Promising composite heat sink material for the divertor of future fusion reactors

We investigate SiC fibre reinforced copper as an additional layer at the highly loaded zone between plasma facing material (W) and heat sink (CuCrZr) for a fusion reactor divertor. Copper has a high thermal conductivity of 380 Wm−1 K−1 but a very low strength and creep resistance at 550 °C. Therefore copper is reinforced with SiC long fibres (SCS6, Specialty Materials) having excellent high temperature strength. The fibres were galvanically coated with an 80 μm-thick copper layer as matrix. Hot isostatic pressing at 650 °C was applied to form the composite material. The interfacial shear strength calculated from push-out tests was ∼6 MPa. Adding a 100 nm-thin titanium interlayer deposited by magnetron sputtering led to a higher adhesion of the SiC fibres in the copper matrix. Titanium reacted with the carbon surface of the fibre to TiC and formed with copper the alloy Cu4Ti during heat treatment and increased the interfacial shear strength to 70 MPa.