Comparative analysis of the physicochemical characteristics of SiO2 aerogels prepared by drying under subcritical and supercritical conditions


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Abstract

SiO2-based aerogels have been produced be removing a solvent (ethanol or hexafluoroisopropanol) from lyogels both above and below the critical temperature of the alcohols (in the range 210–260 and 160–220°C, respectively). The resultant materials have been characterized by low-temperature nitrogen adsorption measurements, X-ray diffraction, thermal analysis, scanning electron microscopy, X-ray microanalysis, and small-angle and ultrasmall-angle neutron scattering. The results demonstrate that removing the solvent 20–30°C below the critical temperature of the solvent yields silica that is characterized by higher specific porosity and has the same or a larger specific surface area in comparison with the aerogels produced by drying under supercritical conditions. The nature of the solvent used and the solvent removal temperature influence the size and aggregation behavior of primary clusters and the cluster aggregate size in the aerogels.

About the authors

S. A. Lermontov

Institute of Physiologically Active Compounds

Author for correspondence.
Email: lermon52@yandex.ru
Russian Federation, Severnyi proezd 1, Chernogolovka, Noginskii raion, Moscow oblast, 142432

A. N. Malkova

Institute of Physiologically Active Compounds

Email: lermon52@yandex.ru
Russian Federation, Severnyi proezd 1, Chernogolovka, Noginskii raion, Moscow oblast, 142432

N. A. Sipyagina

Institute of Physiologically Active Compounds

Email: lermon52@yandex.ru
Russian Federation, Severnyi proezd 1, Chernogolovka, Noginskii raion, Moscow oblast, 142432

Kh. E. Yorov

Moscow State University

Email: lermon52@yandex.ru
Russian Federation, Moscow, 119991

G. P. Kopitsa

Konstantinov Institute of Nuclear Physics; Grebenshchikov Institute of Silicate Chemistry

Email: lermon52@yandex.ru
Russian Federation, Orlova Roshcha 1, Gatchina, Leningrad oblast, 188300; nab. Makarova 2, St. Petersburg, 199034

A. E. Baranchikov

Moscow State University; Kurnakov Institute of General and Inorganic Chemistry

Email: lermon52@yandex.ru
Russian Federation, Moscow, 119991; Leninskii pr. 31, Moscow, 119991

V. K. Ivanov

Kurnakov Institute of General and Inorganic Chemistry; National Research Tomsk State University

Email: lermon52@yandex.ru
Russian Federation, Leninskii pr. 31, Moscow, 119991; pr. Lenina 36, Tomsk, 634050

V. Pipich

Jülich Centre for Neutron Science Outstation at MLZ

Email: lermon52@yandex.ru
Germany, Lichtenbergstrasse 1, Garching, 85747

N. K. Szekely

Jülich Centre for Neutron Science Outstation at MLZ

Email: lermon52@yandex.ru
Germany, Lichtenbergstrasse 1, Garching, 85747

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