A common misconception is that the irradiation of solids with energetic electrons and ions has exclusively detrimental effects on the properties of target materials. In addition to the well-known cases of doping of bulk semiconductors and ion beam nitriding of steels, recent experiments show that irradiation can also have beneficial effects on nanostructured systems. Electron or ion beams may serve as tools to synthesize nanoclusters and nanowires, change their morphology in a controllable manner, and tailor their mechanical, electronic, and even magnetic properties. Harnessing irradiation as a tool for modifying material properties at the nanoscale requires having the full microscopic picture of defect production and annealing in nanotargets. In this article, we review recent progress in the understanding of effects of irradiation on various zero-dimensional and one-dimensional nanoscale systems, such as semiconductor and metal nanoclusters and nanowires, nanotubes, and fullerenes. We also consider the t...

Ion and electron irradiation-induced effects in nanostructured materials

http://oa.upm.es/35412/7/INVE_MEM_2013_192429.pdf

Recent progress in research on tungsten materials for nuclear fusion applications in Europe

IN view of the interest attaching to the vaporisation and diffusion of solids, the following observations may be worthy of record.

The Diffusion of Solids

Recently a new class of metal alloys, of single-phase multicomponent composition at roughly equal atomic concentrations ("equiatomic"), have been shown to exhibit promising mechanical, magnetic, and corrosion resistance properties, in particular, at high temperatures. These features make them potential candidates for components of next-generation nuclear reactors and other high-radiation environments that will involve high temperatures combined with corrosive environments and extreme radiation exposure. In spite of a wide range of recent studies of many important properties of these alloys, their radiation tolerance at high doses remains unexplored. In this work, a combination of experimental and modeling efforts reveals a substantial reduction of damage accumulation under prolonged irradiation in single-phase NiFe and NiCoCr alloys compared to elemental Ni. This effect is explained by reduced dislocation mobility, which leads to slower growth of large dislocation structures. Moreover, there is no observable phase separation, ordering, or amorphization, pointing to a high phase stability of this class of alloys.

/pdf/mechanism-of-radiation-damage-reduction-in-equiatomic-st4bjemwrw.pdf

Mechanism of Radiation Damage Reduction in Equiatomic Multicomponent Single Phase Alloys

Primary radiation damage: A review of current understanding and models

Analytical bond-order potentials for beryllium, beryllium carbide and beryllium hydride are presented. The reactive nature of the formalism makes the potentials suitable for simulations of non-equilibrium processes such as plasma–wall interactions in fusion reactors. The Be and Be–C potentials were fitted to ab initio calculations as well as to experimental data of several different atomic configurations and Be–H molecule and defect data were used in determining the Be–H parameter set. Among other tests, sputtering, melting and quenching simulations were performed in order to check the transferability of the potentials. The antifluorite Be2C structure is well described by the Be–C potential and the hydrocarbon interactions are modelled by the established Brenner potentials.

https://iopscience.iop.org/article/10.1088/0953-8984/21/44/445002/pdf

Interatomic potentials for the Be-C-H system.

While covalently bonded materials such as carbon are well known to be eroded by chemical sputtering when exposed to plasmas or low-energy ion irradiation, pure metals have been believed to sputter only physically. The erosion of Be when subject to D bombardment was in this work measured at the PISCES-B facility and modelled with molecular dynamics simulations. During the experiments, a chemical effect was observed, since a fraction of the eroded Be was in the form of BeD molecules. This fraction decreased with increasing ion energy. The same trend was seen in the simulations and was explained by the swift chemical sputtering mechanism, showing that pure metals can, indeed, be sputtered chemically. D ions of only 7eV can erode Be through this mechanism.

/pdf/chemical-sputtering-of-be-due-to-d-bombardment-3k95magcb3.pdf

Chemical sputtering of Be due to D bombardment

Simulation of irradiation induced deuterium trapping in tungsten

The understanding of the primary radiation damage in Fe-based alloys is of interest for the use of advanced steels in future fusion and fission reactors. In this work Fe-Cr alloys (with 5, 6.25, 10 and 15% Cr content) and Fe-Ni alloys (with 10, 40, 50 and 75% Ni content) were used as model materials for studying the features of steels from a radiation damage perspective. The effect of prolonged irradiation (neglecting diffusion), i.e. the overlapping of single 5 keV displacement cascade events, was studied by molecular dynamics simulation. Up to 200 single cascades were simulated, randomly induced in sequence in one simulation cell, to study the difference between fcc and bcc lattices, as well as initially ordered and random crystals. With increasing numbers of cascades we observed a saturation of Frenkel pairs in the bcc alloys. In fcc Fe-Ni, in contrast, we saw a continuous accumulation of defects: the growth of stacking-fault tetrahedra and a larger number of self-interstitial atom clusters were seen in contrast to bcc alloys. For all simulations the defect clusters and the short range order parameter were analysed in detail depending on the number of cascades in the crystal. We also report the modification of the repulsive part of the Fe-Ni interaction potential, which was needed to study the non-equilibrium processes.

/pdf/the-effect-of-prolonged-irradiation-on-defect-production-and-fb7sv7c7e9.pdf

The effect of prolonged irradiation on defect production and ordering in Fe-Cr and Fe-Ni alloys.

http://www.acclab.helsinki.fi/~knordlun/pub/Hen06a.pdf

K. Vörtler

Papers

Interatomic potentials for the Be-C-H system.

Chemical sputtering of Be due to D bombardment

Simulation of irradiation induced deuterium trapping in tungsten

The effect of prolonged irradiation on defect production and ordering in Fe-Cr and Fe-Ni alloys.

Sticking of atomic hydrogen on the tungsten (0 0 1) surface