Metal Intermetallic Compounds Research Articles

New soft magnetic materials ([formula omitted])[formula omitted]B with tunable magnetic anisotropy

Soft magnetic materials play important roles in both power generation and conversion devices with the rapid development of power semiconductors, however, finding new soft magnetic materials is an urgent problem. It was found that (Y1−xSmx)2Fe14B (0≤x≤1) compounds prepared by vacuum induction melting have a tetragonal structure. In (0≤x≤1) range, the saturation magnetization is higher than 110 A⋅m2/kg, the Curie temperature is over 290 °C, the coercivity and the remanence are less than 5729.8 A⋅m−1 and 7 A⋅m2/kg, respectively. Furthermore, with increasing x the directions of easy magnetization change from the c-axis (x=0.00) to the cone plane (x=0.15), and then to the ab-plane (x≥0.30). For x=0.15 compound, the permeability at 100 kHz is 11.8, that is beyond all of existing rare earth magnetic materials. These indicate that (Y1−xSmx)2Fe14B compounds are the promising candidate for proper soft magnetic materials without x=0. Our work extends the function of rare earth transition metal intermetallic compounds, which open a new way to find advanced soft magnetic materials.

Feasibility analysis of replacing lithium-ion battery with sodium ion battery

Since the beginning of the 21st century, the global energy crisis has become a pressing issue, prompting researchers to explore more efficient ways of utilizing energy production and storage technologies in our daily lives. In recent years, there have been major improvements in lithium-ion batteries (LIBs) technology, considerably improving living conditions globally. LIBs are currently commonly employed in electric cars. However, the efficient distribution of renewable energy and smart grids raises concerns, along with the long-term availability of lithium resources. The scarcity and rising costs of lithium metal in recent years have been attributed to substantial price fluctuations. Thus, LIBs have made it difficult to meet the increasing demands of both small and medium to large energy storage applications. Due to the readily available properties of sodium metal, it has similar chemical properties to LIBs. To alleviate these challenges, sodium-ion batteries (SIBs) can be used as the finest candidates for power supply. In recent years, different materials such as metal oxides and phosphates have been introduced as positive electrode materials for SIBs. The use of selected carbonaceous materials, transition metal oxides, intermetallic compounds, and organic compounds as negative electrode materials for SIBs has also contributed to recent developments. SIB is a promising next-generation replacement, but there are still some challenges in the market acceptance of SIBs. In this research, we summarize and compare the market application status of SIB and lithium iron phosphate (LFP), and propose the future development trajectory of SIB and LFP according to their respective characteristics. This will provide a unique insight into practical application problems and market realities.

A newly developed Cu(Rh) alloy film and its characteristics and applications

A new type of copper (Cu)-rhodium (Rh)-alloy, Cu(Rh), films is developed by co-sputtering copper and rhodium onto silicon (Si) substrates under an argon (Ar) atmosphere. The new films are next annealed at 600 and 670 °C, or alternatively at 100 and 450 °C, for 1 h. Longer annealing to the films, for up to 8 days, is also conducted to explore resistivity variation. The resistivity of the new 300-nm-thick film is 2.19 μΩ cm after annealing at 670 °C for 1 h and drifts to 2.26 and 2.14 μΩ after annealing at 400 and 450 °C, respectively, for 200 h. A 2.7-μm-thick Sn layer is then thermally evaporated atop the new film for stable flip-chip solder joints; their metal and Cu-Sn intermetallic compound (IMC) growth processes vs. various annealing periods are tested. After annealing at 670 °C, the new 300-nm-thick film’s adhesive strength reaches 44.2 ± 0.01 MPa, which is 11 ~ 12-fold that of their pure Cu counterpart. Some key test results of the new film are disclosed herein, including its X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) images, secondary-ion mass spectrometry (SIMS), time-dependent dielectric-breakdown (TDDB) lifetime curves, and adhesive strength. The new film’s antibacterial efficacy arrives at an antibacterial ratio of approximately 100% against Staphylococcus aureus (S. aureus) BCRC 10451 for the 300-nm-thick film and approximately 99.82% for the 8 nm film, far superior to that of a pure Cu film, which is 0 with the same annealing temperature range. The new film, hence, seems to be a remarkable candidate material for various industrial applications, such as ultra-large-scale integrated circuits (ULSIC), micro-electronic circuits, printed circuits, flip-chip technology, medical care concerning antibacteria, and the like.Graphical A new type of copper (Cu)-rhodium (Rh)-alloy, Cu(Rh), films is developed by co-sputtering copper and rhodium onto silicon (Si) substrates under an argon (Ar) atmosphere and then annealing the new films at 600 and 670 °C, or alternatively at 100 and 450 °C, for 1 h. Longer annealing to the films, for up to 8 days, is also conducted to explore resistivity variation. The resistivity of the new 300-nm-thick film is 2.19 mW cm after annealing at 670°C for 1 h and drifts to 2.26 and 2.14 mW after annealing at 400 and 450 °C, respectively, for 200 h. A 2.7-μm-thick Sn layer is next thermally evaporated atop the new film for stable flip-chip solder joints; their metal and Cu-Sn intermetallic compound (IMC) growth processes vs. various annealing periods are tested. After annealing at 670°C, the new 300-nm-thick film’s adhesive strength reaches 44.2 ± 0.01 MPa, which is 11~12-fold that of their pure Cu counterpart. Some key test results of the new film are disclosed herein, including its X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) images, secondary-ion mass spectrometry (SIMS), time-dependent dielectric-breakdown (TDDB) lifetime curves, and adhesive strength. The new film’s antibacterial efficacy arrives at an antibacterial ratio of approximately 100% against Staphylococcus aureus (S. aureus) BCRC 10451 for the 300-nm-thick film and approximately 99.82% for the 8-nm film, far superior to that of a pure Cu film, which is 0 with the same annealing temperature range. The new film, hence, seems to be a remarkable candidate material for various industrial applications, such as ultra-large-scale integrated circuits (ULSIC), micro-electronic circuits, printed circuits, flip-chip technology, medical care concerning antibacteria, and the like.

Metal Hydride Composite Structures for Improved Heat Transfer and Stability for Hydrogen Storage and Compression Applications

Metal alloys and intermetallic compounds offer an attractive method for safely storing hydrogen (H2). The metal alloys absorb H2 into their structure, often swelling and fracturing as a result of phase transformation during hydride formation/decomposition cycles. The absorption of H2 is an exothermic process, requiring the effective and efficient removal of heat. This can be challenging as heat transfer to/from powdered beds is notoriously difficult, and often limited by poor thermal conductivity. Hence, the observed reaction kinetics for absorption and desorption of H2 is dominated by heat flow. The most common method for improving the thermal conductivity of the alloy powders is to prepare them into composite structures with other high thermal conductivity materials, such as carbons and expanded natural graphite. Such composite structures, some also combined with polymers/resins, can also mitigate safety issues related to swelling and improve cyclic durability. This paper reviews the methods that have been used to prepare such composite structures and evaluates the observed impact on thermal conductivity.

Alloy selection for dual stage metal-hydride hydrogen compressor: Using a thermodynamic model to identify metal-hydride pairs

Metal-hydrides offer a potentially competitive method for compressing hydrogen, particularly where waste heat is available. Metal hydrides are metal alloys or intermetallic compounds that react reversibly with H2. They readily absorb low-pressure H2 at low temperature, and then release H2 at a higher pressure when the temperature is raised. The high pressure H2 is released at a pressure above that expected from standard press-temperature relations. The absorption and desorption pressures of the hydrides are determined by their thermodynamic properties (enthalpy and entropy). To achieve compression ratios above about 10, more than one stage of compression is typically required. The challenge is to find alloy pairs that can work together effectively to achieve the desired compression from the heating/cooling available. Previously, a thermodynamic model has been proposed for identifying suitable metal hydrides that can be paired together to achieve a desired compression. This paper describes methods used previously in the literature to select alloy pairs, and applies the current method to an example selection of 33 hydrides with potential for hydrogen compression. The example application aims to find pairs that can compress a H2 stream from 10 to 350 bar using a temperature range of 30–150 °C, however the theory could readily be adapted to different compression ratios and temperature ranges. For the specific example evaluated none of the potential pairs were able to meet the compression target, however, modification of the parameters (heating/cooling availability) or alloy properties could resolve this issue.

Coexistence of Sn and FeSn2 nanoparticles dispersed in glass-ceramics and their electrochemical performance as sodium-ion battery anode

New glassy samples with 55SnO-15Na2O-yFe2O3-(30–y)SiO2 compositions (y = 0–9) were synthesized by the mechanochemical milling method to explore new sodium-ion battery (SIB) anodes with the coexistence of β-Sn and FeSn2 nanoparticles. It was clarified from X-ray diffraction analysis and transmission electron microscopy observations that β-Sn metal and FeSn2 intermetallic compound with the size of ∼100 nm were formed in the glass powders heat-treated at 450 °C for 3–10 h in 10%H2/90%N2 reducing atmosphere. It was suggested that the growth (coarsening) of β-Sn is largely depressed due to the formation of FeSn2, and β-Sn, FeSn2, and the Na2O-SiO2-based amorphous phase are dispersed homogeneously in the glass-ceramics. It was clarified that new glass-ceramics are working as anode materials for SIBs, for example, showing the initial capacity of 350 mAh/g in the sample with y = 6.75 and the reversible alloying behavior between β-Sn/FeSn2 and Na+ ions. The addition of Fe2O3 and the coexistence of FeSn2 with β-Sn contribute to the stable operation of the sodium half-cell.

New fabrication of nonmodel supported catalysts for cellulose to low carbon chemicals with the assistance of mechanochemical abrading

The controllable conversion of cellulose on heterogeneous catalysts is a promising strategy in biomass utilization. However, the catalysts in this field are fabricated by a conventional, calcination/hydrothermal method, both of which are time-consuming, high cost and limit their large-scale applications. In this study, we developed the mechanical force as an auxiliary method to fabricate nonmodel supported catalyst with the assistance of chitosan (CTS). The input kinetic energy facilitated strain refinement and microstructure defects generation by shear force and plastic deformations, which stimulated the metal precursors anchored in situ in the CTS matrix. Based on the interactions between metals (Ni and Sn) and nitrogen atoms, the single metal nanoparticles and intermetallic compounds (NixSny) were well dispersed with 152 μmol/g of Lewis acid and 91 μmol/g of base amount by interaction with nitrogen sites. 62.8% of C2,3 polyols were obtained from cellulose on 15%Ni–15%W/CTS catalyst. More importantly, this catalyst prepared by mechanochemical abrading demonstrated perfect stability with less than 2.0 ppm of etched metal cations for the eighth use in acidic hydrothermal conditions. In accordance, the nitrogen sites in the carbon matrix offered strong covalent bonds regarding as anchoring rope for stabilizing Ni species. This work potentially offers a facile but effective method for the development of supported Ni–Sn catalysts with possible large-scale production.

Evolution mechanism of microstructure and bond strength based on interface diffusion and IMCs of Ti/steel clad plates fabricated by double-layered hot rolling

Ti/steel clad plates have good corrosion resistance and lower titanium cost. However, the low interfacial bond strength severely restricts their wide application. In this study, a new process is proposed for preparing Ti/steel clad plates with high bond strength by employing double-layered slab assembly and hot rolling. The effect of temperature on bond strength is systematically studied. The results show that the shear strength initially increases and then decreases with increasing temperature from 700 °C to 950 °C. The maximum strength value of 311 MPa is obtained at 850 °C with a reduction rate of 30% in a single pass. The mechanism analysis shows that the bond strength is affected by temperature in terms of metal deformation, elemental diffusion and intermetallic compound (IMC) formation. In addition, the shear strength depends on different degrees of dislocation strengthening and recrystallization in the titanium matrix when the fracture is located at titanium matrix near the interface. Finally, a phenomenological prediction mechanism-based model is developed to describe the relationship between the temperature and the bond strength. This research can provide guidance for the hot rolling preparation of Ti/steel clad plates with high bond strength. • Ti/steel plates were fabricated by double-layered slab assembly and hot rolling. • A superior bond strength of 311 MPa was obtained at 850 °C. • Microstructure evolution was characterized. • Bonding mechanism at different temperatures was analyzed. • A phenomenological prediction mechanism-based model was proposed.

Experimental-numerical analysis of the fracture process of Al-Al-Ti laminated composite

In the paper presented a study of the fracture process of explosive welded layered material AA2519-AA1050-Ti6Al4V (Al-Al-Ti laminate) at ambient (+20 °C) and reduced (−50 °C) temperatures. The tensile tests and fracture toughness tests were conducted for both types specimens made of base materials plates and of laminated plate. During tensile tests performed on flat specimens the signals of loading force (P) and specimen extension (uext) were recorded. The signals of loading force (P), specimen deflection (udef) and the crack mouth opening displacement (COD) were recorded while performing the tests on fracture toughness of materials on SENB type specimens. The breakthroughs of the tested specimens were observed by scanning electron microscope (SEM).The results obtained during the experimental tests indicate the complicated nature of the cracking process of specimens from the Al-Al-Ti laminate. The deviation from linearity was observed during loading on the sections where it should be linear. There were also slightly decreases in the force value during the load. During macro observation of the fractured surfaces of SENB specimens, delamination cracks between the Al and Ti layers are clearly visible. The size of these cracks increases as the test temperature decreases. The SEM observations clearly indicate that the delamination crack is formed in the AA1050 layer joining the Ti6Al4V and AA2519 base materials. Precise observation by SEM allowed to establish that the development of a delamination crack begins with different type of particles fracture and material discontinuous in narrow strip (20–40 mm) near at Ti6Al4V material. Then the delamination crack develops in the layer of AA1050 material according to a shear mechanism.In order determine the stress and strain distributions in tested specimens the they numerical models were developed and simulation of loading were performed by ABAQUS program. The results of stress and strain distributions obtained clearly shows on large differences they values in the different layers of the laminate. Maximal differences of stress levels occurs between layers Ti6Al4V and AA1050 materials. Due to the fact that the material of the connecting layer (AA1050) has a low level of yield strength, a very high level of plastic strain occurs.Based on the results obtained during the experimental tests, SEM observation of fracture surfaces and numerical calculations, it can be concluded that the weakest area in the tested laminate is the connecting layer AA1050. Namely is it, a thin strip between AA1050 and Ti6Al4V, which consists of metal base particles, intermetallic compounds, their oxides and discontinuities of the material in form of voids.When using this type of laminate, special attention should be paid to the strength of the AA1050 bonding layer.

Structure and Magnetic Properties of ErFexMn12-x (7.0 ≤ x ≤ 9.0, Δx = 0.2).

The magnetic interactions of iron-rich manganese-based ThMn12 type rare earth metal intermetallic compounds are extremely complex. The antiferromagnetic structure sublattice and the ferromagnetic structure sublattice had coexisted and competed with each other. Previous works are focus on studying magnetic properties of RFexMn12−x (x = 0–9.0, Δx = 0.2). In this work, we obtained a detailed magnetic phase diagram for iron-rich ErFexMn12−x series alloy samples with a fine composition increment (Δx = 0.2), and studied the exchange bias effect and magneto-caloric effect of samples. ErFexMn12−x series (x = 7.0–9.0, Δx = 0.2) alloy samples were synthesized by arc melting, and the pure ThMn12-type phase structure was confirmed by X-ray diffraction (XRD). The neutron diffraction test was used to confirm the Mn atom preferentially occupying the 8i position and to quantify the Mn. The magnetic properties of the materials were characterized by a comprehensive physical property measurement system (PPMS). Accurate magnetic phase diagrams of the samples in the composition range 7.0–9.0 were obtained. Along with temperature decrease, the samples experienced paramagnetic, ferromagnetic changes for samples with x < 7.4 and x > 8.4, and paramagnetic, antiferromagnetic and ferromagnetic or paramagnetic, ferromagnetic and antiferromagnetic changes for samples with 7.4 ≤ x ≤ 8.2. The tunable exchange bias effect was observed for sample with 7.4 ≤ x ≤ 8.2, which resulting from competing magnetic interacting among ferromagnetic and antiferromagnetic sublattices. The maximum magnetic entropy change in an ErFe9.0Mn3.0 specimen reached 1.92 J/kg/K around room temperature when the magnetic field change was 5 T. This study increases our understanding of exchange bias effects and allows us to better control them.

Room temperature magnetocaloric effect of Ce0.65Mg0.35Co3

The magnetocaloric (MC) effect of Ce0.65Mg0.35Co3 alloy is simulated using a phenomenological model (PM). MC parameters of Ce0.65Mg0.35Co3 alloy are obtained from modelling findings as the result of simulation for magnetization vs. temperature in a 0.1 T magnetic field. The full-width at half-maximum of 104 K is impressive, providing an important basis for operating the Ce0.65Mg0.35Co3 alloy in the magnetic refrigerator (MR). Since the Ce0.65Mg0.35Co3 alloy may be used as an effective MC material for MR throughout a wide temperature range, it can cover a significant and crucial range of temperatures, including room temperature and lower temperatures. The MC parameters of Ce0.65Mg0.35Co3 alloy are larger than those of metal oxide nanoparticles, ferrites, intermetallic compounds, and manganites that have been published previously, concluding that Ce0.65Mg0.35Co3 alloy can serve as an advantageous MC magnet for the MR.

Fundamental understanding of the synthesis of well-defined supported non-noble metal intermetallic compound nanoparticles

Fundamental insights into the synthesis of model-like, supported, non-noble metal intermetallic compound nanoparticle catalysts with phase pure bulk and bulk-like 1st-atomic-layer particle surface composition.

(Keynote) New Classes of Copper-Free Electrocatalysts for CO2 Reduction Based on Transition Metal/Post Transition Metal Alloys and Intermetallic Compounds

Binary alloys and intermetallic compounds composed of a first row transition metal and a post transition metal such as aluminum or gallium provide a new source of heterogeneous electrocatalysts for the reduction of CO2. Unlike the related Group 13 and 14 single metal systems (tin and indium which only generate formate and CO, the mixed metal systems form a variety of C1 products, along with carbon-carbon bonded products. The alloy systems resemble the indium and tin systems, in that they show a catalytic dependence on the surface oxides present.We have reported that Ni3Al reduces CO2 to a variety of C3 oxygenates,1-2 while Lewis et. al. has noted that various NixGay alloys generate C2 products from CO2.3 In both cases, the higher order products are observed in low yield. However, these examples are important since they demonstrate that metallic systems that do not contain copper can form carbon-carbon bonds from CO2. Recently we discovered that chromium-gallium bimetallic combinations can produce oxalate in high faradaic yields in aqueous electrolytes.4 Here again an oxide plays a key role in the observed electrocatalysis.The Cr-Ga system, which may best be thought of as an alloy of Cr2O3 and Ga2O3 is particularly intriguing since it produces oxalate at modest potentials (~-1.5 V vs. Ag/AgCl) in aqueous electrolyte. Prior reports on oxalate electrogeneration from CO2 required the use of nonaqueous electrolytes and significantly more negative potentials (>-2.0 V vs. Ag/AgCl). In the current system, we find that CO2 reduction can be carried out at potentials where oxalate formation competes favorably with H2 production yielding faradaic efficiencies in excess of 50%. Our new findings argue for a previously unexplored mechanism for the formation of carbon-carbon bonds that circumvents the generation of a [CO2 –• ] intermediate. Preliminary data hints at a mechanism that goes through a CO intermediate. Interestingly this system is strongly cation dependent, showing reactivity patterns that suggest two distinct active sites are present at the electrode interface.For all of the alloy and intermetallic systems we have investigated, there appears to be strong correlation between the morphology of the mixed metal electrocatalyst and the product distribution. The chemical source of this effect remains under study. It is also observed that the composition of the underlying electrode strongly influences the product composition. For example, while Ni3Al on glassy carbon produces a variety of C3 products, the same catalyst when placed on a p-type CIGS photocathode primarily produces methanol with no indication of carbon-carbon coupling processes.A detailed mechanistic understanding of these systems is likely to offer new opportunities for the electrosynthesis of organic products from CO2 with high faradaic yield and modest overpotential.

Backside Metallization of Ag–Sn–Ag Multilayer Thin Films and Die Attach for Semiconductor Applications

Backside metallization, which offers the advantages of a thin die-attach layer, excellent ohmic contacts, good thermal dissipation, and electrical conduction, is a reliable die-attach method for high-temperature semiconductor devices. Optimized Ag–Sn–Ag thin film structures have been deposited as a backside metal layer and their mechanical and electrical characteristics evaluated as a replacement for conventional Au-based backside metal. The results confirmed that the Ag/Sn/Ag sandwich structure provided more reliable properties than the Sn/Ag and Ag/Sn structures. After the die-bonding process using the Ag/Sn/Ag backside metal, Cu6Sn5, Cu3Sn, and Ag3Sn intermetallic compounds were observed at the interface between the Si chip and Cu-plated Alloy 42 lead frame. The shear strength of the Ag/Sn/Ag backside metal was superior to that of conventional Au-12Ge backside metal, and its electrical characteristics met the requirement specifications of a commercial discrete semiconductor package.

Theoretical investigation of lanthanide and transition metal on Al cathode: Equilibrium potential and atomic radii analysis by a mathematical equation

Partitioning of actinides from the lanthanides is arguably the most difficult separation in radio-chemistry. Since the ionic radii are comparable to that of the trivalent lanthanide ions, the coordination chemistry is similar, resulting in almost no separation option. Meanwhile, due to the radioactivity of actinides and its own dangers, studies of these its theoretical properties are rarely carried out. In this paper, we mainly studied the equilibrium potentials of Al-Ln alloys by cyclic voltammetry and open circuit chronopotentiometry method and established the mathematical equation between the equilibrium potentials of the alloy and the atomic radii by condensation of experimental data. Bold predictions of the equilibrium potential of actinides deposited on Al cathode based on the mathematical equation were made, which shows excellent agreement with previous reports. Meanwhile, the equilibrium potentials of transition metals on Al cathode were tested. It was found that the equilibrium potentials and atomic radii of the Al-transition metal intermetallic compounds accorded with the mathematical equation as well. Hence, the electrochemistry of both lanthanides and actinides as well as transition metal on active cathodes could be reasonably estimated by employing the fitted mathematical equation, which provide a preliminary model and theoretical basis of the behavior of lanthanides elements in electrolysis-based pyroprocessing. From the perspective of development, it provides a unique and rich opportunity to realize both extraction and separation of actinides in spent fuel.

Diffusion and Phase Formation at Matrix-Filler Interfaces in Al–Mg–Si Composites Prepared by Powder Metallurgy

The Al–Mg–Si composites employing aluminum (Al) as matrix, magnesium (Mg) and silicon (Si) as fillers with weight ratio of 60 : 20 : 20 have been prepared by the method of powder metallurgy. The mixed powders were pressed applying pressure of 700 MPa, followed by sintering at 500, 550, and 600°C for 3 h in inert atmosphere. The resulted samples have been studied using a scanning electron microscope (SEM), equipped with energy dispersive X-ray (EDX) and electron probe micro analyzer (EPMA). Experimental results showed that the distribution of Mg and Si were homogeneous in the Al matrix. According to the elemental mapping and diffusion equation under non-steady state condition, the atomic interdiffusion process at the interfaces was studied, resulting in the different diffusion coefficient (D) for each element as diffusant in the sample heated at 550°C. As a filler, the Mg diffusing into the Al matrix has the greater D (=0.708 × 10–16 m2 s–1) than Si (D = 0.231 × 10–16 m2 s–1), while oxygen diffusing into the Mg has the highest D (=8.333 × 10–16 m2 s–1). Further probing by using the X-ray diffractometer (XRD), the phase formation covering metal oxides and intermetallic compounds was identified in the samples. Hardness test on the sample’s surface indicates the variation of Vickers hardness number (VHN) at several points on the sample’s surface.

Copper-Based Intermetallic Electride Catalyst for Chemoselective Hydrogenation Reactions

The development of transition metal intermetallic compounds, in which active sites are incorporated in lattice frameworks, has great potential for modulating the local structure and the electronic properties of active sites, and enhancing the catalytic activity and stability. Here we report that a new copper-based intermetallic electride catalyst, LaCu0.67Si1.33, in which Cu sites activated by anionic electrons with low work function are atomically dispersed in the lattice framework and affords selective hydrogenation of nitroarenes with above 40-times higher turnover frequencies (TOFs up to 5084 h-1) than well-studied metal-loaded catalysts. Kinetic analysis utilizing isotope effect reveals that the cleavage of the H-H bond is the rate-determining step. Surprisingly, the high carrier density and low work function (LWF) properties of LaCu0.67Si1.33 enable the activation of hydrogen molecules with extreme low activation energy (Ea = 14.8 kJ·mol-1). Furthermore, preferential adsorption of nitroarenes via a nitro group is achieved by high oxygen affinity of LaCu0.67Si1.33 surface, resulting in high chemoselectivity. The present efficient catalyst can further trigger the hydrogenation of other oxygen-containing functional groups such as aldehydes and ketones with high activities. These findings demonstrate that the transition metals incorporated in the specific lattice site function as catalytically active centers and surpass the conventional metal-loaded catalysts in activity and stability.

New Metal Phosphide with Topotatic Reaction As an Anode Material for Lithium Ion Rechargeable Battery

The current level of performances of Lithium Ion Batteries (LIBs) is not enough to meet commercial demands for new applications(xEV, ESS), in particular, with respective to energy density. Graphite and hard carbons are commonly used as a negative electrode material for LIBs, but higher-capacity alternatives are being consistently sought due to their limited capacity as an anode material of next generation LIBs for large-scale power applications. Recently, various Si, and Sn based compound including transition metal oxide, multiphase alloy, and intermetallic compounds have been extensively studied as alternatives to the existing carbon based anode material. These materials show much higher capacities than those of carbonaceous material. However, they are suffering from huge lattice volume change (4.4Li+Si ® Li4.4Si, ΔV>300%) through conversion reaction mechanism during Li insertion, which results in poor cycle life of LIBs. In this respect, metal phosphides have been alternatively suggested as a promising anode material for their reversibility, and large amount of lithium uptake at relatively low potential. It is not clarified yet until now, but the electrochemical reaction in metal phosphides with lithium might be classified into two reaction mechanisms, depending on electronegativity difference between metal and phosphorous atoms. Obviously, the large difference in electronegativity between constituting elements inevitably brings about decomposition of host composition (structure) with lithium intercalation, which can be readily understood by considering the Gibbs formation free energy. Even if being composed of elements with the very small difference in electronegativity, however, the reaction mechanisms are different with chemical stoichiometry of metal phosphides (MPx). In case of SnPx (Electronegativity : Sn=1.96, P=2.19) intermetallic compounds, the SnP0.75 equilibrium phase shows typical conversion reaction mechanism, on the other hand, SnP0.94metastable phase has been observed to be on intercalation reaction mechanism during lithiation process [1,2]. In this work, we have investigated the reaction mechanism of MoPx(Electronegativity : Mo=2.16, P=2.19) with various stoichiometry, relating with electrochemical properties. We finally propose newly designed metal phosphide with ternary composition showing topotatic reation.

Semimetallic Band Structure and Cluster-Based Description of a Cubic Quasicrystalline Approximant in the Al–Cu–Ir System

Density functional calculations were performed for a cubic quasicrystalline approximant in the Al–Cu–Ir system. A semimetallic band structure was developed and analyzed on the basis of Wannier functions constructed from the valence and a part of the conduction band manifold. The Wannier functions were s- and p-like orbitals centered on either the centers of conventional clusters or the icosahedron-like vertices of pseudo-Mackay clusters, and d-like orbitals centered on the transition metals. Grouping the orbitals according to their center, we considered a small cluster for each group of the orbitals. Most of the orbitals contribute to the density of states only within the valence bands, i.e., they are valence states. The exceptions are some of p-like orbitals centered on the icosahedron-like vertices of the pseudo-Mackay clusters, and they contribute to both valence and conduction bands. Each of these p-like orbitals forms a covalent bond with one centered on the neighboring small cluster. The resulting bonding and antibonding orbitals are valence and conduction states, respectively. The number of valence bands (173) of our Al39Cu8Ir15 model was then decomposed in terms of the numbers of transition metals (23), clusters (16), and covalent bonds between the clusters (6) as \(23 \times 5 + 16 \times 4 - 6 = 173\). The description for the valence-band formation may also be applicable to some of the group 13 element–transition metal intermetallic compounds, such as RuAl2.

An experimental survey of additives for improving dehydrogenation properties of magnesium hydride

The use of a wide range of additives has been known as an important method for improving hydrogen storage properties of MgH2. There is a lack of a standard methodology, however, that can be used to select or compare the effectiveness of different additives. A systematic experimental survey was carried out in this study to compare a wide range of additives including transitions metals, transition metal oxides, hydrides, intermetallic compounds, and carbon materials, with respect to their effects on dehydrogenation properties of MgH2. MgH2 with various additives were prepared by using a high-energy-high-pressure planetary ball milling method and characterized by using thermogravimetric analysis (TGA) techniques. The results showed that additives such as Ti and V-based metals, hydride, and certain intermetallic compounds have strong catalytic effects. Additives such as Al, In, Sn, Si showed minor effects on the kinetics of the dehydrogenation of MgH2, while exhibiting moderate thermodynamic destabilizing effects. In combination, MgH2 with both kinetic and thermodynamic additives, such as the MgH2–In–TiMn2 system, exhibited a drastically decreased dehydrogenation temperature.