scholarly journals FLUORESCENCE STUDIES FOR IN SITU MONITORING OF THE HYDROLYSIS AND POLYMERIZATION REACTIONS OF ORGANICALLY –MODIFIED TETRAMETHYLORTHOSILICATE

2010 ◽  
Vol 5 (3) ◽  
pp. 290-294
Author(s):  
Eko Sri Kunarti
Keyword(s):  
Condensation Reaction ◽  
Sol Gel ◽  
In Situ Monitoring ◽  
Condensation Polymerization ◽  
Surrounding Water ◽  
Fluorescence Studies ◽  
Hydrolysis And Condensation ◽  
Organically Modified ◽  
Kinetics Of

Monitoring of hydrolysis and condensation polymerization reactions of tetramethylorthosilicate-organosiloxane have been carried out. Proton transfer from the excited state of 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (pyranine) to surrounding water molecules was used as a sensitive fluorescence method for following the kinetics of water consumption during the early stages of the sol-gel polymerisation process. Changes in water/silane ratio, type of organosiloxane, mol ratio of organosiloxane to silica precursor and pH affected markedly the kinetic behavior of the hydrolysis and condensation reaction of tetramethylorthosilicate.   Keywords: hydrolysis, polymerisation, fluorescence, pyranine, tetramethylorthosilicate, organosiloxane.

In Situ Electrochemical Study of Copper Nanoparticles Stabilized with Food Grade Gelatin

2016 ◽  
Vol 705 ◽  
pp. 163-167 ◽  
Author(s):  
Ellaine M. Datu ◽  
Mary Donnabelle L. Balela
Keyword(s):  
Electroless Deposition ◽  
Reduction Rate ◽  
In Situ Monitoring ◽  
Mixed Potential ◽  
Cu Nanoparticles ◽  
Environment Friendly ◽  
Food Grade ◽  
Alternative Material ◽  
Kinetics Of

Commercially available conductive inks are typically made up of precious metal nanoparticles, such as gold (Au) and silver (Ag). Thus, cheaper metals like copper (Cu) are currently being explored as alternative material. Though Cu has a comparable conductivity to that of Ag, they tend to oxidize easily when exposed to air and water, which could limit their application. In this work, oxidation-stable Cu nanoparticles with mean diameter as small as 57 nm were prepared by simple electroless deposition in water. Food-grade gelatin was used as stabilizer, which makes the process more economical and environment-friendly. In situ monitoring of mixed potential was carried out during synthesis to understand the kinetics of the reaction. The mixed potential of the solution shifted negatively as the amount of gelatin was increased. This suggests faster reduction rate.

scholarly journals In situ monitoring of hydrothermal reactions by X-ray diffraction with Bragg–Brentano geometry

2020 ◽  
Vol 53 (4) ◽  
pp. 1163-1166
Author(s):  
Karsten Mesecke ◽  
Winfried Malorny ◽  
Laurence N. Warr
Keyword(s):  
Quantitative Information ◽  
In Situ Monitoring ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Saturated Vapour Pressure ◽  
Concrete Production ◽  
Aerated Concrete ◽  
Kinetics Of

This note describes an autoclave chamber developed and constructed by Anton Paar and its application for in situ experiments under hydrothermal conditions. Reactions of crystalline phases can be studied by successive in situ measurements on a conventional laboratory X-ray diffractometer with Bragg–Brentano geometry at temperatures <483 K and saturated vapour pressure <2 MPa. Variations in the intensity of X-ray diffraction reflections of both reactants and products provide quantitative information for studying the reaction kinetics of both dissolution and crystal growth. Feasibility is demonstrated by studying a cementitious mixture used for autoclaved aerated concrete production. During a period of 5.7 h at 466 K and 1.35 MPa, the crystallization of torbermorite and the partial consumption of quartz were monitored.

Prospects for Chemical Control and Engineering of Organically Modified Ceramics

1998 ◽  
Vol 550 ◽  
Author(s):  
Stephen E. Rankin ◽  
Alon V. McCormick
Keyword(s):  
Material Properties ◽  
Chemical Control ◽  
Sol Gel ◽  
Polymer Structure ◽  
New Materials ◽  
Reliable Model ◽  
Organically Modified ◽  
Silicon Alkoxides ◽  
Simple Pair ◽  
Kinetics Of

AbstractHydrolytic polycondensation of silicon alkoxides and organically modified alkoxides shows promise as a route to new materials for medicine. Mathematical models of this polymerization accelerate the development of these materials and processes for their production. With a reliable model, one can rapidly explore a wide variety of options for controlling material properties. Here we describe a model for kinetics of sol-gel copolymerization of a simple pair of ethoxysilanes: (CH3)3Si(OC2H5) and (CH3)2Si(OC2H5)2. We then describe how reactor configuration alone can be used to control of polymer structure by choosing how to mix the reactants. An example is shown of maximizing homogeneity at any reactor residence time of interest in the model copolymer system by using the time of addition of the faster-reacting monomer.

Sol-gel synthesis of biocompatible silica-chitosan hybrids and hydrophobic coatings

2008 ◽  
Vol 23 (8) ◽  
pp. 2053-2060 ◽  
Author(s):  
S. Smitha ◽  
P. Shajesh ◽  
P. Mukundan ◽  
K.G.K. Warrier
Keyword(s):  
Condensation Reaction ◽  
Sol Gel ◽  
Visible Region ◽  
Reaction Medium ◽  
Optical Transmittance ◽  
Hydrophobic Coatings ◽  
Glass Substrates ◽  
Sol Gel Process ◽  
Sol Gel Synthesis

A new organic–inorganic hybrid synthesized through a sol-gel process starting from alkoxysilane and chitosan is reported. Functionalization of the hybrid was effected through in situ hydrolysis–condensation reaction of methyltrimethoxysilane (MTMS) and vinyltrimethoxysilane (VTMS) in the reaction medium. The process yields highly transparent and hydrophobic silica–chitosan hybrids. The hybrid gel was investigated with respect to chemical modification, thermal degradation, hydrophobicity, and transparency under the ultraviolet-visible region. The extent of hydrophobicity had been tailored by varying the precursor ratio. SiO2–chitosan–MTMS hybrids showed a higher thermal stability than SiO2–chitosan–VTMS (SCV) hybrids with respect to hydrophobicity. Condensation of silsesquioxanes generated from the hydrolysis of MTMS and VTMS over the silica-chitosan particles impart hydrophobicity to the hybrid. The coatings of functionalized SiO2–chitosan precursor sol on glass substrates showed nearly 100% optical transmittance in the visible region. The present hybrid material may find application in optics and other industries.

Effect of the organic groups of difunctional silanes on the preparation of coated clays for olefin polymer modification

Clay Minerals ◽  
2010 ◽  
Vol 45 (4) ◽  
pp. 489-502 ◽  
Author(s):  
F. E. Monasterio ◽  
M. L. Dias ◽  
V. J. R. R. Pita ◽  
E. Erdmann ◽  
H. A. Destéfanis
Keyword(s):  
Condensation Polymerization ◽  
Polymer Modification ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Organically Modified ◽  
Structural Differences ◽  
Intercalated Nanocomposite ◽  
Clay Materials ◽  
Thermal Stability Of

AbstractSodium montmorillonite (MMT) was organically modified with hexadecyltrimethyl-ammonium ions and subsequently treated with dichlorosilanes and water, aimed at in situ silane condensation polymerization and modification of clay platelets by polysiloxane coatings. Dimethyldichlorosilane, methylphenyldichlorosilane, and diphenyldichlorosilane were used to produce three siloxane-modified organoclays. The structure and morphology of the clay materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric studies (TG) and scanning electron microscopy (SEM). XRD results showed that the silanes were effectively polymerized in the clay galleries, forming a nanocomposite of intercalated particles. A fraction of the siloxane formed is bonded to the clay surface by covalent siloxane bonds. Strong structural differences in both morphology and thermal stability of the materials may occur when changing methyl or phenyl groups in the siloxane structure. The formation mechanism of these intercalated nanocomposite particles is considered. Finally, these modified clays were incorporated in an olefin polymer and morphological analyses using transmission electron microscope (TEM) images were carried out.

Highly sensitive in situ monitoring of catalytic reactions by surface enhancement Raman spectroscopy on multifunctional Fe3O4/C/Au NPs

Nanoscale ◽  
2014 ◽  
Vol 6 (14) ◽  
pp. 7954-7958 ◽  
Author(s):  
Wenya Cai ◽  
Xianghu Tang ◽  
Bai Sun ◽  
Liangbao Yang
Keyword(s):  
Magnetic Field ◽  
Raman Spectroscopy ◽  
Catalytic Reaction ◽  
Catalytic Reactions ◽  
In Situ Monitoring ◽  
Au Nps ◽  
Highly Sensitive ◽  
Kinetics Of ◽  
The Magnetic Field

In situ monitoring and characterizing kinetics of catalytic reaction with SERS on multifunctional Fe3O4/C/Au NPs in the magnetic field.

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