A Rutherford backscattering study of interfacial reactions of nickel and cobalt oxides with aluminium oxide

Bolt, P.H.; Lobner, S.F.; Bout, T.P. van den; Geus, J.W.; Habraken, F.H.P.M.

doi:10.1016/0169-4332(93)90426-c

Cited by 31 publications

(4 citation statements)

References 6 publications

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“…At the same time, the high-energy side of the aluminum edge moved to higher energies. These two observations indicate the penetration of cobalt ions into the alumina substrate and/or aluminum ions into the cobalt oxide overlayer (7,8 Fig. 1), led to the formation of CoAl O .…”

Section: Cobalt Oxides On Aluminamentioning

confidence: 91%

Formation of Nickel, Cobalt, Copper, and Iron Aluminates fromα- andγ-Alumina-Supported Oxides: A Comparative Study

Bolt

Habraken

Geus

1998

Journal of Solid State Chemistry

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157

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Section: Cobalt Oxides On Aluminamentioning

confidence: 91%

Formation of Nickel, Cobalt, Copper, and Iron Aluminates fromα- andγ-Alumina-Supported Oxides: A Comparative Study

Bolt

Habraken

Geus

1998

Journal of Solid State Chemistry

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157

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“…However, platinum group metals are relatively rare and expensive and for this reason transition metal oxides are more commercially used as catalysts. The catalytic activity and durability of these oxides can be much improved by a variety of methods, including loading on finely divided and porous support materials, treating with small amounts of certain foreign oxides that act as promoters and/or stabilizers and exposure to radiation (El-Shobaky et al 1997, 2001aBolt et al 1993;Mucka 1993). These methods generally increase the concentration of active sites on the catalyst surface by increasing the degree of dispersion of the catalytically active component, hindering possible undesirable reactions between the catalyst constituents and removing undesirable surface contaminates such -OH groups from the acidic oxides employed in the oxidation reaction of CO with O 2 (Doheim and El-Shobaky 2002;Mokhtar et al 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Treatment of a given catalytic system with small amounts of foreign oxides (doping) may increase the oxidation state of the catalytically active species, thereby increasing their ability to catalyze oxidation-reduction reactions (El-Shobaky 2003). Unloaded and loaded Co 3 O 4 systems act as active catalysts for a variety of oxidation-reduction reactions including dehydrogenation, the dehydration of alcohols and the oxidation of CO with O 2 (Garbowski et al 1990;Jansson et al 2002;Yamaura et al 2000;Grillo et al 2004;Kang et al 2003;Broqvist et al 2002;Ruckenstein and Wang 2002;Zhang and Amiridis 1998;Luo et al 1997;Mendes and Schaml 1997;Li and Ding 2000). The effect of doping with various oxides on the surface and catalytic properties of particular systems has been the subject of several investigations (El-Shobaky and Turky 2000;El-Shobaky et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Physicochemical, Surface and Catalytic Properties of Co₃O₄/Al₂O₃ as Influenced by CeO₂ or V₂O₅ Doping

El-Shobaky

2005

Adsorption Science & Technology

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A pure Co 3 O 4 /Al 2 O 3 sample was prepared by the wet impregnation method using finely powdered aluminium hydroxide and cobalt nitrate dissolved in the least amount of distilled water. Maintaining the amount of Co 3 O 4 constant at 16.7 mol%, different samples were doped by impregnating with known amounts of cerium or vanadium nitrates prior to impregnation with cobalt nitrate. The pure and doped samples were precalcined at 600°C and 800°C, respectively. The dopant concentrations employed were 0.5, 1.0, 2.0 and 3.0 mol% CeO 2 or V 2 O 5. The resulting materials were studied by XRD and EDX methods, N 2 adsorption at −196°C and CO oxidation by O 2 at 130-220°C. The results obtained revealed that the surface concentrations of cobalt species in pure and variously doped Co 3 O 4 /Al 2 O 3 solids precalcined at 600°C were more than twice those present in the bulk of these solids. Heating the doped solid at 600°C and 800°C increased the degree of dispersion of Co 3 O 4 by decreasing the crystallite size. This effect was more pronounced in the case of V 2 O 5 doping, with the surface concentration of cobalt species being increased to a greater extent than with CeO 2 doping. Similarly, heating the doped solid at 600°C resulted in a progressive but measurable increase in the lattice parameter of Co 3 O 4 due to the formation of solid solutions. On heating the V 2 O 5-doped solid at 800°C, a portion of the added V 2 O 5 interacted with Co 3 O 4 to yield cobalt vanadate while the other portion contributed to the formation of a solid solution. Doping followed by heating at 600°C increased the catalytic activity of the doped solids in CO oxidation by O 2. In contrast, solids precalcined at 800°C exhibited the opposite effect. The doping process changed the concentration of active sites involved in the catalytic reaction rather than changing the mechanism of the catalytic reaction.

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“…4) may now be thresholded into "spinel coverage" numbers as a way to evaluate a large amount of surface area across many different environmental conditions. Note that the M,Y-rich phase sustains complete non-ideal oxide surface coverage in all environments, though its composition shifts from NiO to spinel as the environment shifts to higher P H 2 O ; water vapor appears to accelerate the solid state reaction of NiO with alumina to form spinel, as Bolt et al postulated [27]. M,Y-rich phase also yields the thickest bilayer oxide above it -as thick as 5 μm total, 4 μm of which is spinel -but again, the thickness itself does not vary as a function of environment.…”

Section: Microstructural Observationmentioning

confidence: 87%

Transient stage oxidation of MCrAlY bond coat alloys in high temperature, high water vapor content environments

Sullivan

Mumm

2014

Surface and Coatings Technology

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a b s t r a c tIn order to evaluate the effect of water vapor on transient stage oxidation of MCrAlY (M_Ni and Co) bond coats, short-term exposures were carried out on thermally sprayed and cast alloy specimens at 1125°C in a range of N 2 -O 2 -H 2 O environments, and resultant thermally grown oxide (TGO) development was evaluated. On cast metal specimens, for which the three-phase alloy dispersion is coarse, growth of unwanted (Ni,Co)(Al,Cr) 2 O 4 spinel was primarily correlated spatially to the Al-poor phases, namely γ, while the preferred TGO product, α-alumina, correlated to the Al-rich β phase. At higher water vapor contents, spinel nucleated and grew out past the γ boundaries to develop above β, too. By thresholding plan view BSE images of TGO surfaces, the amount of spinel vs. alumina surface area coverage was quantified. Spinel coverage was correlated to increasing P H2O , increasing P O2 and, for the highest surface coverage observed, a combination of high P H2O and low P O2 . When a worst case spinel-creating environment of 30 vol.% H 2 O and 10 vol.% O 2 was presented to the more commercially relevant (i.e. sprayed) version of CoNiCrAlY, complete spinel coverage was achieved, indicating that what is often thought of as a long-term spinel growth problem related to Al-depletion of the bond coat, can be created in several hours. Water vapor may enhance transient spinel growth by extending the lifetime of the metastable γ-and δ-alumina phases, the defect spinel structure of which promotes the diffusion of Cr, Co and Ni cations to the TGO surface, whereupon they participate in the development of non-ideal oxides such as spinel. All exposures were carried out without a yttria-stabilized zirconia (YSZ) top coat present.

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A Rutherford backscattering study of interfacial reactions of nickel and cobalt oxides with aluminium oxide

Cited by 31 publications

References 6 publications

Formation of Nickel, Cobalt, Copper, and Iron Aluminates fromα- andγ-Alumina-Supported Oxides: A Comparative Study

Formation of Nickel, Cobalt, Copper, and Iron Aluminates fromα- andγ-Alumina-Supported Oxides: A Comparative Study

Physicochemical, Surface and Catalytic Properties of Co₃O₄/Al₂O₃ as Influenced by CeO₂ or V₂O₅ Doping

Transient stage oxidation of MCrAlY bond coat alloys in high temperature, high water vapor content environments

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A Rutherford backscattering study of interfacial reactions of nickel and cobalt oxides with aluminium oxide

Cited by 31 publications

References 6 publications

Formation of Nickel, Cobalt, Copper, and Iron Aluminates fromα- andγ-Alumina-Supported Oxides: A Comparative Study

Formation of Nickel, Cobalt, Copper, and Iron Aluminates fromα- andγ-Alumina-Supported Oxides: A Comparative Study

Physicochemical, Surface and Catalytic Properties of Co3O4/Al2O3 as Influenced by CeO2 or V2O5 Doping

Transient stage oxidation of MCrAlY bond coat alloys in high temperature, high water vapor content environments

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Physicochemical, Surface and Catalytic Properties of Co₃O₄/Al₂O₃ as Influenced by CeO₂ or V₂O₅ Doping