Photoinitiated Chain Reactions in Low Temperature Solids.

摘要

One of the primary goals of the Air Force's High Energy Density Materials Research Program is to identify new materials which might serve the nation's needs for revolutionary (as well as evolutionary) new propellant materials. The search for new metastable species is made difficult because thermodynamic instability is often accompanied by kinetic reactivity that is, higher energy materials are often the most reactive and therefore the most difficult to store for finite periods of time. An important key to success will be reducing the kinetic reactivity of a solid propellant until it is ignited. With this in mind, it is likely that any new propellant material will have to be stored as a low temperature solid, or perhaps in a low temperature solid matrix. Our research program was designed to investigate fundamental properties of solid state reactions. Fundamental aspects of chain reactions in amorphous solid films have been investigated at cryogenic temperatures. Mechanisms of reaction initiation, propagation and termination are described. Most of the experimental studies of this type have been focused on photochlorination reactions of simple hydrocarbons with molecular chlorine in the solid state, photopolymerization reactions of solid formaldehyde, and photodestruction of solid ozone and mixtures of ozone with water and chlorine. Methods have been developed for characterizing the physical properties of vapor-deposited films (van der Waals glasses) at low temperatures. Finally, a simple theory of chain reactions in pure amorphous solids and in binary amorphous solid solutions has recently been developed which accounts for most of the experimental observations made on these systems to date.