The unusual morphology, structure, and magnetic property evolution of glassy carbon upon high pressure treatment

Abstract

Glassy carbon (GC) has been high-pressure high-temperature treated. An interesting morphology evolution from the pristine sample to the high pressure products was observed. It is found that GC can be graphitized under pressure at a temperature much lower than that at ambient condition. Furthermore the in − situ structure and electrical measurements of GC and graphitized glassy carbon (GGC) under high temperature and high pressure have been investigated up to 30 GPa. We particularly emphasize the unusual magnetic properties of GC treated under high pressures and high temperatures. A paramagnetic to ferromagnetic-like, and then to superconducting (a diamagnetic signal with hysteresis magnetic response) -like behavior, which can be observed at temperatures as high as 80 K, appears as a successive evolution from the initial GC to GGC in accordance with three regions distinguished by the graphitization temperature. This interesting evolution of magnetic properties probably evokes the new understanding of carbon element.

Thickness Control of Graphene Overlayer via Layer-by-Layer Growth on Graphene Templates by Chemical Vapor Deposition

“…Therefore, we conclude that graphene layers grown at low temperatures (720-744 C) form a disordered stack similar to a turbostratic structure because it needs high-temperature ($2700 C) or low-temperature ($1400 C) annealing under high pressure condition ($5 GPa) for the crystallization of graphite having a turbostratic structure 25,26) and glassy carbon. 28) We also observed that the D-band intensity increases with growth. 21) The grain size evaluated from the G/D ratio is about 50 nm.…”

C60and C70pressure-and-temperature transformations into fullerene-related forms

“…The background is skew, the peaks are broad and asymmetric, and there are no peaks that characterize the threedimensional periodicity of a perfect graphite-like structure. These features were also found in the diffraction patterns of the onion-like carbons [24][25] and glassy carbon [26]. The dilation of the layered structure along the c-axis can explain the broadening and the shift of the first peak Though the XRD patterns of the bulk and HIP-produced samples look similar, there is a difference.…”