Search

Your search keyword '"Ünal, Uğur"' showing total 212 results
Start Over Author "Ünal, Uğur"
212 results on '"Ünal, Uğur"'

3. An Ensemble of Pre-trained Transformer Models For Imbalanced Multiclass Malware Classification

Author

Demirkıran, Ferhat, Çayır, Aykut, Ünal, Uğur, and Dağ, Hasan

Subjects
Computer Science - Cryptography and Security, Computer Science - Artificial Intelligence, Computer Science - Machine Learning, Statistics - Machine Learning
Abstract

Classification of malware families is crucial for a comprehensive understanding of how they can infect devices, computers, or systems. Thus, malware identification enables security researchers and incident responders to take precautions against malware and accelerate mitigation. API call sequences made by malware are widely utilized features by machine and deep learning models for malware classification as these sequences represent the behavior of malware. However, traditional machine and deep learning models remain incapable of capturing sequence relationships between API calls. On the other hand, the transformer-based models process sequences as a whole and learn relationships between API calls due to multi-head attention mechanisms and positional embeddings. Our experiments demonstrate that the transformer model with one transformer block layer surpassed the widely used base architecture, LSTM. Moreover, BERT or CANINE, pre-trained transformer models, outperformed in classifying highly imbalanced malware families according to evaluation metrics, F1-score, and AUC score. Furthermore, the proposed bagging-based random transformer forest (RTF), an ensemble of BERT or CANINE, has reached the state-of-the-art evaluation scores on three out of four datasets, particularly state-of-the-art F1-score of 0.6149 on one of the commonly used benchmark dataset., Comment: 38 pages, 8 Figures, 13 Tables

Published
2021

7. Random CapsNet Forest Model for Imbalanced Malware Type Classification Task

Author

Çayır, Aykut, Ünal, Uğur, and Dağ, Hasan

Subjects
Computer Science - Cryptography and Security, Computer Science - Computer Vision and Pattern Recognition, Computer Science - Machine Learning, Statistics - Machine Learning
Abstract

Behavior of a malware varies with respect to malware types. Therefore,knowing type of a malware affects strategies of system protection softwares. Many malware type classification models empowered by machine and deep learning achieve superior accuracies to predict malware types.Machine learning based models need to do heavy feature engineering and feature engineering is dominantly effecting performance of models.On the other hand, deep learning based models require less feature engineering than machine learning based models. However, traditional deep learning architectures and components cause very complex and data sensitive models. Capsule network architecture minimizes this complexity and data sensitivity unlike classical convolutional neural network architectures. This paper proposes an ensemble capsule network model based on bootstrap aggregating technique. The proposed method are tested on two malware datasets, whose the-state-of-the-art results are well-known., Comment: 30 pages, 10 figures, typos are corrected, references are added

Published
2019

10. Photoelectrochemical Investigation of Hole Scavengers for Photocatalytic Hydrogen Evolution Reaction on Perovskite‐Type Niobate Nanosheets.

Author

Yilmaz, Bengisu and Ünal, Uğur

Subjects
*HYDROGEN evolution reactions, *PHOTOCATALYSTS, *PHOTOELECTROCHEMISTRY, *CYCLIC voltammetry, *PHOTOREDUCTION
Abstract

Hole‐scavengers are a crucial part of particulate photocatalytic systems. The use of hole‐scavengers increases the photocatalytic activity by preventing electron‐hole recombination. The holes are used in photo‐oxidation of the hole‐scavenger molecules increasing the probability of electrons involved in photoreduction of water. In this study, different hole‐scavengers utilized in photocatalytic water splitting reaction were tested. The impact of different hole scavengers on photocatalytic reactions were investigated on [Ca2Nb3O10]− 2D nanosheets mechanistically. Cyclic voltammetry and chronoamperometry tests were employed to assess the impact of hole scavengers on photocatalytic efficiency. The photoelectrochemical tests agree with the results of the photocatalytic reactions. Methanol and EDTA give the largest oxidation photocurrent and the best photocatalytic activity. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

15. Numerical Analysis of Ship Airwake on a Simplified Frigate Model.

Author

Şık, Tunahan and Ünal, Uğur Oral

Subjects
NUMERICAL analysis, SHIPS, ECONOMIC determinism, AERODYNAMICS, COMPUTATIONAL fluid dynamics
Abstract

Modelling ship airwake as well as ship air resistance calculation is of great importance in ships with flight deck. Especially with a flight deck at the stern, the airwake shaped by the superstructure aerodynamics generates a complex, asymmetrical and highly turbulent form in the helicopter operation area. Within the helicopter recovery and launch operations, the turbulent area makes pilot control difficult and can even cause loss of control. It is vital to accurately evaluate the turbulence occurring in the relevant region in order to increase operational efficiency, prevent possible accidents and reduce pilot workload. In this study, the effect of the flow regime in the flight deck airborne on a simple frigate shape has been examined with computational fluid dynamics using scale-resolving simulations. The results have been exhibited a remarkable agreement with the experimental data, and it has been agreed that the solution method could be a priority in ship airwake calculations. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

16. An Experimental Investigation of Tsunami Bore Impact on Coastal Structures.

Author

Erduran, Kutsi S., Akansu, Yahya E., Ünal, Uğur, and Adekoya, Olusola O.

Subjects
VIDEO recording, BATHYMETRY, WATER depth, FLOW measurement, IMAGE processing, TSUNAMI damage
Abstract

This experimental study focused on the measurement and analysis of the impact force caused by a tsunami bore on a coastal structure. The bore wave was produced by a dam break mechanism. The water depth in the reservoir and the location of the coastal structures were varied to simulate different impact scenarios. The time history of the force resulting from the impact of the bore wave on the coastal structure was measured. The propagation of the bore wave along the flume was recorded and the video recordings were converted into digital data using an image-processing technique in order to determine the flow depth variations with time. The hydrostatic forces and the corresponding depth and time-averaged hydrodynamic forces as well as the maximum hydrodynamic forces were acquired for each scenario. The ratio of hydrodynamic to hydrostatic forces were obtained, and it was observed that the calculated averaged ratio was within the recommended design ratio. The results indicate that an increase in the reservoir level caused an increase in the magnitude and intensity of the impact forces, however, the relationship was non-linear. Moreover, it was found that the location of the structure did not play a significant role on the intensity of the impact forces. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

20. Quantifying the influence of gate rudder system (GRS) rudder angle(s) on propeller cavitation

Author

Köksal, Çağatay Sabri, Gürkan, Ahmet Yusuf, Aktas, Batuhan, Ünal, Uğur Oral, Fitzimmons, Patrick, Sasaki, Noriyuki, Korkut, Emin, Atlar, Mehmet, Köksal, Çağatay Sabri, Gürkan, Ahmet Yusuf, Aktas, Batuhan, Ünal, Uğur Oral, Fitzimmons, Patrick, Sasaki, Noriyuki, Korkut, Emin, and Atlar, Mehmet

Abstract

The study is on the propeller cavitation extent analysis of a 90m coastal cargo ship, M/V ERGE, overlaying Computational Fluid Dynamics (CFD) analyses and fullscale observation for the first time. The sea trials with M/V ERGE were performed before and after the first retrofit application of a Gate Rudder System (GRS) on this vessel as a pioneering alternative to its Conventional Rudder System (CRS), the aim of the H2020 Project GATERS. This study's objective is to explore the impact of the rudder angle(s) variations on the cavitation patterns of the GRS' propeller. The cavitation observations during the sea trials were conducted in the trial (ballast) loading conditions, and the gate rudder angle was 8 degrees. The cavitation extensions were monitored and recorded in real-time throughout the sea trials with a specially designed and installed submerged monitoring system at the ship’s aft end. The full-scale CFD analyses comprised the same configurations of the trials set up. The outcome of the analyses concerning the cavitation in varying gate rudder angles demonstrated a reasonable correlation between the observed and predicted patterns. The study revealed that the rudder angle configuration of the GRS influences the cavitation characteristics. These results also contribute to further understanding the cavitation dynamics and extension of the GRS propeller in full-scale for the first time, hence offering valuable insights into the design and optimisation process of this novel propulsion system, GRS.

Published
2024

23. An investigation into the gate rudder system design for propulsive performance using design of experiment method.

Author

Gürkan, Ahmet Yusuf, Ünal, Uğur Oral, Aktaş, Batuhan, and Atlar, Mehmet

Abstract

The Gate Rudder System (GRS) is an innovative energy-saving device integrating the steering and propulsion of ships. Despite demonstrated potential, optimal GRS design remains underexplored. This study used a Design of Experiment (DoE) approach to investigate the sensitivity of key design variables of the GRS on the ship's powering performance. Computational Fluid Dynamics (CFD) analysis was employed to calculate the respective flow variables at each design point, and the most effective geometrical parameter was identified as the rudder angle based on the correlations. Surprisingly, the analyses revealed that the best powering performance was not observed with the highest rudder thrust force generated. Instead, the optimal design was found to be one that maximizes the overall energy savings by achieving the most favorable interaction between the propeller, hull, and GR. High-fidelity CFD validates results. This study bridges the gap in GRS design for powering efficiency, contributing to technology's performance optimisation. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

28. Network intrusion detection system by learning jointly from tabular and text‐based features.

Author

Düzgün, Berkant, Çayır, Aykut, Ünal, Uğur, and Dağ, Hasan

Subjects
DEEP learning, INTRUSION detection systems (Computer security), MACHINE learning, COMPUTER network security, TRANSFORMER models, CYBERTERRORISM, ANOMALY detection (Computer security)
Abstract

Network intrusion detection systems (NIDS) play a critical role in maintaining the security and integrity of computer networks. These systems are designed to detect and respond to anomalous activities that may indicate malicious intent or unauthorized access. The need for robust NIDS solutions has never been more pressing in today's digital landscape, characterized by constantly evolving cyber threats. Deploying effective NIDS can be challenging, particularly in accurately identifying network anomalies amid the ever‐increasing sophisticated and difficult‐to‐detect cyber threats. The motivation for our research stems from the recognition that while NIDS studies have made significant strides, there remains a crucial need for more effective and accurate methods to detect network anomalies. Commonly used features in NIDS studies include network logs, with some studies exploring text‐based features such as payload. However, traditional machine and deep learning models may need to be improved in learning jointly from tabular and text‐based features. Here, we present a new approach that integrates both tabular and text‐based features to improve the performance of NIDS. Our research aims to address the existing limitations of NIDS and contribute to the development of more reliable and efficient network security solutions by introducing more effective and accurate methods for detecting network anomalies. Our internal experiments have revealed that the deep learning approach utilizing tabular features produces favourable results, whereas the pre‐trained transformer approach needs to perform sufficiently. Hence, our proposed approach, which integrates both feature types using deep learning and pre‐trained transformer approaches, achieves superior performance. These findings indicate that integrating both feature types using deep learning and pre‐trained transformer approaches can significantly improve the accuracy of network anomaly detection. Moreover, our proposed approach outperforms the state‐of‐the‐art methods in terms of accuracy, F1‐score, and recall on commonly used NIDS datasets consisting of ISCX‐IDS2012, UNSW‐NB15, and CIC‐IDS2017, with F1‐scores of 99.80%, 92.37%, and 99.69%, respectively, indicating its effectiveness in detecting network anomalies. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

29. Enhanced photocatalytic properties of restacked unilamellar [SrTa(2)O7](2-) nanosheets of aurivillius phase layered perovskites

Author

Khodabakhsh, Mohammadreza; Yılmaz, Bengisu; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079), Firoozi, Sadegh; Fatmehsari Haghshenas, Davoud, Graduate School of Sciences and Engineering; College of Sciences, Department of Materials Science and Engineering; Department of Chemistry, Khodabakhsh, Mohammadreza; Yılmaz, Bengisu; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079), Firoozi, Sadegh; Fatmehsari Haghshenas, Davoud, Graduate School of Sciences and Engineering; College of Sciences, and Department of Materials Science and Engineering; Department of Chemistry

Abstract

In the present work, unilamellar [SrTa(2)O7](2-) perovskite nanosheets with variable lateral dimensions were synthesized via a high-yield, three-step liquid exfoliation route from layered Bi2SrTa2O9. The photocatalytic activity of the parent and exfoliated layered perovskites was evaluated for the photocatalytic dye degradation of Rhodamine B under UV light (254 nm) and reduction of water to H-2 under the full solar spectrum. A comparative study of the photocatalytic behavior of unilamellar [SrTa(2)O7](2-) perovskite nanosheets and parent layered structure showed a significant improvement in both hydrogen evolution (98.20 vs 3 mu mol g(-1)) and Rhodamine B degradation time (180 vs 30 min), with the restacked nanosheets. The exfoliation of layered perovskites not only increases their specific surface area, providing more active sites, but also reduces the recombination probability of electrons and holes due to their unilamellar structure and reduced charge transport pathways. The synthesis and preparation of strong acid solids such as [SrTa(2)O7](2-) perovskite nanosheets can be a promising approach for effective adsorption of pollutants with cationic nature and more efficient electron transfer between the dye and catalyst. Finally, the photocatalytic characteristics of the restacked unilamellar [SrTa(2)O7](2-) nanosheets remained unchanged after three successive cycles of recycling-reusing., Scientific and Technological Research Council of Turkey (TÜBİTAK); TÜBİTAK- MSRT Joint Call; Tabriz University

Published
2023

30. Effect of surface characteristics of graphene aerogels and hydrophilicity of ionic liquids on the CO2/CH4 separation performance of ionic liquid/reduced graphene aerogel composites

Author

Çağlayan, Hatice Pelin; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079); Avcı, Seda Keskin (ORCID 0000-0001-5968-0336 & YÖK ID 40548); Uzun, Alper (ORCID 0000-0001-7024-2900 & YÖK ID 59917), Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM), Graduate School of Sciences and Engineering; College of Sciences; College of Engineering, Department of Chemical and Biological Engineering; Department of Chemistry, Çağlayan, Hatice Pelin; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079); Avcı, Seda Keskin (ORCID 0000-0001-5968-0336 & YÖK ID 40548); Uzun, Alper (ORCID 0000-0001-7024-2900 & YÖK ID 59917), Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM), Graduate School of Sciences and Engineering; College of Sciences; College of Engineering, and Department of Chemical and Biological Engineering; Department of Chemistry

Abstract

Two ionic liquids (ILs) having the same cation with different anions offering opposite hydrophilic/hydrophobic characters, 1-n-butyl-1-methylpyrrolidinium dicyanamide ([BMPyr][DCA]) and 1-n-butyl-1-methylpyrrolidinium hexafluorophosphate ([BMPyr][PF6]), were impregnated onto two different reduced graphene aerogels (rGAs) prepared by the thermal treatment of GAs at 300 and 500 degrees C to investigate the consequences of the changes in the hydrophilic character of ILs and the reduction temperature of the GAs on the corresponding gas sorption and separation performance of the IL/rGAs. The structural analyses of nanoporous rGAs and IL/rGAs pointed to a change in the quantity of oxygenated functional groups upon thermal treatment and a change in the direct interactions between IL molecules and the host rGA surface upon IL deposition. Single-component CO2 and CH4 sorption measurements were performed for each rGA and IL/rGA composite, and both ideal and mixture CO2/CH4 selectivities were calculated. The samples prepared by reducing the GA at 300 and 500 degrees C yielded ideal CO2/ CH4 selectivities of 3.6 and 18 at 1 mbar and 25 degrees C, respectively. Among IL/rGA composites, the one prepared at 300 degrees C displayed a remarkable CO2/CH4 separation performance when combined with the hydrophobic [BMPyr][PF6], offering an ideal selectivity of 450.9 at 1 mbar and 25 degrees C, whereas the composite prepared with rGA500 yielded a substantially high CO2/CH4 selectivity of 173.5 after the incorporation of the hydrophilic [BMPyr][DCA] at 1 mbar and 25 degrees C. The ideal CO2/CH4 selectivities of [BMPyr][PF6]/ rGA300 and [BMPyr][DCA]/rGA500 surpassed most of the previously reported selectivities of carbon-based materials in the literature. These results demonstrate the broad potential of IL/rGAs in sorption-based gas separations owing to the highly tunable nature of both the structure of IL and the surface characteristics of rGA., Scientific and Technological Research Council of Turkey (TÜBİTAK)

Published
2023

31. Screen Adaptation of Chyngyz Aitmatov's Literary Works As an Element of Cultural Diplomacy.

Author

BEKTURGAN KIZI, Tolkun and ÜNAL, Uğur

Subjects
CULTURAL diplomacy, CULTURAL relations, TELEVISION adaptations, LITERARY adaptations, FILM adaptations, AWARDS
Abstract

Copyright of Journal of International Civilization Studies is the property of Kyrgyz-Turkish Manas University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2023
Full Text
View/download PDF

40. An integrated computational-experimental hierarchical approach for the rational design of an IL/UiO-66 composite offering infinite CO2 selectivity

Author

Zeeshan, Muhammad; Gülbalkan, Hasan Can; Durak, Özce; Haşlak, Zeynep Pınar; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079); Avcı, Seda Keskin (ORCID 0000-0001-5968-0336 & YÖK ID 40548); Uzun, Alper (ORCID 0000-0001-7024-2900 & YÖK ID 59917), Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM), College of Engineering; College of Sciences; Graduate School of Sciences and Engineering, Department of Chemical and Biological Engineering; Department of Chemistry, Zeeshan, Muhammad; Gülbalkan, Hasan Can; Durak, Özce; Haşlak, Zeynep Pınar; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079); Avcı, Seda Keskin (ORCID 0000-0001-5968-0336 & YÖK ID 40548); Uzun, Alper (ORCID 0000-0001-7024-2900 & YÖK ID 59917), Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM), College of Engineering; College of Sciences; Graduate School of Sciences and Engineering, and Department of Chemical and Biological Engineering; Department of Chemistry

Abstract

Owing to the possibility of generating theoretically unlimited numbers of ionic liquid (IL)-metal-organic framework (MOF) combinations, experimental studies on IL/MOF composites for gas separation applications are mostly conducted on a trial-and-error basis. To address this problem, an integrated computational-experimental hierarchical approach is presented for selecting the best IL-MOF combination for a target gas separation application. For this purpose, UiO-66 and pyrrolidinium-based ILs are chosen as the parent MOF and IL family, respectively, and three powerful computational tools, Conductor-like Screening Model for Realistic Solvents calculations, density functional theory calculations, and grand canonical Monte Carlo simulations, are integrated to identify the most promising IL-UiO-66 combination as 1-n-butyl-1-methylpyrrolidinium dicyanamide/UiO-66, [BMPyrr][DCA]/UiO-66. Then, this composite is synthesized, characterized in deep detail, and tested for CO2/N-2, CO2/CH4, and CH4/N-2 separations. Results demonstrate that [BMPyrr][DCA]/UiO-66 offers an extraordinary gas separation performance, with practically infinite CO2 and CH4 selectivities over N-2 at 15 degrees C and at low pressures. The integrated hierarchical approach proposed in this work paves the way for the rational design and development of novel IL/MOF composites offering exceptional performance for any desired gas separation application., Scientific and Technological Research Council of Turkey (TÜBİTAK); 1001-Scientific and Technological Research Projects Funding Program; European Research Council (ERC); Europian Union (EU); Horizon 2020; ERC-2017-Starting Grant; Research and Innovation Programme; COSMOS; HEC Pakistan Scholarship

Published
2022

42. High Temperature Oxidation Behavior of the AlCrFeMnTi Light-Weight High-Entropy Alloy

Author

Jahangiri, Hadi, Mohagheghi, Samira, Asghari Alamdari, Armin, Gürcan Bayrak, Kübra, Ayas, Erhan, Ünal, Uğur, and Motallebzadeh, Amir

Abstract

Light-weight high-entropy alloys (LWHEAs) are a class of engineering materials which have attracted wide research study as well as practical attention due to their unique properties along with low density. Future development of LWHEAs demands comprehensive research studies, including those on their high-temperature oxidation behavior. In this work, the microstructure, oxidation behavior, and mechanical properties of AlCrFeMnTi LWHEA was investigated. The samples were manufactured using mechanical alloying followed by spark plasma sintering techniques. After consolidation, a three-phase microstructure was formed, containing the C14, body-centered cubic, and L21phases. The oxidation behavior of the samples in an ambient atmosphere after 1, 10, 30, and 60 h at 700 and 900 °C was investigated. The oxide scale formed at 700 °C exhibits a dense and compact structure, suggesting proper protection of the underlying metal at this temperature. Even though the same oxidation kinetics was detected at these temperatures, the oxidation rate and mass gain at 900 °C are higher. The morphology, size, and distribution of the three phases remain unchanged after the oxidation test, which gives rise to preservation of the mechanical properties, namely, hardness and modulus of elasticity, at both temperatures.

Published
2023
Full Text
View/download PDF

43. Kamu Diplomasisi Bağlamında Ulus Marka İletişimi Yönetimi.

Author

ÜNAL, Uğur

Abstract

Copyright of Journal of International Civilization Studies is the property of Kyrgyz-Turkish Manas University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2022
Full Text
View/download PDF

49. A new class of porous materials for efficient CO2 separation: ionic liquid/graphene aerogel composites

Author

Zeeshan, Muhammad; Yalçın, Kaan; Avcı, Seda Keskin (ORCID 0000-0001-5968-0336 & YÖK ID 40548); Uzun, Alper (ORCID 0000-0001-7024-2900 & YÖK ID 59917); Öztuna, Fatma Eylül Saraç; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079), Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM), Graduate School of Sciences and Engineering; College of Engineering; College of Sciences, Department of Chemical and Biological Engineering; Department of Materials Science and Engineering; Department of Chemistry, Zeeshan, Muhammad; Yalçın, Kaan; Avcı, Seda Keskin (ORCID 0000-0001-5968-0336 & YÖK ID 40548); Uzun, Alper (ORCID 0000-0001-7024-2900 & YÖK ID 59917); Öztuna, Fatma Eylül Saraç; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079), Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM), Graduate School of Sciences and Engineering; College of Engineering; College of Sciences, and Department of Chemical and Biological Engineering; Department of Materials Science and Engineering; Department of Chemistry

Abstract

Here, we report a new post-synthesis modification strategy for functionalizing reduced graphene aerogels (rGAs) towards an exceptional CO2 separation performance. 1-N-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was impregnated on a rGA, prepared by reducing GA at 700 degrees C, at various ionic liquid (IL) loadings of 5, 10, 30, and 50 wt%. The resulting composites were characterized in deep detail by X-ray photoelectron spectroscopy, X-ray diffraction, N-2 physical adsorption measurements, scanning electron microscopy, Fourier transform infrared and Raman spectroscopies, and thermogravimetric analysis. Results indicated the presence of interactions between the rGA surface and the anion of the IL, potentially improving the CO2 affinity. Volumetric gas adsorption measurements using these materials showed that the deposition of [BMIM][PF6] on rGA surface at an IL loading of 50 wt% boosts the CO2/CH4 selectivity by more than 20-times, exceeding an absolute value of 120, a remarkably higher CO2/CH4 selectivity compared to that of other functionalized materials under similar operating conditions. Tunability of both the IL structure and the surface characteristics of rGA offer a tremendous degree of flexibility for the rational design of these IL/rGA composites towards high performance in gas separation applications., Scientific and Technological Research Council of Turkey (TÜBİTAK); Koç University Seed Fund Program; HEC-Pakistan Scholarship; TARLA; METU Prof. Dr. Mustafa N. Parlar Education and Research Foundation's 2019 Research Incentive Award

Published
2021

50. Metal doped layered MgB2 nanoparticles as novel electrocatalysts for water splitting

Author

Sadeghi, Ebrahim; Peighambardoust, Naeimeh Sadat; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079); Aydemir, Umut (ORCID 0000-0003-1164-1973 & YÖK ID 58403), Khatamian, Masoumeh, 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), Graduate School of Sciences and Engineering; College of Sciences, Department of Materials Science and Engineering; Department of Chemistry, Sadeghi, Ebrahim; Peighambardoust, Naeimeh Sadat; Ünal, Uğur (ORCID 0000-0003-4718-1243 & YÖK ID 42079); Aydemir, Umut (ORCID 0000-0003-1164-1973 & YÖK ID 58403), Khatamian, Masoumeh, 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), Graduate School of Sciences and Engineering; College of Sciences, and Department of Materials Science and Engineering; Department of Chemistry

Abstract

Growing environmental problems along with the galloping rate of population growth have raised an unprecedented challenge to look for an ever-lasting alternative source of energy for fossil fuels. The eternal quest for sustainable energy production strategies has culminated in the electrocatalytic water splitting process integrated with renewable energy resources. The successful accomplishment of this process is thoroughly subject to competent, earth-abundant, and low-cost electrocatalysts to drive the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), preferably, in the same electrolyte. The present contribution has been dedicated to studying the synthesis, characterization, and electrochemical properties of newfangled electrocatalysts with the formal composition of Mg1-xTMxB2 (x=0.025, 0.05, and 0.1; TM (transition metal)=Fe and Co) primarily in HER as well as OER under 1 M KOH medium. The electrochemical tests revealed that among all the metal-doped MgB2 catalysts, Mg0.95Co0.05B2 has the best HER performance showing an overpotential of 470 mV at-10 mA cm(-2) and a Tafel slope of 80 mV dec(-1) on account of its high purity and fast electron transport. Further investigation shed some light on the fact that Fe concentration and overpotential for HER have adverse relation meaning that the highest amount of Fe doping (x=0.1) displayed the lowest overpotential. This contribution introduces not only highly competent electrocatalysts composed of low-cost precursors for the water-splitting process but also a facile scalable method for the assembly of highly porous electrodes paving the way for further stunning developments in the field., Turkish Academy of Sciences (TUBA) Outstanding Young Scientist Award Program (GEBIP)

Published
2021

Catalog

Books, media, physical & digital resources
See catalog results