R. Brezny's research while affiliated with University of Pennsylvania and other places
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Publications (4)
We studied the structure of coarse and nano-scale powders of CeO2 using pulsed neutron scattering. The diffraction data were analyzed using Rietveld refinement, and were also Fourier-transformed to obtain the pair-distribution function (PDF). The Frenkel type oxygen defects consisting of vacancies in the oxygen sublattice and oxygen ions in the oct...
Cerium–praseodymium mixed oxides covering a wide range of cerium/praseodymium ratios were synthesized, loaded with 2 wt% palladium,
and characterized by X-ray diffraction and temperature-programmed reduction. Both the degree and average temperature of reduction
of the catalyzed mixed oxides were found to increase with increasing praseodymium concen...
Nanocrystalline powders of Ce0.5Zr0.5O2 were synthesized and characterized for the application as a catalyst support and oxygen storage medium in automotive catalysis. Detailed pair-distribution function analysis of the neutron diffraction data revealed an unusual structure of the nanocrystallites, consisting of domains of Ce0.4Zr0.6O2 composition...
The use of cerium oxide as an oxygen storage component in automotive three-way catalysis has been well established. More recently the need to thermally stabilize these materials against deactivation at higher temperatures has focused attention on doping of the ceria with a wide range of metal oxides. The role of these dopants in the stabilization m...
Citations
... The PDF method was then applied to relaxor ferroelectric Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) [28,29], Pb(Zr x Ti 1Àx )O 3 (PZT) [30,31] and related oxides [32] to characterize its local disorder and the mechanism of their dielectric behavior [33,34]. It was also used on nano-particles of ceria, CeO 2 , and ceria/zirconia, CeO 2 /ZrO 2 , which are used in automotive catalytic converters [35][36][37], and nano-particle RuO 2 used in super-capacitor, batteries and fuel cells [38]. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/282124784553984-1444275198074_Q64/Takeshi-Egami.jpg)
... As both CeO 2 and Pr 6 O 11 adopt closely related crystal structures and contain similarly sized cations with the same valence and close electronic properties, they can form solid solutions (Chun et al. 2006;Ftikos et al. 1993;Knauth and Tuller 1999;Logan and Shelef 1994;Michel et al. 2017;Stefanik and Tuller 2004;Takasu et al. 1984). Knauth and Tuller (1999) studied a mixed Pr 0.7 Ce 0.3 O 2-x oxide between 470 and 640 °C and f O2 of 0.2 to 10 -3 and found that Ce was tetravalent in all conditions, but the Pr 4+ /Pr 3+ ratio (manifested by oxygen vacancies) was increasing with higher f O2 and lower temperatures. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/309098782887939-1450706300911_Q64/Jason-Lupescu.jpg)
... Regarding the first case, Di Sarli et al. [27] reported some Ag-ceria catalysts with significantly enhanced silver-ceria interface, where highly reactive oxygen species were produced yielding an outstanding catalytic activity towards diesel soot combustion during regeneration of a coated DPF. On the other hand, previous studies have demonstrated that doping CeO 2 with tetravalent transition metal cations such as Ti 4+ and Zr 4+ [28,29], or other trivalent rare earth cations such as Tb 3+ , Gd 3+ , Eu 3+ , La 3+ , and Pr 3+ [30][31][32][33], increases both oxygen mobility and the number of oxygen vacancies within the structure, which in turn is reflected in a considerable improvement of its redox properties, in most cases. La 3+ possesses an ionic radius similar to Ce 4+ (116 and 97 pm, respectively), which results in its facile incorporation into the crystalline lattice of cerium oxide. ...
