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The radiation damage response of Ti3SiC2 heated from 120°C to 850°C during 700 keV Si+ irradiation has been investigated. The samples were analyzed using glancing incidence Xray diffraction, Rutherford backscattering spectrometry, Raman spectroscopy, and scanning electron microscopy. For the sample at 120°C, irradiation results in a buildup of a heterogeneous surface and the formation of TiCx. Irradiation at 200°C results in maximum microstrain, a maximum in the c lattice parameter, and the appearance of a β phase in addition to the normal a phase of Ti3SiC2. A minimum in the observed damage level near the surface was seen for irradiation at a sample temperature of 300°C but the damaged phase increases at higher temperatures. Differences between the present work and a previous C irradiation study have been ascribed to the enhanced Si defect transport at low temperatures. [ABSTRACT FROM AUTHOR]

The radiation damage response of Ti 3 SiC 2 irradiated by 110 keV helium ions at room temperature (RT), the subsequent evolution of damage including helium bubble growth as a function of annealing temperatures are investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and transmission electronic microscopy (TEM). In addition to collision cascade effects leading to TiC nanocrystal formation near the surface of Ti 3 SiC 2 , He ion irradiation produces damage due to the growth of He bubbles, which cause a structural transformation into a large grain TiC crystalline phase at high temperatures. The displacement of matrix Si atoms adjacent to the He bubbles along the Si layer in Ti 3 SiC 2 either via bubble growth or the production of inter-bubble fracture is the reason for the structural transformation. Depending on the He damage level, a significant recovery of the He irradiation damage can occur at moderate temperatures. This property may play a positive role in the damage resistance of Ti 3 SiC 2 , making it a potential candidate for future nuclear reactor applications. [ABSTRACT FROM AUTHOR]

MAB phases (M = transition metal, A = aluminium (Al), B = boron (B)), a new family of nano-laminated ternary transition metal borides with an excellent combination of functional and structural properties, are currently being investigated as potential radiation shielding materials in nuclear fusion reactors. Here, we report the fabrication of a solid solution MAB phase Mo 0.75 W 0.25 AlB (Mo - molybdenum, W - tungsten), in the form of dense and high purity pellets, synthesised for the first time using a reactive hot-pressing method. The shielding and irradiation damage properties of the material were also evaluated. Monte Carlo N-Particle (MCNP) calculations showed that W doping in the MoAlB phase is likely to enhance the shielding capacity against neutrons and gamma rays of different energies. The experimental damage tolerance of Mo 0.75 W 0.25 AlB to silicon ion (Si+) irradiation indicated that this solid solution compound has a high resistance to crack formation and other radiation damage effects compared to that of pure MoAlB. Thermal annealing of the amorphous Mo 0.75 W 0.25 AlB layer formed by irradiation showed that the damaged structure easily recrystallizes at high temperatures, completely returning to the virgin state. The results show that this solid solution should be considered as a promising candidate material for radiation shielding components. • A high density and purity Mo 0.75 W 0.25 AlB solid solution was synthesised by sintering at 1100 °C. • Mo 0.75 W 0.25 AlB exhibits excellent shielding capacity against gamma rays and neutrons of different energies. • Unlike MAX phases, no cracks or voids were observed on the surface of the amorphous MAB phase. • The radiation-induced amorphization of the solid solution was almost completely recovered by thermal annealing at 700 °C. [ABSTRACT FROM AUTHOR]

• MAlB phases have a high neutron shielding capacity, especially for low-energy neutrons, compared to present shielding materials. • MoAlB has a strong resistance to crack formation and amorphization under higher temperatures. • The lattice parameter changes are related to the formation of point defects, which was evidenced by refinement of the GIXRD and DFT. A new family of ternary nano-laminated compounds, MAB phases, are studied as a promising class of neutron shielding materials for applications within fusion reactors. The shielding capacity against high-energy neutrons was evaluated, and the damage tolerance of MoAlB against Si+ irradiation was investigated over the temperature range of RT- 600 °C. The linear attenuation coefficients of these materials over wide neutron-energy ranges imply that Mo(W)AlB have a high neutron shielding capacity. MoAlB shows a strong resistance to crack formation and excellent tolerance to amorphization under higher temperatures. The detailed thermal dynamic behaviors (reaction barrier and migration barrier) associated with the defects in MoAlB were studied through DFT calculations. Also, the lattice parameter changes are related to the formation of various point defects and the defect evolution evidenced by Rietveld refinement of the GIXRD and DFT calculations. MoAlB is confirmed to be a great candidate as a neutron shielding material. [ABSTRACT FROM AUTHOR]

The radiation damage effects of Cr 2 AlC film irradiated by 100 keV He ion with a fluence range of 5 × 1015 to 1 × 1017 ions cm−2 at room temperature have been investigated. A range of characterization techniques including grazing-incidence X-ray diffraction, Raman scattering spectroscopy and ion beam analysis were employed to analyze the irradiation damage on the structure in Cr 2 AlC thin film. The Cr 2 AlC film exhibits sensitivity to irradiation of He ions as a result of partial disorder at a relatively low fluence of 5 × 1015 ions cm−2, The atomic arrangement in the crystal structure is seriously damaged at the fluence of 1 × 1017 ions cm−2. The lattice expansion occurs along c direction and the lattice contracts along a/b direction compared to the un-irradiated Cr 2 AlC. No existence of secondary phase is observed after irradiation. The processes of decomposition and phase transition induced by ion irradiation are not influenced by the chemical environment. The carbon atoms in the lattice are easy to dislocate. The carbon precipitation is induced by radiation-enhanced diffusion in the near surface layer. The accumulation has a tendency to increase with the increasing fluence. [ABSTRACT FROM AUTHOR]