Thermal analysis of the oxidation of natural graphite — effect of particle size

Jiang, Wei; Nadeau, Gabrielle; Zaghib, Karim; Kinoshita, K.

doi:10.1016/s0040-6031(00)00416-0

Cited by 145 publications

(104 citation statements)

References 20 publications

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“…It was shown that for a prismatic graphite structure, the fraction of edge sites increases, and the fraction of basal plane sites decreases, as the particle size decreases. This confirms that the ratio between edge sites and basal sites has a strong influence on all thermal parameters for graphite oxidation [7].…”

Section: Introductionsupporting

confidence: 79%

“…We think that the formal kinetic approach used does not give one the possibility to discuss the difference in the kinetic stability based on the distribution of basal and edge active sites with different energies and of the formation of semiquinone and epoxy groups as the reaction progresses [5,7].…”

Section: Resultsmentioning

confidence: 99%

“…The oxidation of natural graphite was considered in several detailed papers [5][6][7]. It was shown that for a prismatic graphite structure, the fraction of edge sites increases, and the fraction of basal plane sites decreases, as the particle size decreases.…”

Section: Introductionmentioning

confidence: 99%

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Reactivity in combustion process for expanded graphites: influence of dimensional effect

Логвиненко¹,

Makotchenko²,

Федоров³

2016

Nanosystems: Phys. Chem. Math.

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Thermal stability in combustion reaction for natural graphite, graphene and several expanded graphite phases were studied; the kinetic parameters of the oxidation reaction were calculated for two samples. Natural graphite (crystalline particles 200 -300 µm) has the maximum stability (E 1 = 201 ± 2 kJ/mol, lg A 1 = 7.1 ± 0.1), while multilayer graphene is the most reactive (E 2 = 120 ± 1 kJ mol −1 , lg A 2 = 4.3 ± 0.10). The different sample grain sizes and their different structures result in different thermal stabilities: both in the reaction zones location (i.e. in the topochemical equation forms), and in the kinetic parameters' values.

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Section: Introductionsupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

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Reactivity in combustion process for expanded graphites: influence of dimensional effect

Логвиненко¹,

Makotchenko²,

Федоров³

2016

Nanosystems: Phys. Chem. Math.

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“…Therefore, in this study, graphene or graphene oxide is used as the base material in preparing the solid organic tribofilms for reduction of friction and also wear. An ideal sheet of graphene consists of a 2D honeycomb structure of carbon atoms in a single layer [11]. It was confirmed that graphene has extremely high rigidity and breaking strength.…”

Section: Introductionmentioning

confidence: 90%

Lube Oil Wear Reduction via Organic Tribofilms

Ismail

2017

Lubricants

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Effective tribofilms are desirable to protect mechanical systems. In the research, the reduction in wear and friction were investigated through the use of organic additives. Graphene-based organic additives were prepared by surface modification of graphene using organic moiety that will provide tribochemical reaction with rubbing metal surface. The role of surface protective additives becomes vital when operating conditions become severe and moving components operate in a boundary lubrication regime. After protecting film is slowly removed by rubbing, it can regenerate through the tribochemical reaction of the additives at the contact. Many researchers demonstrated that organic additives physically or chemically adsorbed on rubbing metal surfaces to form monolayers, with their shear strength deriving primarily from the weak van der Waal interactions between opposing hydrocarbon chains at the interfaces. Experiments were conducted on a base oil where 0.01 wt % of the additive was used. Tribological evaluation was conducted using four-ball tester under room temperature and the morphology of the worn surfaces were characterized using Field emission scanning electron microscopy (FESEM). Experimental results showed a 16% reduction in friction and 30% reduction in wear when compared to the base oil containing no additive.

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“…Pode-se observar que os grafites com menor tamanho médio de cristalito (GM30, GMax e GB) tendem a apresentar as menores temperaturas de oxidação (T onset , o que sugere que uma menor cristalinidade do material acarreta em uma cinética de oxidação mais rápida, o que pode contribuir para um processo de oxidação mais eficiente durante a síntese de OG posteriormente. 9,24,37 Entretanto, apesar de GF e GMax apresentarem valores L c muito próximos, a amostra GF apresenta a maior temperatura de oxidação, o que pode estar associado ao seu elevado tamanho de partícula, verificado através das imagens de MEV. Essa característica pode ter dificultado o acesso da espécie oxidante (O 2 ) à totalidade da amostra durante o processo de decomposição térmica, conforme observado nas curvas de TG.…”

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Estudo Através De RMN De 13c No Estado Sólido Sobre a Síntese De Oxido De Grafite Utilizando Diferentes Precursores Grafíticos

et al. 2017

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(GO) is investigated in the present work. Six different graphitic precursors were used to produce GO following a modified Hummers method, namely: natural graphite, commercial lubricant graphite, milled graphite, graphite flakes, high-purity graphite and graphite recycled from Li-ion batteries. The products were characterized by X-ray diffraction (XRD), thermogravimetry, solid-state 13 C nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). 13C NMR spectra revealed the presence of epoxy, hydroxyl, carbonyl and lactol groups in the synthesized GOs. However, the oxidation degree of each product was found to be dependent on the average crystallite size (L c ) and particle size of the graphitic precursors, with the best GO samples being produced from the milled graphite and the graphite recycled from ion-Li batteries. These results were rationalized in terms of the structural and microstructural differences among the graphitic precursors, as revealed by the XRD patterns and SEM images, evidencing the importance of the correct choice of the precursor aiming the achievement of a well-developed structure for the GO product.Keywords: graphite oxide; recycled graphite; ion-Li battery; solid-state 13 C NMR. INTRODUÇÃOEm 1859, Brodie relatou a descoberta de um material composto por carbono, hidrogênio e oxigênio, ao qual deu o nome de "ácido grafítico", após tentar promover a oxidação do grafite.1 Tal material viria a ser conhecido como óxido de grafite (OG) e, após Novoselov e colaboradores conseguirem isolar uma folha única de grafeno, o interesse em estudos sobre a produção e características do OG ressurgiu de forma intensa, devido ao seu papel como um precursor para a produção de baixo custo e em larga escala de materiais à base de grafeno.2,3 Além disso, a completa esfoliação do OG em meio aquoso permite a obtenção do material conhecido como óxido de grafeno, este também um material com aplicações promissoras em áreas como catálise, adsorção e eletroquímica, dentre outras. 4,5 Desde o estudo pioneiro de Brodie várias rotas químicas foram propostas para sintetizar o OG, como a sugerida por Staudenmaier, 40 anos após Brodie, e por Hummers e Offeman, um século após o primeiro relato.6,7 Os produtos das reações relatadas por esses pesquisadores apresentavam grandes variações em sua composição, em função não somente dos diferentes reagentes oxidantes utilizados em cada uma (KClO 3 /HNO 3 nos métodos de Brodie e Staudenmaier e H 2 SO 4 /KMnO 4 no método de Hummers) mas também da fonte de grafite empregada e das condições reacionais.8 Atualmente, o mé-todo de Hummers é o mais utilizado para síntese do OG. Contudo, as quantidades de cada reagente originalmente usadas eram muito altas, e com o passar dos anos surgiram variações desse método que modificavam não somente as proporções dos reagentes mas também parâmetros de temperatura e tempo reacional. Tais adaptações ao método de Hummers são comumente chamadas de "métodos de Hummers modificados". [8][9][10] A estrutura do OG permanece até os dias atuais obje...

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Thermal analysis of the oxidation of natural graphite — effect of particle size

Cited by 145 publications

References 20 publications

Reactivity in combustion process for expanded graphites: influence of dimensional effect

Reactivity in combustion process for expanded graphites: influence of dimensional effect

Lube Oil Wear Reduction via Organic Tribofilms

Estudo Através De RMN De 13c No Estado Sólido Sobre a Síntese De Oxido De Grafite Utilizando Diferentes Precursores Grafíticos

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