Low Temperature Phase Transition of Ilmenite during Oxidation by Chlorine

Abstract

The phase transition of natural and synthetic ilmenite during oxidation by Cl 2 at 390-560 C was characterized. The ilmenite phase was converted to crystallographic shear (CS) phases during the oxidation. One third of the Fe 2þ in the ilmenite phase was converted to FeCl 3. The remaining Fe 2þ was oxidized to Fe 3þ in the CS phases. The CS phase obtained from synthetic ilmenite was the Fe 2 Ti 3 O 9 (M 5 O 9) phase. A small amount of Mg 2þ impurity in natural ilmenite caused the resulting structure to be the M 13 O 23 structure when it was oxidized to the CS phase at temperatures up to 490 C, with the M 5 O 9 structure also formed at temperatures above 540 C. The presence of Mg 2þ was crucial in determining the particular structure of the CS phase and its thermal stability. These observations provide a useful way to get an oxidation product with a particular structure of the CS phase. They showed that there can be significant effects on the phase transition and thermal stability of the products from the presence of an impurity element.

In Situ Generation of Pseudorutile Oxide as the Cathode for Direct Electrolysis of CO2

“…Actually, the M 5 O 9 phase was found to be very conductive as the Fe 3+ -O-Fe 2+ transition was enhanced during the reoxidation process. 52 The Fe 2 Ti 3 O 9 phase could further adsorb oxygen for more TiO 2 production, 53 and we found that the M 5 O 9 phase can be produced by the partial reduction of ABO 4 (A,B)O 2 oxides.…”

Structural, Textural, and Catalytic Properties of Ti(IV)‐Fe(III) Mixed Oxides Prepared by a Modified Sol‐Gel Route

“…Besides the dominant anatase phase in TiFe15 and TiFe20, the formation of other phases is evident as indicated by the weak diffractions around 2θ of 31 ο and 36 ο in addition to relatively stronger diffraction at 2θ of 54 ο . These features, very likely, indicate the formation of pseudorutile (Pr), Fe 2 Ti 3 O 9 , (JPCDS 19–0635) which is usually poorly crystalline and difficult to characterize . The formation of Fe 2 Ti 3 O 9 on the account of α‐Fe 2 O 3 at 500 °C is more pronounce in the pattern of TiFe50 as indicated by the weaker diffraction at 2θ of 36 ο and stronger diffraction at 54 ο .…”

“…As an example, when nanostructured 1‐D titania was doped with Fe(III), the titania structure was stable at temperatures as high as 400 °C and decomposed to pseudobrookite and rutile at higher temperatures . Similarly, the oxidation of ilmenite was found to result in rutile and pserudobrookite upon heating at temperatures above 700 °C …”

Enhancement of Photo-Oxidation Activities Depending on Structural Distortion of Fe-Doped TiO2 Nanoparticles

“…In particular, in the case of n = 5, d -spacing near 25° and 27° is also evident. Thus, the spectrum is characterized as Fe 2 Ti 3 O 9 (Fe 2 O 3 3TiO 2 ) [ 19 – 21 ].…”