DEGRADATION OF DRIED TI-PEROXY GELS MADE FROM METALLIC TITANIUM AND HYDROGEN-PEROXIDE

Pure aqueous Ti-peroxy gels with a pH of 4, made from metallic titanium and hydrogen peroxide, were heat dried at 60°C or freeze-dried at a final pressure of 1 × 10-2 Torr and then aged. Prior to measurements some samples were evacuated to 1 × 10-7 Torr during 4-24 h. Studies were made also on powders prepared from a solution of phosphate-buffered saline, metallic titanium, and hydrogen peroxide with a pH between 4.25 and 7.85 during the process period and on titania precipitates made from Ti(III) sulfate and KO2. The powders so obtained were examined with FT-IR and ESR methods. During aging, hydrogen peroxide is released from the dried Ti-peroxy gel powders. In a KBr matrix, gel powders first aged and then evacuated to 1 × 10-7 Torr show a vibration at 1385 cm-1. This vibration is shown to emanate from the KBrH2O2 interaction. Titanium superoxide (Ti(IV)O2-) radicals appear, as shown by ESR methods, both in dried pure Ti-peroxy gels and in powders made from buffered Ti-peroxo solutions under weakly acidic or neutral pH conditions. © 1990.