Malzeme Bilimi ve Mühendisliği Bölümü

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Citation - WoS: 7
Citation - Scopus: 7
A Comparison of Radiation Shielding of Stainless Steel With Different Magnetic Properties
(Vinca inst Nuclear Sci, 2014) Calik, Adnan; Akbunar, Sahin; Ucar, Nazim; Yilmaz, Nihat; Karakas, Mustafa Serdar; Akkurt, Iskender; 48915; Malzeme Bilimi ve Mühendisliği
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.
Diffusion Kinetics of Binary Ti-Ni Shape Memory Alloys
(Polish Acad Sciences inst Physics, 2017) Ucar, N.; Dogan, S.; Ozdemir, A. F.; Karakas, S.; Calik, A.; 48915; Malzeme Bilimi ve Mühendisliği; Bankacılık ve Finans
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 - 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) Cetinel, Oktay; Esen, Ziya; Yildirim, Bora; 52373; Ortak Dersler Bölümü
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 - WoS: 5
Citation - Scopus: 5
Investigation of the Erosive Wear Resistance of Boronized Ash-Blowing Nozzles
(Polish Acad Sciences inst Physics, 2017) Calik, A.; Ozbakir, O.; Karakas, S.; Ucar, N.; 48915; Bankacılık ve Finans
In this study, pack boronizing was applied to ash-blowing nozzles manufactured from AISI 1040 steels using Ekabor II powders as the boronizing source at a temperature of 1273 K for a duration of 8 h. Erosive wear tests of boride ash-blowing nozzles were carried out in ash delivery line of thermal reactor under actual working conditions. It was observed that erosive wear resistance of borided ash-blowing nozzles were increased 3 times as a result of the boronizing process. The improved wear resistance of the borided samples can be explained by increased surface hardness and higher work hardening.
Microstructure and Mechanical Properties of CoCrFeNi(TiAl) High Entropy Alloys
(2020) Kalay, Ilkay; 101579; Mekatronik Mühendisliği
The 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 amixture of FCC and double BCC structures. The lattice parameter of FCC increasesupon addition of Al and Ti. The microstructure analysis shows the morphologicaltransition of dendrites from non-equiaxed to equiaxed during the suction casting ofCoCrFeNiTi0.5Al 0.5 alloy. The Vickers microhardness testing of CoCr-FeNi alloy revealssignificant increase in hardness with the addition of Al and Ti. The hardness values areimproved 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 failsat 2344 MPa. The fracture mechanism of CoCrFeNiTi0.5Al 0.5 alloy reveals a cleavage mode.
Citation - Scopus: 171
Nanoscale structure and structural relaxation in Zr 50Cu 45Al 5 bulk metallic glass
(2012) Hwang, J.; Melgarejo, Z.H.; Kalay, Y.E.; Kalay, I.; Kramer, M.J.; Stone, D.S.; Voyles, P.M.; 101579; Mekatronik Mühendisliği
Hybrid 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.
Reaksiyon Bağlı Silisyum Nitrür Seramiklerinde Sinterleme İlavesinin Mikroyapı ve Antibakteriyel Davranışa Etkisinin İncelenmesi
(2021) Kuşhan Akın, Şeniz Reyhan; 224219; İnşaat Mühendisliği
Silisyum 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.
Citation - WoS: 204
Citation - Scopus: 213
Stability of edge states and edge magnetism in graphene nanoribbons
(Amer Physical Soc, 2011) Kunstmann, Jens; Ozdogan, Cem; Quandt, Alexander; Fehske, Holger; Ortak Dersler Bölümü
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.

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