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排序方式: 共有471条查询结果,搜索用时 11 毫秒
41.
Satoshi Wada Hiroaki Yasuno Takuya Hoshina Hirofumi Kakemoto Yoshikazu Kameshima Takaaki Tsurumi 《Journal of Electroceramics》2008,21(1-4):198-201
Barium titanate (BaTiO3) crystallites with various particle sizes from 22 to 500 nm were prepared by the two-step thermal decomposition method of barium titanyl oxalate. Various characterizations revealed that these particles were impurity-free, defect-free, dense BaTiO3 particles. The powder dielectric measurement clarified that the dielectric constant of BaTiO3 particles with a size of around 58 nm exhibited a maximum of over 15,000. To explain this size dependence, the THz region dielectric properties of BaTiO3 fine particles, especially Slater mode frequency, were measured using the far infrared (FIR) reflection method. As the result, the lowest Slater mode frequency was obtained at 58 nm. This tendency was completely consistent with particle size dependence of the dielectric constant. 相似文献
42.
43.
Takashi Nozawa Takaaki Koyanagi Yutai Katoh Hiroyasu Tanigawa 《Journal of the European Ceramic Society》2019,39(8):2634-2647
SiC/SiC composites are promising structural candidate materials for various nuclear applications over the wide temperature range of 300–1000 °C. Accordingly, irradiation tolerance over this wide temperature range needs to be understood to ensure the performance of these composites. In this study, neutron irradiation effects on dimensional stability and mechanical properties to high doses (11–44 dpa) at intermediate irradiation temperatures (?600 °C) were evaluated for Hi-Nicalon Type-S or Tyranno-SA3 fiber–reinforced SiC matrix composites produced by chemical vapor infiltration. The influence of various fiber/matrix interfaces, such as a 50–120 nm thick pyrolytic carbon (PyC) monolayer interphase and 70–130 nm thick PyC with a subsequent PyC (?20 nm)/SiC (?100 nm) multilayer, was evaluated and compared with the previous results for a thin-layer PyC (?20 nm)/SiC (?100 nm) multilayer interphase. Four-point flexural tests were conducted to evaluate post-irradiation strength, and SEM and TEM were used to investigate microstructure. Regardless of the fiber type, monolayer composites showed considerable reduction of flexural properties after irradiation to 11–12 dpa at 450–500 °C; and neither type showed the deterioration identified at the same dose level at higher temperatures (>750 °C) in a previous study. After further irradiation to 44 dpa at 590–640 °C, the degradation was enhanced compared with conventional multilayer composites with a PyC thickness of ?20 nm. Multilayer composites have shown comparatively good strength retention for irradiation to ?40 dpa, with moderate mechanical property degradation beginning at 70–100 dpa. Irradiation-induced debonding at the F/M interface was found to be the major cause of deterioration of various composites. 相似文献
44.
Takaaki Koyanagi Yutai Katoh Caen Ang Derek King Greg E. Hilmas William G. Fahrenholtz 《Journal of the American Ceramic Society》2019,102(1):85-89
The response of polycrystalline TiB2 to neutron irradiation was investigated. The material was fabricated using isotopically enriched 11B powders to minimize helium production via the 10B(n, α)7Li reaction. Neutron irradiation was conducted at temperatures of ~200°C and ~600°C to a fast fluence of 2.4 × 1025 n/m2 (>0.1 MeV). The material exhibited some swelling, but less swelling at the higher irradiation temperature. No macroscopic damage was observed in the irradiated material, although moderate irradiation-induced micro-cracking was found in the irradiated TiB2. This study demonstrated improved radiation resistance of isotopically tailored TiB2 compared with natural boron TiB2, which exhibited macroscopic fracture by irradiation. 相似文献
45.
Yuuya Fujisawa Takaaki Tsuda Shunsuke Hashimoto Takeshi Sugahara Kazunari Ohgaki 《Chemical engineering science》2012,68(1):660-662
Three-phase equilibrium (pressure–temperature) relation of hydrate+aqueous+fluid phases for the hydrogen (H2)+tetra-n-butyl phosphonium bromide (TBPB)+water ternary system was investigated in a temperature range of 281.90–295.94 K and a pressure range up to 170 MPa. The behavior of the three-phase coexisting curve indicates no structural transition in the present experimental region. The Raman spectra obtained in the H2+TBPB mixed semi-clathrate hydrate crystal reveal that H2 molecule occupies only small cage compartmentally and the TBPB molecule is encaged with a set of other large cages. 相似文献
46.
Yoshihiko Nakata Satoshi Ninomiya Chikage Imada Masafumi Nagai Takaaki Aoki Jiro Matsuo Nobutsugu Imanishi 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2005,230(1-4):489-494
We have measured both secondary neutral and ionized particles from an InSb target under 3.0 MeV Si ion bombardment. Measurements of both ions and neutrals have not been carried out so far in the MeV-energy range. The mass spectra and axial emission energy distributions of secondary particles were investigated. Secondary ions were measured with a linear- and a reflective-type time-of-flight technique, whereas secondary neutral particles were photo-ionized by a UV pulsed laser (ArF: 193 nm) and measured with a reflective-type time-of-flight technique. Different results were obtained for neutral particles in comparison with ionized particles. The mean energy of neutral Sb atoms was much lower than that of neutral In atoms, whereas the mean energies of secondary In and Sb ions were nearly equal. 相似文献
47.
Hirofumi Kakemoto Tohru Higuchi Hajime Shibata Satoshi Wada Takaaki Tsurumi 《Journal of Materials Science: Materials in Electronics》2008,19(4):311-314
The modification of thermoelectric figure of merit was estimated from enhanced mobility of [100] oriented beta-FeSi2 film. beta-FeSi2 on Si(001) substrate was prepared by molecular beam epitaxy method using an Fe source. The crystallographic orientation of
beta-FeSi2 film on Si(001) substrate was characterized by using X-ray diffraction. Using scanning electron microscopy, surface morphology
and film thickness of samples were observed and estimated, respectively. The mobility of beta-FeS2 film on Si(001) substrate were also characterized by Hall measurement at room temperature. A part of the enhancement of figure
of merit was evaluated as the functions of mobility and crystallographic orientation of samples. 相似文献
48.
Hiroyuki Mishima Mituo Kakei Toshio Yasui Saori Miyamoto Yasuo Miake Takaaki Yanagisawa 《Frontiers of Materials Science in China》2008,2(2):179-181
The present study was aimed at examining the nature of apatite crystal in the tooth apparatus of a conodont fossil using transmission
electron microscopy (TEM), scanning electron microscopy (SEM), laser Raman microprobe spectrometry and electron-probe microanalysis
(EPMA). The hard tissue of the condont consisted of 2 layers and the organization varied with the size of the crystal. Higher
magnification showed that the crystals were observed in the lattice of (100) and the central dark lines were not present.
Ca, P, and F were detected in the crystal using EPMA. Our results indicate that the apatite crystal in conodont fossils is
not hydroxyapatite but fluorapatite. 相似文献
49.
Inés S. Neira Francisco Guitián Takaaki Taniguchi Tomoaki Watanabe Masahiro Yoshimura 《Journal of Materials Science》2008,43(7):2171-2178
We report an effective method for the synthesis of hydroxyapatite whiskers with sharp faceted hexagonal shape employing a
low temperature (90 °C) hydrothermal route with calcium nitrate tetrahydrate, diammonium phosphate and urea as starting materials.
The key parameters of the synthesis process i.e. duration, temperature cycle of the treatment and starting pH value are carefully
varied and the end products are investigated using powder X-ray diffraction (XRD), Raman-scattering, infrared spectroscopy
(IR), elemental analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron
microscopy (TEM), electron diffraction (ED), and high-resolution TEM (HRTEM) in order to find the optimal reaction conditions
that lead to the desired hexagonal morphology of HA whiskers. The results demonstrate that gradual and greater increase in
solution pH during the hydrothermal process favors large quantity of the single-crystalline hydroxyapatite whiskers with well
defined hexagonal morphology. 相似文献
50.
Gang Zou Xian You Hideki Kohn Takaaki Manaka Mitsumasa Iwamoto 《Thin solid films》2009,518(2):750-753
An azobenzene mesogen-substituted diacetylene (NADA) monolayer has been transferred onto the solid substrate by the traditional Langmuir–Blodgett (LB) method. Solid-state polymerization of NADA LB films can be sensitized in visible light region. In situ UV–vis absorption measurement enables us to study polymerization kinetics of NADA LB films. The polymerization process can be described as a first order rate equation and polymerization rate constants are characterized in detail. Furthermore, achiral NADA molecules can form chiral LB films through overcrowded packing of the azobenzene moiety. 相似文献