| About this Abstract |
| Meeting |
Materials Science & Technology 2012
|
| Symposium
|
MS&T'12 Poster Session
|
| Presentation Title |
H13: Impact of Tungsten on Structure and Thermodynamics of Borosilicate Melts
|
| Author(s) |
John P Nimmo, Peter Kroll, Bill Fahrenholtz |
| On-Site Speaker (Planned) |
John P Nimmo |
| Abstract Scope |
Borosilicate melts (or amorphous SiBO) play a crucial role in the oxidation processes of HfB2/SiC composite ceramics. Part of the improvement of thermal stability of HfB2/SiC composites over single-phase borides is the lower volatility of SiBO in comparison to B2O3. Recent experimental data suggests that addition of tungsten (W) to HfB2 has a similar effect. We modeled amorphous WBO as random mixtures between WO3 and B2O3 using a standard melt-quench approach and ab-initio molecular dynamic simulations. We find that addition of WO3 increases the enthalpy of formation of the mixture. We estimate the solubility of WO3 in B2O3 to be smaller than 10 mol-%, which agrees well with experimental data.Interesting changes are observed when adding WO3 to B2O3: more BO4-tetrahedra occur and WO4- and WO5-units appear. On average, W attains a lower coordination than in pure amorphous WO3, while B adopts a higher coordination. |
| Proceedings Inclusion? |
Definite: A CD-only volume |