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: 1Citation - Scopus: 1Influence of Processing Method of Cocrmo Dental Alloy on the Corrosion Behavior in Artificial Saliva(Wiley, 2022) Pontes, Joana R.; Pinto, Ana M. P.; Ariza, Edith; Alves, Alexandra C.; Toptan, FatihRemovable or fixed dental frameworks are usually made of CoCr alloys. The CoCr dental alloys are produced traditionally by lost-wax casting. However, alternative processing routes, such as hot-pressing, are being studied for dental applications. The purpose of the present work was to assess the corrosion resistance of CoCrMo dental alloy produced by conventional lost-wax casting and hot-pressing. The corrosion behavior was studied in artificial saliva at 37°C by potentiodynamic polarisation tests. Immersion tests were performed to evaluate the growth of the passive film where electrochemical impedance spectroscopy was used at different immersion periods. Results showed slightly better corrosion resistance in terms of ipass for CoCrMo samples obtained by hot-pressing. On the other hand, the immersion tests showed a more stable and thicker passive film formed on hot-pressed CoCrMo dental alloy, pointing out that hot-pressing may be considered a promising technique to produce CoCrMo dental structures.Article Citation - WoS: 2Citation - Scopus: 1Effects of Electrospraying Parameters on Deposition of La0.3sr0.7fe0.7cr0.3o3−δ Cathode Layer on Gdc(Wiley, 2022) Akkurt, Sedat; Sındıraç, Can; Özmen Egesoy, Tuğçe; Atıcı, Gökçe; Erişman, Elif; Erğen, Emre; Büyükaksoy, AligülHigh performance in intermediate temperature solid oxide fuel cells requires improvements especially in the microstructure of the cathode layer. New cobalt-free cathode materials are used because cobalt-containing cathodes have higher thermal expansion coefficients, poor long-term chemical stability, and lower mechanical stability. Recently cobalt-free cathodes have been proposed to solve these issues by using deposition methods other than electrospray deposition (ESD). In this study, ESD method is used to develop a cobalt-free cathode layer. The electrolyte layer is gadolinium-doped ceria that is deposited with La0.3Sr0.7Fe0.7 Cr0.3O3−δ (LSFCr) prepared by 2-butoxyethanol and ethylene glycol solvents as opposed to conventional solvents. Experimental ESD parameters are tested at different levels and combinations by applying statistical experimental design methods to optimize the microstructure. Coating deposited as such demonstrated higher electrochemical performance than similar electrodes fabricated by other methods.Article Citation - WoS: 8Citation - Scopus: 8Design and Fabrication of Polymer Micro/Nano Composites With Two-Level Mechanical Reinforcing Procedure(Wiley, 2022) Kandemir, Ayşe Çağıl; Dönmez, Fatma; Davut, Kemal; Kaplan Can, HaticeBiocompatible composite production was accomplished by utilizing two-level hierarchical approach for mechanical reinforcement. A well-known commodity polymer; low-density polyethylene (LDPE), which has high-fracture toughness, yet low strength and modulus was used as the main matrix material. As the first step of hierarchy, ductile LDPE was blended with brittle polyvinylpyrrolidone (PVP), which is an eco-friendly, nontoxic and biocompatible polymer. This resulted in slight decrease of strength and drastic reduction of toughness (%70), yet modulus was increased by 78%. As the second level of hierarchy, PVP composites were introduced in LDPE. Nano-scaled Halloysite clay and micro-scaled spherical Silica particles were utilized as additives in the aforementioned PVP composites. The reason for the choice of these particles is that they are nontoxic, low-cost and in the case of Halloysite; abundant in nature. Owing to the implementation of the second level; modulus improvement was further enhanced to 150%, with additional benefits of strength increase up to 17% and less reduction in fracture toughness (minimum 51% reduction). Dynamic mechanical analysis also supported these outcomes that storage modulus of composites are higher than both LDPE and LDPE-PVP blend. The proposed biocompatible composites in the end of this study would be utilized in biomedical applications necessitating mechanical improvements.Article Citation - WoS: 4Citation - Scopus: 4Effects of Alkaline Earth Metal Additives on Methylammonium-Free Lead Halide Perovskite Thin Films and Solar Cells(Wiley, 2022) Yüce, Hürriyet; LaFollette, Diana K.; Demir, Mustafa Muammer; Perini, Carlo A.R.; Correa-Baena, Juan-PabloOrganic–inorganic lead halide perovskite solar cells are regarded as one of the most promising technologies for the next generation of photovoltaics due to their high power conversion efficiency (PCE) and simple solution manufacturing. Among the different compositions, the formamidinium lead iodide (FAPbI3) photoactive phase has a bandgap of 1.4 eV, which enables the corresponding higher PCEs according to the Shockley–Queisser limit. However, the photoactive crystal phase of FAPbI3 is not stable at room temperature. The most high-performing compositions to date have reduced this problem by incorporating the methylammonium (MA) cation into the FAPbI3 composition, although MA has poor stability at high temperatures and in humid environments, which can limit the lifetime of FAxMA1−xPbI3 films. CsxFA1−xPbI3 perovskites are also explored, but despite better stability they still lag in performance. Herein, the additive engineering of MA-free organic−inorganic lead halide perovskites using divalent cations Sr2+ and Ca2+to enhance the performances of CsxFA1−xPbI3 perovskite compositions is explored. It is revealed that the addition of up to 0.5% of Sr2+ and Ca2+ leads to improvements in morphology and reduction in microstrain. The structural improvements observed correlate with improved solar cell performances at low additive concentrations.Article Citation - WoS: 7Citation - Scopus: 8Seed-Mediated Synthesis of Colloidal 2d Halide Perovskite Nanoplatelets(Wiley, 2021) Güvenç, Çetin Meriç; Balcı, SinanColloidal synthesis of two-dimensional lead halide perovskite nanoplatelets (2D LHP NPLs) with a general formula of L-2[APbX(3)](n-1)PbX4 has been widely performed by using hot-injection or ligand assisted reprecipitation methods. Herein, for the first time, we report on seed-mediated synthesis of two and three monolayers (n=2, 3) lead halide perovskite nanoplatelets without using A-site cation halide salt (AX; A=Cesium, methylammonium, formamidinium and, X=Cl, Br, I) and long chain alkylammonium halide salts (LX; L=oleylammonium, octylammonium, butylammonium and, X=Cl, Br, I). The nanocrystal seeds have been prepared by reacting lead (II) halide salt and coordinating ligands in a nonpolar solvent and then they have been reacted with cesium oleate, formamidinium oleate or methylamine. Our facile synthesis route enabling further understanding of the growth dynamics of LHP NPLs provides highly stable, monodisperse NPLs with very narrow absorption and emission linewidths (min. 68 meV), and high PLQY (max. 37.6%).Other Macromol. Mater. Eng. 7/2016(Wiley, 2016) Isık, Tuğba; Horzum Polat, Nesrin; Yıldız, Ümit Hakan; Liedberg, Bo; Demir, Mustafa MuammerAn easy-to-use test platform toward the rapid diagnosis of many life-threating diseases was developed. DNA was isolated from the mixture of BSA+DNA using fibrous commodity polystyrene, which was extremely cheap and can be readily electrospun under ambient conditions. Surface modification with Au nanoparticles improved the performance of the fibrous membrane.