Dynamics of structural transformations in the reduction of copper aluminate

Plyasova, L. M.; Yur'eva, T. M.; Molina, I. Yu.; Kriger, T. A.; Балагуров, А.М.; Davydova, L. P.; Zaikovskii, V. I.; Kustova, G. N.; Malakhov, V. V.; Довлитова, Л. С.

doi:10.1007/bf02755383

Cited by 23 publications

(13 citation statements)

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“…Both narrowband resonant and conductive/negative permittivity dielectric behavior have been observed in H 2 ‐fired Al 2 O 3 –CuO composites, which could be useful for the selective absorption of electromagnetic fields in the microwave bands. The behavior is consistent with a collisional Drude model, and the semiconductive phase is hypothesized, based on relevant literature, 8–10 to be a partially reduced copper aluminate (CuAl 2 O 4 spinel or CuAlO 2 ). The transition between resonant/non‐conductive behavior and conductive/negative ɛ′ behavior is possibly due to a percolative process.…”

Section: Summary and Future Worksupporting

confidence: 80%

“…It is well known that copper oxides and Al 2 O 3 form aluminate compounds at temperatures in the 800°–1100°C range (e.g., CuO diffuses into the Al 2 O 3 platelets to form the spinel) 8,9 . When a CuAl 2 O 4 spinel or CuAlO 2 is H 2 fired and some of the oxygen is removed from the crystal lattice, 9,10 a defective semiconducting ceramic would be expected to form (in addition to limited amounts of free Cu). Other examples of oxide ceramics with semiconducting behavior under partial hydrogen reduction are ZnO, Bi 2 O 3 , ZrO 2 , and TiO 2 11…”

Section: Resultsmentioning

confidence: 99%

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Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al₂O₃–CuO Composites

Calame

Battat

2006

Journal of the American Ceramic Society

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The frequency‐dependent microwave complex permittivity of composites based on an Al2O3–CuO system is investigated at room temperature. The composites are formed by solution infusion of copper precursors into a porous Al2O3 matrix, followed by thermal decomposition to copper oxides and localized formation of copper aluminate compounds, and finally, H2 firing. The material exhibits a strong amplitude, with relatively narrowband dielectric resonance in the microwave frequency regime at intermediate levels of mass gain, which is reminiscent of a plasmon resonance. Large mass gains cause negative permittivity behavior below 6 GHz, consistent with a collisional Drude model of a semiconducting oxide phase.

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Section: Summary and Future Worksupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al₂O₃–CuO Composites

Calame

Battat

2006

Journal of the American Ceramic Society

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“…The in situ method was used to study a copper-zinc catalyst for methanol synthesis [94][95][96][97]. Figure 11 presents a diagram for the formation of the active state of the copper-zinc oxide catalyst.…”

Section: Cuo(traces) [Cu ] [Cr ] O (Oh)mentioning

confidence: 99%

In situ high-temperature X-ray diffraction measurements: Application to the study of heterogeneous catalysts

Plyasova

Kardash

2012

J Struct Chem

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When characterizing the phase composition and structure of catalysts, researchers are faced with the problem of reversible effects of temperature and gas medium during their preparation, activation, or operation. Therefore, particular attention is paid to the methods of their research in appropriate conditions, i.e., in situ high-temperature X-ray diffraction. The theoretical framework and experimental features of high-temperature X-ray diffraction techniques are examined. Examples are given of their effective application to the study of the structural features of oxide catalysts under close-to-real conditions. Keywords: in situ high-temperature X-ray diffraction, thermal X-ray diffraction, oxide catalysts, phase composition, structure in the model conditions of preparation, activation, and operation.

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“…[6][7][8] It is widely accepted that the presence of residual precursor rosasite phase could improve the activity of the traditional ternary catalyst. [9][10][11] Plyasova 12 and Tamara et al 13 supposed that the presence of residual carbonate in the calcined catalysts can contribute to the formation of the copper sub-oxide species. Bart et al 14 found that the residual hydroxyl carbonates presumably facilitate the formation of highly active sites during reduction.…”

Section: Introductionmentioning

confidence: 99%

Promoting effect of a Cu–Zn binary precursor on a ternary Cu–Zn–Al catalyst for methanol synthesis from synthesis gas

et al. 2014

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Small amounts of Cu-Zn binary precursor were introduced into traditional ternary Cu-Zn-Al catalysts to produce a series of modified ternary Cu-Zn-Al catalysts for the synthesis of methanol from synthesis gas with high CO content. 2 wt% Cu-Zn (Cu-Zn ¼ 3 : 1 atomic ratio) binary precursor was found to have the most significant improvement for the catalytic performances. Physicochemical characterization of the as-prepared catalysts by TPR, in situ XRD and in situ XAES techniques indicated that the addition of a suitable amount of binary Cu-Zn precursor partially modified the structure of the catalyst, changed the particle size of Cu, copper surface area and the ratio of Cu + /Cu 0 , and thus effectively improved the catalytic performances of the catalyst.

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Dynamics of structural transformations in the reduction of copper aluminate

Cited by 23 publications

References 4 publications

Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al₂O₃–CuO Composites

Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al₂O₃–CuO Composites

In situ high-temperature X-ray diffraction measurements: Application to the study of heterogeneous catalysts

Promoting effect of a Cu–Zn binary precursor on a ternary Cu–Zn–Al catalyst for methanol synthesis from synthesis gas

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Dynamics of structural transformations in the reduction of copper aluminate

Cited by 23 publications

References 4 publications

Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al2O3–CuO Composites

Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al2O3–CuO Composites

In situ high-temperature X-ray diffraction measurements: Application to the study of heterogeneous catalysts

Promoting effect of a Cu–Zn binary precursor on a ternary Cu–Zn–Al catalyst for methanol synthesis from synthesis gas

Contact Info

Product

Resources

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Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al₂O₃–CuO Composites

Narrowband Microwave Dielectric Resonance and Negative Permittivity Behavior in Hydrogen‐Fired Al₂O₃–CuO Composites