Researcher: Motallebzadeh, Amir
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Motallebzadeh, Amir
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Publication Metadata only Influence of sputtering atmosphere on the structural, biological, and electrochemical properties of tantalum-containing coatings on the NiTi alloy(Elsevier B.V., 2024) Soltanalipour, Mahdiyeh; Khalil-Allafi, Jafar; Motallebzadeh, Amir; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM)The magnetron sputtering method was used to deposit tantalum-containing coatings on NiTi shape memory alloys under Ar, Ar[sbnd]O2, and Ar[sbnd]N2 atmospheres. The main focus of this research is on how the deposition atmosphere can significantly impact not only the morphological and microstructural properties of coatings but also their corrosion behavior and in vitro biocompatibility. In this research, FESEM observations, GI-XRD crystallinity measurements, AFM topographical investigations, electrochemical measurements, and MTT assay were employed to determine to what extent the deposition atmosphere affects the morphology, microstructure, roughness, corrosion behavior, and in vitro biocompatibility properties, respectively. FESEM studies reveal that tantalum sputtered under the Ar atmosphere has a more uniform, and compact structure, while round-like particles appear on the surface under Ar[sbnd]O2 and Ar[sbnd]N2 atmospheres. The GI-XRD patterns indicate that the substrate temperature of 300°C is not sufficient for the formation of crystallized structure. It has been shown that the sample deposited under the Ar[sbnd]N2 atmosphere has more negative charges; this is associated with higher protein adsorption on its surface and increases endothelial proliferation rates. Moreover, the presence of Ta2O5 on the surface of the Ar[sbnd]O2 atmosphere leads to the highest corrosion resistance.Publication Metadata only Fracture toughness of AlTiN coatings investigated by nanoindentation and microcantilever bending(Elsevier Science Sa, 2024) Kaygusuz, Burcin; Karadayi, Ozcan; Kazmanli, Kuersat; Ozerinc, Sezer; N/A; Motallebzadeh, Amir; Koç University Surface Science and Technology Center (KUYTAM); N/AMetal nitride coatings are increasingly used in MEMS applications. The brittle nature of these coatings makes fracture one of the main failure mechanisms during operation. Therefore, quantifying the fracture toughness of nitride coatings in a reliable fashion is important to understand the failure behavior and to optimize device performance and reliability. This study investigated the fracture toughness of AlTiN coatings produced by cathodic arc evaporation, a widely used technique in the industry. Nanoindentation and microcantilever bending-based measurements indicated a fracture toughness of 6.6 and 4.8 MPa & sdot;m1/2, respectively. The lower toughness results of microcantilever bending were attributed to the columnar growth of the coating, which promoted crack propagation perpendicular to the film surface. The results provide useful data toward a better understanding of the fracture of hard coatings and give insight into the advantages and disadvantages of different measurement methods.Publication Metadata only Effect of nanoheterogeneities on the fracture toughness and tensile ductility of cuta metallic glass thin films(Elsevier, 2024) Behboud, Ali B.; Fadaie, Amir; Şehirli, Servet; Özerinç, Sezer; Motallebzadeh, Amir; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM)Nanoheterogenenous metallic glasses (MG) can offer improved ductility through a nanoscale modulation in their mechanical properties. However, the relationship between the modulation parameters and the mechanical behavior is not well understood. Physical vapor deposition can directly control the compositional and morphological parameters of nanoheterogeneous MGs and enables the systematic investigation of this problem. This work explores the microstructure and mechanical properties of a range of CuTa-based nanolayered amorphous/amorphous (A/A) and amorphous/semi-crystalline (A/SC) nanoheterogeneous MGs and MG composites. The first step was the identification of three microstructural regimes in CuTa, namely, a fully amorphous form (23–65 at.% Ta), a Ta-rich amorphous-crystalline composite (65–75 at.% Ta), and a Cu-rich amorphous-crystalline composite (16–23 at.% Ta). The hardness of the films increased from 6 GPa to 17 GPa with increasing Ta content. Next, a range of CuxTa1−x/CuyTa1−y nanolayers composed of A/A and A/SC nanolayers were investigated. The hardness of all nanolayers follows the rule of mixture. A/A structures do not provide a significant increase in fracture toughness and only a minor increase in tensile ductility despite the high amplitude modulation of hardness between layers. A/SC nanolayers’ hardness and toughness was higher than A/A nanolayers as well as monolithic amorphous films, but still remained below the monolithic Cu25Ta75 SC film. The results show that the design of nanoheterogeneities in MGs requires careful optimization to achieve a useful improvement in mechanical properties.Publication Metadata only Characterization of structural and mechanical properties of HfNbTaTiZr refractory high entropy alloy after gas nitriding(Elsevier, 2024) Alphan, Yunus; Kaba, Mertcan; Cimenoglu, Huseyin; N/A; Motallebzadeh, Amir; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/AThis study was initiated to improve surface hardness and wear resistance of a HfNbTaTiZr refractory high entropy alloy (RHEA) by gas nitriding at a medium temperature (600 °C) for 3 h. Structural characterizations conducted by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) equipped scanning electron microscope (SEM) revealed that nitriding led to formation of a 1.5 μm thick surface layer containing precipitates of oxides and nitrides of the alloying elements. Detection of oxides within the surface layer was attributed to the presence residual oxygen in the nitriding atmosphere. Nevertheless, the employed gas nitriding provided remarkably higher scratch resistance compared to the untreated state, as the results of increment in the surface hardness and development of larger compressive residual stress. © 2024 Elsevier LtdPublication Metadata only Advanced ceramic coatings for emerging applications(Elsevier, 2023) Gupta, Ram K.; Kakooei, Saeid; Nguyen, Tuan Anh; Behera, Ajit; Motallebzadeh, Amir; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM)Advanced Ceramic Coatings for Emerging Applications covers new developments in automotive, construction, electronic, space and defense industries. The book is one of four volumes that together provide a comprehensive resource in the field of Advanced Ceramic Coatings, also including titles covering fundamentals, manufacturing and classification, energy and biomedical applications. These books will be extremely useful for academic and industrial researchers and practicing engineers who need to find reliable and up-to-date information about recent progresses and new developments in the field of advanced ceramic coatings. These books will also be of value to early career scientists providing background knowledge to the field. Smart ceramic coatings containing multifunctional components are now finding application in transportation and automotive industries, in electronics, and energy, sectors, in aerospace and defense, and in industrial goods and healthcare. Their wide application and stability in harsh environments are only possible due to the stability of the inorganic components that are used in ceramic coatings.Publication Metadata only Advanced ceramic coatings for biomedical applications(Elsevier, 2023) Gupta, Ram K.; Kakooei, Saeid; Nguyen, Tuan Anh; Behera, Ajit; Motallebzadeh, Amir; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM)Advanced Ceramic Coatings for Biomedical Applications covers tissue engineering, scaffolds, implant and dental application, wound healing and adhesives. The book is one of four volumes that together provide a comprehensive resource in the field of Advanced Ceramic Coatings, also including titles covering: fundamentals, manufacturing, and classification;energy applications;and emerging applications. This books will be extremely useful for academic and industrial researchers and practicing engineers who need to find reliable and up-to-date information about recent progresses and new developments in the field of advanced ceramic coatings. It will also be of value to early career scientists providing background knowledge to the field. Smart ceramic coatings containing multifunctional components are now finding application in transportation and automotive industries, in electronics, and energy sectors, in aerospace and defense, and in industrial goods and healthcare. Their wide application and stability in harsh environments are only possible due to the stability of the inorganic components used. Ceramic coatings are typically silicon nitride, chromia, hafnia, alumina, alumina-magnesia, silica, silicon carbide, titania, and zirconia-based compositions. The increased demand for these materials and their application in energy, transportation, and the automotive industry, are considered, to be the main drivers.Publication Metadata only Advanced ceramic coatings: fundamentals, manufacturing, and classification(Elsevier, 2023) Gupta, Ram K.; Kakooei, Saeid; Nguyen, Tuan Anh; Behera, Ajit; Motallebzadeh, Amir; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM)Handbook of Advanced Ceramic Coatings: Fundamentals, Manufacturing and Classification introduces ceramic coating materials, methods of fabrication, characterizations, the interaction between fillers, reinforcers, and environmental impact, and the functional classification of ceramic coatings. The book is one of four volumes that together provide a comprehensive resource in the field of Advanced Ceramic Coatings, also including titles covering energy, biomedical and emerging applications. These books will be extremely useful for academic and industrial researchers and practicing engineers who need to find reliable and up-to-date information about recent progresses and new developments in the field of advanced ceramic coatings. Smart ceramic coatings containing multifunctional components are now finding application in transportation and automotive industries, in electronics, and energy sectors, in aerospace and defense, and in industrial goods and healthcare. Their wide application and stability in harsh environments are only possible due to the stability of the inorganic components used. Ceramic coatings are typically silicon nitride, chromia, hafnia, alumina, alumina-magnesia, silica, silicon carbide, titania, and zirconia-based compositions. The increased demand for these materials and their application in energy, transportation, and the automotive industry, are considered, to be the main drivers.Publication Metadata only Exploring the role of Mo and Mn in Improving the OER and HER performance of CoCuFeNi-Based high-entropy alloys(Amer Chemical Soc, 2024) Igarashi, Keisuke; Matsumoto, Hiroaki; Department of Chemistry; Department of Chemistry; Alamdari, Armin Asghari; Jahangiri, Hadi; Yağcı, Mustafa Barış; Motallebzadeh, Amir; Ünal, Uğur; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; College of SciencesHigh-entropy alloys (HEAs) are a class of metallic materials composed of solid solutions of five or more elements in equi- or near-equiatomic proportions. The fascinating properties of HEAs have recently attracted considerable attention for water-splitting applications. Mechanical alloying (MA) is a method for preparing HEAs that results in crystalline, homogeneous materials at room temperature. In this work, several CoCuFeNi-based HEAs were prepared through MA and evaluated as electrocatalysts for the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting in 1 M KOH. The results showed that CoCuFeNiMnMo1.5 with the highest amount of molybdenum exhibited the best OER performance (375 +/- 15 mV at the current density of 10 mA cm(-2)), and CoCuFeNiMnMo0.5 with the lowest amount of molybdenum exhibited the best HER activity with lower overpotentials (275 +/- 12 mV at the current density of 10 mA cm(-2)) and over 72 h of stability. The assembled CoCuFeNiMnMo1.5 (anode)parallel to CoCuFeNiMnMo0.5 (cathode) couple required 1.76 V to produce 10 mA cm(-2), and the Faradaic efficiency for generated H-2 was determined to be more than 80%.Publication Metadata only Nanoheterogeneous ZrTa metallic glass thin films with high strength and toughness(Elsevier, 2022) Behboud, Ali B.; Ozerinc, Sezer; N/A; Motallebzadeh, Amir; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/AThis study investigated the mechanical behavior of ZrxTa1-x (x = 21-79 at%) thin films and nanolayered films of ZrTa with modulated composition as model systems to gain insight into the hardness and toughness of metallic glasses and metallic glass nanocomposites. The monolithic films exhibit two primary micro-structures, namely, a fully amorphous form (Zr = 35-70at%.) and an amorphous-crystalline composite (21-30 at% Zr). The amorphous films show a monotonic hardness variation with composition over a wide range of 5.5 - 9 GPa. The partial crystallization of the films results in a further jump in hardness, as opposed to the general trend of softening upon crystallization. The emergence of the crystalline phase also improves the ductility of the films, as verified by nanoindentation-based fracture toughness measurements. The indentation pile-up exhibits several shear bands in the fully amorphous films, replaced by a featureless pileup zone for the case of Zr25Ta75, further verifying the superior toughness of the composite. The second part of the analysis pursued obtaining a similar toughening through fully amorphous nanolayered films of Zr35Ta65 / Zr70Ta30. The results indicate that these films provide a balanced combination of high hardness and enhanced ductility, providing an alternative route to the development of tough metallic glass coatings. Data Availability: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.Publication Metadata only Interstitial nitrogen enhances corrosion resistance of an equiatomic cocrni medium-entropy alloy in sulfuric acid solution(Elsevier Science Inc, 2021) Moravcik, Igor; Moravcikova-Gouvea, Larissa; Liu, Chang; Prabhakar, J. Manoj; Dlouhy, Ivo; Li, Zhiming; N/A; Peighambardoust, Naeimeh Sadat; Motallebzadeh, Amir; Researcher; Researcher; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; N/AThe corrosion resistance of the equiatomic CoCrNi medium-entropy alloy (MEA) and its 0.5 atomic % nitrogen alloyed variant in 0.1 M H2SO4 solution was investigated and compared with that of the 316 L stainless steel as a reference material. All of the investigated materials showed single-phase face centered cubic (FCC) microstructures, and nitrogen was fully dissolved in the solid solution structure of the CoCrNi MEA. Both the nitrogen-free and nitrogen-doped MEAs showed significantly higher corrosion resistance (lower corrosion currents and rates) than the 316 L steel. Compared to the nitrogen-free CoCrNi, the interstitial nitrogen dissolved in solid solution causes a significant improvement in the pitting corrosion resistance of the CoCrNiN. Under the same testing condition, pitting corrosion was not observed in the CoCrNiN alloy, while the CoCrNi MEA and 316 L steel showed distinct pitting cavities. The better anti-corrosion performance of the CoCrNiN compared to that of the CoCrNi is correlated with a higher fraction of chromium oxide in the passive films.