Triin Kangur will defend her doctoral thesis titled “Preparation and functional properties of stochastic microstructured sol-gel silica materials” on February 12, 2018 at 10:15 at W. Ostwaldi 1, room B103.
Dr Martin Järvekülg, Institute of Physics, University of Tartu
Dr Valter Kiisk, Institute of Physics, University of Tartu
Dr Ants Lõhmus, Institute of Physics, University of Tartu
Dr. Jānis Ločs, Riga University of Technology
Prof. Urve Kallavus, Tallinn University of Technology
In the present thesis two novel differently microstructured silica coatings were introduced. Our aim was to explore two distinct preparation methods for obtaining silica domes and a silica foam with sphere-like morphology, and to characterize and evaluate the applicability of these structured materials.
Sol-gel phase separation method together with spray-coating is a promising bottom-up technique for preparing structured functional silica surfaces and is potentially suitable for covering large surfaces. We demonstrated that by choosing suitable alkoxide concentration, solvent type, water- and catalyst-alkoxide molar ratios and also relative humidity, it is possible to vary the size, shape and surface density of the domes. Sufficiently dense packing of silica domes in sub-µm range and multilayered coating were leading to a notable antireflection and light scattering effects in the Vis-NIR spectral range. As some produced silica surfaces had water contact angles exceeding 130°, simultaneous superhydrophobicity (contact angle > 150°) can be achieved by further surface functionalization. These surfaces are also found to be biocompatible and it is shown that growth characteristics morphology of fibroblasts is influenced by the morphology of the substrate.
Sol-gel process together with catalytic decomposition of hydrogen peroxide is a novel method for the preparation of thick silica foam film, where well-defined closed-cell porosity appears. Macroporous characteristics and the lowest measured thermal conductivity (0.018 W/(m∙K)) of the prepared foams were similar to silica aerogels. These silica foam materials are potentially applicable as efficient thermal insulation materials.