Measurement of inherent hydrogen and oxygen in graphites using laser release analysis

Inherent concentrations of hydrogen and oxygen in different types of graphites (pyrolytic, isotropic and carbon-fibre-composite) were measured using laser-induced thermal desorption spectrometry. Subsequent to normal system bakeout at 500 K, H/C and O/C ratios of ∝0.1-1% were measured. These levels were progressively reduced by about two orders of magnitude by heating the samples in vacuum to temperatures up to 2300 K. The similar levels of O and H suggest that these species might originate from water or hydroxyl molecules introduced in the material either during manufacture or subsequent atmospheric exposure. (orig.)