The First Alkaline-Earth Azidoaurate(III), Ba[Au(N3 )4 ]2 ⋠4 H2 O.

Transparent, dark orange Ba[Au(N3 )4 ]2 ⋅ 4 H2 O was synthesized by reaction of Ba(N3 )2 and AuCl3 or HAuCl4 in aqueous solution. The novel barium tetraazidoaurate(III) tetrahydrate crystallizes in the monoclinic space group Cc (no. 9) with a=1813.68(17) pm, b=1737.95(11) pm, c=682.04(8) pm and ß=108.849(4)°. The predominant structural features of Ba[Au(N3 )4 ]2 ⋅ 4 H2 O are two crystallographically independent discrete anions [Au(N3 )4 ]- with gold in a tetragonal planar coordination by nitrogen. Vibrational spectra show good agreement with those of other azidoaurates(III). Upon drying, this salt was shown to be a highly explosive material.

Defect-induced B4C electrodes for high energy density supercapacitor devices.

Boron carbide powders were synthesized by mechanically activated annealing process using anhydrous boron oxide (B2O3) and varying carbon (C) sources such as graphite and activated carbon: The precursors were mechanically activated for different times in a high energy ball mill and reacted in an induction furnace. According to the Raman analyses of the carbon sources, the I(D)/I(G) ratio increased from ~ 0.25 to ~ 0.99, as the carbon material changed from graphite to active carbon, indicating the highly defected and disordered structure of active carbon. Complementary advanced EPR analysis of defect centers in B4C revealed that the intrinsic defects play a major role in the electrochemical performance of the supercapacitor device once they have an electrode component made of bare B4C. Depending on the starting material and synthesis conditions the conductivity, energy, and power density, as well as capacity, can be controlled hence high-performance supercapacitor devices can be produced.

LiMg0.1Co0.9BO3 as a positive electrode material for Li-ion batteries.

LiCoBO3 could be a promising cathode material given the electronic and ionic conductivity problems are addressed. Here, Mg substitution in LiCoBO3 is employed to stabilise the structure and improve the electrochemical performance. LiMg0.1Co0.9BO3 is synthesised for the first time via sol-gel method and Mg substitution in the structure is verified by X-ray powder diffraction and energy dispersive X-ray analyses. The electrochemical properties are investigated by galvanostatic cycling and cyclic voltammetry tests. The composite electrode with conductive carbon (reduced graphite oxide and carbon black) delivers a first discharge capacity of 32 mA h g-1 within a 4.7-1.7 voltage window at a rate of 10 mA g-1. The cycling is relatively stable compared to the unsubstituted LiCoBO3. Mg substitution may enhance the electrochemical performance of borate-based electrode materials when combined with suitable electrode design techniques.

Improvement in the transport critical current density and microstructure of isotopic Mg11B2 monofilament wires by optimizing the sintering temperature.

Superconducting wires are widely used in fabricating magnetic coils in fusion reactors. In consideration of the stability of 11B against neutron irradiation and lower induced radio-activation properties, MgB2 superconductor with 11B serving as boron source is an alternative candidate to be used in fusion reactor with severe irradiation environment. In present work, a batch of monofilament isotopic Mg11B2 wires with amorphous 11B powder as precursor were fabricated using powder-in-tube (PIT) process at different sintering temperature, and the evolution of their microstructure and corresponding superconducting properties was systemically investigated. Accordingly, the best transport critical current density (Jc) = 2 × 104 A/cm2 was obtained at 4.2 K and 5 T, which is even comparable to multi-filament Mg11B2 isotope wires reported in other work. Surprisingly, transport Jc vanished in our wire which was heat-treated at excessively high temperature (800 °C). Combined with microstructure observation, it was found that lots of big interconnected microcracks and voids that can isolate the MgB2 grains formed in this whole sample, resulting in significant deterioration in inter-grain connectivity. The results can be a constructive guide in fabricating Mg11B2 wires to be used as magnet coils in fusion reactor systems such as ITER-type tokamak magnet.

Defect structure in aliovalently-doped and isovalently-substituted PbTiO3 nano-powders.

The defect structure of Fe(3+)-, Cu(2+)-, Mn(4+)- and Gd(3+)-doped PbTiO(3) nano-powders has been studied by electron paramagnetic resonance (EPR) spectroscopy. Analogous to the situation for 'bulk' ferroelectrics, Fe(3+) and Cu(2+) act as acceptor-type functional centers that form defect complexes with charge-compensating oxygen vacancies. The corresponding defect dipoles are aligned along the direction of spontaneous polarization, P(S), and possess an additional defect polarization, P(D). Upon the transition to the nano-regime, the defect structure is modified such that orientations perpendicular to P(S), [Formula: see text] and [Formula: see text] also become realized. Moreover, the binding energy for the defect complexes is lowered such that instead 'free' Fe'(Ti) and V··(O)-centers are formed. As a consequence, the concentration of mobile V··(O) that enhances the ionic conductivity through drift diffusion is increased for the nano-powders. Finally, in the nano-regime the ferroelectric 'hardening' is expected to be considerably decreased as compared to the 'bulk' compounds. In contrast to the acceptor-type dopants, the donor-type Gd(3+) dopant is incorporated as an 'isolated' functional center, where charge compensation by means of lead vacancies is performed in distant coordination spheres.

The Cluster Anion Si94.

Solely on the basis of Raman spectra and quantum chemical calculations, the previously unknown cluster anion Si94- (structure shown) was characterized and its structure determined. The anion is formed as a component of solid phases by the thermal decomposition of alkali metal monosilicides.