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Characteristics of the Metal–Metal Oxide Reaction Matrix
Published in Anthony Peter Gordon Shaw, Thermitic Thermodynamics, 2020
In other situations, there might be several plausible products at moderate adiabatic equilibrium temperatures. Three simple reactions are predicted to occur in the Al/Mn3O4 system at points E, F, and G. The products of the first are MnAl2O4 and MnO. In both of these compounds, manganese is in the +2 oxidation state. The former is a manganese spinel called galaxite that could be written as (MnO)(Al2O3). Although, it is important to remember that inorganic metal oxides of this type are not molecular compounds. The other two points occur at the same adiabatic temperature, which is the maximum produced by the Al/Mn3O4 system. At one of these points, the predicted products are galaxite and elemental manganese. At the other, they are alumina and manganese. The manganese is partitioned between the liquid and gas phases at both points. In other words, the Mn(l-g) phase transition limits the maximum temperature that this system can achieve.
Acicular Ferrite
Published in H. K. D. H. Bhadeshia, Bainite in Steels, 2015
Small concentrations of dissolved aluminium seem to promote Widmanstätten ferrite; the mechanism of this is effect is not understood (Abson, 1987; Grong et al., 1988; Thewlis, 1989a,b). It may be that the presence of soluble aluminium correlates with a large overall aluminium concentration, in which case the aluminium oxide becomes γ-alumina instead of galaxite. The former is not an effective nucleant for acicular ferrite, thus allowing grain boundary nucleated Widmanstätten ferrite to grow unhindered.
Microhardness-compositional relationship of Fe3O4-Mn3O4 series spinels from ferromanganese sinter and its relationship to sinter strength
Published in Mineral Processing and Extractive Metallurgy, 2023
M. J. Peterson, S. Hapugoda, J. R. Manuel
Our data also showed that α-vredenburgite with higher Al tended to have lower Mg (R2 = 0.1104, but R2 = 0.2973 if data points with low Al, <1%, are excluded). Magnesium is a common trace element in galaxite (e.g. Essene and Peacor 1983; Cribble and Stanley 1993; Gnos and Peters 1995; Beard and Tracy 2002). Eighty-two per cent of sinter α-vredenburgite analyses had Mg ≥ 0.1%. As Mg2+ would be expected to be tetrahedrally co-ordinated, this supports the proposition that α-vredenburgite with lower Mn contents have more octahedrally co-ordinated Al3+ and tetrahedrally co-ordinated Fe3+, the latter in place of Mn2+/Mg2+. Charge balance may be maintained by the presence of vacancies, as hypothesised by Van Hook and Keith (1958).