LAUSR

The behavior of water in contact with amorphous silica (a-silica) surfaces and penetration into the subsurface has garnered significant interest over many decades.1‒24 In general, water has been shown to weaken silica in tension via stress corrosion cracking at a stress less than the normal fracture stress. Such behavior is caused by the commonly known reaction of a water molecule rupturing the strained siloxane bonds at a crack tip via the Michalske-Freiman model, enabling propagation of the crack.4,5 The MichalskeFreiman model assumes small twoand three-membered siloxane rings that have small siloxane (Si–O–Si) bond angles that show significantly increased bond rupture upon exposure to water.3 However, Tomozawa attributed degradation in strength of silica to the presence of molecular water and surface structural relaxation.25 Based on their IR data of changes in the high-frequency Si–O asymmetric Received: 9 September 2019 | Revised: 25 October 2019 | Accepted: 17 November 2019 DOI: 10.1111/jace.16923