Chemical erosion of first wall materials by atomic hydrogen at high temperatures

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The chemical erosion of C and TiB 2 by reaction with H has been studied from 420 to 1540 K using H pressures characteristic of fusion devices. For graphite, erosion yields range from 2.0 × 10 −4 to 7.4 × 10 −4 C H over this temperature range. A change in the gas phase product distribution is observed as a function of temperature and reaction time. Methane is most abundant at low temperatures and short reaction times, while C 2 and C 3 species increase in abundance at higher temperatures and after extended reaction times. TiB 2 shows no evidence of reaction below 1300 K and lower erosion yields than graphite at higher temperatures. The superior erosion resistance of TiB 2 suggests that it may be a better candidate material than graphite for fusion applications requiring refractory low-Z materials.