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Two different types of microporous lanthanide metal--organic frameworks based on pyridine-3,5-dicarboxylic acid (H2pydc) and succinic acid (H2suc), namely [Ln(pydc)(suc) 0.5⋅3H2O]⋅2H2O (type I) [Ln = Pr (1), Eu (2), Tb (3), Er (4)] and [Ln(pydc)(suc) 0.5⋅2H2O]⋅2H2O (type II) [Ln = Yb (5) and Lu (6)], have been successfully synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis, thermogravimetric analyses (TGA) and powder X-ray diffraction (PXRD). Complexes 1-4 (type I structure) are isomorphous, crystallize in the monoclinic P21/c space group and present three-dimensional (3D) pillar-layered frameworks constructed from two-dimensional (2D) [Ln(pydc)]- layers and suc2- pillars with 1D rhombic channels. The isomorphous compounds 5-6 (type II structure) crystallize in the triclinic P space group and feature a 2D layer made up of 1D ladder-like [Ln(pydc)]- chains and suc2- connectors with the water molecules occupying the interlayer spaces. The results show that structural variation from I to II may be attributed to the lanthanide contraction effect. Furthermore, the sorption ability of compound 2 and the luminescence properties of compounds 2-3 are also investigated. [ABSTRACT FROM AUTHOR]

Two new europium-containing Zintl phases, Eu3Si2As4 and Eu3Ge2As4, were discovered from metal flux reactions and their structures were identified by using single-crystal X-ray diffraction. Both compounds crystallize in the monoclinic space group P21/ c and are isotypic to Sr3Ge2As4. Magnetic property studies were performed and the results proved the long-range antiferromagnetic behavior for Eu3Ge2As4 but with a positive Weiss constant, which suggested the coexistence of both ferromagnetic and antiferromagnetic order of Eu 4f electrons in the structure. Density functional calculations were incorporated to understand the related magnetic properties as well. [ABSTRACT FROM AUTHOR]

Three new rare-earth (RE) niobium stannides, namely, Sc2Nb4-xSn5 (x = 0.37, 0.52), YNb6Sn6, and ErNb6Sn5, have been obtained by reacting the mixture of corresponding pure elements at high temperature and structurally characterized by single-crystal X-ray diffraction studies. Sc2Nb4-xSn5 crystallizes in the orthorhombic space group Ibam (No. 72) and belongs to the V6Si5 type. Its structure features a three-dimensional (3D) network composed of two-dimensionally (2D) corrugated [Nb2Sn2] and [Nb2Sn3] layers interconnected via Nb-Sn bonds, forming one type of one-dimensional (1D) narrow tunnels along the c axis occupied by Sc atoms. YNb6Sn6 crystallizes in the hexagonal space group P6/mmm (No. 191) and adopts the HfFe6Ge6 type, and ErNb6Sn5 crystallizes in the trigonal space group R3m (No. 166) and belongs to the LiFe6Ge5 type. Their structures both feature 3D networks based on 2D [Nb3Sn], [Sn2], and [RESn2] layers (RE = Y, Er). In YNb6Sn6, one type of [Nb3Sn] layer is interconnected by [Sn2] and [YSn2] layers via Nb-Sn bonds to form a 3D network. However, in ErNb6Sn5, two types of [Nb3Sn] layers are interlinked by [Sn2] and [ErSn2] layers via Nb-Sn bonds into a 3D framework. Electronic structure calculations and magnetic property measurements for "Sc2Nb4Sn5" and YNb6Sn6 indicate that both compounds show semimetallic and temperature-independent diamagnetic behavior. [ABSTRACT FROM AUTHOR]

A highly supersaturated nanocrystalline Cr-25 wt% Zr alloy has been prepared by mechanical alloying of elemental crystalline powders. High-purity powders of Cr and Zr were milled for up to 20 h. The development of the microstructure was investigated by X-ray diffraction (XRD) and scanning electron microscopy. XRD patterns confirmed complete alloying of the Zr and Cr. The contribution of grain boundaries, the chemical potential of a solute atom induced by dislocations, and the elastic strain energy arising from the different sizes of Cr and Zr atoms have been calculated. The alloy formation is discussed with respect to the thermodynamic conditions of the material. The role of internal strains and stored enthalpies by dislocations on solute atoms is the major mechanical driving force for alloying and this is critically assessed in this article. [ABSTRACT FROM AUTHOR]

Abstract: K2Mg5−x Sn3 (x=0.28) and K3Mg18 Tt 11 (Tt=Sn, Pb) have been synthesized by reacting the mixture of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. K2Mg5−x Sn3 (x=0.28) is isostructural with Ni7−x SbQ 2 (Q=Se, Te) series and features 2D corrugated [Mg5−x Sn3] layers that are separated by K+ cations. The structure of K3Mg18 Tt 11 (Tt=Sn, Pb) is closely related to the Ho2Rh12As7 structural type and features 3D [Mg18 Tt 11] framework composed of 1D [Mg18 Tt 11] columns that are interconnected via Mg–Tt bonds, forming 1D hexagonal tunnels occupied by the K+ cations. Electronic structure calculations indicate that Mg atoms can function as either electron donor or as a participator in the network along with Tt atoms. Magnetic property measurements and band structure calculations indicate that these compounds are metallic. [Copyright &y& Elsevier]

Abstract: Four new isostructural rare earth manganese stannides, namely RE 3MnSn5−x (x=0.16(6), 0.29(1) for RE=Tm, x=0.05(8), 0.21(3) for RE=Lu), have been obtained by reacting the mixture of corresponding pure elements at high temperature. Single-crystal X-ray diffraction studies revealed that they crystallized in the orthorhombic space group Pnma (No. 62) with cell parameters of a=18.384(9)–18.495(6)Å, b=6.003(3)–6.062(2)Å, c=14.898(8)–14.976(4)Å, V=1644.3(14)–1679.0(9)Å3 and Z=8. Their structures belong to the Hf3Cr2Si4 type and feature a 3D framework composed of 1D [Mn2Sn7] chains interconnected by [Sn3] double chains via Sn–Sn bonds, forming 1D large channels based on [Mn4Sn16] 20-membered rings along the b-axis, which are occupied by the rare earth atoms. Electronic structure calculations based on density functional theory (DFT) for idealized “RE3MnSn5” model indicate that these compounds are metallic, which are in accordance with the results from temperature-dependent resistivity measurements. [ABSTRACT FROM AUTHOR]

Abstract: The title compounds have been obtained by solid state reactions of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. Yb5Ni4Sn10 adopts the Sc5Co4Si10 structure type and crystallizes in the tetragonal space group P4/mbm (No. 127) with cell parameters of a=13.785(4)Å, c=4.492 (2)Å, V=853.7(5)Å3, and Z=2. Yb7Ni4Sn13 is isostructural with Yb7Co4InGe12 and crystallizes in the tetragonal space group P4/m (No. 83) with cell parameters of a=11.1429(6)Å, c=4.5318(4)Å, V=562.69(7)Å3, and Z=1. Both structures feature three-dimensional (3D) frameworks based on three different types of one-dimensional (1D) channels, which are occupied by the Yb atoms. Electronic structure calculations based on density functional theory (DFT) indicate that both compounds are metallic. These results are in agreement with those from temperature-dependent resistivity and magnetic susceptibility measurements. [Copyright &y& Elsevier]

Abstract: Single crystals of Y7Co6Sn23 and RE5Co6Sn18 (RE=Sc, Ho) have been obtained by solid-state reactions of the corresponding pure elements in welded tantalum tubes at high temperature. Their crystal structures have been established by single-crystal X-ray diffraction studies. Y7Co6Sn23 belongs to the Ho7Co6Sn23 type and crystallizes in the trigonal space group P-3m1 (No. 164) whereas RE5Co6Sn18 (RE=Sc, Ho) adopt the Tb5Rh6Sn18 type structure and crystallizes in the tetragonal space group I41/acd (No. 142). Their structures all feature a three-dimensional (3D) anionic framework based on [CoSn6] trigonal prisms. The structure of Y7Co6Sn23 is made from the ordinal stacking one type of 2D slab composed of the same [CoSn6] trigonal prisms via corner-sharing, forming two types of narrow tunnels along the c-axis, which are occupied by Y or residual Sn atoms. The 3D structure of RE5Co6Sn18 is built up from alternately stacking two types of 2D slabs, which are composed of different [CoSn6] trigonal prisms via corner-sharing and Sn–Sn bonds, respectively. The RE and residual Sn atoms are located in the spacers of the 3D framework. Band structure calculations indicate that Y7Co6Sn23 and Sc5Co6Sn18 are metallic. [Copyright &y& Elsevier]

The title three compounds have been synthesized by solid state reactions at high temperatures, with excess indium as flux, and structurally characterized by single-crystal X-ray diffraction studies. Eu3Co2In15 forms a new structure type and crystallizes in the tetragonal space group P4/mbm (No. 127), whereas KM2In9 (M = Co, Ni) in the BaFe2Al9 type crystallizes in the hexagonal space group P6/mmm (No. 191). Their structures all feature a three- dimensional anionic framework based on 1 D [MIn6] single cluster chains composed of face-sharing [MIn9] clusters. in Eu3Co2In15, two adjacent [CoIn6] single cluster chains form a [Co2In11] double cluster chain via corner-sharing In atoms as well as In-In bonds; the latter chains are further interconnected by additional indium atoms via In-In bonds into a complicated 3D framework, forming two types of tunnels along the c-axis, which are filled by the europium atoms. In KM2In9, the [MIn6] single cluster chains are directly interconnected via corner sharing and exo In-In bonds into a 3D framework with the K+ ions encapsulated in the 1 D tunnels along the c-axis. Band structure calculations of three compounds based on density functional theory methods indicate that all three compounds are metallic. [ABSTRACT FROM AUTHOR]

Abstract: The structure and mechanical behavior of Saxidomus purpuratus bivalve shell were investigated. XRD results show that the only form of calcium carbonate present in the shell is aragonite. The inner and middle layers have a cross-lamellar structure, while the outer layer has porosity and does not have tiles, but instead has ‘blocky’ regions. The hardness of middle and inner layer are close in both plane view and cross section, but the hardness of outer layer is significantly less, especially in the plane view. The compressive strengths with loading along the three orientations were established and significant differences were found. The Weibull strength at 50% of the probability of failure varies between 59 and 148MPa and is dependent on the loading orientation and in condition of shell (dry vs. hydrated). These differences are interpreted in terms of the anisotropic structure and coarser structure of the external layer. [Copyright &y& Elsevier]

Abstract: A new rare earth nickel stannide, Sm2NiSn4, has been prepared by reacting the pure elements at high temperature in welded tantalum tubes. Its crystal structure was established by single crystal X-ray diffraction studies. Sm2NiSn4 crystallizes in the orthorhombic space group Pnma (No. 62) with cell parameters of a=16.878(2)Å, b=4.4490(7)Å, c=8.915(1)Å, and Z=4. Its structure can be viewed as the intermediate type between ZrSi2 and CeNiSi2. Sm2NiSn4 features two-dimensional (2D) corrugated [NiSn4]6− layers in which the 1D Sn zigzag chains and the 2D Sn square sheets are bridged by Ni atoms. The Sm3+ cations are located at the interlayer space. Results of both resistivity measurements and extended-Hückel tight-binding band structure calculations indicate that Sm2NiSn4 is metallic. [Copyright &y& Elsevier]

Al2O3-SiO2-TiO2 coatings were synthesized on the surface of three-dimensional (3-D) braided carbon fiber by the sol-gel method. The Al2O3-SiO2-TiO2 coating was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The effect of immension-pyrolysis cycle, immension time and heat treatment temperature on the microstructures and phase composition of the coating was investigated. The mechanical properties of the carbon fiber coated with various coating thickness were also measured. The results showed that the good morphology of the coating obtained was use of heat treatment at 750 °C for 2 immension-pyrolysis cycles by the immersion time of 40 min per cycle. The thickness was about 150-1200 nm along with the increase of immersion time from 40 to 120 min. Tensile strength measurement revealed that the Al2O3-SiO2-TiO2 coated carbon fiber maintained 96.8% of its original strength when the thickness of the coating was 470 nm. [ABSTRACT FROM AUTHOR]