Person: PEKSÖZ, AHMET
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PEKSÖZ
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AHMET
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Publication Copper-electroplating of biodegradable pcl nanofiber mats(E.u. Printing And Publishing House, 2023-01-01) Tezel, Serkan; TEZEL, SERKAN; Gebizli, Şebnem Düzyer; DÜZYER GEBİZLİ, ŞEBNEM; Jadouh, Ahd; KORAL KOÇ, SERPİL; Peksöz, Ahmet; PEKSÖZ, AHMET; Mühendislik Fakültesi; Tekstil Mühendisliği Bölümü; 0000-0003-3737-5896; 0000-0002-0739-8256; C-5123-2013; AFZ-8325-2022; AFO-0698-2022In this study, biodegradable polycaprolactone (PCL) nanofibers were copper (Cu) electroplated in a more environmentally friendly bath compared to conventional electroplating baths. The Cu-plating mechanism and determination of the optimum parameters for the production of Cu-plated PCL nanofiber mats were explained. PCL nanofibers were produced on metal frames by electrospinning. Cu-electroplating needs a conductive surface. To provide this, a gold/palladium (Au/Pd) mixing was sputtered on the PCL samples with different sputtering thicknesses (1-5-10-15 and 20 nm). After determining the minimum sputtering thickness as 5 nm, the samples were Cu-plated for 1, 3, 5, and 30 minutes in a citric acid electroplating bath. The surface properties of the samples were evaluated after Au/Pd sputtering and electroplating, respectively. Elemental analyses, mapping, and electrical characterizations were also performed after electroplating. After Au/Pd sputtering, the SEM images showed that randomly aligned nanofibers with an average diameter of 223 nm were produced. After electroplating, the average nanofiber diameters increased up to 444 nm. It was seen that the coating grew along the surface of the single nanofibers indicating a smooth Cu coating. While elemental analyses presented a Cu content of 79.77%, electrical characterizations gave a sheet resistance value of 5.98 m Omega/sq for the samples Cu-plated for 30 minutes, indicating a highly conductive structure. Every step of the study is described in detail to provide insight for further studies.Publication Electrochemically fabrication of a composite electrode based on tungsten oxide and cobalt on 3d ni foam for high and stable electrochemical energy storage(Elsevier, 2022-08-30) Killi, Halime; Tokgöz, Seyit Rıza; Çarpan, Mürüvvet Arslan; PEKSÖZ, AHMET; TOKGÖZ, SEYİT RIZA; Fen Edebiyat Fakültesi; Fizik Bölümü; GYU-7137-2022; IXW-9711-2023; HRA-2244-2023The present work reports new findings on the electrical energy storage capabilities of WO3/Ni and Co@WO3/Ni electrodes produced via galvanostatic electrochemical deposition. The paper also describes a novel process for cleaning Ni foam, which has significant effect on the electrode's charge accumulation properties. Electro-chemical measurements in an aqueous solution are performed to compare the supercapacitive behavior of the WO3/Ni foam and Co@WO3/Ni foam. The specific capacitance of the former electrode increases from 492.8 to 977.4 F g-1 because of Co adding into tungsten oxide. Furthermore, the former has 42.5% capacitance retention after 7000 charge-discharge cycles, while the latter has 83.7% owing to the Co loading. The specific energies are respectively calculated to be 64.27 Wh kg-1 and 64.44 Wh kg- 1 for the pure WO3/Ni and Co@WO3/Ni elec-trodes. The specific powers are 3761.49 W kg- 1 and 3303.90 W kg- 1 for the former and latter electrodes. Ac-cording to the findings, adding Co to the pure WO3/Ni electrode increases its electrochemical and supercapacitor capabilities, allowing it to be used in energy storage devices.Publication Electrochemically characterized energy storage properties of Ni foam/poly (EGDMA-Co-VPCA)/SWCNT composite electrode produced by surface polimerization method(Elsevier, 2021-05-21) Yıldırım, Hasan; Tokgöz, Seyit Rıza; Peksöz, Ahmet; Kara, Ali; Yıldırım, Hasan; TOKGÖZ, SEYİT RIZA; PEKSÖZ, AHMET; KARA, ALİ; Fen Edebiyat Fakültesi; Fizik Bölümü; 0000-0001-6552-1112; 0000-0003-4050-4222; 0000-0001-9135-1508; 0000-0003-2457-6314; AHB-9353-2022; HRA-2244-2023; IXW-9711-2023; A-8113-2016Poly (EGDMA-co-VPCA)/SWCNT composite film is successfully synthesized on Ni foam substrate by surface polymerization technique. Energy storage properties of Ni foam/poly (EGDMA-co-VPCA)/ SWCNT composite electrode are investigated via cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The as-prepared Ni foam/poly (EGDMA-co-VPCA)/ SWCNT composite electrode exhibits high specific capacitance of 100 F/g at 5 A/g, high power density of 3285.0 W/kg at 8.5 Wh/kg energy density, capacitive retention of 77.7% after 5000 charge-discharge cycles and excellent chemical stability.Publication Fabrication of a new rgo@ppy/ss composite electrode with high energy storage and long cycling life for potential applications in supercapacitors(Elsevier, 2022-10-01) Koşukoğlu, Tülin; Tokgöz, Seyit Riza; TOKGÖZ, SEYİT RIZA; Çarpan, Mürüvvet; Peksöz, Ahmet; PEKSÖZ, AHMET; Fen Edebiyat Fakültesi; Psikoloji Bölümü; HRA-2244-2023; GYU-7137-2022; IXW-9711-2023Electrochemical synthesized PPy/SS and rGO@PPy/SS electrodes are individually characterized from the point of their morphological and structural properties by the SEM, EDX and FTIR techniques. Electrochemical measurements, for instance, CV, EIS, and MS are performed to obtain the supercapacitive behaviour of the electrodes in an aqueous solution of 0.1 M KOH. All the morphological and structural studies confirm the molecular occurrence of PPy and rGO@PPy, and the homogenous distribution of the material onto the SS substrate. The specific capacitances of the electrodes show up as 104.22 F g-1 and 122.53 F g-1 respectively for PPy/SS and rGO@PPy/SS at 10 mV s-1 scan rate. The energy density of rGO@PPy/SS is 212.5 Wh kg- 1 at the current density of 6 A g-1 while the energy density of PPy/SS is 116.66 Wh kg- 1 at the same scan rate. This considerable increase is also shown for the power densities of the electrodes as from 4516.12 W kg- 1 to 6219.51 W kg- 1 at 6 A g-1 by insertion of rGO into PPy/SS. Likewise, with this insertion, an impressive improvement in the cyclic stability of the electrode is seen from 59.5% to 97.6%. In the light of these results, rGO@PPy/SS is considered an extremely promising material for supercapacitor investigations.Publication Intermolecular magnetic spin-spin interactions in solution state at 1.53 mT(Taylor, 2015-01-01) Yıldız, Fevkani; Şahin, Özkan; Peksöz, Ahmet; Yıldız, Fevkani; ŞAHİN, ÖZKAN; PEKSÖZ, AHMET; Fen Edebiyat Fakültesi; Fizik Bölümü; KQV-0698-2024; AAH-6445-2021; AAG-9772-2021; I-9715-2017Overhauser dynamic nuclear polarization (DNP) technique can provide a dramatic increase in the signal obtained from nuclear magnetic resonance experiments owing to the magnetic spin-spin interactions between H-1 nuclei of the solvent and electrons delocalized on the asphaltene in crude petroleum or asphalt. Studies on H-1 Overhauser DNP enhancements at 1.53 mT are reported for benzene solvent medium with three different radical sources: Iran crude petroleum, MC30 liquid asphalt, and MC800 liquid asphalt for a range of radical concentrations. The results show that protons of benzene are good detectors for dipolar coupling.Publication Electrodeposition of In:CdSe precursor thin films in aqueous electrolytes including different selenous acid concentrations as Se source(Elsevier, 2019-08-01) Degdaş, G.; Peksöz, A.; Degdaş, G.; PEKSÖZ, AHMET; Fen Edebiyat Fakültesi; Fizik Bölümü; AAG-9772-2021; ERW-8810-2022In:CdSe precursor thin films were electrochemically grown on indium fin oxide (ITO) coated glass substrates at a constant potential of -0.95 V vs. Ag/AgCl reference electrode. Deposition solutions were composed of 10 mM CdCl2, 10 mM InCl3, 5-10 mM H2SeO3 as precursors, and 200 mM LiCl. The concentration of Se source (H2SeO3) was increased from 5 mM to 35 mM by a step of 5 mM. HCl was used for pH adjustment of the electrolytes. The uniform thin films are characterized by SEM-EDX, XRD, UV-VIS and Hall-Effect measurements. SEM studies show that the surface formations of In:CdSe deposits change depending on the Se content. For all deposits, XRD analyses confirm the formation of CdIn2S4 with a tetragonal crystalline phase. Energy band gap of the films is calculated from Tauc equation using UV-VIS absorbance spectra. Energy band gaps are found to be between 1.98 eV and 2.23 eV. Hall-Effect measurements show all deposits exhibit n-type semiconductor character. The donor density changes between -1.3 x 10(17) cm(-3) and -4.1 x 10(18)cm(-3). The conductivity of the In:CdSe thin films decreases from 73.2 (Omega cm)(-1) to 24.2 (Omega cm)(-1) as the Se atomic percentage in the film increases. The mobility of the films increases with the increasing of Se atomic percentage.The reason of the increasing in mobility is most probably due to the decreasing in the donor concentration depending on Se percentage.Publication Dynamic nuclear polarization in suspensions consisting of pure and mixed chlorobenzene and pyridine and asphaltene extracted from asphalt cement with penetration grad 60(Taylor & Francis Inc, 2008-06-01) Ersözlü, Nihal Uran; Peksöz, Ahmet; Ovalıoğlu, Hüseyin; Kırımlı, Handan Engin; Çimenoğlu, M. Akif; Yalcıner, Aytaç; Ersözlü, Nihal Uran; PEKSÖZ, AHMET; OVALIOĞLU, HÜSEYİN; ENGİN KIRIMLI, HANDAN; Yalcıner, Aytaç; Fen Edebiyat Fakültesi; Fizik Bölümü; AAG-9772-2021; CNW-0707-2022; FEJ-0053-2022; ESV-4962-2022; JMG-7111-2023The Overhauser effect type dynamic nuclear polarization experiments were performed to study suspensions of asphaltene in pure and mixed chlorobenzene and pyridine at a low magnetic field of 1.44 mT and in four different temperatures (-10, 7, 23, and 38 degrees C). The asphaltene was extracted from asphalt cement with penetration grad 60. Intermolecular spin-spin interactions occur between nuclear spins of hydrogen in the suspending fluid medium and the impaired electron spins in the asphaltene micelles. The electron paramagnetic resonance spectrum of the asphaltene was obtained and the saturation experiments were applied to the samples prepared in vacuum. For all suspending fluid media used in this work, the dipole-dipole interaction is predominant due to the negative signal enhancements. In all temperatures, the dipolar part is the smallest (-9.17) for pure pyridine solvent medium at -10 degrees C and the highest (-38.2) for pure chlorobenzene solvent medium at 38 degrees C and between these two limits for mixed solvent media at all temperatures.Publication Energy storage and semiconducting properties of polyaniline/graphene oxide hybrid electrodes synthesized by one-pot electrochemical method(Elsevier, 2021-07-06) Tokgoz, Seyit Rıza; Firat, Yunus Emre; Akkurt, N.; Pat, S.; Peksoz, Ahmet; TOKGÖZ, SEYİT RIZA; Firat, Yunus Emre; PEKSÖZ, AHMET; Fen Edebiyat Fakültesi; Fizik Bölümü; 0000-0003-0510-6640; 0000-0001-9135-1508; IXW-9711-2023; AAK-5283-2021; HRA-2244-2023; AAG-9772-2021Polyaniline/graphene oxide composites are produced by the one-pot electrochemical deposition method and are used as an electrode for supercapacitor energy storage. The electrochemical tests related to the energy storage performance of the PANI/GO electrodes at different mass loading of GO are successfully studied. The biggest specific capacitance for all of the electrodes is observed at a specific current of 0.3 A g(-1). Pure PANI electrode has a specific capacitance of 158.0 F g(-1), a specific energy of 18.2 W h kg(-1), and a corresponding specific power of 118.8 W kg(-1). After the loading of graphene oxide into PANI, the best specific capacitance measured at a current density of 0.3 A g(-1) is 295.9 F g(-1), and the corresponding specific energy and specific power are 34.0 Wh kg(-1) and 126.9 W kg(-1), respectively. The PANI/GO hybrid materials also exhibit a remarkably cycling stability with a capacitance retention range of 62.3%-83.7% after 5000 charge-discharge cycles. Charge transfer resistance of the PANI electrode desreases as GO loading increases. This means that electroactive surface area of the electrode increases due to the addition of GO into PANI. The enhancement in energy storage capability is supported by the increase in electroactive surface area. The high energy storage performance and easy production of PANI/GO materials make them promising electrodes for supercapacitor devices.Publication Electrochemically growth and characterization of CuInTe₂ chalcopyrite thin films(Springer, 2020-07-28) Keser, Gökhan; Peksöz, Ahmet; Keser, Gökhan; PEKSÖZ, AHMET; Fen Edebiyat Fakültesi; Fizik Bölümü; Güneş Pili Laboratuvarı; 0000-0003-2382-6027; AAG-9772-2021; FZX-9393-2022Copper indium tellurite (CIT) chalcopyrite compounds were electrochemically grown from an aqueous electrolyte including water-soluble Cu, In, and Te molecular sources onto indium thin oxide-coated glass substrates. CuSO4 center dot 5H(2)O, InCl3, and Na2TeO3 were used as copper, indium, and tellurium sources, respectively. Deposition mechanisms of the CIT thin films are explained by cyclic voltammetry (CV) studies. It is also noted that the effect of deposition potential on the electrical, optical, and structural facilities of the electrodeposited CIT thin films. Energy bandgap of the electrodeposited CIT films is in the range of 0.97-1.83 eV. Stoichiometry of the CIT films deposited at - 0.5, - 0.6, - 0.7, and - 0.8 V is near to CuInTe2. We report that the produced CIT films is polycrystalline nature, and CuInTe(2)is a major chalcopyrite phase corresponding to (1 1 2), (2 0 4), and (1 1 6) directions at 2 theta similar to 25 degrees, 41 degrees, and 49 degrees, respectively. Hall-effect measurements show that the produced CIT thin films have p-type semiconducting conductivity with the acceptor concentration range of 2.8 x 10(17) and 2.8 x 10(18) cm(-3). The variation of the mobility within 20.4-60.2 cm(2)/V s can be explained by the variation of Cu/In ratio within 2.19-0.59. The resistivity of the films is found to vary within 0.011-0.036 Omega cm, which is in good agreement with the literature data.Publication The sensitive control of semiconductor properties of non-vacuum and electrochemically synthesized cdte thin films(Springer, 2019-05-01) Demiriz, T. M.; Peksöz, Ahmet; Demiriz, T. M.; PEKSÖZ, AHMET; Fen Edebiyat Fakültesi; Fizik Bölümü; Güneş Pili Laboratuvarı; AAG-9772-2021; CPA-7462-2022CdTe thin films are deposited on indium tin oxide (ITO) coated glass substrates by co-electrochemical deposition method. CdTe films are deposited at six different deposition potentials such as -0.4, -0.5, -0.6, -0.7, -0.8 and -0.9V versus Ag/AgCl reference electrode. Deposition time is kept constant for 2min. Deposition electrolyte includes aqueous solutions of 10mM CdCl2, 20mM Na2TeO3 as precursors, and 200mM LiCl. HCl is used for pH adjustment of the electrolyte. The effect of deposition potential on the characteristics of CdTe thin films is investigated by means of some techniques such as scanning electron microscopy (SEM), energy dispersive X-rays analysis (EDX), X-ray diffraction (XRD), Ultraviolet-Visible (UV-Vis) spectroscopy, Mott-Schottky measurements, and electrochemical impedance spectroscopy (EIS). Deposition potential dependency of the film surfaces is seen to be high from the SEM studies. EDX results show that Cd/Te ratios vary between 0.81 and 1.09. XRD analyses show that the films include hexagonal phase of CdTe and Cd1.81Te, and monoclinic phase of CdTe2O5. The optical band gaps (E-g) of all the films are derived from Tauc's relation using absorbance data. E-g values change between 1.54 and 1.92eV depending on the deposition voltage. Donor density of the n-type CdTe thin films deposited in the potential range between -0.4 and -0.8V changes between 10(17) and 10(19)cm(-3), while acceptor density is 10(20)cm(-3) for only one p-type CdTe thin film with a deposition potential of -0.9V. Electronic energy band structure of the synthesized CdTe thin films are also studied in detail. From the equivalent electronic circuit fitted to the EIS data, electronic charge transfer in the CdTe/electrolyte system is determined to be the biggest for the CdTe film deposited at -0.5V.