Determination of the Standard Gibbs Free Energy of Formation of NiMo₂B₂ and the Activity of the Ni-Mo Binary System by EMF Measurement

Abstract

The standard Gibbs free energy of formation of NiMo₂B₂ has been determined in the temperature range from 1183 to 1423 K by measuring electromotive forces of a galvanic cell having a solid oxide electrolyte. Also, the standard Gibbs free energy of formation of MoO₂ and the Gibbs free energy of mixing of the Ni-Mo binary system, which are necessary to determine the standard Gibbs free energy of formation of NiMo₂B₂, have been determined in the temperature range from 1183 to 1423 K, The results obtained are as follows:
(1) ΔG_f^°(NiMo₂B₂)=−250000+19.7T±1000 J/mol (1183∼1423 K).
(2) ΔG_f^°(MoO₂)=−567700+160.0T±200 J/mol (1183∼1423 K).
(3) The standard Gibbs free energy of formation of the intermediate phase, NiMo, which exists in the Ni-Mo binary system is:
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