Characterization of the glass transition in vitreous silica by temperature scanning small-angle X-ray scattering

TL;DR

This study uses temperature scanning small-angle X-ray scattering to investigate the glass transition in silica glasses, revealing hysteresis and differences based on hydroxyl content, with improved data quality over previous methods.

Contribution

It is the first to resolve hysteresis in silica glass during the glass transition using X-ray scattering and provides new kinetic parameters for high hydroxyl content silica.

Findings

Hysteresis observed between heating and cooling.

Higher hydroxyl content broadens and lowers the glass transition.

X-ray scattering derivative matches light scattering within 14%.

Abstract

The temperature dependence of the x-ray scattering in the region below the first sharp diffraction peak was measured for silica glasses with low and high OH content (GE-124 and Corning 7980). Data were obtained upon scanning the temperature at 10, 40 and 80 K/min between 400 K and 1820 K. The measurements resolve, for the first time, the hysteresis between heating and cooling through the glass transition for silica glass, and the data have a better signal to noise ratio than previous light scattering and differential thermal analysis data. For the glass with the higher hydroxyl concentration the glass transition is broader and at a lower temperature. Fits of the data to the Adam-Gibbs-Fulcher equation provide updated kinetic parameters for this very strong glass. The temperature derivative of the observed X-ray scattering matches that of light scattering to within 14%.