Browsing by Author "Öztarhan A."

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    High fluence effects on ion implantation stopping and range
    (2005) Selvi S.; Tek Z.; Öztarhan A.; Akbaş N.; Brown I.G.
    We have developed a code STOPPO which can be used to modify the more-widely used ion implantation codes to more accurately predict the mean nuclear and electronic stopping power, preferential sputtering and range of heavy ions in monatomic target materials. In our simulations an effective atomic number and effective atomic mass are introduced into conveniently available analytical stopping cross-sections and a better fitting function for preferential sputtering yield is carefully evaluated for each ion implantation. The accuracy of the code confirmed experimentally by comparison with measured Rutherford backscattering spectrometry (RBS) concentration profiles for 130 keV Zr ions implanted into Be to fluences of 1 × 1017, 2 × 10 17 and 4 × 1017 ions/cm2. We find a steady increase in the mean nuclear and electronic stopping powers of the target; the increase in nuclear stopping power is much greater than the increase in electronic stopping power. © 2004 Elsevier B.V. All rights reserved.
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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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    Investigating the Applicability of Metal Ion Implantation Technique (MEVVA) to Textile Surfaces
    (2006) Öktem T.; Özdogan E.; Namligöz S.E.; Öztarhan A.; Tek Z.; Tarakçioglu I.; Karaaslan A.
    Polyethylene terephalate (PET) samples were modified by Cu, C, Ti, and Cr implantation using a metal vapor vacuum arc (MEVVA) implanter. The ions were implanted at an accelerating voltage of 30 kV with a dose ranging from 1 × 1014 to 1 × 1017 ions/cm2. In the first part of this study, Cu ions were implanted to improve the electrical properties of PET woven fabrics, and in the second part, C, Ti and Cr ions were implanted to enhance the mechanical properties of PET membrane fabrics. After implantation, the results showed that the half-charge decay time of implanted fabric lessened to milliseconds, and the friction coefficient and wear loss values decreased significantly. The surface morphologies of the samples were examined by scanning electron microscopy and atomic force microscopy. The changes in chemical structure were observed by IR spectra. © 2006, SAGE Publications. All rights reserved.
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    Characterization of Ti + N and Zr ion implanted 316 L stainless steel
    (2007) Tek Z.; Öztarhan A.; Selvi S.
    In this study, polished 316LSS stainless steel has been implanted with Ti + N and Zr ions at fluence of 2 × 1017 ions/cm2 and 1 × 1017 ions/cm2, respectively. Ion charge state distributions of Ti + N and Zr were measured by time-of-flight spectrometry, and the mean energies of these ions were determined. The Zr concentration profiles were obtained by Rutherford backscattering spectrometry. The range distribution of ions in implanted and unimplanted samples were evaluated using TRIM and STOPPO programs and the results were compared with the experimental data, which were in good agreement. The influence of the ions on the mechanical behavior of the 316LSS was investigated. The measurements show that after Ti + N implantation; the friction coefficient decreases, the hardness value increases, the wear resistance decreases and after Zr implantation; the friction coefficient decreases, the hardness value increases and the wear resistance increases with respect to an unimplanted sample. © 2007 Elsevier B.V. All rights reserved.
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    A comparative study of Ti + N and W ion implantation into Ti-6Al-4V alloy
    (2007) Tek Z.; Öztarhan A.; Selvi S.
    The effect of Ti + N hybrid ion implantation and W ion implantation at a dose of 1 × 1017 ions/cm2, and 50 kV and 40 kV extraction voltage on mechanical properties of Ti-6Al-4V samples was studied. Mechanical tests have shown that the friction coefficient decreased with both Ti + N and W ion implantations. It was observed that the Ti + N hybrid ion implanted samples gave better results compared to those of the W ion implanted ones. The results of wear tests showed that both Ti + N hybrid and W ion implanted samples had much better wear resistance compared to unimplanted samples. Hardness values for Ti + N hybrid ion implanted and W implanted samples were much higher than those for unimplanted ones. Ti + N and W ions charge state distributions were measured using time of flight spectrometry. W concentration profiles were obtained by Rutherford backscattering spectrometry. These and the range distribution of ions in implanted and unimplanted samples were evaluated using TRIM and STOPPO programs [S. Selvi, Z. Tek, A. Oztarhan, I. Brown, N. Akbaş 'High fluence effects on ion implantation stopping and range', Nuclear Instruments and Methods in Physics Research B 229 (2005) 60-64; J.F. Ziegler, J.P. Biersack, U. Littmark, (Pergamon, New York, 1985); also http://www.SRIM.org] and the results were compared with the experimental data. © 2007 Elsevier B.V. All rights reserved.
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    A comparative study of single and duplex treatment of martensitic AISI 420 stainless steel using plasma nitriding and plasma nitriding-plus-nitrogen ion implantation techniques
    (2007) Çetin A.; Tek Z.; Öztarhan A.; Artunç N.
    Martensitic AISI 420 is a high chromium mold steel which is suitable for tools for molding corrosive plastics. In this study, micro-pulsed plasma nitriding and plasma nitriding + nitrogen ion implantation techniques have been used to improve the surface hardness and tribological properties of AISI 420 substrates. Firstly polished-AISI 420 samples are nitrided at 530 °C for 15 h at a pressure of 10 mbar. Then nitrided samples are implanted with nitrogen ions to a dose of 2 × 1017 ions/cm2. Mechanical characterization of both of the modified and unmodified samples has been carried out by means of nano-hardness, wear resistance, friction coefficient and surface roughness measurements. It is found that the nano-hardness, wear resistance, friction coefficient and surface roughness values improve 1.6, 3.5, 1.4 and 10 times for plasma nitrided samples, and 2.0, 4.6, 1.1 and 9 times for plasma nitrided-plus-N+ ion implanted samples, respectively, in comparison with unmodified AISI 420 samples. Both the plasma nitriding process and the plasma nitriding-plus-N+ ion implantation treatment sample results are also compared. The improvement of the samples modified using nitriding-plus-N+ ion implantation process is found to be better than that of samples modified by the nitriding process. © 2007 Elsevier B.V. All rights reserved.
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    Modification of friction and wear properties of PET membrane fabrics by MEVVA ion implantation
    (2008) Öktem T.; Tarakçioǧlu I.; Özdoǧan E.; Öztarhan A.; Namligöz E.S.; Karaaslan A.; Tek Z.
    Polyethylene terephthalate (PET) membrane fabrics were modified by Ti, W, Ti + N, Cr + N and C + N implantations using a metal vapor vacuum arc (MEVVA) source at an accelerating voltage of 30 kV with doses ranging from 1 × 1015 to 5 × 1016 ions cm-2 in TUBITAK Textile Research Center in Izmir. After implantation, changes in the mechanical properties of the samples were investigated. The results indicated that friction coefficient and wear loss values decreased significantly. This decrease depended on the used ion species and the doses. The surface morphologies of samples were examined by SEM and AFM. The changes in chemical structure were observed by IR spectra. © 2007 Elsevier B.V. All rights reserved.