Zirconolite-Rich Ceramics for Actinide Wastes

1994 ◽  
Vol 353 ◽  
Author(s):  
Eric R Vance ◽  
B. D. Begg ◽  
R. A. Day ◽  
C. J. Ball
Keyword(s):  
Rare Earths ◽  
Solid Solubility ◽  
Scanning Electron Microscopy Data ◽  
X Ray Diffraction ◽  
Absorption Data ◽  
X Ray ◽  
Electron Microscopy Data ◽  
Trivalent Actinides ◽  
Microscopy Data ◽  
X Ray Absorption

AbstractNew X-ray diffraction and scanning electron microscopy data are given for the incorporation of Np and Pu in zirconolite, at levels of tens of percent. The actinide valences and the cations they replace are deduced from the microanalysis of the zirconolite compositions, and X-ray absorption data are used to obtain more direct information on the valences of Ce and Nd, which are used as simulants of Pu and trivalent actinides respectively. Trivalent rare earths and actinides have extensive solid solubility in zirconolite, mainly but not exclusively in the Ca site. Tetravalent rare earths and actinides have considerable solid solubility in the Zr site of zirconolite, and some solubility in the Ca site, but the strong tendency of zirconolite with ions substituted in the Zr site to undergo phase separation complicates structural interpretation. In zirconolite-rich Synroc-type ceramics designed to immobilise waste actinides, the target actinide waste loading has been set at 20 wt% and early leach results indicate the durability is at least as good as that of Synroc-C.

Synthesis of YBa2Cu3O7−x by chemical precursors

1991 ◽  
Vol 6 (1) ◽  
pp. 11-17 ◽  
Author(s):  
D. E. Peterson ◽  
K. A. Kubat-Martin ◽  
T. G. George ◽  
T. G. Zocco ◽  
J. D. Thompson
Keyword(s):  
Single Phase ◽  
High Temperature Superconductor ◽  
Superconducting Phase ◽  
Synthesis Methods ◽  
Scanning Electron Microscopy Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electron Microscopy Data ◽  
Microscopy Data ◽  
Synthesis Approach

An alternative synthetic route for obtaining bulk forms of the high temperature superconductor YBa2Cu3O7−x has been investigated. The approach is based on first preparing the phases Y2Cu2O5 and BaCuO2, followed by a single sintering of an appropriate mixture of these intermediate compounds to produce the superconducting phase. The resulting materials are largely single-phase as shown by x-ray diffraction, and have densities as high as 86% of the theoretical value, and superconducting onset temperatures of 93 K with magnetic shielding factors ranging from 0.85 to 1.02 (±0.05). Metallography and scanning electron microscopy data were also obtained on the best (high Tc, high shielding factors) of the samples. This synthesis approach is believed to be simpler, more reproducible, and has the potential of producing better materials than previously used bulk synthesis methods.

Effect of the Pulse Laser Radiation on the Stabilization of the ZrO2 and HFO2 High-Temperature Phases

2015 ◽  
Vol 245 ◽  
pp. 200-203 ◽  
Author(s):  
Maxim Alexandrovich Pugachevskii ◽  
Viktor Igorevich Panfilov
Keyword(s):  
High Temperature ◽  
Transmission Electron Microscopy Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Good Thermal Stability ◽  
Quantitative Content ◽  
Electron Microscopy Data ◽  
Cubic Phases ◽  
Transmission Electron ◽  
Microscopy Data

The conditions of formation of the ZrO2 and HfO2 high-temperature (tetragonal and cubic) phases in the ablated nanoparticles were investigated. X-ray diffraction and transmission electron microscopy data demonstrate that laser intensities above 109 W/m2 ensure the formation of the ZrO2 high-temperature phases, while intensities above 5·109 W/m2 do the formation of the HfO2 high-temperature phases. Quantitative content of the high-temperature phases in layers of the ablated nanoparticles increases with raising the intensity. The obtained nanoparticles exhibit good thermal stability.

Determination of Thickness of Multiple Layer Thin Films by X-ray Diffraction Technique

1995 ◽  
Vol 39 ◽  
pp. 637-643
Author(s):  
J. Chaudhuri ◽  
F. Hashmi
Keyword(s):  
Thin Films ◽  
Diffraction Theory ◽  
Scanning Electron Microscopy Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multiple Layer ◽  
Crystal Model ◽  
Microscopy Data ◽  
Secondary Extinction

In this study, the equations based on x-ray diffraction theory were developed to determine the thickness of multiple layer thin films. The kinematical expression of the integrated reflected intensity from the substrate and films was corrected for the primary and secondary extinction effects assuming a mosaic crystal model. As an example of the application of the method, thicknesses of a double heterostructure system, namely AlAs/AIGaAs/GaAs, were determined. Good agreement was obtained between the results from the x-ray measurement and scanning electron microscopy data demonstrating high precision of this technique.

A combined diffraction and EXAFS study of LaCoO3 and La0.5Sr0.5Co0.75Nb0.25O3 powders

2017 ◽  
Vol 32 (S1) ◽  
pp. S52-S55
Author(s):  
E. A. Efimova ◽  
V. V. Sikolenko ◽  
D. V. Karpinsky ◽  
I. O. Troyanchuk ◽  
S. Pascarelli ◽  
...  
Keyword(s):  
Spin State ◽  
State Transition ◽  
X Ray Diffraction ◽  
Absorption Data ◽  
X Ray ◽  
Bond Lengths ◽  
Structural Distortions ◽  
Spin State Transition ◽  
Local Range ◽  
X Ray Absorption

A combination of neutron diffraction, synchrotron X-ray diffraction, and high-resolution extended X-ray absorption fine structure measurements has been used to clarify the correlations between long- and local-range structural distortions across the spin-state transition in powders of LaCoO3 and La0.5Sr0.5Co0.75Nb0.25O3. The analysis of the diffraction data has revealed that the isotropic thermal parameters of Co–O bond abnormally increase below 100 K in both samples, while the temperature dependence of the average Co–O bond lengths is linear from 10 to 300 K. We also have found that the Co–O bond lengths are larger in La0.5Sr0.5Co0.75Nb0.25O3, as compared with the ones in LaCoO3. The X-ray absorption data showed an anomalous decrease of the Co–O bond lengths only for LaCoO3, in contrast to the bond length values obtained by diffraction. The structural anomalies observed by spectroscopy measurements are discussed in terms of the spin-state transition model.

scholarly journals Atomistic structure of alkali-silica reaction products refined from X-ray diffraction and micro X-ray absorption data

2020 ◽  
Vol 129 ◽  
pp. 105958 ◽  
Author(s):  
Guoqing Geng ◽  
Zhenguo Shi ◽  
Andreas Leemann ◽  
Camelia Borca ◽  
Thomas Huthwelker ◽  
...  
Keyword(s):  
Alkali Silica Reaction ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Absorption Data ◽  
X Ray ◽  
X Ray Absorption ◽  
Atomistic Structure

scholarly journals Tissue-Engineered Vascular Graft of Small Diameter Based on Electrospun Polylactide Microfibers

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
P. V. Popryadukhin ◽  
G. I. Popov ◽  
G. Yu. Yukina ◽  
I. P. Dobrovolskaya ◽  
E. M. Ivan’kova ◽  
...  
Keyword(s):  
Vascular Grafts ◽  
Small Diameter ◽  
Degree Of Crystallinity ◽  
Scanning Electron Microscopy Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthetic Fibers ◽  
Deformation Stability ◽  
Strength And Deformation ◽  
Microscopy Data

Tubular vascular grafts 1.1 mm in diameter based on poly(L-lactide) microfibers were obtained by electrospinning. X-ray diffraction and scanning electron microscopy data demonstrated that the samples treated atT=70°C for 1 h in the fixed state on a cylindrical mandrel possessed dense fibrous structure; their degree of crystallinity was approximately 44%. Strength and deformation stability of these samples were higher than those of the native blood vessels; thus, it was possible to use them in tissue engineering as bioresorbable vascular grafts. The experiments on including implantation into rat abdominal aorta demonstrated that the obtained vascular grafts did not cause pathological reactions in the rats; in four weeks, inner side of the grafts became completely covered with endothelial cells, and fibroblasts grew throughout the wall. After exposure for 12 weeks, resorption of PLLA fibers started, and this process was completed in 64 weeks. Resorbed synthetic fibers were replaced by collagen and fibroblasts. At that time, the blood vessel was formed; its neointima and neoadventitia were close to those of the native vessel in structure and composition.

scholarly journals X-ray diffraction and electron microscopy data for amyloid formation of Aβ40 and Aβ42

Data in Brief ◽  
2016 ◽  
Vol 8 ◽  
pp. 108-113 ◽  
Author(s):  
Olga M. Selivanova ◽  
Elizaveta I. Grigorashvili ◽  
Mariya Yu. Suvorina ◽  
Ulyana F. Dzhus ◽  
Alexey D. Nikulin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Amyloid Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electron Microscopy Data ◽  
Microscopy Data

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

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