The structure of germanium niobium oxide, an inherently non-stoichiometric ‘block’ structure

1975 ◽  
Vol 346 (1645) ◽  
pp. 139-156 ◽  
Keyword(s):  
Niobium Oxide ◽  
Profile Analysis ◽  
Extended Defects ◽  
X Ray Diffraction ◽  
Anion Sublattice ◽  
Lattice Imaging ◽  
High Concentration ◽  
Metal Atoms ◽  
Distorted Octahedral ◽  
Cation Sites

Germanium niobium oxide, reported as Ge02. 9Nb20 5, is inherently nonstoichiometric since it appears to be isostructural with P 20 5. 9Nb20 5. To fit this structure, there must be vacant oxygen sites or some sites accommodating ‘interstitial’ metal atoms, in relatively high concentration, and the mode of incorporating a stoichiometric excess of cations should cast some light on other niobium oxide type structures which have a reported range of composition. The structure of germanium niobium oxide has been determined by a combination of three methods: lattice imaging electron microscopy, to establish that the non-stoichiometry was not attributable to extended defects; neutron diffraction, using the powder method and profile analysis, for particular evidence about the anion sublattice and distribution of cations; and X-ray diffraction, for an ab initio refined structure. It has been proved that the anion lattice is essentially complete, and that the cation excess is accommodated by inserting cations into a set of sites, with distorted octahedral coordination, in the square tunnels formed by the junctions between columnar elements of structure. Occupation of these octahedral sites precludes the occupation of adjacent tetrahedral cation sites, proper to the type structure. In consequence, there are constraints on the way that the two kinds of tunnel site can be occupied to produce the observed stoichiometric excess of cations. The resulting model can be generalized to interpret the metal-excess composition ranges found for other niobium oxide structures.

Dislocations and related defects in niobium oxide structures

1977 ◽  
Vol 352 (1670) ◽  
pp. 303-323 ◽  
Keyword(s):  
Chemical Composition ◽  
Niobium Oxide ◽  
Shear Plane ◽  
Extended Defects ◽  
Lattice Imaging ◽  
Lattice Image ◽  
Lattice Images ◽  
Crystallographic Shear ◽  
Third Dimension ◽  
Block Structures

Lattice images of the niobium oxides, structures based on the linkage of octahedral groups in continuous networks, occasionally contain features recognizable as dislocations. Since lattice imaging enables the micro-structure to be resolved in great detail, at the level of local structural organization, it is possible to determine the configuration, and also to infer the chemical composition, of dislocated areas. By treating the niobium oxide ‘block’ structures as superstructures of the ReO 3 (DO 9 ) type, the topology of dislocations can be expressed by relations between the insertion (or deletion) of one or more half-planes of cations, or of oxygen atoms only, changes in the number of crystallographic shear plane interfaces between blocks or columns, changes in (idealized) dimensions and any requisite distortion in the third dimension. Mapping the structure around a dislocation, from the lattice image, is directly equivalent to plotting the Burgers’ circuit. In this way, the precise nature of a dislocating perturbation and its implications for the local chemical composition of the crystal can be directly identified. The method is exemplified by analysis of dislocations and of related extended defects of several types, associated with twinning phenomena, semicoherent intergrowth between different ReO 3 -type superstructures and arrays building up a low angle boundary. The essential features of the analysis are not restricted to structures of the niobium oxide type, but can be extended to other types of polyhedron networks.

Crystal structure of a [(dihydrogen pyrophosphato-K2O,O') bis(1,10-phenanthroline-N,N')nickel(II)]2.5-hydrate [Ni(H2P2O7)(C12H8N2)2] · 2.5H2O

2016 ◽  
Vol 57 (8) ◽  
pp. 1769
Author(s):  
S. Cherni ◽  
F. Zid ◽  
A. Driss
Keyword(s):  
Three Dimensional ◽  
Water Molecules ◽  
Stacking Interactions ◽  
Coordination Geometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Triclinic System ◽  
Metal Atoms ◽  
Distorted Octahedral

Coordination nickel pyrophosphate [Ni(H2P2O7)(C12H8N2)2]×2.5H2O (I) is hydrothermally synthesized and characterized by single crystal X-ray diffraction. The title compound crystallizes in the triclinic system, space group P-1, with cell parameters M = 640.07, a = 10.285(2) Å, b = 10.510(3) Å, c = 12.775(3) Å, α = 88.06(2)°, β = 77.87(2)°, γ = 89.26(2)°, V = 1349.2(5) Å3, Z = 2, R1[I > 2σ(I)] = 0.0438, wR2[I > 2σ(I)] = 0.1244. This compound displays a new structure of ladder-like 2D layers parallel to (010) consisting of [Ni(H2P2O7)(phen)2] entities with the distorted octahedral NiN4O2 coordination geometry arising from two chelating 1,10-phe­nanthroline ligands and diphosphate [H2P2O7] ligand bridged through π⋯π stacking interactions between the neighboring 1,10-phen ligands with interplanar distances of 4.425 Å and 4.525 Å. In the compound, the phen ligands bind in a bidentate fashion to the metal atoms and the ladder-like structure of the compound extends into a three-dimensional supramolecular array via hydrogen bonds (O4—H17…O5) between diphosphate groups, which delimits b axis tunnels where water molecules are located.

Cytomembrane Preservation in Tissue Dehydrated Only With Glutaraldehyde and Epon 812 Resin

1973 ◽  
Vol 31 ◽  
pp. 320-321
Author(s):  
Daniel C. Pease
Keyword(s):  
Diffraction Pattern ◽  
X Ray Diffraction ◽  
High Concentration ◽  
Unpublished Study ◽  
X Ray ◽  
Sectioned Material

A previous study demonstrated that tissue could be successfully infiltrated with 50% glutaraldehyde, and then subsequently polymerized with urea to create an embedment which retained cytomembrane lipids in sectioned material. As a result, the 180-190 Å periodicity characteristic of fresh, mammalian myelin was preserved in sections, as was a brilliant birefringence, and the capacity to bind OsO4 vapor in the hydrophobic bilayers. An associated (unpublished) study, carried out in co-operation with Drs. C.K. Akers and D.F. Parsons, demonstrated that the high concentration of glutaraldehyde (and urea) did not significantly alter the X-ray diffraction pattern of aldehyde-fixed, myelin. Thus, by itself, 50% glutaraldehyde has little effect upon cytomembrane systems and can be used with confidence for the first stages of dehydration.

scholarly journals Ti/RuO2-IrO2-SnO2 Anode for Electrochemical Degradation of Pollutants in Pharmaceutical Wastewater: Optimization and Degradation Performances

2020 ◽  
Vol 13 (1) ◽  
pp. 126
Author(s):  
Guozhen Zhang ◽  
Xingxing Huang ◽  
Jinye Ma ◽  
Fuping Wu ◽  
Tianhong Zhou
Keyword(s):  
Removal Rate ◽  
Inorganic Compounds ◽  
Oxide Coating ◽  
X Ray Diffraction ◽  
Pharmaceutical Wastewater ◽  
High Concentration ◽  
Dimensionally Stable Anodes ◽  
X Ray ◽  
Initial Ph ◽  
Cod Removal Rate

Electrochemical oxidation technology is an effective technique to treat high-concentration wastewater, which can directly oxidize refractory pollutants into simple inorganic compounds such as H2O and CO2. In this work, two-dimensionally stable anodes, Ti/RuO2-IrO2-SnO2, have been developed in order to degrade organic pollutants from pharmaceutical wastewater. Characterization by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) showed that the oxide coating was successfully fabricated on the Ti plate surface. Electrocatalytic oxidation conditions of high concentration pharmaceutical wastewater was discussed and optimized, and the best results showed that the COD removal rate was 95.92% with the energy consumption was 58.09 kW·h/kgCOD under the electrode distance of 3 cm, current density of 8 mA/cm2, initial pH of 2, and air flow of 18 L/min.

scholarly journals Leaching Titaniferous Magnetite Concentrate by Alkaline Aqueous Solution

2021 ◽  
Author(s):  
Ke Guo ◽  
Shaoyan Wang ◽  
Renfeng Song ◽  
Zhiqiang Zhang
Keyword(s):  
Aqueous Solution ◽  
Alkali Concentration ◽  
Water Usage ◽  
X Ray Diffraction ◽  
High Concentration ◽  
X Ray ◽  
Iron Concentrate ◽  
Titaniferous Magnetite ◽  
Magnetite Concentrate ◽  
Kinetics Of

AbstractLeaching titaniferous magnetite concentrate with alkali solution of high concentration under high temperature and high pressure was utilized to improve the grade of iron in iron concentrate and the grade of TiO2 in titanium tailings. The titaniferous magnetite concentrate in use contained 12.67% TiO2 and 54.01% Fe. The thermodynamics of the possible reactions and the kinetics of leaching process were analyzed. It was found that decomposing FeTiO3 with NaOH aqueous solution could be carried out spontaneously and the reaction rate was mainly controlled by internal diffusion. The effects of water usage, alkali concentration, reaction time, and temperature on the leaching procedure were inspected, and the products were characterized by X-ray diffraction, scanning electron microscope, and energy dispersive spectroscopy, respectively. After NaOH leaching and magnetic separation, the concentrate, with Fe purity of 65.98% and Fe recovery of 82.46%, and the tailings, with TiO2 purity of 32.09% and TiO2 recovery of 80.79%, were obtained, respectively.

Polyhedral characteristics of the cosalite-type crystal structures

2019 ◽  
Vol 57 (5) ◽  
pp. 647-662
Author(s):  
Sabina Kovač ◽  
Predrag Dabić ◽  
Aleksandar Kremenović ◽  
Aleksandar Pačevski ◽  
Ljiiljana Karanović ◽  
...  
Keyword(s):  
Crystal Data ◽  
Chemical Formula ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Area Detector ◽  
Octahedral Sites ◽  
Distorted Octahedral ◽  
Cation Substitutions ◽  
Type Crystal

Abstract The crystal structure of cosalite from the Trepča orefield was refined in the orthorhombic space group Pnma [a = 23.7878 (9), b = 4.0566 (3), c = 19.1026 (8) Å, V = 1843.35 (17) Å3, Z = 2] from single-crystal data (MoKα X-ray diffraction, CCD area detector) to the conventional R1 factor 0.031 for 1516 unique reflections with I > 2σ(I). The chemical formula (Cu0.15Ag0.24)+(Fe0.19Pb7.20)2+(Bi7.06Sb1.06)3+S20, calculated on the basis of 20 S atoms per formula unit, was determined by WDX. The unit cell contains 18 + 2 symmetrically nonequivalent atomic sites: 10 occupied by S; two by pure Pb (Pb3 and Pb4); one by pure Bi (Bi1); two by a combination of Bi and small amounts of Sb (Bi2/Sb2, Bi4/Sb3); two by Pb and Bi, and in one of these also by a small amount of Ag [Me1 = Pb2 >> Bi5 > Ag1, Me3 = Pb1 >> Bi3]; and finally one site, Me2 (Bi6 >> □), is partly occupied by Bi and partly split into an additional two adjacent trigonal planar “interstitial positions”, Cu1 and Cu2, where small amounts of Cu, Ag, and Fe can be situated. All atoms are at 4c special positions at y = 0.25 or 0.75. The structure consists of slightly to moderately distorted MeS6 octahedra sharing edges, bicapped trigonal PbS8 coordination prisms, and fairly distorted Cu1S6 and Cu2S4 polyhedra. The effects of the cation substitutions, bond valence sums, and the polyhedral characteristics are compared with other published cosalite-type structures. Among known cosalite-type structures, the largest volume contraction is shown by sample 4 (Altenberg) and involves the replacement of large cations (Bi3+ and Pb2+) by the smaller Sb3+, as well as Cu+ and Ag+. These replacements are reflected in the variations of individual Me–S bond distances, which are accompanied by variations in average Me–S distances. The degree of polyhedral distortion, Δ, progressively increases for the four Bi-hosting sites of nine cosalite-type structures: Me2 < Bi2 < Bi1 < Bi4. The Bi4 and Me3 are the most and the Me1 and Me2 are the least distorted octahedral sites of the nine cosalite-type structures.

X-Ray Diffraction Profile Analysis for Characterizing Isothermal Aging Behavior of M250 Grade Maraging Steel

2008 ◽  
Vol 39 (8) ◽  
pp. 1978-1984 ◽  
Author(s):  
S. Mahadevan ◽  
T. Jayakumar ◽  
B.P.C. Rao ◽  
Anish Kumar ◽  
K.V. Rajkumar ◽  
...  
Keyword(s):  
Maraging Steel ◽  
Isothermal Aging ◽  
Profile Analysis ◽  
X Ray Diffraction ◽  
Aging Behavior ◽  
Diffraction Profile ◽  
X Ray

Magnetism and structure of a novel trinuclear cluster compound of divalent copper

1969 ◽  
Vol 22 (12) ◽  
pp. 2527 ◽  
Author(s):  
R Beckett ◽  
R Colton ◽  
BF Hoskins ◽  
RL Martin ◽  
DG Vince
Keyword(s):  
Structural Data ◽  
Hydroxyl Group ◽  
Cluster Compound ◽  
X Ray Diffraction ◽  
Trinuclear Cluster ◽  
Metal Atoms ◽  
Doublet Ground State ◽  
Molecular Orbital Analysis ◽  
Orbital Analysis ◽  
Unusual Type

The magnetic properties of a series of salts of the type [Cu3L3OH]2+ (where HL is pyridine-2-aldehyde oxime and L is the deprotonated ligand) have been examined. All of the compounds showed a magnetic moment of 1.00 B.M. per copper atom over a wide temperature range which suggests that the cation contains a trinuclear cluster of interacting copper atoms. The crystal structure of Cu3L3OH(SO4),xH2O has been determined by single- crystal X-ray diffraction techniques and confirms that the complex does indeed contain an unusual type of trinuclear cluster of metal atoms. The three copper atoms form an equilateral triangle and the sulphato group exhibits a highly novel ?tripod? bridging function to the Cu3 triangle. On the other side of the triangle, the hydroxyl group also bridges to all the metal atoms. A qualitative molecular orbital analysis not only suggests that the hydroxyl group is involved in four-centre bonding with the Cu3 triads, but also highlights its role in reducing the spin of the trimer so that only a doublet ground state is populated between 80-300�K. However, the alternative super-exchange mechanism cannot be ruled out by the magnetic and structural data.

Microstructure Characterization of Metal Mixed Oxides

MRS Advances ◽  
2017 ◽  
Vol 2 (64) ◽  
pp. 4025-4030 ◽  
Author(s):  
T. Kryshtab ◽  
H. A. Calderon ◽  
A. Kryvko
Keyword(s):  
Mixed Oxides ◽  
Profile Analysis ◽  
Atomic Resolution ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Reconstruction Procedure ◽  
Transmission Electron ◽  
Xrd Patterns ◽  
Co Precipitation

ABSTRACTThe microstructure of Ni-Mg-Al mixed oxides obtained by thermal decomposition of hydrotalcite-like compounds synthesized by a co-precipitation method has been studied by using X-ray diffraction (XRD) and atomic resolution transmission electron microscopy (TEM). XRD patterns revealed the formation of NixMg1-xO (x=0÷1), α-Al2O3 and traces of MgAl2O4 and NiAl2O4 phases. The peaks profile analysis indicated a small grain size, microdeformations and partial overlapping of peaks due to phases with different, but similar interplanar spacings. The microdeformations point out the presence of dislocations and the peaks shift associated with the presence of excess vacancies. The use of atomic resolution TEM made it possible to identify the phases, directly observe dislocations and demonstrate the vacancies excess. Atomic resolution TEM is achieved by applying an Exit Wave Reconstruction procedure with 40 low dose images taken at different defocus. The current results suggest that vacancies of metals are predominant in MgO (NiO) crystals and that vacancies of Oxygen are predominant in Al2O3 crystals.

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