A multi-atmosphere ultra-high temperature in situ x-ray CT apparatus for material characterization up to 2200 °C.

A novel multi-atmosphere ultra-high-temperature in situ testing apparatus has been developed using a laboratory x-ray source. This apparatus enables in situ x-ray computed tomography (x-ray CT) characterization of materials under extreme ultra-high-temperature environments reaching 2200 °C. The ultra-high-temperature environment is achieved through electrical heating based on Joule's law. The apparatus not only meets the requirements for rapid heating, transient temperature changes, and accurate temperature control but also effectively reduces the temperature gradient within the specimen. In addition, to facilitate x-ray penetration through the environmental chamber and the specimen for acquiring high-quality slices, aluminum windows are employed as x-ray transmission windows. Due to the scarcity of in situ data on carbon fiber-reinforced silicon carbide matrix composites at 1800 °C, in situ x-ray tensile tests were conducted on the material using this apparatus at room temperature (RT) and at an ultra-high temperature of 1800 °C in vacuum. The crack initiation and propagation behavior under thermomechanical coupling loads was investigated. Differences in crack initiation locations were observed between RT and the ultra-high-temperature environment at 1800 °C. Furthermore, the main capabilities of the apparatus were verified by conducting in situ tensile tests on C/C composites at 2200 °C in a vacuum environment, alongside high-temperature CT tests of C/SiC under inert and oxidative conditions.