A body-centered cubic W-based refractory high entropy alloy with outstanding radiation resistance has been developed. The alloy was grown as thin films showing a bimodal grain size distribution in the nanocrystalline and ultrafine regimes and a unique 4-nm lamella-like structure revealed by atom probe tomography (APT). Transmission electron microscopy (TEM) and x-ray diffraction show certain black spots appearing after thermal annealing at elevated temperatures. TEM and APT analysis correlated the black spots with second-phase particles rich in Cr and V. No sign of irradiation-created dislocation loops, even after 8 dpa, was observed. Furthermore, nanomechanical testing shows a large hardness of 14 GPa in the as-deposited samples, with near negligible irradiation hardening. Theoretical modeling combining ab initio and Monte Carlo techniques predicts the formation of Cr- and V-rich second-phase particles and points at equal mobilities of point defects as the origin of the exceptional radiation tolerance.

Abstract

No abstract

A novel approach based on conventional solution-coating and wire-drawing processes has been employed for the production of carbon nanotube (CNT) coated conductors. The solution process employs a mesoscopic building block, a CNT fibril dispersion formed in acid from forest-grown, long-length multiwall CNTs, to help bridge the transition from nanomaterials to thick, highly aligned technical coatings. The coatings are formed onto a roughened copper wire former through dip-coating. The roughened surface provides for mechanical attachment between the CNT coating and copper wire core that allows for the composite to be wire-drawn while wet to further shape, densify, and align the CNT coating. The wet chemistry approach offered a facile integration of different CNT and dopant types in the CNT coatings. For the specific process described here, it was observed that the CNT coatings were simultaneously doped with acid and copper nanoparticles. Coated wires were produced with conductivities on par with copper but in an engineered material that is lighter than the pure metal analogue. Dense coatings up to 90 μm in thickness were made that comprised up to 60% of the wire cross-sectional area and enabled composite densities to dip below half that of copper. The CNT coated wires had overall resistivities in the range 2.1–5 μΩ·cm, with specific conductivities relative to copper as high as 108%. The ubiquitous nature of the solution coating and conventional wire drawing processes may enable a novel approach to the light-weighting of advanced conductors for a broad range of applications.