crack healing, microstructure modifications, oxidation healing, MAX phases, preceramic polymers
Ceramic materials able to heal manufacture or damage induced microstructure defects might trigger a change in paradigm for design and application of load bearing ceramics. This work reviews thermodynamic and kinetic aspects governing the regeneration of solid contact able to transfer stress between disrupted crack surfaces in ceramics. Major crack healing processes include perturbation of crack-like pores followed by sintering of isolated pores, as well as reaction with an environmental atmosphere and filling of the crack space with an oxidation product. Since thermally activated solid state reactions require elevated temperatures which may exceed 1000 ℃, processes able to trigger crack healing at lower temperatures are of particular interest for transferring into engineering applications. Generic principles of microstructure modifications able to facilitate crack repair at lower temperatures will be considered: (i) acceleration of material transport by grain boundary decoration and grain size reduction, and (ii) reduction of thermal activation barrier by repair filler activation. Examples demonstrating crack healing capability include oxidation reaction of low energy bonded intercalation metal from nano-laminate MAX phases and catalyzed surface nitridation of polymer derived ceramics containing repair fillers.
Tsinghua University Press
Peter GREIL. Generic principles of crack-healing ceramics. Journal of Advanced Ceramics 2012, 1(4): 249-267.