Chemical erosion of doped graphites for fusion devices

Doping of carbon generally results in a reduction of its chemical reactivit y during hydrogen ion bombardment. Due to preferential sputtering of carbon , the dopants may be enriched at the surface, resulting in an additional re duction of the erosion yield. Dopants in the form of sub-mum precipitates w ith a very homogeneous distribution lead to in a more effective reduction o f both chemical erosion processes, Y-therm and Y-surf. However, dopants may degrade the thermal conductivity of graphite, which has to be avoided. Fir st results on the development of carbon materials doped with different carb ides and with optimized microstructure and thermomechanical properties show that VC acts as an effective catalyst for graphitization causing an improv ement of the thermal conductivity. It leads further to a reduction of both, the Y-therm and the Y-surf chemical erosion processes, which is partly att ributed to surface enrichment but is also the result of a chemical influenc e, (C) 2001 Elsevier Science B.V. All rights reserved.