서지주요정보
Nb이 Zr 합금의 부동태 피막의 전자적 성질과 합금의 재부동태 거동에 미치는 영향 = Effects of Nb on the electronic properties of the passive film and repassivation kinetics of Zr alloys
서명 / 저자 Nb이 Zr 합금의 부동태 피막의 전자적 성질과 합금의 재부동태 거동에 미치는 영향 = Effects of Nb on the electronic properties of the passive film and repassivation kinetics of Zr alloys / 김보영.
저자명 김보영 ; Kim, Bo-Young
발행사항 [대전 : 한국과학기술원, 2002].
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8012903

소장위치/청구기호

학술문화관(문화관) 보존서고

MMS 02012

SMS전송

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초록정보

The effects of Niobium on the tructure and properties(especially electric properties) of passive film of Zirconium alloys in pH 8.5 buffer solution are examined by the photo-electrochemical analysis. For Zr-xNb alloys (x=0, 0.45, 1.5, 2.5 wt%), photocurrent began to increase at the incident energy of 3.5 3.7 eV and exhibited the 1st peak at 4.3 eV and the 2nd peak at 5.7 eV. From $(i_{ph}\nu)1/2$ vs.$\nu$ plot, indirect band gap energies $E_{g1}$=3.01∼3.47 eV , $E_{g2}$ =4.44∼4.91 eV were obtained. With increasing Nb content, the relative photocurrent intensity of 1st peak significantly increased. Compared with photocurrent spectrum of thermal oxide of Zr-2.5Nb, It was revealed that 1st peak in photocurrent spectrum for the passive film formed on Zr-Nb alloy was generated by two types of electron transitions; the one caused by hydrous $ZrO_2$ and the other created by Nb. Two electron transition sources were overlapped over the same range of incident photon energy. In the photocurrent spectrum for passive film formed on Zr-2.5Nb alloy in which Nb is dissolved into matrix by quenching, the relative photocurrent intensity of 1st peak increased, which implies that dissolved Nb act as another electron transition source. Repassivation behaviors of Zr-alloys are also examined by using the rapid scratching electrode techniques under the potentiostatic condition. Repassivation on the scratched surface of the alloy was analyaed in terms of three step; at the initial stage(within 10 msec), passive film grew according to the place exchange model in which logi(t) is linearly proportional to q(t) with a slope of 1/K , and thereafter repassivation after 25 msec occurred according to the high field conduction model in which logi(t) is linearly proportional to 1/q(t) with a slope of cBV. from 10 msec to 25 msec, passive film grew according to both of these model. The value of 1/K, reported that it was directly proportional to the activation energy for the place exchange process of a metal -oxygen pair, could be used as a measure of passive film protectiveness and erosion resistance of the alloy. An alloy/environment system with a higher value of 1/K exhibited faster repassivation rate with a formation of more protective and erosion-resistant passive film. With an addition of Nb into the Zr alloy, 1/K decreased and cBV increased. It means that the protectiveness and erosion resistance of the alloy decreased by Nb alloying. Also, as film formation potential and solution temperature increased, the protectiveness and erosion resistance of the alloy decreased. Using the experimental value of 1/K obtained in relative low temperature, the activation energy for the place exchange of metal-oxygen pair$(W_o)$ in high temperature, in which zirconium alloy is practically used in nuclear reactor, could be predicted.

서지기타정보

서지기타정보
청구기호 {MMS 02012
형태사항 [v], 81 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Bo-Young Kim
지도교수의 한글표기 : 권혁상
지도교수의 영문표기 : Hyuk-Sang Kwon
학위논문 학위논문(석사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 : p. 78-81
주제 지르코늄 합금
부동태 피막의 전자적 성질
재부동태 거동
Zr alloys
electronic properties of the passive film
repassivation kinetics
Nb
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