TY - JOUR A1 - Utech, S. A1 - Scherer, Christian A1 - Krohne, K. A1 - Carrella, L. A1 - Rentschler, E. A1 - Gasi, T. A1 - Ksenofontov, V. A1 - Felser, C. A1 - Maskos, Michael T1 - Magnetic polyorganosiloxane core-shell nanoparticles: Synthesis, characterization and magnetic fractionation JF - Journal of magnetism and magnetic materials N2 - Here, we present the synthesis, characterization and magnetic separation of magnetic polyorganosiloxane nanoparticles. Magnetic iron oxide nanoparticles with average particle radii of 3.2 nm had been synthesized by a simple coprecipitation process of iron(II) and iron(III) salt in basic solution. Afterwards, the particles were successfully incorporated into a polyorganosiloxane network via a polycondensation reaction of trimethoxymethylsilane (T), diethoxydimethylsilane (D) and the functional monomer (chloromethylphenyl)trimethoxysilane (ClBz-T) in aqueous dispersion. A core–shell system was chosen to increase the flexibility of the system concerning size, composition and functionalization possibilities. The magnetic nanocapsules with particle radii below 60 nm were separated from non-magnetic material with a high effectiveness by the use of commercially available separation columns which are commonly used for isolation of microbeads and subsequently characterized via transmission electron microscopy (TEM), asymmetrical flow field-flow fractionation (AF-FFF), superconducting quantum interference device (SQUID) and Mössbauer spectroscopy. KW - Nanoparticle KW - Magnetic KW - Encapsulation KW - Polyorganosiloxane KW - Magnetic separation PY - 2010 DO - https://doi.org/10.1016/j.jmmm.2010.06.056 SN - 0304-8853 VL - 322 IS - 21 SP - 3519 EP - 3526 PB - Elsevier CY - Amsterdam AN - OPUS4-22248 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maslyk, M. A1 - Bach, S. A1 - Li, W. A1 - Shylin, S. A1 - Panthöfer, M. A1 - Barton, B. A1 - Ksenofontov, V. A1 - Xu, K. A1 - Kolb, U. A1 - Schmedt auf der Günne, J. A1 - Tremel, W. A1 - Meermann, Björn T1 - Understanding the Stability and Recrystallization Behavior of Amorphous Zinc Phosphate JF - Understanding the Stability and Recrystallization Behavior of Amorphous Zinc Phosphate N2 - 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 Mössbauer 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. KW - Amorphous Zinc phosphate PY - 2021 DO - https://doi.org/10.1021/acs.jpcc.0c09044 VL - 125 IS - 4 SP - 2636 EP - 2647 AN - OPUS4-52078 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -