Malzeme Bilimi ve Mühendisliği Bölümü

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Citation - WoS: 31
Citation - Scopus: 30
Ionization Energies, Coulomb Explosion, Fragmentation, Geometric, and Electronic Structures of Multicharged Boron Clusters Bn (n=2-13)
(Amer Physical Soc, 2011) Tas, Murat; Ozdogan, Cem; Boustani, Ihsan; Akman, Nurten
Based on the ab initio quantum chemical methods, we have determined fragmentation channels, ionization energies, and the Coulomb explosion of multicharged boron clusters B-n (n = 2-13), where n is the cluster size. The electron-deficient boron clusters sustain more stability and hardly fragment when they are negatively charged. Stability of boron clusters decreases with increasing ionization. Only by the first ionization the odd-size clusters are more stable than the even-size clusters. Further ionizations cause the repulsive Coulomb force between the constituent atoms to get stronger, and lead first to metastable states, then to the Coulomb explosion of clusters. None of the cationic boron clusters studied remain stable after six times ionization. The critical charge for metastability is estimated as Q(m) <= n/2 for even-size clusters, and Q(m) <= 1/2 (n - 1) for odd-size clusters. In addition, the critical charge for the Coulomb explosion is found to be Q(c) = n/2 + 1 for even-size clusters, and Q(c) = 1/2(n + 1) for odd-size clusters. Relative stability of clusters with respect to their nearest neighbors is determined from the analysis of their second energy difference data. Several dissociation channels of B-n(+) and B-13(Q) isomers with the lowest fragmentation energies are presented. All of the vibrational frequencies are found positive indicating that no transition state is possible for the clusters studied. Reliability of our data is verified with a good agreement with experimental results.
Citation - WoS: 34
Citation - Scopus: 43
Clinoptilolite/Pcl-peg-pcl Composite Scaffolds for Bone Tissue Engineering Applications
(Sage Publications Ltd, 2017) Pazarceviren, Engin; Erdemli, Ozge; Keskin, Dilek; Tezcaner, Aysen
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 - WoS: 20
Citation - Scopus: 21
The Effect of Processing Routes on the Structure and Properties of Magnesium-Tini Composites
(Elsevier Science Sa, 2012) Esen, Ziya
TiNi particulate-reinforced magnesium matrix composites were fabricated by rotary hot swaging and post-annealing heat treatment. The magnesium matrix of the processed composites was observed to contain elongated grains comprised of equiaxed recrystallised grains. Each elongated grain was surrounded by thin, non-continuous magnesium oxide layers composed of nanometric magnesium oxide particles. The TiNi reinforcement particles preserved their starting spherical shape during processing and testing. However, the hot deformation and annealing heat treatment changed the underlying room temperature microstructures and transformation behaviours of the reinforcements. In contrast to the majority of the ceramic reinforcements, the ductility of the composites was not significantly degraded by the addition of TiNi reinforcements; conversely, an approximately 25% enhancement was recorded in the elongation values for the Mg-5 vol% TiNi alloy. While the yield strengths of the composites changed linearly with increasing reinforcement content, the highest compression peak strength value was obtained with the addition of 5 vol% TiNi, beyond which the strength was slightly decreased. During mechanical testing, the TiNi particles debonded due to insufficient bonding between the matrix and reinforcement, and fracture resulted largely within the oxide layers present in the interfacial region and the magnesium oxide film in the magnesium grain boundaries. (C) 2012 Elsevier B.V. All rights reserved.
Citation - WoS: 23
Citation - Scopus: 24
Microstructural and Texture Evolution During Thermo-Hydrogen Processing of Ti6al4v Alloys Produced by Electron Beam Melting
(Elsevier Science inc, 2020) Esen, Ziya; Davut, Kemal; Tan, Evren; Gumus, Berkay; Dericioglu, Arcan F.; Dogu, Merve Nur
The 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 Widmanstatten a structure and columnar beta-grains which are parallel to building direction. The main texture component for the alpha phase was (10 (1) over bar0)//building direction, and for beta 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 alpha-grains that were larger than 10 mu m and located at grain boundaries. Moreover, THP randomized the crystallographic texture since it involves beta to alpha phase transformation, at which one beta-grain can produce 12 distinct alpha-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 Widmanstatten alpha phases; moreover, it changed the texture so that the basal planes (0001) rotated 30 degrees around the building direction.
Citation - WoS: 11
Citation - Scopus: 11
Effect of Sn Alloying on the Diffusion Bonding Behavior of Al-Mg Alloys
(Springer, 2017) Esen, Ziya; Dericioglu, Arcan F.; Atabay, Sila Ece
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 - WoS: 32
Citation - Scopus: 36
Optimization of the Mechanical Properties of Ti-6al Alloy Fabricated by Selective Laser Melting Using Thermohydrogen Processes
(Elsevier Science Sa, 2017) Esen, Ziya; Akin, Seniz Kushan; Dericioglu, Arcan F.; Bilgin, Guney Mert
2-step Thermo Hydrogen Process (THP) including hydrogenation and dehydrogenation steps was applied to Ti-6Al-4V alloy fabricated by selective laser melting (SLM) process to refine the microstructure and to increase the ductility of the alloy. It was observed that as-fabricated alloy's surface was composed of oxides of titanium and aluminum, which may alter the hydrogenation kinetics. The hydrogen treatment for 1 hat 650 degrees C, the maximum hydrogen solubility temperature of the alloy, transformed starting non-equilibrium alpha'-martensitic phase to 13 and 8 (TiH2) phases. On the other hand, very fine discontinuous beta-phase was formed along with alpha-phase as a result of dehydrogenation at 700 degrees C for 18 h, which decreased the hydrogen level well below the starting value and caused transformation of delta-phase to fine alpha-phase. In contrast to commonly used THP treatments consisting of betatizing at high temperature, 2-step treatment prevented grain boundary alpha-phase formation as well as excessive grain growth. About 110% and 240% increments were detected in % Elongation (EL) and % Reduction in Area (RA) values, respectively, as a result of 2-step THP, while the strength decrease was limited to 10%. The change in ductility of the alloy was also verified by transformation of flat and shiny fracture surfaces seen in SLM fabricated alloy to a fracture surface containing equiaxed dimples after THP treatment. The hardness drop in the alloy after hydrogenation and dehydrogenation treatments was attributed to relief of residual stress and formation of equilibrium alpha and beta-phases.
Citation - WoS: 8
Citation - Scopus: 9
Effect of Sm on Thermal and Mechanical Properties of Cu-Zr Bulk Metallic Glasses
(Elsevier Science Sa, 2019) Sikan, F.; Atabay, S. E.; Motallebzadeh, A.; Ozerinc, S.; Kalay, I.; Kalay, Y. E.
The effect of rare-earth (Sm) microalloying on the thermal stability and phase selection along with the effect of nanocrystallization on the mechanical properties of amorphous melt-spun ribbons of Zr50Cu40Al10, Zr49Cu39.2Al9.8Sm2 and Zr48Cu38.4Al9.6Sm4 alloys were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), Vickers and nanoindentation hardness tests and micropillar compression analysis. XRD and TEM analyses showed that all samples were fully amorphous in as-spun state; however, crystallization sequences for the Sm-free and the Sm micro-alloyed samples were different during devitrification. Combined study of XRD, DSC and TEM on melt-spun ribbons show that Zr48Cu38.4Al9.6Sm4 have nanocrystallization of Cu2Sm phase with an average diameter of 10 nm, which was absent in Zr50Cu40Al10, prior to crystallization of Cu10Zr7 phase. The nanoindentation and micropillar compression tests revealed Cu2Sm nanocrystals embedded in Zr48Cu38.4Al9.6Sm4 alloy improves strength and hardness. On the other hand, presence of these nanocrystals deteriorate shear band stability and thus result in a catastrophic brittle fracture through a single shear band burst.
Kinetics and mechanisms of isothermal devitrification inamorphous cu50zr50
(Springer, 2015) Cullinan, Tim; Kalay, İlkay; Kalay, Y. Eren; Kramer, Matt; Napolitano, Ralph
The 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.
Epitaxial Graphene and Carbon Nanotubes on Silicon Carbide
(CRC Press-Taylor & Francis Group, 2014) Buke, Göknur Cambaz
Citation - WoS: 15
Citation - Scopus: 17
Characterization of Ti6al7nb Alloy Foams Surface Treated in Aqueous Naoh and Cacl2 Solutions
(Elsevier Science Bv, 2016) Esen, Ziya; Bor, Sakir; Butev, Ezgi
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 - WoS: 7
Citation - Scopus: 7
A Comparison of Radiation Shielding of Stainless Steel With Different Magnetic Properties
(Vinca inst Nuclear Sci, 2014) Akbunar, Sahin; Ucar, Nazim; Yilmaz, Nihat; Karakas, Mustafa Serdar; Akkurt, Iskender; Calik, Adnan
The radiation shielding properties of three different stainless steels have been investigated. For this purpose, linear attenuation coefficients at photon energy levels of 662 keV and 1250 keV have been measured. The obtained results showed that ferritic stainless steel was more capable in stopping the high energy photons than its non-magnetic counterpart.
Citation - WoS: 36
Corrosion of Metallic Biomaterials
(Springer-verlag Berlin, 2015) Esen, Ziya; Duygulu, Ozgur; Gungor, Serap; Dikici, Burak
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 - WoS: 9
Citation - Scopus: 11
Boriding Kinetics and Mechanical Properties of Borided Commercial-Purity Nickel
(Natl inst Science Communication-niscair, 2017) Uçar, Nuri; Calik, A.; Ucar, N.; Delikanli, K.; Carkci, M.; Karakas, S.; Bankacılık ve Finans
Kinetics of boride layer growth and tensile behaviour in bonded commercial-purity nickel was investigated. Bonding was carried out in a solid medium consisting of Ekabor-II powders at 1173, 1223 and 1273 K for periods of 3, 5 and 8 h. Scanning electron microscopy (SEM) and optical microscopy showed column morphology in the boride layer. X-ray diffraction (XRD) analyses indicated that the boride layer formed on the surface consisted mainly of Ni2B, with precipitates of Ni6Si2B. A parabolic relationship between layer thickness and processing temperature was observed. The obtained results showed that although the boride layer thickness increased with increasing boriding temperature and time, boriding parameters had no significant effect on the hardness of the boride layer or the matrix. Tensile properties were negatively influenced by the bonding treatment; both yield and tensile strength values decreased due to the presence of the hard yet brittle surface coating. In addition, the growth kinetics of boride layers was also analysed. The results showed a nearly parabolic relationship between the layer thickness and the process temperature, with activation energy of 47.3 kJ mol(-1).
Citation - WoS: 39
Citation - Scopus: 42
Effect of Post Fabrication Aging Treatment on the Microstructure, Crystallographic Texture and Elevated Temperature Mechanical Properties of In718 Alloy Fabricated by Selective Laser Melting
(Elsevier Science Sa, 2022) Bilgin, Guney Mert; Davut, Kemal; Esen, Ziya; Dericioglu, Arcan F.; Ozer, Seren
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 dis-appeared and converted into a mixture of columnar and equiaxed grains. Nano-sized gamma '' and/or gamma' 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 degrees C for 8 h) tested at 600 degrees 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 degrees C, which was attributed to intermediate temperature embrittlement.
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.
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 - WoS: 5
Citation - Scopus: 6
Compositional Dependence of Raman-Active Mode Frequencies and Line Widths in Tlins2xse2(1-X) Mixed Crystals
(Elsevier Science Bv, 2014) Guler, I.; Gasanly, N. M.
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.
Citation - WoS: 23
Citation - Scopus: 26
In Vitro Bioactivity Investigation of Alkali Treated Ti6al7nb Alloy Foams
(Elsevier, 2015) Esen, Ziya; Bor, Sakir; Butev, Ezgi
Biocompatible Ti6Al7Nb alloy foams with 70% porosity manufactured by space holder method were activated via alkali treatment using 5 M NaOH solution at 60 degrees C. The interconnected pore structures enabled formation of homogenous sodium rich coating on the foam surfaces by allowing penetration of alkali solution throughout the pores which had average size of 200 mu m. The resulted coating layer having 500 nm thickness exhibited porous network morphology with 100 nm pore size. On the other hand, heat treatment conducted subsequent to alkali treatment at 600 degrees C in air transformed sodium rich coating into crystalline bioactive sodium titanate phases. Although the coatings obtained by additional heat treatment were mechanically stable and preserved their morphology, oxidation of the samples deteriorated the compressive strength significantly without affecting the elastic modulus. However, heat treated samples revealed better hydroxyapatite formation when soaked in simulated body fluid (SBF) compared to alkali treated foams. On the other hand, untreated surfaces containing bioactive TiO2 layer were observed to comprise of Ca and P rich precipitates only rather than hydroxyapatite within 15 days. The apatite formed on the treated porous surfaces was observed to have flower-like structure with Ca/P ratio around 1.5 close to that of natural bone. (C) 2014 Elsevier B.V. All rights reserved.
Synthesis, Molecular Structure and Dft Study of 2-(n Benzoate
(Springer/plenum Publishers, 2011) Kazak, Canan; Ozdogan, Cem; Guvenc, Ziya B.; Buyukgungor, Orhan; Arslan, Figen; Odabasoglu, Mustafa; Yuksektepe, Cigdem
The biologically important 2-amino-3-hydroxypyridine reacts with benzoyl chloride to give 2-(N-benzoylbenzamido)pyridine-3-yl benzoate. This synthesized compound has been studied by elemental analysis, X-ray crystallography and also theoretically by density functional theory (DFT) framework with B3LYP/6-311++G(d, p) level of theory. The molecules of this compound crystallize in the orthorhombic space group of P2(1)2(1)2(1) and the crystal packing involves both hydrogen-bonding and C-Ha <-pi interaction. The vibrational normal modes of the molecular structure are investigated by ab initio method for both infrared intensities (IR) and for Raman activities. Furthermore, the corresponding assignments are discussed. Hydrogen and carbon atoms of the benzene rings are found to be highly active. Also, experimentally obtained IR spectrum is presented and compared with the available theoretical data. Experimentally and theoretically obtained IR spectrum are in good agreement.
Citation - WoS: 209
Citation - Scopus: 218
Stability of Edge States and Edge Magnetism in Graphene Nanoribbons
(Amer Physical Soc, 2011) Ozdogan, Cem; Quandt, Alexander; Fehske, Holger; Kunstmann, Jens
We critically discuss the stability of edge states and edge magnetism in zigzag edge graphene nanoribbons (ZGNRs). We point out that magnetic edge states might not exist in real systems and show that there are at least three very natural mechanisms-edge reconstruction, edge passivation, and edge closure-which dramatically reduce the effect of edge states in ZGNRs or even totally eliminate them. Even if systems with magnetic edge states could be made, the intrinsic magnetism would not be stable at room temperature. Charge doping and the presence of edge defects further destabilize the intrinsic magnetism of such systems.
Citation - WoS: 14
Citation - Scopus: 21
Fabrication, Morphology Analysis, and Mechanical Properties of Ti Foams Manufactured Using the Space Holder Method for Bone Substitute Materials
(Mdpi, 2019) Esen, Ziya; Yildirim, Bora; Cetinel, Oktay
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.

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