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search.filters.applied.f.access: openAccess × Has files: Yes × Publisher: Basel : MDPI × Subject: self-assembly × WGL Institute: INM ×

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    Structural and Chemical Hierarchy in Hydroxyapatite Coatings
    (Basel : MDPI, 2020) Gross, Karlis A.; Petzold, Christiane; Pluduma-LaFarge, Liene; Kumermanis, Maris; HAugen, Håvard J.
    Hydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20–40, 40–63 and 63–80 µm) to produce flattened homogeneous splats. The surface was characterized for splat shape by profilometry and Atomic force microscopy (AFM), crystal size by AFM, crystal orientation by X-ray diffraction (XRD) and structural variations by XRD. Chemical composition was assessed by phase analysis, but variations in chemistry were detected by XRD and Raman spectroscopy. The resulting surface electrical potential was measured by Kelvin probe AFM. Five levels of structural hierarchy were suggested: the coating, the splat, oriented crystals, alternate layers of oxyapatite and hydroxyapatite (HAp) and the suggested anion orientation. Chemical hierarchy was present over a lower range of order for smaller splats. Coatings made from smaller splats exhibited a greater electrical potential, inferred to arise from oxyapatite, and supplemented by ordered OH− ions in a rehydroxylated surface layer. A model has been proposed to show the influence of structural hierarchy on the electrical surface potential. Structural hierarchy is proposed as a means to further refine the properties of implant surfaces.
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    Self-Assembly of Polymer-Modified FePt Magnetic Nanoparticles and Block Copolymers
    (Basel : MDPI, 2023) Hartmann, Frank; Bitsch, Martin; Niebuur, Bart-Jan; Koch, Marcus; Kraus, Tobias; Dietz, Christian; Stark, Robert W.; Everett, Christopher R.; Müller-Buschbaum, Peter; Janka, Oliver; Gallei, Markus
    The fabrication of nanocomposites containing magnetic nanoparticles is gaining interest as a model for application in small electronic devices. The self-assembly of block copolymers (BCPs) makes these materials ideal for use as a soft matrix to support the structural ordering of the nanoparticles. In this work, a high-molecular-weight polystyrene-b-poly(methyl methacrylate) block copolymer (PS-b-PMMA) was synthesized through anionic polymerization. The influence of the addition of different ratios of PMMA-coated FePt nanoparticles (NPs) on the self-assembled morphology was investigated using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The self-assembly of the NPs inside the PMMA phase at low particle concentrations was analyzed statistically, and the negative effect of higher particle ratios on the lamellar BCP morphology became visible. The placement of the NPs inside the PMMA phase was also compared to theoretical descriptions. The magnetic addressability of the FePt nanoparticles inside the nanocomposite films was finally analyzed using bimodal magnetic force microscopy and proved the magnetic nature of the nanoparticles inside the microphase-separated BCP films.