Understanding the nature of irradiation damage often requires a multi-scale and multi-physics approach, i.e. it requires a significant amount of information from experiments, simulations and phenomenological models. This paper focuses on the initial stages of irradiation damage, namely neutron-induced displacement cascades in zirconium, as nuclear-grade zirconium alloys are widely used in fuel assemblies. We provide results of large-scale molecular dynamics (MD) simulations based on existing inter-atomic potentials and the two-temperature model to include the effect of electron-phonon coupling. Our data can be used directly in higher scale methods. Furthermore, we analysed summary statistics associated with defect production, such as the number of defects produced, their distribution and the size of clusters. As a result, we have developed a generative model of collision cascades. The model is hierarchical, as well as stochastic, i.e. it includes the variance of the considered features. This development had three main objectives: to establish a sufficient descriptor of a cascade, to develop an interpolator of data obtained from high-fidelity simulations, and to demonstrate that the statistical model of the data can generate representative distributions of primary irradiation defects. The results can be used to generate synthetic inputs for longer length- and time-scale models, as well as to build fast approximations relating dose, damage and irradiation conditions.
One of the challenges in fusion reactors is the discovery of plasma facing materials capable of withstanding extreme conditions, such as radiation damage and high heat flux. Development of fusion materials can be a daunting task since vast combinations of microstructures and compositions need to be explored, each of which requires trial-and-error based irradiation experiments and materials characterizations. Here, we utilize combinatorial experiments that allow rapid and systematic characterizations of composition-microstructure dependent irradiation damage behaviors of nanostructured tungsten…
In this study, the microstructure changes of Ti3SiC2 MAX phase material induced by helium irradiation and evolution with a sequence of different helium irradiation doses of 5E15, 1E16, 5E16 and 1E17cm-2 at room temperature (RT) were characterized with grazing incidence X-ray diffraction (GIXRD) and Raman spectra analysis. The irradiation damage process of Ti3SiC2 can be roughly divided into three stages according to the level of helium irradiation dose: (1) for a low damage dose, only crystal and damaged Ti3SiC2 exit; (2) at a higher irradiation dose, there is some damaged TiC phase additional…
Yttria stabilized Zirconia (YSZ) pellets with different crystallite sizes were irradiated with 80 MeV Ag$^{6+}$ ions at room temperature and 1000 K to understand the role of crystallite size/material microstructure and irradiation temperature on the radiation tolerance against high electronic energy loss (S$_e$). X-ray diffraction and Raman spectroscopy measurements reveal that, irrespective of the irradiation temperature, the nano-crystalline samples suffered more damage as compared to the bulk-like sample. A reduction in the irradiation damage i.e. improvement in the radiation tolerance, was…
We review the results of our research on damage mechanisms in materials irradiated with femtosecond free-electron-laser (FEL) pulses. They were obtained using our hybrid approach, XTANT (X-ray-induced Thermal And Nonthermal Transitions). Various damage mechanisms are discussed with respect to the pulse fluence and material properties on examples of diamond, amorphous carbon, C60 crystal, and silicon. We indicate conditions: producing thermal melting of targets as a result of electron-ion energy exchange; nonthermal phase transitions due to modification of the interatomic potential; Coulomb exp…
Irradiation of TiBe12 and CrBe12 with He+ ions and ex-situ transmission electron microscopy to investigate ion damage as a proxy for neutron irradiation damage in nuclear fusion
Radiation-enhanced precipitation of Cr-rich α' in irradiated Fe-Cr alloys, which results in hardening and embrittlement, depends on the irradiating particle and the displacement per atom (dpa) rate. Here, we utilize a Cahn-Hilliard phase-field based approach, that includes simple models for nucleation, irradiating particle and rate dependent radiation-enhanced diffusion and cascade mixing to simulate α' evolution under neutrons, heavy ions, and electron irradiations. Different irradiating particles manifest very different cascade mixing efficiencies. The model was calibrated using neutron data…
Rapid Primary Radiation Damage Resistance Assessment of Precipitation-Hardened Cu Alloys
Plasma Science and Fusion Center (PSFC)（等离子体科学与聚变中心）；Department of Materials Science & Engineering（材料科学与工程系）；Department of Nuclear Science & Engineering（核科学与工程系）
Fusion and advanced fission power plants require advanced nuclear materials to function under new, extreme environments. Understanding the evolution of mechanical and functional properties during radiation damage is essential to the design and commercial deployment of these systems. The shortcomings of existing methods could be addressed by a new technique - intermediate energy proton irradiation (IEPI) - using beams of 10 - 30 MeV protons to rapidly and uniformly damage bulk material specimens before direct testing of engineering properties. IEPI is shown to achieve high fidelity to fusion an…
Understanding defect production and evolution under irradiation is a long-standing multi-scale problem. Conventionally, experimental examination of irradiation-induced defects (IIDs) has mainly relied on transmission electron microscopy (TEM), which offers high spatial resolution but requires destructive sample preparation. Furthermore, limited field of view and low strain sensitivity make multi-scale characterisation and quantitative strain measurements difficult. Here we explore the potential of using advanced techniques in the scanning electron microscope (SEM) to non-destructively probe ir…
Potentials that could accurately describe the irradiation damage processes are highly desired to figure out the atomic-level response of various newly-discovered materials under irradiation environments. In this work, we introduce a deep-learning interatomic potential for monolayer MoS2 by combining all-electron calculations, an active-learning sampling method and a hybrid deep-learning model. This potential could not only give an overall good performance on the predictions of near-equilibrium material properties including lattice constants, elastic coefficients, energy stress curves, phonon s…
Elastic interactions play an important role in controlling irradiation damage evolution, but remain largely unexplored experimentally. Using transmission electron microscopy (TEM) and high-resolution on-axis transmission Kikuchi diffraction (HR-TKD), we correlate the evolution of irradiation-induced damage structures and the associated lattice strains in self-ion irradiated pure tungsten. TEM reveals different dislocation loop structures as a function of sample thickness, suggesting that free surfaces limit the formation of extended defect structures found in thicker samples. HR-TKD strain ana…
This review concentrates on the specific properties and characteristics of damage structures generated with high-energy ions in the electronic energy loss regime. Irradiation experiments with so-called swift heavy ions (SHI) find applications in many different fields, with examples presented in ion-track nanotechnology, radiation hardness analysis of functional materials, and laboratory tests of cosmic radiation. The basics of the SHI-solid interaction are described with special attention to processes in the electronic subsystem. The broad spectrum of damage phenomena is exemplified for variou…
We present a theoretical investigation of the dynamics of the dielectric constant of noble metals following heating with ultrashort pulsed laser beams and the influence of the temporal variation of the associated optical properties in the thermomechanical response of the material. The effect of the electron relaxation time on the optical properties based on the use of a critical point model is thoroughly explored for various pulse duration values (i.e. from 110fs to 8ps). The proposed theoretical framework correlates the dynamical change of optical parameters, relaxation processes and induced …
Creating mixed-phase states in cadmium sulfide by swift heavy ion irradiation
Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）；Higher Institute of Technologies and Applied Sciences, University of Havana（哈瓦那大学高等技术与应用科学学院）；Institute of Plasma Physics, Czech Academy of Sciences（捷克科学院等离子体物理研究所）
Elastic knock-on is the main electron irradiation damage mechanism in metals including graphene. Atomic vibrations influence its cross-section, but only the out-of-plane direction has been considered so far in the literature. Here, we present a full three-dimensional theory of knock-on damage including the effect of temperature and vibrations to describe ejection into arbitrary directions. We thus establish a general quantitative description of electron irradiation effects through elastic scattering. Applying our methodology to in-plane jumps of pyridinic nitrogen atoms, we show their observed…
Recent developments have renewed the demand for solar cells with increased tolerance to radiation damage. To investigate the specific irradiation damage of 1 MeV electron irradiation in GaInAsP lattice matched to InP for varying In and P contents, a simulation based analysis is employed: by fitting the quantum efficiency and open-circuit voltage simultaneously before and after irradiation, the induced changes in lifetime are detected. Furthermore, the reduction of irradiation damage during regeneration under typical satellite operating conditions for GEO missions (60°C and AM0 illumination) is…
Damage dose dependence of deuterium retention in high-temperature self-ion irradiated tungsten
Max Planck Institute for Plasma Physics（马克斯·普朗克等离子体物理研究所）；Karlsruhe Institute of Technology (KIT), Institute for Applied Materials - Applied Materials Physics（卡尔斯鲁厄理工学院应用材料研究所）
We describe the development of a new object kinetic Monte Carlo code where the elementary defect objects are off-lattice atomistic configurations. Atomic-level transitions are used to transform and translate objects, to split objects and to merge them together. This gradually constructs a database of atomic configurations -- a set of relevant defect objects and their possible events generated on-the-fly. Elastic interactions are handled within objects with empirical potentials at short distances, and between spatially distinct objects using the dipole tensor formalism. The model is shown to ev…
A theoretical investigation of the ultrafast processes and dynamics of the excited carriers upon irradiation of GaAs with femtosecond (fs) pulsed lasers is performed in conditions that induce material damage and eventually surface modification of the heated solid. A parametric study is followed to correlate the produced transient carrier density with the damage threshold for various pulse duration values τp (it increases as ~ at relatively small values of τp while it drops for pulse durations of the order of some picoseconds) based on the investigation of the fundamental multiscale physical pr…
Production rates in long-term predictive radiation damage accumulation models are generally considered independent of the material's microstructure for reactor components. In this study, the effect of pre-existing microstructural elements on primary damage production in alpha-Zr -- and vice-versa -- is assessed by molecular dynamics (MD) simulations. a-type dislocation loops, c-component dislocation loops and a tilt grain boundary (GB) were considered. Primary damage production is reduced in the presence of all these microstructural elements, and clustering behavior is dependent on the microst…
Nanocrystalline metals are promising radiation tolerant materials due to their large interfacial volume fraction, but irradiation-induced grain growth can eventually degrade any improvement in radiation tolerance. Therefore, methods to limit grain growth and simultaneously improve the radiation tolerance of nanocrystalline metals are needed. Amorphous intergranular films are unique grain boundary structures that are predicted to have improved sink efficiencies due to their increased thickness and amorphous structure, while also improving grain size stability. In this study, ball milled nanocry…
Materials are subjected to energetic particles in a number of radiation environments,and are hence prone to undesirable (radiation) damage.We report here the superiority of the nanocrystalline phase over bulk for radiation tolerance under simultaneous irradiation with high energy (electronic energy loss (Se) dominant) and low energy (nuclear energy loss (Sn) dominant) particles.Nano-crystalline yttria stabilized zirconia is found to exhibit lesser radiation damage (viz.degradation in crystallinity),when compared to its bulklike counterpart,against simultaneous irradiation with high energy 27 M…
Ion-irradiated FeCr alloys are useful for understanding and predicting neutron-damage in the structural steels of future nuclear reactors. Previous studies have largely focused on the structure of irradiation-induced defects, probed by transmission electron microscopy (TEM), as well as changes in mechanical properties. Across these studies, a wide range of irradiation conditions has been employed on samples with different processing histories, which complicates the analysis of the relationship between defect structures and material properties. Furthermore, key properties, such as irradiation-i…
We present a theoretical investigation of the yet unexplored dynamics of the produced excited carriers upon irradiation of hexagonal Silicon Carbide (6H-SiC) with femtosecond laser pulses. To describe the ultrafast behaviour of laser induced out-of-equilibrium carriers, a real time simulation based on Density Functional Theory (DFT) methodology is used to compute both the hot carrier dynamics and transient change of the optical properties. A Two-Temperature model (TTM) is also employed to derive the relaxation processes for laser pulses of wavelength 401 nm, duration 50 fs at normal incidence …
Ion implantation is widely used as a surrogate for neutron irradiation in the investigation of radiation damage on the properties of materials. Due to the small depth of damage, micromechanical methods must be used to extract material properties. In this work, nanoindentation has been applied to ion irradiated silicon carbide to extract radiation-induced hardening. Residual stress is evaluated using HR-EBSD, AFM swelling measurements, and a novel microcantilever relaxation technique coupled with finite element modelling. Large compressive residual stresses of several GPa are found in the irrad…
All biological organisms, from plants to living creatures, can heal minor wounds and damage. The realization of a similar self-healing capacity in inorganic materials has been a design target for many decades. This would represent a breakthrough in materials engineering, enabling many novel technological applications, since such materials would be able to resist damage caused by electromagnetic irradiation and/or mechanical impact. Here we demonstrate that a high-entropy oxide is intrinsically capable of undergoing an autonomous self-repairing process. Transmission electron microscopy revealed…
Local chemical order suppresses grain boundary migration under irradiation in CrCoNi
University of California, Irvine（加州大学尔湾分校）；Hopkins Extreme Materials Institute, Johns Hopkins University（约翰斯·霍普金斯大学霍普金斯极端材料研究所）；Johns Hopkins University（约翰斯·霍普金斯大学）
