Thermodynamic Properties of Ni3B and Ni2B by E.M.F Measurements

Abstract

Standard free energies of formation of Ni3B (ΔG°, Ni3B) and Ni2B (ΔG°Ni2B) were determined by E. M. F. measurements of the cells;‹Pt› O2 in air |ZrO2⋅Cao| Ni-22 at %B alloy powder, B2O3 ‹Pt› (for Ni3B)and‹Pt› O2 in air |ZrO2⋅CaO| Ni-32 at %B alloy powder, B2O3 ‹Pt› (for Ni2B).Standard enthalpies and entrppies of formation of Ni3B and Ni2B were calculated by applying Gibbs-Helmholtz's equations to these ΔG°Ni3B and ΔG°Ni2B values, respectively.The results obtained are as follows:ΔG°Ni3B=-31, 720+10.56T±200 cal/molΔH°Ni3B=-31, 720 cal/molΔS°Ni3B=-10.56 cal/mol, °K}(975-1225°K)andΔG°Ni2B=-25, 604+7.24T±200 cal/molΔH°Ni2B=-25, 604 cal/molΔS°Ni2B=-7.24 cal/mol, °K}(1050-1200°K)