Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article The Effect of Layered Cover Plate Material on the Ballistic Performance of Ceramic Armors: Experimental and Numerical Study(Pergamon-Elsevier Science Ltd, 2026) Cellek, Seven Burcin; Tasdemirci, Alper; Cimen, Gulden; Yildiztekin, Faki Murat; Toksoy, Ahmet Kaan; Guden, MustafaThis study investigates the ballistic performance of silicon carbide (SiC) ceramic armor systems reinforced with single and hybrid metallic cover plates composed of Ti-6Al-4V (Ti64) and copper. Controlled ballistic experiments combined with validated LS-DYNA simulations were conducted to examine how cover-plate material, thickness, and stacking sequence influence penetration resistance, energy dissipation, and failure mechanisms. The experimental results revealed that metallic cover plates significantly enhance protection by improving projectile erosion and extending dwell time. While both Ti64 and copper single layers increased the antipenetration capability (APC) compared with bare SiC, hybrid configurations achieved the highest performance. The optimal design, consisting of a 2 mm Ti64 plate placed in front of a 1 mm copper plate, produced the greatest reduction in penetration depth and the highest APC value. Numerical analyses closely replicated the experimental trends and provided insight into stress-wave interactions, pressure evolution, and damage progression within the ceramic. The findings demonstrate that hybrid Ti64-Cu systems not only improve initial impact resistance but also redistribute energy toward the front layers, reducing stress transmission to the backing and mitigating catastrophic ceramic failure. The combined experimental and numerical results establish a clear design framework for developing lightweight, high-efficiency ceramic armor through tailored hybrid layering strategies.Article Citation - WoS: 6Citation - Scopus: 4Regenerable Nickel Catalysts Strengthened Against H2s Poisoning in Dry Reforming of Methane(Elsevier, 2025) Kesan Celik, Nazli; Yasyerli, Sena; Arbag, Huseyin; Tasdemir, H. Mehmet; Yasyerli, NailIn this study, alumina-supported bimetallic Ni-Cu and trimetallic Ni-Cu-Ce catalysts were synthesized to improve catalysts resistant to coke formation and sulfur poisoning for dry reforming of methane (DRM). The effects of parameters such as feed composition, synthesis method, and H2S concentration using the catalyst with the best activity were also investigated. To determine the physical and chemical properties of the synthesized catalysts, XRD, N2 adsorption-desorption, TGA-DTA, ICP-OES, SEM-EDX, XPS, and DRIFTS analyses were performed. XRD analysis showed that the fresh Ni-Cu catalysts have elemental nickel and gamma- alumina phases in their structures. In addition to these structures, the CeO2 crystal structure was determined for the Ni-Cu-Ce catalyst. Type IV isotherm with H1 hysteresis indicating uniform mesoporous structure was obtained with all the catalysts. The activities of the synthesized catalysts in DRM were performed in the presence of different concentrations of H2S (2 ppm, 50 ppm, and 500 ppm) in a fixed bed reactor at 750 degrees C using a gas chromatography-equipped system. The alumina-supported 8Ni-3Cu-8Ce catalyst prepared by the impregnation method exhibited a higher and more stable activity comparing the bimetallic Ni-Cu catalyst in the presence of H2S. Adding copper and cerium to the nickel catalyst has a curative effect on resistance to coke formation and sulfur poisoning. Excess CO2 in the feed stream increased the H2S poisoning resistance of the catalyst. To analyze the reactor exit stream in catalytic activity using different feed stream compositions such as H2S+He, H2S+CO2+He, and H2S+CO2+CH4+He, FTIR with a gas cell was used. The formation of carbonyl sulfide (COS) and H2O, which occurs due to the possible reaction between CO2 and H2S, was observed. Regeneration studies showed that the catalyst could undergo regeneration with a low oxygen concentration (0.3 % O2 in He). 8Ni-3Cu-8Ce@SGA, which gave 71 % CH4 conversion in the first minute of the reaction test in the presence of 50 ppm H2S, was regenerated after completely losing its activity at the end of 5 h. 66 % CH4 conversion was achieved when tested again in the absence of H2S (CH4/CO2/Ar:1/1/1). The 8Ni-3Cu-8Ce@SGA catalyst was deemed worthy of investigation for industrial applications.Article Citation - WoS: 35Citation - Scopus: 41Batch and Column Studies on Heavy Metal Removal Using a Local Zeolitic Tuff(Elsevier Ltd., 2010) Balköse, Devrim; Ülkü, Semra; Can, ÖzgeIon exchange is considered to be one of the most cost effective methods if low cost ion exchangers such as natural zeolites are used in waste water treatment. In this study, a zeolitic tuff rich in clinoptilolite from Gördes Manisa Turkey was examined to evaluate its ion exchange performance for the removal of copper, nickel and cobalt ions from metal (II) nitrate solutions at various concentrations by performing both batch and packed column experiments. A clinoptilolite tuff with purity around 60% was used in ion exchange experiments. Copper, nickel and cobalt exchange capacities of the tuff were determined as 8.3mg (0.26meq) Cu2+/g, 6.6mg (0.23meq) Ni2+/g and 4.5mg (0.15meq) Co2+/g, respectively. The equilibrium behavior of the system was best described by classical Langmuir model. The experimental breakthrough curves from the column experiments were fitted to solid diffusion control model. The study showed that efficient metal ion removal can be done by using the local clinoptilolite rich tuff. © 2010 Elsevier B.V.Article Citation - WoS: 249Citation - Scopus: 268Silver, Zinc, and Copper Exchange in a Na-Clinoptilolite and Resulting Effect on Antibacterial Activity(Elsevier Ltd., 2004) Top, Ayben; Ülkü, SemraAg+-Na+, Zn2+-Na+, and Cu2+-Na+ equilibria for clinoptilolite-rich mineral from Gördes (Western Anatolia) were investigated at 25 °C and 0.1 N total solution normality. While silver exchange was favorable over the whole concentration range, zinc and copper were partially exchanged and preferred only at low concentrations. The standard free energies of exchanges for Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ pairs were found as -6.0, 2.03, and 3.09 kJ/equiv., respectively. From these values, selectivity sequence was determined as Ag+>Na+ >Zn2+>Cu2+. Antibacterial activities of the exchanged samples were measured as a function of exchange level against Pseudomonas aeruginosa and Escherichia coli. Considering the selectivity sequence of the clinoptilolite and antibacterial activity results, Ag-clinoptilolite seemed to be promising antibacterial material.