Kr Ions Research Articles

Effect of sink strength on coherency loss of precipitates in dilute Cu-base alloys during in situ ion irradiation

In situ irradiations with 1 MeV Kr ions at 50~613 K up to a fluence of 6.25 × 1014 ions/cm2 (~1.25 displacements per atom, dpa) have been performed on pre-aged dilute Cu-0.9%Co, Cu-0.9%Fe and Cu-0.8%Cr alloys containing uniform matrix dispersions of coherent precipitates in order to study the effects of initial precipitate sink strength, damage dose and irradiation temperature on radiation-induced coherency loss of precipitates. Coherent precipitates with different point defect sink strengths (2πNd, where N and d are the precipitate density and diameter) were used in this work to examine potential differences in atomic relaxation during absorption of point defects. In all cases, irradiation to low doses (<~1 dpa) was very effective at inducing loss of precipitate coherency. At low sink strengths (~1013 m−2), loss of precipitate coherency could be induced for doses ~0.01 dpa. This suggests there might be an efficient preferential medium-range strain-induced bias for absorption of interstitial defects due to tensile strains emanating from the undersized precipitates, which induces relatively rapid loss of coherency at low precipitate sink strengths. High precipitate sink strength (~1014 m−2) conditions were relatively resistant to the radiation-induced loss of coherency (requiring higher doses approaching ~1 dpa) and this might be due to nearly equal numbers of interstitial and vacancy defects arriving at the precipitate interface for such high sink strength conditions. The precipitate coherency loss was observed to have a weak dependence on irradiation temperature. Molecular dynamics simulations confirm a strong effect of precipitate sink strength on the probability of interstitial absorption at precipitates.

Analysis of properties of krypton ion-implanted Zn-polar ZnO thin films* *Project supported by the National Natural Science Foundation of China (Grant No. 11875088) and the National Key Basic Research Program of China (Grant No. 2015CB921003).

The optical properties of materials are of great significance for their device applications. Different numbers of krypton ions are doped into high-quality Zn-polar ZnO films fabricated by molecular beam epitaxy (MBE) on sapphire substrates through ion implantation. Krypton is chemically inert. The structures, morphologies, and optical properties of films are measured. The x-ray diffraction (XRD) spectra confirm the wurtzite structures of Zn-polar ZnO films. Atomic force microscopy (AFM) results show that the films have pit surface structure and higher roughness after Kr ion implantation. A detailed investigation of the optical properties is performed by using the absorption spectrum, photoluminescence (PL), and spectroscopic ellipsometry (SE). The absorption spectrum is measured by UV-visible spectrophotometer and the bandgap energy is estimated by the Tauc method. The results show that the absorption increases and the bandgap decreases after Kr ion implantation. Moreover, the Kr ion implantation concentration also affects the properties of the film. The ellipsometry results show that the films’ refractive index decreases with the Kr ion implantation concentration increasing. These results can conduce to the design and optimization of Kr ion-implanted polar ZnO films for optoelectronic applications.

Research on Single Event Effects of Ethernet MAC Controller on Manned Spacecraft

In order to realize higher speed and large flow network communication on the new manned spacecraft independently developed in China, it is necessary to apply Ethernet technology. Considering the cost and application prospect, it is planned to use industrial Ethernet control chip. So it is necessary to verify whether it can meet the special requirements of the space environment. According to the space environment of the manned spacecraft design orbit, and the sensitive characteristics of the Ethernet controller chip itself, it is necessary to focus on verifying its single-particle effect. This paper introduces in detail the single-event effect of the Ethernet controller in China for the first time. The Bi-ion and Kr ions of the HIRFL cyclotron are used to carry out the single-event effect on the KSZ8851-16MLLJ Ethernet MAC controller produced by MICREL. The evaluation test, including the single-particle test design, hardware platform, software functions and test data, finally gave the test conclusion.

Assessment of the Irradiation Exposure of PET Film with Swift Heavy Ions Using the Interference-Free Transmission UV-Vis Transmission Spectra.

This paper presents the results of a study of polyethylene terephthalate (PET) films irradiated with Ar and Kr ions at both normal orientation and an angle of 40° to the normal. Normal irradiation was performed using Ar8+ and Kr15+ ions with an energy of 1.75 MeV/au and fluences in the range (2–500) × 1010 cm−2 for Ar8+ ions and (1.6 − 6.5) × 1010 cm−2 for Kr15+ ions. Kr ions with an energy of 1.2 MeV/au and charges of 13+, 14+, and 15+ were used for angled irradiation. For each Kr ion charge value, three fluence values were used: 5 × 1010, 1 × 1011, and 2.5 × 1011 cm−2. It is well known that irradiation of PET films by swift heavy ions results in a red shift of the UV-vis transmission spectra absorption edge. The experimental transmission spectra exhibit well-defined interference fringes, which obscure the underlying transmission response. Using an existing technique to obtain interference-free transmission curves Tα(λ) for both pristine and irradiated PET film samples, we found that S, the total radiation-induced absorption of light by the PET film, is proportional to the logarithm of the fluence F. In addition to this dependence on the irradiating fluence, we also found that the charge of the irradiating ion has a significant influence on the position of the absorption edge in the UV-vis spectra. This provides experimentally independent evidence to confirm our previous results showing that ion charge has an effect on the post-irradiation state of PET films. We present a physical interpretation of the observed absorption edge red shift in irradiated PET films as being due to the growth of extended conjugated systems via the formation of intermolecular helical structures. Our investigations into the stability of irradiation-induced effects in PET films show that comparison of UV-vis transmission spectra before and after annealing can provide information about the structure of deep traps in PET.

In situ transmission electron microscopy with dual ion beam irradiation and implantation

To study the helium effects and their interactions with displacement damage in irradiated materials, an in situ dual-ion beam irradiation capability with transmission electron microscopy was recently established at the IVEM-Tandem Facility at Argonne National Laboratory. Pure nickel was irradiated in situ individually with 1 MeV Kr ions for displacement damage study, 16 keV He ions for helium implantation, and simultaneously with 1 MeV Kr ions and 16 keV He ions at the rate of 1 at.% He/dpa to study the interaction of helium and displacement damage at 500 °C. Helium bubbles were formed and segregated within dislocation loops during the He implantation experiment and no bubbles were observed outside the loops. The loop size increased with increasing helium concentration. In contrast, helium bubbles were formed uniformly in the matrix when nickel was irradiated simultaneously with 1 MeV Kr ions and 16 keV He ions. It is suggested that the uniformly-distributed defect clusters formed under 1 MeV Kr ion irradiation serve as trapping sites of helium atoms resulting in homogeneous nucleation of helium bubbles under the dual-ion beam irradiation in nickel.

On the microstructure evolution of a nuclear-use steel after heavy ion irradiation

A nuclear-use ferritic-martensitic steel was irradiated by 196 MeV Kr ions. Both the low damage level area and the high damage level area were investigated by a transmission electron microscope (TEM), to reveal the irradiated microstructural features. In low damage level area ranging from surface to 6 μm depth, there were a few dislocation loops and black dots induced by Kr irradiation. The type of dislocation loops could be primarily ao<100> or ao/2<100> type. In addition, it was found that the sink effect of grain boundaries and stability of small precipitates were evident.

Irradiation-induced segregation at dislocation loops in CoCrFeMnNi high entropy alloy

To understand the redistribution of alloying elements in high entropy alloys under irradiation, a CoCrFeMnNi alloy was irradiated with 1 MeV Kr ions at room temperature and at 500°C, and characterized with atom probe tomography and transmission electron microscopy. At 500°C, Co and Ni were enriched around the interstitial, faulted and perfect, dislocation loops resulted from the ion irradiation. In contrast, no segregation was observed at room temperature. The inverse Kirkendall effect through vacancy flux, as opposed to the interstitial binding mechanism, was the primary underlying process attributing to the observed segregation. In addition, a ring-shaped segregation pattern was observed at the faulted dislocation loops, indicating a non-equilibrium nature of the defect clustering and solute segregation process in CoCrFeMnNi under irradiation at high temperature.

Void shrinkage in 21Cr32Ni austenitic model alloy during in-situ ion irradiation

Austenitic 21Cr32Ni model alloy thin foils, previously irradiated with 5 MeV Fe++ ions in bulk to create voids, were re-irradiated in-situ in the Intermediate Voltage Electron Microscope Facility (IVEM). The voids which had been formed under bulk-ion irradiation shrank and disappeared after in-situ Kr ion irradiation in the temperature range 50 K-713 K to an additional dose of 1 dpa. The voids were unaffected by eithersuccessive thermal annealing to 673 K and by prolonged exposure to the 200 keV electron beam at the irradiation temperature. The high void shrinkage rate observed did not change significantly for irradiation temperatures between 50 K and 713 K, suggesting that the void shrinkage process in thin foils during in-situ heavy-ion irradiation results from the interactions of displacement cascades with the voids. Possible void shrinkage mechanisms under thin foil irradiation are discussed in this study.

In-situ evolution of microstructural transformation from crystalline to amorphous in PtPb/Pt nanoplates induced by Kr ion irradiation

Ion irradiation is a highly effective approach to boost the catalytic activity in the platinum-lead/platinum (PtPb/Pt) core–shell nanoplates (NPs) through tuning their microstructures for fuel cell technology. We report on the evolution of crystalline to amorphous (c-a) transformation induced by Kr ion irradiation in the PtPb NPs in detail by using in-situ transmission electron microscopy. The results show that PtPb NPs first generate small amorphous domains, followed by a gradual amorphous transition from their edge to inner and finally are changed to be completely amorphous during in-situ Kr ion irradiation. The c-a transformation appears at the edge of NPs at first, which is attributed to high energy of grain boundary and surface. The crystal-amorphous interfaces and geometrical defects induced by moderate irradiation in PtPb NPs are the key factors to enhance the catalytic activity. This study provides the understanding of the microstructural transition of PtPb NPs and the guidance for using ion irradiation approach to boost catalytic properties of nanomaterials by tuning their microstructures.

In-situ observation of nano-oxide and defect evolution in 14YWT alloys

Nanostructured ferritic alloys (NFAs) are considered as candidates for structural components in advanced nuclear reactors due to their excellent radiation resistance as a result of a high density of nano-oxides (NOs) in the microstructure. Therefore, gaining an understanding on the stability of NOs under irradiation is crucial. In this study, we have investigated the evolution of defects and NOs in 14YWT NFAs under in-situ Kr ion irradiation at room temperature (RT) and 450 °C up to 10 dpa. It has been found that irradiations at 450 °C do not create any changes in the NOs, similar to the bulk irradiations. On the other hand, elemental mapping indicates that NOs dissolve mostly after 10 dpa irradiations at RT. Thus, while defects are both annihilated and pinned by NOs at low doses (before the dissolution of NOs), glissile loops start to escape to the foil surface at high doses (after the dissolution of NOs), justifying the significantly low fraction of <111> loops compared to the literature values. High resolution transmission electron microscopy analysis has shown that the NOs are mostly coherent Y2Ti2O7 particles with pyrochlore crystal structure after both RT and 450 °C irradiations, similar to those observed before irradiation.

Ion Species Dependence on the Interfacial Properties of Silicon Homojunctions Bonded Using an Ion Bombardment Treatment

Surfaces of (001) p-type silicon substrates were bombarded with either Ar or Kr ions prior to direct wafer bonding using an EVG© ComBond© high-vacuum wafer-bonding system.1 Previously, we showed that this ion bombardment treatment induces a thin ~nm amorphous region at the bonded interface.2 In this study, we extend upon this previous effort towards a fundamental understanding of this amorphous interfacial region by examining the dependence of the bonded interface’s properties with two different ion species. The ion energies used spanned from a factor of 0.5 to 2.5 times of a baseline energy E0. X-ray reflectivity measurements were performed on single unbonded wafers that were ion bombarded with either Ar or Kr to determine the thickness of the amorphous region as well as its mass density compared to bulk Si. Wafers treated with Ar showed no surface mass density dependence with ion energy, while wafers treated with Kr did show an ion energy dependence. While the Ar treatment reduces the surface density to ~80% of bulk Si density regardless of the energy used, the Kr treatment reduces the surface density to as low as ~70% of bulk Si density at 2.5⋅E0. Furthermore, for a given energy, the Ar treatment resulted in thicker layers than the Kr treatments, which is consistent with SRIM3 simulations because Kr is a heavier species than Ar. Current-voltage measurements were also used to probe the electrical properties of the bonded interfaces. Band structure modeling of the current-voltage measurements revealed that the amorphous region can be modeled with a step barrier that spans the thickness of the amorphous region.References Flötgen, et al., ECS Trans., 64(5), 103 (2014).E. Liao, et al., ECS Trans., 86(5), 55 (2018).F. Ziegler, et al., The Stopping Range of Ions in Solids vol. 1, (1985). Figure 1

Observation of latent ion tracks in semicrystalline polymers by scanning electron microscopy

AbstractAdvances in nanotechnology and materials science require further improvement of metrology of nanostructured polymers, in particular, polymers modified by high energy ion beams. The observation of latent ion tracks using various microscopy methods is an important part of studies on heavy ion effects in solids. However, scanning electron microscopy (SEM) has not been utilized for polymers. In the present study, it is shown how SEM can be used to observe latent tracks in semicrystalline polymers. The procedure includes the embrittlement of a polymer specimen by controlled photooxidation and its subsequent fracture. Latent tracks are clearly visible on fractured surfaces as structureless stripes surrounded by an inhomogeneous semicrystalline matrix. Using this method, the latent tracks of Kr, Xe, Au, and Bi ions with energies of 1–11 MeV/u in polyethylene terephthalate and polypropylene films are observed and their diameters are estimated. In contrast to transmission electron microscopy, the suggested novel technique detects the outer track shell consisting of an amorphized polymer. Therefore, SEM observations can complement other commonly used techniques to comprehensively characterize the structure of ion tracks in polymers.

Microstructural evolution of a silicon carbide-carbon coated nanostructured ferritic alloy composite during in-situ Kr ion irradiation at 300°C 450°C

Abstarct This work focuses on irradiation behaviors of a novel silicon carbide and carbon coated nanostructured ferritic alloy (SiC-C@NFA) composite for potential applications as a cladding and structural material for next generation nuclear reactors. The SiC-C@NFA samples were irradiated with 1 MeV Kr ions up to 10 dpa at 300 and 450 °C. Microstructures and defect evolution were studied in-situ at the IVEM-Tandem facility at Argonne National Laboratory. The effects of ion irradiation on various phases such as α-ferrite matrix, (Fe,Cr)7C3, and (Ti,W)C precipitates were evaluated. The α-ferrite matrix showed a continuous increase in dislocation density along with spatial ordering of dislocation loops (or loop strings) at >5 dpa. The size of the dislocation loops at 450 °C was larger than that at 300 °C. The nucleation and growth of new (Ti,W)C precipitates in α-ferrite grains were enhanced with the ion dose at 450 °C. This study provides new insight into the irradiation resistance of the SiC-C@NFA system.

Defect and structural evolution under high-energy ion irradiation informs battery materials design for extreme environments

Understanding defect evolution and structural transformations constitutes a prominent research frontier for ultimately controlling the electrochemical properties of advanced battery materials. Herein, for the first time, we utilize in situ high-energy Kr ion irradiation with transmission electron microscopy to monitor how defects and microstructures evolve in Na- and Li-layered cathodes with 3d transition metals. Our experimental and theoretical analyses reveal that Li-layered cathodes are more resistant to radiation-induced structural transformations, such as amorphization than Na-layered cathodes. The underlying mechanism is the facile formation of Li-transition metal antisite defects in Li-layered cathodes. The quantitative mathematical analysis of the dynamic bright-field imaging shows that defect clusters preferentially align along the Na/Li ion diffusion channels (a-b planes), which is likely governed by the formation of dislocation loops. Our study provides critical insights into designing battery materials for extreme irradiation environments and understanding fundamental defect dynamics in layered oxides.

Ion Species Dependence on the Interfacial Properties of Silicon Homojunctions Bonded Using an Ion Bombardment Treatment

Direct wafer bonded p-type (001) silicon homojunction structures were prepared with an ion bombardment surface treatment using either Ar or Kr ions prior to bonding in a high-vacuum direct wafer bonding system. The ion energies used spanned from a factor of 0.5 to 5 times of a baseline energy E0 for Ar and 0.5 to 2.5 times for Kr. The ion bombardment surface treatment induces a thin ~nm amorphous region at the Si|Si bonded interface. X-ray reflectivity measurements were performed on ion-bombarded single unbonded wafers. It was found that the Ar treated wafers showed a weak surface mass density dependence with ion energy, while wafers treated with Kr showed a strong ion energy dependence. While the Ar treatment reduces the surface density to ~80% of bulk Si density, the Kr treatment reduces the surface density to as low as ~70% of bulk Si density using an ion energy of 2.5⋅E0. Current-voltage measurements were also used to probe the electrical resistance across the amorphous interfacial region of the bonded structures prepared with Ar ions.

Dual-Beam Irradiation Stability of Amorphous Silicon Oxycarbide at 300°C and 500°C

The irradiation stability of a material in the temperature range from 300°C to 500°C represents an important step for a variety of nuclear applications. Here we used dual-beam irradiation to investigate the response of an amorphous silicon oxycarbide (SiOC) to extreme environments (temperature and irradiation). The amorphous SiOC was prepared in thin film form by sputtering and then fabricated into cross-sectional transmission electron microscopy (TEM) specimens, and finally irradiated with helium (He) and krypton (Kr) ions inside a TEM. In-situ TEM observations revealed that He bubble and void formation are highly suppressed after irradiation up to 95 dpa with simultaneous He implantation up to 231 at.%. Atomic pair-distribution functions suggested that the amorphous structures are almost the same before and after irradiation, and no crystallization, nor phase separation was detected. This study demonstrates the stability of amorphous SiOC under dual-beam irradiation at nuclear reactor operation temperatures, suggesting that this material is applicable as a structural material for advanced nuclear reactors.

Study on radiation damage effects on CdZnTe detectors under 3 MeV and 2.08 GeV Kr ion irradiation

The survivability of CdZnTe gamma ray detectors, when exposed to energetic particles in a radiation environment, is a key issue for their application. Nevertheless, very little attention has been paid to the irradiation particle energy influences on CdZnTe detector performance. The effects of 3 MeV and 2.08 GeV Kr ion irradiation at fluences of 1 × 1012 ions/cm2 on CdZnTe detector performance are investigated. Variations in performance were determined by comparing pre- and post-irradiation detector current-voltage (I–V) curves and the measured energy spectrum of a 59.5 keV gamma ray source, 241Am. Monte-Carlo simulations of the irradiation process were performed using SRIM software to help explain the observed changes in detector performance. Thermally stimulated current measurements were used to reveal crystal defects newly introduced by the Kr ion irradiation. The 3 MeV Kr ion principally losses its energy in the CdZnTe detector due to nuclear collisions and therefore creates more damage than the 2.08 Kr ion irradiation.

Ion beam irradiation of ABO4 compounds with the fergusonite, monazite, scheelite, and zircon structures

AbstractThe effects of irradiation on CaWO4, SrWO4, BaWO4, YVO4, LaVO4, YNbO4, and LaNbO4 were investigated on thin crystals using 1.0 MeV Kr ions at 50‐1000 K. All of the ABO4 compounds can be amorphized with calculated damage cross sections (σa = 1/Fc0) in the range of ~0.30‐1.09 × 10‐14 cm2 ion−1 at zero Kelvin. The analysis of fluence‐temperature data returned critical temperatures for amorphization (Tc) of 311 ± 1, 358 ± 90, 325 ± 19, 415 ± 17, 541 ± 6, 636 ± 26, and 1012 ± 1 K, respectively, for the compounds listed above. Compared with previous in situ irradiation of ABO4 orthophosphate samples using 0.8 MeV Kr ions, the Tc values of LaVO4 and YVO4 are higher than those of LaPO4 and YPO4 by 82 K and 124 K, respectively. The Tc values of the three scheelite structures, CaWO4, SrWO4, and BaWO4, indicate that they are the most radiation tolerant compounds under these conditions. The A‐B cation anti‐site energies, EfAB, determined by DFT range from 2.48 to 10.58 eV and are highly correlated with the A‐B cation ionic radius ratio, rA/rB, but are not correlated with Tc across the different structure types, suggesting that the formation and migration energies of Frenkel defects play a more important role in damage recovery in these compounds. We also discuss the role of cation and anion charge/iconicity as determined by DFT. ABO4 compounds with the zircon structure and B = P or V have a distinct advantage over those with B = Si as the damaged regions do not appear to be significantly affected by polymerization of (PO4)3− or (VO4)3− groups which might stabilize the amorphous fraction and ultimately lead to phase separation as observed in zircon (ZrSiO4).

The formation and accumulation of radiation-induced defects and the role of lamellar interfaces in radiation damage of titanium aluminum alloy irradiated with Kr-ions at room temperature

A transmission electron microscopy (TEM) specimen of a titanium aluminide (TiAl) alloy was irradiated in-situ, at the IVEM-TANDEM facility, with 1 MeV Kr ions to a maximum fluence of 1.25 × 1019 ions m−2 at room temperature. The irradiated microstructure was then investigated ex-situ using advanced analytical TEM in combination with TEM image simulations and molecular dynamics (MD) simulations. The TEM examination showed that dot-like defects first formed in both the α2-Ti3Al and γ-TiAl phases of the irradiated microstructure. With increasing irradiation dose planar defects formed and propagated within the γ phase, and most of the planar defects were accompanied by the dot-like defects. The TEM image simulations and MD irradiation simulations revealed that the origins of the dot-like and planar defects were interstitial clusters and stacking faults, respectively, and large interstitial clusters were surrounded by dislocation loops. The interstitial clusters formed and grew in the irradiated microstructure due to much faster diffusion of interstitials than that of vacancies at room temperature. Local stress concentrations increased near large interstitial clusters and lamellar interfaces, which resulted in the nucleation and propagation of stacking faults. Moreover, the configurations of the lamellar interfaces in the start microstructure were found to play an important role in the formation and accumulation of the radiation-induced interstitial clusters and stacking faults at room temperature.

Disordering of helium gas bubble superlattices in molybdenum under ion irradiation and thermal annealing

Self-organization of gas bubbles causes the formation of an ordered array of nanoscale gas bubbles (a gas bubble superlattice), a highly efficient mechanism for gas storage under irradiation. The stability of helium (He) gas bubble superlattices in molybdenum (Mo) under krypton (Kr) ion irradiation and thermal annealing has been investigated. The He gas bubble superlattices gradually become disordered under Kr ion irradiation at 300°C, and the order-disorder transformation process completes at 2.5 dpa. Both transmission electron microscopy (TEM) and synchrotron-based small-angle X-ray scattering (SAXS) reveal that the order-disorder transformation of He gas bubble superlattices is associated with a slight increase in the average bubble size. Phase-field modeling indicates that the inhomogeneous growth and coarsening of bubbles/voids cause the disordering of imperfect superlattices under irradiation and implies that highly ordered superlattices could potentially exhibit much stronger resistance to irradiation damage. Under thermal annealing, the He gas bubble superlattices in Mo become unstable and disordered at 1000°C with the bubble size increasing from ∼1.1 to ∼1.6 nm. The finding in this research provides insights into the disordering mechanisms of defect superlattices as well as guidance for designing stable defect superlattices in harsh environments.