Development of Secondary Phases on Synroc Leached at 150˚C

Abstract

AbstractElectron microscopy techniques were used to identify secondary phases on the surface of Synroc after exposure to doubly deionized water (DDW) at 150 ˚C for time periods up to 532 days. After one day, Ti02 develops on perovskite in the form of polycrystalline crusts of anatase or epitaxial crystals of brookite (± anatase), and as scattered single crystals on hollandite and rutile-Magnéli phases. With increasing exposure time the anatase crusts exhibit slow grain growth and development of preferred orientation; whereas, the epitaxial brookite crystals appear to grow more rapidly. Dissolution of perovskite and P-bearing intermetallic particles results indirectly in the precipitation of monazite after 84 days. Additional alteration products observed over a range of time include crystalline Al-O-H phases and amorphous to poorly crystalline Fe-O-H phases which form as a result of the dissolution of Al-rich oxides and Fe-bearing intermetallic grains, respectively. A poorly crystalline Ru-O-H phase was found as an alteration product of Ru-bearing intermetallic particles after exposure to DDW for 336 days.