Alloy Glass-Derived Composites in the System of Zr-Pd-Pt-Ce for Catalytic Soot Oxidation

This study investigates the formation and soot removal properties of four composite materials derived from alloy glasses in the system of Zr-Pd-Pt-Ce. Amorphous Zr65Pd35, Zr65Pd30Pt5, Zr60Pd35Ce5, and Zr60Pd30Pt5Ce5 were subjected to a heat treatment at 800 °C for 3 h in air, resulting in the formation of composites containing PdO, Pd and a mixture of tetragonal and monoclinic ZrO2 phases. Their microstructure was identified as composites in which PdO (Pd) precipitates are were dispersed in a ZrO2 matrix. The oxidation of soot over the composites was initiated at lower temperatures, reaching the completion of removal at approximately 600 °C, which was superior to that of non-catalytic soot combustion. The sequence in which the removal temperatures decreased was as follows: Zr65Pd35 > Zr60Pd35Ce5 > Zr60Pd25Pt5Ce5 > Zr65Pd30Pt5. The microstructure emerges as the predominant factor influencing soot oxidation activity, where the oxidation reaction rate was mainly governed by the interface length between PdO and ZrO2. The present results identified a novel bulk-type catalytic composite material, which was derived by a simple process from alloy glasses for the purpose of low-temperature soot oxidation.