Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
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Electrochemical Deposition Characteristics of Ca2+ on Cu Wire Electrode in CaCl2 Molten Salt

CaCl2 용융염에서 Ca2+의 Cu 전극에 대한 전기화학적 증착 특성평가

  • Hwang, Dong Wook (Department of Chemical Engineering, Chungbuk National University) ;
  • Lee, Jong Hyeon (Department of Materials Science and Engineering, Chungnam National University) ;
  • Jeong, Sang Mun (Department of Chemical Engineering, Chungbuk National University)
  • 황동욱 (충북대학교 화학공학과) ;
  • 이종현 (충남대학교 신소재공학과) ;
  • 정상문 (충북대학교 화학공학과)
  • Received : 2021.09.04
  • Accepted : 2021.10.26
  • Published : 2022.05.01
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Abstract

With the expansion of the automobile market, the demand for Nd as an essential rare earth material for automobile motors is rapidly increasing. Research on the calcio-thermic reduction process between Nd2O3 and calcium-based alloys has been extensively studied in order to manufacture Nd. In this study, Ca-Cu, as a reducing for Nd2O3, was prepared by electrolysis in CaCl2 molten salt. Cu wire and graphite were employed as a working electrode and a counter electrode for electrolysis reaction, respectively. The reference electrode was manufactured by putting Ag wire in a mixture of AgCl and CaCl2 at a ratio of 1:99 mol%. The cyclic voltammetry results showed that the deposition of Ca2+ on the surface of working electrode was observed from a potential of -1.8 V, and the reduction potential of Ca2+ decreased as the reaction temperature increased. The diffusion coefficient of Ca2+ calculated by the chronoamperometry experiment was found to be 5.4(±6.8)×10-6 cm2/s. In addition, Ca-Cu liquid alloy was prepared by applying a constant potential to Cu electrodes. The element ratio of Ca-Cu alloy formed by applying a potential of -2.0 V was found to Ca:Cu=1:4.

자동차 시장의 확대에 따라 자동차 모터의 필수 소재로 희토류금속인 Nd에 대한 수요가 급증하고 있다. Nd를 제조하기 위하여 Nd2O3와 Ca계 합금의 열 환원반응에 관한 연구가 활발히 진행되어 왔다. 본 연구에서는 Nd2O3의 환원제로 사용되는 Ca계 합금인 Ca-Cu를 CaCl2 용융염에서 전기분해반응을 통해 제조하였다. 전기분해반응의 작업 전극과 상대전극으로는 Cu 와이어와 흑연을 각각 사용하였다. 기준전극은 AgCl:CaCl2=1:99 mol%로 혼합한 혼합물에 Ag 와이어를 넣어 제작하였다. 순환전압 전류법 결과에 의하면 -1.8 V의 전위부터 작업전극의 표면에 Ca2+의 증착이 관찰되었으며, CaCl2 염의 온도가 증가할수록 Ca2+의 환원전위가 감소하였다. 시간대전류법 실험을 통해 계산된 Ca2+의 확산계수는 5.4(±6.8)×10-6 cm2/s으로 나타났다. 또한, Cu 전극에 일정한 전위를 가해 Ca-Cu 액상합금을 제조하였으며 제조된 합금은 EDS line scan을 통해 인가 전위의 증가에 따라 Ca의 전기화학적 삽입이 증가함을 확인하였다. -2.0 V보다 음의 전위를 인가하여 제조한 Ca-Cu 합금의 조성비는 Ca:Cu=1:4임을 확인하였다.

Keywords

Acknowledgement

이 연구는 2020년도 산업통상자원부 및 산업기술평가관리원(KEIT) 연구비 지원에 의한 연구임(20010551). 이 논문은 2021학년도 충북대학교 연구년제 지원에 의하여 연구되었음.

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