The Fumed Silica Surface:  A Study by NMR

1996 ◽  
Vol 118 (21) ◽  
pp. 5103-5119 ◽  
Author(s):  
Changhua C. Liu ◽  
Gary E. Maciel
Keyword(s):  
Fumed Silica ◽  
Silica Surface

scholarly journals Peculiarities of Chemisorption of Dimethyl Carbonate on Silica Surface

2016 ◽  
Vol 17 (1) ◽  
pp. 88-92
Author(s):  
I.S. Protsak ◽  
E.M. Pakhlov ◽  
V.A. Tertykh
Keyword(s):  
Ir Spectroscopy ◽  
Fumed Silica ◽  
Dimethyl Carbonate ◽  
Silica Surface ◽  
Chemical Interaction ◽  
Spectroscopy Method ◽  
Silanol Groups

This paper presents the results of studies of dimethyl carbonate interaction with sites of the fumed silica surface. The investigations were performed in a vacuum quartz cuvette using IR spectroscopy method. Chemical interaction of dimethyl carbonate with sites of the dehydrated silica surface was shown to occur at temperature of 200 °C and higher, chemisorption processes take place involving both structural silanol groups and siloxane bridges on the surface.

scholarly journals The Morphology and Conductive Properties of Composite Material SiO2 – C

2015 ◽  
Vol 16 (4) ◽  
pp. 700-705
Author(s):  
I.F. Myronyuk ◽  
V.I. Mandzyuk ◽  
V.M. Sachko ◽  
Yu.O. Kyluk
Keyword(s):  
Composite Material ◽  
Fumed Silica ◽  
Silica Surface ◽  
Weight Ratio ◽  
Nitrogen Adsorption ◽  
Carbon Phase ◽  
Fumed Silica Nanoparticles ◽  
Structure Morphology ◽  
Open Porous Structure ◽  
Conductive Properties

The article explores the structure, morphology and conductive properties of composite material SiO2 – C using XRD, SAXS, low-temperature nitrogen adsorption, and impedance spectroscopy methods. It is set that SiO2 – C composite obtained by thermolytic decomposition of D-lactose, previously chemisorbed on fumed silica nanoparticles surface, has an open porous structure, in which mesopores of 6-12 nm in size are dominate. At weight ratio SiO2/C = 5/1 nanocrystallites of carbon phase in form of lamellar sheets of 0,4 × 0,4 × 5,0 nm3 in size contact with entire silica surface that results in composite material conductivity is 49 Оhm-1·m-1.

The Influence of Fumed Silica Properties on the Processing, Curing, and Reinforcement Properties of Silicone Rubber

1993 ◽  
Vol 66 (1) ◽  
pp. 48-60 ◽  
Author(s):  
H. Cochrane ◽  
C. S. Lin
Keyword(s):  
Surface Area ◽  
Silicone Rubber ◽  
Fumed Silica ◽  
Silica Surface ◽  
Silica Network ◽  
Surface Pretreatment ◽  
Structure Level ◽  
Network Strength ◽  
Reinforcement Model ◽  
Mixing Techniques

Abstract The present study uses a commercial heat cured silicone rubber formula (including a process aid) and mixing techniques to investigate the effect of varying fumed silica properties—including load, surface area, silica structure level, and surface pretreatment levels—on the rubber processing, curing, and cured physical properties. Based on the results, a simple silica network reinforcement model was developed to explain the changes in processing, curing, and vulcanizate properties of the silicone elastomers. The network is held together by silica-silica interactions and silica-polymer-silica bridge bonds between the silica aggregates. Increasing the silica loading, surface area, and structure level increases the number of interactions and hence the network strength. The pretreatment of the silica surface with organosilane molecules reduces the strength of silica-silica and silica-polymer interactions, therefore, weakening the silica network. Furthermore, the good interrelations between the initial plasticity, crepe hardening, curing, modulus yield, and durometer values strongly supports the concept of the presence of a silica network within the compounds under the low strain conditions of the tests.

scholarly journals Labeling and Probing the Silica Surface Using Mechanochemistry and 17O NMR Spectroscopy

2021 ◽  
Author(s):  
Chia-Hsin Chen ◽  
Frederic Mentink-Vigier ◽  
Julien Trébosc ◽  
Ieva Goldberga ◽  
Philippe Gaveau ◽  
...  
Keyword(s):  
Fumed Silica ◽  
Silica Surface ◽  
17O Nmr ◽  
Surface Information ◽  
Clear Identification ◽  
Common Interface ◽  
Cost Efficient ◽  
User Friendly ◽  
First Time ◽  
17O Nmr Spectroscopy

In recent years, there has been increasing interest in developing cost-efficient, fast, and user-friendly <sup>17</sup>O enrichment protocols to help understand the structure and reactivity of materials using <sup>17</sup>O NMR. Here, we show for the first time how ball milling (BM) can be used to selectively and efficiently enrich the surface of fumed silica, which is widely used at the industrial scale. Short milling times (up to 15 min) allowed modulation of the enrichment level (up to ca. 5%) without significantly changing the nature of the material. High-precision <sup>17</sup>O-compositions were measured at different milling times using LG-SIMS. High-resolution <sup>17</sup>O NMR analyses (including at 35.2 T) allowed clear identification of the signals from siloxane (Si-O-Si) and silanols (Si-OH), while DNP analyses, performed using direct <sup>17</sup>O polarization and indirect <sup>17</sup>O{<sup>1</sup>H} CP excitation, agreed with selective<sup> </sup>labeling of the surface. Information on the distribution of Si-OH environments at the surface was obtained from 2D <sup>1</sup>H-<sup>17</sup>O D-HMQC correlations. Finally, the surface-labeled silica was reacted with titania and using <sup>17</sup>O DNP, their common interface was probed and Si-O-Ti bonds identified.

Effects of Fumed Silica Treated with Functional Disilazanes on Silicone Elastomers Properties

1982 ◽  
Vol 55 (1) ◽  
pp. 233-244 ◽  
Author(s):  
M. T. Maxson ◽  
C. L. Lee
Keyword(s):  
Fumed Silica ◽  
Silica Surface ◽  
Silicone Elastomer ◽  
Treatment Level ◽  
Silicone Elastomers ◽  
Hardness Values

Abstract The reinforcement obtained with disilazane-treated silica in the platinumcatalyzed silicone elastomer was found to be dependent upon not only the amount of disilazane employed but also the structure of the disilazane and its distribution on the silica surface. Incorporation of a small amount of vinyl-functional disilazane such as (ViMe2Si)2NH along with (Me3Si)2NH (major treating agent) can significantly increase the modulus and hardness of the resulting elastomer. [ViMe2Si(OMe2Si)3]2NH gave higher modulus and hardness than (ViMe2Si)2NH, whereas (HMe2Si)2NH gave lower modulus and hardness values. The random treatment resulted in greater improvement of cured elastomer properties than the heterogeneous treatment at the same treatment level.

scholarly journals Investigation of chemical transformations of thiophenylglycoside of muramyl dipeptide on the fumed silica surface using TPD-MS, FTIR spectroscopy and ES IT MS

2014 ◽  
Vol 9 (1) ◽  
Author(s):  
Liana R Azizova ◽  
Tetiana V Kulik ◽  
Borys B Palianytsia ◽  
Aleksandr E Zemlyakov ◽  
Viktoriya N Tsikalova ◽  
...  
Keyword(s):  
Ftir Spectroscopy ◽  
Fumed Silica ◽  
Silica Surface ◽  
Muramyl Dipeptide ◽  
Chemical Transformations

Fluorescence Decay Study of Anisotropic Rotations of Substituted Pyrenes Physisorbed and Chemically Attached to a Fumed Silica Surface

2001 ◽  
Vol 105 (42) ◽  
pp. 10308-10315 ◽  
Author(s):  
Ilia N. Ivanov ◽  
Reza Dabestani ◽  
A. C. Buchanan ◽  
Michael E. Sigman
Keyword(s):  
Fumed Silica ◽  
Silica Surface ◽  
Fluorescence Decay ◽  
Decay Study

ADSORPTION MODELING OF POLYDIMETHYLSILOXANE ON SILICA: USING HEXAMETHYLDISILOXANE AS A MODEL PROBE

1997 ◽  
Vol 04 (05) ◽  
pp. 873-878 ◽  
Author(s):  
H. BARTHEL ◽  
L. RÖSCH ◽  
J. WEIS
Keyword(s):  
Fumed Silica ◽  
Active Sites ◽  
Gas Adsorption ◽  
Silica Surface ◽  
Surface Adsorption ◽  
Surface Interactions ◽  
Adsorption Modeling ◽  
Technical Interest ◽  
The Impact ◽  
Structure And Activity

Surface interactions play a most important part in the reinforcement of silicone elastomers, owing to the adsorption of the polydimethylsiloxane (PDMS) chain on the filler surface. The impact of the silylation of surface silanol groups on the surface structure and activity is of high technical interest. Hexamethyldisiloxane is an appropriate volatile probe to model the adsorption interactions of the PDMS polymer. In this study we investigated the static-volumetric gas adsorption of hexamethyldisiloxane on hydrophilic and silylated fumed silica, modified by dimethylsiloxy and trimethylsiloxy groups. The degree of silylation was controlled by the silanol content of the silica surface. Adsorption isotherms are discussed in terms of the adsorption energy and the heterogeneity of the active sites of adsorption.

scholarly journals Spectroscopic study on peculiarities of fumed silica hydridesilylation with triethoxysilane under fluidized bed conditions

2021 ◽  
Vol 12 (4) ◽  
pp. 314-325
Author(s):  
P. O. Kuzema ◽  
◽  
A. V. Korobeinyk ◽  
V. A. Tertykh ◽  
◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Surface Area ◽  
Fumed Silica ◽  
Silica Surface ◽  
High Surface ◽  
Space Filling ◽  
Silica Sample ◽  
Widespread Application ◽  
Silanol Groups ◽  
Heating Mode

Fumed silica has found widespread application in industry due to variety of fascinating properties. Owing to its specific manufacturing process, it consists of finely dispersed particles and is featured with large specific surface area covered by profoundly reactive silanol groups which are available for chemical grafting. Spherical shape of fumed silica particles and lacking porosity provides a space-filling structure. These characteristics implement the fume silica’s utilization as high-surface-area carriers for various catalysts, i.e. metallic nanometer-sized particles, organic moieties, etc. Currently a great attention is called to on-surface grafting to improve the silica-based carrier. Most of research is carried out in area of liquid phase chemistry involving an abundance of expensive and often toxic solvents while the space-filling properties of silica are favoring reactions in fluidized bed conditions. In current research fumed silica (A-300) was a subject for hydridesilylation with triethoxysilane under fluidized bed conditions. In all synthesis reported in current research the insignificant amount of solvent (1.00 wt. % of the amount used in typical wet-chemical modifications method) was spent for the silica surface silylation. While the mass ratio of silica/TES was kept constant, other conditions, i.e. solvent/catalyst presence, surface pretreatment, additional treatment with water, and the fluidized bed heating mode have been varied. FTIR spectroscopy revealed the interaction between groups of triethoxysilane and silica surface silanol groups and demonstrated the effect of modification conditions on the density of the hydridesilyl groups coverage. The results of FTIR spectroscopic studies have confirmed the presence of grafted silicon hydride groups on the surface of modified silica, as well as the presence of ethoxy and/or silanol groups – either intact or formed due to hydrolysis of the ethoxy groups. Titrimetric and spectrophotometric analysis was performed to estimate the concentration of grafted SiH groups (in all samples prepared under fluidized bed conditions their concentration ranged within about 0.28–0.55 mmol/g as dependent on the reaction conditions). Other important aspects of fluidization such as the presence of solvent and/or hydrolyzing agent, bed heating mode and the effect of the silica sample thermal pre-treatment are also discussed.

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