Search Results (202)

This article deals with the effect of Kr¹⁵⁺ ion irradiation on the structure and properties of partially stabilized zirconium dioxide (ZrO₂ + 3 mol. % Y₂O₃) ceramics. Ion irradiation is used to simulate radiation damage typical of operating conditions in nuclear reactors and space technology. It is shown that with an increase in the irradiation fluence, point defects are formed, dislocations accumulate, and the crystal lattice parameters change. At high fluences (>10¹³ ions/cm²), a phase transition of the monoclinic (m-ZrO₂) phase to the tetragonal (t-ZrO₂) and cubic (c-ZrO₂) modifications is observed, which is accompanied by a decrease in the crystallite size and an increase in internal stresses. Changes in the mechanical properties of the material were also observed: at moderate irradiation fluences, strengthening is observed due to the formation of dislocation structures, whereas at high fluences (>10¹⁴ ions/cm²), a decrease in strength and a potential amorphization of the structure begins. The change in the phase composition was confirmed by X-ray phase analysis and Raman spectroscopy. The results obtained allow a deeper understanding of the mechanisms of radiation-induced phase transformations in stabilized ZrO₂ and can be used in the development of ceramic materials with increased radiation resistance. Full article

The impact of 230-MeV Xe¹³² ion irradiation on the structural, optical, and luminescent properties of YAG:Ce single crystals is investigated over a fluence range of 10¹¹–10¹⁴ ions/cm². Optical absorption; cathodo-, X-ray, and photoluminescence; and X-ray diffraction are employed to analyze radiation-induced changes. Irradiation leads to the formation of Frenkel (F, F⁺) and antisite defects and attenuates Ce³⁺ emission (via enhanced nonradiative processes and Ce³⁺ → Ce⁴⁺ recharging). A redistribution between the fast and slow components of the Ce³⁺-emission is considered. Excitation spectra show the suppression of exciton-related emission bands, as well as a shift of the excitation onset due to increased lattice disorder. XRD data confirm partial amorphization and a high level of local lattice disordering, both increasing with irradiation fluence. These findings provide insight into radiation-induced processes in YAG:Ce, which are relevant for its application in radiation–hard scintillation detectors. Full article

Body-centered cubic (BCC) refractory high-entropy alloys (RHEAs) demonstrate significant potential as nuclear structural materials due to their exceptional mechanical properties and radiation tolerance. While Zr-containing RHEAs often develop multiphase structures through Zr-rich phase precipitation to enhance high-temperature mechanical performance, their irradiation response mechanisms remain poorly understood. This study investigated the microstructure evolution and radiation damage behavior in equiatomic MoNbTiVZr RHEA under Au-ion irradiation at fluences of 2 × 10¹⁵, 4 × 10¹⁵, and 1 × 10¹⁶ ions/cm². Microstructural characterization revealed that the annealed alloy primarily consisted of near-equiatomic BCC1 phase, Zr-rich BCC2 phase, (Mo,V)Zr Laves phase, and ordered Zr₂C phase. Post-irradiation analysis showed distinct defect evolution patterns: the BCC1 phase developed fine dislocation loops, while the Zr-rich BCC2 and Zr₂C phases exhibited dislocation clusters and dense dislocation networks, respectively. BCC1 phase exhibited the most pronounced irradiation hardening corresponding to its fine, dispersed dislocation loop characteristics. Phase separation induced by Zr precipitation reduced chemical complexity, accelerating irradiation defect evolution. These findings demonstrated that Zr-rich phase precipitation detrimentally impacted the radiation resistance of BCC-structured RHEAs, suggesting that single-phase stability should be prioritized in nuclear material design. Full article

The recovery of radiation damage induced by 231-MeV xenon ions with varying fluence (from 5 × 10¹¹ to 2 × 10¹⁴ cm⁻²) in α-Al₂O₃ (corundum) single crystals has been studied by means of isochronal thermal annealing of radiation-induced optical absorption (RIOA). The integral of elementary Gaussians (product of RIOA spectrum decomposition) OK has been considered as a concentration measure of relevant oxygen-related Frenkel defects (neutral and charged interstitial-vacancy pairs, F-H, F⁺-H⁻). The annealing kinetics of these four ion-induced point lattice defects has been modelled in terms of diffusion-controlled bimolecular recombination reactions and compared with those carried out earlier for the case of corundum irradiation by fast neutrons. The changes in the parameters of interstitial (mobile component in the recombination process) annealing kinetics—activation energy E and pre-exponential factor X—in ion-irradiated crystals are considered. Full article

This study aimed to investigate the distribution of thermal neutron fluence generated during proton-beam therapy (PBT) scanning, focusing on neutrons produced within the body using Monte Carlo simulations (MCSs). MCSs used the Particle and Heavy Ion Treatment Code System to define a 35 × 35 × 35 cm³ water phantom, and proton-beam energies ranging from 70.2 to 228.7 MeV were investigated. The MCS results were compared with neutron fluence measurements obtained from gold activation analysis, showing good agreement with a difference of 3.54%. The internal thermal neutron distribution generated by PBT was isotropic around the proton-beam axis, with the Bragg peak depth varying between 3.45 and 31.9 cm, while the thermal neutron peak depth ranged from 5.41 to 15.9 cm. Thermal neutron generation depended on proton-beam energy, irradiated particle count, and depth. Particularly, the peak of the thermal neutron fluence did not occur within the treatment target volume but in a location outside the target, closer to the source. This discrepancy between the Bragg peak and the thermal neutron fluence peak is a key finding of this study. These data are crucial for optimizing beam angles to maximize dose enhancement within the target during clinical applications of neutron capture-enhanced particle therapy. Full article

A pioneering detailed comparative study of the dynamics of plasma flows generated by high-power nanosecond and high-intensity femtosecond laser pulses with similar fluences of up to $3\times {10}^4$ J/cm² is presented. The experiments were conducted on the petawatt laser facility PEARL using two types of high-power laser radiation: femtosecond pulses with energy exceeding 10 J and a duration less than 60 fs, and nanosecond pulses with energy exceeding 10 J and a duration on the order of 1 ns. In the experiments, high-velocity (>100 km/s) flows of «femtosecond» (created by femtosecond laser pulses) and «nanosecond» plasmas propagated in a vacuum across a uniform magnetic field with a strength over 14 T. A significant difference in the dynamics of «femtosecond» and «nanosecond» plasma flows was observed: (i) The «femtosecond» plasma initially propagated in a vacuum (no B-field) as a collimated flow, while the «nanosecond» flow diverged. (ii) The «nanosecond» plasma interacting with external magnetic field formed a quasi-spherical cavity with Rayleigh–Taylor instability flutes. In the case of «femtosecond» plasma, such flutes were not observed, and the flow was immediately redirected into a narrow plasma sheet (or «tongue») propagating across the magnetic field at an approximately constant velocity. (iii) Elongated «nanosecond» and «femtosecond» plasma slabs interacting with a transverse magnetic field broke up into Rayleigh–Taylor «tongues». (iv) The ends of these «tongues» in the femtosecond case twisted into vortex structures aligned with the ion motion in the external magnetic field, whereas the «tongues» in the nanosecond case were randomly oriented. It was suggested that the twisting of femtosecond «tongues» is related to Hall effects. The experimental results are complemented by and consistent with numerical 3D magnetohydrodynamic simulations. The potential applications of these findings for astrophysical objects, such as short bursts in active galactic nuclei, are discussed. Full article

This study presents a comprehensive analysis of the modifications in electronic structure and magnetism resulting from electronic excitation in pulsed laser-deposited Ba_0.7Sr_0.3Fe_xTi_(1−x)O₃ thin films, specifically for compositions with x = 0, 0.1, and 0.2. To investigate the effects of electronic energy loss (S_e) within the lattice, we performed 120 MeV Ag ion irradiation at varying fluences (1 × 10¹² ions/cm² and 5 × 10¹² ions/cm²) and compared the results with those of the pristine sample. The S_e induces lattice damage by generating ion tracks along its trajectory, which subsequently leads to a reduction in peak intensity observed in X-ray diffraction patterns. Atomic force microscopy micrographs indicate that irradiation resulted in a decrease in average grain height, accompanied by a more homogeneous grain distribution. X-ray photoelectron spectroscopy reveals a significant increase in oxygen vacancy (V_O) concentration as ion fluence increases. Ferromagnetism exhibits progressive deterioration with rising irradiation fluence. Due to the high S_e and multiple ion impact processes, cation interstitial defects are highly likely, which may overshadow the influence of V_O in inducing ferromagnetism, thereby contributing to an overall decline in magnetic properties. Furthermore, the elevated S_e potentially disrupts bound magnetic polarons, leading to a degradation of long-range ferromagnetism. Collectively, this investigation elucidates the electronic excitation-induced modulation of ferromagnetism, employing Fe impurity incorporation and irradiation techniques for precise defect engineering. Full article

Implant-associated infections, particularly those linked to Staphylococcus aureus (S. aureus), continue to compromise the clinical success of β-tricalcium phosphate (β-TCP) implants despite their excellent biocompatibility and osteoconductivity. This investigation aims to tackle these challenges by integrating femtosecond (fs)-laser surface processing with two complementary strategies: ion doping and functionalization with green-synthesized silver nanoparticles (AgNPs). AgNPs were produced via fs-laser photoreduction using green tea leaf extract (GTLE), noted for its anti-inflammatory and antioxidant properties. Fs-laser processing was applied to modify β-TCP scaffolds by systematically varying scanning velocities, fluences, and patterns. Lower scanning velocities generated organized nanostructures with enhanced roughness and wettability, as confirmed by scanning electron microscopy (SEM), optical profilometry, and contact angle measurements, whereas higher laser energies induced significant phase transitions between hydroxyapatite (HA) and α-tricalcium phosphate (α-TCP), as revealed by X-ray diffraction (XRD). AgNP-functionalized scaffolds demonstrated markedly superior antibacterial activity against S. aureus compared to the ion-doped variants, attributed to the synergistic interplay of nanostructure-mediated surface disruption and AgNP-induced bactericidal mechanisms. Although ion-doped scaffolds exhibited limited direct antibacterial effects, they showed concentration-dependent activity in indirect assays, likely due to controlled ion release. Both strategies promoted osteogenic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) under defined conditions, albeit with transient cytotoxicity at higher fluences and excessive ion doping. Overall, this approach holds promise for markedly improving antibacterial efficacy and osteogenic compatibility, potentially transforming bone regeneration therapies. Full article

The dependence of polyethylene deformation on applied mechanical stress under varying load conditions and radiation doses was investigated experimentally. Obtained results reveal significant alterations in the mechanical properties of polyethylene following irradiation with krypton ions at doses of 1.5 × 10⁶, 1.6 × 10⁷, 5.0 × 10⁸, and 1.0 × 10⁹ ions/s. The stress–strain curves obtained for both the unirradiated and irradiated samples are numerically modeled using frameworks developed by the authors. The findings indicate that irradiation with krypton ions at an energy level of 147 MeV exerts a pronounced impact on the deformation and strength characteristics of polyethylene. Notably, increasing the radiation dose to 10⁹ particles/s results in a 2.5-fold increase in the rate of mechanical stress. Furthermore, the degree of deformation distortions in molecular chains induced by high-energy Kr¹⁵⁺ ion irradiation has been quantified as a function of irradiation fluence. Increasing the irradiation fluence from 10⁶ ion/cm² to 10⁷ ion/cm² causes only minor variations in deformation distortions, which are attributed to the localized isolation of latent tracks and associated changes in electron density. A comparative analysis of the mechanical behavior of irradiated polymer materials further revealed differences between ion and electron irradiation effects. It was observed that Teflon films lose their plasticity after irradiation, whereas polyethylene films exhibit enhanced elongation and tearing performance at higher strain values relative to their non-irradiated counterparts. This behavior was consistently observed for films irradiated with both ions and electrons. However, an important distinction was identified: high-energy electron irradiation degrades the strength of polyethylene, whereas krypton ion irradiation at 147 MeV does not result in strength reduction. Full article

The influence of structural modifications on the thermal stability, chemical bonds, and optical properties of zinc oxide (ZnO) thin films (120 nm thick) for optoelectronic devices (solar cells, LEDs) and energy nanodevices was investigated. The films, synthesized via rf-magnetron sputtering, were implanted with V⁺ ions at 170 keV with varying fluences. Optical properties, including bandgap, transmittance, and absorbance, were analyzed using UV–Vis spectroscopy, XRD, AFM, and FTIR. Structural changes such as strain, lattice constant, surface roughness, and crystallite size significantly influenced the optical properties. Increased surface roughness led to a higher optical bandgap (up to 4.10 eV) and transmittance (82.34%), with reduced absorbance (0.12 nm). Crystallite size exhibited similar effects. At an ion fluence of 1 × 10¹⁶ ions/cm², the bandgap and transmittance increased, while absorbance slightly decreased. Thermal stability and chemical bond analysis supported these findings. The study demonstrates that V⁺ ion-induced modifications enhance ZnO thin films’ properties, highlighting their potential for advanced optoelectronic and energy nanodevice applications. Full article

In this study, ion-beam-induced luminescence with 2 MeV H⁺ was used to excite YAG single crystals at different temperatures. Under several constant temperatures, the luminescence intensity of Yb²⁺ monotonically decreases with increasing fluence, eventually reaching approximately 35% of the initial intensity at a fluence of 3.5 × 10¹⁴ cm⁻². The nonmonotonic evolution behavior of Yb²⁺ luminescence intensity with temperature can be effectively described by the intermediate-state model under consecutive temperature variations. The presence of an intermediate state may be the primary cause of the negative thermal quenching of Yb²⁺ luminescence. Yb²⁺ luminescence intensity decreased to 60% of the initial intensity when the temperature was continuously varied in the 100–300 K range, although the peak position remained rather stable. The luminescence of Yb²⁺ exhibits good radiation resistance and thermal stability in the experimental temperature range. Full article

In the present work, we present the process of preparing CdS nanostructures based on templating synthesis using chemical deposition (CD) on a SiO₂/Si substrate. A 0.7 μm thick silicon dioxide film was thermally prepared on the surface of an n-type conduction Si wafer, followed by the creation of latent ion tracks on the film by irradiating them with swift heavy Xe ions with an energy of 231 MeV and a fluence of 10⁸ cm⁻². As a result of etching in hydrofluoric acid solution (4%), pores in the form of truncated cones with different diameters were formed. The filling of the nanopores with cadmium sulfide was carried out via templated synthesis using CD methods on a SiO_2 nanopores/Si substrate for 20–40 min. After CdS synthesis, the surfaces of nanoporous SiO_2 nanopores/Si were examined using a scanning electron microscope to determine the pore sizes and the degree of pore filling. The crystal structure of the filled silica nanopores was investigated using X-ray diffraction, which showed CdS nanocrystals with an orthorhombic structure with symmetry group 59 Pmmn observed at 2θ angles of 61. 48° and 69.25°. Photoluminescence spectra were recorded at room temperature in the spectral range of 300–800 nm at an excitation wavelength of 240 nm, where emission bands centered around 2.53 eV, 2.45 eV, and 2.37 eV were detected. The study of the CVCs showed that, with increasing forward bias voltage, there was a significant increase in the forward current in the samples with a high degree of occupancy of CdS nanoparticles, which showed the one-way electronic conductivity of CdS/SiO₂/Si nanostructures. For the first time, CdS nanostructures with orthorhombic crystal structure were obtained using track templating synthesis, and the density of electronic states was modeled using quantum–chemical calculations. Comparative analysis of experimental and calculated data of nanostructure parameters showed good agreement and are confirmed by the results of other authors. Full article

Polycrystalline zinc oxide (ZnO) thin films were deposited on soda-lime glass substrates using the chemical spray pyrolysis method at 450 °C. The samples were irradiated with 8 keV H⁺ ions at three different fluences using a Colutron ion gun. The effects of the irradiation on the structural, morphological, and optical properties were studied with different techniques, including Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Ultraviolet and Visible Spectroscopy (UV–Vis). The results show that ion irradiation enhances crystallinity, narrowing the optical band gap. The changes in transmittance are related to defect formation within the material, which acts as light absorption and re-emission centers. A shifting of the film’s preferred growth orientation to the c-axis and changing the grain morphology and size distribution was detected. We observed an increase in the lattice parameters observed after irradiation, suggesting an expansion of the crystalline structure due to ions incorporation and defects within the ZnO crystal lattice. The morphological study shows an increase in the average size of the large particles after irradiation. This change is attributed to the emergence of defects and nucleation centers during irradiation. The average size of small particles remained relatively constant after irradiation, suggesting that small particles are more stable and less susceptible to external influences, resulting in fewer changes due to irradiation. Full article

It is known that swift heavy ion (SHI) irradiation induces the shape elongation of metal nanoparticles (NPs) embedded in transparent insulators, which results in anisotropic optical absorption. Here, we report another type of the optical anisotropy induced in CaF₂ crystals without including intentionally embedded metal NPs. The CaF₂ samples were irradiated with 200 MeV Xe¹⁴⁺ ions with an incident angle of 45° from the surface normal. With the increasing fluence, an absorption band at ~550 nm, which is ascribed to Ca aggregates, increases both the intensity and the anisotropy. XTEM observation clarified the formation of the continuous line structures and the discontinuous NP chains parallel to the SHI beam. Numerical simulations of the optical absorption spectra suggested the NP chains but not the continuous line structures as the origin of the anisotropy. The optical anisotropy in CaF₂ irradiated with SHIs is different from the shape elongation of NPs. Full article

Wood–plastic composites (WPCs) combine the properties of plastics and lignocellulosic fillers. A particular limitation in their use is usually a hydrophobic, poorly wettable surface. The surface properties of materials can be modified using ion implantation. The research involved using composites based on polyethylene (PE) filled with sawdust or bark (40%, 50%, and 60%). Their surfaces were modified by argon ion implantation in three fluencies (1 × 10¹⁵, 1 × 10¹⁶, and 1 × 10¹⁷ cm⁻²) at an accelerating voltage of 60 kV. Changes in the wettability, surface energy, and surface colour of the WPCs were analysed. It was shown that argon ion implantation affects the distinct colour change in the WPC surface. The nature of the colour changes depends on the filler used. Implantation also affects the colour balance between the individual variants. Implantation of the WPC surface with argon ions resulted in a decrease in the wetting angle. In most of the variants tested, the most significant effect on the wetting angle changes was the ion fluence of 1 × 10¹⁷ cm⁻². Implantation of the WPC surface also increased the surface free energy of the composites. The highest surface free energy values were also recorded for the argon ion fluence of 1 × 10¹⁷ cm⁻². Full article