Işıl Birlik

Mechanical properties and biocompatibility of the sputtered Ti doped hydroxyapatite

The hydroxyapatite enriched with Ti were prepared as possible candidates for biomedical applications especially for implantable devices that are in direct contact to the bone. The hydroxyapatites with different Ti content were prepared by RF magnetron sputtering on Ti-6Al-4V alloy using pure hydroxyapatite and TiO2 targets. The content of Ti was modified by changing the RF power fed on TiO2 target. The XPS and FTIR analyses revealed the presence of hydroxyapatite structure. The hardness and elastic modulus of the hydroxyapatite were increased by Ti addition. After 5 days of culture, the cell viability of the Ti-6Al-4V was enhanced by depositing with undoped or doped hydroxyapatite. The Ti additions led to an increase in cell viability of hydroxyapatite, after 5 days of culture. The electron microscopy showed the presence of more cells on the surface of Ti-enriched hydroxyapatite than those observed on the surface of the uncoated alloys or undoped hydroxyapatite.

Enhancement of the mechanical properties of hydroxyapatite by SiC addition.

Improvements of mechanical and anticorrosive properties, as well as superior osseointegration of the hydroxyapatite coated titanium alloy were reported in the last years by the addition of different elements (Si or Ti) into hydroxyapatite structure. The aim of this work was to prepare and to investigate the hydroxyapatite (HAP) coatings enriched with SiC in order to enhance the mechanical properties of HAP films. The coatings were deposited on Ti6Al4V alloy substrates by co-sputtering of HAP and SiC targets, using a magnetron sputtering system. The films were characterized in terms of elemental and phase composition, chemical binding, morphology and mechanical properties by EDS, XRD, FTIR, SEM, AFM, and nanoindentation. Overall, improved mechanical properties were found by adding SiC to the basic HAP structure.

Characterization of Buffer Layers on Ni-based Substrates for YBCO Superconductors

Abstract Metal oxide buffer layers provide a continuous, smooth textured and chemically inert surface for growth of the YBCO (YBa2Cu307-x) film and prevent metal diffusion from the substrate into the superconductor. Ce02, Gd203 and EU203 buffer layers were grown on metallic Ni substrates using a sol-gel method by using metal 2,4-pentanedionate and acetate precursors. The films were annealed at 1150°C under 4%H2-Ar gas mixture. Textured, crack free and continuous buffer layers were obtained through the sol-gel technique. Prior to the coating process, solution characterization was performed by turbidimeter, pH meter, contact angle goniometer and rheometer. Heat treatment profiles were determined by using DTA-TG and FTIR. The coated layers were characterized by means of XRD, SEM-EDS, AFM and a scratch tester. As a result, textured growth of Ce02, EU203 and Gd203 thin films on textured Ni tapes by the sol-gel dip coating process were successfully performed.

Tribological Properties of Electric Arc–Sprayed CuSn Coating for Bearing Elements

This study was initiated for the purpose of understanding the tribological behavior of CuSn coatings at different loads under dry and lubricant environments for an application of bearing elements. A pin-on-plate type of apparatus was used to subject the CuSn coating to sliding wear against AISI 303 counter body. The surface roughness was measured from worn and unworn samples. The surface morphology and the elemental analysis of the CuSn coating was evaluated using SEM-EDS. Phase analyses of the coating were performed by XRD. It was found that the microhardness values changed with the depth of the coating and a decrease of surface roughness under dry condition wear test is greater than that under the lubricant environment. The critical load between the coating and the substrate was found to be 11.82 mN using scratch results. CuSn coated samples had higher wear resistance under a lubricated environment than that under a dry environment. Moreover, it was observed that the effect of the environment on the friction coefficient values is more dominant than that of the load levels.

Preparation and Characterization of Ni–TiO2 Nanocomposite Coatings Produced by Electrodeposition Technique

In this paper Ni-TiO2 nanocomposite coatings with different sizes of TiO2 nanoparticles were successfully prepared by electrodeposition process from a nickel electrolyte in which the TiO2 nanoparticles were suspended. The influence of relevant deposition parameters on the nanocomposite coating characteristics was discussed. X-ray diffractometer (XRD) has been applied in order to investigate the phase structure of the nanocomposite coatings. The surface morphology of nanocomposite coatings was characterized by a scanning electron microscopy equipped with an energy dispersive spectroscopy (SEM/EDS). The electrodeposited nanocomposite coatings obtained at different deposition parameters were evaluated for their mechanical and corrosive properties. Obtained results show that the size of TiO2 nanoparticles and applied current density during deposition process has a direct effect on mechanical and corrosive properties of nanocomposite coatings. Increasing current density and smaller nanoparticle size has affirmative effect on mechanical properties whereas corrosion resistance of nanocomposite coatings deposited at 3 A.dm-2 current density are higher than the coatings prepared at higher current density values.

Effect of SiC interlayer between Ti6Al4V alloy and hydroxyapatite films.

Bioactive coatings are frequently used to improve the osseointegration of the metallic implants used in dentistry or orthopaedics. Among different types of bioactive coatings, hydroxyapatite (Ca10(PO4)6(OH)2) is one of the most extensively used due to its chemical similarities to the components of bones and teeth. In this article, production and characterization of hydroxyapatite films deposited on Ti6Al4V alloy prepared by magnetron sputtering were reported. Besides, SiC was deposited on substrate surface to study the interlayer effect. Obtained coatings were annealed at 600 °C for 30 and 120 min in a mixed atmosphere of N2 + H2O vapours with the heating rate of 12 °C min−1. The effects of SiC interlayer and heat treatment parameters on the structural, mechanical and corrosion properties were investigated. After heat treatment process, the crystalline hydroxyapatite was obtained. Additionally, cell viability tests were performed. The results show that the presence of the SiC interlayer contributes a decrease in surface roughness and improves the mechanical properties and corrosion performance of the hydroxyapatite coatings. Biological properties were not affected by the presence of the SiC interlayer.