Anomalous thermal stability in supergiant onion-like carbon fullerenes

Abstract

Onion-like carbon fullerenes (OLCFs) are a promising material for applications in nanoscale devices, medicine, lubrication and superhard materials. Knowledge of the pyrolysis chemistry of OLCFs helps understanding the thermal-induced erosion of carbon-based resources and spacecraft materials. Here, using first-principle-based ReaxFF atomistic simulations, thermal and dynamical characteristics of supergiant 20-shell OLCF having concentric arrangement of C60@C240@ … @C24000 are explored. Fullerenes@20-shell OLCF yield larger average radii than isolated single-walled fullerenes (SWFs) at the same scale. The intershell-spacing@OLCF exhibits a reduction tendency from inner to outer shells, but is higher than that of bulk graphite. Because of nonbonded intershell forces, fullerenes@20-shell OLCF are energetically favorable over the corresponding isolated SWFs. In contrast to nonmonotonic variation of melting point with size and shell-index in SWFs and other nanoparticles, an anomalous shell-dependent melting instability in the 20-shell OLCF is identified due to the combined effects of geometrical size, nanoconfinement and surface; Both inner and outer fullerenes are not so resistive against heating, nor are they as strong as the identical-size isolated SWFs, however, the intermediate shells, locally similar to curved graphite, demonstrate higher heat-resisting property than identical-size isolated SWFs. Topological analysis reveals morphological transformation of four stages involving Stone-Wales rearrangement, heterogeneous defects nucleation, amorphization and fragmentation.