Tritium permeation barrier based on self-healing composite materials

Pores and cracks in ceramic coatings is one of the most important problems to be solved for the thermally sprayed tritium permeation barriers (TPBs) in fusion reactor. In this work, we developed a self-healing composite coating to address this problem. The coating composed of TiC + mixture(TiC/Al2O3) + Al2O3 was deposited on martensitic steels by means of atmospheric plasma spraying (APS). Before and after heat treatment, the morphology and phase of the coating were comparatively investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). In the experiment, NiAl + Al2O3, mixture(TiC/Al2O3) + Al2O3 and NiAl + TiC + mixture(TiC/Al2O3) + Al2O3 films were also fabricated and studied, respectively. The results showed that the TiC + mixture(TiC/Al2O3) + Al2O3 coating exhibited the best self-healing ability and good thermal shock resistance among the four samples after heat treatment under normal atmosphere. The SEM images analyzed by Image Pro software indicated that the porosity of the TiC + mixture(TiC/Al2O3) + Al2O3 coating decreased more than 90% in comparison with the sample before heat treatment. This self-healing coating made by thermal spraying might be a good candidate for tritium permeation barrier in fusion reactors.