Expansion and creep deformation with microstructure evolution in graphite cathode under constant pressure

The deformation and structure stability of graphite cathodes are of importance for its service lifetime. The time dependence and coupling of deformation, elastoplastic property change and microstructure evolution of graphite cathodes were investigated under constant pressure at 940 °C. The deformations from early expansion transiting to the rapid and latter steady creep were found with increased hardness and modulus, in parallel with decreasing interplanar spacing of graphite (002) planes ( d 002 ) and increasing crystallite size along c -axis of graphite lattice ( L c ). The inner fracture among (002) planes may be related to the kink bands structure in graphite. It is clarified that no Na–C intercalation compounds get involved in change of graphite lattice. The crystallite size along a -axis ( L a ) can play an important role in structure stability with deformation-hardening effect on elastoplastic property and pinning effect on creep resistance. The deformation mechanism and the influencing factors on long-term structure stability of graphite cathode are also discussed in detail.