Hasan Erdem Çamurlu

Sol-gel thin films with anti-reflective and self-cleaning properties

Self-cleaning photocatalytic TiO2 films are beneficial since they reduce the maintenance cost and enhance the efficiency of various optical systems, especially thermal and photovoltaic solar systems. However, the presence of a TiO2 layer on glass reduces the transmission of incident light, which leads to a decrease in efficiency. This drawback can be overcome by applying a layer of anti-reflective coating beneath the TiO2 layer. Generally, the anti-reflective layer is porous silica. The presence of the anti-reflective layer compensates for the loss of light transmittance caused by the photocatalytic TiO2 top layer. This paper reviews some of the previous and the latest fundamental studies in the literature on anti-reflective, self-cleaning and multi-functional films.

Formation of Zr(C,N)-ZrB2 composite powders by self-propagating high-temperature synthesis (SHS)

Zirconium carbide, nitride and diboride are ceramic materials suitable for use at high temperatures requiring resistance to wear, oxidation and corrosion. ZrC and ZrN have isotypical lattices and are completely soluble in each other forming zirconium carbonitride. In this study zirconium carbonitride-zirconium diboride composite powders were produced by self-propagating high-temperature synthesis (SHS) from zirconium, hexagonal boron nitride, carbon and boron powders. The ratio of ZrC/ZrN in the Zr(C,N) solid solutions were varied by changing the C and h-BN amount in the reactants. Reaction products were analysed by powder X-ray diffraction. Lattice parameters of ZrC-ZrN solid solutions were determined and they were seen to increase with increasing C content in the structure. Adiabatic temperatures of the reactions were calculated by the HSC software. Grain size and morphology of the reactants and products was examined by scanning electron microscopy. Partial fusion of the grains was observed in some of the products, indicating that the actual temperatures attained at the reaction front were close to the melting points of the products. The grains of the product phases had irregular shape.

Production and characterisation of strontium and magnesium doped lanthanum-gallium oxide (LSGM) ceramics

Strontium and magnesium doped lanthanum-gallium oxide (LSGM) ceramics exhibit high oxygen ionic conductivity at medium temperatures (800°C) as compared to other materials such as yttrium stabilised zirconia. Due to this property, they are candidates to be used as electrolyte materials in solid oxide fuel cells (SOFC). In this study, La0.80Sr0.20Ga0.83Mg0.17O3−δ and La0.90Sr0.10Ga0.80Mg0.20O3−δ powders were prepared from metal-nitrate starting materials by a Pechini type sol-gel process. Obtained powders were sintered at 1430°C for 24 hours in air. Powder X-ray diffraction and scanning electron microscopy analysis were performed on the powders and sintered ceramics and densities of the sintered ceramics were measured. Ceramics having single phase perovskite structure were produced with theoretical densities higher than 97%. LSGM ceramics were subjected to impedance spectroscopy analysis at 300°C, after coating with platinum. No grain boundary contribution was observed on the impedance of the ceramics. Ionic conductivities of the samples were measured in 400-1200°C range. At 800°C, the highest ionic conductivity value was measured as 0.14 S/cm, which was obtained in the La0.80Sr0.20Ga0.83Mg0.17O3−δ composition.