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Hydrothermal SiO2 Nanopowders: Obtaining Them and Their Characteristics

1
Research Geotechnological Center, Far Eastern Branch of Russian Academy of Sciences, 30, Severo-Vostochny Highway, 683002 Petropavlovsk-Kamchatsky, Russia
2
School of Engineering, Far Eastern Federal University, 8, Sukhanova Str., 690950 Vladivostok, Russia
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(4), 624; https://doi.org/10.3390/nano10040624
Received: 21 February 2020 / Revised: 20 March 2020 / Accepted: 25 March 2020 / Published: 27 March 2020
(This article belongs to the Special Issue Sol-Gel Synthesis of Nanomaterials)
The technological mode of obtaining amorphous SiO2 nanopowders based on hydrothermal solutions is proposed in this study. Polycondensation of orthosilicic acid as well as ultrafiltration membrane separation, and cryochemical vacuum sublimation were used. The characteristics of nanopowders were determined by tunneling electron microscopy, low-temperature nitrogen adsorption, X-ray diffraction, and small-angle X-ray scattering. The scheme allows to adjust density, particle diameters of nanopowders, specific surface area, as well as diameters, area and volume of the pore. Thus, the structure of nanopowders is regulated—the volume fraction of the packing of spherical particles in aggregates and agglomerates, the size of agglomerates, and the number of particles in agglomerates. The pour densities of the nanopowders depend on the SiO2 content in sols, which were 0.02 to 0.3 g/cm3. Nanoparticles specific surface area was brought to 500 m2/g by low temperature polycondensation. Nanoparticle aggregates specific pore volume (0.2–0.3 g/cm3) weakly depend on powders density. The volume fraction of the packing of SiO2 nanoparticles in aggregates was 0.6–0.7. Solid samples of compacted nanopowders had a compressive strength of up to 337 MPa. Possible applications of hydrothermal SiO2 nanopowders are considered. View Full-Text
Keywords: hydrothermal solution; polycondensation of orthosilicic acid; ultrafiltration membrane separation; cryochemical vacuum sublimation; diameter of SiO2 nanoparticles; nanopowder structure hydrothermal solution; polycondensation of orthosilicic acid; ultrafiltration membrane separation; cryochemical vacuum sublimation; diameter of SiO2 nanoparticles; nanopowder structure
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Potapov, V.; Fediuk, R.; Gorev, D. Hydrothermal SiO2 Nanopowders: Obtaining Them and Their Characteristics. Nanomaterials 2020, 10, 624.

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