Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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Article Citation - WoS: 3Citation - Scopus: 6Investigation of the Influence of High-Pressure Torsion and Solution Treatment on Corrosion and Tribocorrosion Behavior of Cocrmo Alloys for Biomedical Applications(MDPI, 2023) Yılmazer, Hakan; Caha, İhsan; Dikici, Burak; Toptan, Fatih; Işık, Murat; Niinomi, Mitsuo; Nakai, Masaaki; Alves, Alexandra CruzIn this study, the influence of the high-pressure torsion (HPT) processing parameters and solution treatment (ST) on the corrosion and tribocorrosion behavior of CoCrMo (CCM) alloys was investigated for possible usage in biomedical applications. The corrosion behavior of the CCM alloys was investigated by using potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) tests. Tribocorrosion tests were carried out in a reciprocating ball-on-plate tribometer at 1 Hz, 1 N load, and 3 mm stroke length for 2 h. All electrochemical measurements were performed using a potentiostat in standard phosphate-buffered saline (PBS) solution at body temperature (37 +/- 2 degrees C). The samples were characterized by using a scanning electron microscope (SEM), transmission electron microscope (TEM), optical microscope (OM), and X-ray diffraction (XRD). The deepness and width of wear tracks were examined by using a profilometer. The results showed that HPT and ST processes did not affect significantly the corrosion resistance of samples. However, the ST-treated samples had a higher material loss during sliding in standard phosphate-buffered saline (PBS) at body temperature as compared to HPT-treated samples.Article Citation - WoS: 10Citation - Scopus: 11Improved Tribocorrosion Behavior Obtained by In-Situ Precipitation of Ti2c in Ti-Nb Alloy(MDPI, 2022) Gonçalves, Vinícius Richieri Manso; Çaha, İhsan; Alves, Alexandra Cruz; Toptan, Fatih; Rocha, L. A.Novel in-situ Ti-based matrix composites (TMCs) were developed through the reactive hot pressing of Ti + NbC powder blends. Due to the chemical reaction that occurred in the solid-state during processing, the produced samples were composed of an Nb-rich β-Ti phase that formed a metallic matrix along with Ti2C as a reinforcing phase. By employing different proportions of Ti:NbC, the phase composition of the alloys was designed to contain different ratios of α-Ti and β-Ti. The present work investigated the corrosion and tribocorrosion behavior of the composites, compared to unreinforced Ti, in a phosphate-buffered solution (PBS) at body temperature. Corrosion tests included potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Tribocorrosion tests were carried out using a ball-on-plate tribometer with sliding performed at open circuit potential (OCP) and under anodic potentiostatic conditions. Results showed that the stabilization of the β phase in the matrix led to a decrease in the hardness. However, the formation of the in-situ reinforcing phase significantly improved the tribocorrosion behavior of the composites due to a load-carrying effect, lowering the corrosion tendency and kinetics under sliding. Furthermore, localized corrosion was not observed at the interface between the reinforcing phase and the matrix.Article Citation - WoS: 8Citation - Scopus: 11Spreadability of Metal Powders for Laser-Powder Bed Fusion Via Simple Image Processing Steps(MDPI, 2022) Ahmetoğlu, Çekdar Vakıf; Hasdemir, Beyza; Biasetto, LisaThis paper investigates the spreadability of the spherical CoCrWMo powder for laser- powder bed fusion (PBF-LB) by using image processing algorithms coded in MATLAB. Besides, it also aims to examine the spreadability dependence with the other characteristics such as powder size distribution, apparent density, angle of repose. Powder blends in four different particle size distributions are prepared, characterized, and spreadability tests are performed with the PBF-LB. The results demonstrate that an increase in fine particle ratio by volume (below 10 µm) enhances the agglomeration and decreases the flowability, causing poor spreadability. These irregularities on the spread layers are quantified with simple illumination invariant analysis. A clear relation between powder spreadability and 3D printed structures properties in terms of residual porosity could not be defined since structural defects in 3D printed parts also depends on other processing parameters such as spatter formation or powder size over layer height ratio.Article Citation - WoS: 9Citation - Scopus: 11Synthesis, Bottom Up Assembly and Thermoelectric Properties of Sb-Doped Pbs Nanocrystal Building Blocks(MDPI, 2021) Cadavid, Doris; Wei, Kaya; Liu, Yu; Zhang, Yu; Li, Mengyao; Genc, Aziz; Berestok, TaisiiaThe precise engineering of thermoelectric materials using nanocrystals as their building blocks has proven to be an excellent strategy to increase energy conversion efficiency. Here we present a synthetic route to produce Sb-doped PbS colloidal nanoparticles. These nanoparticles are then consolidated into nanocrystalline PbS:Sb using spark plasma sintering. We demonstrate that the introduction of Sb significantly influences the size, geometry, crystal lattice and especially the carrier concentration of PbS. The increase of charge carrier concentration achieved with the introduction of Sb translates into an increase of the electrical and thermal conductivities and a decrease of the Seebeck coefficient. Overall, PbS:Sb nanomaterial were characterized by two-fold higher thermoelectric figures of merit than undoped PbS.Article Citation - WoS: 9Citation - Scopus: 10Polymeric Planar Microcavities Doped With a Europium Complex(MDPI, 2020) Lova, Paola; Olivieri, Marco; Surace, Alba; Topçu, Gökhan; Emirdağ Eanes, Mehtap; Demir, Mustafa Muammer; Comoretto, DavideOrgano-metallic europium complex tetrakis (dibenzoyl methide) triethylammonium (EuD(4)TEA) shows a sharp emission spectrum, which makes it interesting for photonic applications. In this work, we embedded it into all-polymeric planar microcavities and investigated the effect of the photonic environment on its emission spectrum. To this end, submicron-sized EuD(4)TEA crystals were loaded into a blend of polystyrene and carboxylic terminated polystyrene matrix, which served to stabilize the emitter in the polymer and to make the composite processable. The new composite was then casted by spin-coating as a defect layer in a polymeric planar microcavity. Spectroscopic studies demonstrate that fine spectral tuning of the cavity mode on the sharp organometal luminescence is possible and produces spectral redistribution of the fluorophore emission, along with a remarkable cavity quality factor.