Thermally induced phase transformations of lepidocrocite-like ferrititanate nanosheets synthesized from a low cost precursor by hydrothermal method

Thermal stability and phase transformation paths of Lepidocrocite-like layered titanates (LTs-NS) are not well established. This is especially true for the ferrititanate nanosheets, recently synthesized from mineral sands. High-temperature phase transformation paths of three types of lepidocrocite-l...

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Bibliographic Details
Published in:Materials chemistry and physics 2017-08, Vol.197, p.138-144
Main Authors: Dosen, Anja, Pontón, Patricia I., Marinkovic, Bojan A.
Format: Article
Language:English
Subjects:
Binary systems
Hematite
Iron oxides
Low cost
Nanosheets
Nanostructured materials
Nanostructures
Phase transitions
Powder diffraction
Precursors
Sodium
Synthesis
Thermal evolution
Thermal properties
Thermal stability
Thermodynamic properties
Thermogravimetric analysis
Thermogravimetric analysis (TGA)
Titanates
Titanium oxides
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Summary:Thermal stability and phase transformation paths of Lepidocrocite-like layered titanates (LTs-NS) are not well established. This is especially true for the ferrititanate nanosheets, recently synthesized from mineral sands. High-temperature phase transformation paths of three types of lepidocrocite-like layered ferrititanate nanosheets were examined by in situ HT-XRPD and TG analyses. We analyzed sodium-rich (NaLTs-NS), protonated (pLTs-NS), and a nanohybrid (pLTs-o-2C18-NS) nanosheets, the last one composed from the individual ferrititanate host layers and dimethyldioctadecylammonium cations (2C18+). We investigated how the presence of Na+, H+ and 2C18+ influences the thermal behavior of LTs nanosheets. The three materials show different thermal evolution paths. Na-LTs-NS exhibit the highest thermal stability, where the layered structure is preserved to at least 600 °C. Na-LTs-NS transform to freudenbergite (Na2(Ti,Fe)8O16) at 700 °C. Rutile and pseudobrookite form at higher temperatures in Na-rich ferrititanate system and coexist with freudenbergite. Thermal stability of protonated nanosheets is much lower since the layered structure is destroyed under 500 °C. High temperature phases pseudobrookite (Fe2TiO5) and rutile (TiO2) crystallize at ∼700 °C which is in accordance with the stability field for the Fe2O3–TiO2 binary phase diagram rich in TiO2. In the case of pLTs-o-2C18-NS rutile and hematite form at 650 °C. •Initial nanosheet composition governs the phase transformation paths.•Na-rich LTs exhibit the highest thermal stability.•Layer structure collapse: above 600 °C (Na-LTs-NS) and above 400 °C (pLTs-NS).•Recrystallization occurs at 700 °C (at 650 °C in the case of monolayers).
ISSN:0254-0584
1879-3312
DOI:10.1016/j.matchemphys.2017.05.030