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Year 2018 Volume 16, Issue 3 |
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Issues/2018/vol. 16 /Issue 3 |
L. V. Dubrovina, E. V. Makarova, T. N. Dymytriuk, T. V. Krupskaya, V. V. Turov, and V. V. Goncharuk
«Disperse Water-Containing Composites Based on Hydrophobic Pyrogenic Silica with Bentonite»
535–546 (2018)
PACS numbers: 62.23.Pq, 68.65.-k, 76.60.-k, 78.67.Sc, 81.07.-b, 82.56.Ub, 82.70.Uv
With high-speed mixing of water and hydrophobic fumed nanosilica (methyl silica—fumed silica modified with methyl groups, Ssp???300 m2/g, particles’ size of 5–7 nm), dispersed water-containing composites (DWC) are obtained and contain 90 w.f.% (30.9 vol.%) of water. When incorporating hydrophilic bentonite particles into composites, dispersed water-containing composites form a dry powder. This powder consists of water-filled microdroplets encapsulated in methyl silica shells of 1–3 ?m in size and coated with a layer of a hydrophobic–hydrophilic blend of hydrophobic silica and bentonite nanoparticles, which are formed from the initial bentonite particles due to their mechanical degradation during high-speed mixing of the DWC components. The volume content of water at a concentration of bentonite of 3 w.f.% is increased to 37.06 vol.%. The loss of water during drying of the samples at 40 and 105?Ñ for DWC at this concentration of bentonite decreases by 3–6%. The states of water in disperse water-containing composites from nanosilica and bentonite is applied to study the method of low-temperature 1H NMR-spectroscopy. The thermodynamic parameters of the strongly and weakly bound water layers and the interfacial energy of the water in hydrogels are determined. As found, when 3 w.f.% of bentonite is added to disperse water-containing composites, the concentration of weakly bound water (CuwW) is reduced from 8.75 to 6.675 g/g, and the interfacial energy of water (?S) is decreased from 7.8 to 7.2 J/g. The bentonite introduction does not affect the concentration of strongly bound water (CuwS) and the maximum decrease in free energy in the layer of strongly bound water (?GS). In the presence of bentonite, the interphase water clusters with a radius R???1 nm disappear; the fraction of clusters with a radius of 1.5–1.7 nm slightly increases. The interphase water domains in sizes from 1.7 to 9 nm virtually disappear, but the share of aqueous poly-associates with a radius ??10 nm is increased by several times.
Keywords: dispersed water-containing composite, hydrophobic nanosilica, bentonite, bound water, low-temperature 1H NMR-spectroscopy
https://doi.org/10.15407/nnn.16.03.535
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