X-ray Absorption Fine Structure Studies of Speciation of Technetium in Borosilicate Glasses

2003 ◽  
Vol 802 ◽  
Author(s):  
Wayne W. Lukens ◽  
David K. Shuh ◽  
Isabelle S. Muller ◽  
David A. McKeown
Keyword(s):  
Fine Structure ◽  
Oxidation State ◽  
Organic Material ◽  
Glass Frit ◽  
High Level Waste ◽  
Borosilicate Glasses ◽  
X Ray ◽  
Synthesis Conditions ◽  
High Level ◽  
X Ray Absorption

ABSTRACTA series of glass samples were prepared analogously to high level waste glass using either glass frit or glass precursors combined with a high level waste surrogate containing NaTcO4. Three different technetium species were observed in these glasses depending upon the synthesis conditions. If the glasses were prepared by reducing NaTcO4 to TcO2•2H2O with hydrazine or if a large amount of organic material was present, inclusions of TcO2 were observed. If no organic material was present, technetium was incorporated as TcO4−. If only a small amount of organic material was present, isolated Tc(IV) sites were observed in the glass. The relative technetium retention of these glasses was estimated from the Tc K-edge height, and had no correlation with the oxidation state of the technetium. Pertechnetate was well retained in these glasses.

XAFS Study of Iron and Nickel Speciation in Complex Sodium Aluminophosphate Based Glasses

MRS Advances ◽  
2016 ◽  
Vol 1 (63-64) ◽  
pp. 4209-4214
Author(s):  
S.V. Stefanovsky ◽  
V.Y. Murzin ◽  
M.B. Remizov ◽  
B.F. Myasoedov
Keyword(s):  
Glass Network ◽  
High Level Waste ◽  
Homogeneous Distribution ◽  
Mössbauer Study ◽  
X Ray ◽  
Steel Tanks ◽  
High Level ◽  
Octahedral Oxygen ◽  
X Ray Absorption ◽  
Good Agreement

ABSTRACTIron and nickel oxidation state and coordination in complex sodium aluminophosphate based glasses suggested as potential matrices for immobilization of legacy high level waste currently stored in stainless steel tanks at PA «Mayak» (Ural reg., Russia) were determined by X-ray absorption fine structure spectroscopy (XAFS: XANES/EXAFS). The glasses containing (wt.%) 20-30 Na2O, 6-12 Al2O3, 40-52 P2O5, 2-5 Fe2O3, 1-3 NiO, 0-6 B2O3, 10-15 other waste oxides produced by quenching of their melts were fully amorphous or contained minor Fe and Ni free phases. Fe in the glasses was found to be predominantly trivalent with an average Fe-O distance and a coordination number (CN) in the first shell of 1.94 to 1.97 Å and 5.2 to 5.8, respectively, mostly in octahedral oxygen environment. Ni is divalent in all the glasses and has in the first shell an average Ni-O distance and CN of 1.97 to 2.03 Å and 4.9 to 5.6, respectively. The first shell of both Fe and Ni is somewhat distorted. The second and further coordination shells are weakly appeared exhibiting no clustering and homogeneous distribution of Fe and Ni ions in the glass network. The data on Fe obtained are in good agreement with those from Mössbauer study of same glasses. After annealing glasses were partly devitrified and interpretation of XAFS data is strongly complicated due to Fe and Ni partitioning among crystalline and vitreous phases.

scholarly journals The adsorption of Cu on the CeO2(110) surface

2017 ◽  
Vol 19 (40) ◽  
pp. 27191-27203 ◽  
Author(s):  
Arunabhiram Chutia ◽  
Emma K. Gibson ◽  
Matthew R. Farrow ◽  
Peter P. Wells ◽  
David O. Scanlon ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Fine Structure ◽  
Electronic Properties ◽  
Oxidation State ◽  
Density Functional ◽  
Functional Theory ◽  
Copper Species ◽  
X Ray ◽  
Solvent Environment ◽  
X Ray Absorption

A detailed density functional theory (DFT) study coupled with extended X-ray absorption fine structure (EXAFS) experiments on the geometrical and electronic properties of copper species on CeO2 surface demonstrating the effects of oxidation state and solvent environment.

Migration Behavior of Selenium in the Presence of Iron in Bentonite

2014 ◽  
Vol 1665 ◽  
pp. 157-163
Author(s):  
Kazuya Idemitsu ◽  
Hikaru Kozaki ◽  
Daisuke Akiyama ◽  
Masanao Kishimoto ◽  
Masaru Yuhara ◽  
...  
Keyword(s):  
Oxidation State ◽  
High Level Waste ◽  
Dry Density ◽  
Precipitation Reaction ◽  
Migration Behavior ◽  
Ferrous Ions ◽  
Edge Structure ◽  
Tracer Solution ◽  
High Level ◽  
X Ray Absorption

ABSTRACTSelenium (Se) is an important element for assessing the safety of high-level waste disposal. Se is redox-sensitive, and its oxidation state varies from -2 to 6 depending on the redox conditions and pH of the solution. Large quantities of ferrous ions formed in bentonite due to corrosion of carbon steel overpack after the closure of a repository are expected to maintain a reducing environment near the repository. Therefore, the migration behavior of Se in the presence of Fe in bentonite was investigated by electrochemical experiments. Na2SeO3 solution was used as tracer solution. Dry density range of bentonite was from 0.8 to 1.4 ×103 kg/m3.Results indicated that Se was strongly retained by the processes such as precipitation reaction with ferrous ions in bentonite. Se K-edge X-ray absorption near-edge structure (XANES) measurements were performed at the BL-11 beamline at SAGA Light Source, and the results revealed that the oxidation state of Se in the bentonite remained Se(IV).

X‐Ray Absorption Fine Structure Spectra and the Oxidation State of Nickel in Some of Its Oxycompounds

1994 ◽  
Vol 141 (6) ◽  
pp. L69-L71 ◽  
Author(s):  
A. N. Mansour ◽  
C. A. Melendres ◽  
M. Pankuch ◽  
R. A. Brizzolara
Keyword(s):  
Fine Structure ◽  
Oxidation State ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

CHARACTERISATION OF INTERFACIAL BONDING AND PHOTOCHEMISTRY IN SELF-ASSEMBLED THIOL MONOLAYERS ON GOLD USING NEXAFS AND ARUPS

1994 ◽  
Vol 01 (04) ◽  
pp. 701-704 ◽  
Author(s):  
H. RIELEY ◽  
N.J. PRICE ◽  
R.G. WHITE ◽  
R.I.R. BLYTH ◽  
L. HÅKANSSON ◽  
...  
Keyword(s):  
Fine Structure ◽  
Oxidation State ◽  
Interfacial Bonding ◽  
Ex Situ ◽  
Self Assembled Monolayers ◽  
X Ray ◽  
Thiol Monolayers ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
X Ray Absorption

S K-edge near-edge X-ray absorption fine structure (NEXAFS) has been used to establish the oxidation state of S in self-assembled monolayers (SAMs) of heptane and octane thiols, RSH [ R=CH 3( CH 2)n, n=6, 7] and the analogous halo-alkane disulphides, [(X RS )2, X= Cl , Br ] derivatised ex situ on Au foil. We find that the initially prepared surface thiolate species (RS–) is photo-oxidised by X-radiation, in the presence of coadsorbed oxygen, to sulphonate [Formula: see text]. Angle-resolved UV photoemission (ARUPS) has been used to further characterise the nature of the S-Au interaction in these SAMs following their preparation in UHV on Au(111). The ARUPS results suggest the involvement of the Au d-bands in the S-Au bond.

ChemInform Abstract: X-Ray Absorption Fine Structure Spectra and the Oxidation State of Nickel in Some of Its Oxycompounds.

ChemInform ◽  
2010 ◽  
Vol 25 (41) ◽  
pp. no-no
Author(s):  
A. N. MANSOUR ◽  
C. A. MELENDRES ◽  
M. PANKUCH ◽  
R. A. BRIZZOLARA
Keyword(s):  
Fine Structure ◽  
Oxidation State ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

Effect of cooling profile on crystalline phases, oxidation state, and chemical partitioning of complex glasses

MRS Advances ◽  
2020 ◽  
Vol 5 (11) ◽  
pp. 569-579
Author(s):  
J. Marcial ◽  
O. K. Neill ◽  
M. Newville ◽  
J. V. Crum ◽  
J. McCloy
Keyword(s):  
Oxidation State ◽  
High Level Waste ◽  
Crystal Glass ◽  
Treatment Schedule ◽  
X Ray Diffraction ◽  
Chemical Partitioning ◽  
X Ray ◽  
Spatially Resolved ◽  
Isothermal Heat Treatments ◽  
High Level

Abstract:Investigations of the crystallization of aluminosilicate phases within Hanford nuclear waste glasses typically involve subjecting samples to the canister centerline cooling (CCC) schedule. This cooling schedule is representative of the slowest cooling thermal profile which these glasses will experience after the glass is poured into the high level waste (HLW) container. However, few investigations have observed how the crystallization behavior changes by varying the heat treatment schedule. In the present study, three Hanford HLW glasses are subjected to CCC and isothermal heat treatments (IHT) to better understand the evolution of phases and the chemical partitioning due to temperature schedule. Samples were characterized using electron probe microanalysis, X-ray diffraction, micro X-ray fluorescence, and micro X-ray absorption spectroscopy. From IHT, eucryptite and apatite phases were observed which were not observed during CCC. Spatially-resolved measurements demonstrated that the oxidation state of the iron was similar among glass and crystal, and we suggest a mechanism to describe the compositional fluctuations near the crystal-glass interface which influence crystallization.

In situ X-ray absorption fine structure and optical reflectance studies of electrodeposited nickel hydrous oxide films in alkaline electrolytes

1997 ◽  
Vol 75 (11) ◽  
pp. 1721-1729 ◽  
Author(s):  
Yining Hu ◽  
In Tae Bae ◽  
Yibo Mo ◽  
Daniel A. Scherson ◽  
Mark R. Antonio
Keyword(s):  
Fine Structure ◽  
Oxidation State ◽  
Reflectance Spectroscopy ◽  
Hydrous Oxide ◽  
Optical Reflectance ◽  
X Ray ◽  
Absorption Fine ◽  
Alkaline Electrolytes ◽  
X Ray Absorption

X-ray absorption fine structure (XAFS) and optical reflectance spectroscopy (RS) have been used to examine in situ electronic and structural aspects of nickel hydrous oxide, α-Ni(OH)2(hyd), electrodes supported on gold in alkaline electrolytes as a function of their state of charge. The extended X-ray absorption fine structure (EXAFS) of α-Ni(OH)2(hyd) electrodes in the uncharged (UC, or discharged) and overcharged (OC, orfully charged) states yielded, in each case, a single set of two distinct nearest-neighbor shells, with distances, d(Ni—O)1 = 2.05 ± 0.02 Å and d(Ni—Ni)1 = 3.11 ± 0.02 Å for UC, and d(Ni—O)1 = 1.87 ± 0.02 Å and d(Ni—Ni)1 = 2.83 ± 0.02 Å for OC. The in situ EXAFS of films allowed to self-discharge following overcharge could be fit with contributions from both sets of shells, suggesting that only two types of nickel sites are sufficient to account for the redox chemistry of this material. These data, in addition to information derived both from quantitative X-ray absorption near-edge structure (XANES) and optical RS in the visible range, indicate that the excess anodic charge, i.e., beyond the one-electron oxidation of Ni2+ sites, observed during the first oxidation of freshly prepared α-Ni(OH)2(hyd) electrodes may not be related to oxidation state changes involving nickel sites in the lattice, and, therefore, do not support the existence of nickel sites with a formal oxidation state higher than three for charged or overcharged electrodes in this media. Keywords: nickel oxide, reflectance spectroscopy, EXAFS, in situ measurements.

Extended Core Edge Fine Structure in the E.M.

1980 ◽  
Vol 38 ◽  
pp. 120-121
Author(s):  
R.D. Leapman
Keyword(s):  
Fine Structure ◽  
Electron Scattering ◽  
Inelastic Electron ◽  
High Resolution Imaging ◽  
X Ray ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Core Electrons ◽  
Resolution Imaging ◽  
X Ray Absorption

Extended X-ray Absorption Fine Structure (EXAFS) analysis makes use of synchrotron radiaion to measure modulations in the absorption coefficient above core edges and hence to obtain information about local atomic environments. EXAFS arises when ejected core electrons are backscattered by surrounding atoms and interfere with the outgoing waves. Recently, interest has also been shown in using inelastic electron scattering1-4. Some advantages of Extended X-ray-edge Energy Loss Fine Structure (EXELFS) are: a) small probes formed by the analytical electron microscope give spectra from μm to nm sized areas, compared with mm diameter areas for the X-ray technique, b) EXELFS can be combined with other techniques such as electron diffraction or high resolution imaging, and c) EXELFS is sensitive to low Z elements with K edges from ˜200 eV to ˜ 3000 eV (B to Cl).

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