The damage evolution of He irradiation on Ti3SiC2 as a function of annealing temperature

Annealing effects on the structure and hardness of helium‐irradiated Cr2AlC thin films

“…However, in present study this disordered (Cr, Al) 2 C x is thermally unstable, the damaged crystal can be efficiently recovered under an appropriate temperature due to the high diffusivity of point defects 38 . In our previous investigation on Ti 3 SiC 2 , 39 thermal annealing at high temperature of more than 800℃ does not result in disappear of a small amounts of new similar fcc‐TiC phase in irradiated Ti 3 SiC 2 (we consider it as TiC secondary phase from the presented experimental data, but further confirmation is needed), and indeed, the fcc‐TiC phase grows further. The explanation for the different annealing recovery behavior in damaged Ti 3 SiC 2 is as follows: a large number of Si atoms are lost rather than existing as antisite defects (Ti Si ) after high fluence irradiation due to the relatively high formation energy of the antisite defect; additionally, as thermal annealing proceeds, a significant concentration of C atoms will remain within the Si layer and form SiC/TiC‐like bonding because of the high energy barrier (0.84 eV) for C to migrate from the Si layer 13,40 .…”

“…Our previous calculation on migration energy of He in Cr 2 AlC by first principle 12 has pointed out that the activation energy of 14.5 eV is needed for an interstitial He atom to migrate along the direct pathway from the hexahedral interstitial position on Al plane to another hexahedral interstitial position, but only 1.21 eV if He migrates through an indirect pathway. Some of the He atoms escape from the surface, but most will aggregate into larger clusters or bubbles whose size will increase with annealing temperature as has been observed in Ti 3 SiC 2 39 . However, higher temperatures are needed to release He atoms bound in small He clusters on vacancies because of a higher dissociation energies from the He‐vacancy clusters.…”

“…Some of the He atoms escape from the surface, but most will aggregate into larger clusters or bubbles whose size will increase with annealing temperature as has been observed in Ti 3 SiC 2 . 39 However, higher temperatures are needed to release He atoms bound in small He clusters on vacancies because of a higher dissociation energies from the He-vacancy clusters. The release of He in bubbles can occur either by detrapping of He atoms from the bubbles or by bubble migration, which depends on the bubble density, microstructure, defects, and sample temperature.…”

Defect behavior and radiation tolerance of MAB phases (MoAlB and Fe2AlB2) with comparison to MAX phases

“…The surface roughness is also smoother than in the 150 °C, high dose sample. Even though the irradiation dose was relatively high, no obvious phase transformations were found in either Ti2AlC or Ti3SiC2, which have been observed in some parts of ion irradiated MAX phase materials in earlier studies [43][44][45]. However, partial phase transformation might have occurred in some areas and may require higher magnification TEM or HRTEM to detect.…”

Enhancing the phase stability of ceramics under radiation via multilayer engineering

“…According to previously reported studies ( 34 , 35 ), the fcc Ti 3 SiC 2 forms in the hcp Ti 3 SiC 2 most likely as a result of radiation damage. Two possible mechanisms for this radiation-induced phase transformation have been proposed: (i) The formation of fcc phase is due to the decomposition of Ti 3 SiC 2 into an fcc-structured binary TiC x , in which the process is accompanied by the out-diffusion of Si atoms (chemical compositional changes) ( 36 , 37 ), or (ii) the fcc phase is caused by the formation and accumulation of the antisite defects of Ti and Si, followed by a reconstruction of the unit cell ( 35 ). According to these two mechanisms, the fcc phase could be either TiC x or (Ti 3 Si)C 2 , respectively.…”