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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 Development of ti-based materials for li-ion and na-ion batteries(İnönü Üniversitesi, 2017) Demirel, SerkanBu doktora tez projesinde, Vanadyum katkılaması ile Li-iyon ve Na-iyon piller için Titanyum bazlı anot malzemeleri incelenmiştir. Bu kapsamda, Li4Ti5-xVxO12, Li2Ti3- xVxO7, Li2Ti6-xVxO13, Na4Ti5-xVxO12, Na2Ti3-xVxO7 ve Na2Ti6-xVxO13 x=(0, 0.025, 0.05, 0.1, 0.15) anot malzemeleri katı-hal reaksiyon ve iyon-değişim yöntemleri ile başarılı bir şekilde üretilmiştir. Anot malzemelerin yapısal özellikleri ve pil performansları detaylı bir şekilde incelenmiştir. XRD sonuçları, düşük seviyelerde V değiştirmesi ile ana fazların korunduğunu göstermiştir. Buna ek olarak Na-bazli malzemelerde nano-tel oluşumu gözlemlenmiştir. Raman spektrum analizleri, 1000 döngü sonrasında pillerin anot malzemelerinin bağ yapılarında deformasyon olduğunu göstermiştir. Sonuç olarak, Li4Ti5O12, Li2Ti3O7 ve Na4Ti5O12 anot malzemeleri ile üretilen pillerde, sistemlere yapılan düşük V katkılamaları ile pil ömrü ve pil kapasitelerinde artış sağlanmıştır.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 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 Kızıl ötesi sensörlerin sağlık alanındaki uygulamaları(2016) Demirel, Serkan; Altın, EmineKızılötesi sensör teknolojisi son yıllarda hızlı bir şekilde gelişip güncel hayatımızın farklı alanlarında kullanılmaya başlanmıştır. Özellikle algılama dalga boyu ve hassasiyetine bağlı olarak farklı sensor türleri geliştirilerek teknolojide yerini almaya başlamıştır. Kullanılan malzeme ve üretim tekniklerine bağlı olarak bu tip sensorler farklı isimlerle anılmaktadırlar. Kızılötesi sensör teknolojisi savunma sanayi,enerji sektörü özellikle sağlık alanında uygulamalara sahiptir. Kızılötesi sensörler kullanılarak geliştirilen görüntüleme sistemleri ile insan vücudunda lokal meydana gelen ısısal değişimler tespit edilerek tümör veya kanser gibi hastalıklı bölgelerin teşhis edilmesinin mümkün olduğu görülmektedir. Özellikle bu tür hastalıkların öntanısının yapılmasında kızılötesi sensörlerin kullanımının en önemli avantajlarından birisi ise zararlı bir ışın içermemesi olarak görülebilir.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 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 Sb ve B katkılı Ca3Co4O9 bileşiğinin termoelektrik özelliklerinin incelenmesi(İnönü Üniversitesi, 2013) Demirel, SerkanBu tezde katıhal reaksiyon yöntemi ile üretilen Ca3Co4O9 malzemesinin termoelektrik ve manyetik özellikleri çalışıldı. Ca yerine Sb ve B elementlerinin Ca3Co4O9 malzemesinin ZT katsayısı üzerine etkileri incelendi. Üretilen malzemelerin mikroyapısal, manyetik ve termoelektrik özellikleri incelenerek termoelektrik performansları karakterize edildi. Sb katkılaması örneklerin termoelektrik özelliklerinde düşüşe neden olmuştur. B katkılamasında katkılama düzeyine bağlı olarak farklı termoelektrik davranışlar görülmüştür. B x=0.5 katkılaması ile termoelektrik performansta artma görülmüştür. ZT katsayısı katkılı olmayan örnekleregöre 3.5 kat daha yüksek elde edilmiştir. Oda sıcaklığında ZT katsayısının 25x10-4 olduğu bulunmuştur. Katkılama elementine ve miktarına bağlı olarak örneklerde 19 K civarında paramanyetik-ferrimanyetik faz geçişi gözlenmiştir.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.
