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Annealing FeNi-based amorphous alloys is a promising way to fabricate rare-earth-free L1 0 -FeNi hard magnetic materials. In this study, the effect of Co addition on the magnetic properties of annealed Fe-Ni-P alloys has been investigated. With Co addition, the coercivity of optimized Fe 38 Ni 38 Co 8 P 16 alloys reaches 1145 Oe, which can be attributed to the enhanced magneto-crystalline anisotropy of the L1 0 phase since the remnant coercivity in the out-of-plane direction increases towards 2.35 kOe. By comparing the hysteresis loss and the theoretical magneto-crystalline anisotropic energy of L1 0 -FeNi, the mean volume fraction of L1 0 phase is estimated to be ∼5.5%. The study suggests that Co addition is greatly beneficial to the fabrication of L1 0 -FeNi hard magnetic materials, and this process has a large potential to be further improved. • Co-addition enhanced the intrinsic magneto-crystalline anisotropy of L1 0 -FeNi. • The coercivity of the annealed Fe-Ni-Co-P alloy samples reaches 1145 Oe. • The H cr of the annealed Fe-Ni-Co-P alloy samples reaches 2.35 kOe. • The mean volume fraction of L1 0 -FeNi in the multi-phase alloy samples could be estimated as ∼5.5%. [ABSTRACT FROM AUTHOR]

Ternary transition metal borides (TTMBs) will break materials application limitation in harsh service environments, owing to their structure versatility and high component tunable ability. Herein, we reported a solid solution boride CrFeB synthesized by high pressure and high temperature method. CrFeB yields an asymptotic hardness of 14.2 GPa and thermal stability temperature is up to 1250 K. DC magnetic susceptibility measurements revealed that there is a separation between zero-field cooled and field cooled curve at around 5 K, which indicated the spin glass behavior for CrFeB. Temperature dependence AC susceptibility analysis gives further evidence that the freezing temperature increases with frequency following Vogel-Fulcher law. On the basis of XPS results and first-principle calculations, we speculate that the complex magnetic behaviors may derive from the short-range magnetic exchange of same occupation sites two metal atoms. Cr and Fe atoms tend to have opposite magnetic moments in these short-range exchange behaviors. The intrinsic magnetic disorder and short-range frustration lead to spin random freezing of CrFeB at low temperatures, which conforms to typical spin glass characteristics. These results will contribute to understanding the complex magnetism behavior of CrFeB and provides a new idea to design multifunctional TTMBs. [Display omitted] • Novel ternary solid solution boride CrFeB was fabricated by high pressure and high temperature method. • CrFeB exhibits high hardness, excellent antioxidant capacity and spin-glass behavior at low temperature. • The short-range magnetic exchange and long-range random occupancy of two metals lead to the spin glass behavior for CrFeB. • Regulating the interactions between metal components will help optimize the performance of multicomponent metal borides. [ABSTRACT FROM AUTHOR]

Lightweight strong boron-carbon clathrates adopting sodalite structure have been inspirated by the successful synthesis of the SrB 3 C 3 compounds, which assuming the cubic bipartite sodalite structure. In this work, we designed series of stoichiometric LiB x C 12- x and Li 2 B x C 12- x (x = 1–6) compounds based on boron substitution of carbon in carbon sodalite structure using first-principles calculations. We found that LiB 2 C 10 , LiB 3 C 9 , LiB 4 C 8 , Li 2 B 3 C 9 and Li 2 B 4 C 8 are dynamically stable at high pressure and can be recovered under normal pressure. Strikingly, compared with inserting one Li atom into the B-C framework, inserting two Li atoms exhibit lower enthalpy value and better symmetry. Li 2 B 4 C 8 is identified as the most stable structure among these compounds, and Li 2 B 4 C 8 could potentially be synthesized at moderate pressure. The electron localization function calculations reveal that there is a strong covalent bond between B and C atoms in the clathrates, which forming the rigid three - dimensional crystalline networks. Moreover, the estimated Vickers hardness values of these five stable clathrates are 42 ∼ 51 GPa, which can be classified as superhard materials. At the same time, the pure shear strength of LiB 2 C 10 is found to be 48.1 GPa, which exceeds the threshold value of 40 GPa. The pure shear strength of LiB 3 C 9 (38.0 GPa) and Li 2 B 3 C 9 (38.8 GPa) are found to be close to 40 GPa. Our work presents a new strategy for exploring superhard sodalite-like clathrate candidates. • LiB 2 C 10 , LiB 3 C 9 , LiB 4 C 8 , Li 2 B 3 C 9 and Li 2 B 4 C 8 are evaluated as superhard materials with H v values above of 42 GPa. • Li 2 B 4 C 8 is identified as the most stable structure and can be synthesized at moderate pressure. • In the same ratio of B-C framework, with the increase of Li atom ratio, the lattice constant c will increase and the symmetry will be better. [ABSTRACT FROM AUTHOR]

Biomass-derived hard carbon materials have received promising research interest because of their low cost, high abundance, and renewability. In the present study, high-performance hard carbon material is prepared from soap-nut seeds (SNS-0) using a simple pyrolysis process. Further, N (nitrogen) heteroatoms are introduced into the hard carbon matrix to modify its structure using melamine as the N source. High-resolution transmission electron microscopy images reveal the development of the localized graphite-like structure after the introduction of N atoms in the hard carbon, which are found to be beneficial for the storage and transport of the larger Na ions in the battery. The optimal doping of N (1:1 wt. ratio, SNS-1) in the hard carbon has improved the storage performance of the SNS-0 electrode, providing a reversible capacity of 353 mA h g−1 at a current density of 25 mA g−1. The improved electrochemical characteristics of the SNS-1 electrode over the other compositions are associated with its lesser specific surface area (282.87 m2 g−1) and higher interlayer spacing (0.38 nm). The present study not only reveals the useful conversion of a biomass waste, soap-nut seeds, into a low-cost and sustainable eco-friendly hard carbon material but also its potential use as an efficient anode for Na-ion battery applications. • Development of hard carbon from a biomass waste, soap-nut seeds. • Enhancement in electrochemical performance of hard carbon by N-doping. • Demonstration of the useful conversion of a biomass waste into an efficient anode material for Na-ion battery applications. • Observation of specific discharge capacity ∼ 353 mA h g-1 at a current density of 25 mA g-1. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis and achievement of ternary Al 1−x W x N nitride films as hard coating materials. A dual-target DC reactive magnetron sputtering process was used to coat Al 1−x W x N thin films on Si (100), glass, and transparent quartz substrates. The elemental analysis of the films was calculated by energy dispersion spectroscopy and the corresponding value of x changes from 0 to 1. The X-ray diffraction data showed a-axis orientation of the AlN films with hexagonal phase and amorphous nature for Al 0.78 W 0.22 N and Al 0.58 W 0.42 N films. Atomic force microscopy analysis showed that the surface morphology of Al 0.78 W 0.22 N films was better than that of AlN and Al 0.3 W 0.7 N films, as evidenced by the significantly lower root-mean-square roughness value of 1.79 nm compared to 5.78 and 13.9 nm, respectively. The resistivity of Al 1−x W x N films was determined by a four-probe method and resulted in a record low value of 4.08 × 10−5 Ω-m for WN films. The photoluminescence emission spectra showed distinct peaks in the visible region at different wavelengths, and the deconvoluted blue emission peak was attributed to the native defects in the Al 1−x W x N films. X-ray absorption spectroscopy data showed an increase in feature- a from Al 0.78 W 0.22 N to Al 0.58 W 0.42 N films, indicating stronger hybridization of N 2p with Al 3p and W 5d orbitals due to π * -resonance. The oxygen content calculated by X-ray photoelectron spectroscopy was 34.6, 35.39, and 19.74 at% on the surface of AlN, Al 0.58 W 0.42 N, and WN films, respectively. The surface oxidation of AlN films triggered the transfer of charge from nitrogen to oxygen on the surface of AlN films. The nanoindentation results showed that the Al 0.3 W 0.7 N films have hardness and elastic modulus of 17.84 GPa and 196.96 GPa, which are higher than those of the other Al 1−x W x N films, while the AlN films have higher fracture toughness due to the reduction of contact pressure. • Structural phase changes and chemical composition in Al 1−x W x N (0 ≤ x ≤ 1) alloys were studied by XRD and EDS. • Green emission of PL spectra attributed to N vacancy. • Reduction of N occurred due to red-shift of N absorption edge in XAS spectra. • Surface oxidation of AlN films triggered charge transfer from N to O. • Nanoindentation study revealed that Al 1−x W x N films can be implemented for hard coating materials. [ABSTRACT FROM AUTHOR]

The development of advanced structural materials with a synergistic combination of strength and ductility is currently one of the thrust areas of research for material scientists. An alloy design strategy for such materials takes into consideration the ease of processing, density reduction, and economic viability along with unprecedented mechanical properties. The present study reports a low-density, low-cost medium entropy alloy, designed based on the CALPHAD approach, for structural applications. The designed Ni-Fe-Cr-Al based alloy was cast, homogenized and cold rolled to 75% thickness reduction. The cold-rolled full hard material was isothermally annealed at 900°C for varying duration with a quest for an in-depth understanding of static recrystallization mechanisms. The specimens annealed at 900°C for varying durations were aged at 600°C for 5 h. Based on the systematic understanding of recrystallization and precipitation mechanisms involved, a suitable thermo-mechanical process route was judicially selected for the designed alloy, which contributed to an excellent combination of high tensile strength of > 1 GPa accompanied by an appreciable total elongation of > 50%. This superior strength-ductility synergy surpassed the strength-ductility combination of many existing medium and high entropy alloys and can be investigated further to assess its potential applications in challenging existing solid solution (SS) strengthened superalloys. [Display omitted] • Alloy design and processing of high strength cost-effective Ni-Fe-Cr based alloy. • Recrystallization study to design heterogeneous microstructure. • Suitable thermo-mechanical process design to obtain desired final microstructure. • Achieving excellent strength-ductility synergy of 52530 MPa%. • Potential for elevated temperature applications. [ABSTRACT FROM AUTHOR]

In this study, the effects of co-alloying Ti and V on cemented carbide alloys were investigated. Theoretically, the effects of co-alloying Ti and V on structural stability were studied from the perspective of energy stability criteria and elastic stability criteria. The results show that the face-centered-cubic (FCC) structure (W x ,Ti y ,V 1-x-y)C carbides are stable in two domains, one is the WC-poor domain (the concentration of WC is less than 25 at.%), and the other is WC-rich domain (the concentration of WC ranges from 61.5 at.% to 75 at.%). The calculated hardness of FCC structure (W x ,Ti y ,V 1-x-y)C carbide has a maximum of about 27 GPa. As for the hexagonal-close-packed (HCP) structure (W x ,Ti y, V 1-x-y)C carbides, they are stable in WC-rich domain (the concentration of WC is greater than 75 at.%). The calculated hardness of HCP structure (W x ,Ti y ,V 1-x-y)C carbide has a maximum of about 37.2 GPa. Experimentally, the HCP structure (W x ,Ti y ,V 1-x-y)C-8wt.%Co alloy was prepared by mechanical alloying and hot pressing sintering as the HCP structure (W x ,Ti y ,V 1-x-y) C carbide has higher hardness. The results show that, as the concentration of co-alloying Ti and V increases, the hardness of the (W x ,Ti y ,V 1-x-y)C-8 wt.%Co alloy increases, but the fracture toughness of the (W x ,Ti y ,V 1-x-y)C-8 wt.% Co alloy decreases. The effect of co-alloying Ti and V on the hardness can be attributed to the solid solution strengthening and grain refinement strengthening. The achieved hardness of the (W x ,Ti y ,V 1-x-y)C-8 wt.% Co alloy is higher than that of the conventional binary cemented carbide alloys. The tribological properties studies show that co-alloying Ti and V can effectively improve the wear resistance of (W x ,Ti y ,V 1-x-y)C-8 wt.% Co alloys. The main wear mechanism can be attributed to the adhesive wear. • understanding of multialloying effects based on virtual crystal approximation (VCA). • developing the phase diagram for multicomponent hard materials. • guiding optimization on hard materials with enhanced mechanical properties. • guiding optimization on hard materials with enhanced wear resistance. [ABSTRACT FROM AUTHOR]

Aluminum is widely used in the electrical, automotive, transport and aerospace industries due to its remarkable properties, such as low density and relatively low costs. However, due to the low hardness and low yield strength, there are limitations in application of aluminum. To solve these limitations, aluminum is made with other hard materials in the form of nanocomposites. For this purpose, in this work, using B 4 C nanoparticles, Aluminum-boron carbide nanocomposites (Al-B 4 C) nanocomposites were prepared via ball milling processing. The ball milling process was carried out at room temperature under argon atmosphere using a planetary ball milling for 10 h at 300 rpm. The B 4 C nanoparticles content employed in these nanocomposites were 0, 5 and 10 wt%. To investigate the structural, mechanical and electrical properties of the Al-B 4 C nanocomposites, the powders were pressed and then sintered under argon atmosphere at 650 °C. The structure, density, hardness and electrical conductivity of the Al-B 4 C nanocomposites sintered tablets were investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron microscopy (FESEM) with energy dispersive x-ray spectroscopy (EDS), Archimedes method, nanoindentation and eddy current test, respectively, and the results are discussed. The XRD patterns confirmed the presence of aluminum and B 4 C and the lack of any interphase and secondary phase in the Al-B 4 C nanocomposite. Distribution of B 4 C nanoparticles in Al-B 4 C nanocomposite was described via EDS assisted elemental mapping images. Moreover, with the addition of 5 and 10%wt. B 4 C nanoparticles in aluminum matrix, the hardness values of the Al-B 4 C nanocomposites was measured to be 138HV and 172HV which were higher than 67HV for the pure aluminum, respectively. Consequently, nanoindentation analysis showed that the hardness of Al-B 4 C nanocomposites was better than that of pure aluminum. Density values of Al-B 4 C nanocomposites were measured to be 2.5776 g/cm3 and 2.4949 g/cm3 which were lower than 2.6346 g/cm3 for the pure aluminum, respectively. Electrical conductivity of Al-B 4 C nanocomposites was measured to be 23%IACS and 13%IACS which were lower than 39% IACS for the pure aluminum, respectively. To evaluate the effect of particle size on the properties of Al-B 4 C composites, under the same conditions of Al-B 4 C nanocomposites preparation, Al-B 4 C microcomposites were prepared. With increasing B 4 C content, the hardness of Al-B 4 C nanocomposites were obtained higher than those for Al-B 4 C microcomposites. This behavior has been explained by Hall–Petch Model and Orowan strengthening. The density of the Al-B 4 C nanocomposites was obtained higher than those for Al-B 4 C microcomposites and the electrical conductivity of Al-B 4 C nanocomposites less than the resulting for Al-B 4 C microcomposites. • There have been no reports up now that, at first, B 4 C nanoparticles were prepared and then Al-B 4 C nanocomposites were prepared using it in the ball mill processing. • There have been no reports up now that hardness of Al-B 4 C nanocomposite hardness is evaluated based on two different methods of microhardness and nanoindentation and compared them. • There have been no reports up now that electrical conductivity of Al-B 4 C nano- and microcomposite is investigated and compared them. [ABSTRACT FROM AUTHOR]

The Co-V co-substituted nano Sr-hexaferrite, Sr 0.5 Co 0.5 V x Fe 12−x O 19 (0.00 ≤ x ≤ 0.08) (V→SrCo (0.00 ≤ x ≤ 0.08) NHFs), were manufactured by citrate combustion route. The microstructure, morphology, magnetic features, hyperfine interactions and oxidation state and chemical composition of products explained by XRD, SEM with EDX, HR-TEM, VSM, Mossbauer spectrometry, and XPS, respectively. The D XRD (Average crystallite size) of products were assessed via Scherrer formula as within the range of 37 and 83 nm. The hexagonal morphology and chemical composition of the products was presented by TEM, HR-TEM, SEM and EDX analyses. The XPS analysis provided both the composition and oxidation states of prepared NHFs. Mossbauer spectra showed that the s electron density around Fe3+ ions of all sites except 12k influenced V3+ content. The coercivity data indicates that all samples denote a magnetically hard material at both low and high temperatures. M s , M r and n B fluctuate with respect to dopant concentration and attain their highest magnitudes for the V→SrCo (x = 0.04) NHFs. A SQR of around 0.5 is achieved at each temperature, reflecting a relatively high large anisotropy field. The field-cooling (FC) curves of all samples yield a drop in magnetization with increasing temperature. Their irreversibility temperature is detected to be beyond 325 K. Both M-H and M-T imply the ferrimagnetic behavior of different samples. Microwave properties were measured between 2 and 18 GHz as S11-S21 parameters. It demonstrated non-linear behavior of the microwave properties vs. V concentration. The origin of the reflection losses in NHVs can be explained by the dipole polarization processes. • V co-substituted nano Sr-Cohexaferrite, (V→SrCo (x ≤ 0.08)) NHFs), were manufactured by citrate combustion route. • Magnetic characteristics of V→SrCo NHFs are showed crucial impact of co-doping on SrFe 12 O 19 is exhibited. • Microwave properties were measured between 2 and 18 GHz as S11-S21 parameters. [ABSTRACT FROM AUTHOR]

In order to determine the Zr occupancy site, neutron diffraction study on (R 1−x Zr x)Fe 12−y Mo y (R = rare earth) were performed at 300 K and 573 K respectively. It is found that Zr occupies the 2a site, like the R atoms behavior. Zr is the first neighbor of Y in the periodic table, and has a similar chemic property as Y, but with a smaller atomic radius. Due to the suitable chemic property and atomic dimension, the addition of Zr at 2a site facilitates forming of the 1–12 phase, allowing more Fe atoms to enter the 8i site and decreasing Mo content from 1.5 to 0.8. As a result, Sm 0.9 Zr 0.1 (Fe 0.75 Co 0.25) 11.2 Mo 0.8 shows a large saturation magnetization σs of 137.6 emu/g, a high Curie temperature T C of 775 K and a strong anisotropy field H a of 87.5 kOe, and its estimated value of maximum magnetic energy product (BH) max is up to 50.4 MGOe, favorable for permanent magnet applications. At present, almost rare-earth sintered magnets are made of Nd 2 Fe 14 B, causing the price of the raw material Nd to soar. Therefore, the development of low-cost Sm-Fe based hard magnetic materials is of particular significance. • Study on Pr 0.9 Zr 0.1 Fe 0.8 Mo 1.2 was performed by neutron diffraction technique at 300 K and 573 K. • The addition of Zr facilitates to formation of the 1–12 phase, resulting in the decrease of Mo content to 0.8. • Sm 0.9 Zr 0.1 (Fe 0.75 Co 0.25) 11.2 Mo 0.8 shows large σ s of 137.6 emu/g, high T c of 775 K, and the (BH) max of up to 50.4 MGOe. [ABSTRACT FROM AUTHOR]

Abstract In this study, the heat treatment process was performed to improve the mechanical properties of WC-binderless and WC-Co hard materials pre-fabricated by PCAS process. The microstructural and mechanical properties were varied significantly by the heat treatment process with the treatment time. To increase the fracture toughness value, the heat-treatment process of the WC-binderless, WC-5 wt.% Co and WC-10 wt% Co hard materials were performed at (1,300, 1,150, and 950) °C under (5 and 48) h, respectively. Enhancement of fracture toughness that focused on the major reasons was estimated for four mechanisms. Firstly, the microstructure formation of a mechanism was investigated to demonstrate the grain coarsening behavior for variation of heat treatment time. Secondly, the fraction of the coherent interface at WC/Co to the existing in the specific plane orientation was investigated. In particular, the texture distribution of WC (0001) hcp plane and Co (111) fcc plane were discussed in the EBSD micrograph. Thirdly, the increase of the mean free path by the Co content was exhibited in relation to the variation of mechanical properties. Finally, the mechanism of the decarburization effect of WC, which occurs during the heat treatment process under specific condition were demonstrated in the XRD peaks and FE-SEM analysis. In this chemical reaction, the separated W phases were locally precipitated, resulting in an increase in fracture toughness. Highlights • Microstructural evolution of WC and WC-Co by heat treatment process were discussed. • Mechanical properties of WC-Co were determined depending on contents of the binder. • The four major mechanisms are closely related to fracture toughness of WC and WC-Co. • Residual stress and plastic deformation behaviors due to heat treatment were discussed. [ABSTRACT FROM AUTHOR]

High-entropy monoborides (HEMBs) are promising materials for use in cutting tools and wear-resistant coatings owing to their super hardness. Because of the scarcity of reports on powder synthesis, extensive application of HEMBs is limited. To address this problem, a molten-salt-assisted strategy for synthesising HEMB powders is proposed herein. High-entropy (V 0.2 Cr 0.2 Mo 0.2 W 0.2 Ni 0.2)B powders with CrB-type orthogonal crystal structures were successfully synthesised at 1500 °C and examined by using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Subsequently, the mechanism of powder synthesis using molten salt and the advantages of powders prepared by employing molten salt for the densification and hardness enhancement of ceramics were comprehensively evaluated. The (V 0.2 Cr 0.2 Mo 0.2 W 0.2 Ni 0.2)B powders were densified by applying spark plasma sintering to study the microstructural evolution of bulk ceramics with a super hardness of 42.19 ± 2.66 GPa. This work has expanded the family of superhard HEMBs and provides a strong support for the further application of HEMBs. • High-entropy (V 0.2 Cr 0.2 Mo 0.2 W 0.2 Ni 0.2)B powder was synthesized assisted by molten salt for the first time. • High-entropy (V 0.2 Cr 0.2 Mo 0.2 W 0.2 Ni 0.2)B ceramic with hardness of 42.19 ± 2.66 GPa was successfully prepared. • The corresponding molten salt assisted mechanism was analyzed thought a reasonable hypothesis. [ABSTRACT FROM AUTHOR]

Carbon can be metal, semiconductor or insulator depending on its structures, and its conductivity can be one-dimensional (1D), 2D, and 3D correspondingly. Boron Nitride (BN) is isoelectronic to carbon, but one prominent difference between the two systems is their electronic properties. For many years, the synthesized and predicted BN allotropes were always insulators, irrespective of their structures. In this paper, with the help of structures searching based on first-principles calculations, a sp 2 / sp 3 -hybridized metallic monoclinic 3D BN ( M -BN) structure is proposed. M -BN can be viewed as puckered hexagonal-BN (h-BN) layers bucked by partial sp 3 B N bonds. The electronic property analysis revealed that the metallicity of M -BN is attributed to the delocalized 2 p electrons of the sp 2 B and N atoms. The metallic B atoms and N atoms are aligns in two arrays along a 1D axial direction, resulting in the unusual 1D dual-threaded conduction in 3D M -BN structure. The enthalpy calculation have revealed that M -BN is the most energetically favorable structure among the predicted metallic BN structures so far, and it might be obtained via compressing layered h-BN precursor theoretically. Due to the 3D strong framework, M -BN has an estimated Vickers Hardness of 33.7 GPa, indicating it is a potential hard material with novel 1D conduction. [ABSTRACT FROM AUTHOR]

3 d transition metal chalcogenides have gradually become candidates for magnetic materials due to their unique d -electronic structures. However, a relatively lower Curie temperature (T C) and coercivity (H C) limit their widespread applications. Here, we report a high-temperature organic-solvent-phase method for the synthesis of hexagonal α-Fe 1−x Cr x Se (0 ≤x ≤ 0.6) alloyed nanosheets with high T C through Cr introduction. Without Cr introduction, FeSe nanosheets appear as a mixture of tetragonal β-FeSe and hexagonal α-FeSe phases with a soft/hard decoupled hysteresis loop of H C ∼3.35 kOe at 5 K. With an increase in the Cr content, α-Fe 1−x Cr x Se gradually becomes dominant. The tetragonal-to-hexagonal phase transition is completed at the optimum doping of Cr (x = 0.4), and α-Fe 1−x Cr x Se exhibits hard magnetic behavior. The coercivity (H C) can be as high as 15.80 kOe at 5 K and 4.98 kOe at 300 K when the Cr concentration reaches 60%. The synthesis of α-Fe 1−x Cr x Se alloy provides a potential material for hard magnets. Therefore, the doping-induced phase transition is an effective way to synthesize ideal phase nanomaterials. [Display omitted] • The α-FeCrSe alloying phase were synthesized by Cr introduction. • α-Fe 0.6 Cr 0.4 Se nanosheets shows hard magnetic properties with Hc of 9.66 kOe at 5 K. • Tc of α-FeCrSe alloy is significantly higher than room temperature. • Hc of α-Fe 0.4 Cr 0.6 Se is 15.80 kOe at 5 K and 4.98 kOe at 300 K. [ABSTRACT FROM AUTHOR]

Ternary transition metal nitrides (TMNs) films with B1 structure (NaCl type) have been widely explored as hard protective materials. Their structure and mechanical performances are influenced by the stoichiometric coefficients (TM: N), while the films with high hardness yet sound toughness could be obtained by regulating the nitrogen content. In this case for the sub-stoichiometric B1 Ta-Mo-N x films, the microstructure, mechanical properties and the toughening mechanisms by N atoms were investigated. The NaCl-structure sub-stoichiometric Ta 0.44 Mo 0.56 N x films with N concentrations at 0.42 ≤x ≤ 0.73 grown by reactive magnetron sputter deposition. The film with x = 0.59 shows higher hardness (∼36.4 GPa), combined with shorter cracks around indentation and higher scratch resistance, reveals the enhanced fracture toughness (K IC =∼1.67 MPa*m1/2, H/E = 0.14); the film simultaneously obtained a lower wear rate (∼6.6 × 10−7 mm3/N * m) and friction coefficient (∼0.4). The formed point defects in sub-stoichiometric Ta-Mo-N x films are responsible for the enhanced toughness, while the film with x = 0.59 exhibit an increased p (N) - d-e g (Me) strength character accompanied with high d-t 2 g (Me) - d-t 2 g (Me) metallic states for the TM-N bonds according to the XPS results. • Ta-Mo-N x films with x = 0.42–0.73 are FCC single phase solid-solution. • The H and E of Ta-Mo-N x films can be monitored by controlling the N. • The films with sub-stoichiometric show high populated d-t 2 g metallic state. • The film with x = 0.59 shows high H (36.4 GPa), H/E (0.14) and H3/E2 (0.74 GPa). • Low wear rate of ∼6.6 × 10−7 mm3/N * m is obtained from Ta 0.44 Mo 0.56 N 0.59 film. [ABSTRACT FROM AUTHOR]

Bulk (W 0.5 Al 0.5 )C 0.65 without any binder phase was successfully produced by reactive hot-pressing from the ball-milled powders of W 0.5 Al 0.5 and C. Pure (W 0.5 Al 0.5 )C 0.65 without precipitated graphite or the brittle sub-carbide phase was synthesized due to the carbon vacancy in (W 0.5 Al 0.5 )C y can reach 50%. Grain growth of (W 0.5 Al 0.5 )C 0.65 could be suppressed with full densification by reactive hot-pressing for a short sintering time. Nearly full dense product (99.3%) with grain size of about 0.2 μm could be accomplished at 1550 °C for 10 min, with a pressure of 50 MPa. The bulk ultrafine binderless (W 0.5 Al 0.5 )C 0.65 exhibited excellent mechanical properties. [ABSTRACT FROM AUTHOR]

The effects of Si on the microstructures and various properties of Co 0.2 CrAlSi x Ni (in mole ratio, x = 0, 0.1, 0.3, 0.5, and 0.7) multi-component high entropy alloys were investigated. Co 0.2 CrAlNi was selected as the matrix, and Si was doped as the reinforcement. Microstructure analysis revealed that the Co 0.2 CrAlSi x Ni high entropy alloys consisted of two body-centered cubic (BCC) phases, the Cr-rich phase and nano-scale Ni-Al phase. With the addition of Si, the new Cr 3 Si phase was precipitated, and the crystallite size decreased to some extent in the alloys. Hardness test indicated that the alloys had high hardness with the maximum value of 973 at x = 0.5. The crystallite size and Cr 3 Si phase content were two key factors significantly affecting the hardness of Co 0.2 CrAlSi x Ni HEAs. Electrochemical test results indicated that Si affected the formation of the passivation film, the corrosion potential of Co 0.2 CrAlSi 0.1 Ni was − 0.37 V and the self-corrosion current density was 1.15 × 10−6 A/cm2, respectively. The main contribution in which Si doping affected the corrosion resistance of HEA was reduced oxidized Cr3+ and Ni2+ on the alloy surface. This study is of great significance to develop light and hard engineering materials for practical applications. • A new Co 0.2 CrAlSi x Ni HEA system was designed and proposed. • Doping Si improved the hardness values of Co 0.2 CrAlSi x Ni HEAs. • Co 0.2 CrAlSi 0.1 Ni HEA had a better corrosion resistance in Si doped alloys. [ABSTRACT FROM AUTHOR]

Cemented carbides are widely used in the cutting tools industry for their mechanical properties. They are composite materials made of hard tungsten carbide grains jointed together by a ductile cobalt binder. Due to the extreme conditions of use of the tools, understanding the evolution of the microstructure of the two phases is essential. This evolution can be followed by Mechanical Spectroscopy, either as a function of the temperature, or of the frequency. A general overview of the spectrum reveals three mechanical loss peaks. The second peak presents a transition in its Arrhenius plot at 1140 K, when measured in isothermal frequency scans. The temperature of this transition corresponds with the Curie temperature of the cobalt in WC-Co. However, temperature scans do not reveal any shift in the Arrhenius plot. This result shows how the presence of a phase transition leads to the measurement of apparent activation energies when a relaxation peak is measured in out-of-equilibrium conditions. • The Temperature and Frequency Dependent Internal Friction spectra of a WC-Co cemented carbide are determined. • A shift of the relaxation time of one of the peaks is observed in the Arrhenius plot of the second peak at 1140 K. • This shift is correlated with the magnetic transition of the cobalt phase. • This shift can only be observed by measuring Frequency Dependent Internal Friction. [ABSTRACT FROM AUTHOR]

As a promising candidate of rare-earth free hard magnetic materials, L1 0 -FeNi has been paid much attention in the last decades. However, it is difficult to be artificially fabricated due to its low thermal stability and sluggish diffusion ability of atoms below the crucial temperature of 320 °C. In this study, a promising method of annealing amorphous precursor was extensively developed through (Fe 50 Ni 50) 84−x Si x P 16 (x = 0, 4 at%) and (Fe 50 Ni 50) 86−x Si x P 14 (x = 2, 4, 8 at%) alloys. Especially, the effect of Si on the formation of L1 0 phase in annealed FeNi-based alloys was investigated and clarified. It is found Fe 42 Ni 42 P 16 with a much low crystallization temperature could be an appropriate basic amorphous alloy for the formation of L1 0 phase. The addition of Si enhanced the thermal stability of Fe-Ni-P amorphous alloys. Interestingly, Si could stabilize the L1 0 phase in annealed samples and increase its disordering temperature above which L1 0 -FeNi phase could deteriorate into soft magnetic phase. As expected, appropriate Si addition indeed improved the hard magnetic properties of the annealed alloys and samples with high coercivity above 900 Oe was obtained. Further Si addition would deteriorate the magnetic-crystalline anisotropy of L1 0 phase and decrease the coercivity of annealed Fe-Ni-Si-P alloys. Nevertheless, the results indicate that increasing the order-disorder transition temperature through element doping in L1 0 lattice would be a promising strategy for the massive formation of L1 0 -FeNi like other ordered phases (i.e. L1 2 -FeNi, L1 0 -CoPt), and could substantively contribute to the artificial fabrication of FeNi-based rare-earth free magnets in future. • Sample with the high coercivity above 900 Oe is obtained by annealing Fe-Ni-Si-P amorphous alloy. • The addition of Si increases the crystallization temperatures and thermal stability of Fe-Ni-P amorphous alloys. • Si could enhance the thermal stability and the disordering temperature of L1 0 phase. • Excessive Si addition would deteriorate the intrinsic magnetic hardness of L1 0 phase. [ABSTRACT FROM AUTHOR]

The NaCl:XEu (with X = 0.0, 0.002, 0.004, 0.006, 0.008, 0.01, 0.02 and 0.04) crystals have been grown in air by the melt (Czochralski) method and have investigated the Eu concentration dependence of the structural, physical and optical (optical absorption, photoluminescence and thermo-luminescence) properties by using the available characterization techniques. X-ray diffraction and photoluminescence (PL) studies on the doped crystals have confirmed the presence of Eu ions (existing as Eu2+ and Eu3+ ions) in the NaCl crystal matrix. Hardness measurement has shown that the Eu doped crystals belong to the hard material category and the hardness and elastic stiffness constant decrease with the load increase and increase with the Eu concentration increase. Optical absorption spectra have revealed that five new peaks appear on doping with Eu ions. PL spectra have shown increase in emission intensity with the increase in concentration of Eu2+ and Eu3+ ions. Thermo-luminescence (TL) glow curves exhibit two peaks at ~103.7 and ~199.9 ℃. The TL peak intensities observed for the Eu doped NaCl crystals are much larger than the pure NaCl crystal. NaCl:XEu crystal with X = 0.008 has been found to possess the optimal luminous (both PL and TL) properties. The TL parameters calculated prove that the activation energy (E) values vary with the Eu concentration and the trap concentration (n 0) values of the high temperature peak are larger than that for the low temperature peak. • Large size NaCl:XEu crystals were grown in air by the Czochralski method. • The hardness of the crystals decrease with the increase in load and increase with the increase in Eu concentration. • The emission intensity of the Eu ions increase with the increase in Eu concentration and attain maximum at X = 0.008. [ABSTRACT FROM AUTHOR]

Hard carbon with high specific capacity and cost-effective characteristics has emerged as a critical material in the study of sodium-ion batteries (SIBs) anodes. However, their unsatisfactory initial coulombic efficiency (ICE) and ineluctable structural deformation during long-cycling work seriously hinder their application in practice. Here, phosphorus/sulfur co-doped hard carbon with a porous bowl-like structure (denoted as P/S-HCB) is developed to achieve high performance. The experimental data show that the doping of S increased the interlayer spacing of graphite in the surface/subsurface region, the doping of P promoted the formation of C-S-P and P-O bonds, which can contribute to abundant structural defects and redox reaction sites that not only improves structural stability but also contributes to the capacitive process under high rate. The as-fabricated P/S-HCB electrode demonstrates outstanding Na-ion storage performance regarding high ICE of 88.71%, the high-reversibility capacity of about 450 mA h g−1 after 140 cycles at 0.2 A g−1, extraordinary rate capability of 216.3 mA h g−1 at 10 A g−1, and long-term cycling stability of 276 mA h g−1 after 3000 cycles at 10 A g−1. These results show a novel approach to developing advanced hard carbon materials for sodium storage. Phosphorus/sulfur co-doped hard carbon with well-designed porous bowl-like structure (P/S-HCB) was synthesized by facile hard-template strategy, which exhibited high ICE, extraordinary long-term cycling stability and remarkable rate performance. [Display omitted] • Facile method for the preparation of P/S co-doped bowl-like hard carbon was proposed. • P/S-HCB electrode exhibited high ICE, extraordinary long-term cycling stability and remarkable rate performance. • The porous bowl-like structure and the co-presence of C-S-P and P-O bonds provides more active sites for Na+ adsorption. • The dominant contribution of the pseudocapacitance was determined by kinetic analysis. [ABSTRACT FROM AUTHOR]

Using the first-principles calculations, we have designed six types of hard materials B 3 N 4 . The calculation of the elastic constants and cohesive energies shows that the new types of the B 3 N 4 are mechanically and thermodynamically stable and the c -B 3 N 4 phase is the most stable, while the stability of γ -B 3 N 4 is weakest. The Vickers hardness shows that all of them are hard materials except for g -B 3 N 4 and β -B 3 N 4 . For c -B 3 N 4 possesses a large hardness of 34.3 GPa, we can draw the conclusion that c -B 3 N 4 is potentially superhard materials. The three-dimensional dependences of reciprocals of Young's and bulk modulus of B 3 N 4 have been systematically studied and discussed, showing the g -B 3 N 4 exhibit a strong anisotropic character. In addition, the Debye temperature is obtained, and reveals the c -B 3 N 4 possesses a rather stiff lattice and good thermal conductivity. The present work has great implications for designing and researching novel superhard materials. [ABSTRACT FROM AUTHOR]

• Five high entropy carbide ceramics as potential high-hardness and ultra-high temperature materials in extreme environments. • First and systematical investigation of stability, mixing behavior, mechanical and temperature-dependent properties. • (TiZrHfTaNb)C is the most stable and hardest material. • (TiZrHfTaW)C has good mechanical properties. • (TiZrHfTaV)C possesses best thermal performance, followed by (TiZrHfTaNb)C. Multicomponent high entropy carbide ceramics (HECCs) have drawn increasing attention because of their potential applications as ultra-high temperature and super-hard materials. In this work, the stability, mixing behavior, mechanical, and temperature-dependent properties of rock-salt (TiZrHfTaM)C (M = Nb, Mo, W, V, or Cr) HECCs were first systematically investigated by density functional theory (DFT) and Debye-Grüneisen model methods. The five HECCs are thermodynamically stable owing to the negative formation enthalpies and cohesive energies. They could form the single-phase high entropy solid solution ceramics, owing to the evaluation of atom size and lattice differences, as well as mixing enthalpy criteria. Except for the system containing Cr, the others have already been confirmed by experimental findings. Among these, (TiZrHfTaNb)C most readily forms homogeneous solid solution phase, and is the most stable, brittlest, and hardest HECC material. Significantly, (TiZrHfTaV)C behaves slightly better than (TiZrHfTaNb)C with increasing temperature, owing to the comparable bulk modulus and Debye temperature, smaller volumetric expansion, and lower anharmonic effects. This work provides the instructive information for predicting and designing the high-performance ultra-high temperature ceramic materials applicable in extreme environments. [ABSTRACT FROM AUTHOR]

• We studied the phase equilibria at heating and crystallization of Fe 85−x Cr 15 C x (x = 10–17) alloys. • Fe 85−x Cr 15 C x (x = 10–17) phase diagram at high-temperatures is the eutectic type one. • Minimum of undercoolability of Fe 85−x Cr 15 C x (x = 10–17) melts is observed near 14 at% C. • Nonequilibrium crystallization of Fe 85−x Cr 15 C x (x = 10–17) melts is due to the peculiarities of interatomic interaction. [Display omitted] The Fe-Cr-C alloys are promising hard facing materials with excellent wear resistance to address extreme technological environments which is provided by the presence of carbide chemical bonds stipulating high hardness. In this research, we study the influence of the carbon concentration from 10 to 17 at% on phase equilibria during heating, as well as crystallization processes of Fe-Cr-C alloys at 15 at% Cr and their relationship with the structure of the undercooled liquid state. The concentration dependence of undercoolability of Fe 85−x Cr 15 C x (x = 10–17) melts revealed the minimum value in the region of the equilibrium eutectic near 14 at%C. Crystallization of Fe-Cr-C melts under cooling at a rate of 100 °C/min proceeds according to a nonequilibrium mechanism with the formation at the first stage of a solid solution based on fcc-Fe. Structure analysis of the undercooled Fe 85−x Cr 15 C x melts (x = 10–17) showed that the nonequilibrium crystallization is related to peculiarities of interatomic interaction. Moreover, there is formation of structures with microhardness decreasing with growing carbon concentration in the alloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] The RhB1.1 phase is more stable than the IrB1.1 phase. [•] The calculated intrinsic hardness of RhB1.1 is about of 49.9GPa. [•] The intrinsic hardness of RuB1.1 with tetragonal phase is about of 53.9GPa. [•] The lower hardness of IrB1.1 is determined by the two sub-boundary B layers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Using high-frequency induction heated sintering (HFIHS), the rapid consolidation of the nanostructured (W,Ti)C, (W,Ti)C-5vol.%NiAl3, and (W,Ti)C-10vol.%NiAl3 was accomplished successfully. [•] The densification temperature of (W,Ti)C was reduced remarkably by the addition of NiAl3. [•] The addition of NiAl3 to (W,Ti)C improved the fracture toughness of cemented (W,Ti)C without an extensive loss of its hardness. [•] The hardness values of (W,Ti)C added as novel binder of NiAl3 were higher than those of WC added as conventional binder of Ni or Co. [Copyright &y& Elsevier]

● GdB 6 is extremely stable under high pressure. ● Contrary to most other materials, the smooth X-ray diffraction rings of GdB 6 become spotty under high pressure. ● High-pressure spotty diffraction rings of GdB 6 are caused by the regional texture effect, which is reversible. ● Grain rotation behavior motivated by stress difference dominates the regional texturing in GdB 6. [Display omitted] As hard and refractory materials with high chemical resistance and mechanical strength, lanthanide hexaborides (LnB 6) have attracted much attention. Among the family of LnB 6 , gadolinium hexaboride (GdB 6) occupies a special position due to the half-filled 4 f shell of Gd. Here, using in situ synchrotron radiation angle-dispersive X-ray diffraction in a diamond anvil cell at room temperature, the structural stability and compression behavior of GdB 6 are investigated extensively, GdB 6 is observed to be structurally stable up to 73 GPa, and the bulk modulus of 177 GPa is obtained under hydrostatic compression. In this paper, an interesting observation of pressure-induced spotty diffraction rings of GdB 6 is reported, its formation mechanism can be well described by the reversible regional texture effect, which highlights the rearrangement of crystal grains under high pressure. The rearrangement mechanism has been well explained by investigating the pressure dependence of full width at half maximum, macro-differential stress and grain size. Collective grain rotation behavior motivated by stress difference is critical for the rearrangement process, the strong isotropy and strong stability of GdB 6 structure also provide necessary conditions for high-pressure grain rotation behavior. These results will help to promote the understanding of high-pressure structural properties of GdB 6 , and provide novel insights on the high-pressure grain behavior in hard materials with strong isotropy and three-dimensional skeleton constituted of strong covalent bonds. [ABSTRACT FROM AUTHOR]

• Synthesis of polycrystalline Mo 2 C specimens has been carried out firstly under high pressure and high temperature. • Mo 2 C presents superconductivity below 7.5 K and the hardness is far higher than the traditional superconductive materials. • Covalent [Mo6C] octahedral unit related to good conductivity and high hardness. • Mo 2 C is a hard superconductor to bridging the gap between high hardness and superconductivity communities. [Display omitted] Hard superconducting materials are of particular interest for electromechanical applications under high strain and stress. In this work, Mo 2 C was synthesized using high temperature and high pressure (HPHT) methods. In view of characterizations, Mo 2 C transforms into a superconductivity state below the temperature of 7.5 K and the asymptotic Vickers hardness is about 13.4 GPa. Its hardness is compatible with that of commonly used hard alloys, which is a potential hard superconducting material. Based on the results of our first-principle calculations, superconductivity and hardness come from the high density of states at the Fermi energy level and high hardness originates from the strong hybridization between Mo-4 d orbitals and C-2 p orbitals. By introducing the light element C atoms into the transition metal Mo to form a 'covalent metal' structure, the hardness and mechanical properties of the superconducting material can be improved which gives a way to design hard superconducting materials. [ABSTRACT FROM AUTHOR]

Abstract: Cemented carbides hard alloy (W0.5Al0.5)C0.5–13.3vol% Ni was successfully prepared by reactive sintering of carbon, nickel powder and W0.5Al0.5 alloy powder. The novel cemented carbide hard alloy has superior mechanical properties. The influence of sintering time and temperature on the microstructure, mechanical properties and density of the specimens are well described. Interestingly, both sintering time and temperature have amazing influence on the mechanical properties, density and microstructure of the specimen. During the reactive sintering process, Ni was the binder phase for sintering (W0.5Al0.5)C0.5–Ni cemented carbide, and it also accelerated the reaction rate of synthesizing (W0.5Al0.5)C0.5. The reactive sintering is a good method for preparing cemented carbide hard alloy (W0.5Al0.5)C0.5–Ni. Another phenomenon is that no WNi/W3Ni3C/NiC x type phases are found in the bulk specimens, although it was prepared by reactive sintering the carbon, nickel powder and W0.5Al0.5 alloy powder directly and the carbon vacancy reach to the astonished 50% value. [ABSTRACT FROM AUTHOR]

Abstract: The rapid sintering of NbC hard materials in a short time was investigated with a focus on the manufacturing potential of the high-frequency induction-heating sintering process. The advantage of this process is that it allows for very quick densification to near theoretical density. A dense pure NbC hard material with a relative density of up to 98% was produced within 2min from heating sample by the simultaneous application of a pressure of 80MPa and an induced current corresponding to 70% of the total output powder capacity (15kW). The finer the initial NbC powder size, the higher the density and the better the mechanical properties. The fracture toughness and hardness values obtained were 7.0MPam1/2 and 2200kg/mm2, respectively. [Copyright &y& Elsevier]

B 4 N is expected to be a superhard material with outstanding mechanical properties like B 4 C. The longstanding uncertainty in its stable structural information impeded the understanding of its physical and chemical properties. Here, we systematically investigated the thermodynamically stable phases of B 4 N and their corresponding functional properties by using the particle swarm optimization method combined with first-principles calculations. Two new icosahedra-based B 4 N phases that different from the rhombohedral boron carbide type structure were predicted to be more thermodynamically stable in the pressure range of 0–300 GPa. Their dynamical stability has been identified by the theoretical phonon dispersion curves. By contrast, the long-assumed rhombohedral boron carbide type structure of B 4 N was currently determined to have much higher formation enthalpy and large imaginary phonon branches at zero pressure. As a result, it is obviously less stable than the newly predicted two phases. The calculated electrical and mechanical properties of these two new phases show that they possess both metallic and superhard characters, which will stimulate further high-pressure studies on synthesis and characterization. • Two new icosahedra-based B 4 N structures were predicted. • The new phases are energetically and dynamically more stable than the long assumed B 4 C like R -3 m structure. • These two phases combines metallic and superhard characters and are promising functional superhard materials. [ABSTRACT FROM AUTHOR]

Using particle swarm optimization algorithm, we predicted two new atmospheric phases and two new high pressure phasess for OsB 2 in the pressure range from 0 to 100 GPa. By first-principles calculations with density functional theory, we further investigate the structure, phase stability, elastic properties, hardness, electronic properties for these structures. Results show that they are all thermodynamically and mechanically stable. The calculations of the enthalpy-pressure relationship was calculated to discuss the possible phase transition of OsB 2 at high pressure condition. The bulk modulus, shear modulus, Young's modulus and Poisson's ratio were computed to discuss their elastic properties. The calculations of hardness show that they are all hard materials. Especially for atmospheric I4/mmm phase and high pressure Fddd phase, their hardness are larger than 32 GPa, not far from the hardness of superhard materals. Density of states and charge density of various OsB 2 phases were presented to explore the reason for their high hardness. • We predicted two new atmospheric phases and two new high pressure phasess for OsB 2. • Our predicted atmospheric I4/mmm phase and high pressure Fddd phase are hard materals. • Density of states and charge density are studied to explore the reason for their high hardness. [ABSTRACT FROM AUTHOR]

Abstract: A novel hard material of (W0.25Al75)C has been successfully prepared by the high-pressure sintering process without the addition of any binder phase. The high-pressure is a suitable and powerful technique for sintering the binderless hard material, the relative density of the hard material can reach 99.6% under high-pressure sintering. The density of the novel light hard material is only 6.2371gcm−3, which is much lighter than the normal hard material. The hardness of the light hard material can reach 18.89GPa even the aluminum content get the astonished 75%. [Copyright &y& Elsevier]

Cobalt (Co) is one of the most important 3d transition metal elements used in the development of magnetic materials, especially in hard magnetic materials, from the early Co-based steel magnets to the rare-earth permanent magnets based on the 3d-4f compounds. Like iron (Fe), Co possesses a high saturation magnetization (M S) and a high Curie temperature (T C). Unlike Fe, Co has high magnetocrystalline anisotropy due to its spin-orbit coupling. As a result, it can be used to achieve a high degree of magnetic hardening in its elemental, alloy or compound materials. For instance, Co-based magnetic recording media is based on its elemental material. On the other hand, nano-structuring of Co-based alloys gives important hard magnetic materials including Alnico magnets and Fe–Cr–Co magnets, which are probably the earliest nanostructured hard magnetic materials. Recent progress in the development of Co-containing nanoscale hard magnetic materials has been very encouraging and promising based on the outstanding magnetic properties we have seen in L1 0 CoPt, tetragonally distorted FeCo and Co-based intermetallics. Particularly, the morphology of the nanoparticles has also been modulated to develop high coercivity via utilizing shape anisotropy, leading to extraordinarily high coercivity in Co nanowire assemblies. This review presents an overview of the development of Co-based hard and semi-hard magnetic materials and their intrinsic and extrinsic magnetic properties in view of fundamental understanding and technological applications. Image 1 • Research progress of Co-based hard and semi-hard magnetic materials is reviewed. • The magnetic properties are discussed in view of technological applications. • Fabrication process and magnetic properties of Co-based nanomaterials are discussed. • The effects of microstructure parameters on ferromagnetic properties are presented. [ABSTRACT FROM AUTHOR]

The search of ultra hard materials is inevitable in high pressure device applications. Nitrides of group-14 elements have been foreseen as potential candidates in replacing existing hard materials. In a recent experiment, pyrite structures of SiN 2 , GeN 2 and SnN 2 have been synthesized at high pressure and are shown to have high bulk modulus. Though their existence and bulk modulus are known, limited studies have been devoted to SiN 2 , GeN 2 and SnN 2. In the present work, we have performed the first principles calculations to investigate structural, electronic, mechanical and vibrational properties at ambient as well as high pressure condition. The physical properties of SnN 2 and high pressure lattice dynamical properties of SiN 2 and GeN 2 are explored for the first time. SiN 2 has higher bulk modulus among all MN 2 (where M = Si, Sn and Ge), and increases further with increase in pressure. The increase in elastic moduli of MN 2 have been related to the shortening of M-N bond length at high pressure. Electronic properties of these pyrites suggest that the bandgap increases with pressure. We further characterize these MN 2 at high pressure using theoretically calculated Raman spectra. Frequency of N–N stretching A g and T g modes confirms the single bond character of nitrogen dimer in all studied MN 2 compounds. • Elastic moduli increases with pressure for MN 2. • We predicted the electronic band gap of SiN 2 , GeN 2 and SnN 2 at high pressures. • The lattice dynamical stability of MN 2 were confirmed by phonon dispersion calculations. • The high pressure structures of MN 2 were further characterized using Raman spectra. [ABSTRACT FROM AUTHOR]

In this work, light-weight, high toughness and high strength AlMgB 14 –Al composites were prepared by hot pressing sintering. The wettability of aluminum on AlMgB 14 was improved by increasing sintering temperature and prolonging sintering time. Density of composites can be improved to 97–99% of theoretical densities at the sintering temperature of 1500 °C. Aluminum plays an active role in the growth of AlMgB 14 grains. The barrier action of high-toughness second phase can also reduce the stress intensity factor at the crack tip and increase the fracture toughness of composites. As the amount of aluminum increased, the fracture toughness increased while the bending strength decreased. The hardness with AlMgB 14 –5Al was 22.4 ± 0.5 GPa, and the fracture toughness with AlMgB 14 –30Al was about 10.7 ± 0.4 MPa m1/2. Image 1 • The wettability of aluminum on AlMgB 14 is improved by increasing sintering temperature and prolonging sintering time. • The density of the composites can be improved to 97–99% of theoretical densities at the sintering temperature of 1500 °C. • With the increase in aluminum, the hardness and bending strength decreased, and the fracture toughness increased. • The hardness with AlMgB 14 –5Al is 22.4 ± 0.5 GPa and the fracture toughness with AlMgB 14 –30Al is about 10.7 ± 0.4 MPa m1/2. • Aluminum can reduce the stress intensity factor at the crack tip and increase the fracture toughness of composites. [ABSTRACT FROM AUTHOR]

Practical application of hard carbon materials in sodium-ion batteries is largely limited by their low initial Coulombic efficiency and poor rate performance. An efficient structure design with appropriate porous structure and optimized graphitic degree is highly desired to tackle these problems. Herein, we report a new design of hierarchically porous hard carbon with rich graphite nanocrystals (PHCG). The graphite nanocrystals enable a high-level ordered structure inside hard carbon, leading to an improved initial Coulombic efficiency. And hierarchically porous structure supplies more entrance for Na+ ion diffusion and decreases Na+ ions diffusion distance, leading to a great rate performance. Therefore, the obtained hard carbon as the free-standing anodes exhibit 312 mAh g−1 with an improved initial Coulombic efficiency (77.4%) and excellent cycle performance at high rate (112 mAh g−1 at 5 A g−1 after 3000 cycles). • We report a new design of hierarchically porous hard carbon with rich graphite nanocrystals (PHCG). • The graphite nanocrystals enable an improved initial Coulombic efficiency. • Hierarchically porous structure supplies more entrance for Na+ ion diffusion, leading to a great rate performance. [ABSTRACT FROM AUTHOR]

Composites of metals and carbon nanotubes (CNTs) are of interest due to their better mechanical properties compared to neat materials. Aluminum (Al) composites with multi-walled carbon nanotubes (MWCNTs) have been prepared by room-temperature electrodeposition in a relatively inexpensive and safe organic solvent, i.e. diglyme (G2). Successful dispersion of MWCNTs in an AlCl 3 –G2 electrodeposition bath was achieved by surface modification i.e. acid treatment of MWCNTs, similar to the case of aqueous baths. Scanning electron microscopy images showed that MWCNTs filled and/or bridged the gap between Al particles, which can be attributed to the high Vickers hardness of 205 ± 14 HV, exceeding 160 HV for Al–MWCNTs obtained by powder metallurgical methods. Additionally, while the Vickers hardness of electroplated Al–MWCNTs composites has been reported to be 75 HV, an almost three times harder material is reported in the present study. Image 1 • Acid-treated MWCNTs have been successfully dispersed into a diglyme solution, similar to the case of aqueous solutions. • Al-MWCNTs composites has a hardness of 205 ± 14 HV, three times higher than that obtained by previous electrochemical methods. • MWCNTs filled and/or bridged the gap between Al particles to show 24% larger hardness than that of neat Al electrodeposits. [ABSTRACT FROM AUTHOR]

Axially symmetric magnets with good mechanical properties in the surface layer and good magnetic properties in the volume of material are essential in the production of increasing number of modern electrical devices. In order to obtain this type of gradient structure, two phase (α + γ) hard magnetic FeCr22Co15 alloy was subjected to tension and torsion in temperature range 725–850 °C. The microstructure observations of deformed samples showed the formation of gradient microstructure with minimum grain size (about 1 μm) in the surface layer of material. On the basis of TEM observations, it was found that the deformation resulted in the martensitic transformation of γ into α γ phase. The microstructure observations also showed the presence of intermetallic σ phase (Fe–Cr) with the maximum precipitates amount in the surface layer of material. The measurements of magnetic properties showed decreasing coercive force of FeCr22Co15 alloy after deformation due to preservation of α γ phase (about of 35%) in the microstructure after magnetic treatment. On the other hand, α γ phase might have appeared as a plastic constituent among brittle grains of α phase, which had a positive influence on mechanical properties of the material. [ABSTRACT FROM AUTHOR]