1. High-temperature stabilization of bulk amorphous Al2O3Andraž Mavrič, Mattia Fanetti, Gregor Mali, Matjaž Valant, 2018, original scientific article Abstract: We present a method for high temperature stabilization of bulk amorphous aluminium oxide. The stabilization is achieved by dispersing polysilane dendritic molecules in aluminium hydroxide gel, which upon thermal treatment gives amorphous aluminium oxide stable up to 900 °C. The dispersed macromolecules covalently bind to the alumina matrix and induce homogeneously distributed strain fields that keep the alumina amorphous. The thermal conversion of the precursor system was followed by thermogravimetry with an evolved gas analysis, infrared spectroscopy and 29Si NMR. The amorphous structure of aluminium oxide was confirmed with an X-ray and electron diffraction. Additionally, the amorphous state was supported by presence of penta-coordinated aluminium detected by 27Al NMR and a low bandgap measured by a UV–visible absorption spectroscopy.
Keywords: Amorphous aluminium oxide, Polysilane, Nanocomposite, Stabilization
Published in RUNG: 30.07.2018; Views: 5012; Downloads: 24
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2. FROM SPINODAL DECOMPOSITION AND MOLECULAR DISPERSION OF POLYSILANES TO SUPER-HARD NANOCOATINGArtem Badasyan, Boštjan Mavrič, Matjaž Valant, published scientific conference contribution abstract Abstract: Conformations of polymer molecules in solution crucially depend on the sign of the
effective potential energy of interaction between the monomers, also known as the
quality of solvent. Therefore in “poor” solvent regime, when effective attraction
overwhelms, the experimental measurements of polymer sizes are complicated by the
agglomeration of macromolecules, followed by precipitation. This phenomenon, also
known as spinodal decomposition, causes serious problems when the goal is to
determine properties of individual macromolecules. Interestingly, while in the case of
carbon-based polymers the precipitation-related problems can be easily avoided with
dilution, this is not the case for polysilanes, i.e. polymeric chains on basis of silicon.
Although the linear polysilanes were first synthesized in early 1920’s, the aggregationrelated
problems have hampered their studies and applicability until recently.
In the Materials Research Laboratory of University of Nova Gorica we have developed
a technology to strengthen the scratch-resistance nanocoating for glass on the basis of
polysilane dendritic polymers we synthesized. Through the prism of the Flory-Huggins
theory, that provides a miscibility phase diagram in temperature-volume fraction
variables, the quality of polymer solution can be manipulated by changing the
temperature. Using Dynamic Light Scattering (DLS) and Differential Scanning
Calorimetry (DSC) we have managed to show, that at temperatures in the range of 40-
50 C the deagglomeration of the dendritic polysilane takes place in tetrahydrofuran
(THF) [1], and the system becomes a true molecular dispersion with particles 20 nm in
size [2]. Introducing such molecular dispersion into the alumina precursor solution
yields an amorphous nanocomposite stabilized by a high level of strain. This resulted in
an extraordinary increase of hardness and scratch resistance of the alumina – polymer
nanocomposite coating that can be used for glass protection [3].
Keywords: Polysilane, dendrimer, solubility
Published in RUNG: 12.09.2017; Views: 4979; Downloads: 0
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