Irradiated Layer Research Articles

Effect of Xenon Ion Irradiation on the Properties of Austenitic Steel AISI 316.

This study investigated changes in the crystal lattice, tribological properties and friction mechanism of AISI 316 steel irradiated with swift 160 MeV xenon ions. The irradiation process caused the increased roughness of the steel surface and the swelling of the material. The thickness of the irradiated layer increased by about 13 nm. Following irradiation with the fluences 2.5 × 1014 and 3.2 × 1014 (Xe24+/cm2), martensite formed in the surface layer. Fluctuating changes were also observed with respect to the coefficient of friction and the degree of wear of the AISI 316 steel samples. Irradiation also increased the microhardness of the steel.

The influence of irradiation time and layer thickness on the optical properties of NiO/CO3O4 nanocomposite for optoelectronic applications

This paper offers insights into optical properties of NiO/Co3O4 nanocomposite, demonstrating how X-ray irradiation affects it which offers information for optoelectronic applications. FTIR results showed existence of chemical bonds that have been presented in our composite. The HRTEM images revealed the presence of clusters of molecules in various shapes and an average grain size approaching 19 nanometers. The optical investigations shows an increase in optical absorbance of a NiO/Co3O4 nanocomposite after irradiation with X-rays up to 60 min. The calculated indirect energy gap of the material increases response to X-ray radiation which attributed to defects in the material's crystal structure.

Surface Modification of Additively Manufactured Inconel 718 Alloy by Low‐Energy High‐Current Electron Beam Irradiation

The effect of low‐energy high‐current electron beam (LEHCEB) irradiation on the microstructure and nanohardness of Inconel 718 alloy produced by laser powder bed fusion additive manufacturing is investigated. The LEHCEB irradiation is applied to the alloy at three energy levels, and the resulting microstructural analysis of irradiated surfaces is conducted. The findings from this study demonstrate that the LEHCEB irradiation substantially changes the as‐built microstructure showing intragranular dendrites of different shapes and irregular‐shaped Laves phases. The columnar structure is formed in the modified near‐surface layer as a result of rapid heating and cooling during LEHCEB irradiation. Furthermore, all Laves phases dissolve in the modified layer. Nanoindentation hardness of the irradiated layer of the alloy increases from 593 ± 23 to 693 ± 13 Hv with the highest energy density of 15 J cm−2. This increment is attributed mainly to the dissolution of Laves phases and the formation of an ultrafine columnar structure where the columns are separated from each other by the district regions containing very thin interlayers of a secondary phase and a high amount of dislocations.

Thermally stable photoluminescence centers at 1240 nm in silicon obtained by irradiation of the SiO2/Si system

The study of light-emitting defects in silicon created by ion implantation has gained renewed interest with the development of quantum optical devices. Improving techniques for creating and optimizing these defects remains a major focus. This work presents a comprehensive analysis of a photoluminescence line at a wavelength of 1240 nm (1 eV) caused by defects arising from the ion irradiation of the SiO2/Si system and subsequent thermal annealing. It is assumed that this emission is due to the formation of defect complexes WM with trigonal symmetry similar to the well-known W-centers. A distinctive feature of these defects is their thermal resistance up to temperatures of 800 °C and less pronounced temperature quenching compared to the W-line. The difference in the properties of these defect centers and W-centers can be explained by their different defect environments, resulting from the larger spatial separation between vacancies and interstitial atoms diffusing from the irradiated layer. This, in turn, is associated with the difference in the distribution of primary radiation defects during irradiation of the SiO2/Si system and silicon not covered with a SiO2 film. The patterns of changes in the WM line depending on various factors, such as the thickness of the SiO2 film, type of conductivity and impurity concentration in the original silicon, irradiation parameters, and annealing regimes, is studied and explained in detail. These findings demonstrate the benefits of this new approach when compared to previous methods.

Mechanisms of deformation induced by high-current pulsed electron beam irradiation

AA2024 aluminum alloy was irradiated by a high-current pulsed electron beam with the following parameters: beam energy ∼0.3 MeV, current ∼2000A, pulse duration ∼5·10−6 s, beam diameter ∼3 cm. The thickness of the surface remelted layer reached 100 μm. Dynamic thermal stresses caused by irradiation, induced the development of deformation processes in the irradiated layer. Based on the study of surface morphology and structural state of the remelted layer, it was shown that deformation processes occur in the surface layer by the grain boundary sliding mechanism. The level of residual stresses in the irradiated layer was low and amounted to 34 MPa.

FEATURES OF EXCITATION OF LINEAR AND NONLINEAR THERMAL WAVES IN DIELECTRIC FILMS ON A SUBSTRATE UNDER IRRADIATION WITH A HARMONICALLY MODULATED ION BEAM

A mathematical model has been formulated for the problem of generating linear and nonlinear thermal waves in dielectric films attached to a substrate and in the air by means of a harmonically frequency-modulated ion beam. To solve the formulated problem, a system of nonlinear heat conduction equations is used for two layers of the sample and the substrate. The temperature dependence of the thermophysical quantities of both parts of the sample and, as well as the heat transfer coefficient and emissivity degree, is taken in linear form using thermal coefficients. Temperature disturbances are presented as the sum of stationary and oscillatory components, and the oscillatory part as the sum of linear and nonlinear. In turn, the nonlinear part consists of the sum of oscillations at the fundamental and second harmonics. Due to the fact that the temporary change in the heat source due to the absorption of the ion flow has a harmonic form, the time dependence of the temperature fluctuation in the original equations is also presented in a harmonic form. By solving the boundary value problem, an explicit form of expression was obtained for all parts of the oscillatory component of the temperature disturbance. It was discovered that the frequency dependence of the amplitude of the linear component of the excited thermal wave in the irradiated layer, while for the non-irradiated layer and substrate

Irradiation-Hardening Model of TiZrHfNbMo0.1 Refractory High-Entropy Alloys.

In order to find more excellent structural materials resistant to radiation damage, high-entropy alloys (HEAs) have been developed due to their characteristics of limited point defect diffusion such as lattice distortion and slow diffusion. Specially, refractory high-entropy alloys (RHEAs) that can adapt to a high-temperature environment are badly needed. In this study, TiZrHfNbMo0.1 RHEAs are selected for irradiation and nanoindentation experiments. We combined the mechanistic model for the depth-dependent hardness of ion-irradiated metals and the introduction of the scale factor f to modify the irradiation-hardening model in order to better describe the nanoindentation indentation process in the irradiated layer. Finally, it can be found that, with the increase in irradiation dose, a more serious lattice distortion caused by a higher defect density limits the expansion of the plastic zone.

A study on the thermal conductivity of proton irradiated CVD-SiC and sintered SiC, measured using a modified laser flash method with multi-step machining

CVD-SiC and sintered SiC (SPS-SiC) were proton irradiated at 340 ̊C receiving different levels of damage (0.05–0.25 dpa). A novel multi-step machining and measurement method using laser flash analysis (LFA) was developed to derive the thermal conductivity of the irradiated layer (∼46 µm). Before irradiation, the thermal conductivity of SPS-SiC was much lower than CVD-SiC, primarily due to its higher intrinsic defect concentration and smaller grain size which provide a greater density of barriers to phonon transmission. Following irradiation, major thermal conductivity degradation (∼90%) was found to occur to both types of SiC after only a low dose (∼0.1 dpa), with both saturating at a similarly low value (a few W/K⋅m), as the thermal resistivity due to the presence of high density of grain boundaries became less important. Thermal conductivity degradation after irradiation was primarily caused by point defects in both types of SiC, as reflected by Raman spectra.

Revealing the temperature-dependent hardening mechanisms of non-uniformly distributed defects for ion-irradiated metals: Experiments and modeling

In this work, an integrated approach including experimental examinations and theoretical modeling was employed to examine the temperature-dependent hardening of structural materials under ion irradiation. Experimental procedures involved the characterization of grain morphology and size distribution by electron backscatter diffraction (EBSD). Irradiation experiments were conducted utilizing high-energy Au-ions at elevated temperatures, with transmission electron microscopy (TEM) employed for observing irradiation-induced defects. Moreover, mechanical properties were assessed through high-temperature nano-indentation tests (HTNIT), revealing the concurrent occurrence of irradiation hardening and high-temperature softening in the considered materials. For theoretical modeling, a mechanistic model was developed to address the depth-dependent hardness. This model innovatively characterized the hardening mechanisms resulting from non-uniformly distributed defects in the irradiated layer while simultaneously incorporating the temperature effect. Calibration of the model demonstrated its capability to elucidate the hardness-depth relationships at different irradiation doses and testing temperatures. Further theoretical analyses indicated distinct evolution laws in irradiation hardening behavior with varying indentation depths, while the increment in temperature accelerated the expansion of the plastic zone, resulting in a moderate indentation size effect (ISE). With increasing indentation depth, the hardening contributions of geometrically necessary dislocations (GNDs) and irradiation-induced defects gradually diminished. At substantial indentation depths, the dominant hardening mechanism was then controlled by statistically stored dislocations (SSDs).

Grazing-incidence synchrotron radiation diffraction studies on irradiated Ce-doped and pristine Y-stabilized ZrO2 at the Rossendorf beamline.

In this work, Ce-doped yttria-stabilized zirconia (YSZ) and pure YSZ phases were subjected to irradiation with 14 MeV Au ions. Irradiation studies were performed to simulate long-term structural and microstructural damage due to self-irradiation in YSZ phases hosting alpha-active radioactive species. It was found that both the Ce-doped YSZ and the YSZ phases had a reasonable tolerance to irradiation at high ion fluences and the bulk crystallinity was well preserved. Nevertheless, local microstrain increased in all compounds under study after irradiation, with the Ce-doped phases being less affected than pure YSZ. Doping with cerium ions increased the microstructural stability of YSZ phases through a possible reduction in the mobility of oxygen atoms, which limits the formation of structural defects. Doping of YSZ with tetravalent actinide elements is expected to have a similar effect. Thus, YSZ phases are promising for the safe long-term storage of radioactive elements. Using synchrotron radiation diffraction, measurements of the thin irradiated layers of the Ce-YSZ and YSZ samples were performed in grazing incidence (GI) mode. A corresponding module for measurements in GI mode was developed at the Rossendorf Beamline and relevant technical details for sample alignment and data collection are also presented.

Single-source thermal deposition of (BA)2(MA)3Pb4I13 perovskite for a novel SnO2NRs/comp-TiO2@ irradiated-ITO based 2D/3D perovskite solar cell: Comparative study of irradiated ITO layer and its effect on device performance

Perovskite solar cells have achieved very good efficiency but their stability is still a big issue. To achieve an efficient a stable perovskite solar cell; a new simple single source thermal evaporation approach has been used to deposit 2D/3D (BA)2(MA)3Pb4I13 perovskite active layer, for realization of novel architecture of stable perovskite solar cell. Bi ions irradiated ITO electrode, coated with compact TiO2 and SnO2 nano-rods (NRs) layers, has been used as ETL. A unique approach is adopted to deliberately place SnO2 NRs horizontally on the surface comp-TiO2 coated irradiated ITO. Four, SnO2NRs/comp-TiO2@ irradiated-ITO based 2D/3D perovskite devices, have been fabricated with 1.2 GeV Bi ions irradiated ITO, at four different fluences (1.3 × 1011, 6.5 × 1011, 1.3 × 1012 and 2.6 × 1012 ions/cm2). Nano-hillocks formed by irradiation proved to contribute for the better performance to a certain point. It was found that the choice of using horizontally place SnO2-NRs in ETL contributed for better performance and stability of proposed device. Among four fabricated devices highest efficiency of 13.6 % is obtained for ITO irradiated with 1.3 × 1012 ions/cm2 fluence which is very encouraging for 2D/3D hybrid perovskite based solar cells in addition to improved performance all the devices showed good stability.

INFLUENCE OF PULSED BEAM-PLASMA IMPACTS ON THE STRUCTURAL CHARACTERISTICS AND MECHANICAL PROPERTIES OF THE SURFACE LAYER IN INCONEL 718 ALLOY

The results of studying the effects of pulsed flows of helium ions (HI) and helium plasmas (HP) on the Inconel 718 alloy prepared by additive technology by selective laser melting followed by heat treatment are presented. The main structural changes in the irradiated surface layer (SL) are determined for two modes of irradiation - soft (with radiation power density q = 2 ∙108 W/cm2 at pulse duration τ = 50 ns) and hard (at q = 1.5 ∙109 W/cm2, τ = 25 ns). The number of pulsed actions in each mode was N = 10 and 20. It has been found that in the initial state and after irradiation, the alloy under study is a single-phase nickel-based solid solution with an fcc lattice. The impact on the alloy of pulsed HI and HP flows leads to a change in the initial texture in the 220 direction to texture 111. This change in the texture favored the occurrence of the plastic deformation (PD) process observed in the irradiated SL, during which in metals with an fcc lattice, under the action of applied thermal stresses, slip occurs predominantly along the {111} planes. The influence of the irradiation mode of the investigated alloy on the parameter of its crystal lattice is noted. In the soft mode of exposure to HI and HP flows, the lattice parameter a decreases compared to the initial value, which may be due to the action of residual macrostresses, as well as to the evaporation of atoms of impurity elements located in lattice interstices from the SL. In the hard irradiation regime, the parameter a increases, which is due to the dominant influence of the mechanism of implantation of helium ions into the alloy, which contributes to the increase in the value of a. It have been shown that the observed structural changes in the SL of the alloy lead to a decrease in microhardness and softening of the remelted layer. The role of thermal and shock-wave effects in the processes of PD and structural changes in SL under the implemented irradiation conditions was estimated by numerical simulation.

Light-controllable hybrid aligning layer based on LIPSS on sapphire surface and PVCN-F film

The creation of aligning layers for the uniform orientation of liquid crystals is significant for both research and the application of liquid crystals. For all applications, the creation of aligning layers possessing controllable characteristics such as azimuthal and polar anchoring energies, easy-axis of director alignment and pretilt angle, in the same way as it is achieved by using photoaligning layers processed by light, is very important. Here, aligning properties of hybrid aligning layers created on the basis of sapphire surfaces additionally coated by photoaligning layer of PVCN-F are studied. These hybrid layers possess the properties of the nano-structured sapphire layer and the photosensitive PVCN-F layer, and complement each other. The irradiation time dependence of the azimuthal anchoring energy of the hybrid layers is studied. By using certain experimental conditions during irradiation of hybrid layers, e.g., polarization of light and irradiation time, a minimum value of the azimuthal anchoring energy, close to zero, was obtained. Atomic force microscope studies of the irradiated hybrid layers were also carried out. It was found that the behavior of the contact angle of nematic droplets placed on treated sapphire surfaces are in good agreement with properties of hybrid aligning layers and parameters of structuring surface obtained from AFM images.

Formation mechanism of craters on the surface of AA6111 aluminum alloy irradiated by quasi-relativistic high-current electron beam

The factors contributing to the formation of craters on the surface of the AA6111 aluminum alloy after processing with a high-current pulsed electron beam were investigated. Microstructural studies of the crater formation area were conducted both on the surface of the irradiated layer and on the cross-sectional side. Inhomogeneity in the distribution of alloying elements was observed both across the irradiated surface and along the cross-sectional surface of the irradiated alloy layer. The regularities of crystallization of phases in the presence of various alloying elements and their effects on the formation of crater geometry were identified. The size and shape of craters were analyzed, and it was determined that the depth of all craters was less than the thickness of the layer remelted by the high-current pulsed electron beam. A mechanism was proposed whereby the formation of craters in the AA6111 alloy is the result of uneven crystallization of the surface layer melted by the high-current pulsed electron beam.

Depth-distribution of resistivity within ion-irradiated semiconductor layers revealed by low-kV scanning electron microscopy

Low-kV scanning electron microscopy imaging was used to visualize the 2D profiles of internal resistivity distribution in 600 keV He2+ ion-irradiated epitaxial GaAs and Al(0.55)Ga(0.45)As. The influence of the dopant concentration on DIVA (damage-induced voltage alteration) contrast formation has been studied in this paper. The threshold irradiation fluencies (the fluencies below which no damage-related contrast is observed) were defined for each studied material. The results show that the same level of damage in the material caused by ion irradiation becomes visible at lower threshold fluence in the case of lower-doped sample of the same composition. The aluminum content in the composition of materials exposed to ion irradiation and subsequent DIVA contrast formation mechanism was considered as well. The carrier concentration in irradiated layers has been studied by Raman spectroscopy and photoluminescence measurements, which confirmed that the increase of the resistivity of the material caused by ion-irradiation damage generation is resulting from the formation of deep states in the bandgap trapping free carriers.

Exploring UV-Laser Effects on Al-Implanted 4H-SiC

In this paper, we explore the effects of excimer laser irradiation on heavily Aluminum (Al)-implanted silicon carbide (4H-SiC) layer. 4H-SiC layers were exposed to UV-laser radiation (308 nm, 160 ns), at different laser fluences and the effects of the laser exposure surface were evaluated from morphological, micro-structural and nano-electrical standpoints. Depending on the irradiation condition, significant near-surface changes were observed. Moreover, the electrical characteristics of the implanted layer, evaluated by means of transmission line method, gave a sheet-resistance of 1.62×104 kW/sq for the irradiated layer, linked to a poor activation of the p-type dopant and/or a low mobility of the carriers in the laser-modified 4H-SiC layer. This study can be useful for a fundamental understanding of laser annealing treatments of 4H-SiC implanted layers.

Nature-inspired mechano-bactericidal nanostructured surfaces with photothermally enhanced antibacterial performances

Nature-inspired nanostructured surfaces with intrinsic mechano-bactericidal behaviors have drawn particular attention, owing to the advantages of biocompatibility, no cytotoxicity and free of biocides. However, when encountered with different bacterial strains, those nanostructured surfaces show significant different antibacterial activities because of the obvious variability in bacterial cell wall and morphology. Herein, a mechano-bactericidal nanostructured surface with photothermally enhanced antibacterial performances has been developed, which exhibits synergistic antimicrobial performances with significantly enhanced antibacterial efficiency against both Gram-positive and Gram-negative bacteria. Firstly, a nanopillar surface with mechano-bactericidal properties is replicated by AAO template methods. Afterwards, a thin photothermal layer of polydopamine (PDA) was rapidly deposited on the nanostructured surface. The resultant nanopillar surface displays remarkably high antibacterial activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). The main reason is due to the photothermal (PTT) effect from the NIR irradiated PDA layer makes the bacterial cell membranes more susceptible to be killed by the structural rupture of the nanopillar surface. Additionally, the nanopillar surface also exhibited excellent hemocompatibility and cytocompatibility properties. Benefiting from the obviously enhanced mechano-bactericidal performances with no antibacterial agents involved, our study might display promising potentials in broad antibacterial applications, ranging from healthcare settings, biomedical ingredients, and other high risk instruments.

Polymer composition with phenanthrenequinone for recording relief holographic gratings

The formation of periodic reliefs of the thickness of photosensitive polymer layers after recording holographic gratings in them and stimulating material deformations by reversible plasticization in a non-solvent liquid is considered. The phenomenon was studied for the composition of a copolymer with side anthracene groups — phenanthrenquinone. Phenantrenquinone transfers the energy of electronic excitation to oxygen molecules entering through the open surface of the polymer layer which then cause the oxidation of anthracene fragments. Holographic gratings with a period of 2–5 μm were recorded by laser radiation at a wavelength of 532 nm in layers about 1 μm thick. The photoreliefs were formed during the subsequent swelling of the layer in the medium of a hydrocarbon developer. The photosensitized oxidation of the anthracene groups of the new polymer under the action of optical radiation in the spectral range 408–532 nm was studied using the electron absorption spectra. It is shown that approaching the excitation wavelength to the long-wavelength absorption maximum of phenanthrenquinone (410 nm) makes it possible to increase the sensitivity of the material layer by a factor of 15 compared to layers with methylene blue as a photosensitizer. It has been experimentally established that the amplitude of weak periodic reliefs of a deformation nature (height less than 0.01 μm), which appear immediately after the recording of holographic gratings, increases many times during the treatment of the layer with liquid hydrocarbon. Their maximum value reaches 25 % of the thickness of the recording layer. Presumably, the deformation of the inhomogeneously irradiated layer is stimulated by the transfer of the polymer material into a highly elastic state during its swelling. Photoreliefs are stable after drying. Their strength can be increased by photocrosslinking the material as a result of photodimerization of residual anthracene groups under uniform irradiation with light at a wavelength of 365 nm. The non-sinusoidality of the photorelief reduces the diffraction efficiency achievable with total reflection to values less than 0.20. The studied polymer composition can be used to form relief-phase diffractive optical elements by radiation in the blue-green region of the spectrum, provided by a number of high-power laser sources.

Experimental and theoretical study on the production of carbide-rich composite nano-coatings

Carbides are known for high hardness and corrosion resistance and therefore applicable as protective coatings. C/Si and C/W multilayers (the individual layer thicknesses were between 10 and 20 nm) have been irradiated at room temperature by argon and xenon ions. The energies varied between 40 and 120 keV while the fluences were in the range of 0.07 - 6 × 1016 ions/cm2. The SRIM simulation was applied to have the proper ion energy. The irradiation induced intermixing and carbide (SiC and WC) formation at the interfaces already for the lowest irradiation fluence. The component in-depth distribution has been determined by AES depth profiling which showed that it varied greatly as a function of the irradiation conditions and layer structure. In both material pair the thickness of the produced carbide increased with square root of fluence but the mixing mechanism were different: local spike for C/W and ballistic for C/Si. The mixing efficiency was lower for the C/Si than for the C/W.

Features of the combined technology based on laser metal deposition with layered laser heat treatment

The results of combined using of laser metal deposition technology with layer-by-layer laser heat treatment technology are presented and the experimental setup is described to unite the laser metal deposition technology with layer-by-layer laser remelting and/or laser surface hardening implementation. The layers formed at the stages of laser metal deposition and additional layer-by-layer laser heat treatment alternate in the material. The ratio between the thicknesses of the layers obtained during crystallization at the laser metal deposition stage and at the laser remelting stage is shown to vary widely depending on the technological parameters. The surface temperature of the irradiated layer is maintained in laser surface hardening mode in the range of 1100 °C – 1400 °C with present laser power function. It is proposed to use this mode for local structural-phase transformation of the material.