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Öğe Cationic versus anionic Pt complex: The performance analysis of a hybrid-capacitor, DFT calculation and electrochemical properties(Pergamon-Elsevier Science Ltd, 2019) Akkoc, Mitat; Demirel, Serkan; Oz, Erdinc; Altin, Serdar; Bayri, Ali; Dorcet, Vincent; Roisnel, ThierryThe synthesis and characterization of cationic versus anionic platinum(II) complex of the type [PtCl3(DMSO)](-)[NHC](+) (NHC: N-heterocyclic carbene) is reported for the first time. The complex 3 was synthesized from silver(I)-NHC2, and K-2[PtCl4] in DMSO at 80 degrees C under exclusion of light. The ionic platinum(II) complex was obtained in high yield and fully characterized by H-1, C-13, Pt-195 NMR and HRMS spectroscopy, X-ray diffraction and elemental analysis. The structural properties of the complex were investigated by using Gaussian suit and the obtained parameters were crosschecked with the X-ray data. The HOMO-LUMO energies and electrostatic surface mapping of the complex were calculated and the results were discussed with the capacitive properties of the complex. Electrochemical analysis by cyclic voltammetry (CV) of the complex shows reversible redox peaks about platinum center. The complex was used as an electrode material for the capacitor device and result is promising that the highest performance of complex 3 was found as 10.22 F/g. (C) 2018 Elsevier Ltd. All rights reserved.Öğe High-performance Na-ion full-cells with P2-type Na0.67Mn0.5-xNixFe0.43Al0.07O2 cathodes: Cost analysis for stationary battery storage systems(Elsevier, 2024) Kalyoncuoglu, Burcu; Ozgul, Metin; Altundag, Sebahat; Bulut, Fatih; Oz, Erdinc; Sahinbay, Sevda; Altin, SerdarNa -ion batteries are viable alternatives to Li-ion batteries especially for stationary applications. Developing suitable electrode materials, half-cell and full-cell studies and cost analysis are major steps and challenges for their commercialization. In this study, we report the synthesis of a promising cathode material, Na0.67Mn0.5- xNixFe0.43Al0.07O2 (x = 0.02-0.10 with Delta x = 0.02), using a modified solid-state synthesis technique. The materials were heated at high temperature for 6 h in air and quenched in liquid N-2. We determined the solubility limit of Ni in Na0.67Mn0.5Fe0.43Al0.07O2 as x <= 0.06. The interlayer separation increases with increasing Ni content due to the ionic radii difference between Mn and Ni. X-ray photoelectron spectroscopy (XPS) measurements evidence the valance state of Ni in the x = 0.06 sample as 2+ and 3+. Cyclic voltammetry (CV) analysis of the half-cells were performed at 10 C-degrees, room temperature, and 50 degrees C to observe the effect of environmental temperature on redox mechanism. The highest half-cell capacity of the cells was determined as 181 mAh/g for x = 0.06 at C/3-rate. Artificial solid electrolyte interface (SEI) formation was performed on the hard carbon anode by presodiation technique and the full-cells of Na0.67Mn0.44Ni0.06- Fe0.43Al0.07O2/hard carbon were assembled in CR2032 coin cells. The capacity values of the cells at C/2, C, and 2C-rate were determined as 131.4 mAh/g, 116 mAh/g and 100.8 mAh/g for the 1 cycle and 33 mAh/g, 40.6 mAh/g and 49.9 mAh/g for the 500th cycle, respectively. The cost analysis for the commercial package for stationary energy storage system was performed by BatPac program and results are discussed.Öğe Investigation of hybrid-capacitor properties of ruthenium complexes(Wiley-Hindawi, 2019) Altin, Serdar; Oz, Erdinc; Altundag, Sebahat; Bayri, Ali; Roisnel, Thierty; Dorcet, Vincent; Bruneau, ChristianRu complexes were successfully produced, and their structural properties were investigated using FTIR, Raman, and single crystal XRD patterns. The HOMO, LUMO, Eg, and electronic surface potential (ESP) values of the molecules were calculated by a Gaussian program. The complexes were used for producing hybrid capacitor cells as electrode materials. According to electrochemical analysis, complex 2 showed the best CV graph between -1 V and +1 V and had the highest current value and hysteresis area when compared with the other complexes. The performance analysis and the capacity fade of the cells were investigated. The first capacity values of the complexes were 57.5, 22.1, 16.9, and 0.0021 F/g for complexes 1, 2, 3, and 4, respectively. The capacitive mechanism of the cells as relates to molecular interactions was also investigated. We suggested that the ESP values of the molecules were directly related to the capacitive performance of the cells. In addition to this, the best cycling performance was obtained for complex 2, which has the lowest Eg value among the complexes. We speculate that the charged regions on the complex materials have a crucial role in the increasing the capacitance of the cells.Öğe Investigation of physical and electrochemical properties of Ni-doped Tunnel/P2 hybrid Na0.44MnO2 cathode material for sodium-ion batteries(Academic Press Inc Elsevier Science, 2023) Oz, Erdinc; Altin, Serdar; Avci, SevdaThe increasing demand for energy in recent years has accelerated the efforts to increase the efficiency of energy storage systems. Although lithium-ion batteries are very popular in energy storage systems, the dramatic increase in costs due to the decrease in lithium resources has greatly increased the interest in sodium-ion batteries. Na0.44MnO2 has recently received increasing attention due to the fact that the tunnel structures in the crystal structure are suitable for the diffusion of Na ions. However, rapid structural degradation is an important problem that must be overcome to move into practical applications. In this study, the tunnel/P2 hybrid type Na0.44MnO2 was synthesized by a one-step heat treatment with the Ni substitution to Mn sites for improving cyclic perfor-mance. It was demonstrated by various physical analyses, that biphasic hybrid material starts forming with Ni substitution, and Ni occupied the Mn sites in the P2 phase. Electrochemical measurements provide that after 100 cycles at 0.3C, while Na0.44MnO2 has 77% capacity retention, 1% and 5% Ni substituted samples have 86.4% and 77.3%, respectively. The results show that tunnel-P2 hybrid cathode materials can be developed for practical applications in sodium-ion batteries.Öğe Investigation of potential hybrid capacitor property of chelated N-Heterocyclic carbene Ruthenium(II) complex(Elsevier Science Sa, 2018) Akkoc, Mitat; Oz, Erdinc; Demirel, Serkan; Dorcet, Vincent; Roisnel, Thierry; Bayri, Ali; Bruneau, ChristianThe synthesis of chelated ruthenium(II) complex type Ru(eta(6)-HMB) (NHC) Cl (NHC = N-heterocyclic carbene, HMB = hexamethylbenzene) is presented. The ruthenium(II)-NHC complex 6 was obtained in good yield and was fully characterised by NMR spectroscopy, X-ray diffraction and HRMS analysis. Electrochemical analysis by cyclic voltammetry (CV) revealed reversible redox behaviour at the ruthenium centre in 6. DFT studies and the catalytic activity of complex 6 on transfer hydrogenation reaction of aryl ketones are also presented. The potential hybrid capacitor applications of Ru-NHC complex is discussed and reported firstly in the literature. It was found that the highest performance was found at 20.1 F/g, which is a promising result for energy storage applications. (c) 2018 Elsevier B.V. All rights reserved.Öğe Investigation of Ti-substitution effects on structural and electrochemical properties of Na0.67Mn0.5Fe0.5O2batterycells(Wiley-Hindawi, 2020) Altin, Serdar; Altundag, Sebahat; Altin, Emine; Oz, Erdinc; Harfouche, Messaoud; Bayri, AliTi-substituted Na(0.67)Mn(0.5)Fe(0.5)O(2)powders were fabricated by quenching at high temperatures, and the structural properties were investigated by Fourier transform infrared (FTIR), Scanning Electron Microscope (SEM), X-ray powder diffraction (XRD), and X-ray absorption spectroscopy (XAS) measurements. According to XRD analysis, it was not observed any impurity phases and it was found that the lattice constants of the powders were slightly increased by Ti content. The change in the valence state of both Mn and Fe ions was investigated by X-ray absorption near edge structure (XANES), and it was found that Ti-substitution caused a decrease in the valance state of Fe in Na0.67Mn0.5Fe0.5O2. Fourier transform (FT) of XANES showed that the local structure around the metal ions changed with the addition of Ti ions. The cycling voltammetry (CV) graphs of Ti-substituted cells were almost the same as the pure sample, which may not change the cycling mechanism in the cells. According to galvanostatic cycling measurements at room temperature, the best performance was obtained with Ti-substitution of 0.06 to 0.09 in the structure. The effect of environmental temperature in the battery cells was investigated at 10 degrees C to 50 degrees C, and it was found that the battery performance depends on the environmental temperatures.Öğe Investigations of the capacity fading mechanism of Na0.44MnO2via ex situ XAS and magnetization measurements(Royal Soc Chemistry, 2018) Altin, Serdar; Oz, Erdinc; Altin, Emine; Demirel, Serkan; Bayri, Ali; Avci, SevdaNa-ion batteries represent a promising complementary alternative to Li-ion batteries due to their high energy density and natural abundancy of Na. However, these batteries have short cycle life and extensive research activities on these batteries are required to understand the mechanism of such drawbacks. In this report, we investigate the capacity fading mechanism of Na(0.44)MnO(2)via ex situ X-ray diffraction, X-ray absorption spectroscopy, Fourier transform infrared spectroscopy and magnetization measurements. Our results show that the unit cell volume, the effective mass of Mn-O bonds, the number of Mn4+ ions and the effective magnetic moment decrease upon repeated cycling. We propose that some Mn4+ ions in the octahedral environment become Mn3+ ions in a square pyramidal environment, causing oxygen release upon cycling. Any free oxygen in the battery is expected to react with the electrolyte and cause capacity fade.Öğe The leakage study between restorative and pulp capping materials and diffusion analysis by Fick laws(Biointerface Research Applied Chemistry, 2016) Kamalak, Hakan; Demirel, Serkan; Oz, Erdinc; Altin, SerdarThe investigation of adhesion behaviour of restorative and pulp Capping Materials in dental treatment is an important subject for the development of new maerials and prevent unwanted conditions such as secondary carriers prevelance and pain due to the leakage. The aim of the study is the development of new methods for leakage studies between the restorative and pulp capping materials. The micro-CT experiment was supported by the obtained mechanism by using Fick diffusion laws for leakage. It is found that the X-ray micro tomography analysis should be supported by the other techniques like electron microscopy and energy dispersive X-ray spectroscopy. Diffusion mechanism calculations have been identified by EDX analysis and it is found that there are two different diffusion mechanisms in the interface region between the pulp capping and the restorative materials. So the suffer duration after dental treatment is strongly dependent on the strong of inner part of the interface region.Öğe Magnetic and thermoelectric properties of B-substituted NaCoO2(Springer Heidelberg, 2015) Altin, Emine; Oz, Erdinc; Demirel, Serkan; Bayri, AliWe report the structural, electrical, thermal and magnetic properties of NaCo1-xBxO2 from 300 K down to 5 K. XRD analysis shows that B ions successfully incorporate in the crystal structure for x < 0.25. The resistivity of the samples increases with increasing B content and the transport mechanism change for x = 0.5. The highest thermopower value is obtained for x = 0.5 sample, and the thermoelectric behavior at low temperature is explained by Mott approximation. The experimentally obtained thermal conductivity data are analyzed by this model including the carrier thermal term, kappa(c), and the lattice thermal conductivity term, kappa(L). We found that phonon-phonon interaction and point defect contribution to kappa are affected by the B content and the temperature. The Co valance states are analyzed by Heike formula, and the effective magnetic moment is determined by these values. The chi-T curves of the samples are fitted by Curie-Weiss law, and the obtained mu(eff) values match well with the theoretically calculated values (0.9 mu(B)/Co). We observed a strong correlation between magnetic properties and thermopower.Öğe Magnetic Properties and Environmental Temperature Effects on Battery Performance of Na0.67Mn0.5Fe0.5O2(Wiley-V C H Verlag Gmbh, 2021) Altin, Serdar; Bayri, Ali; Altin, Emine; Oz, Erdinc; Yasar, Sedat; Altundag, Sebahat; Harfouche, MessaoudHerein, a modified solid state synthesis of Na0.67Mn0.5Fe0.5O2 and the results of a detailed investigation of the structural and magnetic properties via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis are reported. The magnetic properties of Na0.67Mn0.5Fe0.5O2 do not fit the Curie-Weiss law and a model regarding the spin configuration of the Mn and Fe ions and a possible ferrimagnetic order is suggested. Electrochemical measurements and ex situ structural analysis of the cathode material confirm the reversible structural transitions for the cells charged up to 4.0 V. Environmental temperature-dependent electrochemical measurements reveal a strong temperature dependence of both, the initial capacity and the capacity retention. Ex situ SEM, FTIR, and XRD studies on the battery membrane verify the formation of a Na2CO3 phase on the membrane, which blocks the Na ion diffusion through membrane pores and is responsible for the capacity fade for this compound.Öğe The mechanical and heat conducting properties of dental composites(Biointerface Research Applied Chemistry, 2016) Kamalak, Hakan; Oz, Erdinc; Demirel, Serkan; Altin, SerdarIn this study, it was studied the microstructural, mechanical and heat conducting properties of Ca added and un-added commercial light-cure restorative composite resins, in detail. The main goal of the study is the investigation of the mechanical strength and the thermal conductivity of the samples by Ca addition which the Ca ions have biocompatible properties. We used 0 %, 3 %, 6 % and 9 % Ca addition in the commercial light-cure restorative composite resin named Cavex Nano, Amaris, Tetrik N Flow, Solitare. The structural properties were analyzed by using XRD, FTIR, SEM, and optical microscope. The mechanical and heat conducting properties of the samples were investigated by micro hardness and thermal conductivity measurement system, respectively. It is found that there are two main structures in the materials; one is the organic content and the other is the crystalline content. We found that the Ca addition causes diffusion in the main matrix or accumulated in the inergranular region of the composite resins depending on the commercial materials. The thermal and mechanical properties showed a strong relation between the composite resin and Ca content. It is concluded that the diffusion of Ca into the main matrix causes an improvement of both the mechanical and thermal conducting properties which can be used in commercial composite resins in the near future.Öğe P2-type Na0.67Mn0.5-xVxFe0.43Ti0.07O2 powders for Na-ion cathodes: Ex-situ structural analysis and full-cell study(Pergamon-Elsevier Science Ltd, 2024) Dogan, Ebru; Altundag, Sebahat; Altin, Emine; Oz, Erdinc; Altin, SerdarThis study used a modified solid-state synthesis technique to synthesize Na0.67Mn0.5-xVxFe0.43Ti0.07O2 (x = 0.02 0.1) cathode materials. The XRD pattern shows that there are no impurity phases in the samples for x <= 0.06. The granular grain formation was observed in each sample and the largest surface area was obtained for x = 0.06 Vdoped composition. According to XPS analysis of the x = 0.06 sample, the V and Ti ions have three different valence states in the structure and the ratio of V3+/V4+/V5+ ions in the powders was calculated as 13 %/36 %/51 % and the spin splitting binding energy gaps were found as 7.1 eV for each V-ions and they affected by cycling process. The redox mechanism of the half cells was investigated at 10 degrees C and room temperature. The diffusion coefficient values of Na+ were calculated by cycling voltammetry (CV) and GITT techniques for the x = 0.06. Although the highest capacity of the half cells for the V-substituted samples was found to be 188.3 mAh/g for x = 0.02 V-doping in the cells for C/3-rate, the best capacity fade among the cells was obtained for x = 0.06 as 36.9 %. The ex-situ analysis of the electrodes after 100 cycles at the environmental temperatures of 10 degrees C, 50 degrees C, and 60 degrees C was investigated and it was found that the valence state of the elements changed by the cycling process. The artificial solid electrolyte interface (SEI) formation on the anode surface was performed by presodiation technique and the full cells were assembled using Na0.67Mn0.44V0.06Fe0.43Ti0.07O2/hard carbon architecture and the obtained first capacity values for C/3-rate were 90.1 mAh/g and 66.6 mAh/g, respectively, and the capacity value decreased with the cycling process up to 60 cycles and then gave a plateau with increasing cycle numbers up to 500 cycles.Öğe Structural and magnetic characterisation of Co substituted Ni2MnSb Heusler alloy: effect of cobalt substitution on magnetism and Curie temperature(Taylor & Francis Ltd, 2021) Oz, Erdinc; Ak, Fermin; Saatci, BuketIn this study, Ni2-xCoxMnSb full-Heusler alloys (1.00 <= x <= 1.75) were prepared by arc melting process, and examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and SQUID. The L2(1)crystal structure of the synthesised Heusler alloy was confirmed by XRD patterns, and it was observed that the use of Co instead of Ni caused a decrease in the interatomic distance. The magnetisation results revealed that all samples show ferromagnetic (FM) behaviour, and substitution Co for Ni leads to increasing FM interactions in the samples. The calculated magnetic moment per formula unit increase from 4.38 mu B(x = 1) to 5.17 mu B (x = 1.75). On the other hand, the increase in FM interaction caused an increase in ferromagnetic-paramagnetic (PM) phase transition (T-C) temperatures from 513 (x = 1) to 568 K (x = 1.75). The ability to control the Curie temperature with Co substitution makes these alloys suitable candidates for future spintronics and magnetoelectronic applications.Öğe Structural, magnetic, electrical, and electrochemical properties of Sr-Co-Ru-O: A hybrid-capacitor application(Wiley, 2018) Altin, Serdar; Bayri, Ali; Demirel, Serkan; Oz, Erdinc; Altin, Emine; Avci, SevdaIn this study, we report the synthesis of SrCo1-xRuxO3- nominal compositions, where x=0.0-1.0, using solid-state reaction technique. XRD analysis confirms the structure of x=0 sample as hexagonal Sr6Co5O15. As the Co ions are substituted by Ru, a two-phase structure (hexagonal R32 and orthorhombic Pbnm) emerges up to x0.5. As the Ru content is increased further, the hexagonal R32 phase disappears completely and an orthorhombic Pbnm phase becomes the main phase. SEM images show that grain size of the samples decreases with increasing Ru content. Temperature-dependent electrical conductivity studies indicate upon Ru substitution in the nominal SrCo1-xRuxO3- compounds, resistivity decreases due to appearance of metallic SrRuO3 phase. The cyclic voltammogram (CV) of the samples show capacitive properties upon Ru substitution. The cycle measurements of the capacitors yield promising results for potential supercapacitor applications.Öğe Thermally Induced Spin State Transition in LiCoO2 and Its Effects on Battery Performance(Pergamon-Elsevier Science Ltd, 2017) Oz, Erdinc; Demirel, Serkan; Altin, Serdar; Altin, Emine; Bayri, Ali; Avci, SevdaLiCoO2 is the most widely used and extensively studied cathode material for Li-ion batteries. The studies based on the improvement of the performance have focused on the structural and electrochemical properties of LiCoO2. However, significantly less attention has been paid to its magnetic properties and their effects on battery performance. For the first time to our knowledge, we report a thermally induced magnetic spin state transition from low spin (LS) to intermediate spin (IS) at similar to 800 K in bulk LiCoO2 via magnetic susceptibility measurements. We quench the LiCoO2 from above the spin state transition temperature (similar to 810 K) into liquid nitrogen to preserve the IS state at room temperature. We use this quenched sample (q-LiCoO2) as an active cathode material. We observe a significant improvement (similar to 15% better capacity retention after 200 cycles at 1C) in cell performance of q-LiCoO2 compared to the ref-LiCoO2 which is used as a reference material. Our results show that it is possible to tailor the magnetic properties and electronic structure of cathode materials to achieve better battery performance. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Tunnel/Layer Composite Na0.44MnO2 Cathode Material with Enhanced Structural Stability via Cobalt Doping for Sodium-Ion Batteries(Amer Chemical Soc, 2023) Oz, Erdinc; Altin, Serdar; Avci, SevdaSodium-ion batteries (SIBs) are the most promising alternativeto lithium-ion batteries (LIBs) due to their low cost and environmentalfriendliness; therefore, enhancing the performance of SIBs'components is crucial. Although most of the studies have focused onsingle-phase cathode electrodes, these materials have difficulty inmeeting the requirements in practice. At this point, composite materialsshow superior performance due to balancing different structures andare offered as an alternative to single-phase cathodes. In this study,we synthesized a Na0.44MnO2/Na0.7MnO2.05 composite material in a single step with cobaltsubstitution. Changes in the crystal structure and the physical andelectrochemical properties of the composite and bare structures werestudied. We report that even if the initial capacity is slightly lower,the rate and cyclic performance of the 1% Co-substituted compositesample (CO10) are superior to the undoped Na0.44MnO2 (NMO) and 5% Co-substituted (CO50) samples after 100 cycles.The results show that with the composite cathode phase transformationsare suppressed, structural degradation is prevented, and better batteryperformance is achieved.Öğe Unveiling the outstanding full-cell performance of P2-type Na0.67(Mn0.44Ni0.06Fe0.43Ti0.07)O2 cathode active material for Na-ion batteries(Elsevier, 2024) Kalyoncuoglu, Burcu; Ozgul, Metin; Altundag, Sebahat; Harfouche, Messaoud; Oz, Erdinc; Avci, Sevda; Ji, XiaoboIn this study, we unravel the effect of Ni doping on the half-cell and full-cell performances of the Na0.67Mn0.5-xNixFe0.43Ti0.07O2 cathode materials where x varies between 0.02 and 0.1. The cyclic voltammetry (CV) analysis of the half-cells is performed at 10 degrees C, room temperature (RT), and 50 degrees C to elucidate the redox reaction mechanisms at different temperatures. Among the studied cathodes, the highest specific capacity is obtained fox = 0.06 which delivered a specific capacity of 186 mAh g-1 at C/3-rate. The full cell of Na0.67Mn0.44Ni0.06-Fe0.43Ti0.07O2/hard carbon couple is assembled in coin cell format and the specific capacity of the cell at C/2, 1C, and 2C rates are found as 153 mAh g- 1, 125 mAh g-1 and 120 mAh g-1, respectively. At the C/2-rate, the excellent capacity retention of the full cell is around 70% after 500 cycles delivering a specific capacity of 103 mAh g- 1. Along with the conventional physicochemical characterization methods such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman and Fourier-transform Infrared Spectroscopies (FTIR), we also utilize X-ray photoelectron spectroscopy (XPS) to bridge the nexus between the performance and the structure properties of the studied materials. Furthermore, we also employ synchrotron-based X-ray Absorption (XAS) to understand the local geometry of the optimized cathode materials in operando.Öğe X-ray Raman spectroscopy of lithium-ion battery electrolyte solutions in a flow cell(Int Union Crystallography, 2018) Ketenoglu, Didem; Spiekermann, Georg; Harder, Manuel; Oz, Erdinc; Koz, Cevriye; Yagci, Mehmet C.; Yilmaz, EdaThe effects of varying LiPF6 salt concentration and the presence of lithium bis(oxalate)borate additive on the electronic structure of commonly used lithium-ion battery electrolyte solvents (ethylene carbonate-dimethyl carbonate and propylene carbonate) have been investigated. X-ray Raman scattering spectroscopy (a non-resonant inelastic X-ray scattering method) was utilized together with a closed-circle flow cell. Carbon and oxygen K-edges provide characteristic information on the electronic structure of the electrolyte solutions, which are sensitive to local chemistry. Higher Li+ ion concentration in the solvent manifests itself as a blue-shift of both the pi* feature in the carbon edge and the carbonyl pi* feature in the oxygen edge. While these oxygen K-edge results agree with previous soft X-ray absorption studies on LiBF4 salt concentration in propylene carbonate, carbon K-edge spectra reveal a shift in energy, which can be explained with differing ionic conductivities of the electrolyte solutions.
