Formation of Structural Intermetallics by Reactive Metal Penetration of Ti and Ni Oxides and Aluminates
Alumina-aluminum composites can be prepared by reactive metal penetration (RMP) of mullite by aluminum. The process is driven by a strong negative free energy for the reaction (8 +x)Al + 3Al6Si2013 → 13Al2O3 + 6Si + xAl. Thermodynamic calculations reveal that titanium oxide, aluminum titanate, nickel oxide, and nickel aluminate all have a negative free energy of reaction with aluminum from 298 to 1800 K, indicating that it may be possible to form alumina-intermetallic composites by reactions of the type (2 +x)Al + (3/y) MOy → Al2O3 + AlxM3/y. Experiments revealed that aluminum reacts with titanium oxide, nickel oxide, and nickel aluminate, but not aluminum titanate, at 1673 K. Reaction with the stoichiometric amount of aluminum (x = 0) leads to the formation of alumina and either titanium or nickel. In some cases, reactions with excess aluminum (x > 0) produce intermetallic compounds such as TiAl3 and NiAl.
W. Fahrenholtz et al., "Formation of Structural Intermetallics by Reactive Metal Penetration of Ti and Ni Oxides and Aluminates," Metallurgical and Materials Transactions A, Springer Verlag, Aug 1996.
The definitive version is available at http://dx.doi.org/10.1007/BF02651864
Materials Science and Engineering
Keywords and Phrases
Physical Chemistry; Materials Science; Structural Materials; Metallic Materials; Ceramics; Glass; Composites; Natural Methods
Article - Journal
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