Fabrication of Uranium Dioxide Microspheres by Classic and Novel Sol-Gel Processes

2014 ◽  
Vol 1683 ◽  
Author(s):  
A. Deptuła ◽  
M. Brykala ◽  
M. Rogowski ◽  
T. Smolinski ◽  
T. Olczak ◽  
...  
Keyword(s):  
Uranium Dioxide ◽  
National Laboratory ◽  
Sol Gel ◽  
Nitrate Solution ◽  
Hydrogen Atmosphere ◽  
Substantial Improvement ◽  
Complexing Agent ◽  
Reduction Step ◽  
Oak Ridge ◽  
Sol Gel Process

ABSTRACTUranium dioxide (UO2) microspheres were fabricated by two sol-gel processes. First used was a classical process variant, as developed at Oak Ridge National Laboratory, consisting of (1) reduction of commercial uranyl to U(IV) nitrate; (2) preparation of a sol by precipitation of uranium hydroxide, its peptization, and solvent extraction of nitrates; and (3) gelation to microspheres by extraction of water through addition of a dewatered 2-ethyl-1-hexanol emulsion. Substantial improvement in microsphere production was achieved by application of a sol-gel process in which ascorbic acid was used as strong complexing agent. In this method, the reduction step was omitted and uranyl (VI) ascorbate sols/hydroxyl sols were formed from a suspension of either a uranium trioxide or a uranyl nitrate solution. Gelation through water extraction yielded perfect microspheres. Other metals can be easy added to these sols. Thermal treatment of the UO2 microspheres by calcination and reduction in hydrogen atmosphere was designed on the basis of differential thermal analysis and thermogravimetric analysis.

scholarly journals Magnetic Resonance as a Structural Probe of a Uranium (Vi) Sol-Gel Process

1990 ◽  
Vol 180 ◽  
Author(s):  
Charles M. King ◽  
R. Bruce King ◽  
A. Ronald Garber ◽  
Major C. Thompson ◽  
Bruce R. Buchanan
Keyword(s):  
Magnetic Resonance ◽  
National Laboratory ◽  
Sol Gel ◽  
Structural Formula ◽  
Chemical Mechanism ◽  
Nmr Studies ◽  
Technical Literature ◽  
Oak Ridge ◽  
Sol Gel Process ◽  
Gel Processing

ABSTRACTNuclear Magnetic Resonance (NMR) investigations on the Oak Ridge National Laboratory process for sol-gel synthesis of microspherical nuclear fuel (UO2), has been extremely useful in sorting out the chemical mechanism in the sol-gel steps. 13C, 15N, and 1H NMR studies on the HMTA gelation agent (hexamethylenetetramine, C6H12N4) has revealed near quantitative stability of this adamantane-like compound in the sol-gel process, contrary to its historical role as an ammonia source for gelation from the worldwide technical literature. 17O NMR of uranyl (UO2++) hydrolysis fragments produced in colloidal sols has revealed the selective formation of a uranyl trimer, [(UO2)3 (μ3-O)(μ2-OH)3]+, induced by basic hydrolysis with the HMTA gelation agent. Spectroscopic results will be presented to illustrate that trimer condensation occurs during sol-gel processing leading to layered polyanionic hydrous uranium oxides in which HMTAH+ is occluded as an ‘intercalation’ cation. Subsequent sol-gel processing of microspheres by ammonia washing results in in-situ ion exchange and formation of a layered hydrous ammonium uranate with a proposed structural formula of (NH4)2 [(UO2)8 O4 (OH)10]- 8H2)O. This compound is the precursor to sintered UO2 ceramic fuel.

New Magnetic Materials Produced By The Sol-Gel Process: A Possibility Of Producing Exotic Devices

1986 ◽  
Vol 73 ◽  
Author(s):  
G. Kordas
Keyword(s):  
Line Width ◽  
Sol Gel ◽  
Resonance Field ◽  
Relaxation Mechanism ◽  
Hydrogen Atmosphere ◽  
Film Plane ◽  
Local Fields ◽  
Oxide Thin Film ◽  
Sol Gel Process ◽  
Oriented Parallel

ABSTRACTFerromagnetic resonance (FMR) spectra of an iron-oxide thin film with a thickness of 70 A were recorded between 100 and 410 K at 9.5 GHz after heat treatment at about 500 °C in hydrogen atmosphere. The FMR-signal of this film consisted of two components (A and B) when the film plane was oriented parallel to the external fieTp The intensity of these components is not proportional toT3/2 in the range from 100 to 410 K. The line width of the A-component is determined by inhomogeneities in the magnetic structure. The line width of the B-component may be influenced by the spin-spin relaxation mechanism and skin effect. The temperature behavior of the resonance field of the A- and B-components was tentatively attributed to variation of the local fields with the temperature of measurements.

Preparation of La1-xCexNiO3 (x= 0 ~ 0.4) Perovskite-Type Oxide by Sol-Gel Using Polyvinyl Alcohol

2010 ◽  
Vol 434-435 ◽  
pp. 442-445 ◽  
Author(s):  
Kanit Soongprasit ◽  
Duangdao Aht-Ong ◽  
Viboon Sricharoenchaikul ◽  
Duangduen Atong
Keyword(s):  
Metal Ion ◽  
Sol Gel ◽  
Complexing Agent ◽  
Air Oxidation ◽  
X Ray Diffraction ◽  
Wet Air Oxidation ◽  
Energy Dispersion Spectroscopy ◽  
Sol Gel Process ◽  
Synthesized Materials ◽  
Perovskite Type

Perovskite-type oxides catalyst are of interest for various application such as auto-thermal reforming (ART), catalytic wet air oxidation (CWOA) and piezoelectric (PZT). In this paper, La1-xCexNiO3 (x= 0-0.4) perovskite-type oxides have been prepared b sol-gel process using PVA. The precursor was mixed metal ion and PVA with a mole ratio of 1:1 and 1:2. The decomposition during the calcinations process was evaluated by thermogravimetric analysis and differential thermal analysis. Phase of synthesized materials were characterized with X-ray diffraction. Morphological analysis and elemental composition of catalysts was determined by Scanning electron microscope and energy dispersion spectroscopy. The characterization results show that highly crystalline and homogeneous phase of these perovskite oxides were successfully synthesized by the sol-gel method via PVA as a complexing agent.

Effect of pH Value on Preparation of La2CuO4 Microcrystallites Synthesized by Sol-Gel Process

2012 ◽  
Vol 512-515 ◽  
pp. 231-234 ◽  
Author(s):  
Yi Feng Li ◽  
Jian Feng Huang ◽  
Li Yun Cao ◽  
Jian Peng Wu
Keyword(s):  
Optical Band Gap ◽  
Ph Value ◽  
Raw Materials ◽  
Sol Gel ◽  
Complexing Agent ◽  
Solution Ph ◽  
Crystallization Property ◽  
Water As Solvent ◽  
Sol Gel Process ◽  
Single Sphere

La2CuO4 crystallites were prepared via a sol-gel process using lanthanum nitrate and cupric nitrate as raw materials, distilled water as solvent, citric acid as complexing agent and ammonia to control the pH value. The as-prepared La2CuO4 crystallites were characterized by XRD, FESEM, TEM and UV-Vis spectra. Results show that the crystallization property of La2CuO4 crystallites increases firstly and then decreases with increasing of the solution pH value from 1.0 to 2.5, but all of the samples exhibit single sphere-like morphology. It is found that when the solution pH value is controlled at 2.0, the grains display uniform distribution and the size ranges from 100nm to120nm after sintering at 600°C for 2 hours. The optical band gap of the as-prepared La2CuO4 crystallites is calculated to be 1.38eV.

INFLUENCE OF THE INDEX METALLIC SALTS - COMPLEXING AGENT IN A SOL-GEL PROCESS TO OBTAIN NANOSCALED ZIRCONIUM SUBSTITUTED YTTRIUM (YSZ) TO ELECTROLYTE APPLICATION IN SOLID OXIDE FUEL CELL (SOFC)

2012 ◽  
Vol 1386 ◽  
Author(s):  
Rene Fabian Cienfuegos-Pelaes ◽  
Alejandro Ehécatl Correa ◽  
Ramona Alicia Salazar ◽  
L. Chávez-Guerrero ◽  
M. Hinojosa
Keyword(s):  
Low Cost ◽  
Sol Gel ◽  
Complexing Agents ◽  
Complexing Agent ◽  
X Ray Diffraction ◽  
Crystalline Powder ◽  
Easy Method ◽  
X Ray ◽  
Metallic Salts ◽  
Sol Gel Process

ABSTRACTThe objective of the present study is to obtain the electrolyte material YSZ at low cost via sol gel, through exploration of the index rate between the complexing agents and the metallic salts (HMTA / metallic salts) from 1 to 5, prepared by a polymeric way in a sol gel process. We show an easy method that could be used in the industrial scale in order to obtain solid electrolyte material for its application in SOFC to operate at temperatures in the range of 700 800°C. This study has as reference the papers from Lenormand and Rieu about their synthesis of zirconium substituted to 8% of yttrium (CYSZ= 0.2 mol*L-1 metallic salts concentration-). The presence of the phase in the materials has been confirmed by X-ray diffraction assisted by thermal analysis tests, for indexes from 2 to 5 at a temperature of 1000°C for 5 hours at a calcination rate (from amorphous dust obtained at 400°C) of 1000°C per hour. The grain size mean for crystalline powder has an average near 50 nm and standard deviation close to 9 nm, it was confirmed by scanning electron microscope (SEM).

scholarly journals Characterization of LiCo Nanopowders Produced by Sol-Gel Processing

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Sina Soltanmohammad ◽  
Sirous Asgari
Keyword(s):  
Thermal Analyses ◽  
Sol Gel ◽  
Lithium Ion ◽  
Chelating Agent ◽  
Complexing Agents ◽  
Complexing Agent ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Size And Morphology ◽  
Gel Processing

LiCo nanopowders, one of the most important cathode materials for lithium-ion batteries, were synthesized via a modified sol-gel process assisted with triethanolamine (TEA) as a complexing agent. The influence of three different chelating agents including acrylic acid, citric acid, and oxalic acid on the size and morphology of particles was investigated. Structure and morphology of the synthesized powders were characterized by thermogravimetric/differential thermal analyses (TG/DTA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results indicate that the powder processed with TEA and calcinated at 800 had an excellent hexagonal ordering of -NaFe-type (space group Rm). Also, the other three complexing agents had a decisive influence on the particle size, shape, morphology, and degree of agglomeration of the resulting oxides. Based on the data presented in this work, it is proposed that the optimized size and distribution of LiCo powders may be achieved through sol-gel processing using TEA as a chelating agent.

Mechanical Characterization of Zirconia Synthesized by the Sol-Gel Process

2012 ◽  
Vol 727-728 ◽  
pp. 945-950
Author(s):  
Ana Márcia Barbosa da Silva Antunes ◽  
Carlos Antonio Reis Pereira Baptista ◽  
Simone Pereira Taguchi
Keyword(s):  
Mechanical Characterization ◽  
Sol Gel ◽  
Zirconia Ceramic ◽  
Complexing Agent ◽  
Zirconia Ceramics ◽  
Crystalline Phases ◽  
Structural Applications ◽  
Sol Gel Process ◽  
Small Grains

Zirconia ceramics (ZrO2) are bioinert materials with excellent biocompatibility, high resistance to corrosion and to wear, high toughness in comparison with other advanced ceramics, and suitable for various structural applications. These properties are related to their microstructure and effects caused by crystalline phases transformation, intrinsic of zirconia. In this work, stabilized zirconia ceramic (ZrO2 with 3 mol % yttria) was produced using the synthesized powder obtained by the sol-gel process, in which citric acid was chosen as complexing agent and maize starch as gelling. The zirconia ceramic was characterized with respect to relative density (99.75±0.10 %), crystalline phases (predominantly tetragonal), microstructure (homogeneous and small grains), flexural strength (510±60 MPa), Vickers hardness (11.6±0.3 GPa) and fracture toughness (Niihara = 11.8±2.9 MPa.m1/2 and Evans = 10.9±1.2 MPa.m1/2). It can be concluded that the sol-gel process is an attractive route to obtain zirconia ceramics with good mechanical properties.

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