Person: SARIOĞLU, CEVAT
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SARIOĞLU
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Publication Metadata only The effect of plasma detonation parameters on residual stresses developed in the plasma modified layer(PERGAMON-ELSEVIER SCIENCE LTD, 2014) SARIOĞLU, CEVAT; Ozbek, Yildiz Yarali; Sarioglu, Cevat; Durman, MehmetThe surface modification of the AISI 4140 steel by pulse plasma detonation process resulted in residual stresses. The residual stresses in modified surfaces measured using XRD tilting technique were determined for different process parameters. The results indicated that residual stress developed in modified surface increased from -200 MPa to -1000 MPa with decreasing in nozzle distance and increased from -554 MPa to -823 MPa with increasing in battery capacity. In shortest nozzle distance (60 mm), the increasing in number of pulse from 5 to 10 resulted in decreasing residual stress from -1000 MPa to -340 MPa. It was clearly demonstrated at first time that pulse plasma detonation process parameters significantly influenced the value of residual stress. (C) 2014 Elsevier Ltd. All rights reserved.Publication Metadata only Synthesis of SnS2 photocatalyst for photocatalytic hydrogen production(2022-06-30) OK, ALAADDİN CEM; SARIOĞLU, CEVAT; Ok A. C., Sarıoğlu C.Hydrogen could be generated from both renewable and non-renewable sources of energy. Usingnonrenewable energy sources to produce hydrogen will result in greenhouse CO2 gas emissions andcause global warming. Photocatalytic systems for generating hydrogen from solar energy have a greatdeal of potential to solve the global warming problem because of the totally renewable green source ofsun and water. Because of its superior properties, such as a proper and narrow bandgap, betterchemical stability, non-toxic, photo-corrosion resistance, and suitable optimum conduction and valanceband potentials, the tin disulfide (SnS2) photocatalyst has great potential to be used for producing H2from the splitting of water via solar energy. In this study, SnO2 powders were successfully thermallysulfurized to SnS2 powders at 500°C for 24 hours under an Argon (Ar) atmosphere. The XRD analysisverified the hexagonal SnS2 crystals. UV-vis spectroscopy was used to determine the band gap valueof the generated powder, which is 2.24 eV.Publication Metadata only Photoelectrochemical performance of thermally sulfurized CdxZn1-xS photoanode: Enhancement with reduced graphene oxide support(PERGAMON-ELSEVIER SCIENCE LTD, 2020) ÖZKAYA, ALİ RIZA; Ayaz, RanaMuhammad Zunain; Akyuz, Duygu; Uguz, Ozlem; Tansik, Irem; Sarioglu, Cevat; Karaca, Fatma; Ozkaya, Ali Riza; Koca, AtifIn this study, photoelectrochemical performance of reduced graphene oxide (RGO)-CdxZn1-xS compos-ites, which were synthesized through a novel two-steps thermal sulfurization process by using elemental sulfur, was reported. This is the first time that the two-step thermal sulfurization process with elemental sulfur for the preparation of photoanode based on RGO-CdxZn1-xS. The electrodes exhibited high photostability and photocurrent response in the presence of visible light. The presence of RGO in CdxZn1-xS as electron collector and transporter increased the photocurrents approximately 40%. Among the RGOCdxZn1-xS composites, RGO-CdS photoanode yielded an extremely high photocurrent density of 6.5 mAcm(-2) with the rate of hydrogen production rate of 551.1mmolh(-1)cm(-2). This value of photocurrent density is almost 89% of its theoretical value. This is the maximum attained photocurrent density with superior stability in comparison with related literature. (c) 2020 Elsevier Ltd. All rights reserved.Publication Metadata only Fast and low-cost fabrication of 1D hematite photoanode in pure water vapor and air atmosphere: Investigation the effect of the oxidation atmosphere on the PEC performance of the hematite photoanodes(PERGAMON-ELSEVIER SCIENCE LTD, 2017) SARIOĞLU, CEVAT; Demirci, Selim; Sarioglu, CevatIn this study, hematite photoanodes were successfully fabricated by thermal oxidation of the commercial cold-rolled steel at 500 degrees C in pure water vapor and air atmosphere. The crystal phase structure, surface morphology, and optical properties of the hematite photoanodes were characterized using an X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM) and UV-VIS spectrophotometer, respectively. The results showed that hematite photoanodes had high crystalline phase and the annealing atmosphere influenced the morphology of the hematite photoanodes. Moreover, nanowhisker and nanorod shaped nanostructures were observed on the substrate. The optical band gap values of the hematite photoanodes varied between 2.38 and 2.70 eV. Photoelectrochemical (PEC) studies of the hematite photoanodes were assessed in the 0.1 M NaOH electrolyte solution using the Mott-Schottky analysis and electrochemical impedance spectroscopy techniques. The PEC findings exhibited that the hematite photoanode annealed 15-min in water vapor had best PEC performance achieving photocurrent density 0.244 mA/cm(2) at 1.6 V vs. V-RHE and highest carrier density value (N-D = 1.15 x 10(21) cm(-3)). Furthermore, the photoanodes annealed in water vapor atmosphere revealed at least three times higher PEC performance than that of photoanodes annealed in air. Thermal oxidation method in water vapor is an efficient methods for fabrication of hematite photoanodes. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Publication Open Access Synthesizing of SnS2 photocatalyst from SnO2 powders by thermal sulfurization with varying temperature (400 °C and 500 °C) and time(2023-01-01) OK, ALAADDİN CEM; SARIOĞLU, CEVAT; OK A. C., SARIOĞLU C.SnS2 from SnO2 powders was successfully produced by the thermal sulfurization method to obtain pure SnS2 powders by varying the sulfurization temperature and time. XRD analysis confirmed pure hexagonal SnS2 powders at 400 and 500 °C after 24 h of sulfurization. Grain size analysis in SEM indicated that the average grain size of powders synthesized at 400 °C and 500 °C were 1 and 11 μm, respectively. The band gap values of the obtained powders at 400 and 500 °C was determined by UV–vis spectroscopy as 2.26 eV and 2.24 eV, respectively. The photoelectrochemical analysis of the SnS2 photoelectrode produced at 500 °C revealed a flat band potential of −0.50 V, a charge carrier density of 1.49 × 1020 cm −3 and photocurrent density of 2.5 μA/cm2 at 0 V vs SCE. These results indicated that SnS2 synthesized for the first time by the thermal sulfurization technique from SnO2, which was a simple and cheap technique, was a promising candidate to be used as a photocatalysts.Publication Metadata only Photocatalytic-electrocatalytic dual hydrogen production system(PERGAMON-ELSEVIER SCIENCE LTD, 2016) ÖZKAYA, ALİ RIZA; Aydemir, Mehmet; Akyuz, Duygu; Agopcan, Burag; Sener, M. Kamm; Albayrak, Fatma Karaca; Sarzoglu, Ceuat; Koca, AtifIn this paper, in order to produce efficient and low cost hydrogen by using alternative energies with simple ways; a photocatalytic electrocatalytic dual hydrogen production system (PEHPS) which combined discontinuous photocatalytic and electrocatalytic systems in one continuous dual system was designed and optimized. In the photocatalytic chamber of PEHPS, nano-sized Cd(1-x)ZnxS/Pt photocatalysts were utilized. The synthesized Cd(1-x)ZnxS/Pt photocatalysts were characterized with scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and diffuse reflectance UV Vis spectroscopy. The most active photocatalyst having CdZnS2 core and 10% Pt shell showed 24.0 mLg(-1) h(-1) (963.6 gmol g 1 h(-1)) hydrogen evolution rate with 4.01% solar energy conversion efficiency (SECE%). S2O3-2 produced in the photocatalytic chamber of PEHPS was used as redox species in the electrocatalytic chamber. This process decreased the cell potential of water electrolysis from 2.50 V to 1.70 V on glassy carbon electrodes. Moreover, usage of electro-polymerized metallophthalocyanines (Poly-MPc) as cathode active electrocatalyst, the over-potential of cathode of the electrocatalytic chamber for hydrogen reduction reaction decreased by 0.230 V. (C) 2015 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only Fabrication and characterization of novel iodine doped hollow and mesoporous hematite (Fe2O3) particles derived from sol-gel method and their photocatalytic performances(ELSEVIER SCIENCE BV, 2018) SARIOĞLU, CEVAT; Demirci, Selim; Yurddaskal, Metin; Dikici, Tuncay; Sanoglu, CevatIn this work, iodine (1) doped hollow and mesoporous Fe2O3 photocatalyst particles were fabricated for the first time through sol-gel method. Phase structure, surface morphology, particle size, specific surface area and optical band gap of the synthesized Fe2O3 photocatalysts were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), BET surface analysis, particle size analyzer and UV-vis diffuse reflectance spectrum (UV-vis DRS), respectively. Also, electrochemical properties and photoluminescence spectra of Fe2O3 particles were measured. The results illustrated that high crystalline, hollow and mesoporous Fe2O3 particles were formed. The optical band gap values of the Fe203 photocatalysts changed between 2.104 and 1.93 eV. Photocatalytic efficiency of Fe2O3 photocatalysts were assessed via MB solution. The photocatalytic activity results exhibited that I doping enhanced the photocatalytic efficiency. 1% mole iodine doped (I-2) Fe2O3 photocatalyst had 97.723% photo degradation rate and 8.638 x 10(-2) min(-1) kinetic constant which showed the highest photocatalytic activity within 45 min. Moreover, stability and reusability experiments of Fe2O3 photocatalysts were carried out. The Fe2O3 photocatalysts showed outstanding stability after four sequence tests. As a result, I doped Fe2O3 is a good candidate for photocatalysts. (C) 2017 Elsevier B.V. All rights reserved.Publication Metadata only Heat capacity measurements on BaTa2O6 and derivation of its thermodynamic functions(SPRINGER, 2017) SARIOĞLU, CEVAT; Ilhan, Mustafa; Mergen, Ayhan; Sarioglu, Cevat; Yaman, CemalettinHeat capacity measurements of barium tantalate (BaTa2O6) were carried out by using a differential scanning calorimeter at temperatures between 323 and 1323 K. From the heat capacity values of BaTa2O6, other thermodynamic functions (enthalpy and entropy increments) were derived between 298.15 and 1323 K. The C (p,m) (298.15) value of BaTa2O6 was computed as 184.857 J mol(-1) K-1. Moreover, fitted heat capacities exhibited good agreement with Neumann-Kopp rule at the temperatures between 298.15 and 1300 K.Publication Metadata only A new sulfur source for the preparation of efficient Cd(1-x)ZnxS photocatalyst for hydrogen evolution reaction(PERGAMON-ELSEVIER SCIENCE LTD, 2018) KOCA, ATIF; Agopcan, Burag; Akyuz, Duygu; Karaca, Fatma; Sarioglu, Cevat; Koca, AtifCd(1-x)ZnxS hexagonal crystals were for the first time synthesized via thermal sulfurization of Cd(1-x)ZnxO particles by using the elemental sulfur as the sulfur source. A temperature profile in the tube furnace was designed to obtain the proposed particle size, crystal structure, and morphology. Synthesized Cd(1-x)ZnxS particles were characterized with scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance UV Vis spectroscopy. It was seen that there was a polynomial relationship between the band gap and Cd: Zn ratio in the Cd(1-x)ZnxS. Cd0.58Zn023S has shapeless particles between 250 and 500 nm particle size. It was observed that particle size decreased as Zn ratio increased in the Cd(1-x),ZnxS. Cd(1-x),ZnxS hexagonal crystals had nano step surfaces which were one of the desired factors for achieving high photocatalytic efficiency. Finally, Synthesized Cd(1-x.)ZnxS particles were used as photocatalysts for the photocatalytic hydrogen evolution reaction (HER). Cd0.77Zn0.23S structure behaved the most active one among the different compositions of Cd(1-x)ZnxS nanoparticles. Cd0.77Zn0.23S showed almost high photocatalytic activity for HER with 1927 mu mol g(-1) h(-1) hydrogen evolution rate without using noble co-catalyst such as platinum. This good photocatalytic activity was believed to be due to the nanostep surface structure Cd0.77Zn0.23S which led the separation of the reduction and oxidation reaction sites and inhibited the recombination of the generated electrons and holes. Observation of considerably high photocurrent and open circuit potentials and changes in the electrochemical impedance spectroscopy responses supported the photocatalytic activity of the Cd0.77Zn0.23S particles. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only Metal chalcogenide based photocatalysts decorated with heteroatom doped reduced graphene oxide for photocatalytic and photoelectrochemical hydrogen production(PERGAMON-ELSEVIER SCIENCE LTD, 2019) ÖZKAYA, ALİ RIZA; Akyuz, Duygu; Ayaz, Rana Muhammad Zunain; Yilmaz, Seda; Uguz, Ozlem; Sarioglu, Cevat; Karaca, Fatma; Ozkaya, Ali Riza; Koca, AtifHeteroatom (N, B and P) doped reduced graphene oxide (RGO)-metal chalcogenide nanocomposites (RGO-Cd0.60Zn0.40S) were prepared by the solvothermal method, and then they were characterized with X-ray diffraction, Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV-Vis diffuse reflectance spectroscopy and photoluminescence techniques. Doping of RGO with heteroatoms of N, B and P increased charge-transfer capability of nanocomposites and thus, improved both photocatalytic and photoelectrochemical hydrogen production activities of them. N-doped RGO-Cd0.60Zn0.40S photocatalyst exhibited the highest photocatalytic hydrogen production rate (1114 mu molh(-1) g(-1)) in photocatalytic (PC) system amongst other and it was 1.5 times higher than that of RGO-Cd0.60Zn0.40S photocatalyst. Having a current density of 0.92 mAcm(-2), photoelectrochemical hydrogen production activity of N-RGO-Cd0.60Zn0.40S electrode was found to be 3 times higher than RGO-Cd0.60Zn0.40S photoelectrode without any applied bias potential under visible light irradiation in photoelectrochemical system. In general, these results clearly showed that heteroatom doping of RGO led to promising materials for renewable hydrogen production in the photocatalytic and photoelectrochemical systems. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.