Synthesis of palladium nanoparticles in a ceramic matrix using radiation grafting method

Silicon carbide (SiC) ceramics containing palladium (Pd) nanoparticles were synthesized by the combination of the radiation grafting method, which allowed for uniform dispersion of Pd ions in polycarbosilane (PCS), and subsequent heat treatment, which was used to promote the bleedout phenomenon. The size and distribution of the Pd nanoparticles varied with the heat-treatment temperature. TEM and XRD analyses indicated that Pd nanoparticles of 2-5 nm in size were homogeneously distributed in the SiC ceramic matrix at temperatures lower than 1173 K. At a temperature of 1373 K, the size of these particles was found to increase and a portion of Pd was changed into Pd silicide. The Pd nanoparticles in samples heated at temperatures lower than 1173 K showed catalytic activity for hydrocarbon oxidation, whereas samples treated at 1373 K did not show any catalytic activity. These results suggest that Pd nanoparticles were formed on the SiC matrix at temperatures lower than 1173 K. The bleedout process enables the production of Pd nanoparticles as a combustion catalyst from radiation-grafted Pd-PCS.