Open AccessIrreversible phase transitions in structural elements of synthetic opal
Author(s) -
N. I. Yurasov,
I. I. Yurasova,
А. И. Плохих,
N. K. Galkin,
V. A. Tetyanchuk,
E. B. Dolgikh
Publication year - 2019
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/1348/1/012082
Subject(s) - differential scanning calorimetry , phase transition , materials science , porosity , gravimetric analysis , amorphous solid , phase (matter) , cristobalite , chemical physics , mineralogy , analytical chemistry (journal) , thermodynamics , crystallography , chemistry , chromatography , composite material , physics , organic chemistry , quartz
The globular photonic crystal of artificial opal was synthesized by Stœber process in order to study its internal structure. Two methods were used to measure density and to determine porosity, which was 0.368. A fractal model of pores formation was considered for different silica phases, including the amorphous one. Assumptions were made on the type of pores inside globules. The differential scanning calorimetry method was used to reveal the fine multisection structure of the heat flow thermogram through the sample. The second-order phase transition was revealed. The experimental substantiation was given that phase transition is connected with the creation of β-cristobalite. A model was proposed for calculation of the number of component molecules leaving a sample at heating. Independent confirmation of calculation as per the proposed model was obtained by the gravimetric analysis.