•The effect of injected interstitials on Ni containing solid solution alloys varies.•A refined defect cluster migration mechanism is proposed for NiCo.•The dose-dependent swelling is studied for two ion fluences.Pure nickel and three nickel containing single-phase concentrated solid solution alloys (SP-CSAs) have been irradiated using 3 MeV Ni2+ ions at 500°C to fluences of 1.5×1016 and 5.0×1016cm−2. The radiation-induced voids were characterized using cross sectional transmission electron microscopy that distributions of voids and dislocation loops were presented as a function of depth. A various degree of void suppression was observed on the tested samples and a defect clusters migration mechanism was proposed for NiCo. In order to sufficiently understand the defect dynamics in these SP-CSAs, the injected interstitial effect has been taken into account along with the 1-dimentional (1-D) and 3-dimentional (3-D) interstitial movement mechanisms.

•The microstructure changes of two ODS steels before and after helium ion implantation have been elucidated.•The mechanism of the microstructures of ODS steels under varied thermal mechanical processing paths have been explored.•The dependence of the size, density and distribution of helium bubbles on the specific microstructure features are explored.Two 9Cr-ODS steels with the same nominal composition were consolidated by hot isostatic pressing (HIP, named COS-1) and spark plasma sintering (SPS, named COS-2). Helium ions were implanted into COS-1, COS-2 and non-ODS Eurofer 97 steels up at 673 K. Microstructures before and after helium ion implantations were carefully characterized. The results show a bimodal grain size distribution in COS-2 and a more uniform grain size distribution in COS-1. Nanoscale clusters of GP-zone type Y–Ti–O and Y2Ti2O7 pyrochlore as well as large spinel Mn(Ti)Cr2O4 particles are all observed in the two ODS steels. The Y–Ti-enriched nano-oxides in COS-1 exhibit higher number density and smaller size than in COS-2. The Y–Ti-enriched nano-oxides in fine grains of COS-2 show higher number density and smaller size than that in coarse grains of COS-2. Nano-oxides effectively trap helium atoms and lead to the formation of high density and ultra-fine helium bubbles.

To determine the void swelling resistance of reduced-activation ferritic–martensitic steels CNS I and CNS II at high doses, ion irradiation was performed up to 188 dpa (4.6 × 1017 ion/cm2) at 460 °C using 5 MeV Fe++ ions. Helium was pre-implanted at levels of 10 and 100 appm at room temperature to investigate the role of helium on void swelling. Commercial FM steel T91 was also irradiated in this condition and the swelling results are of included in this paper as a reference. Voids were observed in all conditions. The 9Cr CNS I samples implanted with 10 appm helium exhibited lower swelling than 9Cr T91 irradiated at the same condition. The 12Cr CNS II with 10 and 100 appm helium showed significantly lower swelling than CNS I and T91. The swelling rate for CNS I and CNS II were determined to be 0.02%/dpa and 0.003%/dpa respectively. Increasing the helium content from 10 to 100 appm shortened the incubation region and increased the void density but had no effect on the swelling rates.

A 14Cr-ODS ferritic steel with the nominal compositions of Fe–14Cr–2 W–0.3Ti–0.3Y2O3 (wt.%) was produced by mechanical alloying (MA) and hot isostatic pressing (HIP). Helium ion was implanted into the 14Cr-ODS steel along with Eurofer 97 steel as reference at 400 °C to a fluence of 1 × 1017 He+/cm2. High resolution transmission electron microscopy (HRTEM), high angle annual dark field (HAADF) scanning TEM (STEM) and atom probe tomography (APT) were used to characterize the microstructure of 14Cr-ODS and Eurofer 97 steels before and after helium implantation. High-density Y–Ti–O-rich nanoclusters and Y2Ti2O7 precipitates as well as large Cr–Ti rich oxides were observed in the 14Cr-ODS steel. The average size of Y–Ti–O nanoclusters and Y2Ti2O7 precipitates is 9 nm. After helium implantation, the helium bubbles formed in the 14Cr-ODS steel exhibit the smaller size and the lower volume fraction than that in Eurofer 97 steel, indicating high-density nano-scale precipitates can effectively suppress the coarsening of helium bubbles.

Tungsten was irradiated with 400 keV Kr+ ions using the IVEM-Tandem Facility at Argonne National Laboratory. The evolution of microstructure and gas bubbles during the irradiation was observed by in situ transmission electron microscopy. Under irradiation, dislocation loops were created and grew into an increased density of network dislocations with increasing Kr+ ion fluence. The irradiation induced final microstructure consists of dislocation cells ∼50 nm in diameter separated by dislocation walls. The irradiation also induced formation of Kr gas bubbles with an average diameter of 1.4 nm after 3.0 × 1016 ions/cm2 at 525 K. The gas bubbles were observed to grow to 2.6 nm diameter after additional Kr-irradiation of 5.0 × 1016 ions/cm2 at 815 K. The relationship between bubble size and irradiation time was obtained from experimental data obtained at 815 K and an empirical formula for calculating Kr bubble size was developed by fitting bubble growth equations with experiment data. The growth mechanisms of Kr gas bubbles in tungsten are discussed.

The effect of crystal orientation on the behavior of a tungsten surface under a 30 keV focused Ga+ ion beam with different bombardment angles has been investigated by in situ scanning electron microscopy and electron backscatter diffraction. Results indicate that the grains of tungsten with various orientations behave quite differently. Grains with a (0 0 1) direction parallel to the ion beam always maintain a much smoother surface morphology with less mass removal after ion bombardment, indicating a lower sputtering yield. The orientation dependence of surface sputtering of tungsten can be used to guide the fabrication of tungsten-based first wall component in a nuclear fusion reactor.Highlights► We in situ investigated the microstructure evolution during FIB bombardment. ► The irradiation behaviors depended significantly on the crystal orientation. ► Tungsten grain with (0 0 1) crystal orientation showed good irradiation resistance.

We demonstrate that a variety of intriguing patterns can be induced by several keV Argon ions on the ultrathin polymer films at glancing angles of incidence with the simultaneous sample rotation. These periodic structure films can be used as the templates to fabricate densely packed nanometer-scale structures by deposition of atoms. Well-ordered arrays of stripe-like Si nanostructures with 7 nm wavelength and uniformly sized and shaped nanoparticles of copper in diameter of 7 nm were produced on the thin polymer film. This approach represents a convenient route for fabricating nanometer-scale wires and dots for metals and semiconductors.Ripples induced on the polymer film have been used as templates for fabrication of useful patterns of nanostructures.

Nano-particles of Au embedded in TiO2 (rutile) single crystals have been synthesized by 260 keV Au ion implantation up to a fluence of 5 × 1016 ions/cm2. Cross-sectional and high resolution transmission electron microscopy (TEM) has been utilized to characterize the size and depth distribution as well as the microstructure of Au nano-particles. The size of Au nano-particles varies 1–20 nm in the TiO2 matrix and the maximum particle size increased with the increasing implantation fluence. These large particles gradually moved toward the surface as implantation fluence increases. Most of Au nano-particles have a specific orientation relationship with the original TiO2 matrix in both as-implanted and post-implantation annealed samples, which is: [1 1 0]Au∥[110]TiO2 and (0 0 2)Au∥(2¯2¯0)TiO2, although the implanted regions of TiO2 were entirely amorphized. The influences of dose rate and annealing on the size and distribution of Au nano-particles are also discussed.

Magnetic Ni nano-particles in the near surface regions of MgO single crystals have been synthesized by 64 keV Ni ion implantation to 1 × 1017 cm−2 followed by thermal annealing. Transmission electron microscopy (TEM) and magnetic properties measurement system (MPMS) equipped with a superconducting quantum interference device (SQUID) detector have been employed to characterize the microstructure and magnetic properties of the Ni nano-particles. The average particle size ranges 3–5 nm in the as-implanted sample and 8–10 nm in the annealed sample. The orientation of Ni particles is perfectly matched with that of the MgO matrix. The M–H hysteresis loop measured at 10 K revealed the coercivity, Hc, ∼195 Oe. The superparamagnetism of Ni particles was evident in as-implanted sample at the temperature above 35 K but did not show in the annealed sample.

Two-dimensionally (2D) ordered arrangements of Au micro-discs formed on the surfaces of TiO2 and SrTiO3 after “patterned” ion implantation. Cross-sectional TEM revealed that the Au micro-discs consisted of Au nanoparticles with a very narrow depth distribution (single-layered) and a narrow size range (2–6 and 3–5 nm in the implanted TiO2 and SrTiO3, respectively). They are located in the near surface layer surrounded by an amorphized matrix.

Cesium, iodine and strontium ions have been implanted into yttria-stabilized cubic zirconia (YSZ) to determine the effects of fission product incorporation in YSZ that is considered as an inert nuclear fuel matrix. The ion implantation was conducted at room temperature to 1×1021 ions/m2 for each ion with ion energies ranging from 70 to 400 keV. The peak displacement damage level and the peak ion concentration in YSZ reached 205–330 displacement per atoms (dpa) and 11–26 at.%, respectively. The microstructure of the implanted YSZ was studied by in situ and cross-sectional transmission electron microscopy (TEM). In the iodine and strontium implanted samples, a damaged layer with a high density of defect clusters was observed, while in the cesium implanted specimen, most of the damaged layer is amorphous.Nanocrystalline precipitates were observed in the strontium implanted specimen after annealing at 1273 K. The results are discussed in terms of the ionic size, mobility and the solubility of the implanted species in YSZ.

A group of single-phase concentrated solid-solution alloys (SP-CSAs), including NiFe, NiCoFe, NiCoFeCr, as well as a high entropy alloy NiCoFeCrMn, was irradiated with 3 MeV Ni2+ ions at 773 K to a fluence of 5 × 1016 ions/cm2 for the study of radiation response with increasing compositional complexity. Advanced transmission electron microscopy (TEM) with electron energy loss spectroscopy (EELS) was used to characterize the dislocation loop distribution and radiation-induced segregation (RIS) on defect clusters in the SP-CSAs. The results show that a higher fraction of faulted loops exists in the more compositionally complex alloys, which indicate that increasing compositional complexity can extend the incubation period and delay loop growth. The RIS behaviors of each element in the SP-CSAs were observed as follows: Ni and Co tend to enrich, but Cr, Fe and Mn prefer to deplete near the defect clusters. RIS level can be significantly suppressed by increasing compositional complexity due to the sluggish atom diffusion. According to molecular static (MS) simulations, “disk” like segregations may form near the faulted dislocation loops in the SP-CSAs. Segregated elements tend to distribute around the whole faulted loop as a disk rather than only around the edge of the loop.Figure optionsDownload full-size imageDownload high-quality image (567 K)Download as PowerPoint slide