Surface oxides of boron and B12O2 as determined by XPS

Mound Laboratoires has been investigating pyrotechnic materials for several years. Prior studies on the mechanism of ignition have been performed on Ti/KCIO4 and Ti/2B mixtures. These studies have shown the importance of the surface oxides of these materials in determining the mechanism of ignition. In the present study, XPS spectra of fused metal, oxidized fused boron and boron metal powder have been recorded. The spectra are interpeted by including the presence of a continuous boron suboxide layer. The results presented here are different from those previosuly reported, which suggests that the formation of boron oxide occurs in islets. The predominant suboxide will be shown to be BxOy, where x/y = 3. This oxide was found to be present independent of the degree of oxidation. Including this oxide in thickness calculations shows the oxidation of powders to be five layers or so thick, and also aids in understanding Ti/2B ignition.