Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article A Critical Analysis of Pulverization Mechanism During Hydrogen Decrepitation of End-Of Ndfeb Magnets(Elsevier Science Sa, 2025) Habibzadeh, Alireza; Gokelma, MertolGiven the increasing demand and limited availability of rare earth elements (REEs), innovative solutions are critical to managing supply risks. Recycling is a key strategy in mitigating these risks, particularly for NdFeB magnets, which consume a large portion of REEs. Among the various recycling processes, hydrogen decrepitation (HD) has gained popularity due to its efficiency in producing fine powders for magnet-to-magnet recycling. While the HD mechanism is commonly attributed to hydride formation in the Nd-rich grain boundary phase, this study presents new findings that challenge this assumption. Through the hydrogenation of End-of-Life (EoL) NdFeB magnets at temperatures ranging from 25 to 400 & ring;C, the results indicate that the primary mechanism of pulverization arises from hydride formation in the Nd2Fe14B matrix rather than in the Nd-rich phase, especially at low temperatures where NdH2 formation is kinetically unfavorable. This revised mechanism was supported by evidence from X-ray diffraction, BSE and SE-SEM imaging, particle size analysis, diffusion modeling, and stress analysis.Article Citation - WoS: 2Citation - Scopus: 1A Novel Framework for Droplet/Particle Size Distribution in Suspension Polymerization Using Physics-Informed Neural Network (PINN)(Elsevier Science Sa, 2025) Turan, Meltem; Dutta, AbhishekA Machine Learning (ML) based neural network can capture the complex evolution of polymer chain distributions, accounting for factors such as initiation, propagation, and termination steps in a suspension polymerization process, by integrating stagewise molar balance model (MBM) and population balance model (PBM) with Physics-Informed Neural Network (PINN). The integrated PINN framework is proposed to efficiently solve these equations, incorporating known physical laws as constraints and minimizing errors in both the distribution and dynamics of the polymer chains. By optimizing the neural network parameters such as weight matrices and bias vector, the model reproduces the moments of the polymer molecular weight distribution in close alignment with numerical solutions, and it generates population balance solutions that exhibit excellent agreement with their analytical counterparts. Sensitivity analyses for the depth of the neural network architecture to quantify how structural choices affect model fidelity has been performed. The resulting MBM-PINN and PBM-PINN integrated framework demonstrates robustness and versatility in accurately capturing (96-97%) droplet/particle dynamics. The proposed methodology has the capability to provide a powerful tool for faster and scalable simulations of polymerization reactions, enabling better prediction of product properties which could be used for optimizing reaction conditions in industrial applications.Article Citation - WoS: 4Citation - Scopus: 4Zn/Na Co-Doped Hydroxyapatites: Synthesis, Antibacterial, and Bioactivity Studies(Elsevier Science Sa, 2025) Samadi, Hamed; Pakchin, Parvin Samadi; Mohammadpourfard, Mousa; Adibkia, KhosroThe most crucial challenge of post-orthopedic surgery is related to bacterial film formation, which leads to implant failure. In this work, zinc/sodium (Zn/Na) co-doped hydroxyapatite nanoparticles (HA NPs) with different Zn/Na concentrations, including 1, 3, and 5 mol.% were synthesized using a hydrothermal method. Several analyses such as X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), and N2 ad/desorption were used to pinpoint the properties of as-prepared materials. Field Emission Scanning Electron Microscopy (FE-SEM) and EDX analysis demonstrated that the HA NPs possess an average size of about 30-40 nm and hexagonal morphology with no impurity. XRD patterns confirm that by the increasing amounts of Zn/Na, the crystal size of samples was decreased. FT-IR affirms the correct doping of metal ions. Brunauer-Emmett-Teller (BET) results of co-doped samples demonstrated a microporous structure, which can improve fluid flow in the inner structure of implants. The colony-forming unit (CFU) method conducted the antibacterial test, which confirmed that 5 mol.% Zn/Na co-doped HA NPs showed the highest antibacterial properties against Escherichia coli (PTCC 1276) (E. coli). Cytotoxicity results affirmed that 1 and 3mol.% Zn/Na co-doped HA NPs demonstrated low toxicity. Bioactivity tests revealed that the Zn/Na co-doped samples showed a higher ability to facilitate bone marrow stem cells; thus, improving the proliferation after the immersion in simulated body fluid (SBF). Therefore, Zn/Na co-doped HA NPs could be a promising candidate for bone tissue engineering applications.Article Citation - WoS: 6Citation - Scopus: 10Influence of the Heat Treatment on the Microstructure, Mechanical and High-Temperature Oxidation Behavior of Hastelloy X Alloy Fabricated Via Laser Powder Bed Fusion(Elsevier Science Sa, 2025) Ozer, Seren; Yalcin, Mustafa Alp; Bilgin, Gueney Mert; Davut, Kemal; Esen, Ziya; Dericioglu, Arcan F.The effect of building direction and heat treatment on the microstructure, mechanical properties, and high- temperature oxidation behavior of Hastelloy X (HX) alloy fabricated by the laser powder bed fusion (L-PBF) method was studied. Electron backscatter diffraction analyses revealed that the development of textured columnar grains with varying average grain sizes, boundary fractions, and dislocation densities induced the mechanical anisotropy observed in both horizontally and vertically fabricated samples. The yield strength (YS) values of the horizontally and vertically as-fabricated samples were determined as 605.7 +/- 15.9 MPa and 552.3 +/- 8.5 MPa, respectively. The post-processing heat treatment increased the ductility remarkably and reduced YS value down to similar to 445 MPa for all samples by the elimination of microstructural anisotropy and increased grain size subsequent to recrystallization. Oxidation tests conducted at 900 degrees C up to 100 h on as- fabricated samples exhibited severe intergranular oxidation, which was accompanied by the formation of large voids and microcracks as well as spallation of the oxide layer. In contrast, the heat-treatment improved the oxidation resistance of the alloy possibly due to the formation of uniform and dense Cr2O3 layer on the substrate surface.Article Citation - WoS: 2Citation - Scopus: 2The Spheroidization Behavior of Low Alloy White Cast Iron and Its Effect on Impact Toughness and Wear Resistance(Elsevier Science Sa, 2025) Camkerten, Ruziye; Davut, Kemal; Yilmaz, Tolga; Nalcaci, Burak; Erdogan, MehmetThe effect of spheroidization on impact toughness and wear resistance, together with the spheroidization kinetics of a low alloy white cast iron (LAWCI) have been studied. Spheroidization process was carried out using two different routes; intercritical annealing and subcritical annealing both of which were followed by furnace cooling to room temperature. Both routes involve a process window, which is determined by holding time and temperature. For the intercritical annealing the spheroidization window is significantly shorter (0.5-3 h) than the conventional subcritical spheroidization (6 - 12 h); and that process window narrows with increasing intercritical annealing temperature. The intercritical spheroidization involves 3 distinct stages; (i) partial, followed by (ii) fully spheroidization of lamellar pearlitic matrix by divorced eutectoid transformation (DET); and (iii) partially spheroidization by pearlitic structure formation in previous fully spheroidized region. The end of third stage produces almost fully pearlitic matrix, which is coarser than the as-cast condition. In case of subcritical spheroidization, the process window opens after about 6 hours and the size of spherical carbides gets larger with time. The as-cast LAWCI having a microstructure composed of eutectic carbide network and pearlite matrix exhibits and impact toughness of 4.6 J. Spheroidization process not only changes the lamellar pearlitic structure into spheroidized carbides but also slightly reduces the amount of eutectic carbides. Those microstructural changes greatly improve the impact toughness of LAWCI up to 11.8 J; whereas some decrease in the wear resistance. For spheroidized LAWCI, mean diameter of carbides (D), interparticle spacing of carbides (s), and number of carbides per area (n) seems to be important microstructural variations to determine the impact toughness and wear properties. Taking properties of the current material into consideration, spheroidized white cast irons may be a viable alternative material for industrial applications, offering a trade-off between wear resistance and toughness.Review Citation - WoS: 4Citation - Scopus: 7Optimizing Lighting Design in Educational Settings for Enhanced Cognitive Performance: a Literature Review(Elsevier Science Sa, 2025) Celik, Meric; Didikoglu, Altug; Kazanasmaz, TugceLighting has more functions than simply illuminating spaces. For humans, light is the main signal that aligns our body's internal clock, regulating circadian rhythms. This process instructs our bodies to wake up in the morning, become alert during the day, and feel sleepy at night. Disruption of these rhythms can impact neurological and psychiatric health, including cognitive performance. We can utilize light for mood improvements and better cognitive performance to create a suitable learning environment for students in educational buildings. These non-visual effects of light need to be considered from the beginning of the design process, making an interdisciplinary effort necessary. Even with adequate light and dark, the human eye reacts differently under various conditions, influenced by light's photometric and colorimetric properties. While natural sunlight is ideal for aligning with our biological clock, it is not always sufficient, making artificial lighting essential indoors. LED technology offers promising solutions, catering to our non-visual needs in the absence of natural light and providing energy efficiency. This study reviews the literature that includes students' cognitive performance and well-being, energy efficiency, running costs, and environment-related issues such as light pollution. It aims to explore the impact of lighting design in learning environments.Article Citation - WoS: 2Citation - Scopus: 2Sleep Quality: Design of Bedroom Ventilation and Evaluation Within the Scope of Current Standards(Elsevier Science Sa, 2025) Cobanoglu, Nur; Karadeniz, Ziya Haktan; Sofuoglu, Sait Cemil; Toksoy, MacitIndoor air pollution is one of the leading environmental risks to public health considering people now spending nearly 90 % of their day in indoor environments. A significant portion of this time indoors is devoted to sleeping, making it crucial to address the impact of indoor environmental conditions on sleep quality. International ventilation standards such as ASHRAE and CEN, as well as country-specific guidelines, offer valuable recommendations for ventilation design in residential buildings, including bedrooms. This study aims to evaluate the importance of determining ventilation rates in sleeping spaces using Indoor Air Quality Procedure (IAQP) compared to Ventilation Rate Procedure (VRP) in accordance with current standards. Here, the IAQP approach for determining air flow rate is based on the CO2 balance by maintaining CO2 levels in any sleeping environment below specified upper limits of 750 ppm and 1000 ppm. This study focused on the adult population, which forms the majority of society, with analyses conducted for both single and double occupancy sleeping conditions. The volume of environment where ventilation is not required during sleep (Vf) is inaccessible in conventional sleeping environments (10-21.6 m3 per person). Therefore, proper ventilation is of great importance for any sleeping space that is smaller than the Vf. The results of the analyses show that for the conventional sleeping volumes, CO2 levels reach 750 ppm (upper limit for comfortable sleep) in the first hour and increase to the disturbed sleep zone in about 2 h. Additionally, a chart outlining the necessary ventilation flow rates is suggested for maintaining maximum CO2 concentrations of 750 and 1000 ppm during different sleep durations and in various sleeping environments with varying volumes. Finally, the ventilation rates determined based on unit area and/or occupancy levels in standards (referred to as VRP) may not always be adequate or may be excessive in order to maintain CO2 concentrations below the recommended limits of 750 and 1000 ppm. It is advised to utilize demand-controlled ventilation by considering the system design as recommended by IAQP.Article Citation - WoS: 5Citation - Scopus: 8Micro-Arc and Thermal Oxidized Titanium Matrix Composites for Tribocorrosion-Resistant Biomedical Implants(Elsevier Science Sa, 2024) Sousa, Luis; Costa, Natalia A.; Rossi, Andre; Simoes, Sonia; Toptan, Fatih; Alves, Alexandra C.Superior tribocorrosion resistance is offered by titanium matrix composites (TMCs) compared to their unreinforced matrix metal, but bioactivity concerns are raised for biomedical applications. Simple methods such as micro -arc oxidation (MAO) and thermal oxidation (TO) are employed to enhance the bioactivity and degradation resistance of Ti. However, the impact of those surface treatments on TMC surfaces is poorly understood. Therefore, the present work aimed to explore the influence of MAO and TO treatments on the surfaces of in - situ Ti-TiB-TiC and ex - situ Ti-B 4 C composites, and to assess their corrosion and tribocorrosion performance. Corrosion and tribocorrosion tests were conducted in phosphate-buffered saline solution (PBS) at body temperature. Electrochemical assays were performed by means of potentiodynamic polarization scans while additional potentiostatic tests were performed for the untreated ex - situ composites. Tribo-electrochemical assays were conducted under open circuit potential (OCP) and under normal loads of 0.5 and 10 N against a 10 mm diameter alumina ball in a reciprocating ball -on -plate tribometer. Results revealed reinforcement detachments in ex - situ composites after both treatments. This was primarily attributed to oxide layer growth at the reinforcement/reaction zone interface. Hence, the use of MAO and TO on ex - situ Ti-B 4 C composites may not be appropriate for biomedical applications, mainly because the B 4 C particles tend to detach during the treatment. In contrast, TOtreated in - situ composites displayed excellent combination of corrosion and tribocorrosion performance, even under elevated applied loads, mainly due to the existence of the oxygen diffusion zone (ODZ) beneath the oxide surface produced by TO, together with the more stable electrochemical properties observed during steady -state conditions.Article Free-Standing Three-Dimensional Graphene Scaffolds for Protease Functional Assay(Elsevier Science Sa, 2024) Ng, Zhi Kai; Yan, Evelias; Goyal, Garima; Gudlur, Sushanth; Kanagavel, Deepankumar; Yildiz, Umit Hakan; Teo, Edwin Hang TongThree-dimensional graphene scaffolds (3d-GS) of high porosity possessing good fluorescence quenching properties are potential candidates for the development of optical biosensors. Herein, we demonstrate the feasibility of utilising intact and free-standing 3d-GS for sensitive detection of proteases, a class of disease diagnosis bio-markers of significant interest. Recombinant OmpT was employed as a model protease for validating the pro-posed methodology. A short (15-residue) peptide sequence encoding a specific recognition site for OmpT was end-labelled with a fluorescent dye (5-FAM) whose fluorescence is quenched when the peptide is anchored to 3d-GS. However, in the presence of OmpT, the peptide is cleaved and released from 3d-GS, resulting in a sig-nificant recovery in fluorescence. The functional assay described herein involves a single step fabrication process of anchoring the peptide to 3d-GS. The integrity of the 3d-GS is hypothesised to overcome the concern of dynamic requenching associated with the typical homogeneous assays based on graphene, yielding a limit of detection (LOD) of similar to 140 nM, which is over an order higher than homogeneous assays performed using the same composition of graphene in powdered form. To the best of our knowledge, this is the first report on utilising free-standing 3d-GS for facile assaying of proteases.