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Nanocarbon synthesis by high-temperature oxidation of nanoparticles.

Nomura K, Kalia RK, Li Y, Nakano A, Rajak P, Sheng C, Shimamura K, Shimojo F, Vashishta P - Sci Rep (2016)

Bottom Line: Initial oxidation produces a molten silica shell that acts as an autocatalytic 'nanoreactor' by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment.Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp(2) carbons with pentagonal and heptagonal defects.This work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.

View Article: PubMed Central - PubMed

Affiliation: Collaboratory for Advanced Computing and Simulations, Department of Physics &Astronomy, Department of Computer Science, Department of Chemical Engineering &Materials Science, and Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-0242, USA.

ABSTRACT
High-temperature oxidation of silicon-carbide nanoparticles (nSiC) underlies a wide range of technologies from high-power electronic switches for efficient electrical grid and thermal protection of space vehicles to self-healing ceramic nanocomposites. Here, multimillion-atom reactive molecular dynamics simulations validated by ab initio quantum molecular dynamics simulations predict unexpected condensation of large graphene flakes during high-temperature oxidation of nSiC. Initial oxidation produces a molten silica shell that acts as an autocatalytic 'nanoreactor' by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment. Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp(2) carbons with pentagonal and heptagonal defects. This work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.

No MeSH data available.


Related in: MedlinePlus

Fractal nanocarbon formed by percolation during nSiC oxidation.(a) The time evolution of sp2 carbon atoms at temperatures 2,400 K (blue) and 2,800 K (red) for D = 10 nm. (b) A simulation snapshot at 2 ns shows the structure of the nanocarbon synthesized by oxidation of nSiC (D = 10 nm) at 2,800 K. (c) Graphene-like carbon clusters produced on the surface of an oxidizing nSiC of diameter D = 100 nm at time 0.2 and 0.4 ns, exhibiting a percolation transition. The color represents the cluster mass in atomic mass unit (amu). (d) The size of the largest carbon cluster in amu as a function of time (D = 100 nm), where the blue dashed line marks the percolation transition. (e) Number of clusters, C(i), as a function of the cluster size, i, just before the percolation transition (0.3 ns) for D = 100 nm. The blue line shows the power-law fit for larger clusters, C(i) > 10.
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f2: Fractal nanocarbon formed by percolation during nSiC oxidation.(a) The time evolution of sp2 carbon atoms at temperatures 2,400 K (blue) and 2,800 K (red) for D = 10 nm. (b) A simulation snapshot at 2 ns shows the structure of the nanocarbon synthesized by oxidation of nSiC (D = 10 nm) at 2,800 K. (c) Graphene-like carbon clusters produced on the surface of an oxidizing nSiC of diameter D = 100 nm at time 0.2 and 0.4 ns, exhibiting a percolation transition. The color represents the cluster mass in atomic mass unit (amu). (d) The size of the largest carbon cluster in amu as a function of time (D = 100 nm), where the blue dashed line marks the percolation transition. (e) Number of clusters, C(i), as a function of the cluster size, i, just before the percolation transition (0.3 ns) for D = 100 nm. The blue line shows the power-law fit for larger clusters, C(i) > 10.

Mentions: To quantify the growth of graphene-like flakes, we show in Fig. 2a the number of sp2-bonded carbon atoms with three carbon neighbors as a function of time at temperatures 2,400 K and 2,800 K for D = 10 nm. Larger number of sp2 carbons are produced at 2,800 K than at 2,400 K, and a significant fraction of the total number of carbon atoms (~ 2×104) at 2,800 K becomes part of the solid carbon product at the end of the simulation.


Nanocarbon synthesis by high-temperature oxidation of nanoparticles.

Nomura K, Kalia RK, Li Y, Nakano A, Rajak P, Sheng C, Shimamura K, Shimojo F, Vashishta P - Sci Rep (2016)

Fractal nanocarbon formed by percolation during nSiC oxidation.(a) The time evolution of sp2 carbon atoms at temperatures 2,400 K (blue) and 2,800 K (red) for D = 10 nm. (b) A simulation snapshot at 2 ns shows the structure of the nanocarbon synthesized by oxidation of nSiC (D = 10 nm) at 2,800 K. (c) Graphene-like carbon clusters produced on the surface of an oxidizing nSiC of diameter D = 100 nm at time 0.2 and 0.4 ns, exhibiting a percolation transition. The color represents the cluster mass in atomic mass unit (amu). (d) The size of the largest carbon cluster in amu as a function of time (D = 100 nm), where the blue dashed line marks the percolation transition. (e) Number of clusters, C(i), as a function of the cluster size, i, just before the percolation transition (0.3 ns) for D = 100 nm. The blue line shows the power-law fit for larger clusters, C(i) > 10.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837334&req=5

f2: Fractal nanocarbon formed by percolation during nSiC oxidation.(a) The time evolution of sp2 carbon atoms at temperatures 2,400 K (blue) and 2,800 K (red) for D = 10 nm. (b) A simulation snapshot at 2 ns shows the structure of the nanocarbon synthesized by oxidation of nSiC (D = 10 nm) at 2,800 K. (c) Graphene-like carbon clusters produced on the surface of an oxidizing nSiC of diameter D = 100 nm at time 0.2 and 0.4 ns, exhibiting a percolation transition. The color represents the cluster mass in atomic mass unit (amu). (d) The size of the largest carbon cluster in amu as a function of time (D = 100 nm), where the blue dashed line marks the percolation transition. (e) Number of clusters, C(i), as a function of the cluster size, i, just before the percolation transition (0.3 ns) for D = 100 nm. The blue line shows the power-law fit for larger clusters, C(i) > 10.
Mentions: To quantify the growth of graphene-like flakes, we show in Fig. 2a the number of sp2-bonded carbon atoms with three carbon neighbors as a function of time at temperatures 2,400 K and 2,800 K for D = 10 nm. Larger number of sp2 carbons are produced at 2,800 K than at 2,400 K, and a significant fraction of the total number of carbon atoms (~ 2×104) at 2,800 K becomes part of the solid carbon product at the end of the simulation.

Bottom Line: Initial oxidation produces a molten silica shell that acts as an autocatalytic 'nanoreactor' by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment.Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp(2) carbons with pentagonal and heptagonal defects.This work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.

View Article: PubMed Central - PubMed

Affiliation: Collaboratory for Advanced Computing and Simulations, Department of Physics &Astronomy, Department of Computer Science, Department of Chemical Engineering &Materials Science, and Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-0242, USA.

ABSTRACT
High-temperature oxidation of silicon-carbide nanoparticles (nSiC) underlies a wide range of technologies from high-power electronic switches for efficient electrical grid and thermal protection of space vehicles to self-healing ceramic nanocomposites. Here, multimillion-atom reactive molecular dynamics simulations validated by ab initio quantum molecular dynamics simulations predict unexpected condensation of large graphene flakes during high-temperature oxidation of nSiC. Initial oxidation produces a molten silica shell that acts as an autocatalytic 'nanoreactor' by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment. Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp(2) carbons with pentagonal and heptagonal defects. This work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.

No MeSH data available.


Related in: MedlinePlus