HYDROGEN AND HELIUM RETENTION PROPERTIES OF B4C AND SIC CONVERTED GRAPHITES

The hydrogen or helium retention properties of B4C converted graphite, SiC converted graphite and isotropic graphite were examined, by the i rradiation of a hydrogen or helium ion, followed by a thermal desorpti on spectroscopy measurement. The energy of the hydrogen or helium ion was 1.7 or 5.0 keV, respectively. For both B4C and SIG, two peaks appe ared in the H-2 desorption spectra. The lower temperature peaks of B4C and SiC correspond to detrappings of B-H and Si-H bonds, respectively . It is considered that the higher peak is due to detrapping of the C- H bond. The amounts of retained hydrogen at room temperature (RT), obt ained from the H-2 desorption spectra, were 6.71 x 10(17), 1.0 x 10(18 ) and 5.8 x 10(17) H cm(-2) for isotropic graphite, B4C and SiC, respe ctively. For the He desorption spectrum in the case of B4C, two peaks appeared at 300 and 950 degrees C. For SiC, a sharp desorption peak wa s observed at 850 degrees C, in addition to the low temperature peak a t approximate to 300 degrees C. For graphite, the spectrum had a singl e peak at 300 degrees C. When the helium fluence was increased, this p eak temperature shifted to the higher temperature region. The amount o f retained helium in B4C, SIC and isotropic graphite at RT were 2.7 x 10(17), 4.2 x 10(17) and 3.4 x 10(17) He cm-2, respectively. It is see n that the trapped amount of helium is not negligibly small. (C) 1998 Elsevier Science S.A. All rights reserved.