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    Epoxy/block copolymer and nanocomposites: Advancements and applications in aerospace
    (Elsevier, 2025) Whba, Rawdah; Whba, Fathyah; Sahinbay, Sevda; Altin, Serdar
    The development of materials for aerospace applications has increasingly focused on epoxy resins, block copolymers (BCPs), and nanocomposites due to their excellent mechanical, thermal, and environmental properties. Epoxy resins are valued for their strength, stiffness, and chemical resistance, but their brittleness and cracking tendencies pose challenges. BCPs address these issues by improving toughness and flexibility. Nanocomposites, incorporating nanoparticles such as graphene, carbon nanotubes, and nanoclays, further enhance the thermomechanical properties and environmental resistance of epoxy/BCP systems. These advanced materials are ideal for aerospace components exposed to harsh conditions, offering improved durability, reduced weight, and enhanced performance. This chapter examines recent progress in integrating epoxy resins and BCPs, focusing on the role of nanocomposites in overcoming material limitations for aerospace applications. It also discusses the challenges of achieving uniform nanoparticle dispersion, ensuring long-term durability under extreme conditions, and overcoming manufacturing complexities. Despite these challenges, these materials have the potential to revolutionize the aerospace industry, improving performance, reducing weight, and increasing durability, thus driving future innovations in aircraft design and performance. © 2026 Elsevier Inc. All rights reserved..
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    High-performance Na-ion full-cells with P2-type Na0.67Mn0.5-xNixFe0.43Al0.07O2 cathodes: Cost analysis for stationary battery storage systems
    (Elsevier, 2024) Kalyoncuoglu, Burcu; Ozgul, Metin; Altundag, Sebahat; Bulut, Fatih; Oz, Erdinc; Sahinbay, Sevda; Altin, Serdar
    Na -ion batteries are viable alternatives to Li-ion batteries especially for stationary applications. Developing suitable electrode materials, half-cell and full-cell studies and cost analysis are major steps and challenges for their commercialization. In this study, we report the synthesis of a promising cathode material, Na0.67Mn0.5- xNixFe0.43Al0.07O2 (x = 0.02-0.10 with Delta x = 0.02), using a modified solid-state synthesis technique. The materials were heated at high temperature for 6 h in air and quenched in liquid N-2. We determined the solubility limit of Ni in Na0.67Mn0.5Fe0.43Al0.07O2 as x <= 0.06. The interlayer separation increases with increasing Ni content due to the ionic radii difference between Mn and Ni. X-ray photoelectron spectroscopy (XPS) measurements evidence the valance state of Ni in the x = 0.06 sample as 2+ and 3+. Cyclic voltammetry (CV) analysis of the half-cells were performed at 10 C-degrees, room temperature, and 50 degrees C to observe the effect of environmental temperature on redox mechanism. The highest half-cell capacity of the cells was determined as 181 mAh/g for x = 0.06 at C/3-rate. Artificial solid electrolyte interface (SEI) formation was performed on the hard carbon anode by presodiation technique and the full-cells of Na0.67Mn0.44Ni0.06- Fe0.43Al0.07O2/hard carbon were assembled in CR2032 coin cells. The capacity values of the cells at C/2, C, and 2C-rate were determined as 131.4 mAh/g, 116 mAh/g and 100.8 mAh/g for the 1 cycle and 33 mAh/g, 40.6 mAh/g and 49.9 mAh/g for the 500th cycle, respectively. The cost analysis for the commercial package for stationary energy storage system was performed by BatPac program and results are discussed.
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    High-performance P2-Na0.67Mn0.85Cu0.15O2/Hard carbon full cell Na-ion battery: Pre-Sodiation of anode, p/n ratio optimizations, and Operando XAS studies
    (Pergamon-Elsevier Science Ltd, 2023) Altundag, Sebahat; Altin, Emine; Altin, Serdar; Ates, Mehmet Nurullah; Ji, Xiaobo; Sahinbay, Sevda
    Na-ion batteries have gained significant attention as a cost-effective and efficient energy storage option for large scale applications, serving as an alternative to the Li-ion batteries. However, commercialization of these batteries is still many steps away since most cathode materials suffer from significant capacity loss and more full-cell studies are required. In this work, we report the electrochemical properties of half-and full-cells of P2-type Na0.67Mn0.85Cu0.15O2 synthesized by solid state technique. X-ray diffraction, FT-IR, and Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques are used to determine the structural properties. Surface properties are studied by X-ray photoelectron spectroscopy and Bru-nauer-Emmett-Teller techniques. Half cells and full cells were constructed with Na-metal and hard carbon, respectively. Na-ion diffusion kinetics at 10 degrees C, room temperature, and 50 degrees C were determined experimentally. Galvanostatic cycling tests on half-cells show capacity values of 165/124 mAh/g for the 1./100. cycles with 24.8 % capacity fade. Operando x-ray absorption spectroscopy measurements were utilized to study local structural modification around transition metal ions during charge/discharge. In the full-cell studies, electrode mass ratio (p/n) and parameters for presodiation of hard carbon were optimized. Using 30 mA/g current density, the un-processed and the pre-sodiated full-cells reach capacity values of 48 mAh/g (p/n = 2.5) and 150 mAh/g (p/n = 0.75 and 1.15), respectively.
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    Influence of precursor selection on the structural integrity and electrochemical performance of α-NaMnO2 cathode
    (Wiley, 2025) Dogan, Ebru; Whba, Rawdah; Canbay, Canan Aksu; Arshad, Muhammad; Sahinbay, Sevda; Altin, Serdar
    In this study, the alpha-NaMnO2 phase was successfully synthesized using three different combinations of starting materials: Na2O2/Mn2O3, Na2O2/MnO2, and Na2CO3/Mn2O3. A one-step heat treatment at 900 degrees C for 5 h under air with quenching was applied. X-ray diffraction analysis confirmed the formation of pure alpha-NaMnO2 phase in all three samples, with only slight variations in lattice parameters. Elemental and oxidation state analyses were conducted using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy-dispersive X-ray spectroscopy, and inductively coupled plasma measurements. XPS results revealed noticeable differences in Mn ion valence states, suggesting variations in oxygen stoichiometry and the presence of oxygen-excess structures. Electrochemical evaluations were performed in both half-cell and full-cell configurations. The samples exhibited distinct performance characteristics, with capacity fade over 100 cycles at C/3 between 1.5 and 4.3 V measured at 83.6%, 73.9%, and 83.1%, respectively. These differences correlated with the average oxidation state of Mn and O content. Full-cells, paired with presodiated commercial hard carbon anodes, showed the highest capacity for the Na2O2/MnO2 system and the best retention for the Na2CO3/Mn2O3 sample. Overall, this work demonstrates how even small variations in starting materials can significantly influence the structural and electrochemical behavior of alpha-NaMnO2.
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    Unlocking the Potential of Epoxidized Natural Rubber (ENR)-Based Polymer Electrolytes: Key Strategies, Bibliometric Insights, and Future Directions
    (Amer Chemical Soc, 2025) Whba, Rawdah; Sahinbay, Sevda; Whba, Fathyah; Nakir, Muhammed Yusuf; Altin, Serdar
    Natural rubber (NR) and its modified forms, such as epoxidized NR (ENR), are widely used in industries due to their versatility, biodegradability, and unique elastomeric properties. ENR has recently gained attention as a sustainable alternative to synthetic polymer electrolytes (PEs) in low- to moderate-temperature electrochemical devices, including lithium-ion batteries (LIBs), supercapacitors, and proton exchange membrane fuel cells (PEMFCs). It offers advantages such as low cost, eco-friendliness, and excellent film-forming ability. However, its practical application is hindered by poor mechanical strength, low ionic conductivity, and limited thermal and chemical stability, making it unsuitable for high-temperature systems like solid oxide fuel cells (SOFCs). Advanced modification techniques-such as blending with reinforcing polymers, chemical cross-linking, graft copolymerization, and nanofiller incorporation-have been explored to overcome these limitations. These strategies significantly enhance ENR's mechanical robustness, ionic transport, and resistance to heat and solvents, improving its viability for targeted electrochemical applications. This perspective discusses recent progress in ENR-based PEs, emphasizing conductivity, moisture resistance, and long-term durability improvements. Sustainable fabrication methods are also critical to developing high-performance membranes that minimize fuel crossover while maintaining efficient ion transport. Therefore, future research should optimize ENR's electrochemical properties and thermal stability to support performance under challenging operating conditions.