Dissolution of used Candu Fuel at Various Temperatures and Redox Conditions

1985 ◽  
Vol 50 ◽  
Author(s):  
S. Stroes-Gascoyne ◽  
L. H. Johnson ◽  
P. A. Beeley ◽  
D. M. Sellinger
Keyword(s):  
Potential Importance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Long Term Stability ◽  
Saturated Water ◽  
Reducing Conditions ◽  
Release Studies ◽  
Show Evidence ◽  
Radionuclide Release

AbstractSamples of used UO2 fuel exposed to air-saturated water at 25°C for eight years have been examined using electron microscopy and X-ray diffraction techniques. The results, in conjunction with solution analysis uata, show evidence for a UO3.2H2O precipitate on the fuel surface, and confirm the importance of grain-boundary leaching in controlling Cs-137 release. Studies of useo-fuel dissolution under both oxidizing and reducing conditions at 150°C show significantly lower radionuclide release to solution for reducing conditions, illustrating the potential importance of reoox chemistry in determining the long-term stability of used fuel after disposal.

Synthesis of Trilaminar Core–Shell Au/α-Fe2O3@SnO2Nanocomposites and their Application for Nonenzymatic Dopamine Electrochemical Sensing

NANO ◽  
2019 ◽  
Vol 14 (11) ◽  
pp. 1950138 ◽  
Author(s):  
Sai Zhang ◽  
Shijun Yue ◽  
Jiajia Li ◽  
Jianbin Zheng ◽  
Guojie Gao
Keyword(s):  
Electron Microscopy ◽  
High Sensitivity ◽  
Electrochemical Sensing ◽  
Synthesis Process ◽  
Core Shell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Long Term Stability ◽  
Transmission Electron

Au nanoparticles anchored on core–shell [Formula: see text]-Fe2O3@SnO2 nanospindles were successfully constructed through hydrothermal synthesis process and used for fabricating a novel nonenzymatic dopamine (DA) sensor. The structure and morphology of the Au/[Formula: see text]-Fe2O3@SnO2 trilaminar nanohybrid film were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical properties of the sensor were investigated by cyclic voltammetry and amperometry. The experimental results suggest that the composites have excellent catalytic property toward DA with a wide linear range from 0.5[Formula: see text][Formula: see text]M to 0.47[Formula: see text]mM, a low detection limit of 0.17[Formula: see text][Formula: see text]M (S/[Formula: see text]) and high sensitivity of 397.1[Formula: see text][Formula: see text]A[Formula: see text]mM[Formula: see text][Formula: see text]cm[Formula: see text]. In addition, the sensor exhibits long-term stability, good reproducibility and anti-interference.

Carbon Dioxide Reforming of Methane over Ni/Mo/La2O3-SBA-15 Сatalyst

2012 ◽  
Vol 455-456 ◽  
pp. 960-965
Author(s):  
Jian Huang ◽  
T. Huang ◽  
A. Rongzhang ◽  
Wei Huang ◽  
Ren Xiong Ma
Keyword(s):  
Carbon Dioxide ◽  
Strong Interaction ◽  
Carbon Deposition ◽  
Catalytic Performance ◽  
Stability Test ◽  
X Ray Diffraction ◽  
Carbon Dioxide Reforming ◽  
X Ray ◽  
Long Term Stability

Carbon dioxide reforming of methane over Ni/Mo/ La2O3-SBA-15 was studied. The catalyst was characterized by N2 adsorption, X-ray diffraction, H2-TPR,CO2-TPD and TG-GTA analysis. The results indicated that the introduction of an appropriate amount of La2O3 exhibited a higher activity and stability. In the long term stability test, La2O3 impregnated Ni/Mo-SBA-15 gave the highest conversion and stable activity at 800°C for 250 h. The effect of La was suggested to be due to its lower tendency to carbon deposition. Characterization results showed a strong interaction between La and Mo or Ni which facilitated the improvement of catalytic performance.

Structural characterization of free-standing gallium arsenide coiled membranes produced by micromachining

1999 ◽  
Vol 32 (1) ◽  
pp. 60-64
Author(s):  
Krishan Lal ◽  
S. Niranjana N. Goswami ◽  
J. Miao ◽  
H. L. Hartnagel
Keyword(s):  
High Resolution ◽  
Beam Width ◽  
Thin Strip ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray ◽  
Long Term Stability ◽  
Diffraction Peaks

High-resolution X-ray diffraction techniques have been employed successfully to evaluate crystalline quality and long-term stability of coiled membranes. The process of fabrication involves photolithography, implantation by 2 MeV N^{2+} ions inn-type GaAs substrates, followed by selective etching. A five-crystal X-ray diffractometer was employed in (+, −, +) setting with an Mo Kα1exploring beam for high-resolution X-ray diffractometry and topography experiments. The exploring-beam width was reduced to illuminate different segments of the coiled membrane. Diffraction curves recorded from the bulk crystal surrounding the sensor had a half width of 26 arcseconds, whereas the half widths from sensor segments were in the range ∼58 to ∼166 arcseconds. Different segments (particularly vertical ones) were identified from the observed angular separations between different diffraction peaks as well as from the shape of the diffraction peaks. It was found that different segments of the sensor were tilted with respect to one another and the tilt angles were in the range 15–212 arcseconds. High-resolution X-ray diffraction topographs recorded from (5\bar 11) and (400) diffracting planes revealed that the sides of the trough below the membrane created by etching are not vertical, but tapered. Also, there is a thin strip of crystal freely hanging over the tapered regions as a result of underetching. The surface of the cavity is uneven. The structural perfection of different membrane segments could also be ascertained from the contrast in topographs.

scholarly journals Graphene Langmuir-Schaefer films Decorated by Pd Nanoparticles for NO2 and H2 Gas Sensors

2019 ◽  
Vol 19 (2) ◽  
pp. 64-69 ◽  
Author(s):  
Dmytro Kostiuk ◽  
Stefan Luby ◽  
Peter Siffalovic ◽  
Monika Benkovicova ◽  
Jan Ivanco ◽  
...  
Keyword(s):  
Gas Sensing ◽  
Pd Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Si Substrates ◽  
Long Term Stability ◽  
Atomic Force ◽  
Few Layer Graphene

Abstract NO2 and H2 gas sensing by few-layer graphene (FLG) were studied in dependence on the annealing and decoration of graphene by palladium nanoparticles (NPs). Graphene was deposited onto SiO2 (500 nm)/Si substrates by a modified Langmuir-Schaefer technique. A solution of FLG flakes in 1-methyl-2-pyrrolidone was obtained by a mild sonication of the expanded milled graphite. FLG films were characterized by atomic force microscopy, X-ray diffraction, Raman spectroscopy, and the Brunnauer-Emmett-Teller method. Average FLG flake thickness and lateral dimension were 5 nm and 300 nm, respectively. Drop casting of Pd NP (6–7 nm) solution onto FLG film was applied to decorate graphene by Pd. The room temperature (RT) resistance of the samples was stabilized at 15 kΩ by vacuum annealing. Heating cycles of FLG film revealed its semiconducting character. The gas sensing was tested in the mixtures of dry air with H2 gas (10 to 10 000 ppm) and NO2 gas (2 to 200 ppm) between RT and 200 °C. The response of 26 % to H2 was achieved by FLG with Pd decoration at 70 °C and 10 000 ppm of H2 in the mixture. Pure FLG film did not show any response to H2. The response of FLG with Pd to 6 ppm of NO2 at RT was ≥ 23 %. It is 2 times larger than that of the pure FLG sample. Long term stability of sensors was studied.

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.

scholarly journals The long-term stability of residual stresses in steel

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Eckehard Mueller
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Compressive Residual Stress ◽  
List Type ◽  
X Ray Diffraction ◽  
X Ray ◽  
Term Stability ◽  
Long Term Stability ◽  
The Stability

Abstract There is frequent debate over the long-term stability of calibration specimens. It is an essential component of monitoring, especially for X-ray diffraction equipment used to determine residual stresses. If residual stresses are stable, a second consideration is that the residual stress should not be close to 0 MPa. If such specimens are available for monitoring, it is more sensitive concerning changes. These are key requirements when developing calibration specimens. In this study five specimens were observed, one of them was tested for more than 20 years. The stresses were determined with X-ray diffractometers. In the last four years two different X-ray methods for determination were used. It can be shown that high compressive residual stress does not change in steel if the specimens had no dynamic or static load and were stored under normal laboratory conditions. Article Highlights Finding a material in which compressive residual stress is stable Showing that the stability of compressive residual stress is over a long term The stability of the compressive residual stress is in a great range

scholarly journals One-Step Electrodeposition Synthesized Aunps/Mxene/ERGO for Selectivity Nitrite Sensing

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1892
Author(s):  
Tan Wang ◽  
Cong Wang ◽  
Xianbao Xu ◽  
Zhen Li ◽  
Daoliang Li
Keyword(s):  
Phosphate Buffer Solution ◽  
Oxidation Peak ◽  
Applied Potential ◽  
X Ray Diffraction ◽  
Buffer Solution ◽  
Solution Ph ◽  
X Ray ◽  
Long Term Stability ◽  
One Step

In this paper, a new nanocomposite AuNPs/MXene/ERGO was prepared for sensitive electrochemical detection of nitrite. The nanocomposite was prepared by a facile one-step electrodeposition, HAuCl4, GO and MXene mixed in PBS solution with the applied potential of –1.4 V for 600 s. The modified material was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and cyclic voltammetry (CV). The electrochemical behavior of nitrite at the modified electrode was performed by CV and chronoamperometry. The AuNPs/MXene/ERGO/GCE showed a well-defined oxidation peak for nitrite at +0.83 V (Vs. Ag/AgCl) in 0.1 M phosphate buffer solution (pH 7). The amperometric responses indicated the sensor had linear ranges of 0.5 to 80 μM and 80 to 780 μM with the LOD (0.15 μM and 0.015 μM) and sensitivity (340.14 and 977.89 μA mM–1 cm–2), respectively. Moreover, the fabricated sensor also showed good selectivity, repeatability, and long-term stability with satisfactory recoveries for a real sample. We also propose the work that needs to be done in the future for material improvements in the conclusion.

The Stability of the WHO Reference Thromboplastin NIBS & C 67/40

1979 ◽  
Vol 42 (04) ◽  
pp. 1135-1140 ◽  
Author(s):  
G I C Ingram
Keyword(s):  
Human Brain ◽  
Collaborative Study ◽  
Calibration Constant ◽  
Long Term Stability ◽  
Freeze Dried ◽  
Show Evidence ◽  
Human Material ◽  
Reference Preparation ◽  
The Stability

SummaryThe International Reference Preparation of human brain thromboplastin coded 67/40 has been thought to show evidence of instability. The evidence is discussed and is not thought to be strong; but it is suggested that it would be wise to replace 67/40 with a new preparation of human brain, both for this reason and because 67/40 is in a form (like Thrombotest) in which few workers seem to use human brain. A �plain� preparation would be more appropriate; and a freeze-dried sample of BCT is recommended as the successor preparation. The opportunity should be taken also to replace the corresponding ox and rabbit preparations. In the collaborative study which would be required it would then be desirable to test in parallel the three old and the three new preparations. The relative sensitivities of the old preparations could be compared with those found in earlier studies to obtain further evidence on the stability of 67/40; if stability were confirmed, the new preparations should be calibrated against it, but if not, the new human material should receive a calibration constant of 1.0 and the new ox and rabbit materials calibrated against that.The types of evidence available for monitoring the long-term stability of a thromboplastin are discussed.

scholarly journals Enhancing carbonation and chloride resistance of autoclaved concrete by incorporating nano-CaCO3

2020 ◽  
Vol 9 (1) ◽  
pp. 998-1008
Author(s):  
Guo Li ◽  
Zheng Zhuang ◽  
Yajun Lv ◽  
Kejin Wang ◽  
David Hui
Keyword(s):  
Cement Hydration ◽  
Mercury Intrusion Porosimetry ◽  
Hardened Concrete ◽  
Optimal Dosage ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Carbonation Depth ◽  
X Ray ◽  
Chloride Resistance

AbstractThree nano-CaCO3 (NC) replacement levels of 1, 2, and 3% (by weight of cement) were utilized in autoclaved concrete. The accelerated carbonation depth and Coulomb electric fluxes of the hardened concrete were tested periodically at the ages of 28, 90, 180, and 300 days. In addition, X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry were also performed to study changes in the hydration products of cement and microscopic pore structure of concrete under autoclave curing. Results indicated that a suitable level of NC replacement exerts filling and accelerating effects, promotes the generation of cement hydration products, reduces porosity, and refines the micropores of autoclaved concrete. These effects substantially enhanced the carbonation and chloride resistance of the autoclaved concrete and endowed the material with resistances approaching or exceeding that of standard cured concrete. Among the three NC replacement ratios, the 3% NC replacement was the optimal dosage for improving the long-term carbonation and chloride resistance of concrete.

Structural and electrochemical properties of Ti–Ru–Fe–O alloys prepared by high energy ball-milling

1998 ◽  
Vol 13 (5) ◽  
pp. 1171-1176 ◽  
Author(s):  
S-H. Yip ◽  
D. Guay ◽  
S. Jin ◽  
E. Ghali ◽  
A. Van Neste ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
High Energy ◽  
X Ray Diffraction ◽  
Long Term Stability ◽  
Ternary Metal ◽  
Oxide Phases ◽  
Energy Ball ◽  
Diffraction Patterns ◽  
B2 Structure

The structural and electrochemical properties of the Ti–Ru–Fe–O system have been studied over the whole ternary metal compositional range, keeping constant the oxygen content at 30 at.%. The phase diagram was explored systematically by varying the composition of the material along one of the following axes: (i) constant Ru content of 16 at. %; (ii) constant Ti/Ru ratio of 2; (iii) constant Ti/Fe ratio of 1.6. For O/Ti ratios equal or below unity, the most prominent peaks observed in the x-ray diffraction patterns belong to a B2 structure. For O/Ti ratio larger than unity, stable titanium oxide phases are formed, which coexist with a cubic Fe-like or hcp-Ru like phases depending on the Fe/Ru ratio. Powder compositions with stoichiometry close to Ti2RuFeO2 are of interest due to good electrocatalytic properties, long-term stability, and low Ru content.

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