Preparation and characterization of the catalytically active forms of rare earth oxides

Fierro, J.L.G.; Mendioroz, S.; Oliván, and Montserrat

doi:10.1016/0021-9797(84)90437-5

Cited by 17 publications

(7 citation statements)

References 13 publications

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“…6 Several researchers have already carried out various methods to prepare CeO 2 nanocrystals. Among these methods are precipitation, 9 urea decomposition, 10 combustion, 11 thermal decomposition, 12 spray pyrolysis, 13 microemulsion, 14 and electrochemical synthesis. 15 Recently, preparation of nanocrystal CeO 2 by hydrothermal synthesis was developed.…”

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confidence: 99%

Structural and Morphological Characterization of Cerium Oxide Nanocrystals Prepared by Hydrothermal Synthesis

et al. 2007

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Colloidal cerium oxide (CeO2) nanocrystals prepared by hydrothermal synthesis were characterized by high-resolution transmission electron microscopy (HRTEM) and three-dimensional electron tomography (3D-ET). HRTEM images of individual CeO2 nanocrystals were then simulated by Blochwave and multislice simulations to determine the atomic arrangement and terminating atoms. The edge length distributions were between 5.0 and 8.0 nm with an average edge length of 6.7 nm. The HRTEM images showed that the CeO2 particles were slightly truncated revealing {220} facets. 3D-ET revealed that the CeO2 nanocrystals exposed predominantly {200} cubic facets. The nanocrystals were truncated at the corners exposing {111} octahedral facets and at the edges {220} dodecahedral facets. Furthermore, 3D-ET revealed the presence of some tetragonal-shaped CeO2 nanocrystals.

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confidence: 99%

Structural and Morphological Characterization of Cerium Oxide Nanocrystals Prepared by Hydrothermal Synthesis

et al. 2007

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“…This band is a typical signature of the stretching vibration of the carbonate structure bonded to the topmost layer of the oxide. 19 Along with this doublet, a small shoulder at 1620 cm −1 , overlapping the band at 1525 cm −1 , is attributed to the ␦H-O-H vibration of adsorbed H 2 O in the RE-based oxides. 19 Less intense bands corresponding to the ͑Tb,Dy͒ carbonates were observed at 1100 and 845 cm −1 .…”

Section: C316mentioning

confidence: 96%

“…19 Along with this doublet, a small shoulder at 1620 cm −1 , overlapping the band at 1525 cm −1 , is attributed to the ␦H-O-H vibration of adsorbed H 2 O in the RE-based oxides. 19 Less intense bands corresponding to the ͑Tb,Dy͒ carbonates were observed at 1100 and 845 cm −1 . The band at 1100 cm −1 was also associated with a small shoulder at 1020 cm −1 ͑see Fig.…”

Section: C316mentioning

confidence: 96%

“…[19][20][21][22] The formation of carbonate on oxides has been reported both as a surface phenomenon 23,24 as well as a bulk transformation [25][26][27] in the case of RE elements. The latter is reported to occur due to aging of the oxides in atmosphere.…”

Section: C316mentioning

confidence: 98%

“…The formation of carbonates ͑hydrated and hydroxy-͒ takes place as a result of interaction between sesquioxides or hydroxides and CO 2 from atmosphere. [19][20][21][22] The formation of carbonate on oxides has been reported both as a surface phenomenon 23,24 as well as a bulk transformation [25][26][27] in the case of RE elements. The latter is reported to occur due to aging of the oxides in atmosphere.…”

Section: Corrosion Products Of Pure Res (Tb and Dymentioning

confidence: 99%

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On the Mechanism of Corrosion of Terfenol-D (Tb[sub 0.3]Dy[sub 0.7]Fe[sub 1.92])

Sachdeva

Balasubramaniam

2008

J. Electrochem. Soc.

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The effect of constituent elements Tb, Dy, and Fe on corrosion of Terfenol-D ͑Tb 0.3 Dy 0.7 Fe 1.92 ͒ was studied by potentiodynamic polarization studies in freely aerated, deaerated, and fully aerated 3.5% NaCl and 0.01 N Na 2 SO 4 solutions. The corrosion products obtained from immersion and cyclic spray tests were characterized by Fourier transform infrared ͑FTIR͒ spectroscopy and scanning electron microscopy ͑SEM͒. The polarization behavior of Terfenol-D closely resembled that of pure iron in all environments. Characterization of spalled corrosion products after immersion testing revealed a higher rare earth ͑RE͒ content. An increase in iron content of the adherent corrosion products with increasing duration of exposure pointed out the significant role of iron in the general corrosion processes of Terfenol-D. The polarization and characterization results have been related to the dealloying corrosion mechanism, wherein selective dissolution of REs from the surface results in corrosion from an essentially iron-enriched surface.The corrosion of rare earth ͑RE͒ magnetic materials has been an important subject of study. The extensively studied materials in this category are materials based on Nd-Fe-B and Sm-Co alloys. A relatively new RE magnetic material is based on the Tb-Dy-Fe alloy. Detailed studies on several aspects of corrosion of commercial-grade Tb 0.3 Dy 0.7 Fe 1.92 ͑commercially called Terfenol-D͒ have recently been concluded. 1-5 Corrosion of these ͑Tb,Dy͒Fe 2 -based magnetostrictive materials is of scientific, commercial, and strategic concerns, as this material is the nextgeneration material for active sonar applications. Apart from this, Terfenol-D finds varied applications, such as in tools for well cleaning in the petroleum, oil, and gas industries, in fuel injection, and in medical appliances.The known aspects of corrosion of Terfenol-D are reviewed briefly. Terfenol-D is particularly corrosion prone in the presence of chloride ions. 3,4 Moreover, corrosion rates are higher in the absence of oxygen and with increased duration of hydrogen charging. 2 Hydrogen embrittlement accompanies the corrosion process of Terfenol-D, 2 which undermines the structural integrity of the material.The objective of the present communication is to understand the effect of constituent elements ͑Tb, Dy, and Fe͒ on the corrosion behavior of Terfenol-D. Understanding the corrosion mechanism of an alloy may be very complex when the components of the alloy differ widely in their corrosion behavior. Therefore, it may be convenient to understand the corrosion mechanisms of individual alloy components and then relate them to the alloy system under study. Characterization of corrosion products formed in different environments has been used extensively for understanding the corrosion mechanisms. The most common metallic corrosion products in atmospheric and corrosive environments include oxides ͑hydrated͒ and ͑oxy-͒ hydroxides.This study also characterizes the corrosion product on Terfenol-D and its constituents under similar t...

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Transition Metal Oxides

Landau

2002

Handbook of Porous Solids

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Preparation and characterization of the catalytically active forms of rare earth oxides

Cited by 17 publications

References 13 publications

Structural and Morphological Characterization of Cerium Oxide Nanocrystals Prepared by Hydrothermal Synthesis

Structural and Morphological Characterization of Cerium Oxide Nanocrystals Prepared by Hydrothermal Synthesis

On the Mechanism of Corrosion of Terfenol-D (Tb[sub 0.3]Dy[sub 0.7]Fe[sub 1.92])

Transition Metal Oxides

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