Pulsed Ion Beam Irradiation Research Articles

Solid-State Dewetting of Thin Silver Films into Spherical Nanoparticles under High-Current Pulsed Ion Beam Irradiation.

Noble metal nanoparticles (NPs) are important in many applications, including light trapping of photovoltaic cells, photoelectrochemical applications, etc. The present study reports the formation of silver NPs from the as-deposited silver coatings on fused silica substrates by solid-state dewetting induced by high-current intense pulsed ion beam (IPIB) irradiation. We described the effects of IPIB irradiation with different ion beam current densities and numbers of pulses on NP morphology and compared the results with conventional rapid thermal annealing (RTA). IPIB irradiation enables superfast heating (higher than 109 K/s) and cooling, providing a superfast annealing solid-state dewetting mechanism. Our results demonstrate that the sphericity of silver NPs is enhanced after IPIB irradiation relative to RTA-annealed silver NPs. Our results suggest further possibilities of shape and sphericity control of silver NPs with very fast heating/cooling annealing rates.

Surface microstructure and phase structure of zirconia ceramics under intense pulsed ion beam irradiation

The surface microstructure and phase structure of zirconia (ZrO2) ceramics under intense pulsed ion beam (IPIB) irradiation were investigated in this work. Experiments were carried out on TEMP-4M accelerator with peak accelerating voltage, current density, and pulse duration of 220 kV, 150 A/cm2, and 80 ns. Micro-cracks with a height of up to 150 nm above the surface were observed and were deduced to be formed by the tensile stress during the shrinking process. The cross-sectional observation indicates that columnar structure thin layer with thickness about 1.23 μm was produced after IPIB irradiation. The GIXRD pattern indicates that obvious preferred orientation in (110) and (200) of t-ZrO2 was occurred in near-surface region after IPIB irradiation. Opposite micro-stress in bulk and near-surface region was revealed by W-H plot after Rietveld refinement. The evolution of mass loss and surface roughness of samples with pulse number was also investigated.

Surface Modification of the EBM Ti-6Al-4V Alloy by Pulsed Ion Beam

The effect of surface modification of Ti-6Al-4V samples manufactured by electron beam melting (EBM) using a pulsed carbon ion beam is studied in the present work. Based on the results of XRD, SEM, and TEM analysis, patterns of changes in the microstructure and phase composition of the EBM Ti-6Al-4V alloy, depending on the number of pulses of pulsed ion beam exposure, are revealed. It was found that gradient microstructure is formed as a result of pulsed ion beam irradiation of the EBM Ti-6Al-4V samples. The microstructure of the surface layer up to 300 nm thick is represented by the (α + α”) phase. At depths of 0.3 μm, the microstructure is mixed and contains alpha-phase plates and needle-shaped martensite. The mechanical properties were investigated using methods of uniaxial tensile tests, micro- and nanohardness measurements, and tribological tests. It was shown that surface modification by a pulsed ion beam at an energy density of 1.92 J/cm2 and five pulses leads to an increase in the micro- and nanohardness of the surface layers, a decrease in the wear rate, and a slight rise in the plasticity of EBM Ti-6Al-4V alloy.

Study of phase transformation and surface microstructure of alumina ceramic under irradiation of intense pulsed ion beam

Intense pulsed ion beam (IPIB), featured with pulsed high-power density, has been widely used in the modification of structural material, especially in high strength materials. The effects of IPIB treatment on phase transformation and surface microstructure of alumina ceramics were investigated in this work. Experiments were carried out on the BIPPAB-450 accelerator with peak accelerating voltage and current density of 360 kV and 170 A/cm2. X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM) were used to analyze the phase transformation and cross-section and surface morphology of alumina ceramics under IPIB treatment. The XRD pattern indicated that phase transformation from α-Al2O3 to γ-Al2O3 occurred on the irradiated area due to the combined effect of rapid re-solidification and thermal stress caused by IPIB. The SEM cross-section images indicated that homogeneous modified layer with thickness up to 1.53 μm was produced and cracks inside sample were observed as well after IPIB irradiation. The evolution of cracks on surface of samples with pulse number was investigated in this work. Micro-holes distributed on the net structure of cracks were observed after IPIB irradiation and the evolution of size and number of micro-holes with pulse number was discussed.

Investigation of the Effects of an Intense Pulsed Ion Beam on the Surface Melting of IN718 Superalloy Prepared with Selective Laser Melting

Intense pulsed ion beam irradiation on IN718 superalloy prepared with selective laser melting as an after-treatment for surface melting is introduced. It is demonstrated that intense pulsed ion beam composed of protons and carbon ions, with a maximum current density of 200 A/cm2 and a pulse length of 80 ns, can induce surface melting and the surface roughness changes significantly due to the generation of micro-defects and the flow of the molten surface. Irradiation experiments and thermal field simulation revealed that the energy density of the ion beam plays a predominant role in the irradiation effect—with low energy density, the flow of molten surface is too weak to smooth the fluctuations on the surface. With high energy density, the surface can be effectively melted and smoothened while micro-defects, such as craters, may be generated and can be flattened by an increased number of pulses. The research verified that for the surface melting with intense pulsed ion beam (IPIB), higher energy density should be used for stronger surface fluidity and a greater pulse number is also required for the curing of surface micro-defects.

Dynamic mechanism of crater formation induced by inclusion during intense pulsed ion beam irradiation

Crater is a general defect appeared on metallic target after intense pulsed ion beam (IPIB) treatment, which greatly limits the utilization and development of this technology. Understanding the mechanism of crater formation is of great significance for IPIB application. It is reported that inclusion in metallic target is associated with crater formation. In this work, the inclusions exposed to vacuum environment on target surface were found to lead to crater formation during 2.0 J/cm2 IPIB irradiation via a positioning observation experiment on high speed steel. To investigate the dynamic mechanism of crater formation, thermal conduction model and laminar flow model were performed successively. The flow field analysis revealed that surface tension coefficient difference between molten inclusion and molten matrix is the primary reason to drive melt flow and generate crater. In the subsequent evolution of the crater, surface curvature also plays an important part.

Study on the damage of Fe80B13Si7 alloy with different structure by high-intensity pulsed ion beam irradiation

In this study, Fe80B13Si7 alloys with the same components but different structure, amorphous and crystal, were irradiated by high-intensity pulsed ion beams (HIPIB) with different parameters. The irradiation damage behavior of amorphous and crystal alloy by the HIPIB irradiation was studied. TEM analysis of the cross-section showed that after HIPIB irradiation, the atoms in amorphous alloy were aggregated and migrated, and the arrangement of atoms became uneven, no nanocrystal was observed. For the crystal, Fe3B, Fe3Si, Fe2B and Fe3C nanocrystals appeared besides the main structure of the α-Fe phase after HIPIB irradiation. A mass of defects appeared in the crystal. Meanwhile, XRD results showed that the lattice parameters of α-Fe phase were decreased. The effect range of the structure and defects of the crystal and the atomic arrangement of amorphous alloy by irradiation were far beyond the incident ion range. After HIPIB irradiation, the surface of amorphous alloy showed no obvious irradiation damage, and the surface of crystal showed wavy undulations. The roughness of both two alloys was increased, and the surface diffusion caused by the thermal driving and ion induction was the main mechanism of surface evolution. The decrease of the surface reflectivity of the amorphous alloy was smaller than that of the crystal.

The influence of metal surface topography on ablation behavior during intense pulsed ion beam irradiation

As a flash heat source, intense pulse ion beam (IPIB) has extensive applications in material surface modification. The ablation effect during IPIB irradiation on target can impact the results of material modification. Therefore, the understanding of ablation mechanism is of great significance for IPIB application. In this work, to investigate the influence mechanism of surface topography on ablation behavior, pure zinc targets with different surface roughness were bombarded by IPIB with various energy densities at TEMP-4M accelerator. The experiments results showed that the ablation mass increased with the surface roughness increasing. Combining Monte Carlo method and finite element method, a heat conduction model was constructed to describe the ablation process of zinc target with different surface roughness. The simulation results agreed with the experiments, and the mechanism of ablation influenced by the surface topography was proposed.

Shielding of energy deposition by ablation of plastics under intense pulsed ion beam irradiation

With high power density in solid targets, intense pulsed ion beam with a pulse length of hundreds of ns and cross-sectional energy density of several J/cm2 may induce surface ablation and this effect can be used for thin-film preparation and nanopowder synthesis. Nevertheless, with ablation by the pulsed ion beam, the energy deposition of ions in targets may be affected and this further toughens the analysis of ablation and related material response in applications and ion beam diagnostics. In this study, the energy deposition of nanosecond pulsed ion beam composed of protons and carbon ions on stainless steel and plastics on BIPPAB-450 pulsed ion beam accelerator was investigated with infrared diagnostics. It is revealed that on plastics, under nanosecond IPIB irradiation with energy density of 1.5 J/cm2, ablation plume can be formed at the beginning stage of beam irradiation and the ablation plume may impose strong stopping to the ions in the pulsed ion beam and thus the energy deposition of the ion beam is shielded from reaching the target with over 80% of the beam energy screened. The influence of this energy shielding effect on applications such as beam measurement and material treatment was discussed reasonably.

Effect on mechanics properties and microstructure of molybdenum by high intensity pulsed ion beam irradiation

In this paper, high intensity pulsed ion beam (HIPIB) of 85% Cn+ + 15% H+ was used to irradiate crystalline molybdenum. Before and after irradiation, the surface structure and mechanical properties were studied with different irradiation times and energy densities. After HIPIB irradiation, stress was generated inside the molybdenum. As the energy density increases, the thermal effect which was enhanced apparently causes a preferred orientation in the molybdenum. When the energy density reaches 1.6–2.5 J/cm2 with 3 pulses, craters and cracks appear on the surface of molybdenum. Besides, the α-Mo2C phase formed in the near-surficial region of molybdenum is beneficial to the hardness increasement. After HIPIB irradiation, the ratio of average hardness (Hirr/Hunirr) and Nix-Gao model show that the macro hardness of molybdenum decreases with the increase of pulse number and energy density. Compared with the effect of ion implantation on hardness improvement, the annealing effect of HIPIB thermal irradiation plays a more important role in the reduction of molybdenum hardness. The hardness of the molybdenum decreases under the combined action.

Influence of ablation on energy deposition in polymer material under irradiation of intense pulsed ion beam

Short-pulse length and high-power density, intense pulsed ion beam (IPIB) has been widely studied in material processing during past decades. Ablation effect plays a great role in the interaction between IPIB and material and may affect the energy deposition of IPIB, thus further influencing the beam application and diagnostics. Therefore, the investigation of ablation effect on energy deposition of IPIB in the irradiated material is of great significance for its applications and diagnostic techniques. In this work, experiments on the IPIB irradiation are carried out on the BIPPAB-450 accelerator at Beihang University. Its maximum accelerating voltage is 450 kV, peak current density is 150 A/cm<sup>2</sup>, energy density is 1.5–1.8 J/cm<sup>2</sup> and pulse duration (FWHM) is 80 ns. Polymer materials which have low thermal conductivity, low decomposition temperature and thus yield to ablation under low beam density, such as polycarbonate (PC), polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA), are chosen in the present research. The 304 stainless steel is used for calorimetric beam diagnostics and comparative analysis. Energy deposition in polymer material and 304 stainless steel are obtained by high infrared imaging diagnostics. It is revealed that the distributions of energy deposition in these two kinds of materials differ from each other obviously. The highest energy density deposited in the 304 stainless steel appears in the center of the irradiated area where focused is the beam with a higher energy density. However, the central energy density in polymer material turns out to be lower than the surrounding area, indicating that a large portion of the ion beam is prevented from reaching the target. Meanwhile, the simulation based on the finite element method is carried out for the thermal filed distribution and evolution under the IPIB irradiation. The simulation result indicates that the strong ablation can be generated on the target surface since the highest temperature caused by IPIB irradiation is much higher than its decomposition temperature. According to the results of experiments and simulation, the polymer material can start to be ablated at the initial stage of IPIB irradiation which will consume partial energy and the products of ablation may act as shielding to block the energy deposition in the same pulse.

Structure and electrochemical characterization of SnOx/Sn@MWCNT composites formed by pulsed ion beam irradiation

The influence of irradiation by pulsed ion beam on the morphology, structure, and chemical composition of a composite based on multiwalled carbon nanotubes (MWCNTs) and tin dioxide (SnO2-x@MWCNTs) was investigated. It has been established that irradiation of the composite by pulsed ion beam leads to the formation of Sn/SnOx core-shell nanoparticles, which adhere to the surface of the MWCNTs. The “core” is metallic Sn and the “shell” is amorphous SnOx. A uniform distribution of Sn/SnOx nanoparticles on the surface of the MWCNTs was noted, and the maximal concentration of tin in both volume and surface layer was achieved by triple irradiation with an energy density of 0.5 J/cm2. This composite exhibited good electrochemical performance as an anode material for lithium-ion batteries, delivering 1494 mA h g−1 as a first discharge capacity and 634 mA h g−1 discharge capacity (72% capacity retention) after 30 cycles of charge/discharge.

Effects of high-intensity pulsed ion beam irradiation on the structural thermal stability of Fe80Si7.43B12.57 metallic glass

A high-intensity pulsed ion beam was used to irradiate Fe80Si7.43B12.57 metallic glass at different energy densities and numbers of pulses to study its structural thermal stability. A large number of round holes and a few bumps appeared on the surface of the glass after 300 pulses. No obvious damage was observed on the surface after irradiation at different energy densities. High-resolution transmission electron microscopy showed that this irradiation had a strong influence on the near-surface atomic arrangement of the glass. Irradiation induced strong migration and aggregation of atoms within the glass, causing an uneven atomic arrangement. Although there was an ordered arrangement of atoms, the metallic glass remained amorphous. The surface reflectivity of the metallic glass decreased slightly after irradiation. The number of irradiation pulses had greater impact on this Fe-based metallic glass than their energy density.

A Numerical Study of Cracks Appearance on Tungsten Surface After High Intense Pulsed Ion Beam Irradiation

Due to the outstanding physical properties, Tungsten has been proposed for use in the divertor of future fusion devices. However, tungsten shall face strong particle bombardment from the plasma, which causes severe damage to the material. The purpose of this work is to build such an accurate analytical model which can predict the damages in target material like crack production and propagation after high intense pulsed ion beam irradiation. Hence, a two-dimensional finite element method is used to study the effect of high intense pulsed ion beam on tungsten surface numerically. To judge temperature and stress distribution in material, thermal conduction model is combined with non-linear fracture mechanics model and J-Integral parameter is used as a criterion to judge the crack propagation. Simulation results reveal that different crack heights and sizes can affect the results and there is a critical depth for crack propagation. The model gives good results to real experimental observations and has potential applications for different intense pulsed electron/plasma beams and different target materials as well.

Anisotropy effect of crater formation on single crystal silicon surface under intense pulsed ion beam irradiation

Abstract Due to the induced extremely fast thermal and dynamic process, Intense Pulsed Ion Beam (IPIB) is widely applied in material processing, which can bring enhanced material performance and surface craters as well. To investigate the craters’ formation mechanism, a specific model was built with Finite Element Methods (FEM) to simulate the thermal field on irradiated single crystal silicon. The direct evidence for the existence of the simulated 6-fold rotational symmetric thermal distribution was provided by electron microscope images obtained on single crystal silicon. The correlation of the experiment and simulation is of great importance to understand the interaction between IPIB and materials.

Hydrodynamic effects on the surface morphology evolution of aluminum alloy under intense pulsed ion beam irradiation

As widely observed in many studies, the surface morphology of solids may change significantly after irradiation of intense pulsed ion beams (IPIB). This effect is crucial for surface treatments and may limit the utilization of IPIB as a novel method for surface processing in some cases. In present work, taking 6061 aluminum alloy for instance, the hydrodynamic behavior of the molten surface formed by IPIB irradiation was studied. By taking IPIB-induced heat transfer and level-set method flow field analysis with finite element method (FEM) it is revealed that under IPIB irradiation, the surface tension caused by the unevenness of curvature distribution of molten surface leads to mass transportation and a smoothening trend in the surface morphology evolution, meanwhile surface tension release is achieved. Irradiation of 6061 aluminum alloy was carried out and the trend in surface morphology evolution is consistent with the theoretical prediction.

Simulation analysis of zinc ablation process and mass by intense pulsed ion beam irradiation

AbstractAs the strong thermal effect in the surface, intense pulsed ion beam (IPIB) has been extensively used in material surface modification. The ablation is an important part in the interaction process between IPIB and material. In order to investigate the ablation mechanism, combined with IPIB dynamic energy spectrum and infrared imaging diagnostic results, a two-dimensional axisymmetric heat conduction model considering the effect of ablated material was constructed to describe the ablation process and calculate the lost mass of the targets. The influences of beam parameters and ablated matter on the ablation rate were discussed. The experimental and simulative results of ablation threshold and mass were compared.

Hydrodynamic Effects on Surface Morphology Evolution of Titanium Alloy under Intense Pulsed Ion Beam Irradiation**Supported by the National Natural Science Foundation of China under Grant No 1175012, the China Postdoctoral Science Foundation under Grant No 2016M600897, and the National Science and Technology Major Project of the Ministry of Science and Technology of China under Grant No 2013ZX04001-071.

The hydrodynamic effects of molten surface of titanium alloy on the morphology evolution by intense pulsed ion beam (IPIB) irradiation are studied. It is experimentally revealed that under irradiation of IPIB pulses, the surface morphology of titanium alloy in a spatial scale of μm exhibits an obvious smoothening trend. The mechanism of this phenomenon is explained by the mass transfer caused by the surface tension of molten metal. Hydrodynamic simulation with a combination of the finite element method and the level set method reveals that the change in curvature on the molten surface leads to uneven distribution of surface tension. Mass transfer is caused by the relief of surface tension, and meanwhile a flattening trend in the surface morphology evolution is achieved.

The tensile effect on crack formation in single crystal silicon irradiated by intense pulsed ion beam

Improving antifatigue performance of silicon substrate is very important for the development of semiconductor industry. The cracking behavior of silicon under intense pulsed ion beam irradiation was studied by numerical simulation in order to understand the mechanism of induced surface peeling observed by experimental means. Using molecular dynamics simulation based on Stillinger Weber potential, tensile effect on crack growth and propagation in single crystal silicon was investigated. Simulation results reveal that stress-strain curves of single crystal silicon at a constant strain rate can be divided into three stages, which are not similar to metal stress-strain curves; different tensile load velocities induce difference of single silicon crack formation speed; the layered stress results in crack formation in single crystal silicon. It is concluded that the crack growth and propagation is more sensitive to strain rate, tensile load velocity, stress distribution in single crystal silicon.

Study on ablation products of zinc by intense pulsed ion beam irradiation

AbstractAs a kind of flash heat source, intense pulsed ion beam (IPIB) can be used for material surface modification. The ablation effect has important influence on interaction between IPIB and material. Therefore, the understanding of ablation mechanism is of great significance to IPIB application. In this work, pure zinc targets were irradiated and ablated by IPIB. In the ablation process under the different ion beam energy densities, the ablation products were collected by a monocrystalline silicon substrate. By analyzing the ablation products with scanning electron microscope and energy-dispersive spectrometer, the surface morphology, and the spatial distribution of ablation products quantity were obtained. The results are useful for clearing the ablation process and the influence of beam parameter on the ablation effect.