Browsing by Author "Eskizeybek, Volkan"

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Citation - WoS: 12
Citation - Scopus: 11
Combined Effect of Fiber Hybridization and Matrix Modification on Mechanical Properties of Polymer Composites
(Sage Publications Ltd, 2023) Demir, Okan; Yar, Adem; Eskizeybek, Volkan; Avci, Ahmet
Glass/carbon fiber reinforced hybrid composites are great candidates for wind turbine blade manufacturers to make larger blades. Variation of stacking sequences ensures design freedom to the composite engineers to optimize the composite structure's mechanical performance. On the other hand, matrix modification of polymer composites with nanoparticles is also of interest to introduce multifunctional properties. This research aims to scrutinize the influence of simultaneous fiber hybridization and matrix modification on polymer composites' tensile, flexural, and low-velocity impact properties. Hybrid glass/carbon epoxy composites and hybrid glass/carbon/multi-walled carbon nanotube (MWCNT) multiscale polymer composites of stacking sequences [GCGCGC](S), [CGCGCG](S), and [G(6)C(6)] were manufactured. Fiber hybridization dramatically improved tensile strength between 51% and 76% compared to glass fiber composite. Depending on the stacking sequence, the flexural strength of the hybrid composites was improved between 10% and 16% concerning carbon fiber composite. With the introduction of MWCNTs, a slight increase in the tensile strength for unsymmetrical hybrid composites by around 5% and decreases by 7% for symmetrical ones were observed. Similar behavior was seen for bending characteristics. Additionally, low-velocity impact tests showed that it is achievable to bring greater impact peak forces up to 70% for hybrid composites than carbon fiber epoxy composites. MWCNTs modification of the matrix restrained the impact damage propagation, as proved by C-scan analysis.
Cuo Nanoparçacıkların Kolay ve Amorf Yapıda Sentezi
(Konya Technical University, 2019) Üstün, Tugay; Eskizeybek, Volkan; Avcı, Ahmet
Bakır oksit (CuO) nanoparçacıkları, sıvı bir ortamda ark deşarj yöntemi ile başarılı bir şekilde sentezlendi. İki bakır elektrot arasında ark boşalması gerçekleşerek üretimi tamamlanan bakır oksit nanoparçacıkların morfolojisi ve Kristal yapısı ayrıntılı bir şekilde incelenmesi yapıldı. Elektron mikroskobu incelemeleri sonucunda üretilen CuO nanoparçacıkların 10-50 nm aralığında nominal çaplarda düzensiz şekilli olduğu görülmektedir. XRD sonuçları ise sentezlenen parçacıkların herhangi bir safsızlık olmadan sadece CuO piklerini içerdiğini göstermektedir. Sonuçlara göre tek fazlı CuO nanoparçacıkların üretilmesi için ark deşarj yöntemi basit, ucuz ve esnek bir yöntemdir.
Citation - WoS: 3
Citation - Scopus: 3
Enhanced Performance of Mxene-Based Supercapacitor Via New Activated Carbon-Nafion Composite Cathode
(Pergamon-elsevier Science Ltd, 2025) Akilli, Aleyna; Taymaz, Bircan Haspulat; Eskizeybek, Volkan; Kamis, Handan
Asymmetric supercapacitors leverage differences in the work functions of electrode materials to achieve an extended operating potential window and enhanced energy storage capacity. In this study, an asymmetric supercapacitor was developed using Ti3C2Tx MXene as the working electrode and a composite of activated carbon-nafion (AC-N) and activated carbon-polyvinylidene fluoride (AC-P) as the counter electrode. The work functions of MXene and AC-N were measured as 7.06 and 9.6 eV, respectively, enabling a potential window expansion to 2 V with the AC-N counter electrode. Electrochemical evaluations in H2SO4, MgSO4, and KOH electrolytes revealed specific capacitance values of 555, 367.5, and 425 F g-1 in, respectively. Additionally, corresponding power densities reached 1023, 999.86, and 1980.25 W kg- 1 , while energy densities were determined to be 81.2, 40.55, and 26 Wh kg- 1 . These findings highlight a straightforward strategy to enhance energy storage performance by leveraging the distinctive properties of MXene.
Citation - WoS: 48
Citation - Scopus: 48
Enhanced Salty Water Durability of Halloysite Nanotube Reinforced Epoxy/Basalt Fiber Hybrid Composites
(KOREAN FIBER SOC, 2019) Ulus, Hasan; Kaybal, Halil Burak; Eskizeybek, Volkan; Avcı, Ahmet
In this study, we report the effect of halloysite nanotube (HNT) modification on salty water aging durability of epoxy (Ep)/basalt fiber (BF) hybrid composites. For this, various amounts of HNTs were introduced into the Ep matrix, and the HNTs/Ep mixture was used to impregnate basalt fabrics to fabricate hybrid laminated composites. The hybrid composites were exposed substantial increases in the tensile strength and the fracture toughness. Besides, after salty water aging for 6 months, the hybrid composites exhibited remarkably improved aging performance with almost 10 % less reduction in both tensile and flexural strengths and fracture toughness compared to the neat basalt-epoxy composites. SEM analysis showed relatively less number of cracks, micro-voids and better interfacial bonding for the 2 wt% HNTs reinforced hybrid composite specimens in comparison to the neat counterpart, similarly conditioned in all cases. The consequences of salty water aging on micro-scale morphology were discussed based on the fracture morphologies to reveal degradation mechanisms in the existence of HNTs reinforcement.
Citation - WoS: 2
Citation - Scopus: 2
Gan/Zno Hybrid Nanostructures for Improved Photocatalytic Performance: One-Step Synthesis
(Scientific And Technological Research Council Turkey, 2023) Üstün, Tugay; Haspulat Taymaz, Bircan; Eskizeybek, Volkan; Kamış, Handan; Avcı, Ahmet
Nanostructured semiconductor materials are considered potential candidates for the degradation of textile wastewater via the photocatalytic process. This study aims to produce hexagonal gallium nitride (GaN) nanoplates and zinc oxide (ZnO) nanoparticles in a deionized water environment utilizing a one-step arc discharge process. Detailed characterization of samples has been completed via scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV visible spectroscopy methods. The hybrid nanostructure morphologies consist of nanoplates and nanorods of different sizes. The photoperformance of GaN/ZnO hybrid nanostructures was assessed via the malachite green (MG) dye degradation under UV exposure. Under UV exposure, the degradation yield reached 98% in 60 min. Compared to individual ZnO and GaN nanoparticles, the photocatalytic reaction rate of the GaN/ZnO photocatalyst is 2.2 and 3.6 times faster, respectively. Besides, the GaN/ZnO hybrid nanostructures show excellent photocatalytic stability. The energy consumption of the photocatalytic degradation in the presence of GaN/ZnO hybrid nanostructures was 1.688 kWhL-1. These results demonstrate that the GaN/ZnO hybrid nanostructures with improved photocatalytic activity are a reasonable option for the decomposition of textile wastewater under UV light exposure.
Citation - WoS: 45
Citation - Scopus: 48
Halloysite Nanotube Reinforcement Endows Ameliorated Fracture Resistance of Seawater Aged Basalt/Epoxy Composites
(SAGE PUBLICATIONS LTD, 2020) Ulus, Hasan; Kaybal, Halil Burak; Eskizeybek, Volkan; Avcı, Ahmet
Seawater aging-dominated delamination failure is a critical design parameter for marine composites. Modification of matrix with nanosized reinforcements of fiber-reinforced polymer composites comes forward as an effective way to improve the delamination resistance of marine composites. In this study, we aimed to investigate experimentally the effect of halloysite nanotube nanoreinforcements on the fracture performance of artificial seawater aged basalt-epoxy composites. For this, we introduced various amounts of halloysite nanotubes into the epoxy and the halloysite nanotube-epoxy mixtures were used to impregnate to basalt fabrics via vacuum-assisted resin transfer molding, subsequently. Fracture performances of the halloysite nanotubes modified epoxy and basalt/epoxy composite laminated were evaluated separately. Single edge notched tensile tests were conducted on halloysite nanotube modified epoxy nanocomposites and the average stress intensity factor (K-IC) was increased from 1.65 to 2.36 MPa.m(1/2) (by 43%) with the incorporation of 2 wt % halloysite nanotubes. The interlaminar shear strength and Mode-I interlaminar fracture toughness (G(IC)) of basalt-epoxy hybrid composites were enhanced from 36.1 to 42.9 MPa and from 1.22 to 1.44 kJ/m(2), respectively. Moreover, the hybrid composites exhibited improved seawater aging performance by almost 52% and 34% in interlaminar shear strength and G(IC) values compared to the neat basalt-epoxy composites after conditioning in seawater for six months, respectively. We proposed a model to represent fracture behavior of the seawater aged hybrid composite based on scanning electron microscopy and infrared spectroscopy analyses.
Citation - WoS: 4
Citation - Scopus: 5
Impact Response of Nanoparticle Reinforced 3d Woven Spacer/Epoxy Composites at Cryogenic Temperatures
(SAGE PUBLICATIONS LTD, 2021) Yildirim, Ferhat; Tatar, Ahmet Caner; Eskizeybek, Volkan; Avcı, Ahmet; Aydın, Mustafa
Fiber-reinforced polymer composites serving in harsh conditions must maintain their performance during their entire service. The cryogenic impact is one of the most unpredictable loading types, leading to catastrophic failures of composite structures. This study aims to examine the low-velocity impact (LVI) performance of 3D woven spacer glass-epoxy composite experimentally under cryogenic temperatures. LVI tests were conducted under various temperatures ranging from room temperature (RT) to -196 degrees C. Experimental results reveal that the 3D composites gradually absorbed higher impact energies with decreasing temperature. Besides, the effect of multi-walled carbon nanotube and SiO2 nanofiller reinforcements of the matrix on the impact performance and the damage characteristics were further assessed. Nanofiller modification enhanced the impact resistance up to 30%, especially at RT. However, the nanofiller efficiency declined with decreasing temperature. The apparent damages were visually examined by scanning electron microscopy to address the damage formation. Significant outcomes have been achieved with the nanofiller modification regarding the new usage areas of 3D woven composites.
Citation - WoS: 2
Citation - Scopus: 2
Lightweight and Sustainable Recycled Cellulose Based Hybrid Aerogels With Enhanced Electromagnetic Interference Shielding
(Springer, 2025) Taymaz, Bircan Haspulat; Eskizeybek, Volkan
Developing lightweight, sustainable, high porosity, and high-performance electromagnetic interference (EMI) shielding apparatus is essential to diminish electromagnetic contamination for protecting human health and electronic devices. Herein, 1D carbon nanotubes (CNTs) and 2D graphene nanoplatelets (GNPs) functionalized recycled cellulose aerogel (RCA) were fabricated via a facile method by freeze, solvent exchange, and ambient drying. The effect of nanofiller type and quantity on the structural, morphological, electrical, thermal and EMI shielding performance of the RC-based aerogel were investigated. The as-prepared hybrid aerogel displays the maximum 40.2 dB electromagnetic interference shielding efficiency (SE) at 8.92 dB GHz with absorption dominant characteristic. CNTs:GNPs nanofillers in recycled cellulose matrix provoked conductivity mismatching and increased interfacial polarization loss. At a density of 0.087 gcm-3, CNTs:GNPs; 7:7%wt. doped RCA exhibits a highly specific SE (SSE) value of 461.95 dBcm3g-1 and an absolute SE (SSE/t) value of 2309.29 dBcm2g-1. These results show that the CNTs:GNPs; 7:7%wt. doped RCA can meet practical applications' lightweight and high-efficiency EMI shielding requirements.
Citation - WoS: 38
Citation - Scopus: 39
A Novel Polyaniline/Nio Nanocomposite as a Uv and Visible-Light Photocatalyst for Complete Degradation of the Model Dyes and the Real Textile Wastewater
(SPRINGER HEIDELBERG, 2021) Haspulat Taymaz, Bircan; Eskizeybek, Volkan; Kamış, Handan
The textile processing industry utilizes enormous amounts of water. After the dying process, the wastewater discharged to the environment contains carcinogens, non-biodegradable, toxic, and colored organic materials. This study aimed to develop a nanocomposite material with improved photocatalytic activity to degrade textile dyes and without a need for a post-separation process after the use. For this, nickel oxide nanoparticles (NiO NPs) were synthesized by a simple method in aqueous media. Then, NiO-doped polyaniline (PANI/NiO) with efficient absorption in the visible region (optical band gap of 2.08 eV) synthesized on a stainless steel substrate with electropolymerization of aniline in the aqueous media. The photocatalytic activity of PANI/NiO film was also investigated by the degradation of model dyes. Under UV and visible light irradiation, the PANI/NiO film degraded methylene blue and rhodamine B dyes entirely in 30 min. Moreover, the PANI/NiO film was also utilized to degrade real textile wastewater (RTW) without applying any pre-process; it was entirely decomposed by the nanocomposite film in only 45 min under UV light irradiation. The photocatalytic reaction rate of the pure PANI film is increased as 2.5 and 1.5 times with the addition of NiO NPs under UV and visible light irradiations for degradation RTW, respectively. The photocatalytic efficiency was attributed to reduced electron-hole pair recombination on the photocatalyst surface. Furthermore, the photocatalytic stability is discussed based on re-use experiments. The photocatalytic performance remains nearly unchanged, and the degradation of dyes is kept 94% after five cycles.
Citation - WoS: 1
Citation - Scopus: 1
Optimized Size Sorting of Mxene Particles Via Centrifugal Sedimentation: a Practical Approach Using an Empirical Model and Image Processing Technique
(Taylor & Francis inc, 2025) Onat, Buket; Taymaz, Bircan Haspulat; Eskizeybek, Volkan; Kamis, Handan
Controlling the physical, mechanical, and electrochemical properties of MXene-based materials is crucial for their effectiveness in macroscale applications and is closely tied to the particle size distribution of MXene. This study aimed to accomplish dimensional control and sorting of MXene colloids with different particle sizes using centrifugal sedimentation based on an empirical model. Centrifuge time and rotating speed were identified as key parameters and optimized using a mathematical formula generated from the model, considering particle forces in the solution. A novel image processing technique aimed at ease of use was devised to evaluate the separation process, assuring the audience of its usability. The separation efficiencies were measured individually at rotating speeds ranging from 2900 to 6000 rpm. The optimal experimental settings differed between the supernatant and sediment fractions. The maximum separation efficiency was reached at 86% for the supernatant at 3500 rpm for 49 min and 43% for the sediment at 4200 rpm for 34 min, suggesting that supernatant-based separation is more efficient than sediment-based techniques. This study offers a valuable guideline for separating the sizes of 2D materials. Image processing offers scalable particle size measurement, which improves material property control for a variety of applications.
Citation - WoS: 3
Citation - Scopus: 3
Pani/Coo Nanocomposite Films With Excellent Photocatalytic Performance for Real Textile Wastewater Treatment
(Springer Int Publ Ag, 2023) Haspulat Taymaz, Bircan; Eskizeybek, Volkan; Kamış, Handan
Textile wastewater becomes the primary root of environmental pollution due to the rapid infection rates of freshwater, subsurface water, soil, and air. Due to the high absorption abilities of UV and visible light, polymer nanocomposite photocatalyst films (PNPFs) are recognized as potential candidates for textile wastewater treatment. Here, we developed novel cobalt monoxide (CoO)/polyaniline (PANI) PNPFs with high photocatalytic efficiency and stability. The photocatalytic efficiencies of PANI/CoO films were estimated utilizing the degradation of organic dyes and real-textile wastewater (RTW) under various lighting conditions. PANI/CoO PNPF completely decomposed methylene blue and RTW samples in 30 and 45 min under UV light illumination, respectively. We found that the CoO nanoparticles doubled the PANI's photocatalytic decomposition rate. However, under visible light irradiation, their photocatalytic efficiencies almost halved. Moreover, PANI/CoO PNPF exhibited excellent photocatalytic stability by maintaining the photocatalytic performance for up to five cycles with over 95% removal efficiency. This study yielded an efficient and alternative polymer nanocomposite to decompose wastewater sources contaminated with various textile dyes and may be examined for industrial-scale applications in the future.
Citation - WoS: 11
Citation - Scopus: 10
Selectively Reinforced Functionally Graded Composite-Like Glass/Carbon Polymer Nanocomposites: Designed for Efficient Bending and Impact Performance
(KOREAN FIBER SOC, 2022) Demir, Okan; Tatar, Ahmet Caner; Eskizeybek, Volkan; Avcı, Ahmet
Offshore wind turbine blades (OWTBs) are exposed to various types of loadings during their service life. Moreover, due to their tremendous size, huge investment costs are established, including advanced engineering materials and production process solutions. To decrease their investment cost without sacrificing their mechanical performances, advanced engineering solutions in the view of material selection and design should be implemented. With this motivation, we aimed to develop a novel laminated composite design considering reducing investment costs without compromising the bending and impact resistance of an OWTB. For this, an efficient and cost-effective design of a functionally graded composite (FGM)-like glass/carbon fibers reinforced hybrid polymer composite with a specific stacking sequence was presented. To evaluate mechanical performance of the composite structure, tensile, flexural, and to simulate environmental conditions, low-velocity impact tests were conducted. Furthermore, multi-walled carbon nanotubes (MWCNTs) were also introduced into the polymer matrix to evaluate their effectiveness in the hybridized composite. Drastic improvements in the bending strength (55.8 %) and strain (39.7 %) were obtained compared to the neat carbon fiber reinforced epoxy composites (CFs), especially with the aid of MWCNTs. According to impact tests, it was pointed out that it is possible to obtain higher impact peak forces (around 15 %) compared to neat CFs. However, MWCNTs contributed with slight increments in impact resistance but effectively restricted the impact damage propagation. This study reveals it is possible to tune the bending performance, the absorbed energy, and the damage extension by utilizing glass and carbon fiber laminates in an FGM-like structure.