Manganese borohydride (Mn(BH4)(2)) was successfully synthesized by a mechano-chemical activation synthesis (MCAS) from lithium borohydride (LiBH4) and manganese chloride (MnCl2) by applying high energy ball milling for 30 mm. For the first time a wide range of molar ratios n = 1, 2, 3, 5, 9 and 23 in the (nLiBH(4) + MnCl2) mixture was investigated. During ball milling for 30 mm the mixtures release only a very small quantity of H-2 that increases with the molar ratio n but does not exceed similar to 0.2 wt.% for n = 23. However, longer milling duration leads to more H-2 released. For the equimolar ratio n = 1 the principal phases synthesized are Li2MnCl4, an inverse cubic spinel phase, and the Mn(BH4)(2) borohydride. For n = 2 a LiCl salt is formed which coexists with Mn(BH4)(2). With the n increasing from 3 to 23 LiBH4 is not completely reacted and its increasing amount is retained in the microstructure coexisting with LiCl and Mn(BH4)(2). Gas mass spectrometry during Temperature Programmed Desorption (TPD) up to 450 degrees C shows the release of hydrogen as a principal gas with a maximum intensity around 130-150 degrees C accompanied by a miniscule quantity of borane B2H6. The intensity of the B2H6 peak is 200-600 times smaller than the intensity of the corresponding H-2 peak. In situ heating experiments using a continuous monitoring during heating show no evidence of melting of Mn(BH4)(2) up to about 270-280 degrees C. At 100 degrees C under 1 bar H-2 pressure the ball milled n = 2 and 3 mixtures are capable of desorbing quite rapidly similar to 4 wt.% H-2 which is a very large amount of H-2 considering that the mixture also contains 2 mol of LiCl salt. The H-2 quantities experimentally desorbed at 100 and 200 degrees C do not exceed the maximum theoretical quantities of H-2 expected to be desorbed from Mn(BH4)(2) for various molar ratios n. It clearly confirms that the contribution from B2H6 evolved is negligibly small (if any) when desorption occurs isothermally in the practical temperature range 100-200 degrees C. It is found that the ball milled mixture with the molar ratio n = 3 exhibits the highest rate constant k and the lowest apparent activation energy for dehydrogenation, E-A similar to 102 kJ/mol. Decreasing or increasing the molar ratio n below or above 3 increases the apparent activation energy. Ball milled mixtures with the molar ratio n = 2 and 3 discharge slowly H-2 during storage at room temperature and 40 degrees C. The addition of 5 wt.% nano-Ni with a specific surface area of 60.5 m(2)/g substantially enhances the rate of discharge at 40 degrees C. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

AbstractThe title compounds are prepared by mechanical alloying of Mg with stoichiometric amounts CeCo4 or Ce2Co9 (obtained by arc‐melting in Ar) followed by annealing at 800 °C for 7 h under 1 bar argon.

Hydrogenation of orthorhombicKHg 2 -type R(Cu,Ni) 2 pseudobinary intermetallic compounds (R = Ce, Pr, Nd) was found to lead to the formation of an orthorhombic insertion-type hydride, which readily transforms into a hexagonal Fe 2 P-type hydride.This "post-hydrogenation" structural transformation can be accelerated by heating in vacuum at 100-120°°°°C and is accompanied by release of ¼ of the available hydrogen, as has been confirmed by PND studies.Further heating in vacuum leads to disproportionation of the hydride and recombination with recovery of the orthorhombic R(Cu,Ni) 2 compound after complete elimination of hydrogen from the material.Metal hydrides / Crystal structure / X-ray diffraction / Powder neutron diffraction

The hollandite Ba1Cs0.28Fe0.82Al1.46Ti5.72O16, which has been proposed for the cesium-specific conditioning, can be synthesized either by an alcoxyde or a dry route. In both cases, a two-step protocol is applied, i.e., a calcination at 1000°C followed by a sintering at 1200°C. After sintering, both synthetic processes lead to a tetragonal form. According to the X-ray diffraction (XRD) patterns collected at the barium and the cesium K absorption edges, the different positions of these two elements have been evidenced with a more centered position in the oxygen cubic site of the tunnel for Ba than for Cs. On the contrary, after calcination, the two synthetic routes yield different products. The alcoxyde route gives rise to a mixture of the aforementioned Cs- and Ba-containing tetragonal I4/m hollandite, a Cs-only-containing monoclinic I2/m hollandite and an unidentified phase with a weak coherence length containing only Ba. The dry route yields a single tetragonal hollandite material containing Ba and Cs slightly different in composition from the targeted compound.

For Abstract see ChemInform Abstract in Full Text.

Yvonite, Cu(AsO3OH)2H(2)O, was found in the Salsigne mine near Carcassone (Aude, France). It forms aggregates or radiating spherules consisting of individual crystals (maximal size 0.3 x 0.15 x 0.06 mm) of turquoise blue color. They are elongated in c, flattened on (010), and have a perfect cleavage on (100). The mineral is triclinic, P (1) over bar, a = 7.632(3), b = 11.168(3), c = 6.020(3) Angstrom, alpha = 89.32(3), beta = 86.55(5), gamma = 74.43(3)degrees, V = 493.4(3) Angstrom(3), Z = 4, D-meas = 3.20(2) g/cm(3), and D-calc = 3.22(1) g/cm(3). Mohs hardness 3.5-4. Luster vitreous transparent, streak blue; optically biaxial (-) with alpha = 1.615(2), beta = 1.660(2), and gamma = 1.700(2) at 589 nm; 2 V-obs = 82(2)degrees, 2 V-calc = 84(1)degrees. Pleochroism weak with Z = blue, Y = light blue, and X = light blue to colorless. Associated minerals: geminite, lindackerite, arsenopyrite, native bismuth, chalcopyrite, and pushcharovskite. The crystal structure was solved by direct methods (MoK alpha radiation) and refined using 1429 observed unique reflections to R = 0.069, R-w = 0.043. There are two symmetrically independent distorted CuO5(H2O) octahedra in the structure. They share edges and form cis [CuO3(H2O)] chains parallel to [001]. Two symmetrically independent distorted AsO3(OH) tetrahedra cross-link these chains to form sheets parallel to (100). Two symmetrically independent H2O molecules are located between the sheets, which are linked by a network of hydrogen bonds, accounting for the perfect cleavage of yvonite. The mineral is structurally related to geminite, Cu(AsO3OH)(H2O), and fluckite, CaMn[(AsO3OH)(H2O)](2).

The intermetallic compound Zr7Ni10 is a structure-type representative which was previously reported to crystallize in the non-centrosymmetric space group Aba2. In the present work we show that the correct space group is centrosymmetric Cmca.