REAL-TIME PROBE OF REACTION CENTERS IN SOLID COMBUSTIONS BY QEXAFS ONTHE SUB-2ND TIME-SCALE

A QEXAFS (quick-scanning EXAFS) technique has been devised to follow t he local atomic coordination changes about selected reactants in a cla ss of highly exothermic solid combustion reactions. Real-time EXAFS me asurements during the combustion were made in the time frame of a few seconds. By tuning the monochromator to a specific energy, at which ma ximum changes occur in an EXAFS feature of an element transforming fro m the reactant to the product phase, a time resolution of 20 ms was ac hieved. The Ni + Al -> NiAl reaction has been investigated in some det ail in light of a possible intermediate phase in the so-called after-b urn region. The present QEXAFS findings together with the recent time- resolved diffraction data on the same system lends, for the first time , experimental insights into the structural macrokinetics of this clas s of combustion systems.