Investigation of W-SiC compositionally graded films as a divertor material

TL;DR

This study investigates the synthesis, microstructure, and plasma performance of W-SiC compositionally graded films as a promising plasma-facing divertor material, highlighting their stability and compatibility in tokamak conditions.

Contribution

It presents a novel fabrication and characterization of W-SiC graded films, demonstrating their microstructural stability under plasma exposure for potential use in tokamak divertors.

Findings

W-SiC films are polycrystalline W with amorphous SiC layers.

No delamination or microstructural damage after plasma exposure.

Films show stability under mild plasma conditions.

Abstract

W-SiC composite material is a promising plasma-facing material candidate alternative to pure W due to the low neutron activation, low impurity radiation, and low tritium diffusivity of SiC while leveraging the high erosion resistance of the W armor. Additionally, W and SiC have high thermomechanical compatibility given their similar thermal expansion rates. The present study addresses the synthesis and performance of compositionally graded W-SiC films fabricated by pulsed-DC magnetron sputtering. Compositional gradients were characterized using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS), and crystallographic information was obtained using electron diffraction and X-ray diffraction (XRD). Samples were exposed to L-mode deuterium plasma discharges in the DIII-D tokamak using the Divertor Material Evaluation System (DiMES). Post-mortem characterizations were performed using scanning electron microscopy (SEM) and XRD. Electron diffraction and XRD showed that the compositionally graded W-SiC films were composed of polycrystalline W and amorphous SiC with amorphous W+SiC interlayers. No macroscopic delamination or microstructural changes were observed under mild exposure conditions. This study serves as a preliminary examination of W-SiC compositionally graded composites as a potential candidate divertor material in future tokamak devices.