Nanocarbon synthesis by high-temperature oxidation of nanoparticles

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 sp2 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.

Effects of point defects on oxidation of 3C–SiC

“…This high pressure used in our simulations is necessary to observe reactions on the time scales of MD simulations. Similar pressures were used in earlier MD simulations of SiC oxidation, where it was shown that such simulations give a reasonable description of chemical reactions [14,16,17]. Periodic boundary conditions were applied along x and y dimensions of the simulation cell.…”

Meteorite impacts on ancient oceans opened up multiple NH3 production pathways

“…In our previous AIMD simulations of similar high-temperature reactions, we compared spin-restricted and spin-unrestricted DFT calculations and indeed found that spin polarization plays a negligible role. 28 The DFT-D method was employed for the semi-empirical correction of the van der Waals interaction. 29 The momentum-space formalism 30 was utilized, where the plane-wave cutoff energies were set to be 30 and 250 Ry for the electronic pseudo-wave functions and the pseudo-charge density, respectively.…”

Shift-Collapse Acceleration of Generalized Polarizable Reactive Molecular Dynamics for Machine Learning-Assisted Computational Synthesis of Layered Materials

“…This variable Ncharge problem is commonly solved iteratively, e.g., with the conjugate gradient (CG) method [3]. Though recent advancements in parallel ReaxFF algorithms [4][5][6] have enabled large RMD simulations [7] involving multimillion atoms, QEq computation remains to be the major bottleneck for studying long time trajectories of such large RMD simulations.…”