[en] Three new compounds add to the family of the Mn₅Si₃ type host-guest lattice. These are La₅Sn₃X (X=Cl, Br, I) synthesized from stoichiometric mixtures of La, LaX₃ and Sn heated under Ar atmosphere in sealed Ta ampoules at 850-990 deg. C for 13-62 days. La₅Sn₃X crystallize in the space group P6₃/mcm (No. 193) with lattice parameters a=9.603(1) A, 9.637(1) A and 9.673(1) A; c=6.890(1) A, 6.931(1) A and 6.987(1) A, respectively, for X=Cl, Br and I. Computational analysis using both the extended Hueckel and the local density functional methods showed that the Sn and La site acts as electron reservoir, providing electrons to the interstitials as necessary. This gives rise to a metallic behavior. Susceptibility and conductivity measurements confirmed these predictions. The single crystal structure of La₅Bi₃Br is also reported

[en] Graphical abstract: An enhanced photoelectrochemical activity for water splitting was achieved over porous Ti-doped α-Fe_2O_3 nanocubes. - Highlights: . • Ti-doped hematite nanocubes were successfully prepared by NaF-assisted hydrothermal deposition and subsequent annealing. • Ti-doped α-Fe_2O_3 nanocubes showed an enhanced PEC activity with an IPCE of 25.2% at 340 nm at 1.23 V vs. RHE. • The enhanced activity of Ti-doped hematite nanocubes can be ascribed to high surface area and fast charge transportation. - Abstract: Ti-doped α-Fe_2O_3 nanocubes on FTO substrate was prepared by hydrothermal deposition β-FeOOH onto FTO glass with a solution of FeCl_3, TiOCl_2 and NaF, followed by an appropriate annealing. In comparison to Ti-doped α-Fe_2O_3 nanorods Ti-doped α-Fe_2O_3 nanocubes showed an enhanced photoelectrochemical activity for water splitting, with a remarkable IPCE of 25.2% at 340 nm at the potential of 1.23 V vs. RHE. The hematite films were studied in detail by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis absorption spectroscopy and electrochemical impedance spectroscopy. On the basis of the obtained results, the improved performance of Ti-doped α-Fe_2O_3 nanocubes can be ascribed to the porous structure, good electrical conductivity and fast charge transportation of hematite.

[en] 3D arrays of molybdenum sulphide nanosheets on Mo mesh exhibited enhanced electro-catalytic activity for hydrogen evolution reaction. - Highlights: • 3D arrays of molybdenum sulphide nanosheets were obtained by a facile hydrothermal method. • The mesh structure could be beneficial to promote the electrolyte diffusion onto the electrode surface and thus promote the electron transfer. • 3D arrays of molybdenum sulphide nanosheets demonstrate an enhanced HER activity with a low onset overpotential of 120 mV and a Tafel slope of 46 mV/dec. - Abstract: Molybdenum sulphide has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER). Toward further improving its activity, tremendous efforts have been made to preferentially expose active edge sites of molybdenum sulphide-based catalysts by engineering their surface structure. In this work, 3D arrays of molybdenum sulphide nanosheets were synthesized by hydrothermal treatment of Mo mesh in aqueous thiourea solution. Their compositional, morphological and structural properties as well as electrocatalytic activities were investigated in details. The results reveal that 3D arrays of molybdenum sulphide nanosheets demonstrate an enhanced HER activity with a low onset overpotential of 120 mV and a Tafel slope of 46 mV/dec, which is superior to that of 2D arrays molybdenum sulphide nanosheets grown on Mo foil. The high activity for HER can be ascribed to the superstructure of the catalysts with a large fraction of edge sites and a high surface area

[en] Synthesis of the superconducting V₂Ga₅ compound was achieved using molten Ga as the flux material. Large single crystals of 30 mm in length can be obtained with this method. Single crystal X-ray diffraction and computational studies were carried out for this compound. V₂Ga₅ crystallizes in the tetragonal lattice P4/mbm (No. 127) with lattice constants a=8.936(3) A, c=2.683(2) A, V=214.3(2) A³, and Z=2. Computational study shows that bonding in this compound is delocalized, and the majority states at the Fermi level are the vanadium d-band. Resistivity and magnetization measurements have confirmed that the solid is a bulk type II superconductor with T_C=3.59 K

[en] The aim of present work is study the effcet of Al-Nb-B₂O₃-CuO system reaction products on microstructure and properties of A356 alloy. B₂O₃ powder, Al powder, CuO powder and Nb powder were used as raw materials to form Al–Nb–B₂O₃–CuO reaction system, and A356 alloy was refined by in situ reaction and near-liquidus casting. The size, phase, morphology and distribution of in situ reaction products were observed and analysed by optical microscope, x-ray diffractometer, scanning electron microscope and transmission electron microscope. The products of the Al–Nb–B₂O₃–CuO reaction system are mainly Al₃Nb, NbB₂ and Al₂O₃. The ratio of the prefabricated block is 8:1:1:2 . When the prefabricated block was added at 2.5 wt%, the particle size of NbB₂, Al₃Nb and Al₂O₃ is 0.5–1 μm. The microstructure of A356 alloy is fine and uniform. The average grain size is refined to less than 20 μm. Compared with untreated A356 alloy, the wear rate is reduced from 2.091% to 0.882%, and the average hardness of the alloy is increased from 41.3HRC to 58.2HRC. (paper)

[en] Two rare earth oxysulfides Ln${}_5$V${}_3$O${}_7$S${}_6$ (Ln = La, Ce) have been synthesized and their structures determined. The two isostructural compounds crystallize in the orthorhombic space group Pmmn (no. 59). The structure features one-dimensional edge-sharing VS${}_4$O${}_2$ octahedron chains parallel to the b axis. The bonding between V and S/O is covalent, and between Ln${}^{3+}$ and the rest of the matrix ionic. Magnetic susceptibility measurement revealed that V is in a mixed valence state of V${}^{3+}$ and V${}^{4+}$. Its magnetic behavior follows the Curie-Weiss law.

[en] The title compound was prepared from the pure elements by sintering. The crystal structure was investigated by means of powder X-ray diffraction data. Ho${}_5$Pd${}_{19}$P${}_{12}$ exhibits the hexagonal Ho${}_5$Ni${}_{19}$P${}_{12}$-type structure with space group $P\stackrel{¯<!--\; ??\; -->}{6}2m$ , a = 13.1342(2), c = 3.9839(1) Å, R${}_I$ = 0.060, R${}_p$ = 0.080. The crystal structure can be described as a combination of two types of the structural units, [HoPd${}_6$P${}_3$] and [Ho${}_3$Pd${}_{10}$P${}_6$], respectively, mutually displaced by 1/2 along the crystallographic c axis. Quantum chemical calculations have been performed to analyze the electronic structure and provide deeper insight into the structure-property relationships. The results of the quantum chemical calculations indicate that the material features metallic bonding between Ho and Pd and covalent bonding between Pd and P.

[en] A new rare earth carbide boride halide, La₃Cl₃BC, has been prepared by heating a mixture of stoichiometric quantities of LaCl₃, La, B and C at 1050 C for 10 days. La₃Cl₃BC (La₃Br₃BC type) crystallizes in the monoclinic system with space group P2₁/m (No. 11), a = 8.2040(16), b = 3.8824(8), c = 11.328(2) Aa, β = 100.82(3) . In the structure, monocapped trigonal prisms containing B-C units are condensed into chains along the b direction, and the chains are further linked by Cl atoms in the a and c directions. The condensation results in a polymeric anion _∞¹[BC] with a spine of B atoms in a trigonal prismatic coordination by La, and the C atoms attached in a square pyramidal coordination. The B-B and B-C distances are 2.16 and 1.63 Aa, respectively. La₃Cl₃BC is metallic. The EH calculation shows that the distribution of valence electrons can be formulated as (La³⁺)₃(Cl^-)₃(BC)^5- . e^-. (orig.)

[en] The title compound was synthesized from La, LaCl₃ and Co under Ar atmosphere at 800 deg. C. It crystallizes in space group P4₂/n (no. 86) with lattice constants a=11.308(2) A and c=14.441(3) A. The structure features an isolated Co-centered La₆ octahedron with all corners and edges, and 2 of its 8 triangular faces coordinated by Cl atoms. The La₆Co octahedron is significantly distorted, and the La coordination by Cl atoms deviates from the common close-packing arrangements found in other reduced rare earth metal halides. Structure, bonding and physical properties of the compound have been investigated. - Graphical abstract: La₆Cl₁₁Co octahedron exhibiting a mixed M₆X₁₂/M₆X₁₂ coordination environment.

[en] The title compound was prepared from the elements by arc-melting. The crystal structure was investigated by means of single-crystal X-ray diffraction. It crystallizes in the TbFeSi${}_2$ structure type, orthorhombic space group Cmmm, a = 4.0496(8), b = 16.416(2), c = 3.9527(6) Å, Z = 4, R1 = 0.041, wR2 = 0.11 for 207 unique reflections with I${}_o$ > 2 σ(I${}_o$) and 19 refined parameters. The Fe position is not fully occupied and the refinement results in a composition GdFe${}_{0.68}$Si${}_2$ in agreement with a chemical analysis. The structure consists of zig-zag chains of Si(1) atoms which are terminally bound to additional Si(2) atoms. For an ordered variant GdFe${}_{0.5}$Si${}_2$ the Zintl concept can be applied which results in formal oxidation states Gd${}^{3+}$(Fe${}^{2+}$)${}_{0.5}$Si(1)${}^{1-<!--\; ???\; -->}$Si(2)${}^{3-<!--\; ???\; -->}$. The electronic structure of this variant GdFe${}_{0.5}$Si${}_2$ was analyzed using the tightbinding LMTO method and the results confirm the simple bonding picture.