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数十MeV以上の高速重イオンをセラミックス材料に照射すると、高い電子的阻止能に起因した照射損傷(イオントラック)が形成される。イオントラックの形成メカニズムである熱スパイク理論を用いると、多くの材料において、イオントラックの寸法が正確に予測できる。しかし、ある時期から、熱スパイク理論の予測が通用しない材料が相次いで報告されるようになった。なぜ、特定の材料でこの理論が通用しないのか?材料表面のイオン入射点に形成される10nm弱のナノ隆起物(ナノヒロック)を透過型電子顕微鏡で観察していくうちに、その理由が明らかになってきた。我々の研究によって、照射損傷のメカニズム解明がどのように進んだかを解説する。

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 re...

Radiation dose rate effects to 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 to the system, properties related to the Nd:YAG laser operation were measured as a function of the radiation dose rate from 0 to 10 kGy/hr such as oscillation threshold, output energy, oscillation timing, temporal pulse shape, and beam profile in view of their influences to LIBS signal. LIBS spectra of zirconium metal were measured under irradiation. Although signal intensity decreased considerably by irradiation, informative spectra were well observed even at the maximum dose rate. From the comparison of the LIBS related parameters among the laser properties, the signal reduction was mostly ascribed to the pulse energy reduction. Scintillation emission spectra were also measured from the ceramice during the irradiation, and the signal intensity increased linearly with the dose rate. The results show that the developed system is applicable to the efficient remote elemental analysis and also radiation dose rate monitor in hazardous environments such as for nuclear fuel debris inspection.

In this study, a compact fiber-optic laser-induced breakdown spectroscopy (LIBS) system is developed using a microchip laser (MCL) with a monolithic Nd:YAG/Cr:YAG composite ceramic for application to the fiber-optic remote analysis of hazardous environments, such as nuclear reactor cores. Laser pulses of short pulse duration and near-Gaussian beam profile were obtained. The properties of the output laser, such as pulse energy, pulse repetition rate, temporal pulse shape, and beam profile, were measured as the parameters for LIBS application, and were found to be suitable for the purpose. The spectra of zirconium metal were observed, and the signal intensity was further enhanced by multi-burst mode irradiation. The results of this study indicate that the fiber-optic microchip-laser induced breakdown spectroscopy (FO-MCLIBS) system, which is advantageous for efficient remote analysis of hazardous environments, is applicable to analyze the inside of nuclear reactor cores.

In this study, a compact fiber-optic laser-induced breakdown spectroscopy (LIBS) system was developed using a microchip laser (MCL) with a monolithic Nd:YAG/Cr:YAG composite ceramic, for remote ana...

The formation of novel structured SiC nanomaterials with new properties is required because there is the possibility that they have novel properties relative to bulk SiC materials. Polycrystalline double-thick-walled (DTW) SiC nanotubes were successful synthesized by the reaction of multi-walled carbon nanotubes with Si powder. We also synthesized novel amorphous DTW SiC nanotubes for the first time. The degree of crystallinity of the SiC nanotube was decreasing with growing irradiation damage, and the SiC crystals were completely amorphized when irradiated at 3.2 dpa. According to these TEM images, the double-walled structure in the amorphous SiC nanotube was maintained even after ion irradiation. When the irradiation damage increased up to 24.0 dpa, the amorphous DTW SiC nanotube altered to the amorphous SiC nanowire., Materials Research Meeting 2021

The synthesis of new structured SiC nanomaterials with novel properties is required because there is the possibility that they have novel properties relative to bulk SiC materials. We also have synthesized polycrystalline double-thick-walled (DTW) SiC nanotubes. Herein, we report the successful synthesis of novel amorphous DTW SiC nanotubes for the first time. The degree of crystallinity of the SiC nanotube was decreasing with growing irradiation damage, and the SiC crystals were completely amorphized when irradiated at 3.2 dpa. According to these TEM images, the double-walled structure in the amorphous SiC nanotube was maintained even after ion irradiation. When the irradiation damage increased up to 24.0 dpa, the amorphous DTW SiC nanotube altered to the amorphous SiC nanowire., The 9th International Symposium on Surface Science (ISSS9)

常圧近傍ではいずれも水素化物を形成しないAlとFeを組み合わせたAl13Fe4合金が7万気圧以上の超高圧下で新規水素化物Al3FeH4を形成することを発見した。さらに合成された水素化物は常圧近傍でも安定であることを示す結果が得られた。, 第62回高圧討論会

Among the various functionalities of hydrides, their use in hydrogen storage has been the most intensively studied because hydrides can store hydrogen compactly and safely. Thus, hydrides are key materials for the hydrogen economy. Here, the hydrogen storage material Al3FeH3.9 has been synthesized from cost-effective earth-abundant metals, Fe and Al. Hydrides consisting of Al and transition metals with low hydrogen affinities are rare because such alloys are unstable. However, it is expected that appropriate mixing of the chemical states of hydrogen atoms would allow synthesis of Al-Fe hydrides. The experimentally determined crystal structure of Al3FeD3.9 suggests realization of the mixing of the chemical state of hydrogen. Al3FeH3.9 is more thermodynamically stable than AlH3, and it is likely that the mixing of the chemical state of hydrogen atoms is the source of increased stability. The results of this study confirm that by controlling the chemical states of hydrogen, it is possible to tune the thermodynamic stability of hydrides and thus realize novel functional hydrides.

私たちのグループでは、従来の金属水素化物の合成方針である「水素化し易い金属と、水素化し難い金属（難水素化金属）を組み合わせる」から探索範囲を広げて、難水素化金属どうしの組み合わせからなる新規水素化物の探索を進めている。本発表ではAl-TM合金水素化物の合成に関するこれまでの成果、および、新たな取組、今後の方針を紹介する。, 日本金属学会2021年秋期(第169回)講演大会

Photovoltaic properties of solar cell sensitized with c-phycocyanin protein complex were measured. Solar cell incorporated with pigment protein complex was made. Optimum conditions for maximum photo energy generation were investigated. Properties such as photo responses, I-V curve, wavelength dependence, incident photo intensity dependence were measured as a sensitized solar cell., 2021年光化学討論会

A novel hybrid carbon nanomaterial was synthesized by ion irradiation of a C–SiC coaxial nanotube. The hybrid consisted of one-dimensionally stacked graphene nanodisks with diameters less than 50 nm and cylindrical multiwalled carbon nanotubes inside an amorphous SiC tubular layer. A sudden emergence of new continuous graphitic layers in the microstructure were observed by in situ transmission electron microscopy following ion irradiation, where these layers were perpendicular to the nanotube's length direction. The SiC crystals in the C–SiC coaxial nanotube became amorphous, also due to the ion irradiation, although the critical amorphization dose was higher than that for bulk SiC. Most remarkably, the carbon layer remained crystalline, even after an irradiation dose higher than 20 dpa (displacement per atom). Such results show that these carbon layers possess better resistance against amorphization when subjected to ion irradiation than the SiC layers in the C–SiC coaxial nanotube. The lattice plane spacing of the carbon layer increases up to the point when irradiation damage lead to the complete amorphization of SiC crystals, after which it starts to decrease. This demonstrates that the carbon layer experiences high compression stress during ion irradiation. Thus, the ion irradiation of C–SiC coaxial nanotubes gives rise to a novel development of the microstructure and can be considered as one of the new synthetic processes for making novel carbon nanomaterials.

Dissipative structures often appear as an unstable counterpart of ordered structures owing to fluctuations that do not form a homogeneous phase. Even a multiphase mixture may simultaneously undergo one chemical reaction near equilibrium and another one that is far from equilibrium. Here, we observed in real time crystal seed formation and simultaneous nanocrystal aggregation proceeding from CeIV complexes to CeO2 nanoparticles in an acidic aqueous solution, and investigated the resultant hierarchical nanoarchitecture. The formed particles exhibited two very different size ranges. The hierarchically assembled structures in solutions were CeO2 colloids, viz. primary core clusters (1–3 nm) of crystalline ceria and secondary clusters (20–30 nm) assembled through surface ions. Such self-assembly is widespread in multi-component complex fluids, paradoxically moderating hierarchical reactions. Stability and instability are not only critical but also complementary for co-optimisation around the nearby free energy landscape prior to bifurcation.

Previously, we showed that the irradiation of a nanosecond pulsed UV laser with high pulse energy into the Pd(II) solution forms the Pd particle with submicron size (100–500 nm), which has not been generated in the photo-induced particle formation using a UV lamp. It indicates that the laser irradiation with high pulse energy promotes the Pd particle growth, the mechanism of which is unclear. In this work, we studied the particle formation in the Pd(II) solution in the laser irradiation with high pulse energy using time-resolved X-ray absorption fine structure (XAFS) spectroscopy., 6th International Conference on Advanced Nanoparticle Generation & Excitation by Lasers in Liquids

これまでに、多層カーボンナノチューブとSi粉末との真空熱処理により、多結晶炭化ケイ素（SiC）ナノチューブの合成に成功している。さらに、熱処理条件を最適化することで、これまでにない多結晶二層厚壁SiCナノチューブの合成にも成功した。今回は、この多結晶二層厚壁SiCナノチューブを、室温にてイオン照射することにより、アモルファス二層厚壁SiCナノチューブを合成することができたので報告する。室温にて、多結晶二層厚壁SiCナノチューブを200keVのSiイオン照射することにより、アモルファス二層厚壁SiCナノチューブの合成に成功した。外径が約200nmの外側ナノチューブと、外径が約80nmの内側ナノチューブの二層構造であることが分かった。SiC結晶はイオン照射損傷量が増加するとともに、結晶構造が乱れていき、約3.2dpaの損傷量で全領域がアモルファス状になった。二層厚壁SiCナノチューブの外径や内外ナノチューブ間距離等の形状変化に及ぼす照射量依存性についても、報告する。, 日本顕微鏡学会 第77回学術講演会

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., 荷電変換フォイルを用いたH$^{-}$ビーム多重入射方式はMW級の大強度陽子ビームを実現するための重要な技術である。大強度陽子加速器施設(Japan Proton Accelerator Research Complex: J-PARC)3GeVシンクロトロン加速器(Rapid Cycling Synchrotron: RCS)では、高エネルギー加速器研究機構(KEK)で開発され耐ビーム寿命が大幅に更新した、ホウ素添付炭素薄(Hybrid type Boron-doped Carbon: HBC)フォイルを採用している。これまで、RCSの利用運転時に使用しており、大強度ビーム照射に対して優れた長寿命性能を有することを確認した。HBCフォイルの性能評価のために、RCSにおいて長期間照射に対する形状観察や荷電変換効率測定を実施してきた。また量子科学技術研究機構(Quantum and Radiological Science and Technology: QST)高崎量子応用研究所(高崎研)のイオン加速器(Takasaki Ion Accelerators for Advanced Radiation Application: TIARA)においてイオンビーム照射試験を実施し、組成分析や不純物同定などの物性解析や電子顕微鏡によるミクロ観察を行ってきた。その結果、フォイル破損に至るメカニズムとして、照射欠陥による密度変化とピンホールの成長、温度上昇にともなうガス化などが重要な鍵ではないかとの兆候を得た。近年、HBCフォイルの蒸着装置をJAEA東海サイトに移設し、フォイル製作を開始した。(以降のフォイルをJ-HBCフォイルと称する。)J-HBCフォイルの性能評価をこれまで同様にQST高崎研のTIARAで実施してきた。さらに、蒸着パラメータを変えてHBCフォイルの耐ビーム性能について試験を行った。その結果、これまで重要なパラメータと考えられていたカソード・アノード電極の消費比率よりも、ボロンの混入率がより重要なパラメータであることが分かった。

これまでに、多層カーボンナノチューブとSi粉末との真空中熱処理により、多結晶炭化ケイ素（SiC）ナノチューブの創成に成功している。今回熱処理条件を制御することにより、これまでにない二層の厚壁SiCナノチューブの合成に成功したので報告する。 透過型電子顕微鏡観察結果から、外径が約210nmの外側ナノチューブと、外径が約120nmの内側ナノチューブで、二重構造になっていることがわかった。また、内外ナノチューブ間の平均隙間は、約20nmであった。, 日本顕微鏡学会 第76回学術講演会

Ion-track-etched capillaries containing nanoparticles of precious metals (e.g., Pt, Au, and Ag) can be applied to plasmonic absorber materials. The precipitation of homogeneous and highly dispersed precious metal nanoparticles inside capillaries represents a key process. Ion-track-etched capillaries (diameter: 500 nm, length: 25 m) were created in polyimide film by 350 MeV Xe irradiation (3 &times, 107 ions/cm2) and chemical etching (using a sodium hypochlorite solution). The films with capillaries were immersed in an aqueous solution containing 0.1&ndash, 10 mmol/L H2PtCl6 and 0.5 vol% C2H5OH, and then irradiated with a 2 MeV electron beam up to a fluence of 1.4 &times, 1016 e/cm2. The Pt particles inside the capillaries were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The precipitation of Pt nanoparticles and isolated aggregates inside the capillaries was confirmed by TEM. The Pt nanoparticles tended to aggregate under increasing concentrations of H2PtCl6 in the aqueous solution, meanwhile, no changes in nanoparticle size were noted under increasing electron beam fluence. The results suggest that the proposed method can be used to form metal nanoparticles in nanosized capillaries with a high aspect ratio.

The reaction kinetics of laser-induced particle formation in an aqueous/EtOH solution of PdCl42– without a photoactivator was investigated by transmission electron microscopy (TEM) and dispersive X-ray absorption fine structure (DXAFS) measurements. Pd particles were generated by the irradiation of a nanosecond pulsed 266 nm laser with a fluence of 19.9–59.7 mJ/cm2. The TEM observation showed the dependence of the particle size on the laser fluence and the promotion of particle growth by the irradiation of a high-fluence laser. The DXAFS data were analyzed by three methods: deconvolution of the X-ray absorption near-edge structure (XANES) spectrum by a linear combination fitting, model fitting of the extended XAFS (EXAFS) oscillation of the PdCl42– ion, and fitting of the spectrum edge of XANES using an error function. These methods give the ratio of Pd2+, the coordination number of Pd–Cl bond, and the edge width of XANES, which are related to the Pd2+ concentration. Temporal changes of the Pd2+ concentra...

The R&D on SiC/SiC composites under the broader approach (BA) activities between Japan and the EU for fusion DEMO developed a fundamental database of mechanical (Task-1) and physical/chemical (Task-2) properties, with a primary target of the application of SiC/SiC composites as functional structure to be used in the dual coolant breeding blanket concept. This paper aims to summarize previous 10-years activities of the R&D of Japan and to provide the key deliverables toward the DEMO design. In Task-1, good creep and fatigue durability were first demonstrated. Besides, in-plane and inter-laminar strength anisotropy maps at elevated temperatures were comprehensively identified. In parallel, the irradiation effects of SiC materials were specifically determined as input parameters of the analytical model to provide for the irradiation-induced residual stresses. In Task-2, the apparent dose-dependence of the radiation-induced electrical conductivity and the indicative radiation-induced electrical degradation was identified by various irradiation sources. In addition, good gas confinement was identified. Furthermore, no accelerated corrosion for duration of 3000 h at below 1173 K was first demonstrated. With these achievements, it is suggested that the in-vessel component technology, e.g., material corrosion database development, activated corrosion product evaluation code development, compact module tests for validation of the key functions of the components, technology integration assessment for fusion nuclear tests, etc., should be further developed toward DEMO in near-term.

A glassy carbon (GC) substrate was irradiated with 380 keV argon ions (Ar+), and platinum nanoparticles (Pt NPs) were then deposited on it by a radio-frequency magnetron sputtering method. The interfacial effect of the Ar+-induced defects in the GC substrate on the size and electronic structure of the Pt NPs was investigated. The irradiation defects in the carbon support promoted the growth of the Pt NPs on the substrate, leading to a larger NP size. Density functional theory calculations revealed that the lattice vacancies in the graphitic structure lowered the position of the Pt d-band center via the interfacial charge transfer. This down-shift in the d-band center would be a reason for the higher catalytic activity, which was reported in our previous research.

In the accelerator driven system, oxygen sensors, on which yttria-stabilized-zirconia (YSZ) is used for the electrolyte, will be irradiated by gamma-ray in activated lead bismuth eutectic (LBE) adopted as a both coolant and spallation target. Partially stabilized zirconia, like a 3Y-YSZ, has high strength due to the stress induced phase transformation from tetragonal (T) to monoclinic (M) phase. The mechanical properties of YSZ specimens after gamma-ray irradiation, thermal aging and immersion in LBE have been investigated in terms of the fracture surface structure. In the case of 6Y and 8Y-YSZ, the 4-point bend strength did not change even after gamma-ray irradiation and thermal aging. The 3Y-YSZ, however, showed that the strength was decreased a little by the gamma-ray irradiation, thermal aging and also immersion in LBE. The XRD results indicate that in the case of 3Y-YSZ after the annealing and soaking in LBE, the pristine surface, which is not fractured and strained by bending test, shows M phase much more than the surface of as-received one. After surface polishing of 3Y-YSZ the XRD intensity of M phase increased with increasing gamma-ray dose for the pristine surface. The bend strength of irradiated 3Y-YSZ after polishing, however, did not change in this study. These results suggest that the process of gamma-ray irradiation and thermal process around 450 °C cause pre-phase transformation from T to M, which prevents the stress induced phase transformation previously.

In-situ TEM was used to observe the microstructural changes of SiC nanotubes under ion irradiation, and the results are significantly different from those of bulk SiC. The nanotubes possess better resistance against amorphization by irradiation, having a higher critical irradiation dose at room temperature. At room temperature, both the outer and inner diameters of the SiC nanotubes increase during irradiation till complete amorphization, and decrease afterwards. The lattice plane spacing of SiC crystals increases with increasing ion fluence due to the increasing disorder. At 700 °C, both the inner and outer diameters change very little during ion irradiation; and the lattice plane spacing decreases slightly, which is not consistent with previous studies of bulk SiC. The reason is that, in the nanotubes, the number of inherent defects that buffer the residual stress in it can be reduced. A new structure with smaller crystal segments is produced in the SiC grains of nanotubes to relieve the residual stress, instead of inducing structural defects and nanotube contraction. From these results, ion irradiation clearly induces novel microstructural changes in SiC nanotubes, due to the nanosizing and tubal configuration of the material.

SiC nanotubes were synthesized by the reaction of multi-walled carbon nanotubes (MWCNTs) with Si powder. In order to eliminate any remaining elemental carbon in the nanotubes and unreacted MWCNTs, heat treatments were carried out in air at various temperatures. The evaluated characterization in this study are relative to the SiC nanotubes after heat treatment in air. Photoluminescence (PL) spectra of SiC nanotubes with and without alkali and acid treatments were evaluated at room temperature by microspectroscopy. The PL spectrum of the SiC nanotubes heat treated at 700 °C consisted of a dominant peak around 2.5 eV, while no definite peak was observed in the PL spectra of those heat treated at 800 and 900 °C. The reason is believed to be that SiO 2 layers were produced on the surface of the SiC nanotubes. Treatment by NaOH followed by HCl solution was carried out to remove the SiO 2 layers after the heat treatment. The results show that stronger PL bands emerged after the NaOH-HCl treatment. From these results, we conclude that the PL bands of SiC nanotubes are closely related to their surface state and surface defects.

In this study, double-thick-walled (DTW) silicon carbide (SiC) nanotubes, the walls of which comprise connected disordered polycrystalline nanograins, were successfully synthesized for the first time via the reaction of multiwalled carbon nanotubes (MWCNTs) with Si powder. DTW SiC nanotubes are expected to exhibit novel properties unlike other SiC nanomaterials, owing to their intriguing geometries. The DTW SiC nanotubes had a wall thickness exceeding 20 nm, regardless of the external diameter, as indicated by transmission electron microscopy results. The DTW SiC nanotubes with a spacing of above 30 nm between the outer and inner nanotubes exhibited perfect double-walled structures. The inner and outer nanotubes were not connected in any region. When all the carbon was transformed into SiC, the volume of carbon increased to 2.2 times the initial value. These results reveal that DTW SiC nanotubes with perfect structures cannot be synthesized without an MWCNT wall thickness of at least 50 nm. Several types of DTW SiC nanotubes with different morphologies, such as diameter, end structure, and distance between the inner and outer nanotubes, were synthesized. The morphology of DTW SiC nanotubes can be controlled by changing the wall thickness and/or diameter of the original MWCNTs and the reaction conditions.

荷電変換フォイルを用いたH$$^{-}$$ビーム多重入射方式はMW級の大強度陽子ビームを実現するための重要な技術である。大強度陽子加速器施設(Japan Proton Accelerator Research Complex: J-PARC)3GeVシンクロトロン加速器(Rapid Cycling Synchrotron: RCS)では、高エネルギー加速器研究機構(KEK)で開発され耐ビーム寿命が大幅に更新した、ホウ素添付炭素薄(Hybrid type Boron-doped Carbon: HBC)フォイルを採用している。これまで、RCSの利用運転時に使用しており、大強度ビーム照射に対して優れた長寿命性能を有することを確認した。HBCフォイルの性能評価のために、RCSにおいて長期間照射に対する形状観察や荷電変換効率測定を実施してきた。また量子科学技術研究機構(Quantum and Radiological Science and Technology: QST)高崎量子応用研究所(高崎研)のイオン加速器(Takasaki Ion Accelerators for Advanced Radiation Application: TIARA)においてイオンビーム照射試験を実施し、組成分析や不純物同定などの物性解析や電子顕微鏡によるミクロ観察を行ってきた。その結果、フォイル破損に至るメカニズムとして、照射欠陥による密度変化とピンホールの成長、温度上昇にともなうガス化などが重要な鍵ではないかとの兆候を得た。近年、HBCフォイルの蒸着装置をJAEA東海サイトに移設し、フォイル製作を開始した。(以降のフォイルをJ-HBCフォイルと称する。)J-HBCフォイルの性能評価をこれまで同様にQST高崎研のTIARAで実施してきた。さらに、蒸着パラメータを変えてHBCフォイルの耐ビーム性能について試験を行った。その結果、これまで重要なパラメータと考えられていたカソード・アノード電極の消費比率よりも、ボロンの混入率がより重要なパラメータであることが分かった。

Amorphizable ceramics (LiNbO3, ZrSiO4, and Gd3Ga5O12) were irradiated with 200 MeV Au ions at an oblique incidence angle, and the as-irradiated samples were observed by transmission electron microscopy (TEM). Ion tracks in amorphizable ceramics are confirmed to be homogenous along the ion paths. Magnified TEM images show the formation of bell-shaped hillocks. The ion track diameter and hillock diameter are similar for all the amorphizable ceramics, while there is a tendency for the hillocks to be slightly bigger than the ion tracks. For SrTiO3 (STO) and 0.5 wt% niobium-doped STO (Nb-STO), whose hillock formation has not been fully explored, 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. The material dependence of the nanostructure formation is explained in terms of the intricate recrystallization process.

The size of ion tracks and hillocks produced during heavy ion irradiation of Y3Fe5O12 is analyzed by transmission electron microscopy. The cross sections of hillocks and ion tracks produced by ions with electronic stopping power Se in the range of 20–35 keV/nm are found to be comparable. In this range, the characteristic dimensions of the hillocks (both cross section and height) increase as a function of Se. The data show that there is a correlation between hillock height and hillock cross section, which is linked to the relation between lifetime of the melt along the ion trajectory and the maximum molten area. In addition, the results clearly show that the size of the hillocks produced by low velocity ions is larger than those produced by high velocity ions of the same Se, due to the so-called velocity effect.

円柱状ナノ空間構造内にPt、Auなどの金属ナノ粒子を高密度に集積できれば、触媒反応場や局在型表面プラズモン共鳴吸収による光発熱場としてガス改質材料への応用が期待できる。本研究では、350 MeV Xeイオンビーム照射と化学エッチングよりポリイミドフィルム（厚さ2.5μm）に形成したイオン穿孔（直径約500 nm、長さ2.5μm）内に電子線還元法によりPtナノ粒子の形成を試みた。実験では、塩化白金酸濃度（0.1～10 mM）及び電子線照射量(最大1.4 × 1016 e/cm2)をパラメータに塩化白金酸水溶液中でイオン穿孔膜に2 MVの電子線を照射して試料を作製した。イオン穿孔内に析出したPt粒子の形態及び集積度合は、断面観察試料を作製して走査型電子顕微鏡、透過型電子顕微鏡観察により評価した。その結果、塩化白金酸濃度0.5 mMではイオン穿孔内壁に粒径が5 nm程度のPtナノ粒子が一様に分散して担持し、濃度が10 mMになると100 nm程度の凝集体を形成することがわかった。一方、Ptナノ粒子の形態は電子線照射量に影響されないことがわかった。

The chemical state and local structure of 2.6-nm-sized platinum (Pt) nanoparticles on an ion-irradiated glassy carbon (GC) substrate were investigated by X-ray absorption fine structure measurements. The partial oxidation of the Pt nanoparticles was confirmed by the peak intensity in the near-edge region of the absorption spectrum. The analysis of the extended region revealed a higher coordination number and shorter bond length of Pt–Pt compared to those of the Pt nanoparticles on the non-ion-irradiated GC. Thus, Pt nanoparticles on the ion-irradiated GC substrate were found to hold a rigid metallic coordination during the oxidation.

Amorphous SiC nanotubes are successfully synthesized for the first time by the irradiation of polycrystalline SiC nanotubes with 340 keV Si + ions. A polycrystalline/amorphous heterostructured SiC nanotube, in which polycrystalline SiC and amorphous SiC coexist in the same nanotube, is also synthesized by ion irradiation with a mask in front of the polycrystalline SiC nanotube. According to evaluation by electron energy loss spectroscopy, the plasmon energies of the SiC nanotube change rapidly at the interface between the polycrystalline and amorphous regions. The volume swelling induced by amorphization, as evaluated from the differences in plasmon energies, is approximately 5.0%. This result reveals that more relaxed amorphous SiC nanotubes with higher densities can be produced. The graphitic shells in the carbon layer of C–SiC nanotubes are found to gradually bend to align with the radial directions of the nanotubes by ion irradiation. Since graphite (002) spots in the selected-area electron diffraction pattern are clearly observed even after ion irradiation, the carbon layer in the C–SiC nanotube maintains crystallinity. Moreover, a new multi-walled carbon nanotube with graphitic shells completely parallel to the radial direction of the nanotube is also produced inside the amorphous SiC tubular layer, in the case of large-caliber C–SiC nanotubes.

In J-PARC, the 3 GeV rapid cycling synchrotron (RCS) applied hybrid type thick boron-doped carbon (HBC) foils as charge stripper in the multi-turn injection. Although HBC foils have successfully operated to provide a high-power beam for experimental users since the operation of the accelerator started, the deformation and radio-activation of the foils occurred as serious problems. We investigated the cause of the problems, as result we found that impurities in the foil led to these phenomena. In this report, we describe why impurities were mixed in the foil, and which kinds of impurities were found by various methods of analysis. The effect of impurities is also discussed.

SiO 2 nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO 2 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 2 was α-cristobalite. We also demonstrate that single-crystal SiO 2 nanotubes can be transformed into amorphous SiO 2 nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO 2 composite nanotube, in which crystalline and amorphous SiO 2 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 2 nanotubes is crucial. We can also obturate, capsulate, and cut a SiO 2 nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique.

Metal separation by using laser-induced particle formation was applied to the recovery of Pd from a mixed solution with Mo. In this separation, the Pd ions in the mixed solution containing 1 vol% ethanol were selectively reduced by irradiation of pulsed laser (10 Hz repetition rate) and high-repetition-pulse (HRP) laser (30 kHz repetition rate) with the wavelength of 355 nm while keeping irradiation power constant. The laser-induced reduction resulted in the generation of the Pd neutrals, which is followed by the aggregation of Pd neutrals in the absence of a stabilizing agent. The generated Pd particles were recovered and separated from the Mo ions by filtration. ICP-AES analysis of the filtrate elucidated that the Pd metals were successfully separated from Mo with a high recovery efficiency (84%). The recovery efficiency of Pd was different in the irradiation between the pulsed and HRP lasers; the efficiency obtained using the pulsed laser was 12% higher than that from the HRP laser. XRD analyses demonstrated that the Pd particles subjected to pulsed laser irradiation were 30 times larger than those subjected to the HRP laser. Based on TEM observations, the sizes of the Pd primary particles were approximately 200 nm (pulsed laser) and

In a previous study, we found that hillocks (i.e. surface ion tracks) can be imaged using transmission electron microscopy (TEM) by irradiating thin CeO2 samples with swift heavy ions (SHI) at oblique incidence. In the present study, the same TEM method is applied to Y3Fe5O12 (YIG) and three fluorides (CaF2, SrF2 and BaF2) for observing hillocks. For YIG, which is one of the amorphizable materials, hillocks are found to have amorphous features consistent with amorphous features of ion tracks. For the fluorides, it is found that the hillocks do not exhibit amorphous features, and they are composed of nanocrystallites. Although hillocks for YIG and CaF2 exhibit different crystallographic features, hillock diameter agrees with the molten region diameter predicted by the thermal spike model for both materials. It is found 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 present result shows the existence of the velocity effect for ion track diameter in CaF2. It is also found that for fluorides both hillock and ion track diameters vary in the order of cation mass (i.e. CaF2

Conjugate materials can provide chemical functionality, enabling an assembly of the ligand complexation ability to metal ions that are important for applications, such as separation and removal devices. In this study, we developed ligand immobilized conjugate adsorbent for selective cesium (Cs) removal from wastewater. The adsorbent was synthesized by direct immobilization of dibenzo-24-crown-8 ether onto inorganic mesoporous silica. The effective parameters such as solution pH, contact time, initial Cs concentration and ionic strength of Na and K ion concentrations were evaluated and optimized systematically. This adsorbent was exhibited the high surface area-to-volume ratios and uniformly shaped pores in case cavities, and its active sites kept open functionality to taking up Cs. The obtained results revealed that adsorbent had higher selectivity toward Cs even in the presence of a high concentration of Na and K and this is probably due to the Cs–π interaction of the benzene ring. The proposed adsorbent was successfully applied for radioactive Cs removal to be used as the potential candidate in Fukushima nuclear wastewater treatment. The adsorbed Cs was eluted with suitable eluent and simultaneously regenerated into the initial form for the next removal operation after rinsing with water. The adsorbent retained functionality despite several cycles during sorption-elution-regeneration operations.

This work was focused on the promising inorganic and ligand immobilized conjugate materials for selective and high capacity of radioactive cesium (Cs) removal from radioactive liquid waste in Fukushima after an accident at Daiichi Nuclear Power Plant hit by the Great East Japan Earthquake and tsunami on 11 March 2011. The conjugate adsorbent was prepared by direct immobilization of dibenzo-18-crown-6 ether onto mesoporous silica monoliths. The Cs sorption behavior was investigated using batch equilibrium technique. The applicability of the inorganic conjugate adsorbent for Cs removal from aqueous test solutions was assessed, and the effective parameters such as solution pH, contacting time, initial Cs concentration and ionic strength of Na and K ion concentrations were evaluated systematically. The effective pH range for high Cs capacity was possible within the pH range 5.5–7.0 and the maximum sorption capacities were 50.23 and 27.40 mg/g for conjugate adsorbent and inorganic adsorbent, respectively. The results clarified that conjugate adsorbent had the higher selectivity towards Cs even in the presence of high concentration of Na and K ions rather than the inorganic adsorbent due to strong Cs–π interaction of benzene ring. The conjugate adsorbent was efficiently decontaminated the radioactive Cs from waste solution with high sorption efficiency. The data also revealed that both adsorbents worked well for removing of dissolved radioactive Cs even in the presence of high concentration competing ions. The adsorbents were reused in several cycles after elution operation with a suitable eluent (0.20 M HCl). Therefore, the prepared adsorbents could be used as low-cost potential adsorbents for the selective radioactive Cs decontamination from Fukushima wastewater samples.