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
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
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
Igawa, 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
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
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-17-010021), 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
Awual, M. R.; Yaita, Tsuyoshi; Miyazaki, Yuji; Matsumura, Daiju; Shiwaku, Hideaki; Taguchi, Tomitsugu
Scientific Reports (Internet), 6, p.19937_1 - 19937_10, 2016/01
Taguchi, Tomitsugu; Yamamoto, Shunya; Kodama, Katsuaki; Asaoka, Hidehito
Carbon, 95, p.279 - 285, 2015/12
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.
Ishikawa, Norito; Okubo, Nariaki; Taguchi, Tomitsugu
Nanotechnology, 26(35), p.355701_1 - 355701_8, 2015/09
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.
Taguchi, Tomitsugu; Igawa, Naoki; Birumachi, Atsushi; Asaoka, Hidehito; Miwa, Shuhei; Osaka, Masahiko
e-Journal of Surface Science and Nanotechnology (Internet), 13, p.339 - 342, 2015/06
Rare-earth doped ceria exhibits both ionic and electronic conductions, and those ceria with higher ratio of ionic conduction against electronic conduction is used as a solid electrolyte for solid oxide fuel cells. The electron density distributions in crystals are closely related to the electron diffusing pathway which affects the electronic conduction. In this study, we investigated the electron density distribution of doped ceria as a function of the content of NdO-dopant to deduce the ratio of the electronic to ionic conduction. The crystal structure was refined with the space group, -3, which is the same as undoped ceria. Ce and Nd ions randomly occupied the 4 site and O ion the 8 site. The electron conduction pathway was distributed through the 4-8 and 8-8 sites. The relationship between crystal structural change and electron density distribution as a function of the content of NdO dopant will be discussed.
Taguchi, Tomitsugu; Yamaguchi, Kenji
Nuclear Instruments and Methods in Physics Research B, 350, p.1 - 5, 2015/05
SiO nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO nanotubes in the previous studies always have an amorphous wall, and here we demonstrate the successful synthesis of single-crystal nanotubes for the first time by the heat treatment of SiC nanotubes at 1300 C for 10 h under low-vacuum conditions. According to TEM observations, the single-crystal SiO was -cristobalite. We also demonstrate that single-crystal SiO nanotubes can be transformed into amorphous SiO nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO composite nanotube, in which crystalline and amorphous SiO coexisted in different localized regions. In addition, for biomedical applications such as drug delivery systems, controlling the configuration of the open end, the diameter, and capsulation of SiO nanotubes is crucial. We can also obturate, capsulate, and cut a SiO nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique.
Igawa, Naoki; Kodama, Katsuaki; Birumachi, Atsushi; Taguchi, Tomitsugu
e-Journal of Surface Science and Nanotechnology (Internet), 13, p.247 - 252, 2015/05
The nuclear and electron density distributions of LiMnO which is one of the primitive cathode materials for secondary Li-ion batteries, were analyzed by applying Rietveld refinement and MEM to neutron and X-ray diffraction data, to estimate the Li diffusing pathway. The crystal structure of LiMnO could be refined with the space group, -3 in the temperature range from 240 to 573 K. The structure was transformed to below 240 K. The isotropic thermal displacement parameter of Li was proportional to the temperature excluding 240 to 300 K. According to the MEM analyses it was indicated that the Li ions diffuse through 8 and 16 around 300 K.
Saeki, Morihisa; Taguchi, Tomitsugu; Nakashima, Nobuaki*; Oba, Hironori
Journal of Photochemistry and Photobiology A; Chemistry, 299, p.189 - 193, 2015/02
Awual, M. R.; Yaita, Tsuyoshi; Taguchi, Tomitsugu; Shiwaku, Hideaki; Suzuki, Shinichi; Okamoto, Yoshihiro
Journal of Hazardous Materials, 278, p.227 - 235, 2014/08
Awual, M. R.; Suzuki, Shinichi; Taguchi, Tomitsugu; Shiwaku, Hideaki; Okamoto, Yoshihiro; Yaita, Tsuyoshi
Chemical Engineering Journal, 242, p.127 - 135, 2014/04
Taguchi, Tomitsugu; Miyazaki, Toshiki*; Iikubo, Satoshi*; Yamaguchi, Kenji
Materials Science & Engineering C, 34, p.29 - 34, 2014/01
SiC nanotubes can become candidate reinforcement materials for dental and orthopedic implants due to their light weight and excellent mechanical properties. However, it has not been reported about the development of bioactive SiC materials. In this study, hydroxyapatites were found to on SiC nanotubes treated with NaOH and subsequently HCl solution after soaking in simulated body fluid. On the other hand, hydroxyapatites did not deposit on as-received SiC nanotubes, the SiC nanotubes with NHOH solution treatment and SiC bulk materials with NaOH and subsequently HCl solution treatment. Therefore, we succeeded in the development of bioactive SiC nanotubes by downsizing SiC materials to nanometer size and treating with NaOH and subsequently HCl solutions for the first time.
Taguchi, Tomitsugu; Fazle Kibria, A. K. M.*; Shamoto, Shinichi
Journal of Physics; Conference Series, 417, p.012037_1 - 012037_6, 2013/03
The different behaviour between morphology changes of as-received mult-walled carbon nanotube (MWCNT) and MWCNT with SiC coating was investigated by the electron irradiation. High resolution-TEM images revealed that the deformation and bending of graphitic shells occurred in both as-received MWCNT and MWCNT with SiC coating by electron irradiation. Both of deformation and bending curvature in CNT part of MWCNT with SiC coating were smaller than those in as-received MWCNT. The electron irradiation began changing the outer and inner diameters of as-received MWCNT within 3 minutes exposure, whereas it began changing their diameters changes of MWCNT with SiC coating after 10 minutes exposure. The outer diameter of as-received MWCNT increased up to irradiation time of 9 min and then decreased rapidly. On the other hand, the outer diameter of MWCNT with SiC coating increased monotonically up to irradiation time of 50 min and then was saturated in the MWCNT with SiC coating. It might become hard to knock C atoms out from both inner and outer surfaces of CNT part by coating with SiC layer on MWCNT. These results lead that the morphology stability of MWCNT against electron irradiation is improved by coating with the SiC layer on MWCNT.
Saeki, Morihisa; Esaka, Fumitaka; Taguchi, Tomitsugu; Oba, Hironori
JAEA-Research 2012-030, 16 Pages, 2012/11
We proposed separation technique of platinum-group metals (PGMs) from a solution of high-level radioactive waste by using laser-induced particle formation, and performed its proof-of-principle experiment. The simulated solution of high-level radioactive liquid wastes (HLLW) was prepared by dissolving palladium (Pd), rhodium (Rh), ruthenium (Ru) and neodymium (Nd) into distilled water. The Nd metal was added as representative of lanthanide and minor actinide. After 40-min irradiation of a mixture of the simulated solution of HLLW and ethanol (v/v = 1/1) with a UV laser (266 nm, 20 mJ), the Pd, Rh and Ru metals were separated from the Nd ion as particle with sub-micron size. The PGM particles were recovered by filtration and centrifugation. Analysis of ion concentration in the sample solution by ICP-AES suggested that the Pd, Rh and Ru metals were recovered with efficiency of 100%, 94-99%, 65-69%, while the Nd ion was completely kept in the sample solution.