1989•Journal of the Japan Society of Powder and Powder MetallurgyOpen access

Determination of standard gibbs free energy of formation of NiW2B2 and activity of Ni-W binary system by EMF Measurement.

Koichiro Koyama, Yasuhiko Hashimoto, Kenji Suzuki, Hideki Matsuo

Abstract

The standard Gibbs free energy of formation of NiW2B2 was determined in the temperature range from 1273 K to 1423 K by measuring electromotive forces of a galvanic cell having a solid oxide electrolyte. Also, the standard Gibbs free energies of formation of WO2 and WO49/18 and the Gibbs free energy of mixing of the Ni-W binary system, which were necessary to determine the standard Gibbs free energy of formation of NiW2B2, were determined. The results obtained are as follows:(1) ΔG°f(NiW2B2)=-199000+3.08T±1000J/mol (1273-1423 K).(2) ΔG°f(WO2)=-573100+167.0T±100J/mol (1223-1473 K).(3) ΔG°f(WO49/18)=-755400+213.2 T+200J/mol (1223-1423 K).(4) The Gibbs free energy of mixing of the Ni-W solid solution (Ni-16.4 mol%W), which is in equilibrium with NiW2B2, is:ΔGm(Ni-16.4 mol%W)=-4040+0.280T±3J/mol (1273-1423 K).

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Key concepts: Gibbs free energy, Electromotive force, Galvanic cell, Chemistry, Thermodynamics, Electrolyte, Binary system, Analytical Chemistry (journal)