High-resolution electron microscopy of a microporous carbon

Abstract

The structure of a microporous carbon prepared by the carbonization of sucrose was examined using high-resolution electron microscopy. It was found to be disordered and isotropic and primarily made up of tightly curved individual carbon layers, enclosing pores typically about 1 nm in size. Completely closed carbon particles were also present. These observations suggest that the carbon may have a fullerene-related structure, in which pentagons and heptagons are distributed randomly throughout a hexagonal network, producing continuous curvature.

New Perspectives on the Structure of Graphitic Carbons

“…Occasionally, however, very small closed particles can be found in the carbons. 30 The presence of such particles provides circumstantial evidence that the surrounding carbon may have a fullerenerelated structure. Direct imaging of pentagonal rings by HRTEM has not yet been achieved, but recent developments in TEM imaging techniques suggest that this may soon be possible, as discussed in the Conclusions.…”

“…The present author and colleagues initiated a series of studies of typical non-graphitizing microporous carbons using this technique in the mid 1990s. 30,38,39 The first such study involved examining carbons prepared from PVDC and sucrose, after heat treatments at temperatures in the range 2100…”

“…30 als that cannot be transformed into crystalline graphite even at temperatures of 3000 • C and above. The low density of nongraphitizing carbons is a consequence of a microporous structure, which gives these materials an exceptionally high internal surface area.…”

“…• C. 30 The inset shows a diffraction pattern recorded from an area approximately 0.25 µm in diameter. The image shows the structure to be disordered and isotropic, consisting of tightly curled single carbon layers, with no obvious graphitization.…”

Curved Surfaces in Disordered Carbons by High Energy X-ray Scattering

“…penta gons or hepta gons) b esides the gra phi ti c six-m embered ri ng [5{ 8 ]. Recentl y, the presence of curved ful l erene-and nano tub e-l ike fra gments i n non-gra phi ti zing carb ons has been reveal ed by careful observ ati on by hi gh resol uti on tra nsm i ssio n el ectro n m icro scopy observ ati on (HR TE M) [5,8,9] and by Ram an scatteri ng (R S) [10 , 11]. On the other ha nd, the hi gh Ûexibi li t y of gra phene sheets expl ains thei r tendency to fol di ng.…”