The Radiation Compaction of Vitreous Silica

Abstract

The dilatations (negative) caused by neutrons, 40–600 keV electrons, 140 keV H+, D+, He+, and gamma rays are given as a function of dose and are compared. The presaturation dependence is linear for neutrons, He+, and D+, and depends on the 0.5–0.7 power of dose for H+, electrons, and gamma rays. The dilatations are not temperature dependent from about 0°–100°C, hence are not thermally activated. The dilatations are explained as compaction of the silica structure resulting from oxygens moving into some of the ``free volume,'' the structural change being similar to that occurring on pressure, shock, or thermal compaction of vitreous silica. The mechanism given for the neutron-induced compaction involves the state of high vibrational excitation developed in the slowing down of scattered atoms. The compaction by gamma rays, electrons, protons, or deuterons is explained as caused by transient ionization relaxing Si–O binding to permit oxygens to move into the ``free volume'' where they may be locked-in on recombination by similar incidents occurring nearby. The reduced power dependence is explained as a ``hardening'' effect; succeeding events are more difficult to perform or are performed with lower probability. The compaction caused by He+ (140 keV) seems to possess an equal contribution from ionization compaction and that caused by energy transfer to atomic vibrations.

Kinetics of Thermally Activated Physical Processes in Disordered Media

“…It is known that it is possible to achieve compaction in pure silica by the same means [9], but it is also possible to obtain compaction by ion or electron irradiation. Primak [10] is probably the author who studied these processes the most.…”

Photoexpansion inAs2S3glass

“…36,38 Accordingly, irradiation can give the densification with mechanisms presently speculative. [15][16][17] We can also offer coherent explanation for a few exceptional cases listed in Table I. For Ge 1 As 4 Se 5 , a ternary nonstoichiometric glass, the structure is assumed to be fairly random and three-dimensional.…”

“…13 For instance, As 2 S 3 exposed at room temperature to light emitted from a He-Ne laser exhibits volume expansions of ϳ5%, which can be utilized as microlenses. 14 It may be valuable to mention here that, in SiO 2 glass, irradiation gives rise to an opposite effect, ''radiation compaction,'' [15][16][17] i.e., densification induced by irradiation, which can also be thermally recovered.…”

A Novel Approach for Preparation and In Situ Tensile Testing of Silica Glass Membranes in the Transmission Electron Microscope

“…The high energy e-beam generates structural and bonding defects and facilitates the bond-switching mechanism, which favors the rotation and migration of atomic clusters to accommodate plastic flow in the amorphous network (Zheng et al, 2010). However, high energy e-beam irradiation can also result in structural changes, such as densification in case of vitreous silica (Primak and Kampwirth, 1968;Dellin et al, 1977) and local deformations in case of amorphous silica films (Storm et al, 2005). These examples altogether indicate that under certain circumstances the conventionally brittle silica glass in general can exhibit enormous ductility and/ or superplasticity.…”