Precipitation of Mixed-Alkali Molybdates During HLW Vitrification

2010 ◽  
Vol 1265 ◽  
Author(s):  
Scott Kroeker ◽  
Carolyn Higman ◽  
Vladimir K Michaelis ◽  
Nicholas B Svenda ◽  
Sophie Schuller
Keyword(s):  
Nuclear Waste ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
X Ray ◽  
Mixed Alkali ◽  
Model Glass ◽  
Sodium Cesium

AbstractCrystalline precipitates from molybdenum-containing nuclear waste glasses are complex, often containing multiple cations which confound routine structural techniques. A simplified mixed-alkali borosilicate model glass was found to have minor crystalline phases which could not be identified by x-ray diffraction. Multinuclear magnetic resonance (NMR) spectroscopy revealed sharp peaks characteristic of crystallinity superimposed on the broader glass signals, but were unattributable to any known molybdate phases. When a comprehensive range of cesium molybdates failed to reveal any matches with the observed 133Cs magic-angle spinning (MAS) NMR peaks in the composite glass/crystalline material, a series of mixed-alkali sodium-cesium molybdate phases was synthesized. 23Na, 133Cs and 95Mo MAS NMR revealed the formation of two mixed-cation molybdates which correlate with the observed NMR peaks for the phase-separated model glass. This work highlights the prominence of multiple crystalline phases in Mo-bearing nuclear waste glasses, and demonstrates the unique utility of solid-state NMR as a fingerprinting approach to identifying complex phases, especially where x-ray diffraction is limited by multiple phases, low concentrations or substitutionally disordered precipitates.

scholarly journals Single-crystal X-ray diffraction and NMR crystallography of a 1:1 cocrystal of dithianon and pyrimethanil

2017 ◽  
Vol 73 (3) ◽  
pp. 149-156 ◽  
Author(s):  
Ann-Christin Pöppler ◽  
Emily K. Corlett ◽  
Harriet Pearce ◽  
Mark P. Seymour ◽  
Matthew Reid ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Chemical Shifts ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Double Quantum ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nmr Crystallography

A single-crystal X-ray diffraction structure of a 1:1 cocrystal of two fungicides, namely dithianon (DI) and pyrimethanil (PM), is reported [systematic name: 5,10-dioxo-5H,10H-naphtho[2,3-b][1,4]dithiine-2,3-dicarbonitrile–4,6-dimethyl-N-phenylpyrimidin-2-amine (1/1), C14H4N2O2S2·C12H13N2]. Following an NMR crystallography approach, experimental solid-state magic angle spinning (MAS) NMR spectra are presented together with GIPAW (gauge-including projector augmented wave) calculations of NMR chemical shieldings. Specifically, experimental 1H and 13C chemical shifts are determined from two-dimensional 1H–13C MAS NMR correlation spectra recorded with short and longer contact times so as to probe one-bond C—H connectivities and longer-range C...H proximities, whereas H...H proximities are identified in a 1H double-quantum (DQ) MAS NMR spectrum. The performing of separate GIPAW calculations for the full periodic crystal structure and for isolated molecules allows the determination of the change in chemical shift upon going from an isolated molecule to the full crystal structure. For the 1H NMR chemical shifts, changes of 3.6 and 2.0 ppm correspond to intermolecular N—H...O and C—H...O hydrogen bonding, while changes of −2.7 and −1.5 ppm are due to ring current effects associated with C—H...π interactions. Even though there is a close intermolecular S...O distance of 3.10 Å, it is of note that the molecule-to-crystal chemical shifts for the involved sulfur or oxygen nuclei are small.

Mixed Carbides via Polymer Route

1990 ◽  
Vol 180 ◽  
Author(s):  
Gian D. Soraru ◽  
Florence Babonneau ◽  
John D. Mackenzie
Keyword(s):  
Magic Angle Spinning ◽  
Transformation Process ◽  
Mas Nmr ◽  
Magic Angle ◽  
Pyrolysis Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metallic Element ◽  
Angle Spinning

ABSTRACTSeveral polymetallocarbosilanes, pre-ceramics precursors for Si-M-C-O systems, have been prepared from polycarbosilane and metallic alkoxides, M(OR)n with M = Ti, Zr and Al. Polymers have essentially been characterized by Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR). The pyrolysis process has been followed for each system with X-Ray Diffraction (XRD) and MAS-NMR. The role of the metallic element M on the transformation process of these systems will be discussed.

scholarly journals High-temperature in situ crystallographic observation of reversible gas sorption in impermeable organic cages

2015 ◽  
Vol 112 (46) ◽  
pp. 14156-14161 ◽  
Author(s):  
Seung Bin Baek ◽  
Dohyun Moon ◽  
Robert Graf ◽  
Woo Jong Cho ◽  
Sung Woo Park ◽  
...  
Keyword(s):  
Single Crystal ◽  
High Temperatures ◽  
Direct Detection ◽  
Variable Temperature ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dynamic Motion

Crystallographic observation of adsorbed gas molecules is a highly difficult task due to their rapid motion. Here, we report the in situ single-crystal and synchrotron powder X-ray observations of reversible CO2 sorption processes in an apparently nonporous organic crystal under varying pressures at high temperatures. The host material is formed by hydrogen bond network between 1,3,5-tris-(4-carboxyphenyl)benzene (H3BTB) and N,N-dimethylformamide (DMF) and by π–π stacking between the H3BTB moieties. The material can be viewed as a well-ordered array of cages, which are tight packed with each other so that the cages are inaccessible from outside. Thus, the host is practically nonporous. Despite the absence of permanent pathways connecting the empty cages, they are permeable to CO2 at high temperatures due to thermally activated molecular gating, and the weakly confined CO2 molecules in the cages allow direct detection by in situ single-crystal X-ray diffraction at 323 K. Variable-temperature in situ synchrotron powder X-ray diffraction studies also show that the CO2 sorption is reversible and driven by temperature increase. Solid-state magic angle spinning NMR defines the interactions of CO2 with the organic framework and dynamic motion of CO2 in cages. The reversible sorption is attributed to the dynamic motion of the DMF molecules combined with the axial motions/angular fluctuations of CO2 (a series of transient opening/closing of compartments enabling CO2 molecule passage), as revealed from NMR and simulations. This temperature-driven transient molecular gating can store gaseous molecules in ordered arrays toward unique collective properties and release them for ready use.

X-ray diffraction and solid-state 119Sn CP-MAS NMR studies of some triaryltin(IV) chlorides

2003 ◽  
Vol 81 (11) ◽  
pp. 1187-1195 ◽  
Author(s):  
Jordan M Geller ◽  
Ian S Butler ◽  
Denis FR Gilson ◽  
Frederick G Morin ◽  
Ivor Wharf ◽  
...  
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Spin Coupling ◽  
Magic Angle ◽  
X Ray ◽  
Tin Chloride ◽  
Angle Spinning ◽  
Spin Spin Coupling

The solid-state 119Sn cross-polarization (CP) magic angle spinning (MAS) NMR spectra of a series of triaryltin chlorides of the form Ar3SnCl have been acquired. The indirect spin-spin coupling constants (J(119Sn-35Cl)), quadrupolar-dipolar shifts (d(119Sn-35Cl)), and the 119Sn chemical shift tensors were extracted. For the spectrum of triphenyltin chloride (I) the validity of the first-order perturbation approximation was tested by comparing results of both the perturbation and cubic-equation approaches and a variable-temperature NMR study undertaken to investigate the influence of the previously reported molecular motion in the solid. The X-ray crystal structures of the tris(o-tolyl)tin chloride (II) and tris(p-tolyl)tin chloride (IV) complexes have been examined. They belong to the monoclinic and triclinic space groups P21/n and P[Formula: see text], respectively, which are different from the previously reported tris(m-tolyl)tin chloride (III) complex, which crystallizes in the space group R3 and has threefold molecular symmetry. The structures and NMR properties of the complexes with meta-substituents are quite different from those with ortho- or para-substituents having axially symmetric shift tensors with small spans and larger J values.Key words: aryltin chlorides, magic angle spinning NMR, tin-chlorine spin-spin coupling, 119Sn chemical shift tensor, crystal structure.

scholarly journals Structure of nanocrystalline calcium silicate hydrates: insights from X-ray diffraction, synchrotron X-ray absorption and nuclear magnetic resonance

2016 ◽  
Vol 49 (3) ◽  
pp. 771-783 ◽  
Author(s):  
Sylvain Grangeon ◽  
Francis Claret ◽  
Cédric Roosz ◽  
Tsutomu Sato ◽  
Stéphane Gaboreau ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Calcium Silicate ◽  
Electron Probe ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Calcium Silicate Hydrates ◽  
Angle Spinning ◽  
X Ray Absorption

The structure of nanocrystalline calcium silicate hydrates (C–S–H) having Ca/Si ratios ranging between 0.57 ± 0.05 and 1.47 ± 0.04 was studied using an electron probe micro-analyser, powder X-ray diffraction,29Si magic angle spinning NMR, and Fourier-transform infrared and synchrotron X-ray absorption spectroscopies. All samples can be described as nanocrystalline and defective tobermorite. At low Ca/Si ratio, the Si chains are defect free and the SiQ3andQ2environments account, respectively, for up to 40.2 ± 1.5% and 55.6 ± 3.0% of the total Si, with part of theQ3Si being attributable to remnants of the synthesis reactant. As the Ca/Si ratio increases up to 0.87 ± 0.02, the SiQ3environment decreases down to 0 and is preferentially replaced by theQ2environment, which reaches 87.9 ± 2.0%. At higher ratios,Q2decreases down to 32.0 ± 7.6% for Ca/Si = 1.38 ± 0.03 and is replaced by theQ1environment, which peaks at 68.1 ± 3.8%. The combination of X-ray diffraction and NMR allowed capturing the depolymerization of Si chains as well as a two-step variation in the layer-to-layer distance. This latter first increases from ∼11.3 Å (for samples having a Ca/Si ratio <∼0.6) up to 12.25 Å at Ca/Si = 0.87 ± 0.02, probably as a result of a weaker layer-to-layer connectivity, and then decreases down to 11 Å when the Ca/Si ratio reaches 1.38 ± 0.03. The decrease in layer-to-layer distance results from the incorporation of interlayer Ca that may form a Ca(OH)2-like structure, nanocrystalline and intermixed with C–S–H layers, at high Ca/Si ratios.

Synthesis, X-ray diffraction and solid-state 31P magic angle spinning NMR study of ?-tricalcium orthophosphate

1996 ◽  
Vol 7 (7) ◽  
pp. 457-463 ◽  
Author(s):  
M. Bohner ◽  
J. LeMa�tre ◽  
A. P. LeGrand ◽  
J.-B. D'Espinose de la Caillerie ◽  
P. Belgrand
Keyword(s):  
Solid State ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nmr Study ◽  
Angle Spinning

Synthesis and characterization of montmorillonite-type phyllosilicates in a fluoride medium

Clay Minerals ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. 177-190 ◽  
Author(s):  
M. Reinholdt ◽  
J. Miehé-Brendlé ◽  
L. Delmotte ◽  
R. Le Dred ◽  
M.-H. Tuilier
Keyword(s):  
Atomic Ratio ◽  
Magic Angle Spinning ◽  
Crystallization Time ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Angle Spinning ◽  
Mg Content ◽  
Fluoride Medium

AbstractThe fluorine route is thoroughly investigated for the hydrothermal synthesis of montmorillonite in the Na2O-MgO-Al2O3-SiO2-H2O system. Using the optimal conditions suggested by Reinholdt et al. (2001) for the crystallization of pure montmorillonites with the formula Na2x(Al2(1-x)Mg2x☐)Si4O10(OH)2, several parameters (x, Mg content, duration of crystallization, F/Si atomic ratio, pH, nature of counterbalance cation) are varied independently from their ideal values. The products are analysed by various techniques (X-ray diffraction, thermogravimetric analysis-differential thermal analysis, 29Si, 27Al and 19F magic angle spinning-nuclear magnetic resonance). It appears that a pure montmorillonite can only be obtained within a narrow x range (0.10 ≤ x ≤ 0.20). The presence of F in the starting hydrogel and the crystallization time also have significant effects on the purity of the final products. It is shown that a small amount of fluorine is needed for the crystallization of pure montmorillonite phyllosilicates.

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