Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye
Tezin Onay Tarihi: 2008
Öğrenci: NUSRET SERHAT ÜN
Danışman: CANER DURUCAN
Özet:A processing route for development of hydroxyapatite (Ca10(PO4)6(OH)2 or HAp)-titania (TiO2) hybrid coatings on titanium alloy (Ti6Al4V) has been established. HAp powders of different size and morphology were synthesized by aqueous precipitation techniques using different precursor couples and XRD, SEM and FTIR were performed for complete characterization. Hybrid coatings were then prepared via sol-gel by incorporating presynthesized HAp powders into a titanium-alkoxide dip coating solution. Titania network is formed by hydrolysis and condensation of Ti-isopropoxide (Ti[OCH(CH3)2]4) based sols. The effect of titania sol formulation, specifically the effect of organic solvents on the microstructure of the dip coated films calcined at 500 ºC has been investigated. The coatings exhibit higher tendency for cracking when a high vapor pressure solvent, such as ethanol (C2H5OH) is used causing development of higher macroscopic stresses during evaporation of the sol. Titania sol formulations replacing the solvent with n-propanol (CH3(CH2)2OH) and acetly-acetone (C5H8O) combinations enhanced the microstructural integrity of the coating during evaporation and calcination treatments. Sol-gel processing parameters such as multilayer coating application and withdrawal rate can be employed to change the titania thickness in the range of 0.120 - 1.1 microns and to control the microstructure of HAp-titania hybrid coatings. Slower withdraw rates and multi-layer dip coating lead to coatings more vulnerable to cracking. A high calcination temperature in the range of 400 ºC-600 ºC lead to more cracking due to combined effect of densification originated stresses and thermal stresses upon cooling.