Effects Of Helium Ion Irradiation Research Articles

Effect of helium ion irradiation on the microstructure, mechanical properties and surface morphology of Inconel 625 alloy

Inconel 625 alloy is mainly used for reactor pressure vessel, fuel cladding, nuclear fuel elements and cryogenic channels for cooling high temperature superconductors in Tokamaks. This study focuses on deciphering the impact of helium ion irradiation on the properties of Inconel 625 alloy. Helium-ions interaction with material leads to blistering, void formation, swelling, and degradation of mechanical properties. To understand these effects, the samples of Inconel 625 alloy were irradiated by helium-ion fluence beams at three different helium-ion beam fluence (1 × 1013, 1 × 1014, 1 × 1015 He/cm2). A decrease in grain size was observed from 34.4 to 19.0 nm with an increase in the ion fluence. According to the results, the residual strain is increased, from 1.8 to 43.0 micro-strain with the increase in helium-ion fluence, however structure is relaxed with decrease in micro-strain at higher helium-ion fluence (1 × 1015 He/cm2) and also there is a prominent increase in grain size. The surface morphology as observed by scanning electron microscope (SEM) illustrates the fuzz formation at low fluence (1 × 1013 He/cm2), while samples irradiated with high helium ion fluence (1 × 1015 He/cm2) showed grain growth, voids and surface blistering (deep valleys). An increase in hardness value at low helium-ion beam fluence is observed due to the presence of large population of defects. However, at higher helium-ion beam fluence, a decrease in hardness value is observed. This decrease might be attributed to the dislocation clustering and grain growth.

Composite effect of helium ion irradiation and transient thermal shock on recrystallized pure W and W-Y2O3 alloys

Tungsten (W) is the material of choice for the thermal nuclear fusion reactors of the future. In this research, pure W (PW) and W-Y2O3 alloys made by the SWIP (Southwestern Institute of Physics) wet chemical process are chosen. Simulation of long-term extreme operating conditions of fusion reactor materials by annealing and recrystallization of forged tungsten materials. The thermal shock resistance of recrystallized PW and W-Y2O3 alloys to radiation by helium (He) ions at a flux of 1.4 × 1022 ions/(m2s) was investigated. The surface microscopic pictures of recrystallized W and W-Y2O3 alloys were analyzed using scanning electron microscopy (SEM) and a laser surface profiler under the conditions of helium ion irradiation and electron beam transient thermal shock. After helium ion irradiation, the surface of PW and W-Y2O3 alloys exhibits a fuzzy structure. Under the same 0.33 GW/m2 thermal shock condition, the average width of the main cracks of PW and W-Y2O3 alloys significantly increases after helium ion irradiation, indicating that helium ion irradiation can reduce the thermal shock resistance of the surface of recrystallized W materials.

Effect of helium ion irradiation on pure W, W-5Ta and W-5Re: a micro-tensile and nanoindentation investigation of mechanical properties

Effect of helium ion irradiation on pure W, W-5Ta and W-5Re: a micro-tensile and nanoindentation investigation of mechanical properties

The Microstructure of Zr/Nb Nanoscale Multilayer Coatings Irradiated with Helium Ions

The effect of helium ion irradiation on the microstructure and properties of composites based on Zr/Nb nanoscale multilayer coatings (NMCs) was studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), and variable-energy Doppler broadening spectroscopy (DBS) were used for the in-depth analysis of defects in the irradiated NMCs. After irradiation of the Zr/Nb NMCs with helium ions at a 1017 ion/cm2 dose, the layered structure was generally retained, but the internal stresses in the layers were increased, which caused wave-like distortion in the ion deposition zone. The Zr/Nb NMCs with an individual layer thickness of 25 nm were characterized by the smallest microstress changes, but single blisters were formed in the near-surface region. The microstructure of the Zr/Nb NMCs with a layer thickness of 100 nm exhibited relatively smaller changes upon helium ion irradiation. The prevailing positron-trapping center was the reduced-electron-density area at the interfaces before and after irradiation of the Zr/Nb NMCs regardless of the layer thickness. However, the layer thickness affected the DBS parameter profiles depending on the positron energy, which was probably due to the different localization of implanted ions within the layers or at the interfaces.

Effect of Helium Ion Irradiation on FP479 Graphite

Effect of Helium Ion Irradiation on FP479 Graphite

Ion irradiation and implantation modifications of magneto-ionically induced exchange bias in Gd/NiCoO

Magneto-ionic control of magnetic properties through ionic migration has shown promise in enabling new functionalities in energy-efficient spintronic devices. In this work, we demonstrate the effect of helium ion irradiation and oxygen implantation on magneto-ionically induced exchange bias effect in Gd/Ni0.33Co0.67O heterostructures. Irradiation using He+ leads to an expansion of the Ni0.33Co0.67O lattice due to strain relaxation. At low He+ fluence (≤2 × 1014 ions cm−2), the redox-induced interfacial magnetic moment initially increases, owing to enhanced oxygen migration. At higher fluence, the exchange bias is suppressed due to reduction of pinned uncompensated interfacial Ni0.33Co0.67O spins. For oxygen implanted samples, an initial lattice expansion below a dose of 5 × 1015 cm−2 is subsequently dominated at higher dose by a lattice contraction and phase segregation into NiO and CoO-rich phases, which in turn alters the exchange bias. These results highlight the possibility of ion irradiation and implantation as an effective means to tailor magneto-ionic effects.

Effect of helium ion irradiation on short-time corrosion behavior of two novel high-entropy alloys in simulated PWR primary water

The effect of helium ion irradiation on the short-time corrosion behavior of two novel high-entropy alloys (HEAs) was investigated in simulated PWR primary water. The results revealed that a double-layer oxide film consisting of Ti, Nb and V oxides was formed on both HEAs, including outer oxide particles and a protective inner oxide layer with a maximum depth of ∼500 nm. Irradiation up to 10.5 dpa may hardly promote corrosion kinetics since severe lattice distortion and sluggish diffusion in HEAs. The corrosion processes with and without irradiation were discussed in detail.

Synergistic effect of irradiation and molten salt corrosion: Acceleration or deceleration?

The effect of helium ion irradiation with low and high ion fluences on the corrosion behaviour of nickel-based alloys in FLiNaK molten salt at 700 °C was investigated. The microstructure and element distribution were characterized to explore the corrosion behaviour of matrix and grain boundaries. The results showed that irradiation accelerates matrix corrosion in both Inconel 617 and GH3535 alloys. Moreover, the irradiation decelerated and accelerated intergranular corrosion were respectively observed under irradiation with low and high helium ion fluence, which is caused by the combined effects of the self-healing mechanism and diffusion of interstitials and helium atoms.

Synthesis and resistance to helium swelling of Li2TiO3 ceramics

The work is devoted to the study of the effect of helium ion irradiation on the properties of ceramics based on Li2TiO3, which have great potential as a breeding blanket in the design of thermonuclear reactors. The choice of the type of ions and irradiation doses of 1–5 × 1017 ion/cm2 is due to the possibility of modeling the processes of defect formation as a result of the accumulation of helium in the structure of the surface layer of ceramics during their operation. As research methods, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used and the dielectric properties were studied by impedance spectroscopy. It was found that at irradiation doses of 1–3 × 1017 ion/cm2, these ceramics have high radiation resistance to structural changes, while increasing the radiation dose above 5 × 1017 ion/cm2 leads to significant changes in the properties of ceramics, which are caused by partial degradation of the surface layer of ceramics in the process exposure. As a result of measuring the strength characteristics, it was determined that the greatest decrease in the hardness of the surface layer occurs at an irradiation dose of 5 × 1017 ion/cm2. In the course of studying the dielectric characteristics, it was found that the main changes are associated with a decrease in the dielectric constant, as well as an insignificant shift of the maximum towards high temperatures, which is due to an increase in the concentration of defects in the structure of ceramics arising during irradiation.

Effects of helium ion irradiation on the high temperature oxidation resistance of Inconel 718 alloy

The Ni-based Inconel 718 alloy was irradiated using 50 keV helium ion to doses of 0.4, 4 and 40 dpa. The oxidation behaviors of un-irradiated and irradiated samples were studied under isothermal conditions at 900 °C. The phase constitution, oxide layer morphology and microstructure variation were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). It was found that the oxidation kinetics of un-irradiated and irradiated samples obeyed a parabolic law. The oxidation rate was lower in the sample with higher dose irradiation. The oxide layer was comprised of outer oxide scale (mainly Cr2O3) and inner oxide layer (mainly Al2O3 and TiO2). Irradiation raised the surface layer's energy and facilitated the nucleation of fine oxide particles. While fine oxide particles improved the densification of outer oxide scale. Due to the irradiation-induced defects, fast-diffusion paths were provided for Cr to the surface. This accelerated the forming of dense outer Cr2O3 oxide scale, and restricted the inward penetration of O. Therefore, the thickness of oxide layer especially the inner oxide layer significantly decreased. The enhanced oxidation resistance of irradiated samples was essentially attributed to the combination of improved surface layer's energy and irradiation defects.

Detrimental Effects of Helium Ion Irradiation on Cognitive Performance and Cortical Levels of MAP-2 in B6D2F1 Mice.

The space radiation environment includes helium (4He) ions that may impact brain function. As little is known about the effects of exposures to 4He ions on the brain, we assessed the behavioral and cognitive performance of C57BL/6J × DBA2/J F1 (B6D2F1) mice three months following irradiation with 4He ions (250 MeV/n; linear energy transfer (LET) = 1.6 keV/μm; 0, 21, 42 or 168 cGy). Sham-irradiated mice and mice irradiated with 21 or 168 cGy showed novel object recognition, but mice irradiated with 42 cGy did not. In the passive avoidance test, mice received a slight foot shock in a dark compartment, and latency to re-enter that compartment was assessed 24 h later. Sham-irradiated mice and mice irradiated with 21 or 42 cGy showed a higher latency on Day 2 than Day 1, but the latency to enter the dark compartment in mice irradiated with 168 cGy was comparable on both days. 4He ion irradiation, at 42 and 168 cGy, reduced the levels of the dendritic marker microtubule-associated protein-2 (MAP-2) in the cortex. There was an effect of radiation on apolipoprotein E (apoE) levels in the hippocampus and cortex, with higher apoE levels in mice irradiated at 42 cGy than 168 cGy and a trend towards higher apoE levels in mice irradiated at 21 than 168 cGy. In addition, in the hippocampus, there was a trend towards a negative correlation between MAP-2 and apoE levels. While reduced levels of MAP-2 in the cortex might have contributed to the altered performance in the passive avoidance test, it does not seem sufficient to do so. The higher hippocampal and cortical apoE levels in mice irradiated at 42 than 168 cGy might have served as a compensatory protective response preserving their passive avoidance memory. Thus, there were no alterations in behavioral performance in the open filed or depressive-like behavior in the forced swim test, while cognitive impairments were seen in the object recognition and passive avoidance tests, but not in the contextual or cued fear conditioning tests. Taken together, the results indicate that some aspects of cognitive performance are altered in male mice exposed to 4He ions, but that the response is task-dependent. Furthermore, the sensitive doses can vary within each task in a non-linear fashion. This highlights the importance of assessing the cognitive and behavioral effects of charged particle exposure with a variety of assays and at multiple doses, given the possibility that lower doses may be more damaging due to the absence of induced compensatory mechanisms at higher doses.

Self-organized nanostructure formation on the graphite surface induced by helium ion irradiation

The effects of helium ion irradiation on the graphite surface are studied by employing a plasma focus device. The device emits helium ion pulse having energies in the range of a few keV to a few MeV and flux on the order of 1025 m−2 s−1 at 60 mm axial position from the anode tip. The field emission scanning electron microscopy confirms the formation of multi-modal spherical and elongated agglomerated structures on irradiated samples surface with increase in agglomerate size with increasing number of irradiation shots. The transient annealing in each irradiation was not enough to cause the Oswald ripening or sintering of particles into bigger particle or crystal size but only resulted in clustering. The atomic force micrographs reveal an increase in average surface roughness with increasing ion irradiation. The Raman study demonstrates increase in disordered D peak along with reduced crystallite size (La) with increasing number of irradiation shots.

Helium ion irradiation effects on neodymium and cerium co-doped Gd2Zr2O7 pyrochlore ceramic

This paper studies the helium ions irradiation effects on Nd and Ce co-doped Gd2Zr2O7 ceramics, where Nd replaces the Gd site and Ce replaces the Zr site respectively. A series of (Gd1-xNdx)2(Zr1-yCey)2O7 (0 ≤ x, y ≤ 1) ceramics were irradiated with a 500 keV He ions at room temperature at fluences ranging from 1 × 1015 to 1 × 1017 ions/cm2. The irradiated samples were characterized using GIXRD, Raman and SEM measurements. From the GIXRD and Raman observations, the results indicate that all the samples display a deficient fluorite structure after irradiation. The irradiation toleration increases with the irradiation depth increasing under experimental conditions, and Nd2Ce2O7 has the best irradiation stability in the (Gd1-xNdx)2(Zr1-yCey)2O7 (0 ≤ x, y ≤ 1). Based on SEM results, the irradiated samples are still relatively dense and uniform, and no second phase exists.

Fluence dependence of helium ion irradiation effects on the microstructure and mechanical properties of tungsten

Abstract To understand the effect of helium ion irradiation on the microstructure and mechanical properties of tungsten (W), recrystallized W is irradiated by 80 keV helium ions with fluence of 3 × 1015, 3 × 1016 and 3 × 1017 ions/cm2. Transmission electron microscope (TEM) observation suggests that large numbers of dislocation loops are generated in W and the size of the dislocation loop increases with irradiation fluence. The results of micro-hardness and nanoindentation show that the irradiation hardening can be clearly detected after helium ion bombardment with displacements per atom (dpa) of

Effects of Helium Ion Irradiation on Properties of Crystalline and Amorphous Multiphase Ceramic Coatings

The Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings were prepared on a martensitic steel by laser in situ reaction technique and impose irradiation with 200 keV He ions at different doses. The helium ion irradiation goes 1.55 μm deep from the surface of coating, and the displacement per atom (dpa) for the Al2O3-TiO2 coating is 20.0. When the irradiation fluency is 5 × 1017 ions/cm2, defects are identified in crystalline areas and there form interfacial areas in the coating. These crystal defects tend to migrate and converge at the interfaces. Moreover, helium ion irradiation is found to exert no effect on surface chemical composition and phase constitution of the coatings, while surface mechanical properties for the coatings after irradiation differ from those before irradiation. Further nano-indentation experiments reveal that surface nano-hardness of the Al2O3-TiO2 multiphase coatings decreases as the helium ions irradiation flux increases. Such Al2O3-TiO2 crystalline and amorphous multiphase ceramic coatings exhibit the strongest resistance against helium ion irradiation which shall be applied as candidate structural materials for accelerator-driven sub-critical system to handle the nuclear waste under extreme conditions.

Effect of Helium ion irradiation on the structure, the phase stability, and the microhardness of TiN, TiAlN, and TiAlYN nanostructured coatings

The radiation resistance of nanostructured TiN, TiAlN, and TiAlYN coatings is studied after 500-keV He+ ion irradiation in the fluence range 5 × 1016–3 × 1017 ions/cm2. The radiation-induced changes in the phase composition, the structure, the lattice parameters, the morphology, and the mechanical properties of coatings are investigated. Blistering is found to be absent, and the radiation fluence is shown to affect the strength properties of the thin coatings nonlinearly. A significant decrease in the grain sizes is detected upon ion irradiation, which causes an increase in the microhardness and the radiation resistance of the coatings. The TiN, TiAlN, and TiAlYN coatings are found to be radiation-resistant coatings, which do not undergo serious degradation during high-fluence ion irradiation.

Spectroscopic study of energetic helium-ion irradiation effects on nuclear graphite tiles

Helium ion-irradiation effects on the nuclear graphite tiles were studied in order to understand the structural modifications and damages that can be produced by fusion reaction in tokamaks. The surface morphological changes due to increasing dose of the irradiation were examined by the field-effect scanning electron microscopy, and X-ray photoelectron spectroscopy elucidated the changes in the shallow surface bonding configurations caused by the energetic irradiation. Raman spectroscopy revealed the structural defects and diamond-like carbon sites that increased with increasing irradiation dose, and the average inter-defect distance was found from the Raman peak intensities as a function of the irradiation dose.

Effects of helium ion irradiation on bubble formation in AlN/TiN multilayered system

The effects of helium ion irradiation on immiscible AlN/TiN multilayered system were studied. The structure consisted of 30 alternate AlN (~8nm) and TiN (~9.3nm) layers of a total thickness around 260nm, deposited on (100) Si substrates by reactive sputtering. The system was then implanted with 30keV He+ to very high irradiation doses, 1–4×1017ions/cm2. Evaluated projected ion range was 153.1±45.4nm and maximum displacements per atom for the applied doses from 6 to 24. It was found that the multilayers remained well separated and stable after irradiation to 1×1017ions/cm2, which introduces up to 10at.% of He within the structure. The main effects were agglomeration of He bubbles around the projected ion range, mostly concentrated at the AlN edges of the interfaces, and a slight increase of the mean grain size within the affected zone. Increasing of the ion dose induced further agglomeration of bubbles, splitting of the layers at the interfaces, and final destruction of the structure. The evaluated He content was consistent with the implanted dose up to 2×1017ions/cm2. For the highest dose the implanted gas is partially released from the structure. The results can be interesting towards the development of radiation tolerant materials.

Effect of Helium Ion Irradiation on the Tunneling Behavior in Niobium/Aluminum–Aluminum Oxide/Niobium Josephson Junctions

The study of the effects of high-energy particle irradiation on trilayer Josephson junctions has allowed us to investigate the influence of defects and interfacial intermixing on the junction electrical characteristics. In this paper, we investigated the influence of 2-MeV helium ion irradiation with doses up to 5.25 × 1016/cm2 on the tunneling behavior of Nb/Al-AlOx/Nb Josephson junctions. The modeling of the irradiation-induced chemical changes, combined with transmission-electron-microscopy characterization, indicates that over 2 nm of atomic intermixing occurs at all interfaces. Surprisingly, the quality of the tunneling characteristics is not significantly degraded, although some properties were affected: 1) The onset of the quasi-particle current characteristic of the electrodes' sum gap, Δ1 + Δ2, decreased from 2.8 to 2.6 mV; 2) the temperature onset of the Josephson current dropped from 9.2 K to 9.0 K; and 3) the normal resistance, Rn, increased by <; ~ 20%. The dependence of the Josephson current on the magnetic field was not significantly altered. Modeling using proximity theory indicated that the irradiation-induced changes in the current-voltage (I -V) characteristics are likely due to an increased drop in the order parameter near the barrier interface as a result of a reduced mean free path in the Al proximity layer from Nb and O contamination.

Effects of Helium Ion Irradiation on Deuterium Retention Behavior of SiC/SiC Composites as Plasma Facing Materials for Fusion Reactors

Effects of Helium Ion Irradiation on Deuterium Retention Behavior of SiC/SiC Composites as Plasma Facing Materials for Fusion Reactors