The chromium trioxide-graphite system

Hooley, J.G.; Reimer, Monica

doi:10.1016/0008-6223(75)90008-1

Cited by 35 publications

(3 citation statements)

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“…The exfoliation occurs spontaneously at temperatures above 220 ~ as this is above the point of decomposition ofCrO s itself [20,21]. The exfoliation effects taking place in GIC-CrO3's above 220 ~ were reported earlier [10,12]. In light of the above facts, the rise in all curves demonstrated in the present paper in the range 220-280 ~ is quite clear.…”

Section: Resultssupporting

confidence: 67%

“…It has been shown [10,12,14,16] that the DTA curves of the intercalation compounds do not demonstrate the endothermic peak associated with the melting of CrO 3 . This fact was attributed to the changes in energy bonding of CrO3 as a consequence of intercalation.…”

Section: Resultsmentioning

confidence: 97%

“…The process ofdeintercalation can be observed in the TG curves if the released intercalant itself undergoes thermal decomposition and/or participates in a secondary reaction with the graphite carbons. The occurrence of both processes has been reported for graphite-CrO 3 intercalation compounds (GIC-CrO3's) [10][11][12]. When flakes of GIC-CrO3's are heated above 220 ~ lower oxides of chromium are formed, not only due to the thermal decomposition of the intercalated CrO3, but also as a result of the reduction of CrO 3 by the graphite carbons.…”

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confidence: 95%

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Thermogravimetric changes influenced by the compaction of graphite-CrO3 intercalation compounds

Skowroński

1988

Journal of Thermal Analysis

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The changes resulting from the compression of graphite-CrO a intercalation compounds are demonstrated in the TG curves. In comparison with the samples examined in the form of a flake bed, the compacted compounds begin to decompose at lower temperatures and their weight loss is higher, particularly above 220 ~ To explain the obtained results, the pressure-induced changes in the structures and the activities of the compounds are considered in relation to the method of intercalation, the concentration of the intercalant and the extent of exfoliation, Intercalation compounds of graphite (GIC) are formed in reactions between graphite and certain elements or molecules. The alternating sequence of n hexagonal graphite layers and a monolayer of foreign species, called the stage number, is a characteristic feature of their structure. The insertion of the guest species between the host graphite interspaces results in the creation of new, interesting properties. The structural, electrical and thermal changes effected by intercalation have been the most intensivelY explored [1,2].The thermal studies have often related to the exfoliation phenomenon caused by the thermal decomposition of GIC [3][4][5][6][7][8][9], Above a critical temperature, the intercalant escapes from the graphite interspaces, as demonstrated by a large expansion of the sample along the c-direction and consequently a very swollen product is formed. The process ofdeintercalation can be observed in the TG curves if the released intercalant itself undergoes thermal decomposition and/or participates in a secondary reaction with the graphite carbons. The occurrence of both processes has been reported for graphite-CrO 3 intercalation compounds (GIC-CrO3's) [10][11][12]. When flakes of GIC-CrO3's are heated above 220 ~ lower oxides of chromium are formed, not only due to the thermal decomposition of the intercalated CrO3, but also as a result of the reduction of CrO 3 by the graphite carbons. Consequently, a two-phase mixture of these oxides and the depleted John Wiley & Sons, Limited, Chichester Akad~miai Kiad6, Budapest

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 97%

mentioning

confidence: 95%

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Thermogravimetric changes influenced by the compaction of graphite-CrO3 intercalation compounds

Skowroński

1988

Journal of Thermal Analysis

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Oxides

Ebert¹

1990

Inorganic Reactions and Methods

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Intercalation and Graphitizability of Electrode Cokes

Preiss¹,

Lunkenheimer²,

Nissel³

1986

Cryst. Res. Technol.

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Experimental results show in case of intercalation by SbCI,, CrO, and Sr, the influence of the degree of perfection and size of graphite crystals on synthesis, intercalant distribution and stage disordering of intercalation compounds. High temperature treatiiient of electrode cokes improves steeply the ability of intercalation by SbCI, and Bre between 1900 and 2000 "C. A gradual increase of intercalated CrO, with temperature have been found in cokes annealed between 2000 and 2800 "C. By nieans of Cr0,-intercalation a distinction of graphitized cokes is possible. Filling of galleries between carbon layers by CrO, have been only completed in crystals of natural graphite with low flake diairieter. EPMA showed Cr0,-intercalation in large crystals only in the prismatic edge area. SbC1,-intercalation exhibits an increase in stage disordering with decreasing degree of crystallite perfection and increasing degree of grinding of original graphites.Experiinentelle Befunde weisen bei Intercalation niit SbCI,, CrO, und Br2 den EinfluB der Perfektion und GroDe der Graphitkristalle auf Synthese, Intercalantverteilung und Stufenfehlordnung der Intercalationsverbindungen aus. Die Intercalationsfiihigkeit von Elektrodenkoksen durch SbC1, und Br, setzt sprungartig nach einer Temperaturbehandlung der Kokse zwischen 1900 und 2000 "C ein. Die intercalierte Cr0,-Menge in den Koksen steigt allriiahlich mit der Gluhtemnperatur der Kokse von 2000 bis 2800 "C an und erlaubt eine Differenzierung zwischen verschiedenen graphitierten Elektrodenkoksen. 1 lie Graphitzwischenschichtriiunie werden durcli CrO, nur dann koinplett aufgefullt, wenn die Korndurchniesser einen Grenzwert unterschreiten, der umso niedriger ist je geringer die Perfektion der Graphitkristelle kt. Mit ESMA konnte gezeigt werden, daB in groBen Naturgraphitplkttchen nur die prismatische Randzone intercaliert wird. Die SbC1,-Intercalation gibt AnlaB zu Stufenfehlordnung, die mit fallender Kristallperfektion und steigendem Vermahlungsgrad der Graphite zunimmt.

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The chromium trioxide-graphite system

Cited by 35 publications

References 8 publications

Thermogravimetric changes influenced by the compaction of graphite-CrO3 intercalation compounds

Thermogravimetric changes influenced by the compaction of graphite-CrO3 intercalation compounds

Oxides

Intercalation and Graphitizability of Electrode Cokes

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