STRUCTURAL-PROPERTIES OF AMORPHOUS HYDROGENATED CARBON .1. A HIGH-RESOLUTION NEUTRON-DIFFRACTION STUDY

The structure of samples of amorphous hydrogenated carbon, prepared fr om acetylene and propane precursors, containing 35 and 32 at.% hydroge n, respectively, was investigated by time-of-flight neutron diffractio n in the range 0.2-50 angstrom-1 using the ISIS spallation source. The large dynamic range of the data ensures a real-space resolution suffi cient to reveal directly the proportions of sp2 and sp3 hybridized car bon. The results show that, in these hard carbon materials, the carbon -atom sites are predominantly sp2 bonded, and the carbon-carbon single bond:carbon-carbon double bond ratio is about 2.5:1. The detailed inf ormation on atomic correlations thus provided is used to discuss curre nt structural models, and in particular the data are used to show that these models require significant modification.