Thesis supervisors: Dr. Ants Lõhmus, Institute of Physics, University of Tartu
Dr. Rünno Lõhmus, Institute of Physics, University of Tartu
Dr. Irina Hussainova, Department of Materials Engineering, Tallinn University of Technology
Opponents: Dr. Karin Mougin, Institut de Science des Matériaux de
Dr. Valdek Mikli, Tallinn University of Technology
The conventional industry is undergoing a dramatic change towards an innovative, high-technology, knowledge-based grounds. Increasing competition on the global market constantly demands for materials with advanced properties and producing technology. During recent decades researchers have paid great attention to new materials that are stable at extreme environmental conditions as candidates for technological applications like supersonic flights and rockets. Metal carbides and oxides are promising candidates for extreme environmental conditions due to their excellent and unique combination of high melting point, good thermal-shock resistance and high hardness. The development of nanocomposites and nanostructured coatings are more relevant and preferable research directions in modern material science.
The particular aim of this thesis is related to elaboration of ceramic nanocomposites and functional coatings with desired properties by sol-gel method. It is chosen since in contrast to conventional ceramic materials synthesis methods, in sol-gel process reactants are mixed together in liquid state at molecular level, the synthesis conditions enable to decrease synthesis temperatures and prepare homogeneous and pure multi component systems.
In particular, the thesis describes the synthesis of titanium / zirconium carbide blend (TiC-ZrC), titanium carbide / carbonnanotube composites (TiC/CNT) and titanium oxide / silver nanowires (AgNW/TiO2) nano-composites precursors. The problems of dispersion and thermal stability of filler material are treated. Moreover, the thesis reports mechanical characterisation of individual nanofillers like Al2O3 nanofibers and AgNW using advanced experimental set-up installed inside a scanning electron microscope. Development and construction of experimental equipment are also involved. As a part of the study, the thesis also includes development of experimental set-up, which was used for in situ SEM mechanical characterisation of individual one-dimensional nanostructures (1DNS) served as reinforcing phase or functional filler in the considered nanocomposites.