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Öğe Analytical Approximation for Cahn-Hillard Phase-Field Model for Spinodal Decomposition of a Binary System(2021) Tozar, Ali; Tasbozan, Orkun; Kurt, AliPhase transformations which lead to dramatical property change are\rvery important for engineering materials. Phase-eld methods are one of the most\rsuccessful and practical methods for modelling phase transformations in materials.\rThe Cahn-Hillard phase-eld model is among the most promising phase-eld models.\rThe most successful aspect of the model is that it can predict spinodal decomposition\r(which is essential to determining the microstructure of an alloy) in a binary system.\rIt is used in both materials science and many other elds, such as polymer science,\rastrophysics, and computer science. In this study, the Cahn-Hillard phase-eld model\ris evaluated by an analytical approach using the (1=G0)-expansion method. The so-\rlutions obtained are tested for certain thermodynamic conditions, and their accuracy\rof predicting the spidonal decomposition of a binary system is conrmed.Öğe Analytical solutions of Cahn-Hillard phase-field model for spinodal decomposition of a binary system(Iop Publishing Ltd, 2020) Tozar, Ali; Tasbozan, Orkun; Kurt, AliSpinodal decomposition is a very important and challenging issue not for only materials science but for also many other fields in science. Phase-field models, which have become very popular in recent years, are very promising for the evaluation of phase transformations such as spinodal decomposition. In this study, the Cahn-Hillard equation which is one of the most trending phase-field models is analytically solved by the double exp-function and the modified extended exp-function methods. Spatio-temporal energy and concentration distributions were evaluated by applying two of the ten obtained analytical solutions to the free energy equation. The results obtained were found to be successful in predicting spinodal decomposition as is expected from the Cahn-Hillard model.Öğe Applying the New Extended Direct Algebraic Method to Solve the Equation of Obliquely Interacting Waves in Shallow Waters(Ocean Univ China, 2020) Kurt, Ali; Tozar, Ali; Tasbozan, OrkunIn this study, the potential Kadomtsev-Petviashvili (pKP) equation, which describes the oblique interaction of surface waves in shallow waters, is solved by the new extended direct algebraic method. The results of the study show that by applying the new direct algebraic method to the pKP equation, the behavior of the obliquely interacting surface waves in two dimensions can be analyzed. This article fairly clarifies the behaviors of surface waves in shallow waters. In the literature, several mathematical models have been developed in attempt to study these behaviors, with nonlinear mathematics being one of the most important steps; however, the investigations are still at a level that can be called 'baby steps'. Therefore, every study to be carried out in this context is of great importance. Thus, this study will serve as a reference to guide scientists working in this field.Öğe Bilgisayar destekli optimizasyon kullanılarak biyomimetik yaklaşımla elektroforetik depolanan hidroksiapatit/kitosan/kollajen/h-BN biyokompozit kaplamaların mekanik, tribolojik ve korozyon özelliklerinin incelenmesi(Hatay Mustafa Kemal Üniversitesi, 2017) Tozar, Ali; Karahan, İsmail HakkiOrtopedik cerrahide kullanılan biyomalzemeler genelde karmaşık servis ortamlarıyla karşılaşırlar ve bu nedenle çok yönlü performans özelliklerine sahip olmaları istenir. Ti6Al4V alaşımları da son yıllarda ortopedik cerrahide en çok kullanılan metalik biyomalzemedir. Ancak üstün mekanik mukavemeti nedeniyle birçok biyomedikal uygulamada tercih edilen Ti6Al4V alaşımları vücut sıvısıyla etkileşime girerek korozyona uğrayabilmektedir. Ayrıca kemik implant ara yüzeyinde stresin homojen olarak dağılmamasından kaynaklanan gerilme yığılması ve hareketli bölgelerde kullanılan implantlarda meydana gelen aşınma nedeniyle uygulanan implant tamamen başarısız olabilmektedir. Bu gibi sorunların üstesinden gelebilmek için en uygun girişim, implantın kemiğin mineral yapısını oluşturan Hidroksiapatit ile kaplanması olarak görülmektedir. Ancak hidroksiapatit kaplamada endüstriyel olarak kullanılan plazma sprey yöntemi yüksek sıcaklık koşulları nedeniyle hidroksiapatitin çözünmesine sebep olabilmektedir. Yüksek sıcaklık gerektirmeyen kaplama yöntemlerinde ise hidroksiapatit kaplamaları yeterli mekanik dayanıma sahip olarak üretilememektedir. Bu çalışmada hidroksiapatit kaplamaların mekanik, korozyon ve aşınma (wear) mukavemetlerini geliştirmek ve biyouyumluluklarını arttırmak için doğanın mükemmel konseptlerini kopyalanmaya çalışmak ve doğa model alınarak tersine mühendislik olarak nitelendirilebilecek biyomimetik yaklaşım kullanılmıştır. Hidroksiapatit/kitosan/kollajen/hegzagonal bor nitrür biyokompozit kaplamalar, elektroforetik depolama yöntemiyle Ti6Al4V alaşımları üzerine kaplanmıştır. Üretilen biyokompozit kaplamaların kristalografik yapı, yüzey morfolojisi, kimyasal bağ yapısı, mekanik ve tribolojik özellikleri, korozyon koruma özellikleri, termal davranışları ve in-vitro biyouyum özellikleri açısından incelenmiştir. Ayrıca elektroforetik depolama parametreleri bilgisayar destekli optimizasyon çalışmaları yanıt yüzey metodolojisi yardımıyla gerçekleştirilmiştir.Öğe 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.Öğe A comprehensive research on gamma-ray attenuation characteristics of the metal-doped hap and natural animal bone(Gümüşhane Üniversitesi, 2020) Köksal, Oğuz Kağan; Cengiz, Erhan; Tozar, Ali; Karahan, İsmail Hakkı; Apaydın, GökhanThis investigation focuses on the gamma ray attenuation parameters of natural animal bone, iron, cobalt, copper and zinc doped Nano hydroxyapatite artificial bone powders and pure hydroxyapatite. The present specimens were excited by means of gamma ray photons with 59.5 keV energy radiated from a 241-Amercium annular radioactive source with 50 mCi activity by means of narrow beam transmission geometry. The transmitted gamma-rays were counted with using Ultra Low Energy Germanium (Ultra-LEGe) detector with a resolution 150 eV at 5.95 keV. The gamma-ray attenuation characteristics such as mass attenuation coefficient (MAC) (µ/ρ), linear attenuation coefficient (LAC) (µ), half value layer (HVL), tenth value layer (TVL) and mean free path (MFP), which has a significant role in the attenuation studies, are also calculated. The values obtained were checked with the predicted values from the XCOM NIST. The results show that the attenuation data of the metal-doped hydroxyapatite synthetic bone dust is very close to the value of the natural animal bone.Öğe 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.Öğe Düşük karbonlu çeliğın çevreci ZnNi(Hatay Mustafa Kemal Üniversitesi, 2012) Tozar, Ali; Karahan, İsmail HakkıBu çalışmada endüstride çokça kullanılan bir yumuşak (düşük karbonlu) çelik çeşidi olan st-37 altlıklar üzerine Zn, Ni, ZnNi, Polianilin (PANİ) filmler galvanostatik olarak değişik akım yoğunluklarında depolandı. Ayrıca çelik altlıklar üzerine çok katmanlı alaşım ve iletken polimer filmler değişik sıralamarda ve değişik akım yoğunluklarında depolanarak alaşım kaplamaların katodik koruma özellikleriyle, iletken polimer kaplamaların anodik koruma özellikleri kombine edilmeye çalışıldı.Üretilen filmlerin elektrokimyasal davranışları dönüşümlü voltametri tekniğiyle, yüzey morfolojileri SEM ile, kristal yapıları XRD ile, kompozisyonları ICP ve XRF ile incelendi. Ayrıca korozyon performansları kütlece %3,5'luk NaCl çözeltisinde açık devre potansiyeli, tafel ekstrapolasyon metodu ile ve elektrokimyasal empedans spektroskopisi yöntemiyle incelendi. Yapılan incelemeler sonrasında ZnNi filmleri için akım yoğunluğu arttıkça Ni oranının arttığı ve tanecik boyutunun küçüldüğü, korozyon performansının ise arttığı gözlemlendi. İletken polimer PANİ filmler için ise artan akım yoğunluklarıyla korozyon performansının arttığı gözlemlendi.Tek katmanlı Çelik/ZnNi ve Çelik/PANİ, filmlerin üzerine sırasıyla PANI ve ZnNi depolanması ile elde edilen çok katmanlı Çelik/ZnNi/PANİ ve Çelik/PANİ/ZnNi sistemler arasında çeliği en iyi Çelik/PANİ/ZnNi sisteminin koruduğu görüldü.Öğe 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.Öğe The effect of the ceramic amount on the radiation shielding properties of metal-matrix composite coatings(Pergamon-Elsevier Science Ltd, 2020) Usta, Metin; Tozar, AliIn this study, Ni-B metal matrix composite coatings reinforced with hexagonal boron nitride (hBN) nanoparticles were fabricated on 304L steel substrate with electrochemical deposition method. The volume fraction of hBN was 6-26%. The phase and morphological characteristics were determined via XRD and FE-SEM, respectively. Ni-B/hBN composite coatings were irradiated with Am-241, Sr-90 and Co-60 radioactive sources, which are typical alpha, beta and gamma-ray sources, respectively. Percent absorption rates were acquired according to the hBN volume fractions of each irradiated sample. Accordingly, it was found that the absorption rates also raised as the volume fractions of the hBN in the coating increased. In order to control the findings, stopping power and range values were procured with SRIM and ESTAR databases. Similar to the absorption rate, increasing volume fractions increased the stopping power and decreased the range values. Nuclear radiation shielding properties of metal matrix composite materials are presented here for the first time. This study revealed the importance of Ni-B/hBN composite coatings in terms of radiation shielding properties.Öğe Effects of ultrasonic agitation time on wet chemical synthesis of nanohydroxyapatite(Ice Publishing, 2018) Tozar, Ali; Karahan, Ismail HakkiIn this study, the synthesis of the nanohydroxyapatite (nHAp) powders by way of wet chemical method is reported. Calcium nitrate tetrahydrate (Ca(NO3)(2)center dot H2O) and dibasic ammonium phosphate ((NH4)(2)HPO4) were used as calcium and phosphorus sources, respectively. The effect of ultrasonic agitation time has been systematically studied between 30 and 150 min at the temperature of 70 degrees C. Structural, morphological, spectroscopic and thermal analysis have been carried out by way of X-ray powder diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy and thermogravimetry-differential scanning calorimetry analysis. It is shown that the ultrasonic agitation conditions significantly affect the crystallite size, dislocation density and microstrain of the powders calculated by way of the Debye-Scherrer formula. Thermal analyses reveal that the ultrasonic agitation treatment has a very beneficial effect on the fabrication of the powders by the wet chemical method due to the inhibition of physisorbed and chemisorbed water and the calcium deficiency. Magnetic stirring treatment is found to lead to larger nHAp nanoparticle agglomerations due to more water absorption. The results offer a promising route towards the scalable synthesis of the pure-phase nHAp powders with controllable structural and morphological properties, which could be useful in various types of basic and applied research on HAp-based materials.Öğe Electrophoretic deposition of collagen-reinforced HA/CTS biocomposite coatings(Ice Publishing, 2019) Tozar, Ali; Karahan, Ismail HakkiIn this study, the biomimetic approach described as reverse engineering by trying to copy the excellent concepts of nature and taking nature as a model has been used. In order to mimic the structure of natural bone, hydroxyapatite (HA), chitosan (CTS) and collagen have been combined as a novel type of biocomposite coating. HA/CTS/collagen biocomposite coatings have been successfully electrophoretically deposited on Ti6Al4V biomedical implants. A novel type of a polyelectrolyte consisting of ethanol, water and isopropyl alcohol has been used for the electrophoretic deposition process. The effect of collagen concentration on the structural and corrosion protection performance of the biocomposite coatings has been investigated by X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, potentiodynamic polarization (Tafel extrapolation) and electrochemical impedance spectroscopy techniques. The electrophoretically deposited HA/CTS/collagen biocomposite coatings have exhibited corrosion protection against simulated physiological body fluid up to five times better than that of bare Ti6Al4V alloy.Öğe Farklı Moleküler Ağırlıklı Kitosan Katkılı Hidroksiapatit/Kitosan Biyokompozit Kaplamaların Araştırılması(2023) Dilsizoğlu, Tuncay; Karahan, İsmail Hakki; Tozar, AliKemiğin yapısına en yakın olan kalsiyum fosfat; (Ca10(PO4)6(OH)2) oranının olduğu hidroksiapatittir (HA). Ancak polimer katkısıyla hidroksiapatitin (HA) mukavemet ve sertlik gibi mekanik özelliklerinin arttırıldığı bilinmektedir. Düşük toksiklik ve yüksek biyouyumluluk özelliklerinden dolayı kitosan (CTS) polimer olarak kullanıldı. HA/CTS kaplamaları yapılırken orta moleküler ağırlıklı (MMW) ve yüksek moleküler ağırlıklı (HMW) olmak üzere iki farklı moleküler ağırlıklı kitosan kullanıldı. Orta ve yüksek moleküler ağırlıklı kitosan katkılanarak HA/CTS biyokompozit kaplamalarının etkisi incelendi. Kaplamalar ultasonik destekli elektroforetik yöntemle üretildi. Kristalografik, morfolojik yapıları FT-IR, XRD ve SEM ile incelendi. Yüksek moleküler ağırlıklı kitosan değeri arttıkça numunenin yapısının daha homojen olduğu belirlendi.Öğe Generalized Sub-Equation Method for the (1+1)- Dimensional Resonant Nonlinear Schrodinger’s Equation(2021) Tasbozan, Orkun; Tozar, Ali; Kurt, AliInterest in studying nonlinear models has been increasing in recent years. Dynamical systems, in which the state of the system changes continuously over time, have nonlinear interactions. The use of unique nonlinear differential equations is inescapable in the evaluation of such systems. In mathematical point of view, for obtaining analytical solutions of nonlinear differential equations, it must be fully integrable. Consequently, the importance of fully integrable nonlinear differential equations for nonlinear science has become indisputable. Among these equations, one of the most studied by physicists and mathematicians is the nonlinear Schrödinger equation. This equation has undergone many modifications to evaluate different phenomena. In this study, the resonant nonlinear Schrödinger equation, which is the most important of these physical equations in terms of explaining many physical phenomena, is solved analytically with the generalized sub-equation method.Öğe Investigating the hexadecylamine as a new nonionic surfactant candidate for electrodeposition of wear-resistant metal-matrix composites(Taylor & Francis Ltd, 2020) Tozar, AliIn this study, Ni-B/hBN composite coatings were galvanostatically electrodeposited on 304 L grade steel substrates with 50 mA cm(-2) of current density from a modified Watt type nickel electrodeposition bath including trimethylamine-borane complex (TMAB), and hBN with the average particle size of 100 nm. The effect of the concentration of hexadecylamine (HDA) as a nonionic surfactant has been investigated. The concentration range was 0-400 ppm. HDA has a significant positive effect on mechanical, tribological and corrosion protection properties of the electrodeposited composite coatings due to its increasing effect on the hBN volume fraction in the coating. According to the results of this study, HDA may be a new nonionic surfactant alternative for metal-matrix composite electrodeposition.Öğe 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.Öğe New Analytical Solutions of Fractional Complex Ginzburg-Landau Equation(Emrah Evren KARA, 2020) Tozar, AliIn recent years, nonlinear concepts have attracted a lot of attention due to the deep mathematics and physics they contain. In explaining these concepts, nonlinear differential equations appear as an inevitable tool. In the past century, considerable efforts have been made and will continue to be made to solve many nonlinear differential equations. This study is also a step towards analytical solution of the complex Ginzburg-Landau equation (CGLE) used to describe many phenomena on a wide scale. In this study, the CGLE was solved analytically by (1/G?)-expansion method. © 2020, Emrah Evren KARA. All rights reserved.Öğe New optical solutions of complex Ginzburg-Landau equation arising in semiconductor lasers(Springer Heidelberg, 2019) Tasbozan, Orkun; Kurt, Ali; Tozar, AliNonlinear optics draws much attention by physicists and mathematicians due to its challenging mathematical structure. The study of non-hamiltonian and dissipative systems is one of the most complicated and challenging issues of nonlinear optics. Recent studies showed that there is a close relationship between superconductivity, Bose-Einstein condensation, and semiconductor lasers. Therefore, the cubic complex Ginzburg-Landau (CGLE) equation is thought to be a useful tool in investigating nonlinear optical events. On the other hand, the CGLE is a very general type of equation that governing a vast variety of bifurcations and nonlinear wave phenomena in spatiotemporally extended systems. In this article, we acquire the new wave solution of time fractional CGLE with the aid of Jacobi elliptic expansion method.Öğe New wave solutions of an integrable dispersive wave equation with a fractional time derivative arising in ocean engineering models(Academic Publication Council, 2020) Tozar, Ali; Kurt, Ali; Tasbozan, OrkunThe fractional Camassa-Holm equation is generally used as a powerful tool in computer simulations of water waves in shallow water, coastal and harbor models. In this paper, new wave solutions of this equation are obtained by using a new extended direct algebraic method. Thirty-six completely new solutions are obtained and are graphically represented. These solutions may motivate future research on the topic.Öğe Optical soliton solutions for the (1+1)-dimensional resonant nonlinear Schrondinger's equation arising in optical fibers(Springer, 2021) Tozar, Ali; Tasbozan, Orkun; Kurt, AliSolitons which can be described as a localized wave form that maintain their shape after a collision with another soliton have became a very important phenomena in nonlinear optics due to their potential. They can be used as lossless information carriers in optical fibers due to their robustness arising from their particle grade stability upon a collision. Many scientists from various areas including electronic communication engineers have made solitons the main subject of study. Analytical solutions of nonlinear Schrodinger equation have a very important place in these studies. With the progress of nonlinear optics, some types of nonlinear Schrodinger equation have been derived for better understanding. Resonant nonlinear Schrodinger equation which is being used for describing nonlinear optical phenomena is a generic example for newly derived nonlinear Schrodinger equation. In this study, resonant nonlinear Schrodinger equation has been solved by using functional variable method and sixteen new soliton solutions have been obtained.
