Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
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Article Citation - WoS: 7Citation - Scopus: 7Breaking the Boundaries of the Goldschmidt Tolerance Factor With Ethylammonium Lead Iodide Perovskite Nanocrystals(American Chemical Society, 2024) Güvenç, Çetin Meriç; Toso, Stefano; Ivanov, Yurii P.; Saleh, Gabriele; Balcı, Sinan; Divitini, Giorgio; Manna, LiberatoWe report the synthesis of ethylammonium lead iodide (EAPbI3) colloidal nanocrystals as another member of the lead halide perovskites family. The insertion of an unusually large A-cation (274 pm in diameter) in the perovskite structure, hitherto considered unlikely due to the unfavorable Goldschmidt tolerance factor, results in a significantly larger lattice parameter compared to the Cs-, methylammonium- and formamidinium-based lead halide perovskite homologues. As a consequence, EAPbI3 nanocrystals are highly unstable, evolving to a nonperovskite delta-EAPbI3 polymorph within 1 day. Also, EAPbI3 nanocrystals are very sensitive to electron irradiation and quickly degrade to PbI2 upon exposure to the electron beam, following a mechanism similar to that of other hybrid lead iodide perovskites (although degradation can be reduced by partially replacing the EA+ ions with Cs+ ions). Interestingly, in some cases during this degradation the formation of an epitaxial interface between (EA x Cs1-x )PbI3 and PbI2 is observed. The photoluminescence emission of the EAPbI3 perovskite nanocrystals, albeit being characterized by a low quantum yield (similar to 1%), can be tuned in the 664-690 nm range by regulating their size during the synthesis. The emission efficiency can be improved upon partial alloying at the A site with Cs+ or formamidinium cations. Furthermore, the morphology of the EAPbI3 nanocrystals can be chosen to be either nanocube or nanoplatelet, depending on the synthesis conditions.Article Citation - Scopus: 4One-step hydrothermal synthesis of spinel manganese oxide ion-sieve from commercial Γ-Mno2 and its uptake performance for lithium(Elsevier Ltd, 2024) Toprak, Seyra; Demir, Mustafa MuammerThe selective extraction of lithium from aqueous systems necessitates efficient sorbent materials. Spinel-type lithium manganese oxide ion sieves (LMOs) have been bee recognized for their high performance in this application. However, the elevated market cost of the spinel form (λ-MnO2) raises economic concerns, posing challenges to the feasibility of the extraction process. In this study, the one-step hydrothermal synthesis of Li1.33Mn1.67O4 was carried out at 200 °C for 7 days using commercial γ-MnO2 powder and aqueous LiOH solution as reactants. The synthesized powder exhibited characteristic XRD reflections consistent with spinel Li1.33Mn1.67O4. Lithium ion-sieve (H1.33Mn1.67O4) was obtained by leaching the LMO product with dilute hydrochloric acid solution. The sorption capacity of γ-MnO2 is increased from 8.4 to 23.1 mg/g (C0=200 mg/L), this capacity is very close to the one of the commercial λ-MnO2. The synthesized spinel HMO sorbent achieved a maximum Langmuir adsorption capacity of 52.1 mg/g. The extraction efficiency reached 94% at the sorbent dose of 20 g/L. The distribution coefficients of metal ions were in the order Li+ > Ca2+ > K+ > Na+, emphasizing selective Li+ extraction from brines with high Na+ content. These findings highlight the successful development of a spinel-type lithium manganese oxide ion sieve from γ-MnO2 polymorph, which is nearly an order of magnitude cheaper than the selective λ-MnO2. The study addresses critical issue of economic feasibility in lithium extraction processes, providing a potential solution for the selective recovery of bulk lithium. © 2024 Elsevier LtdArticle Citation - WoS: 3Citation - Scopus: 2Electrocaloric Behaviour of Tape Cast and Grain Oriented Nbt-Kbt Ceramics(Elsevier Sci Ltd, 2024) Unal, Muhammet Ali; Karakaya, Merve; Irmak, Tugce; Yildirim-Ozarslan, Gokce; Avci, A. Murat; Fulanovic, Lovro; Adem, UmutWe have investigated the effects of grain orientation and tape casting process on the electrocaloric properties of 0.82Na(0.5)Bi(0.5)TiO(3)-0.18 K0.5Bi0.5TiO3 (0.82NBT-0.18KBT) ceramics at the Morphotropic Phase Boundary (MPB), using direct and indirect measurements. We observe a larger electrocaloric response for the template-free ceramics compared to 7 and 10 wt% template containing ones, suggesting that grain orientation along rhombohedral < 100 > does not improve the electrocaloric response. Indirect measurements yielded a large adiabatic temperature change of around 3 K under an electric field of 50 kV/cm, which is significantly higher than 0.9 K reached at a lower electric field of 40 kV/cm using the direct measurement.Article Citation - WoS: 3Citation - Scopus: 2Electrocaloric Behaviour of Tape Cast and Grain Oriented Nbt-Kbt Ceramics(Elsevier Sci Ltd, 2024) Unal, Muhammet Ali; Karakaya, Merve; Irmak, Tugce; Yildirim-Ozarslan, Gokce; Avci, A. Murat; Fulanovic, Lovro; Adem, UmutWe have investigated the effects of grain orientation and tape casting process on the electrocaloric properties of 0.82Na(0.5)Bi(0.5)TiO(3)-0.18 K0.5Bi0.5TiO3 (0.82NBT-0.18KBT) ceramics at the Morphotropic Phase Boundary (MPB), using direct and indirect measurements. We observe a larger electrocaloric response for the template-free ceramics compared to 7 and 10 wt% template containing ones, suggesting that grain orientation along rhombohedral < 100 > does not improve the electrocaloric response. Indirect measurements yielded a large adiabatic temperature change of around 3 K under an electric field of 50 kV/cm, which is significantly higher than 0.9 K reached at a lower electric field of 40 kV/cm using the direct measurement.Article Citation - WoS: 11Citation - Scopus: 13Magnesium-Ion Battery Anode From Polymer-Derived Sioc Nanobeads(Wiley, 2023) Guo, Wuqi; Kober, Delf; Gurlo, Aleksander; Bekheet, Maged F.; İçin, Öykü; Ahmetoğlu, Çekdar VakıfTin-containing silicon oxycarbide (SiOC/Sn) nanobeads are synthesized with different carbon/tin content and tested as electrodes for magnesium-ion batteries. The synthesized ceramics are characterized by thermogravimetric-mass spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, N2 sorption analysis, scanning electron microscope, energy-dispersive X-ray, and elemental analysis. Galvanostatic cycling tests, rate performance tests, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) tests, and ex situ XRD measurements are conducted. Results of battery performance tests present a high capacity of 198.2 mAh g-1 after the first discharging and a reversible capacity of 144.5 mAh g-1 after 100 cycles at 500 mA g-1. Excellent rate performance efficiency of 85.2% is achieved. Battery performances in this research are influenced by surface area, and tin contentof the SiOC/Sn nanobeads. EIS, CV tests, and ex situ XRD measurements reveal that higher surface area contributes to higher capacity by providing more accessible Mg2+ ion storage sites and higher rate capability by improving the diffusion process. Higher Sn content increases battery capacity through reversible Mg-Mg2Sn-Mg alloying/dealloying process and improves the rate performances by increasing electrical conductivity. Besides, SiOC advances cycling stability by preventing electrode collapse and enhances the capacity due to higher surface capacitive effects. SiOC nanobeads containing Sn nanoparticles are synthesized and tested as anode for magnesium-ion batteries. The anodes show high performance with reversible capacity of 144.5 mAh g-1 after 100 cycles at 500 mA g-1 and excellent rate performance efficiency of 85.2% from 50 to 500 mA g-1.imageArticle Citation - WoS: 5Citation - Scopus: 6Formation of Monolithic Srtio3-Tio2 Ceramic Heterostructures by Reactive Hydrothermal Sintering(Elsevier, 2023) Karacasulu, Levent; Kartal, Uğur; İçin, Öykü; Bortolotti, Mauro; Biesuz, Mattia; Ahmetoğlu, Çekdar VakıfIn a one-pot approach, monolithic SrTiO3-TiO2 ceramic heterostructures were obtained using the reactive hydrothermal liquid phase densification (rHLPD). Structural, morphological, and photocatalytic properties of the obtained ceramics were analyzed. The relative density of the formed components reached about 80% with reaction time, temperature, and NaOH concentration variation. It was observed via Rietveld refinement that there was no XRD detectable phase other than TiO2 and SrTiO3 in the final structure. The monolithic SrTiO3-TiO2 ceramics obtained by hydrothermal reaction at 120 °C for 24 h in 1 M NaOH concentration showed a dielectric constant being around 500, and the dielectric loss was below 0.25 at frequencies higher than 10 kHz. The SrTiO3-TiO2 heterostructured monoliths having only 20 vol% total porosity and low specific surface area, demonstrated ∼60% efficiency (in 5 h) in degrading Methylene Blue photo-catalytically. © 2023 Elsevier LtdArticle Citation - WoS: 14Citation - Scopus: 20Influence of Al2o3 Reinforcements and Ti-Al Intermetallics on Corrosion and Tribocorrosion Behavior of Titanium(Elsevier, 2023) Sousa, Luis; Antunes, Rui D. M.; Fernandes, Joao C. S.; Alves, Alexandra Cruz; Toptan, FatihTi-Al2O3 composites have demonstrated favorable characteristics for use in load-bearing biomedical implant applications; however, the influence of Al2O3 reinforcement particles and Ti-Al intermetallics on the electrochemical and tribo-electrochemical responses of Ti are not well-understood. This study explored the corrosion and tribocorrosion characteristics of powder metallurgy-manufactured Ti-Al2O3 composites in a simple physiological saline solution at body temperature. Electrochemical analysis was performed by electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization and tribo-electrochemical mechanisms were explored under open circuit potential (OCP) against a 10 mm diameter alumina ball in a ball-on-plate tribometer with reciprocating configuration. Results revealed that the corrosion behavior of Ti was adversely affected by the development of a heterogeneous oxide film on the Ti matrix and the Ti-Al intermetallic phases formed by the interaction of Ti and Al2O3 particles. However, there was a drastic improvement in tribocorrosion behavior, evidenced by decreased corrosion tendency under sliding and a marked reduction in wear volume, primarily as a result of the decreased wear damage resulting from the load-bearing reinforcements.Article Citation - WoS: 5Citation - Scopus: 4Influence of Partitioning Treatment on Microstructure and Mechanical Properties of an Alloyed Ductile Iron Austempered at Different Temperatures(Walter de Gruyter GmbH, 2023) Neite, Maximilian; Münstermann, Sebastian; Nalçacı, Burak; Davut, Kemal; Erdoğan, MehmetThe present study was conducted to uncover effects of partitioning treatment on Cu-Ni-Mo alloyed ductile iron (DI) austempered at different temperatures. For this purpose, the DI samples, produced via sand casting, were austenitized at 900 °C for 60 min, followed by austempering at the temperatures of 275-325-375 °C for 120 min and afterwards a partitioning treatment was applied at 200 °C for 15 min. In the characterization studies, dilatometer, image analysis, JMat-Pro, mechanical tests, XRD, optical microscope, and scanning electron microscope (SEM) equipped with EBSD detector were utilized. Characterization studies showed that the effects of partitioning treatment were directly correlated with austempering temperature and high carbon austenite volume fraction changed in the range of 19.48-35.45%. That redistribution of carbon (C) between bainitic ferrite and high carbon austenite occurred, in turn, the carbon content of high carbon austenite increased with the partitioning treatment irrespective of austempering temperature were uncovered. Furthermore, the partitioning treatment considerably changed the grain morphologies of both high carbon austenite and banitic ferrite. As a consequence of these microstructural differences, the highest tensile strength of 1489.2 MPa was established in the sample austempered at 275 °C and partitioned at 200 °C, whereas the highest ductility of 5.61% acquired at the austempering temperature of 375 °C. © 2023 Walter de Gruyter GmbH, Berlin/Boston.Article Citation - WoS: 3Citation - Scopus: 3Amperometric Detection of Nh3 by Aromatic Sam-Modified Graphene(IEEE, 2023) Yağmurcukardeş, Nesli; Bayram, Abdullah; Aydın, Hasan; Can, Mustafa; Demiç, Şerafettin; Açıkbaş, Yaşar; Çelebi, CemAmmonia (NH3) is a toxic substance resulting in various acute and chronic effects on individuals. NH3 detection, monitoring methods, and detection tools are desperately needed. In this work, we improved the NH3 sensing capabilities of grapheme (GP) films deposited by chemical vapor deposition (CVD) by modifying aromatic self-assembled monolayer (SAM) molecules such as 5-[(3-methylphenyl) (phenyl) amino] isophthalic acid (MeIPA) and 5-(diphenyl)amino] isophthalic acid (PhIPA) on amperometric detection method. Morphological investigations of the films were carried out by optical and scanning electron microscopy (SEM). Surface potential was characterized with Kelvin probe force microscopy (KPFM), and vibrational properties were characterized with Raman spectroscopy. MeIPA modification increased NH3 uptake by two times compared to unmodified GP. The results indicated that the SAM modification enhanced NH3 molecule adsorption and improved its periodic reversible and reproducible response using the amperometric detection system, indicating that SAM molecules might be a feasible probe for NH3. © 2001-2012 IEEE.Article Citation - WoS: 3Citation - Scopus: 2Targeted Multidrug Delivery Systems To Kill Antibiotic-Resistant Staphylococcus Aureus(Editions de Sante, 2023) Özalp, Veli Cengiz; Ucak, Samet; Dursun, Ali D.; Sudağıdan, Mert; İçin, Öykü; Ahmetoğlu, Çekdar Vakıf; Henning, Laura M.; Simon, Ulla; Gurlo, AleksanderDifferent ordered mesoporous silica (OMS) nanoparticles, ranging from regular COK-12 to COK-12 modified in terms of pore shape and size, have been employed as standard drug carriers for the controlled adsorption and release of drug molecules in comparison to well-known OMS SBA-15 and MCM-41. The cytotoxicity analysis demonstrated that regular COK-12 particles were less harmful to mammalian cultured cells, causing lower apoptosis induction than modified COK-12, MCM-41, and SBA-15 particles. Thus, regular COK-12 was further used to prepare a dual antibiotic-loaded drug delivery material, followed by surface functionalization with Staphylococcus aureus-specific aptamers for targeting. The results demonstrated that the joint loading of lysozyme and vancomycin in regular COK-12 improved the ability of the antibiotic treatments to kill methicillin-resistant Staphylococcus strains via aptamer targeting. The minimum inhibitory concentration (MIC) values decreased 4.1-fold and 12-fold compared to the non-targeted use of the antimicrobial agents in homogeneous solutions for vancomycin and lysozyme, respectively, clearly demonstrating the high potential of COK-12 to be used as a carrier in multidrug therapy. © 2023 Elsevier B.V.