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1
Content available remote

Raman Studies of ZnO Products Synthesized by Solution Based Methods

100%
Gültekin D., Akbulut H.
Acta Physica Polonica A
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2016
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vol. 129
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issue 4
803-805
EN
In this study, nanostructured ZnO thin film coatings produced by sol-gel method have been examined and characterized. ZnO thin film coatings synthesized by the preparation of ZnO sols in the liquid phase from homogeneous solutions with precursor of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O). Ethanol (C₂H₅OH) has been used as a solvent material and monoethanolamine (MEA) has been used as a complexing agent. The final solutions have 0.1, 0.3, 0.5, 0.7 and 1 molar concentrations. General morphologies and detailed structural characterizations have been obtained by using scanning electron microscope (SEM). Qualitative analyses of the synthesized coatings were performed using X-ray diffraction (XRD) and Raman spectroscopy. The Raman spectroscopy studies of precursor, solution and final products were carried out to investigate transformation of the chemical compounds from the initial material to the final coating.
2
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Electrochemical Performance of SnO₂ and SnO₂/MWCNT/Graphene Composite Anodes for Li-Ion Batteries

100%
Cevher O., Akbulut H.
Acta Physica Polonica A
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2017
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vol. 131
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issue 1
204-206
EN
In this study, tin oxide (SnO₂) coatings on Cr coated stainless steel and multi-walled carbon nanotube (MWCNT)/graphene substrates were prepared using a radio frequency magnetron sputtering process as anode materials in lithium-ion batteries. SnO₂ thin film and SnO₂/MWCNT/graphene composite were characterized with field-emission scanning electron microscopy, X-ray diffraction, and electrochemical tests (cyclic voltammetry and galvanostatic cycling). The electrochemical properties of SnO₂ and SnO₂/MWCNT/graphene composite anodes were studied using 2016-type coin cells assembled in an argon-filled glove box. The cells were cyclically tested on a MTI BST8-MA battery analyzer. The cyclic voltammograms of SnO₂ anode and SnO₂/MWCNT/graphene composite anode were obtained over the potential range of 0.05-3.0 V and 0.05-2.5 V at a scan rate of 0.05 mV s¯¹, respectively.
3
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The Effect of Calcination Temperature on the Electrochemical Performance of ZnO Coated LiMn_2O_4/MWCNT Nanocomposite Cathodes

81%
Akbulut A., Cetinkaya T., Guler M., Akbulut H.
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vol. 125
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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.
4
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Electrical Conductivity, Viscosity and Thermal Properties of TEGDME-Based Composite Electrolytes for Lithium-Air Batteries

81%
Kartal M., Alp A., Akbulut H.
Acta Physica Polonica A
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2016
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vol. 129
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issue 4
816-818
EN
Some important properties of the electrolytes used in Li-air batteries were investigated. Electrolyte composed of a solution of 1 M LiPF₆ in tetra ethylene glycol dimethyl ether (TEGDME) was reinforced with SiO₂, Al₂O₃, poly(ethylene) oxide (PEO) and tris (pentafluorophenyl) borane (TPFPB) additives. The effects of these reinforcements on conductivity, viscosity and thermal stability were investigated. Electrical conductivity tests were carried out using a multiparameter meter. Viscosity tests were performed in a viscometer using tuning-fork vibration method. Thermal stability of the electrolytes was tested by both TG and DSC.
5
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The Superior Surface Discharge Capacity of Core-Shell Tinoxide/Multi Walled Carbon Nanotube Nanocomposite Anodes for Li-Ion Batteries

81%
Akbulut H., Alaf M., Gultekin D.
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vol. 125
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issue 2
335-337
EN
In this study, tin/tinoxide/multiwalled carbon nanotube (Sn/SnO_2/MWCNT) nanocomposites were produced as anode materials for Li-ion batteries by a two-step process. Metallic tin was evaporated onto free-standing MWCNT buckypapers having controlled porosity and subsequently rf plasma oxidized in Ar:O_2 (1:1) gas mixture. Besides, Sn/SnO_2 nanocomposites were produced in the same conditions onto stainless steel substrates to make a comparison. X-ray diffraction and scanning electron microscopy were used to determine the structure and morphology of the obtained nanocomposites. The discharge/charge tests, cyclic voltammetry and electrochemical impedance spectroscopy were carried out to characterize the electrochemical properties of these composites. Promising results were obtained in the tin based MWCNT nanocomposites for next-generation micro battery applications because of the high active surface area of the SnO_2/MWCNT core-shell structures.
6
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The Effect of Temperature on Grain Size of SnO_2 Nanoparticles Synthesized by Sol-Gel Method

81%
Köse H., Aydin A., Akbulut H.
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vol. 125
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issue 2
345-347
EN
Tin dioxide nanoparticles were synthesized by sol-gel method and calcined at different temperatures in the range 350-750°C. The SnO_2 precursor solution was prepared from SnCl_2 ·2H_2O (tin (II) chloride dihydrate), and chloride ions were removed from the solution before the sol-gel synthesis was applied. SnO_2 powders were characterized by thermal analyses, X-ray diffraction, field emission gun-scanning electron microscopy, and energy dispersive X-ray spectroscopy, and grain size of nanoparticles were determined by using the Debye-Scherrer formula.
7
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The Effect of Different Organic Gelating Agents on Grain Size of ZnO Nanoparticles

81%
Karaal Ş., Köse H., Aydin A., Akbulut H.
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vol. 125
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issue 2
338-340
EN
In this work, sol-gel method was used in order to synthesize ZnO nanoparticles. Zn(CH_3COO)_2 ·2H_2O was used to obtain ZnO precursor solution. To investigate the effect of organic gelating agents on grain size, various organic gelating agents such as triethanolamine (TEA), glycerin (GLY), ethylene glycol (EG), citric acid (CA) and tartaric acid (TA) were used. X-ray diffraction analysis was used for phase identification and grain size calculation. ZnO powders were characterized by using Fourier-transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy.
8
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Sol-Gel Synthesis of Nanostructured SnO_2 Thin Film Anodes for Li-Ion Batteries

81%
Köse H., Aydin A., Akbulut H.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
227-229
EN
Sol-gel technique was employed to prepare semiconductor tin dioxide (SnO_2) thin films. Comparatively, it gives an advantage over other techniques by its low reaction temperature, easy process and low cost. The effect of glycerin addition on the structure and preventing crack formation has been investigated. Scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis were performed to characterize nanostructured films.
9
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Effects of Substrate Temperature on Structural Properties of Tin Oxide Films Produced by Plasma Oxidation after Thermal Evaporation

81%
Alaf M., Guler M., Gultekin D., Akbulut H.
Acta Physica Polonica A
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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.
10
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Tin/Tinoxide (Sn/SnO_2) Nanocomposites Thin Films as Negative-Electrode Materials for Li-Ion Batteries

81%
Alaf M., Gultekin D., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
323-325
EN
In this study, tin/tinoxide (Sn/SnO_2) nanocomposites thin films were produced by thermal evaporation and plasma oxidation as anode materials for Li-ion batteries. To produce Sn/SnO_2 thin films, pure metallic tin (Sn) was thermally evaporated on the stainless steel substrates in argon atmosphere. The Sn films were subjected to plasma oxidation process at oxygen/argon gas mixture. Three different plasma oxidation times (30, 45, and 60 min) were used to investigate oxidation kinetics and physical and microstructural properties. The surface properties were studied by scanning electron microscopy and atomic force microscopy. For structural analysis, X-ray diffraction measurements were carried out. Sn/SnO_2 coated stainless steel substrates were used as the working electrode in coin-type (CR2016) test cells. The energy storage capacity Sn/SnO_2 electrodes were determined depending on the oxidation time and Sn:SnO_2 ratio.
11
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Effects of pH Value on the Growth and Structural Properties of Sol-Gel Synthesized Nanostructured ZnO

81%
Gültekin D., Alaf M., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
330-332
EN
The aim of the research presented is to investigate the effect of pH value on the structural and morphological properties of nanostructured ZnO products. Zinc acetate dihydrate (Zn(CH_3COO)_2·2H_2O) has been used as precursor whereas distilled water is used as a solvent. The pH value of the sol was adjusted with monoethanolamine (MEA) and it changed from acid to base in nature. X-ray diffractometer has been used to determine preferred crystal orientation and particle size of the thin films. Film morphologies have been examined by using JEOL JSM 6060 LV scanning electron microscope equipped with energy-dispersive spectroscopy.
12
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Characteristics Bronze/Al_2O_3(Ni) Reinforcement Metal Matrix Composite Produced by Current Activated Sintering

81%
Uysal M., Karslioğlu R., Akbulut H., Alp A.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
235-237
EN
In this study, a bronze matrix (90 wt% Cu + 10 wt% Sn) was reinforced with Al_2O_3 particles using mechanical alloying and then produced by a subsequent rapid current sintering technique. The mechanically ball milled bronze powders were reinforced with electroless Ni coated 20 vol.% Al_2O_3 particles with three different particle sizes of 90, 70, and 50 μm. Microhardness testing, and scanning electron microscopy were used for the structural characterization of the composites. The tribological behavior of the resultant composites was tested by the ball-on-disk method at 1.0 N applied load with 0.3 m/s sliding speed for determination the wear loss and friction coefficient features against a counterface steel ball.
13
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Cyclic Performance Tests of Si/MWCNT Composite Lithium Ion Battery Anodes at Different Temperatures

81%
Tocoglu U., Cevher O., Akbulut H.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1059-1061
EN
In this study silicon-multi walled carbon nanotube (Si-MWCNT) lithium ion battery anodes were produced and their electrochemical galvanostatic charge/discharge tests were conducted at various (25°C, 35°C, 50°C) temperatures to determine the cyclic behaviors of anode at different temperatures. Anodes were produced via vacuum filtration and DC magnetron sputtering technique. Silicon was sputtered onto buckypapers to form composite structure of anodes. SEM analysis was conducted to determine morphology of buckypapers and Si-MWCNT composite anodes. Structural and phase analyses were conducted via X-ray diffraction and Raman Spectroscopy technique. CR2016 coin cells were assembled for electrochemical tests. Cyclic voltammetry test were carried out to determine the reversibility of reactions between anodes and reference electrode between 0.01-2.0 V potential window. Galvanostatic charge/discharge tests were performed to determine cycle performance of anodes at different temperatures.
14
Content available remote

Nanostructured ATO Anodes Produced by RF Magnetron Sputtering for Li-Ion Batteries

81%
Cevher O., Tocoglu U., Akbulut H.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1065-1067
EN
In this study, the reversible capacities, as well as the cycling behavior, of crystalline antimony-doped tin oxide (ATO) films have been investigated. ATO films were deposited on Cr-coated stainless steel substrates by the RF magnetron sputtering technique, with antimony-doped tin oxide (SnO₂:Sb) target in a mixed oxygen/argon gas environment. The ATO films were deposited for 1.0 h in a mixture of Ar and O₂ environment with O₂/Ar ratio of 10/90, at sputtering power of 75 W, 100 W and 125 W RF. ATO films were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). The electrochemical properties of ATO anodes were studied using 2016-type coin cells assembled in an argon-filled glove box.
15
Content available remote

The Preparation of Core-Shell Al_2O_3/Cu Composite Powders by Electroless Plating in the Alkaline Solution

81%
Uysal M., Karslioğlu R., Alp A., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
238-240
EN
In this study, Cu-coated Al_2O_3 composite powders were synthesized by using electroless plating method. The influence of the plating bath composition and ceramic powder concentration on the Cu plating was characterized by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction techniques. The results showed that the electroless bath composition plays an important role for the structure of nano core-shell Al_2O_3/Cu composite powders. The content of copper in the composite powders could be effectively controlled by adjusting the content of copper sulfate and formaldehyde in the plating solution. Furthermore, the pretreatment of the Al_2O_3 powders is also a key factor to form a uniform shell copper layer coating on Al_2O_3 particles.
16
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A New Approach to Synthesis of Free-Standing ZnO/MWCNT Nanocomposites by Vacuum Infiltration

81%
Alaf M., Gultekin D., Akbulut H.
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vol. 125
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issue 2
426-428
EN
In this study, free-standing zincoxide/multiwalled carbon nanotube nanocomposite was synthesized by a multistep technique. Buckypapers having controlled porosity were prepared by vacuum filtration from oxidized multiwalled carbon nanotubes. Zinc acetate dihydrate (ZnAc) (Zn(CH_3COO)_2 ·2H_2O) was used as zinc source and ethanol used as solvent. An appropriate amount of monoethanolamine was added to sol to change acid-base media. The solution was vacuum filtered through buckypaper and annealed at 350C in air. It was found that the zinc oxide grows around the multiwalled carbon nanotubes to form a uniform composite. Morphology of zine oxide/multiwalled carbon nanotube was also studied in detail. Nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy.
17
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Synthesis and Characterization of ZnO Nanopowders and ZnO-CNT Nanocomposites Prepared by Chemical Precipitation Route

81%
Gültekin D., Alaf M., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
274-276
EN
The aims of this work are synthesis of ZnO nanopowders and producing nanocomposites by mixing with carbon nanotubes. ZnO nanopowders have been synthesized by chemical precipitation route. Different amount of collected nanosized Zn-based precipitates and chemically oxidized carbon nanotubes powder have been mix together and annealed at 400°C. Characterization of produced nanopowders and nanocomposites have been carried out by X-ray diffractometer and scanning electron microscope.
18
Content available remote

Sol-Gel Synthesis of Nanocomposite Cu-Li₄Ti₅O_{12} Structures for Ultrahigh Rate Li-Ion Batteries

81%
Erdas A., Ozcan S., Guler M., Akbulut H.
Acta Physica Polonica A
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2015
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vol. 127
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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.
19
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Reciprocating Wear Behavior of Ni-Co Alloys Produced by Pulse Current Electrodeposition

81%
Karslioğlu R., Uysal M., Alp A., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
424-426
EN
In the present work, Ni-Co alloy coatings were prepared from a modified Watt type electrolyte by direct current. For this purpose, current density was investigated for optimization to obtain high quality coatings on the steel copper substrates. The depositions were controlled to obtain specific thickness (between 50 and 200 μm). The characterization of the coatings was investigated by scanning electron microscopy and X-ray diffraction facilities. The hardness of the resultant coatings was also measured. The effects of the current density on the tribological properties of Ni-Co coatings were investigated. The results showed that although increasing current density showed increasing coating thickness, the wear resistance of the Ni-Co alloys was decreased due to Co depletion in the deposited layer.
20
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Tribological Behavior of Copper/MWCNT Nanocomposites Produced by Pulse Electrodeposition

81%
Gül H., Uysal M., Akbulut H., Alp A.
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vol. 125
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issue 2
254-256
EN
Copper coatings containing well-distributed multiwalled carbon nanotubes were obtained by pulse electrodeposition in acidic sulfate bath in order to improve the microhardness and wear resistance of coatings. Multiwalled carbon nanotubes concentration was determined as the most significant factor for the incorporation of multiwalled carbon nanotubes in copper based electrolyte. The amount of embedded multiwalled carbon nanotubes and the microhardness of nanocomposites were found to increase with the increase of multiwalled carbon nanotubes in the electrolyte. The tribological properties of nanocomposites deposited by pulse electrocodeposition technique were studied by reciprocating ball on-disk method. The characterization of the coatings was investigated by scanning electron microscopy and X-ray diffraction facilities. The experimental results indicated that the wear resistance of copper composite is superior to that of pure copper. The friction coefficient and wear rates decreased with the increase in the concentration of multiwalled carbon nanotubes in the electrolyte.
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