Malzeme Bilimi ve Mühendisliği Bölümü Yayın Koleksiyonu

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A novel approach for synthesis of monticellite based bioactive ceramic powders from boron derivative waste
(Elsevier Science BV, 2017) Köroğlu, Levent; Bütev, Ezgi; Esen, Ziya; Ayaş, Erhan; 47423
Monticellite bioactive ceramics have a high usage potential as bone graft substitutes due to their superior mechanical properties compared to hydroxyapatite and excellent bioactivity. Turkey has almost 72% of the global boron reserves and the fairly high amount of emerged boron derivative waste causes storage problems and environmental pollutions. The aim of this study was the solid state synthesis of monticellite based ceramic powders from boron derivative waste and the evaluation of bioactivity characteristic of produced powders. The monticellite based ceramic powders were synthesized at low temperature (800 degrees C). The powders were incubated in Simulated Body Fluid and their surfaces were examined using a scanning electron microscope. The surfaces of synthesized powders were bioactive and allowed formation of bone-like apatite layer within 15 days. Results of the study confirmed that cost-effective and ecofriendly monticellite based bioactive ceramic powders can be synthesized from boron derivative waste. (C) 2017 Elsevier B.V. All rights reserved.
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.; 224219
Silicon 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.
Citation Count: Butev, Ezgi; Esen, Ziya; Bor, Sakir, "Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions", Journal of the Mechanical Behavior of Biomedical Materials, Vol. 60, pp. 127-138, (2016).
Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions
(Elsevier Science BV, 2016) Bütev, Ezgi; Esen, Ziya; Bor, Şakir; 47423; 52373
Ti6Al7Nb alloy foams having 53-73% porosity were manufactured via evaporation of magnesium space holders. A bioactive 1 mu m thick sodium hydrogel titanate layer, NaxH2-xTiyO2y+1., formed after 5 M NaOH treatment, was converted to crystalline sodium titanate, Na2TiyO2y+1, as a result of post-heat treatment. On the other hand, subsequent CaCl2 treatment of NaOH treated specimens induced calcium titanate formation. However, heat treatment of NaOH-CaCl2 treated specimens led to the loss of calcium and disappearance of the titanate phase. All of the aforementioned surface treatments reduced yield strengths due to the oxidation of the cell walls of the foams, while elastic moduli remained mostly unchanged. Accordingly, equiaxed dimples seen on the fracture surfaces of as-manufactured foams turned into relatively flat and featureless fracture surfaces after surface treatments. On the other hand, Ca- and Na-rich coating preserved their mechanical stabilities and did not spall during fracture. The relation between mechanical properties of foams and macro-porosity fraction were found to obey a power law. The foams with 63 and 73% porosity met the desired biocompatibility requirements with fully open pore structures and elastic moduli similar to that of bone. In vitro tests conducted in simulated body fluid (SBF) showed that NaOH-heat treated surfaces exhibit the highest bioactivity and allow the formation of Ca-P rich phases having Ca/P ratio of 1.3 to form within 5 days. Although Ca-P rich phases formed only after 15 days on NaOH-CaCl2 treated specimens, the Ca/P ratio was closer to that of apatite found in bone. (C) 2016 Elsevier Ltd. All rights reserved.
Citation Count: Pazarceviren, Engin...et al. (2017)."Clinoptilolite/PCL-PEG-PCL composite scaffolds for bone tissue engineering applications", Journal Of Biomaterials Applications, Vol.31, No.8, pp.1148-1168.
Clinoptilolite/PCL-PEG-PCL composite scaffolds for bone tissue engineering applications
(Sage Publications LTD, 2017) Pazarçeviren, Engin; Erdemli, Özge; Keskin, Dilek; Tezcaner, Ayşen; 163717
The aim of this study was to prepare and characterize highly porous clinoptilolite/poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) composite scaffolds. Scaffolds with different clinoptilolite contents (10% and 20%) were fabricated with reproducible solvent-free powder compression/particulate leaching technique. The scaffolds had interconnective porosity in the range of 55-76%. Clinoptilolite/poly(epsilon-caprolactone)-poly(ethylene glycol)poly(epsilon-caprolactone) scaffolds showed negligible degradation within eight weeks and displayed less water uptake and higher bioactivity than poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) scaffolds. The presence of clinoptilolite improved the mechanical properties. Highest compressive strength (5.6 MPa) and modulus (114.84 MPa) were reached with scaffold group containing 20% clinoptilolite. In vitro protein adsorption capacity of the scaffolds was also higher for clinoptilolite/poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) scaffolds. These scaffolds had 0.95 mg protein/g scaffold adsorption capacity and also higher osteoinductivity in terms of enhanced ALP, OSP activities and intracellular calcium deposition. Stoichiometric apatite deposition (Ca/P = 1.686) was observed during cellular proliferation analysis with human fetal osteoblasts cells. Thus, it can be suggested that clinoptilolite/poly(epsilon-caprolactone)poly(ethylene glycol)-poly(epsilon-caprolactone) composite scaffolds could be promising carriers for enhancement of bone regeneration in bone tissue engineering applications.
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; 224219
Silicon 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.
Citation Count: Guler, I.; Gasanly, N. M., "Compositional Dependence of Raman-Active Mode Frequencies and Line Widths in Tlıns2xse2(1-X) Mixed Crystals", Applied Surface Science, 318, pp. 113-115, (2014).
Compositional Dependence of Raman-Active Mode Frequencies and Line Widths in Tlıns2xse2(1-X) Mixed Crystals
(Elsevier Science, 2014) Güler, I.; Gasanly, N. M.; Korkmaz, F.
The Raman spectra of mixed crystals TlInS2xSe2(1-x) have been investigated in the composition range of 0.25 <= x <= 0.75 and in the high-frequency region of 250-350 cm(-1) at room temperature. It was observed that Raman-active mode frequencies decrease as the selenium atoms content increases in the mixed crystals. The effect of crystal disorder on the line broadening of three high-frequency modes is reported. (C) 2014 Elsevier B.V. All rights reserved.
Corrosion of Metallic Biomaterials
(Springer Verlag, 2015) Dikici, Burak; Esen, Ziya; Duygulu, Özgür; Güngör, Serap; 52373
Metallic materials have been used as biomedical implants for various parts of the human body for many decades. The physiological environment (body fluid) is considered to be extremely corrosive to metallic surfaces; and corrosion is one of the major problems to the widespread use of the metals in the human body since the corrosion products can cause infections, local pain, swelling, and loosening of the implants. Recently, the most common corrosion-resistant metallic biomaterials are made of stainless steels and titanium and its alloys along with cobalt chromium molybdenum alloys. It is well known that protective surface films of the alloys play a key role in corrosion of the metallic implants. Key documents on the corrosion behavior of the metallic biomaterials in human body have been compiled under this chapter as a review.
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.; 101579
The 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
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.; 52373
Ti-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.
Citation Count: Ucar, N...et al. (20169. Diffusion Kinetics of Binary Ti-Ni Shape Memory Alloys. (2017)Conference: 3rd International Conference on Computational and Experimental Science and Engineering (ICCESEN) Location: Antalya, TURKEY Date: OCT 19-24. Acta Physica Polonica A, 132(3), 524-526.
Diffusion Kinetics of Binary Ti-Ni Shape Memory Alloys
(Polish Acad Sciences Inst Physics, 2017) Uçar, Nazım; Doğan, Şule; Özdemir, Ahmet Faruk; Karakaş, Mustafa Serdar; Çalık, A.; 48915
In this work, the boriding of binary Ti-Ni shape memory alloys was carried out in a solid medium at 1173 and 1273 K for 2, 4, and 8 h using the powder pack method with Ekabor-Ni powders. The boride layer was characterized by optical microscopy and scanning electron microscopy. The obtained results show that boride layer thickness increases with the increasing boriding temperature and time. Depending on temperature and boride layer thickness, the diffusion process is thermally activated, with the mean value of the activation energy being close to 67 kJ/mol.
Citation Count: Günen, Ali...et.al.,"Effect of borotitanizing on microstructure and wear behavior of Inconel 625", Surface & Coatings Technology, Vol.311, pp.374-382, (2017).
Effect of borotitanizing on microstructure and wear behavior of Inconel 625
(Elsevier Science BV, 2017) Kanca, Erdoğan; Günen, Ali; Çakır, Hüseyin; Karakaş, Mustafa Serdar; Gök, Mustafa Sabri; Küçük, Yılmaz; Demir, Mehmet; 48915
nconel 625, a nickel-based superalloy, is used in a wide range of applications including the marine and petroleum industries under where it is subjected to harsh conditions such as high temperatures and highly corrosive environments. However, its wear resistance is limited and can be often considered unsatisfactory in some applications. If this alloy were to be used under abrasive wear conditions, its surface would have to be protected by a wear resistant coating. In this study, a two-step thermo-chemical borotitanizing treatment (including an initial boriding step followed by titanium diffusion) is proposed. Microstructural characterization (optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction) and mechanical properties (induding micro-hardness and micro-abrasion wear) of the coated samples were conducted. Microstructural studies revealed a compact, homogenous, silicide-free coating, consisting of four distinct regions: a TiB2 layer, a multi-phase boride layer, a diffusion zone and the substrate. Hardness values were significantly higher than those obtained by standard boriding treatments. Due to the nano-sized bodding agents used, the coatings formed on the surface were thicker than coatings obtained by methods such as nitriding, paste bodding and pack-boriding, and comparable to that of laser boriding. The wear resistance was improved by up to ten times in comparison with untreated Inconel 625. Grooving was the effective wear mechanism in untreated Inconel 625. How-ever the increase in surface hardness achieved by the borotitanizing treatment changed the wear mechanism in the coated samples from grooving to rolling.
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.; 22421
The 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.
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.; 52373
The 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.
Citation Count: Akin, Seniz Reyhan Kushan...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
(Elsevier SCI LTD, 2017) Kuşhan Akın, Seniz Reyhan; Turan, Servet; Gençoğlu, Pervin; Mandal, Hasan; 224219
Despite 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 alpha- and beta-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 beta-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 a and -beta-SiAlON ceramics were recorded to examine the SiC particle distribution.
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; 224219
Despite 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.
Citation Count: Atabay, Sila Ece; Esen, Ziya; Dericioğlu, Arcan F., "Effect of sn alloying on the diffusion bonding behavior of al-mg-si alloys", Metallurgical And Materials Transactions A-Physical Metallurgy And Materials Science, Vol.48A, No.7, pp.3181-3187, (2017).
Effect of sn alloying on the diffusion bonding behavior of al-mg-si alloys
(Springer, 2017) Atabay, Sıla Ece; Esen, Ziya; Dericioğlu, Arcan F.; 52373
Effect of Sn as an alloying element on the diffusion-bonding behavior of Al-Mg-Si alloy has been studied by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical testing of the diffusion-bonded joint. XRD results revealed the formation of Mg2Sn and (Sn) phases during solidification following induction casting. DSC results showed local liquid (Sn) formation during the bonding process for Sn-containing alloys, where its amount was found to be increasing with the increasing Sn content. Results revealed that Sn addition leads to an increase in the bond shear strength of the diffusion-bonded joints and elimination of the irregularities formed on the bonded interface. Fractured surfaces showed that formation of (Sn) layer at the bonded interface causes the fracture to transform from the ductile to the mixed fracture mode.
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; 224219
Common 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.
Citation Count: Buke, Goknur C., "Epitaxial Graphene and Carbon Nanotubes on Silicon Carbide", Carbon Nanomaterials, 2nd Edition, pp. 115-133, (2014).
Epitaxial Graphene and Carbon Nanotubes on Silicon Carbide
(CRC Press-Taylor & Francis Group, 2014) Buke, Göknur Cambaz
Citation Count: Cetinel, Oktay; Esen, Ziya; Yildirim, Bora, "Fabrication, Morphology Analysis, and Mechanical Properties of Ti Foams Manufactured Using the Space Holder Method for Bone Substitute Materials", Metals, Vol. 9, No. 3, (March 2019)
Fabrication, Morphology Analysis, and Mechanical Properties of Ti Foams Manufactured Using the Space Holder Method for Bone Substitute Materials
(MDPI, 2019) Çetinel, Oktay; Esen, Ziya; Yıldırım, Bora; 52373
Porous titanium (Ti) offers several key attributes as a biomedical material. Among the known characteristics of Ti relevant to biomedical applications, the mechanical performance and effects of a pore structure on the deformation characteristics under compressive loading were examined. The space holder method was employed to generate Ti foams with target porosities of 60%, 70%, and 80%. A micro-computed to mography analysis and light and scanning electron microscopy were performed to examine the pore morphology and microstructure. The mechanical properties along with the elastic modulus and compressive strength were evaluated via uniaxial compression testing. Ti foam samples with three porosity levels displayed average elastic moduli and compressive strengths comparable with those of human cancellous and cortical bone. All the Ti foam samples had elastic moduli similar to those of cancellous bone with their open porous structures. Although the foam samples with similar to 60% porosity had compressive strength comparable to that of cortical bone, the samples with similar to 80% porosity displayed compressive strength similar to that of cancellous bone. The results indicate that Ti foam scaffolds produced using the space holder method have great potential for applications in hard tissue engineering, as their mechanical properties and pore structures are similar to those of bone.
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; 40569
We 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.

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