Energetic Particle Irradiation Research Articles

Development of highly sensitive electrochemical immunosensor using PPy-MoS2-based nanocomposites modified with 90MeV C6+ ion beams.

Theevaluation of electrochemical sensing activity of hydrothermally derived PPy-MoS2-based nanocomposites subjected to 90MeV C6+ ion beam with fluence ranging, 1.0 × 1010-1.0 × 1013 ions/cm2, is reported. Cross-linking, chain scissioning, and ion track formation could occur in the irradiated systems, as revealed from Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FE-SEM)studies. Electrochemical studies, viz., cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed in 0.1M phosphate buffer solution (PBS) containing 5mM K3[Fe(CN)6] as redox probe. High redox activity, lower charge transfer resistance (Rct = 490 Ω) and larger electroactive area (A = 0.4485 cm2) were obtained in case of the composite system irradiated with a fluence of 3.5 × 1011 ions/cm2. Immunosensor fabrication was executed via immobilization of mouse IgG over the pristine and post-irradiated electrodes. Afterwards, differential pulse voltammetry (DPV) was performed within thepotential window - 0.2 to + 0.6V (vs. Ag/AgCl) for the detection of specific analyte. Noticeably, the electrode system irradiated with a fluence of 3.5 × 1011 ions/cm2 ischaracterized by a lower limit of detection (LOD) of 0.203nM and a higher sensitivity value of 10.0 µAmLng-1cm-2. The energetic particle irradiation at a modest fluence can offer beneficial effects to thePPy-MoS2-based nanohybrid system providing immense scope as advanced electrochemical biosensor.

Plasma damage-free deposition of transparent Sn-doped In2O3 top cathode using isolated plasma soft deposition for perovskite solar cells

We developed an isolated plasma soft deposition (IPSD) technique for the plasma damage-free deposition of a Sn-doped In2O3 (ITO) top cathode on semi-transparent perovskite solar cells (PSCs). Unlike the directly faced plasma in conventional magnetron sputtering, the isolated plasma region in the IPSD process prevents the direct irradiation of plasma and facilitates plasma damage-free sputtering. Effective confinement of high-density plasma in isolated regions by using a specific Nd-Fe-B45 magnet array also prevents irradiation of energetic particles sputtered from faced ITO targets. In addition, linear scanning of the substrate in the isolated plasma region resulted in a low-temperature and large-area coating of the ITO top cathode without plasma damage for semi-transparent PSCs. Without intentional substrate heating, the IPSD-processed ITO film with a thickness of 100 nm under optimal conditions exhibited a low sheet resistance of 33.02 Ohm/square, high optical transmittance of 91.27%, root mean square roughness of 0.252 nm, and work function of 4.33 eV. To demonstrate the feasibility of IPSD, we fabricated PSCs with thermally evaporated perovskite active layers. Compared with the power conversion efficiency (PCE: 4.35%) of PSCs with magnetron-sputtered ITO cathode, the PSC with IPSD-processed ITO cathode exhibited a similar PCE (15.52%) because of the absence of plasma damage. Considering the commercialization of PSCs, the IPSD-based top cathode coating process possesses great potential as a key technique for bidirectional or semi-transparent PSCs.

From high-entropy alloys to high-entropy ceramics: The radiation-resistant highly concentrated refractory carbide (CrNbTaTiW)C

High-entropy materials represent the state-of-the-art on the alloy design strategy for future applications in extreme environments. Recent data indicates that high-entropy alloys (HEAs) exhibit outstanding radiation resistance in face of existing diluted alloy counterparts due to suppressed damage formation and evolution. An extension of the HEA concept is presented in this paper towards the synthesis and characterization of novel high-entropy ceramics as emergent materials for application in environments where energetic particle irradiation is a major concern. A novel carbide within the quinary refractory system CrNbTaTiW has been synthesized using magnetron-sputtering. The material exhibited nanocrystalline grains, single-phase crystal structure and C content around 50 at.%. Heavy-ion irradiation with in-situ Transmission Electron Microscopy was used to assess the irradiation response of the new high-entropy carbide (HEC) at 573 K and a comparison with the HEA within the system is made. No displacement damage effects appear within the microstructures of both HEA and HEC up to a dose of 10 displacements-per-atom. Surprisingly, the HEC has not amorphized under the investigated conditions. Xe was implanted in both materials and bubbles nucleated, but smaller sizes compared with conventional nuclear materials shedding light they are potential candidates for use in nuclear energy.

Dynamic modeling of total ionizing dose-induced threshold voltage shifts in MOS devices

The total ionizing dose (TID) effect is a key cause for the degradation/failure of semiconductor device performance under energetic-particle irradiation. We developed a dynamic model of mobile particles and defects by solving the rate equations and Poisson’s equation simultaneously, to understand threshold voltage shifts induced by TID in silicon-based metal–oxide–semiconductor (MOS) devices. The calculated charged defect distribution and corresponding electric field under different TIDs are consistent with experiments. TID changes the electric field at the Si/SiO2 interface by inducing the accumulation of oxide charged defects nearby, thus shifting the threshold voltage accordingly. With increasing TID, the oxide charged defects increase to saturation, and the electric field increases following the universal 2/3 power law. Through analyzing the influence of TID on the interfacial electric field by different factors, we recommend that the radiation-hardened performance of devices can be improved by choosing a thin oxide layer with high permittivity and under high gate voltages.

Accelerated radiation tolerance testing of Ti-based MAX phases

MAX phases have recently attracted significant attention for potential nuclear applications due to their novel properties such as unique hexagonal-compact nanolayered crystal structure, high-machinability due to lower hardness levels than conventional ceramics, and high-chemical inertness. In order for MAX phases to be used in nuclear reactors, two aspects deserve detailed investigations: (i) their phase stability at high-temperatures and (ii) microstructural defect formation and recovery induced by energetic particle irradiation. To date, degradation mechanisms of MAX phases at high-temperatures and following irradiation are largely unexplored fields of research. This work focuses on the evaluation of two Ti-based MAX phases—Ti2AlC and Ti3SiC2—within the context of extreme environments. To accomplish this, a one-of-a-kind comparison between neutron irradiations, performed over a decade of research at the high flux isotope reactor, and heavy-ion irradiations, carried out in situ in a transmission electron microscope, has been conducted. The results show Ti-based MAX phases are prone to accelerated decomposition under the conditions investigated. This questions the hypothesis that MAX phases exhibit high phase stability, especially when used in future nuclear energy systems where energetic particle irradiation is a dominating degradation mechanism.

Study on the Heat Absorption Coefficient of Tungsten as the Plasma-Facing Material for the Upgraded EAST Lower Divertor

Divertor is one of the key plasma-facing components (PFCs) for Experimental Advanced Superconducting Tokamak (EAST) since they play important roles in resisting the energetic particle irradiation and huge heat deposition from the core plasma as well as efficaciously dispelling such energy load. Tungsten is used as the plasma-facing material for PFCs due to the excellent properties. During the thermal analysis and the high heat flux test of the PFCs, the heat absorption coefficient is an important parameter that directly affects the availability and reliability of the design structure. Previous studies have shown that there is a large deviation in the measured heat absorption coefficient of tungsten. Therefore, it is very important to accurately measure the heat absorption coefficient of tungsten. In this article, the heat absorption coefficient of tungsten was tested by the e-beam device of the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). In this test, 36 sets of inlet and outlet water temperature data were obtained by changing the water flow rate and the incident heat flux. The heat absorption coefficient of tungsten was calculated by the theoretical calculation using water calorimetry. The results indicate that the heat absorption coefficient of tungsten is stable at ~0.54, which can be used as a reference for the engineering design of PFCs of the upgraded EAST lower divertor. All test parameters for EAST will provide important reference and guidance to the next-generation fusion facility China Fusion Engineering Test Reactor (CFETR).

A Kinetic Monte Carlo Algorithm to Model the Annealing Process and Compute the Dark Current Nonuniformity

A simulation chain, composed of GEANT4 and a kinetic Monte Carlo (KMC) algorithm, dedicated to study the annealing process of defects produced after energetic particle irradiation is presented. Results will be used to compute dark current nonuniformity (DCNU).

Compositional patterning in irradiated alloys: Effective potentials and effective interfacial energy

Compositional patterning (CP) in binary alloys during energetic particle irradiation is studied using a kinetic model that considers two competing kinetic processes, a thermally activated one promoting macroscopic phase separation (MPS) of the concentration field $c(\mathbf{r},t),$ and a forced one resulting in finite-range random atomic mixing. The forced mixing is modeled by a Gaussian relocation distribution with a characteristic distance $R$. A series of approximate kinetic models are introduced by expanding the mixing function into a series of $n$ terms, thus replacing the nonlocal evaluations of the concentration field $c({\mathbf{r}}^{\ensuremath{'}}\ensuremath{-}\mathbf{r},t)$ by local derivatives of $c(\mathbf{r},t)$. This approach makes it possible to obtain exact effective potentials and build steady-state diagrams for each order-n model. Phase-field (PF) simulations using these order-n models reveal that near the onset of patterning, phase evolution is accurately described using an order-3 model, which changes smoothly from an extended Cahn-Hilliard free energy in the MPS regime to a one-mode Swift-Hohenberg functional in the CP regime. Deeper into the patterning regime, higher-order models are required to achieve convergence, yielding squarelike concentration profiles characteristic of a strong segregation regime. These higher-order effective free energies are analogous to multimodal Swift-Hohenberg functionals. An alternative definition for the effective interfacial energy is proposed in the CP regime, since the interfacial area is no longer an excess quantity in that regime, precluding the use of the standard thermodynamic definition of interfacial energy.

Comparative irradiation response of an austenitic stainless steel with its high-entropy alloy counterpart

Two metallic alloys in the quaternary system Fe–Cr–Mn–Ni were irradiated in situ within a transmission electron microscope (TEM) using Xe+ heavy ions in the temperature range of 293–873 K and in the regime of low- (30 keV) and medium-energies (300 keV) with respective maximum doses of around 40 and 140 dpa. The first alloy is the FeCrMnNi high-entropy alloy (HEA) synthesised with the alloying elements close to equimolar composition. The second alloy is a commercial austenitic stainless steel AISI-348 (70.5Fe-17.5Cr-1.8Mn-9.5Ni wt.%), selected as the “low-entropy” counterpart of the FeCrMnNi HEA. Microstructural characterisation was carried out in the TEM with in situ heavy ion irradiation to investigate the role of entropy on radiation induced segregation and precipitation (RIS and RIP). The results demonstrated that among all the irradiation cases investigated, the FeCrMnNi HEA had its random solid solution matrix phase preserved in 80% of the experiments whilst the austenite matrix of the AISI-348 steel underwent RIP in 80% of the cases. It is therefore demonstrated that small differences between two alloys can lead to different radiation responses, confirming the trend that, by tuning the elemental composition superior radiation resistance can be achieved in metallic alloy systems, but emphasising that some of the constitutive core-effects of HEAs are still in need of further confirmation especially when the application of HEAs in energetic particle irradiation environments is considered.

Radiation Damage Suppression in AISI-316 Steel Nanoparticles: Implications for the Design of Future Nuclear Materials

The self-healing capability of point and extended defects that are introduced by energetic particle irradiation is a desired behavior to be attained in the design and selection in potential materia...

The thermal conductivity of defected copper at finite temperatures

Copper-based materials have been selected as heat-sink materials in some nuclear fusion reactors, where a great number of structural defects will be created due to the irradiation of energetic particles. In the practice of fusion reactors, an important issue is how the defects in copper heat-sink material affect its thermal transport property. However, there is no systematic study on the relation between thermal conductivity and the concentrations of various point defects in copper up to now. Our theoretical calculations show that the thermal conductivity ($$ \kappa $$) of Cu is significantly reduced by the presence of vacancies, self-interstitial atoms, SIA–vacancy pairs and the doped impurity tungsten (W) at finite temperatures. Among these concerned point defects, the doped impurity W plays the strongest role in impeding the thermal transport of conduction electrons, and the presence of 4% W impurity in Cu leads to about 80% reduction in $$ \kappa $$ as compared to that of the defect-free Cu system ($$ \kappa_{0} $$). Furthermore, it is revealed that during the cascade, the thermal transport property of Cu changes as the structural defects evolve, and the thermal transport of electrons is impeded significantly in the initial stages of cascade. In addition, our calculations show that the Wiedemann–Franz law is still valid in defected copper systems.

On the detection and classification of material defects in crystalline solids after energetic particle impact simulations

We present a fingerprint-like method to analyze material defects after energetic particle irradiation by computing a rotation invariant descriptor vector for each atom of a given sample. For ordered solids this new method is easy to use, does not require extreme computational resources, and is largely independent of the sample material and sample temperature. As illustration we applied the method to molecular dynamics simulations of deuterated and pristine tungsten lattices at 300 K using a primary knock-on atom (PKA) of 1 keV with different velocity directions to emulate a neutron bombardment process. The number of W atoms, which are affected after the collision cascade, have been quantified with the presented approach. At first atoms at regular lattice positions as well as common defect types like interstitials and vacancies have been identified using precomputed descriptor vectors. A principal component analysis (PCA) is used to identify previously overlooked defect types and to derive the corresponding local atomic structure. A comparison of the irradiation effects for deuterated and pristine tungsten samples revealed that deuterated samples exhibit consistently more defects than pristine ones.

Key factors in radiation tolerance of BCC metals under steady state

Different materials would exhibit discrepant behaviors of radiation tolerance under energetic particle irradiation, due to the effect of intrinsic features (like defect migration energy and sink strength of grain boundaries) and extrinsic conditions (like irradiation rate and temperature) on defect accumulation. We wonder what the general rules of radiation tolerance are in body-centered cube (BCC) transition metals. Based on the steady state chemical rate theory, the influence of these intrinsic features and extrinsic conditions on vacancy accumulation is thus investigated in typical BCC metals including V, Cr, Fe, Nb, Mo, Ta and W. It shows that V, Cr, Fe and Nb exhibit obvious advantage in radiation resistance than that of Ta, Mo and W under typical service conditions, due to their higher vacancy diffusivities. In addition, the smaller grain size and lower irradiation rate, the higher anti-irradiation ability of BCC metals. Therefore, we propose that, under practical irradiation rates and temperatures, BCC metals with low vacancy migration energy and small grain size should be recommended in the selection of new nuclear materials, at least in the view of steady state.

Radiation-Induced Helium Bubbles in Metals.

Helium (He) bubbles are typical radiation defects in structural materials in nuclear reactors after high dose energetic particle irradiation. In the past decades, extensive studies have been conducted to explore the dynamic evolution of He bubbles under various conditions and to investigate He-induced hardening and embrittlement. In this review, we summarize the current understanding of the behavior of He bubbles in metals; overview the mechanisms of He bubble nucleation, growth, and coarsening; introduce the latest methods of He control by using interfaces in nanocrystalline metals and metallic multilayers; analyze the effects of He bubbles on strength and ductility of metals; and point out some remaining questions related to He bubbles that are crucial for design of advanced radiation-tolerant materials.

Energetic particle irradiation study of TiN coatings: are these films appropriate for accident tolerant fuels?

Coating nuclear fuel cladding alloys with hard thin films has been considered as an innovative solution to increase the safety of nuclear reactors, in particular during a of loss-of-coolant accident (LOCA). In this context, and due to its suitable mechanical properties and high corrosion resistance, titanium nitride thin films have been proposed as candidate coatings for zirconium alloys in new accident tolerant fuels for light water reactors. Although the properties of TiN hard coatings are known to be adequate for such applications, the understanding of how the exposure to energetic particle irradiation changes the microstructure and properties of these thin films is still not fully understood. Herein, we report on heavy ion irradiation in situ within a Transmission Electron Microscopy (TEM) of magnetron-sputtered TiN thin films. The coatings were irradiated with 134 keV Xe + ions at 473 K to a fluence of 6.7 × 1015 ions⋅cm−2 corresponding to 6.2 displacements-per-atom where significative microstructural alterations have been observed. Post-irradiation analytic characterisation with Energy Filtered TEM and Energy-Dispersive X-ray spectroscopy carried out in a Scanning Transmission Electron Microscope indicates that TiN thin films are subjected to radiation-induced segregation. Additionally, the nucleation and growth of Xe bubbles appears to play a major role in the dissociation of the TiN thin film.

Influences of vacancy and doping on electronic and magnetic properties of monolayer SnS

Based on the first-principles calculations, we investigate the structural, electronic, and magnetic properties of defects in monolayer SnS. We study the formation and migration of vacancies at both Sn- and S-sites. In comparison to the S-site vacancy, our calculations show that creating a vacancy at the Sn-site requires lesser energy, indicating that the vacancy at the Sn-site is more likely to be formed in experiments with energetic particle irradiation. For the Sn-rich (S-rich) environment, the vacancy at the S-site (Sn-site) is more likely to be found than the vacancy at the Sn-site (S-site). Reducing the formation of vacancy clusters, the S vacancy remains at the position where it is created because of the high vacancy migration barrier. Both types of vacancies remain nonmagnetic. To induce magnetism in monolayer SnS, we also study the transition metal (TM = Mn, Fe, and Co) doping at the Sn-site and find a significant influence on the electronic and magnetic properties of monolayer SnS. The doping of TM changes non-magnetic monolayer SnS to magnetic one and keeps it semiconducting. Additionally, long-range ferromagnetic behavior is observed for all the doped system. Hence, doping TM atoms in monolayer SnS could be promising to realize a two-dimensional diluted magnetic semiconductor. More interestingly, all the doped TM configurations show a high spin state, which can be used in nanoscale spintronic applications such as spin-filtering devices.

Atom probe tomography analysis of radiation-induced solute clustering in austenite stainless steels

ABSTRACTVarious types of defects are produced by the irradiation of energetic particles onto a structural material. The large number of mobile vacancies and self-interstitial atoms during irradiation induce defect fluxes and the diffusion of solute atoms in the matrix. The preferential interaction between the solute atoms and radiation-induced defects leads to the enrichment/depletion or clustering of the solutes at defect sinks. In the current work, atom probe tomography (APT) was used for the analysis of radiation-induced solute clustering in ion-irradiated austenite stainless steel 316. Quantitative analysis of the localised clustering of chemical elements was implemented and a parameter selection procedure was proposed. The number density and size distribution of Si clusters in APT specimens irradiated at various temperatures were examined. At high temperature, the number density of the clusters decreased and their size increased. The localized Si atoms in variously shaped defects were clearly identified. The APT method was demonstrated to be suitable for identifying defect structures and for the quantitative analysis of clustering in irradiated specimens.

Modeling the long-term evolution of dilute solid solutions in the presence of vacancy fluxes

This work investigates the long-term evolution of dilute solute atoms in face-centered-cubic (fcc) alloys driven by sustained vacancy fluxes, as for instance in the case of materials subjected to energetic particle irradiation. Employing the five-jump frequency framework, we provide compact analytic expressions of the Onsager matrix for dilute vacancy-solute systems in form of a ratio of polynomial functions of jump frequencies. The drag ratio is found to be a function of only two independent variables, which enables a systematic study of both the flux coupling and trapping behavior between solutes and point defects. Using an existing diffusivity database for a total of 182 solutes in 5 fcc solvents, we show that, while most vacancy-binding solutes have indeed a positive drag ratio, there are some solutes with positive, but small, or even negative drag ratio. This previously unnoticed feature is interesting as it would ensure that the trapping solute remains in the matrix despite the accumulation of irradiation dose. In the case where the drag ratio is positive, we propose a kinetic model of solute depletion over time due to flux coupling with vacancies and apply it to a Cu-1 at. % Sb alloy. This study reveals that solutes are not simply dragged to sinks by point defects, but affect the flux of point defects to sinks by modifying the transport coefficients and the driving force for point-defect elimination.

SOLIS IV. Hydrocarbons in the OMC-2 FIR4 Region, a Probe of Energetic Particle Irradiation of the Region∗

Abstract We report new interferometric images of cyclopropenylidene, c-C3H2, toward the young protocluster OMC-2 FIR 4. The observations were performed at 82 and 85 GHz with the NOrthern Extended Millimeter Array (NOEMA) as part of the project Seeds Of Life In Space (SOLIS). In addition, IRAM-30 m data observations were used to investigate the physical structure of OMC-2 FIR 4. We find that the c-C3H2 gas emits from the same region where previous SOLIS observations showed bright HC5N emission. From a non-LTE analysis of the IRAM-30 m data, the c-C3H2 gas has an average temperature of ∼40 K, a H2 density of ∼3 × 105 cm−3, and a c-C3H2 abundance relative to H2 of (7 ± 1) × 10−12. In addition, the NOEMA observations provide no sign of significant c-C3H2 excitation temperature gradients across the region (about 3–4 beams), with T ex in the range 8 ± 3 up to 16 ± 7 K. We thus infer that our observations are inconsistent with a physical interaction of the OMC-2 FIR 4 envelope with the outflow arising from OMC-2 FIR 3, as claimed by previous studies. The comparison of the measured c-C3H2 abundance with the predictions from an astrochemical PDR model indicates that OMC-2 FIR 4 is irradiated by an FUV field ∼1000 times larger than the interstellar one, and by a flux of ionizing particles ∼4000 times larger than the canonical value of 1 × 10−17 s−1 from the Galaxy cosmic rays, which is consistent with our previous HC5N observations. This provides an important and independent confirmation of other studies that one, or more, source inside the OMC-2 FIR 4 region emits energetic (≥10 MeV) particles.

Photocarrier Radiometry for Non-contact Evaluation of Monocrystalline Silicon Solar Cell Under Low-Energy (< 200 keV) Proton Irradiation

A three-layer theoretical model is developed for the characterization of the electronic transport properties (lifetime τ, diffusion coefficient D, and surface recombination velocity s) with energetic particle irradiation on solar cells using non-contact photocarrier radiometry. Monte Carlo (MC) simulation is carried out to obtain the depth profiles of the proton irradiation layer at different low energies (< 200 keV). The monocrystalline silicon (c-Si) solar cells are investigated under different low-energy proton irradiation, and the carrier transport parameters of the three layers are obtained by best-fitting of the experimental results. The results show that the low-energy protons have little influence on the transport parameters of the non-irradiated layer, but high influences on both of the p and n-region irradiation layers which are consisted of MC simulation.