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1
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The Effect of Calcination Temperature on the Electrochemical Performance of ZnO Coated LiMn_2O_4/MWCNT Nanocomposite Cathodes

100%
Akbulut A., Cetinkaya T., Guler M., Akbulut H.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
331-334
EN
In this study, it is aimed to develop LiMn_2O_4/MWCNT nanocomposite cathode materials by using different calcination temperatures (300, 500, 700°C). The aim of using MWCNTs in the active material is to overcome poor conductivity and to increase stability of the electrodes during charging and discharging. The nanocomposites were produced by sol-gel method, which allows producing very fine particle size of LiMn_2O_4. LiMn_2O_4 and LiMn_2O_4/MWCNT were uniformly coated on an Al-foil to obtain 500 μm thicknesses with a specific amount of binder and conducting agent. The surfaces of cathodes were coated with ZnO by using magnetron sputtering PVD with a thickness of 10 nm. Coin-type (CR2016) test cells were assembled, directly using the LiMn_2O_4/MWCNTs and surface coated LiMn_2O_4/MWCNTs as anode and a lithium metal foil as the counter electrode.
2
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Effects of Substrate Temperature on Structural Properties of Tin Oxide Films Produced by Plasma Oxidation after Thermal Evaporation

100%
Alaf M., Guler M., Gultekin D., Akbulut H.
Acta Physica Polonica A
|
2013
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vol. 123
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issue 2
326-329
EN
In this study, tin film was thermally evaporated onto a stainless steel substrate in an argon atmosphere. The tin films were then subjected to a DC plasma oxidation process using an oxygen/argon gas mixture. Three different substrate temperatures (100°C, 150°C, and 200°C) and three different oxygen partial pressures (12.5%, 25%, and 50%) were used to investigate the physical and microstructural properties of the films. The surface properties were studied by scanning electron microscopy, X-ray diffraction, atomic force microscopy and a four-point probe electrical resistivity measurement. The grain size and texture coefficient of the tin oxide films were calculated. Both SnO and SnO_2 films with grain sizes of 13-43 nm were produced, depending on the oxygen partial pressure. SnO films have flower- and flake-like nanostructures, and SnO_2 films have grape-like structures with nanograins. The resistivity values for the SnO_2 phase were found to be as low as 10^{-5} Ω cm and were observed to decrease with increasing substrate temperature.
3
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Sol-Gel Synthesis of Nanocomposite Cu-Li₄Ti₅O_{12} Structures for Ultrahigh Rate Li-Ion Batteries

100%
Erdas A., Ozcan S., Guler M., Akbulut H.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 4
1026-1028
EN
In this study, spinel Li₄Ti₅O_{12} materials were successfully synthesized by a simple and facile sol-gel process and electroless copper deposition techniques. The characteristics of the as-prepared Li₄Ti₅O_{12} and Cu-Li₄Ti₅O_{12} were examined by X-ray diffraction and scanning electronic microscopy, while the electrochemical performances including charge/discharge and rate performance tests were also investigated. Cu-Li₄Ti₅O_{12} electrode demonstrated the superior initial discharge capacity and rate capability to Li₄Ti₅O_{12} electrode, cycled between 1.0 and 2.5 V. The enhanced rate capability can be attributed to the higher Li^{+} diffusivity and lower charge-transfer resistance due to the electroless deposition of copper. Moreover, when both electrodes discharged with 80 C state of discharge conditions, the reversible capacities were further increased ım70 mAh g^{-1} with excellent cycling stability and almost no irreversible capability was observed during cycling.
4
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Preparation and Characterisation of Silicon/Carbon Nanotube Composite Electrodes for Li-Ion Battery Systems

88%
Cetinkaya T., Tocoglu U., Cevher O., Guler M., Akbulut H.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 2
398-400
EN
Silicon powders and different amounts of multiwalled carbon nanotube were mechanically alloyed in polyacrynitrile solution via high speed planetary ball milling. Produced composite was characterised via X-ray diffraction pattern, scanning electron microscopy, energy dispersive spectroscopy and thermogravimetric analysis.
5
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Electrochemical Characterization of the Powder Silicon Anodes Reinforced with Graphite Using Planetary Ball Milling

88%
Cetinkaya T., Cevher O., Tocoglu U., Guler M., Akbulut H.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 2
393-395
EN
Mixed silicon/graphite anode materials were produced via mechanical milling process. The morphologies of mixed powders and electrodes were characterized via scanning electron microscopy and X-ray diffraction pattern. Electrochemical tests were performed by coin-type (CR2016) test cells. The cells were cyclically tested on a battery tester, and discharge capacities of produced anode materials were investigated with using constant current 300 mA/g over a voltage range of 80 mV-1.2 V.
6
Content available remote

Synthesis and Characterization of Antimony Doped Tin Oxide Nanocomposites for Li-Ion Batteries

88%
Guler M., Cevher O., Tocoglu U., Cetinkaya T., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
|
issue 2
383-385
EN
High content carbon nanotubes mats have been produced to multi-walled carbon nanotubes. Sb doped SnO_2 films were then deposited by rf magnetron sputtering on buckypapers substrates. The effect of oxidation pressure on the structural, compositional, and electrochemical properties of the films was investigated.
7
Content available remote

Electrochemical Performance of Silicon/MWCNT Composite Electrodes for Lithium Ion Batteries

88%
Cetinkaya T., Tocoglu U., Cevher O., Guler M., Akbulut H.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
285-287
EN
Silicon/MWCNT composite electrodes were produced using high-speed planetary ball milling. Content of MWCNT were altered in silicon/MWCNT composite electrodes and effect of MWCNT content on the electrochemical performance of silicon electrodes were characterized by scanning electron microscopy and X-ray diffraction techniques. Coin type CR2016 test cells were assembled by using produced nanocomposite electrodes. Prepared test cells were electrochemically cycled at a current density of 200 mA/g. Furthermore, cyclic voltammetry curve of composite electrodes were performed to investigate electrochemical reactions between electrode and electrolyte.
8
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Nanocomposite ZnO:MWCNT Thin Films for Li-Ion Batteries Prepared via Reactive Magnetron Sputtering

88%
Guler M., Cetinkaya T., Cevher O., Tocoglu U., Akbulut H.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
319-321
EN
In this study, ZnO/MWCNT buckypaper nanocomposite structures were obtained as an anode electrode material for Li-ion batteries. MWCNT based buckypapers were produced via vacuum filtration techniques and the surfaces of the buckypapers were coated with ZnO in order to increase stability and mechanical integrity during charging and discharging processes. The effect of deposition powers on the battery performance is also investigated.
9
Content available remote

Cyclic Performance Study of Silicon/Carbon Nanotube Composite Anodes Using Electrochemical Impedance Spectroscopy

88%
Tocoglu U., Cevher O., Cetinkaya T., Guler M., Akbulut H.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
290-292
EN
Silicon based carbon nanotube composites were produced and their galvanostatic cycling properties analyzed depended on the electrochemical impedance spectroscopy. Composite anodes were produced via vacuum filtration and DC magnetron sputtering technique. Carbon nanotube papers were produced with vacuum filtration as substrate for silicon deposition and silicon was sputtered onto carbon nanotube papers via DC magnetron sputtering. Scanning electron microscopy and X-ray diffraction analysis were conducted for structural analysis of anodes. CR2016 coin cells were assembled for electrochemical tests. Electrochemical performance of anodes was tested via galvanostatic charge/discharge (100 cycles) analysis. Electrochemical impedance spectroscopy was carried out at every 25 charge/discharge cycle to determine relation between cyclic performance and electrochemical impedance of cells.
10
Content available remote

Characteristics and Electrochemical Performance of TiO_2:MWCNT Nanocomposite Anodes for Li-Ion Batteries

88%
Guler M., Cetinkaya T., Cevher O., Tocoglu U., Akbulut H.
Acta Physica Polonica A
|
2014
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vol. 125
|
issue 2
322-324
EN
In this study, highly porous buckypapers were manufactured via vacuum filtration techniques and nanocrystalline TiO_2 thin films were deposited on buckypapers using reactive radio frequency magnetron sputtering to understand the role of the deposition power. In addition, the effects of the deposition parameters on the electrochemical properties as an anode electrode for Li-ion batteries have also been studied.
11
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Investigation of Tin Oxide Based Nanocomposites for Li-Ion Batteries

88%
Cevher O., Cetinkaya T., Tocoglu U., Guler M., Akbulut H.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 2
358-360
EN
In this work, tin oxide (SnO_2) films were deposited on multiwall carbon nanotube buckypaper using a rf magnetron sputter process in a mixed oxygen/argon (1/9) gas environment. Conditions for the growth of SnO_2 thin films on multiwall carbon nanotube buckypaper by rf sputtering are: target composition SnO_2 (99.999 wt%); total system pressure 1 Pa; sputtering power (rf) 75, 100 and 125 W, respectively; O_2/Ar (1/9) gas mixture. The surface morphology of the SnO_2 multiwall carbon nanotube composite films was investigated by scanning electron microscopy. The crystallographic structure of the sample was determined by X-ray diffraction. The electrochemical properties of SnO_2 multiwall carbon nanotube composite anodes were investigated by galvanostatic charge-discharge experiments.
12
Content available remote

Preparation and Electrochemical Performance of ZnO Films as Anode Materials for Li-Ion Batteries

88%
Cevher O., Cetinkaya T., Tocoglu U., Guler M., Akbulut H.
Acta Physica Polonica A
|
2013
|
vol. 123
|
issue 2
355-357
EN
In this work, the effect of rf power on the structural, electrical and electrochemical properties of ZnO thin films was investigated. ZnO thin films were deposited on glass and Cr coated stainless steel substrates by rf magnetron sputtering in pure Ar gas environment. ZnO thin films for different rf powers (75, 100, and 125 W) were deposited keeping all other deposition parameters fixed. ZnO thin films were used as negative electrode materials for lithium-ion batteries, whose charge-discharge properties, cyclic voltammetry and cycle performance were examined. A high initial discharge capacity about 908 mAh g^{-1} was observed at a 0.5 C rate between 0.05 and 2.5 V. The crystallographic structure of the sample was determined by X-ray diffraction. The electrical resistivity of the deposited films was measured by the four-point-probe method. The thickness of the ZnO thin films was measured using a profilometer.
13
Content available remote

Cr and V Substitution in the LiMn₂O₄Spinel Positive Electrode Li-Ion Batteries

88%
Akbulut A., Cetinkaya T., Guler M., Uysal M., Akbulut H.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1019-1022
EN
In this study, LiCr_{0.2}V_{0.4}Mn_{1.4}O₄ cathode active electrode materials were produced via a facile sol-gel method at 800°C. The surfaces of the LiCr_{0.2}V_{0.4}Mn_{1.4}O₄ cathode active electrode materials were then coated with Cu in order to increase the conductivity and suppress the manganese ion dissolution into the electrolyte. The structure and electrochemical properties of the obtained Cr and V substituted LiMn₂O₄ powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge- discharge test and electrochemical impedance spectroscopy (EIS). The improvement in the cycling performances attributed to stabilization of spinel structure by bication ion substation and Cu coating on the spinel particles. EIS analysis confirmed that bication doping and conductive Cu coating contributed stability of the spinel electrodes and provided stable electrolyte/electrode interface due to the suppression of electrolyte decomposition
14
Content available remote

Evaluation of Li-Air Batteries With EC-DEC Based Nanocomposite Electrolytes

88%
Akbulut A., Guler M., Cetinkaya T., Uysal M., Akbulut H.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1023-1025
EN
Electrolytes based on organic carbonate solvents of ethylene carbonate (EC) and diethyl carbonate (DEC) were prepared by using LiPF₆ as the Li-source. Nano sized Al₂O₃ (50 nm) was used as a reinforcing component in order to control corrosion and Li₂CO₃ formation. Corrosion of the Li foil anode and electrochemical tests were performed by using EC/DEC/LiPF₆ and nanocomposite EC/DEC/LiPF₆/5wt.% Al₂O₃ electrolytes. Electrochemical tests were performed in the swagelok cells by using Li foil anode and carbon air cathode electrodes. Structural tests were carried out by using scanning electron microscopy (SEM), x-ray diffraction (XRD) and Raman spectroscopy. Results revealed that incorporation of nano Al₂O₃ leads to a decrease of corrosion rate of Li anode and a small decrease in the capacity of the air cells.
15
Content available remote

Thin Film Nanostructured ATO and ATO Based Composite Anodes for Li-Ion Batteries

76%
Cevher O., Guler M., Tocoglu U., Cetinkaya T., Akbulut H., Okumus S.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
296-298
EN
In this study, antimony doped tin oxide films were deposited on multiwall carbon nanotube buckypaper and Cr coated stainless steel substrates using a radio frequency magnetron sputtering process in a mixed oxygen/argon (5/95) gas environment. The depositions of antimony doped tin oxide on the multiwall carbon nanotube buckypaper and stainless steel substrates were carried out using the parameters organized as: target composition antimony doped tin oxide (SnO_2:Sb = 90:10 wt%); total system pressure 1 Pa; sputtering power (RF) 100 W. The surface morphology of the antimony doped tin oxide films was investigated by field emission scanning electron microscopy. The crystallographic structure of the samples was determined by X-ray diffraction. The electrochemical properties of antimony doped tin oxide and antimony doped tin oxide-multiwall carbon nanotube nanocomposite anodes containing CR2016 cells were measured by galvanostatic charge-discharge experiments.
16
Content available remote

Effects of RF Power on Electrical and Structural Properties of Sputtered SnO_2:Sb Thin Films

76%
Cevher O., Guler M., Tocoglu U., Cetinkaya T., Akbulut H., Okumus S.
Acta Physica Polonica A
|
2014
|
vol. 125
|
issue 2
293-295
EN
In this work, antimony doped tin oxide (SnO_2:Sb) thin films were fabricated using a radio frequency magnetron sputtering system on Si wafer and glass substrates. The base pressure in the sputtering chamber was 1.0 Pa. The SnO_2:Sb thin films were deposited for 1.0 h in a mixture of Ar and O_2 environment with O_2/Ar ratio of 10/90 at 75, 100, and 125 W RF sputtering powers. The microstructure of SnO_2:Sb thin films was assessed using a field emission scanning electron microscopy. The crystallographic structure of the sample was determined by X-ray diffraction. The average surface roughness (R_{a}) was measured with atomic force microscopy. The electrical resistivity of the deposited films was measured by the four-point-probe method. The thicknesses of the films were measured by surface profiler.
17
Content available remote

The Electrochemical Properties of Cu Coated LiCr_{0.2}V_{0.2}Mn_{0.6}O₂ Nanocomposites for High Rate Li-Ion Batteries

76%
Algul H., Erdas A., Tokur M., Guler M., Akbulut H., Alp A.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 4
1038-1041
EN
Several reported problems of commercial LiCoO₂ electrode materials such as high cost, toxicity, limited rate capability and safety concerns are still remain to be problematic to develop the lithium ion consumer electronics such as mobile phones, tablets and notebook computers. In this study, an alternative nanocomposite electrode material based on LiCr_{0.2}V_{0.2}Mn_{0.6}O₂ and copper coated one were produced via a facile sol-gel method and electroless Cu deposition techniques. The resulting samples were characterized by X-ray diffraction (Rigaku DMax 2200 diffractometer) using a monochromatized Cu-Kα source (λ=1.5406 Å) and 2θ scan range from 10° to 80° with a speed of 1° min^{-1}. The scanning electron microscope (SEM) was used in order to characterize the morphology of the active materials. The as-synthesized Cu/LiCr_{0.2}V_{0.2}Mn_{0.6}O₂ composite cathode exhibits a stable capacity on cycling and good rate capability after 50 cycles and total capacity retention of 93% is obtained. The unique 2D structure of the composite cathode material, its good electrochemical performances and its relatively low cost comparing to LiCoO₂, make this material very promising for applications.
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