Materials: Seeing the evolution of red-hot cracks

The quantitative imaging of microcrack evolution in ceramic materials under load, at extreme temperatures, and in corrosive environments, is reported online in Nature Materials this week. Made possible by a specially designed X-ray computed-tomography set-up, the findings may help advance the design of stronger and tougher microstructured materials for high-performance aerospace applications.

In X-ray computed microtomography, which is widely used to image body tissues or hard structural materials without destroying them, a digital replica of the sample is reconstructed from hundreds or even thousands of slices collected from the penetrating X-rays beamed at different angles. However, it has been challenging to design a device that allows imaging of high-performance materials at the conditions they are designed to work at, such as temperatures above 1,000 oC, under tensile or compressive loads, and in the presence of corrosive species. Robert Ritchie and colleagues designed equipment that scans, at high resolution and in real time, microcrack paths, and crack surface areas and orientations, from micrometres to several millimetres, in ceramic-matrix and textile-based composites in hostile environmental conditions.

The wealth of information that the technique can generate can contain vital information on the underlying failure mechanisms of these materials.