Key words: sol-gel method, supercritical carbon dioxide, synthetic opals, α-cristobalite, supercritical drying, electron microscopy (SEM), X-ray diffraction, Raman spectroscopy
The article describes the method of obtaining opal matrix by the sol-gel method, their
drying in supercritical carbon dioxide and the preparation of α-cristobalite by high
temperature annealing. The conditions for preparation of synthetic opals matrices
and the concentration of reagents for this process are described. A supercritical drying
regime of a silica xerogel with the production of porous matrices for further use and
subsequent annealing to obtain high-purity α-cristobalite is proposed. The transition
of a silica xerogel from an amorphous to a crystalline state as a result of supercritical
drying and annealing is shown. All processes were carried out under the control of
electron microscopy (SEM), Raman spectroscopy and X-ray diffraction analysis.
doi:10.1134/S1990793119070030