Browsing by Author "Nikolaev A."

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    Metal vapour vacuum arc ion implantation facility in Turkey
    (2005) Öztarhan A.; Brown I.; Bakkaloglu C.; Watt G.; Evans P.; Oks E.; Nikolaev A.; Tek Z.
    A vacuum arc ion source based metal ion implantation facility is built and in operation at TUBITAK (The Scientific and Technical Research Council of Turkey), Izmir, Turkey and a surface modification research and development program is being carried out here. The system is similar to the one in Lawrence Berkeley Laboratory, which was first built and developed by Brown et al. The broad-beam ion source can be repetitively pulsed at rates up to ∼50 pulses per second and the extracted ion beam current can be up to ∼1 A peak or ∼10 mA time averaged. The ion source extraction voltage can be increased up to 110 kV. Additionally, mixed metal and gas ion beams were generated by a magnetic field, which was obtained through a magnet coil located in front of anode plate and by adding gas in the discharge region. This modified system was used to form buried layers of mixed metal-gas species such as Ti+N (on 316 SS and Ti alloy samples) and Zr and W (316 SS and Ti alloy samples, respectively) of which their hardness, coefficient of friction and wear volumes were measured and their RBS results were obtained. The anodic electrochemical tests showed that the corrosion resistance of Ti implanted 304 SS samples was increased with the dose. Micro structures of Ti implanted surfaces of 304 SS samples were examined with SEM before and after the corrosion tests and the results showed that the pittings were formed mostly in the areas where implanted Ti concentration was less. Recently, the system is equipped with TOF for measuring the charge state distribution of ions. R&D work is planned for the purpose of forming tribologically enhanced materials for industrial applications by using ion implantation, PVD coating, plasma nitriding and their combinations. The results showed that the hardness and performance of ion implanted (with various metals and N) PVD coated cutting inserts increased remarkably. The use of ion implantation techniques in modifying the properties of textile and other materials and optimising the performance of textile and other industrial machine parts and tools is also being investigated and some of the results are presented in this work. © 2004 Elsevier B.V. All rights reserved.
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    Polymeric thermal analysis of C + H and C + H + Ar ion implanted UHMWPE samples
    (2007) Kaya N.; Oztarhan A.M.; Urkac E.S.; Ila D.; Budak S.; Oks E.; Nikolaev A.; Ezdesir A.; Tihminlioglu F.; Tek Z.; Cetiner S.; Muntele C.
    Chemical surface characterization of C + H hybrid ion implanted UHMWPE samples were carried out using DSC (differential scanning calorimeter) and TGA (thermal gravimetric analysis) techniques. Samples were implanted with a fluence of 1017 ion/cm2 and an extraction voltage of 30 kV. The study of TGA and DSC curves showed that: (1) Polymeric decomposition temperature increased, (2) Tm, ΔCp and ΔHm values changed while ΔCp and ΔHm increased. Tg value could not be measured, because of some experimental limitations. However, the increase in ΔHm values showed that Tg values increased, (3) the branch density which indicated the increase in number of cross-link (Mc) decreased in ion implanted samples and (4) increase in ΔHm values indicated increase in crystallinity of implanted surface of UHMWPE samples.
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    Thermal characterization of Ag and Ag + N ion implanted ultra-high molecular weight polyethylene (UHMWPE)
    (2007) Sokullu Urkac E.; Oztarhan A.; Tihminlioglu F.; Kaya N.; Ila D.; Muntele C.; Budak S.; Oks E.; Nikolaev A.; Ezdesir A.; Tek Z.
    Most of total hip joints are composed of ultra-high molecular weight polyethylene (UHMWPE ). However, as ultra-high molecular weight polyethylene is too stable in a body, wear debris may accumulate and cause biological response such as bone absorption and loosening of prosthesis. In this study, ultra-high molecular weight polyethylene samples were Ag and Ag + N hybrid ion implanted by using MEVVA ion implantation technique to improve its surface properties. Samples were implanted with a fluence of 1017 ion/cm2 and extraction voltage of 30 kV. Implanted and unimplanted samples were investigated by thermo-gravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), optical microscopy (OM) and contact Angle measurement. Thermal characterization results showed that the ion bombardment induced an increase in the % crystallinity, onset and termination degradation temperatures of UHMWPE. © 2007 Elsevier B.V. All rights reserved.
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    Modification of surface morphology of UHMWPE for biomedical implants
    (Materials Research Society, 2007) Oztarhan A.; Urkac E.S.; Kaya N.; Yenigul M.; Tihminlioglu F.; Ezdesir A.; Zimmerman R.; Budak S.; Muntele C.; Chhay B.; Ila D.; Oks E.; Nikolaev A.; Tek Z.; Eltem R.
    Ultra High Molecular Weight Polyethylene (UHMWPE) samples were implanted with metal and metal-gas hybrid ions (Ag, Ag+N, C+H, C+H+Ar, Ti+O) by using improved MEVVA Ion implantation technique [1,2]. An extraction voltage of 30 kV and influence of 1017 ions/cm2 were attempted in this experiment, to change their surface morphologies in order to understand the effect of ion implantation on the surface properties of UHMWPEs. Characterizations of the implanted samples with RBS , ATR - FTIR, spectra were compared with the un-implanted ones . Implanted and unimplanted samples were also thermally characterized by TGA and DSC. It was generally observed that C-H bond concentration seemed to be decreasing with ion implantation and the results indicated that the chain structure of UHMWPE were changed and crosslink density and polymer crystallinity were increased compared to unimplanted ones resulting in increased hardness. It was also observed that nano size cracks (approx.10nm) were significantly disappeared after Ag implantation, which also has an improved antibacterial effect. Contact angle measurements showed that wettability of samples increased with ion implantation. Results showed that metal and metal+gas hybrid ion implantation could be an effective way to improve the surface properties of UHMWPE to be used in hip and knee prosthesis. © 2007 Materials Research Society.