Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijhydene.2020.07.215

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.cplett.2019.137053

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijhydene.2019.07.035

Language：Japanese   Publishing type：Research paper (scientific journal)  

要 旨
カーボンナノチューブ(CNT)はナノサイズの直径で長さが μm 以上と非常に高いアスペクト比の繊維状 炭素材料であることから，他の材料との複合材料において 少ない添加で高い電気伝導性，熱伝導性や強度特性を発現 することができる.本研究では，CNT/ゴム複合材料の高 圧水素特性を評価し，CNT，その中でも単層カーボンナノ チューブ (SWCNT) をゴム中に均一に分散させることで，高 圧水素に曝露後の水素侵入量が低く，かつ，体積変化も小 さくすることができることを明らかとした.また，CNT の 分散度と高圧水素特性の関係から，水素侵入量は組成が支 配的で，体積変化は分散構造が支配的であることが示唆さ れた.本報のカーボンナノチューブ/ゴム複合材料は，その 高圧水素特性から高圧水素環境下での変化が小さく，高圧 水素環境下における高耐久シール材として期待される.

DOI： 10.1295/koron.2019-0008

Language：Japanese   Publishing type：Research paper (scientific journal)  

We developed an ethylene vinyl alcohol copolymer with 1,2 diol side chains (hereinafter new EVOH) that can be melt-molded even though the ethylene content is about 16 mol%, and the properties of polymer alloy that consists of nylon 6-66 (hereinafter PA) and new EVOH were studied. The polymer alloy showed compatibility on the PA rich side,but the crystallinity of each component decreased at the same time. Especially when the PA content is 85wt.% for polymer alloy, PA crystals were not confirmed. The free volume of the composite increased linearly with the PA blend ratio,but the specific volume deviated from the linear relationship,which increased on the PA rich side. The normalized free volume was calculated using the amorphous ratio calculated from solid state NMR(T _1C : ¹³ C spin-lattice relaxation time) and I ₃ (the relative intensity of the long time component) from PALS. It was confirmed that high pressure hydrogen resistance of PA blended with new EVOH was improved by using normalized free volume even on the PA rich side. This result is thought to be due to the amorphous part of PA reinforced by interaction with new EVOH.

DOI： 10.2472/jsms.68.34

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1149/2.0331805jes

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Properties of polymer solid electrolytes composed of poly(ethylene carbonate) [PEC], lithium bis(trifluoromethane sulfonimide) [LiTFSI, LiN(CF3SO2)2] and propylene carbonate [PC] as plasticizer have been analyzed using Raman spectroscopy and ac impedance spectroscopy. Including 14 wt% of PC in the PEC based polymer electrolyte with LiTFSI concentration of 0.2 mol per polymer repeat unit, made it possible to increase the ionic conductivity (σ) by one order of magnitude to a practical-use level of 1.3 mS cm−1 at 20°C. The correlation between σ and temperature fits well the Williams-Landel-Ferry equation, so it is considered that ionic conductivity depends on thermal activation of the polymer chains. From the correlation between σ and temperature, it is concluded that PC (with greater mobility than the polymer chains) partly solvates with lithium ions, and σ is improved by lowering its activation energy.

Language：English   Publishing type：Research paper (scientific journal)  

The redox reaction of tetravalent Mn4 + ions has attracted much interest since it is considered that this reaction is closely related to the generation of high capacity in layered cathodes with excess lithium.
We considered that to investigate materials, which include tetravalent Mn4 + ions and have a different crystal structure from Li2MnO3, is valuable for understanding the reaction mechanism. The result will reveal whether Mn4 + ion in the Li2MnO3 structure is essential or only existence of Mn4 + ion is sufficient for appearance of the high capacity. In this work, we investigated Li-rich Li1 + xMn2 − xO4 (x = 0.20, 0.25, 0.30, 0.33) stoichiometric spinels. For a Li content of x = 0.33, a capacity of 50 mAh g− 1 was observed in 5-V region. It is possible that the Li-rich spinel includes a small amount of Li 2MnO 3 impurity, which exhibits the 5-V plateau. No significant changes in lattice constants are observed from x = 0.25 to 0.33, which indicates generation of Li 2MnO 3. We estimated the amount as 9.2 wt.% for x = 0.33 by standard addition analysis, and true Li concentration of the spinel component as 0.23. However, the observed 5-V capacity cannot be attributed to only the impurity phase of Li 2MnO 3, because the specific capacity must exceed 540 mAh g − 1 to explain it. It is considered that the observed 5-V capacity is caused by two components of the Li-rich spinel and the other phase like a composite material of Li 2MnO 3/Li-rich spinel. The 5-V capacity for the pure spinel component estimated by extrapolating the 5-V capacity vs. impurity-concentration plot is 7.9 mAh g − 1.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

To identify components with different spin–spin relaxation times, T2, in the solid-echo pulse proton nuclear magnetic resonance (1H-NMR) spectra of crude acrylonitrile (AN)–butadiene rubbers (NBRs) with five different AN contents, we tried to understand the inhomogeneity in the crude NBRs in terms of their microstructures and molecular mobilities. The results of small-angle X-ray scattering, differential scanning calorimetry and dynamic mechanical analysis showed that crude NBRs have a single-phase and homogeneous morphology on the nanoscale. The microstructure of the crude NBRs shows alternately copolymerized AN–butadiene (BU) and BU block sequences, as indicated by 1H-NMR spectra. The T2 of the crude NBRs revealed three components with different molecular mobilities, even in homogeneous samples. The content of the highest-mobility component with T2l is negligible. Judging from the AN content dependence of the 1H ratio of these components, the low-mobility component with T2s and high-mobility component with T2m were assigned to the alternately copolymerized AN–BU sequences and BU block sequences, respectively.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

In order to establish a hydrogen energy system, the reliability of sealing rubber for high-pressure hydrogen has been required. The rubber O-ring for hydrogen energy system is used with pressurized-decompress cycle of high-pressure hydrogen. It causes internal cracks referred as blister fracture. Degradation of seal performance originated from blister fracture is one of the important issues to improve the reliability. This study focused on the blister initiation behavior and the effect of materials, gas species and decompression rate on blister fracture in terms of visualizing O-ring behavior under high-pressure gas. For the visualizing evaluation, a transparent ethylene-propylene rubber (EPDM) and vinyl-methyl silicone rubber (VMQ) O-rings were molded, and a special viewable high-pressure vessel with a glass viewport was developed. The O-ring specimens were exposed to high-pressure hydrogen, helium, and nitrogen at 10 MPa until gas solubility content in O-ring was saturated; afterwards, these gases were decompressed with some rate. It was obviously visualized that the blister fracture did not occur in VMQ O-ring but occurred in EPDM. The blister fracture of the EPDM O-ring in nitrogen was the most serious in the tested gases. These blister behaviors are considered to be related to gas diffusivity of hydrogen, helium and nitrogen.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Eight carbon black (CB)-filled ethylene–propylene–diene–methylene linkage (EPDM) rubbers were manufactured by varying the content and type of CB. Then, the relationship among crack damage caused by high-pressure hydrogen decompression, the hydrogen permeation properties, and the mechanical properties of the rubbers was investigated. The hydrogen gas permeability of the rubbers decreased with an increase in the CB content and depended little on primary particle size. In contrast, the hydrogen gas diffusivity and solubility depended on both the CB content and primary particle size, that is, the hydrogen gas diffusivity decreased with an increase in the CB content and a decrease in the primary particle size, and the hydrogen gas solubility increased with an increase in the CB content and a decrease in the primary particle size. As for the mechanical properties, the CB-filled rubbers were more strongly reinforced by an increase in the CB content and a decrease in the primary particle size. The crack damage by high-pressure hydrogen decompression became larger as the ratio of the hydrogen gas solubility to estimated internal pressure at crack initiation relating to the mechanical properties became larger. As a smaller CB particle increases the hydrogen gas solubility of EPDM rubbers, while at the same time it reinforces the rubbers, the crack damage in the CB-filled rubbers was not influenced by the primary particle size.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

When a rubber O-ring was used as a sealing material of a pressure vessel for high-pressure hydrogen gas such as 70MPa, which is the hydrogen pressure for fuel cell electric systems, the O-ring was extruded from the pressure vessel due to an increase in volume by gas absorption, and consequently cracks initiated in the previous study. Therefore, it is important to clarify the influence of hydrogen pressure on the increase in volume and mechanical properties in order to design the rubber O-ring for high-pressure hydrogen gas. From this viewpoint, unfilled and carbon black-filled sulfur-vulcanized NBR composites were exposed to hydrogen gas at a maximum pressure of 100MPa ; then, the influence of hydrogen exposure on volume increase and tensile properties of the composites was investigated. The residual hydrogen content which was measured 35 min after decompression increased with an increase in the hydrogen pressures ranging from 0.7 to 100MPa for the unfilled composite (NF) and the filled composite (CB). In contrast, the volume of NF and CB was hardly changed less than 10MPa, and the increase in volume by gas absorption was observed more than 10MPa. The elastic modulus of NF and CB decreased with an increase in volume, and this tendency can be successfully explained in term of the decrease in the crosslink density and elongation by volume increase. Although the tensile strength of NF hardly depended on the volume of specimen, the tensile strength of CB clearly decreased with an increase in volume. This is considered to be because a boundary structure between carbon black and rubber matrix was changed by hydrogen exposure.

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

When a cylindrical specimen (φ29.0mm × 12.5mm) made from sealing rubbers was exposed in high-pressure hydrogen gas, it was clarified that cracks initiated in the specimen after decompression in previous studies. However, it was not clear whether crack damage obtained from the cylindrical specimen was the same as that obtained from an O-ring specimen used for practical sealing or not, because the shapes and dimensions of these specimens were different. From this viewpoint, seven cylindrical specimens (φ13.0mm × 2.0, 4.0, 6.0, 8.0, 10.0, 12.0 mm, and φ29.0mm × 12.5mm) made from an unfilled peroxide-crosslinked EPDM composite were exposed to high-pressure hydrogen gas at a maximum pressure of 10MPa ; then, the influence of the shape of specimen on crack initiation and growth behavior was investigated. Micrometer-sized defects, facets, and notch-like regions were observed at fracture origins of internal cracks by SEM observation. It was inferred that micrometer-sized bubbles were formed at these sites by the coalescence of submicrometer-sized bubbles, and internal cracks initiated due to stress concentration of the micrometer-sized bubbles. Measurement of AE (acoustic emission) was also conducted to confirm the existence of the sub-micrometer-sized bubbles. The crack damage became more serious with an increase in the thickness of specimen as well as an increase in hydrogen pressure. Although the critical hydrogen pressures at crack initiation of the specimens with thicknesses from 2.0 to 6.0mm decreased with an increase in the thickness of specimen, those of the specimens with thicknesses from 6.0 to 12.0mm were the same. The influence of the shape of specimen on the crack damage and the critical hydrogen pressure was successfully explained in terms of retained hydrogen content and fracture mechanics.

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

In order to evaluate the influence of environmental condition on durability and permeation properties of sealing rubber materials under high pressure hydrogen gas, a durability tester which enables the sealing rubber to expose repeatedly high pressure hydrogen gas at arbitrary test conditions (maximum pressure is 90 MPa and the range of ambient temperature is from –60 to 100 °C) was developed. In this study, durability and hydrogen permeation properties of peroxide- vulcanized EPDM composite filled with white reinforcing filler were evaluated under hydrogen gas at a maximum pressure of 70 MPa and the range of ambient temperature from 0 to 100 °C. The dependence of the ambient temperature on permeability, diffusivity, and solubility was not influenced by the hydrogen pressure and the shape of specimen. Moreover, although we can regard that hydrogen content was approximately proportional to the hydrogen pressure at ≤10 MPa, this relationship became non-linear when a hydrogen pressure became higher. As for durability, blister damage became more serious with an increase in the hydrogen pressure and ambient temperature. Furthermore, damage by extrusion was also observed at ≥35 MPa due to large gas absorption.

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Event date： 2009.12

Presentation type：Oral presentation (general)  

Venue：東京理科大学森戸記念館   Country：Japan  

Event date： 2009.12

Presentation type：Oral presentation (general)  

Venue：東京理科大学森戸記念館   Country：Japan  

Event date： 2009.10

Presentation type：Oral presentation (general)  

Venue：愛媛大学工学部   Country：Japan  

Event date： 2009.10

Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場   Country：Japan  

Event date： 2009.10

Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場   Country：Japan  

Event date： 2009.10 - 2009.11

Venue：九州大学馬出病院キャンパス医学部百年講堂（福岡市）   Country：Japan  

Event date： 2009.9

Presentation type：Oral presentation (general)  

Venue：大阪市立大学   Country：Japan  

Event date： 2009.9

Presentation type：Oral presentation (general)  

Venue：熊本大学   Country：Japan  

Event date： 2009.9

Presentation type：Oral presentation (general)  

Venue：熊本大学   Country：Japan  

Event date： 2009.5

Presentation type：Oral presentation (general)  

Venue：パシフィコ横浜   Country：Japan  

Event date： 2009.5

Presentation type：Oral presentation (general)  

Venue：ホテルアウィーナ大阪   Country：Japan  

Event date： 2009.5

Presentation type：Oral presentation (general)  

Venue：ホテルアウィーナ大阪   Country：Japan  

Event date： 2009.5

Presentation type：Oral presentation (general)  

Venue：ホテルアウィーナ大阪   Country：Japan  

Event date： 2008.12

Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場   Country：Japan  

Event date： 2008.12

Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場   Country：Japan  

Event date： 2008.9

Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2008.8

Presentation type：Oral presentation (general)  

Venue：岩手大学   Country：Japan  

Event date： 2008.8

Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2008.5

Presentation type：Oral presentation (general)  

Venue：パシフィコ横浜   Country：Japan  

Event date： 2008.5

Presentation type：Oral presentation (general)  

Venue：鹿児島大学工学部   Country：Japan  

Audience： General,　Scientific,　Company,　Civic organization,　Governmental agency

Type：Seminar, workshop