The Raman spectra of Cr3O8 and Cr2O5

Maslar, James E.; Hurst, Wilbur S.; Vanderah, Terrell A.; Levin, Igor

doi:10.1002/jrs.687

Cited by 40 publications

(12 citation statements)

References 28 publications

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“…3 in the spectra acquired at t ϭ 9.6 h and t ϭ 14.5 h. The small band is not currently identified, but several Cr VI species scatter in that general region and it is possible that the small 800 cm Ϫ1 band arose from some type of Cr VI species. 9,22 Two other bands in Fig. 3 merit discussion.…”

Section: Resultsmentioning

confidence: 98%

Raman Spectroscopy of Monolayers Formed from Chromate Corrosion Inhibitor on Copper Surfaces

Hurley

McCreery

2003

J. Electrochem. Soc.

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Surface enhanced Raman scattering ͑SERS͒ was used to observe interactions of dilute Cr VI solutions with silver and copper surfaces in situ. Using silver as a model surface which supports strong SERS with a 514.5 nm laser, it was possible to observe Cr III at the near monolayer level, and the spectra were compared to those from Cr III oxyhydroxide species and Cr III /Cr VI mixed oxide. Similar experiments were conducted with Cu surfaces and 785 nm excitation. Upon exposure to Cr VI solution, the characteristic Cu oxide Raman bands disappeared, and a Cr III band increased in intensity over a period of ϳ20 h. The intensity of the Cr III band on Cu became self-limiting after the formation of several Cr III monolayers, as supported by chronoamperometry experiments. This Cr III spectrum was stable after Cr VI was removed from the solution provided the potential remained negative of Ϫ200 mV vs. Ag/AgCl. The results support the conclusion that Cr VI is reductively adsorbed to Cu at the near neutral pH and open circuit potentials expected for Cu/Al alloys in field applications. The Cr III film is stable and is a strong inhibitor of electron transfer in general and oxygen reduction in particular. An important mechanistic feature of Cr III formation is the substitution lability of Cr VI compared to Cr III . The Cr VI -O bond can be broken much more rapidly than the substitution inert Cr III -O bond, making formation of Cr III /Cr VI mixed oxide kinetically favorable. Once reduced to Cr III , however, the substitution inert oxyhydroxide film is much less labile. An important and central feature of Cr VI as a corrosion inhibitor is its transformation via reductive adsorption from a mobile, substitution labile Cr VI form to an insoluble, substitution inert Cr III oxyhydroxide. Furthermore, Cr VI reduction is likely to occur at cathodic sites previously responsible for oxygen reduction, which are then permanently blocked by a stable Cr III film with a thickness of a few monolayers.Currently, chromate conversion coatings ͑CCCs͒, and chromatebased barrier coatings and paints are preferred for the treatment of aluminum alloys because they provide both excellent adhesion properties and corrosion inhibition. Routine maintenance activities on these alloys, however, are a large source of environmentally hazardous waste containing the hexavalent chromium present in these coatings. Hexavalent chromium is a danger to worker health and its use has been limited or prohibited by various local, state, and federal regulations. In the search for suitable nonchromate replacements, a basic understanding of the mechanism by which chromate-based protection systems provide such excellent protection will be invaluable.Considerable research has centered on the use of chromate conversion coatings on aluminum aircraft alloy AA-2024 T3 which contains, by weight, 3.8-4.9% copper, 1.2-1.8% magnesium, and less than 1% each of other trace metals, the balance being aluminum.

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Section: Resultsmentioning

confidence: 98%

Raman Spectroscopy of Monolayers Formed from Chromate Corrosion Inhibitor on Copper Surfaces

Hurley

McCreery

2003

J. Electrochem. Soc.

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“…2). It has been suggested that these vibrations may be associated with the spectral features of edge-sharing Cr III O 6 octahedra and possibly the O-Cu I -O linear bond [24]. As shown in Fig.…”

Section: Raman Spectroscopymentioning

confidence: 96%

Metal transition doping effect on the structural and physical properties of delafossite-type oxide CuCrO2

Jlaiel

Amami

Boudjada

et al. 2011

Journal of Alloys and Compounds

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“…For x = 0, it shows three typical vibration modes at 209, 455, and 705 cm −1 , which are identified as σ(A g ), σ(E g ) and σ(A 1g ) modes, respectively. These modes have been supposed to be associated with the spectral features of the edge‐sharing CrO 6 octahedra and possibility the O–Cu–O linear bond . The A 1g and E g modes correspond to the vibrations of Cu–O bonds along the c ‐axis and vibrations in the triangular lattice perpendicular to the c ‐axis, respectively .…”

Section: Resultsmentioning

confidence: 99%

Slight Ti‐Doping‐Induced Strong Time‐Dependent Electrical Transport Behavior in CuCr_1−xTi_xO₂

Zhang

2015

J. Am. Ceram. Soc.

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We investigate the effect of slight Ti substitution (≤0.5%) for Cr in CuCr1−xTixO2 by measuring the structural, magnetic, and electrical transport properties. Upon Ti doping, the antiferromagnetic transition becomes blurred without a change in Néel temperature. Ti4+ substituting to Cr3+ site is found to significantly enhance the resistivity due to the diminishing conducting holes. We find strong time‐dependent electrical transport behavior in CuCr1−xTixO2 induced by slight Ti doping. The key observation is that a metastable behavior occurs in Ti‐doped CuCr1−xTixO2. A strong resistive relaxation (RR) behavior occurs in Ti‐doped CuCr1−xTixO2 with its magnitude remarkably increasing with increasing Ti content, while it is absent in undoped CuCrO2. The RR is found to be described by the combination of an exponential function and a logarithmic dependence at long time. The relaxation behavior in CuCr1−xTixO2 is found to show a correlation with the local lattice deformation.

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The Raman spectra of Cr₃O₈ and Cr₂O₅

Cited by 40 publications

References 28 publications

Raman Spectroscopy of Monolayers Formed from Chromate Corrosion Inhibitor on Copper Surfaces

Raman Spectroscopy of Monolayers Formed from Chromate Corrosion Inhibitor on Copper Surfaces

Metal transition doping effect on the structural and physical properties of delafossite-type oxide CuCrO2

Slight Ti‐Doping‐Induced Strong Time‐Dependent Electrical Transport Behavior in CuCr_1−xTi_xO₂

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The Raman spectra of Cr3O8 and Cr2O5

Cited by 40 publications

References 28 publications

Raman Spectroscopy of Monolayers Formed from Chromate Corrosion Inhibitor on Copper Surfaces

Raman Spectroscopy of Monolayers Formed from Chromate Corrosion Inhibitor on Copper Surfaces

Metal transition doping effect on the structural and physical properties of delafossite-type oxide CuCrO2

Slight Ti‐Doping‐Induced Strong Time‐Dependent Electrical Transport Behavior in CuCr1−xTixO2

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The Raman spectra of Cr₃O₈ and Cr₂O₅

Slight Ti‐Doping‐Induced Strong Time‐Dependent Electrical Transport Behavior in CuCr_1−xTi_xO₂