Multifunctional nanocomposite transparent UV-blocking films synthesized by sol-gel process for optical, automotive and a
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Multifunctional nanocomposite transparent UV-blocking films synthesized by sol-gel process for optical, automotive and aeronautic applications A. R. Phani and S. Santucci INFM and Department of Physics -University of L’Aquila, via Vetoio, 67010 Coppito, L’Aquila - ITALY ABSTRACT Development of UV blocking thin films with effective cut-off features with steep edges and high transmission in the visible and IR region have been developed. The unique optical, mechanical and chemical properties of silica and ceria nanocomposites with surface functional groups making them most promising candidate for applications in opto-electronic, automotive, and aeronautic industries. On the other hand, highly hydro and oleophobic films are being actively considered in optical, automotive and aeronautic industries to increase adhesion and scratch, abrasion resistance properties. In order to fill the gap, and fulfill the requirements to meet both ends, it could be proved that morphological changes in the nanometer range influences the water contact angles and their hystersis of low energy materials. Nanocomposite films of SiO2 and CeO2 with surface functionalisation with decafluorooctly-triethoxy silane itself forms nanohemispheres (similar to lotus leaf) at and above 100°C favoring an increase in water contact angle from 122° (25°C) to 145°(400°C). The structural, optical, and hydrophobic properties have been examined by employing X-ray diffraction, UV-visible spectroscopy, contact angle techniques, respectively. The cut-off behavior of the deposited and annealed nanocomposite thin films have been tuned by varying different amounts of CeO2 in SiO2. INTRODUCTION Fluorine containing polymers exhibit weak intermolecular interactions, and have very low surface tensions, which render these polymers extremely difficult to wet with aqueous or organic liquids [1]. These surfaces are not adhesive with a low friction coefficient and consequently are oil and water repellent. For this reason, fluorine derivatives- monomers, oligomers or polymers are widely used for the coating of substrates such as textiles, papers, leather, wood, etc. in order to obtain oil and water repellent surfaces. Apart from this fluorocarbon compounds are commercially very important for various applications such as surfactants, fire extinguishing agents, coolants, electrical insulators, inhalation anaesthetics, and transport agents for dissolved oxygen in medical applications such as artificial blood and organ preservation transplants [2]. On the other hand coatings with self-cleaning or super water repellent properties are very useful for solar cell panel on roofs, antennas exposed to a lot of snow, and glasses on high-rise buildings, because the surfaces remain clean without maintenance. Among the fluorocarbons, polytetrafluoroethylene (PTFE) is widely used as coatings for antiadhesion agents and chemical insulators because of its surface energy [3]. Unfortunately, PTFE is difficult to handle because of its viscosity, melt strength (mechanical stre
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