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Surface modifications of hydrogen storage alloy by heavy ion beams with keV to MeV irradiation energies
Nuclear Instruments and Methods in Physics Research B 365 (2015) 214–217
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Surface modifications of hydrogen storage alloy by heavy ion beams with keV to MeV irradiation energies Hiroshi Abe a,⇑, Shinnosuke Tokuhira b, Hirohisa Uchida b, Takeshi Ohshima a a b
Environment and Materials Research Division, Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan Depertment of Applied Science, Graduate School of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan
a r t i c l e
i n f o
Article history: Received 1 October 2014 Received in revised form 1 June 2015 Accepted 15 July 2015 Available online 19 August 2015 Keywords: Surface modification Hydrogen storage alloy Initial hydrogen absorption reaction rate Ion irradiation
a b s t r a c t This study deals with the effect of surface modifications induced from keV to MeV heavy ion beams on the initial reaction rate of a hydrogen storage alloy (AB5) in electrochemical process. The rare earth based alloys like this sample alloy are widely used as a negative electrode of Ni–MH (Nickel–Metal Hydride) battery. We aimed to improve the initial reaction rate of hydrogen absorption by effective induction of defects such as vacancies, dislocations, micro-cracks or by addition of atoms into the surface region of the metal alloys. Since defective layer near the surface can easily be oxidized, the conductive oxide layer is formed on the sample surface by O+ beams irradiation, and the conductive oxide layer might cause the improvement of initial reaction rate of hydriding. This paper demonstrates an effective surface treatment of heavy ion irradiation, which induces catalytic activities of rare earth oxides in the alloy surface. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction Although research on renewable energy is advanced in the world, general utilization from these researches takes time. On the other hand, there is ‘‘hydrogen’’ which exists in natural environment. Much hydrogen storage research is studied in the region of research of hydrogen use. There is also much research already put in practical use. The hydrogen storage alloys are used for negative electrode of Ni–MH battery which have been used for hybrid vehicles (HV), and Ni–MH rechargeable batteries known well is one of them [1]. It is very important to improve these battery characteristics. We aimed at improving the absorption ability of the hydrogen absorption material as a cathode of a battery. So far, we have systematically investigated the effect of surface oxide layers on the kinetics of hydrogen absorption by hydriding metals [2,3] and reported several methods of surface modification such as metallic coating [4], fluorination treatment [5,6] and alkaline treatment. In particular, the surface modification of material was examined using ion irradiation technique. Then the various ion irradiation treatment improved the initial hydrogen absorption reaction rate (initial reaction rate of hydriding) [7–12]. The surface modifications are crucial to improve the reactivity of hydrogen with hydrogen storage materials. In previous studies, the induction of vacancies in a hydrogen absorption alloy was found to be effective to increase in the hydrogen absorption rate. ⇑ Corresponding author. http://dx.doi.org/10.1016/j.nimb.2015.07.085 0168-583X/Ó 2015 Elsevier B.V. All rights reserved.
In this study, the ion irradiation effects on the initial reaction rate of hydriding of LaNi4.6Al0.4 was investigated in electrochemical process and the structure changes of a hydrogen storage materials by ion irradiation using an oxygen ion (O+) beam were made onto the surface of the alloy at TIARA (Takasaki Ion Accelerators for Advanced Radiation Application), JAEA. The hydriding rate was measured electrochemically for samples with and without the surface irradiation. 2. Experimental procedures In this study, a powder samples of a LaNi4.6Al0.4 alloy was used. The particle size was smaller than 38 lm in diameter. The alloy powder was mixed with a copper (Cu) powder in a ratio alloy to Cu powders = 1:3 in weight. The mixed powder was pressed at 8 tons/cm2 to form a pellet with a size of 12.3 mm/ and 1.3 mm thickness as an electrode for electrochemical hydriding measurement. Surface modification were made by O+ irradiation. Ion irradiation onto the surface for a sample was made in an acceleration energy of 100 keV, 350 keV, 3 MeV and 12 MeV, and a dose of 2 1016 cm2, 2 1016 cm2, 3 1016 cm2 and 1 1016 cm2 respectively, using a 400 kV ion implanter for energy of keV order and a 3 MV tandem accelerator for MeV order. The initial reaction rate of hydriding was measured in electrochemical process where a pellet samples (ion irradiated and un-irradiated samples) were used as a cathode, and Ni(OH)2 as an anode. An Hg/HgO electrode was used as a reference electrode
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H. Abe et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 214–217
in an open cell [13,14]. The initial reaction rate of hydriding of the sample was measured in a 6 M-KOH using the open cell as the charge of current density mA (g-alloy)1 at a constant voltage 0.93 V and at 298 K. The hydrogen concentration absorbed by the negative electrode was calculated. Here, the calculation of an amount of hydrogen storage is was follows,
DX ¼ DQ ð3600=1000Þ M=F
ð1Þ
where DX [H/M] is, the amount of hydrogen absorption, the hydrogen density change of the alloy material electrode inside and DQ [mAh/g] is the quantity of electrically of the electrode inside that increase/decrease by electrical charge/discharge and M is an average atomic weight of alloy (LaNi4.6Al0.4 = 420.89 [g/mol]) and F is the Faraday constant (96,485 [C/mol]) and 3600/1000 is the conversion factors of the time.
Table 1 The initial rate of hydriding, amount of hydrogen absorption and LET in the each ion beam energies. Ion beam energy
Initial rate of hydriding: r [min1]
Amount of hydrogen absorption: DX [H/M]
LET [keV/(mg/cm2)]
Un-irradiated 100 keV 350 keV 3 MeV 12 MeV
3.52 103 3.35 101 1.89 101 3.42 103 2.98 103
0.267 1.89 1.28 0.393 0.230
– 7.29 102 1.80 103 3.56 103 4.26 103
3. Results and discussions The curve of the reaction rate by LaNi4.6Al0.4 alloy samples irradiated at two different doses of 1 1016 and 3 1016 cm2 of an O+ (see, Fig. 1). The ordinate indicate the ratio of absorbed hydrogen atom to LaNi4.6Al0.4 alloys and a horizontal axis is the time of onset of charge by an electrochemical effect. With increasing O+ beam energies up to 12 MeV, the initial reaction rate of hydriding and the amount of hydrogen absorption DX value at 120 minutes were decreased. It turned out that the reaction rate of the irradiation energy lower than high energy becomes fast. Here, the initial reaction rate of hydriding, amount of hydrogen absorption and LET (liner energy transfer, i.e. SRIM simulation [15]) in the each irradiation beam energies, is shown in Table 1. It is possible to derive the initial reaction rate of hydriding r of the respective samples from hydrogen absorption starting by the DX value of the initial stage which is early time. An inclination part in the initial stage of a hydrogen absorption curve line is decided about as the initial reaction rate of hydriding r. In the irradiation energy of 100 keV which was the highest as for the effect, in comparison with un-irradiated sample, 7 times of a DX value improved and 95 times as initial hydrogen absorption reaction rate improved. As mentioned above, the reaction rate and the hydrogen absorption curve shows ion irradiation energy dependence.
Fig. 2. Vacancy distributions induced by the irradiation ion as function of depth from the surface of the LaNi4.6Al0.4 alloy using a SRIM code.
Fig. 3. The relation between the irradiation energy of LaNi4.6Al0.4 and LET of the initial reaction rate before after several energy of an O+ irradiation.
Fig. 1. Hydriding curve of samples irradiated by oxygen ion (O+) at energy of 100 keV to 12 MeV. Each ion dose was in the range from 1 1016 to 3 1016 cm2.
The distribution of induced vacancy can be simulated using a transport of ions in matter, SRIM code. Fig. 2 show the results of
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H. Abe et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 214–217
outermost surface so that the O+ irradiation energy is low (Fig. 2). Moreover, the O ion irradiation were formed not only defects but also oxide. It is also showed by the XPS spectra of La4d and La oxide in the LaNi4.6Al0.4 on Fig. 4. It was compared the most effective 100 keV O+ irradiation with un-irradiation about La oxide formation. The La oxide are not formed into the outermost surface in case of un-irradiation. On the other hand, in case of after irradiation, the formation of the La oxide can be confirmed in the outermost surface layer. These could be identified with the La2O3. It found out that it is not formed in a surface layer in both of un-irradiation and irradiation about Ni oxide formation. There is a possibility of the correlation between these defects and the La oxide formation, but the current state has not been checked yet. The mention above, it found out that the initial reaction rate of hydriding is improved by O+ irradiation on outermost surface region. When the defect was not formed into the outermost surface even if the defect was introduced deeply to the surface depth direction, it was revealed that it is almost the same as a case of non-irradiation. As a result, in the initial stage of a hydriding process, the hydrogen is trapped by the defects [16] and it is surmised that the initial reaction rate of hydriding becomes fast. 4. Conclusion
Fig. 4. The XPS spectra of La4d and La oxide on the LaNi4.6Al0.4 by un-irradiated and 100 keV O+ irradiated.
The ion irradiation using an energy from keV to MeV order O+ can enhance the initial reaction rate of hydriding of electrochemical hydrogen absorption by LaNi4.6Al0.4. The induction of a high vacancy concentration in the surface of the alloys seems to be responsible for the enhancement of the initial reaction rate of hydriding. The increasing ion beam energy and the decreasing irradiation energy are effective to enhance the initial reaction rate of hydriding. The results obtained suggest that the intentional induction of high concentration of vacancies in metals by the ion implantation is useful for the activation treatment of hydrogen absorbing alloys. As for the dissociation of the hydrogen molecule, at the surface of the LaNi4.6Al0.4 sample, the nucleation site of the hydride formation might be effective for the hydrogen atom in the LaNi4.6Al0.4 surface region according to the formation vacancies with high concentration. Based on obtained results, the effect of the surface modifications induced by heavy ion irradiation is discussed with respect to the initial reaction rate of hydriding of the hydrogen storage alloy. The irradiation treatment seems effective for the promotion of the dissociation rate of H2O in electrochemical process, and according enhancement of the initial reaction rate of hydriding. Acknowledgment
the vacancy distributions induced by the irradiation ion as function of depth from the surface of the LaNi4.6Al0.4 alloy using a SRIM simulation at an ion dose from 1 1016 to 3 1016 cm2, and at an irradiation energy from 100 keV to 12 MeV O+. The result of simulation shows that concentrate on from the sample surface to 400 nm, and forming the defect has improved faculty of the hydrogen absorption. Fig. 3 shows the relation between the irradiation energy of LaNi4.6Al0.4 and the LET of the initial reaction rate of hydriding before after several O+ irradiation. As for the initial reaction rate of hydriding, the LET decreased and energy of O+ irradiation increased with increasing initial reaction rate. When the O+ irradiation energy became increase, the LET also became increase, but it was revealed to decelerate the initial reaction rate of hydriding reversely. The initial reaction rate of an un-irradiated LaNi4.6Al0.4 sample is 3.52 103 [min1] as reference data (see, Table 1). Some defects introduction are formed into the material
This work was party supported by the Grant-in-Aid for Science Research C (No. 26420891) from the Ministry of Education, Culture, Sports, Science, and Technology in Japan. References [1] H. Uchida, Paper Presented as an Invited Plenary Talk at the 18th World Hydrogen Energy Conference 2010 (WHEC 2010), Essen, Germany, May 16– 21st, 2010, pp. 1–10. [2] H. Uchida, Int. J. Hydrogen Energy 24 (1999) 861–869. [3] H. Uchida, Y. Ohtani, M. Ozawa, T. Kawahata, T. Suzuki, J. Less Common Met. 172–174 (1991) 983–996. [4] E. Fromm, Poisoning of hydrogen reactions, in: Kinetics of Metal–Gas Interactions at Low Temperatures, Springer Verlag, Berlin, 1998, p. 126. ISBN 3-540-63975-6. [5] H. Uchida, T. Inoue, T. Tabata, S. Seki, H.H. Uchida, F. Aono, T. Nakazawa, H. Kikuyama, R. Hirayama, J. Alloys Compd. 253–254 (1997) 547–549. [6] H. Uchida, F. Aono, in: Proceedings of the 13th world Hydrogen Energy Conference (WHEC 2000), Beijing, China, June 12–15, 2000, pp. 1088–1092.
H. Abe et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 214–217 [7] H. Abe, H. Uedono, H. Uchida, A. Komatsu, S. Okada, H. Itoh, Mater. Sci. Forum 363–365 (2001) 156–158. [8] H. Abe, H. Uchida, Y. Azuma, A. Uedono, Z.Q. Chen, H. Itoh, Nucl. Instr. Meth. B 206 (2003) 224–227. [9] H. Abe, R. Morimoto, F. Satoh, Y. Azuma, H. Uchida, J. Alloys Compd. 404–406 (2005) 288–292. [10] H. Abe, S. Aone, R. Morimoto, H. Uchida, T. Ohshima, Trans. Mater. Res. Soc. Jpn. 36 (1) (2011) 133–135. [11] H. Abe, R. Morimoto, F. Satoh, Y. Azuma, H. Uchida, J. Alloys Compd. 408–412 (2006) 348–350.
217
[12] H. Abe, S. Aone, R. Morimoto, H. Uchida, J. Alloys Compd. 580 (2013) 5219– 5221. [13] H. Uchida, M. Sato, W. Cui, T. Tabata, M. Kumagai, H. Takano, T. Kondo, J. Alloys Compd. 293–295 (1999) 30–33. [14] H. Uchida, K. Yamashita, T. Tabata, H.H. Uchida, M. Iwase, Y. Katoh, J. Alloys Compd. 293–295 (1999) 751–755. [15] J.F. Ziegler, The Stopping and Range of Ions in Matter, Pergamon Press, New York, 1985. [16] S.B. Gesari, M.E. Pronsato, A. Juan, Int. J. Hydrogen Energy 34 (2009) 3511– 3518.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Surface modifications of hydrogen storage alloy by heavy ion beams with keV to MeV irradiation energies Hiroshi Abe a,⇑, Shinnosuke Tokuhira b, Hirohisa Uchida b, Takeshi Ohshima a a b
Environment and Materials Research Division, Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan Depertment of Applied Science, Graduate School of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan
a r t i c l e
i n f o
Article history: Received 1 October 2014 Received in revised form 1 June 2015 Accepted 15 July 2015 Available online 19 August 2015 Keywords: Surface modification Hydrogen storage alloy Initial hydrogen absorption reaction rate Ion irradiation
a b s t r a c t This study deals with the effect of surface modifications induced from keV to MeV heavy ion beams on the initial reaction rate of a hydrogen storage alloy (AB5) in electrochemical process. The rare earth based alloys like this sample alloy are widely used as a negative electrode of Ni–MH (Nickel–Metal Hydride) battery. We aimed to improve the initial reaction rate of hydrogen absorption by effective induction of defects such as vacancies, dislocations, micro-cracks or by addition of atoms into the surface region of the metal alloys. Since defective layer near the surface can easily be oxidized, the conductive oxide layer is formed on the sample surface by O+ beams irradiation, and the conductive oxide layer might cause the improvement of initial reaction rate of hydriding. This paper demonstrates an effective surface treatment of heavy ion irradiation, which induces catalytic activities of rare earth oxides in the alloy surface. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction Although research on renewable energy is advanced in the world, general utilization from these researches takes time. On the other hand, there is ‘‘hydrogen’’ which exists in natural environment. Much hydrogen storage research is studied in the region of research of hydrogen use. There is also much research already put in practical use. The hydrogen storage alloys are used for negative electrode of Ni–MH battery which have been used for hybrid vehicles (HV), and Ni–MH rechargeable batteries known well is one of them [1]. It is very important to improve these battery characteristics. We aimed at improving the absorption ability of the hydrogen absorption material as a cathode of a battery. So far, we have systematically investigated the effect of surface oxide layers on the kinetics of hydrogen absorption by hydriding metals [2,3] and reported several methods of surface modification such as metallic coating [4], fluorination treatment [5,6] and alkaline treatment. In particular, the surface modification of material was examined using ion irradiation technique. Then the various ion irradiation treatment improved the initial hydrogen absorption reaction rate (initial reaction rate of hydriding) [7–12]. The surface modifications are crucial to improve the reactivity of hydrogen with hydrogen storage materials. In previous studies, the induction of vacancies in a hydrogen absorption alloy was found to be effective to increase in the hydrogen absorption rate. ⇑ Corresponding author. http://dx.doi.org/10.1016/j.nimb.2015.07.085 0168-583X/Ó 2015 Elsevier B.V. All rights reserved.
In this study, the ion irradiation effects on the initial reaction rate of hydriding of LaNi4.6Al0.4 was investigated in electrochemical process and the structure changes of a hydrogen storage materials by ion irradiation using an oxygen ion (O+) beam were made onto the surface of the alloy at TIARA (Takasaki Ion Accelerators for Advanced Radiation Application), JAEA. The hydriding rate was measured electrochemically for samples with and without the surface irradiation. 2. Experimental procedures In this study, a powder samples of a LaNi4.6Al0.4 alloy was used. The particle size was smaller than 38 lm in diameter. The alloy powder was mixed with a copper (Cu) powder in a ratio alloy to Cu powders = 1:3 in weight. The mixed powder was pressed at 8 tons/cm2 to form a pellet with a size of 12.3 mm/ and 1.3 mm thickness as an electrode for electrochemical hydriding measurement. Surface modification were made by O+ irradiation. Ion irradiation onto the surface for a sample was made in an acceleration energy of 100 keV, 350 keV, 3 MeV and 12 MeV, and a dose of 2 1016 cm2, 2 1016 cm2, 3 1016 cm2 and 1 1016 cm2 respectively, using a 400 kV ion implanter for energy of keV order and a 3 MV tandem accelerator for MeV order. The initial reaction rate of hydriding was measured in electrochemical process where a pellet samples (ion irradiated and un-irradiated samples) were used as a cathode, and Ni(OH)2 as an anode. An Hg/HgO electrode was used as a reference electrode
215
H. Abe et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 214–217
in an open cell [13,14]. The initial reaction rate of hydriding of the sample was measured in a 6 M-KOH using the open cell as the charge of current density mA (g-alloy)1 at a constant voltage 0.93 V and at 298 K. The hydrogen concentration absorbed by the negative electrode was calculated. Here, the calculation of an amount of hydrogen storage is was follows,
DX ¼ DQ ð3600=1000Þ M=F
ð1Þ
where DX [H/M] is, the amount of hydrogen absorption, the hydrogen density change of the alloy material electrode inside and DQ [mAh/g] is the quantity of electrically of the electrode inside that increase/decrease by electrical charge/discharge and M is an average atomic weight of alloy (LaNi4.6Al0.4 = 420.89 [g/mol]) and F is the Faraday constant (96,485 [C/mol]) and 3600/1000 is the conversion factors of the time.
Table 1 The initial rate of hydriding, amount of hydrogen absorption and LET in the each ion beam energies. Ion beam energy
Initial rate of hydriding: r [min1]
Amount of hydrogen absorption: DX [H/M]
LET [keV/(mg/cm2)]
Un-irradiated 100 keV 350 keV 3 MeV 12 MeV
3.52 103 3.35 101 1.89 101 3.42 103 2.98 103
0.267 1.89 1.28 0.393 0.230
– 7.29 102 1.80 103 3.56 103 4.26 103
3. Results and discussions The curve of the reaction rate by LaNi4.6Al0.4 alloy samples irradiated at two different doses of 1 1016 and 3 1016 cm2 of an O+ (see, Fig. 1). The ordinate indicate the ratio of absorbed hydrogen atom to LaNi4.6Al0.4 alloys and a horizontal axis is the time of onset of charge by an electrochemical effect. With increasing O+ beam energies up to 12 MeV, the initial reaction rate of hydriding and the amount of hydrogen absorption DX value at 120 minutes were decreased. It turned out that the reaction rate of the irradiation energy lower than high energy becomes fast. Here, the initial reaction rate of hydriding, amount of hydrogen absorption and LET (liner energy transfer, i.e. SRIM simulation [15]) in the each irradiation beam energies, is shown in Table 1. It is possible to derive the initial reaction rate of hydriding r of the respective samples from hydrogen absorption starting by the DX value of the initial stage which is early time. An inclination part in the initial stage of a hydrogen absorption curve line is decided about as the initial reaction rate of hydriding r. In the irradiation energy of 100 keV which was the highest as for the effect, in comparison with un-irradiated sample, 7 times of a DX value improved and 95 times as initial hydrogen absorption reaction rate improved. As mentioned above, the reaction rate and the hydrogen absorption curve shows ion irradiation energy dependence.
Fig. 2. Vacancy distributions induced by the irradiation ion as function of depth from the surface of the LaNi4.6Al0.4 alloy using a SRIM code.
Fig. 3. The relation between the irradiation energy of LaNi4.6Al0.4 and LET of the initial reaction rate before after several energy of an O+ irradiation.
Fig. 1. Hydriding curve of samples irradiated by oxygen ion (O+) at energy of 100 keV to 12 MeV. Each ion dose was in the range from 1 1016 to 3 1016 cm2.
The distribution of induced vacancy can be simulated using a transport of ions in matter, SRIM code. Fig. 2 show the results of
216
H. Abe et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 214–217
outermost surface so that the O+ irradiation energy is low (Fig. 2). Moreover, the O ion irradiation were formed not only defects but also oxide. It is also showed by the XPS spectra of La4d and La oxide in the LaNi4.6Al0.4 on Fig. 4. It was compared the most effective 100 keV O+ irradiation with un-irradiation about La oxide formation. The La oxide are not formed into the outermost surface in case of un-irradiation. On the other hand, in case of after irradiation, the formation of the La oxide can be confirmed in the outermost surface layer. These could be identified with the La2O3. It found out that it is not formed in a surface layer in both of un-irradiation and irradiation about Ni oxide formation. There is a possibility of the correlation between these defects and the La oxide formation, but the current state has not been checked yet. The mention above, it found out that the initial reaction rate of hydriding is improved by O+ irradiation on outermost surface region. When the defect was not formed into the outermost surface even if the defect was introduced deeply to the surface depth direction, it was revealed that it is almost the same as a case of non-irradiation. As a result, in the initial stage of a hydriding process, the hydrogen is trapped by the defects [16] and it is surmised that the initial reaction rate of hydriding becomes fast. 4. Conclusion
Fig. 4. The XPS spectra of La4d and La oxide on the LaNi4.6Al0.4 by un-irradiated and 100 keV O+ irradiated.
The ion irradiation using an energy from keV to MeV order O+ can enhance the initial reaction rate of hydriding of electrochemical hydrogen absorption by LaNi4.6Al0.4. The induction of a high vacancy concentration in the surface of the alloys seems to be responsible for the enhancement of the initial reaction rate of hydriding. The increasing ion beam energy and the decreasing irradiation energy are effective to enhance the initial reaction rate of hydriding. The results obtained suggest that the intentional induction of high concentration of vacancies in metals by the ion implantation is useful for the activation treatment of hydrogen absorbing alloys. As for the dissociation of the hydrogen molecule, at the surface of the LaNi4.6Al0.4 sample, the nucleation site of the hydride formation might be effective for the hydrogen atom in the LaNi4.6Al0.4 surface region according to the formation vacancies with high concentration. Based on obtained results, the effect of the surface modifications induced by heavy ion irradiation is discussed with respect to the initial reaction rate of hydriding of the hydrogen storage alloy. The irradiation treatment seems effective for the promotion of the dissociation rate of H2O in electrochemical process, and according enhancement of the initial reaction rate of hydriding. Acknowledgment
the vacancy distributions induced by the irradiation ion as function of depth from the surface of the LaNi4.6Al0.4 alloy using a SRIM simulation at an ion dose from 1 1016 to 3 1016 cm2, and at an irradiation energy from 100 keV to 12 MeV O+. The result of simulation shows that concentrate on from the sample surface to 400 nm, and forming the defect has improved faculty of the hydrogen absorption. Fig. 3 shows the relation between the irradiation energy of LaNi4.6Al0.4 and the LET of the initial reaction rate of hydriding before after several O+ irradiation. As for the initial reaction rate of hydriding, the LET decreased and energy of O+ irradiation increased with increasing initial reaction rate. When the O+ irradiation energy became increase, the LET also became increase, but it was revealed to decelerate the initial reaction rate of hydriding reversely. The initial reaction rate of an un-irradiated LaNi4.6Al0.4 sample is 3.52 103 [min1] as reference data (see, Table 1). Some defects introduction are formed into the material
This work was party supported by the Grant-in-Aid for Science Research C (No. 26420891) from the Ministry of Education, Culture, Sports, Science, and Technology in Japan. References [1] H. Uchida, Paper Presented as an Invited Plenary Talk at the 18th World Hydrogen Energy Conference 2010 (WHEC 2010), Essen, Germany, May 16– 21st, 2010, pp. 1–10. [2] H. Uchida, Int. J. Hydrogen Energy 24 (1999) 861–869. [3] H. Uchida, Y. Ohtani, M. Ozawa, T. Kawahata, T. Suzuki, J. Less Common Met. 172–174 (1991) 983–996. [4] E. Fromm, Poisoning of hydrogen reactions, in: Kinetics of Metal–Gas Interactions at Low Temperatures, Springer Verlag, Berlin, 1998, p. 126. ISBN 3-540-63975-6. [5] H. Uchida, T. Inoue, T. Tabata, S. Seki, H.H. Uchida, F. Aono, T. Nakazawa, H. Kikuyama, R. Hirayama, J. Alloys Compd. 253–254 (1997) 547–549. [6] H. Uchida, F. Aono, in: Proceedings of the 13th world Hydrogen Energy Conference (WHEC 2000), Beijing, China, June 12–15, 2000, pp. 1088–1092.
H. Abe et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 214–217 [7] H. Abe, H. Uedono, H. Uchida, A. Komatsu, S. Okada, H. Itoh, Mater. Sci. Forum 363–365 (2001) 156–158. [8] H. Abe, H. Uchida, Y. Azuma, A. Uedono, Z.Q. Chen, H. Itoh, Nucl. Instr. Meth. B 206 (2003) 224–227. [9] H. Abe, R. Morimoto, F. Satoh, Y. Azuma, H. Uchida, J. Alloys Compd. 404–406 (2005) 288–292. [10] H. Abe, S. Aone, R. Morimoto, H. Uchida, T. Ohshima, Trans. Mater. Res. Soc. Jpn. 36 (1) (2011) 133–135. [11] H. Abe, R. Morimoto, F. Satoh, Y. Azuma, H. Uchida, J. Alloys Compd. 408–412 (2006) 348–350.
217
[12] H. Abe, S. Aone, R. Morimoto, H. Uchida, J. Alloys Compd. 580 (2013) 5219– 5221. [13] H. Uchida, M. Sato, W. Cui, T. Tabata, M. Kumagai, H. Takano, T. Kondo, J. Alloys Compd. 293–295 (1999) 30–33. [14] H. Uchida, K. Yamashita, T. Tabata, H.H. Uchida, M. Iwase, Y. Katoh, J. Alloys Compd. 293–295 (1999) 751–755. [15] J.F. Ziegler, The Stopping and Range of Ions in Matter, Pergamon Press, New York, 1985. [16] S.B. Gesari, M.E. Pronsato, A. Juan, Int. J. Hydrogen Energy 34 (2009) 3511– 3518.