İlgi alanları

• MakaleAçık Erişim2025/r/gumushane/12531
  Influence of Silver Doping and Anodization Current Density on Aluminum Surface Properties and Surface Adhesion of Staphylococcus aureus and Escherichia coli

  Erbakan, Mustafa; Taşdemir, Muharrem; Şenaslan, Fatih; Sarıbıyık, Oğuz Yunus

  In this study, we investigated the influence of crystal structure, topography, and elemental composition of aluminum oxide surfaces on bacterial adhesion. The structural properties of the surfaces were systematically controlled by varying the current density (1.5, 2.0, and 2.5 A/dm2) and silver doping during the anodization process. The resulting changes in structural and morphological properties were examined by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), contact angle measurements, and profilometry. Using FE-SEM analysis, we evaluated the adhesion of model bacteria, Escherichia coli and Staphylococcus aureus, to surfaces exhibiting diverse morphologies and elemental compositions. The surface roughness and crystal size of the aluminum oxide increased proportionally with the applied current density and silver doping. According to the XRD results, the slip plane crystal structure of (311) increased proportionally to the current density but decreased with silver doping. Specifically, while stepped atomic alignment of (311) planes facilitates bacterial attachment, smoother (200) planes reduce the adhered bacteria population. Further analysis via XPS revealed that the oxide crystal structure of undoped surfaces shifted from the tetrahedral to octahedral form with increasing current density, while silver-doped surfaces exhibited the opposite trend. Additionally, increasing current density during the preparation of silver-doped surfaces diminished the ratio of ionic silver to metallic silver, suggesting a lowered propensity for bacterial adhesion. S. aureus adhesion to undoped surfaces increased 4.46-fold for surfaces prepared at 2.5 A/dm2 compared to that at 1.5 A/dm2. Moreover, E. coli adhesion was completely inhibited on silver-doped surfaces anodized at 1.5 A/dm2. Reducing the surface roughness and incorporating silver during the anodization of aluminum surfaces decrease the number of bacteria adhering to aluminum oxide surfaces.

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• MakaleYalnız künye2023/r/gumushane/12756
  Enhanced wear resistance and surface properties of oxide film coating on biocompatible Ti45Nb alloy by anodization method

  Şenaslan, Fatih; Taşdemir, Muharrem; Çelik, Ayhan; Bozkurt, Yusuf Burak

  β-Titanium alloys have become increasingly popular as biomaterials because of their low modulus of elasticity and superior corrosion properties in recent years. β-titanium alloy containing niobium is also a biocompatible and non-toxic material. Among β-Ti alloys, Ti45Nb is one of the most remarkable alloys for its superior properties as a biomaterial. This alloy has superior properties due to low elasticity modulus and non-toxic elements, but its surface properties are inadequate for biomaterial applications. Therefore, various surface treatments are applied to improve the surface properties of these alloys. In this study, an oxide film layer was formed on the Ti45Nb surface under different potential conditions by the anodizing method. The effects of these factors on friction, wear, and contact angle measurements were investigated. The structural properties of the oxide film coated samples were analyzed with XRD and their surfaces and cross-sectional images were observed by SEM. Also, the surface roughness and nanoindentation tests were performed. In this regard, it was determined that oxide film thickness, surface roughness and hardness increased with the increase of anodization potential. The contact angle of the samples decreased with the increase in the anodization potential and the surface tension of the materials increased. The highest nanohardness of about 4.19 GPa was obtained from 150 TA samples. The elasticity modulus of the untreated sample was about 63 GPa, while the anodized samples ranged from an average of 31 to 83 GPa. The wear results revealed that the anodization process improved the wear resistance of the Ti45Nb alloy. As a result, the sample anodized at 200 V for 30 min exhibited optimum surface roughness, morphology and high wear resistance.

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• MakaleAçık Erişim2022/r/gumushane/14789
  Production of high-transparent MgO films by radio-frequency sputtering method; [Yüksek geçirgen MgO filmlerin radyo frekansı saçtırma yöntemiyle üretimi]

  Şenaslan, Fatih; Çelik, Ayhan; Taşdemir, Muharrem

  Magnesium oxide (MgO) thin films were deposited on silicon and glass substrates by the radio frequency (RF) sputtering method. The MgO films were annealed at 400 ⁰C for 4h. The effect of working pressure on the structure and optical properties of MgO films was investigated. Structural characterization of thin films was determined using the X-ray diffraction (XRD) method. XRD results showed the presence of dominant peaks corresponding to the (200) and (220) lattice planes of MgO. However, peaks corresponding to (111), (311) and (222) lattice planes of the MgO also appeared in the films deposited at low pressure. It was determined that the average crystal size decreased as the working pressure reduced, while the deposition rate increased. SEM analysis showed that the microstructure of the nano-spherical MgO film transformed into a coarse-grained nano-pyramidal shape after annealing. The optical properties of MgO films were investigated by UV-Vis spectroscopy. Accordingly, it was determined that the absorption threshold of the films was around 310 nm wavelength and the optical band gap of the films varied between 4.07 and 4.14 eV. As a result, MgO films with high transmittance reaching an average of 95% in the visible region were obtained.

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• DüzeltmeAçık Erişim2022/r/gumushane/12656
  Production of high-transparent MgO films by radio-frequency sputtering method; [Yüksek geçirgen MgO filmlerin radyo frekansı saçtırma yöntemiyle üretimi]

  Şenaslan, Fatih; Çelik, Ayhan; Taşdemir, Muharrem

  In the article with " Şenaslan, F., Çelik, A. & Taşdemir, M. (2022). Production of high-transparent MgO films by radio-frequency sputtering method. Gümüşhane University Journal of Science, 12(1), 320-326. DOI: 10.17714/gumusfenbil.1006430” citation information which was published in the first issue of the twelve volume of the Gümüşhane University Journal of Science, it was noticed that the “4. Conclusion (4. Sonuçlar)” section of the acceptance article Publisher was unintentionally removed by preparing for a publish, although authors given a “4. Conclusion (4. Sonuçlar)” section in the acceptance article. We apologize to the readers for the mistake. In this erratum, the unintentionally removed conclusion section is presented in the related article.

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• MakaleAçık Erişim2022/r/gumushane/12614
  Investigation of microstructural change and damping behaviour of Zn–27Al– 1Cu alloy in different aging periods; [Zn–27Al–1Cu alaşımının farklı yaşlandırma periyotlarında mikroyapısal değişiminin ve darbe davranışının incelenmesi]

  Şenaslan, Fatih; Aydin, Murat

  The ternary Zn–27Al–1Cu alloy is produced from raw materials by the gravity casting method. The produced alloy was subjected to aging after solutionizing and quenching. The effect of aging at different periods on the microstructure and damping behaviour of the alloy was investigated. The microstructural investigations revealed that the microstructure of the alloy in the as-cast state consisted of aluminium(Al)-rich α dendrites surrounded by eutectoid β phase, and zinc(Zn)-rich η phase and copper(Cu)-rich ε phase. The heat treatment eliminated the dendritic microstructure of the casting alloy and transformed it into a coarse-grained (β-matrix) stable form containing Zn-rich and Cu-rich precipitates. The microstructural changes after aging process were directly affected the mechanical properties of the alloy. The hardness and tensile strength increased with increasing ageing time up to 2.5 hours, but the percent elongation decreased. When the aging time reached 5 hours, hardness and tensile strength decreased while percent elongation increased significantly. The impact energy, namely toughness, increased in the early stage of aging, reduced sharply with increasing aging time and remained stable with a small increase in the prolonged stage of aging. The highest impact energy was attained from the aged alloy for 0.5 hours. The variation in damping energy was dependent on the changes in microstructural and mechanical properties caused by different aging periods. The prolonged aging process transformed the fracture characteristic of the as-cast alloy from relatively brittle to ductile fracture.

  İncele
• MakaleAçık Erişim2021/r/gumushane/14836
  Investigation of corrosion and thermal behavior of PU-PDMS-coated AISI 316L

  Taşdemir, Muharrem; Senaslan, Fatih; Çelik, Ayhan

  Polydimethylsiloxane (PDMS) is widely used from biomedical to industrial applications due to its nontoxic, hydrophobic, and transparent characteristics. PDMS has good thermal and adhesion properties; however, its mechanical properties are comparatively weak. Therefore, PDMS is blended with various polymers to effectively improve its mechanical properties. In this study, polyurethane (PU)-polydimethylsiloxane (PDMS) blended coatings of different concentrations were applied on the AISI 316L stainless steel surface. Their effects on corrosion and tribocorrosion properties were investigated in Ringer's solutions. The blended polymer coatings were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The thermal properties of samples were examined by TGA and DSC. The surface images and cross-sectional were investigated using scanning electron microscopy (SEM). Tribocorrosion tests were carried out at open circuit potential (OCP). It was determined that hydrophobicity and thermal stability of polymer coating increased, while corrosion resistance slightly decreased with the increasing PDMS concentration in the polymer blended. The friction coefficient of blends decreased as the PU concentration increased. As a result, it was determined that the polymer-coated samples containing up to 50% PDMS prevented corrosive wear under the OCP wear test in Ringer's solutions.

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• MakaleAçık Erişim2021/r/gumushane/14664
  Wear, Corrosion and Tribocorrosion Behavior of Polyurethane and Polyvinylpyrrolidone Blends as Coating for Corrosion Protection of AISI 316L Stainless Steel

  Taşdemir, Muharrem; Şenaslan, Fatih; Çelik, Ayhan

  Polyurethanes (PUs) are used across a widely from biomaterials to industrial applications due to their versatile properties. Polyurethane is blended with other polymers to improve their physical and thermal properties. In this study, different concentrations of polyurethane and polyvinylpyrrolidone (PVP) blends were applied to AISI 316L stainless steel using the dip coating method as protection against wear and corrosion. The effects of different concentrations of blends on the mechanical, corrosion and tribocorrosion properties of the AISI 316L stainless steel were investigated. The phase structure of polymer coatings were investigated by X-ray diffraction (XRD), and their surfaces were examined by scanning electron microscopy (SEM). Corrosion and tribocorrosion tests of the polymer coated samples were carried out in 3.5% NaCl solutions. The surface roughness and nanohardness of the polymeric coated samples were also measured. It was found that surface roughness and friction coefficient increased with raised concentration of PVP, while wear and corrosion resistance decreased with the increased of PVP concentration in the coating. As the penetration depth of the PU coated sample increased, the nanohardness and elasticity modulus decreased. Coatings containing PVP up to 25% protected the substrate surface under tribocorrosion conditions in NaCl solutions.

  İncele
• MakaleYalnız künye2021/r/gumushane/13294
  Effect of working pressure and post-annealing on structural, optical and electrical properties of p-type NiO thin films produced by RF magnetron sputtering technique

  Şenaslan, Fatih; Taşdemir, Muharrem; Çelik, Ayhan

  Nickel oxide (NiO) films were deposited on glass and silicon substrates using a Ni target by radio-frequency (RF) sputtering at various working pressure ranging from 5 to 20 mTorr. The films were annealed for 2 h at 400 °C in the air ambient. The effect of working pressure on structural, optical and electrical properties of NiO films was investigated in detail. The deposition rate of the films gradually increased with decreasing working pressure. The X-ray diffraction (XRD) presented that the crystal quality and the average crystallite size of annealed films increased with decreasing working pressure. The X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ni2+ and Ni3+ ions along with the main peak and satellite peaks in the NiO films. Raman spectroscopy exhibited the one-phonon and two-phonon vibrations modes corresponding to Ni–O bond. UV–Visible analyses showed that annealed NiO thin films have higher transmittance than deposited ones. The band gap of the films increased from 3.33 to 3.52 eV with decreasing working pressure and further increased after the annealing process. The electrical properties were affected by the varying crystallinity and lattice defects depending on the deposition condition. All annealed NiO films exhibited p-type conductivity. The lowest resistivity (4.2 Ω.cm) was obtained from the annealed film after deposition at 5 mTorr.

  İncele
• MakaleAçık Erişim2020/r/gumushane/17869
  The Effect of Anodization Potential on Wear Behaviour of Ti45Nb Alloy

  Taşdemir, Muharrem; Şenaslan, Fatih; Çelik, Ayhan

  Titanium and its alloys are used in many industrial fields because of their low density-high strength ratio, excellent biocompatibility and good corrosion properties. Nevertheless, titanium and its alloys have poor surface properties. Titanium and its alloys are applied various surface treatments for increasing wear resistance and service life. In this study, the oxide layer was formed under different anodization conditions on the surface of Ti45Nb alloy. The effects of thickness and hardness of oxide layer was investigated under dry wear conditions. The TiO2 phase form of samples was obtained by XRD. Structural properties and cross-section view of samples examined with SEM. Also, the surface hardness of samples was measured by micro hardness. In conclusion, the thickness and hardness of oxide layer increased within increasing anodization potential on Ti45Nb surface. Accordingly, it was determined that wear resistance of anodized Ti45Nb alloy improved. In addition, the surface roughness and porosity of the material increased with increasing anodization potential.

  İncele
• MakaleYalnız künye2018/r/gumushane/15874
  The effect of quench-aging on the mechanical properties of Zn-27Al-1Cu alloy

  Aydin, Murat; Senaslan, Fatih

  The ternary alloy Zn-27Al-1Cu was produced by permanent mold casting. As-cast alloy was aged for different periods after being subjected to solution treatment followed by water quenching. The microstructure, mechanical properties and fatigue behavior of as-cast and heat-treated alloy were then investigated. The quench-aging eliminated the as-cast dendritic structure and produced a uniform microstructure consisting of large grains combined with precipitates. The hardness and tensile strength generally increased, whereas the ductility slightly decreased with aging time. Under all conditions, the longest fatigue life was obtained from the alloy that had been aged for 0.5 h, while the alloy which had been aged for 10 h exhibited the shortest. The fatigue properties were found to be more dependent on impact toughness and elongation, rather than tensile strength.

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