Ternary Metal Borides Research Articles

Accelerated Exploration of Empty Material Compositional Space: Mg-Fe-B Ternary Metal Borides.

Borides are a family of materials with valuable properties for various applications. Their diverse structures and compositions, yet disparity in the constituent chemical elements for the known compounds, give elemental substitutions for prototypes great potential for material discovery. To explore uncharted material compositional space, we develop a workflow that joins high-throughput crystal structure prediction and automated diffraction pattern matching to discover new compounds with significant prediction and synthesis hurdles. Utilizing the workflow, we explore the empty Mg-Fe-B ternary compositional space, previously uncharted largely due to the immiscibility of Mg and Fe, as a paradigm. A total of 275 ternary boride prototypes are classified, using which we predict 23 (158) stable and metastable ternary phases within 50 (200) meV/atom above the convex hull. We identify Gd2(FeB)7-type Mg2Fe7B7 and ZrCo3B2-type MgFe3B2 to match previously unsolved experimental powder X-ray diffraction (PXRD) patterns. The discovered Mg2Fe7B7 and related channeled structures feature mismatched Mg and (FeB) sublattice periods, for which we conduct structural analyses with respect to the PXRD. They are predicted to exhibit exceptionally fast superionic transport of Mg and outstanding electrochemical performance, which serve as post-Li-ion battery candidate electrode materials. This result opens a new avenue for borides' potential applications as electrode materials and fast ionic conductors. This work also portrays the map and landscape of ternary metal borides with similar chemical environments. With high efficiency, the prototype- and PXRD-assisted crystal structure prediction workflow opens a new avenue for exploring various material compositional spaces across the periodic table.

Synthesis, Characterization, and Magnetocaloric Properties of the Ternary Boride Fe2AlB2 for Caloric Applications.

The ternary transition metal boride Fe2AlB2 is a unique ferromagnetic "MAB" phase that demonstrates a sizable magnetocaloric effect near room temperature-a feature that renders this material suitable for magnetic heat pump devices (MHP), a promising alternative to conventional vapor compression technology. Here, we provide a comprehensive review of the material properties of Fe2AlB2 (magnetofunctional response, transport properties, and mechanical stability) and discuss alloy synthesis from the perspective of shaping these materials as porous active magnetic regenerators in MHPs. Salient aspects of the coupled magnetic and structural phase transitions are critically assessed to elucidate the fundamental origin of the functional response. The goal is to provide insight into strategies to tune the magnetofunctional response via elemental substitution and microstructure optimization. Finally, outstanding challenges that reduce the commercial viability of Fe2AlB2 are discussed, and opportunities for further developments in this field are identified.

Unveiling a Family of Dimerized Quantum Magnets, Conventional Antiferromagnets, and Nonmagnets in Ternary Metal Borides.

Dimerized quantum magnets are exotic crystalline materials where Bose-Einstein condensation of magnetic excitations can happen. However, known dimerized quantum magnets are limited to only a few oxides and halides. Here, we unveil 9 dimerized quantum magnets and 11 conventional antiferromagnets in ternary metal borides MTB4 (M = Sc, Y, La, Ce, Lu, Mg, Ca, and Al; T = V, Cr, Mn, Fe, Co, and Ni), where T atoms are arranged in structural dimers. Quantum magnetism in these compounds is dominated by strong antiferromagnetic (AFM) interactions between Cr (Cr and Mn for M = Mg and Ca) atoms within the dimers, with much weaker interactions between the dimers. These systems are proposed to be close to a quantum critical point between a disordered singlet spin-dimer phase, with a spin gap, and the ordered conventional Néel AFM phase. They greatly enrich the materials inventory that allows investigations of the spin-gap phase. Conventional antiferromagnetism in these compounds is dominated by ferromagnetic Mn (Fe for M = Mg and Ca) interactions within the dimers. The predicted stable and nonmagnetic (NM) YFeB4 phase is synthesized and characterized, providing a scarce candidate to study Fe dimers and Fe ladders in borides. The identified quantum, conventional, and NM systems provide a platform with abundant possibilities to tune the magnetic exchange coupling by doping and study the unconventional quantum phase transition and conventional magnetic transitions. This work opens new avenues for studying novel magnetism in borides arising from spin dimers and establishes a theoretical workflow for future searches for dimerized quantum magnets in other families of materials.

Mechanical effects of Cr and V substitutions in AlFe2B2 by first-principles calculations

MAB phase AlFe2B2 has attracted a lot of attention as a ternary transition metal boride with layered structure due to its near-room temperature magneto-caloric effect (MCE), composed of earth-abundant elements and other properties. In this work the electronic structure, chemical bonding characteristics, mechanical stability, elastic properties, and elastic anisotropy of AlFe2B2-based compounds (borides) have been investigated using first-principles calculations based on density functional theory (DFT). The substitution effect of transition metals (TM) Cr and V in AlFe(2-x)TMxB2 (x = 0–1), (TM = Cr, V) compounds have been investigated. It was determined that all the elements added instead of the removed Fe element in the borides increased the mechanical properties such as hardness, brittleness, and isotropy. Moreover, it has been observed that hardness, brittleness, and isotropy increase with the increasing amount of the fourth alloying element. In AlFe(2-x)TMxB2, it has been observed that for x = 0.25 and 0.5 values, V causes an increase in stiffness more than Cr; however, for x = 1, while the increase in Cr continues to have an effect, a reverse trend is observed for V. Additionally, it has been observed that an increase in isotropy is significantly more influenced by Cr than by V. Among borides, it has been determined that AlFeCrB2 exhibits the highest elastic moduli (bulk, shear, and Young's modulus), hardness, and isotropy.

Ternary Lithium Nickel Boride with 1D Rapid-Ion-Diffusion Channels as an Anode for Use in Lithium-Ion Batteries.

Anode materials with high-rate performances and good electrochemical stabilities are urgently required for the grid-scale application of lithium-ion batteries (LIBs). Theoretically, transition metal borides are desirable candidates because of their appropriate working potentials and good conductivities. However, the reported metal borides exhibit poor performances owing to their lack of favorable Li+ storage sites and poor structural stabilities during long-term charging/discharging. In this work, a ternary alkali metal boride, Li1.2Ni2.5B2, which displays a high Li+ storage capacity and remarkable electrochemical stability and an excellent rate performance is studied. In contrast to conventional transition metal borides, the introduction of Li atoms facilitates the formation of 1D Ni/B-based honeycomb channels during synthesis. This Ni/B framework successfully sustains the strain during Li+ intercalation and deintercalation, and thus, the optimized Li1.2Ni2.5B2 anode exhibits an excellent cycle stability over 500 charge/discharge cycles. This electrode also exhibits superior reversible capacities of 350, 183, and 80mAhg-1 at 0.1, 1, and 5Ag-1, respectively, indicating the considerable potential of the 1D Ni/B framework as a commercially available fast-charging LIB anode.

Soft Chemistry of Hard Materials: Low-Temperature Pathways to Bulk and Nanostructured Layered Metal Borides.

Conspectus"Synthesis by design" is often considered to be the primary goal of chemists who make molecules and materials. Synthetic chemists usually have in mind a target they want to make, and they want to be able to design a pathway that can get them to that target as quickly and efficiently as possible. Chemists who synthesize refractory solids, which have melting points above 1000 °C and are often chemically inert at these high temperatures, have access to only a small number of synthetic strategies due to the need to overcome solid-state diffusion, which is the rate-limiting step in such reactions. The use of extremely high temperatures to facilitate diffusion among two or more refractory solids, which precedes any chemical reaction that must occur, generally drives the system to form only the product that is the most thermodynamically stable-the global minimum on an energy landscape-for a certain combination of elements. When trying to target a different product in the same system, one generally cannot rely on thermally driven reactions. Lower-temperature reactions that side step this diffusion limitation can succeed where high temperatures fail by providing access to local minima on an energy landscape. These local minima represent metastable phases that are primed for synthesis, but only if an appropriate pathway and set of reactions can be identified. It is therefore important to develop and understand low-temperature, or "soft", chemical reactions in "hard" refractory systems. These reactions allow us to apply the retrosynthetic framework that molecular chemists rely on to systems where chemists have not previously had such control over reactions, reactivities, and metastable product formation.In this Account, we discuss the development of soft chemical reactions of hard materials in the context of a class of layered, refractory metal borides that are precursors to an emerging family of two-dimensional nanomaterials. Layered ternary metal boride phases such as MoAlB have layers of metal borides, which are chemically unreactive, interleaved with layers of aluminum, which are reactive. Some of the interlayer aluminum can be deintercalated at room temperature in dilute aqueous sodium hydroxide, transforming stable MoAlB into destabilized MoAl1-xB. Mild thermal treatment of submicrometer grains of this destabilized MoAl1-xB sample allows it to traverse the energy landscape and crystallize as Mo2AlB2, a metastable compound. Further thermal treatment transforms Mo2AlB2 into a Mo2AlB2-alumina nanolaminate and ultimately mesoporous MoB, all through continued traversing of the energy landscape using mild chemical and thermal treatments. Similar topochemical manipulations, which maintain structure but change composition, are emerging for other MAB phases and are opening the door to new types of metastable compounds and nanostructured materials in traditionally refractory systems.

Accelerating the Discovery of Transition Metal Borides by Machine Learning on Small Data Sets.

Accurate and efficient prediction of the stability and structure-stability relationship is important to discover materials; however, it requires tremendous efforts via traditional trial-and-error schemes. Here, we presented a small-data set machine learning (ML) method to accelerate the discovery of promising ternary transition metal boride (MAB) candidates. Based on data sets obtained by ab initio calculations, we developed three robust neural networks to predict the decomposition energy (ΔHd) and assess the thermodynamic stability of 212-typed MABs (M2AB2). The quantitative relation between ΔHd and stability was unraveled by several composition-and-structure descriptors. Three hexagonal M2AB2, i.e., Nb2PB2, Nb2AsB2, and Zr2SB2, were discovered to be stable with negative ΔHd, and 75 metastable MABs were identified with ΔHd less than 70 meV/atom. Finally, the dynamical stability and mechanical properties of MABs were investigated by ab initio calculations, whose results further verified the reliability of our ML models. This work provided a ML approach on small data sets to accelerate the discovery of compounds and expanded the MAB phase family to VA and VIA groups.

Sol–gel combustion derived novel ternary transition metal boride-anisotropic magnetic powders and their magnetic property

We investigated the auto-ignition based sol–gel approach for the synthesis of ternary transition metal boride (TTMB) powders and studied their magnetic property. The obtained TTMB powders were found to have different crystallinity and magnetic behavior, based on the boron to metal ratio and further introduction of dysprosium into one of the sample lattice. The magnetic results obtained by vibrating sample magnetometer shows that TTMB is a soft magnet which demonstrates high ferromagnetic behavior with increased magnetic saturation based on the boron content, while the dysprosium based TTMB on contrary was found to exhibit an antiferromagnetic behavior. The TTMB powder showed no impurities as observed in Raman spectroscopy. The morphology of the powders obtained microscopically displays distinctive facets in the crystalline samples. The TTMB powders can be prospectively used in different polymer matrix to fabricate novel devices for sensors, environmental catalysts, radiation shielding and contrasting agents etc., to name a few.

Broadband Nonlinear Response and Ultrafast Photonics Applications in Few-Layer MBene

2D MBenes, the latest derivatives of bulk ternary or quaternary transition metal boride (MAB) phases, have gradually attracted increasing research attention as novae in the flatland. However, the fabrication of MBenes is still a great challenge at present, leading to the lack of reported MBene applications in the photonic field (e.g., ultrafast lasers). Hence, we successfully fabricated few-layer Mo4/3B2–xTz MBenes by selectively etching nanolaminated 3D parent boride (Mo2/3Y1/3)2AlB2. Density functional theory calculations were used to theoretically analyze its electronic and optical properties. By employing the Z-scan technique, the nonlinear absorption characteristics of Mo4/3B2–xTz MBenes from the visible to mid-infrared regime were revealed for the first time. Compared with mainstream 2D materials and common MXenes, Mo4/3B2–xTz has more potential as a nonlinear optical (NLO) material, such as stronger nonlinear absorption (about 100 times of graphene) and lower saturation intensity (about 1% of black phosphorus). Furthermore, by integrating Mo4/3B2–xTz as a saturable absorber (SA) into three similar gain fiber-based laser resonators, broadband stable ultrafast pulses were obtained with pulse durations of 358.7 ps (1 μm), 582.3 fs (1.5 μm), and 2.31 ps (2 μm). Innovation in MBenes as SA will allow the design of novel photonic systems and devices with broadband functionality, opening a promising paradigm for the conscious design of high-performance NLO materials.

2D MBenes: A Novel Member in the Flatland

2D MBenes, early transition metal borides, are a very recent derivative of ternary or quaternary transition metal boride (MAB) phases and represent a new member in the flatland. Although holding great potential toward various applications, mainly theoretical knowledge about their potential properties is available. Theoretical calculations and preliminary experimental attempts demonstrate their rich chemistry, excellent reactivity, mechanical strength/stability, electrical conductivity, transition properties, and energy harvesting possibility. Compared to MXenes, MBenes' structure appears to be more complex due to multiple crystallographic arrangements, polymorphism, and structural transformations. This makes their synthesis and subsequent delamination into single flakes challenging. Overcoming this bottleneck will enable a rational control over MBenes' material-structure-property relationship. Innovations in MBenes' postprocessing approaches will allow for the design of new functional systems and devices with multipurpose functionalities thus opening a promising paradigm for the conscious design of high-performance 2D materials.

Friction and wear characteristics of the nanolaminated ternary transition metal boride: Mn2AlB2

Herein, the wear and friction behavior, under unlubricated sliding in ambient air, of the MAB phase Mn2AlB2 is reported. Various sliding pairs (WC, Al2O3, Si3N4, and chromium-bearing steel 100Cr6) were used in a ball-on-disc apparatus at a normal load of 10 N and a sliding velocity of 20 cm/s. Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy were used to identify the wear mechanisms and tribo-oxidation products involved during the dry sliding contacts. Against WC, Al2O3, and Si3N4, the Mn2AlB2 exhibited wear by tribo-oxidation accompanied with delamination and abrasion, which led to high wear rates on the order of ∼10-3 mm3/N · m and coefficients of friction of 0.72–0.87. However, Mn2AlB2/100Cr6 tribopair showed relatively mild wear behavior. The evolution of COF and wear rate for this tribopair, under different loads (5, 10, 15 N) and speeds (5, 25, 50 cm/s), showed the existence of load and speed thresholds (15 N at 25 cm/s and 10 N at 50 cm/s), beyond which an abrupt transition from mild to severe wear of Mn2AlB2 takes place. Below the thresholds, the Mn2AlB2 surfaces remain undamaged with the formation of a protective transfer layer, composed of a mixture of iron and manganese oxides. Above the thresholds, both friction and wear increase, and the Mn2AlB2 wears by microfracture and grain pullout.

An efficient amorphous ternary transition metal boride (WFeNiB) electrocatalyst for oxygen evolution from water

To improve the overall efficiency of water electrolysis, it is urgent to develop an efficient and inexpensive catalyst toward the oxygen evolution reaction (OER).

Cerium decorated amorphous ternary Ni-Ce-B catalyst for enhanced electrocatalytic water oxidation

Metal borides have been acknowledged as promising candidates for alkaline oxygen evolution reaction (OER). Here, amorphous ternary metal borides (Ni-Ce-B) with different molar ratios of Ce% are achieved by a facile wet chemical method. With the optimal 5% of Ce, the as-prepared Ni-Ce-B-5/NF electrode exhibits comparable OER performance with lower overpotential (240 mV) than that of pure Ni-B/NF electrode (330 mV) and other metal borides. The high activity of Ni-Ce-B/NF is attributed to the amorphous structure and synergistic effect of binary metal Ni and Ce in Ni-Ce-B materials. Additionally, CeO2-x forms and serves as an electron acceptor during the self-electrooxidation process, facilitating the formation of crystalline high-valence nickel species, resulting in robust electrocatalysis and long-term stability. This work presents a Ce-based metal boride as a promising candidate for the low-cost and highly efficient OER catalyst.

Structural, electronic, mechanical, and thermodynamic properties of ultra-high-temperature ceramics α- and β-YAlB4: A first-principles study

In this work, we performed first-principles calculations to study the structural, electronic, mechanical, and thermodynamic properties of α- and β-YAlB4. α- and β-YAlB4 was an ultra-high-temperature ceramic. α-YAlB4 belonged to the type of YCrB4, the space group was Pbam, β-YAlB4 belonged to the type of ThMoB4, and the space group was Cmmm. The bulk modulus B, Young's modulus E, and shear modulus G of YAlB4 in the (100), (010), and (001) planes were calculated, and the results revealed that the elastic modulus of YAlB4 had obvious anisotropy. An analysis of state density showed that YAlB4 was a ternary metal boride that had the properties of metal, and the chemical bond was the combination between covalent bonds and metal. We also discuss the minimum thermal conductivity of α- and β-YAlB4 using Clark and Cahill's models. The dynamic stability of YAlB4 was verified by the phonon dispersion curve.

Exploring the hydrogen evolution capabilities of earth-abundant ternary metal borides for neutral and alkaline water-splitting

Amorphous ternary metal borides in the form of Co-M-B (where, M = Fe, Ni, Cu, Mo, Mn, W or Cr) were developed for electrocatalytic hydrogen evolution in neutral and alkaline solutions. Except for Co-Cr-B, all the Co-M-B catalysts showed better hydrogen evolution rate than Co-B, with the lowest overpotential of 95 mV and 67 mV (at 10 mA/cm2) recorded for optimized Co-Mo-B catalyst, in pH 7 and pH 14, respectively. The reasons for enhancement in electrocatalytic rate, with inclusion of a second metal in Co-B, were investigated by considering several material related factors, such as, physical and electrochemical surface area, turn-over frequency, surface elemental states & composition and charge-transfer resistance. These experimental results were complemented with computational investigations to identify the most suitable sites for hydrogen adsorption and determine their H-adsorption energies. In the end, industrial feasibility of the developed Co-M-B catalysts was illustrated by performing stability and recycling tests.

The investigation of electronic, anisotropic elastic and lattice dynamical properties of MAB phase nanolaminated ternary borides: M2AlB2 (M=Mn, Fe and Co) under spin effects

Abstract In the present study, the structural, electronic, magnetic, anisotropic elastic and lattice dynamic properties of the ternary metal borides M 2 A l B 2 ( M = M n , F e and C o ) known as MAB phases have been investigated by density functional theory. The obtained results from the structural optimizations show that all these compounds have negative formation enthalpy implying the thermodynamic stability and synthesizability. The spin effects on the M 2 A l B 2 phases have been studied with the plotted energy-volume curves for different magnetic phases (antiferromagnetic (AFM), ferromagnetic (FM), and paramagnetic (PM)) of these compounds. The stable magnetic phase for the M n 2 A l B 2 compound is found to be AFM while the magnetic nature of F e 2 A l B 2 and C o 2 A l B 2 compounds are FM. The calculated electronic band structures with the total and orbital projected partial density of electronic states imply that these ternary metal borides have metallic behavior. Also, the mentioned compounds have mechanical and dynamic stability due to the calculated elastic constants and the observed phonon dispersion curves. Some thermodynamic properties have been investigated by means of phonon dispersion curves. Furthermore, the anisotropic elastic properties have been visualized in three dimensions (3D) for Young’s modulus, linear compressibility, shear modulus, Poisson’s ratio, and sound wave velocities.

The synthesis of binary and ternary cobalt based metal borides by inorganic molten salt technique

Crystalline metal boride powders were synthesized via low temperature method in inorganic molten salt medium, and binary and ternary metal boride composite powders were investigated using anhydrous metal chlorides and sodium borohydride powder mixtures. The reactions were carried out in an aluminum crucible placed in a silica tube under argon which was put in a vertical tube furnace. At the end of the reaction, the resulting powder mixture was leached with hot water to remove any undesirable chloride phases. In order to improve crystalline properties, some of pure powders were selected and annealed at 1100°C. Characterization of synthesized and annealed powders was carried out using X-ray diffractometer (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM / EDX) and dynamic light scattering technique (DLS). The results showed the positive effect of inorganic molten salt technique (LiCl/KCl eutectic mixture) on the formation of phases during the reaction between CoCl2, NiCl2 and NaBH4 powder mixtures. Following the reactions at between 750-950 °C, the binary and ternary metal boride powders consisting of CoB-Ni2B-CoBx, CoB-Ni4B3 ve CoB-NiB-Ni2Co0.67B0.33 phases were obtained. The measured particle size of the final particles had an average of 60 nm.

Facile Synthesis of Amorphous Ternary Metal Borides-Reduced Graphene Oxide Hybrid with Superior Oxygen Evolution Activity.

Metal borides represent an emerging family of advanced electrocatalyst for oxygen evolution reaction (OER). Herein, we present a fast and simple method of synthesizing iron-doped amorphous nickel boride on reduced graphene oxide (rGO) sheets. The hybrid exhibits outstanding OER performance and stability in prolonged OER operation. In 1.0 M KOH, only 230 mV is required to afford a current density of 15 mA cm-2 with a small Tafel slope of 50 mV dec-1. DFT calculations lead to a suggestion that the in situ formation of MO xH y during electrochemical activation acts as active sites for water oxidation. The superior OER activity of the as-prepared catalyst is attributed to (i) its unique amorphous structure to allow abundant active sites, (ii) synergistic effect of constituents, and (iii) strong coupling of active material and highly conductive rGO. This work not only provides new perspectives to design a highly effective material for OER but also opens a promising avenue to tailor the electrochemical properties of metal borides, which could be extended to other materials for energy storage and conversion technologies.

Design principles describe new superhard metal borides

Doping ternary metal borides to alter both the atomic arrangement and grain size in the material could give a new generation of cost-effective superhard materials.

Study of structural, electronic, optical and thermal properties of refractory material (CrAlB)

The structural, electronic, optical and thermal properties of ternary transition metal boride (CrAlB) are studied using full potential linearized augmented plane wave method in the framework of the density functional theory. The exchange-correlation potential is solved using the modified Perdew-Burke-Ernzerhof generalized gradient approximation (PBEsol-GGA). The structural parameters are optimized to obtain equilibrium lattice constant, bulk modulus and its pressure derivative. The calculated band structure, density of states and electronic charge density show that the material possesses metallic nature and have covalent band character. Optical spectra calculations such as the real and imaginary part of dielectric constant, refractive index, extinction coefficient, reflectivity, absorption coefficient, conductivity, and loss function are performed within the photon energy range of 0–40 eV. In this case the obtained plasma frequency corresponds to 24.12eV. For radiation above this energy the property of CrAlB changes from metallic to dielectric. The calculations of the thermal properties using Gibb's program have been performed in the range 0–5000 K at 0, 20 and 50 GPa of pressure. The studies of optical and thermal properties show that it is an eligible candidate for optoelectronic devices, and the devices working at high temperature. The results for CrAlB are reported for the first time as neither CrAlB has been synthesized nor any theoretical calculation has been performed till so far.