Replication micrography of ammonium perchlorate surfaces during their initial stages of thermal decomposition

The textural modifications that occur during the initiation, establishment and development of growth product nuclei in the thermal decomposition of ammonium perchlorate have been investigated by a replication technique which provides information concerning sub-surface structural changes. Soon after attaining reaction temperature, (001) crystal faces develop residual saucer-like hemispherical depressions ascribed to bubble formation during water loss from superficial layers. Subsequently small holes develop, which penetrate into the crystal, together with regions containing parallel-oriented surface ridges. The subsurface morphology of the holes shows branching below the surface, possibly guided along subsurface dislocations. From examinations of replicas of growth nuclei it was concluded that intranuclear pores were continuous, interconnected and tortuous.