Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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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 LtdBook Part Citation - Scopus: 3Advances and Future Perspective of Graphene Field Effect Transistors (gfets) for Medical Diagnostics and Point-Of Tools(World Scientific Publishing, 2022) İnanç, Dilce; Mutlu, Mustafa Umut; Karabacak, Soner; Yıldız, Ümit HakanRecently, major focus has been centered to enhance the capability of graphenebased devices and to facilitate utilization of graphene for biological applications by lowering its toxicity. In this chapter, from synthesis to applications, many of the conspicuous characteristics of graphene have been elaborately reviewed. We primarily focused on graphene-based field effect transistor (FET) for medical diagnostics and point-of-care applications. The device configurations and their application potential as well as sensing capability of various graphene FETs (GFETs) have been discussed. Here, we have also presented several aspects and advantages of GFETs in medical applications while discussing their pros and cons in commercialization. We address the advances and challenges for GFET-based sensing platforms for the medical applications and elaborate the combination strategy of GFETs with the existing commercial systems. © 2023 by World Scientific Publishing Co. Pte. Ltd.Article Citation - WoS: 3Citation - Scopus: 4A Facile Method for Boosting the Graphitic Carbon Nitride's Photocatalytic Activity Based on 0d/2d S-Scheme Heterojunction Nanocomposite Architecture(Elsevier, 2024) Kahraman, Zeynep; Kartal, Uğur; Gent, Aziz; Alp, EmreGraphitic carbon nitride (g-C 3 N 4 ) has received significant interest as a metal -free photocatalyst. The S -scheme photocatalytic system has great potential to improve the charge separation in semiconductor photocatalysts. In this study, we have fabricated non-toxic and low-cost photocatalytic nanocomposites of 0D/2D S -scheme heterojunction composed of iron oxide and graphitic carbon nitride by a facile method. The developed facile method provides a sustainable way with a high atom economy to further enhance the photocatalytic performance of exfoliated g-C 3 N 4 . The 0D -iron oxide/2D-C 3 N 4 exhibited nearly 10 times better than bulk g-C 3 N 4 and almost 60 % better than exfoliated g-C 3 N 4 under simulated solar light irradiation. The experimental results demonstrated that the effective charge -carrier mechanism led to an improved generation of reactive oxygen species (ROSs), resulting in an impressive photocatalytic performance. A serial photocatalytic test was also conducted to understand photocatalytic reaction mechanisms with various scavengers.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: 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.Conference Object Citation - WoS: 1Citation - Scopus: 1Assessment of Separation and Agglomerationt Tendency of Non-Metallic Inclusions in an Electromagnetically Stirred Aluminum Melt(Springer international Publishing Ag, 2023) Li, Cong; Dang, Thien; Gokelma, Mertol; Zimmermann, Sebastian; Mitterecker, Jonas; Friedrich, BerndPresence of non-metallic inclusions (NMIs) reduces surface quality and mechanical properties of aluminum products. The development of good NMIs removal practices relies on the understanding of inclusion behaviors with respect to separation and agglomeration particularly in the turbulent flow. In the scenario of electromagnetically induced recirculated turbulent flow, the concerned behaviors of inclusions with different sizes have rarely been investigated experimentally. In the presented study funded by AMAP Open Innovation Research Cluster, reference materials were prepared with uniformly distributed NMIs (SiC and MgAl2O4) via an ultrasoundinvolved casting route. Reference materials were charged into an aluminum melt where turbulent flow was promoted via electromagnetic force. Microscopical analysis shows non-significant agglomeration tendency of SiC, MgAl2O4, and TiB2 inclusion. Time-weight filtration curve, PoDFA, and Spark Spectrometer results suggest a strong dependence of separation rate on particle size. Analytical models were established to estimate the collision rate of particles and to evaluate separation probability of different sized particles.Article Citation - WoS: 3Citation - Scopus: 3Nondestructive Microstructural Characterization of Austempered Ductile Iron(Walter de Gruyter GmbH, 2023) Tüzün, Mert Yağız; Yalçın, Mustafa Alp; Davut, Kemal; Kılıçlı, VolkanAustempered ductile iron (ADI) has been preferred in a wide range of applications due its unique combination of high strength, good ductility, wear resistance and fracture toughness together with lower cost and lower density compared to steels. Magnetic Barkhausen noise (MBN) measurement offers a better alternative to traditional characterization techniques by being fast and non-destructive. A simple linear regression using only one single independent variable cannot correlate the MBN with the microstructure of ADI, since its microstructure is multi component. Multiple linear regression analysis (MLRA) was used to build a model that uses the characteristic features of microstructural constituents as input parameters to predict the MBN. For that purpose, Cu-Ni-Mo alloyed ductile iron samples austempered between 325 and 400 degrees C and for 45-180 min duration were used. The results show that MBN is most sensitive to the size and shape of acicular ferrite and retained austenite. Moreover, MBN is almost insensitive to the size, morphology and volume fraction of graphite particles. This indicates that retained austenite pins the domain walls more effectively than the graphite particles. Considering the results MLRA, MBN technique can be used to characterize the ausferritic microstructure of ADI.Research Project Darbe altında ışıma yapan polimerik filmler ve lif demetlerinin üretilmesi ve uygulamaları(2016) Demir, Mustafa M.; İncel, AnılTribolüminesans (TL) malzemeler darbe altında ışıma özelliğine sahip kristal yapılardır. Bu projede, organik ve metal yapıları bir arada bulunduran iki TL kristal (EuD4TEA ve Cu(NCS)(py)2(PPh3)) elde edilmiş ve mikrometre büyüklüğündeki tanecikler PMMA (poli metil metakrilat), PS (polistiren), PU (poliüretan) ve PVDF (polivinilflorür) saydam özellikteki polimerler kullanılarak ince-katmanlı film, elektrospun lif demetleri ve nano boyutundaki tanecikler elde edilen matrisler ile entegre edilmiştir. Kompozit malzemelerin elde edilmesi için iki farklı deneysel metod geliştirilmiştir: i) yükleme işlemi ve ii) yüzeye depolama işlemi. Kompozit malzemelerin TL performansları bu tez için özel tasarlanan atış kule sistemi ile ölçülmüştür. Bunun yanı sıra, atomik kuvvet mikroskobu (AFM), taramalı elektron mikroskobu (SEM) polimerlerin ve kompozit malzemelerin topografik ve morfolojik özellklerini değerlendirmek için kullanılmıştır. Ayrıca, flüoresans mikroskobu kullanılarak kompozit malzemelerin emisyon sırasındaki renk sinyalleri belirlenmiştir. Son olarak piezoelektrik özellikleri osiloskop kullanılarak belirlenmiştir. Tüm bu cihazlardan elde edilen sonuçlar değerlendirildiğinde, deneysel prosedür, kristal taneciklerin boyutları, polimer malzemenin formu ve yüzey özelliği, kullanılan kristallerin kompozit içindeki miktarı bu çalışmada temel parametreler olarak belirlenmiştir. PU esaslı elde edilen film ve lif demeti kompozitler PMMA, PS, ve PVDF esaslı kompozitlerden daha iyi sonuç göstermiştir. Bunun nedeni olarak, film esaslı kompozitler için ince katmanlı PU filmin daha engebeli ve saydam bir yüzey olması; lif esaslı kompozitler için elektrospun PU liflerin daha küçük yapılardan oluşması, tüm bunlara ek olarak PU’nın kimyasal olarak TL özellikteki iki kristalle kimyasal etkileşim oluşturulması gösterilebilir.Article Citation - WoS: 2The Effect of the Temperature of Heat Treatment Process and the Concentration and Duration of Acid Leaching on the Size and Crystallinity of Nano-Silica Powders Formed by the Dissociation of Natural Diatom Frustule(American Scientific Publishers, 2022) Ülker, Sevkan; Güden, MustafaThe present study focused on the processing of nano-silica powders in varying sizes and crystallinities through IP: 846247.10 On: Wed, 14 Dec 2022 07:29:25 heat treatment (900-1200 degrees C), hydrofluoric acid leaching (1-7 N), and ball milling (1 h, 500 rpm) of natural Copyright American Scentfic P blishers diatom frustules. The starting natural frustules were determined to be composed of amorphous silica (88%) Delivered by Ingenta and quartz. The partially ordered crystalline low-quartz and or precursor to low-cristobalite started to form at-900 degrees C. As the heat treatment temperature increased, the crystallinity of the frustules increased from 9.3% at 25 degrees C to 46% at 1200 degrees C. Applying a ball milling reduced the mean particle sizes of the as-received and heat-treated frustules from 15.6-13.7 mu m to 7.2-6.7 mu m, respectively. Acid leaching of the as-received and heat-treated frustules resulted in a further increase in the crystallinity. Furthermore, a ball milling applied after an acid leaching was very effective in reducing the particle size of the as-received and heat-treated frustules. The mean particle size of the acid-leached frustules decreased to 774-547 nm with a crystallinity varying between 12 and 48% after ball milling. A partially dissolved amorphous phase was observed in between crystalline silica grains after acid leaching, which resulted in a rapid fracture/separation of the frustules in ball milling.Article Citation - WoS: 3Citation - Scopus: 5Physically Unclonable Security Patterns Created by Electrospinning, and Authenticated by Two-Step Validation Method(IOP Publishing, 2022) Taşcıoğlu, Didem; Atçı, Arda; Sevim Ünlütürk, Seçil; Özçelik, SerdarCounterfeiting is a growing economic and social problem. For anticounterfeiting, random and inimitable droplet/fiber patterns were created by the electrospinning method as security tags that are detectable under UV light but invisible in daylight. To check the authenticity of the original security patterns created; images were collected with a simple smartphone microscope and a database of the recorded original patterns was created. The originality of the random patterns was checked by comparing them with the patterns recorded in the database. In addition, the spectral signature of the patterns in the droplet/fiber network was obtained with a simple and hand-held spectrometer. Thus, by reading the spectral signature from the pattern, the spectral information of the photoluminescent nanoparticles was verified and thus a second-step verification was established. In this way, anticounterfeiting technology that combines ink formula, unclonable security pattern creation and two-level verification is developed.