B2 Structure Research Articles

Computational study of effects of doping Ni and Pd on CoAl for hydrogen storage capacity, elastic and electronic properties

Intermetallic compounds in B2 structure which have low density, fracture, and high strength have important applications in different engineering applications. For energy storage apparatus, the researchers have investigated new materials to improve effective efficiency in energy storage devices such as batteries and green energy technologies. The investigation of transition metal–aluminide alloys has increased due to their attractive elastic features. Like many hydrogen storage alloys, B2-type hydrogen storage alloys such as ZrCo utilize the systems of hydrogen storage in atomic gaps. If hydrogen atoms settle in the interstitial spaces, lattice expansion forms due to lattice distortion. Since plastic and elastic deformations change pressure and temperature, they are important for the material during hydrogen desorption and absorption. According to the literature, element doping effects boost hydrogen storage sufficiency. The effects of Ni- and Pd-substituted dopants on hydrogen storage, electronic and elastic features of a Cobalt-Aluminum alloy were performed using the first-principles calculations with and without spin-polarized configurations. Obtained lattice parameters for Co8Al8 are good agreement with literature values. Interstitial H doping has changed the crystal structure from cubic (BCC) to tetragonal. It is concluded that all investigated CoAl alloys included H doping has negative formation energies showing thermodynamically stabilities. All investigated alloys are stable mechanically and dynamically. Doping of H2 atoms to CoAl changes from a brittle to ductile nature. Also, Ni contributions improve ductility behavior to improve the cycle performance of the Co7NiAl8 and Co8Al7Ni alloy. It can be concluded from electronic band structure that they exhibite metallic behavior. Our obtained gravimetric and volumetric capacities which are comparable with B2 hydrogen storage material such as ZrCo, FeAl, indicate that CoAl alloys may be suitable for hydrogen storage applications.

Phase stability, elastic properties, and hardness of Ti1-xAlxN from first-principles calculations

The curve of the hardness of ternary nitride Ti1-xAlxN against the Al content x is convex shaped with a maximum at x ∼0.6, of which the mechanism remains to be further explored. The present work scrutinizes the phase stability and elastic modulus of Ti1-xAlxN against the Al content x by using a first principles method as they are highly pertinent to the hardness of the system. It is shown that the cubic B1 structure is more stable than the hexagonal structure (Bk) for x < ∼0.75 whereas the hexagonal structure (B4) is more stable than the cubic B1 structure for x > ∼0.75. The hardness of both B1- and B4–Ti1-xAlxN evaluated with the calculated elastic modulus become higher with increasing x. B1–Ti1-xAlxN is harder than B4–Ti1-xAlxN. Besides the composition dependent hardness of the individual B1- and B4–Ti1-xAlxN, the phase decomposition contributes to the convex shaped hardness of Ti1-xAlxN against x. The work presents a clear picture on how the chemical composition and phase transition influence jointly on the hardness of Ti1-xAlxN.

Observation of itinerant ferromagnetic behaviour in equiatomic medium entropy AlNiCo alloy

A medium entropy AlNiCo alloy has been synthesized by vacuum arc melting, which shows single phase B2 structure. Atom probe tomography analysis showed that the elements are homogeneously and randomly distributed in AlNiCo alloy without any clustering tendency. A detailed analysis of temperature and field dependent magnetization data suggests an itinerant ferromagnetic ground state of AlNiCo alloy. The magneto crystalline anisotropy is evaluated to be 1.03 × 105 ergs/cm3 at 5 K. A broad maximum at low temperature in zero-field-cooled (ZFC) magnetization, as well as irreversibility of ZFC and field-cooled (FC) curves indicated a glassy behavior. This observation is supported by the memory effects observed at low temperature. The observed anomalous magnetic behavior is discussed in terms of modifications in exchange interactions. To the best of our knowledge, this is the first report on microstructure and magnetic properties of an equiatomic ternary AlNiCo alloy.

Phase Composition and Thermoelectric Properties of Epitaxial CrMoVN Thin Films

Thin films of CrMoVN are deposited on c‐plane sapphire (Al2O3 (0001)) by direct current reactive magnetron sputtering, to investigate the effects of Mo and V addition to CrN‐based films. All films grow epitaxially, but Mo incorporation affects the crystal structure and nitrogen content. All films in the CrMoVN series are understoichiometric in nitrogen, but largely retain the NaCl B1 structure of stoichiometric CrN films. Addition of vanadium increases the phase‐stability range of the cubic phase, allowing for higher solubility of Mo than what has previously been reported for cubic CrN. The Seebeck coefficient and electrical resistivity are greatly affected by the alloying, showing a decrease of the Seebeck coefficient along with a decrease in resistivity. Cr0.83Mo0.11V0.06Nz shows a 70% increase in power factor (S2σ = 0.22 mW m−1 K−2) compared to the reference CrNz (S2σ = 0.13 mW m−1 K−2).

Development of a rapid and sensitive fluorescent probe for high-throughput detecting SO2 in food samples

Sulfur dioxide (SO2), widely used as an antioxidant and preservative in food production, has been associated with detrimental cardiovascular and neurological effects when consumed excessively. This highlights the pressing need to develop a fast and sensitive probe capable of high-throughput screening for the quantitative determination of SO2 in food. Herein, we synthesized a new fluorescent probe, namely B3, specifically designed for high-throughput detection of SO2 in food. The vinyl chloride aldehyde within the B3 structure engages in a nucleophilic addition reaction with SO2, contributing to B3′s exceptional selectivity for SO2, and fast response time within 9 s. Furthermore, by integrating B3 with a microplate reader, we effectively achieved high-throughput detection of SO2 concentration up to 45 μM within a pH range of 5.5 to 8.0 in real food samples. This accomplishment serves as a significant contribution to ensuring consumer safety and facilitating health assessments.

The cobalt-free Fe35Mn15Cr15Ni25Al10 high-entropy alloy with multiscale particles for excellent strength-ductility synergy

The evolution of microstructure and tensile properties of a newly designed cobalt-free high entropy alloy, Fe35Mn15Cr15Ni25Al10 (at.%), has been investigated during the annealing and aging processes. A dual-phase alloy with a face-centered cubic (FCC) and body-centered cubic (BCC) or ordered B2 structure, along with multiscale heterogeneous precipitates, has been formed. The precipitated phases consist of bulk primary B2–NiAl and secondary BCC/B2 particles that range in size from the nanometer to micrometer scale. By prolonging the aging time, the yield strength is strongly enhanced, increasing from 250 MPa to 860 MPa at the peak aging stage. The primary sources of strengthening are precipitation hardening and hetero-deformation-induced strengthening from the BCC or ordered B2 phase. Furthermore, the incorporation of various strengthening mechanisms and high-strain hardening capability at cryogenic temperatures (77 K) results in improved strength and ductility simultaneously. A highly cost-effective high-entropy alloy, doped with a high concentration of aluminum, has been developed.

(Invited) New Class of Plasmonic Alloy Nanoparticles

The past 150 years of research on inorganic nanomaterials that exhibit intrinsic localized surface plasmon resonance (LSPR) in the visible region has focused on well-disperse nanoparticles (NPs) composed of coinage metals (Au, Ag, and Cu). Recent theoretical studies on photo-excited electron dynamics in Au NPs have revealed that not only the interband transition but also the screening caused by the vibrations of bound electrons by visible light are important for visible LSPR [1]. However, the correlation between the electronic and crystal structure (as a means to control the screening effect) remains unclear because most alloys based on coinage metals have a face-centred cubic (fcc)-based structure. Here, we show that well-disperse pseudospherical intermetallic Pd-based alloy NPs with a B2 structure and PtIn2 NPs with a C1 (CaF2-type) structure intrinsically exhibit LSPR absorption in the visible region.It is well known that chemical conversion of inorganic NPs via element substitution reactions, such as ion exchange reactions [2] and galvanic replacement reactions, can overcome the difficulties associated with controlling the size, shape, chemical composition, and crystal structure in conventional syntheses [3-5]. Especially, alloying enables us to drastically modulate the electronic properties of metallic NPs. The retained shape of the parent-NPs in element replacement reactions provides an opportunity to obtain non-equilibrium unique structures and even new structures of inorganic NPs. We demonstrate that various Pd-based alloy NPs with a B2 structure were synthesized by the element replacement reactions with Pd–P NPs and showed LSPR in the visible region [6]. This is an alchemy in nanoplasmonics in the sense that the plasmonic properties of group 11 elements are reproduced by using non-group 11 elements. On the other hand, we successfully synthesized pseudospherical PtIn2 intermetallic NPs with a C1 structure as uncommon types of visible plasmonic NPs [7].Simulations of above alloy NPs and fcc-Au NPs indicate that both the reduction in the interband transition and the strong screening by a small number of bound d-electrons are the main origins of the visible plasmonic features of alloy NPs. Our results demonstrate that the composition and crystal structure of the intermetallic NPs of our work determine the interband transition and the screening effect. Our findings dramatically expand the plasmonic NP library and highlight remarkable NPs that are far superior, in terms of physical and chemical properties, to conventional plasmonic NPs.[1] Iida, K.; Noda, M.; Ishihara, K.; Nobusada, K. J. Phys. Chem. A 2014, 118, 11317–11322.[2] Saruyama, M.; Sato, R.; Teranishi, T. Acc. Chem. Res. 2021, 54, 765–775.[3] Wu, H.-L.; Sato, R.; Teranishi, T. et al., Science 2016, 351, 1306–1310.[4] Li, Z.; Saruyama, M.; Asaka, T.; Tatetsu, Y.; Teranishi, T. Science 2021, 373, 332–337.[5] Matsumoto, K.; Sato, R.; Tatetsu, Y.; Teranishi, T. et al., Nat. Commun. 2022, 13, 1047.[6] Sato, R.; Takekuma, H.; Teranishi T. et al., to be submitted.[7] Takekuma, H.; Sato, R.; Iida, K.; Teranishi, T. et al., submitted.

Oxidation Behaviour of Refractory (HfCo)100−x(NbMo)x High-Entropy Alloys with a bcc+B2 Structure

Herein, the oxidation behaviour of refractory (HfCo)100−x(NbMo)x (x = 0; 10; 25; 40; 75; 100 (at.%)) high-entropy alloys with a bcc+B2 structure subjected to cyclic oxidation at 1000 °C was studied. The single-phase B2-ordered HfCo alloy demonstrated the best spallation resistance and retained a pristine form after 100 h. The oxidation kinetics of the HfCo alloy was near-parabolic, accompanied by the formation of external HfO2 or CoO layers after 1 or 100 h, respectively. Additions of (NbMo)x deteriorated the spallation resistance (x ≤ 25 at.%) or led to complete disintegration (x &gt; 25 at.%). Among the (NbMo)-containing alloys, the (HfCo)90(NbMo)10 alloy with the dual-phase bcc+B2 structure showed the most promising oxidation resistance. This alloy withstood cyclic oxidation up to 15 h with a mass gain close to the HfCo alloy and survived 100 h without changes in geometry of the specimen. Unlike the HfCo alloy, in the (HfCo)90(NbMo)10 alloy, the external CoO layer was found already after 1 h. The effect of chemical and phase compositions on the formation of certain oxides was discussed. Comparison with the other refractory high-entropy alloys was also presented.

Effect of sub-solvus treatment on discontinuous precipitation behavior and mechanical properties of AlCrFeNiV multi-principal element alloy

The discontinuous precipitation (DP) behavior of AlCrFeNiV multi-principal element alloys (MPEAs) based on initial face-centered-cubic (FCC) single-phase structure is investigated in this work. The investigation focuses on the impact of a novel sub-solvus (SS) treatment, which accelerates the DP transformation kinetics by refining the microstructure, as compared to the conventional total-solution (TS) treatment. This acceleration is attributed to an increase in nucleation sites or localized changes in chemical composition. The presence of NiAl phases with a B2 structure, which precipitate along prior grain boundaries, is believed to play a dominant role in grain refinement. Additionally, highly dispersed L12 nano-precipitates are observed within the FCC matrix in both TS- and SS-treated samples. Building upon the strengthening effect of L12 nanoprecipitates, further optimization strategies are explored through variations in isothermal aging treatments. This leads to the preparation of DP structures with various degrees and morphologies, consisting of BCC phases and a coherent FCC/L12 microstructure. The additional HDI hardening stemming from the resulting DP/non-DP heterogeneous structure and the spheroidization of the ultrafine DP lamellar structure allowed the alloy to exhibit excellent mechanical properties, the latter of which yielded an interesting combination of strength (1907 MPa tensile strength, 1694 MPa yield strength) and ductility (10.1% elongation). These findings highlight the effect of the prior grain refinement on the DP transition kinetics, BCC lamellae stability, and the overall mechanical performance of AlCrFeNiV multi-principal element alloys (MPEAs).

Third element diffusion induced amorphization of NiTi in a NiTi-Nb nanocomposite

The paper reports a unique and rare phenomenon observed in a NiTi-Nb nanowire in-situ composite system. The phenomenon is the amorphization of the B2 NiTi matrix caused by the diffusion of Nb through the B2 lattice. The diffusion of Nb through the NiTi matrix is driven by the effect of Oswald ripening associated with the fragmentation and granulation of Nb nanowires at elevated temperatures and the amorphization of the NiTi matrix is attributed to the effect of Ni-Ti atomic swapping, i.e., the formation of anti-site defects in the B2 structure, caused by the substitutional diffusion of a third element, Nb in this case. The phenomenon is observed by transmission electron microscopy examination and x-ray diffraction measurement and the hypothesis of explanation is supported by molecular dynamic simulation studies.

Effect of O/N content on the phase, morphology, and optical properties of titanium oxynitride thin films

Phase formation, morphology, and optical properties of Ti(O,N) thin films with varied oxygen-to- nitrogen ration content were investigated. The films were deposited by magnetron sputtering at 500 °C on Si(100) and c-plane sapphire substrate. A competition between a NaCl B1 structure TiN1−xOx, a rhombohedral structure Ti2(O1−yNy)3, and an anatase structure Ti(O1−zNz)2 phase was observed. While the N-rich films were composed of a NaCl B1 TiN1−xOx phase, an increase of oxygen in the films yields the growth of rhombohedral Ti2(O1-yNy)3 phase and the oxygen-rich films are comprised of a mixture of the rhombohedral Ti2(O1−yNy)3 phase and anatase Ti(O1−zNz)2 phase. The optical properties of the films were correlated to the phase composition and the observation of abrupt changes in terms of refractive index and absorption coefficient. The oxide film became relatively transparent in the visible range while the addition of nitrogen into films increases the absorption. The oxygen rich-samples have bandgap values below 3.75 eV, which is higher than the value for pure TiO2, and lower than the optical bandgap of pure TiN. The optical properties characterizations revealed the possibility of adjusting the band gap and the absorption coefficient depending on the N-content, because of the phases constituting the films combined with anionic substitution.

Selective oxidation induced wear degradation in cemented carbides

Understanding the wear micro-mechanisms of metallic binders is a prerequisite to designing durable cemented carbides for drilling applications. Here we studied the oxidational wear behaviors of WC-based composites encompassing particularly the CoAl binder (α phase, comprised of 5.7 wt% Al and bal. Co) and the CoFeAl binder (B2 phase) with same Al content. Unlike the oxidation of Co in the CoAl, selective oxidation of Al occurred unexpectedly in the CoFeAl, which weakened the binder integrity and aggravated the wear losses. Such unique behavior was rationalized computationally, where the Al2O3 formation was attributed to the low energy barrier to Al diffusion in the B2 structure. These findings could lay a useful basis for future development of robust cemented carbides.

Thermal stability of (HfCo)90(NbMo)10 and (HfCo)75(NbMo)25 refractory high entropy alloys with a bcc + B2 structure

The effect of long-term (700 h) annealing at 1000 °С on the structure and mechanical properties of the as-cast (HfCo)90(NbMo)10 and (HfCo)75(NbMo)25 (in at.%) refractory high entropy alloys was examined. The as-cast alloys consisted of a mixture of (Nb, Mo)-rich bcc and (Hf, Co)-rich B2 phases with bcc / B2 ratios close to NbMo / HfСo ratios. Annealing did not result in the formation of additional phases, which agreed with the Thermo-Calc predictions. However, annealing led to the formation of (i) B2 / bcc nanoprecipitates inside the initial bcc / B2 phases and (ii) separate Nb-rich and Mo-rich bcc phases. Annealing also caused significant strengthening of the alloys; for example, the room-temperature yield strength of the (HfCo)90(NbMo)10 alloy increased from 640 to 1340 MPa. Hardening was induced by the bcc nanoprecipitates in the B2 phase according to the Orowan mechanism. The results obtained suggest novel routes for the development of refractory high entropy alloys with a stable bcc + B2 structure.

Mechanical, vibration, and optical properties of IrAl intermetallic compound via DFT calculations: high-pressure effect

In this study, the effect of pressure on the structural, elastic, anisotropy, electronic, phonon, and optical properties of the IrAl compound in B2 structure was investigated by the first-principles method. The lattice constant, volume, density, and bulk modulus parameters were compared with theoretical and experimental data at zero pressure, and their variations with pressure effect were also examined. The IrAl compound fullfills the Born criteria at all pressure values, indicating structural stability, as no instability is observed even with increasing pressure. The compound exhibits ductile properties according to Paugh ratio (B/G), Cauchy pressure (C12–C44, C’), and Poisson ratio (λ) criteria. Electronically metallic in nature, it has maintained this nature with pressure variation. The absence of negative frequencies in the phonon dispersion curve explains that the compound is dynamically stable. Mulliken Atom Populations analysis was used to understand the bond properties between Ir-Al atoms, focusing on charge transfer and ionicity. The complex dielectric function was employed to determine the optical properties and evaluate their variations under pressure. Finally, the effect of pressure on the physical and electronic properties of the IrAl compound useful for coating applications were evaluated.

Deformation mechanism of highly textured Alnico magnets

Deformed Alnico magnets were prepared by hot isostatic pressing (HIP) spherical powders and hot rolling (HR), and the hot-rolled magnets were solution-treated at 1250 ℃, magnetic heat treated at 835 ℃, and three-stage aged at 600 – 500 ℃, respectively. The results show that Alnico spherical powder comprises 77.5% α phase, 8.6% α1 phase, and 13.9% α2 phase. The HIP magnet has spinodal decomposed during the preparation, and HR improved α content. The magnet has spinodal decomposed thoroughly after magnetic heat treatment (MHT) and aging heat treatment (AHT), composed of 62.1% α1 phase with a B2 structure and 37.9% Fe2NiAl-type α2 phase with the L21 structure. Moreover, the HIP and HR magnet preferentially produces the< 100 > texture, which is also enhanced along the< 211 > directions. The preferred deformation of the α1 phase is carried out under the synergistic action of the α2 phase. The HIP deformation mechanism is that composition diffusion and structural transformation are carried out in different stages, resulting in four kinds of two-phase structures. The rolling deformation mechanism is that the grains parallel or nearly parallel to the rolling direction are directly rolled into lath-like ones, and four kinds of microstructures are formed in the grains. Compared to the HIP magnet, the MHT and AHT promote the formation of the fibrous structure, and the maximum aspect ratio of α1 phase reaches ∼35:1. The coercivity of the heat-treated magnet increased by 160.9%, and the remanence and magnetic energy product also increased simultaneously.

Atomistic simulation of local chemical order in NbTiZrMoV high entropy alloy based on a newly-developed interatomic potential

Numerous studies have demonstrated the importance of local chemical order (LCO) in influencing the mechanical properties of high entropy alloys (HEAs). However, experimental investigation of LCO remains a challenging task. In this paper, the potential parameters for NbTiZrMoV system based on the modified embedded atom method are determined by fitting the lattice constants and formation enthalpies of various binary and ternary alloys. A comparison with the results from first-principles calculations shows that the newly-developed potential has a relatively high accuracy. A hybrid MD/MC simulation is performed using the newly-developed potential to investigate the microstructural evolution of equimolar NbTiZrMoV HEA at room temperature. The simulation results show that clustering and dispersion of different elemental pairs can occur after prolonged annealing. Additionally, the Zr-V pair is observed to form LCOs with B2 structure, which may be an early stage of the experimentally observed Laves phase. Furthermore, the simulation results reveal a relationship between LCO and lattice distortion, indicating that an increase in LCO can lead to a decrease in lattice distortion, which is a significant factor in the investigation of HEA mechanical properties.

RETRACTED: Realization of chiral multifold semimetal RhSi crystalline thin films

Nonmagnetic topological semimetals that combine chirality in real and momentum spaces host unconventional multifold fermions and exhibit exotic electronic and optical properties endowed by their topologically nontrivial electronic band structure. Although the synthesis of nonmagnetic chiral single crystals with a noncentrosymmetric cubic B20 structure is well established, their heteroepitaxial growth in crystalline thin films remains a notable challenge. In this study, we present the structural, magnetic, and electrical magnetotransport properties of 24- and 51-nm-thick films of a B20-RhSi stoichiometric compound grown by magnetron sputtering. RhSi crystalline thin films on Si (111) single-crystal substrates exhibit a preferred (111) orientation with twin domains. The RhSi films display a nonmagnetic ground state, and their electrical resistivity demonstrates a clear and nonsaturating metallic behavior from 300 to 5 K. Magnetotransport measurements reveal that hole-type carriers dominate the Hall response with multiband contributions to electronic transport in the system. The good agreement with the Bloch-Grüneisen model and our first-principles calculations confirms that temperature-dependent electrical resistivity is governed by electron-phonon scattering. The ability to grow textured-epitaxial thin films of nonmagnetic B20 chiral topological semimetals is an important step toward accessing and controlling their remarkable topological surface states for designing chiraltronic devices with novel optoelectronic or spintronic functionalities. Published by the American Physical Society 2023

Phase formation in CrFeCoNi nitride thin films

As a single-phase alloy, CrFeCoNi is a face centered cubic (fcc) material related to the archetypical high-entropy Cantor alloy CrFeCoNiMn. For thin films, CrFeCoNi of approximately equimolar composition tends to assume an fcc structure when grown at room temperature by magnetron sputtering. However, the single-phase solid solution state is typically not achieved for thin films grown at higher temperatures. The same holds true for Cantor alloy-based ceramics (nitrides and oxides), where phase formation is extremely sensitive to process parameters such as the amount of reactive gas. This study combines theoretical and experimental methods to understand the phase formation in nitrogen-containing CrFeCoNi thin films. Density functional theory calculations considering three competing phases (CrN, Fe-Ni and Co) show that the free energy of mixing, \ensuremath{\Delta}$G$ of ${(\mathrm{CrFeCoNi})}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ solid solutions has a maximum at $x=0.20\ensuremath{-}0.25$, and \ensuremath{\Delta}$G$ becomes lower when $x&lt;0.20$ and $x&gt;0.25$. Thin films of ${(\mathrm{CrFeCoNi})}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ ($0.14\ensuremath{\ge}x\ensuremath{\le}0.41$) grown by magnetron sputtering show stabilization of the metallic fcc when $x\ensuremath{\le}0.22$ and the stabilization of the NaCl B1 structure when $x&gt;0.33$, consistent with the theoretical prediction. In contrast, films with intermediate amounts of nitrogen $(x=0.22)$ grown at higher temperatures show segregation into multiple phases of CrN, Fe-Ni-rich and Co. These results offer an explanation for the requirement of kinetically limited growth conditions at low temperature for obtaining single-phase CrFeCoNi Cantor-like nitrogen-containing thin films and are of importance for understanding the phase-formation mechanisms in multicomponent ceramics. The results from the study further aid in making correlations between the observed mechanical properties and the crystal structure of the films.

First-principles study of the effect of pressure on the physical properties of PbC

Silicon carbide has been used as a cutting material and as a semiconductor in lighting and power electronics. Results from some studies, carried out on IV-IV group carbides like GeC and SnC, allow to identify potential technological applications of these carbides in extreme environments, opening the possibility to find new carbides for similar applications. For this work, the PbC was studied under hydrostatic pressure in the framework of the Density Functional Theory, obtaining relevant information on its structural, electronic, mechanical, vibrational, thermodynamical, and optical properties. The optimized lattice parameter and volume, and electronic bands structures type agree with the available theoretical data at zero GPa. The calculated enthalpy values show a phase transition, from the B3 structure (CsCl-type) to the B1 structure (rocksalt or NaCl-type), at 23.5 GPa. The PbC is energetically, mechanically, and dynamically stable for all the pressure values in the studied range; it is a metallic, anisotropic, and brittle material with paramagnetic ionic-covalent bonds and good hardness (the highest mechanical resistance was found above T = 370 K). As the pressure increases, it was noted: (i) the increase of the electronic cloud around the C and Pb atoms, (ii) the DOS spread, (iii) the change to be a ductile material with a tendency to the metallic bonds and (iv) an increase of the hardness and the Young modulus, due to C 2p and Pb 6p-orbitals. Our results show that the PbC is a promising material for applications in the development of optical and optoelectronic devices, and to be used as a protective coating against the low frequencies in the UV and infrared and visible regions.

Searching for medium entropy alloys with desired mechanical property by adaptive design combined with experiments

To overcome the problems caused by the “trial and error” method in the vast element composition space and to rapidly design and discover new medium entropy alloys (MEAs) with required mechanical properties, an efficient data-driven machine learning (ML) strategy based on random forest regression (RFR) algorithm was proposed, utilizing existing data. The alloys were represented by chemical composition and additional features composed of material descriptors. Through correlation analysis, recursive elimination, and exhaustive screening, three key additional features from 20 material descriptors were identified, including six power of work function (W6), valence electron concentration (VEC), and mean Yong's modulus (E). Furthermore, an Efficient Global Optimization (EGO) algorithm was adopted to search for the optimal alloys to guide synthesis. After evaluating >448,000 kinds of alloy systems, the most strongly recommended alloy Al52Co24Cr18Ni4Mn2 with the highest predicted hardness value of 802.5 HV was determined. Interestingly, experimental validation of the synthesized alloy revealed mainly BCC and ordered B2 structure, with a hardness of 815.4 HV, which is approximately 5.2% higher than the highest value in the original dataset. Given the independence of the problem, the proposed approach could be extended to other potential multi-component regression problems.