Pulsed Ion Beam Irradiation Research Articles

Characteristics of metal ablation product by intense pulsed ion beam irradiation

Intense pulse ion beam (IPIB) has been extensively used in material surface modification. The ablation effect plays an important role in the interaction between IPIB and material. Therefore, the understanding of ablation mechanism is of great significance for IPIB application. Here, to investigate the ablation process and the characteristics of ablation products, pure zinc targets are bombarded by IPIB of 1.2-1.5 J/cm2 energy density at TEMP-4M accelerator. The ablation products are collected by monocrystalline silicon substrates in the IPIB irradiation process. By using the scanning electron microscopy, energy dispersive spectrometer and high precision balance, the surface morphology of the substrate and the characteristics of ablation products are obtained. The majority of observed ablation products are nearly circular particles with diameters of 0.03-2.00 m. There are a small number of zinc droplets and solid debris with large irregular shapes on the silicon substrate. Combining Monte Carlo method and infrared imaging diagnostic results, a heat conduction model is constructed by finite element method to describe the distribution and evolution of thermal field formed by IPIB on a zinc target. The results show that the zinc target can be melted and evaporated under a 1.2 J/cm2 IPIB irradiation. By comparing the experimental resuls with the simulation results, it is found that the gaseous, liquid and solid ablation products are generated collectively in the zinc ablation process. The causes of the different ablation products are also studied.

Formation of tin-tin oxide core–shell nanoparticles in the composite SnO2−x/nitrogen-doped carbon nanotubes by pulsed ion beam irradiation

The complex methods of transmission electron microscopy, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy were used to investigate the changes in the morphology, phase composition, and electronic structure of the composite SnO2−x/nitrogen-doped multiwalled carbon nanotubes (SnO2−x/N-MWCNTs) irradiated with the pulsed ion beam of nanosecond duration. The irradiation of the composite SnO2−x/N-MWCNTs leads to the formation of nanoparticles with the core–shell structure on the surface of CNTs with a sharp interfacial boundary. It has been established that the “core” is a metal tin (Sn0) with a typical size of 5–35nm, and the “shell” is a thin amorphous layer (2–6nm) consisting of nonstoichiometric tin oxide with a low oxygen content. The “core–shell” structure SnSnOx is formed due to the process of heating and evaporation of SnO2−x under the effect of the ion beam, followed by vapor deposition on the surface of carbon nanotubes.

The ablation mass of metals by intense pulsed ion beam irradiation

Ablation effect plays an important role in the process of material modification by intense pulsed ion beam (IPIB). As a direct observable in the process of target irradiated by IPIB, the ablation mass is a crucial physical quantity for understanding the interaction between IPIB and target material. Moreover, it is critical to uncover the mechanism of ablation by IPIB. In the present work, we used IPIB provided by BIPPAB-450 accelerator at Beihang University to bombard Zn, Pb, Sn, Cu, and W targets. By measuring the ablation masses under different energy densities, the ablation thresholds of Zn and Pb have been obtained. In addition, correlations between experimental data and incident beam parameters have been investigated. The results are helpful to understand the influence of beam parameter and material properties on the ablation mass.

Novel microstructures on the surfaces of single crystal silicon irradiated by intense pulsed ion beams

An ion beam treatment of high purity single crystal silicon specimens was performed with different shots by the irradiation of intense pulsed ion beams (IPIB), which were generated by an accelerating voltage of 350kV and with the current density of 130A/cm2. As the result of irradiation, the formation of various microstructures caused by the irradiation effect, especially the thermal effect is confirmed by SEM and XRD analysis, and the corresponding processes are described and related explanations are given.

Significance of surface integrity on high-performance manufacturing by surface modification

It has been proved that surface integrity involving numerous surface integrity parameters has a profound influence on component performance. However, it is still difficult to achieve a high performance of combined functional properties since the surface integrity of the high-performance component is frequently limited by merely using material removal manufacturing. In this work, surface modification is alternatively employed to explore influence of various surface integrity parameters in a controllable way on achieving the high-performance manufacturing of components with combined properties including anti-fatigue performance and corrosion resistance, thermal insulating and oxidation resistance, temperature sensing and wear resistance, otherwise unattainable in conventional material removal manufacturing. Three typical surface modification techniques principally based on a series of processing loads, such as thermochemical load from plasma-based low-energy ion implantation, thermomechanical load from ion beam shock processing by high-intensity pulsed ion beam irradiation, and chemical load from non-aqueous sol-gel thin film deposition respectively, were selected for generating a new surface layer on base materials of components toward an improved surface integrity with desired multiple surface integrity parameters. In all cases, two categories of surface integrity parameters are identified in relation to the functional properties of components, i.e., surface features and surface characteristics, where the former include the features of topography and chemical composition, grain morphology, and phase structure, etc. on surface and subsurface directly created by the surface modification, and the latter include all the physical and chemical properties associated with the new surface layer, such as microhardness, residual stress, electrical potential, optical properties, etc. The surface features and surface characteristics in surface integrity present a synergetic effect on the high performance with combined properties as a result of coupled interactions between the surface integrity parameters. Therefore, the multiple surface integrity parameters controllable with active interactions achieved by surface modification processes effectively improve the surface integrity according to the desired high-performance component of combined properties, enabling a high-performance manufacturing.

Thermo-hydrodynamic process simulation of craters formation and evolution on metal surfaces caused by intense pulsed ion beams

As observed in many studies, craters may appear on the surfaces of metals after irradiation of intense pulsed ion beams (IPIB). These craters limit the utilization of IPIB as a novel method for surface processing in some cases. In this work, taking stainless steel as an example, the hydrodynamic behavior of molten surface formed by IPIB was taken into consideration, by taking IPIB-induced heat transfer and level-set method flow field analysis with finite element method (FEM) we deduced that prior temperature rise by the thermal resistance of grain boundary is the causes of craters. For metals and alloys with relatively higher viscosity and surface tension, the uneven distribution in the curvature and stress in the molten surface leads to the mass redistribution and the flattening trend in the surface morphology.

Influence of high-intensity pulsed ion beam irradiation energy on magnesium alloy surface modification

Magnesium alloys surface modified by high-intensity pulsed ion beam irradiation are studied by MD simulation. The specimens containing defects were modeled to investigate the effect of high-intensity pulsed ion beam irradiation on surface area and defect size. It was found that the surface area mainly depend on the value of irradiation energy. The kinds of defects in the sub-surface have little influence on the surface area. The inner surface of the defect decreases with the increasing irradiation energy. There was a nonlinear relationship between the irradiation energy and the defect size.

Surface morphology, microstructure and properties of as-cast AZ31 magnesium alloy irradiated by high intensity pulsed ion beams

Abstract High intensity pulsed ion beam (HIPIB) irradiation was performed as surface modification to improve the properties of as-cast AZ31 magnesium (Mg) alloys. The surface morphology and microstructure of the irradiated Mg alloys were characterized and their microhardness, wear resistance and corrosion resistance before and after HIPIB irradiation were measured. The results show that the formation of crater on the surface was attributed to the particles impacted from the irradiated cathode material. HIPIB irradiation resulted in more vacancy defects on the surface of the material. Moreover, new dislocations were generated by the reaction between vacancies, and the dislocation configuration was also changed. These variations caused by the HIPIB are beneficial for improving the material properties. After 10 shots of irradiation, the average microhardness increased by 27.1% but the wear rate decreased by 38.5%. The corrosion rate was reduced by 24.8% according to the salt spray corrosion experiment.

Nonlinear Wear Response of WC-Ni Cemented Carbides Irradiated by High-Intensity Pulsed Ion Beam

Surface hardening on WC-Ni cemented carbides was achieved by high-intensity pulsed ion beam (HIPIB) irradiation, with formation of a binderless, densified, and “hilly” remelted top layer of a few μm in depth and a shock strengthened underlayer down to a hundred μm. The tribological behavior of the samples was studied under dry sliding against GCr15 bearing steel on a block-on-ring tribometer with 98 N and 0.47 m/s. The specific wear rate/wear resistance presented an exponential dependence on the surface hardness, in contrast to the commonly reported linear dependence of the specific wear rate or wear resistance on the hardness of WC based cemented carbides among both WC-Ni and WC-Co systems. The original samples underwent a severe abrasive wear due to the Ni binder micro-abrasion and WC grain fragmentation/pullout, whereas the irradiated samples began with a gradual abrasion of the binderless hard tops, followed by a mild abrasive wear accompanied by local adhesive wear. The wear resistance has been also compared with the reported data concerning the relative hardness of friction pairs in a value range of 2–7 on block-on-ring tribometer tests with the friction pairs of WC cemented carbides and steels in unlubricated condition. The nonlinear wear response is explained by the wear mechanism transition otherwise unobtainable in the case of the reported hardening by either lowering the binder content or refining the WC grains. It is revealed that the interfacial bonding enhancement of the WC/binder and the binder strengthening are pronounced for improving the wear resistance of the cemented carbides, by the effective suppressing of the WC grain fragmentation/pullout and binder micro-abrasion, even though they have limited contribution to the hardness enhancement.

Research on Thermo Effects of Silver Modified by High-Intensity Pulsed Ion Beam

We report a modification method for Silver target by high-intensity pulsed ion beam (HIPIB) irradiation. Based on the temporal and spatial distribution models of the ion beam density detected by Faraday cup in the chamber and the ions accelerating voltage, the energy deposition of the beam ions in Ag is calculated by Monte Carlo method. Taking this time-dependent nonlinear deposited energy as the source term of two-dimensional thermal conduction equation, we obtain the temporal and spatial ablation process of metal Ag during a pulse time. The top-layer silver material in thickness of about 0.33μm is ablated by vaporization and the layer in thickness of 1.6μm is melted after one shot at the ion beam density of 300 A/cm2.

Surface and phase transformation characteristics of titanium hydride film under irradiation of pulsed ion beam

Titanium hydride films irradiated by intense pulsed ion beam have been investigated by using scanning electronic microscopy, surface profilometer, X-ray diffraction and secondary ion mass spectroscopy in order to explore the mechanisms of interactions between intense pulsed ion beam and titanium hydride. Three sets of titanium hydride films are irradiated respectively for several times at energy density of 0.1J/cm2, 0.3J/cm2 and 0.5J/cm2. Surface morphologies start to reveal a feature of intense melting and network cracks only after energy density reaches close to 0.5J/cm2. Additionally, desorption of hydrogen from the film has been confirmed by X-ray diffraction, and a titanium dihydride (TiH2(x)) with a body centered tetragonal structure, seldom reported by researchers and formed under extreme conditions, has also been identified under this condition. Depth profile of hydrogen isotope with secondary ion mass spectroscopy seems to suggest that the bulk hydrogen isotope seems to serve as a reservoir for the drainage of top hydrogen, and its fast diffusion can quickly compensate for the exhaustion of top hydrogen isotope atoms.

The Irradiation Effects of Metal Gold Surface by Intense Pulsed Ion Beam

We report a modification method for Gold target by intense pulsed ion beam (IPIB) irradiation. Based on the temporal and spatial distribution models of the ion beam density detected by Faraday cup in the chamber and the ions accelerating voltage, the energy deposition of the beam ions in Au is calculated by Monte Carlo method. Taking this time-dependent nonlinear deposited energy as the source term of two-dimensional thermal conduction equation, we obtain the temporal and spatial ablation process of metal Au during a pulse time. The top-layer Gold material in thickness of about 0.25μm is ablated by vaporization and the layer in thickness of 1.40μm is melted after one shot at the ion beam density of 300 A/cm2.

The effect of high-intensity pulsed ion beam on surface structures of MAO film on magnesium alloy AZ31

Micro-arc oxidation (MAO) films on AZ31 magnesium alloy were modified by high-intensity pulsed ion beam (HIPIB) irradiation with ion energy of 300keV at 200A/cm2 with up to 10 shots. Scanning electron microscopy, X-ray diffractometry and micro-hardness testers were used to characterize the surface properties of the irradiated MAO films. The thickness of remelted layer increased and then decreased, and the maximal value of 10μm was obtained at 200A/cm2 with 5 shots. The phase structure of the ablated surface still consisted of Mg2SiO4 and MgO, which are the same as that of the original ones. Surface roughness of the ablated surface increased and then decreased with the increase of shot number. The surface roughness for the original MAO film is about 2.10μm, it decreased to 1.18μm with 1 shot irradiation and then increased to 4.13μm with irradiation shots up to 10. Correspondingly, the surface energy of the ablated surface augmented, resulting in the tedious decrease of static contact angle from 145.9° for original film to 49.7° for the film with 10 shots. The ablation modification enhanced the continuity and compaction of the MAO films on AZ31 magnesium alloy.

Stability of expanded austenite, generated by ion carburizing and ion nitriding of AISI 316L SS, under high temperature and high energy pulsed ion beam irradiation

Expanded austenite can be generated on austenitic stainless steels either by ion carburizing or ion nitriding. In both cases the resulting fcc crystal structure, supersaturated with nitrogen or carbon, is strongly hardened with improved wear-resistance, while maintaining the original resistance to corrosion. In this work, we have studied the stability of expanded austenite, generated by ion nitriding and ion carburizing on AISI 316L SS with N and C, under: a—high temperature (225°C – 504°C), and b—under irradiation with high energy (30keV – 500keV), high fluence (~1015cm−2), short duration (~400ns) light (deuterium and helium) ion beams. It was found that expanded austenite is stable below 325°C. Between 325°C and 504°C expanded austenite lattice parameter presents gradual reduction with increasing temperature. We observed microstructural changes related only to the temperature treatment. We did not observe any microstructure change due to the duration of the heat treatment. Over 504°C, the lattice parameter returns to the material's austenite original parameter. On the other hand, when irradiated with pulsed ion beams, a gradual reduction of the lattice parameter corresponding to the expanded austenite with the number of pulses was observed. This behavior can be explained through the thermal shock induced on the surface by each beam, consisting in fast heating followed by fast cooling that induces the gradual exo-diffusion of N (or C). Nevertheless, after 20 ion pulses, a final lattice parameter slightly higher than the corresponding to the original austenite was found as stable limit. This residual expansion can be attributed to partial amorphization of the first few micrometers that induces stresses on the crystals of austenite which are closer to the surface layers.

强流脉冲离子束辐照铜靶热效应数值研究

为了研究强脉冲离子束辐照改性铜靶的行为，建立了基于靶室中法拉第杯检测的离子束流密度和离子加速电压时空分布模型；采用蒙特卡罗方法计算了束流在铜靶中的能量沉积，并将这随时间变化的非线性沉积能量作为热传导方程的热源项，计算得到了脉冲期间靶材内部温度场的演化规律。一次脉冲后与液化烧蚀相比，靶材表面较小区域的物质气化烧蚀掉，辐照中心处熔化的厚度最大；气、液化烧蚀厚度随偏离中心位置而减小。当束流密度为300 A/cm2时，中心区域气化烧蚀和液化烧蚀的厚度分别达到0.2微米和1.3微米；脉冲期间热量延纵深方向的传播距离小于2微米。 A modification method for Copper target by intense pulsed ion beam (IPIB) irradiation has been reported. Based on the temporal and spatial distribution models of the ion beam density detected by Faraday cup in the chamber and the ions accelerating voltage, the energy deposition of the beam ions in Cu is calculated by Monte Carlo method. Taking this time-dependent nonlinear deposited energy as the source term of two-dimensional thermal conduction equa- tion, the temporal and spatial ablation process of metal Cu during a pulse time was obtained. Only a little area of mate- rial is ablated off due to the vaporization compared with the melting ablation area on the surface after a shot. The most deep melting depth is in the irradiation centre. The melting and vaporizing thicknesses decrease with the increasing dis- tance from the irradiation centre. The top-layer Copper material in thickness of about 0.2 μm is ablated by vaporization and the layer in thickness of 1.3 μm is melted after one shot under the ion beam density of 300 A/cm2. The thermal transportation along the longitudinal direction in the specimens is less than 2.0 μm during a pulse.

Electrochemical corrosion behavior of modified MAO film on magnesium alloy AZ31 irradiated by high-intensity pulsed ion beam

Micro-arc oxidation (MAO) films on AZ31 magnesium alloy were modified by high-intensity pulsed ion beam(HIPIB) irradiation with ion energy of 300keV at 200A/cm2 with 1–10 shots. A compact and solidified layer was prepared on the irradiated MAO films. The electrochemical impedance spectrum (EIS) of the MAO films in 3.5% NaCl solution was measured with varying the immersion time. The Nyquist plots for EIS showed typical capacitive arc and inductive loop. The diameters for capacitive arc and inductive loop are both increased and then decreased with increasing irradiation shot number, the maximal value for diameters obtained at 200A/cm2 with 5 shots at immersion time of 5h achieved to 6×107Ω and 1.5×105Ω, respectively. With immersion time augment, the diameters for capacitive arc and inductive loop of Nyquist plots both decreased. Based on the results of EIS measurements, appropriate equivalent circuits for the modified layers were proposed to fit the EIS for MAO films. It is found that the enhancement in corrosion property of ablated MAO films is mainly caused by improvement of continuity and compaction of films irradiated by HIPIB, which suppressed the corrosion process by holding back the transfer of electrolyte through the modified films to magnesium substrate during immersion.

Structure and Performance of YSZ Thermal Barrier Coatings Irradiated by High Intensity Pulsed Ion Beam

The thermal barrier coatings (TBC) of the yttria-stabilized zirconia (YSZ) has been deposited by the atmospheric plasma spraying (APS),followed by the irradiation of high intensity pulsed ion beam (HIPIB) with the voltage of 250 KV and the ion current density of 300 A/cm2 and pulsed times of 2, 5, 10 and 20, respectively. The X-ray diffraction (XRD) analysis reveals that the coating is characterized by the tetragonal ZrO2 phase instead of the cubic phase and the original monoclinic phase after the irradiation. The scanning electron micros cope analysis demonstrates that the HIPIB treatment leads to a smooth TBC surface, but produces micro-cracks and round grain at the surface. This implies that the plasma erupts during the ion beam interaction with the coatings with poor thermal conductivity, and the micro-cracks were produced in the cooling process. The isothermal oxidation experiment performed at 1050°C in air and suggests that the oxidation resistance of the coating can be largely enhanced after HIPIB treatment.

Surface nanostructure of a directionally solidified Ni-based superalloy DZ4 induced by high intensity pulsed ion beam irradiation

A high intensity pulsed ion beam (HIPIB) was used to irradiate directionally solidified nickel-based superalloy DZ4 with the following parameters: ion content consisting of Cn+ (30at.%) and H+(70at.%), an accelerating voltage of 250kV, a pulse duration of 70ns, a beam current density of 100A/cm2, irradiation times of 15. As revealed by SEM and TEM, the thermal effect was confined in a ∼1.3μm thick surface zone, in which rapid melting and cooling occurred. A two-phase nanostructured layer of ∼10nm thick was formed on the outmost surface. The component phases are the γ phase and the carbide with a particle size of ∼5–10nm. The presence of dense dislocation networks was observed in depth in the substrate metal, for instance ∼20μm away from the sample surface, which is caused by shock wave impact.

Microstructural evolution and its correlation with hardening of WC-Ni cemented carbides irradiated by high-intensity pulsed ion beam

Modification of WC-Ni cemented carbides was studied by using high-intensity pulsed ion beam (HIPIB) irradiation. Surface hardening can be achieved for all the HIPIB-irradiated surfaces but of different degree at ion current density of 50–300A/cm2 up to 10 shots. Thermal and dynamic process of remelting and ablation under HIPIB irradiation led to significant changes in surface morphology, phase structures and composition of the irradiated surfaces. Gradual transitions to remelting densification, selective ablation of Ni binder and phase transformation from hexagonal α-WC to cubic non-stoichiometric β-WC1−x were found by adjusting the irradiation intensity and shot number, explaining the hardness enhancement of cemented carbides. It is revealed that the densification with defects healing and the lower binder content can significantly enhance the hardness whereas occurrence of the metastable non-stoichiometric phase and limited surface cracking may slightly lower the hardness. The parameter-dependent variation of surface hardening degree is thus attributed to single or multiple contributions from remelting densification, binder removal and phase transformation. It is demonstrated by the HIPIB processing that mechanical properties of WC based cemented carbides may be effectively improved by decreasing the binder phase content and enhancing the bonding strength between carbide grain and binder with less defect density.

铸态AZ31镁合金强流脉冲离子束改性

High intensity pulsed ion beam (C+, H+) irradiation of casting magnesium alloy AZ31 target is carried out with shot times of 1, 5, 10, 20, 30, 50 and 100, respectively. The surface morphologies, phase structure, surface and cross-sectional microhardness ofirradiated samples are characterized. The results show that the shot times of HIPIB irradiation play a great role on the target morphology, subsequent irradiation on the melting crater has previously generated fuzzy or eliminated the trend; melting craters appear again along with increasing the times of irradiation. The surface microhardness increases straightly after the first to 30th irradiation, lying in grain refinement and micro-strain caused by the crystal defects;the 30th to 50th exposure,there is a significant reduction in microhardness,which lies in the evolution of crystal defects, such as dislocation movement leading to the formation of small angle grain boundaries, or even reply recrystallization;the 50th to 100th irradiation slightly reduced the surface hardness, the reason is that radiation's organizational structure and thermodynamic behavior of the surface to reach a steady state. The shock-wave effects the formation of long-hardening.The cross-sectional microhardness away from the surface 30 and 240 m of AZ31,which is 20th irradiation,reach a great value 1.0 GPa and 1.3 GPa,respectively.