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Aoyagi, Noboru; Motokawa, Ryuhei; Okumura, Masahiko; Ueda, Yuki; Saito, Takumi*; Nishitsuji, Shotaro*; Taguchi, Tomitsugu*; Yomogida, Takumi; Sazaki, Gen*; Ikeda, Atsushi
Communications Chemistry (Internet), 7, p.128_1 - 128_13, 2024/06
Times Cited Count：0 Percentile：0.00(Chemistry, Multidisciplinary)Ishikawa, Norito; Fukuda, Shoma; Nakajima, Toru; Ogawa, Hiroaki; Fujimura, Yuki; Taguchi, Tomitsugu*
Materials, 17(3), p.547_1 - 547_21, 2024/02
Times Cited Count：1 Percentile：71.29(Chemistry, Physical)Natural monoclinic zirconia (baddeleyite) was irradiated with 340-MeV Au ions, and the irradiation-induced nanostructures (i.e., ion tracks and nanohillocks) were observed using transmission electron microscopy. The diameter of the nanohillocks is approximately 10 nm, which is similar to the maximum molten region size calculated using the analytical thermal spike model. Ion tracks are imaged as strained regions that maintain their crystalline structure. The cross-sections of most of the ion tracks are imaged as parallelopiped or rectangular contrasts as large as 10 nm. These results strongly indicate that the molten region is recrystallized anisotropically, reflecting the lattice structure. Furthermore, low-density track cores are formed in the center of the ion tracks. The formation of low-density track cores can be attributed to the ejection of molten matter toward the surface.
Entani, Shiro*; Sato, Shinichiro*; Honda, Mitsunori; Suzuki, Chihiro*; Taguchi, Tomitsugu*; Yamamoto, Shunya*; Oshima, Takeshi*
Radiation Physics and Chemistry, 199, p.110369_1 - 110369_7, 2022/10
Times Cited Count：1 Percentile：19.69(Chemistry, Physical)Ni silicide synthesis by Ni ion beam irradiation into Si attracts attention due to its advantages including the ability of formation of local structures, the controllability of ion beams, the formability of silicide without heat treatment and the high reproducibility of the resulting specimen. In this work, we investigate the local atomic structure of Si implanted with 3.0 MeV Ni
ions. Analysis of Ni K-edge fluorescent-yield extended X-ray absorption fine structure reveals that Ni atoms have mixed structure of metallic-like face-centered cubic Ni and NiSi
phases at the initial stage of the irradiation and the formation of NiSi promotes significantly with the ion fluence above 10 
ions cm
. With consideration of the agreement between the ion fluence threshold for the structural transition and the critical Si-amorphization fluence, it is concluded that the amorphization of Si plays an important role in the synthesis of the NiSi phase in Ni-irradiated Si.
irradiated with swift heavy ions at grazing incidenceIshikawa, Norito; Fujimura, Yuki; Kondo, Keietsu; Szabo, G. L.*; Wilhelm, R. A.*; Ogawa, Hiroaki; Taguchi, Tomitsugu*
Nanotechnology, 33(23), p.235303_1 - 235303_10, 2022/06
Times Cited Count：6 Percentile：59.05(Nanoscience & Nanotechnology)A single crystal of SrTiO doped with niobium (Nb-STO) was irradiated with 200 MeV Au ions at grazing incidence. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to study the relation between irradiation-induced change of surface topography and corresponding material property changes. As expected, multiple hillocks as high as 5-6 nm are imaged by AFM observation. It is also found that the region in between the adjacent hillocks is slightly elevated rather than depressed. Line-like contrasts along the ion paths are found in both AFM phase images and SEM images, indicating the formation of continuous ion tracks in addition to multiple hillocks. Cross-sectional transmission electron microscopy (TEM) observation shows that the ion tracks in the near-surface region are found to be relatively large, whereas buried ion tracks in the deeper region are relatively small. The results suggest that recrystallization plays an important role in the formation of small ion tracks in the deep region, whereas formation of large ion tracks in the near-surface region is likely due to the absence of recrystallization.
Yoshimoto, Masahiro; Nakanoya, Takamitsu; Yamazaki, Yoshio; Saha, P. K.; Kinsho, Michikazu; Yamamoto, Shunya*; Okazaki, Hiroyuki*; Taguchi, Tomitsugu*; Yamada, Naoto*; Yamagata, Ryohei*
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.850 - 854, 2021/10
no abstracts in English
Ishikawa, Norito; Taguchi, Tomitsugu*; Okubo, Nariaki
Shototsu, 18(3), p.43 - 55, 2021/05
Radiation damage mechanism in ceramics irradiated with swift heavy ions has been studied by using transmission electron microscopy (TEM). We introduce how the mechanisms are unveiled by our recent TEM studies.
Tamura, Koji; Oba, Hironori; Saeki, Morihisa; Taguchi, Tomitsugu*; Lim, H. H.*; Taira, Takunori*; Wakaida, Ikuo
Journal of Nuclear Science and Technology, 58(4), p.405 - 415, 2021/04
Times Cited Count：13 Percentile：81.94(Nuclear Science & Technology)Radiation dose rate effects on the properties of a compact fiber-optic laser-induced breakdown spectroscopy (LIBS) system with a monolithic Nd:YAG/Cr:YAG composite ceramics were investigated for remote analysis in hazardous environment. To investigate radiation effects on the LIBS signal, properties related to the Nd:YAG laser operation such as oscillation threshold, output energy, oscillation timing, temporal pulse shape, and beam profile were measured as a function of the radiation dose rate from 0 to 10 kGy/hr in view of their influences to the signal. LIBS spectra of zirconium metal were measured under irradiation. Although signal intensity decreased considerably by irradiation, informative spectra were well obtained even at the maximum radiation dose rate. From the comparison of the LIBS-related parameters among the laser properties, signal reduction was mainly ascribed to the pulse energy reduction. Scintillation emission spectra were also measured from the ceramics during the irradiation, where the signal intensity increased linearly with the dose rate. The results show that the developed system.
Yoshimoto, Masahiro; Nakanoya, Takamitsu; Yamazaki, Yoshio; Saha, P. K.; Kinsho, Michikazu; Yamamoto, Shunya*; Okazaki, Hiroyuki*; Taguchi, Tomitsugu*; Yamada, Naoto*; Yamagata, Ryohei*
JPS Conference Proceedings (Internet), 33, p.011019_1 - 011019_7, 2021/03
The multi-turn charge-exchange H
beam injection scheme with stripper foils is one of the key techniques to achieve a MW-class high power proton beam. The J-PARC RCS adopts Hybrid type Boron-doped Carbon (HBC) stripper foil, which was developed in KEK to improve the lifetime. Indeed, the RCS user operation confirmed that HBC foil has the great advantage of a longer lifetime against high beam irradiation. To examine characteristics of the HBC foils, various beam studies were performed, such as the stripping efficiency measurement and long-term observation with an H beam in the J-PARC RCS, foil analysis using RBS, EDR and PIXE methods, and SEM and TEM observation after the ion beam irradiation in Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) on National Institutes for Quantum and Radiological Science and Technology (QST). Recently, the deposition apparatus for the HBC foils from the KEK Tsukuba-site was relocated to the JAEA Tokai-site, and we started fabrication of new HBC foil in 2017. (The new one fabricated in JAEA we call J-HBC foil.) And, we continue investigations in TIARA with the J-HBC foils. Furthermore, in-depth researches by changing the process parameters of the foil deposition are carried on. Recent results suggest that the amount of the boron doped in the foil is more important parameter than the ratio of the discharge amount of carbon from cathode and anode electrodes. In this presentation, we will report the details of recent analysis of the J-HBC foil.
Ishikawa, Norito; Taguchi, Tomitsugu*; Ogawa, Hiroaki
Quantum Beam Science (Internet), 4(4), p.43_1 - 43_14, 2020/12
Amorphizable ceramics were irradiated with 200 MeV Au ions, and the as-irradiated samples were observed by transmission electron microscopy (TEM). The ion track diameter and hillock diameter are similar for all the amorphizable ceramics. For SrTiO and niobium-doped STO, 200 MeV Au ion irradiation and TEM observation were also performed. The ion track diameters in these materials are found to be markedly smaller than the hillock diameters. The ion tracks in these materials exhibit inhomogeneity, which is similar to that reported for non-amorphizable ceramics. On the other hand, the hillocks appear to be amorphous, and the amorphous feature is in contrast to the crystalline feature of hillocks observed in non-amorphizable ceramics. No marked difference is recognized between the nanostructures in STO and those in Nb-STO.
Fe
O
Ishikawa, Norito; Taguchi, Tomitsugu*; Kitamura, Akane; Szenes, G.*; Toimil-Molares, M. E.*; Trautmann, C.*
Journal of Applied Physics, 127(5), p.055902_1 - 055902_7, 2020/02
Times Cited Count：7 Percentile：38.96(Physics, Applied)Hillock formation is one of the important aspects of radiation-induced modification of solid material. To our knowledge this is first result showing that the hillock formation in ceramics is affected by the velocity effect. The present result include Se-dependences of hillock dimensions based on precise measurement using TEM (transmission electron microscopy). The paper should be published to make researchers aware that hillock size is actually comparable to ion-track size in wide Se range. In addition, the results include important insight about the hillock formation mechanism of ceramics irradiated with swift heavy ions.
Saeki, Morihisa*; Matsumura, Daiju; Yomogida, Takumi; Taguchi, Tomitsugu*; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*
Journal of Physical Chemistry C, 123(1), p.817 - 824, 2019/01
Times Cited Count：16 Percentile：54.35(Chemistry, Physical)Reaction kinetics of laser-induced particle formation in an aqueous solution of PdCl
was investigated by transmission electron microscope (TEM) and dispersive X-ray absorption fine structure (DXAFS). The Pd particle was generated by irradiation of nanosecond pulsed 266-nm laser. The TEM observation showed dependence of the particle size on the laser fluence and promotion of the particle growth by irradiation of high-fluence laser. The DXAFS data give us the Pd
concentration. Temporal changes of the Pd concentration analyzed based on Finke-Watzky two step mechanism. The analysis elucidates that the laser photon contributes to the reduction of the PdCl ion by the one-photon process and to the autocatalytic growth of the Pd particles by the multi-photon process.
Kakitani, Kenta*; Kimata, Tetsuya*; Yamaki, Tetsuya*; Yamamoto, Shunya*; Matsumura, Daiju; Taguchi, Tomitsugu*; Terai, Takayuki*
Radiation Physics and Chemistry, 153, p.152 - 155, 2018/12
Times Cited Count：3 Percentile：27.63(Chemistry, Physical)
InO
analyzed by neutron diffraction/ atomic pair distribution functionIgawa, Naoki; Kodama, Katsuaki; Taguchi, Tomitsugu*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Hoshikawa, Akinori*; Ishigaki, Toru*
Transactions of the Materials Research Society of Japan, 43(6), p.329 - 332, 2018/12
For the understanding of the crystal structural effect on the electrical properties, the local disorder in BaSnInO which is one of the excellent proton conductors for solid oxide fuel cells was estimated by using the Atomic Pair Distribution Function (PDF) analysis method with the neutron diffraction. The local structure is almost the same as the average structure which was estimated by the Rietveld analysis using the cubic crystal structure (space group, 
) in the atomic distance range of 
6
. The PDF profile was fitted better using the tetragonal crystal structure with the space group of 
4/
than those with in the range 
6. Those results indicate the presence of the local disorder in the lattice. In this work, the relationship between the average and local structures of BaSnInO will be discussed.
Okubo, Nariaki; Okuno, Yasuki; Kitamura, Akane; Taguchi, Tomitsugu*
Nuclear Instruments and Methods in Physics Research B, 435, p.198 - 202, 2018/11
Times Cited Count：2 Percentile：19.79(Instruments & Instrumentation)Accelerator driven system (ADS) adopts the lead-bismuth eutectic (LBE) as both coolant and spallation target. The oxygen concentration control is one of the most important technical developments. Estimation of durability under gamma-ray irradiation for the oxygen sensor is necessary for the integrity evaluation of ADS components. The Zirconia added by Yttria (YSZ) is the main element in oxygen sensor. Effect of gamma-ray irradiation on the mechanical property and structural change for three types of YSZ with 3, 6, 8 mol% Yttria was evaluated by using 4 points bend test, XRD, SEM and Raman spectroscope. The gamma-ray irradiations were conducted at 1 and 2 kGy/h, which corresponded to the LBE activity after 1 year ADS operation. In the cases of 8Y and 6Y, degradation of strength was not measured and the fracture surface did not change the morphology. In the case of 3Y, however, the strength did not change but phase transformation from tetragonal to monoclinic crystal structure was observed in XRD results, depending on the irradiation dose. This implies that the gamma-ray irradiation causes the phase transformation in 3Y-YSZ.
Ishikawa, Norito; Taguchi, Tomitsugu*; Okubo, Nariaki
Nanotechnology, 28(44), p.445708_1 - 445708_11, 2017/11
Times Cited Count：23 Percentile：69.35(Nanoscience & Nanotechnology)TEM method is applied to YFeO (YIG) and three fluorides (CaF, SrF and BaF) for observing hillocks. For YIG which is one of the amorphizable materials, hillocks are found to have amorphous feature which is consistent with amorphous feature of ion-tracks. For the fluorides, it is found that the hillocks do not exhibit amorphous feature, and they are composed of nano-crystallites. It is found for the first time that for YIG the hillock diameter is comparable to the ion-track diameter, whereas for the fluorides it is always larger than the ion-track diameter. The results indicate that recrystallization after transient melting plays an important role for formation of hillocks and ion-tracks in fluorides.
Saeki, Morihisa*; Taguchi, Tomitsugu*; Oba, Hironori*; Matsumura, Daiju; Tsuji, Takuya; Yomogida, Takumi
Denki Gakkai Kenkyukai Shiryo, Denshi Zairyo Kenkyukai (EFM-17-010
021), p.15 - 18, 2017/09
Irradiation of nanosecond pulsed UV laser into a solution of palladium ion leads to formation of palladium particles with sub-micron size particles by time-resolved X-ray absorption spectroscopy.
Awual, M. R.; Miyazaki, Yuji; Taguchi, Tomitsugu; Shiwaku, Hideaki; Yaita, Tsuyoshi
Chemical Engineering Journal, 291, p.128 - 137, 2016/05
Times Cited Count：238 Percentile：99.28(Engineering, Environmental)Awual, M. R.; Yaita, Tsuyoshi; Miyazaki, Yuji; Matsumura, Daiju; Shiwaku, Hideaki; Taguchi, Tomitsugu
Scientific Reports (Internet), 6, p.19937_1 - 19937_10, 2016/01
Times Cited Count：197 Percentile：97.50(Multidisciplinary Sciences)Taguchi, Tomitsugu; Yamamoto, Shunya; Kodama, Katsuaki; Asaoka, Hidehito
Carbon, 95, p.279 - 285, 2015/12
Times Cited Count：11 Percentile：34.21(Chemistry, Physical)Amorphous SiC nanotubes are successfully synthesized by 340 keV Si ions irradiation of polycrystalline SiC nanotubes for the first time. A polycrystalline/amorphous heterostructure SiC nanotube, in which polycrystalline SiC and amorphous SiC coexist in the same nanotube, is also synthesized by ions irradiation with a mask in front of polycrystalline SiC nanotube. According to electron energy loss spectroscopy evaluation, the plasmon energies of SiC nanotube change rapidly at the interface between polycrystalline and amorphous regions. The volume swelling by amorphization evaluated from the differences of plasmon energies is approximately 5.0%. This result reveals that the further relaxed amorphous SiC nanotubes with higher density can be produced. The graphitic shells in carbon layer of C-SiC nanotube gradually bend to the radial direction of nanotube by the ion irradiation. Since the graphite (002) spots in the selected area electron diffraction pattern are clearly observed even after the ion irradiation, the carbon layer in C-SiC nanotube has certain crystallinity. Moreover, the new multi-walled carbon nanotube with the graphitic shells completely parallel to the radial direction of nanotube is also produced inside the amorphous SiC tubular layer in the case of C-SiC nanotube with large caliber.
with swift heavy ions; TEM studyIshikawa, Norito; Okubo, Nariaki; Taguchi, Tomitsugu
Nanotechnology, 26(35), p.355701_1 - 355701_8, 2015/09
Times Cited Count：32 Percentile：75.85(Nanoscience & Nanotechnology)In this study, CeO was irradiated with 200 MeV Au ions at oblique incidence. Observation of as-irradiated samples by transmission electron microscope (TEM) shows that hillocks are created not only at the wide surfaces, but also at the crack faces of the thin samples. Since the hillocks created at the crack faces can be imaged by TEM, their shape and crystallographic features can be revealed. From the images of hillocks created at the crack faces, many of the hillocks are found to be spherical. We present a first experimental evidence that hillocks created for CeO irradiated with swift heavy ions have a crystal structure whose lattice spacing and orientation coincide with those of the matrix. The mechanism of spherical crystalline hillock formation is discussed based on the present results.
