APPARENT VISCOSITY AND RELAXATION MECHANISM OF GLASSES BELOW GLASS-TRANSITION TEMPERATURE

The deformation mechanism of silicate glasses was analysed by the fibr e bending method far below the glass transition temperature based on a stretched exponential decay function of relaxation time; I - psi = ex p[-(t/tau) b]. The effects of atmospheric humidity were not observed. The relaxation time was found to increase with decreasing temperature and with pre-annealing heat treatment below glass transition temperatu re. In addition the stretching parameter increased with pre-annealing heat treatment of temperature suggesting wider distribution of relaxat ion time in the quenched sample, and that the glass approaches a more stable state by pre-annealing heat treatment even far below the glass transition temperature. It was also found that the activation energy f or relaxation inn eases with ina easing pre-annealing temperature and time.