Cr2AlC MAX phases were deposited using magnetron sputtering. The synthesis was performed via layer-by-layer deposition from elemental targets onto Si wafer and polished Inconel® 718 superalloy substrates at 650 K and 853 K. Transmission Electron Microscopy (TEM) characterisation showed that the thin films had a thickness of about 0.8 and 1.2 m for Si and Inconel® substrates, respectively, and a MAX phase crystalline structure. Depositions onto Inconel substrate was performed in order to measure film mechanical properties. The films have hardness at around 15 GPa, reduced Young's modulus at around 260 GPa, do not delaminate and showed characteristic ductile behaviour during nanoscratching. Ion irradiations with in situ TEM were performed with 320 keV Xe + ions up to fluence 1×10 16 ions•cm-2 at 300 K and 623 K. At 300 K the Cr2AlC started to amorphise at around 0.3 dpa. At displacement levels above 3.3 dpa all crystalline structure was almost completely lost. Conversely, irradiations at 623 K showed no recordable amorphisation up to 90 dpa. It is discussed that the presence of many grain boundaries and low defect recombination energy barriers are responsible for high radiation hardness of Cr2AlC MAX phase at 623 K. The thin film Cr2AlC MAX phases have mechanical and radiation stability which makes them a candidate for fuel rod coating as Accident Tolerant Fuels (ATF) material for the next generation of nuclear reactors.

A dual-phase Cr2AlC material was synthesized using magnetron sputtering at a temperature of 648 K. A stoichiometric and nanocrystalline MAX phase matrix was observed along with the presence of spherical-shaped amorphous nano-zones as a secondary phase. The irradiation resistance of the material was assessed using a 300-keV Xe ion beam in situ within a transmission electron microscope up to 40 displacements per atom at 623 K: a condition that extrapolates the harmful environments of future fusion and fission nuclear reactors. At the maximum dose investigated, complete amorphization was not observed. Scanning transmission electron microscopy coupled with energy-dispersive x-ray revealed an association between swelling due to inert gas bubble nucleation and growth and radiation-induced segregation and clustering. Counterintuitively, the findings suggest that preexisting amorphous nano-zones can be beneficial to Cr2AlC MAX phase under extreme environments.

Near stoichiometric and under stochiometric Cr2AlxC (x=0.9 and 0.75) amorphous compositions were deposited onto silicon substrate at 330 K in a layer-by-layer fashion using magnetron sputtering from elemental targets. The film thickness found to be 0.9 µm and 1.2 µm for the near and under stoichiometric compositions respectively. A transmission Electron Microscope (TEM) heating holder was used to heat thin sample lamellae prepared using focussed ion beam milling. Near stoichiometric Cr2AlC thin films consisted of nano MAX phase after crystallisation at 873 K. Under stoichiometric Cr2AlxC (x=0.75) thin films contained MAX phase along with nanocrystalline chromium aluminides after crystallisation at 973 K. Ion irradiations with 320 keV xenon ions were performed at 623 K using a TEM with in-situ ion irradiation (MIAMI) facility. Near stoichiometric Cr2AlC nanocrystalline films irradiated up to 83 displacements per atom (dpa) showed no observable changes. Also, irradiations of under stoichiometric nanocrystalline thin films up to 138 dpa did not show any observable amorphisation and recrystallization was observed. This radiation resistance of near and under stoichiometric thin films is attributed to the known self-healing property of Cr2AlxC compositions further enhanced by nanocrystallinity.