Structure of Microphase-Separated Silica/Siloxane Molecular Composites

1989 ◽  
Vol 171 ◽  
Author(s):  
Dale W. Schaefer ◽  
James E. Mark ◽  
David Mccarthy ◽  
Li Jian ◽  
C. -C. Sun ◽  
...  
Keyword(s):  
Phase Separation ◽  
Kinetic Studies ◽  
Organic Content ◽  
Small Particles ◽  
X Ray ◽  
Filled Elastomers ◽  
Polymeric Networks ◽  
Large Particles ◽  
Molecular Composites

ABSTRACTThe structure of several classes of silica/siloxane molecular composites is investigated using small-angle x-ray and neutron scattering. These filled elastomers can be prepared through different synthethic protocols leading to a range of fillers including particulates with both rough and smooth surfaces, particulates with dispersed interfaces, and polymeric networks. We also find examples of bicontinuous filler phases that we attribute to phase separation via spinodal decomposition. In-situ kinetic studies of particulate fillers show that the precipitate does not develop by conventional nucleation-and-growth. We see no evidence of growth by ripening whereby large particles grow by consumption of small particles. Rather, there appears to be a limiting size set by the elastomer network itself. Phase separation develops by continuous nucleation of particles and subsequent growth to the limiting size. We also briefly report studies of polymer-toughened glasses. In this case, we find no obvious correlation between organic content and structure.

The AMPIX electrochemical cell: a versatile apparatus forin situX-ray scattering and spectroscopic measurements

2012 ◽  
Vol 45 (6) ◽  
pp. 1261-1269 ◽  
Author(s):  
Olaf J. Borkiewicz ◽  
Badri Shyam ◽  
Kamila M. Wiaderek ◽  
Charles Kurtz ◽  
Peter J. Chupas ◽  
...  
Keyword(s):  
Electrochemical Cell ◽  
Function Analysis ◽  
Kinetic Studies ◽  
Spectroscopic Measurements ◽  
Battery Materials ◽  
X Ray ◽  
Complex Processes ◽  
Electrochemical Cycling ◽  
Ray Scattering

This article presents a versatile easy-to-use electrochemical cell suitable forin operando,in situmeasurements of battery materials during electrochemical cycling using a variety of X-ray techniques. Argonne's multi-purposein situX-ray (AMPIX) cell provides reliable electrochemical cycling over extended periods owing to the uniform stack pressure applied by rigid X-ray windows and the formation of a high-fidelity hermetic seal. The suitability of the AMPIX cell for a broad range of synchrotron-based X-ray scattering and spectroscopic measurements has been demonstrated with studies at eight Advanced Photon Source beamlines to date. Compatible techniques include pair distribution function analysis, high-resolution powder diffraction, small-angle scattering and X-ray absorption spectroscopy. These techniques probe a broad range of electronic, structural and morphological features relevant to battery materials. The AMPIX cell enables experiments providing greater insight into the complex processes that occur in operating batteries by allowing the electrochemical reactions to be probed at fine reaction intervals with greater consistency (within the charge–discharge cycle and between different methodologies) with potential for new time-dependent kinetic studies or studies of transient species. Representative X-ray and electrochemical data to demonstrate the functionality of the AMPIX cell are presented.

scholarly journals Synchrotron X-ray In Situ Tomography of Thermally Induced Phase Separation of Polylactic Acid in 1,4-Dioxane Solution

2018 ◽  
Vol 18 (12) ◽  
pp. 7496-7503 ◽  
Author(s):  
Swann Gay ◽  
Brice Calvignac ◽  
Landry Ouanssi Kamtcheu ◽  
Thomas Beuvier ◽  
Elodie Boller ◽  
...  
Keyword(s):  
Phase Separation ◽  
Polylactic Acid ◽  
Dioxane Solution ◽  
Thermally Induced Phase Separation ◽  
Thermally Induced ◽  
X Ray

In situ high temperature X-ray diffraction study of the kinetics of phase separation in the uranium-plutonium mixed oxide (U0.55Pu0.45)O2-x

2014 ◽  
Vol 1645 ◽  
Author(s):  
Romain VAUCHY ◽  
Renaud.C. BELIN ◽  
Anne-Charlotte ROBISSON ◽  
Fiqiri HODAJ
Keyword(s):  
Phase Separation ◽  
Room Temperature ◽  
Mixed Oxides ◽  
Oxygen Stoichiometry ◽  
X Ray Diffraction ◽  
Fundamental Interest ◽  
X Ray ◽  
Uranium Plutonium ◽  
Kinetics Of

ABSTRACTUranium-plutonium mixed oxides incorporating high amounts of plutonium are considered for future nuclear reactors. For plutonium content higher than 20%, a phase separation occurs, depending on the temperature and on the oxygen stoichiometry. This phase separation phenomenon is still not precisely described, especially at high plutonium content. Here, using an original in situ fast X-ray diffraction device dedicated to radioactive materials, we evidenced a phase separation occurring during rapid cooling from 1773 K to room temperature at the rate of 0.05 and 2 K per second for a (U0.55Pu0.45)O2-x compound under a reducing atmosphere. The results show that the cooling rate does not impact the lattice parameters of the obtained phases at room temperature but their fraction. In addition to their obvious fundamental interest, these results are of utmost importance in the prospect of using uranium-plutonium mixed oxides with high plutonium content as nuclear fuels.

Kinetics of high-pressure mineral phase transformations using in situ time-resolved X-ray diffraction in the Paris-Edinburgh cell: a practical guide for data acquisition and treatment

2008 ◽  
Vol 72 (2) ◽  
pp. 683-695 ◽  
Author(s):  
J. P. Perrillat
Keyword(s):  
High Pressure ◽  
Phase Transformations ◽  
Kinetic Studies ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Practical Guide ◽  
Set Up ◽  
Isothermal Kinetic

AbstractSynchrotron X-ray diffraction (XRD) is a powerful technique to study in situ and in real-time the structural and kinetic processes of pressure-induced phase transformations. This paper presents the experimental set-up developed at beamline ID27 of the ESRF to perform time-resolved angle dispersive XRD in the Paris-Edinburgh cell. It provides a practical guide for the acquisition of isobaric-isothermal kinetic data and the construction of transformation-time plots. The interpretation of experimental data in terms of reaction mechanisms and transformation rates is supported by an overview of the kinetic theory of solid-solid transformations, with each step of data processing illustrated by experimental results of relevance to the geosciences. Reaction kinetics may be affected by several factors such as the sample microstructure, impurities or differential stress. Further high-pressure kinetic studies should investigate the influence of such processes, in order to acquire kinetic information more akin to natural or technological processes.

scholarly journals Goethite Nanorods: Synthesis and Investigation of the Size Effect on Their Orientation within a Magnetic Field by SAXS

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2526
Author(s):  
Stephan Hinrichs ◽  
Larissa Grossmann ◽  
Eike Clasen ◽  
Hannah Grotian genannt Klages ◽  
Dieter Skroblin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Aspect Ratio ◽  
Small Particles ◽  
X Ray ◽  
Sensing Applications ◽  
X Ray Scattering ◽  
Weak Magnetic Fields ◽  
Large Particles ◽  
Alkaline Conditions ◽  
High Fields

Goethite is a naturally anisotropic, antiferromagnetic iron oxide. Following its atomic structure, crystals grow into a fine needle shape that has interesting properties in a magnetic field. The needles align parallel to weak magnetic fields and perpendicular when subjected to high fields. We synthesized goethite nanorods with lengths between 200 nm and 650 nm in a two-step process. In a first step we synthesized precursor particles made of akaganeite (β-FeOOH) rods from iron(III)chloride. The precursors were then treated in a hydrothermal reactor under alkaline conditions with NaOH and polyvinylpyrrolidone (PVP) to form goethite needles. The aspect ratio was tunable between 8 and 15, based on the conditions during hydrothermal treatment. The orientation of these particles in a magnetic field was investigated by small angle X-ray scattering (SAXS). We observed that the field strength required to trigger a reorientation is dependent on the length and aspect ratio of the particles and could be shifted from 85 mT for the small particles to about 147 mT for the large particles. These particles could provide highly interesting magnetic properties to nanocomposites, that could then be used for sensing applications or membranes.

Molecular Weight Dependence of Domain Structure in Silica-Siloxane Molecular Composites

1992 ◽  
Vol 274 ◽  
Author(s):  
Tamara A. Ulibarri ◽  
Greg Beaucage ◽  
Dale W. Schaefer ◽  
Bernard J. Olivier ◽  
Roger A. Assink
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Composite Materials ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Precursor Polymer ◽  
Molecular Weight Dependence ◽  
Molecular Composites ◽  
Filler Phase

ABSTRACTA detailed investigation of the molecular weight dependence of silica growth in in situ filled polydimethylsiloxane/tetraethylorthosilicate (PDMS/TEOS) materials was conducted using small angle neutron scattering (SANS). Composite materials were produced by using TEOS to simultaneously produce the glassy filler phase and to crosslink linear, hydroxyl terminated PDMS of variable molecular weight, M. Correlated domains of glassy filler were produced. The morphology of the in situ filled material showed a definite dependence on the molecular weight of the precursor polymer. The scale, R, of the glassy domains follows de Gennes' description of phase separation in a crosslinked system (R ∝ M1/2).

scholarly journals Synchronized fractionation and phase separation in binary colloids

Soft Matter ◽  
2020 ◽  
Vol 16 (39) ◽  
pp. 9042-9046
Author(s):  
Lian Dan Yao ◽  
Hong Yu Chen ◽  
Yan Shi ◽  
Ying Liang ◽  
Tian Hui Zhang
Keyword(s):  
Phase Separation ◽  
Size Fractionation ◽  
Small Particles ◽  
Large Particles ◽  
Step Crystallization

In binary colloids, size fractionation proceeds as two-step crystallization in which small particles and large particles crystallize sequentially.

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