Transactions of the Korean hydrogen and new energy society (한국수소및신에너지학회논문집)

The Korean Hydrogen and New Energy Society (한국수소및신에너지학회)
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Thermodynamics of Hydrogen-Induced Phase Separation on Pd-Co Alloys

수소유기에 따른 Pd-Co합금들의 상 분리 현상에 대한 열역학적 고찰

  • Song, D.M. (Department of Materials Science Engineering, Chonnam National University) ;
  • Park, C.N. (Department of Materials Science Engineering, Chonnam National University) ;
  • Choi, J. (Department of Advanced Material Engineering, Hanlyo University)
  • 송도민 (전남대학교 신소재공학부) ;
  • 박충년 (전남대학교 신소재공학부) ;
  • 최전 (한려대학교 신소재공학부)
  • Published : 2005.09.15
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Abstract

It is very interesting and important in the academic point of view and in practical use the hydrogen-induced phase separation(HIPS) which appears during hydrogen heat treatment. Since hydrogen can be removed very fast by pumping it out the hydrogen-induced new lattice phase which can not be obtained without hydrogen can be preserved as meta-stable state. In this study it has been investigated whether the HIPS appear in Pd-Al, Pd-Co, Pd-Cr, Pd-Ti, Pd-V and Pd-Zr alloys and discussed thermodynamic representation of the HIPS. The Pd alloys were arc-melted under argon atmosphere and remelted 4 or 5 times for homogenization. The alloys were annealed at 600$^{\circ}C$ under vacuum for 24 hrs and then subjected to pressure-composition isotherm measurements at 100$^{\circ}C$. The hydrogen heat treatment(HHT) of samples was carried out at 600$^{\circ}C$ under hydrogen pressure of 70 bar for 6 days and PC isotherms at 100$^{\circ}C$ were measured. By comparing the PC isotherms measured before and after HHT, occurrence of phase separation was determined. The experimental results showed that the HIPS appeared only in Pd-0.05Co alloy. For Pd-Co alloys with various composition the PC isotherms were measured. By adopting Park-Flanagan model for ternary thermodynamics the Gibbs free energy change for Pd-Co-H solid solution was calculated and subsequently with this the HIPS in Pd-Co alloy was explained fairly.

Keywords

References

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