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Hirade, Tetsuya; Michishio, Koji*; Kobayashi, Yoshinori*; Oshima, Nagayasu*
Chemical Physics Letters, 795, p.139507_1 - 139507_4, 2022/05
Times Cited Count：2 Percentile：14.89(Chemistry, Physical)We obtained the temperature dependence up to 150
C of the triplet positronium (
-Ps) lifetime in N,N,N-Trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI) by the vertical slow positron beamline installed at AIST. Positrons penetrate into the liquid surface of TMPA-TFSI with the positron energies of 2 keV and 12 keV to investigate at the near-surface and the balk. The surface structure was visible at 150C, 120C above the melting temperature. The -Ps lifetime became shorter at higher temperatures for both positron energies. Similar temperature dependence had appeared just in water as the result of the reaction of -Ps and radiolysis products such as the OH radicals. The temperature dependence observed for TMPA-TFSI suggested that the chemical reaction of -Ps occurred.
Hirade, Tetsuya; Michishio, Koji*; Kobayashi, Yoshinori*; Oshima, Nagayasu*
Acta Physica Polonica A, 137(2), p.109 - 112, 2020/02
Times Cited Count：0 Percentile：0.00(Physics, Multidisciplinary)Recently, it was reported that the positronium (Ps) bubble in Room Temperature Ionic Liquids (RTILs) showed some phenomena that were very different from them observed in other molecular liquids. Now the reason of these interesting phenomena is being understood. The structure caused by the ionic interaction between anions and cations can exist even at the higher temperatures than the melting temperatures. It was the reason why the oscillation of Ps bubble was observed at the temperatures near the melting temperatures in RTILs. The temperature dependence of the Ps bubble size estimated by the triplet Ps (-Ps) pick-off annihilation lifetime indicated that there was a nano-meter structure remained by ionic interactions even at high temperatures. The -Ps pick-off annihilation lifetime will be a strong tool to study nano-structure in RTILs.
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).
Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Oshima, Nagayasu*; Hirade, Tetsuya
ISIJ International, 52(2), p.198 - 207, 2012/02
Times Cited Count：68 Percentile：92.55(Metallurgy & Metallurgical Engineering)Hydrogen behavior and hydrogen-enhanced lattice defect formation under elastic stress of tempered martensitic steel were clarified with respect to dislocations and vacancies by thermal desorption analysis (TDA) using hydrogen as a probe of defects and a positron probe microanalyzer (PPMA). The relationship between hydrogen embrittlement and lattice defects associated with hydrogen was also investigated. The amount of lattice defects increased gradually with increasing time of applied stress. The specimen fractured under elastic stress. The enhanced vacancies due to interactions between dislocations and hydrogen under elastic stress directly caused ductility loss. Even though hydrogen was completely removed by degassing the vacancies remain. Besides hydrogen content and applied stress, the time of formation and accumulation of vacancies are also concluded to be important factors causing hydrogen embrittlement.
Doshida, Tomoki*; Takai, Kenichi*; Hirade, Tetsuya; Oshima, Nagayasu*
no journal, ,
Hydrogen behavior and hydrogen-enhanced lattice defect formation under elastic stress of tempered martensitic steel were clarified with respect to dislocations and vacancies by a positron probe microanalyzer (PPMA). The relationship between hydrogen embrittlement and lattice defects associated with hydrogen was also investigated. The specimen fractured under elastic stress. The enhanced vacancies under elastic stress directly caused ductility loss. Even though hydrogen was completely removed by degassing the vacancies remain. Besides hydrogen content and applied stress, the time of formation and accumulation of vacancies are also concluded to be important factors causing hydrogen embrittlement.
Sakai, Hiroaki; Minei, Shuntaro; Hirade, Tetsuya; Oshima, Nagayasu*; Kobayashi, Yoshinori*; Kinomura, Atsushi*; Suzuki, Ryoichi*
no journal, ,
It was reported that the positronium (Ps) formation in polymers was enhanced near breakdown voltage. It cannot be explained by the Spur Reaction Model. We investigated the electric field effect on positron annihilation lifetime for Kapton that has no Ps formation. We observed elongation of the free positron annihilation lifetime instead of the enhancement of Ps formation. It is possible to explain that drift of positrons causes smaller annihilation probability, i.e. longer lifetime. Now it is possible to explain the Ps formation enhancement reported previously could be caused by the elongation of the lifetime of the free positrons.
Jiang, L.*; Oshima, Nagayasu*; O'Rourke, B. E.*; Suzuki, Ryoichi*; Harada, Yoshihisa*; Suzuki, Takayuki*; Takatsu, Shuhei*; Hirade, Tetsuya; Takai, Kenichi*
no journal, ,
Positron annihilation spectroscopy (PAS) is a sensitive method for detection of defects such as vacancies, vacancy clusters and nano-voids. The positron probe microanalyzer (PPMA) in AIST can investigate defect distribution of materials using a scanning positron microbeam. For the application of the PPMA for analysis of such materials it is important to consider the defects introduced during the sample preparation. we are investigating two kinds of sample preparation process, electrical discharge machining (EDM) and colloidal silica polishing after EDM. We are studying the depth dependence of the density of the defects induced by these processes in various metals, including SUS316L, using PAS.
Kai, Takeshi; Ishida, Akira*; Oshima, Nagayasu*
no journal, ,
When a positron was injected into the condensed phase, positronium (Ps) which constructs of an electron and a positron was generated. Although we expect that Bose-Einstein condensation (BEC) using the densely positroniums creates newly physics such as gravity accurate measurement of antimatter and annihilation gamma-rays laser, the BEC have never been achieved. The aims of this study are that fundamental explication of Ps generation as well as elucidation of experimental condition for Ps-BEC achievement from the positrons deceleration simulation in the condensed phase. For the aims, we applied a dynamic Monte Carlo code of the electrons to deceleration simulation of positrons bunch. We present current states of development of the high dense positrons transport simulation in the condensed phase.
Kai, Takeshi; Ishida, Akira*; Oshima, Nagayasu*
no journal, ,
When a positron was injected into the condensed phase, positronium (Ps) which constructs of an electron and a positron was generated. Although we expect that Bose-Einstein condensation (BEC) using the densely positroniums creates newly physics such as gravity accurate measurement of antimatter and annihilation gamma-rays laser, the BEC have never been achieved. The aims of this study are that fundamental explication of Ps generation as well as elucidation of experimental condition for Ps - BEC achievement from the positrons deceleration simulation in the condensed phase. For the aims, we applied a dynamic Monte Carlo code of the electrons to deceleration simulation of positrons bunch. We present current states of development of the high dense positrons transport simulation in the condensed phase.
Hirade, Tetsuya; Michishio, Koji*; Kobayashi, Yoshinori*; Oshima, Nagayasu*
no journal, ,
Positronium (Ps) forms bubbles in liquids, and the bubbles become larger due to the lower surface tension at higher temperatures, resulting in longer o-Ps lifetimes. In room-temperature ionic liquids, it has been shown that the structure of Ps bubble is different and depends on the structure formed by the Coulomb force of the ions. We successfully obtained that the o-Ps lifetime did not increase at high temperatures. The existence of new state of Ps bubble was further clarified.
Yabuuchi, Atsushi*; Hirade, Tetsuya; Fujinami, Masanori*; Awaji, Ryo*; Oshima, Nagayasu*; Takai, Kenichi*; Taira, Yoshitaka*; Sugita, Kento*
no journal, ,
In situ measurements of positron annihilation lifetimes have been performed at the UVSOR synchrotron radiation facility to characterise defects formed during tensile deformation of pure iron using the gamma-ray induced positron annihilation spectroscopy (GiPAS) technique. A dumbbell-shaped specimen was attached to a small tensile tester and stretched to a nominal strain of 7 or more at a strain rate of 2.2
10
/s. Positron lifetime changes during tensile deformation of a pure iron specimen were observed using positrons generated in the sample by irradiating the centre of the sample with a 66MeV gamma-ray pulse beam of 3mm in diameter. Unlike the results reported so far, the change in the positron lifetime, especially at the early deformation stage, was very small, making clear the importance of in-situ measurement.
Yabuuchi, Atsushi*; Awaji, Ryo*; Hirade, Tetsuya; Fujinami, Masanori*; Oshima, Nagayasu*; Takai, Kenichi*; Taira, Yoshitaka*
no journal, ,
In situ measurements of positron annihilation lifetimes have been performed at the UVSOR synchrotron radiation facility to evaluate defects formed during tensile deformation in pure iron using the gamma-ray induced positron annihilation spectroscopy technique. A 66 MeV gamma-ray pulse beam with a diameter of 3 mm was irradiated to the centre of the sample while stretching it to a nominal strain of 7 or more at a strain rate of 2.210/s. The positron lifetime change during the tensile deformation of iron specimens was observed. Positron lifetime measurements have often been performed after the deformation of the sample. Unlike these results, it was found that the lifetime change at the initial deformation stage was very small in these In situ measurements.
Sakai, Hiroaki; Minei, Shuntaro; Hirade, Tetsuya; Oshima, Nagayasu*; Kobayashi, Yoshinori*; Kinomura, Atsushi*; Suzuki, Ryoichi*
no journal, ,
It was reported that positronium (Ps) formation probability was enhanced very much with very high electric fields. The spur reaction model can not explain this Ps formation. We tried to investigate this Ps formation with high electric fields in polyimide (kapton) that has no Ps formation with no electric field. Then we found out that Ps formation was not possible even at high electric fields. However, the annihilation lifetime of free positrons was elongated and it was probably caused by the positron drift movement.
Sakai, Hiroaki; Minei, Shuntaro; Hirade, Tetsuya; Oshima, Nagayasu*; Kobayashi, Yoshinori*; Kinomura, Atsushi*; Suzuki, Ryoichi*
no journal, ,
It was reported that psoitronium (Ps) formation probability in polymers under high electric fields were enhanced. The spur reaction model explaining Ps formation in insulating materials cannot be applied for the enhancement under high electric fields. Then we studied the Ps formation mechanism under high electric fields by observing positron annihilation lifetime in Kapton (polyimide) that does not have any Ps formation. Then Ps was not formed even under high electric fields and the elongation of the lifetime of the positrons free from Ps formation. The elongation of the lifetime of the positron and Ps formation enhancement could not be judged by the methods applied in the previously reports.
Minei, Shuntaro; Oshima, Nagayasu*; Sakai, Hiroaki; Okubo, Nariaki; Kondo, Keietsu; Suzuki, Ryoichi*; Hirade, Tetsuya
no journal, ,
In nuclear reactor materials, subnanometer-size vacancy type defects are induced by neutron irradiation. Although positron annihilation methods are effective techniques for evaluation of the vacancy type defects, it may be difficult to apply the methods for neutron irradiated samples, because of 
-rays from highly neutron irradiated, i.e. radioactivated, samples. Recently, positron micro beam has been developed at AIST. Therefore, we are suggesting that smaller radioactivated samples emit fewer -rays. Focused Ion beam (FIB) is one of the tools to prepare micrometer scale samples by ion sputtering, for example, for the transmission electron microscope. There is some possibility to have vacancy type defects in the samples induced by the FIB processing and it can make estimation of the pre-existing defects in the samples difficult. The results investigated by positron annihilation lifetime measurements for SUS316L showed that FIB can be applied.
Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Oshima, Nagayasu*; Hirade, Tetsuya
no journal, ,
Changes in hydrogen content and lattice defect formation associated with hydrogen under elastic tensile stress of tempered martensitic steel were examined. The relationship between hydrogen embrittlement and lattice defects associated with hydrogen was also investigated. The results obtained in this study can be summarized as follows. Besides hydrogen content and applied stress, time of the formation and accumulation of vacancies was also closely involved in hydrogen embrittlement and is concluded to be an important factor causing hydrogen embrittlement.
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.
Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Hirade, Tetsuya; Oshima, Nagayasu*
no journal, ,
Hydrogen embrittlements of materials occur under elastic stress. Therefore we tried to investigate the defects in high-strength steel caused by hydrogen under elastic stress by the thermal desorption analysis of hydrogen gas and positron annihilation lifetime analysis by use of positron micro analyzer. We successfully obtained results showing the defects created by hydrogen under elastic stress cause the embrittlements.
Kai, Takeshi; Ishida, Akira*; Oshima, Nagayasu*
no journal, ,
When a positron was injected into the condensed phase, positronium (Ps) which constructs of an electron and a positron was generated. Although we expect that Bose-Einstein condensation (BEC) using the densely positroniums creates newly physics such as gravity accurate measurement of antimatter and annihilation gamma-rays laser, the BEC have never been achieved. The aims of this study are that fundamental explication of Ps generation as well as elucidation of experimental condition for Ps - BEC achievement from the positrons deceleration simulation in the condensed phase. For the aims, we applied a dynamic Monte Carlo code of the electrons to deceleration simulation of positrons bunch. We present current states of development of the high dense positrons transport simulation in the condensed phase.
Doshida, Tomoki*; Suzuki, Hiroshi*; Takai, Kenichi*; Hirade, Tetsuya; Oshima, Nagayasu*
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 thermal desorption analysis (TDA) and positron probe microanalyzer (PPMA).
