Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Conference Object Investigation of Ha Cement Preparation and Properties by Using Central Composite Design(Trans Tech Publications, 2012) Çetin, Ali Emrah; Şimşek, Deniz; Çiftçioğlu, Muhsin; Akdeniz, Yelda; Özmıhçı, Filiz; Aykut Yetkiner, ArzuThe goal of the present work was to investigate the effects of several cement preparation parameters on setting and hardening reaction mechanisms and hydroxyapatite (HA) cement properties. A central composite experimental design (CCD) was conducted by choosing particle size, solid to liquid ratio, pH, seed concentration and buffer concentration as design parameters along with compressive strength and setting time being the responses. Tetracalcium phosphate (TTCP) powders were prepared by heat treatment of calcium and phosphate source mixtures in the 1200-1400°C temperature range followed by quenching to room temperature in a dessicator. The second phase used in the formulations (brushite) was prepared by aqueous chemical methods. A series of HA pastes/cements were prepared by changing the above mentioned design parameters. Cements were characterized by a standardized setting time test, mechanical testing machine, SEM and XRD. HA cements with the desired properties can be formulated by using CCD in which the responses were expressed by a second order polynomial equation of the parameters. Compressive strengths for the majority of HA cements were determined to be in the 100-160 MPa range which is significantly higher than those reported in the literature. © (2012) Trans Tech Publications.Article Citation - WoS: 11Citation - Scopus: 13Co2 Adsorption and Dehydration Behavior of Linax, Knax, Canax and Cenax Zeolites(Springer Verlag, 2008) Erten, Yasemin; Güneş Yerkesikli, Alev; Çetin, Ali Emrah; Çakıcıoğlu Özkan, Seher FehimeIn this study, NaX synthetic zeolite was modified by following the conventional cation exchange method at 70°C. 82, 81, 79 and 48% of sodium were exchanged with Li+, K+, Ca2+ and Ce3 +, respectively. Thermal analysis data obtained by TG/DSC was used to evaluate the dehydration behavior of the zeolites. The strongest interaction with water and the highest dehydration enthalpy (ΔH) value were found for Li-exchanged form and compared with the other forms. The temperature required for complete dehydration increased with decreasing cation size (cation size: K+>Ce3+>Ca2+>Na+>Li +). CO2 adsorption at 5 and 25°C was also studied and the virial model equation was used to analyze the experimental data to calculate the Henry's law constant, K o and isosteric heat of adsorption at zero loading Q st. K o values decreased with increasing temperature and the highest Qst was obtained for K rich zeolite. It was observed that both dehydration and CO2 adsorption properties are related to cation introduced into zeolite structure.