Oxidation Behavior And Crack Healing Mechanism Of Ti₂SnC

as a tenary layered structrue ceramic has wide applications, due to its excellent properties combining both metals and ceramics. It is highly desirable that Ti2SnC can have crack healing ability, which not only improves service life and safety of ceramic components, also decreases their replacement and maintenance costs.However, work has less focused on crack healing of it.In the present study, high-purity and dense Ti2SnC bulks have been prepared by using hot pressing technique. Isothermal oxidation behavior of Ti2SnC at temperature range500-800℃in air has been investigated. Tests on crack healing of Ti2SnC were performed. The main results has been listed as follows:①A high-purity and dense Ti2SnC ceramic has been prepared by hot pressing a mixture of Ti, Sn and C at1250℃for1h with30MPa. Microstructure and phase composition were characterized with SEM and XRD.②The oxidation behavior of Ti2SnC at500-800℃in air for1h shows that at500-600℃, the weight gain increases slowly, and the scale is thinner, with thickness of less than1μm. The main oxidative products are SnO2and TiO2. While at700℃and800℃, the weight gain increases rapidly. The scales composed of TiO2as main phases and minor SnO2are2.3μm and11.4μm after oxidation at700℃and800℃, respectively.③Thermal shock at500-800℃can effectively introduce cracks into Ti2SnC. For example, cracks with a maximum width of5-6μm and3cm in length were introduced in Ti2SnC after thermal shock at800℃. The thermal-shock-induced cracks resulted in decreases in electrical conducitivity and flexural strength.④Ti2SnC exhibits good crack healing ability. All cracks induced by thermal shock can heal completely after healing at800℃for1h in air. The main healing mechanism is the formation of TiO2and SnO2at high temperatures filling the cracks. The recovered electrical conductivity is close to the value of the original electrical conductivity, and the recovered flexural strength so does. For example, the recovered strength increases from the residual strength of30MPa for the samples induced by thermal shock at800℃to150MPa after healing at800℃for1h in air.⑤Ti2SnC also shows a repeatable crack healing behavior. It withstands4cylces of "crack induced and healing" at different shock and healing temperatures with electrical conductivity recoveries.