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.

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.

Sol-Gel Process form Heterometallic Alkoxides to Incorporate Alkaline- and Rare Earths in Alumina for automotive Applications

1996 ◽  
Vol 431 ◽  
Author(s):  
C. K. Narula
Keyword(s):  
Elevated Temperatures ◽  
Sol Gel ◽  
Automotive Applications ◽  
Automotive Catalysts ◽  
Heterometallic Alkoxides ◽  
Sol Gel Process ◽  
Alkaline Earths ◽  
Cost Of Materials ◽  
Gel Processing

AbstractThe high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, we briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. We will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.

scholarly journals Synthesis and Characterization of Modified Cellulose Acetate Propionate Nanocomposites via Sol-Gel Process

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Patrycja Wojciechowska ◽  
Zenon Foltynowicz ◽  
Marek Nowicki
Keyword(s):  
Cellulose Acetate ◽  
Sol Gel ◽  
Hybrid Nanocomposites ◽  
Organic Polymer ◽  
Nmr Studies ◽  
Force Microscopy ◽  
Atomic Force ◽  
Cellulose Acetate Propionate ◽  
Sol Gel Process ◽  
Modified Cellulose

In this study novel organic-inorganic hybrid nanocomposites were synthesized from modified cellulose acetate propionate (MCAP) via sol-gel reaction at ambient temperature. The inorganic phase was introduced in situ by hydrolysis-condensation of tetraethoxysilane (TEOS) in different concentrations, under acid catalysis, in the presence of organic polymer dissolved in acetone. The chemical modification of CAP was monitored by infrared spectroscopy (IR). The nanocomposites structure was characterized by IR analysis and solid state29Si NMR studies. The spectral data revealed that organic and inorganic phases are linked through covalent bound. Surface morphology of the samples and the degree of dispersion of inorganic phase in the polymer matrix were investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The actual incorporation of the inorganic component into the hybrid nanocomposites was deducted from the residual weight according to thermogravimetric analysis (TGA).

A Solid State Multinuclear Magnetic Resonance Study of the Sol-Gel Process using Polysilicate Precursors

1986 ◽  
Vol 73 ◽  
Author(s):  
W. G. Klemperer ◽  
V. V. Mainz ◽  
D. M. Millar
Keyword(s):  
Solid State ◽  
Magnetic Resonance ◽  
Sol Gel ◽  
Building Blocks ◽  
Magnetic Resonance Study ◽  
Solvent Content ◽  
Molecular Building Blocks ◽  
Nmr Study ◽  
Sol Gel Process ◽  
Nmr Techniques

ABSTRACTA solid state multinuclear NMR study of the sol-gel process was performed using the molecular building blocks tetramethoxysilane, hexamethoxydisiloxane, octamethoxytrisiloxane and octamethoxyoctasilsesquioxane as precursor monomers. Water content, solvent content, and hydrolysis/condensation processes were monitored using 17O, 13C, and 29Si FT, FTMAS and CPMAS NMR techniques.

Undoped and Doped Perovskite Films: Sol-Gel Processing and Characterization

1991 ◽  
Vol 243 ◽  
Author(s):  
Mareike Klee ◽  
Rainer Waser
Keyword(s):  
Crystal Structure ◽  
Field Strength ◽  
Remanent Polarization ◽  
Sol Gel ◽  
Insulation Resistance ◽  
Sol Gel Process ◽  
Gel Processing

AbstractThin undoped Pb(ZrxTi1−x)O3 (x=0.2-0.75), BaTiO3, SrTiO3 as well as acceptor (Mn, Ni) and donor (La, Ce) doped films with thicknesses of 0.2-1 μm have been deposited by a modified sol-gel process. The crystal structure and the morphology of the films as a function of the processing and composition were analyzed. The films were characterized with respect to their ferroelectric and dielectric properities e.g. permittivity, remanent polarization, coervice field strength, insulation resistance.

Ultrasmooth metal halide perovskite thin films via sol–gel processing

2016 ◽  
Vol 4 (21) ◽  
pp. 8308-8315 ◽  
Author(s):  
Ross A. Kerner ◽  
Lianfeng Zhao ◽  
Zhengguo Xiao ◽  
Barry P. Rand
Keyword(s):  
Thin Film ◽  
Film Formation ◽  
Sol Gel ◽  
Metal Halide ◽  
Film Morphology ◽  
Metal Halide Perovskite ◽  
Sol Gel Process ◽  
Thin Film Formation ◽  
Halide Perovskite ◽  
Gel Processing

We show that metal halide perovskite thin film formation is a sol–gel process which allows us to improve film morphology, achieving roughness ∼1 nm via process and additive engineering.

Influence Of Hybridation With A Silicate Network On The Properties Of An Eu 3+ Complex Derived From Dipicolinic Acid

1999 ◽  
Vol 576 ◽  
Author(s):  
A. C. Franville ◽  
D. Zambon ◽  
R. Mahiou ◽  
Y. Troin ◽  
J. C. Cousseins
Keyword(s):  
Organic Molecules ◽  
Dipicolinic Acid ◽  
Sol Gel ◽  
Silicate Network ◽  
Hybrid Gels ◽  
Organic Species ◽  
Covalent Grafting ◽  
Sol Gel Process ◽  
Gel Processing ◽  
The Eu

ABSTRACTIn this paper, the preparation, the characterization and the optical features of organicinorganic materials incorporating a trivalent europium organic chelate into a silicate network are described. The covalent grafting and the sol-gel process allow to obtain monophasic hybrid gels in which the structure and the activity of the organic molecules were retained. The Eu3+ coordination mode is not sensitive to the sol-gel processing conditions whereas the morphology of materials, their thermal resistance and their luminescence properties may be adjusted. Characteristics of hybrid compounds are compared to those of the corresponding organic species.

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.

Sol-Gel Processing of Advanced Dielectric Ceramics for Microwave Applications

1989 ◽  
Vol 155 ◽  
Author(s):  
M. Schnoeller ◽  
W. Wersing
Keyword(s):  
Sol Gel ◽  
Wet Milling ◽  
X Ray Diffraction ◽  
Powder Morphology ◽  
Drying Procedures ◽  
Microwave Components ◽  
Sol Gel Process ◽  
Dielectric Ceramics ◽  
Gel Processing

ABSTRACTHighly dielectric ceramics make it possible to markedly miniaturize passive microwave components. We have successfully synthesized ceramic powders of the most important microwave ceramic systems (ZrTiSn)O2, Ba(TiNiZnTa)O3 and Ba(MgTa)O3 by using the sol-gel process. Nonaqueous solutions of metal organics together with different inorganic metal salts were used as precursors. The gels derived from these solutions are homogeneous and transparent. Different drying procedures were investigated in order to optimize powder morphology. Thermoanalytic methods and high -temperature x-ray diffraction were used to study the decomposition of xerogels and the formation of crystal phases, respectively. The calcination process was found to be complete at temperatures well below 750 °C.For the production of barium-containing powders, wet milling must be avoided because this washes out barium and thus causes undesired phases to appear. A dry milling step of the xerogel solves this problem. The prepared (ZrTiSn)O2 and Ba(TiNiZnTa)O3 already equal or surpass the quality of conventionally prepared ceramics.

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