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ACS Omega May 2021This paper reported a dry synthesis and characterization of cerium tetrafluoride (CeF) and cerium trifluoride (CeF) nanoscale polycrystals (NPs). The CeF NPs were...
This paper reported a dry synthesis and characterization of cerium tetrafluoride (CeF) and cerium trifluoride (CeF) nanoscale polycrystals (NPs). The CeF NPs were spherical or flaky and approximately 10 ± 2 nm in diameter. The CeF NPs were rod-shaped nanorods with a length of about 150 ± 5 nm and a diameter of about 20 ± 2 nm. The first step was to synthesize the intermediate product-(NH)CeF by mixing CeO and NHHF at a molar ratio of 1:6 at 390 K. The structural characterization was analyzed by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Then, (NH)CeF was heated in an argon gas flow to synthesize the CeF and CeF NPs. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The properties of CeF and CeF NPs were further evaluated by transmission electron microscopy (TEM), selected area electron diffraction pattern (SAED), and high-resolution transmission electron microscopy (HRTEM). The findings provided an alternative strategy for the synthesis of nanometer fluorides, which could be a reference for high-performance research on other nanometer fluorides.
PubMed: 34056290
DOI: 10.1021/acsomega.1c00332 -
Proceedings of the National Academy of... Feb 2023Electronic structure calculations indicate that the SrFeSbO double perovskite has a flat-band set just above the Fermi level that includes contributions from ordinary...
Electronic structure calculations indicate that the SrFeSbO double perovskite has a flat-band set just above the Fermi level that includes contributions from ordinary subbands with weak kinetic electron hopping plus a flat subband that can be attributed to the lattice geometry and orbital interference. To place the Fermi energy in that flat band, electron-doped samples with formulas SrLaFeSbO (0 ≤ ≤ 0.3) were synthesized, and their magnetism and ambient temperature crystal structures were determined by high-resolution synchrotron X-ray powder diffraction. All materials appear to display an antiferromagnetic-like maximum in the magnetic susceptibility, but the dominant spin coupling evolves from antiferromagnetic to ferromagnetic on electron doping. Which of the three subbands or combinations is responsible for the behavior has not been determined.
PubMed: 36787357
DOI: 10.1073/pnas.2218997120 -
Molecules (Basel, Switzerland) Dec 2020Eltrombopag, of CHNO chemical formula, is a drug used against thrombocytopenia, marketed worldwide under different tradenames in the form of its bis-olamine salt. The...
Eltrombopag, of CHNO chemical formula, is a drug used against thrombocytopenia, marketed worldwide under different tradenames in the form of its bis-olamine salt. The free acid (CAS no. 496775-61-2) is an intermediate species used for the final drug isolation and is reported to crystallize in more than 20 distinct crystal forms, including a large number of hydrates and solvates. Their identification, and, ultimately, their quantification in industrial lots require the usage of accurately measured X-ray powder diffraction pattern, as well as the assessment of the metrical features (crystal symmetry and lattice parameters), nowadays accessible by powerful crystallographic software. Here, the complete indexing of 13 monophasic samples, prepared using literature or newly tailored crystallization methods, jointly to simultaneous thermogravimetric and calorimetric analyses and to variable temperature X-ray diffraction studies, provide a clear picture of the stability fields of the different crystal phases and their mutual interconversion processes, leading, in a few cases, to new and unexpected crystalline polymorphs or solvates of the pristine unsolvated Form I.
Topics: Benzoates; Crystallization; Crystallography, X-Ray; Humans; Hydrazines; Hydrogen Bonding; Molecular Structure; Powder Diffraction; Pyrazoles; Solvents; Thermogravimetry; Thrombocytopenia; Water; X-Ray Diffraction
PubMed: 33375645
DOI: 10.3390/molecules26010065 -
Journal of Applied Crystallography Jun 2021A sapphire single-crystal gas-pressure cell without external support allowing unobstructed optical access by neutrons has been developed and optimized for elastic...
A sapphire single-crystal gas-pressure cell without external support allowing unobstructed optical access by neutrons has been developed and optimized for elastic neutron powder diffraction using hydrogen (deuterium) gas at the high-intensity two-axis diffractometer D20 at the Institut Laue-Langevin (Grenoble, France). Given a proper orientation of the single-crystal sample holder with respect to the detector, parasitic reflections from the sample holder can be avoided and the background can be kept low. Hydrogen (deuterium) gas pressures of up to 16.0 MPa at 298 K and 8.0 MPa at 655 K were tested successfully for a wall thickness of 3 mm. Heating was achieved by a two-sided laser heating system. The typical time resolution of investigations of the reaction pathway of hydrogen (deuterium) uptake or release is on the order of 1 min. Detailed descriptions of all parts of the sapphire single-crystal gas-pressure cell are given, including materials information, technical drawings and instructions for use.
PubMed: 34188615
DOI: 10.1107/S1600576721002685 -
Journal of Research of the National... 2016X-ray powder diffraction (XRD) has been used for several decades to identify and measure the mass fractions of various crystalline phases in portland cement. More...
X-ray powder diffraction (XRD) has been used for several decades to identify and measure the mass fractions of various crystalline phases in portland cement. More recently, a combination of scanning electron microscopy with X-ray microanalysis (SEM/XMA) and image processing has been shown to enable the quantitative characterization of microstructural features in these materials. Each technique can furnish some information that is not accessible from the other. For example, SEM/XMA can identify the microstructural location and morphology of calcium sulfate minerals, while only XRD can determine the relative abundance of the different forms of calcium sulfate, such as gypsum (CaSO · 2HO), bassanite , and anhydrite (CaSO). This document describes how XRD and SEM/XMA can be used together to establish and validate the portland cement phase composition and microstructure. Particular emphasis is laid on step-by-step procedures and best practices for XRD specimen preparation, data collection, and intepretation. Similar detail has been given recently for SEM/XMA [Stutzman et al., NIST Tech Note 1877, U.S. Department of Commerce, April 2015]. The methods are demonstrated for three portland cement powders, through which apparent discrepancies between the results of the two methods are identified and procedures are described for resolving the discrepancies and quantifying uncertainty.
PubMed: 34434615
DOI: 10.6028/jres.121.004 -
Physical Chemistry Chemical Physics :... Apr 2018Ammonia absorption has been investigated in metal-organic frameworks (UiO-67, HKUST-1 and CPO-27-Co) using custom-built apparatus that allows simultaneous neutron powder...
Ammonia absorption has been investigated in metal-organic frameworks (UiO-67, HKUST-1 and CPO-27-Co) using custom-built apparatus that allows simultaneous neutron powder diffraction (NPD), microwave dielectric characterisation and out-gas mass spectroscopy of solid-state materials during ammonia adsorption. Deuterated ammonia was flowed through the sample and absorption monitored using mass flow meters and mass spectroscopy. Argon gas was then flowed through the ammoniated sample to cause ammonia desorption. Changes in structure found from NPD measurements were compared to changes in dielectric characteristics to differentiate physisorbed and metal-coordinated ammonia, as well as determine decomposition of sample materials. The results of these studies allow the identification of materials with useful ammonia storage properties and provides a new metric for the measurement of gas absorption within mesoporous solids.
PubMed: 29617020
DOI: 10.1039/c8cp00259b -
Nanomaterials (Basel, Switzerland) Jul 2023This article focuses on the NaO-GaO-TiO system, which is barely explored in the study of transparent conductive oxides (TCOs). NaGaTiO (n = 5, 6, and 7 and x ≈...
This article focuses on the NaO-GaO-TiO system, which is barely explored in the study of transparent conductive oxides (TCOs). NaGaTiO (n = 5, 6, and 7 and x ≈ 0.7-0.8) materials were characterized using neutron powder diffraction and aberration-corrected scanning transmission electron microscopy. Activation energy, as a function of different structures depending on tunnel size, shows a significant improvement in Na ion conduction from hexagonal to octagonal tunnels. New insights into the relationship between the crystal structure and the transport properties of TCOs, which are crucial for the design and development of new optoelectronic devices, are provided.
PubMed: 37513065
DOI: 10.3390/nano13142054 -
Polymers Jan 2023Nanocomposites of methacrylate-based polyhedral oligomeric silsesquioxane (POSS) are used as resins in dentistry to fill dental cavities. In this article, molecular...
Nanocomposites of methacrylate-based polyhedral oligomeric silsesquioxane (POSS) are used as resins in dentistry to fill dental cavities. In this article, molecular dynamics simulations (MDS) are used to study and understand the interactions of monofunctional and multifunctional methacrylate groups on hybrid resins containing POSS additives for dental applications. These interactions are further related to the structural properties of the nanocomposites, which in turn affect their macro-properties that are important, especially when used for specific uses such as dental resins. For monofunctional methacrylate, nanocomposite of methacryl isobutyl POSS (MIPOSS) and for multifunctional methacrylate, methacryl POSS (MAPOSS) are used in this study. Molecular dynamic simulations (MDS) are performed on both MIPOSS and MAPOSS systems by varying the amount of POSS. On a weight percent basis, 1%, 3%, 5%, and 10% POSS are added to the resin. Density calculations, stress-strain, and powder diffraction simulations are used to evaluate the macro-properties of these nanocomposites and compare them with the experimental findings reported in the literature. The observations from the simulation results when compared to the experimental results show that MDS can be efficiently used to design, analyze, and simulate new nanocomposites of POSS.
PubMed: 36679311
DOI: 10.3390/polym15020432 -
IUCrJ May 2017Denisovite is a rare mineral occurring as aggregates of fibres typically 200-500 nm diameter. It was confirmed as a new mineral in 1984, but important facts about its...
The structure of denisovite, a fibrous nanocrystalline polytypic disordered 'very complex' silicate, studied by a synergistic multi-disciplinary approach employing methods of electron crystallography and X-ray powder diffraction.
Denisovite is a rare mineral occurring as aggregates of fibres typically 200-500 nm diameter. It was confirmed as a new mineral in 1984, but important facts about its chemical formula, lattice parameters, symmetry and structure have remained incompletely known since then. Recently obtained results from studies using microprobe analysis, X-ray powder diffraction (XRPD), electron crystallography, modelling and Rietveld refinement will be reported. The electron crystallography methods include transmission electron microscopy (TEM), selected-area electron diffraction (SAED), high-angle annular dark-field imaging (HAADF), high-resolution transmission electron microscopy (HRTEM), precession electron diffraction (PED) and electron diffraction tomography (EDT). A structural model of denisovite was developed from HAADF images and later completed on the basis of quasi-kinematic EDT data by structure solution using direct methods and least-squares refinement. The model was confirmed by Rietveld refinement. The lattice parameters are = 31.024 (1), = 19.554 (1) and = 7.1441 (5) Å, β = 95.99 (3)°, = 4310.1 (5) Å and space group 12/1. The structure consists of three topologically distinct dreier silicate chains, . two xonotlite-like dreier double chains, [SiO], and a tubular loop-branched dreier triple chain, [SiO]. The silicate chains occur between three walls of edge-sharing (Ca,Na) octahedra. The chains of silicate tetrahedra and the octahedra walls extend parallel to the axis and form a layer parallel to (100). Water molecules and K cations are located at the centre of the tubular silicate chain. The latter also occupy positions close to the centres of eight-membered rings in the silicate chains. The silicate chains are geometrically constrained by neighbouring octahedra walls and present an ambiguity with respect to their position along these walls, with displacements between neighbouring layers being either Δ = /4 or -/4. Such behaviour is typical for polytypic sequences and leads to disorder along [100]. In fact, the diffraction pattern does not show any sharp reflections with odd, but continuous diffuse streaks parallel to * instead. Only reflections with even are sharp. The diffuse scattering is caused by (100) nano-lamellae separated by stacking faults and twin boundaries. The structure can be described according to the order-disorder (OD) theory as a stacking of layers parallel to (100).
PubMed: 28512570
DOI: 10.1107/S2052252517002585 -
Acta Crystallographica. Section E,... Oct 2020The crystal structures of the isostructural compounds dipotassium rubidium citrate monohydrate, KRbCHO(HO), and potassium dirubidium citrate monohydrate, KRbCHO(HO),...
Structures of dipotassium rubidium citrate monohydrate, KRbCHO(HO), and potassium dirubidium citrate monohydrate, KRbCHO(HO), from laboratory X-ray powder diffraction data and DFT calculations.
The crystal structures of the isostructural compounds dipotassium rubidium citrate monohydrate, KRbCHO(HO), and potassium dirubidium citrate monohydrate, KRbCHO(HO), have been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The compounds are isostructural to KCHO(HO) and RbCHO(HO), but exhibit different degrees of ordering of the K and Rb cations over the three metal-ion sites. The K and Rb site occupancies correlate well to both the bond-valence sums and the DFT energies of ordered cation systems. The O and O coordination polyhedra share edges to form a three-dimensional framework. The water mol-ecule acts as a donor in two strong charge-assisted O-H⋯O hydrogen bonds to carboxyl-ate groups. The hydroxyl group of the citrate anion forms an intra-molecular hydrogen bond to one of the central carboxyl-ate oxygen atoms.
PubMed: 33117565
DOI: 10.1107/S2056989020011846