High-energy Radiation Research Articles

Relationships between crystallization behavior and application properties of chemically coupled PAI-PTFE coatings

AbstractPoly(tetrafluoroethylene) (PTFE) is well known for its very low friction coefficient and thus widely used for antifriction applications, e.g., sliding lacquers, for many years. Because of the high wear rate and cold flow of the original polymer, PTFE is usually added in higher amounts to other polymer matrices as a lubricant. However, the incompatibility of PTFE requires lots of efforts to perform a homogeneous breaking down of agglomerates and particle distribution as well as dispersion stabilization of the physical mixtures during application and curing. PTFE can be functionalized by high energy irradiation and subsequently compatibilized with a polymer matrix by reactive extrusion resulting in chemical bonding of both polymers via suitable reactive groups. In this manner, poly(amide imide) (PAI) was coupled to γ-radiation modified PTFE micro-powder prior to the dispersion procedure. This study deals with the thermal and crystallization behavior of the PTFE lubricant in chemical bonded (cb) PAI-PTFEcb compound thin layers in comparison with those of the plain radiation modified PTFE depending on the cooling rate by DSC, Flash-DSC and WAXS. A morphological characterization of the extrudate as well as the coating gives information about the fragmentation and distribution of the PTFE phase in the PAI matrix. Furthermore, mechanical and surface properties of sliding lacquer films were analyzed after application on steel substrates by varying dry film thickness and curing. Graphical Abstract

Exploring the Effect of High-Energy Heavy Ion Beam on Rice Genome: Transposon Activation.

High-energy heavy ion beams are a new type of physical mutagen that can produce a wide range of phenotypic variations. In order to understand the mechanism of high-energy heavy ion beams, we resequenced the whole genome of individual plants with obvious phenotypic variations in rice. The sequence alignment results revealed a large number of SNPs and InDels, as well as genetic variations related to grain type and heading date. The distribution of SNP and InDel on chromosomes is random, but they often occur in the up/downstream regions and the intergenic region. Mutagenesis can cause changes in transposons such as Dasheng, mPing, Osr13 and RIRE2, affecting the stability of the genome. This study obtained the major gene mutation types, discovered differentially active transposons, screened out gene variants related to phenotype, and explored the mechanism of high-energy heavy ion beam radiation on rice genes.

Determination of Tissue Phantom Ratios of High Energy Photon Beams Using Monte Carlo Code

Monte Carlo codes are veritable tools in radiotherapy to understand the transport mechanism, dose distributions, and energy depositions of ionizing radiations traversing in different media. In some beam calibration protocols, a tissue-phantom-ratio at depths 20 cm and 10 cm (TPR20,10) in a phantom is used to determine the beam-quality conversion factor for different ion chambers. Thus, this study aims to evaluate the efficiency of Monte Carlo code in the determination of beam quality of high radiation energy beams similar to what is expected in clinical settings. Electron Gamma Shower National Research Council in Canada (EGSnrc) Monte Carlo Code was used to design complex ion chamber geometries according to the manufacturer’s specifications. Phase space files were used as x-ray beam radiation sources. Two set-ups (SAD and SSD) methods were used for the determination of TPR20,10 to conform to the accepted clinical procedures. Beam collimation was 10 cm by 10 cm field size with an ionization chamber placed at 20 cm and 10 cm in the water phantom to obtain doses at two points respectively. The TPR20,10 of each energy was obtained using the appropriate equations. The obtained results showed no significant difference between the measured and available TPR 20,10 data (p = 0.995). Ion chamber configurations and specifications were also found not to have a significant effect (p = 0.33) on the TPR 20,10 obtained values. The results obtained in this study are in agreement with the recommended standard values. The findings of this study show that the Monte Carlo codes can be used as a tool in determining x-ray beam quality indices of designed clinical linear accelerator (Linac) machines.

Enhancement of Radiation Sensitivity by Cathepsin L Suppression in Colon Carcinoma Cells.

Cancer is one of the main causes of death globally. Radiotherapy/Radiation therapy (RT) is one of the most common and effective cancer treatments. RT utilizes high-energy radiation to damage the DNA of cancer cells, leading to their death or impairing their proliferation. However, radiation resistance remains a significant challenge in cancer treatment, limiting its efficacy. Emerging evidence suggests that cathepsin L (cath L) contributes to radiation resistance through multiple mechanisms. In this study, we investigated the role of cath L, a member of the cysteine cathepsins (caths) in radiation sensitivity, and the potential reduction in radiation resistance by using the specific cath L inhibitor (Z-FY(tBu)DMK) or by knocking out cath L with CRISPR/Cas9 in colon carcinoma cells (caco-2). Cells were treated with different doses of radiation (2, 4, 6, 8, and 10), dose rate 3 Gy/min. In addition, the study conducted protein expression analysis by western blot and immunofluorescence assay, cytotoxicity MTT, and apoptosis assays. The results demonstrated that cath L was upregulated in response to radiation treatment, compared to non-irradiated cells. In addition, inhibiting or knocking out cath L led to increased radiosensitivity in contrast to the negative control group. This may indicate a reduced ability of cancer cells to recover from radiation-induced DNA damage, resulting in enhanced cell death. These findings highlight the possibility of targeting cath L as a therapeutic strategy to enhance the effectiveness of RT. Further studies are needed to elucidate the underlying molecular mechanisms and to assess the translational implications of cath L knockout in clinical settings. Ultimately, these findings may contribute to the development of novel treatment approaches for improving outcomes of RT in cancer patients.

Diamond-based detection systems for tomorrow's precision dosimetry

Radiation therapy is now widely applied for cancer care. For an effective and safe treatment, accurate dosimetry is mandatory. The evolution and widespread adoption of modern dynamic and conformal radiotherapy techniques have imposed several challenges from a dosimetric perspective. Commonly employed radiation beams include high-energy (6–18 MeV) photons or electron beams for external treatments, as well as low-energy (tens of keV) photons for intraoperative procedures. Recently, the emerging FLASH technique is posing additional challenges in the field of dosimetry. This work involved the fabrication and test of a custom-made diamond dosimeter. The detector was exposed to high-energy and low-energy X-ray radiation, as well as to FLASH beams, highlighting its versatility under all these conditions. The sensitivity of the dosimeter was estimated to be 73.96 nC Gy−1 mm−3 under MeV photons and 2.76 nC Gy−1 mm−3 under FLASH MeV electrons. Furthermore, this paper aims to illustrate the accuracy of dosimetry using the synchronous detection technique, enabling real-time monitoring of the dose delivered in each pulse, a crucial aspect for the beam diagnostics in the emerging FLASH radiotherapy.

High-energy Radiation and Ion Acceleration in Three-dimensional Relativistic Magnetic Reconnection with Strong Synchrotron Cooling

We present the results of 3D particle-in-cell simulations that explore relativistic magnetic reconnection in pair plasma with strong synchrotron cooling and a small mass fraction of nonradiating ions. Our results demonstrate that the structure of the current sheet is highly sensitive to the dynamic efficiency of radiative cooling. Specifically, stronger cooling leads to more significant compression of the plasma and magnetic field within the plasmoids. We demonstrate that ions can be efficiently accelerated to energies exceeding the plasma magnetization parameter, ≫σ, and form a hard power-law energy distribution, f i ∝ γ −1. This conclusion implies a highly efficient proton acceleration in the magnetospheres of young pulsars. Conversely, the energies of pairs are limited to either σ in the strong cooling regime or the radiation burnoff limit, γ syn, when cooling is weak. We find that the high-energy radiation from pairs above the synchrotron burnoff limit, ε c ≈ 16 MeV, is only efficiently produced in the strong cooling regime, γ syn < σ. In this regime, we find that the spectral cutoff scales as ε cut ≈ ε c (σ/γ syn) and the highest energy photons are beamed along the direction of the upstream magnetic field, consistent with the phenomenological models of gamma-ray emission from young pulsars. Furthermore, our results place constraints on the reconnection-driven models of gamma-ray flares in the Crab Nebula.

A simulation study of the soft and hard radiations using jets at the LHC

In this work, different aspects of the high-energy radiation are looked at considering the LHC scenario. An event-shape variable and several jet substructure observables are studied with the Mote Carlo event simulators at the 13 TeV center of mass energy scale to mimic the current LHC environment. The event-shape and the jet substructure observables are chosen such that they are not only sensitive to the different aspects of the high energy radiation measurement but also exhibit promising features to distinguish the possible existence of new physics that considers a dark matter candidate decaying into semi-visible jet. It is verified that the observables exhibit significant sensitivities to disentangle two jets to multi-jet radiations, presence of a final state and initial state radiations, presence of a large amount of missing transverse energy as a strong indication of the possible existence of a dark matter as well as couple of promising features of a semi-visible jet are explored.

Linking Circumstellar Disk Lifetimes to the Rotational Evolution of Low-mass Stars

The high-energy radiation emitted by young stars can have a strong influence on their rotational evolution at later stages. This is because internal photoevaporation is one of the major drivers of the dispersal of circumstellar disks, which surround all newly born low-mass stars during the first few million years of their evolution. Employing an internal EUV/X-ray photoevaporation model, we have derived a simple recipe for calculating realistic inner disk lifetimes of protoplanetary disks. This prescription was implemented into a magnetic-morphology-driven rotational evolution model and is used to investigate the impact of disk locking on the spin evolution of low-mass stars. We find that the length of the disk locking phase has a profound impact on the subsequent rotational evolution of a young star, and the implementation of realistic disk lifetimes leads to an improved agreement of model outcomes with observed rotation period distributions for open clusters of various ages. However, for both young star-forming regions tested in our model, the strong bimodality in rotation periods that is observed in h Per could not be recovered. h Per is only successfully recovered if the model is started from a double-peaked distribution with an initial disk fraction of 65%. However, at an age of only ∼1 Myr, such a low disk fraction can only be achieved if an additional disk dispersal process, such as external photoevaporation, is invoked. These results therefore highlight the importance of including realistic disk dispersal mechanisms in rotational evolution models of young stars.

Study of High-Energy Proton Irradiation Effects in Top-Gate Graphene Field-Effect Transistors

In this article, the effects of high-energy proton irradiation on top-gate graphene field-effect transistors (GFETs) were investigated by using 20 MeV protons. The basic electrical parameters of the top-gate GFETs were measured before and after proton irradiation with a fluence of 1 × 1011 p/cm2 and 5 × 1011 p/cm2, respectively. Decreased saturation current, increased Dirac sheet resistance, and negative drift in the Dirac voltage in response to proton irradiation were observed. According to the transfer characteristic curves, it was found that the carrier mobility was reduced after proton irradiation. The analysis suggests that proton irradiation generates a large net positive charge in the gate oxide layer, which induces a negative drift in the Dirac voltage. Introducing defects and increased impurities at the gate oxide/graphene interface after proton irradiation resulted in enhanced Coulomb scattering and reduced mobility of the carriers, which in turn affects the Dirac sheet resistance and saturation current. After annealing at room temperature, the electrical characteristics of the devices were partially restored. The results of the technical computer-aided design (TCAD) simulation indicate that the reduction in carrier mobility is the main reason for the degradation of the electrical performance of the device. Monte Carlo simulations were conducted to determine the ionization and nonionization energy losses induced by proton incidence in top-gate GFET devices. The simulation data show that the ionization energy loss is the primary cause of the degradation of the electrical performance.

Dimensionality Engineering of Organic-Inorganic Halide Perovskites for Next-Generation X-Ray Detector.

The next-generation X-ray detectors require novel semiconductors with low material/fabrication cost, excellent X-ray response characteristics, and robust operational stability. The family of organic-inorganic hybrid perovskites (OIHPs) materials comprises a range of crystal configuration (i.e., films, wafers, and single crystals) with tunable chemical composition, structures, and electronic properties, which can perfectly meet the multiple-stringent requirements of high-energy radiation detection, making them emerging as the cutting-edge candidate for next-generation X-ray detectors. From the perspective of molecular dimensionality, the physicochemical and optoelectronic characteristics of OIHPs exhibit dimensionality-dependent behavior, and thus the structural dimensionality is recognized as the key factor that determines the device performance of OIHPs-based X-ray detectors. Nevertheless, the correlation between dimensionality of OIHPs and performance of their X-ray detectors is still short of theoretical guidance, which become a bottleneck that impedes the development of efficient X-ray detectors. In the review, the advanced studies on the dimensionality engineering of OIHPs are critically assessed in X-ray detection application, discussing the current understanding on the "dimensionality-property" relationship of OIHPs and the state-of-the-art progresses on the dimensionality-engineered OIHPs-based X-ray detector, and highlight the open challenges and future outlook of this field.

Nanodiamond Effects on Cancer Cell Radiosensitivity: The Interplay between Their Chemical/Physical Characteristics and the Irradiation Energy

Nanoparticles are being increasingly studied to enhance radiation effects. Among them, nanodiamonds (NDs) are taken into great consideration due to their low toxicity, inertness, chemical stability, and the possibility of surface functionalization. The objective of this study is to explore the influence of the chemical/physical properties of NDs on cellular radiosensitivity to combined treatments with radiation beams of different energies. DAOY, a human radioresistant medulloblastoma cell line was treated with NDs—differing for surface modifications [hydrogenated (H-NDs) and oxidized (OX-NDs)], size, and concentration—and analysed for (i) ND internalization and intracellular localization, (ii) clonogenic survival after combined treatment with different radiation beam energies and (iii) DNA damage and apoptosis, to explore the nature of ND–radiation biological interactions. Results show that chemical/physical characteristics of NDs are crucial in determining cell toxicity, with hydrogenated NDs (H-NDs) decreasing either cellular viability when administered alone, or cell survival when combined with radiation, depending on ND size and concentration, while OX-NDs do not. Also, irradiation at high energy (γ-rays at 1.25 MeV), in combination with H-NDs, is more efficient in eliciting radiosensitisation when compared to irradiation at lower energy (X-rays at 250 kVp). Finally, the molecular mechanisms of ND radiosensitisation was addressed, demonstrating that cell killing is mediated by the induction of Caspase-3-dependent apoptosis that is independent to DNA damage. Identifying the optimal combination of ND characteristics and radiation energy has the potential to offer a promising therapeutic strategy for tackling radioresistant cancers using H-NDs in conjunction with high-energy radiation.

Influence mechanisms of electron beam irradiation on surface flashover in vacuum: Electron modification, deposition, and migration

In surface science, surface flashovers are discharge phenomena that occur at the gas/vacuum-solid interface. Spacecraft in the universe suffers from high-energy electron irradiation while it works under a high DC operating voltage, and thus, surface flashover threatens the safe operation of spacecraft and limits human’s deeper exploration of the universe. To unravel the influence mechanisms of electron beam irradiation (EBI), surface flashover voltages (Vf) of epoxy composites during EBI, short-term after EBI, and long-term after EBI are investigated, and the behaviors of molecular structure, deposited electrons near chains, and radiation electrons under EBI and their effects on Vf are separately clarified. For long-term after EBI, EBI induces crosslinking of molecular chains and introduces deep traps to the solid surface, which impedes electron emission and surface charging, and thus Vf increases. For short-term after EBI, the deposited electrons suppress charge injection to the solid, and Vf further increases. During EBI, the high-energy radiation electrons stimulate gas desorption and directly participate in plasma propagation, leading to a sharp decrease in Vf. This work comprehensively explains the influence mechanisms of EBI electron modification, deposition, and migration on the Vf, which offers a theory to guide the prevention of flashover for spacecraft.

Creation of NV Centers in Diamond under 155 MeV Electron Irradiation

AbstractSingle‐crystal diamond substrates presenting a high concentration of negatively charged nitrogen‐vacancy centers (NV−) are on high demand for the development of optically pumped solid‐state sensors such as magnetometers, thermometers, or electrometers. While nitrogen impurities can be easily incorporated during crystal growth, the creation of vacancies requires further treatment. Electron irradiation and annealing is often chosen in this context, offering advantages with respect to irradiation by heavier particles that negatively affect the crystal lattice structure and consequently the NV− optical and spin properties. A thorough investigation of electron irradiation possibilities is needed to optimize the process and improve the sensitivity of NV‐based sensors. In this work, the effect of electron irradiation is examined in a previously unexplored regime: extremely high energy electrons, at 155 MeV. A simulation model is developed to estimate the concentration of created vacancies and an increase of NV− concentration by more than three orders of magnitude following irradiation of a nitrogen‐rich HPHT diamond over a very large sample volume is experimentally demonstrated, which translates into an important gain in sensitivity. Moreover, the impact of electron irradiation in this peculiar regime on other figures of merits relevant for NV sensing is discussed, including charge state conversion efficiency and spin relaxation time. Finally, the effect of extremely high energy irradiation is compared with the more conventional low energy irradiation process, employing 200 keV electrons from a transmission electron microscope, for different substrates and irradiation fluences, evidencing 60‐fold higher yield of vacancy creation per electron at 155 MeV.

Controllable Carrier Doping in Two-Dimensional Materials Using Electron-Beam Irradiation and Scalable Oxide Dielectrics.

Two-dimensional (2D) materials, characterized by their atomically thin nature and exceptional properties, hold significant promise for future nano-electronic applications. The precise control of carrier density in these 2D materials is essential for enhancing performance and enabling complex device functionalities. In this study, we present an electron-beam (e-beam) doping approach to achieve controllable carrier doping effects in graphene and MoS2 field-effect transistors (FETs) by leveraging charge-trapping oxide dielectrics. By adding an atomic layer deposition (ALD)-grown Al2O3 dielectric layer on top of the SiO2/Si substrate, we demonstrate that controllable and reversible carrier doping effects can be effectively induced in graphene and MoS2 FETs through e-beam doping. This new device configuration establishes an oxide interface that enhances charge-trapping capabilities, enabling the effective induction of electron and hole doping beyond the SiO2 breakdown limit using high-energy e-beam irradiation. Importantly, these high doping effects exhibit non-volatility and robust stability in both vacuum and air environments for graphene FET devices. This methodology enhances carrier modulation capabilities in 2D materials and holds great potential for advancing the development of scalable 2D nano-devices.

Irradiation hardening of FeCrAl ODS alloys with Zr/Hf addition after high-energy self-ions irradiation

FeCrAl ODS steel is the promising candidate cladding material for the accident tolerant fuel (ATF) of the light water reactors (LWR), due to the formation of Al2O3 in alloys which could suppress the oxidation reaction with hot steam. In the present work, change in microstructures and the corresponding irradiation hardening of two kinds of FeCrAl ODS alloys (15.5Cr-4Al), with 0.6 wt% Zr (denoted as P1) or 0.8 wt% Hf addition (denoted as P2), were investigated. Electron backscattered diffraction (EBSD) and transmitted electron microscopy (TEM) were used to characterize grains and dispersion morphology of oxides, respectively. Compared to P1, P2 has finer and denser oxides. 56Fe17+ ions with kinetic energy of 352.8 MeV were used to produce a quasi-uniformly distributed damage region from the near-surface to a depth of 24 μm in the specimens by using an energy degrader. A damage level of 0.8 dpa (displacement per atom) was attained in the specimens of both alloys simultaneously at 200℃. The Vickers hardness test shows that both specimens exhibited an apparent irradiation hardening. The extent of hardening of P2 (6 %) is significantly lower than P1 (12 %). TEM results show that irradiation-induced dislocation loops occur in both specimens but with a relatively smaller average size in P2. The results demonstrate that compared to the 0.6 wt% Zr addition, the 0.8 wt% Hf addition improves more significantly the hardening resistance, which was discussed in terms of the calculated sink strength originating from the oxides/matrix interface.

Mix and measure - Combining in situ X-ray powder diffraction and microtomography for accurate hydrating cement studies

It is reported an innovative methodology based on in situ MoKα1 laboratory X-ray powder diffraction (LXRPD) and microtomography (μCT) avoiding any sample conditioning. The pastes are injected in 2.0 mm capillaries and the extremes are just sealed. The measurements take place in the same region of the hydrating paste. Thick capillaries are key to avoiding self-desiccation, which dictates the need of high-energy X-ray radiation for the diffraction study. This approach has been tested with a PC 42.5 R paste having w/c = 0.50. μCT data were collected at 12 h and 1, 3, 7 and 79 days. LXRPD data were acquired at 1, 3, 7 and 77 days. In this proof-of-principle research, the same paste was also cured ex situ. Portlandite contents obtained by thermal analysis, ex situ powder diffraction, in situ mass balance calculation and in situ powder diffraction were 13.8, 13.1, 13.1 and 12.5 wt%, respectively. From the μCT study, the grey value histogram evolution with time showed a crossing point which allowed us to distinguish (appearing) hydrated products from (dissolving) unhydrated cement particles. Segmentations were carried out by global thresholding and the random forest approach (one type of supervised Machine Learning). The comparison of the segmented results for the unhydrated cement fraction and the Rietveld quantitative phase analysis outputs gave an agreement of 2 %. The potential of this methodology to deal with more complex binders is also presented.

Theory and prospects of the pulsar study

After the pulsar was discovered by Hewish, the relevant research has become one of the hottest research fields. Astronomers have noticed that pulsars are of great academic significance in the field of basic scientific research. Due to the large mass and small radius of pulsars, their surface gravitational field is very strong. The existence of general relativity effects cannot be ignored, making pulsars a natural laboratory for the study of strong gravitational fields. the strong magnetic field provides an identical place for the study of radio radiation process, magnetospheric particle acceleration mechanism and high energy radiation. Pulsar as the product of supernova burst after the collapse of massive stars, it is very important for the study of supernova burst theory and understand the formation mechanism of pulsars. In terms of application research, due to the high stability of its rotation period, it has significant applicating prospect in measuring time standard and X-ray pulsar navigation system. The Pulsar has made great remarkable achievements in the past 50 years since its discovery. In short, the discovery and research significance of pulsars are highly anticipated.

Aqueous-Based Inorganic Colloidal Halide Perovskites Customizing Liquid Scintillators.

Compared to solid scintillators and organic liquid scintillators, aqueous-based liquid scintillators (AbLS) have more superiority in highly flexible scalability, yet are now limited by their low light yield (≈100 photons MeV-1 ). Here, aqueous-based inorganic colloidal halide perovskites with high photoluminescence quantum yield (PLQY) of three primary color luminescence up to 88.1% (red), 96% (green), and 81.8% (blue) are respectively synthesized, and a new generation of colloidal perovskite-mediated AbLS (PAbLS) with light yield increased in comparison with the commercial scintillator AbLS is fabricated. This paper exhibits that the excellent PLQY and colloidal dispersion of halide perovskites benefit from poly(ethylene glycol) modification and this modification ensures the vacancy inhibition and formation of defect-free surfaces in an aqueous solution. Moreover, their high luminescent emission can be maintained for 100 days at low temperatures, and such modification also promises the heat-to-cold customization of operating temperature even in ice below 0 °C. Finally, depending on the light yield of around 3058 and 8037 photons MeV-1 at room temperature and low temperature, PAbLS with shape/size scalability exhibit their robust radiation hardness (dose rate as high as 23 mGy s-1 ) and conceptual application potential in high-energy ray radiation detection from every angle of 360°.

Comprehensive study of optical, thermal, and gamma-ray shielding properties of Bi2O3–ZnO–PbO–B2O3 glasses

Abstract The Bi2O3–ZnO–PbO–B2O3 (BiZPB) glasses are prepared using the melt-quenching technique. As the concentration of lead oxide increases, the band gap energy (E g) decreases from 2.864 to 2.671 eV. The BiZPB glasses exhibit remarkable stability under thermal stress, as indicated by the thermogravimetric analysis graph, with only a marginal 0.5% loss in their initial mass. The decrease in the glass transition temperature (T g) of BiZPB glasses, with an increase in the PbO concentration, can be attributed to the specific influence of PbO on the glass structure and properties. The radiation shielding performance for the prepared glasses is evaluated using Phy-X software. The transmission factor (TF) for the 10B2O3–10ZnO–40PbO–40B2O3 glass sample is almost zero at 0.122 MeV, which means that this glass sample can attenuate almost all the photons with an energy of 0.122 MeV, whereas the TF values for this sample with thicknesses of 0.5 and 1 cm are 88 and 77%, respectively., it can be observed from the TF values that the prepared glasses have good attenuation performance against low energy (0.122, 0.245, and 0.344 MeV), while they have weak shielding performance against high energy radiation. The addition of PbO causes a reduction in TF, which means that the addition of an extra amount of PbO into the glasses results in an enhancement in the radiation shielding competence of the samples. The average half-value layer ( HVL ̅ \bar{{\rm{HVL}}} ) is also calculated. The results demonstrated that HVL ̅ \bar{{\rm{HVL}}} is at its lowest between 0.248 and 0.411 MeV, ranging between 0.396 and 0.513 cm.

Atomic imaging reveals in-situ growth behavior of bi nanoparticles by high-energy electron irradiation

Herein, we present an in-situ investigation of Bi nanoparticles (NPs) growth on BiVO4 substrates using high-energy electron beams in transmission electron microscopy (TEM). High-Resolution (HR)TEM images at atomic level reveal a four-step growth mechanism in which Bi NPs transform from metastable droplets to solid nanocrystals. The disappearance behavior is essentially opposite to the growth behavior, with the exception that the Bi particles do not exhibit droplet-like morphology throughout the disappearance. As demonstrated, the aggregation behavior is significantly influenced by particle size, lattice matching degree and interparticle distance. These findings are significant for the practical use of bismuth-based materials in irradiation environments.