Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 3Citation - Scopus: 3Particulate Sol Route Hydroxyapatite Thin Film-Silk Protein Interface Interactions(Gazi Üniversitesi, 2010) Özcan, Selçuk; Çiftçioğlu, MuhsinHydroxyapatite (HAp) thin film coatings were prepared on bioinert glass slides by a particulate sol method and the effects of intermediate silk fibroin and silk sericin coatings on the HAp film formation and surface topography were examined. The films prepared with smaller crushed particle sols had a higher agglomeration tendency during the drying consolidation step of the thin film formation, and contained agglomerates larger in number and size, which was demonstrated experimentally and in accordance with the DLVO theory. In the thin films prepared on intermediate sericin and fibroin films the number and size of agglomerates were decisively reduced, forming homogeneous films of predominantly primary particles, especially for the larger particle size sols. The regular surface electrostatic potential arrangements of the β-sheet structures of the sericin and fibroin, and of hydroxyapatite crystals, gave rise to the coulombic attraction driven surface energy minimization, enhancing the hydroxyapatite thin film formation process. The positive degree of cooperativity in the hydroxyapatite particle deposition on the silk protein coatings was disrupted by the particle agglomeration tendency.Article Citation - WoS: 4Citation - Scopus: 3Evaluation of the Effectiveness of the Bulk Thermal Stresses for Kraft Recovery Boiler Fireside Deposit Cleaning(Tappi Press, 2006) Özcan, Selçuk; Tran, HonghiRemoval of fireside deposits from the heat transfer tubes in kraft recovery boilers is carried out by sootblowing and occasionally "chill-and- blow" practices. During chill-and-blow, black liquor flow is reduced to rapidly cool the deposits.Thermal stresses generated in the deposit as a result of thermal shock can effectively weaken the deposit, facilitating its cleaning. For this study, we investigated the mechanical weakening effect of thermal stresses generated by the transient temperature gradients. We quantified the mechanical weakening effect due to thermal shock by measuring the decrease in biaxial flexure strength of a preheated sodium chloride disk at various quenching times and surface heat transfer coefficients. We observed that the mechanical weakening occured by transient thermal stresses as well as crack propagation. Approximately 35% loss in biaxial flexure strength could be achieved at heat transfer coefficients above 3.3·103 W/m 2K, and at quenching durations above 40 s.