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A number of new ternary magnesium based alloys AMgNi4 (where A=Ca, La, Ce, Pr, Nd, and Y) have been synthesized by direct combination of the elements in the atomic ratio A:Mg:Ni=1:1:4. The crystal structures were determined by Guinier–Ha¨gg X-ray powder diffraction. The compounds have a cubic SnMgCu4 (AuBe5 type) structure, which is related to the (C15) MgCu2 structure. All interatomic distances indicate metallic-type bonding. [Copyright &y& Elsevier]

Abstract: NaAl2Ga2 intermetallic compound has been synthesized by direct combination of the elements in the atomic ratio Na:Ga:Al=1:2:2. Guinier–Hägg X-ray and neutron powder diffraction determined a ThCr2Si2 type structure for the new compound with tetragonal unit cell axis a =4.1817(5) and c =11.388(2)Å. [Copyright &y& Elsevier]

Abstract: By substituting Si− with (Al–H)− in trigonal BaSi2, a series of hydrides has been synthesized with compositions BaAl2−x Si x H2−x (0.4< x <1.6). DFT calculations show that the end compositions BaSi2 and BaAl2H2 are conductors whereas the intermediate BaAlSiH is a semiconductor. The cell parameters for the trigonal cell vary linearly as a function of the Si−/(Al–H)− substitution in this MgB2 related structure type, opening up the possibility of continuously tunable electric properties. [ABSTRACT FROM AUTHOR]

Abstract: In this article, sub-C size cylindrical NiMH cells were constructed for the performance investigation under long-term overcharge and elevated temperatures. The influence of operated conditions on cell performance and electrode materials was examined. The experimental results revealed that the NiMH cells had good tolerance for 1-month overcharge at a 0.2C rate, remaining the capacity and capacity-rate performance and showing promise as a candidate for backup power sources. However, the sub-C size NiMH cells did not exhibit good performance at elevated temperatures, and the cycling stability with 100% DOD (depth of discharge) at temperature of >50°C is necessary to be further improved. The deterioration of electrochemical capacity and cycling stability at elevated temperatures was analyzed and the reasons were discussed. [Copyright &y& Elsevier]

Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A 2 B 7 -type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La 2- x Y x Ni 6.50 Mn 0.33 Al 0.17 , x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.

During formation and cycling of nickel-metal hydride (NiMH cells), surface corrosion on the metal hydride particles forms a porous outer layer of needle-shaped rare-earth hydroxide crystals. Under this layer, a denser but thinner oxidized layer protects the inner metallic part of the MH electrode powder particles. Nano-sized nickel-containing clusters that are assumed to promote the charge and discharge reaction kinetics are also formed here. In this study, mechanical treatments are tested to recycle hydrogen storage alloys from spent NiMH batteries. This removes the outer corroded surface of the alloy particles, while maintaining the catalytic properties of the surface. Scanning electron microscopy images and powder X-ray diffraction measurements show that the corrosion layer can be partly removed by ball milling or sonication, combined with a simple washing procedure. The reconditioned alloy powders exhibit improved high rate properties and activate more quickly than the pristine alloy. This indicates that the protective interphase layer created on the alloy particle during their earlier cycling is rather stable. The larger active surface that is created by the mechanical impact on the surface by the treatments also improves the kinetic properties. Similarly, the mechanical strain during cycling cracks the alloy particles into finer fragments. However, some of these particles form agglomerates, reducing the accessibility for the electrolyte and rendering them inactive. The mechanical treatment also separates the agglomerates and thus further promotes reaction kinetics in the upcycled material. Altogether, this suggests that the MH electrode material can perform better in its second life in a new battery.

Products of the reaction of C(60) with H(2) gas have been monitored by high-resolution atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS), X-ray diffraction, and IR spectroscopy as a function of hydrogenation period. Samples were synthesized at 673 K and 120 bar hydrogen pressure for hydrogenation periods between 300 and 5000 min, resulting in the formation of hydrofullerene mixtures with hydrogen content ranging from 1.6 to 5.3 wt %. Highly reduced C(60)H(x) (x > 36-40) and products of their fragmentation were identified in these samples by APPI FT-ICR MS. A sharp change in structure was observed for samples with at least 5.0 wt % of hydrogen. Low-mass (300-500 Da) hydrogenation products not observed by prior field desorption (FD) FT-ICR MS were detected by APPI FT-ICR MS and their elemental compositions obtained for the first time. Synthetic and analytical fragmentation pathways are discussed.

Studies on nanoscale materials have received great interest in both fundamental and applied aspects in recent years. In this letter, we report the synthesis of CoOOH nanorods and their possible applications as coating materials on nickel hydroxide for high-temperature nickel-metal hydride (Ni-MH) cells. The morphology and structure of CoOOH nanorods and coated nickel hydroxide particles are investigated by transmission electron microscopy, X-ray diffraction, and scanning electron microscopy, respectively. The electrochemical properties in the cylindrical AA size Ni-MH cells are evaluated. Our results show that the Ni-MH cells, where the positive electrodes are composed of such nanometer sized CoOOH coatings, have a higher capacity available and good performance at elevated temperatures of >50 degrees C.

The molecular structure of one diastereomer of the dinucleoside methylphosphonate Tp(Me)sT (1) has been determined by X-ray diffraction methods. The crystal asymmetric unit contains one molecule of 1 and one methanol in an orthorhombic unit cell of dimensions a = 13.241(4), b = 13.844(3), c = 14.944(7) A, space group P2(1)2(1)2(1). Both pyrimidine bases in 1 are oriented anti relative to the 2'-deoxyribose rings, and the sugar conformations are 2E and 2(3)T in the 4-thiothymidine and thymidine moieties, respectively. The deoxyribose-phosphonate backbone has an extended conformation with the bases completely unstacked and almost parallel. The absolute configuration at the phosphorus center in 1 is Sp.