Job Rijssenbeek

Ammine Magnesium Borohydride Complex as a New Material for Hydrogen Storage: Structure and Properties of Mg(BH4)2·2NH3

The ammonia complex of magnesium borohydride Mg(BH4)2.2NH3 (I), which contains 16.0 wt % hydrogen, is a potentially promising material for hydrogen storage. This complex was synthesized by thermal decomposition of a hexaaammine complex Mg(BH4)2.6NH3 (II), which crystallizes in the cubic space group Fm3 m with unit cell parameter a=10.82(1) A and is isostructural to Mg(NH3) 6Cl2. We solved the structure of I that crystallizes in the orthorhombic space group Pcab with unit cell parameters a=17.4872(4) A, b=9.4132(2) A, c=8.7304(2) A, and Z=8. This structure is built from individual pseudotetrahedral molecules Mg(BH4)2.2NH3 containing one bidentate BH4 group and one tridentate BH4 group that pack into a layered crystal structure mediated by N-H...H-B dihydrogen bonds. Complex I decomposes endothermically starting at 150 degrees C, with a maximum hydrogen release rate at 205 degrees C, which makes it competitive with ammonia borane BH 3NH3 as a hydrogen storage material.

Structure of Unsolvated Magnesium Borohydride Mg(BH4)2

We have determined the structures of two phases of unsolvated Mg(BH(4))(2), a material of interest for hydrogen storage. One or both phases can be obtained depending on the synthesis conditions. The first, a hexagonal phase with space group P6(1), is stable below 453 K. Upon heating above that temperature it transforms to an orthorhombic phase, with space group Fddd, stable to 613 K at which point it decomposes with hydrogen release. Both phases consist of complex networks of corner-sharing tetrahedra consisting of a central Mg atom and four BH(4) units. The high-temperature orthorhombic phase has a strong antisite disorder in the a lattice direction, which can be understood on the basis of atomic structure.

Coexistence of superconductivity and ferromagnetism in 1212-Ru1 - xMxSr2GdCu2O8 (M = Ti, V, Nb)

Abstract The coexistence of superconductivity and ferromagnetism in 1212-RuSr 2 GdCu 2 O 8 is unique among high- T c materials. Samples of Ru 1− x M x Sr 2 GdCu 2 O 8 , with M=Ti, V and Nb; and 0≤ x ≤1, were prepared to elucidate the role of the RuO 2 planes in this interesting layered 1212 cuprate. The solubility ranges of M=Ti and V are limited to x x >0.2), however with vanadium substitution the T c increases from 20 K to 25 K. The ferromagnetism of the RuO 2 layers is dramatically affected by the electronic configuration of the substituting ion, weakened for M=Ti and Nb and enhanced for M=V. These results indicate that the superconductivity and ferromagnetism are intimately linked to the layered architecture of this 1212 structure.

Electrical and magnetic properties of Ru1−xMxSr2GdCu2O8 (MTi, V and Nb)

Abstract Samples of Ru1−xMxSr2GdCu2O8, with MTi, V andNb; and 0 ≤ × ≤1 were synthesized to shed light on the role of the RuO2 planes in this 1212-type compound which is a ferromagnetic superconductor (Tc = 10–40 K) when x = 0. We show that the ferromagnetism and the superconductivity are weakened for MTi and Nb, and enhanced for MV, although superconductivity is suppressed for all compounds of higher doping levels (x > 0.2). Jonker analysis of the high-temperature electrical properties of RuSr2GdCu2O8 shows that it falls within the characteristic range for other known superconductors.

Dipentaerythritol: a novel additive for the precipitation of dispersed Ni particles in polyols

Highly dispersed uniform Ni particles ranging in size from 0.1 to 1.2 μm were synthesized by reducing nickel carbonate in polyols in the presence of dipentaerythritol (DPE) and noble metal salts. DPE was essential in preventing the aggregation of nickel particles, while the noble metal (‘seeding’ approach) effectively tailored their size. Ferromagnetic particles with a cubic closed packed (ccp) crystal habit were obtained using short reduction times at temperatures below 200 °C. Non-magnetic particles with hexagonal closed packed (hcp) structure were obtained after extended heating times (>16 hours) at temperatures above 220 °C. The temperature of the reduction and heat-treatment process was adjusted by using polyols with different boiling points.

Sodium-metal halide batteries in diesel-battery hybrid telecom applications

GE is commercializing the Durathon™* sodium-metal halide battery for stationary power and electrified transportation applications. Attributes of the technology, which include high energy capacity, long cycle life, safe failure modes, and compatibility with extreme operating environments, make it particularly suitable for applications such as stationary back up power in areas where the electrical grid is unavailable. In off-grid or weak-grid telecom applications, cell towers that rely on backup generators and batteries can operate more fuel-efficiently by utilizing Durathon batteries instead of lead acid batteries for energy storage, reducing fuel usage and associated emissions. This manuscript describes the battery technology, performance in hybrid telecom applications and demonstrates the value Durathon batteries bring to off-grid and weak-grid telecom customers.

High Throughput Quantitative Phase Mapping Using Synchrotron X-Ray Diffraction

The X-Ray diffraction (XRD) technique has been used to characterize crystalline phases in mixtures ever since its discovery. In contrast to the spectroscopy, it can provide quantitative phase information via Rietveld refinement [1]. While spectroscopy is commonly used to map surface elemental distributions, XRD has not been popular for such mapping applications – likely due to the lack of suitable instruments and analysis software. Nowadays, high brilliance and high energy synchrotron Xrays are available, that can penetrate relatively thick bulk materials. And with highly collimated micronsize beams, the technique can generate tens of thousands diffraction patterns in a few hours – which can cover a few cm 2 surface with sub-mm resolution. Quantitative analysis of such big data sets remains a challenge since most Rietveld refinement programs were not developed with such applications in mind.