ELECTROCHEMICAL HEALING OF MAX PHASE CERAMICS

Earlier work [1] has shown that metallo-ceramic MAX phase materials, such as Ti3AlC2, not only have very attractive properties, combining those usually attributed to metals and those attributed to ceramics, but also display self healing properties when exposed to high temperatures. The restoration of the tensile strength is due to the formation of an oxidic residue, in particular well-adhering Al2O3 and loosely-bound TiO2, within the crack zone leading to quite adequate load transfer. However this healing mechanism does not operate below typically 1173K in realistic times because of low oxidation rates. In this work we present a novel approach to heal the cracks on Ti-Al-C ceramic samples at ambient temperatures. The approach is based on inducing localized electrochemical reactions in the crack zone using various types of aqueous solutions and DC voltammetry. In the presentation we will present the initial results on this new mode of inducing electrochemical healing and will compare the morphology and composition of the electrochemical products with that created by oxidative healing. The electrochemical response of the Ti2AlC sample to various DC voltammetry was investigated in 3.5 % NaC1 solutions, 16.35 % H2SO4, or 10.6 % Na2CO3 solutions. In all the experiments The MA