scholarly journals Gas-phase crosslinking of the lignin on the nanoscale fumed silica surface

2021 ◽  
Vol 22 (4) ◽  
pp. 724-728
Author(s):  
L.V. Nosach ◽  
E.F. Voronin ◽  
E.M. Pakhlov ◽  
L.P. Golovkova ◽  
O. Sevastyanova ◽  
...  
Keyword(s):  
Gas Phase ◽  
Fumed Silica ◽  
Dispersion Medium ◽  
Silica Surface ◽  
Phenol Formaldehyde ◽  
Crosslinking Agent ◽  
Gas Dispersion

A method for the polymerization modification of nanoscale fumed silica by crosslinking a lignin layer adsorbed on a nanosilica surface under a gas dispersion medium is described. A mixture of phenol and formaldehyde in the presence of HCl proved to be the most effective crosslinking agent. It has been suggested that the crosslinking of lignin molecules occurs by a mechanism similar to the production of phenol-formaldehyde resins.

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 Atmospheric chemistry and physics in the atmosphere of a developed megacity (London): an overview of the REPARTEE experiment and its conclusions

2012 ◽  
Vol 12 (6) ◽  
pp. 3065-3114 ◽  
Author(s):  
R. M. Harrison ◽  
M. Dall'Osto ◽  
D. C. S. Beddows ◽  
A. J. Thorpe ◽  
W. J. Bloss ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Urban Atmosphere ◽  
Trace Gas ◽  
Chemical Components ◽  
Chemical Transformations ◽  
Specific Chemical ◽  
Gas Dispersion ◽  
Wide Range

Abstract. The REgents PARk and Tower Environmental Experiment (REPARTEE) comprised two campaigns in London in October 2006 and October/November 2007. The experiment design involved measurements at a heavily trafficked roadside site, two urban background sites and an elevated site at 160–190 m above ground on the BT Tower, supplemented in the second campaign by Doppler lidar measurements of atmospheric vertical structure. A wide range of measurements of airborne particle physical metrics and chemical composition were made as well as measurements of a considerable range of gas phase species and the fluxes of both particulate and gas phase substances. Significant findings include (a) demonstration of the evaporation of traffic-generated nanoparticles during both horizontal and vertical atmospheric transport; (b) generation of a large base of information on the fluxes of nanoparticles, accumulation mode particles and specific chemical components of the aerosol and a range of gas phase species, as well as the elucidation of key processes and comparison with emissions inventories; (c) quantification of vertical gradients in selected aerosol and trace gas species which has demonstrated the important role of regional transport in influencing concentrations of sulphate, nitrate and secondary organic compounds within the atmosphere of London; (d) generation of new data on the atmospheric structure and turbulence above London, including the estimation of mixed layer depths; (e) provision of new data on trace gas dispersion in the urban atmosphere through the release of purposeful tracers; (f) the determination of spatial differences in aerosol particle size distributions and their interpretation in terms of sources and physico-chemical transformations; (g) studies of the nocturnal oxidation of nitrogen oxides and of the diurnal behaviour of nitrate aerosol in the urban atmosphere, and (h) new information on the chemical composition and source apportionment of particulate matter size fractions in the atmosphere of London derived both from bulk chemical analysis and aerosol mass spectrometry with two instrument types.

scholarly journals Axial dispersion and mixing of coolant gas within a separate-effect prismatic modular reactor

2018 ◽  
Vol 4 (3) ◽  
pp. 167-178 ◽  
Author(s):  
Ibrahim Said ◽  
Shaoib Usman ◽  
Muthanna Al-Dahhan ◽  
Mahmoud Moharam ◽  
Vineet Alexander
Keyword(s):  
Gas Phase ◽  
Flow Rate ◽  
Dispersion Coefficient ◽  
Dispersion Model ◽  
Heat Fluxes ◽  
Axial Dispersion ◽  
Experimental Setup ◽  
Gas Dispersion ◽  
Axial Dispersion Coefficient ◽  
Separate Effect

Multiphase Reactors Engineering and Applications Laboratory performed gas phase dispersion experiments in a separate-effect cold-flow experimental setup for coolant flow within heated channels of the prismatic modular reactor under accident scenario using gaseous tracer technique. The separate-effect experimental setup was designed on light of local velocity measurements obtained by using hot wire anemometry. The measurements consist of pulse-response of gas tracer that is flowing through the mimicked riser channel using air as a carrier. The dispersion of the gas phase within the separate-effect riser channel was described using one-dimensional axial dispersion model. The axial dispersion coefficient and Peclet number of the coolant gas phase and their residence time distribution within were measured. Effect of heating intensities in terms of heat fluxes on the coolant gas dispersion along riser channels were mimicked in the current study by a certain range of volumetric air flow rate ranging from 0.0015 to 0.0034 m3/s which corresponding to heating intensity range from 200 to 1400 W/m2. Results confirm a reduction in the response curve spreads is achieved by increasing the volumetric air velocity (representing heating intensity). Also, the results reveal a reduction in values of axial dispersion coefficient with increasing the air volumetric flow rate.

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
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