|
| |
|
| |
|
| |
|
| |
|
|
Organized Nanostructured TiO2 Materials: Synthesis, Characterization, Applications
Zukalová, Markéta ; Rathouský, Jiří (advisor) ; Mička, Zdeněk (referee) ; Šubrt, Jan (referee)
CONCLUSIONS It has been known for a long time that material properties change on the nanoscale and are different from those of single crystals or conventional microstructured, monolithic or composite materials32. The presented thesis aimed at demonstration of the diversity in these properties for various morphologies of TiO2. Despite the fact that the chemical composition is identical, the structure of different morphologies matters and it is respon-sible for their specialty. The successfully mastered syntheses of desirable particle size materials open the pathway towards applications taking advantage of size dependent properties. DSC employing 2μm mesoporous TiO2 film as a photoanode exhibited the solar conversion efficiency as high as 4.63% due to the large surface area (roughness fac-tor). Optimized pore size together with the framework consisting of anatase nanocrystals are responsible for the high dye adsorption capacity improving the performance. Incorporating an additional inverse opal layer in DSC represents an example of its further possible upgrade. This optimized set up can increase the short circuit photocurrent effi-ciency of this device of about 26 % (Ref.39). Owing to the diffusion coefficient of an order of 10-13 cm2/s for microcrystalline spinel and even less for nanocrystalline spinel...
|
|
| |
|
| |
|
|
Hydrophobization of sandstone and limestone materials with a thin hydrophilic coating
Rathouský, Jiří
Hydrophobization of the surface of sandstone and limestone materials is an effective method of their protection against the effects of weathering. Effective hydrophobizing agents are solutions of alkyltrialkoxysilanes, especially methyl- or octyltriethoxysilane in a suitable organic solvent (in particular white spirit), and solutions containing polymeric organosilicon compounds also in mineral spirits. It is a major disadvantage of hydrophobization that there is a change in the original appearance of the material due to the increased deposition of dirt on the hydrophobic surface, which is unevenly washed away by rain water, which results in unsightly stains on the surface. Another general disadvantage of hydrophobization is that it renders it very difficult to impossible to carry out another treatment particularly with hydrophilic agents. With the proposed method it is possible to create a thin hydrophilic layer on a hydrophobized surface to ensure the uniform washing away of dirt and to enable the mentioned additional surface treatment. Given that the depth of its removal may be precisely controlled in this process, the hydrophobization will be removed only to the desired depth and will not therefore undermine the effectiveness of the hydrophobization. The new method of hydrophobization of sandstone and limestone materials with a thin hydrophilic coating is based on a two-step process comprising the surface hydrophobization using an agent comprising alkyltrialkoxysilanes or polydimethylsiloxane polymers in an organic solvent to a sufficient depth, and the removal of a thin surface layer of the hydrophobization, bound to the surface of the material, with a thickness of approximately 1 mm.
|
|
| |
|
| |
guest ::
