Applications of Graphite Fibers and Filaments

Dresselhaus, M. S.; Dresselhaus, G.; Sugihara, Kō; Spain, Ian L.; Goldberg, Harris A.

doi:10.1007/978-3-642-83379-3_12

Cited by 8 publications

(14 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This expansion is huge and beyond any thermal value. The thermal linear expansion coefficient ( being the expansion and T the temperature change) for graphite is 7:9 10 ÿ6 K ÿ1 [6], and such change would correspond to a temperature jump of more than 1500 K. Given our fluence and the heat capacity of graphite, the maximum expected temperature rise is around 40 K. Finally, the reported experimental results suggest further theoretical examination with MD simulations. The timedependent ab initio calculations, reported in Ref.…”

mentioning

confidence: 78%

See 1 more Smart Citation

Structural Preablation Dynamics of Graphite Observed by Ultrafast Electron Crystallography

Carbone

Baum

Rudolf³

et al. 2008

Phys. Rev. Lett.

141

View full text Add to dashboard Cite

By means of time-resolved electron crystallography, we report direct observation of the structural dynamics of graphite, providing new insights into the processes involving coherent lattice motions and ultrafast graphene ablation. When graphite is excited by an ultrashort laser pulse, the excited carriers reach their equilibrium in less then one picosecond by transferring heat to a subset of strongly coupled optical phonons. The time-resolved diffraction data show that on such a time scale the crystal undergoes a contraction whose velocity depends on the excitation fluence. The contraction is followed by a large expansion which, at sufficiently high fluence, leads to the ablation of entire graphene layers, as recently predicted theoretically. DOI: 10.1103/PhysRevLett.100.035501 PACS numbers: 61.82.ÿd, 07.78.+s, 63.20.Kÿ, 78.47.ÿp The unique semimetal physical properties of graphite and its chemical inertness make possible numerous applications [1][2][3] including the use in nuclear reactors [4,5]. When subjected to a shock, the structure distorts, and the ablation to form graphene [6] may result from its instability. It is of fundamental importance to visualize the associated dynamics with atomic-scale spatial and temporal resolutions. Here, by means of ultrafast electron crystallography, we report direct observation of the structural dynamics of graphite following an impulsive near infrared excitation. The diffraction shows that the structure of graphite first contracts perpendicular to the layer planes on the time scale of 0.5 to 3 ps, depending on fluence, and then nonthermally expands in 7 ps. The excitation fluence dependence of both processes indicates a distinct behavior. The highly anisotropic transfer of carrier energy to a subset of phonons of the quasi-2D-structure alters the forces between layers which control the time scale and amplitude of structural change. These atomic motions on different time scales for compression, expansion and restructuring determine the degree of the instability, which at sufficiently high fluences reaches that of graphene ablation [7,8], as predicted theoretically [9].Previous optical studies have focused on the carrier dynamics induced by both high [10,11] and low fluence [12] optical excitation, revealing features of the unique phonon excitations in quasi-two-dimensional graphite and the coherent modes involved. In order to resolve details of the structure, diffraction is our method of choice. In ultrafast electron crystallography, the probing wavelength is 0.07 Å at 30 keV electron acceleration energy, and we use femtosecond (fs) near infrared pulses (800 nm) for the optical excitation of the system of graphite. The overall resolution is determined by group velocity mismatch [13], but as shown here, by tilting the optical wave front, see the inset in Fig. 4, we are able to resolve subpicosecond coherent dynamics. Highly oriented and single crystal graphite were studied, and indeed the static diffraction patterns of both display the characteristic structural features...

show abstract

mentioning

confidence: 78%

“…When subjected to a shock, the structure distorts, and the ablation to form graphene [6] may result from its instability. It is of fundamental importance to visualize the associated dynamics with atomic-scale spatial and temporal resolutions.…”

mentioning

confidence: 99%

Structural Preablation Dynamics of Graphite Observed by Ultrafast Electron Crystallography

Carbone

Baum

Rudolf³

et al. 2008

Phys. Rev. Lett.

141

View full text Add to dashboard Cite

show abstract

“…As nanofibras de carbono são materiais compostos por placas de grafite empilhadas ao longo de um eixo com formato de cone. 25,26 Através de uma análise da Figura 3c (obtida no microscópio de transmissão com alta resolução) é possível observar o enfileiramento das placas de grafite. Outra estrutura formada apresentou paredes corrugadas, com curvaturas acentuadas e superfícies irregulares, como observado nas Figuras 2c e 3a.…”

Section: Análise Microestrutural Dos Materiais Formadosunclassified

“…A grafita pode ser encontrada na forma mineral ou obtida sinteticamente através de fontes de carbono. 26 …”

Section: Análise Microestrutural Dos Materiais Formadosunclassified

Síntese de nanomateriais de carbono a partir do resíduo de milho (DDGS)

Alves¹,

Zhuo²,

Levendis³

et al. 2012

Quím. Nova

View full text Add to dashboard Cite

Recebido em 13/11/11; aceito em 23/4/12; publicado na web em 20/7/2012 SYNTHESIS OF CARBON NANOMATERIALS FROM CORN WASTE (DDGS). The world's largest ethanol producer (USA) uses corn as feedstock. DDGS (distillers dried grains with solubles) is the main waste generated from this process (around 32 million t/ year). DDGS samples were pyrolyzed at 1000 °C in a furnace with controlled atmosphere. The effluent was channeled to a second furnace, in which catalyst substrates were placed. Chromatographic analysis was used to evaluate the gaseous effluents, showing that the catalyst reduced hydrocarbon emissions. The solid products formed were analyzed by SEM and TEM. Graphitic structures and carbon nanofibers, 50 μm in length and with diameters of 80-200 nm, were formed.Keywords: nanomaterials; DDGS; pyrolysis. INTRODUÇÃOO interesse pela energia da biomassa tem aumentado consideravelmente devido à necessidade de fontes de energia renováveis e limpas. O etanol proveniente da biomassa possui potencial para substituir grandes quantidades de combustíveis derivados do petróleo. A redução dos gases do efeito estufa tem sido amplamente discutida devido ao aquecimento global; o emprego do etanol em substituição aos combustíveis fósseis é considerado uma das principais medidas a serem adotadas, uma vez que os combustíveis fósseis são responsáveis por 73% da produção de CO 2 . 1 As propriedades do etanol, como o teor de oxigênio (cerca de 35% do total em massa), possibilitam uma combustão com melhor desempenho dos motores e menores índices de poluição, mesmo quando misturado à gasolina. 2 De acordo com a Global Renewable Fuels Alliance (GRFA), a produção mundial de etanol em 2010 foi de aproximadamente 8,6 x 10 10 L, representando um aumento da produção de 16,2% em relação ao ano anterior. 3 A indústria do etanol é tradicionalmente liderada por EUA e Brasil, responsáveis por cerca de 90% da produção mundial. A China apresentou um crescimento acelerado nos últimos anos, embora ainda apresente volume de produção distante dos lí-deres mundiais. A principal matéria-prima para o etanol empregada no Brasil é a cana-de-açúcar, enquanto que nos EUA predomina a aplicação do grão de milho. 4 A produção de etanol a partir do grão de milho apresenta crescimento consolidado nos últimos anos, em 2006 cerca de 1,9 x 10 10 L foram produzidos nos EUA, enquanto que, em 2009, foi registrada uma expansão para 3,8 x 10 10 L. 5 As atuais políticas de incentivos fiscais por parte do governo norte-americano tendem a aumentar ainda mais a competitividade deste setor, criando uma maior expectativa de produção para os próximos anos. 6 Maior produtor mundial de etanol (46% do total), os EUA possuem o milho como matéria-prima base para 98% das indústrias produtoras deste combustível. A produção de etanol norte-americana se concentra na região chamada de Cinturão do Milho, com destaque para os estados de Iowa e Illinois. 5 O grão de milho é convertido em etanol, basicamente, por dois processos: moagem úmida ou moagem seca. Na moagem úmida, a semente de milho ...

show abstract

“…Nevertheless, evolution of the synthesis and characterization of carbon materials (on both microscopic and nanoscopic length scales) went through several stages, during the last 50 years to reach their present level of sophistication [7]. As principal developments, we can cite the studies on graphite intercalation compounds in the 1970s [8], carbon fibers in the 1980s [9,10], the fullerene discovery in 1985 [11] by Kroto, Curl, and Smalley (the first time that a molecular level carbon nanostructure was discovered), the single wall carbon nanotube identification in 1993 by Iijima [12], and, finally, the single layer graphene separation by Novoselov and Geim in 2004 [4,13]. Graphene is the basic building block of several carbon nanomaterials.…”

mentioning

confidence: 99%

News and Views: Perspectives on Graphene and Other 2D Materials Research and Technology Investments

Ribeiro-Soares

Dresselhaus

2013

Braz J Phys

View full text Add to dashboard Cite

With the actual experimental realization of graphene samples, it became possible not only to exploit the special physical properties of graphene but also to exploit its technological applications. As the field developed, the discovery of other 2D materials occurred and this opened up access to a plethora of combinations of a large variety of electrical, optical, mechanical, and chemical properties. Now there are large investments being made around the world to develop the graphene research area and to boost graphene use in technology. Here, we discuss current research and some future prospects for this area of layered nanomaterials. [2]. The transition metal dichalcogenides, for example, form a set of more than 30 layered solids with large varieties of optical, thermal, mechanical, and electronic properties, offering even more possibilities for technological applications. KeywordsFrom a scientific standpoint, the reduction of the sample size in terms of one or a few 2D layers in graphite, reaching graphene in the monolayer limit, opened the possibility to explore many new physical phenomena, such as the study of Dirac-like particles in condensed matter systems [3] and the quantum Hall effect which is observed when electrons (here behaving like Dirac fermions) are under the influence of a magnetic field [4,5]. This two-dimensional form of organization of carbon atoms with sp 2 hybrid bonds has been studied theoretically since 1947, when Wallace proposed the linear dispersion relation (E(k)) for monolayer graphene [6]. Nevertheless, evolution of the synthesis and characterization of carbon materials (on both microscopic and nanoscopic length scales) went through several stages, during the last Braz J Phys (2014) 44:278-282

show abstract

Applications of Graphite Fibers and Filaments

Cited by 8 publications

References 0 publications

Structural Preablation Dynamics of Graphite Observed by Ultrafast Electron Crystallography

Structural Preablation Dynamics of Graphite Observed by Ultrafast Electron Crystallography

Síntese de nanomateriais de carbono a partir do resíduo de milho (DDGS)

News and Views: Perspectives on Graphene and Other 2D Materials Research and Technology Investments

Contact Info

Product

Resources

About