Point defect formation in M2AlC (M = Zr,Cr) MAX phases and their tendency to disorder and amorphize

Resistivity changes of magnetron sputtered, amorphous Cr 2 AlC thin films were measured during heating in vacuum. Based on correlative X-ray diffraction, in-situ and ex-situ selected area electron diffraction measurements and differential scanning calorimetry data from literature it is evident that the resistivity changes at 552 ± 4 and 585 ± 13 °C indicate the phase transitions from amorphous to a hexagonal disordered solid solution structure and from the latter to MAX phase, respectively. We have shown that phase changes in Cr 2 AlC thin films can be revealed by in-situ measurements of thermally induced resistivity changes.

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“…Thus, Cr 2 AlC may be of interest e.g. for nuclear applications 21,22 , heat exchangers 23 or aero-engines 20 .…”

Section: Introductionmentioning

confidence: 99%

Remote Tracking of Phase Changes in Cr2AlC Thin Films by In-situ Resistivity Measurements

Stelzer

Chen

Bliem

et al. 2019

Sci Rep

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“…So named Mn+1AXn (M: an early transition metal, A: group III or IV element and X: carbon or nitrogen) phases (n≥1) are nanolaminated ceramics with hexagonal crystal structure. The crystal structures are formed by layers of carbides or nitrides separated by layer of A atoms [5][6][7]. Attention in MAX phases have increased since their properties can be engineered to combine of both ceramic-and metal-like behaviours.…”

Section: Introductionmentioning

confidence: 99%

Radiation resistance and mechanical properties of magnetron-sputtered Cr2AlC thin films

Imtyazuddin

Mir

Tunes

et al. 2019

Journal of Nuclear Materials

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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.

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“…Defects with the lowest formation energies are the most likely to be created as a result of ion bombardment. Ab initio simulations of defect formation in Zr2AlC have been reported by Shah et al [28]. Although these calculations can only suggest the irradiation tolerance of this phase, they can give an indication on the likelihood of certain elements to form defects, as well as their corresponding defect types.…”

Section: Defect Evolution In Zr2alcmentioning

confidence: 99%

Heavy ion irradiation damage in Zr2AlC MAX phase

Qarra

Knowles

Vickers

et al. 2019

Journal of Nuclear Materials

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Zr2AlC MAX phase-based ceramic material with 33 wt.% ZrC has been irradiated with 22 MeV Au 7+ ions between room temperature and 600 o C, achieving a maximum nominal midrange dose of 3.5 displacements per atom. The response of the material to irradiation has been studied using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Under room temperature irradiation, the ions caused a partial amorphisation of the MAX phase. At high temperatures, irradiated Zr2AlC remained crystalline, but developed an increased density of dislocations and stacking faults in the (0001) basal planes. The irradiated material also exhibited a temperaturedependent microcracking phenomenon similar to that previously reported in other MAX phase materials.

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Point defect formation in M2AlC (M = Zr,Cr) MAX phases and their tendency to disorder and amorphize

Cited by 17 publications

References 36 publications

Remote Tracking of Phase Changes in Cr2AlC Thin Films by In-situ Resistivity Measurements

Remote Tracking of Phase Changes in Cr2AlC Thin Films by In-situ Resistivity Measurements

Radiation resistance and mechanical properties of magnetron-sputtered Cr2AlC thin films

Heavy ion irradiation damage in Zr2AlC MAX phase

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