Thermal stability of oxygen storage properties in a mixed CeO2-ZrO2 system

Hori, Carla Eponina

doi:10.1016/s0926-3373(97)00060-x

Cited by 514 publications

(176 citation statements)

References 11 publications

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“…2. Decrease in tetragonal zirconia peaks Hori et al 17) demonstrated that a solid solution of CeO2-ZrO2 released oxygen (as CO2 or H2O) during a short CO2 laser pulse, via the Ce 4+ to Ce 3+ redox reaction. This implied that the CeO2-ZrO2 solid solution stored oxygen and released oxygen easily to produce oxygendeficient zirconia.…”

Section: Effect On Surface Changesmentioning

confidence: 99%

Surface damages of zirconia by Nd:YAG dental laser irradiation

et al. 2010

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The purpose of this study was to characterize the surface damages of zirconia by Nd:YAG dental laser irradiation through a systematic evaluation of the associated microstructural changes. Disk specimens of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/Al2O3 nanocomposite) were irradiated by Nd:YAG dental laser. The specimens were characterized using scanning electron microscopy, X-ray diffractometry, and wavelength dispersive X-ray spectroscopy. Every single irradiated spot was indicated by a circular black pit surrounded by a circular raised rim with a sunken depression at the center. On surface changes, many cracks were formed inside each irradiated pit. On changes in elemental composition, the concentration of oxygen decreased while that of zirconium increased. After heating in air, the assembly of circular black pits turned white, although the depression and raised rim remained. This study showed that Nd:YAG dental laser irradiation induced cracking and reduced oxygen content on the surface of zirconia. Consequently, these phenomena reduced the mechanical strength of zirconia. Therefore, Nd:YAG dental laser welding should not be performed on tetragonal zirconia.

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Section: Effect On Surface Changesmentioning

confidence: 99%

Surface damages of zirconia by Nd:YAG dental laser irradiation

et al. 2010

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“…The 50% CH 4 conversion level was reached at a temperature 130 o C lower using Ce 0.8 Zr 0.2 O 2 compared to CeO 2 alone. Hori et al (1998) report an increase in reversibly stored oxygen by a factor of 1.7-2.5 for phase separated CeO 2 -ZrO 2 compared to CeO 2 alone, and by a factor 0f 3-5 for solid solutions of CeO 2 -ZrO 2 . The optimum Zr concentration was 25 mol%, but performance was relatively insensitive to Zr loading between 15 mol% and 50 mol%.…”

Section: Ceria-zirconia Catalyst Researchmentioning

confidence: 94%

High Efficiency Desulfurization of Synthesis Gas

Yi¹,

Podlaha²,

Harrison³

2002

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Mixed metal oxides containing CeO 2 and ZrO 2 are being studied as high temperature desulfurization sorbents capable of achieving the DOE Vision 21 target of 1 ppmv or less H 2 S. The research is justified by recent results in this laboratory that showed that reduced CeO 2 , designated CeO n (1.5 < n < 2.0), is capable of achieving the 1 ppmv target in highly reducing gas atmospheres. The addition of ZrO 2 has improved the performance of oxidation catalysts and three-way automotive catalysts containing CeO 2 , and should have similar beneficial effects on CeO 2 desulfurization sorbents.An electrochemical method for synthesizing CeO 2 -ZrO 2 was developed and the products were characterized by XRD and TEM during year 01. Nanocrystalline particles having a diameter of about 5 nm and containing from approximately 10 mol% to 80 mol% ZrO 2 were prepared. XRD showed the product to be a solid solution at low ZrO 2 contents with a separate ZrO 2 phase emerging at higher ZrO 2 levels. Unfortunately, the quantity of CeO 2 -ZrO 2 that could be prepared electrochemically was too small to permit full testing in our desulfurization reactor.Also during year 01 a laboratory-scale fixed-bed reactor was constructed for desulfurization testing. All components of the reactor and analytical systems that may be exposed to low concentrations of H 2 S are constructed of quartz, Teflon, or silcosteel. Reactor product gas composition as a function of time is determined using a Varian 3800 gas chromatograph equipped with a pulsed flame photometric detector (PFPD) for measuring low H 2 S concentrations (<~10 ppmv) and a thermal conductivity detector (TCD) for higher concentrations of H 2 S.Larger quantities of CeO 2 -ZrO 2 mixtures from other sources, including mixtures prepared in this laboratory using a coprecipitation procedure, have been obtained. Characterization and desulfurization testing of these sorbents began in year 02 and is continuing. To properly evaluate the effect of ZrO 2 addition on desulfurization capability, the physical properties of the sorbent mixtures must be similar. That is, a CeO 2 -ZrO 2 mixture from source A would not necessarily be superior to pure CeO 2 from source B if the properties were dissimilar. Therefore, current research is concentrating on CeO 2 and CeO 2 -ZrO 2 mixtures prepared in this laboratory using the coprecipitation procedure. The structure of these sorbents is similar and the effect of ZrO 2 addition can be separated from other effects.X-ray diffraction tests of the sorbents prepared in house have confirmed the existence of a solid solution of ZrO 2 in CeO 2 . Reduction tests using an electrobalance reactor have confirmed that CeO 2 -ZrO 2 mixtures are more easily reduced than pure CeO 2 . Reduction of CeO 2 -ZrO 2 begins at a lower temperature and the final value of n in CeO n (1.5

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“…(4) Finally, it is known that the addition of ZrO 2 enhances the ability of CeO 2 to store oxygen. (5) In fact, compounds of the system Ce 1-x Zr x O 2 have been proposed as "oxygen storage devices", taking advantage in that case of the simultaneous and reversible occurrence of oxygen loss (or retrapping) and Cerium reduction (or oxidation). (6) We present in this work the fabrication and structural and spectroscopic characterization of crystalline rods of Ce 0.4 Zr 0.6 O 2 composition.…”

Section: +mentioning

confidence: 99%

Caracterización estructural y espectroscópica de fibras cristalinas de Ce0.4Zr0.6O2 crecidas mediante el método de fusión zonal asistida por láser

Sanjuán¹,

Oliete²,

Várez³

et al. 2008

Bol. Soc. Esp. Ceram. Vidr.

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A structural and spectroscopic characterization of crystalline rods of Ce 0.4 Zr 0.6 O 2 grown by the laser floating zone (LFZ) method is presented. A precursor rod of Ce 0.4 Zr 0.6 O 2 composition was sintered at 1500 ºC in air atmosphere and then processed by the LFZ technique with a CO 2 laser. The processed material was characterized by XRD, SEM and Raman spectroscopy. In the as-grown, dark-color processed rod, the Raman spectrum evolves radially from a t'-like one, corresponding to Ce 0.37 Zr 0.63 O 2 composition, at the edge of the rod, to a very broad and weak, cubic-like one, at the center. The degree of cerium reduction and oxygen non-stoichiometry were determined through measurements of the electronic Raman spectrum of Ce 3+. A strong Ce 3+ signal was found at the core of the rod, indicating strong reduction, whereas no Ce 3+ signal was detected at the edge. To restore oxygen and Ce 4+ content a section of the fiber was reoxidized at 620 ºC for 24 h. A very homogeneous spectrum was found in the reoxidized sample, that was assigned to a t'-phase of composition Ce 0.42 Zr 0.58 O 2 .

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Thermal stability of oxygen storage properties in a mixed CeO2-ZrO2 system

Cited by 514 publications

References 11 publications

Surface damages of zirconia by Nd:YAG dental laser irradiation

Surface damages of zirconia by Nd:YAG dental laser irradiation

High Efficiency Desulfurization of Synthesis Gas

Caracterización estructural y espectroscópica de fibras cristalinas de Ce<sub>0.4</sub>Zr<sub>0.6</sub>O<sub>2</sub> crecidas mediante el método de fusión zonal asistida por láser

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