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Journal Articles

Journal Articles

Determination of detrapping and trapping rate constants for hydrogen based on experimental thermal desorption spectra

Ebihara, Kenichi; Saito, Kei*; Takai, Kenichi*

Proceedings of 2016 International Hydrogen Conference (IHC 2016); Materials Performance in Hydrogen Environments, p.470 - 477, 2017/00

For understanding hydrogen (H) embrittlement of steels, it is necessary to infer the state that defects trap H in the steels. Thermal desorption spectra of H obtained by the thermal desorption spectrometry (TDS) are used for inferring such a state. Because the thermal desorption spectra include the influence of experimental conditions and hydrogen diffusion as well as information of the defects trapping H, it is necessary to interpret the spectra using the numerical simulation. In the presentation, we determined the detrapping and the trapping rate constants which are necessary for the simulation from the experimental spectra obtained for plate specimens which is so small that H diffusion is ignorable. Then we confirmed that the model using the obtained rate constants can simulate the spectra of larger cylindrical specimens, so that it was found that the rate constant for small specimens can be used for the simulation of the spectra for specimens of different shape or size.

Journal Articles

Study on modeling of thermal desorption spectra of hydrogen including variation of vacancy-type trap sites

Ebihara, Kenichi; Saito, Kei*; Takai, Kenichi*

"Suiso Zeika No Kihon Yoin To Tokusei Hyoka Kenkyukai Chukan Hokokukai" Shimposium Yokoshu (USB Flash Drive), p.30 - 35, 2016/09

no abstracts in English

Journal Articles

Numerical reproduction of hydrogen thermal desorption spectra of tempered martensitic steel based on experimental data

Ebihara, Kenichi; Saito, Kei*; Takai, Kenichi*

"Suiso Zeika No Kihon Yoin, Kaiseki To Hyoka" Shimposium Yokoshu (USB Flash Drive), p.27 - 33, 2015/09

The thermal desorption spectra which reflect the H segregation state can be obtained by heating a specimen including H at a constant rate. However, the simulation of spectra needs to extract information of the H segregation state because spectra is affected by experimental conditions and H diffusion. The detrapping activation energy E$$_a$$ and the pre-exponential factor of detraping rate constant which are simulation parameters are fixed from the data previously reported or by fitting experimental spectra. Instead, we evaluated both of them from the experimental spectra of the specimen in which the H diffusion effect can be ignored, and simulated the spectra using them. As a result, in the case of iron, we could simulate spectra better than by the previous parameters. In the case of tempered martensitic steel, we could simulate spectra by the value obtained by adjusting the evaluated p$$_0$$ along with the evaluated E$$_a$$.

Journal Articles

Enhanced lattice defect formation associated with hydrogen and hydrogen embrittlement under elastic stress of a tempered martensitic steel

Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Hirade, Tetsuya; Oshima, Nagayasu*

NanotechJapan Bulletin (Internet), 8(3), 5 Pages, 2015/07

Studying the creation and time evolution of defects is an important issue for interpreting the hydrogen embrittlement mechanism of steels. We have been studied the relationship between hydrogen embrittlement of high strength steel and lattice defects associated with hydrogen by thermal desorption analysis (TDA) and positron probe microanalyzer (PPMA).

Journal Articles

Atomistic and continuum comparative studies on the stress distribution around a nano-crack on the grain boundary for modeling hydrogen embrittlement of iron

Ebihara, Kenichi; Kaburaki, Hideo; Itakura, Mitsuhiro

"Hagane No Kikaiteki Tokusei Ni Oyobosu Suiso No Koka To Sono Hyoka" Shimpojium Yokoshu (USB Flash Drive), 6 Pages, 2014/09

Since hydrogen(H) embrittlement is one factor causing degradation and/or fracture of steel, understanding its mechanism is required. The grain-boundary(GB) decohesion due to segregation of H is considered to cause the delayed fracture of high strength steels and the cold cracking in welding. In the model based on GB decohesion, information of strength of GBs estimated in the atomic scale is used for the estimation of strength or crack propagation in the macroscopic scale. However the modeling between the atomic and the macroscopic scales is not clear. In particular, the validity of the model using the elastic continuum around nano-cracks for stress concentration at the crack tip is not clear. Thus, we examined the difference of the stress distribution around the nano-crack which was estimated by molecular dynamics and by a continuum calculation. As a result, the discrepancy became remarkable at high strain. The stress concentration was not simulated by the elastic continuum model.

Journal Articles

First-principles study on segregation energy and embrittling potency of hydrogen in Ni$$Sigma$$5(012) tilt grain boundary

Yamaguchi, Masatake; Shiga, Motoyuki; Kaburaki, Hideo

Journal of the Physical Society of Japan, 73(2), p.441 - 449, 2004/02

 Times Cited Count:12 Percentile:39.44(Physics, Multidisciplinary)

The electronic structures of $$Sigma$$5(012) symmetrical tilt grain boundary (GB) and (012) free surface (FS) systems for nickel including hydrogen are calculated by the full-potential linearized augmented plane wave method with the generalized gradient approximation. The difference of the binding energies between the $$Sigma$$5(012)GB/FS site and the inner bulk site is obtained as the GB/FS segregation energy, and the difference between GB and FS segregation energies as the embrittling potency energy. The segregation position of hydrogen atom is determined by the force minimization. We find that hydrogen atom prefers $$Sigma$$5(012)GB to inner bulk energetically by about 0.3 eV/H, while it prefers (012)FS to the GB by about 0.3-0.4 eV/H. The open space at GB may be occupied by an additional interstitial Ni atom since it increases the GB energy by only about 10%. In this case, the GB segregation energy of hydrogen reduces, which makes the segregation difficult. The calculated zero-point energies of hydrogen at inner bulk, GB, and FS sites are within 0.12-0.16eV/H.

Journal Articles

Low activated materials as plasma facing components

Hino, Tomoaki*; Hirohata, Yuko*; Yamauchi, Yuji*; Sengoku, Seio

Proceedings of IAEA 18th Fusion Energy Conference (CD-ROM), 5 Pages, 2001/00

no abstracts in English

Journal Articles

Hydrogen retention of V-alloy under plasma irradiation of JFT-2M

Oda, Tomomasa*; Hirohata, Yuko*; Hino, Tomoaki*; Sengoku, Seio

Shinku, 43(3), p.325 - 328, 2000/03

no abstracts in English

Journal Articles

Metal-hydride characterization and mechanical properties of Ti-6Al-4V alloy

Ishiyama, Shintaro; Fukaya, Kiyoshi; Eto, Motokuni; Miya, Naoyuki

Journal of Nuclear Science and Technology, 37(2), p.144 - 152, 2000/02

no abstracts in English

Journal Articles

Mechanical properties of chromic oxide coating film on zirconium alloy formed by chemical densified coating method

*; Kawamura, Hiroshi; *;

Nippon Seramikkusu Kyokai Gakujutsu Rombunshi, 98(1139), p.721 - 725, 1990/07

no abstracts in English

Journal Articles

Effects of impurities on hydrogen permeability through palladium alloy membrane at comparatively high pressure and temperatures

; ; Katsuta, Hiroji; Naruse, Yuji

J.Less-Common Met., 89, p.429 - 436, 1983/00

 Times Cited Count:56 Percentile:3.19

no abstracts in English

JAEA Reports

Effects of Impurities on Hydrogen Permeability Through Palladium Alloy Membrane at Comparatively High Pressure and Temperature

; Konishi, Satoshi; Katsuta, Hiroji; Naruse, Yuji

JAERI-M 82-013, 21 Pages, 1982/03

JAERI-M-82-013.pdf:0.53MB

no abstracts in English

Oral presentation

Vacancy analysis with a positron microprobe for hydrogen embrittlement under elastic stress of tempered martensitic steels

Oshima, Nagayasu*; Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Hirade, Tetsuya

no journal, , 

Studying the creation and time evolution of defects is an important issue for interpreting the hydrogen embrittlement mechanism of steels. We have been studied the relationship between hydrogen embrittlement of high strength steel and lattice defects associated with hydrogen by a positron probe microanalyzer (PPMA) which is positron lifetime measurement system with a pulsed positron microbeam. The results with the mean positron lifetime measurements indicated that vacancies or vacancy clusters were additionally formed with hydrogen embrittlement under elastic stress. We also have tried to see the detail of the change with hydrogen embrittlement by applying the multicomponent analysis of positron annihilation lifetime spectra. The results indicated a possibility that the vacancies were formed as the complex with dislocations.

Oral presentation

Numerical simulation for thermal desorption analysis of hydrogen in steels

Ebihara, Kenichi

no journal, , 

no abstracts in English

Oral presentation

Numerical simulation for thermal desorption analysis of hydrogen

Ebihara, Kenichi

no journal, , 

no abstracts in English

Oral presentation

Size effect on evaluation of detrapping rate constants for hydrogen in thermal desorption analysis of ferritic steels

Ebihara, Kenichi; Kaburaki, Hideo; Takai, Kenichi*

no journal, , 

In order to understand the mechanism of hydrogen(H) embrittlement it is necessary to grasp properly the H state in steels. In the thermal desorption analysis, the H state is deduced from thermal desorption spectra which are obtained by measuring hydrogen desorbed from a steel specimen heated at a constant rate. However, because the desorption spectra include the influence of experimental conditions and of initial H distribution as well as information of the H state, the spectra must be interpreted using the numerical simulation. In the presentation, we examined the influence of the initial H distribution, which varies according to experimental conditions, on the specimen size dependence of the method to evaluate the detrapping rate constant from experimental spectra. As a result, though the influence of the initial distribution becomes remarkable when the size is large, its influence was very small in the range less than 2mm for iron and less than 8mm for tempered martensitic steels.

Oral presentation

Numerical study on thermal desorption spectra of hydrogen for pure aluminium

Ebihara, Kenichi; Yamaguchi, Masatake; Tsuru, Tomohito; Itakura, Mitsuhiro

no journal, , 

no abstracts in English

22 (Records 1-20 displayed on this page)