Synthesis and Characterization of 5- and 6- Coordinated Alkali Pertechnetates

MRS Advances ◽  
2017 ◽  
Vol 2 (10) ◽  
pp. 525-542 ◽  
Author(s):  
Jamie Weaver ◽  
Chuck Soderquist ◽  
Paul Gassman ◽  
Eric Walter ◽  
Wayne Lukens ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Nuclear Waste ◽  
Synthesis Method ◽  
Oxide Glasses ◽  
Paramagnetic Resonance ◽  
Synthesis Conditions ◽  
Pure Compounds ◽  
Temperature Electron

ABSTRACTThe local chemistry of technetium-99 (99Tc) in oxide glasses is important for understanding the incorporation and long-term release of Tc from nuclear waste glasses, both those for legacy defense wastes and fuel reprocessing wastes. Tc preferably forms Tc(VII), Tc(IV), or Tc(0) in glass, depending on the level of reduction of the melt. Tc(VII) in oxide glasses is normally assumed to be isolated pertechnetate TcO4-anions surrounded by alkali, but can occasionally precipitate as alkali pertechnetate salts such as KTcO4and NaTcO4when Tc concentration is high. In these cases, Tc(VII) is 4-coordinated by oxygen. A reinvestigation of the chemistry of alkali-technetium-oxides formed under oxidizing conditions and at temperatures used to prepare nuclear waste glasses showed that higher coordinated alkali Tc(VII) oxide species had been reported, including those with the TcO5-and TcO6-anions. The chemistry of alkali Tc(VII) and other alkali-Tc-oxides is reviewed, along with relevant synthesis conditions.Additionally, we report attempts to make 5- and 6-coordinate pertechnetate compounds of K, Na, and Li, i.e. TcO5-and TcO6-. It was found that higher coordinated species are very sensitive to water, and easily decompose into their respective pertechnetates. It was difficult to obtain pure compounds, but mixtures of the pertechnetate and other phase(s) were frequently found, as evidenced by x-ray absorption spectroscopy (XAS), neutron diffraction (ND), and Raman spectroscopy. Low temperature electron paramagnetic resonance (EPR) measurements showed the possibility of Tc(IV) and Tc(VI) in Na3TcO5and Na5TcO6compounds.It was hypothesized that the smaller counter cation would result in more stable pertechnetates. To confirm the synthesis method, LiReO4and Li5ReO6were prepared, and their Raman spectra match those in the literature. Subsequently, the Tc versions LiTcO4and Li5TcO6were synthesized and characterized by ND, Raman spectroscopy, XANES, and EXAFS. The Li5TcO6was a marginally stable compound that appears to have the same structure as that known for Li5ReO6. Implications of the experimental work on stability of alkali technetate compounds and possible role in the volatilization of Tc are discussed.

Synthesis and Characterization of Empty Silicon Clathrates for Anode Applications in Li-ion Batteries

MRS Advances ◽  
2016 ◽  
Vol 1 (45) ◽  
pp. 3043-3048 ◽  
Author(s):  
Kwai S. Chan ◽  
Michael A. Miller ◽  
Carol Ellis-Terrell ◽  
Candace K. Chan
Keyword(s):  
Coulombic Efficiency ◽  
Synthesis Method ◽  
Li Ion Batteries ◽  
Solution Synthesis ◽  
Silicon Clathrates ◽  
Potential Applications ◽  
Li Ion ◽  
Lower Capacity

ABSTRACTSeveral processing methods were developed and evaluated for synthesizing empty silicon clathrates. A solution synthesis method based on the Hofmann-elimination oxidation reaction was successfully utilized to produce 20 mg of empty Si46. Half-cells using the Si46 electrodes were successfully cycled for 1000 cycles at rate of 5.3C. The capacity of the Si46 electrode in long-term tests was 675 mAh/g at the 4th cycle, but increased to 809 mAh/g at 50 cycles. The corresponding Coulombic efficiency was better than 99%. The capacity dropped from 809 to 553 mAh/g after 1000 cycles while maintaining a 99% Coulombic efficiency. In comparison, a Ba8Al8Si38 electrode could be cycled for about 200 cycles with a lower capacity and Coulombic efficiency. Potential applications of empty silicon clathrates as anode materials in Li-ion batteries are discussed.

scholarly journals Experimental techniques for the characterization of carbon nanoparticles – a brief overview

2014 ◽  
Vol 5 ◽  
pp. 1760-1766 ◽  
Author(s):  
Wojciech Kempiński ◽  
Szymon Łoś ◽  
Mateusz Kempiński ◽  
Damian Markowski
Keyword(s):  
Electrical Conductivity ◽  
Raman Spectroscopy ◽  
Carbon Nanoparticles ◽  
Carrier Transport ◽  
Structural Changes ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray

The review of four experimental methods: X-ray diffraction, Raman spectroscopy, electron paramagnetic resonance and four-point electrical conductivity measurements is presented to characterize carbon nanoparticles. Two types of carbon nanoparticle systems are discussed: one comprising the powder of individual carbon nanoparticles and the second as a structurally interconnected nanoparticle matrix in the form of a fiber. X-ray diffraction and Raman spectroscopy reveal the atomic structure of the carbon nanoparticles and allow for observation of the changes in the quasi-graphitic ordering induced by ultrasonic irradiation and with the so-called quasi-high pressure effect under adsorption conditions. Structural changes have strong influence on the electronic properties, especially the localization of charge carriers within the nanoparticles, which can be observed with the EPR technique. This in turn can be well-correlated with the four-point electrical conductivity measurements which directly show the character of the charge carrier transport within the examined structures.

scholarly journals Advanced Synthesis and Characterization of Vanadia/Titania Catalysts through a Molecular Approach

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 322
Author(s):  
Eleni Tella ◽  
Antonios Trimpalis ◽  
Athanasios Tsevis ◽  
Christos Kordulis ◽  
Alexis Lycourghiotis ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Temperature Dependent ◽  
In Situ Raman Spectroscopy ◽  
Monomeric Species ◽  
Synthesis Conditions ◽  
In Situ Raman ◽  
Titania Surface ◽  
Inner Sphere

Vanadia/titania catalysts were synthesized by the equilibrium deposition filtration (EDF) method, which is a synthesis route that follows a molecular-level approach. The type of interfacial deposition as well as the interfacial speciation of the deposited oxo-V(V) species were determined by means of a model that takes into account experimental “proton-ion” curves and “adsorption edges”. It is shown that at pH ≥ 9.5, the deposition proceeds exclusively through the formation of mono-substituted inner sphere monomeric species in an “umbrella”-like Ti–OV(OH)2O configuration, whilst with lowering of the pH, a second species, namely the disubstituted inner sphere quadrameric species in a (Ti-O)2V4O10 configuration possessing two mono-oxo V=O and two di-oxo V(=O)2 terminations gradually prevails, which is in co-existence with the monomeric species. Raman spectroscopy is used for verifying the solution speciation, which is different compared to the interfacial speciation of the deposited oxo-V(V) species. Furthermore, in situ Raman spectroscopy was used to verify the model-predicted interfacial speciation of the deposited oxo-V(V) species and to monitor the temperature-dependent evolution up to 430 °C. Hence, a controlled formation of a specific vanadia species on a titania surface is enabled, which, depending on the synthesis conditions, can result in specific catalyst characteristics and thus possibly different catalytic behavior for a specific reaction.

Internal pressure effect on cathodoluminescence enhancement of ZnS:Mn2+ synthesized by a sealed vessel

2007 ◽  
Vol 22 (10) ◽  
pp. 2838-2844 ◽  
Author(s):  
B.J. Park ◽  
W.B. Im ◽  
W.J. Chung ◽  
H.S. Seo ◽  
J.T. Ahn ◽  
...  
Keyword(s):  
Synthesis Method ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Synthesis Conditions ◽  
Epr Signal ◽  
Xrd Patterns ◽  
Electron Paramagnetic ◽  
Mn Concentration

ZnS:Mn2+ phosphors were synthesized by a modified solid-state reaction method. In the synthesis method, a sealed vessel is used, where heat and pressure are simultaneously utilized. The effects of various synthesis conditions such as temperature, Mn concentration, and pressure on the cathodoluminescence (CL) were investigated. Among them, pressure had an effect on CL property as much as others. It was observed that CL intensities of ZnS:Mn2+ phosphors increased with the increase of pressure and the best sample showed higher intensity than that of a commercial one by 180%. X-ray diffraction (XRD) and electron paramagnetic-resonance (EPR) were used to understand the enhancement. No change of XRD patterns was observed but the full width at half-maximum (FWHM) of the most intense cubic (111) peak of ZnS:Mn2+ decreased with the increase of pressure. EPR signal intensity of Mn2+ increased with the increase of pressure. The improved crystallinity and more substitution of Zn2+ with Mn metal were believed to be responsible for the enhancement.

Synthesis and characterization of magnetic copper–iron-titanate and uptake studies of americium from nuclear waste solutions

RSC Advances ◽  
2016 ◽  
Vol 6 (113) ◽  
pp. 111822-111830 ◽  
Author(s):  
Krishnan Muthukumar ◽  
D. Shanthana Lakshmi ◽  
Rajesh B. Gujar ◽  
Arvind B. Boricha ◽  
Prasanta K. Mohapatra ◽  
...  
Keyword(s):  
Magnetic Materials ◽  
Nuclear Waste ◽  
Synthesis And Characterization ◽  
Synthesis Conditions ◽  
Iron Titanate ◽  
Benign Nature ◽  
Uptake Studies ◽  
Foreign Materials

Magnetic materials, which find enormous applications due to their benign nature, can have their efficiency and stability enhanced by incorporation of foreign materials and controlling the synthesis conditions.

scholarly journals Colloidal Cu2ZnSnS4-based and Ag-doped Nanocrystals: Synthesis and Raman Spectroscopy Study

2021 ◽  
Vol 22 (2) ◽  
pp. 260-268
Author(s):  
V. Dzhagan ◽  
O. Kapush ◽  
S. Budzulyak ◽  
N. Mazur ◽  
E. Gavryliuk ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Structural Characterization ◽  
Critical Role ◽  
Partial Substitution ◽  
Optical Absorption Spectroscopy ◽  
Synthesis Conditions ◽  
Synthetic Routes ◽  
New Generation

Cu2ZnSnS4 (CZTS) is one of the promising materials for absorber layers of new-generation thin film solar cells. Various synthetic routes of materials preparation and structural characterization have been explored so far. Further tuning of the CZTS properties is realized via partial substitution of the cations. Here we have used an affordable and scalable method of synthesizing colloidal CZTS nanocrystals (NC) in an aqueous solution. Variation of the synthesis parameters, in particular pH of the solution, was employed to improve the crystallinity of the NCs. Furthermore, CZTS NCs with partial substitution of Cu for Ag were also successfully synthesized. Raman spectroscopy was employed as a prime tool of structural characterization of the NCs obtained, along with optical absorption spectroscopy and ab initio DFT lattice dynamics calculations. An experimentally observed slight upward shift of the main phonon Raman peak upon increase of the Ag content in (AgxCu1-x)2ZnSnS4 NCs is in agreement with the trend predicted by DFT calculation. No pure Ag2ZnSnS4 NCs could be formed, indicating a critical role of Cu in forming the kesterite structure NCs under given synthesis conditions in an aqueous medium.

Raman studies of technetium in borosilicate waste glass

2007 ◽  
Vol 95 (5) ◽  
Author(s):  
David A. McKeown ◽  
Andrew C. Buechele ◽  
Wayne W. Lukens ◽  
D. K. Shuh ◽  
Ian L. Pegg
Keyword(s):  
Raman Spectroscopy ◽  
Waste Glass ◽  
Borosilicate Glasses ◽  
Coordination Environment ◽  
X Ray ◽  
Waste Vitrification ◽  
X Ray Absorption ◽  
Raman Spectral

The characterization of technetium (Tc) environments in borosilicate glasses is important with regard to the long-term isolation of Tc in nuclear wastes from the environment by waste vitrification. In this study, Raman spectroscopy was used to detect Tc in various borosilicate waste glass formulations in which Tc valence and average coordination environment were previously characterized by X-ray absorption spectroscopy. Raman spectral comparisons between chemically equivalent Tc-containing and Tc-free borosilicate glass pairs indicate Tc-dependent features near 320 and 910 cm

Longevity of Borehole and Shaft Sealing Materials: Characterization of Ancient Cement Based Building Materials

1983 ◽  
Vol 26 ◽  
Author(s):  
Christine A. Langton ◽  
Della M. Roy
Keyword(s):  
Nuclear Waste ◽  
Building Materials ◽  
Materials Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Long Term Stability ◽  
Sealing Materials ◽  
National Effort

ABSTRACTDurability and long-term stability of cements in plasters, mortars, and/or concretes utilized as borehole plugging and shaft sealing materials are of present concern in the national effort to isolate nuclear waste within deep geological repositories. The present study consists of an examination of selected ancient building materials and provides insights into the durability of certain ancient structures. These data were combined with knowledge obtained from the behavior of modern portland cements and natural materials to evaluate the potential for longevity of such materials in a borehole environment. Analyses were conducted by petrographic, SEM, chemical, and x-ray diffraction techniques.

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