Synthesis and high temperature corrosion behaviour of nearly monolithic Ti3AlC2 MAX phase in molten chloride salt

Highlights: • Nearly monolithic MAX phase containing 95 wt.% Ti₃AlC₂ and 5 wt.% TiC_x was synthesized by spark plasma sintering under vacuum sintering conditions. • The decomposition of hexagonal Ti₃AlC₂ into substoichiometric cubic TiC_x during synthesis is linked to high-temperature de-intercalation of Al and subsequent evaporation. • Corrosion behaviour of Ti₃AlC₂ from a microstructure point of view was investigated in molten LiCl–KCl salt at 600 °C under a dry Ar atmosphere. • Al dissolution led to delamination of the layered structure which in turn favoured the ingress of chlorine and its subsequent intercalation into the Al–site plane to form a Ti₃C₂Cl₂ exfoliation layer. Nearly monolithic MAX phase containing 95 wt.% Ti₃AlC₂ and 5 wt.% TiC_x was synthesized by spark plasma sintering under vacuum sintering conditions. Corrosion behaviour of Ti₃AlC₂ was investigated in molten LiCl–KCl salt at 600 °C under a dry Ar atmosphere. Evolution of microstructure and surface chemistry of the exposed sample was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and glancing angle X-ray diffraction (GAXRD). Results showed that Al dissolution led to delamination of the layered structure which favoured the ingress of chlorine and its subsequent intercalation into the Al–site plane to form a Ti₃C₂Cl₂ exfoliation layer. De-twinning of the Ti₃C₂ layers possibly due to Cl⁻ anions substitution by O results in non-stoichiometric TiC_0.67 formation.