Alloy Engineering Research Articles

Electronic Structure Engineering of RuNi Alloys Decrypts Hydrogen and Hydroxyl Active Site Separation and Enhancement for Efficient Alkaline Hydrogen Evolution.

Rational design of the active sites of hydrolysis dissociation intermediates to weaken their active site competition and toxicity is a key challenge to achieve efficient and stable hydrogen evolution reaction (HER) in ruthenium-containing alloys. Density Functional Theory (DFT) simulations reveal that the transfer of the d-band electrons from Ru to Ni in RuNi alloys results in a Gibbs free energy of -0.12eV for the Ru0.250Ni Fcc-site H*. In addition, the high spin state of the electrons outside the Ru nucleus strengthens the adsorption of OH* on the Ru─Ni bond, which weakens the active-site competition and toxicity successfully. This theoretical prediction is confirmed by electrodeposition of prepared aRuxNi, and the RuNi alloys obtained by Ru atom doping have excellent HER properties. aRu0.250Ni has overpotentials of 38 and 162.4mV at -10 and -100mAcm-2, respectively, and can be stably operated at -100mAcm-2 Dual-electrode system aRu0.250Ni//bRu0Ni demonstrates an ultra-low battery voltage (1.86V @500mAcm-2) and excellent stability (24h@300mAcm-2). This holistic work resolves the mechanism of active site separation and strengthening in RuNi alloys, and provides a new design idea for the preparation of highly efficient alkaline HER electrodes.

2D Multifunctional Phototransistor Based on MoTe2/Graphene/SnS0.25Se0.75 Heterostructure with High Photogain and Reconfigurable Polarized Detection

Abstract2D van der Waals (vdWs) heterojunctions exhibit facile fabrication process and tunable optoelectronic properties. However, suppressing interfacial charge traps and multifunctional photoresponse remain significant challenges. Here, the study designs a 2D multifunctional phototransistor based on ambipolar MoTe2/graphene (Gr)/p‐type SnS0.25Se0.75 double vdWs vertical heterostructure via alloy engineering. The middle Gr interlayer is pivotal in reducing interfacial charge traps, facilitating vertical photocarrier transportation, and enhancing light absorption coefficient. Under photogating effect, the trapped electrons in SnS0.25Se0.75 promote the photogating effect, resulting in the maximum photogain of 8084 and specific detectivity (D*) of 8.2 × 1012 Jones. Under photoconductive effect, a high responsivity (R) of 36.9 A W−1 and D* of 7.17 × 1011 Jones are achieved. Under photovoltaic effect, the devices exhibit a remarkable R of 501 mA W−1, D* of 1.4 × 1011 Jones. Notably, a self‐driven photocurrent polarized ratio of 8 under 635 nm is achieved because of the anisotropic nature of SnS0.25Se0.75 and the effective double built‐in electric fields. By varying the gate voltage, the polarization ratio can be modulated from 1 to 2.5, enabling reconfigurable polarized‐sensitive detection. Above all, the designed heterojunction with multifunctional and reconfigurable polarization detection.

Homogeneous Mo1−xRexS2 monolayer and lateral 1T’@2H heterostructures for significantly enhanced and highly reproducible SERS responses and mechanistic insights

As a promising surface-enhanced Raman scattering (SERS) substrate, two-dimensional (2D) nanomaterials ensure the uniformity and reproducibility of the SERS response. However, their extremely flat surfaces are not beneficial for high-capacity binding of analytes and significant enhancement of Raman signals. In this contribution, monolayer Mo0.27Re0.73S2 alloys with distorted lattice and modulated optoelectronic structure are facilely fabricated by space-confined chemical vapor deposition (CVD), exhibiting a significantly enhanced SERS performance with an enhancement factor of 2.0 × 1011. As demonstrated, the continuous increment of Re ratio results in a phase transition from 2H to 1T’ for homogeneous Mo1−xRexS2 monolayers. As a result, the 1T’-phase Mo0.27Re0.73S2 alloys achieve a sensitive detection of down to 10−15 M for Rhodamine 6G while the value on MoS2 or ReS2 is only 10−9 M. Additionally, the alloy-based SERS substrate demonstrates excellent SERS detection reproducibility, long-term stability, and universality. Referring to the space-confined CVD, a dynamics-controlled process is further employed for the in-situ fabrication of 1T’@2H Mo1−xRexS2 heterostructures, providing a new approach and insight for facilely building varied phases-based lateral heterostructures by the control of composition ratio. Overall, this work demonstrates the enormous potential of alloy engineering in improving the SERS performance of TMDs and the convenient fabrication of out-of-phase TMD alloys.

Understanding the Effect of Corrosion Resistance in Welded AA2198‐T8 Alloy: Microstructural‐Electrochemical Insights

ABSTRACTIn this study, we explore the corrosion resistance of AA2198‐T8 alloy in friction stir‐welded zones, focusing on microstructure changes and resulting corrosion susceptibility. Macrogalvanic coupling effects are observed in weldment under corrosive conditions, particularly in the welding joint (WJ), heat‐affected zones, and base metal (BM). Severe localized corrosion is prevalent in anodic zones, revealing intricate trenching patterns around micrometric particles in cathodic domains. Investigating isolated zones exposes SLC across all welding‐affected regions and BM, underscoring the involvement of microgalvanic cells in corrosion. The novel utilization of a syringe cell as an electrochemical tool proves to be instrumental in delineating the electrochemical characteristics of welding testing zones. Notably, stir zone within WJ emerges as the region depicting the lowest corrosion resistance, a critical finding substantiated by localized electrochemical impedance spectroscopy. These insights into the interplay of electrochemical phenomena and microstructural attributes have implications for advancing corrosion mitigation strategies and alloy engineering in materials science.

ScAlInN/GaN heterostructures grown by molecular beam epitaxy

Rare-earth (RE) elements doped III-nitride semiconductors have garnered attention for their potential in advanced high-frequency and high-power electronic applications. We report on the molecular beam epitaxy of quaternary alloy ScAlInN, which is an encouraging strategy to improve the heterointerface quality when grown at relatively low temperatures. Monocrystalline wurtzite phase and uniform domain structures are achieved in ScAlInN/GaN heterostructures, featuring atomically sharp interface. ScAlInN (the Sc content in the ScAlN fraction is 14%) films with lower In contents (less than 6%) are nearly lattice matched to GaN, exhibiting negligible in-plane strain, which are excellent barrier layer candidates for GaN high electron mobility transistors (HEMTs). Using a 15-nm-thick Sc0.13Al0.83In0.04N as a barrier layer in GaN HEMT, a two-dimensional electron gas density of 4.00 × 1013 cm−2 and a Hall mobility of 928 cm2/V s, with a corresponding sheet resistance of 169 Ω/□, have been achieved. This work underscores the potential of alloy engineering to adjust lattice parameters, bandgap, polarization, interfaces, and strain in emerging RE-III-nitrides, paving the way for their use in next-generation optoelectronic, electronic, acoustic, and ferroelectric applications.

High oxidation state on porous Ga-Ag9In4 catalyst enhance CO2 electroreduction to CO

The oxidation state of Ga, In and Ag active sites for the selective electrochemical conversion of CO2 to CO has been successfully modulated through the construction of a porous Ga-Ag9In4 liquid alloy catalyst. X-ray photoelectron spectroscopy measurements confirmed the formation of a higher amount of oxidized states on the high-performing Ga-Ag9In4 electrode surface during the CO2 reduction reaction process. Based on density functional theory calculations, the Ga-Ag9In4 catalyst with a high oxidized species exhibits an electronic-rich surface that promotes CO2 adsorption and activation. In a H-type electrolysis cell, the porous Ga-Ag9In4 catalyst exhibits a maximum Faradaic efficiency of 88 % for CO production, with current densities of 30.2 mA·cm−2. This strategy of porous liquid alloy engineering and oxidation state modulation in multicomponent systems has good application prospect and research value for enhancing electrocatalytic performance.

Alloy Reconstruction in Pyrolytic Bowknot-like Heteronuclear CoFe Clusters for Electrocatalytic Application.

The construction of doped molecular clusters is an intriguing way to perform bimetallic doping for electrocatalysts. However, efficiently harnessing the benefits of a doping strategy and alloy engineering to create a nanostructure for electrocatalytic application at the molecular level has consistently posed a challenge. Here we propose an in situ reconstruction strategy aimed at producing an alloy nanostructure through a pyrolysis process, originating from bowknot-like heterometallic clusters. The Schiff base, denoted as ligand L1 (o-vanillin ethylenediamine), was introduced as a precursor to coordinate Fe and Co metals, thereby yielding a heteronuclear metal cluster [(FeCo)(L1)2O]CH3CN. Subsequently, a comprehensive investigation of the in situ reconstruction process [(FeCo)(L1)2O](CH3CN) → [(FeCo)(L1)2O] → [M-O-M/M-O] [CH3+/CH3O+/H2C═N/C2H5+/C4H4+] → [FeCo/Fe3O4/Fe2O3/Co3O4][carbon layer] led to the formation of MOx/CoFe@NC-700 during the pyrolysis. This process reveals that the metals Fe and Co in the clusters undergo partly in situ evolution into FeCo alloys, resulting in the successful preparation of MOx/CoFe@NC (M = Fe, Co) nanomaterials that leverage the advantages of both doping strategies and alloy engineering. The synergistic interaction between alloy particles and metal oxides establishes active sites that contribute to the excellent oxygen evolution (OER) and hydrogen evolution (HER) catalytic behaviors. Notably, these materials exhibit outstanding OER and HER properties under alkaline conditions, with overpotentials of 191 and 88 mV for OER and HER, respectively, at 10 mA cm-2. Investigation of the in situ conversion of Schiff base bimetal clusters into alloy materials through pyrolysis offers a novel strategy for advancing electrocatalytic applications.

Two-Dimensional SnSe2(1-x)S2x/MoTe2 Antiambipolar Transistors with Composition Modulation for Multivalued Inverters.

Two-dimensional (2D) van der Waals heterostructures that embody the electronic characteristics of each constituent material have found extensive applications. Alloy engineering further enables the modulation of the electronic properties in these structures. Consequently, we envisage the construction and modulation of composition-dependent antiambipolar transistors (AATs) using van der Waals heterostructures and alloy engineering to advance multivalued inverters. In this work, we calculate the electron structures of SnSe2(1-x)S2x alloys and determine the energy band alignment between SnSe2(1-x)S2x and 2H-MoTe2. We present a series of vertical AATs based on the SnSe2(1-x)S2x/MoTe2 type-III van der Waals heterostructure. These transistors exhibit composition-dependent antiambipolar characteristics through the van der Waals heterostructure, except for the SnSe2/MoTe2 transistor. The peak current (Ipeak) decreases from 43 nA (x = 0.25) to 0.8 nA (x = 1) at Vds = -2 V, while the peak-to-valley current ratio (PVR) increases from 4.5 (x = 0.25) to 6.7 × 103 (x = 1) with a work window ranging from 30 to 47 V. Ultimately, we successfully apply several specific SnSe2(1-x)S2x/MoTe2 devices in binary and ternary logic inverters. Our results underscore the efficacy of alloy engineering in modulating the characteristics of AATs, offering a promising strategy for the development of multivalued logic devices.

Mechanical properties and microstructure of magnesium alloy with in situ formed Al2RE phases

The advancement of magnesium alloys has historically faced challenges due to their inherently low modulus and the inverse relationship between modulus and ductility. In this study, an Mg-15Gd-8Y–11Al-0.3Mn alloy containing Al2RE phases was developed through an in-situ synthesis process, exhibiting exceptional mechanical properties, including a high elastic modulus of 57.6 GPa coupled with a satisfactory elongation of 7.3 %. The findings indicate the presence of polygonal Al2RE phases of varying sizes within the alloy, with α-Mg observed in some Al2RE phases, forming a coherent interface. The grain size of the alloy was refined, and the dimensions of the Al2RE particles were reduced through the extrusion process. The effective strain transfer between α-Mg and Al2RE, facilitated by the coherent interface, endowed the alloy with commendable ductility, even at a substantial Al2RE volume fraction of 23 %. Furthermore, the formation of the Al2RE phase was identified as the key contributor to the alloy's enhanced modulus. This study provides novel insights for the engineering of high-modulus magnesium alloys, thereby paving the way into their broader industrial application.

Effect of Carbon on Void Nucleation in Iron.

The study reports the significance of carbon presence in affecting void nucleation in Fe. Without carbon, void nucleation rates decrease gradually at high temperatures but remain significantly high and almost saturated at low temperatures. With carbon present, even at 1 atomic parts per million, void nucleation rates show a low-temperature cutoff. With higher carbon levels, the nucleation temperature window becomes narrower, the maximum nucleation rate becomes lower, and the temperature of maximum void nucleation shifts to a higher temperature. Fundamentally, this is caused by the change in effective vacancy diffusivity due to the formation of carbon-vacancy complexes. The high sensitivity of void nucleation to carbon comes from the high sensitivity of void nucleation to the vacancy arrival rate in a void. The void nucleation is calculated by first obtaining the effective vacancy diffusivity considering the carbon effect, then calculating the defect concentration and defect flux change considering both carbon effects and pre-existing dislocations, and finally calculating the void nucleation rate based on the recently corrected homogeneous void nucleation theory. The study is important not only in the fundamental understanding of impurity effects in ion/neutron irradiation but also in alloy engineering for judiciously introducing impurities to increase swelling resistance, as well as in the development of simulation and modeling methodologies applicable to other metals.

Carburization-induced surface modification of Ti-6Al-7Nb alloy and its characterization

The Ti-6Al-7 Nb alloy and its carbide possess a wide range of engineering applications, therefore, it is utmost required to fabricate high-quality carburized layers on the alloy surface. In this study, the carburization of Ti-6Al-7 Nb alloy was conducted using molten salts (including Carbon Nano Tubes, LiCl, KCl, and KF) in a planetary ball mill, followed by placement in an alumina tube furnace under a nitrogen atmosphere at 1050 °C for various durations. Several characterization techniques were employed to analyze the results, including X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The XRD results reveal that as the carburization duration increased, the alloy achieved complete carburization, forming a 120 µm thick layer of TiC0.3N0.7. After 24 h of carburization, the crystallite size of TiC0.3N0.7 increased, and the micro-strain decreased, indicating improved structural quality. The morphology of the carburized layer at shorter durations exhibits micro-cracks and defects due to incomplete carburization, where carbon (C) and nitrogen (N) could not effectively occupy in the grain boundaries of alloy. After 24 h, an agglomerated, cauliflower-like layer of TiC0.3N0.7 formed, enhancing the alloy's engineering properties. XPS confirmed the presence of carbon and nitrogen in the carburized sample, which contributed to the formation of the TiC0.3N0.7 layer on the alloy surface. AFM analysis supported the SEM findings, revealing broad islands with microgrooves on the carburized layer. These features indicate a thick and well-formed carburized layer, confirming the successful carburization of Ti-6Al-7 Nb. Overall, the study demonstrates that a 24-h carburization process at 1050 °C in molten salts under a nitrogen atmosphere effectively produces a high-quality, thick, and adherent TiC0.3N0.7 layer on Ti-6Al-7 Nb alloy, significantly enhancing its engineering properties.

Phase engineering and surface reconstruction of FeNiMo alloys as high efficient electrode for oxygen evolution reaction

In the field of electrocatalysis, most of the electrodes have the problem of poor mechanical properties, which leads to the electrode can not be used on a large scale. At present, most bulk electrodes are used to study their mechanical properties due to their unique phase composition distribution and facile fabricate methods. But their novel properties in the field of electrocatalysts have not been fully developed. Multi-element bulk electrodes not only diversified the electronic states, but also build complex surface morphology by different dissolution rate between multi-phase distribution. In this paper, we synthesized the FeNiMo bulk electrode for oxygen evolution reaction (OER) with two-phase coexistence of Mo-doped face center cubic phase (FCC) and Mo-rich intermetallic compound (IMC) phase. During cyclic voltammetry activation, the surface reconstruction of Mo-rich IMC phases generated by ion leaching leaves Fe–Ni pore structures with more active area, which enhances OER performance. Meanwhile, the electron states get more diverse on the surface of remaining FCC phases due to Mo doping, which provides more suitable sites for four-step OER process. The FeNiMo electrode shows an ultra-low overpotential of 212 mV and 293.4 mV at a current density of 10 mA cm−2 and 100 mA cm−2, respectively. Moreover, it can maintain stability at 100 mA cm−2 for up to 72 h. This work provides a strategy for studying the relationship between phase composition and electrochemical performance of alloy bulk electrodes.

Harmonizing microstructures and enhancing mechanical resilience: Novel powder metallurgy approach for Zn–Mg alloys

Zinc alloys are recognised for their excellent biocompatibility and favourable corrosion rates, making them suitable for bioabsorbable implants. However, their mechanical properties necessitate improvement to fulfil the rigorous requirements of biomedical applications. This research focuses on engineering pseudo-harmonic structures within zinc alloys through a comprehensive method combining mechanical alloying, spark plasma sintering, and hot extrusion techniques. This fabrication process results in a composite material characterised by a soft core surrounded by a continuous, three-dimensional, ultrafine-grained hard shell. The experiment involved blending pure zinc with Zn–1Mg alloy powder, leading to the formation of both ductile zinc and fine-grained Zn–1Mg regions. While the Mg2Zn11 intermetallic phase was found to enhance the alloy's mechanical strength, the presence of oxide shells adversely affected the material's properties. The elimination of these shells via hot extrusion markedly improved the alloy's tensile strength, reaching an average value of tensile strength of 333 ± 7 MPa. This study provides significant insights into the material engineering of zinc-based alloys for biodegradable implant applications, demonstrating a viable approach to optimising their mechanical performance.

MIL-101(Fe) supported Au-Cu nanoalloy for enhanced electrochemical nitrogen fixation in gas–liquid-solid three-phase reactor

Low-temperature electrocatalytic nitrogen fixation technology is a green artificial nitrogen fixation technology. Here, we designed and synthesized AuxCuy/MIL-101 series catalysts, i.e., using simple alloy engineering strategy, the synthesized AuCu nanoalloy particles were efficiently loaded onto MIL-101(Fe) by one-step co-reduction. Experiments and calculations show that (Ⅰ) MIL-101(Fe) as support not only enhances the N2 enrichment ability of catalysts, but also facilitates the high dispersion of AuCu nanoparticles. (II) In AuCu nanoalloy, the strong coupling between Au-Cu sites bridges its effective electron transfer, improves the charge structure of Au sites, thereby enhancing the Au 5d-N2 π* interaction, which not only facilitates the adsorption of N2 by catalysts, but also weakens the N≡N triple bond and reduces RDS (N2 → NNH*, 0.38 eV). (III) Au-Cu alloying increases the hydrogen adsorption free energy (0.76 eV), which weakens the competitive adsorption between H+ and N2 by catalysts, and optimizes the charge transfer efficiency of AuxCuy/MIL-101 catalysts. Therefore, the overall NH3 yield and FE of AuxCuy/MIL-101 catalysts are higher than those of MIL-101, Cu/MIL-101 and Au/MIL-101. After optimization, Au1Cu1/MIL-101 with the highest ECSA and suitable Rct has the highest NRR activity (NH3 yield: 161.07 μg h−1 mg-1cat., FE: 58.86 %), which exceeds most Au-based catalysts. Meanwhile, the in-situ FTIR test results further indicate that Au-Cu alloying can accelerate the cleavage of N≡N and the adsorption of N2 by catalysts. This study demonstrates that the gold-copper alloying strategy not only promotes Au 5d feedback to N≡N bond, reduces RDS but also increases ΔGH*, inhibits proton adsorption, ultimately promoting Au1Cu1/MIL-101 catalyst to perform highly efficient NRR performance.

Surface engineering of aerospace aluminium alloys: Understanding alloying effects on chemical pre-treatment and sol-gel coating adhesion

The sol–gel process is a chemical surface preparation method based on hydrolysis and polycondensation reactions for enhanced adhesion for metallic substrates in adhesive bonding and coating applications. This paper describes an investigation into the effect of the microstructural complexity of two commonly used aerospace aluminium alloys (AAs) 2024-T3 and 7075-T6, on the response to different surface pre-treatments before deposition of the sol-gel coating and subsequent adhesive bonding.Different surface pre-treatments, including two abrasive treatments and three chemical surface pre-treatments were used, and their effect on surface chemistry, wettability and roughness was assessed. Surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, profilometry and static contact angles. A hybrid silane sol-gel film was deposited on the differently pre-treated aluminium alloys, an epoxy adhesive was applied and the adhesion properties were evaluated using pull-off testing. The role of the altered physicochemical properties of the pre-treated surfaces was related to the adhesion strength of the sol–gel reinforced epoxy/aluminium interfaces.The microstructural complexity of the aerospace alloys caused non-uniform responses to the pre-treatments, proving the importance of compatibility between material and treatment conditions. Statistical analysis revealed that, despite that overall higher adhesion values were obtained on rougher surfaces, only a strong correlation exists between the surface hydroxyl fraction and adhesion strength. The relation of roughness and water contact angle to interfacial adhesion was found to be non-significant.The findings of this study underscore the critical role of surface pre-treatments and their impact on adhesion strength in aerospace aluminium alloys, providing valuable insights for the effective utilization of sol-gel coatings in adhesive bonding and coating processes.

The transition from strain rate insensitivity to sensitivity of Ti–6Al–4V alloys deformed at cryogenic temperature

The aim of the present study is to elucidate the strain rate (ε˙) dependency of Ti–6Al–4V alloys under cryogenic deformation conditions, inspired by our recent observations of strain rate insensitivity in pure titanium as well as the temperature effect on the stacking fault energy. Unlike the pronounced strain rate sensitivity at ambient temperatures, a strain rate insensitivity when ε˙ < 10−2 s−1 and strain rate sensitivity when ε˙ > 10−2 s−1 were observed during cryogenic deformation. Subsequent analyses underscored the pivotal role of stacking faults in modulating the transition from strain rate insensitivity to sensitivity with increasing strain rates. The present study therefore enriches the existing knowledge on the mechanism of cryogenic deformation, offering guidance for the engineering of high-performance titanium alloys.

2D Free-Standing GeS1-xSex with Composition-Tunable Bandgap for Tailored Polarimetric Optoelectronics.

Germanium-based monochalcogenides (i.e., GeS and GeSe) with desirable properties are promising candidates for the development of next-generation optoelectronic devices. However, they are still stuck with challenges, such as relatively fixed electronic band structure, unconfigurable optoelectronic characteristics, and difficulty in achieving free-standing growth. Herein, it is demonstrated that two-dimensional (2D) free-standing GeS1-xSex (0 ≤ x ≤ 1) nanoplates can be grown by low-pressure rapid physical vapor deposition (LPRPVD), fulfilling a continuously composition-tunable optical bandgap and electronic band structure. By leveraging the synergistic effect of composition-dependent modulation and free-standing growth, GeS1-xSex-based optoelectronic devices exhibit significantly configurable hole mobility from 6.22 × 10-4 to 1.24 cm2V-1s⁻1 and tunable responsivity from 8.6 to 311 AW-1 (635nm), as x varies from 0 to 1. Furthermore, the polarimetric sensitivity can be tailored from 4.3 (GeS0.29Se0.71) to 1.8 (GeSe) benefiting from alloy engineering. Finally, the tailored imaging capability is also demonstrated to show the application potential of GeS1-xSex alloy nanoplates. This work broadens the functionality of conventional binary materials and motivates the development of tailored polarimetric optoelectronic devices.

Bandgap engineering of spinel-structured oxide semiconductor alloys

We investigated bandgap engineering of spinel-structured MgB 2O4 (B = Al, Ga, In) alloys. The trend of bandgap change was tunable from approximated 7.8–3.6 eV by substituting group III cation atoms in MgB 2O4. To evaluate the doping possibility, we have calculated the natural band alignment and doping pinning energy of the normal and inverse spinel structures of MgB 2O4 alloys. The calculated doping pinning energies show that spinel-structured MgB 2O4 alloys can potentially control the electron concentration, but hole doping is difficult. Our computational results are expected to provide new insights into the doping control of ultra-wide bandgap semiconductors.

Entropy Stabilized Medium High Entropy Alloy Anodes for Lithium‐Ion Batteries

AbstractOne often proposed route to improved energy density for lithium‐ion batteries is to use alloy anodes, such as silicon, able to store large amounts of lithium. Mechanical instability caused by the large expansion and contraction associated with (de)lithiation, and hence bad cyclability, has, however, so far hindered progress. As proof‐of‐concept of a remedy, we here present BiSbSe1.5Te1.5, a medium high‐entropy alloy with improved cycling stability for conversion‐alloying (de)lithiation reactions. We attain five to twenty times more stable cycles than previously reported for comparable metal‐Se and ‐Te‐based anodes, with a very good reversible capacity (464 mAh g−1) for up to 110 cycles‐ and this without using any carbonaceous materials to create a composite. Altogether, this highlights how alloy engineering and increased entropy materials can stabilize conversion‐alloying electrodes.

TEM and X-ray diffraction studies of structure of TiNi SMA treated by low-energy high-current electron beam

Advanced scientific and technological achievements in the surface engineering of TiNi shape memory alloys are closely related with their mechanical performance. Electron-beam treatments could be applied in order to modify surface properties of smart materials and promote stress-induced martensitic transformations. The fundamental issue of electron-beam processing is residual elastic stresses arising from the ultrafast quenching (∼108 K/s) of thin (∼2–4 μm) surface layers. We report the experimental results on phase composition, structure and residual elastic stresses formed in the binary TiNi SMA irradiated by a low-energy (< 25 keV) high-current (∼ 25 kA) electron beam. Microstructure, fracture mechanisms and phase analysis of the as-cast and deformed tensile specimens have been studied by X-ray diffraction and electron microscopy. After electron-beam treatment, both martensitic B19′ and R phases are found in the near surface layer. The X-ray diffraction studies indicate that compressive stresses in the B2 phase of the irradiated TiNi alloy reach –460 MPa. In the fractured specimen (after tensile test) the residual stresses decrease to –160 MPa and release through the B2→B19′→B2 martensitic transformation. In-depth gradient distribution of the defect substructures responsible for the mechanical behavior of TiNi alloys was revealed.