The process of colloidal centre formation in alkali halide crystals during irradiation

Abstract

In this paper are analysed the processes of electronic centre aggregation to colloidal alkali metal particles in alkali halide crystals under radiation. It is shown that the existing theories of particle coalescence do not describe the experimentally observed kinetics of radiolysis. A new model of radiation colloid formation in these systems is proposed in which the interaction between colloidal centres is taken into account. In the present model the experimentally observed dose and temperature dependences, as well as the size distribution of the electron products of radiolysis, are explained.

Radiation-Induced Long-Lived Transients and Metal Particle Formation in Solid KCl–MgCl2 Mixtures

“…The impact of Mg 2+ concentration on speciation is complicated. Among the main processes determining electron trapping at room temperature are efficient formation of Cl 3 – and colloidal aggregation. , Colloidal centers are generally referred for aggregates of F-centers (regions with a high density of cations), which can be seen as small metal (fractal) particles of several hundred cations or alkali metal atoms embedded in ionic media with absorption and magnetic properties determined by size, shape, and composition . Some colloids are found after high doses of irradiation (or severe dose rate), while others require extra annealing to promote the diffusion of mobile F-centers.…”

“…40,41 Colloidal centers are generally referred for aggregates of F-centers (regions with a high density of cations), which can be seen as small metal (fractal) particles of several hundred cations or alkali metal atoms embedded in ionic media with absorption and magnetic properties determined by size, shape, and composition. 40 Some colloids are found after high doses of irradiation (or severe dose rate), while others require extra annealing to promote the diffusion of mobile F-centers. If the heating continues close to melting temperatures, eventually metallic particles will corrode through recombination reactions.…”

Effect of irradiation parameters on defect aggregation during thermal annealing of LiF irradiated with swift ions and electrons

“…25 The observation of metallic Li colloids was also reported from electron microscopy investigations of LiF irradiated with thermal neutrons. [26][27][28] Depending on the fluence ͑10 17 -10 20 neutrons/ cm 2 ͒, the average size of the Li colloids was in the range from several tens up to several hundred of nanometers. For these samples, optical measurements were not possible because the irradiation resulted in strong coloration and thus high optical density.…”