New poster at GRC Ceramics Conference 2018

Synthesis and characterization of graphene quantum dot containing ceria-zirconia
Özgür Keleş, Andrew C. Dina, Daniel Fok 
Abstract: Zirconia-based nanoparticles are used in various applications, such as catalyst, filter, oxygen storage, and sensor. Among many synthesis methods to produce zirconia-based nanoparticles, aqueous sodium borohydride (NaBH4) coprecipitation produces zirconia containing nano-pores. In this work, we extended the NaBH4 coprecipitation method to include ceria and graphene quantum dots (GQDs) in zirconia and characterized Ce-ZrO2 and GQD-Ce-ZrO2 nano-particles. These particles were calcined at 400 °C, 600 °C, and 700 °C to observe structural and phase changes. Aminated or carboxylated GQDs at 0.1 and 0.5 wt. % were added to the precursors to control nucleation sites for coprecipitation and to incorporate GQDs in zirconia. We performed SEM, TEM, XPS, XRD, and DSC characterization on calcined particles. SEM results showed agglomerated particles with clusters of few crystallites. DSC results were used to choose the calcination temperature and XRD results confirmed the tetragonal phase for calcinations >600 °C. Addition of ceria reduced the amorphous-to-tetragonal phase change temperature from 702 °C to 663 °C. XRD results showed that pure zirconia had ~19 nm crystal size; whereas, the ceria-zirconia had ~15 nm crystal size. TEM also supported the average crystal sizes found by the XRD. XPS compositional analysis showed that the Ce-ZrO2 was synthesized to a stoichiometric composition of Ce0.14Zr0.86O2. We observed agglomerated GQDs in the doped samples. Addition of GQDs changed the nano-porosity observed in zirconia via TEM. More studies are needed to elucidate nano-particle synthesis-structure relationships in the presence of GQDs.
TEM image was taken at EAG by Yulia Grozman, special thanks to Dr. Yanika Schneider.

Posted 23rd July 2018 by Ozgur Keles

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