Titanium as coupling agent in SiC fibre reinforced copper matrix composites

SiC fibre reinforced copper matrix composites are candidate materials for heat sinks in future fusion reactors, as they combine high thermal conductivity and high mechanical strength for operating temperatures of up to 550 °C under neutron irradiation. To improve their properties via interlayer design, titanium as coupling agent was deposited on carbon-coated SiC fibres by magnetron sputtering, followed by a copper deposition using electroplating. After a heat treatment at 550 °C for the formation of TiC and the reduction of porosity, the wrapped fibres were packed in a copper capsule and hot-isostatically pressed at 650 °C to form a composite. The interlayer between fibre and matrix was characterised by high-resolution and analytical transmission electron microscopy and by push-out tests. During the heat treatment, the titanium completely reacts with the carbon coating of the fibre, forming TiC which enhances the bonding between the SiC fibre and the copper matrix. The resulting bonding strength is about 10-fold higher for composites with titanium interlayers compared to those without such layers.