Search

Development of fine grain 316L with small amount of TiC for high radiation-tolerant performance was tried considering the fabrication process of thermo-mechanical treatments. The materials obtained are UFG316L+2.0 mass% TiC with the grain size of 90–270 nm, depending on the final annealing temperature from 700 ℃ to 900 ℃. The materials were examined by transmission electron microscopy observation, X-ray absorption near-edge structure spectroscopy, high voltage electron microscope electron irradiation and stress corrosion cracking by crevice bent beam method in high-temperature water with 8 ppm dissolved oxygen. The test results showed that the material is generally of excellent quality. Especially void swelling induced by the electron irradiation at 400 ℃ is less than 1/10 compared to the commercial SUS316L.

Four π∗ resonance peaks were observed in the B-K near edge x-ray absorption fine structure spectra of boron nitride thin films prepared by magnetron sputtering. In the past, these peaks have been explained as the K-absorption of boron atoms, which are present in environment containing nitrogen vacancies, the number of which is 1–3 corresponding to the three peaks at higher photon energy. However, the authors found that there was a strong correlation between the intensities of these three peaks and that of O-K absorption after wide range scanning and simultaneous measurement of nitrogen and oxygen K-absorptions of the BN films. Therefore, the authors conclude that these three peaks at the higher energy side correspond to boron atoms bound to one-to-three oxygen atoms instead of three nitrogen atoms surrounding the boron atom in the h-BN structure. The result of the first-principles calculation with a simple cluster model supported the validity of this explanation.

Novel precision machining using gas cluster ion beams (GCIB) is proposed to fabricate a small lens or free-surface mold. Properties of GCIB such as surface smoothing, high-rate etching and ease of forming a collimated beam are promising for novel precision machining. In this study, GCIB machining of a small mold (0.56 mm in diameter) and a free-surface mold was demonstrated. Before irradiation, a hillock (height 195 nm and width 240 μm) was observed on the center of the mold. By collimated GCIB irradiation with precise ion dose and position controls, the difference between designed and measured shape was decreased from 195 to 26 nm. Also, free-surface mold fabrication was demonstrated using position controlled GCIB. The error of etching depth from the designed shape was 10 nm for free-surface mold.

In order to overcome the irradiation embrittlement in metallic materials, ultra-fine grained SUS316L steels with their grain sizes between 0.1 and 1 μm have been developed by mechanical alloying, and nanocrystalline Ni and Ni–W alloys with their grain sizes between about 6 nm and 20 μm have been developed by electrodeposition. In order to clarify the effects of the neutron irradiation on mechanical properties of the nanocrystalline materials, Vickers microhardness measurements and transmission electron microscopy (TEM) were performed before and after the irradiation of 1.14 × 10 23 and 1.14 × 10 24 n/m 2 . When the grain sizes were less than about 0.3 μm in the SUS316L and the Ni–W alloys, Vickers hardness was almost unchanged, and the irradiation defects could not observed by TEM.

Surface segregation phenomena of several transition elements (Fe, Ni, Mn, Co, Cr) in high purity aluminum foils annealed at various temperatures were studied by Rutherford back scattering spectroscopy (RBS) and transmission electron microscopy (TEM). These all elements segregated at the foil surface and detail segregation position was the interface between aluminum oxide and matrix. The degree of surface segregation (α=surface segregation composition/foil composition) depended on the element, annealing temperature and initial foil composition. The empirical rule for the surface segregation was obtained in this study as follows: the maximum α of each element was roughly dependent on the inverse of solid solubility of each element in aluminum.

Austenitic stainless steel specimens of type 316SS were irradiated by 200 keV He + ions or 200 keV N + ions. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were employed to study the fine surface deformation of the irradiated specimens. At the high temperatures of He + ion irradiation, distinct swelling was observed at grain interior and grain boundaries by AFM and helium bubbles were found by TEM. It is suggested that helium atoms agglomerate in high doses and high temperatures. The nanometer-level step height of surface swelling induced by He + ion irradiation has obvious dependence on the irradiation dose and temperature. In the case of N + ion irradiation, the swelling was observed at grain interior but the step height was less remarkable than in the case of He + ions. The swelling is induced by void formation. The caved-in grain boundaries were recognized in N + ion irradiated area.

Surface segregation of Pb in Al-0.13–13 at.-ppm Pb foils and Fe in Al-6–140 at.-ppm Fe foils after heat treatment was studied by Rutherford back-scattering spectroscopy (RBS) and transmission electron microscopy (TEM). The degree of segregation (segregated composition/foil composition) was greater than 1500 in the Al–Pb system but is less than 160 in the Al–Fe system. The maximum segregation temperature was 923 K in the Al–Pb system, but was 723 K in the Al–Fe system. Lead segregated not to the aluminum surface but to the oxide film. Iron, however, segregated at the aluminum surface, i.e., at the interface of the oxide film/aluminum matrix.

Sputtering processes of silicon in the bombardment of highly charged ions (HCIs) are studied using molecular dynamics simulation. Assuming the potential energy of the HCI transferred to target is stored as the electrostatic energy of Si atoms ionized by the HCI, the Si ions up to 375 are embedded on a Si(1 0 0) surface as an initial condition, resulting in Coulomb explosion. The dynamics of particle ejection (sputtering) from the surface and crater formation on the surface are simulated. The formation and propagation of shock wave and rapid increase of the sputtering yield are seen during relaxation process. Strong dependence of the sputtering yield on the HCIs potential energy is found and discussed in comparison with experiment.

Fe–TiN, Ni–TiN, and SUS316–TiC nanocomposite powders were prepared by ball-milling Fe–Ti, Ni–Ti, and SUS316–TiC powder mixtures in a nitrogen or argon gas atmosphere. Fe–63vol.% TiN and Ni–44–64vol.% TiN milled powders were dynamically compacted by use of a propellant gun to produce bulk materials of nanocrystalline structure and having grain sizes between about 5 and 400 nm. SUS316–2.8–5.6vol.% TiC milled powders were consolidated by hot isostatic pressing (HIP) to produce bulk materials having grain sizes between about 100 and 400 nm. The possibility of using fine-dispersed TiN/TiC particles to pin grain boundaries and thereby maintain ultra-fine grained structures of grain sizes down to the nanocrystalline scale has been discussed.

Surface segregation of iron in high purity aluminum alloys, containing 50 and 280 ppm iron, was investigated by Rutherford back scattering spectroscopy (RBS) and transmission electron microscopy (TEM). The specimens were heat treated at various temperatures ranging from 423 K to 923 K for 72 ks in Ar atmosphere. The surface segregation of iron by heat treatment was detected by RBS measurement. The strongest segregation was observed in the Al–280 ppmFe annealed at 723 K for 72 ks. The surface segregation quantities in Al–50 ppmFe alloy was smaller than those in Al–280 ppmFe alloy, but the degree of segregation (segregation concentration/bulk concentration) in Al–50 ppmFe alloy was larger than that in Al–280 ppmFe alloy. TEM–EDX indicated that almost of iron segregated at the interface between oxide film and the matrix, but a few iron in the oxide films just above aluminum matrix was detected.

O2 cluster ion assisted deposition was demonstrated to form optical multilayer films for advanced optical communications. With O2 cluster ion assisted deposition, high refractive index 2.20 at 550 nm and very smooth surface (Ra=0.37 nm) of Ta2O5 films were realized. From a scanning electron microscope (SEM) image, dense film structure were observed without porous or columnar structures at the O2 cluster ion assisted layers. The surface and interface of Ta2O5/SiO2 multilayer films were very flat due to surface smoothing effect of cluster ion beams, and it can be realized even though the beneath surface was rough. The shift of a center wavelength of multilayer film was quite small after an environmental test.

Austenitic stainless steel specimens of Type 316SS were irradiated with 200 keV He+ or N+ ions, and the irradiated specimen surfaces were observed by atomic force microscopy (AFM). At the ion irradiation in high temperatures the specimens show surface step-up. In case of He+, the surface swelling is remarkable and increases linearly with He ion fluence, which indicates the swelling is due to formation of He bubbles. The irradiated surface is sometimes in irregularity, especially at and near grain boundary, remarkable ridging is observed. In case of N+, the surface step-up is less remarkable compared with He+. The swelling shows a so-called bi-linear behavior, i.e. a threshold of N+ fluence appears and beyond the threshold the swelling increase is almost linearly presumably due to evolution of voids induced by the N+ irradiation in high temperature. Denudation of void formation adjacent to grain boundary is recognized.

In order to investigate the secondary ion emission from the surface of conductive materials bombarded by highly charged heavy ions, we have done two types of experiments. First, we have measured the yield of the sputtered ions from the surface of solid targets of conductive materials (Al, Si, Ni, Cu) bombarded by Xeq+ (q=15–44) at 300 keV (v p =0.30 a.u ) and at 1.0 MeV (v p =0.54 a.u ) . In view of the secondary ion yields as a function of the potential energy of the projectile, the increase rates below q=35, where the potential energy amounts to 25.5 keV, were rather moderate and showed a prominent increase above q=35. These phenomena were rather strong in the case of the metal targets. Second, we have measured the energy dependence of the yield of the sputtered ions from the surface of solid targets of conductive materials (C, Al) bombarded by Xeq+ (q=30,36,44) between 76 keV (v p =0.15 a.u ) and 6.0 MeV (v p =1.3 a.u ) . A broad enhancement of the secondary ion yield has been found for Al target bombarded by Xe44+. From these experimental results, the electronic excitation effects in conductive materials for impact of slow highly charged heavy ions bearing high potential energy is discussed.

Surface segregation of Pb in the annealed Al-foils has been studied by Rutherford back scattering spectroscopy (RBS) and transmission electron microscopy (TEM). High-purity Al-foils containing 100 mass-ppm Pb were heat-treated for 1 h or 4 h at 540°C. Almost all of Pb segregate in a thin layer, 0.1 μm from the surface. Lead contents in the Pb-enriched surface layers were estimated to be 0.1∼0.14 at% Pb which were about 100–fold higher than the initial bulk concentration. TEM observations show that Pb-particles are formed at foil surfaces and their size increases from about 80 nm to 240 nm when final annealing time increases from 1 h to 4 h at 540°C. The Pb particles have a cube-cube orientation relationship with Al matrix and are bounded by {100} and {111} facets.

Atomic force microscopy (AFM) was employed to confirm the validity for studying the surface deformation by radiation damage. Distinct swelling was noted by AFM observation in austenitic stainless steel SUS316 specimens which were irradiated by 200 keV He + ions in the range of dose from 2.4×10 16 He / cm 2 (0.6 dpa) to 7×10 17 He / cm 2 (17.5 dpa) at 673, 773, 823 and 873 K. The step height due to He ion-induced swelling showed an obvious dependence on irradiation dose and temperature. It was found for the first time that sharp ridging along the grain boundaries occurred, suggesting He atom agglomeration at high doses and temperatures.

The radiation damage and the radiation-induced segregation (RIS) in type 304 austenitic stainless steel single crystal were investigated with 1.6 MeV He ion irradiation up to 2.5 × 1017 cm−2 at RT by using RBS and PIXE with channeling conditions (RBS-C and PIXE-C). By the RBS-C experiments, it is found that radiation-induced damage for (1 1 0) orientation increased more slowly than those for (1 0 0) and (1 1 1) orientations with He ion dose. By the PIXE-C experiments, it is found that the Si atoms are displaced from the lattice sites and segregate significantly to the surfaces of (1 0 0), (1 1 0) and (1 1 1) orientations and the S atoms also seem to be enriched slightly in the (1 0 0) and (1 1 0) surfaces during He ion irradiation.

Effects of Ni ion implantation on MgO (1 0 0) single crystals were examined by Rutherford backscattering spectrometry with channeling and optical absorption measurements. Ni ions with energy of 1.0 MeV and 200 keV were implanted at room temperature in the dose range, 1 × 1015–1 × 1017 cm−2. By applying thermal annealing method, recovery of the radiation induced damage was followed and the distribution and lattice location of implanted Ni ions was analyzed. It was observed that the radiation induced defects in the as-implanted sample were formed near Ni ion distribution, which is different from the theoretical prediction by the E-DEP-1 code. After thermal annealing above 500°C, defects began to recover, and rapid recovery of the lattice order and simultaneous diffusion of implanted Ni were observed above 1100°C until they reach full recovery at 1400°C. A part of these changing phenomena was supported by the optical absorption measurements.

Nitrogen ions were implanted in high purity titanium at various doses. The nitride phase, TiN, was identified using either grazing incidence X-ray analysis or transmission electron microscopy. AES depth profile of nitrogen was altered from Gaussian-like to a rectangle with increasing nitrogen doses. Both dissolved nitrogen and tendency to form TiN increased precipitates with increasing nitrogen doses. These TiN precipitates that size were several tens of nm were observed at a lower dose. They grew larger as nitrogen dose increased. The dynamic ultra-microhardness rose to a thickness of within 200 nm of the surface owing to TiN formation, resulting in improved wear resistance of titanium. The wear volume was minimum at a dose of 5×10 21 N 2 + m −2 .

We have measured the yield of the sputtered ions from the surface of solid targets of conductive materials (Al, Ni, Cu, Ag, Si) bombarded by Xe q + ( q =15–44) at 1.0 MeV ( v p =0.55 a.u). The experiment was performed using micro-bunched highly charged Xe ion beams from CRYEBIS at Kansas State University. The secondary ions were detected and mass analyzed by a TOF spectrometer. The secondary ion yields showed a significant increase with increasing projectile charge state q , demonstrating the electronic sputtering in the interaction of slow highly charged ions with conductive materials. The increase rate became larger above q =26 compared to lower charge states, and showed a more prominent increase above q =35. These strong onsets of the increase rate at particular incident charge states can be attributed to the opening up of new inner shell holes in the incident highly charged ions. This is the first systematic observation of electronic sputtering of conductive materials using slow highly charged heavy ions bearing high potential energy.

Helium bubble structure was examined on a helium-implanted stainless steel after applying two kinds of heat input. Helium ions were implanted on Type 304 stainless steel at 573 K from 2 to 200 appm to a peak depth of 0.5 μm from the surface. After that, weld thermal history was applied by an electron beam. The cooling rates were selected to be 370 and 680 K/s from 1023 to 773 K. TEM observation revealed that nucleation and growth of helium bubbles were strongly dependent on the cooling rate after welding and the helium concentration.

The effects of columnar defects with splayed configurations on flux pinning and flux creep were investigated experimentally. Parallel columnar defects and splayed columnar defects were introduced into specimens of La2−xSrxCuO4 by high-energy heavy-ion irradiation. A large enhancement of the flux pinning and the critical current density Jc due to the splayed columnar defects was observed. At temperature T

We have measured the fluence dependence of the c -axis lattice parameter in EuBa 2 Cu 3 O y (EBCO) irradiated with various ions from He to Au over the wide energy range from 0.85 MeV to 3.80 GeV. We have observed a linear increase of the c -axis lattice parameter with increasing fluence for all irradiations. The slope of c -axis lattice parameter against fluence, which corresponds to the defect production rate, is separated into two contributions; the effect via elastic displacement and the effect via electronic excitation. The former contribution exhibits a linear increase against the nuclear stopping power, S n . The latter contribution is scaled by the primary ionization rate, d J /d x , rather than by the electronic stopping power, S e , and is nearly proportional to (d J /d x ) 4 .

An X-ray crystal spectrometer using a position sensitive proportional counter combined with tandem microbeam line at Osaka National Research Institute have been developed. This system realizes high energy resolution PIXE analysis using a heavy ion microbeam (E < 6 MeV) with reasonable detection efficiency. The design of the spectrometer, such as detection geometry, detectable energy range and energy resolution, are described. This system was applied to high energy resolution PIXE analysis of Ti, SUS and Si with 2 MeV proton and 5 MeV Si3+ focused or collimated beams. The best energy resolution was 2 eV for the Si Kα line.

Magnetization measurements were performed on polycrystalline La 1.85 Sr 0.15 CuO 4 irradiated by 40 Ar ions with high energy of 13 GeV and 26 GeV up to 3.0 × 10 11 ions/cm 2 . An enhancement of magnetic irreversibility was observed. However the critical current density J c did hardly change after irradiation, suggesting a little effect on the magnetic flux-line pinning. On the other hand, a large increase in the lattice parameter c was found in the Ar ion irradiation at the energy as high as 13 and 26 GeV in comparison with that in the low-energy irradiation.

The implantation with nitrogen ions accelerated at 150 kV has been performed on sheets of high purity iron (99.99%) annealed for 1.8 ks at 773 K and/or cold-rolled with 90% reduction. Dose of the ions was changed in the range of 8 × 1018 to 4 × 1020 N2+/m2. Hardness increased for a wide range in depth and its increments is large in the deformed specimen compared with the annealed and implanted specimen. Iron nitride, Fe16N2 (α″), is formed in both the deformed and the annealed specimens, and the size of α″ particle in the former is smaller than that in the latter. The formation of α″ in the deformed specimen is accompanied by the disappearance of dislocation substructures.

Elastic recoil detection analysis (ERDA) using 16 MeV 16 O 5+ ions as a probe, was applied to measure depth distribution of implanted deuterium in polycrystalline nickel specimens. Depth distribution of deuterium in helium pre-irradiated nickel at room temperature was in good agreement with the calculated damage distribution induced by the deuterium and helium ions, while no adequate correlation of deuterium distribution with radiation induced defects was observed in the specimens implated with only deuterium. It was found that deuterium can easily migrate at room temperature in helium non-irradiated nickel. It was suggested that the implanted deuterium was trapped in the helium associated damage.

Depth distribution of ion-implanted deuterium in polycrystalline nickel specimens was measured and the effect of preimplanted helium to the deuterium distribution was analyzed by using the elastic recoil detection analysis (ERDA) method using 16 MeV 16 O 5+ ions. Depth distribution of deuterium after helium ion irradiation was in good agreement with the depth distribution of damage induced by the helium ions which was calculated using TRIM91 simulation code, while the distribution in the specimens implanted with only deuterium ion was not clear. It was found that deuterium can easily migrate at room temperature in helium-non-irradiated nickel. It was suggested that helium ions introduced vacancy clusters in the irradiated depth region and the implanted deuterium was trapped in the damages.

The creation of defects and radiation-induced segregation (RIS) in single crystals of type 304 stainless steel, 1.6 MeV He irradiated up to 2.5 × 10 17 cm −2 at RT, has been investigated by using a combination of RBS and PIXE with channeling (RBS-C and PIXE-C). From the RBS-C, it is found that radiation-induced defects for 〈110〉 orientation increased more slowly with irradiation dose from those for the 〈100〉 and 〈111〉 orientations. The PIXE-C measurements show that Si atoms segregate to the (100), (110) and (111) surfaces and S atoms seem to enrich slightly in the (100) and (110) surfaces during 1.6 MeV He ion irradiation. It is the first time that the phenomenon of radiation-induced segregation is observed in stainless steels at room temperature irradiation.

The radiation effect on the lattice structure of single-crystal austemtic stainless steel SUS310S under He ion bombardment was studied. The He+ ions, with an energy of 1.7 MeV, were incident along the 〈100〉, 〈110〉 or 〈111〉 axes of the specimen. constituent elements induced by He ions as well as Rutherford-backscattered He ions were measured. The lattice location of the alloying and impurity atoms, and their disordering caused by the He irradiation were investigated. It was shown that aligned X-ray yields in the angular scans increase with the irradiation dose except for P atoms, and the degree of the increase depends very much on the crystallographic orientation and the constituent elements. Some of the impurity P atoms were found to be situated at the body-centered site of the fcc crystal and to be displaced from this site under He ion irradiation.

An in‐situ straining device has been developed, which enables one to apply a load of 240 N to a specimen in hot water at 561 K and a pressure of 8 MPa, simulating the environment in a boiling water reactor (BWR). The device is equipped with sapphire glass windows for a light path, that is, the device can be used for dynamic measurements of stress induced in the specimen using a synchrotron radiation facility. In‐situ stress measurements have been carried out at SPring‐8 (BL02B1) on a specimen prepared from SUS316L stainless steel. Inhomogeneity in stress distribution and time‐dependent changes in stress were successfully measured.

X-ray fluorescence holography (XFH) is a new technique enabling the determination of the three-dimensional local atomic structure around a certain element. This method has been applied to analyze the local structure around Cu in 300 nm thin films of EuBa(2)Cu(3)O(7-delta) (EBCO) epitaxially grown on MgO (100) substrate, using the newest system for XFH measurement and high-brilliance synchrotron radiation at SPring-8. Here, the results of a study on the irradiation effect on the local atomic structure of EBCO superconductor with XFH measurements are presented.

Suppressing the stress corrosion cracking (SCC) by reducing the carbon content in austenitic stainless steels is apparently not effective on core shrouds used in boiling water reactors in Japan: trans-granular cracking was found in the shrouds. To clarify the mechanism of the cracking, in situ stress measurements on specimens under stretched conditions in hot water have been attempted in the present study. An in situ device for diffraction measurements at synchrotron radiation facilities has been developed, and in situ experiments have been carried out at SPring-8. The SUS316L steel specimen was solution heat-treated, surface-ground and then placed in the in situ device. Sapphire windows were used for the light path in the device. A sufficient diffracted beam intensity was obtained through two sapphire windows and water. The side-inclination method was used for measuring the stress exerted on the specimen. A 2theta-sin2psi plot showed that a tensile stress was induced. The measured stress value is considered to be the summation of stresses owing to pre-straining, in situ loading and residual stress owing to surface grinding.

In order to investigate the analyzing depth of N-K absorption spectra measured using the TEY and TFY methods, the spectra of Si3N4 crystals covered with Cr thin films were measured. The thicknesses of Cr films were 1 – 100 nm. The N-K absorption intensity of Si3N4 measured using the TEY method was observed at Cr thickness of less than 3 nm, while that measured with the TFY method was observed for more than 100 nm. The decrease in the TFY peak intensity was explained by the transmittance of Cr film. The results were applied to estimate the damage depth of plasma-etched GaN crystal. The deformation of the crystal structure in n-GaN etched by Ar plasma was restricted in a shallow region of less than 3 nm from the surface.

The level structure of 151 Pm has been studied through the measurements of γ- and β-rays from the decay of 12 min 151 Nd. Among many excited levels of 151 Pm presented in the previous papers, 13 levels have been confirmed and 16 new levels have been introduced. Spin and parity assignments for several levels in the medium- and higher-energy regions are proposed. In the lower-energy region the third members of the 5/2(413) and 3/2(411) bands and in the medium-energy region two members of the 3/2(541) band have been newly detected.