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A recent study has shown the thermoelectric performance of Al-doped Mg2Si materials can be significantly enhanced at moderate pressure. To understand the cause of this phenomenon, we have performed in situ angle dispersive X-ray diffraction and infrared reflectivity measurements up to 17 GPa at room temperature. Contrary to previous experiment, using helium as a pressure transmission medium, no structural transformation was observed in pure Mg2Si. In contrast, a phase transition from cubic anti-fluorite (Fm-3m) to orthorhombic anti-cotunnite (Pnma) was observed in the Al-doped sample at 10 GPa. Infrared reflectivity measurements show the electrical conductivity increases with pressure and is further enhanced after the phase transition. The electron density of states at the Fermi level computed form density functional calculations predict a maximum thermoelectric power factor at 1.9 GPa, which is in good agreement with the experimental observation.

Due to the emerging needs of electrical and hybrid electrical vehicle applications, more research effort has been directed towards the next generation Li-ion storage materials, especially on high-capacity cathode materials. In this context, lithium transition metal silicates Li2 M SiO4 ( M = Fe, Mn, Co, etc.) 1-5 are drawing increasingly more attention thanks to their high theoretical capacity due to the two lithium-ion extraction per formula unit. However lack of phase purity control during synthesis and phase transition reactions during delithiation/lithiation have imposed obstacles to their study and further development. Hereby, we investigate a novel dual step organic-assisted hydrothermal-annealing approach to obtain different lithium iron silicate polymorphs (monoclinic, orthorhombic, and mixed) for subsequent electrochemical evaluation and probing of their phase transition behavior. During the hydrothermal synthesis step, organic additives are used to control nanocrystal growth, which upon annealing lead to in-situ coating with nitrogen-doped carbon. The silicates are characterized by various techniques including XRD, FE-SEM, TEM, XPS, Raman spectroscopy, and XANES and demonstrate different structures and morphologies with various synthesis conditions, including annealing temperature, pH etc., which critically impact on their electrochemical properties. References 1. Nyten, A., Abouimrane, A., Armand, M., Gustafsson, T. & Thomas, J. O. Electrochemical performance of Li2FeSiO4 as a new Li-battery cathode material. Electrochem Commun 7, 156-160, (2005). 2. Nishimura, S. I. et al. Structure of Li2FeSiO4. J Am Chem Soc 130, 13212-13213, (2008). 3.Boulineau, A. et al. Polymorphism and structural defects in Li2FeSiO4. Dalton Trans 39, 6310-6316, (2010). 4. Eames, C., Armstrong, A. R., Bruce, P. G. & Islam, M. S. Insights into Changes in Voltage and Structure of Li2FeSiO4 Polymorphs for Lithium-Ion Batteries. Chem Mater 24, 2155-2161, (2012) 5. R.J. Gummow, Y. He / Journal of Power Sources 253 (2014) 315-331, Recent progress in the development of Li2MnSiO4 cathode materials

Mesoporous Li deficient Li4Ti5O12 nanosheets with major [110] preferred orientation were prepared by a novel low T (+ reaches the following over-stoichiometrical composition: Li7.92Ti5O12. As determined by XANES the excess Li-ion storage is the result of preferential crystal orientation along the (110) and (111), facets. During lithiation, it was further determined the charge compensation to occur primarily by oxygen, rather than by titanium. Finally, both the oxygen and titanium in the near surface region exhibit different electronic structure from bulk. Those results point to the importance of surface reconstruction and relaxation in accommodating excess Li storage. As a consequence, the newly prepared Li4Ti5O12 nanosheets exhibit superior Li-ion storage performance exceeding by far most of the alternatively prepared LTO anode materials.

Silicon stabilized tricalcium phosphate (Si-TCP) is formed, among other phases, as a result of sintering hydroxyapatite (HA) in the presence of silica (SiO2) at >800°C. Calcium phosphate films sintered at 1000°C on quartz substrates are examined with and without additional SiO2 added to the starting precipitate. Data from transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) separate the undoped film morphology into a surface layer with a monoclinic crystal structure P21/a characteristic of α or Si-tricalcium phosphate and grain size in the range 100–1000 nm and a substrate layer with a crystal structure which is predominantly apatitic P63/m and grain size in the range 30–100 nm. The silicon content is greatest in the substrate layer. The addition of SiO2 to the film material during fabrication induces a more uniform grain size of 10–110 nm and a higher Si content. The structural and phase evolution of these films suggests the nucleation of α-TCP by the local formation of Si-TCP at a SiO2-hydroxyapatite interface. The results are consistent with X-ray diffraction studies and are explained by a model of nucleation and growth developed for bulk powders.

Powder diffraction (PXRD) is an important tool for synergistic synchrotron studies of mining issues. Quantitative phase analysis with powder diffraction often provides basic information required to guide additional studies such as X-ray absorption (XAS) or micro-diffraction (μ-XRD). Elemental speciation in dilute and complex mineralogical systems with X-ray absorption near edge structure (XANES) spectroscopy is critically dependent on high quality phase pure standards, which are generally appraised using PXRD. This talk will examine the powder diffraction capabilities at the CLS, and discuss application of PXRD to mining issues as part of a combined synchrotron approach using examples.

Resorbable calcium phosphate (CaP) thin films previously prepared only on quartz substrates were fabricated on Ti-6Al-4V implant grade titanium alloy. In order to maintain the characteristic phase composition and surface morphology of the CaP thin film, an intermediate silica barrier layer was deposited on the titanium alloy via chemical vapour deposition (CVD) using a metal organic precursor. CaP thin films were subsequently deposited on the intermediate SiO2 layer using the dip coating method, and sintered at 1000°C. The final sintered films have a multiphase composition consisting of calcium hydroxyapatite (HA) and a silicon stabilized form of alpha tri-calcium phosphate, or Si-TCP. The thickness of the silica barrier layers were evaluated in terms of the main CVD processing parameters using variable wavelength fixed angle ellipsometry and these parameters were optimized to best reproduce the characteristic CaP thin film. The phase composition and surface morphology of the CaP thin films were characterized using glancing angle X-ray diffraction and scanning electron microscopy.

The microbial degradation or propylene glycol (PG) and ethylene glycol (EG) was assessed under normal operating conditions and during periods of upset in batch studies with mixed liquor from a pure-oxygen industrial activated sludge, system. The mixed liquor microbial community exhibited rapid PG turnover times on all sample dates, however EG turnover times were consistenly greater than the hydraulic residence time, of the reactor. EG degradation significantly decreased when PG flow to the reactor ceased, suggesting that PG stimulates EG degradation. Contradictory to this, EG degradation by the community and by pure cultures from the system was found to be inhibited in the presence of PG. It appears that PG and EG degradation in the reactor are bi-phasic with PG being degraded preferentially over EG, but PG being required to maintain a viable community. Physiological and kinetic studies revealed that the microbial community of the system is not metabolically diverse. While all cultures isolated from the system were capable of degrading PG, only two were capable of degrading EG. PG and EG degradation appear to be dominated by cultures with similar enzyme kinetics. Failure to isolate cultures capable of utilizing EG as a sole carbon and energy source and the antagonistic effects of PG on EG degradation suggest that the microbial community of the system requires PG as a carbon and energy source and that EG is cometabolized by non-specific constituitive enzymes wlth a greater affinity for PG than EG.