Dual-beam Irradiation Research Articles

Dual ion beam irradiation of polymeric materials for the modification of optical properties with improved adhesion

Metallic (chromium) coating has often been applied on the surface of polymeric components, mainly to improve their appearance with a metallic luster and to protect from degradation under UV and visible light. However, the toxic nature of hexavalent chromium and delamination problems are an increasing concern in the plating industry. A similar metallic luster and the UV–visible light protection can be achieved by treating the surface of polymers by ion beams. However, a degradation by weathering including cracks, loss of glossiness, blistering, and eventual delamination have been problematic for ion beam processed polymers, particularly with a single ion beam irradiation. The main cause of adhesion failure is the abrupt change in material properties at the interface between coating and polymer or ion beam treated surface and the underlying untreated bulk polymer. In this work, therefore, a method is developed that improves adhesion by producing a graded interface by employing a dual ion beam processing. For demonstration purposes in this work, polycarbonate/acrylonitrile butadiene styrene blends were irradiated first with nitrogen ions followed by helium ions, achieving the desired metallic luster with improved adhesion. The experimental findings are explained in light of the stopping range of ions in materials and their interaction mechanisms with polymeric materials.

Effect of He-pre-injection on dislocation loop formation and irradiation-induced segregation of Fe–12%Cr–15%Mn austenitic steel

The effect of He-injection on irradiation-induced segregation of aging treated Fe–12%Cr–15%Mn austenitic steels, which are candidate materials as the reduced radio-activation of structure material for nuclear and/or fusion reactors was investigated by using the 1250kV high voltage electron microscope (HVEM) connected with an ion accelerator. The Fe–Mn–Cr steel has been irradiated at 573K by three irradiation modes of single electron-beam irradiation, electron-beam irradiation after He-injection and electron/He+-ion dual-beam irradiation in a HVEM. Irradiation-induced segregation analyses were carried out by an energy dispersive X-ray analyzer (EDX) in a 200kV FE-TEM with beam diameter of about 0.5nm. Dislocation loops with strain contrast were formed during irradiation and the loop numbers density increased rapidly with irradiation dose for He-pre-injected specimens. Voids were not observed after irradiations with three irradiation modes up to 5.4dpa at 573K. Irradiation-induced segregations of Cr and Mn near grain boundary were observed in each irradiation condition, but the amounts of Mn segregation decreased in the cases of electron/He+-ion dual-beam irradiation compared with single electron-beam and electron-beam irradiation after He-injection conditions.

Dual-beam irradiation of friction stir spot welding of nanostructured ferritic oxide dispersion strengthened alloy

Nanostructured ferritic oxide dispersion strengthened (ODS) alloys usually contain a high density of Y–Al–O and Y–Ti–O nanoparticles, high dislocation densities and fine grains. Friction stir spot welding (FSSW) is a very promising technique for the joining of ODS materials without oxide particle agglomeration and loss in mechanical properties in the weld zone. Heating and severe plastic deformation can significantly alter the originally as-received material. The local microstructure determines the weld mechanical properties, which are analyzed by nanoindentation. The FSSW region consists of three different zones: the base material, the thermo-mechanically affected zone and the heat affected zone. Irradiation of the FSSW area was performed with a Fe+/He+ dual ion beam. Hardness changes within the welding zones and variation with irradiation damage are discussed.

Dual-beam irradiation of α-iron: Heterogeneous bubble formation on dislocation loops

In order to understand the evolution of materials under irradiation conditions similar to those in future fusion reactors, we have irradiated high purity iron in situ in a transmission electron microscope with 1 MeV Fe + ions while simultaneously implanting 15 keV He + ions, at 500 °C. Once ∼1 dpa/500 appm He were reached, helium bubbles and large dislocation loops were observed. The study reveals that helium bubbles nucleated heterogeneously: a majority of them were observed inside the large dislocation loops.

Swelling of CLAM steel irradiated by electron/helium to 17.5 dpa with 10 appm He/dpa

To investigate irradiation/helium effects on microstructure of China Low Activation Martensitic (CLAM) steel, single beam (e−) and dual-beam (e−/He+) irradiation to 17.5 dpa with 10 appm He/dpa at 400 °C and 450 °C on CLAM steel was carried out with high voltage electron microscope HVEM. Evolution of microstructure was in situ observed during irradiation and annealing procedure. Preliminary results showed that size and density of voids and helium bubbles increased with irradiation dose. And swellings of voids and bubbles are ∼0.5% and 1–1.5%, respectively after irradiation.

Dual beam irradiation of nanostructured FeCrAl oxide dispersion strengthened steel

Nanostructured ferritic oxide dispersion strengthened (ODS) alloy is an ideal candidate for fission/fusion power plant materials, particularly in the use of a first-wall and blanket structure of a next generation reactor. These steels usually contain a high density of Y–Ti–O and Y–Al–O nanoparticles, high dislocation densities and fine grains. The material contains nanoparticles with an average diameter of 21 nm and was treated by several cold rolling procedures, which modify the dislocation density. Structural analysis with HRTEM shows that the chemical composition of the initial Y 2O 3 oxide is modified to perovskite YAlO 3 (YAP) and Y 2Al 5O 12 garnet (YAG). Irradiation of these alloys was performed with a dual beam irradiation of 2.5 MeV Fe +/31 dpa and 350 keV He +/18 appm/dpa. Irradiation causes atomic displacements resulting in vacancy and self-interstitial lattice defects and dislocation loops. Extended SRIM calculations for ODS steel indicate a clear spatial separation between the excess vacancy distribution close to the surface and the excess interstitials in deeper layers of the material surface. The helium atoms are supposed to accumulate mainly in the vacancies. Additionally to structural changes, the effect of the irradiation generated defects on the mechanical properties of the ODS is investigated by nanoindentation. A clear hardness increase in the irradiated area is observed, which reaches a maximum at a close surface region. This feature is attributed to synergistic effects between the displacement damage and He implantation resulting in He filled vacancies. Fine He cavities with diameters of a few nanometers were identified in TEM images.

Irradiation effects in nanostructured FeCrAl oxide dispersion strengthened steel

Nanostructured ferritic oxide dispersion strengthened (ODS) alloy is an ideal candidate for fission/fusion power plant materials, particularly in the use of a first-wall and blanket structure of a next generation reactor. These steels usually contain a high density of Y-Al-O nanoparticles, high dislocation densities and fine grains. The material contains nanoparticles with an average diameter of 21 nm. Irradiation of these alloys was performed with a dual beam irradiation of 2.5 MeV Fe+/31 dpa and 350 keV He+/18 appm/dpa. Irradiation causes atomic displacements resulting in vacancy and self-interstitial lattice defects and dislocation loops. Additionally to structural changes, the effect of the irradiation generated defects on the mechanical properties of the ODS is investigated by nanoindentation. A clear hardness increase in the irradiated area is observed, which reaches a maximum at a close surface region. This feature is attributed to synergistic effects between the displacement damage and He implantation resulting in He filled vacancies

Multiple-beam irradiation effects in electron-beam-welded F82H joint

Electron-beam-welded reduced-activation ferritic/martensitic steel F82H, which is one of prime candidate materials for experimental fusion reactors, have been irradiated by electron and helium ion beams using a High Voltage Electron Microscope (HVEM) as the experimental evaluation of the modeling and simulations. Growth rate and saturated number density of dislocation loops have been measured to calculate the migration energies of point defects. Electron irradiation experiment indicated that net migration energy of vacancy in the welded metal of F82H tended to be lower compared to that in base metal, which could be relating to difference of carbon concentration in matrix. In the case of dual beam (electron and helium) irradiation, net migration energies of vacancy were slightly higher than that in electron beam irradiation. This result indicates that vacancy would be trapped by implanted helium due to their strong interaction and appeared to have higher migration energy.

HRTEM study of oxide nanoparticles in K3-ODS ferritic steel developed for radiation tolerance

Crystal and interfacial structures of oxide nanoparticles and radiation damage in 16Cr–4.5Al–0.3Ti–2W–0.37 Y 2O 3 ODS ferritic steel have been examined using high-resolution transmission electron microscopy (HRTEM) techniques. Oxide nanoparticles with a complex-oxide core and an amorphous shell were frequently observed. The crystal structure of complex-oxide core is identified to be mainly monoclinic Y 4Al 2O 9 (YAM) oxide compound. Orientation relationships between the oxide and the matrix are found to be dependent on the particle size. Large particles (>20 nm) tend to be incoherent and have a spherical shape, whereas small particles (<10 nm) tend to be coherent or semi-coherent and have a faceted interface. The observations of partially amorphous nanoparticles and multiple crystalline domains formed within a nanoparticle lead us to propose a three-stage mechanism to rationalize the formation of oxide nanoparticles containing core/shell structures in as-fabricated ODS steels. Effects of nanoparticle size and density on cavity formation induced by (Fe 8+ + He +) dual-beam irradiation are briefly addressed.

Superior Radiation Resistance of ODS Ferritic Steels

The oxide dispersion strengthened (ODS) ferritic steel and non-ODS reduced-activation ferritic (RAF) steel were irradiated at 773 K by means of a dual-beam ion irradiation technique to a dose of 0.4 dpa with simultaneous helium implantation up to 1000 appm. Microstructural changes were investigated by transmission electron microscopy. The RAF steel showed a preferential formation of cavities at grain boundaries, precipitate interfaces and dislocations. In contrast, the ODS ferritic steel showed a homogeneous and fine distribution of cavities in the matrix. This paper discusses the superior resistance of the ODS ferritic steel against development of cavities in terms of the effects of nano-oxide particles dispersed in the matrix.

Effect of hydrogen ion/electron dual-beam irradiation on microstructural damage of a 12Cr-ODS ferrite steel

The effect of hydrogen ion/electron dual-beam irradiation on the microstructural evolution of a new 12Cr-ODS ferrite steel made by chemical soaking method (CSM) was investigated. The results showed that the dislocations were introduced at the initial stage of irradiation and then developed into dislocation networks. The void swellings after the irradiation to a dose of 15 dpa were less than 0.15%. The interface between the dispersed oxide particle and the matrix became irregular due to the irradiation; while the macroscopic size change of the oxide particle was not recognized, thus suggesting that the steel had a good resistance to irradiation during the dual-beam irradiations between 623 K and 823 K. The formation of voids with small mean size and high number density was closely concerned with hydrogen which would assist the void nucleation as a result of hydrogen ion trapping vacancies during the irradiation.

Stability of Y–Ti complex oxides in Fe–16Cr–0.1Ti ODS ferritic steel before and after heavy-ion irradiation

The mechanical strength of oxide dispersion strengthened (ODS) ferritic steels depends on the dispersion and microstructural stability of the oxide particles. Yttria is normally selected as dispersion particles to strengthen ODS ferritic steels, and other additional elements such as titanium and aluminum are added to obtain finer dispersion particles for the improvement of the mechanical properties of the ODS steels. Kyoto University is involved with the development of new ODS ferritic steels. 16Cr–0.1Ti–0.35Y 2O 3 ODS steel is a fusion structural material. In this research, the irradiation resistance of 16Cr–0.1Ti–0.35Y 2O 3 (16Cr0.1Ti) ODS steel was investigated by high-resolution TEM and by performing an ion irradiation experiment. The ODS steel was consolidated by hot extrusion at 1150 °C and annealed at 1050 °C for 1 h for recrystallization. Oxides in 16Cr0.1Ti ODS steel were characterized by HRTEM and STEM-EDX and specified as (Y, Ti) complex oxides with an atomic ratio of Y:Ti = 2:1. A 1.7 MeV tandem accelerator for heavy-ion irradiation at the dual-beam material irradiation facility for energy technology (DuET), Kyoto University, was used to introduce irradiation damages in materials. The comparison of the dispersion, shape, and chemical composition of the oxides between the pre- and post-irradiated materials revealed that (Y, Ti) complex oxides were stable under the ion irradiation up to 60 dpa at 650 °C.

JANNUS: experimental validation at the scale of atomic modelling

Ion irradiation is well suited to simulate neutron irradiation because primary knock-on atoms (PKA) produced by neutron collisions are self ions of the target. As the main difference, the energy spectrum of ion-produced PKAs is somewhat broader than in the case of fast neutrons. Studies of the combined effects of target damaging, ion implantation effects, helium and hydrogen production, and the occurrence of nuclear reactions should be performed by co-irradiation experiments (dual or triple beam irradiation). The JANNUS project (Joint Accelerators for Nanosciences and NUclear Simulation) was started in 2002 in the frame of a collaboration between CEA (Commissariat à l'Énergie Atomique) and CNRS–IN2P3 (Centre National de la Recherche Scientifique–Institut National de Physique Nucléaire et de Physique des Particules). Two experimental sites are involved. At Saclay, three electrostatic accelerators are being coupled: a new 3 MV Pelletron™ machine equipped with an ECR multi-charged ion source, a 2.5 MV single ended Van de Graaff and a 2.25 MV General Ionex tandem. At Orsay, the 2 MV tandem ARAMIS and the 190 kV ion implanter IRMA are being coupled with a 200 kV TECNAI™ transmission electron microscope to allow simultaneous co-irradiation and observation. This paper will first discuss both advantages and limitations of the use of ion beam irradiation to simulate neutron irradiation. A technical description of both set-ups is then presented, and some details will be given concerning multi-irradiation facilities running worldwide. The main application fields of JANNUS will be further detailed. To cite this article: Y. Serruys et al., C. R. Physique 9 (2008).

Microstructural evolution analysis of NITE SiC/SiC composite using TEM examination and dual-ion irradiation

Irradiation effects in a SiC/SiC composite reinforced by Tyranno-SA fibers and produced by an innovative processing method, nano-powder infiltration and transient eutectic phase (NITE) processing, were investigated. Dual-beam ion irradiation methods and energy-filtered transmission electron microscopy were used in the investigation. The NITE SiC matrix had dense, isotropic grains several hundreds nm in diameter. A small amount of secondary phases from residual additives were found within the SiC fiber bundles. Dual-ion irradiations achieved a dose of 60 dpa at 1200 °C. TEM investigation showed no significant modification by irradiation in either the Tyranno-SA fibers or the NITE SiC matrix, except for a small amount of micro-cavity formation. The synergistic effects of heavy irradiation and helium atoms in NITE SiC/SiC composites at elevated temperature are discussed.

Laser Singulation of Thin Wafers &amp; Difficult Processed Substrates: A Niche Area over Saw Dicing

Laser beam has found its more extensive applications in microelectronics industry based on the advantages of low cost, non-contact and fast speed microfabrication. In this paper, laser singulation to separate wafer and multi-layer device structures is studied. It shows that laser can achieve superior cutting quality challenged to mechanical dicing saw with the proper tuning of laser processing parameters. Heat induced crack during the laser irradiation is discussed. Critical issues which are limiting laser application to singulation, such as surface contamination, laser power and balance between cutting speed & edge quality are investigated. It is found that laser singulation can find its niche area over saw dicing to separate thin wafers & difficult processed substrates with special designed approaches. Techniques on pocket scanning and dual laser beam irradiation are developed for multi-layer devices.

Proton-HZE-Particle Sequential Dual-Beam Exposures Increase Anchorage-Independent Growth Frequencies in Primary Human Fibroblasts

The radiation field in deep space contains high levels of high-energy protons and substantially lower levels of high-atomic-number, high-energy (HZE) particles. Calculations indicate that cellular nuclei of human space travelers will be hit during a 3-year Mars mission by approximately 400 protons and approximately 0.4 HZE particles. Thus most cells in astronauts will be hit by a proton(s) before being hit by an HZE particle. To investigate effects of dual ion irradiations on human cells, we irradiated primary human neonatal fibroblasts with protons (1 GeV/nucleon, 20 cGy) followed from 2.5 min to 48 h later by iron or titanium ions (1 GeV/nucleon, 20 cGy) and then measured clonogenic survival and frequency of anchorage-independent growth. This frequency depends on the interval between hydrogen- and iron-ion irradiation, with a critical window between 2.5 min and 1 h producing about three times more anchorage-independent colonies per survivor than expected from simple addition of the two ions separately. The hydrogen-titanium-ion dual-beam irradiation produced similar increases that persisted to approximately 6 h. At longer intervals, anchorage-independent growth frequencies were similar to those expected for additivity. However, irradiation of cells with either an iron or a titanium particle first followed by protons produced only additive levels.

Effect of Helium and Aging Treatment on Radiation Damage Behavior in Low Activation Fe-Cr-Mn (W, V) Alloy

The effects of helium and aging treatment on radiation damage behavior in low activation Fe-Cr-Mn ( W, V) alloy were investigated by electron and helium ion dual-beam irradiation in a high voltage electron microscope. Specimens were aged at 673 K, 823 K and 923 K for 1000, 3000 and 10000 hours. Electron and He ion dual-beam irradiations were performed at 627 K to 10 dpa. M23C6 type carbides were precipitated in the aged specimens, and the amount of the precipitates was increased with increasing aging temperature and aging time. He bubbles were formed during dual-beam irradiation in all of the specimens. The cavity swelling under dual-beam irradiations was increased with increasing the aging temperature and aging time. It was suggested that cavity swelling is closely related to the concentration of solutes such as Cr and C in the matrix, namely cavity growth rate becomes higher with decreasing of the solutes in solution.

Effect of He-Injection on Irradiation Damage of High Mn-Cr Steel

The high Mn-Cr austenitic steel for structure material of nuclear and/or fusion reactors from the point of view of the reduced radio-activation has been irradiated by using three irradiation modes of electron-beam irradiation, electron-beam irradiation after He-injection and electron/He+-ion dual-beam irradiation in 1250kV high voltage electron microscope (HVEM) connected with an ion accelerators to study the effect of He-injection on irradiation damage. Irradiation-induced segregation analyses were carried out by an energy dispersive X-ray analyzer (EDX) in a 200kV FE-TEM with beam diameter of about 0.5nm. Void formation was not observed in each irradiation condition. Grain boundary migration was observed in the case of electron/He+-ion dual-beam irradiation. Irradiation-induced segregations of Cr and Mn at grain boundary were observed in each irradiation condition. The amounts of Cr and Mn segregation decreased in the cases of electron-beam irradiation after He-injection compared with other irradiation conditions.

Damage Behavior of Electron/Helium Dual-Beam Irradiation on Fe-Cr-Mn (W, V) Alloy

The effect of helium on irradiation damage behavior in Fe-Cr-Mn(W,V) steel was investigated by electron/helium ion dual-beam irradiation. The results indicate that helium can promote the increase of dislocation density and enhance the void nucleation and void swelling of Fe-Cr-Mn(W、V) alloy. The segregation of solute elements near grain boundary was suppressed by existence of helium. Also the interface of carbide-matrix migration and the change of solute concentration near the interface were observed during dual-beam irradiation.

Synergistic effect of displacement damage and helium atoms on radiation hardening in F82H at TIARA facility

Micro-indentation hardness was measured for the irradiated F82H steels by single (10.5 MeV Fe 3+) beam or dual (10.5 MeV Fe 3+ and 1.05 MeV He + ions) beam at the TIARA facility in JAERI. The extra component of radiation hardening due to helium was slightly detected in the dual-beam (10 appmHe/dpa) irradiation at 633 K up to 33 dpa. As increased the ratio of He/dpa (100 appmHe/dpa), the extra component due to helium was increased. The microstructures in single/dual (10 appmHe/dpa) ion beam irradiated F82H steels consisted of interstitial loops and defect clusters at 50 dpa. However, at a higher ratio of He/dpa (100 appmHe/dpa), nano-voids were also observed in dual ion irradiated F82H.