Browsing by Author "ALPER, MÜRSEL"

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A study on total thickness dependency: Microstructural, magnetoresistance and magnetic properties of electrochemically deposited permalloy based multilayers
(Springer, 2015-07-01) Kuru, Hilal; Koçkar, Hakan; Alper, Mürsel; ALPER, MÜRSEL; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; AAG-8795-2021
Electrochemically deposited permalloy based NiFe/Cu multilayers, relating their magnetic and magnetoresistance properties with crystal structure and the corresponding film composition were studied as a function of the total film thickness. The permalloy based multilayers were grown on strong (110) textured copper sheets with electrodeposition under potentiostatic control. The total multilayer film thickness was changed from 0.3 to 5 mu m while ferromagnetic nickel-iron and nonmagnetic copper layer thickness was kept constant at 3 and 1 nm, respectively. Energy dispersive X-ray analysis revealed that the nickel and iron content of the multilayers decreased and copper content increased as the total film thickness increased. All multilayers exhibited face-centred cubic structure with (110) preferred orientation. The highest peak intensity changed from (220) to (111) when the total thickness was higher than 2 mu m. The multilayers exhibited giant magnetoresistance (GMR). The maximum GMR magnitude of similar to 4 % was obtained for the films with total thickness less than 1 mu m and the GMR decreased down to similar to 1 % with increasing film thickness to 5 mu m. The saturation magnetisation and coercivity decreased from 78 to 11 emu/cm 3 and from 24 to 12 Oe as the total thickness of the multilayers increased from 0.3 to 5 mu m, respectively. The variations in magnetic and magnetoresistive properties related to the microstructure were attributed to the variation of the film contents caused by total film thickness.
Change in planar hall effect ratio of Ni-Co films produced by electrodeposition
(Elsevier, 2015-01-01) Karpuz, Ali; Koçkar, Hakan; Alper, Mürsel; ALPER, MÜRSEL; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021
Ni-Co Films were produced by the electrodeposition technique and their magnetotransport properties were studied. The anisotropic magnetoresistance (AMR) and the planar Hall effect (PRE) ratios were Found using the van der Pauw setup at room temperature. It was observed that the ORE ratios were larger than the obtained AMR ratios. While the maximum changes in longitudinal and transversal magnetoresistance ratios were 6.8% and 140%, respectively, the change in ORE values was up to 500%. In the ORE measurements, the magnetoresistance orientation depends on the electrical resistance values which occur in branches of the films.
Characterizations of electrodeposited NiCoFe ternary alloys: Influence of deposition potential
(Springer, 2015-06-01) Kuru, Hilal; Koçkar, Hakan; Demirbaş, Özen; Alper, Mürsel; ALPER, MÜRSEL; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021
Microstructural, magnetoresistance and magnetic properties of electrodeposited NiCoFe ternary alloys were investigated in terms of deposition potentials changing from -1.8 to -3.0 V with respect to saturated calomel electrode. The alloys were grown on polycrystalline Titanium substrates. The potentials were obtained from cyclic voltammetry and the current-time transients were also recorded to control the growth of proper alloys. From the structural analysis by X-ray diffraction, all alloys had a face-centred cubic structure. The alloy compositions by energy dispersive X-ray spectroscopy revealed that the Ni content increases whereas the Co and Fe contents decrease as the deposition potential increase. And, the scanning electron microscope images disclosed that the alloy morphologies changed as the deposition potential changed. All alloys showed anisotropic magnetic resistance and their magnitudes were between 4.5 and 8.7 %. The vibrating sample magnetometer measurements showed that the saturation magnetization of the alloys increases from 748 to 786 emu/cm(3) and coercivity decreases from 28.7 to 25.9 Oe as the deposition potential increases. The easy axis of magnetization was found to be parallel to the film plane for all alloys. The variations in magnetic and magnetoresistive properties related to the microstructure were attributed to the compositional changes caused by the deposition potential.
Development of electrodeposited multilayer coatings: A review of fabrication, microstructure, properties and applications
(Elsevier, 2021-08-12) Aliofkhazraei, M.; Walsh, Frank C.; Zangari, Giovanni; Koçkar, Hakan; Alper, Mürsel; Rizal, Conrad; Magagnin, Luca; Protsenko, Vyacheslav; Arunachalam, Ramanathan; Rezvanian, Amirreza; Moein, Arian; Assareh, Sahar; Allahyarzadeh, Mohammad Hossein; ALPER, MÜRSEL; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; AAG-8795-2021
The demand for robust engineering materials demonstrating good tribological performance under arduous service conditions has forged the development of novel coating materials and techniques. In the field of surface engineering, multilayer structures have attracted great interest. Electrodeposition offers a versatile and controlled route to engineering coatings in tribology. Electrodeposited coatings can provide tailored electronic, magnetic, mechanical, wear-resistant and corrosion-resistant characteristics as well as an improved load-bearing capability. The performance of multilayered electrodeposits can significantly exceed that of single layers. This paper critically reviews the fabrication, microstructure, engineering properties and potential applications of electrodeposited multilayer coatings. Such coatings can provide powerful, complementary additions to the toolkit for engineering electrodeposition, enabling future advances. Critical aspects requiring further R & D endeavors are identified.
Effect of deposition potential and saccharin addition on structural, magnetic and magnetoresistance characteristics of nicofecu films
(Walter De Gruyter Gmbh, 2023-08-03) Kuru, Hilal; Koçkar, Hakan; Alper, Mürsel; ALPER, MÜRSEL; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Psikoloji Bölümü.; 0000-0002-4862-0490
NiCoFeCu films were electrodeposited on Ti substrates at different deposition potentials and different concentrations of saccharin added to solution. Compositional analysis showed that although Ni was the highest concentration in solution at low potentials of - 1.0 V and - 1.5 V, the Ni content was lower than the Co content in the films. Anomalous co-deposition behaviour of iron group metals was observed. When the deposition potential increased to - 2.0 V and - 2.5 V, the Ni content of films increased while the Co, Fe and Cu content decreased. In the case of saccharin addition to the solution, there is a slight change in the film content. All films have face-centred cubic structure. Structural analysis clearly showed that the potential has a significant effect on the texture degree of the films, since the crystal texture changed from (111) to (220) with increasing potential. The surface morphology of the films was observed to be affected by the deposition potential and saccharin concentration. For the magnetic analysis, saturation magnetisation, M-s value gradually decreased from 905 to 715 emu/cm(3) with the variation of film content caused by the increase of the potential from -1.0 V to -2.5 V. And, a slight increase in M-s was detected with the addition of saccharin. Besides, the longitudinal and transverse magnetoresistance magnitudes increased from similar to 2.5 % to 7.0 % with increasing deposition potential and all films exhibit anisotropic magnetoresistance. Films with desired magnetic properties can be obtained for potential use as magnetic materials in electronics such as magnetoresistive devices.
Effect of l-ascorbic acid on electrochemically deposited fecocu/cu magnetic multilayer granular films: Structural, magnetic and magnetoresistance properties
(Elsevier, 2020-09-01) Şahin, Turgut; Koçkar, Hakan; ALPER, MÜRSEL; Tekgül, Atakan; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; 0000-0001-6737-3838; 0000-0002-4862-0490; AAG-8795-2021; P-2124-2016
The FeCoCu/Cu multilayer granular films were prepared by the electrochemical deposition technique, and the effect of the L-ascorbic acid molarity on their structural, magnetic, and magnetoresistance properties was investigated. The structure of multilayer granular films is a face-centered cubic at room temperature, and the crystallite size increases from 5 to 14 nm with increasing the molarity of the L-ascorbic acid in the electrolyte. The recorded current-time curves indicate that 0.06 M L-ascorbic acid causes high current (200 mA) in the deposition of the magnetic layer during the electrochemical deposition process. The compositional analysis indicates that Fe deposition amount increases with increasing the L-ascorbic acid for the 0.04 and 0.06 M. The saturation magnetization decreases in the thin films due to increasing the molarity of L-ascorbic acid in the electrolyte. However, some of the Co and Fe reduces as a form of their oxide in the multilayer granular films containing a high amount of magnetic materials, and the antiferromagnetic behavior suppresses the ferromagnetic behavior. The multilayer granular film produced from the electrolyte with 0.04 M L-ascorbic acid exhibits both high magnetoresistance as 12% and 3.5% anisotropic magnetoresistance effect, and also, about 1 nm particle size.
Effect of mn doping on structural, optical and magnetic properties of zno films fabricated by sol-gel spin coating method
(Springer, 2023-02-01) GÜLTEKİN, ZAFER; ALPER, MÜRSEL; Akay, Cengiz; AKAY, CENGİZ; Hacıismailoğlu, M. Cüneyt; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Fizik Bölümü.; 0000-0002-0781-3376; 0000-0002-8037-0364; K-7950-2012; W-1656-2017
We have fabricated undoped ZnO and Mn-doped ZnO thin films on glass substrates using sol-gel spin coating method and investigated their structural, optical, magnetic and magnetoresistance properties depending on the Mn doping ratio. X-ray diffraction (XRD) patterns showed that all the films under study are predominantly crystalized in a single-phase wurtzite structure. Scanning electron microscope (SEM) images revealed that the films become more homogeneous, continuous and pinhole-free coatings as the Mn content of the films increases. Optical characterizations by UV-visible spectrometer indicated that transmittance spectra of all films have a high transmittance above 85% in visible region, while they show the absorbance spectra in 300-400 nm range. In addition, it was observed that the optical energy band edges shift to red with increasing Mn content, due to probably increasing the carrier concentration. The refractive index and the dielectric constant are also affect by the Mn content. Magnetic measurements by vibrating sample magnetometer showed that the film magnetic properties change from diamagnetic to ferromagnetic as the Mn content increases. Furthermore, it was found that the magnetoresistance measurements support their magnetic behavior of the films.
Electrodeposited CoFeCu films at high and low ph levels: Structural and magnetic properties
(Springer, 2015-04-01) Koçkar, Hakan; Özergin, Ercüment; Karaağaç, Öznur; Alper, Mürsel; Kuru, Hilal; Hacıismailoğlu, Mürside; ALPER, MÜRSEL; ŞAFAK HACIİSMAİLOĞLU, MÜRŞİDE; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0001-5648-3230; AAH-9719-2021; AAG-8795-2021
CoFeCu films were electrodeposited at high and low pH, and their structural, magnetic and magnetoresistance properties were studied. Current-time transients were recorded to observe the proper deposition of the films. Crystal structure was displayed with X-ray diffraction. All films had a face centered cubic structure and the crystal structure was dominated by fcc-Co. The morphology and elemental composition of the films were determined by scanning electron microscope and energy dispersive X-ray spectroscopy, respectively. The surface of the film deposited at low pH has larger roundish shapes than that of the film deposited at high pH. The saturation magnetization increases from 1,210 to 1,413 emu/cm(3) and coercivity increases from 29 to 39 Oe as the electrolyte pH increases. All CoFeCu films showed anisotropic magnetoresistance. It is seen that electrolyte pH has an substantial affect on the morphological and magnetic properties of the films.
Optimization of fe content in electrodeposited fecocu/cu magnetic multilayer
(Elsevier, 2019-03-01) Koçkar, Hakan; Tekgül, Atakan; Alper, Mürsel; ALPER, MÜRSEL; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi; 0000-0001-6737-3838; 0000-0002-4862-0490; P-2124-2016; AAG-8795-2021
The structural, magnetic and magnetoresistance properties of FeCoCu/Cu multilayers prepared by electrochemical deposition from a single bath containing 0.025, 0.05 and 0.1 M Fe under potentiostatic control are investigated. The deposition potentials were selected - 1.5 V for magnetic layers and - 0.4 V for non-magnetic layers concerning saturated calomel electrode. The multilayers exhibited face-centered-cubic structure in the X-ray diffraction. In the multilayer produced from the electrolyte containing 0.05 M Fe, the high saturation magnetization value (572.3 kA/m) was observed and it value drastically decreased 140.6 kA/m in the electrolyte containing 0.1 M Fe. The magnetoresistance measurements were carried out in magnetic fields in the range of +/- 955 kA/m. The high giant magnetoresistance value (18.7%) were obtained in the multilayer with 0.05 M Fe. In the magnetic sublayers of the multilayers, the more than Cu atoms deposited and due to this, the magnetoresistance curves exhibited the 2.5, 4.7, 2.4% anisotropic magnetoresistance contributions between longitudinal and transverse magnetoresistance.
Relation between ferromagnetic layer thickness (NiCu) and properties of NiCu/Cu multilayers (vol 26, pg 5014, 2015)
(Springer, 2015-07-01) Kuru, Hilal; Koçkar, Hakan; Alper, Mürsel; Hacıismailoğlu, Mürşide; ALPER, MÜRSEL; ŞAFAK HACIİSMAİLOĞLU, MÜRŞİDE; Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü.; 0000-0001-5648-3230; AAH-9719-2021; AAG-8795-2021
Structural, magnetic and GMR properties of FeCo(Cu)/Cu magnetic multilayers electrodeposited at high cathode potentials of the magnetic layer
(Natl Inst Optoelectronics, 2020-03-01) Tekgül, Atakan; Şahin, T.; Koçkar, H.; Alper, Mürsel; Tekgül, Atakan; ALPER, MÜRSEL; Bursa Uludağ Üniversitesi/Fen-Edebiyat Fakültesi/Fizik Bölümü; 0000-0001-6737-3838; AAG-8795-2021; P-2124-2016
Structural, magnetic and giant magnetoresistance properties of the electrochemically deposited FeCo(Cu)/Cu multilayers at the various cathode potentials for magnetic layers were investigated. The cathode potentials were -1.8, -2.0, -2.5 and -2.8 V for magnetic layers and -0.3 V for non-magnetic layers with respect to a saturated calomel electrode. The multilayers have a face-centred-cubic structure. The obtained composition was found to be close the nominal composition at -2.8 V cathode potential. The highest giant magnetoresistance value (16.50 %) was obtained in the multilayer produced at -1.8 V. The highest sensitivity was found in the multilayer produced at -1.8 and -2.8 V.
Synthesis of di- and tricationic surfactants and comparison of their activity on oxidation of metal in hcl media
(Maik Nauka/interperiodica/springer, 2023-11-02) Öztürk, Serkan; ÖZTÜRK, SERKAN; Gültekin, Zafer; GÜLTEKİN, ZAFER; Akgül, Gülsen; Alper, Mürsel; ALTINÖLÇEK GÜLTEKİN, NURAY; ALPER, MÜRSEL; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Kimya Bölümü.; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Psikoloji Bölümü.; Bursa Uludağ Üniversitesi/Yenişehir Meslek Yüksekokulu.
In this study, two surfactants with the same long chain were synthesized. One shows dicationic and the other tricationic properties. Various spectroscopic methods such as FT-IR, H-1 NMR and C-13 NMR were used to confirm the structures of the synthesized surfactants. The inhibition activities of two synthesized surfactants against mild steel corrosion in 1.0 M HCl solution were determined using the weight loss method. The 24-h corrosion tests on metal coupons immersed in acidic solutions were carried out using different inhibitor concentrations and similar and successful inhibition was obtained for both surfactants. Current density was determined by potentiodynamic polarization at a single inhibitor concentration to compare with the inhibition efficiency results obtained by decrease in weight method. Based on the current density, the inhibition efficiencies of the surfactants were calculated by Tafel extrapolation method. The inhibition efficiency results obtained by both weight loss and Tafel method were close and consistent. According to both methods, the corrosion inhibition of dicationic surfactant was slightly better than that of tricationic surfactant. By determining the critical micelle concentration for the two surfactants, some physicochemical parameters such as surface tensions and free energy of micelle formation at this concentration were calculated and correlated with their corrosion inhibitory activity. Scanning electron microscopy was used to ascertain the surface roughness conditions of metals submerged in an acidic solution, thus visually proving that surfactants protect the metal surface from corrosion.