Hydrogen absorption and transport in graphite materials

Hydrogen absorption and transport in graphite materials have been studied to obtain fundamental information for a fusion reactor application and for hydrogen storage materials. Two kinds of hydrogen trapping sites should exist. One will be carbon dangling bonds located at the edge surface of a crystallite with an adsorption enthalpy of 2.6 eV, the other will be a solitary carbon dangling bond introduced by ion or neutron irradiation, such as an interstitial cluster loop edge, with an enthalpy of 4.4 eV. The results are compared with thermal desorption spectra of deuterium from graphites which were gas charged, ion irradiated and nano-structured by ball milling. These spectra can be well represented with three kinds of desorption process with activation energies of 1.3, 2.6 and 4.4 eV.