Abstract
The energetics of some manganese oxides: pyrolusite MnO2, bixbyite Mn2O3, hausmannite Mn3O4 and manganosite MnO were studied by transposed temperature drop calorimetry and high temperature drop solution calorimetry in molten 2PbO·B2O3 at 977 K. The enthalpies of oxidation at 298 K in the Mn-O system, determined by appropriate thermodynamic cycles, are (in kJ/mol O2): -441.4 ±5.8 for the reaction 6 MnO + O2 → 2 Mn3O4, -201.8 ± 8.7 for 4 Mn3O4 + O2 → 6 Mn2O3 and -162.1 ± 7.2 for 2 Mn2O3 + O2 → 4 MnO2. These values agree very well with previous data obtained by equilibrium pO2 measurements and indicate that direct calorimetric measurements are well suited to obtain reliable enthalpy of formation data for oxides containing manganese in the 2+, 3+ and 4+ states. The phase diagram of the Mn-O system was calculated using these new values of enthalpies.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 667-672 |
| Number of pages | 6 |
| Journal | Materials Research Society Symposium - Proceedings |
| Volume | 398 |
| State | Published - 1996 |
| Externally published | Yes |
| Event | Proceedings of the 1995 MRS Fall Meeting - Boston, MA, USA Duration: Nov 26 1995 → Dec 1 1995 |
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering