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/mol
ΔH°Ni3B=-31, 720 cal/mol
ΔS°Ni3B=-10.56 cal/mol, °K
}(975-1225°K)
and
ΔG°Ni2B=-25, 604+7.24T±200 cal/mol
ΔH°Ni2B=-25, 604 cal/mol
ΔS°Ni2B=-7.24 cal/mol, °K
}(1050-1200°K)
