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Öğe Proton conductivity and dielectric studies on chitosan/polyvinyl alcohol blend electrolytes: synergistic improvements with ionic liquid and graphene oxide(Elsevier B.V., 2024) Yılmazoğlu, Mesut; Okkay, Hikmet; Abacı, Ufuk; Çoban, OzanThis study investigates the impact of ionic liquid, 1-methylimidazolium tetrafluoroborate (IL) and graphene oxide (GO) on the performance of chitosan/polyvinyl alcohol (CS/PVA)-based composite electrolytes. Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirm the successful incorporation of IL and GO, affecting the structural and morphological properties of the electrolytes. Thermogravimetric analysis (TGA) reveals enhanced thermal stability in GO-doped samples, with increased residual weight at high temperatures, while IL addition leads to higher initial weight loss due to its hygroscopic nature. Ionic conductivity measurements demonstrate that the CS/PVA/IL-GO(4.0) composite achieves the highest proton conductivity of 1.76 × 10−3 S/m at 300 K and 1 MHz, surpassing other samples and aligning with top values reported in literature. Dielectric studies show a significant increase in dielectric constant to 9.55 × 104 at 300 K and 20 Hz for CS/PVA/IL-GO(4.0), attributed to enhanced dipole alignment and polarization effects. The loss tangent analysis indicates the shortest relaxation time of 2.07 × 10−4 s for CS/PVA/IL-GO(4.0), correlating with its superior proton conductivity. These findings highlight the potential of CS/PVA/IL-GO electrolytes for advanced energy storage and conversion applications, suggesting further research into GO dispersion and long-term stability for optimized performance in practical devices.Öğe Tailored proton conductive membranes of PVdF-co-HFP: investigating the synergistic effects of ammonium tetrafluoroborate and phosphoric acid dopants on dielectric characteristics(Institution of Chemical Engineers, 2024) Yılmazoğlu, Mesut; Abacı, Ufuk; Erdemi, Hamit; Çoban, OzanThis study investigates the structural, thermal, and dielectric properties of pure PVdF-co-HFP matrix and its composite electrolytes, PVdF-co-HFP/NH4BF4[x], both before and after PA doping, using FTIR, SEM, TGA, and dielectric analyses. FTIR spectra reveal characteristic vibrational bands, confirming the presence of various functional groups and phases. SEM images display a smooth and homogeneous surface morphology for pure PVdF-co-HFP, while the composite electrolytes exhibit irregular dispersion of NH4BF4 salt and rougher surfaces upon PA doping. TGA analysis shows that the onset of thermal degradation occurs at approximately 370 ℃ for pure PVdF-co-HFP, while PA-doped samples demonstrate higher decomposition temperatures, exceeding 400 ℃ due to hydrogen bonding and ionic complex formation. The presence of NH4BF4 and PA doping also affects the crystallinity of the PVdF-co-HFP matrix, notably shifting the transition temperatures of the alpha and beta phases. Ionic conductivity measurements indicate that PA doping significantly enhances conductivity by increasing charge carrier concentration and facilitating ion transport. PA-doped PVdF-co-HFP/NH4BF4[10] showed the highest conductivity reaching 1.68 × 10−3 S.cm−1 at 1 MHz and 400 K. Dielectric studies reveal frequency-dependent behavior, with dielectric constant (ε') and loss (ε") showing distinct trends influenced by salt concentration and PA doping. The dielectric tangent loss (tanδ) of PA-doped PVdF-co-HFP/NH4BF4 composite membranes exhibits frequency and temperature dependence. At higher temperatures, tanδ increases with frequency, showing a resonance peak that shifts towards higher frequencies. The study elucidates the impact of PA doping on the structural, thermal, and electrochemical performance of PVdF-co-HFP/NH4BF4 composites, providing insights for their potential applications in advanced electrolyte systems.Öğe YÜKSEK MUKAVEMETLİ BALİSTİK ZIRH ÇELİKLERİNİN KAYNAKLANABİLİRLİĞİ(2023) Çelik, Ceren; Göçmen, Müesser; Çoban, Ozan; Baykal, Hakan; Gürol, Uğur; Koçak, MustafaSavunma sanayisinin zırhlı araçları için geliştirilen düşük alaşımlı yüksek mukavemetli zırh çeliklerinin ark kaynak teknolojisi uygulamaları metalurjik bilgi ve deneyim isteyen zor uygulamalardır. Bu çeliklerin yüksek karbon eşdeğeri ve yüksek mukavemeti sağlayan martenzitik mikroyapıları nedeniyle kaynak proseslerinde güçlüklerle karşılaşılmaktadır. Seçilecek kaynak telinin yüksek süneklilik kapasitesi olan östenitik ya da yüksek mukavemetli olan ferritik yapıda olması kaynak metalinin sahip olacağı mekanik özellikleri ve kaynaklı bağlantının balistik özelliklerini belirlemektedir. Bu seçimler, doğası gereği kaynak parametrelerini ve proses adımlarını da farklılaştırmaktadır. Bu çalışmada; zırh çeliklerinin sınıflandırılması ile kaynak yönteminin, kaynak konfigürasyonun, kaynak metalinin, ısı girdisinin, ısıl işlem uygulamalarının ve gerçekleşen ısıl çevrimlerden dolayı elde edilen mikroyapısal değişimlerin mekanik ve balistik özelliklere etkileri tartışılmıştır.