Thin film coating of vanadium oxides produced by solution combustion synthesis its optical and electrochemical characterization

Production of vanadium pentoxide will be carried out by solution combustion synthesis. Combustion synthesis which is a kind of self-propagating high temperature synthesis and it is used for the production of advanced materials which consist of ceramic, intermetallic compound, composite and functional materials close to the powder or final product. Solution combustion synthesis which is one of the combustion synthesis types, is an easy, simple and rapid method that allows the production of many nano-dimensional materials. This method involves the self-propagating reaction of homogeneous solutions which has different oxidative precursors (metal nitrates) and fuels (urea, glycine, hydrazide etc.). The solution combustion synthesis occurs in the form of volumetric or linear combustion depending on the nature of precursors and application of the method. Although there are different types of this technique, generally solution combustion synthesis consists some basic step which are preparation of oxidizer and fuel-containing mixture solutions, preheating of these solutions and subsequent self-propagating reaction. Determination of conditions which are related to production vanadium pentoxide by solution combustion synthesis with different precursors is one of the specific values of this proposed thesis. Another unique value of this thesis; vanadium oxides which is produced by solution combustion synthesis as raw materials, is coated by wet coating techniques and the optical and electrochemical properties of the resulting films of different thicknesses after the coating process are examined. The raw material which will be used in the coating processes by wet coating methods will be lower cost when it is produced by solution combustion synthesis. Appropriate using areas will be determined depending on the functionality of the coatings in the direction of the results to be obtained. In the first step of this thesis study, precursors which is used production of vanadium oxide by solution combustion synthesis, are selected. At this stage, ammonium metavanadat (NH4VO3) is used as the oxidizer. As fuel, experimental studies are carried out using different kinds of fuel type. Glycine, citric acid, their mixture (glycine + citric acid) and starch are used as fuel sources for solution combustion synthesis experiments. Thermodynamic calculations are performed which depending on the fuel / fuel mixture, to determine the combustion temperature at which the solution combustion synthesis reaction will occur. In addition, the effect of fuel and oxidant ratios on the product properties are examined during the production of vanadium oxide by solution combustion synthesis. X-ray diffraction analysis and thermogravimetric analysis (TG) shall be performed on the produced powders. Calcination temperature (to be determined according to TGA results), atmospheric conditions, reductive atmosphere and calcination time (1-24 hours) will be examined if it is necessary. After this step X-ray diffraction analysis are performed to determine phases and also scanning electron microscopy (SEM) analysis are also performed to examine grain size distribution and grain shape determination in powder materials obtained. In the second step, the vanadium oxide powders which is produced by the solution combustion synthesis method, are coated in thin film form by wet coating methods. Vanadium oxide are coated on indium tin oxide (ITO) coated glass or glass substrates. In later stages, thin film coatings are treated at 400 C. After that, characterization process is applied. Firstly, in the obtained coatings, X-ray diffraction analysis are performed. The crystal structure of the coatings is characterized by scanning electron microscopy (SEM) analysis. In the last step, the electrochemical and optical properties of the resulting thin film coatings are determined by analysis of cyclic voltammetry (CV) analyses and UV-Visible analysis. V2O5 powder which produced by solution combustion synthesis method is obtained very pure even different fuel types and O/F ratios (Oxidizer/Fuel). Morphology of final products is changed with different fuel type. Columnar morphology is seen in glycine and citric acid which are used as fuel sources. Spherical morphology is seen in mixture fuel which is used as a fuel source during the solution combustion synthesis. It is proved that, pure V2O5 powder which obtained by solution combustion method can be coated as a thin film by sol-gel coating method. Conclusion of characterization of thin films are used to find optimum usage areas in terms of electrochromic and optical properties of thin films. For example, V2O5 thin films could be used as a counter electrode for lithium ion batteries because of unique electrochromic properties. It has not found in the literature like this thesis which consists of the production of vanadium oxide powders by solution combustion synthesis, and the subsequent coating by wet coating method which is spin coating and examination of the optical and electrochemical properties of coatings. With this thesis, it is aimed to develop a method which will enable the production of functional materials with superior properties.