The designed plasma facing materials for the divertor-components in ITER are up to now carbon (graphite or CFC) and tungsten. The heat flux loading can result in temperatures of up to 550°C at the interface between the plasma facing material and the CuCrZr heat sink, an operation temperature which is too high for CuCrZr. Additionally the temperature gradient and the mismatch in thermal expansion (CTE) of both parts of the divertor result in high stresses at the interface. A tungsten-copper composite material with a gradation from pure copper on the one side to pure tungsten on the opposite side is supposed to support the stress reduction. The tungsten contributes to the strength of the composite, whereas the copper provides the required thermal conductivity (TC) of at least 200 W/mK. The graded W/Cu layers were produced by the "chemical mixing" method and subsequent liquid phase sintering. Here the use of sub-μm W-particle sizes offers an opportunity to gain well dispersed W-particles with high Cu-containing composites resulting in lower CTE values and higher thermal conductivities compared to coarser W-powders. Brazing of the functionally graded W/Cu interlayers to CuCrZr and CFC materials resulted in adjoined mockups.
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