Göktuğ Günkaya

Electrophoretic deposition of nanocrystalline BaTiO₃ in ethanol medium

Electrophoretic deposition technique is a versatile coating method. With this method not only flat surfaces but also curved or rough surfaces can be coated in various thicknesses. In this study, BaTiO3 nanocrystals were synthesized with a novel nonaqueous method. In a simple one pot reaction process, the metallic barium is directly dissolved in benzyl alcohol at slightly elevated temperatures. After the addition of titanium isopropoxide and subsequent solvothermal treatment nearly spherical BaTiO3 nanocrystals typically 5 nm in diameter were obtained. The stability of the suspension in ethanol and nanocrystalline particle size distribution was measured by Malvern Nano-ZS. The BaTiO3 suspensions were directly used in an electrophoretic deposition process without any additional operation. Pt plated alumina was used as substrate. Various voltages were applied by altering the cathode to anode distance as well as deposition time for optimal process control. Because of the ethanol adsorbed on the surface of the nanoparticles, application of high voltages was possible without causing hydrolysis. The deposited surface coatings were dried in air atmosphere and sintered at different temperatures. SEM, EDX and XRD analysis were employed for the investigation of the coating.

Electrospray deposition of SnO2 films from precursor solution

The electrospray deposition (ESD) of SnO2 films from SnCl4.5H2O precursor solution was performed for gas sensor applications. Deposition time, solution flow rate and solution concentration were the main control parameters in the ESD process. The morphological properties of the deposited films were characterised by scanning electron microscopy. X-ray diffraction and energy dispersive X-ray analyses were employed to confirm the crystal phases and composition of the films. The best coatings with an island of particle agglomerates were observed at a flow rate of 0.12 ml min−1, for 60 min, and at a 0.05M concentration. The crystallisation of SnO2 films was observed at 650°C. The grain size and surface morphology of the films were influenced by the sol concentrations. Larger grain size and cracked surface were observed by increasing the sol concentration. The film thickness of 6 µm and a grain size of less than 100 nm were achieved.

Electrophoretic Deposition of SnO2 Nanoparticles and Its LPG Sensing Characteristics

Homogenized nanoparticles (60 nm) in acetylacetone mediums, both with and without iodine, were deposited onto platinum coated alumina substrate and interdigital electrodes using the electrophoretic deposition (EPD) method for gas sensor applications. Homogeneous and porous film layers were processed and analyzed at various coating times and voltages. The structure of the deposited films was characterized by a scanning electron microscopy (SEM). The gas sensing properties of the films were investigated using liquid petroleum gas (LPG) for various lower explosive limits (LEL). The results showed that porous, crack-free, and homogeneous films were achieved for 5 and 15 sec at 100 and 150 V EPD parameters using an iodine-free acetylacetone based suspension. The optimum sintering for the deposited nanoparticles was observed at 500°C for 5 min. The results showed that the sensitivity of the films was increased with the operating temperature. The coated films with EPD demonstrated a better sensitivity for the 20 LEL LPG concentrations at a 450°C operating temperature. The maximum sensitivity of the sensors at 450°C to 20 LEL LPG was 30.

Electrophoretic deposition of SnO 2 nanoparticles in non-aqueous medium for sensor applications

Nanosized SnO2 based sensors are widely used for gas sensing applications because of their low operating temperature and high surface area. SnO2 films are conventionally deposited by chemical vapor deposition, evaporation, sol-gel and sputtering which are very expensive, time consuming processes and complex. In contrast, electrophoretic deposition (EPD) is simple, cost effective which makes it possible to fabricate reliable porous coatings. The aim of this work is to deposit porous and homogenous SnO2 films by using EPD and to investigate the surface morphology of the films for gas sensor production. In this study nanosized SnO2 (60nm) particles were used in non-aqueous mediums with and without iodine to prepare stabilized EPD suspension. Homogeneous and porous film layers were processed and analyzed at various time and voltages. The results showed that highly porous, crack free and homogeneous SnO2 films on Pt coated alumina substrate were achieved for 5 and 15 seconds at 100V EPD parameters. Optimum sintering between the SnO2 nanoparticles was observed at 500oC. Deposited film thickness of 5 μm was measured by scanning electron microscopy. According to initial results, EPD deposited SnO2 films showed high sensitivity to liquified petroleum gas (LPG) at various gas concentration and operation temperature.

Electrophoretic Deposition of ZnO

Electrophoretic phonemenon is applied in different parts of science. Electrophoretic Deposition (EPD) is effective, fast and controllable process for obtaining various thin or thick film layers. In this study application of EPD to functional ceramics especially for sensors is aimed. Submicron ZnO powder was synthesized by using homogeneous precipitation method. A 5 wt% ZnO aqueous suspension prepared for EPD and an anionic dispersant was used as stabilizer. ZnO powder is deposited on alumina substrate at various voltages which is made conductive. Coated samples were sintered at 1200°C for two hours. Characterization of the sintered ZnO deposited substrates were examined by SEM and XRD techniques.