Graduate School of Natural and Applied Sciences
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Browsing Graduate School of Natural and Applied Sciences by Subject "Chemical Engineering"
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thesis.listelement.badge DEVELOPMENT OF PLATINUM CONTAINING ELECTROCATALYSTS SUPPORTED ON HYBRID MATERIAL OF PEM FUEL CELL(2023-01-27) ALJANABI, Ahmed; YAMAN, Şeniz Özalp; DEVRİM, YılserIncreasing energy demand in the world has increased the need for alternative energy technologies. Fuel cells using hydrogen, an important alternative energy source, have attracted great interest in recent years. Among the fuel cell types, proton exchange membrane fuel cells (PEMFC) are the most interesting fuel cell type due to their modular structure, high efficiency and low operating temperatures. Particularly, component development studies attract attention to increase the performance of PEMFCs. In this thesis multiwalled carbon nanotube-graphene MWCNT-supported Pt catalysts are synthesized using the microwave-assisted approach to examine the method to investigate the PEMFC performance. MWCNT-supported platinum catalysts were prepared for PEMFC application by using [(NH4)2[Pt2(HPO4)4(H2O)2] (Ptcomplex-1) & [(NH4)2[Pt2(SO4)4(H2O)2] (Ptcomplex-2) complexes as starting materials. TGA, XRD, HR-TEM and XPS analyzes were applied to examine the microstructure and morphology of the catalysts. Among the prepared catalysts Ptcomplex-1/MWCNT-3 and Ptcomplex-2/MWCNT-3 catalysts were tested in PEMFC with H2/air at the range of 60- 80 °C. The maximum power density values were determined for a membrane electrode assembly (MEA) prepared using Ptcomplex-1/MWCNT-3 catalyst as 0.36, 0.39, 0.41, and 0.26 W/cm2 and 0.38, 0.423, 0.44 and 0.28 W/cm2 for Ptcomplex-2/MWCNT-3 catalyst at 60, 65, 70 and 80 ⁰C, respectively. It was determined that the prepared Ptcomplex/MWCNT catalysts showed a better PEMFC performance than that of the Pt/C catalyst. The performance of the catalysts can be further improved with MEA optimization studies to be carried out with the catalysts prepared in the future.thesis.listelement.badge INVESTIGATION OF THE EFFECT OF SENESCENCE ON ANTIOXIDANT RESPONSES FOR MG-63 (HUMAN OSTEOSARCOMA) AND MC3T3-E1 (MOUSE PRE-OSTEOBLAST) CELL LINES(2023-02-01) AYAN, Fırat; İŞGÖR, Sultan BelginAging and its effects have been revealed by many researchers, the effects of aging on living systems are still being investigated today. In this study, antioxidant enzyme responses of mouse osteosarcoma (MG-63) and mouse preosteoblast cells (MC3T3- E1) against aging, which are used in many scientific studies; Superoxide Dismutase Glutathione-S-Transferase (GST), Glutathione Peroxidase (GPx) and DPPH activities were investigated. In this study before performing the enzyme assays, the protein contents of the cells were found, and they were determined as 0.05 mg/mL for MG-63 young, 0.05 mg/mL for MG-63 young, 0.05 mg/mL for MC3T3-E1 young and 0.03 mg/mL for MC3T3-E1 young were found, respectively. Enzyme activities were analyzed comparatively for passages 10, 15, 20, 25, 30, 35, 40 and 45. As can be seen, GST, GPX activities are higher in senescent cancer cells. However, SOD activity was found to be higher in aging progenitor bone cells. In DPPH activity, senescent cancer cells were found to have the highest oxidant scavenging effect with 71.2%. On the other hand, both cell lines were stained with S-A-β-Galactosidase, and β-Galactosidase accumulations due to senescence were qualitatively investigated, and blue stain accumulation was found to be higher in aged osteosarcoma cells. Finally, cell kinetics were examined, and doubling times and specific growth rates were found for the old and young passages of both cell lines used. Doubling times of cells were found to be as respectively, 4.45 hours for MG-63 young, 2.48 hours for MG-63 young, 3.04 hours for MC3T3-E1 old and 3.30 hours for MC3T3-E1 young.