Understanding the Stability and Recrystallization Behavior of Amorphous Zinc Phosphate
| Autor: | Martin Panthöfer, Vadim Ksenofontov, Ute Kolb, Jörn Schmedt auf derGünne, Bastian Barton, Sergii I. Shylin, Ke Xu, Marcel Maslyk, Björn Meermann, Sven Bach, Wolfgang Tremel, Wenyu Li |
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| Rok vydání: | 2021 |
| Předmět: |
inorganic chemicals
Recrystallization (geology) Materials science 02 engineering and technology 010402 general chemistry 01 natural sciences Metal chemistry.chemical_compound Impurity Physical and Theoretical Chemistry technology industry and agriculture Zinc phosphate 021001 nanoscience & nanotechnology Phosphate 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Amorphous solid General Energy Chemical engineering chemistry Conversion coating visual_art visual_art.visual_art_medium 0210 nano-technology Powder diffraction |
| Zdroj: | The Journal of Physical Chemistry C. 125:2636-2647 |
| ISSN: | 1932-7455 1932-7447 |
| DOI: | 10.1021/acs.jpcc.0c09044 |
| Popis: | Zinc phosphate, an important pigment in phosphate conversion coatings, forms protective films on rubbing surfaces. We have simulated the underlying reactions under shear by ball-milling zinc phosphate and monitored the reaction of hopeite (Zn3(PO4)2·4H2O) and the retarded recrystallization of the amorphous reaction product by powder X-ray diffraction (PXRD) and quantitative infrared (IR) spectroscopy. Abrasion of stainless steel was simulated by addition of pure 57Fe. The results provide insight into the chemistry of phosphate conversion coatings or during battery cycling of metal phosphates and give theoretical guidance for the preparation of amorphous phosphates. Thermal analysis revealed that the release of structural water is a key step during the reaction of hopeite under shear to ball-milled amorphous zinc phosphate. The back-reaction and associated recrystallization kinetics of amorphous zinc phosphate show a classical Langmuir behavior. Fe impurities inhibit the recrystallization of ball-milled amorphous zinc phosphate strongly. 57Fe Mossbauer spectroscopy and PXRD revealed that Fe is oxidized to Fe2+ and Fe3+ during ball-milling and incorporated locally at the tetrahedral and octahedral sites of the structure. Ball-milled amorphous zinc phosphate is metastable as γ-Zn3−xFex(PO4)2. EPR studies showed the incorporation of Fe3+ to be coupled with the formation of Zn2+ vacancies. The Fe3+ defect sites bind water because of their higher Pearson hardness (compared to Fe2+ and Zn2+), thereby reducing water mobility and inhibiting further reactions like the recrystallization to hopeite. Our findings reveal the amorphization mechanism of Zn3(PO4)2·4H2O in stainless steel ball mills at the atomic scale and highlight how the reactivity of amorphous products is affected by impurities associated with the processing method. |
| Databáze: | OpenAIRE |
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