Determination of the Standard Gibbs Free Energy of Formation of NiMo<SUB>2</SUB>B<SUB>2</SUB> and the Activity of the Ni-Mo Binary System by EMF Measurement

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) ΔGf°(NiMo2B2)=−250000+19.7T±1000 J/mol (1183∼1423 K).(2) ΔGf°(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:(This article is not displayable. Please see full text pdf.)