Healing of Glass in Humid Environments

Abstract

Chill checks of controlled depth were produced in soda-lime-silica glass, and an optimum humidity of 30 kPa (300 mbar) water vapor pressure was found to heal these checks in an annealing cycle. Critical factors were found to be afEuxing effect, having a direct dependence on moisture, followed by a drying operation at the annealing temperature. A four-step model is proposed for crack healing: (I) exposure of the crack surface to moisture at temperatures below TB, (2) formation of a gel layer, (3) closure of the crack resulting from the relief of stress (a minimum of 10 to 20 MPa applied compressive stress was determined to be necessary f o r complete closure), and ( 4 ) drying in the presence of a controlled atmosphere. [

Influence of Water on Crack Self-Healing in Soda-Lime Silicate Glass

“…The furnace atmosphere, and especially the relative humidity (RH), has also been observed to have a significant role. Holden and Frechette 10 analyzed the critical factor influencing healing of cracks formed from thermal down‐shock by a metal probe in soda‐lime silica glass for different annealing cycles. They found that a humidity of 30 kPa water vapor pressure was optimum for an annealing cycle at 550°C.…”

Contact residual stress relaxation in soda-lime glass

“…This was accompanied by a change in crack configuration in the surface of the specimen. The change included crack tip rounding, widening of crack opening and material pileup adjacent to the surface trace of the sides of the crack as has been reported by Hrma et al 10 Decrease in crack length especially under elevated temperature and humid conditions, has been studied extensively in the literature for glass, [17][18][19][20] and the phenomenon has been called crack healing. It is believed 10,20 that viscous flow at the temperatures involved is responsible for the changes in crack morphology that are observed.…”

High-Temperature Fracture Strength of a CVD-SiC Coating Layer for TRISO Nuclear Fuel Particles by a Micro-Tensile Test

“…In a previous study of the crack healing phenomenon of soda-lime glass, crack healing appears around the glass transition temperature and with an increase in the fracture strength. [26][27][28] From the results of the soda-lime glass, the developed micro-tensile test was standardized and verified successfully.…”