Mechanical activation of perovskite-type oxides for catalytic combustion

The effect of grinding on the catalytic properties of La-0.8Sr0.2MnO3 +/- l ambda powders prepared via a ceramic or sol-gel process was studied with re spect to the carbon black combustion temperature (T-C). For the ceramic pro cess, a milling time of 5 h led to a decrease of 77 degreesC in the T-C (fr om 615 to 538 degreesC) in relation with increasing BET surface area. Regar ding the sol-gel process, the T-C decreased from 535 to 505 degreesC after 1 h of grinding. Nevertheless, upon further milling (10 h), the benefit of the grinding effect disappeared due to a continuous decrease in the BET sur face area. Finally, grinding (when well controlled) enabled one to obtain c eramic powders showing performances as good as sol-gel materials (T(C)appro ximate to 540 degreesC).