nanostructures with the improved electrochemical performance for non-enzymatic glucose determination

Bimetallic nanostructured electrodes are promising candidates for non-enzymatic glucose detection due to their excellent selectivity and high sensitivity. In this work, a bimetallic Ni/Au non-enzymatic glucose sensor was developed by the electrodeposition of nickel nanostructures on Au nanoparticles (NP). Physical vapor deposition followed by thermal annealing was used for the growth of seeding Au (NP) on fluorine doped tin oxide (FTO) substrates. The electrochemical growth of Ni nanostructures on the Au-seeded substrates led to enhanced electrochemical responses from the modified electrodes. Cyclic voltammetry results showed considerable improvement of the electrocatalytic activity of the Ni/Au bimetallic structure in comparison to monolithic Ni and Au structures due to the synergistic effect. The sensor showed two linear ranges of 5 μM–3.5 mM and 3.5–7 mM for glucose detection with the sensitivity of 893 (μA mM−1 cm−2). The low detection limit of 0.7 μM and the fast response time of 5 s was achieved. The selectivity, reproducibility and accuracy of the fabricated sensor in determination of human serum glucose suggest its potential for large-scale production as commercial non-enzymatic glucose detection.

Effect of deposition layer on microstructure of Ti–Al bimetallic structures fabricated by wire and arc additive manufacturing

Ti–Al bimetallic components present extensive application prospects and have attracted considerable attention owing to their low cost and light weight. In this study, Ti–Al bimetallic structures with one, two, and five Al layers were fabricated via wire and arc additive manufacturing by cold metal transfer welding. During the deposition process of the first Al layer, the matrix was TiAl, and a needle-shaped Ti3Al was formed. Subsequently, from the second deposition layer of the Al alloy, however, TiAl3 was formed, and it exhibited an exceptional morphology with two types of structures: coarse columnar grain structures with identical growth orientation, and long strip-like structures with a random distribution. The formation order of Ti–Al intermetallic compounds was TiAl3, TiAl, and Ti3Al.

In Situ Fabrication of Nickel-Iron Oxalate Catalysts for Electrochemical Water Oxidation at High Current Densities.

Ni-Fe-based electrode materials are promising candidates for the oxygen evolution reaction (OER). The synergy between Fe and Ni atoms is crucial in modulating the electronic structure of the active site to enhance electrochemical performance. Herein, a simple chemical immersion technique was used to grow Ni-Fe oxalate nanowires directly on a porous nickel foam substrate. The as-prepared Ni-Fe oxalate electrode exhibited an excellent electrochemical performance of the OER with ultralow overpotentials of 210 and 230 mV to reach 50 and 100 mA cm-2 current densities, respectively, in a 1 M KOH aqueous solution. The excellent OER performance of this Ni-Fe oxalate electrode can be attributed to its bimetallic composition and nanowire structure, which leads to an efficient ionic diffusion, high electronic conductivity, and fast electron transfer. The overall analysis indicates a suitable approach for designing electrocatalysts applicable in energy conversion.

Rational design of PdCu nanoparticles supported on a templated Ni foam: The cooperation effect of morphology and composition for electrocatalytic oxidation of ethanol

In this study, with the goal of the production of a cost effective anode for ethanol oxidation, the surface of Ni foam is covered with templated PdCu nanoparticles via the galvanic replacement reaction. The use of the templating method results in the uniform formation of the spongiform bimetallic structure on the surface of Ni foam. The role of the templating method in the synthesis of a stable catalyst towards dealloying process is considered by the electrochemical pretreatment of t-PdCu/NF and PdCu/NF in H2SO4 solution. The excellent stability of t-PdCu/NF for ethanol oxidation in the alkaline media is proved by the achievement in the steady state after 14 s with survival of 60% current density and 12% increase in the current density after 100 consecutive cycles. The electrochemical impedance spectroscopy gives evidence that the templating method and elemental composition cooperate in the improvement of the reactant diffusion and charge transfer on the surface of the synthesized catalyst. Finally, the mechanism of the ethanol oxidation and the effect of morphology and composition on this mechanism are studied using the cyclic voltammetry and chronoamperometry methods.

Bimetallic Oxygen Evolution Electrocatalysts: Relationships of Structure, Activity and Stability

Acidic oxygen evolution reaction (OER) electrocatalysts that have high activity, extended durability, and lower costs are needed to further the development of proton-exchange membrane (PEM) electrolyzers. Within acidic OER catalysts, stability remains a critically important but significantly less studied factor relative to activity. Our work involves investigating relationships between structure, activity, and stability within bimetallic acidic OER electrocatalysts. Bimetallic catalysts that interact iridium or ruthenium with non-noble metals provide an approach to lower the amount of noble metal and increase the OER activity and stability. Non-noble metals have different electronegativities and atomic radii compared to iridium and ruthenium which alters the surface atomic and electronic structure and influences both OER activity and metal dissolution. Our prior work showed that the inclusion of nickel or cobalt within iridium-metal two-dimensional nanoframes resulted in differences in the surface structure that significantly changed the OER activity and electrochemical degradation.1,2 Bimetallic structures can undergo very different degradation processes compared to monometallic structures, as shown by our prior study.1 Our recent work has explored the effects of interacting non-noble metals within ruthenium oxide on the structure, OER activity and stability. Nanostructured bimetallic oxides were synthesized using solution-phase chemistry and through utilizing various temperature/atmosphere treatments. The synthesis and processing conditions significantly affected the resulting material’s structure and properties. The materials’ composition, morphology and structure are probed using energy dispersive X-ray spectroscopy, scanning electron microscopy, nitrogen physisorption, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Rotating disk electrode measurements are used to evaluate the electrochemical oxygen evolution activity and stability of the bimetallic oxides which were compared to baseline OER catalysts. Metal dissolution that occurs during accelerated durability testing is evaluated using inductively coupled mass spectroscopy measurements. Our recent efforts towards understanding the relationships between structure, activity, and stability within nanostructured bimetallic oxides/hydroxides will be presented. References Ying, Y.; Godínez-Salomón, J.F.; Moreno, A.; Lartundo-Rojas, L.; Meyer, B.; Damin, C.A.; Rhodes, C.P. Hydrous Cobalt-Iridium Oxide Two-Dimensional Nanoframes: Insights into Activity and Stability of Bimetallic Acidic Oxygen Evolution Electrocatalysts. Nanoscale Advances 2021, 3, 1976-1996. DOI: 10.1039/D0NA00912A Godínez-Salomón, F.; Albiter, L.; Alia, S.M.; Pivovar, B.S.; Camacho-Forero, L.E.; Balbuena, P.B.; Mendoza-Cruz, R.; Arellano-Jimenez, M.J.; Rhodes, C.P. Self-Supported Hydrous Iridium-Nickel Oxide Two-dimensional Nanoframes for High Activity Oxygen Evolution Electrocatalysts. ACS Catalysis 2018, 8, 10498-10520. DOI: 10.1021/acscatal.8b02171

Bimetallic polyphenol networks structure modified polyethersulfone membrane with hydrophilic and anti-fouling properties based on reverse thermally induced phase separation method

In order to improve the hydrophobicity of traditional polyethersulfone (PES) membranes, this study combined the reverse thermally induced phase separation (RTIPS) method with the constructed bimetallic polyphenol networks (BMPNs) to prepare hydrophilic anti-fouling membranes. As for BMPNs, tannic acid (TA) was served as an intermediate to construct both the inner and surface hydrophilic layers of the PES membranes. On the one hand, etching Zeolitic imidazolate framework-8 (EZIF-8) with synergistic etching and surface functionalization via TA not only retained the high pore structure of MOFs, but also had good hydrophilicity. On the other hand, the MPN hydrophilic layer was formed on the membrane surface by the combination of TA from the surface of EZIF-8 and iron ions in the coagulation bath. Therefore, BMPNs structure penetrated the interior and surface of PES membrane, which greatly improved the hydrophilic properties. In addition, the membrane with porous surfaces and spongy cross sections by RTIPS method improved the permeability and mechanical properties of the membrane by several times compared with the membrane via NIPS method. The obtained membranes in this experiment showed excellent permeability, just like pure water flux reached 1662.16 L/m2 h, while BSA rejection rate remained at 92.78%. Compared with pure membrane, it showed a better flux recovery rate (FRR = 83.33%) after cleaning, and the reduction of irreversible (Rir = 16.67%) fouling indexes indicated that the adsorption of protein was inhibited. These results suggested that the hydrophilic anti-fouling PES membranes prepared by this method possessed great application potential in membrane separation technology.

Metallurgical Assessment of Additive Manufactured Nickel Aluminum Bronze-316L Stainless Steel Bimetallic Structure: Effect of Deposit Geometry on the Interfacial Characteristics and Cracking

Metallurgical Assessment of Additive Manufactured Nickel Aluminum Bronze-316L Stainless Steel Bimetallic Structure: Effect of Deposit Geometry on the Interfacial Characteristics and Cracking

High-throughput computational-experimental screening protocol for the discovery of bimetallic catalysts

To accelerate the discovery of materials through computations and experiments, a well-established protocol closely bridging these methods is required. We introduce a high-throughput screening protocol for the discovery of bimetallic catalysts that replace palladium (Pd), where the similarities in the electronic density of states patterns were employed as a screening descriptor. Using first-principles calculations, we screened 4350 bimetallic alloy structures and proposed eight candidates expected to have catalytic performance comparable to that of Pd. Our experiments demonstrate that four bimetallic catalysts indeed exhibit catalytic properties comparable to those of Pd. Moreover, we discover a bimetallic (Ni-Pt) catalyst that has not yet been reported for H2O2 direct synthesis. In particular, Ni61Pt39 outperforms the prototypical Pd catalyst for the chemical reaction and exhibits a 9.5-fold enhancement in cost-normalized productivity. This protocol provides an opportunity for the catalyst discovery for the replacement or reduction in the use of the platinum-group metals.

Effect of Deposition Sequence on Microstructure and Properties of 316L and Inconel 625 Bimetallic Structure by Wire Arc Additive Manufacturing

Effect of Deposition Sequence on Microstructure and Properties of 316L and Inconel 625 Bimetallic Structure by Wire Arc Additive Manufacturing

Experimental Characterization and Microstructural Evaluation of Silicon Bronze-Alloy Steel Bimetallic Structures by Additive Manufacturing

Experimental Characterization and Microstructural Evaluation of Silicon Bronze-Alloy Steel Bimetallic Structures by Additive Manufacturing

Microstructure and mechanical properties of NiTi-SS bimetallic structures built using Wire Arc Additive Manufacturing

Dissimilar joining of Nickel-titanium (NiTi) alloy with other metallic alloys can be used to widen the applications of NiTi for developing artificial bones and joints, guidewires, and stents. This paper presents the microstructure and mechanical properties of Wire Arc Additive Manufactured NiTi-SS bimetallic structures for the first time. Defect-free deposit with a smooth transition in the composition across the joint is observed. NiTi shows a dendritic microstructure and TiCr2, TiNi3 and FeNi intermetallic phases are observed at the interface that imparts reasonable mechanical properties. The interface showed an average hardnes of 400 HV and the ultimate compressive strength is observed to be 570 MPa, with brittle fracture due to the presence of brittle intermetallics.

Fiber laser welding of Ti–6Al–4V to Inconel 718 bimetallic structure via Cu/Ta multi-interlayer

In current work, we have used fiber laser welding (FLW) technology to manufacturing the Ti–6Al–4V (TC4) and Inconel 718 (IN718) bimetallic structure and to prevent the formation of brittle phases via Cu/Ta multi-interlayer. The results of this study showed that Cu/Ta multi-interlayer was very effective in preventing the formation of continuous brittle intermetallic layers of Ti–Ni and Ti–Cu. The good metallurgical bonds were presented at these interfaces between TC4 and IN718. As a result, the joints with gradational structure, i.e. TC4| (α+β Ti, Ta)ss| (β Ti, Ta)ss| Ta(s, s)+ (Cu(s, s)+ Ta(s, s)+ Ti3Ni4)| Cu(s, s)+ (Cu(s, s)+ Ta(s, s))| Ni(Ta, Fe, Cr)ss| IN718 can be formed, which can contribute high tensile strength of joints with the value of 396 MPa.

Focused ion beam fabrication of Janus bimetallic cylinders acting as drift tube Zernike phase plates for electron microscopy

Modern nanotechnology techniques offer new opportunities for fabricating structures and devices at the micrometer and sub-micrometer level. Here, we use focused ion beam techniques to realize micrometer-sized Janus bimetallic cylinders acting as drift tube devices, which are able to impart a controlled phase shift to an electron wave. The phase shift results from the presence of contact potentials in the cylinders, in a similar manner to the electrostatic Aharonov–Bohm effect in bimetallic wires. We use electron Fraunhofer interference to demonstrate that such bimetallic structures introduce phase shifts that can be tuned to desired values by varying the dimensions of the pillars, in particular their heights. Such devices are promising for electron beam shaping and for the realization of electrostatic Zernike phase plates (i.e., devices that are able to impart a constant phase shift between an unscattered and a scattered electron wave) in electron microscopy, in particular, cryo-electron microscopy.

Forming feasibility and interface microstructure of Al/Cu bimetallic structure fabricated by laser powder bed fusion

PurposeThe purpose of this paper is to analyze and investigate heat accumulation caused by temperature changes and interface microstructure effected by element diffusion.Design/methodology/approachAl/Cu bimetallic structure is initially manufactured through laser powder bed fusion process. To minimize trial and error, finite element modeling is adopted to simulate temperature changes on the Al-based and Cu-based substrate.FindingsThe results show that forming pure copper on Al-based substrate can guarantee heat accumulation, providing enough energy for subsequent building. The instantaneous laser energy promotes increase of diffusion activation energy, resulting in the formation of transition zone derived from interdiffusion between Al and Cu atoms. The interface with a thickness of about 22 µm dominated by Kirkendall effect moves towards Al-rich side. The interface microstructure is mainly composed of a-Al, a-Cu and CuAl2 phase.Originality/valueThe bonding mechanism of Al/Cu interface is atom diffusion-induced chemical reaction. The theoretical basis provides guidance for structural design and production application.