APAM Faculty & Students Featured on NSLS Science Highlights
Prof. Siu-Wai Chan, Dr. Feng Zhang, Prof. Irving Herman, Dr. Richard Robinson, and Dr. Joan Raitano were featured in Science Highlights, National Synchrotron Light Source at Brookhaven National Laboratory, for their recent paper entitled “Phases in ceria-zirconia binary oxide (1-x)CeO2--xZrO2 nanoparticles: the effects of particle size, the redox environment and the Ce3+ concentration”. J. of Appl. Physics, 99, 0843131-0843138 (2006).
"Cerium oxide has been widely investigated as a key component in catalysts and as an electrolyte for solid oxide fuel cells because of its ability to release or store oxygen when in its cubic fluorite structure. This property, which is the alleged source of the oxygen storage capacity (OSC) of ceria, is much enhanced by a large surface area and a small particle size. Particle-size stability at high temperatures is a major issue for pure ceria, however. At high temperatures, ceria particles are easily coarsened, resulting in a smaller total surface area and a lower catalytic efficiency. Alloying with other metal oxides can halt this coarsening process; in particular, zirconia is most effective in this regard without significantly decreasing the oxygen activity. However, the zirconia content for most effective catalytic use will cause the binary oxide in micron-sized particles to contain a substantial amount of tetragonal phase that does not have the OSC properties, i.e. it does not supply and support the oxygen transport in and out of the solid oxide. In our study, nanoparticles of ceria-zirconia were found to have a stable cubic fluorite phase despite what was predicted by the normal “bulk” phase diagram. Furthermore, we proved that a reducing environment stabilizes the cubic phase to 90% zirconia."