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A time resolved high energy X-ray diffraction study of cooling liquid SiO2
L B Skinner1, C J Benmore, J K R Weber
1X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
Physical Chemistry Chemical Physics : PCCP
|April 17, 2013
Summary
Researchers studied silica (SiO2) cooling from a melt using X-ray diffraction. Key structural changes were observed near the glass transition temperature and at higher temperatures correlating with density shifts.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Geochemistry
Background:
- Understanding the structural evolution of silica (SiO2) is crucial for materials science and geochemistry.
- The relationship between structural changes and thermodynamic properties like glass transition temperature (Tg) requires detailed investigation.
Purpose of the Study:
- To investigate the structural evolution of SiO2 upon cooling from the melt.
- To correlate observed structural changes with thermodynamic transitions and density variations.
Main Methods:
- High-energy X-ray diffraction was employed to measure the X-ray structure factor and pair distribution function.
- Aerodynamic levitation was used to handle SiO2 samples at high temperatures without container contamination.
Main Results:
- Small but significant changes in Si-O bond distance and peak width were detected around 1500 K, near the calorimetric glass transition temperature (Tg).
- Deviations from linear behavior in the first sharp diffraction peak (width, height, area) were observed around 1750 K, coinciding with a density maximum.
Conclusions:
- The study reveals distinct structural rearrangements in SiO2 occurring at specific temperatures during cooling from the melt.
- These structural changes are directly linked to the glass transition and density anomalies in SiO2.
