Browsing by Author "Dikici, B."

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Corrosion Characteristics of Al-cu/B4c (T6) Mmcs and Their Microstructure Evaluation
(Redakcia Kovove Materialy, 2009) Dikici, B.; Bedir, F.; Gavgali, M.; Kiyak, T.
In this study, the pitting susceptibilities of Al-Cu alloy based metal matrix composites (MMCs) reinforced with boron carbide (B4C) particles have been investigated using cyclic polarization (CP) technique in aerated and deaerated 3.5 wt.% NaCl solution. The effects of reinforcement particle volume fraction and artificially aged (T6) process on corrosion behaviour of the composites have been also examined. It has been found that the 30 % B4C MMC is more susceptible to pitting attack compared with 10 % B4C MMC.
Corrosion Protection of Aa6061-T4 Alloy by Sol-Gel Derived Micro and Nano-Scale Hydroxyapatite (Ha) Coating
(Springer, 2012) Sonmez, S.; Aksakal, B.; Dikici, B.
Micron and nano-scale hydroxyapatite (HA) were coated successfully on AA6061-T4 substrates by sol-gel method. Besides, the effects of coating thickness on adhesion strength and corrosion behaviour of the coatings were studied. Corrosion resistance was measured by potentiodynamic polarization test using a potentiostat under in vitro conditions. The coatings before and after corrosion tests were characterized by adhesion tests, a scanning electron microscopy attached with EDS and X-ray diffraction analysis. The results revealed that all the coatings exhibit a passive behaviour in Ringer's solution. Specimens coated with nano-scale HA had the higher corrosion resistance than micro-scale coatings. The highest corrosion resistance appeared to be for the similar to 30 mu m nano-scale HA coated substrates. However, for micro-scale HA coatings, the highest adhesion resistance was obtained at similar to 30 mu m film thickness.
Detrimental Effect of Particle Sol-Gel Coating on the Corrosion Behavior of A380-Sic Composite
(Pergamon-elsevier Science Ltd, 2009) Dikici, B.; Tekmen, C.; Yigit, O.; Gavgali, M.; Cocen, U.
In this study, the corrosion susceptibility of aluminum matrix composites reinforced with artificially oxidized SiO(2) and sol-gel Fe/TiO(2) coated silicon carbide particles (SiC(p)) has been investigated. Corrosion behavior of the composites, fabricated by the liquid metal infiltration technique, was established in chloride containing alkaline environments by cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS) techniques. It has been found that, sol-gel coating of SiC particles with Fe/TiO(2) has a detrimental effect on the corrosion characteristics of A380-SiC metal matrix composite. (C) 2009 Elsevier Ltd. All rights reserved.
The Effect of Arc Current on the Corrosion Behaviour of Coated Niti Alloy on Aisi304 by Plasma Transferred Arc Process
(Maik Nauka/interperiodica/springer, 2012) Dikici, B.; Ozel, S.; Gavgali, M.; Somunkiran, I.
In this study, the effect of arc current on the corrosion behaviour of NiTi coating on stainless steel has been investigated. NiTi powder mixture was alloyed on surface austenitic AISI304 by using plasma transferred arc (PTA) method. Surface alloying process is turned out using 80, 90, 100 A current densities and Ar atmosphere which is plasma and protective. The corrosion resistance of the coatings was analyzed by measuring the potentiodynamic polarization scanning (PDS) technique. Results indicate that corrosion resistances of the coatings decrease with increasing the arc current. In addition, the localized corrosion on the surface of produced coating at 100A is more activated than other coatings and the most passive coating in view of corrosion was obtained at produced coating at 80A.
The Effect of Coating Thickness on Corrosion Resistance of Hydroxyapatite Coated Ti6al4v and 316l Ss Implants
(Springer, 2010) Aksakal, B.; Gavgali, M.; Dikici, B.
Hydroxyapatite (HAP) has been coated onto Ti6Al4V and 316L SS substrates by sol-gel method. The coating thicknesses for the analysis were about 40 and 72 mu m. Adhesion and corrosion tests have been conducted on uncoated and HAP-coated substrates. The coatings were characterized by XRD, SEM, and adhesion analysis. The corrosion resistance was examined in vitro by potentiodynamic polarization technique in Ringer's solution at room temperature. Electrochemical analysis indicated that the highest corrosion susceptibility was found on 72-mu m-coated 316L SS, and the 40-mu m HAP-coated Ti6Al4V showed the highest corrosion resistance. It was observed that the coating thickness was an effective parameter on both adhesion and corrosion resistance. It was shown that adhesion and corrosion resistance decreased with increasing coating thickness on both substrates.
The Effect of Cold-Worked Ratio on Corrosion Behavior of T8 Tempered Al-si-mg/Sicp Metal Matrix Composites
(International Committee on Composite Materials, 2007) Dikici, B.; Tekmen, C.; Gavgali, M.; Tsunekawa, Y.
The corrosion behaviors of T8 tempered Al-Si-Mg/SiCp metal matrix composites (MMCs) were investigated in aerated and deaerated 3.5wt% NaCl solutions by potentiodynamic polarization technique in this study. In order to determine the effect of cold work on the electrochemical behavior, the composites were cold-worked to a plastic strain of 4, 6, 10, 25 and 50%. A major change in the corrosion morphologies were observed cold working ratio increased from 4 to 50%. For example, electrochemical analysis indicated that the corrosion current densities (icor) of 20% vol. SiC composite increased from 0.8 to 5.9 with increasing cold-worked ratio after T8 temper. In addition, we find that there is a significant coloration between corrosion susceptibility and level of cold work.
The Effect of Post-Heat Treatment on Microstructure of 316l Cold-Sprayed Coatings and Their Corrosion Performance
(Springer, 2016) Dikici, B.; Yilmazer, H.; Ozdemir, I.; Isik, M.
The combined effects of process gases and post-heat treatment temperature on the microstructure of 316L cold-sprayed coatings on Al5052 substrates have been investigated in this study. The stainless steel coatings were subjected to heat treatment at four different temperatures (250, 500, 750, and 1000 degrees C) to study the effect of heat treatment. In addition, the corrosion performances of the coatings at different process temperatures have been compared using the potentiodynamic scanning technique. Microstructural characterization of the coatings was carried out using scanning and transmission electron microscopy and x-ray diffraction. The results of present study showed that cold-sprayed stainless steel coatings processed with helium exhibited higher corrosion resistance than those of coatings sprayed with nitrogen process gas. This could partially be attributed to the reduction in porosity level (4.9%) and improvement of particle-particle bonding. In addition, evaluation of the mechanical and microstructural properties of the coatings demonstrated that subsequent heat treatment has major influence on the deposited layers sprayed with He process gas.
Electrochemical Behaviors of Biomedical Nano-Grained Β-Type Titanium Alloys
(Trans Tech Publications Ltd, 2017) Yilmazer, H.; Dikici, B.; Niinomi, M.; Nakai, M.; Lui, H.; Todaka, Y.; Ozcivan, A.N.
The microstructural evolution and its effect on biocompatibility of TNTZ through HPT processing were investigated systematically in this study. TNTZAHPT shows an enhanced mechanical biocompatibility, which is characterized by a higher tensile strength (1375 MPa) and hardness (450 HV) than those of TNTZST, TNTZAT, and Ti64 ELI while maintaining a relatively low Young’s modulus. In this study, such microstructural refinement of TNTZ and its effect on electrochemical biocompatibility through HPT processing are investigated systematically in this study. The microstructure of TNTZAT consists of randomly distributed needle-like α precipitates in the equiaxed β grains with a diameter of approximately 40 m. The microstructure of TNTZAHPT consists of nano-grained (NG) elongated β grains that have subgrains of non-uniform morphologies resulting from distortion by severe torsional deformation. Furthermore, the β grains and subgrains are surrounded by non-equilibrium grain boundaries. The needle-like α precipitates are completely refined to a nano-grained. TNTZAHPT exhibits an enhanced combination of excellent corrosion performance and improved cellular response compared to TNTZST, TNTZAT, and Ti64 ELI. © 2017 Trans Tech Publications, Switzerland.
Feb and Feb/H-bn Based Anti-Corrosive Composite Coatings for Aluminium Alloys
(Emerald Group Publishing Limited, 2012) Dikici, B.; Ozdemir, I.
Purpose - The purpose of this paper is to investigate the corrosion behaviour of ferroboron (FeB) and FeB/h-BN (hexagonal boron nitride) coatings deposited onto A383 substrates by atmospheric plasma spraying. Design/methodology/approach - Potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion susceptibilities of the composite coatings. Microstructural characterizations were carried out by using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). Findings - It was observed that the coatings resisted localized corrosion in NaCl solutions and protective oxide films on the coatings repaired themselves over the corrosion potential. Hexagonal-BN is not only a limiting factor in the corrosion of the FeB based coatings. The corrosion morphologies of the coatings are strictly dependent on pores and micro-cracks in the coating. Practical implications - The iron-based borides act as solid lubricants and have a positive influence on tribological properties such as hardness, friction and corrosion of the coating. Originality/value - Knowledge of the effects of FeB on the corrosion behaviour of thermal spray coatings is still incomplete and this is the most important obstacle to the widespread use of the coatings in engineering applications. The paper reports electrochemical test results of the coatings and discusses the morphologic effects of h-BN on the corrosion behaviour.
Influence of Hydroxyapatite Coating Thickness and Powder Particle Size on Corrosion Performance of Ma8m Magnesium Alloy
(Elsevier Science Sa, 2014) Sonmez, S.; Aksakal, B.; Dikici, B.
To improve the corrosion resistance of MA8M magnesium alloy, sol-gel derived coatings of micron and nano-scale hydroxyapatite (HA) were coated successfully on MA8M magnesium alloy substrates. The effects of coating thickness and HA powder particle size on the adhesion strength and corrosion resistance on magnesium alloy was investigated. Potentiodynamic polarization (PDS) tests were performed in a Ringer solution. The coatings before and after corrosion tests were characterized by adhesion tests, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results show that the micro-scale-HA coated Mg substrates were more corrosion resistant than the nano-scale-HA coatings. Corrosion susceptibilities of the nano-scale-HA coated samples were influenced inversely. The anodic activity of the micro-scale-HA coatings increased with increased coating thickness. The coated film provided good barrier characteristics and achieved good corrosion protection for Mg substrates when compared to substrates without any coatings. The best corrosion resistance was obtained at 30 mu m film thickness for micro-scale-HA coatings. (C) 2014 Elsevier B. V. All rights reserved.
Multifunctional Coatings for Biomedical Applications
(CRC Press, 2025) Yigit, O.; Topuz, M.; Dikici, B.
In recent years, there has been a growing interest in the development of multifunctional coatings for biomedical applications. These coatings have the potential to improve the biocompatibility, durability, and functionality of biomedical implant materials. Multifunctional coatings can provide a range of benefits, including enhanced biocompatibility, reduced infection rates, improved mechanical properties, and increased drug delivery capabilities. They can also be tailored to specific applications, such as antimicrobial coatings for implant surfaces or drug-eluting coatings for stents. There are many different types of materials that can be used to create multifunctional coatings, including polymers, ceramics, metals, and composites. The choice of material depends on the specific application and desired properties of the coating. Various techniques can be used to apply multifunctional coatings, including physical and chemical vapor deposition, electrospinning, sol-gel, or spray coating. These techniques can also be combined to create more complex coatings with multiple functions. Overall, the development of multifunctional coatings for biomedical applications is an exciting area of research that has the potential to significantly improve the performance and longevity of biomedical implant materials. © 2025 selection and editorial matter, Ajit Behera, Kuldeep K Saxena, Dipen Kumar Rajak and Shankar Sehgal. All rights reserved.
Preparation and Characterization of Chitosan/Hydroxyapatite Sol-Gel Coating on Ti-6al
(Certex, INCDTP-ICPI, 2016) Gungor Koc, S.; Dikici, B.; Topuz, M.; Yilmazer, H.; Ozdemir, I.; Niinomi, M.; Nakai, M.
A biocomposite coating containing chitosan and hydroxyapatite was developed on Ti-6Al-4V substrate by a sol-gel method in order to obtain a biocompatible and antimicrobial implant surface which can be used to create a smooth transmucosal region for a faster and better wound healing and an increased bioactivity. The coatings characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and differential thermal analysis (DTG). Scratch test was carried out to evaluate the adhesion between the coated film and the substrates. The critical load at which the coating film was peeled off from the substrate is determined by using the spherical diamond stylus. The results revealed that the coating roughness is approximately 0.23. The critical load for debonding the coating film from the substrate was determined between 6 to 11N. Only a little wear debris was come out from the coating film in the initial stage of a small-applied load. With increasing the load, the coating film became crushed and finally worn away. © 2016 Certex, INCDTP-ICPI.
Production Technique–structure Relationship in Bioceramic-Coated Scaffold Applications
(Elsevier, 2023) Aslan, N.; Topuz, M.; Aksakal, B.; Dikici, B.
It is well known that the surface of metal-based implants is very resistive in aggressive body environments due to the noble oxide layer naturally formed on their surfaces. However, their osseointegration properties are very low. By the way, specific cells attached are desired on the implant surface when the surface of an implant connects with tissue in many circumstances. Thus in parallel with technological developments, biomedical engineering focuses on the growth of new tissue on the implant surface or in the porosities of the implant. The bulk properties of metallic scaffolds, especially Young’s modulus, can be controlled by the porosity ratio of the scaffold but cannot form a bond between the implant and tissue interfaces. Thus the coating of scaffold walls with a bioactive material is required. In this chapter, bioceramic coating techniques of scaffolds, mechanical and corrosion behavior, biocompatibility, and interactions of surface/tissue interface, especially considering the last published reports, were reviewed, in detail. © 2023 Elsevier Ltd. All rights reserved.
Synthesis and Characterization of Hydroxyapatite/Tio2 Coatings on the Β-Type Titanium Alloys With Different Sintering Parameters Using Sol-Gel Method
(Maik Nauka/interperiodica/springer, 2018) Dikici, B.; Niinomi, M.; Topuz, M.; Say, Y.; Aksakal, B.; Yilmazer, H.; Nakai, M.
In this study, hydroxyapatite (HA) based composite films were successfully syntheses on the beta-type Ti29Nb13Ta4.6Zr (TNTZ). The solutionized TNTZ substrates coated with HA and HA/Titania (TiO2) bioactive composite coatings by sol-gel method under various sintering parameters related to sintering temperatures and heating ramp rates. Microstructural observations of the coatings revealed that apatite was formed on the substrates. The hardness values of the coatings increase with increasing both the sintering temperature and the TiO2 concentration in the coatings layer. However, it was found that the heating ramp rate of the sintering was not affecting the hardness values so much. Also, the hardness values of the HA/TiO2 composite coatings at all sintering temperatures were higher than only HA coated TNTZ samples due to the existence TiO2 phases in the HA matrix. Results indicating that the doping of HA with TiO2, improve the physical consistency between the coating layer and the substrates and provide a better inter-particle bonding due to the existence TiO2 phases in the HA.
Synthesis of Implantable Ceramic Coatings and Their Properties
(Elsevier, 2023) Topuz, M.; Yigit, O.; Kaseem, M.; Dikici, B.
Nowadays, emphasis on metallic materials, coating materials, and coating technology to improve osseointegration and increase the lifespan of biological fixation prostheses has become a topic of great interest in the field of prosthetic research. Many published studies showed that the bioactivity-coated surfaces increase the implant–tissue compatibility with their similarities to the bone structure. Therefore several coatings are widely used to increase osteoconductivity on implant material surfaces in the biomedical industry. In this section, synthesis techniques, mechanical and corrosion behavior, osseointegration, and esthetic responses of implantable ceramic coatings, especially considering the last published reports, are reviewed in detail. Besides, an answer to the “are the coatings suitable for in vivo conditions?” is investigated. © 2023 Elsevier Ltd. All rights reserved.
Synthesis of in Situ Tic Nanoparticles in Liquid Aluminum: the Effect of Sintering Temperature
(Sage Publications Ltd, 2011) Dikici, B.; Gavgali, M.; Bedir, F.
In this study, in situ TiC nanoparticles with a diameter range of 70-400 nm have been successfully synthesized in liquid aluminum by conventional hot-pressing method. The effect of production temperature on the formation of the TiC phase during sintering was investigated by differential thermal analysis, X-ray diffraction, and scanning and transmission electron microscopies. The results show that the synthesizing temperature has a great effect on the formation of the TiC. Also, increase of producing temperature accelerates the formation of in situ TiC nanoparticles and decreases the portion of Al3Ti intermetallic phase in the liquid aluminum.
Systematic Characterization and Enhanced Corrosion Resistance of Novel Β-Type Ti-30zr Biomedical Alloys With Halloysite Nanotubes (Hnts) and Zirconia (zro2)-Reinforced Polylactic Acid (Pla) Matrix Coatings
(Elsevier Ltd, 2024) Topuz, M.; Dikici, B.; Kasapoglu, A.E.; Zhao, X.; Niinomi, M.
This study investigates synthesis, the in-vitro corrosion resistance and adhesion performance of PLA-based composite coatings reinforced with halloysite nanotubes (HNT) and zirconia (ZrO2) on beta-type Ti-30Zr-5Mo biomedical alloys. The coatings were synthesized using the sol-gel method and characterized for their surface morphology, chemical composition, and electrochemical properties. SEM analysis revealed the presence of micropores and cracks, particularly in HNT and HNT/ZrO2 bilayer coatings. XPS and Raman spectroscopy confirmed the successful integration of HNT and ZrO2 into the PLA matrix. The potentiodynamic polarization scans and electrochemical impedance spectroscopy (EIS) showed enhanced corrosion resistance for coatings containing HNT and ZrO2, with the HNT/ZrO2 bilayer demonstrating the best performance. Contact angle measurements indicated hydrophilic properties, crucial for bioactive surfaces. Overall, the study demonstrates that HNT and ZrO2 reinforcements in PLA coatings significantly improve the corrosion resistance and bioactivity of Ti-30Zr-5Mo alloys, making them promising candidates for biomedical applications. Details are compared and discussed in the text. © 2024 Elsevier Ltd
Two Simple Methods for Surface Modification of Lithium Disilicate Dental Blocks With Hydroxyapatite
(MIM RESEARCH GROUP, 2020) Topuz, M.; Dikici, B.
Crowns are materials that attracting the attention and lithium disilicates among them widely used because of their high bulk mechanical features. Increasing the bioactivity of crowns has generally been a common aspect of all studies. In this study, lithium disilicate dental blocks were coated with bioactive calcium-phosphate components using sol-gel dip-coating methods to increase their surface bioactivity. Two coating methods called as slurry and powder methods were proposed to obtain dense and remarkable layer on the lithium disilicate substrates. The coating layers were characterized by scanning electron microscopy attached with energy dispersive spectroscopy. Coating procedures have successfully accomplished and show enhanced surface properties with terms of calcium/phosphate ratios. Tri-calcium phosphate obtained by the slurry method, which has 1.5 calcium/phosphate ratio, is a favorable structure for bio-absorbable. However, the powder method has approximately 1.67 calcium/phosphate ratio which necessary for hydroxyapatite (HA) structure for higher crystallinity and lower solubility properties. © 2019 MIM Research Group. All rights reserved.
Wear Behavior of Plasma Sprayed Composite Coatings With in Situ Formed Al2o3
(Elsevier Sci Ltd, 2009) Mindivan, H.; Tekmen, C.; Dikici, B.; Tsunekawa, Y.; Gavgali, M.
In the present study, the wear behavior of in situ formed Al2O3 reinforced hypereutectic Al-18Si matrix composite coatings have been investigated. These coatings were successfully fabricated with mechanically alloyed Al-12Si and SiO2 powder deposited on aluminum substrates by atmospheric plasma spraying (APS). The produced samples were characterized by means of microscopic examinations, hardness measurements and wear tests. The obtained results pointed out that the amount of in situ formed Al2O3 particles increased with increasing spray distance and decreasing in-flight particle velocity and temperature, which was accompanied by an improvement in hardness and wear resistance. (C) 2009 Elsevier Ltd. All rights reserved.