Details
| Original language | English |
|---|---|
| Pages (from-to) | 13002-13007 |
| Number of pages | 6 |
| Journal | Chemistry – A European Journal |
| Volume | 25 |
| Issue number | 56 |
| Early online date | 9 Sept 2019 |
| Publication status | Published - 8 Oct 2019 |
Abstract
Hematite (α-Fe 2O 3) is thermodynamically stable under ambient conditions, of vast geological importance, and widely used in applications, for example, as corrosion protection and as a pigment. It forms at elevated temperatures, whereas room-temperature reactions typically yield metastable akaganéite or ferrihydrite. The mechanistic key changes underlying this observation were explored in the present study. The entropic contribution to the prenucleation hydrolysis reaction categorically implies the presence of prenucleation clusters (PNCs) as fundamental precursors. The formation of hematite is then due to a change in the reaction mechanism above approximately 50 °C, whereby the reaction limitation towards oxolation in phase-separated clusters is overcome. A model that rationalizes the occurrence of hematite, akaganéite, and ferrihydrite based on the chemistry of olation PNCs is proposed. Supersaturation and the temperature dependence of olation and oxolation rates from monomeric precursors are irrelevant in this nonclassical mechanism.
Keywords
- aggregation, crystal growth, hematite, iron oxides, prenucleation clusters
ASJC Scopus subject areas
- Chemical Engineering(all)
- Catalysis
- Chemistry(all)
- Organic Chemistry
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In: Chemistry – A European Journal, Vol. 25, No. 56, 08.10.2019, p. 13002-13007.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Nucleation of Hematite: A Nonclassical Mechanism
AU - Scheck, Johanna
AU - Fuhrer, Lisa M.
AU - Wu, Baohu
AU - Drechsler, Markus
AU - Gebauer, Denis
N1 - Funding Information: D.G. was a Research Fellow of the Zukunftskolleg of the University of Konstanz during this work. We acknowledge support by the Fond der Chemischen Industrie and the German Research Foundation (DFG) within project GE 2278/6-1, which was part of the NSF-DFG ?Materials World Network for Particle-mediated Control over Crystallization: From the Pre-nucleation Stage to the Final Crystal.? M.D. thanks the Bavarian Polymer Institute (BPI) and the collaborative research center SFB840 of the German Research Foundation (DFG) for financial support. SAXS experiments were performed on beamline ID02 at the European Synchrotron Radiation Facility (ESRF), Grenoble, France (proposal IHSC-1379). We thank Dr. Peter Boesecke for the assistance in using beamline ID02.
PY - 2019/10/8
Y1 - 2019/10/8
N2 - Hematite (α-Fe 2O 3) is thermodynamically stable under ambient conditions, of vast geological importance, and widely used in applications, for example, as corrosion protection and as a pigment. It forms at elevated temperatures, whereas room-temperature reactions typically yield metastable akaganéite or ferrihydrite. The mechanistic key changes underlying this observation were explored in the present study. The entropic contribution to the prenucleation hydrolysis reaction categorically implies the presence of prenucleation clusters (PNCs) as fundamental precursors. The formation of hematite is then due to a change in the reaction mechanism above approximately 50 °C, whereby the reaction limitation towards oxolation in phase-separated clusters is overcome. A model that rationalizes the occurrence of hematite, akaganéite, and ferrihydrite based on the chemistry of olation PNCs is proposed. Supersaturation and the temperature dependence of olation and oxolation rates from monomeric precursors are irrelevant in this nonclassical mechanism.
AB - Hematite (α-Fe 2O 3) is thermodynamically stable under ambient conditions, of vast geological importance, and widely used in applications, for example, as corrosion protection and as a pigment. It forms at elevated temperatures, whereas room-temperature reactions typically yield metastable akaganéite or ferrihydrite. The mechanistic key changes underlying this observation were explored in the present study. The entropic contribution to the prenucleation hydrolysis reaction categorically implies the presence of prenucleation clusters (PNCs) as fundamental precursors. The formation of hematite is then due to a change in the reaction mechanism above approximately 50 °C, whereby the reaction limitation towards oxolation in phase-separated clusters is overcome. A model that rationalizes the occurrence of hematite, akaganéite, and ferrihydrite based on the chemistry of olation PNCs is proposed. Supersaturation and the temperature dependence of olation and oxolation rates from monomeric precursors are irrelevant in this nonclassical mechanism.
KW - aggregation
KW - crystal growth
KW - hematite
KW - iron oxides
KW - prenucleation clusters
UR - http://www.scopus.com/inward/record.url?scp=85071920989&partnerID=8YFLogxK
U2 - 10.1002/chem.201902528
DO - 10.1002/chem.201902528
M3 - Article
VL - 25
SP - 13002
EP - 13007
JO - Chemistry – A European Journal
JF - Chemistry – A European Journal
SN - 0947-6539
IS - 56
ER -