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Noboru Akao

Section

Graduate School of Engineering

Job title

Research Associate

Degree

researchmap

https://researchmap.jp/read0168416

J-GLOBAL ID

200901085060643036

Education 4

Tohoku University

- 1990
Tohoku University　Graduate School, Division of Engineering

- 1990
Tohoku University　Faculty of Engineering

- 1988
Tohoku University　Faculty of Engineering

- 1988

Committee Memberships 2

腐食防食協会　編集委員

2005 -
腐食防食協会　編集委員

2005 -

Professional Memberships 1

日本金属学会

Research Areas 3

Nanotechnology/Materials / Thin-film surfaces and interfaces /
Nanotechnology/Materials / Composite materials and interfaces /
Nanotechnology/Materials / Material fabrication and microstructure control /

Papers 18

A Combinatrial Screening Method for Corrosion Research Using Ion-Beam-Deposited Thin-Film Alloys and Microelectrochemical Measurements Peer-reviewed

Izumi Muto, Tetsuji Kaneko, Noboru Akao, Nobuyoshi Hara

Materials Transactions　50　(7)　1894-1897　2009/07/01

DOI： 10.2320/matertrans.M2009130 　
Pinhole Defect Density of CrNx Thin Films Formed by Ion-Beam-Enhanced Deposition on Stainless Steel Substrates Peer-reviewed

Hiroshi Goto, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Journal of the Electrochemical Society　154　(4)　C189-C194　2007/04/15

DOI： 10.1149/1.2433041 　
Formation and breakdown of surface films on magnesium and its alloys in aqueous solutions Peer-reviewed

Nobuyoshi Hara, Yasuhiro Kobayashi, Daisuke Kagaya, Noboru Akao

Corrosion Science　49　166-175　2007/01/01

DOI： 10.1016/j.corsci.2006.05.033 　
Effect of Alloying Elements on Corrosion Resistance of Carbon Steel in Compressed Bentonite Containing Alkaline Solution Peer-reviewed

M.Koike, T.Hiotani, N.Akao, N.Hara, K.Sugimoto

Zairyo-to-Kankyo　55　(10)　445-451　2006/10/01
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr.55.445 　

ISSN： 0917-0480

More details Close

Carbon steels are considered to be the most promising material for an overpack container used for the geological disposal of radioactive wastes. In order to know effective alloying elements that increase the corrosion resistance in the disposal environment, corrosion tests of a commercial carbon steel and several kinds of low alloy steels were performed in compressed bentonite containing a simulated solution of bentonite contact water with chloride at pH 8 to 13. The most effective alloying element in the solutions from pH 8 to 12 was Ni. The second effective one was Al. The addition of Ti, Cr, Si, Cu, or Nb slightly increased the corrosion resistance. The most harmful element that decreased the corrosion resistance was Mo. In the solution with pH 13, all the steels except Mo- and Si-containing steels were passivated and the difference in the effect of alloying elements was very small. An FeCO₃ layer was formed on all the steels as a corrosion product in the solutions with pH 8 to 12.
Ellipsometric Analysis of Growth Process of Oxidation Films on Magnesium and its Alloys in Neutral Aqueous Solutions”, Passivation of Metals and Semiconductors, and the Properties of Thin Oxide Layers Peer-reviewed

N. Hara, D. Kagaya, N. Akao

Passivation of Metals and Semiconductors, and the Properties of Thin Oxide Layers　217-223　2006/04/01

DOI： 10.1016/B978-044452224-5/50036-6 　
Electrochemical Properties of Fe-Cr-Mo Alloys and Fe₂O₃-Cr₂O₃-MoO₂ Artificial Passivation Films in 1M HCl Invited Peer-reviewed

K. Sugimoto, M. Saito, N. Akao, N. Hara

Passivation of Metals and Semiconductors, and the Properties of Thin Oxide Layers　3-8　2006/04/01

DOI： 10.1016/B978-044452224-5/50001-9 　
Al₂O₃-Ta₂O₅-ZrO₂ Thin Films Having High Corrosion Resistance to Strong Acid and Alkali Solutions Peer-reviewed

Shinji Katayama, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Journal of the Electrochemical Society　152　(8)　B286-B290　2005/08

DOI： 10.1149/1.1945607 　
In Situ Ellipsometry Analysis on Formation Process of Al₂O₃-Ta₂O₅ Films in Ion Beam Sputter Deposition Peer-reviewed

Tetsuji. Kaneko, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Journal of the Electrochemical Society　152　(4)　B133-B139　2005/04

DOI： 10.1149/1.1861173 　
Electrochemical Properties of Fe₂O₃-Cr₂O₃ Thin Films and Pitting Behavior of Fe-Cr Alloys in Neutral NaCl Solutions Peer-reviewed

K. Sugimoto, Y. Ohya, N. Akao, N. Hara

Pits and Pores III: Formation, Properties, and Significance for Advanced Materials　194-204　2004/04/01
Al2O3-Ta2O5-ZrO2 thin films having high corrosion resistance to strong acid and alkali solutions Peer-reviewed

K Sugimoto, S Katayama, N Akao, N Hara

SURFACE OXIDE FILMS　2003　(25)　192-201　2004
Self-healing Corrosion Protection Ability of Composition-Gradient Al₂O₃•Nb Nanocomposite Thin Films Peer-reviewed

Mika Yasuda, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Journal of the Electrochemical Society　150　(10)　B481-B487　2003/10

DOI： 10.1149/1.1604787 　
Corrosion and Electrochemical Properties of Sn-8%Zn Alloy-Coated Steel in Methanol Containing H₂O, NaCl and HCOOH Peer-reviewed

Rie Umebayashi, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Journal of the Electrochememical Society　150　(7)　B295-B302　2003/07

DOI： 10.1149/1.1574808 　
Deposition Condition and Pinhole Defect Density of CrNx (1>x>0) Thin Films Formed by Ion-Beam-Enhanced Deposition Peer-reviewed

Hirotsugu Kondo, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Journal of The Electrochemical Society　150　(2)　B60-B67　2003/02

DOI： 10.1149/1.1536993 　
The Effect of Minor Elements on Corrosion Resistance of Carbon Steel for High Level Nuclear Waste Disposal Container Peer-reviewed

Takashi Tsushima, Motohiko Suzuki, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo-to-Kankyo (Corrosion Engineering)　52　(2)　92-101　2003/02
Publisher:
DOI： 10.3323/jcorr1991.52.92 　

ISSN： 0917-0480
Corrosion resistance of tungsten and tungsten alloys for spallation target in stagnant and flowing water Peer-reviewed

N Noji, K Kashiwagura, N Akao, S Soma, N Hara, K Sugimoto

JOURNAL OF THE JAPAN INSTITUTE OF METALS　66　(11)　1107-1115　2002/11

ISSN： 0021-4876

eISSN： 1880-6880
Histrical understanding of acid chloride passivity breakdown on Fe-Cr alloys and new insight derived from artificial passivation film experiments Peer-reviewed

K Sugimoto, M Son, Y Ohya, N Akao, H Hara

CORROSION SCIENCE: A RETROSPECTIVE AND CURRENT STATUS IN HONOR OF ROBERT P FRANKENTHAL　2002　(13)　289-298　2002
Response Characteristics of YSZ Oxygen Sensor with a Ag-YSZ Composite Thin Film Electrode Peer-reviewed

Toru Usami, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Journal of the Japan Institute of Metals　65　(10)　916-921　2001/10
Publisher:
DOI： 10.2320/jinstmet1952.65.10_916 　

ISSN： 0021-4876
Al₂O₃-Nb₂O₅ Composite Thin Film Coating Having Self-Healing Ability Peer-reviewed

Syota Shimonishi, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo-to-Kankyo　49　(8)　500-507　2000/08

DOI： 10.3323/jcorr1991.49.500

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Misc. 55

Development of resistant materials to beam impact and radiation damage

Masayoshi Kawai, Hiroyuki Kokawa, Hiroshi Okamura, Akira Kawasaki, Tsutomu Yamamura, Nobuyoshi Hara, Noboru Akao, Masatoshi Futakawa, Kenji Kikuchi

Journal of Nuclear Materials　356　(1-3)　16-26　2006

DOI： 10.1016/j.jnucmat.2006.05.021 　
Corrosion Resistance and Electrochemical Properties of ZnO Thin Films Formed by Ion-Beam-Sputter Deposition

HARA Nobuyoshi

CAMP-ISIJ　17　(6)　1155-1155　2004/09/01

ISSN： 0914-6628
Degradation of air-formed films on titanium in simulated solution of bentonite contact water

Hideo Shibuya, Jigen Takahashi, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　53　(7)　372-381　2004
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.53.372 　

ISSN： 0917-0480
Degradation of air-formed films on titanium in simulated solution of bentonite contact water

Hideo Shibuya, Jigen Takahashi, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　53　(7)　372-381　2004
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.53.372 　

ISSN： 0917-0480
Electrochemical Characteristics of ZnO Thin Films Formed by Ion-Beam-Sputter Deposition

HARA Nobuyoshi

16　(6)　1254-1257　2003/09/01

ISSN： 0914-6628
Electrochemical evaluation of adhesion between photoresist and invar alloy for fine etching

Tetsuya Ezure, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　52　(5)　267-274　2003
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.52.267 　

ISSN： 0917-0480
Electrochemical evaluation of adhesion between photoresist and invar alloy for fine etching

Tetsuya Ezure, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　52　(5)　267-274　2003
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.52.267 　

ISSN： 0917-0480
Corrosion and its mechanism of Al-10% Si alloy-coated steel in methanol containing H2O, NaCl, and HCOOH

R Umebayashi, N Akao, N Hara, K Sugimoto

JOURNAL OF THE ELECTROCHEMICAL SOCIETY　149　(3)　B75-B83　2002/03

DOI： 10.1149/1.1447943 　

ISSN： 0013-4651
Corrosion and its mechanism of aluminum in methanol environment

Rie Umebayashi, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　51　(8)　343-349　2002
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.51.343 　

ISSN： 0917-0480
Corrosion resistance of tungsten and tungsten alloys for spallation target in stagnant and flowing water

Noriaki Noji, Keisuke Kashiwagura, Noboru Akao, Saiko Soma, Nobuyoshi Hara, Katsuhisa Sugimoto

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　66　(11)　1107-1115　2002
Publisher: Japan Institute of Metals (JIM)
DOI： 10.2320/jinstmet1952.66.11_1107 　

ISSN： 0021-4876
Corrosion and its mechanism of aluminum in methanol environment

Rie Umebayashi, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　51　(8)　343-349　2002
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.51.343 　

ISSN： 0917-0480
Corrosion resistance of tungsten and tungsten alloys for spallation target in stagnant and flowing water

Noriaki Noji, Keisuke Kashiwagura, Noboru Akao, Saiko Soma, Nobuyoshi Hara, Katsuhisa Sugimoto

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　66　(11)　1107-1115　2002
Publisher: Japan Institute of Metals (JIM)
DOI： 10.2320/jinstmet1952.66.11_1107 　

ISSN： 0021-4876
Corrosion and Electrochemical Characteristics of NiO-Cr₂O₃-Fe₂O₃ Artificial Passivation Films Formed by MOCVD

Mamoru Ishida, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Passivity of Metals and Semiconductors　305-312　2001
Electrochemical Charcteristics of Fe-Cr Stainless Steel Films prepared by Ion-Beam-Sputter and Ion-Beam-Assisted Deposition Methods

N.Akao, H.Chujo, N.Hara, K.Sugimoto

Passivity of Metals and Semiconductors　828-833　2001
Corrosion and Electrochemical Characteristics of NiO-Cr₂O₃-Fe₂O₃ Artificial Passivation Films Formed by MOCVD

Mamoru Ishida, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Passivity of Metals and Semiconductors　305-312　2001
Electrochemical Charcteristics of Fe-Cr Stainless Steel Films prepared by Ion-Beam-Sputter and Ion-Beam-Assisted Deposition Methods

N.Akao, H.Chujo, N.Hara, K.Sugimoto

Passivity of Metals and Semiconductors　828-833　2001
Electrochemical ellipsometry study on corrosion resistance of Fe2O3-Cr2O3-MxOy (M : valve metals and Si) artificial passivation films in acid solutions

K Sugimoto, M Son, N Akao, N Hara

STATE-OF-THE ART APPLICATION OF SURFACE AND INTERFACE ANALYSIS METHODS TO ENVIRONMENTAL MATERIALS INTERACTIONS: IN HONOR OF JAMES E. CASTLE'S 65TH YEAR, PROCEEDINGS　2001　(5)　215-223　2001
Development of wide range EIS capacitor pH sensor using corrosion- resistant Al2O3-Ta2O5 and Al2O3-ZrO2 thin films as insulator layer

K Sugimoto, S Yoshida, N Akao, N Hara

CORROSION AND CORROSION PROTECTION　2001　(22)　714-721　2001
Electrochemical and corrosion properties of Fe2O3-Cr2O3-MoO2 artificial passivation films in HCl solutions

M Son, N Akao, N Hara, K Sugimoto

JOURNAL OF THE ELECTROCHEMICAL SOCIETY　148　(1)　B43-B50　2001/01

DOI： 10.1149/1.1344531 　

ISSN： 0013-4651
Electrochemical Properties of Fe₂O₃-Cr₂O₃-MoO₂ Artificial Passivation Films in HCl Solutions

Katsuhisa Sugimoto, Myungsook Son, Noboru Akao, Nobuyoshi Hara

Oxide Films (Proceedings of the Symposium on Oxide Films)　12-23　2000
Electrochemical Properties of Fe₂O₃-Cr₂O₃ Artificial Passivation Films in a HCl Solution

Katsuhisa Sugimoto, Myungsook Son, Noboru Akao, Nobuyoshi Hara

Pits and Pores II (Proceedings of the Symposium on Pits and Pores II)　155-161　2000
Corrosion resistance of iron thin films prepared by ion-beam-sputter and ion-beam-assisted deposition

Tetsuji Kaneko, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　49　(5)　301-306　2000
Publisher: Japan Soc of Corrosion Engineering
DOI： 10.3323/jcorr1991.49.301 　

ISSN： 0917-0480
Electrochemical Properties of Fe₂O₃-Cr₂O₃-MoO₂ Artificial Passivation Films in HCl Solutions

Katsuhisa Sugimoto, Myungsook Son, Noboru Akao, Nobuyoshi Hara

Oxide Films (Proceedings of the Symposium on Oxide Films)　12-23　2000
Electrochemical Properties of Fe₂O₃-Cr₂O₃ Artificial Passivation Films in a HCl Solution

Katsuhisa Sugimoto, Myungsook Son, Noboru Akao, Nobuyoshi Hara

Pits and Pores II (Proceedings of the Symposium on Pits and Pores II)　155-161　2000
Corrosion resistance of iron thin films prepared by ion-beam-sputter and ion-beam-assisted deposition

Tetsuji Kaneko, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　49　(5)　301-306　2000
Publisher: Japan Soc of Corrosion Engineering
DOI： 10.3323/jcorr1991.49.301 　

ISSN： 0917-0480
Formation of Al2O3-Ta2O5 double-oxide thin films by low-pressure MOCVD and evaluation of their corrosion resistances in acid and alkali solutions

N Hara, S Nagata, N Akao, K Sugimoto

JOURNAL OF THE ELECTROCHEMICAL SOCIETY　146　(2)　510-516　1999/02

DOI： 10.1149/1.1391636 　

ISSN： 0013-4651
Electrochemical characteristics of CrN thin films prepared by ion-beam-enhanced deposition

Daisuke Mizuno, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　48　(9)　589-596　1999
Publisher: Japan Soc of Corrosion Engineering
DOI： 10.3323/jcorr1991.48.589 　

ISSN： 0917-0480
Electrochemical characteristics of CrN thin films prepared by ion-beam-enhanced deposition

Daisuke Mizuno, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　48　(9)　589-596　1999
Publisher: Japan Soc of Corrosion Engineering
DOI： 10.3323/jcorr1991.48.589 　

ISSN： 0917-0480
Electrochemical characteristics of Fe-Cr alloy thin films prepared by ion-beam-sputter deposition

N Iwamoto, H Chujo, N Akao, N Hara, K Sugimoto

JOURNAL OF THE JAPAN INSTITUTE OF METALS　62　(10)　877-886　1998/10

DOI： 10.2320/jinstmet1952.62.10_877 　

ISSN： 0021-4876

eISSN： 1880-6880
Comparison of corrosion resistances between Fe2O3-TiO2 artificial passivation film and passivation film on Fe-Ti alloy

H Kim, N Akao, N Hara, K Sugimoto

JOURNAL OF THE ELECTROCHEMICAL SOCIETY　145　(8)　2818-2826　1998/08

DOI： 10.1149/1.1838720 　

ISSN： 0013-4651
Corrosion behavior of metals and alloys in downstream environment of microwave plasma with CF4/O2 gas mixture

Eiji Ohtsuki, Atsushi Nakafuji, Noboru Akao, Nobuyoshi Kara, Matsuho Miyasaka, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　47　(2)　136-145　1998
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.47.136 　

ISSN： 0917-0480
Development of solid electrolyte reference electrode for high temperature water system

Yasufumi Fujiki, Saikou Souma, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　47　(8)　528-533　1998
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.47.528 　

ISSN： 0917-0480
Electrochemical characteristics of Fe-Cr alloy thin films prepared by ion-beam-sputter deposition

Naoki Iwamoto, Hiroki Chujo, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　62　(10)　877-886　1998
Publisher: Japan Institute of Metals (JIM)
DOI： 10.2320/jinstmet1952.62.10_877 　

ISSN： 0021-4876
Corrosion behavior of metals and alloys in downstream environment of microwave plasma with CF4/O2 gas mixture

Eiji Ohtsuki, Atsushi Nakafuji, Noboru Akao, Nobuyoshi Kara, Matsuho Miyasaka, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　47　(2)　136-145　1998
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.47.136 　

ISSN： 0917-0480
Development of solid electrolyte reference electrode for high temperature water system

Yasufumi Fujiki, Saikou Souma, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　47　(8)　528-533　1998
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.47.528 　

ISSN： 0917-0480
Formation of Al₂O₃-ZrO₂ Double Oxide Thin Films and Evaluation of their Corrosion Resistance

E.Takahashi, N.Akao, N.Hara, K.Sugimoto

Organic and Inorganic Coationgs for Corrosion Prevention - Research and Experiences　299-312　1997
Corrosion of multilayers used for magnetoresistive head in aqueous solution environment

Mamoru Ishida, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto, Sigeo Fujii

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　61　(1)　64-70　1997
Publisher: Japan Institute of Metals (JIM)
DOI： 10.2320/jinstmet1952.61.1_64 　

ISSN： 0021-4876
Development of EIS capacitor pH sensor for highly corrosive environment

Fumihiko Tamura, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　46　(4)　243-250　1997
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.46.243 　

ISSN： 0917-0480
Formation of Al₂O₃-ZrO₂ Double Oxide Thin Films and Evaluation of their Corrosion Resistance

E.Takahashi, N.Akao, N.Hara, K.Sugimoto

Organic and Inorganic Coationgs for Corrosion Prevention - Research and Experiences　299-312　1997
Corrosion of multilayers used for magnetoresistive head in aqueous solution environment

M Ishida, N Akao, N Hara, K Sugimoto, S Fujii

JOURNAL OF THE JAPAN INSTITUTE OF METALS　61　(1)　64-70　1997/01

DOI： 10.2320/jinstmet1952.61.1_64 　

ISSN： 0021-4876

eISSN： 1880-6880
Development of EIS capacitor pH sensor for highly corrosive environment

Fumihiko Tamura, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Zairyo to Kankyo/ Corrosion Engineering　46　(4)　243-250　1997
Publisher: Japan Society of Corrosion Engineering
DOI： 10.3323/jcorr1991.46.243 　

ISSN： 0917-0480
Ellipsometric analysis of relationship between formation condition and corrosion resistance of CVD-ZrO2 thin films

T Kubota, N Akao, N Hara, K Sugimoto

JOURNAL OF THE JAPAN INSTITUTE OF METALS　60　(10)　980-987　1996/10

DOI： 10.2320/jinstmet1952.60.10_980 　

ISSN： 0021-4876

eISSN： 1880-6880
Formation of Fe2O3-TiO2 thin oxide films by low pressure MOCVD and evaluation of their corrosion resistance

H Kim, N Akao, N Hara, K Sugimoto

JOURNAL OF THE JAPAN INSTITUTE OF METALS　60　(6)　600-606　1996/06

DOI： 10.2320/jinstmet1952.60.6_600 　

ISSN： 0021-4876

eISSN： 1880-6880
Corrosion resistance of Fe2O3-TiO2 thin films prepared by low pressure MOCVD

K Sugimoto, H Kim, N Akao, N Hara

PROCEEDINGS OF THE SYMPOSIUM ON SURFACE OXIDE FILMS　96　(18)　194-205　1996
Formation of Fe2O3-TiO2 thin oxide films by low pressure MOCVD and evaluation of their corrosion resistance

Hyunsoo Kim, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　60　(6)　600-606　1996
Publisher: Japan Institute of Metals (JIM)
DOI： 10.2320/jinstmet1952.60.6_600 　

ISSN： 0021-4876
Ellipsometric analysis of relationship between formation condition and corrosion resistance of CVD-ZrO2 thin films

Takeo Kubota, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　60　(10)　980-987　1996
Publisher: Japan Institute of Metals (JIM)
DOI： 10.2320/jinstmet1952.60.10_980 　

ISSN： 0021-4876
Corrosion Resistance of Fe₂O₃-TiO₂ Thin Films Prepared by Low Pressure MOCVD

K.Sugimoto, H.Kim, N.Akao, N.Hara

Surface Oxide Films (Proceedings of the Symposium on Surface Oxide Films)　195-204　1996
CORROSION BEHAVIOR OF TBFECO MAGNETOOPTICAL RECORDING FILMS WITH PROTECTION COATING IN AQUEOUS ENVIRONMENT

N AKAO, E SHIMIZU, K SUGIMOTO

JOURNAL OF THE JAPAN INSTITUTE OF METALS　59　(8)　840-845　1995/08

DOI： 10.2320/jinstmet1952.59.8_840 　

ISSN： 0021-4876

eISSN： 1880-6880
Corrosion behavior of TbFeCo magneto-optical recording films with protection coating in aqueous environment

Noboru Akao, Eiji Shimizu, Katsuhisa Sugimoto

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　59　(8)　840-845　1995
Publisher: Japan Inst of Metals
DOI： 10.2320/jinstmet1952.59.8_840 　

ISSN： 0021-4876
THE INFLUENCE OF CO CONTENT ON THE CORROSION-RESISTANCE OF SPUTTER-DEPOSITED TBFECO THIN-FILMS IN AQUEOUS ENVIRONMENTS

N AKAO, T KATO, T SASAKI, K SUGIMOTO

JOURNAL OF THE ELECTROCHEMICAL SOCIETY　141　(5)　1199-1205　1994/05

DOI： 10.1149/1.2054896 　

ISSN： 0013-4651
INFLUENCE OF DY CONTENT ON AQUEOUS CORROSION OF TBDYFECO MAGNETOOPTICAL RECORDING FILMS

N AKAO, T MATSUDA, K SUGIMOTO

JOURNAL OF THE JAPAN INSTITUTE OF METALS　58　(3)　309-317　1994/03

DOI： 10.2320/jinstmet1952.58.3_309 　

ISSN： 0021-4876

eISSN： 1880-6880
Influence of Dy content on aqueous corrosion of TbDyFeCo magneto-optical recording films

Noboru Akao, Takayuki Matsuda, Katsuhisa Sugimoto

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　58　(3)　309-317　1994
Publisher: Japan Inst of Metals
DOI： 10.2320/jinstmet1952.58.3_309 　

ISSN： 0021-4876
ANODIC POLARIZATION BEHAVIOR AND SURFACE-FILMS OF CVD-SIC IN AQUEOUS-SOLUTIONS

D TANAKA, N AKAO, N HARA, K SUGIMOTO

JOURNAL OF THE JAPAN INSTITUTE OF METALS　57　(10)　1166-1173　1993/10

DOI： 10.2320/jinstmet1952.57.10_1166 　

ISSN： 0021-4876

eISSN： 1880-6880
水溶液中におけるCVD-SiCのアノ-ド分極挙動と表面皮膜

田中大輔, 赤尾昇, 原信義, 杉本克久

日本金属学会報　57　(10)　1166-1173　1993

DOI： 10.2320/jinstmet1952.57.10_1166 　
CORROSION MECHANISM OF SPUTTER-DEPOSITED TBFE THIN-FILMS IN AQUEOUS ENVIRONMENT

N AKAO, K SUGIMOTO

JOURNAL OF THE ELECTROCHEMICAL SOCIETY　139　(6)　1560-1565　1992/06

DOI： 10.1149/1.2069455 　

ISSN： 0013-4651

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Research Projects 23

Development of pit initiation mechanism from MnS inclusions in stainless steel and new principles for improving pitting resistance

HARA NOBUYOSHI, MUTO Izumi, SUGAWARA Yu, AKAO Noboru

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (A)

Institution: Tohoku University

2012/04/01 - 2015/03/31

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In order to improve the pitting corrosion resistance of stainless steels without the addition of a large amount of rare metals such as Cr and Mo, the mechanism of pit initiation at MnS inclusions has been examined and an new method for improving pitting resistance has been developed. While the inclusions dissolve under anodic polarization, elemental sulfur is deposited at the boundaries between the inclusions and steel matrix. The synergistic effect of the elemental sulfur and chloride ions causes the breakdown of passivity at the boundaries to form trenches, in which pit is initiated when pH and potential satisfy a critical condition of pit growth. Based on this pit initiation mechanism, the inhibition of the active dissolution of steel matrix in acidic chloride solutions seems to be beneficial. By using the combinatorial approach, it was proposed that the addition of a small amount of Sn (<1%) was effective to improve pitting resistance.
A resource-saving technology for high corrosion-resistant steels by improving electrochemical property of non-metallic inclusions

MUTO Izumi, HARA Nobuyoshi, SUGAWARA Yu, AKAO Noboru

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Challenging Exploratory Research

Institution: Tohoku University

2011 - 2012

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To analyze microscopic corrosion mechanisms of metals, a microelectrochemical system for in situ high-resolution optical microscopy was developed and applied to the real-time observation of pit initiation at MnS inclusion in stainless steels. It was directly observed that pits were initiated at the MnS/steel boundaries, and that deep trenches were generated at these boundaries during anodic polarization. The metal-oxide enriched surface layer on inclusions was found to be the predominant factor affecting the electrochemical properties and the corrosion protection ability of the inclusions.
Development of prevention technology of hydrogen absorption for steels by improving electrochemical property of non-metallic inclusions

MUTO Izumi, HARA Nobuyoshi, AKAO Noboru

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2010 - 2012

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A micro permeation cell for studying hydrogen absorption behavior in a small area on metals was developed. The preferential sites of hydrogen absorption of carbon steel surfaces were found to be MnS inclusions in near-neutral environments. It was demonstrated that the hydrogen permeation currents were extremely increased by the dissolution of MnS inclusions. HS- ions released from the sulfide dissolution promote the hydrogen absorption reaction on steel surfaces. Ti(C,N) inclusions do not dissolve and do not promote the hydrogen absorption in near-neutral environments.
Development of CWD process for surface treatment of magnesium

HARA Nobuyoshi, MUTO Izumi, AKAO Noboru

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Challenging Exploratory Research

Institution: Tohoku University

2010 - 2011

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In order to develop a cyclic wet-dry (CWD)process as a new surface treatment method for improving corrosion resistance of Mg alloys, the composition of starting solution, the process conditions and the corrosion resistance of reaction products have been examined. It was found that hydrotalcite ((Mg_6Al_2(OH)_<16> CO_3・4H_2O))or hydrotalcite-like compounds can be formed under well-controlled CWD conditions using NaCl+ AlCl_3 or Na_2SO_4+ Al_2(SO_4)_3 solutions and they improves the corrosion resistance of Mg alloys.
マイクロドット蛍光イメージングプレートによる実在表面における不均一腐食の機構解析

武藤泉, 原信義, 赤尾昇

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 挑戦的萌芽研究

Institution: 東北大学

2009 - 2010

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本研究において新規に開発した蛍光イメージングプレートを用い、ステンレス鋼のすき間腐食発生過程における水素イオン濃度(pH)と塩化物イオン濃度の面分布をリアルタイム可視化分析した。試験片には、マンガンを添加したオーステナイト系ステンレス鋼(Fe-18Cr-10Ni-5.4Mn)を使用した。試験液としては、希硫酸でpHを3.0に調整した0.01M NaCl(298K)を用い、Ag/AgCl(3.33M KCl)電極基準で0.3Vに定電位分極を行った。イメージングプレートの外観を100秒ごとに光学顕微鏡で撮影し、その色調(RGB値)からpHおよび塩化物イオン濃度への換算を行った。定電位分極開始と共に、電流値は低下し、3000秒程経過した後に、すき間腐食の発生により徐々に増加することが分かった。水素イオン濃度(pH)は、最初の500秒程は変化が見られないが、その後徐々に低下し、pH2を下回ったところ(約1.8)でエッチピットが発生することが分かった。そして、このエッチピットの発生により、その周囲のpHが0.5程度まで直ちに低下し、すき間腐食がマクロ的に広がって行くことが解明された。一方、塩化物イオン濃度に関しては、すき間腐食が発生する前に顕著な濃度上昇は見られなかった。これは、Cl^-イオンがステンレス鋼から溶出したCr^<3+>イオンと錯イオンCrCl^<2+>を形成し、Cl^-イオンとしては高い濃度に到達しないためであると推察される。しかし、塩化物イオンを含まないpH3.0のNa_2SO_4を用いた場合には、すき間腐食は発生しなかったため、すき間腐食を引き起こすエッチピットの発生には0.O1M程度の塩化物イオン濃度の存在は不可欠であると推定される。また、同様の実験を窒素添加オーステナイト系ステンレス鋼(Fe-18Cr-10Ni-5.4Mn-0.28N)に対して実施した。その結果、すき間腐食の発生過程であるエッチピットは発生するものの、すき間腐食へ成長しないケースが多く見られた。窒素はすき間腐食発生過程であるエッチピットを再不働態化させる作用があるものと考えられる。
Development of green stainless steels by micro-and nano-scale surface design and control

HARA Nobuyoshi, MUTO Izumi, AKAO Noboru

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (A)

Institution: Tohoku University

2008 - 2010

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In order to develop a new passivation method for removing MnS from the surface of stainless steels and forming a Cr enriched passive film on the surface, microelectrochemical electrochemical properties of MnS and chemical dissolution behaviors of MnS in chelate-containing solutions have been examined. It was found that citric acid system solutions are effective to remove MnS and to improve corrosion resistance of stainless steels.
Relationship between Nano-topology and Corrosion Resistance of Metallic Thin Films Prepared by Ion-Beam-Sputter Deposition Method

AKAO Noboru, HARA Nobuyoshi, MUTO Izumi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (C)

Institution: Tohoku University

2007 - 2008
Visualization of change in solution chemistry during corrosion process and its application to improve corrosion resistance of metallic materials

MUTO Izumi, HARA Nobuyoshi, AKAO Noboru

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

2006 - 2008
太陽光照射により防食機能を自己再生する有機コーティングの創製

武藤泉, 原信義, 赤尾昇

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 萌芽研究

Institution: 東北大学

2006 - 2007

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導電性ポリマーであるポリアニリンを用い、Fe-11Cr鋼の表面に酸化重合膜を形成し、乾湿繰り返し下での防食機構解析を実施。腐食試験用に屋外の気温と相対湿度の日変化を忠実に再現できる気象シミュレータを作製し、この中で塩化物イオン付着量を0.001〜1.0g/m^2の範囲で変化させた。膜が健全な部分では1.0g/m^2の塩化物イオン付着量でも、赤さび発生は見られないことから、膜自体の環境遮断機能は優れていることが分かった。膜欠陥部(クロスカット部)に関しては、研磨ままの試験片では塩化物イオン付着量0.001〜0.1g/m^2の条件で軽微な赤さび発生が見られたが、ポリアニリン酸化重合膜をコーティングした場合には赤さび発生が見られなかった。腐食試験後、クロスカットの周囲のみポリアニリンが変色していたことから、ポリアニリン膜と露出金属部との電気化学的なカップリングにより防食機能を示す可能が示唆された。しかし、塩化物イオン付着量1.0g/m^2の条件では、グロスカット部からポリアニリン膜/下地界面に塗膜下腐食が起こり、コーティング膜の剥離が生じた。乾湿が繰り時の電位変化を解析した結果、ポリアニリン酸化重合膜をコーティングした試験片は、乾湿繰り返し環境で、研磨ままの材料よりもやや貴な電位を示すことが分かった。塩化物イオン付着量が少なく孔食発生電位が低い際には、酸化体被覆により不働態化が促進される。しかし、塩化物イオン付着量が高く孔食発生電位が低下する環境では、酸化体の有する貴な電位が、皮膜欠陥部において、孔食を誘発する危険性があることが明らかになった。尚、厳しい腐食環境でのポリアニリンの塗膜下腐食を防止するため現在用いられているクロメート(SrCrO_4)について端面防錆機構をケルビンプローブで解析したところ鋼母地のアノードおよびカソード反応速度を抑制していることが分かった。
Development of Alloy-Coated Steel having High Corrosion Resistance for Methanol fuel tanks of Fuel Cell Electric Vehicles

AKAO Noboru, HARA Nobuyoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (C)

Institution: Tohoku University

2003 - 2004

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Corrosion and electrochemical properties of Sn-8%Zn alloy-coated steel prepared by a melt-dipping method have been investigated in methanol containing H_2O, NaCl and HCOOH, which are known as contaminants in methanol fuel. The coated steel showed high corrosion resistance in methanol containing 0.1-30%H_2O and 0.1-30%H_2O+0.1%NaCl. The corrosion rates of the coated steel in these solutions were less than 0.66 μg・m^<-2>・s^<-1>. However, the coated steel showed slight corrosion in methanol containing 0.1-30%H_2O+0.1%HCOOH and its corrosion rates were 2.4 -3.5 μg・m^<-2>・s^<-1>. Anodic and cathodic polarization curves measured in methanol containing 0.1-30%H_2O+0.1%NaCl showed that the corrosion potential of the coated steel was close to that of Zn, while the pitting potential of the coated steel was close to that of Sn. According to AES and XPS analyses, the surface film of the coated steel after an immersion corrosion test in methanol containing 0.1%H_2O+0.1%NaCl was composed of a large amount of oxide and hydroxide of Zn and a small amount of those of Sn. It was presumed that the corrosion of the coated steel proceeded through the selective dissolution of Zn component in the coating layer in methanol containing H_2O and NaCl.
Development of an External Pressure Balance Reference Electrode for Use in Supercritical Water Systems

HARA Nobuyoshi, AKAO Noboru

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: TOHOKU UNIVERSITY

2002 - 2004

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Supercritical water oxidation (SCWO) is a promising method for decomposing hazardous organic wastes into harmless inorganic compounds in a high efficiency and a short time. However, SCWO reactors suffer from severe corrosion by hydrogen halide, nitrate, sulfate, and phosphate, which are formed during destruction of the wastes. Consequently, it is necessary to make clear corrosion mechanism in the SCWO environment and to establish the countermeasure to prevent corrosion. For this purpose, the development of electrochemical measurement is necessary. The objective of this study is to develop a new type of external pressure balanced reference electrode (EPBRE) for electrochemical measurement in supercritical water, to evaluate its performance, and to apply it to the measurement of anode polarization curves in supercritical water. A Ag/AgCl electrode was installed in a small pressure vessel at room temperature. The pressure of this external reference electrode was maintained at the same values as that of an autoclave at high temperature by pumping an internal solution (0.1M KCl) with a high-pressure pump. In this reference electrode system, liquid junction is set in the room temperature side, so that thermal liquid junction potential (TLJP) generates between the EPBRE and a test electrode in the high temperature side. In order to evaluate the value of TLJP, a Pt-hydrogen electrode (PHE) was first installed in the high temperature autoclave, and the potential difference between PHE and EPBRE electrodes was measured. 0.1M KCl, 0.05M Na_2SO_4, 1mM Na_2SO_4, pure water, 1mM HCl and 1mM NaOH were used for the test solution and TLJPs for the solutions were measured in the temperature range of 298〜773K. Thus evaluated TLJPs can be used to convert the measured potential into the potential referred to SHE. Anode polarization curves of SUS304 stainless steel were measured in the temperature range of 563-673K. It was found that there is little or no difference in the value of TLJP for 1mM Na_2SO_4 and 0.05M Na_2SO_4, indicating that the TLJP is independent of the concentration Na_2SO_4 over the range used in this experiment. The TLJP in 0.1 M KCl was approximately the same as that in Na_2SO_4. The change of TLJP with solution composition is small in neutral solutions used in this experiment. The anode polarization curves of SUS304 steel in 0.05M Na_2SO_4 solution showed four characteristic regions : active dissolution, passivity, transpassivity, and oxygen evolution. Starting potentials of transpassivity and oxygen evolution shifted to negative direction with increasing temperature. In supercritical 0.1M KCl solution at 673K, SUS304 steel was suffered from pitting. In the anode polarization curves of SUS304 steel at 673K, the starting potential of transpassive dissolution shifted to the positive direction with decreasing pH and at the same time the transpassive dissolution current density increased.
自己修復性防食機能を有する酸化物・金属ナノ構造薄膜の創製

原信義, 赤尾昇, 杉本克久

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 萌芽研究

Institution: 東北大学

2002 - 2003

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酸化物と金属から成るナノラミネート薄膜および傾斜組成ナノコンポジット薄膜をイオンビームスパッタ蒸着法(IBS)法によって合成し,自己修復性防食機能を発現させることを目的として一連の検討を行い,以下のような成果を得た。 1.酸化物/金属ナノラミネート薄膜作製装置の開発:現有するデュアルイオンビームスパッタ蒸着装置に,ターゲットホルダーの回転によって酸化物と金属ターゲットを交互に切り替え機構を導入し,酸化物/金属ナノラミネート薄膜の作製が可能な装置に改造した。 2.Al_2O_3/Nbナノラミネート薄膜の作製:Al_2O_3およびNb層の厚さと層数を種々変えたAl_2O_3/Nbナノラミネート薄膜を作製した。透過電子顕微鏡観察により,各層の厚さを5nm以下にすると,全層数の多少に関わらず薄膜はアモルファスになることが分かった。また,X光電子分光法を用いて皮膜中の化学種の結合状態を調べた結果,薄膜中のNbは主に金属状態で存在することが分かった。 3.Al_2O_3/Nbナノラミネート薄膜の自己修復性の評価:Na_2SO_4およびNaCl溶液中においてAl_2O_3/Nbナノラミネート薄膜の電気化学スクラッチ試験を行い,自己修復性の有無を調べた。各層の厚さを5nm以下にし,全層数を増加させるとピンホール欠陥が少なく,かつ良好な自己修復性をもつ薄膜が得られることなどが分かった。
高精度微細エッチング用ホトレジストの密着性の電気化学的評価法

杉本克久, 赤尾昇, 原信義

Offer Organization: 日本学術振興会

System: 科学研究費助成事業

Category: 萌芽研究

Institution: 東北大学

2000 - 2002

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CRT用シャドウマスクの高精度化を図るためには,エッチングマスクとなるホトレジストと素地金属の密着性を改善することが重要である。そのためには,まず,ホトレジストの密着性を定量的に評価する方法が必要である。本研究では,ホトレジストの密着性を電気化学的に評価する方法を開発することを目的として一連の検討を行い,以下のような成果を得た。 1.密着性ファクターの決定前年度までに開発した電気化学的手法による密着性評価をより定量的なものとするために,密着性が良好な条件で測定される通過電気量を基準値とし,これに対する試験試料の通過電気量の比を密着性ファクターとして定義し,各前処理条件による密着性ファクターの変化を調べた。 2.エッチングファクターの測定および密着性ファクターとの比較実操業で用いられる塩化第2鉄溶液を用いてエッチングを行い,エッチング深さとサイドエッチング量を計測することによってエッチングファクターを求めた。このエッチングファクターと電気化学的手法により得られたる密着性ファクターとを比較した結果,両者の間には良い相関関係があることが分かった以上の結果を総合して,電気化学的手法による密着性の定量的評価法を確立した。
Development of Low-Alloy Steel for High Level Radioactive Waste Disposal Container

SUGIMOTO Katsuhisa, AKAO Noboru, HARA Nobuyoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: TOHOKU UNIVERSITY

2000 - 2002

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In order to develop a low-alloy steel container for use in geological disposal of high-level radioactive wastes, a series of 0.12%C steels containing a small amount of alloying elements, which are effective in inhibiting cathodic reactions on Fe_3O_4, were prepared and their corrosion resistance was examined. 1. A series of composite oxide films consisting of Fe_3O_4 and MO_x(M: Cr, Mo, Si, Al, Ti, Cu, Ni, Nb) were prepared by ion-beam-sputter deposition and their cathodic polarization characteristics were examined in a simulated solution of water in contact with bentonite (5.72mM-Na_2SO_4+7.99mM-NaHCO)_3 The results showed that the addition of Cr_2O_3, TiO_2, Al_2O_3 and MoO_2 to Fe_3O_4 is effective in suppressing reductive dissolution of Fe_3O_4. 2. A series of low-alloy steels containing alloying elements (Cr, Mo, Si, Al, Ti, Cu, Ni, Nb), which are effective in inhibiting reductive dissolution of Fe_3O_4 and in increasing hydrogen overvoltage, were prepared by vacuum induction melting. The corrosion tests were performed in compressed bentonite exposed to the simulated solution of bentonite-contacting water containing 0.5M-NaCl. In the absence of Fe_3O_4film the steels containing 0.5% Cu, Al, Cr or Ti showed good corrosion resistance, while in the presence of Fe_3O_4film those containing Cu, Nb, or Ti exhibited high corrosion resistance. This suggests that Cu is the most promising alloying element for improving corrosion resistance. 3. Anodic and cathodic polarization curves of the low-alloy steels developed in the present study were measured in the simulated solution of bentonite-contacting water. The steels having excellent corrosion resistance in the corrosion tests showed a high hydrogen overvoltage and a low reductive dissolution rate of Fe_3O_4.
Development of a Dynamic Imaging Spectroscopic Ellipsometer Equipped with a CCD Image Sensor

SUGIMOTO Katsuhisa, AKAO Noboru, HARA Nobuyoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B).

Institution: TOHOKU UNIVERSITY

1998 - 2000

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A dynamic imaging spectroscopic ellipsometer (DISE) has been constructed using a two-dimensional CCD sensor and a variable wavelength light source. The ellipsometer has been applied to the real-time analysis of growth and dissolution processes of CVD oxide thin films, and also to the analysis of spatial variations in thickness and spectroscopic properties of passive films on stainless steels and crabon steels. The principal findings of this study are summarized as follows : 1. The DISE equipment developed enables to be applied to both real-time spectroscopic ellipsometric (RTSE) and imaging ellipsometric (IE) measurements. Spectra with 512 wavelength points could be measured within 100ms by the RTSE mode and images with a 25mm resolution could be obtained within 5s by the IE mode. 2. The growth process of ZrO_2 thin films, deposited by MOCVD, was analyzed using RTSE.It was found that the growth of the films proceeds in three consecutive stages ; cluster nucleation, bulk layer growth and surface roughness evolution. It was also demonstrated that the selective dissolution of a Fe_2O_3 component occurs during reductive dissolution of Fe_2O_3-Cr_2O_3 thin films, formed by MOCVD, while that of a Cr_2O_3 component does during oxidative dissolution of the films. 3. The changes in spatial distribution of thickness and optical constants of passive films on 18-8 stainless steel were examined in 0.1M-NaCl. It was found that in the incubation period of pitting, the spatial variation in film thickness occurs and the pit tends to initiate at a site where the variation is large. The results of the analysis of spatial distributions of the thickness and optical spectra of passive films on carbon steel (0.12%C) showed that the films formed on a ferrite structure is about 10% thicker than those formed on a pearlite structure.
Cathodic Degradation of Passive Films on Ti in High-Level Radioactive Waste Disposal Environments

HARA Nobuyoshi, AKAO Noboru, SUGIMOTO Katsuhisa

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B).

Institution: TOHOKU UNIVERSITY

1998 - 2000

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In order to better understand the corrosion behavior of Ti over-packs used for the underground disposal of high-level radioactive wastes, the degradation processes of surface oxide films on Ti and the stress corrosion cracking (SCC) behavior of the metal have been examined. The principal findings of this study are summarized as follows : 1. The immersion corrosion tests of Ti were performed for about 3 years in water in contact with bentonite containing 0-0.5M NaCl at 50 and 95℃. Changes in the corrosion potential and properties of surface oxide films were examined as a function of immersion time. It was found that the corrosion potential stays approximately constant and was almost independent of the concentration of NaCl. There was no significant change in the thickness of the oxide films, while the composition of the films changes with time : the ratio of OH bonds in the films increased with increasing immersion time up to 1.5 years, and then became constant as the immersion time was increased further. 2. The changes in the thickness, optical constants and chemical composition of surface oxide films on Ti were analyzed under electrochemical cathodic polarization in water in contact with bentonite. There was little or no change in the properties of the films in the potential range between the corrosion potential and -0.8V.At potentials lower than -0.8V, the changes in film properties became evident : the thickness decreased, the refractive index decreased, and the extinction coefficient increased with decreasing potential. 3. The results of SCC tests in water in contact with bentonite showed that hydrogen embrittlement-induced cracking initiated in the potential region where hydrogen evolution takes place, while no cracking occurred in the potential region corresponding to the waste disposal environments.
Development of Dissolved Hydrogen Sensors for High Temperature Water Systems

HARA Nobuyoshi, AKAO Noboru, SUGIMOTO Katsuhisa

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: Tohoku University

1997 - 1999

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For in situ measurements of the concentration of hydrogen in aqueous solutions at elevated temperatures, a newly designed hydrogen sensor, which is based on an electrochemical cell employing a yttria-stabilized zirconia (YSZ) solid electrolyte and a noble metal working electrode, has been developed. The hydrogen response of the sensor has been examined at temperatures as high as 300℃. The principal findings of this work are summarized as follows : 1. YSZ oxygen sensors equipped with Ag powder or thin film electrodes were fabricated. The thin film electrodes were prepared by ion-beam-sputter (IBS) deposition. The sensors showed a fast, Nernstian response to changes in oxygen partial pressure at temperatures of 200℃ to 300℃, indicating that both the Ag powder and thin film electrodes can be used as an internal reference electrode of hydrogen sensor. 2. Hydrogen sensors equipped with painted or IBS-deposited Pt and Pd were fabricated and the response to hydrogen in NィイD22ィエD2HィイD22ィエD2 gas mixtures was examines. The response rate in the gas mixtures was faster for sensors employing thin IBS-Pt and -Pd electrodes compared with those employing thick painted electrodes. However, the hydrogen electrode reaction in aqueous solutions was not affected by the difference in the preparation method of the electrodes. The corrosion resistance of Pt in high temperature aqueous solution was higher than that of Pd. 3. Hydrogen sensors employing a YSZ tube, a Ag-OィイD22ィエD2 internal reference electrode, and a hydrogen-sensitive Pt working electrode covered with a PTFE diffusion membrane has been fabricated and the response to hydrogen in aqueous solutions was examined at temperatures over the range of 200℃ to 300℃. The sensors displayed rapid and Nernstian responses to changes in hydrogen concentration in the temperature range of 250℃ and 300℃. Oxygen in solution had little effect on the potential of the sensor, when the concentration of oxygen is lower than that of hydrogen. The potential of the sensor was independent of the solution pH.
Corrosion Mechanism of Metals and Alloys in CFィイD24ィエD2/OィイD22ィエD2 Plasma Downstream Environments

SUGIMOTO Katsuhisa, AKAO Noboru, HARA Nobuyoshi

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (B)

Institution: TOHOKU UNIVERSITY

1997 - 1999

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The corrosion characteristics of pure metals (Al, Ti, Cr, Fe, Co, Ni, Cu, Mo, Ta, and W), stainless steels (SUS 304 and 316), and cast iron in downstream environments of CFィイD24ィエD2-OィイD22ィエD2 plasma have been studied. The principal findings of this study are summarized as follows. 1. At 573K, pure metals such as Ti, Cr, Mo, Ta, and W suffered from corrosion leading to a decrease in mass. Pure Fe, cast iron and the stainless steels showed an increase in mass, while Al, Co, Ni, and Cu no change in mass. The corrosion rates of Ti, Cr, Mo, Ta, and W increased with rising test temperature in the range of 298 to 573K. At a given temperature the corrosion rates reached a maximum at OィイD22ィエD2 concentrations of 15 to 20%. 2. The emission spectroscopic and mass spectrometric analysis of gas phase showed that main gaseous species are F, HF, O, CFィイD23ィエD2, COFィイD22ィエD2, and COィイD22ィエD2. The concentration of F and HF reached a maximum when the concentration OィイD22ィエD2 in a feed gas increased to 18%. 3. The corroded surface of Cr, Mo and Ta was covered with a thin film of parent metaloxyfluorides, and that of W with a thin oxide film Thin films of metal fluorides were formed on Co, Ni, and Cu. Thicker films consisting of metal fluorides and oxyfluorides existed on Fe and stainless steels. 4. In the downstream environment of CFィイD24ィエD2/OィイD22ィエD2 plasmas, metal fluorides are thermodynamically favored for all the metals examined. The vapor pressures of MoFィイD26ィエD2, TaFィイD25ィエD2 and WFィイD26ィエD2 in the temperature range of 298 to 573K are high enough to evaporate when they are formed. Therefore, the corrosion of metals and alloys in the downstream environment of CFィイD24ィエD2/OィイD22ィエD2 plasmas is primarily controlled by the rates of reactions with fluorine atoms, which are generated in the plasmas, and the vapor pressures of metal fluorides formed by the reactions.
Development of Solid Electrolyte ECP Sensor for High Temperature Water System

HARA Nobuyoshi, AKAO Noboru, SUGIMOTO Katsuhisa

Offer Organization: Japan Society for the Promotion of Science

System: Grants-in-Aid for Scientific Research

Category: Grant-in-Aid for Scientific Research (C)

Institution: TOHOKU UNIVERSITY

1996 - 1997

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A newly designed electrochemical potential (ECP) sensor has been developed for electrochemical measurement in high temperature water systems and its thermodynamic response has been confirmed at temperatures up to 523K.The principal findings of this work are summerized as follows. 1.A solid electrolyte ECP sensor was designed and fabricated. This sensor is composed of an yttria stabilized zirconia (YSZ,ZrO_2-8mol%Y_2 O_3) disk electrode with a sputter-deposited Ni・NiO composite film on the backside, an asbestos plug soaked with a neutral phosphate buffer solution as an internal solution, and an oxidized zircaloy-4 body. 2.The potential of the solid electrolyte ECP sensor with respect to an Ag/AgCl (0.1kmol・m^<-3>KCl) internal refernce electrode was independent of solution pH at temperatures over the range of 473K to 523K. 3.The ECP sensor had the following linear relationship with temperature in the range of 473 to 523K : E_<YSZ/NiO>=2395-5.37T/mV vs.SHE 4.The long-term stability of the sensor was confirmed through the potential measuremet combined with Pt-hydrogen electrode. 5.Using the solid electrolyte ECP sensor, the measurement of anodic polarization curves of SUS 304 stainless steel in a 0.5kmol・m^<-3>Na_2SO_4 solution at temperatures up to 563K has been performed. Anodic polarization curves measured with the ECP sensor coincided with those with the Ag/AgCl internal reference electrode in the temperature range from 473 to 563K.
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1990 - 1990
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1990 - 1990
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