Effect of Synthesis Parameters on the Composition
and Properties of the Product Silica

G. F. Krysenko, E. I. Mel’nichenko, and D. G. Epov

Institute of Chemistry, Far East Division, Russian Academy of Sciences,
pr. Stoletiya Vladivostoka 159, Vladivostok, 690022 Russia

Received May 4, 2007

Abstract—The properties of two silica samples were studied; one sample precipitated by ammonia from a sat-
urated (NH₄)₂SiF₆ solution and the other washed out from the sublimate obtained by joint evaporation of
(NH₄)₂SiF₆ and Si₂. These silicas are fundamentally different compounds. Their chemical composition was
determined. Evolution of samples during heating to 1000 was interpreted using chemical analysis, IR spec-
troscopy, and X-ray powder diffraction. A possibility of removing fluorine and ammonia from test samples by
heat and chemical treatment is demonstrated. Fluorine impurities in the form of fluoroammonium salts are
removed completely during heating to 300400; surface fluoride ions are removed only upon heating to
800.

DOI: 10.1134/S0036023608070073

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