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- ArticleYalnız künye2026Optimization of MXene/CNT free-standing composite electrodes for enhanced electrochemical performance in symmetric supercapacitors
Yesilbag, Yasar Ozkan; Salih, Ahmed Jalal Salih
The integration of one-dimensional (1D) and two-dimensional (2D) materials into three-dimensional (3D) structures shows great potential for improving energy storage. This study investigates the optimization of interlayer spacing in MXene structures by incorporating conductive materials. Free-standing Ti3C2Tx MXene and carbon nanotube (CNT) composite electrodes were fabricated via vacuum filtration, with CNT weight ratios of 10 %, 20 %, and 30 %. The MXene/CNT10 (MX1) composite exhibited superior electrochemical performance, with a specific capacitance of 254 F g⁻1 and remarkable durability, retaining 101.2 % of its initial capacitance after 10,000 cycles. A symmetric supercapacitor (SSC) using the MX1 electrode achieved a stable voltage window of 0–1.2 V, a specific capacitance of 70.1 F g⁻¹, and retained 85 % of its capacitance after 5000 cycles. With an energy density of 14.1 Wh kg⁻1 and a power density of 13.9 kW kg⁻1, MXene/CNT composites demonstrate significant potential for advanced energy storage applications.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye20262D/2D Borophene/Ti2NbC2Tx MXene hybrids as advanced electrodes for supercapacitors
Yesilbag, Yasar Ozkan; Tuzluca Yesilbag, Fatma Nur; Huseyin, Ahmad; Salih, Ahmed Jalal Salih; Ertugrul, Mehmet
Two-dimensional (2D) hybrid electrodes combining complementary charge-storage mechanisms represent a promising approach for advanced supercapacitors. In this work, few-layer β-borophene nanosheets were synthesised via a modified Hummers' method and integrated with Ti2NbC2Tx MXene to form 2D/2D hybrid electrodes. Structural characterization confirmed successful borophene exfoliation, MXene–borophene heterostructure formation with locally ordered domains and enhanced ion accessibility. Electrochemical measurements demonstrated that hybrid electrodes significantly outperformed pristine MXene and borophene. The MX-B10 composition exhibited the highest specific capacitance, superior rate capability, and optimal charge-transfer kinetics attributed to synergistic surface-controlled capacitance from borophene and diffusion-assisted ion transport in MXene. A symmetric solid-state supercapacitor (SSSC) assembled with MX-B10 electrodes achieved 54 Wh kg−1 at ~300 W kg−1, retaining 23.2 Wh kg−1 at ~7.6 kW kg−1 with ~97% capacitance retention after extended cycling, These results highlight the potential of borophene–MXene heterostructures for high-performance energy storage applications.
RDL Kalıcı Kaydıİncele - Book ChapterYalnız künye2025Natural-derived electrolytes for supercapacitors
Yildirim, Ipek Deniz; Güngör, Ahmet; Kocabas Akgul, Berfu; Tuc Altaf, Cigdem; Yesilbag, Fatma Nur Tuzluca; Yesilbag, Yasar Ozkan; Rostas, Arpad Mihai; Sankir, Mehmet; Sankir, Nurdan Demirci; Erdem, Emre
A growing need for sustainable energy-management solutions has highlighted the limitations of conventional electrolytes, leading to an examination of alternative options. Traditional electrolytes, often based on non-renewable resources, exhibit limited environmental sustainability and increase greenhouse gas emissions, therefore increasing global warming. Their production processes are frequently energy-intensive, further accelerating climate change. In response to these challenges, researchers have focused on nature-derived electrolytes, which offer a promising pathway to sustainable, eco-friendly, and high-performance energy storage. These electrolytes can reduce environmental impact by leveraging renewable biomass sources, natural polymers, and biocompatible materials while enhancing electrochemical properties. This shift towards nature-derived electrolytes is driven by the need to minimize our reliance on fossil fuels, decrease carbon emissions, and promote environmentally responsible technologies. This chapter overviews the latest research on nature-derived electrolytes, highlighting their advantages and potential applications in supercapacitors. We explore the diverse natural materials investigated, including plant-based polymers, algae-derived compounds, and microbially produced substances. By examining the properties and performance of these innovative materials, we can unlock new opportunities for sustainable energy storage. Herein, a comprehensive coverage of the topics related to nature-derived electrolytes has been given. The authors examine the present state of research on this topic, emphasizing the significant difficulties and potential. Additionally, we provide an in-depth analysis of the properties and performance of nature-derived electrolytes, by emphasizing how they can be utilized potentially in energy storage devices. Our goal is to offer essential resources for individuals in academia, government, and the private sector who are looking to promote progress in the area of sustainable energy storage.
RDL Kalıcı Kaydıİncele - Book ChapterYalnız künye20252D Materials for Solar-Assisted Hybrid Energy Storage Devices: Photo-Supercapacitors
Yesilbag, Yasar Ozkan; Yesilbag, Fatma Nur Tuzluca; Huseyin, Ahmad; Salih, Ahmed Jalal Salih; Ertugrul, Mehmet
Photo-supercapacitors (PSCs) are gaining recognition as a feasible option for future electronic devices and have attracted considerable research attention in recent years. These devices, designed for storing light energy, are viewed as a promising energy source for smart electronics, flexible technologies, and wearable devices. PSCs integrate solar cells with supercapacitors, facilitating the conversion of light energy into electrical energy, which is subsequently stored in chemical energy. Their exceptional light conversion efficiency and outstanding energy storage capabilities distinguish PSCs as key players in light-operated energy storage solutions. Recent studies have extensively explored the application of nanomaterials (1D, 2D, and 3D) as potential electrode materials in these devices. Furthermore, there has been a notable shift toward research to decrease dependence on traditional energy sources. This chapter delves into PSCs’ structure, mechanisms, and operational principles alongside an overview of the available types. It concludes with significant recommendations for improving PSC performance by innovating new materials that exhibit optical and capacitive properties. Additionally, it addresses PSC’s challenges and issues and proposes appropriate solutions.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2025Electrochemical performance of Fe2Al1-xB2 MBene as a novel electrode material for supercapacitor applications
Tuzluca Yesilbag, Fatma Nur; Yesilbag, Yasar Ozkan; Huseyin, Ahmad; Salih, Ahmed Jalal Salih; Ertugrul, Mehmet
The growing global demand for efficient and sustainable energy storage systems has intensified the need for advanced electrode materials with superior performance and stability. This study focuses on the synthesis and characterization of Fe2AlB2 MAB phase and Fe2Al1-xB2 MBene, highlighting their potential for energy storage applications. The Fe2AlB2 MAB phase was synthesized using FeB and Al powders via high-temperature sintering (1200 °C for 2 h), followed by selective etching of aluminum layers with a 2 M HCl solution to produce Fe2Al1-xB2 MBene. Electrochemical measurements demonstrated that Fe2Al1-xB2 MBene exhibits excellent pseudocapacitive behavior, achieving a specific capacitance of 276 F g−1 at 0.5 A g−1 in a three-electrode system. An asymmetric supercapacitor (ASC) configuration achieved an energy density of 20.6 Wh kg−1 at a power density of 306.4 W kg−1, with 96 % capacitance retention after 10,000 cycles. This research represents one of the pioneering studies on Fe2Al1-xB2 MBene, emphasizing its potential as a high-performance electrode material for next-generation energy storage devices. The findings provide valuable insights into the design and application of 2D MBenes for energy-related technologies.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2025Interface-engineered al/SWCNT-resin composite wires with improved electrical and mechanical performance
Ghaforyan, Hossein; Khalilpour, Habib; Ebrahimzadeh, Majid; Farhangmehr, Mojtaba; Oral, Emin Argun; Yesilbag, Fatma Nur Tuzluca; Yesilbag, Yasar Ozkan; Keles, Sedanur; Ertugrul, Mehmet
This study presents the fabrication and characterisation of novel ultra-conductive aluminium wires achieved through the conformal coating of single-walled carbon nanotubes (SWCNTs) in a unique sandwich composite structure (Al/SWCNT-resin). Electrothermal characterisation results indicated a significant enhancement in thermal stability and effective suppression of thermal runaway at high current densities in the composite wires compared to pure Aluminium, despite a marginal increase in electrical resistivity. Notably, the Al/SWCNT-resin composite wire exhibited a resistivity of 2.965 μΩ cm and ampacity of 1.45 × 104 A cm−2. These findings highlight the substantial potential of the Al/SWCNT-resin composite wire as an advanced conductor for high-current applications that require superior thermal and long-term durability.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2025Ti2NbC2Tx MXene Nanosheets as an Ordered Double Transition Metal Electrode for High-Performance Supercapacitors
Tuzluca Yesilbag, Fatma Nur; Yesilbag, Yasar Ozkan; Huseyin, Ahmad; Salih, Ahmed Jalal Salih; Ertugrul, Mehmet
The increasing demand for advanced materials in energy storage underscores the importance of chemical diversity in nanomaterials. Ordered double transition metal (DTM) MXenes have emerged as promising atomically layered 2D materials. This study investigates the flexible Ti2NbC2Tx MXene, synthesized from the ordered Ti2NbAlC2 MAX phase, as a supercapacitor electrode material. Electrochemical analyses revealed specific capacitances of 322 and 642 F g-1 at a current density of 0.5 A g-1 in Na2SO4 (Na) and H2SO4 (H) electrolytes, respectively. Ti2NbC2Tx MXene exhibited exceptional cycling stability, retaining 95% capacitance in Na2SO4 and 100% in H2SO4 after 10,000 charge/discharge cycles. Furthermore, an asymmetric supercapacitor (ASC) was fabricated using Ti2NbC2Tx MXene as the positive electrode and overcapacitive activated carbon as the negative electrode with PVA-Na and PVA-H gel electrolytes. The ASC achieved energy densities of 31.1 and 34.0 W h kg-1 for PVA-Na and PVA-H electrolytes, respectively. These results highlight the potential of Ti2NbC2Tx MXene, with its unique ordered structure and double transition metal composition, for foundational research and applications in advanced energy storage technologies.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Self-Powered Quasi-Solid-State Photoelectrochemical Photodetectors Based on MXene Paper Modified by ZnO Nanostructured Architecture
Karagoz, Emine; Tuc Altaf, Cigdem; Tuzluca Yesilbag, Fatma Nur; Yesilbag, Yasar Ozkan; Erdem, Emre; Bakan Misirlioglu, Feray; Demirci Sankir, Nurdan; Sankir, Mehmet
In this work, we report a self-powered quasi-solid-state photodetector (PD) device prepared from flexible two-dimensional (2D) nanocomposites of a zinc oxide nanowire (ZnO-NW) in various weight percents (5, 10, 30, 50%) and Ti3C2Tx (MXene) paper, constructed with manganese (Mn)-doped zinc oxide nanorods (ZnO NRs) using an ionic gel electrolyte and carbon paper. All PD performance tests revealed that 5% ZnO-MXene-based devices were superior to the other samples. The maximum detectivity of 1.44 × 1013 Jones at 367 nm (0.1 mW cm-2) and zero bias was calculated for the 5% ZnO-MXene-based device. Additionally, a very high on/off ratio of nearly 106, which is approximately 35-fold higher than that of the 50% ZnO-MXene-based PDs, was achieved for 5% ZnO-MXene PD at a zero bias under 367 nm (2.52 mW cm-2) illumination. The rise time for this device was 9.25 ms. Furthermore, the PD device exhibited excellent stability by enduring 1000 s of light on/off cycles. As a result, a simple, compact, and cost-effective self-powered ZnO-NW:MXene-based PD configuration showed fast photoresponse and excellent detecting performance.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2024Photo-supercapacitors based on zinc oxide/MXene paper dual acting electrodes
Colak, Tuluhan Olcayto; Altaf, Cigdem Tuc; Yesilbag, Fatma Nur Tuzluca; Yesilbag, Yasar Ozkan; Yildirim, Ipek Deniz; Erdem, Emre; Misirlioglu, Feray Bakan; Sankir, Nurdan Demirci; Sankir, Mehmet
Photo-supercapacitors (PSCs) have great potential as devices that enable both the conversion and storage of solar energy. However, it remains challenging to design new dual-acting electrodes providing high energy density and capacitance with self-powering capacity. Herein, we successfully prepared dual electrodes using ZnO-nanoflake and Ti3C2Tx-based MXene paper. By utilization of the MXene to the PSC device, capacitive contribution to the total capacitance increased ∼4 times compared to the bare ZnO-nanoflake-based PSC due to the surface redox reactions and electrically double layer formation. Maximum energy and power density of 57.3 μWhcm−2 and 11.1 mWcm−2, respectively were obtained for ZnO/MXene//MXene-PSC@UV irradiation and at a 2.5 V. Areal capacitance of this device calculated from CV was as high as 151.5 mFcm−2. Moreover, the ZnO/MXene//MXene-PSC device was highly stable over 10,000 GCD cycles with 100 % CE and 98 % Cp-retention under daylight.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023All-in-one supercapacitors with high performance enabled by Mn/Cu doped ZnO and MXene
Ammar, Ameen Uddin; Bakan-Misirlioglu, Feray; Aleinawi, Mohamad Hasan; Franzo, Giorgia; Condorelli, Guglielmo Guido; Yesilbag, Fatma Nur Tuzluca; Yesilbag, Yasar Ozkan; Mirabella, Salvo; Erdem, Emre
Here, we report the development of high-performance supercapacitor devices using manganese-doped zinc oxide nanowires (Mn-doped ZnO NWs) and copper-doped zinc oxide nanoparticles (Cu-doped ZnO NPs) as a positive electrode with MXene as a negative electrode. Both transition metal (TM)-based electrodes were used separately with MXene, and the performance was tested. When used in combination with MXene as a second electrode, TM-ZnO samples displayed a major increase in the supercapacitors’ performance. The highest-performance supercapacitor recorded values of 151 F/g specific capacitance along with 84 Wh/kg energy density and a power density of 75 kW/kg. Electron paramagnetic resonance and photoluminescence spectroscopy of Mn/Cu-doped ZnO reveals intrinsic and extrinsic defect signals, which were discussed and attributed to the enhancement of the capacitive performance. The presence of the aforementioned defects optimizes the intrinsic properties and boosts the reaction kinetics, thus providing increased electrochemical activity and superior supercapacitor device performance.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Enhancing radar absorption performance of Sr-hexaferrite by hybridization with coiled carbon nanotubes via chemical vapour deposition method
Zulkimi, Muhammad Misbah Muhammad; Azis, Raba'ah Syahidah; Ismail, Ismayadi; Mokhtar, Nurhidayaty; Ertugrul, Mehmet; Hamidon, Mohd Nizar; Hasan, Intan Helina; Yesilbag, Yasar Ozkan; Tuzluca, Fatma Nur; Ozturk, Gokhan
A strategy of a highly feasible method to achieve a broad bandwidth of radar absorbing materials (RAM) is reported. Herein the magnetic Sr-hexaferrite were prepared using a conventional sintering process at 900 °C and later hybridized with coiled carbon nanotubes (CNT) via a chemical vapour deposition (CVD) method. X-ray diffraction (XRD) detected two phases of compounds after sintering which were 36 % of SrFe2O4 and 64 % of SrFe12O19. Two groupings of nanoparticle size showed no significant effect on reflection loss (RL) performance. Interestingly after hybridization of coiled CNT with the magnetic materials, the permittivity was increased tremendously hence enhancing the RL. Multiple relaxations of dielectric and eddy current losses were responsible for the enhancement. The RL was increased as the thickness was increased from 1 mm to 3 mm. 6 % of coiled CNT/Sr-hexaferrite hybrid resulted in low RL of -19 dB with the broadest bandwidth of 3GHz over X-band frequency. The report is important for paving future work in obtaining a desired broad bandwidth RAM.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2023Rational design of MXene/Boron Carbon Nitride nanotube composite electrode for supercapacitors with improved electrochemical properties
Tuzluca Yesilbag, Fatma Nur; Yesilbag, Yasar Ozkan; Huseyin, Ahmad; Salih, Ahmed Jalal Salih; Ertugrul, Mehmet
3D structures obtained using 1D and 2D materials are promising materials in energy storage. Optimizing the interlayer spacing of 2D MXene through flexible conductive materials is an important step in synthesizing 3D composite electrodes. In this study, flexible and conductive MXene/BCN nanotube composite film electrodes were prepared by vacuum filtration using BCN nanotubes in different weight ratios (10 %, 20 %, and 30 %) in mixed and sandwiched structures. The mixed MXene/BCN10 (m-MX/BCN10) composite film electrode structure attained a specific capacitance of 678 F g−1, the highest of all tested electrodes, and exhibited remarkable cycle stability by retaining 95 % of its capacitance even after 10,000 charge/discharge cycles. In the symmetric supercapacitor (SSC), the cell exhibited a specific capacitance of 97 % after 10,000 charge/discharge cycles. Moreover, SSC showed an energy density of 32 Wh kg−1 and a power density of 11.5 kW kg−1. The composite electrodes made of 2D Ti3C2Tx MXene and 1D BCN nanotube materials open up a new avenue for synthesizing promising materials for energy storage in transition metal carbides and 1D nanotubes or nanowires.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2022The hierarchical synthesis of tungsten disulfide coated vertically aligned boron carbon nitride nanotubes composite electrodes for supercapacitors
Yesilbag, Yasar Ozkan; Tuzluca Yesilbag, Fatma Nur; Huseyin, Ahmad; Ertugrul, Mehmet
This study investigated the specific capacitance, energy density and cyclic stability parameters of a WS2 coated vertically aligned BCN nanotubes (VA-BCN-NTs) composite electrode structure. The specific capacitance of VA-BCN-NTs was found to be 364 F g−1 at a current density of 0.5 A g−1. This electrode had 97% of their initial specific capacitance after 10,000 cycles at a current density of 20 A g−1, exhibiting excellent cyclic stability. In the three-electrode cell, the specific capacitance of the VA-BCN-NT@WS2 electrode at a current density of 0.5 A g−1 was calculated to be 690 F g−1. After 5000 cycles at a current density of 20 A g−1, the electrode structure had a capacitance value of 74%, showing good stability. In the two-electrode cell, the specific capacitance of the VA-BCN-NT@WS2 symmetrical supercapacitor at a current density of 1 A g−1 was found to be 170 F g−1. It was observed to have retained 85% of its capacitance after 10,000 cycles over a 1 V potential range. While the energy density of this structure was 23.6 Wh kg−1, the power density was 4250 W kg−1.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2022Effect of Mn and Zn doping on natural resonance frequency of strontium U-type hexaferrite and its performance as electromagnetic wave absorbers
Ismail, Ismayadi; Muhammad Zulkimi, Muhammad Misbah; Azis, Raba'ah Syahidah; Mustaffa, Muhammad Syazwan; Hamidon, Mohd Nizar; Ertugrul, Mehmet; Yesilbag, Yasar Ozkan; Tuzluca, Fatma Nur; Hasan, Intan helina; Ozturk, Gokhan
In the present work, substitution of strontium U-type hexaferrite with the composition of Sr4Mn2-xZnxFe36O60 (x = 0.5,0.6,0.8, and 1.0) was prepared via high energy ball milling (HEBM) and sintered at 1100 °C. The phase, microstructure, magnetic, dielectric and electromagnetic wave absorbing properties of U-type strontium hexaferrite composites were measured using XRD, FESEM, and Vector Network Analyzer in the frequency range of 8–18 GHz (X-band and Ku-band). MnZn doping was found to shift the natural resonance of the materials by affecting its magnetocrystalline anisotropy. The reflection loss (RL) indicated that the composite possessed good microwave-absorbing properties with U-type strontium hexaferrite ( Sr4Mn2-xZnxFe36O60) of x = 0.8 resulted in high minimum RL value for all thickness of 1 mm and two peaks at approximately − 32.50 and − 41.50 dB at 14.00 and 15.60 GHz, with bandwidth of 0.60 and 0.80 GHz for losses less than − 10 dB.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2022MnO2 nanosheets synthesized on nitrogen-doped vertically aligned carbon nanotubes as a supercapacitor electrode material
Yesilbag, Yasar Ozkan; Tuzluca Yesilbag, Fatma Nur; Huseyin, Ahmad; Salih, Ahmed Jalal Salih; Ertugrul, Mehmet
In the present study, nitrogen-doped vertically aligned carbon nanotubes (N-VACNTs) were synthesized on carbon cloth (CC) using the floating catalyst chemical vapor deposition (FCCVD) method, and MnO2 nanosheets were grown on them using the hydrothermal method to produce an N-VACNT@MnO2 nanocomposite structure. In this structure, a synergistic effect was obtained by combining N-VACNTs, which allow high electrical conductivity and fast ion transfer. In the galvanostatic charge-discharge (GCD) measurements performed separately in a three-electrode test cell using 1 M of Na2SO4 electrolyte, the specific capacitance of the N-VACNTs was found to be 53.7 F g−1 at a current density of 0.5 A g−1, and the specific capacitance of the N-VACNT@MnO2 electrode structure was found to be 497 F g−1. In addition, after 10,000 charge-discharge cycles at a current density of 10 A g−1, the N-VACNT electrode retained 99 % of its initial specific capacitance, while the N-VACNT@MnO2 electrode exhibited outstanding cyclic stability with 76 % of its initial specific capacitance. Moreover, in the as-fabricated asymmetric supercapacitor (ASC) using N-VACNTs and N-VACNTs@MnO2, the negative and positive electrodes achieved a stable voltage window of 0–1.7 V, with a specific capacitance of 59.4 F g−1 at a current density of 1 A g−1. Additionally, this ASC showed good cycling stability retaining 84 % of its specific capacitance at the end of 10,000 cycles. Therefore, this ASC structure with an energy density of 24.7 Wh kg−1 and a power density of 15.7 kW kg−1 are promising electrode materials for energy storage.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2021Effects of MWCNTs/graphene nanoflakes/MXene addition to TiO2 thick film on hydrogen gas sensing
Chachuli, Siti Amaniah Mohd; Hamidon, Mohd Nizar; Ertugrul, Mehmet; Mamat, Md Shuhazlly; Coban, Omer; Tuzluca, Fatma Nur; Yesilbag, Yasar Ozkan; Shamsudin, N.H.
Various doping materials, such as MWCNTs, graphene nanoflakes and MXene, have been doped into TiO2 and the hydrogen sensing properties investigated. Using a similar volume, MWCNTs (5 wt.%) and graphene nanoflakes (5 wt.%) and MXene (10 wt.%) were added to TiO2 and prepared in a paste form by mixing the sensing material with the organic binder. The sensing film was deposited on an alumina substrate using a screen-printing technique and annealed at 500 °C for 30 min in ambient air. The crystallinity of TiO2 and the doped material in the sensing film after the annealing treatment were verified using FESEM, EDX, XRD and Raman Spectroscopy. By depositing an interdigitated electrode at the bottom of the sensing film, the thick film gas sensors (TiO2/MWCNT, TiO2/Gr, TiO2/MXene) were exposed to 100–1000 ppm of hydrogen at an operating temperature of 100–250 °C. The responses showed that the addition of MWCNTs and MXene to TiO2 reduced the operating temperature of the TiO2 gas sensor from 150 °C to 100 °C, while the addition of graphene nanoflakes did not affect the operating temperature of the TiO2 gas sensor. The TiO2/MWCNT gas sensor showed linear sensitivity as hydrogen concentrations increased for operating temperatures of 100–250 °C. The optimal operating temperature for TiO2/MXene occurred at 100 °C, while the optimal operating temperature for the TiO2/Gr gas sensor occurred at 200 °C. The highest sensitivity for 100–500 ppm hydrogen was generated by the TiO2/MXene gas sensor, and for 600–1000 ppm hydrogen was generated by the TiO2/MWCNT gas sensor at an operating temperature of 250 °C. The TiO2/MWCNT gas sensor produced the highest sensitivity to hydrogen at the operating temperature of 250 °C with sensitivity values of approximately 6.36, 33.61, 67.64, 102.23 and 159.07 for 100, 300, 500, 700 ppm and 1000 ppm of hydrogen, respectively.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2021Synthesis and characterization of graphene/carbon nanotube hybrid: effects of Ni catalyst thickness and H2 flow rate on growth and morphological structure
Yesilbag, Yasar Ozkan; Tuzluca Yesilbag, Fatma Nur; Huseyin, Ahmad; Tuzluca, Metin; Ismail, Ismayadi; Ertugrul, Mehmet
We reported a combination of the unique properties of (2D) graphene and (1D) carbon nanotubes (CNTs) by synthesizing a novel graphene/CNTs hybrid structure. Graphene and CNTs were synthesized by a two-step chemical vapor deposition (CVD) system. In the first step, multilayer graphene (MLG) was grown on nickel substrates by changing the methane gas flow rate and growth time. In the second step, the CNTs were then grown on the synthesized MLG surface previously. Both the Ni catalyst film thickness and H2 gas flow rate were changed to investigate their effects on the growth densities and average diameters of the hybrid structures. Structural and morphological analysis of both MLG and MLG/CNT hybrid structures were determined using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman analysis. As the Ni catalyst film thickness was increased, CNTs grew more densely on the MLG. It was observed that CNTs with smaller diameters and longer lengths formed with increasing H2 gas flow rate. This hybrid structure is useful in electronic, optoelectronic, and energy storage applications.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2019SEM, XRD ve EDX yöntemleriyle insan aort kapaklarında kalsiyum mineralizasyon analizi
Yesilbag, Yasar Ozkan; Ates, Azman
Kalsifik aort darlığı, kalsiyum mineral birikimi ile yavaş ilerleyen bir hastalıktır. Literatürde aort kapağındaki yapısal kusurları araştırmak için çeşitli çalışmalar bildirilmiştir. Bununla birlikte, bugüne kadar, aort kapağının dokusundaki kireçlenme oluşumunun morfolojik yapısı hakkında çok az şey bilinmektedir. Bu çalışmada, aort kapağında morfoloji ve kalsifikasyon yapısal analizi yapılmıştır. Aort kapak dokusunda biriken kalsifikasyon yapılarının morfolojisini belirlemek için taramalı elektron mikroskopisi (SEM) kullanılmıştır. SEM tarafından gözlemlenen morfolojik yapıları karakterize etmek için Enerji Dağılımlı Xışını Analizi (EDX) ve X-ışını Difraktometresi (XRD) kullanılmıştır. Sonuçlar, eser elementlerin kalsifikasyon oluşum sırasında çekirdeklenmede rol oynayabileceği ortaya koyulmuştur.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Synthesis of ultra-long boron nanowires as supercapacitor electrode material
Tuzluca, Fatma Nur; Yesilbag, Yasar Ozkan; Ertugrul, Mehmet
The aim of the present study was to examine the electrochemical performance of boron nanowires (BNWs) grown using the vapor-liquid-solid (VLS) growth mechanism in the chemical vapor deposition (CVD) system at 1200 °C on a silicon wafer in the presence of iron (Fe) catalyst nanodroplets as a supercapacitor electrode material in 1 M Na2SO4 aqueous electrolyte solution. The structure and morphology of BNWs were examined using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM) analyses, while their electrochemical performances were determined by measuring the cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectra (EIS). BNWs showed great cycle stability with an areal capacitance of 30 mF cm−2 and 93.4% of the initial areal capacitance even after a 10,000 GCD cycle at a current density of 0.1 mA cm−2.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019The use of α-MnOOH nanosheets as battery-type electrode for supercapacitor applications
Yesilbag, Yasar Ozkan; Tuzluca, Fatma Nur; Ertugrul, Mehmet
This study investigated MnOOH nanosheets, which were synthesized at different manganese molarities on 3D-nickel foam by hydrothermal synthesis, for use as battery-type electrodes. The crystal structures and morphologies of the MnOOH nanosheets were determined by using X-ray diffraction, field emission scanning electron microscopy, energy dispersion X-ray spectroscopy, Raman Spectroscopy and X-ray photoelectron spectroscopy. Cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy analysis of the MnOOH nanosheets were performed in 1 M of a KOH aqueous electrolyte solution. The specific capacity values obtained from GCD measurements taken at a current density of 0.5 A g-1 from samples called Mn-0.2, Mn-0.5, Mn-1 and Mn-2-according to their manganese molarities-were 230, 557, 766 and 493 C g-1, respectively. Furthermore, the Mn-1 sample, which had the highest specific capacitance value, showed excellent cycle stability by retaining 79% of the initial specific capacity after 10000 charge-discharge cycles.
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