Graphite melting under laser pulse heating

Ronchi, C.; Beukers, R.; Heinz, H.; Hiernaut, J.-P.; Selfslag, R.

doi:10.1007/bf00503360

Cited by 30 publications

(7 citation statements)

References 9 publications

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“…Our preliminary findings [18] suggest that the defective nanotube remained intact even at temperatures comparable to the melting point of graphite [22]. At these very high temperatures, we observed the formation of bonds bridging the gap created by the monatomic vacancy, similar to those formed during the electronically induced self-healing.…”

Section: Resultssupporting

confidence: 54%

Can photo excitations heal defects in carbon nanotubes?

Miyamoto

Berber

Yoon

et al. 2004

Chemical Physics Letters

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Section: Resultssupporting

confidence: 54%

Can photo excitations heal defects in carbon nanotubes?

Miyamoto

Berber

Yoon

et al. 2004

Chemical Physics Letters

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“…Diamond was removed as it transforms to graphite at atmospheric pressure. Melting temperature of carbon is given corresponding to melting of graphite at 3800°C at 100 bar.…”

Section: Applications Above 1500°cmentioning

confidence: 99%

Experimental Approaches to the Thermodynamics of Ceramics Above 1500°C

Ushakov

Navrotsky

2012

J. Am. Ceram. Soc.

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Traditionally, the nuclear and aerospace industries have been the main drivers behind the development of high‐temperature materials. These applications demand a high degree of reliability and extensive characterization of every new material. There is a lack of experimental thermodynamic data above 1500°C even for HfO2, ZrO2, La2O3, Y2O3, and other constituents of widely used ceramic systems. Such data, as are available, were often obtained half a century ago using custom‐built instruments. We review classic experimental approaches for the measurement of formation enthalpies, high‐temperature enthalpy increments by the drop method, and also discuss more recent developments which include mass spectrometric measurements of vapor pressures, pulsed laser relaxation methods for heat capacity, and melting temperature determination and high‐temperature oxide melt solution calorimetry in application to refractory compounds. Approaches to the experimental determination of phase diagrams at high temperature are introduced using studies of liquid immiscibility in the Zr(O)–UO2 system as an example. Thermal analysis above 2000°C is now possible with commercially available instruments, as shown by the first experimental measurements of the phase transition and fusion enthalpies of La2O3. New results on a premelting phase transition in Y2O3 in oxygen are reported from in situ synchrotron X‐ray diffraction study on levitated samples.

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“…3,4 On the other hand, fullerenes in nanotube peapods 5 have been observed to fuse 6,7 at relatively low temperatures near 1100°C, significantly below the decomposition temperature of fullerenes 8 or graphite 9 near 4000°C. No information is available about the detailed fusion process except the obvious conclusion that strong sp 2 bonds should not be broken during structural rearrangements leading to fusion.…”

mentioning

confidence: 99%

Microscopic mechanism of fullerene fusion

et al. 2004

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Combining total energy calculations with a search of phase space, we investigate the microscopic fusion mechanism of C 60 fullerenes. We find that the ͑2+2͒ cycloaddition reaction, a necessary precursor for fullerene fusion, may be accelerated inside a nanotube. Fusion occurs along the minimum energy path as a finite sequence of Stone-Wales transformations, determined by a graphical search program. Search of the phase space using the "string method" indicates that Stone-Wales transformations are multistep processes, and provides detailed information about the transition states and activation barriers associated with fusion. The discovery of fullerenes 1 and nanotubes 2 has ignited strong interest in these and related carbon nanostructures. Due to the unusual stability of the graphitic sp 2 bond, largescale structural changes in bulk fullerene crystals occur only under extremely high pressures and temperatures.3,4 On the other hand, fullerenes in nanotube peapods 5 have been observed to fuse 6,7 at relatively low temperatures near 1100°C, significantly below the decomposition temperature of fullerenes 8 or graphite 9 near 4000°C. No information is available about the detailed fusion process except the obvious conclusion that strong sp 2 bonds should not be broken during structural rearrangements leading to fusion. In view of the fact that even minor structural changes in carbon nanostructures may modify significantly their physical properties, including magnetism, 10,11 there is additional interest in understanding fusion as a way to control large-scale structural transformations.Here we study the microscopic fusion mechanism of fullerenes. We show that large-scale structural changes, including fusion, can be achieved by a finite sequence of generalized Stone-Wales transformations, which involve only bond rotations and avoid bond breaking. Using a graphical search program, 12 we determine the optimum reaction pathway for thermal fusion of fullerenes. Search of the phase space by the "string method" provides detailed information about the optimum pathway, including the identification of activation barriers and transition-state geometries. We find the fusion process to be exothermic. The fusion dynamics is fast in spite of the formidable total activation barrier close to 5 eV, associated with each Stone-Wales transformation. These bond rotations turn out to be multistep processes with lower individual activation barriers.We calculate the total energy of the fullerene system using an electronic Hamiltonian that had been applied successfully to describe the formation of peapods, 13 multiwall nanotubes, 14 the dynamics of the "bucky shuttle," 15 and the melting of fullerenes. 8 Our numerical results are compared to those of ab initio density functional calculations, which use a numerical basis to represent localized atomic orbitals, 16 and which have been applied successfully to nanotubes and fullerenes. 17 Structural optimization is performed using the conjugate gradient technique. Our total energy formalism describe...

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Graphite melting under laser pulse heating

Cited by 30 publications

References 9 publications

Can photo excitations heal defects in carbon nanotubes?

Can photo excitations heal defects in carbon nanotubes?

Experimental Approaches to the Thermodynamics of Ceramics Above 1500°C

Microscopic mechanism of fullerene fusion

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