Abstract:

Hydroxyl groups， as ubiquitous extrinsic species present during preparation and service， significantly influence the comprehensive properties of silica glass. In this study， commercial JGS1 （high-hydroxyl concentration） and JGS3 （low-hydroxyl concentration） high-purity synthetic silica glass were selected to systematically investigate the effects of hydroxyls on material properties using differential scanning calorimetry （DSC）， temperature-dependent modulus testing， Raman spectroscopy， and vacuum ultraviolet spectroscopy. The results demonstrate that the hydroxyl incorporation leads to a 64 K reduction in the glass transition temperature and an increase in the isobaric heat capacity. In the temperature range of 300~1 300 K， both samples exhibit anomalous modulus hardening behavior， and the elastic modulus of JGS1 remains consistently lower than that of JGS3. Raman and vacuum ultraviolet spectral analyses indicate that JGS1 possesses fewer three-membered ring structures， and the introduction of hydroxyls effectively repairs oxygen-deficient defects， eliminating the absorption peak at 163 nm and causing a 7 nm blue shift in the ultraviolet cut off edge （from 172 nm to 165 nm）. This work elucidates the impact of hydroxyls on the thermomechanical and optical properties of silica glasses， providing a scientific basis for the compositional design of high-performance silica glasses.

Key words: silica glass, hydroxyl, chemical weakening, structural relaxation, vacuum ultraviolet transmittance