On the dependence of true hydrogen equilibrium pressure on the granular size distribution of the Zr(Fe

F Ghezzi, M De Angeli

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The influence of grain size distribution on the achievement of the chemical equilibrium between the solid solution region and the hydrogen gas phase for the St909 alloy isotherms has been investigated for two different grain size distributions to test the possibility of using this alloy without a previous cycling treatment. The small grain size distribution gave ΔH̄=-33.54±1.03 kJ/molH, ΔS̄=-18.31±3.43 J/K molHin a H2concentration range 0.05≤x≤0.09, and ΔH̄=-42.30±1.06 kJ/molD, ΔS̄=-21.78±4.49 J/K molDin a D2concentration range 0.02≤x≤0.09. A comparison with ΔH̄ and ΔS̄ values in the infinite dilution range for H2and T2obtained for the conditioned St737 alloy suggested that the small grain distribution gave H2pressure values close to but not yet at equilibrium. A qualitative inquiry on the possible factors limiting the achievement of equilibrium is also presented and suggests surface dissociation phenomena as the most probable cause. © 2002 Elsevier Science B.V. All rights reserved.
Original languageEnglish
Pages (from-to)76 - 80
Number of pages5
JournalJournal of Alloys and Compounds
Publication statusPublished - 17 Jan 2002
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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