Location of deuterium atoms absorbed in nanocrystalline graphite prepared by mechanical alloying

Abstract

Neutron diffraction is an important technique for studying the structure of hydride materials. H/D isotopic substitution was employed to observe the location of deuterium atoms in deuterated nano-graphite because the coherent scattering length of deuterium is large enough to be observed in comparison with that of the metal atoms forming hydrogen absorbing materials. The preparation of the nano-crystalline graphite and the absorption of deuterium atoms in the graphite were carried out simultaneously by mechanical alloying under D 2 gas atmosphere. The transformation from the hexagonal graphite as a starting material into amorphous-like carbon was observed by neutron diffraction. The conformation in the graphite was changed by the creation of dangling bonds and deuterium was absorbed by the solid-gas reaction when the milling proceeded. Two types of the deuterium coordinations were found in radial distribution function, RDF(r). One is the C–D covalent bond and the other is deuterium located between layers of the graphite.