Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques.

MAX phase materials are emerging as attractive engineering materials in applications where the material is exposed to severe thermal and mechanical conditions in an oxidative environment. The Ti2AlC MAX phase possesses attractive thermomechanical properties even beyond a temperature of 1000 K. An attractive feature of this material is its capacity for the autonomous healing of cracks when operating at high temperatures. Coupling a specialized thermomechanical setup to a synchrotron X-ray tomographic microscopy endstation at the TOMCAT beamline, we captured the temporal evolution of local crack opening and healing during multiple cracking and autonomous repair cycles at a temperature of 1500 K. For the first time, the rate and position dependence of crack repair in pristine Ti2AlC material and in previously healed cracks has been quantified. Our results demonstrate that healed cracks can have sufficient mechanical integrity to make subsequent cracks form elsewhere upon reloading after healing.

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The rich elemental composition, surface chemistry, and outstanding electrical conductivity of MXenes make them a promising class of two-dimensional (2D) materials for electrochemical energy storage. To translate these properties into high performance devices, it is essential to develop fabrication strategies that allow MXenes to be assembled into electrodes with tunable architectures and investigate the effect of their pore structure on the capacitive performance. Here, we report on the fabrication of MXene aerogels with highly ordered lamellar structures by unidirectional freeze-casting of additive-free Ti3C2T x aqueous suspensions. These structures can be subsequently processed into practical supercapacitor electrode films by pressing or calendering steps. This versatile processing route allows a wide control of film thickness, spacing within lamellae (to give electrolyte accessible sites), and densities (over 2 orders of magnitude) and hence gives control over the final properties. The as-prepared MXene aerogel with a density of 13 mg cm–3 achieves 380 F g–1 capacitance at 2 mV s–1 and 75 F g–1 at 50 mV s–1. The calendering of the MXene aerogel into a porous 60 μm thick film with a density of 434 mg cm–3 leads to a superior rate capability of 309 F g–1 at 50 mV s–1. In addition, the rolled electrodes present an improvement in volumetric capacitance of 104 times as compared to the as-prepared MXene aerogel. Finally, the outstanding cyclability of rolled electrodes strengthens their nomination for supercapacitor applications. In this paper we demonstrate the possibilities in tuning the porosity and the electrochemical properties of aerogels highlighting the importance of evaluating new and hybrid processing methods to develop energy storage applications. The simplicity and versatility of the developed fabrication strategy open opportunities for the utilization of MXene lamellae architectures in a wide range of applications requiring controlled porosity including catalysis, filtration, and water purification.