High temperature stability of onion-like carbon vs highly oriented pyrolytic graphite.

ABSTRACT: The thermodynamic stability of onion-like carbon (OLC) nanostructures with respect to highly oriented pyrolytic graphite (HOPG) was determined in the interval 765-1030 K by the electromotive force (emf) measurements of solid electrolyte galvanic cell: (Low) Pt|Cr3C2,CrF2,OLC|CaF2s.c.|Cr3C2,CrF2,HOPG|Pt (High). The free energy change of transformation HOPG = OLC was found positive below 920.6 K crossing the zero value at this temperature. Its trend with temperature was well described by a 3rd degree polynomial. The unexpected too high values of [Formula: see text] jointly to the HR-TEM, STEM and EELS evidences that showed OLC completely embedded in rigid cages made of a Cr3C2/CrF2 matrix, suggested that carbon in the electrodes experienced different internal pressures. This was confirmed by

SUBMITTER: Latini A 

PROVIDER: S-EPMC4143374 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature