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Abstract: First-principles calculations of the crystal structure and the elastic properties of α-Ta4AlC3 have been carried out with the plane-wave pseudopotential density functional theory method. The calculated values are in very good agreement with experimental data as well as with some of the existing model calculations. The pressure dependence of the elastic constants c ij , the aggregate elastic moduli (B, G, E), the Poisson''s ratio, and the elastic anisotropy has been investigated. Using the quasi-harmonic Debye model considering the phonon effects, the temperature and pressure dependencies of isothermal bulk modulus, and the thermal expansions, and Grüneisen parameters, as well as Debye temperatures are investigated systematically in the ranges of 0–60GPa and 0–1500K as well as compared to available data. [Copyright &y& Elsevier]

Abstract: First-principles calculations of the crystal structures, and elastic properties of wurtzite-type indium nitride (w-InN) have been carried out with the plane-wave pseudopotential density functional theory method. The calculated values (for crystal structures) are in very good agreement with experimental data as well as with some of the existing model calculations. The dependence of the elastic constants c ij , the aggregate elastic modulus (B, G, E), and the elastic anisotropy on pressure have been investigated. Moreover, the variation of the Poisson ratio, Debye temperature, and the compressional and shear elastic wave velocities with pressure P up to 10GPa at 0K have been investigated for the first time. [Copyright &y& Elsevier]

With promising mechanical properties and biodegradability, magnesium (Mg) and its alloys are considered as potential candidates in both industrial and biomedical fields. However, rapid corrosion is a major obstacle that severely prevents their widespread applications. Surface modification is a cost-effective way to prevent the corrosive medium from contacting with Mg substrate. Generally, fabricating a dense and stable coating as a physical barrier can effectively inhibit the corrosion of Mg substrates. However, in some complex service environments, the coatings are inevitable to be damaged during use. In this case, it is essential to equip coatings with smart self-healing abilities. This article reviews recent advances in conventional physical barrier coatings and smart self-healing coatings on Mg alloys for industrial and biomedical applications. For physical barrier coatings, metal-based coatings, metal hydroxides and hydrotalcite coatings, metal oxide coatings, silane sol-gel coatings, polymer coatings, Ca–P coatings, and others like graphene-based coatings are mainly reviewed. For smart self-healing coatings, chemical conversion coatings, encapsulation coatings, and layer-by-layer assembled coatings are reviewed. • Review focuses on the coating material compositions, preparation methods and designs. • Physical barrier coatings are at the dominant position for protection of Mg alloys. • Coating with the self-healing ability is vital during use in complex environments. [ABSTRACT FROM AUTHOR]

BaTiO 3 ceramics doped with different contents of Sm (0.5–7 mol%) are prepared by a homogeneous precipitation method and sintered in air (A- x Sm) and reducing (R- x Sm) atmosphere respectively. With the increase of doping amount, the phase structure of Sm-doped BaTiO 3 ceramics gradually changes from tetragonal phase to cubic phase, and the cubic phase is stronger in R- x Sm. In the air atmosphere, Sm ions preferentially replace Ba sites as donors at low doping concentration, which is easy to convert Ti4+ ions into Ti3+ ions, resulting high dielectric constant (>104) and semiconductor like properties. As the doping amount increases, Sm ions start to replace Ti sites as acceptors to generate oxygen vacancies, which capture the electrons generated by donor doping, thus decreasing the percentage of Ti3+ ions. As a result, the dielectric loss and permittivity are decreased, and the electrical insulation properties of A- x Sm ceramics are gradually improved. However, in the reducing atmosphere, oxygen atoms in the lattice are easy to escape, resulting in many oxygen vacancies and free electrons. The increase of oxygen vacancy inhibits the substitution of Sm ion to Ti site, and the free electron leads to the increase the percentage of Ti3+ ions and R- x Sm ceramics exhibit semiconductor like properties. Thermally stimulated depolarization currents (TSDC) testing verified that oxygen vacancies of A- x Sm ceramics mainly capture space charges, and a small part of oxygen vacancies form defective dipoles [ 2 Sm Ti ′ − V O.. ]. The complex impedance test shows that the change of resistivity of A- x Sm ceramics is mainly closed to the influence of Sm doping on the grain not grain boundary of BaTiO 3 ceramic. • Sm-doped BaTiO 3 ceramics were prepared by homogeneous precipitation method sintering in air and reducing atmosphere. • The oxygen vacancy defect in reducing atmosphere inhibits Sm ion substitution of B site. • Oxygen vacancy defects mainly capture the electrons produced by the donor doping in the air. • Sm ion mainly affects the electrical insulation performance of BaTiO 3 grain. [ABSTRACT FROM AUTHOR]

Using an unbiased structure search method based on particle-swarm optimization algorithms in combination with density functional theory calculations, we investigate the phase stability and electronic properties of WB 4 under high pressures. Through structural searching as implemented in the CALYPSO code, we obtained the most state hexagonal phase (P6 3 /mmc, named hp 10) at ambient condition and a new monoclinic phase (C2/m structure, mp5) at high pressures for WB 4 . The P6 3 /mmc structure transforms to the C2/m phase at about 71 GPa. Surprisingly, the two phases are both dynamically and mechanically stable at ambient conditions. The high bulk and shear modulus, low Poisson’s ratio for both phases in WB 4 , place WB 4 as a promising low compressible material. Both phases with high hardness are stable due to the strong covalent bonding nature from electronic density of states and electron localization function analysis. To guide experimental finding of more metastable superhard materials, the high pressure high temperature phase diagram of WB 4 is established within the quasi-harmonic approximation. [ABSTRACT FROM AUTHOR]

Abstract: The transition phase of MgTe from rock salt structure (B1) to cesium chloride structure (B2) is investigated by ab initio plane-wave pseudopotential density functional theory method. The thermodynamic properties of the B1 and B2 structures are obtained through the quasi-harmonic Debye model. Our results indicated that MgTe undergoes a structural phase transition from B1 to B2 at about 90.32GPa. The dependences of the relative volume V/V 0 on the pressure P, the Debye temperature Θ and heat capacity C V on the pressure P, the Grüneisen parameter ratio (γ − γ 0)/γ 0 on pressure P, the bulk moduli ratio (B − B 0)/B 0 on pressure P, as well as the heat capacity C V on the temperature T are estimated. [Copyright &y& Elsevier]

Abstract: We have investigated the structural and elastic properties of γTiAl under high pressures using the norm-conserving pseudopotentials within the local density approximation (LDA) in the frame of density functional theory. The calculated pressure dependence of the elastic constants is in excellent agreement with the experimental results. The elastic constants and anisotropy as a function of applied pressure are presented. Through the quasi-harmonic Debye model, we also investigate the thermodynamic properties of γTiAl. [Copyright &y& Elsevier]

Both particle size and processing conditions can affect the magnetic properties of ferrite materials. In this work, the two-step hot-press procedures (hot-press magnetic orientation followed by hot-press sintering) is designed for fabrication of high quality BaFe 12 O 19 thick films. The effects of pre-sintering particle size (G pre) on the microstructure and magnetic properties of the thick films are investigated. Results show that reducing G pre increase c -axis orientation and remanence ratio (RR) of sintered thick film greatly. This should be due to the reduced energy barriers for grain orientation during the hot-press magnetic orientation process. Decreasing G pre from 920 nm to 170 nm leads to larger coercivity (H c), while the saturation magnetization does not change notably above G pre = 170 nm. The H c mechanism is further analyzed by the G pre dependent anisotropy field H k and the first-order-reversal curves of the thick film. Results show that H k increases with reducing G pre , while the inter-grain interactions are not notably affected by G pre. Therefore, the increase of H c should be contributed by both the decrease of sintered particle size and the improved RR of the film after hot-press magnetic field orientation. The above results show that the two-step hot-press sintering prepared hexaferrite thick films with optimized G pre is a good candidate for the realization of self-biased high frequency devices. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) and its alloys are promising candidates in both industrial and biomedical fields due to their excellent mechanical properties and biodegradability. However, their rapid corrosion severely hinders their widespread applications. Constructing coating is an effective method to prevent direct contact between corrosive ions and the Mg substrate. However, coatings are inevitably damaged in complex service environments, which compromises their corrosion protection ability. Therefore, it is essential to develop self-healing coating that can repair damage. This review focuses on recent advances in self-healing coatings for Mg alloy in both industrial and biomedical applications. Several types of self-healing coatings including conversion coating, encapsulation coating, layer-by-layer assembly coating, and external stimuli-responsive coating are reviewed, and their self-healing mechanisms are discussed, which discussions provides guidelines for designing self-healing coatings for Mg/Mg alloy. [Display omitted] [ABSTRACT FROM AUTHOR]

Mechanical anisotropy is among the most concerned properties for selective laser melting produced metals, such as steels and titanium alloys, but is rarely investigated for high-strength Al alloys. In this study, crack-free high-strength Al-Mg-Si-Sc-Zr was prepared by selective laser melting. Systematical tensile tests revealed that Al-Mg-Si-Sc-Zr has intrinsically quasi-isotropic tensile properties. Uniform elongations in horizontal and building directions are comparable and the difference between the two tensile strengths is less than 3%. Al-Mg-Si-Sc-Zr exhibits bi-modal microstructures consisting of 39 vol% equiaxed ultrafine grains and 61 vol% columnar grains. The presence of equiaxed ultrafine grains interrupts epitaxial growth of columnar grains and thus prevents the development of the fiber texture intensity. The tiny grain size and Mg 2 Si stripes on grain boundaries make equiaxed ultrafine grains brittle and susceptible to cavity nucleation and intergranular cracking. A weak fiber texture and randomly orientated cracking-prone equiaxed ultrafine grains endow Al-Mg-Si-Sc-Zr with intrinsically quasi-isotropic tensile properties. • Crack-free high-strength Al-Mg-Si-Sc-Zr was successfully prepared by selective laser melting. • High-strength Al-Mg-Si-Sc-Zr has intrinsically quasi-isotropic tensile strengths and uniform elongations. • The tensile quasi-isotropy originates from random orientations and intergranular cracking of equiaxed grains. [ABSTRACT FROM AUTHOR]

Catalytic conversion efficiency from aqueous formaldehyde (HCHO) into hydrogen (H 2) on non-noble metal catalysts is much lower than that on noble metal catalysts. Modulating the electronic properties of non-noble metal-based catalysts has been demonstrated an effective approach to improve their catalytic performance. In this work, assisted by light irradiation, photoinduced electron-rich surface structure was designed for the thermal catalytic conversion of HCHO to H 2. In detail, a heterostructure of CuNi@C composited with TiO 2 was obtained, in which TiO 2 can be photoexcited under light irradiation to provide photoinduced electrons onto the surface of CuNi@C. On the photoinduced electron-rich surface of the CuNi@C/TiO 2 heterostructure, the H 2 evolution rate reached 254.65 mmol h−1 g−1, which was 1.88 times higher than that on CuNi@C. It is worth noting that the catalytic HCHO conversion efficiency outperforms the current reported non-noble metal catalysts for this reaction. Combining with density functional theory (DFT) calculations and experimental studies, it is concluded that the electron-rich CuNi@C dramatically reduced the activation energies of the dissociation of HCHO and H 2 O and accelerated the overall reaction rate. • CuNi@C alloy is composited with TiO 2 to form a CuNi@C/TiO 2 heterostructure. • The CuNi@C/TiO 2 exhibits high efficiency HCHO reforming H 2 evolution. • Photoexcited TiO 2 enhances the electron density on the surface of CuNi@C. • The electron-rich CuNi@C dramatically reduced the activation energy of HCHO to H 2. [ABSTRACT FROM AUTHOR]

Dual-transition-metal oxide (DTMO) nanostructures are emerging materials for lithium-ion battery (LIB) anodes with improved structural stability, electronic conductivity and electrochemical performance compared to their single-metal counterpart. Herein, composites of graphene with DTMOs (MFeO, M = Co, Mn, Zn) were controllably prepared by harnessing the synthesis atmospheres and the nanoscale diffusion couple. Their composition and morphology were characterized by TEM, EDS mappings, XRD and XPS. The NH 3 treatment resulted in the formation of hollow DTMO nanoparticles on nitrogen-doped graphene, while H 2 and Ar gave graphene-supported hollow and solid DTMO particles, respectively. Electrochemical tests were applied to compare the performance of these composites as LIB anodes. The superior anode performance DTMO electrodes was demonstrated to the corresponding iron oxide composite. CoFe 2 O/RGO composites exhibit excellent rate capability and high-rate cycling stability for lithium storage, due to its stable solid structure. However, the hollowing of DTMO particles cannot elevate the capacity and stability, due to the interfacial resistance and structural changes upon cycling. [ABSTRACT FROM AUTHOR]

• Strength-ductility synchronization of as-cast β -phase Mg-Li alloy can be achieved by Zn alloying. • θ (MgLiZn) with coherent α-Mg phase precipitates along grain boundaries (GBs) in LZ116 alloy. • Massive spherical nano-sized θ′ (MgLi 2 Zn) phase precipitates and disperses in β-Li matrix. • The improved strength is attributed to massive θ' precipitates uniformly distributed inside grains. • The θ/α-Mg phases precipitated along the GBs contribute to the enhanced ductility. [Display omitted] Effect of Zn addition on the microstructure and mechanical properties of as-cast BCC Mg-11Li based alloys were investigated. The results revealed that a certain amount of θ (MgLiZn) with coherent α-Mg phase precipitated along grain boundaries (GBs) and a high density of dispersing spherical small-sized θ′ (MgLi 2 Zn) precipitates distributed inside grains were contained in β-phase Mg-11Li-6Zn (in wt%, LZ116) alloy, and the volume fraction of both phases increased with the elevating Zn content under the lever of less than 6.2 wt%. After solution treatment, the θ / α-Mg phases located at the GBs and the spherical θ' phase inside the grains were dissolved, whilst a high density of fine-laminar θ' phase precipitated concomitantly in LZ116 alloy. The as-cast LZ116 alloy exhibited high ultimate tensile strength and ductility of 184 MPa and 30% at room temperature, respectively, which were much higher than those (72 MPa and 19%) of as-cast Mg-11Li (L11) alloy. The strength of the LZ116 alloy was further elevated to 235 MPa via solid-solution treatment at 350 °C for 4 h (the treated alloy is denoted as S-LZ116), but the elongation was dramatically reduced to 1.2%. As a result, the softening θ/α-Mg precipitates distributed at GBs enhanced the plasticity and the hardening θ′ phase elevated the strength of as-cast LZ116 alloy. Meanwhile, the intergranular fracture and dimple feature was observed in as-cast LZ116 alloy, and the fracture behavior is correlated with the softening GBs with θ/ α-Mg phases and the hardening grains reinforced by dispersed θ′ phase particles. [ABSTRACT FROM AUTHOR]

• CdS/ZnS has high photocatalytic activity and excellent stability for H 2 production. • The existence of zinc vacancy is verified by the photoluminescence emissions. • Kelvin probe force microscopy intuitively proves the electron transfer direction. • Zinc vacancy induces CdS/ZnS to form Z-scheme structure. An integrated Z-scheme hybrid structure is constructed with the zinc vacancy mediated CdS/ZnS for hydrogen production with superior stability. The distribution of surface photovoltage (SPV) intuitively proved the efficient transfer of photogenerated electrons from the CdS to the ZnS, forming a Z-scheme photocatalytic system. [Display omitted] Photocatalytic hydrogen evolution reaction (HER) has been considered as a promising technology to provide a better energy supply and address the environmental concerns. CdS/ZnS hybrid composite structure has been proved an ideal system for photocatalytic hydrogen production. It is commonly referred to as a type-I semiconductor heterostructure. After an in-depth research work, it is found that the CdS/ZnS has a type II structure or direct Z-scheme structure due to the defect energy levels of zinc vacancies. In this work, the zinc vacancy mediated CdS/ZnS core/shell hybrid structure on FTO was synthesized. The best hydrogen production rates of CdS/ZnS reached 6.27 µmol cm−2 h−1 and 137 μmol cm−2 h−1 in the photocatalytic and photoelectrochemical (PEC) systems. More importantly, it exhibited excellent stability of 5 cycles in 25 h. The photoluminescence emissions spectra peaking in the visible light region verified the existence of zinc vacancies. Kelvin probe force microscopy (KPFM) proved the efficient transfer of photogenerated electrons from the CdS to the ZnS, thus forming a Z-scheme photocatalytic system. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO) is harmful to environment and human health, even at extremely low concentrations. Catalytic oxidation on metal oxides is an effective method for HCHO removal. Transition metal oxides have attracted much attention due to its advantages of low cost and good redox properties, but it requires the high reaction temperature and energy consumption to reach the good catalytic activity for HCHO removal. In this work, Mn-Co mixed oxides supported on carbon nanotubes (CNTs) were prepared for enhancing the low-temperature catalytic activity of HCHO removal. The results of XRD, TEM and XPS characterization confirmed the formation of CoMn 2 O 4 solid solution on CNTs. The highest relative content of Co3+, Mn3+ and active lattice oxygen were achieved at the optimal composition of 3Mn-1Co. The HCHO oxidation test showed that CoMn 2 O 4 /CNTs (3Mn-1Co) had the best catalytic activity at 160 °C, obtaining 95% HCHO (100 ppm) removal efficiency and 95% CO 2 selectivity at GHSV = 30,000 mL g cat -1 h-1. Compared with the similar catalysts previously reported in literatures, CoMn 2 O 4 /CNTs was of the lower T 90 value for HCHO oxidation. Image 1 • Mn/Co molar ratio of 3:1 was prone to form CoMn 2 O 4 solid solution on CNTs. • The formation of active lattice oxygen on CoMn 2 O 4 was beneficial to HCHO oxidation. • The combination of CNTs and Co-Mn oxides solid solution is promising to prepare catalysts for HCHO removal. [ABSTRACT FROM AUTHOR]