Understanding uranium oxide hardening during prolonged storage

2020 ◽  
Vol 108 (12) ◽  
pp. 943-953
Author(s):  
Kevin J. Pastoor ◽  
Shane L. Robinson ◽  
R. Allan Greenwell ◽  
Camila V. Quintero Hilsaca ◽  
Jenifer C. Shafer ◽  
...  
Keyword(s):  
Uranium Oxide ◽  
Uranium Hexafluoride ◽  
Intermediate Compound ◽  
Prolonged Storage ◽  
X Ray Diffraction ◽  
X Ray ◽  
Aging Study ◽  
Underlying Causes ◽  
Humidity Environment ◽  
Partial Reversal

AbstractUranium ore concentrates (UOCs), the product of uranium mining and milling, are primarily comprised of uranium oxide (U3O8 and UO2) or peroxide (UO4·4H2O and UO4·2H2O) compounds. Following production, UOCs are typically placed in storage until they are converted to uranium hexafluoride (UF6) at a uranium conversion facility. In this study, the chemical changes responsible for an interesting hardening phenomenon observed in UOCs stored for prolonged periods was investigated to understand underlying causes. Powder X-ray diffraction and thermogravimetric analysis were used to characterize free-flowing and hardened UOC samples and revealed the hardened material had undergone hydration and oxidation as indicated by increased moisture content and the presence of metaschoepite [(UO2)4O(OH)6](H2O)5 and/or schoepite [(UO2)4O(OH)6](H2O)6. Additionally, an aging study found metaschoepite in UOCs after 3 months exposure to a high relative humidity environment. The same study found agglomerated, but not fully hardened, material in nearly all aged UOCs samples. These results suggest metaschoepite and schoepite are indicative of UOCs exposed to elevated levels of H2O during storage. Lastly, a drying/calcining study of hardened U3O8 material demonstrated a means of remediation and identified an intermediate compound of potential interest, dehydrated schoepite. Dehydrated schoepite results from heating metaschoepite or schoepite between 100 and 300 °C and indicates partial reversal of hardened U3O8 to its original condition.

scholarly journals Shedding Light on Phase Stability and Surface Engineering of Formamidinium Lead Iodide (FaPbI3) Thin Films for Solar Cells

2021 ◽  
Vol 12 (1) ◽  
pp. 1
Author(s):  
Julia Marí-Guaita ◽  
Amal Bouich ◽  
Bernabé Marí
Keyword(s):  
Thin Films ◽  
Surface Engineering ◽  
Optical Analysis ◽  
X Ray Diffraction ◽  
Lead Iodide ◽  
X Ray ◽  
Structure Surface ◽  
Uv Visible ◽  
The Stability ◽  
Humidity Environment

In this work, FAPbI3 thin films with different antisolvents (toluene, diethyl ether and chlorobenzene) were successfully elaborated by the spin coating technique to study the influence of the different antisolvents in the films. The crystal structure, surface morphology and optical properties were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) photoluminescence and UV–visible spectrometry. According to XRD, the crystalline structure of FAPbI3 was found in the orientation of the (110) plane, and it is observed that the type of antisolvent content in the absorber layer plays an important role in the growth and stabilization of the film. Here, chlorobenzene leads to a smooth and homogenous surface, a large grain size and a pinhole-free perovskite film. Additionally, the optical analysis revealed that the band gap is in the range from 1.55 to 1.57 eV. Furthermore, in an approximately 60% humidity environment and after two weeks, the stability and absorption of FaPbI3 showed low degradation.

1,2-Di(silyl)benzene and 1,4-Dibromo-2,5-di(silyl)benzene

1994 ◽  
Vol 49 (8) ◽  
pp. 1036-1040 ◽  
Author(s):  
Robert Schröck ◽  
Alexander Sladek ◽  
Hubert Schmidbaur
Keyword(s):  
Methanesulfonic Acid ◽  
Intermediate Compound ◽  
Molecular Structures ◽  
High Yield ◽  
Electronic Effects ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Yields ◽  
Experimental Findings ◽  
Silylation Reaction

1,2-Di(silyl)benzene (3), has been prepared in a three-step process starting with the reac­tion of 1,2-dibromobenzene and p-tolyl(chloro)silane with magnesium in tetrahydrofuran. which affords 1,2-bis(p-tolylsilyl)benzene (1) as a stable high-yield intermediate. Compound 1 has been converted into 1,2-bis(trifluoromethanesulfonatosilyl)benzene (2) with trifluoro- methanesulfonic acid, and finally into 3 by reduction with lithiumaluminiumhydride, both again in high yields. - In an attempt to prepare 1,2,4,5-tetra(silyl)benzene in an analogous way. only the bis-silylated species could be obtained (from 1,2,4,5-C6H2Br4. p-MeC6H4SiClH2 and Mg powder: 1,4-dibromo-2,5-bis(p-tolylsilyl)benzene. 4, and 1,4-dibromo-2,5-di(silyl)- benzene, 6, via 1,4-dibromo-2,5-bis(trifluoromethanesulfonatosilyl)benzene, 5). The crystal structures of compounds 4 and 6 have been determined by X-ray diffraction. The results indicate no steric hindrance in these molecules and it is thus not obvious from the molecular structures why the silylation reaction does not proceed any further to give the tetrasilylated benzene derivatives. Electronic effects have to be invoked to rationalize the experimental findings.

scholarly journals 1-Laurin-3-Palmitin as a Novel Matrix of Solid Lipid Particles: Higher Loading Capacity of Thymol and Better Stability of Dispersions Than Those of Glyceryl Monostearate and Glyceryl Tripalmitate

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 489 ◽  
Author(s):  
Hao Shi ◽  
Shuangshuang Huang ◽  
Junbo He ◽  
Lijuan Han ◽  
Weinong Zhang ◽  
...  
Keyword(s):  
Model Compound ◽  
Entrapment Efficiency ◽  
Bioactive Molecules ◽  
Prolonged Storage ◽  
Loading Capacity ◽  
X Ray Diffraction ◽  
Glyceryl Monostearate ◽  
X Ray ◽  
Solid Lipid ◽  
Solid Lipid Particles

To develop solid lipid nanoparticles (SLNs) with a new lipid matrix for delivery of hydrophobic bioactive molecules, high purity 1-laurin-3-palmitin (1,3-LP) was synthesized and the prepared 1,3-LP SLNs were compared with those of two common SLN matrices in glyceryl monostearate (GMS) and glyceryl tripalmitate (PPP). Conditions of preparing SLNs were first optimized by evaluating the particle size, polydispersity index (PDI), zeta-potential, and stability. Thereafter, the performance of SLN loading of a model compound in thymol was studied. The loading capacity of thymol in 1,3-LP SLNs was 16% of lipids and higher than 4% and 12% for GMS- and PPP-SLNs, respectively. The 1,3-LP SLNs also had the best efficiency to entrapment thymol during the prolonged storage. X-ray diffraction (XRD) analyses confirmed the excellent crystalline stability of 1,3-LP leading to the stable entrapment efficiency and better stability of thymol-loaded SLNs. Conversely, the polymorphic transformation of GMS and PPP resulted in the declined entrapment efficiency of thymol in the corresponding SLNs. This work indicated the 1,3-diacylglycerol (DAG) SLNs could be used as a promising delivery system for the encapsulation of hydrophobic bioactive molecules with high loading capacity and stability.

scholarly journals Suppression of the Uranium-Hydrogen Reaction using High-Dose Carbon Implantation

1987 ◽  
Vol 93 ◽  
Author(s):  
R. G. Musket
Keyword(s):  
Auger Electron Spectroscopy ◽  
Oxide Layer ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Room Temperature ◽  
Uranium Oxide ◽  
High Dose ◽  
X Ray Diffraction ◽  
X Ray ◽  
Glancing Angle

ABSTRACTWe have previously reported the delay and reduction of the hydriding of uranium by implantation of oxygen. The reduced hydriding was attributed to the presence of the uranium oxide layer created near room temperature. In this paper we present results for the layers formed by implantation of 80 keV C+ to a dose of 8E17 C/cm2. The carbide layers formed were characterized by Auger electron spectroscopy, Rutherford backscattering, and glancing angle x-ray diffraction. Hydriding properties of both nonimplanted and implanted uranium were measured for 76 Torr hydrogen at 130°C. The implanted specimens had significantly longer incubation times for the start of the reaction after exposure to hydrogen and less area participating in the reaction.

scholarly journals Phase Transformation of Alumina, Silica and Iron Oxide during Carbothermic Reduction of Fly Ash for Ceramics Production

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1165
Author(s):  
Qingchun Yu ◽  
Yong Deng ◽  
Yuebin Feng ◽  
Ziyong Li
Keyword(s):  
Phase Transformation ◽  
Fly Ash ◽  
Carbothermic Reduction ◽  
Energy Dispersive Spectrometry ◽  
Intermediate Compound ◽  
Added Value ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reduced Products ◽  
Electronic Microscope

Fly ash is a by-product from burning of coal. Utilization of fly ash by carbothermic reduction is an effective way to recover aluminum, silicon, and iron to enhance product-added value. This work is focused on the phase transformation of Al2O3, SiO2 and Fe2O3 during carbothermic reduction of fly ash in air. A comparative analysis of carbothermic reduction of fly ash in air and in nitrogen was made. Thermodynamics analysis was performed to illustrate the possible reactions for residue and condensate. X-ray diffraction (XRD), scanning electronic microscope (SEM), and energy dispersive spectrometry (EDS) were employed to characterize the phase composition, surface morphology, and microstructure of the reduced products. Results show that Fe3Si and Fe2Si appear sequentially with increasing of temperature. Al5O6N is an intermediate compound. Residue of Al9FeSi3, Al, and Si, and condensate of SiC, AlN and C are obtained. β-SiAlON was not found in the residue. Nitrogen is involved in the reduction of Al2O3 but not in the reduction of SiO2 and Fe2O3. Carbothermic reduction of fly ash in air did not behave the same as fly ash in nitrogen.

scholarly journals MECHANISM OF THERMAL DECOMPOSITION OF AMMONIUM METAVANADATE

1964 ◽  
Vol 42 (11) ◽  
pp. 2467-2473 ◽  
Author(s):  
M. Taniguchi ◽  
T. R. Ingraham
Keyword(s):  
Thermal Decomposition ◽  
Intermediate Compound ◽  
Gaseous Product ◽  
Ammonium Metavanadate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Second Stage ◽  
Mechanism Of Thermal Decomposition ◽  
Exothermic Process ◽  
Last Stage

When ammonium metavanadate is roasted at 225 °C, ammonia and water are eliminated in the ratio 2:1 and an intermediate compound identified by weight loss and chemical analysis as (NH4)2•O•V2O5• is formed. An X-ray diffraction pattern for this material is reported. Transpiration experiments have been used to establish the free energy of this reaction. The second stage of the decomposition involves an endothermic and an exothermic process, both of which occur with the production of a gaseous product. The liberation of ammonia is not quantitative, and its oxidation on the vanadium pentoxide, in the last stage of decomposition, is suggested as a possible source of the exothermic heat.

scholarly journals Phase Transformation of Doped LiCoPO4 during Galvanostatic Cycling

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3810
Author(s):  
Wen Zhu ◽  
Dongqiang Liu ◽  
Catherine Gagnon ◽  
Vincent Gariépy ◽  
Michel L. Trudeau ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Reaction Pathway ◽  
Intermediate Compound ◽  
Discharge Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Changes ◽  
Biphasic Reaction ◽  
C 30 ◽  
Ray Patterns

In situ X-ray diffraction was employed to investigate the crystal structure changes in Cr/Si co-doped Li(Co,Fe)PO4 cathode material during a galvanostatic charge/discharge process at a slow rate of C/30. The evolution of the X-ray patterns revealed that the phase transformation between the Cr/Si-Li(Co,Fe)PO4 and Cr/Si-(Co,Fe)PO4 is a two-step process, which involves the formation of an intermediate compound of Cr/Si-Li0.62(Co,Fe)PO4 upon the extraction of Li ions from the pristine phase. Different from the previously reported two biphasic transition steps, the phase transformation of the Cr/Si-Li(Co,Fe)PO4 followed a solid solution and a biphasic reaction pathway at different stages of the delithiation/lithiation process, respectively.

scholarly journals Chlorination of antimony and its volatilization treatment of waste antimony-uranium composite oxide catalyst

2011 ◽  
Vol 1 (1) ◽  
pp. 97-100
Author(s):  
K. Sawada ◽  
Y. Enokida
Keyword(s):  
Weight Loss ◽  
Nitric Acid ◽  
Acid Solution ◽  
Uranium Oxide ◽  
Oxide Catalyst ◽  
X Ray Diffraction ◽  
Composite Oxide ◽  
X Ray ◽  
Almost All ◽  
Oxide Sample

Abstract For the waste antimony-uranium composite oxide catalyst, the chlorination of antimony and its volatilization treatment were proposed, and evaluated using hydrogen chloride gas at 873–1173 K. During the treatment, the weight loss of the composite oxide sample, which resulted from the volatilization of antimony, was confirmed. An X-ray diffraction analysis showed that uranium oxide, U3O8, was formed during the reaction. After the treatment at 1173 K for 1 h, almost all the uranium contained in the waste catalyst was dissolved by a 3 M nitric acid solution at 353 K within 10 min, although that of the non-treated catalyst was less than 0.1%. It was found that the chlorination and volatilization treatment was effective to separate antimony from the composite oxide catalyst and change uranium into its removable form.

Interaction of UO2 and Zircaloy During the Chernobyl Accident

1996 ◽  
Vol 465 ◽  
Author(s):  
S. V. Ushakov ◽  
B. E. Burakov ◽  
S. I. Shabalev ◽  
E. B. Anderson
Keyword(s):  
Chernobyl Accident ◽  
Uranium Oxide ◽  
Chemical Interaction ◽  
Liquid Immiscibility ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
The West ◽  
X Ray ◽  
The Core ◽  
Different Types

ABSTRACTA summary of the results collected during the studies of the products of a chemical interaction between uranium oxide fuel and Zircaloy cladding in the Chernobyl accident is presented in this paper. The reaction products are mainly Zr-U-containing phases with different U/Zr ratio and are described on the basis of electron microprobe and X-ray diffraction (XRD) analyses. The Zr-U-bearing phases were discovered among the inclusions in different types of Chernobyl fuel-containing masses (”lava”) inside the destroyed 4th Unit and in hot particles collected up to 12 km from the 4th Unit along the West Plume. A correlation of data on the chemical composition and phase interrelations obtained in investigated samples with a phase diagram of Zr(O) - UO2 shows, that a temperature >1900 °C was reached in a part of the core before the explosion. The detection of hot particle with segregated morphology points out that liquid immiscibility existed between U-rich and Zr-rich melts. This and other observations indicate that the core temperature locally was above 2400–2600°C.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Sign in / Sign up

Export Citation Format

Share Document