Joel Reid

Thermoelectric and electrical transport properties of Mg2Si multi-doped with Sb, Al and Zn

Enhanced thermoelectric and electrical transport properties of Mg2Si-based thermoelectric materials have been achieved by multi-doping with Sb, Al and Zn. Results on the investigation of the electrical transport and thermoelectric properties of multi-doped samples prepared using the spark plasma sintering technique are reported. Synchrotron radiation powder X-ray diffraction was used to characterize the structures of the doped samples. The electrical transport properties were determined from mid-infrared reflectivities, Hall effect and conventional quasi-four probe conductivity measurements. Using the electron concentrations (N) determined from the Hall coefficients, the effective masses (m*) were calculated from the frequency of the plasma edge (ωP) of the infrared reflectivities. The thermoelectric performance and thermoelectric figure of merits (ZT) in the temperature range of 300 K to 900 K of the doped Mg2Si compounds were calculated from the measured temperature dependent electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (κ). A maximum ZT of 0.964 was found for Sb0.5%Zn0.5% doped Mg2Si at 880 K. This value is comparable to those of PbTe based thermoelectric materials.

Analysis of the Mo speciation in the JEB tailings management facility at McClean Lake, Saskatchewan.

The JEB Tailings Management Facility (TMF) is central to reducing the environmental impact of the uranium ore processing operation located at the McClean Lake facility and operated by AREVA Resources Canada (AREVA). The geochemical controls of this facility are largely designed around the idea that elements of concern, such as Mo, will be controlled in the very long term through equilibrium with supporting minerals. However, these systems are far from equilibrium when the tailings are first placed in the TMF, and it can take years, decades, or centuries to reach equilibrium. Therefore, it is necessary to understand how these reactions evolve toward an equilibrium state to understand the very long-term behavior of the TMF and to ensure that the elements of concern will be adequately contained. To this end, the Mo speciation in a series of samples taken from the JEB TMF during the 2008 sampling campaign has been analyzed. This analysis was performed using powder X-ray diffraction (XRD), X-ray fluorescence mapping (μ-XRF), and X-ray absorption near-edge spectroscopy (XANES). These results show that only XANES was effective in speciating Mo in the tailings samples, because it was both element-specific and sensitive enough to detect the low concentrations of Mo present. These results show that the predominant Mo-bearing phases present in the TMF are powellite, ferrimolybdite, and molybdate adsorbed on ferrihydrite.

Characterizing Zinc Speciation in Soils from a Smelter-Affected Boreal Forest Ecosystem.

HudBay Minerals, Inc., has mined and/or processed Zn and Cu ore in Flin Flon, MB, Canada, since the 1930s. The boreal forest ecosystem and soil surrounding these facilities have been severely impacted by mixed metal contamination and HSO deposition. Zinc is one of the most prevalent smelter-derived contaminants and has been identified as a key factor that may be limiting revegetation. Metal toxicity is related to both total concentrations and speciation; therefore, X-ray absorption spectroscopy and X-ray fluorescence mapping were used to characterize Zn speciation in soils throughout the most heavily contaminated areas of the landscape. Zinc speciation was linked to two distinct soil types. Group I soils consist of exposed soils in weathered positions of bedrock outcrops with Zn present primarily as franklinite, a (ZnFeO) spinel mineral. Group II soils are stabilized by an invasive metal-tolerant grass species, with Zn found as a mixture of octahedral (Fe oxides) and tetrahedral Mn oxides) adsorption complexes with a franklinite component. Soil erosion influences Zn speciation through the redistribution of Zn and soil particulates from Group I landscape positions to Group II soils. Despite Group II soils having the highest concentrations of CaCl-extractable Zn, they support metal-tolerant plant growth. The metal-tolerant plants are probably preferentially colonizing these areas due to better soil and nutrient conditions as a result of soil deposition from upslope Group I areas. Zinc concentration and speciation appears to not influence the colonization by metal-tolerant grasses, but the overall soil properties and erosion effects prevent the revegetation by native boreal forest species.

Pressure-induced phase transition and electrical properties of thermoelectric Al-doped Mg2Si

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.

Typical values of Rietveld instrument profile coefficients

GSAS instrument parameters are tabulated for a variety of laboratory and synchrotron diffractometers to give users an idea of the typical ranges of profile parameters when they generate their own instrument parameter files. For modern high-resolution laboratory diffractometers, the parameters fall in the ranges 0<U<3, V=0, 0<W<4, 1<X<3, 0<Y<3, 1<asym<3, and 0<S/L<0.03. For synchrotron diffractometers, the parameters fall in the ranges 0<U<1.2, −1<V<0, 0<W<1, 0<X<1, 0<Y<1, 0<asym<0.5, 0<S/L<0.001, and 0<H/L<0.007. FULLPROF equivalents are also reported. The factors which are convoluted together to generate the instrument profile are described.

The crystal structure of trandolapril, C24H34N2O5: an example of the utility of raw data deposition in the powder diffraction file

The crystal structure of trandolapril has been solved by parallel tempering using the FOX software package with laboratory powder diffraction data submitted to and published in the Powder Diffraction File. Rietveld refinement was performed with the software package GSAS yielding orthorhombic lattice parameters of a = 19.7685(4), b = 15.0697(4), and c = 7.6704(2) A (C 24 H 34 N 2 O 5 , Z = 4, space group P 2 1 2 1 2 1 ). The Rietveld refinement results were compared with density functional theory (DFT) calculations performed with CRYSTAL14. While the structures are similar, discrepancies are observed in the configuration of the octahydroindole ring between the Rietveld and DFT structures, suggesting the refined and calculated molecules are diastereomers.

Welcoming Gallium- and Indium-fumarate MOFs to the Family: Synthesis, Comprehensive Characterization, Observation of Porous Hydrophobicity, and CO2 Dynamics

The properties and applications of metal-organic frameworks (MOFs) are strongly dependent on the nature of the metals and linkers, along with the specific conditions employed during synthesis. Al-fumarate, trademarked as Basolite A520, is a porous MOF that incorporates aluminum centers along with fumarate linkers and is a promising material for applications involving adsorption of gases such as CO2. In this work, the solvothermal synthesis and detailed characterization of the gallium- and indium-fumarate MOFs (Ga-fumarate, In-fumarate) are described. Using a combination of powder X-ray diffraction, Rietveld refinements, solid-state NMR spectroscopy, IR spectroscopy, and thermogravimetric analysis, the topologies of Ga-fumarate and In-fumarate are revealed to be analogous to Al-fumarate. Ultra-wideline 69Ga, 71Ga, and 115In NMR experiments at 21.1 T strongly support our refined structure. Adsorption isotherms show that the Al-, Ga-, and In-fumarate MOFs all exhibit an affinity for CO2, with Al-fumarate being the superior adsorbent at 1 bar and 273 K. Static direct excitation and cross-polarized 13C NMR experiments permit investigation of CO2 adsorption locations, binding strengths, motional rates, and motional angles that are critical to increasing adsorption capacity and selectivity in these materials. Conducting the synthesis of the indium-based framework in methanol demonstrates a simple route to introduce porous hydrophobicity into a MIL-53-type framework by incorporation of metal-bridging -OCH3 groups in the MOF pores.

Powder diffraction data for ferrous gluconate

Synchrotron powder diffraction data have been obtained and indexed for ferrous gluconate, a common supplement used for the treatment and prevention of iron-deficiency anemia. Ferrous gluconate (Fe(C 6 H 11 O 7 ) 2 · x H 2 O, Z = 4) crystallizes in a monoclinic cell (space group I 2, #5) with lattice parameters a = 19.953 16(9) A, b = 5.513 92(3) A, c = 18.470 58(9) A, and β = 111.3826(3)°. The pattern shows no evidence of impurity reflections.

Effects of Dolomitic Limestone Application on Zinc Speciation in Boreal Forest Smelter-Contaminated Soils

Anthropogenic activities at the HudBay Minerals, Inc., Flin Flon (Manitoba, Canada) mining and processing facility have severely affected the surrounding boreal forest ecosystem. Soil contamination occurred via a combination of metal and sulfuric acid deposition and has resulted in forest dieback and ineffective natural recovery. A community-led effort to revegetate areas of the landscape through the application of a dolomitic limestone has been met with varied success. Zinc (Zn) speciation has shown to be closely linked to the presence or absence of an invasive metal-tolerant grass species, with soils being broadly classed into two revegetation response groups. Group I, characterized by the absence of metal-tolerant grasses, and group II, characterized by the presence of metal-tolerant grasses. The systematic approach used to lime areas of the landscape produced a liming chronosequence for each group. This study used a combination of X-ray absorption spectroscopy, X-ray fluorescence mapping, and X-ray diffraction techniques to determine the effect of liming on Zn speciation in these chronosequences. Liming group I soils resulted in the formation of a neo-phase Zn-Al-hydroxy interlayer coprecipitate and subsequent rapid boreal forest revegetation. The effect of liming on Zn speciation on the group II soils resulted in a gradual transition of increasingly stable adsorption species, culminating with a stable Zn-Al-layered double hydroxide precipitate. Boreal forest vegetation has failed to recolonize group II soils during the study. However, the formation of the layered double hydroxide species resulted in a significant reduction in CaCl-extractable Zn. Further research is required to determine how to promote the revegetation of these soils.

Crystal structure of solifenacin hydrogen succinate, C[subscript 23]H[subscript 27]N[subscript 2]O[subscript 2](HC[subscript 4]H[subscript 4]O[subscript 4])

The crystal structure of solifenacin hydrogen succinate [C 23 H 27 N 2 O 2 (HC 4 H 4 O 4 )] has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Solifenacin hydrogen succinate crystallizes in space group P 2 1 (#4) with a = 6.477 03(2), b = 7.830 95(2), c = 23.848 72(7) A, β = 90.2373(3)°, V = 1209.63(1) A 3 , and Z = 2. The hydrogen succinate anions form a chain linked by strong hydrogen bonds parallel to the a -axis. Discrete N–H···O hydrogen bonds lie on the sides of this chain, resulting in a layer parallel to the ab -plane rich in hydrogen bonds. Halfway between these layers the molecules meet in a herringbone packing of aromatic rings. The powder pattern has been submitted to ICDD for inclusion in future releases of the Powder Diffraction File™.The crystal structure of solifenacin hydrogen succinate [C 23 H 27 N 2 O 2 (HC 4 H 4 O 4 )] has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Solifenacin hydrogen succinate crystallizes in space group P 2 1 (#4) with a = 6.477 03(2), b = 7.830 95(2), c = 23.848 72(7) A, β = 90.2373(3)°, V = 1209.63(1) A 3 , and Z = 2. The hydrogen succinate anions form a chain linked by strong hydrogen bonds parallel to the a -axis. Discrete N–H···O hydrogen bonds lie on the sides of this chain, resulting in a layer parallel to the ab -plane rich in hydrogen bonds. Halfway between these layers the molecules meet in a herringbone packing of aromatic rings. The powder pattern has been submitted to ICDD for inclusion in future releases of the Powder Diffraction File™.