Effects of carbon nanotubes on high-quality bonding of W and CuCrZr

Abstract

Confronting the extreme working conditions of plasma facing components, carbon nanotubes (CNTs) were introduced into the bonding of W and CuCrZr alloys by employing a Cu-CNTs interlayer to obtain the joints with excellent thermal and mechanical properties. The bonding process includes Cu-CNTs co-deposition on the surface of W substrate, annealing of Cu-CNTs composite coating, and diffusion bonding with the CuCrZr alloy. The morphological evolutions of Cu-CNTs composite coating and the interface structure of the W/Cu-CNTs/CuCrZr alloy joint were studied by scanning electron microscopy, energy-dispersive spectroscopy, and high-resolution transmission electron microscopy. The Cu-CNTs composite coating was continuous after co-deposition and annealing, and CNTs were uniformly mixed in the coating without significant entanglement. By exploiting the intrinsic strength of individual CNTs, a high shear strength (202 MPa) of the W/Cu-CNTs/CuCrZr alloy joint was obtained through the load transfer effect. The thermal conductivity of the joint increased with temperature in the range of 260–280 W/(m·K), which are about 12 % higher than that of the direct-bonded W/CuCrZr alloy joints. The thermal properties of the W/Cu-CNTs/CuCrZr alloy joints were enhanced due to the reduced thermal mismatch between W and Cu-CNTs interlayer and the thermal conductive network constructed at the interface. This enhancement was achieved by taking advantage of the high thermal conductivity, extremely low coefficient of thermal expansion, and large aspect ratio of the CNTs. The developed bonding process of the W/Cu-CNTs/CuCrZr alloy joint provides an effective support for plasma-facing components in future fusion reactors.