Synthesis and Structural Analysis of Copper-Zirconium Oxide

A new copper–zirconium oxide was synthesized at ambient pressure in air during a thermal treatment. Its crystal structure was analyzed using X-ray Powder Diffraction, and the atomic ratio between copper and zirconium was found performing a Rietveld analysis. An accurate analysis, also comparing this new compound with others present in the literature and which present a similar structure, enables us to characterize the new mixed oxide well. Scanning electron microscopy and thermogravimetric analyses were also performed in order to completely characterize this new material, which is interesting both from an academic point of view for its crystal structure and from an industrial one due to the formation of copper–zirconium-based shape memory alloys during thermal treatment

Synthesis and Structural Analysis of Copper-Zirconium Oxide

A new copper–zirconium oxide was synthesized at ambient pressure in air during a thermal treatment. Its crystal structure was analyzed using X-ray Powder Diffraction, and the atomic ratio between copper and zirconium was found performing a Rietveld analysis. An accurate analysis, also comparing this new compound with others present in the literature and which present a similar structure, enables us to characterize the new mixed oxide well. Scanning electron microscopy and thermogravimetric analyses were also performed in order to completely characterize this new material, which is interesting both from an academic point of view for its crystal structure and from an industrial one due to the formation of copper–zirconium-based shape memory alloys during thermal treatment

Effect of outgassing temperature on the performance of porous materials

[EN] This work illustrates the consequences of an inadequate outgassing temperature of porous materials of different nature (zeolites and activated carbons) on their performance on gas storage and wastewater remediation. Outgassing at low temperature in thermally stable materials leads to an incomplete cleaning of the porous surface; as a result, the gas storage ability based on adsorption isotherms is underestimated. In contrast, outgassing at elevated temperature in temperature-sensitive materials provokes irreversible changes in their composition and structure, which also affects strongly their stability and performance. Two examples illustrating wrong interpretation data on CO2 capture on zeolites and wastewater treatment using activated carbons are addressed. The results show how the performance of a given material can be significantly modified or misunderstood after the outgassing pretreatment.This work was supported by the Spanish MICINN (CTM2008-01956). COA thanks her Ramon y Cajal Research Contract. LFV thanks her JAE predoctoral fellowship.Peer reviewe

Redetermination of Mg2B25 based on single-crystal X-ray data

The crystal structure of Mg2B25, dimagnesium pentaeicosaboride, was reexamined from single-crystal X-ray diffraction data. The structural model previously reported on the basis of powder X-ray diffraction data [Giunchi et al. (2006). Solid State Sci. 8, 1202–1208] has been confirmed, although a much higher precision refinement was achieved, leading to much smaller standard uncertainties on bond lengths and refined occupancy factors. Moreover, all atoms were refined with anisotropic displacement parameters. Mg2B25 crystallizes in the β-boron structure type and is isostructural with other rhombohedral compounds of the boron-rich metal boride family. Magnesium atoms are found in interstitial sites on special positions (two with site symmetry .m, one with .2 and one with 3m), all with partial occupancies

Crystal and molecular structures of the organometallic species [Rh2(bim)2(cod)2]Cl2•2H2O [bim = bis-(1-imidazolyl)methane; cod = 1,5-cyclooctadiene [Rh2(bim)2(cod)2]Cl2•2H2O [bim = bis-(1-imidazolyl)methane; cod = 1,5-cyclooctadiene

The synthesis and X-ray powder diffraction data for the organometallic [Rh2(bim)2(cod)2]Cl2·2H2O species are reported. Its crystal and molecular structures were determined by simulated annealing and full-profile Rietveld refinement methods. [Rh2(bim)2(cod)2]Cl2·2H2O was found to crystallize in the orthorhombic Cmca space group. The lattice parameters were determined to be a =21.3574(6), b=10.7764(3), c=14.2795(4) Å, V=3286.5(2) Å3, for Z=4. The crystal structure was found to contain dimeric [Rh2(bim)2(cod)2]2+ cations, in which the bim ligands bridge Rh(cod) fragments with an intermetallic separation of ca. 8.90 Å. The crystal structure is completed by chloride ions and hydrogen-bonded water molecules, situated in the small cavities of the large cation substructure. The conformation of the bim ligand, lying on a crystallographic mirror plane, is rigorously Cs

Effect of outgassing temperature on the performance of porous materials

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Structures from Powders: Polynuclear Hg(II) Complexes Containing the Flexible Bisimidazolylmethane Ligand

Several polynuclear Hg(II) complexes containing the flexible ditopic bisimidazolylmethane ligand (C7H8N4, bim) have been prepared by reaction of equimolar quantities of mercury salts (acetate, cyanide, thiocyanate, chloride, and iodide) in EtOH or acetonitrile solution. Their crystal and molecular structures were retrieved from laboratory powder diffraction data, and their thermal properties were fully characterized, including the determination of the thermal expansion coefficients and the related strain tensor using thermodiffractometric methods. [Hg(bim)(CH3COO)2]2 consists of cyclic dimers with chelating acetates, while the [Hg(bim)X2]n species (X = Cl, CN, SCN, and I) are one-dimensional polymers, with dangling X groups. A further complex of nominal Hg2(bim)Cl2 formulation was also prepared, but the complexity and nonideality of its powder diffraction traces prevented the determination of its main structural features

A Re-Entrant MgB_2 Cavity for Dynamic Casimir Experiment

The use of radio frequencies (RF) superconducting re-entrant cavities has been suggested in the framework of some research to detect photon generation from the vacuum, due to the dynamical Casimir effect. A thin semiconducting slab, put inside the cavity, will be excited by a train of laser pulses of a frequency twice the resonant frequency of the cavity, so that a periodic modulation of the dielectric constant of the slab will be realized. In order to produce a RF cavity that can safely work at temperatures larger than 4 K, we have designed and constructed a MgB2 re-entrant cavity having a resonant frequency in the range of 2-3 GHz. The cavity is made by a cylindrical cup of about 40 mm of internal diameter and 40 mm of height and on its base is standing a cylindrical coaxial nose on which the semiconductor slab will be deposited. The details of the construction of the MgB2 cavity will be presented as well as the measurements of its quality factor, as a function of the temperature