Person: OKTAR, FAİK NÜZHET
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OKTAR
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FAİK NÜZHET
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Publication Metadata only Preparation and evaluation of cerium oxide-bovine hydroxyapatite composites for biomedical engineering applications(ELSEVIER SCIENCE BV, 2014) OKTAR, FAİK NÜZHET; Gunduz, O.; Gode, C.; Ahmad, Z.; Gokce, H.; Yetmez, M.; Kalkandelen, C.; Sahin, Y. M.; Oktar, F. N.The fabrication and characterization of bovine hydroxyapatite (BHA) and cerium oxide (CeO2) composites are presented. CeO2 (at varying concentrations 1, 5 and 10 wt%) were added to calcinated BHA powder. The resulting mixtures were shaped into green cylindrical samples by powder pressing (350 MPa) followed by sintering in air (1000-1300 degrees C for 4 h). Density, Vickers microhardness (HV), compression strength, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were performed on the products. The sintering behavior, microstructural characteristics and mechanical properties were evaluated. Differences in the sintering temperature (for 1 wt% CeO2 composites) between 1200 and 1300 degrees C, show a 3.3% increase in the microhardness (564 and 582.75 HV, respectively). Composites prepared at 1300 degrees C demonstrate the greatest compression strength with comparable results for 5 and 10 wt% CeO2 content (106 and 107 MPa) which are significantly better than those for 1 wt% and those that do not include any CeO2 (90 and below 60 MPa, respectively). The results obtained suggest optimal parameters to be used in preparation of BHA and CeO2 composites, while also highlighting the potential of such materials in several biomedical engineering applications. (C) 2014 Elsevier Ltd. All rights reserved.Publication Metadata only Synthesis, characterization, and biological properties of composites of hydroxyapatite and hexagonal boron nitride(WILEY, 2018) OKTAR, FAİK NÜZHET; Unal, Semra; Ekren, Nazmi; Sengil, Ahmet Z.; Oktar, Faik N.; Irmak, Ster; Oral, Ozlem; Sahin, Yesim M.; Kilic, Osman; Agathopoulos, Simeon; Gunduz, OguzhanHydroxyapatite (HA), obtained from bovine bones, was successfully reinforced with hexagonal boron nitrite (h-BN). h-BN/HA composites, with BN content up to 1.5 wt %, were sintered at various temperatures between 1000 and 1300 degrees C, in air. Well-sintered samples were obtained after sintering at 1200 and 1300 degrees C. The presence of h-BN contributed to dense, fine, and well-crystallized microstructure. The results of X-ray diffraction analysis and FT-IR spectroscopy showed that the produced composites comprised biphasic beta-TCP/HCA (HCA: carbonate partially substituted HA). High values of mechanical properties were achieved, namely compression strength 155 MPa for the sample 0.5% h-BN/HA and Vickers microhardness of 716 HV for the samples 1.5% h-BN/HA, both sintered at 1300 degrees C. U2OS human bone osteosarcoma proliferation and cell viability showed no adverse effect in the presence of h-BN/HA, suggesting the potential use of the produced materials as safe biomaterials in bone tissue engineering. (C) 2017 Wiley Periodicals, Inc.Publication Metadata only Sintering effects of mullite-doping on mechanical properties of bovine hydroxyapatite(ELSEVIER SCIENCE BV, 2017) OKTAR, FAİK NÜZHET; Yetmez, M.; Erkmen, Z. E.; Kalkandelen, C.; Ficai, A.; Oktar, F. N.In this study, sintering effects on microstructural behavior of bovine derived hydroxyapatite doped with powder mullite are considered in the temperature range between 1000 C-omicron and 1300 C-omicron. Results show that maximum values of both compressive strength and microhardness are achieved in the samples sintered at 1200 C-omicron for all mullite additions of 5, 7.5, 10 and 12.5 wt. Moreover, above 1000 C-omicron, decomposition of HA and new phase formations such as whitlockite and gehlenite play a major role in both compressive strength and microhardness properties which increase up to 10 wt mullite reinforcement. (C) 2017 Elsevier B.V. All rights reserved.Publication Metadata only Novel doped hydroxyapatite thin films obtained by pulsed laser deposition(ELSEVIER SCIENCE BV, 2013) OKTAR, FAİK NÜZHET; Duta, L.; Oktar, F. N.; Stan, G. E.; Popescu-Pelin, G.; Serban, N.; Luculescu, C.; Mihailescu, I. N.We report on the synthesis of novel ovine and bovine derived hydroxyapatite thin films on titanium substrates by pulsed laser deposition for a new generation of implants. The calcination treatment applied to produce the hydroxyapatite powders from ovine/bovine bones was intended to induce crystallization and to prohibit the transmission of diseases. The deposited films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Pull-off adherence and profilometry measurements were also carried out. X-ray diffraction ascertained the polycrystalline hydroxyapatite nature of the powders and films. Fourier transform infrared spectroscopy evidenced the vibrational bands characteristic to a hydroxyapatite material slightly carbonated. The micrographs of the films showed a uniform distribution of spheroidal particulates with a mean diameter of similar to 2 mu m. Pull-off measurements demonstrated excellent bonding strength values between the hydroxyapatite films and the titanium substrates. Because of their physical-chemical properties and low cost fabrication from renewable resources, we think that these new coating materials could be considered as a prospective competitor to synthetic hydroxyapatite used for implantology applications. (C) 2012 Elsevier B.V. All rights reserved.