Malzeme Bilimi ve Mühendisliği Bölümü Yayın Koleksiyonu
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Article Citation Count: uşhan Akın, Şeniz Reyhan (2023). "Coating of Si3N4 with HAp via atomic layer deposition", Journal of Ceramic Processing Research, Vol. 24, No. 4, pp. 736-741.Coating of Si3N4 with HAp via atomic layer deposition(2023) Kuşhan Akın, Şeniz Reyhan; 224219Silicon nitride (Si3N4) is an attractive implant material, particularly in orthopedic surgery. Although it has only been on the market for spinal fusion surgery requirements so far, it is also a promising candidate for other implant applications where load-bearing is crucial. In this study, we aimed to examine the potential of making the material surface more advantageous for various implant applications by coating it with a very thin hydroxyapatite (HAp) layer using the atomic layer deposition (ALD) method. This was done to improve the material's bioactivity without sacrificing its mechanical properties. Characterization results showed that using a 3:1 CaO:PO4 ALD cycle ratio resulted in the formation of very fine crystalline HAp after heat treatment at 500 °C. The bioactivity assessment made by immersing the coated film in SBF revealed HAp formation on the surface, and it was observed that the bioactivity of this surface improved compared to the uncoated one.Article Citation Count: Kuşhan Akın, Şeniz Reyhan. (2021). "Reaksiyon Bağlı Silisyum Nitrür Seramiklerinde Sinterleme İlavesinin Mikroyapı ve Antibakteriyel Davranışa Etkisinin İncelenmesi", Uluslararası Mühendislik Araştırma ve Geliştirme Dergisi, Vol.13, No.2, pp.375-381.Reaksiyon Bağlı Silisyum Nitrür Seramiklerinde Sinterleme İlavesinin Mikroyapı ve Antibakteriyel Davranışa Etkisinin İncelenmesi(2021) Kuşhan Akın, Şeniz Reyhan; 224219Silisyum Nitrür (Si3N4) genellikle yüksek sıcaklık ve yapısal uygulamalarda tercih edilen, üstün özellikli bir oksit dışı seramiktir. Çok sert bir malzeme olmasının yanı sıra, çubuksu beta () tanelerin gelişimi ile seramik malzemeler içinde yüksek kabul edilebilecek tokluk değerleri elde etmek mümkün olabilmektedir. Bu özelliklerine ilave olarak biyo uyumluluğunun da anlaşılması ile birlikte özellikle, bu malzemenin biyoseramik olarak kullanım potansiyelini arttırmak amacıyla son on yılda yapılan çalışmaların sayısı da artmıştır. Bu çalışmada da reaksiyon bağlama tekniği ile, çevre biyolojik dokularla entegrasyon açısından avantajlı olan gözenekli Si3N4 seramiklerinin üretilmesi amaçlanmıştır. Sinterleme ilavesi olarak sisteme yapılan CaO, Y2O3 ve CeO2 katkılarının, elde edilen Si3N4 seramiklerin fiziksel ve mikroyapısal özelliklerine ve bunların sonucu olarak antibakteriyel davranışlarına etkileri incelenmiştir. Elde edilen sonuçlar CeO2’in hem E. coli hem de S. aureus açısından dezavantajlı bir sinterleme ilavesi olduğunu, Y2O3’in ise en avantajlı ilave olduğunu görülmüştür. CaO ilavesi yapılan sistem ise E. coli için düşük, S. aureus için yüksek oranda bakteri üremesi ile sonuçlanmıştır.Conference Object Citation Count: Bilgin, Güney Mert...et al. "Microstructural Refinement of Ti-6Al-4V Alloy Fabricated by Additive Manufacturing Using Thermochemical Processes", 18th International Metallurgy & Materials Congress, İstanbul, Türkiye, (29 Eylül - 01 Ekim 2016).Microstructural Refinement of Ti-6Al-4V Alloy Fabricated by Additive Manufacturing Using Thermochemical Processes(2016) Bilgin, Güney Mert; Esen, Ziya; Kuşhan Akın, Şeniz Reyhan; Dericioğlu, Arcan Fehmi; 52373; 224219Article Citation Count: Ozer, Seren;...et.al. (2022). "Effect of post fabrication aging treatment on the microstructure, crystallographic texture and elevated temperature mechanical properties of IN718 alloy fabricated by selective laser melting", Journal of Materials Processing Technology, Vol.306.Effect of post fabrication aging treatment on the microstructure, crystallographic texture and elevated temperature mechanical properties of IN718 alloy fabricated by selective laser melting(2022) Ozer, Seren; Bilgin, Güney Mert; Davut, Kemal; Esen, Ziya; Dericioglu, Arcan F.; 52373The effect of building direction and post fabrication aging treatment on the microstructure, crystallographic texture and high temperature mechanical properties of Inconel 718 (IN718) alloy fabricated by selective laser melting (SLM) method was investigated. After aging, arc-shaped structures seen in as-fabricated samples disappeared and converted into a mixture of columnar and equiaxed grains. Nano-sized γ″ and/or γ′ precipitates were formed upon aging; however, MC type carbides and Laves phase encountered in as-fabricated samples were not dissolved completely after aging. Moreover, aging did not alter the texture ((001)//building direction (BD)) of as-fabricated samples. Mechanical properties of the alloys under tension were influenced by the build direction, aging time and test temperature. As-fabricated samples produced in vertical direction exhibited higher room temperature strengths with lower ductility due to orientation of overlapped prior melt pools. Room temperature tensile test results revealed that peak aging caused a significant improvement in ultimate tensile strength (UTS), from 1066.5 MPa and 998.4 MPa to 1408.5 MPa and 1330.4 MPa whereas elongation values decreased from 27.5% and 32.2% to 19.6% and 23.7% in vertically and horizontally built samples, respectively. Peak-aged samples (aged at 700 °C for 8 h) tested at 600 °C displayed serrated regions in their stress-strain curves due to dynamic strain aging (DSA). Although strength values of the samples displayed an expected decrease by temperature, ductility of the samples reduced to minimum at temperatures around 700–800 °C, which was attributed to intermediate temperature embrittlement.Conference Object Citation Count: Esen, Ziya...et al. "Designing thermochemical processes for ti-alloys produced by additive manufacturing techniques", 4th INTERNATIONAL CONGRESS ON 3D PRINTING (ADDITIVE MANUFACTURING) TECHNOLOGIES AND DIGITAL INDUSTRY, pp. 1383-1387, 2019.Designing thermochemical processes for ti-alloys produced by additive manufacturing techniques(2019) Esen, Ziya; Doğu, Merve Nur; Bilgin, Güney Mert; Tan, Evren; Berkay Gümüş, Berkay; Dericioğlu, Arcan F.; 52373Ti-6Al-4V alloys are extensively used in biomedical, aerospace and petro-chemical applications mainly due to their high specific strength, excellent corrosion resistance and high fatigue strength. In contrast to conventional techniques, additive manufacturing techniques make possible production of parts with complex geometries in one step by minimizing the usage of raw materials. However, post heat treatment processes need to be applied to reduce residual stresses created and to get uniform controllable microstructure so as to obtain desired mechanical properties. Conventional annealing heat treatments are effective in eliminating the residual stress and increasing the ductility. But, they usually degrade the strength and result in coarsening the microstructure. In this study, thermochemical process, called thermo-hydrogen process (THP), was applied to Ti-6Al-4V alloy parts produced by selective laser melting (SLM) and electron beam melting (EBM) with the aim of increasing ductility without degrading the alloy strength. Additively manufactured parts initially hydrogenated at 650oC for 1 h under H2+Ar gas mixture and then, dehyrogenated at 700oC for 18 h under high vacuum. As a result of alloying with hydrogen and dealloying turned martensitic microstructure in SLM parts into fine + lamellar phase mixture. On the other hand, microstructural refinement in EBM parts were limited since as-manufactured parts were already composed of fine lamellar microstructure. THP prevented grain growth and grain boundary α-phase formation in SLM parts. Ductility of the alloys increased by 110 %, while the strength decreased slightly only by 10 %. However, the effect of the THP on mechanical properties of EBM samples couldn’t be observed due to their high surface roughness which induced notch effect.Article Citation Count: Kuşhan Akın, Şeniz Reyhan...et al. (2017). "Effect of SiC addition on the thermal diffusivity of SiAlON ceramics", Ceramics International, Vol. 43, No. 16, pp. 13469-13474.Effect of SiC addition on the thermal diffusivity of SiAlON ceramics(2017) Kuşhan Akın, Şeniz Reyhan; Turan, Servet; Gençoğlu, Pervin; Mandal, Hasan; 224219Despite the fact that thermal conductivity is a crucial parameter for SiAlON ceramics with respect to their suitability in various applications, including high-temperature structural components, wear parts, and cutting tools, studies on SiAlON ceramics reported thus far mainly focus on the improvement of their mechanical properties. In view of the lack of sufficient studies on the thermal conductivity of SiAlON ceramics, this study investigates the improvement in the thermal diffusivity behaviour of SiAlON ceramics by the addition of highly conductive SiC particles. As solid-solution SiAlON ceramics exhibit complex crystal structures typically composed of defects, the phonon scattering increases, subsequently decreasing diffusivity. In particular, the improvement in the thermal diffusivity of both α- and β-SiAlONs was investigated by the addition of 0.25 wt% SiC. In addition, the effect of the SiC particle size on the thermal diffusivity of β-SiAlON was examined. Using inverse diffusivity data, intrinsic and extrinsic scattering parameters were determined, and compared to intrinsic scattering, extrinsic scattering was a dominant factor. Furthermore, transmission electron microscopy (TEM) images of SiCp-reinforced α and -β-SiAlON ceramics were recorded to examine the SiC particle distribution.Article Citation Count: Saltik, Simge; Esen, Ziya; Dericioglu, Arcan F. (2022). "Wetting behavior and reaction layer formation in C/SiC composite-titanium alloy joints", Advances in Materials and Processing Technologies, Vol. 8, No. 4, pp. 3685-3705.Wetting behavior and reaction layer formation in C/SiC composite-titanium alloy joints(2022) Saltik, Simge; Esen, Ziya; Dericioglu, Arcan F.; 52373The present study investigates the effect of brazing parameters on reaction layer formation, and mechanical properties of C/SiC composite-Ti6Al4V alloy joints produced by brazing technique. The wetting mechanism of the C/SiC composite surface by the Ag-Cu-Ti-based active brazing filler alloy has also been studied and correlated with the reaction layer formation. The strength of C/SiC composite/Ti6Al4V alloy joints increased at first and then decreased with increasing reaction layer thickness. The joints with ⁓1-µm-thick reaction layer, which were obtained by brazing at 915°C for 15 min, had the highest shear strength of ⁓33 MPa. Brazing filler alloy presented a minimum contact angle of 15° on the C/SiC composite surface at 915°C during the wetting experiments. 915°C and 15 min were determined to be the optimised brazing parameters to ensure almost complete wetting and a uniform reaction layer for effective adhesion of the C/SiC composite surface.Article Citation Count: Hwang, Jinwoo...et al. (2012). "Nanoscale structure and structural relaxation in Zr 50Cu 45Al 5 bulk metallic glass", Physical Review Letters, Vol. 108, No. 19.Nanoscale structure and structural relaxation in Zr 50Cu 45Al 5 bulk metallic glass(2012) Hwang, Jinwoo; Melgarejo, Z.H.; Kalay, Y.E.; Kalay, İlkay; Kramer, M.J.; Stone, D.S.; Voyles, P.M.; 101579Hybrid reverse Monte Carlo simulations of the structure of Zr 50Cu 45Al 5 bulk metallic glass incorporating medium-range structure from fluctuation electron microscopy data and short-range structure from an embedded atom potential produce structures with significant fractions of icosahedral- and crystal-like atomic clusters. Similar clusters group together into nanometer-scale regions, and relaxation transforms crystal-like clusters into icosahedral clusters. A model refined against only the potential does not agree with the fluctuation microscopy data and contains few crystal-like clusters. © 2012 American Physical Society.Article Citation Count: Doğu, Merve Nur...et al. (2020). "Microstructural and texture evolution during thermo-hydrogen processing of Ti6Al4V alloys produced by electron beam melting", Materials Characterization, Vol. 168.Microstructural and texture evolution during thermo-hydrogen processing of Ti6Al4V alloys produced by electron beam melting(2020) Doğu, Merve Nur; Esen, Ziya; Davut, Kemal; Tan, Evren; Gümüş, Berkay; Dericioğlu, Arcan F.; 52373The present study was conducted to reveal the effects of building angles and post heat-treatments (2-step Thermo-Hydrogen Processing (THP) and conventional annealing treatment) on the density, microstructure and texture of Ti6Al4V alloy parts produced by Electron Beam Melting (EBM). The results showed that regardless of the building angle; the density, microstructure and crystallographic texture (defined with respect to building angle) of the as-produced samples were identical; having Widmanstätten α structure and columnar β-grains which are parallel to building direction. The main texture component for the α phase was (101¯0)//building direction, and for β phase (001)//building or heat flow direction. The first step of THP, namely, the hydrogenation step, produced a needle-like microstructure and increased the local misorientations due to lattice distortion. On the other hand, after application of the second step of THP, dehydrogenation step, microstructure was refined, particularly α-grains that were larger than 10 μm and located at grain boundaries. Moreover, THP randomized the crystallographic texture since it involves β to α phase transformation, at which one β-grain can produce 12 distinct α-variants. The grain boundary misorientation distributions also changed in accordance with the microstructural changes during the 2-step THP. On the other hand, annealing coarsened the grain boundary and Widmanstätten α phases; moreover, it changed the texture so that the basal planes (0001) rotated 30° around the building direction. © 2020 Elsevier Inc.Article Citation Count: Cullinan, Tim...et al. (2015). "Kinetics and Mechanisms of Isothermal Devitrification in Amorphous Cu50Zr50", Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, Vol. 46, No. 2, pp. 600-613.Kinetics and Mechanisms of Isothermal Devitrification in Amorphous Cu50Zr50(2015) Cullinan, Tim; Kalay, İlkay; Kalay, Y. Eren; Kramer, Matt; Napolitano, Ralph; 101579The crystallization kinetics and microstructural dynamics associated with devitrifying a meltspun Cu50Zr50 metallic glass were investigated using isothermal treatments, in situ high-energy synchrotron X-ray diffraction, conventional and high-resolution transmission electron microscopy, and differential scanning calorimetry. The analysis of isothermal transformations allows us to more clearly unravel the complex interplay between nucleation and growth of competing stable and metastable phases. The isothermal devitrification response was found to involve the Cu10Zr7, CuZr2, and CuZr phases, consistent with previously reported constant heating rate experiments, but here we have resolved the phase evolution and structural characteristics of the transformation,including the very early stages of crystallization. At 671 K (398C),the isothermal transformation starts with the formation of the Cu10Zr7 phase, which grows in a generally equiaxed morphology. At a size of approximately 100 nm, the growth of the Cu10Zr7 particles is interrupted by the precipitation of a thin layer of the CuZr2 phase, upon which the metastable CuZr (B2) grows epitaxially. Crystallization kinetics are quantified here though in situ measurements (HEXRD, DSC) and ex situ microstructural analysis (TEM, HRTEM). Finally, the influences of chemical partitioning, diffusion, and crystallographic orientation on this sequence are examined. © 2014, The Minerals, Metals & Materials Society and ASM International.Article Citation Count: Taş, Murat..at all (2012). "Fragmentation and Coulomb explosion of multicharged small boron clusters", Physical Review B - Condensed Matter and Materials Physics, Vol. 85, No. 23.Fragmentation and Coulomb explosion of multicharged small boron clusters(2012) Taş, Murat; Akman, Nurten; Özdoǧan, Cem; Boustani, Ihsan; 40569We extensively study the fragmentation and Coulomb explosion of multiply charged small boron clusters B n (n=2-13), where n is the cluster size. Our calculations are based on ab initio quantum-chemistry methods. Highly charged unstable clusters dissociate spontaneously into several neutral or charged fragments, and large amounts of energy are produced, depending on the charge of the parent cluster. We argue that this mechanism makes boron clusters a clean, safe, and cheap energetic material. © 2012 American Physical Society.Article Citation Count: Ürtekin, Levent...et al. (2021). "Experimental Investigation on Wire Electric Discharge Machining of Biodegradable AZ91 Mg Alloy", Journal of Materials Engineering and Performance, Vol. 30, No. 10, pp. 7752-7761.Experimental Investigation on Wire Electric Discharge Machining of Biodegradable AZ91 Mg Alloy(2021) Ürtekin, Levent; Özerkan, Hacı Bekir; Çoğun, Can; Genç, Asım; Esen, Ziya; Bozkurt, Fatih; 3837; 52373The AZ91 magnesium alloy, used commonly as a biodegradable material in biomedical applications, is generally formed by conventional casting method (CCM) and high-pressure die casting method (HPDCM). The AZ91 alloys exhibit poor machinability with conventional chip removal methods since they degrade at elevated temperatures. In this study, the wire electric discharge machining (WEDM) was presented as a candidate process to machine the AZ91 alloy since no cutting stresses and plastic deformations were applied by the cutting tool to the part causing elevated temperatures. In this context, the WEDM machinability of the AZ91 alloy samples produced by cold chamber HPDCM and CCM at different process parameters, was experimentally investigated. The machining performance outputs (the machining current (I), the machining rate (MR), the average surface roughness (Ra), and surface topography) were found for the varying process parameters [pulse time (ts), pulse-off time (toff), dielectric flushing pressure (Pd), and wire speed (Vw)]. The present study revealed that the I and the MR were significantly dependent on the density, the porosity, and the micro structure of the samples, and the HPDCM samples gave the higher MR and the smoother surface than that of the CCM. © 2021, ASM International.Article Citation Count: Akın, Şeniz R. Kuşhan; Dölekçekiç, Emrah; Webster, Thomas J. (2021). "Effect of nitrogen on the antibacterial behavior of oxynitride glasses", Ceramics International, Vol. 47, No. 13, pp. 18213-18217.Effect of nitrogen on the antibacterial behavior of oxynitride glasses(2021) Akın, Şeniz R. Kuşhan; Dölekçekiç, Emrah; Webster, Thomas J.; 22421The main drawback of bioglasses is their restricted use in load bearing applications and the consequent need to develop stronger glassy materials. This has led to the consideration of oxynitride glasses for numerous biomedical applications. This paper investigated two different types of glasses at a constant cationic ratio, with and without nitrogen (a N containing and a N-free glass composition) to better understand the effect of N on the biological properties of glasses. The results revealed that the addition of N increased the glass transition temperature, isoelectric point (IEP) and slightly increased wettability. Moreover, compared to N including glass, N-free glass exhibited better anti-bacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), two key bacteria that infect implants. In summary, these in vitro results indicated that amine functional groups existing in N containing glasses which are missing in N-free glasses, caused a slight difference in wetting behavior and a more obvious change in isoelectric point and in bacterial response. N-free glasses exhibited better inhibitory results both against E. coli and S. aureus compared to N including glass suggesting that oxygen rich glasses should be further studied for their novel antibacterial properties.Article Citation Count: Kuşhan Akın, Şeniz R.; Dölekçekiç, Emrah; Webster, Thomas J. (2021). "Antibacterial behavior of oxynitride glasses as a glassy grain boundary phase for silicon nitride-based ceramics", Internatİonal Journal of Applied Glass Science, Vol. 12, No. 3, pp. 328-336.Antibacterial behavior of oxynitride glasses as a glassy grain boundary phase for silicon nitride-based ceramics(2021) Kuşhan Akın, Şeniz R.; Dölekçekiç, Emrah; Webster, Thomas J.; 224219Silicon nitride-based ceramics have provided significant advantages due to their high chemical resistance, high elastic modulus, and combination of hardness and fracture toughness (depending on self-reinforcement). Over the past two decades, a significant amount of interest has been generated for the bio-applications of these materials. However, the effect of the grain boundary phase on such applications is still not very well understood. In this study, the effect of different cations on biological (such as antibacterial and cytocompatibilty) and material properties (like wetting angles and isoelectric points [IEP]) of oxynitride glasses, mimicking the grain boundary phase in Si3N4 and SiAlON ceramics, were investigated. Results revealed that the antibacterial behavior and mammalian cell viability were inversely correlated in glasses with rare-earth cation additions. Ca was the best cation when the two properties (bacterial response and cell proliferation) were considered together, and, thus should be further studied for a wide range of applications.Article Citation Count: Kalay, İlkay (2020). "Microstructure and Mechanical Properties of CoCrFeNi(TiAl) High Entropy Alloys", Hittite Journal of Science and Engineering, Vol. 7, No. 2, pp. 157-162.Microstructure and Mechanical Properties of CoCrFeNi(TiAl) High Entropy Alloys(2020) Kalay, İlkay; 101579The structure and mechanical properties of CoCrFeNi and CoCrFeNiTi0.5Al0.5 (in molar ratio) high entropy alloys were investigated using X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM), hardness and compression tests. With the addition of Ti and Al, the crystal structure of CoCrFeNi changed from FCC to a mixture of FCC and double BCC structures. The lattice parameter of FCC increases upon addition of Al and Ti. The microstructure analysis shows the morphological transition of dendrites from non-equiaxed to equiaxed during the suction casting of CoCrFeNiTi 0.5Al 0.5 alloy. The Vickers microhardness testing of CoCr-FeNi alloy reveals significant increase in hardness with the addition of Al and Ti. The hardness values are improved in as-suction cast CoCrFeNi and CoCrFeNiTi0.5Al 0.5 alloys compared to their ascast alloys due to strengthening. The CoCrFeNiTi0.5Al 0.5 alloy yields at 1997 MPa and fails at 2344 MPa. The fracture mechanism of CoCrFeNiTi 0.5Al 0.5 alloy reveals a cleavage mode.Article Citation Count: Genç, Ayşe Merve...et al. (2019). "Investigation of phase selection hierarchy in Mn-Al alloys", Intermetallics, Vol. 115.Investigation of phase selection hierarchy in Mn-Al alloys(2019) Genç, Ayşe Merve; Acar, Özgün; Turan, Servet; Kalay, İlkay; Savacı, Umut; Kalay, Yunus Eren; 101579Primarily attributed to the formation of the ferromagnetic tau-phase, near equiatomic composition of Mn-Al have recently received much attention in permanent magnet industry. Several mechanisms have been proposed in literature for the tau-phase formation but controversy still arises regarding the dominating mode. In the current work, MnAl-based alloys having different compositions in a range between Mn50.5Al49.5 and Mn57Al43 have been studied by means of in-situ high energy X-ray diffraction, differential scanning calorimetry (DSC) and magnetic measurements. Synchrotron and DSC experiments showed the dependence of the tau-MnAl on the intermediate disordered epsilon'-phase. Alloys having 53.4 at% or less Mn (S1, S2) followed a transformation route of epsilon+epsilon'-> tau ->beta+gamma(2) upon annealing. Alloys having more than 53.4 at% of Mn had only epsilon-phase. High energy X-ray diffraction patterns showed that epsilon-phase directly transformed into stable phases in the absence of epsilon'-phase. It is observed that epsilon' not only promoted the ferromagnetic tau-phase but also stabilized it by delaying the nucleation of stable phases.Article Citation Count: Günhan, Büşra...et al. (2020). "Effects of Process Parameters on Fe2O3/α-Al2O3 Luster Pigments Produced By Precipitation Method", International Journal of Advanced Research, Vol. 8, No. 6, pp. 155-164.Effects of Process Parameters on Fe2O3/α-Al2O3 Luster Pigments Produced By Precipitation Method(2020) Günhan, Büşra; Kaya, Güray; Kök, Mesut; Weinekotter, Çiğdem; Poyraz, H. Bogaç; Ceylantekin, Rasim; Kuşhan Akın, Şeniz Reyhan; 224219Common known examples of substrate-based pigments are mica/TiO2 and mica/Fe2O3 luster pigments produced using wet chemical methods and gas-phase reaction techniques. Luster coatings, in particular those prepared using iron(III) oxide, come into prominence thanks to their characteristics of good hiding power and weather resistance, to name a few. Mica/Fluorphlogopite/Silica-based luster pigments have certain disadvantages due to following reasons: natural mica contains iron (Fe2O3) impurity which imparts a yellow color to the material, synthetic fluorphlogopite is quite expensive compared to natural mica and silica has a high production cost. In addition to these, fragility of mica bases due to their low mechanical strength adversely affects the luster effect. Reaction kinetics control is easier in wet chemical methods than in gas-phase reaction techniques since the coarse substrate particles can be kept suspended more easily by stirring. In this study, α-Al2O3/Fe2O3 luster pigments were produced using the wet chemical method/precipitation method by preferring plate-like alumina substrates in order to eliminate the afore-said problems. The pigments produced were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) methods and color analysis was performed. As a result, it was determined that the increase in titration flow rate and stirring rate in the production process of Fe2O3/α-Al2O3 luster pigment using the wet chemical method had no effect on the crystal structure of the resulting coating. However, while the stirring rate does not have a significant effect on the quality of coating, the increase in titration flow rate adversely affects the quality of coating.Article Citation Count: Tülbez, Simge; Esen, Ziya; Dericioğlu, Arcan F. (2020). "Effect of CNT impregnation on the mechanical and thermal properties of C/C-SiC composites", Advanced Composites and Hybrid Materials, Vol. 3, No. 2, pp. 177-186.Effect of CNT impregnation on the mechanical and thermal properties of C/C-SiC composites(2020) Tülbez, Simge; Esen, Ziya; Dericioğlu, Arcan F.; 52373The present study investigates the effect of additional carbon source, in the form of carbon nanotubes (CNTs), on mechanical and thermal properties of carbon fiber reinforced silicon carbide (C/C-SiC) ceramic matrix composites (CMC) produced by liquid silicon infiltration (LSI) technique. The CNTs used in this study were impregnated into the C/C preforms before the liquid silicon infiltration stage. The results showed that the addition of excess carbon to the C/C preforms in the form of CNTs enhanced Si infiltration efficiency significantly resulting in C/C-SiC composites with higher density and microstructural uniformity. Accordingly, the addition of CNTs improved the flexural strength of the composites by 40% with respect to no-CNT-containing composites due to a lower amount of residual porosity and additional reinforcement effect of the unreacted CNTs. The thermal conductivity of the resulting C/C-SiC composites has been also increased by 31% and 18% parallel and perpendicular to the carbon fiber-woven fabric surface, respectively, by CNT addition.Graphical abstractArticle Citation Count: Cullinan, Tim...et.al., "Kinetics and mechanisms of isothermal devitrification inamorphous cu50zr50" Metallurgical And Materials Transactions A-Physical Metallurgy And Materials Science, Vol.46A, No.2, pp.600-613, (2015).Kinetics and mechanisms of isothermal devitrification inamorphous cu50zr50(Springer, 2015) Cullinan, Tim; Kalay, İlkay; Kalay, Y. Eren; Kramer, Matt; Napolitano, Ralph; 101579The crystallization kinetics and microstructural dynamics associated with devitrifying a melt-spun Cu50Zr50 metallic glass were investigated using isothermal treatments, in situ high-energy synchrotron X-ray diffraction, conventional and high-resolution transmission electron microscopy, and differential scanning calorimetry. The analysis of isothermal transformations allows us to more clearly unravel the complex interplay between nucleation and growth of competing stable and metastable phases. The isothermal devitrification response was found to involve the Cu10Zr7, CuZr2, and CuZr phases, consistent with previously reported constant heating rate experiments, but here we have resolved the phase evolution and structural characteristics of the transformation, including the very early stages of crystallization. At 671 K (398 A degrees C), the isothermal transformation starts with the formation of the Cu10Zr7 phase, which grows in a generally equiaxed morphology. At a size of approximately 100 nm, the growth of the Cu10Zr7 particles is interrupted by the precipitation of a thin layer of the CuZr2 phase, upon which the metastable CuZr (B2) grows epitaxially. Crystallization kinetics are quantified here though in situ measurements (HEXRD, DSC) and ex situ microstructural analysis (TEM, HRTEM). Finally, the influences of chemical partitioning, diffusion, and crystallographic orientation on this sequence are examined.Article Citation Count: Kalay, Ilkay; Kramer, Matthew J.; Napolitano, RE., "Crystallization kinetics and phase transformation mechanisms incu56zr44 glassy alloy" Metallurgical And Materials Transactions A-Physical Metallurgy And Materials Science, Vol.46A, No.6, pp.3356-3364, (2015).Crystallization kinetics and phase transformation mechanisms incu56zr44 glassy alloy(Springer, 2015) Kalay, İlkay; Kramer, Matthew J.; Napolitano, R. E.; 101579The kinetics and phase selection mechanisms involved in the crystallization of an amorphous Cu-Zr alloy of eutectic composition (Cu56Zr44) were investigated using in situ high-energy X-ray diffraction (HEXRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) under isothermal and constant heating rate conditions. In situ HEXRD results for 10 K/min (10 A degrees C/min) heating indicate that the amorphous alloy devitrifies into CuZr2 and mainly Cu10Zr7 at the crystallization temperature of 725 K (452 A degrees C). The sequence continues with the precipitation of CuZr (B2) at 1004 K (731 A degrees C), where these three phases coexist until the decomposition of CuZr2 is observed at 1030 K (757 A degrees C). The two equilibrium phases Cu10Zr7 and CuZr (B2) remain present on further heating until melting at the eutectic temperature for the Cu56Zr44 alloy. TEM investigation of the isothermal [705 K (432 A degrees C)] crystallization sequence reveals primary nucleation and growth of the Cu10Zr7 phase, where growth of the Cu10Zr7 crystals is initially planar with a transition to a cellular morphology, associated with partitioning of Zr at the growth front. Related cellular structures and composition profiles are quantified. (C) The Minerals, Metals & Materials Society and ASM International 2015
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