Gregor Ferk

Macroporous poly(dicyclopentadiene) γFe2O3/Fe3O4 nanocomposite foams by high internal phase emulsion templating

The high internal phase emulsion (HIPE) templating approach to macroporous poly(dicyclopentadiene) γFe2O3/Fe3O4 nanocomposite foams via ring opening metathesis polymerisation was elaborated and the influence of the formulation of the HIPE on structural and mechanical properties of the magnetic composite foams of 80% nominal porosity was studied. HIPEs solely stabilized with the nanoparticles resulted in considerably shrunken monolithic specimens characterized by an open cellular morphology with cavities bigger than 265 μm. Nanoparticles were situated in the bulk and on the surface of the polymeric foam skeleton. Precise control over the feature sizes could not be obtained in this case. In contrast, HIPE formulations co-stabilized with a surfactant yielded samples of good casting quality characterized by a fully open cellular morphology in all cases. The cavity and the window size could be controlled by the amount of surfactant in the emulsion. A low surfactant loading of 1.5 v% with respect to the monomer yielded diameters of the cavities of the order of 20 μm interconnected with windows with diameters in the order of 4 μm, while 10 v% surfactant resulted in smaller cavities (10 μm) and windows (2 μm). All these feature sizes are hardly affected by the nanoparticle loading which was varied from 1 to 30 wt%. Surfactant stabilized and cured HIPEs featured the nanoparticles predominantly on the surface of the cavities. Mechanical properties of the composite foams were assessed by stress–strain tests and revealed a strengthening of the foams prepared with 10 v% surfactant upon addition of the nanoparticles. Indicative of the strengthening is an increase of the Youngs modulus from 13 ± 2 MPa in the case of a sample without nanoparticles to 104 ± 4 MPa in the case of the composite foam with 15 wt% nanoparticles. This trend was accompanied by a decrease of the elongation at break from 21 ± 4 to less than 1%. Specimens prepared with 1.5 v% surfactant are ductile and gave the same high Youngs modulus (104 ± 9 MPa) irrespective of the nanoparticle loading and became stronger upon raising the nanoparticle amount reaching an ultimate strength of 3.4 ± 0.4 MPa at an elongation at break of 13 ± 4%.

Monolithic Magneto-Optical Nanocomposites of Barium Hexaferrite Platelets in PMMA

The incorporation of magnetic barium hexaferrite nanoparticles in a transparent polymer matrix of poly(methyl methacrylate) (PMMA) is reported for the first time. The barium hexaferrite nanoplatelets doped with Sc3+, i.e., BaSc0.5Fe11.5O12 (BaHF), having diameters in the range 20 to 130 nm and thicknesses of approximately 5 nm, are synthesized hydrothermally and stabilized in 1-butanol with dodecylbenzenesulfonic acid. This method enables the preparation of monolithic nanocomposites by admixing the BaHF suspension into a liquid monomer, followed by in-situ, bulk free-radical polymerization. The PMMA retains its transparency for loadings of BaHF nanoparticles up to 0.27 wt.%, meaning that magnetically and optically anisotropic, monolithic nanocomposites can be synthesized when the polymerization is carried out in a magnetic field. The excellent dispersion of the magnetic nanoparticles, coupled with a reasonable control over the magnetic properties achieved in this investigation, is encouraging for the magneto-optical applications of these materials.

Synthesis and Characterization of Silica-Coated Cu

The synthesis of magnetic Cu1-xNix nanoparticles was carried out in cationic water-in-oil (w/o) microemulsions of water/cetyl-trimethyl-ammonium bromide (CTAB), n-butanol/isooctane by the reduction of nickel and copper chlorides with hydrazine and NaOH. The synthesized Cu1-xNix particles were heat treated to maintain their proper homogeneity and Curie temperature. Some alloy particles with the composition CU27.5M72.5 were coated with silica prior to the thermal homogenization in order to retain the pristine morphology. The magnetic particles were characterized using XRD, transmission electron microscopy (TEM) and magnetic measurements. The thermal demagnetization in the vicinity of the Curie temperature of the nanoparticles was studied using a modified TGA/SDTA method.

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Abstract A proton transfer compound, (ABTH)+(PydcH)− (1), obtained from 2-aminobenzothiazole (ABT) and 2,6-pyridinedicarboxylic acid (Pydc) as well as its Eu(III), Tb(III), and Cu(II) complexes (ABT)3[Eu(Pydc)3]·5H2O (2), (ABT)3[Tb(Pydc)3]·5H2O (3), and (ABT)[Cu(Pydc)(PydcH)]·3H2O (4) were obtained under ambient conditions and structurally verified by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and magnetic measurements. Compounds 2–4 are the first known solids containing complex anions with Pydc ligands, 2-aminobenzothiazole cations (ABT), and solvate water molecules. During the synthesis of 3, a secondary phase with the formula ABTCl∙H2O was obtained and characterized by elemental analysis and single-crystal X-ray diffraction. The asymmetric unit of 5 consists of six symmetry independent ABT cations, six chlorides, and six water molecules. The two lanthanide complexes showed characteristic emissions of Eu3+ and Tb3+ ions. The good solubilities of these complexes in water and their luminescence properties make them attractive luminescent labels of biological molecules.