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DDC: 540 × Subject: Silicates ×

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    Large-area wet-chemical deposition of nanoporous tungstic silica coatings
    (London [u.a.] : RSC, 2015) Nielsen, K.H.; Wondraczek, K.; Schubert, U.S.; Wondraczek, L.
    We report on a facile procedure for synthesis of nanoporous coatings of tungstic silica through wet-chemical deposition and post-treatment of tungsten-doped potassium silicate solutions. The process relies on an aqueous washing and ion exchange step where dispersed potassium salt deposits are removed from a 150 nm silicate gel layer. Through an adjustment of the pH value of the washing agent within the solubility regime of a tungstic salt precursor, the tungsten content of the remaining nanostructured coating can be controlled. We propose this route as a universal approach for the deposition of large-area coatings of nanoporous silica with the potential for incorporating a broad variety of other dopant species. As for the present case, we observe, on the one hand, antireflective properties which enable the reduction of reflection losses from float glass by up to 3.7 percent points. On the other hand, the incorporation of nanoscale tungstic precipitates provides a lever for tailoring the coating hydrophilicity and, eventually, also surface acidity. This may provide a future route for combining optical performance with anti-fouling functionality.
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    Halloysite Nanotubes Noncovalently Functionalised with SDS Anionic Surfactant and PS-b-P4VP Block Copolymer for Their Effective Dispersion in Polystyrene as UV-Blocking Nanocomposite Films
    (New York, NY : Hindawi Publ., 2017) Tzounis, Lazaros; Herlekar, Shreya; Tzounis, Antonios; Charisiou, Nikolaos D.; Goula, Maria; Stamm, Manfred
    Asimple and versatilemethod is reported for the noncovalent functionalisation of natural and "green" halloysite nanotubes (HNTs) allowing their effective dispersion in a polystyrene (PS) thermoplastic matrix via solvent mixing. Initially, HNTs (pristine HNTs) were modified with physically adsorbed surfactant molecules of sodium dodecyl sulphate (SDS) and PS-b-P4VP [P4VP: poly(4-vinylpyridine)] block copolymer (BCP). Hereafter, SDS and BCP modified HNTs will be indicated as SDS-m-HNT and BCP-m-HNT.Nanocomposite films with 1, 2, and 5 wt.%HNTloadingswere prepared, abbreviated as PS-SDS-m-HNT1, PS-SDS-m-HNT2, and PS-SDS-m-HNT5 and PS-BCP-m-HNT1, PS-BCP-m-HNT2, and PS-BCP-m-HNT5 (where 1, 2, and 5 correspond to the wt.% of HNTs). All nanocomposites depicted improved thermal degradation compared to the neat PS as revealed by thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) confirmed the good dispersion state of HNTs and the importance of modification by SDS and BCP. X-ray diffraction (XRD) studies showed the characteristic interlayer spacing between the two silicate layers of pristine and modified HNTs. The PS/HNT nanocomposite films exhibited excellent ultraviolent-visible (UV-vis) absorbance properties and their potential application as UV-filters could be envisaged.
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    Hexacyanidosilicates with Functionalized Imidazolium Counterions
    (Weinheim : Wiley-VCH, 2020) Harloff, Jörg; Laatz, Karoline Charlotte; Lerch, Swantje; Schulz, Axel; Stoer, Philip; Strassner, Thomas; Villinger, Alexander
    Functionalized imidazolium cations were combined with the hexacyanidosilicate anion, [Si(CN)6]2–, by salt metathesis reactions with K2[Si(CN)6], yielding novel ionic compounds of the general formula [R–Ph(nBu)Im]2[Si(CN)6] {R = 2-Me (1), 4-Me (2), 2,4,6-Me = Mes (3), 2-MeO (4), 2,4-F (5), 4-Br (6); Im = imidazolium}. All synthesized imidazolium hexacyanidosilicates decompose upon thermal treatment above 95 °C (96 – 164 °C). Furthermore, the hexa-borane-adduct [Mes(nBu)Im]2{Si[(CN)B(C6F5)3]6}·6CH2Cl2 (7), which is thermally stable up to 215 °C, was obtained from the reaction of 3 with Lewis acidic B(C6F5)3. In CH3CN solution, decomposition of the hexaadduct to the Lewis-acid-base adduct CH3CN–B(C6F5)3 and [(C6F5)3B·(µ-CN)·B(C6F5)3]– was observed. All synthesized compounds were isolated in good yields and were completely characterized including single crystal structure elucidations. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.