Nucleation and Growth of Fe(III)/PO4 Clusters

1996 ◽  
Vol 432 ◽  
Author(s):  
J. Rose ◽  
A. M. Flank ◽  
A. Manceau ◽  
A. Masion ◽  
J. Y. Bottero ◽  
...  
Keyword(s):  
Local Structure ◽  
3D Model ◽  
Nucleation And Growth ◽  
Local Scale ◽  
Exafs Spectroscopy ◽  
Hydrolysis Of

AbstractThe first stages of the hydrolysis of Fe(III) in presence of PO4 were studied at the local (P k-edge and Fe k-edge EXAFS spectroscopy) and semi-local scale (SAXS). The presence of PO4 hinders the polymerization of iron at the edge sharing dimer step. Phosphate probably governs the local structure leading to the formation of small and dense clusters. The fitting of both k-edge EXAFS spectroscopies requiered the use of a new 3D model of each nucleation step.

Local Structure of Ferrihydrite and Feroxyhite by Exafs Spectroscopy

Clay Minerals ◽  
1993 ◽  
Vol 28 (2) ◽  
pp. 165-184 ◽  
Author(s):  
A. Manceau ◽  
V. A. Drits
Keyword(s):  
Local Structure ◽  
Temperature Stability ◽  
Coherent Scattering ◽  
Structural Features ◽  
Exafs Spectroscopy ◽  
Partial Hydrolysis ◽  
Ferric Nitrate ◽  
Static Disorder ◽  
Local Structures ◽  
Hydrolysis Of

AbstractSynthetic 2-line and 6-line ferrihydrite and feroxyhite samples prepared from ferric salt solutions have been investigated by EXAFS spectroscopy. All these materials have been found to be short-range ordered, consisting of Fe octahedra linked by comers, edges, and faces. Their local structures are related to those of well-crystallized (oxyhydr)oxides, and the absence of hkl reflections in some samples is attributed to the small size of coherent scattering domains. The presence of face sharings indicates that these materials have structural similarities with hematite. Based on Fe-Fe distances and the analysis of the static disorder, it has been concluded that the local structure of feroxyhite is close to that of hematite, whereas ferrihydrite has common structural features with both hematite (αFe203) and cdβFeOOFI. The local structure of ferrihydrite thus differs from that of aqueous Fe polymers obtained by the partial hydrolysis of ferric nitrate and chloride solutions. Differences of local structures among hydrous Fe oxides and aqueous polymers have been interpreted on the basis of a room temperature stability phase diagram established for well-crystallized (oxyhydr)oxides.

EPR of Cu(II) in Sol-Gel Prepared SiO2 Glass

1986 ◽  
Vol 73 ◽  
Author(s):  
S. Dave ◽  
R. K. Maccrone
Keyword(s):  
Local Structure ◽  
Copper Ions ◽  
Sol Gel ◽  
Epr Spectra ◽  
Sio2 Glass ◽  
Structural Probe ◽  
Hydrolysis Of

ABSTRACTSiO2 glass has been prepared by the hydrolysis of TEOS in alcohol using HCl and NH4OH to control the pH. Copper ions were incorporated from the acetate to act as structural probe ions during the process of gellation and calcination. The local structure of copper ions was investigated using EPR determined at 300 K and 10 K.It was found that the pH of the solution had a profound effect on the EPR spectra of the copper in the gels and glasses, indicating differences in the local structure.

X-ray diffraction, neutron scattering and EXAFS spectroscopy of monoclinic zirconia: analysis by Rietveld refinement and reverse Monte Carlo simulations

2002 ◽  
Vol 35 (4) ◽  
pp. 434-442 ◽  
Author(s):  
Markus Winterer ◽  
Robert Delaplane ◽  
Robert McGreevy
Keyword(s):  
Monte Carlo ◽  
Neutron Scattering ◽  
Rietveld Refinement ◽  
Local Structure ◽  
Exafs Spectroscopy ◽  
Scattering Data ◽  
Accurate Information ◽  
Reverse Monte Carlo ◽  
Monoclinic Zirconia ◽  
X Ray

Extended X-ray absorption fine structure (EXAFS) and neutron scattering data from monoclinic zirconia are analysed independently and simultaneously by reverse Monte Carlo (RMC) modelling. X-ray and neutron powder diffraction data are analysed by Rietveld refinement. The results are compared with respect to the local structure around the zirconium cations. Monoclinic zirconia was chosen as a model system for the comparison of structural information obtained by EXAFS spectroscopy and scattering methods because it is crystalline but also has some local disorder. In the case of zirconia, analysis of EXAFS spectra by RMC modelling results in reliable and accurate information on the local structure, consistent with neutron scattering and diffraction experiments.

Local scale-based 3D model retrieval for design reuse

2008 ◽  
Vol 43 (3-4) ◽  
pp. 294-303 ◽  
Author(s):  
Xiao-Jun Zheng ◽  
Yi-Shou Wang ◽  
Hong-Fei Teng ◽  
Fu-Zheng Qu
Keyword(s):  
3D Model ◽  
Local Scale ◽  
3D Model Retrieval ◽  
Design Reuse ◽  
Model Retrieval

Preparation and Characterization of Monodispersed Colloidal Particles

MRS Bulletin ◽  
1989 ◽  
Vol 14 (12) ◽  
pp. 23-28 ◽  
Author(s):  
Tadao Sugimoto
Keyword(s):  
Metal Ions ◽  
Colloidal Particles ◽  
Fine Particles ◽  
Science And Technology ◽  
Monomer Concentration ◽  
Nucleation And Growth ◽  
Constituent Particle ◽  
Monodispersed Particles ◽  
Critical Supersaturation ◽  
Hydrolysis Of

Recently the science and technology of fine particles have been greatly advanced to meet the urgent demands of modern industries for specific and sophisticated functions for various materials, including catalysts, sensors, electromagnetic devices, and photosensitive materials. Monodispersed colloidal Systems are invaluable for this purpose because the entire system's uniform physicochemical properties directly reflect the properties of each constituent particle. Procedures for modifying monodispersed particles have progressed remarkably in recent years so that specific characteristics can be achieved. This article focuses on the backgrounds of science and technology for controlling the properties of inorganic monodispersed particles and on new developments in this field.Colloidal particles are normally formed through a sequential process of nucleation and growth of the nuclei. To obtain a monodisperse System, the two stages must be strictly separated and nucleation avoided during the growth period. Since the steady concentration of monomers in the growth stage is determined by the balance between the rates of generation of monomers and their consumption by particle growth, the generation or introduction rate of monomers must be controlled so that it is low enough to keep the balanced monomer concentration below the critical supersaturation after the nucleation period. Typically, the initial concentrations of metal sait, pH, and temperature are adjusted to meet this requirement for the formation of monodispersed metal hydrous oxide particles by forced hydrolysis of metal ions.An artificial separation between nucleation and growth processes may be achieved by “seeding,” in which foreign particles are introduced into the solution of monomers below the critical supersaturation. One may also lower the pH in hydrolysis of metal ions, dilute with solvent, add chelating agents, or suddenly change the temperature just after limited nucleation. All these procedures could cause the monomer concentration above the critical supersaturation to plunge to a level below it.

Rod-Like Rutile Nanoparticles: Synthesis, Structure and Morphology

2017 ◽  
Vol 50 ◽  
pp. 32-40 ◽  
Author(s):  
Volodymyr Kotsyubynsky ◽  
Ivan Myronyuk ◽  
Volodymyr Chelyadyn ◽  
Andrii Hrubiak ◽  
Volodymyr Moklyak ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Hydrochloric Acid ◽  
Specific Surface ◽  
Reaction Medium ◽  
Nucleation And Growth ◽  
Molar Ratio ◽  
Structure And Morphology ◽  
Nanoparticles Synthesis ◽  
Preferred Oriented ◽  
Hydrolysis Of

Nanodispersed rutile with rod-like particles is synthesized by hydrolysis of TiCl4 in hydrochloric acid - ethanol alcohol aqueous solution. It is found that the specific surface area, crystallite size and degree of agglomeration are determined by molar ratio of ethanol in reaction medium. According to HR-TEM images and XRD data rutile crystallites are preferred oriented along the [001] axis. The analysis of the Raman spectra for samples with different morphology is performed. The model of rutile nanorods nucleation and growth is proposed.

scholarly journals Reconciling structure prediction of alloyed, ultrathin nanowires with spectroscopy

2021 ◽  
Author(s):  
Scott C. McGuire ◽  
Amani M. Ebrahim ◽  
Nathaniel Hurley ◽  
Lihua Zhang ◽  
Anatoly I. Frenkel ◽  
...  
Keyword(s):  
Local Structure ◽  
Structure Prediction ◽  
Exafs Spectroscopy ◽  
Combined Approach ◽  
Complementary Techniques

EDS and EXAFS spectroscopy are used as complementary techniques to investigate the local structure of bimetallic ultrathin nanowires. Results highlight the importance of using a combined approach to achieve an accurate understanding of these systems.

Titania Nanocrystals-Dispersed Coatings from SiO2-TiO2 Gel Films through Hydrolysis and Dissolution

2006 ◽  
Vol 317-318 ◽  
pp. 565-568 ◽  
Author(s):  
Atsunori Matsuda ◽  
T. Kogure ◽  
Hiroyuki Muto ◽  
Mototsugu Sakai ◽  
Kiyoharu Tadanaga ◽  
...  
Keyword(s):  
Sol Gel ◽  
Nucleation And Growth ◽  
Hot Water ◽  
Crystal Habit ◽  
Hot Water Treatment ◽  
Photocatalytic Activities ◽  
New Applications ◽  
Water Treatments ◽  
Hydrolysis Of ◽  
Component Migration

Anatase nanocrystals were formed on sol-gel derived SiO2-TiO2 coatings with water vapor or hot water treatments. The anatase nanocrystals were precipitated through hydrolysis of Si-O-Ti bonds, dissolution of SiO2 component, migration of hydrolyzed titania species, and nucleation and growth. The process temperatures can be lowered below 60oC, which should open new applications. It was found that the crystal habit of titania was changes from roundish anatase to sheet-like titania by applying vibration during the hot water treatment. The nanosheets were identified as hydrated titania, TiO2 . mH2O, with layerd structure. The coatings of hydrated titania showed high photocatalytic activities and excellent antifogging properties due to their unique morphology.

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