Yazar "Karahan, Ismail H." seçeneğine göre listele

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    A comparative study on the effect of collagen and h-BN reinforcement of hydroxyapatite/chitosan biocomposite coatings electrophoretically deposited on Ti-6Al-4V biomedical implants
    (Elsevier Science Sa, 2018) Tozar, Ali; Karahan, Ismail H.
    Solo and Combined effect of collagen (COL) and hexagonal boron nitride (h-BN) reinforcement on the corrosion protection, mechanical and tribological properties of electrophoretically deposited hydroxyapatite/chitosan biocomposite coatings are investigated. Crystallographic, surface morphology and topography, spectroscopic, corrosion protection characteristics, thermal behaviour, mechanical and tribological properties of the electrophoretically deposited biocomposite coatings are investigated via XRD, FE-SEM and SPM, FF-IR, Tafel and electrochemical impedance spectroscopy (EIS), thermogravimetric analysis, nanoindentation and nanoscratch techniques, respectively. Both solo reinforcement of collagen and h-BN exhibits positive effect on the corrosion protection, mechanical and tribological properties of the HA/CTS biocomposite coatings. However the combined use of these two supporting materials has had a much more positive effect on the physical properties of the coating thanks to the synergetic effect.
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    A comprehensive study on electrophoretic deposition of a novel type of collagen and hexagonal boron nitride reinforced hydroxyapatite/chitosan biocomposite coating
    (Elsevier Science Bv, 2018) Tozar, Ali; Karahan, Ismail H.
    A novel family of Hydroxyapatite/Chitosan/Collagen/h-BN biocomposite coatings were successfully produced by electrophoretic deposition (EPD). A new type of polyelectrolyte consisting of water, ethanol and isopropyl alcohol was used for EPD process. Collagen (main ligament of human bone) and h-BN (a promising solid lubricant) has been used as supporting materials for biocomposite coatings. The effect of h-BN concentration in the EPD suspension has been investigated. Crystallographic, morphological, spectroscopical, corrosion protection performance, thermal behaviour, mechanical and tribological, topographical and in-vitro biocompatibility investigations have been carried out by XRD, FE-SEM, FTIR, Tafel extrapolation and EIS, TGA/DSC, nanoindentation and nanoscratch, SPM and 12-weeks of immersion into r-SBF, respectively. Corrosion protection performance and mechanical and tribological properties of the coatings have been improved with increase in h-BN concentration in deposition suspension up to 5 g.L-1 and worsen with further increase. The results are encouraging for in-vivo applications of HA/CTS/COL/h-BN biocomposite coatings. (C) 2018 Elsevier B.V. All rights reserved.
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    Computer-Assisted Optimization of Electrodeposited Hydroxyapatite Coating Parameters on Medical Alloys
    (Springer, 2016) Coskun, M. Ibrahim; Karahan, Ismail H.; Yucel, Yasin; Golden, Teresa D.
    CoCrMo bio-metallic alloys were coated with a hydroxyapatite (HA) film by electrodeposition using various electrochemical parameters. Response surface methodology and central composite design were used to optimize deposition parameters such as electrolyte pH, deposition potential, and deposition time. The effects of the coating parameters were evaluated within the limits of solution pH (3.66 to 5.34), deposition potential (-1.13 to -1.97 V), and deposition time (6.36 to 73.64 minutes). A 5-level-3-factor experimental plan was used to determine ideal deposition parameters. Optimum conditions for the deposition parameters of the HA coating with high in vitro corrosion performance were determined as electrolyte pH of 5.00, deposition potential of -1.8 V, and deposition time of 20 minutes.
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    Effect of octylphenyl ether group nonionic surfactant on the electrodepositon of the hexagonal boron nitride reinforced Ni-B matrix composite coatings
    (Elsevier Science Sa, 2020) Tozar, Ali; Karahan, Ismail H.
    Hexagonal boron nitride (hBN) nanoparticle reinforced Ni-B matrix composite coatings were electrodeposited on steel substrates at a constant current of 50 mA cm(-2). Nickel (II) sulfate hexahydrate and nickel (II) chloride hexahydrate were used as the nickel source and borane trimethylamine complex (TMAB) was used as a source of boron. The average particle size of hBN was 100 nm. Octylphenyl ether (Triton X-100) was used as the surfactant. The effect of surfactant concentration in terms of structural, nano-micro mechanical, tribological and corrosion protection performance of the coatings was investigated. The results of the study showed that Triton X-100 has beneficial effect on the mechanical, tribological and corrosion protection properties of the composite coatings thanks to its stabilizing effect on the deposition suspension. According to this study, Triton X-100 may be used as a surfactant for the electrodeposition of metal matrix composites.
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    Investigation of the mechanical properties of Ni-B/hBN composite coatings electrodeposited in presence of CTAB as the surfactant
    (Iop Publishing Ltd, 2019) Tozar, Ali; Karahan, Ismail H.
    The effect of hexadecyltrimethylammonium bromide (CTAB) concentration on the galvanostatic electrodeposition of Ni-B matrix nano hexagonal boron nitride (hBN) reinforced composite coatings was investigated. XRD and FE-SEM analyzes were used for crystallographical and morphological investigations, respectively. Vickers indentation, nanoindentation, and nanoscratch experiments were carried out to investigate the micromechanical, nanomechanical and tribological properties, respectively. Potentiodynamic polarization and electrochemical impedance spectroscopy techniques were applied for corrosion characterization. The investigated properties have been improved with the increasing CTAB concentrations up to 900 mu M. In a general manner, CTAB has a beneficial effect at lower concentrations and can be useful for metal matrix nano ceramic reinforced composite coating electrodeposition in the lower concentration range.
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    Modeling corrosion performance of the hydroxyapatite coated CoCrMo biomaterial alloys
    (Elsevier Science Sa, 2018) Coskun, M. Ibrahim; Karahan, Ismail H.
    Using artificial intelligence (AI) applications such as, Artificial neural network (ANN) and Gene expression programming (GEP) to model corrosion performance of the hydroxyapatite coated metallic biomaterials were performed. Created models were analyzed and compared with a response surface methodology (RSM) study. Electrodeposition parameters of the hydroxyapatite on CoCrMo implant materials were used as independent variables in the modeling study. Corrosion potential, E-corr values calculated from potentiodynamic polarization measurements were used as dependent variable (output data) in AI models. Effect of the deposition parameters on the in vitro corrosion performance of the hydroxyapatite coatings were modeled by ANN and GEP models. ANN models were built with 3 input and 1 output variables using Multilayer Perception Topology. Total 21 electrodeposition and corrosion experiments were used in the ANN and GEP modeling. AI applications were successful for modeling the effect of deposition parameters on the corrosion performance of the hydroxyapatite coatings. Individual effect of the each parameter was investigated statistically. According to the model results predictive capacity and effectiveness of the ANN model is slightly better compared to the GEP and RSM model. (c) 2018 Elsevier B.V. All rights reserved.
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    Modeling the Effect of Temperature and Potential on the In Vitro Corrosion Performance of Biomedical Hydroxyapatite Coatings
    (Springer, 2016) Coskun, M. Ibrahim; Karahan, Ismail H.; Yucel, Yasin; Golden, Teresa D.
    CoCrMo biomedical alloys were coated with a hydroxyapatite layer to improve biocompatibility and in vitro corrosion performance. A fast electrodeposition process was completed in 5 minutes for the hydroxyapatite coating. Effect of the solution temperature and applied potential on the in vitro corrosion performance of the hydroxyapatite coatings was modeled by response surface methodology (RSM) coupled with central composite design (CCD). A 5-level-2-factor experimental plan designed by CCD was used; the experimental plan contained 13 coating experiments with a temperature range from 283 K to 347 K (10 A degrees C to 74 A degrees C) and potential range from -1.2 to -1.9 V. Corrosion potential (E (corr)) of the coatings in a simulated body fluid solution was chosen as response for the model. Predicted and experimental values fitted well with an R (2) value of 0.9481. Response surface plots of the impedance and polarization resistance (R (P)) were investigated. Optimized parameters for electrodeposition of hydroxyapatite were determined by RSM as solution temperature of 305.48 K (32.33 A degrees C) and potential of -1.55 V. Hydroxyapatite coatings fabricated at optimized parameters showed excellent crystal formation and high in vitro corrosion resistance.
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    Optimization of electrochemical step deposition for bioceramic hydroxyapatite coatings on CoCrMo implants
    (Elsevier Science Sa, 2016) Coskun, M. Ibrahim; Karahan, Ismail H.; Yucel, Yasin; Golden, Teresa D.
    CoCrMo metallic implants were coated with a bioceramic hydroxyapatite layer using a modified step electro-deposition at room temperature. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to model and optimize the step deposition parameters, such as initial potential, scan rate and peak potential. Interactions between step deposition parameters and in vitro corrosion performance of the coatings were modeled by response surface plots. Predicted and experimental values were fitted with high accuracy. The effects of the step deposition parameters were evaluated within the limits of lowest applied potential (-0.03 to -1.17 V), scan rate (3.43-116.57 mV/s) and highest applied deposition potential (-1.08 to -1.92 V). A 5-level-3-factor experiment plan was used to optimize step deposition parameters. Optimum conditions for the modified step deposition parameters were determined as initial potential of -0.76 V, peak potential of -1.67 V and scan rate of 59.33 mV/s. (C) 2015 Elsevier B.V. All rights reserved.
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    Optimized Electrodeposition Concentrations for Hydroxyapatite Coatings on CoCrMo biomedical alloys by computational techniques
    (Pergamon-Elsevier Science Ltd, 2014) Coskun, M. Ibrahim; Karahan, Ismail H.; Yucel, Yasin
    A bioactive hydroxyapatite layer deposited on the CoCrMo bio-metallic alloys by electrodeposition under different concentrations of calcium, phosphate and H2O2. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to optimize electrolyte concentrations. RSM and CCD were used to understand the concentration effects on the in vitro corrosion performance of biomaterials. 5-level-3-factor CCD was employed to evaluate effects of deposition parameters such as calcium concentration (0.016-0.184 M), phosphate concentration (0.005-0.055 M) and H2O2 concentration (2.4-27.6 ml/L) on the hydroxyapatite coatings and their corrosion resistance. Data obtained from RSM were subjected to analysis of variance (ANOVA) and analysed using a second order polynomial equation. Optimum conditions for the deposition parameters of the hydroxyapatite layer coating were found to be a calcium concentration of 0.05 M, phosphate concentration of 0.04 M and H2O2 concentration of 22.11 ml/L. Maximum phase angle under the optimum conditions was determined to be 85.4 degrees. Ringer's simulated body fluid was used for in vivo electrochemical impedance spectroscopy analyses of biomaterials. (C) 2014 Elsevier Ltd. All rights reserved.