Maximum incorporation of oxygen radicals, O- and O2-, into 12CaO•7Al2O3 with a nanoporous structure

The effects of oxygen partial pressure (po) up to 400 atm on the generation of active oxygen radicals in 12CaO.7Al(2)O(3) (C12A7) was examined using a hot isostatic pressing technique. Concentrations of superoxide (O-2(-)) and oxygen anion radicals (O-), which were analyzed from a combination of electron paramagnetic spin resonance (EPR) and Raman spectroscopy, increased with po(2) The total concentration of the radicals reached 1.7 x 10(21) cm(3), which is comparable to the theoretical maximum, confirmed that dominant radical incorporation process is O2- (cage) + O-2 (atmosphere) --> O- (cage) + O-2(-) (cage). The radical incorporated C12A7 has a large magnetic susceptibility that obeys Curie's law down to 2.5 K without magnetic ordering, although a weak exchange interaction was suggested by the line narrowing of the EPR signal.