Immiscibility in the Fe3O4–FeCr2O4 spinel binary

Immiscibility in the nickel ferrite–zinc ferrite spinel binary

“…Mixing in spinel binaries is expected to follow from a thermodynamic model of cation disordering, refined previously [12] and applied to mixing in the Fe(Fe 1-n Cr n ) 2 O 4 system. Without solving the model equations to determine cation disordering as functions of temperature and thereby )G mix (T), it is possible to characterize the source of immiscibility by analyzing each of the modeling terms that contributes to the entropy of mixing at room temperature:…”

“…Lattice parameters for the cubic spinel phases, as determined from a whole pattern fit of XRD peak positions found for five high angle reflection planes: [6,6,4], [9,3,1], [8,4,4], [10,2,0] and [9,5,1] are compared in Table II. Also included in Table II Due to the asymmetric nature of the solvus and the smaller difference in composition between the zinc-rich solvus (n 1 ) and the equivalent (single phase) composition of the reactant mixture, i.e., n = 0.5, lesser amounts of the nickel-rich solvus (n 2 ) were present at 700°C than in other syntheses at lower temperatures (see Fig.…”

“…Based on our successful application of a molten salt method for investigating trivalent ion mixing in the Ni(Fe 1-n Cr n ) 2 O 4 spinel binary [8], this method is again employed to investigate divalent cation mixing in the (Ni 1-n Zn n )Fe 2 O 4 spinel binary.…”

Complementary Methods for the Characterization of Corrosion Products on a Plant-Exposed Superheater Tube

“…However, for the spinel phase, the effect of Cr fraction on the lattice parameter is not straightforward. In the Cr rich spinel (x=2 in FeCrxFe2-xO4), Cr 3+ , due to its high octahedral stabilization energy [39][40][41], preferentially occupies octahedral sites, thus, preserving a normal spinel structure with Fe 2+ ions in tetrahedral sites. In the Fe-rich spinel, (x=0 in FeCrxFe2-xO4), structurally equivalent positions become occupied by different atoms such that Fe 3+ ions are distributed between octahedral and tetrahedral sites resulting in an inversed spinel structure [42,43].…”

Development of a microfluidic setup to study the corrosion product deposition in accelerated flow regions

“…There are forbidden stoichiometries of Fe/Ni chromites at temperatures observed within a PWR which leads to the formation of mixed Fe/Ni ferrites that form the outer corrosion layer. 24,25 From previous reactor experience, the CRUD deposits that form in restrictions such as orifice plates and steam generator tubing tend to form annular ridges downstream of the initial restriction. This observation has been interpreted based on the electrokinetic mechanism described earlier.…”