Nanoscale Alloy Research Articles

Recycling the spent cobalt-based perovskites for the high-active oxygen catalysts in zinc-air batteries

Cobalt (Co) is widely used in energy storage and conversion devices, although its content on our planet is not adequate. Therefore, recycling Co from the spent Co-enriched materials is indispensable. Co-based perovskites, which contain abundant Co, are extensively utilized in solid oxide fuel cells, three-way catalysts, and oxygen-permeable membranes, and the recovery of Co from the spent Co-based perovskites is necessary to meet the long-term requirement of Co. In this work, a facile and universal thermal reduction method (750 °C and N2 atmosphere) is employed to convert the spent cobalt-based perovskites into high-performance bifunctional oxygen catalysts for zinc-air batteries (ZABs), achieving high-efficient Co recovery and re-utilization. At high temperatures, melamine and dopamine hydrochloride are transformed into carbon nanotubes, C3N4 and reducing gases (such as NH3 and H2). Simultaneously, the metal elements in the spent Co-based perovskites (SrNb0.1Co0.7Fe0.2O3,SNCF) are converted into nano-scale alloy particles and metal nitrides. Then, the phase structures, micromorphology, and element valences of the obtained multiphase oxygen catalyst (SNCF–Ni-PM) are characterized by X-ray diffraction, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemical properties, including oxygen catalytic activities and stability, of SNCF-Ni-PM are measured by linear sweep voltammetry, chronopotentiometry, chronoamperometry, and cyclic voltammetry methods. Considering the practical applications, the aqueous and solid-state ZABs are assembled and measured. The results demonstrate that the multiphase SNCF-Ni-PM mainly includes carbon nanotubes, C3N4 nanosheets, and FeNiN or CoFe nanoparticles. Moreover, SNCF-Ni-PM exhibits excellent bifunctional oxygen catalytic activity, with an oxygen evolution reaction (OER) potential at 10 mA cm−2 of 1.51 V and an oxygen reduction reaction (ORR) half-wave potential of 0.77 V, outperforming most of the reported oxygen catalysts. Using SNCF-Ni-PM, the aqueous and solid-state ZABs can achieve high power densities of 295.9 and 228.4 mW cm−2, respectively, being superior to most ZABs. In addition, the aqueous ZAB with SNCF-Ni-PM can operate stably for 300 h with a slight degradation. This work provides a feasible method for effectively recycling Co from the spent Co-based perovskites.

Terahertz characterization of nano-scale high-entropy alloy films and their high-contrast grating applications

We investigated the optical constants of thin films of the Nb25Mo25Ta25W25 alloy, which belongs to high-entropy alloys (HEAs), with a transmission terahertz (THz) measurement system and discovered that the refractive index, extinction coefficient, and conductivity of the HEA thin film measured in the range of 0.3–1.0 THz all increased as the thickness of the thin film increased (the thickness was maintained in the range between 10 and 40 nm). According to the experimental results, this alloy with a high refractive index is suitable for producing high-contrast gratings (HCGs). The principle behind achieving a high contrast with a high-reflection HEA grating is to harness the confined plasmonic energy within the grating, thereby enhancing the localized plasmonic energy within the grating. This work elucidates that we can not only fabricate THz components by controlling the thickness of the thin film but also utilize the high refractive index of this material to create HCGs.

Probing the multi-disordered nanoscale alloy at the interface of lateral heterostructure of MoS2–WS2

Abstract Transition metal dichalcogenide (TMDs) heterostructure, particularly the lateral heterostructure of two different TMDs, is gaining attention as ultrathin photonic devices based on the charge transfer (CT) excitons generated at the junction. However, the characteristics of the interface of the lateral heterostructure, determining the electronic band structure and alignment at the heterojunction region, have rarely been studied due to the limited spatial resolution of nondestructive analysis systems. In this study, we investigated the confined phonons resulting from the phonon-disorder scattering process involving multiple disorders at the lateral heterostructure interface of MoS2–WS2 to prove the consequences of disorder-mediated deformation in the band structure. Moreover, we directly observed variations in the metal composition of the multi-disordered nanoscale alloy Mo1−x W x S2, consisting of atomic vacancies, crystal edges, and distinct nanocrystallites. Our findings through tip-enhanced Raman spectroscopy (TERS) imply that a tens of nanometer area of continuous TMDs alloy forms the multi-disordered interface of the lateral heterostructure. The results of this study could present the way for the evaluation of the TMDs lateral heterostructure for excitonic applications.

Programmable Synthesis of High-Entropy Nanoalloys for Efficient Ethanol Oxidation Reaction.

Controllable synthesis of nanoscale high-entropy alloys (HEAs) with specific morphologies and tunable compositions is crucial for exploring advanced catalysts. The present strategies either have great difficulties to tailor the morphology of nanoscale HEAs or suffer from narrow elemental distributions and insufficient generality. To overcome the limitations of these strategies, here we report a robust template-directed synthesis to programmatically fabricate nanoscale HEAs with controllable compositions and structures via independently controlling the morphology and composition of HEA. As a proof of concept, 12 kinds of nanoscale HEAs with controllable morphologies of zero-dimension (0D) nanoparticles, 1D nanowires, 2D ultrathin nanorings (UNRs), 3D nanodendrites, and vast elemental compositions combining five or more of Pd/Pt/Ag/Cu/Fe/Co/Ni/Pb/Bi/Sn/Sb/Ge are synthesized. Moreover, the as-prepared HEA-PdPtCuPbBiUNRs/C demonstrates the state-of-the-art electrocatalytic performance for the ethanol oxidation reaction, with 25.6- and 16.3-fold improvements in mass activity, relative to commercial Pd/C and Pt/C catalysts, respectively, as well as greatly enhanced durability. This work provides a myriad of nanoscale HEAs and a general synthetic strategy, which are expected to have broad impacts for the fields of catalysis, sensing, biomedicine, and even beyond.

Combustion Synthesis of Magnetic Nanomaterials for Biomedical Applications.

Combustion synthesis is a green, energy-saving approach that permits an easy scale-up and continuous technologies. This process allows for synthesizing various nanoscale materials, including oxides, nitrides, sulfides, metals, and alloys. In this work, we critically review the reported results on the combustion synthesis of magnetic nanoparticles, focusing on their properties related to different bio-applications. We also analyze challenges and suggest specific directions of research, which lead to the improvement of the properties and stability of fabricated materials.

Simulation of cathode spots crater formation on electrodes with micro-scale and nano-scale alloy materials in a vacuum arc

In the field of vacuum interrupting, an important research is to improve the erosion resistance properties of contacts. In this paper, a two-dimensional axisymmetric swirl model based on basic parameters has been proposed to describe the formation and development of cathode spots of micro-scale alloy and nano-scale alloy electrode in a vacuum arc. In this model, the peak ion density of the plasma cloud, the mean charge state in near-cathode region, the electron temperature, and the near-cathode voltage drop are adopted as external parameters. Ions and electrons originating from the plasma cloud, thermo-field (T-F) emission, vaporization of metal atoms, backing ions and back-diffused electrons are all taken into consideration. The morphology and temperature of cathode spots crater and the liquid metal velocity of pure copper electrode (Cu), copper-chromium (Cu-Cr) electrode and tungsten-copper (W-Cu) electrode under the conditions of micro-scale grains and nano-scale grains are compared, respectively. Simulation results show that the cathode spot crater of the Cu-Cr electrode is smaller than that of the pure copper electrode. Moreover, it can hold more current and inhibit the formation of new cathode spots nearby. Cathode spots appearing on tungsten grains are smaller in size and have a lower probability of forming liquid metal droplets than Cu-Cr electrodes. Contacts made of nano-scale grain alloys have stronger erosion resistance properties than that of micro-scale alloy contacts and can reduce the maximum temperature of the cathode. The simulation results are in good agreement with other researchers’ results.

Cobalt-nickel alloy nanoparticles surface-functionalized with cyclodextrin for delivering 5-fluorouracil

Magnetic alloys represent a unique class of nanomaterials, suitable for application in magnetic field-guided anticancer drug transport. Herein, we report nanoscale cobalt-nickel alloy nanoparticles surface modified with a biocompatible β-cyclodextrin citrate. The reaction of cyclodextrin with citric acid forms the β-cyclodextrin citrate. The citrate groups allow the functionalization of the nanoparticles by adsorbing getting adsorbed onto their surface. It keeps the cyclodextrin open for accommodating drug molecules. The surface-modified nanoparticles were characterized by XRD, TEM, EDX, XPS, and VSM. The cyclodextrin citrate-modified-Co-Ni nanoparticles were formed in spherical morphology and belong to the cubic crystalline system. The material showed a saturation magnetization of 92.53 emu g−1, narrow hysteresis loops, and low coercivity values. The UV-vis-NIR spectrum of the material displayed a broad spectral band, extending up to the long NIR wavelength (1200 nm). We loaded the anticancer drug 5-fluorouracil in the nanocarrier with a calculated loading efficiency of about 90%. Further, the release rate of the drug from the nanocarrier was investigated. The release was sustained, occurring over many days. The in vitro anticancer activity of the empty- and the 5-fluorouracil-loaded nanoparticles was examined on breast carcinoma (MDA-MB-231) cell lines. The apoptosis of the cells induced by the cargo-carrying nano vehicle was followed using Annexin V FITC/PI staining. The cells were inhibited by the controlled release of 5-fluorouracil from the nanocarrier, showing the properties of a suitable chemotherapeutic carrier.

Fatigue and fracture of shape memory alloys in the nanoscale: An in-situ TEM study

This study is aimed at demonstrating the fatigue and fracture mechanisms in nanoscale NiTi shape memory alloy thin films. During functional fatigue, permanent strains are attributed to residual martensite pinned by Ni4Ti3 precipitates and interfacial dislocations parallel to type II internal twins of the martensite. These residual martensite-austenite interfaces acted as heterogeneous nucleation sites for stress-induced martensite in subsequent cycles thereby explaining the reduction in transformation stress. Finally, structural failure was observed to occur along the dislocation-rich austenite-martensite interface, making it the weakest link in the microstructure thus establishing a direct link between mechanisms of functional fatigue that result in the accumulation of permenant strain and mechanisms of structural fatigue that result in fracture. This work provides a comprehensive understanding of deformation mechanisms in nanoscale shape memory alloys and points to fundamental mechanisms that are applicable to macro scales.

Integrating Low Pt-Based Ternary NiRuPt Nanoalloy on Hybrid TiO2-Based Oxide–Carbon Composite for Enhanced Ethanol Oxidation

Ternary NiRuPt nanoscale alloy on hybrid Ti0.9Ir0.1O2-C composite is herein reported to overcome the high cost and tenuous catalytic efficiency of anode catalysts in direct ethanol fuel cells. The small-size NiRuPt alloy is anchored on the Ti0.9Ir0.1O2-C surface via a NaBH4-ethylene glycol-assisted coreduction route. Benefiting from advantages of favorable structure and synergistic effects of compounds, the NiRuPt/Ti0.9Ir0.1O2-C catalyst exhibits high electrocatalytic performance for the ethanol electro-oxidation reaction (EOR) with mass activity of 720.75 mA mgMetal-1 and specific activity of 2.15 mA cm-2, which are 2.25- and 5-fold increases compared to those of the Pt/C (E-TEK) catalyst. The as-synthesized EOR catalyst also shows impressive anti-CO-poisoning ability and great electrocatalytic stability after 5000-cycling ADT. This work can open up an efficient strategy for designing multicomponent catalysts to reduce Pt content and enhance the catalytic performance of electrocatalysts in renewable energy-related technologies.

Unusual Compositions of Fe-Nb Alloy Precipitates in Iron-Implanted LiNbO3

The results of a study of heavy implantation of a LiNbO3 crystal with iron ions are reported for the first time. The X-cut LiNbO3 substrate was implanted with 40-keV Fe+ ions to the fluence of 1.5·1017 ions/cm2. The sample reveals pronounced ferromagnetic properties at room temperature. However, the ferromagnetic response observed in the iron-implanted LiNbO3 differs from the magnetic behavior of other oxides implanted with iron ions under the same conditions. This difference occurs from the unusual magnetic phase composition of the implanted surface layer of the LiNbO3 in which the iron implant precipitates in the form of the nanoscale alloy of metallic iron with niobium. Based on Mössbauer spectroscopy data, we estimated the Nb content in the ion-synthesized nanosized alloy as ~12 at.%, which is much higher than the solid solubility limit of Nb in bulk Fe.

Surface segregation and relaxation in free-standing Ni1–x Cux alloy nanofilms

The interaction between mechanics and chemistry plays an essential and critical role in the surface segregation and relaxation in nanoscale alloys. Following the thermodynamics analysis based on surface eigenstress, the present study takes the free-standing nanometer thick films of Ni1–xCux solid solutions with face-centered cubic (fcc) crystalline structures as an example to investigate surface segregation of Cu and relaxation of the films. Hybrid Monte Carlo and Molecular Dynamics (MCMD) simulations are conducted on free-standing Ni1–xCux alloys of (100) and (111) nanofilms. The MCMD simulations verify the theoretical analytic results and determine the values of parameters involved in the theoretical analysis. Especially, the parameter of the differentiation in reference chemical potential behaves like the molar free energy of segregation in the McLean adsorption isotherm, and the differentiation in chemical composition induced eigenstrain plays also an important role in surface segregation and relaxation. The integrated theoretical and numerical study exhibits that both surface excess Cu concentration and apparent biaxial Young's modulus of Ni1–xCux nanofilms depend on the nominal Cu concentration and the film thickness.

Nano-AgCu Alloy on Wood Surface for Mold Resistance.

The mold infection of wood reduces the quality of its surface and potentially endangers human health. One category of the most popular mold inhibitors on the market is water-soluble fungicides. However, easy leaching due to ionic forms is a problem, which reduces the effectiveness of their antimicrobial action, as well as causing environmental pollution. Interestingly, nanometer-sized sterilizing agents present strong permeability and highly fungicidal behavior, and they are not easily leached, due to the unique nanoscale effect, and they have become alternative candidates as marketable anti-mold agents for wood protection. In this study, we first designed and explored a nanoscale alloy (nano silver–copper alloy, nano-AgCu) to treat wood surfaces for mold growth resistance. The results showed that three molds, i.e., Aspergillus niger, Penicillium citrinum and Trichoderma viride, mainly grew on the surface of wood within a depth of 100 μm; and that the nano-AgCu alloy with a particle size of ~15 nm presented improved retention and anti-mold efficiency at a nanomaterial concentration on the wood surface. Its leaching rate increased non-linearly with the increase in nano-AgCu retention and then it showed a gradually decreasing trend. When the concentration reached 1000 mg/L, the nano-AgCu alloy uniformly distributed on the wood surface in a monodispersed state and exhibited a lower retention of 0.342 g/m2, with an anti-mold efficiency of more than 75% and a leaching rate of only 7.678%. Such results positioned 1000 mg/L as the toxic threshold concentration of nano-AgCu against the three molds. This study can provide a scientific basis for the analysis of the anti-mold mechanisms of nano-AgCu alloy on wood surfaces and guide the application of nano-metal alloy materials in the field of wood antimicrobials.

Composition-dependent ordering transformations in Pt–Fe nanoalloys

SignificanceDynamically understanding the microscopic processes governing ordering transformations has rarely been attained. The situation becomes even more challenging for nanoscale alloys, where the significantly increased surface-area-to-volume ratio not only opens up a variety of additional freedoms to initiate an ordering transformation but also allows for kinetic interplay between the surface and bulk due to their close proximity. We provide direct evidence of the microscopic processes controlling the ordering transformation through the surface-bulk interplay in Pt-Fe nanoalloys and new features rendered by variations in alloy composition and chemical stimuli. These results provide a mechanistic detail of ordering transformation phenomena which are widely relevant to nanoalloys as chemical ordering occurs in most multicomponent materials under suitable environmental bias.

ПОДГОТОВКА КАДРОВ ВЫСШЕЙ КВАЛИФИКАЦИИ В ОБЛАСТИ МАШИНОСТРОЕНИЯ

The article presents the analysis results of highly qualified personnel training in 2018–2020 in the field of mechanical engineering in the specialties falling within the competence of the Expert Council No. 18 of the Higher Attestation Commission of the Republic of Belarus, which showed that the most successful tasks in dissertation research are solved in the areas of developing technologies for creating: materials with gradient-oriented physical and mechanical characteristics; composite materials and protective coatings using nanoscale alloying and modifying materials; polymer materials and technologies, as well as the development of methods for assessing the durability of steel structures under their cyclic loads. However, despite the presence of a modern material and experimental base at the enterprises of the Republic of Belarus, among the applicants for academic degrees, there is a very small proportion of representatives of the real sector of the economy, training of which could make a scientific and practical contribution to machine science and provide significant support in solving the problems of ensuring the competitiveness and liquidity of products produced by successfully functioning major GDP generating domestic enterprises with production belonging mainly to the fourth technological paradigm. In fact, the main number of dissertations in these areas were executed by specialists of educational institutions and the National Academy of Sciences of Belarus, which have the appropriate field of activity and research equipment.

Nanocrystalline strengthened Mg-Li alloy with a bcc structure prepared via heat treatment and rolling

Due to the low recrystallization temperature and rapid growth of recrystallized grains in high-lithium content Mg-Li alloy. Nanoscale high-lithium Mg-Li alloys are difficult to obtain by traditional processing. This paper found that the homogenization treatment of the as-cast Mg-14Li-0.5Ni alloy causes the transformation of the bcc structure to an hcp structure, which can effectively improve the strength and plasticity. After further rolling at room temperature, a nanocrystalline strengthened β-phase Mg-Li alloy was successfully prepared, and its strength was 150% higher than that of the as-cast alloy.

Nanoscale-Thick Ni-Based Half-Heusler Alloys with Structural Ordering-Dependent Ultralow Magnetic Damping: Implications for Spintronic Applications

Atomic ordering and its consequence on the crystal structure are fundamental issues in the application of half-metallic Heusler alloys considered as a high spin-polarized electron source. NiMnSb is a promising half-metallic half-Heusler alloy for spintronic devices due to its low magnetic damping, non-centrosymmetric crystal structure, and rich anisotropies. Here, we report a high-quality half-metallic epitaxial nano-scale thick NiMnSb alloy film grown on a Cr/Ag-buffered MgO (001) single crystalline substrate. High temperature deposition is a crucial parameter for crystal growth and magneto-dynamic properties such as damping, anisotropy, magnetization, etc. After investigating the ferromagnetic resonance (FMR) spectroscopy using a time-resolved magneto-optical Kerr (TRMOKE) microscope and calculating the crystal structure using VESTA and the density of states from first-principles calculations, we discuss how the deposition temperature influences the crystal ordering, damping, and magnetization. Ultralow Gilbert damping with high anisotropic field and saturation magnetization were found for the highly ordered C1b structured nano-scale thick NiMnSb film deposited at 573 K. We also found quite nice agreement between theoretical and experimental data of crystal ordering and damping that explains how the ordering affects the magnetic parameter as well as sample quality. Furthermore, the negative anisotropic magnetoresistance ratio implies the robust bulk half-metallicity. Such unique combination of highly ordered half-metallic NiMnSb alloy in the nano-scale regime with ultralow damping can be regarded as an advantage for applications in spintronic devices.

Selective hydrogenation of cinnamaldehyde using palladium based bimetallic catalysts Pd-M/TiO2 (M=Cu, Ag and Au)

Pd based bimetallic catalysts, Pd-M, (M=Cu, Ag, and Au) supported on TiO 2 P-25, have been prepared by chemical reduction with glucose and characterized by XRD, TEM, XPS, DRS, TPR and H 2 TPD. Activity for the conversion of cinnamaldehyde (CAL) and selectivity to hydro-cinnamaldehyde (HCAL), cinnamyl alcohol (COL) and hydrocinnamyl alcohol (HCOL) have been evaluated in the temperature range of 120-140°C for 1 hr and 10 bar hydrogen pressure. For comparison, monometallic Cu, Ag and Au (1% w/w in each case) catalysts supported on TiO 2 P-25 have been prepared and evaluated. DRS and XPS studies reveal nanoscale alloy formation and re-distribution of charges in bimetallic catalysts. Bimetallic Pd-Cu displays higher CAL conversion compared to Pd-Ag and Pd-Au. Besides the favorable electronic and ensemble effects, availability of reactive hydrogen on Pd-Cu, as revealed by the lowest hydrogen desorption temperature, is an additional factor that contributes towards the higher activity of Pd-Cu. Bimetallic catalysts are stable up to five reaction cycles, without any loss of Pd or structural integrity.

Ultrafine nano-scale Cu2Sb alloy confined in three-dimensional porous carbon as an anode for sodium-ion and potassium-ion batteries

Ultrafine nano-scale Cu2Sb alloy confined in three-dimensional porous carbon as an anode for sodium-ion and potassium-ion batteries

Enhanced thermal coarsening resistance in a nanostructured aluminum-cerium alloy produced by additive manufacturing

Decreasing microstructural length scales to the nanoscale is a proven way of increasing strength, but the intrinsic metastability of such structures typically makes them susceptible to thermally activated coarsening. Recent advances in additive manufacturing permit bulk-nanostructured materials to be produced through rapid solidification, but like other metastable materials the as-built structures typically coarsen rapidly with even modest thermal exposure. Here, selective laser melting is employed to produce an Al-Ce-based alloy with high mechanical strength arising from the as-built microstructure, which can be controlled by build conditions. In addition, the alloy exhibits extreme resistance to thermal coarsening up to 400 °C and superior strength retention compared to conventional Al alloys after extended thermal exposure. The near-zero solubility of Ce in Al and potent solid solution strengthening of Mg enable this behavior without requiring heat treatment. This result demonstrates that combining insoluble alloying elements with additive manufacturing is a viable method of producing exceptionally stable bulk nanoscale alloys.

Cu–Pd–B Alloy Nanoparticles Synthesized by External Boron Doping Method

Abstract We present a new synthetic approach for Cu–Pd–B nanoscale alloys. Crystalline face-centered cubic Cu–Pd–B alloy nanoparticles were successfully obtained via an amorphous structure phase caused by external heavy B doping. Elemental mapping with simultaneous energy-dispersive X-ray spectroscopy and energy loss spectroscopy in a scanning transmission electron microscope revealed a solid-solution structure composed of the three elements.