Determination of Gibbs Energy of Mixing of Tungsten-Boron Binary System by Electromotive Force Measurement Using Solid Electrolyte
Abstract
The thermodynamic properties for the tungsten-boron binary system were determined by measuring electromotive forces of galvanic cells using an Y2O3-stabilized ZrO2 solid oxide electrolyte. Assuming that W2B and αWB are the stoichiometric compounds, and W2B5- x and W1- x B3 are the nonstoichiometric compounds having solubility widths of 0.670 ≤ X B ≤ 0.690 and 0.805 ≤ X B ≤ 0.822, respectively, they were treated as the intermediate phases of W0.667B0.333, αW0.50B0.50, W0.330B0.670 W0.310B0.690, and W0.195B0.805 W0.178B0.822. The Gibbs energies of mixing, Δmix G, determined in the present study are listed as follows: Δ_{{mix}} G({W}_{0.667} {B}_{0.333} )/{{J}} {{mol}}^{ - 1} = {-}78070 + 26.01T ± 70 [1305{-}1422{{ K}}(1032{-}1149°C)], Δ_{{mix}} G(α {W}_{0.50} {B}_{0.50} )/{{J}} {{mol}}^{ - 1} = {-}86140 + 20.19T ± 200 [1310{-}1399{{ K }}(1037{-}1126°C)], Δ_{{mix}} G({W}_{0.330} {B}_{0.670} )/{{J}} {{mol}}^{ - 1} = {-}78910 + 18.11T ± 200 [1228{-}1410{{ K }}(955{-}1137°C)], ; Δ_{{mix}} G({W}_{0.310} {B}_{0.690} )/{{J}} {{mol}}^{ - 1} = {-}77350 + 17.52T ± 500 [1228{-}1410{{ K }}(955{-}1137°C)], Δ_{{mix}} G({W}_{0.195} {B}_{0.805} )/{{J}} {{mol}}^{ - 1} = {-}63920 + 12.08T ± 500 [1170{-}1340{{ K }}(897{-}1067°C)], Δ_{{mix}} G({W}_{0.178} {B}_{0.822} )/{{J}} {{mol}}^{ - 1} = {-}60090 + 11.15T ± 200 [1170{-}1340{{ K }}(897{-}1067°C)]. Using the thermodynamic properties determined in the present study, the composition-oxygen partial pressure diagram of the tungsten-boron-oxygen system was constructed under the conditions at 1273 K (1000 °C) and a total pressure of 1 bar (100 kPa). It is useful to understand the oxidation property of tungsten-boron binary alloys.
- Publication:
-
Metallurgical and Materials Transactions B
- Pub Date:
- June 2017
- DOI:
- 10.1007/s11663-017-0938-4
- Bibcode:
- 2017MMTB...48.1703Y