| Abstrakt: |
In an effort to better determine the thermodynamic properties of Al(g) and Al2O(g) the vapour in equilibrium with Al(l) + 4 at.% yttria-stabilized zirconia (YSZ) was compared to the vapour in equilibrium with Al(l) + Al2O3(s) over the temperature range 1197 – 1509 K. This comparison was made directly by Knudsen effusion-cell mass spectrometry with an instrument configured for a multiple effusion-cell vapour source (multi-cell KEMS). Second-law enthalpies of vaporization of Al(g) and Al2O(g) together with activity measurements show that Al(l) + YSZ is thermodynamically equivalent to Al(l) + Al2O3(s), indicating that Al(l) remained pure and Al2O3(s) was present in the YSZ-cell. Subsequent observation of the Al(l)/YSZ and vapour/YSZ interfaces revealed a thin Al2O3-layer had formed, separating the YSZ-cell from Al(l) and Al(g) + Al2O(g), effectively transforming it into an Al2O3effusion-cell. This behaviour agreed with observations made for β-NiAl(Pt) alloys measured in YSZ effusion-cell. |
