Malzeme Bilimi ve Mühendisliği Bölümü Koleksiyonu

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https://hdl.handle.net/20.500.12428/2688

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Feasibility and performance evaluation of randomly oriented strand recycled composite skins in sandwich structures: A green cost-effective solution for aerospace secondary load-bearing applications
(Wiley, 2025) Özbek, Yağız; Al-Nadhari, Abdulrahman; Elmas, Sinem; Eskizeybek, Volkan; Yıldız, Mehmet; Sas, Hatice S.
Despite the advantages of recycled randomly oriented strand (ROS) composites over recycled grinded ones, the warpage issue hinders their adaptation in the industry due to tolerance requirements. To address this challenge, ROS composites are incorporated into secondary bonded sandwich structures such that the core material ensures the straightness of the ROS composite skins. Additionally, atmospheric plasma activation (APA) is utilized to enhance the skin/core bonding to prevent skin separation under loading. The ROS composite skins are manufactured via vacuum-assisted hot press to achieve a cost-effective aerospace-grade quality. The structural integrity of the sandwich structure is assessed through flatwise tensile and edgewise compression tests, while the mechanical and thermomechanical performance is evaluated using flexural, impact, and dynamic mechanical analysis (DMA) tests. The flatwise tensile and edgewise compression tests confirm that APA effectively prevents core detachment, as evidenced by an average tensile strength of 2.28 MPa and an average compressive strength of 171.7 MPa. Moreover, the flexural and impact tests show that no premature skin failure occurs, supported by an average facing strength of 59.23 MPa in flexural testing and an average impact energy of 49.96 kJ/m(2). The DMA test indicates that most of the stiffness loss is due to the core material. This comprehensive analysis highlights recycled ROS composites as a sustainable and cost-effective alternative for quasi-isotropic skins in aerospace secondary load-bearing sandwich structures such as floors, doors, engine cowls, and spoilers.
Impact of basalt powder on the rheological, thermal, mechanical, and tribological properties of natural and polychloroprene rubber composites: A study on aging and filler interaction
(Wiley, 2025) Yıldız, Enes; Değirmenci, Talha; Esen, Melih; Göksüzoğlu, Mert; Kuru, Gözde; Eskizeybek, Volkan; Şükür, Emine Feyza
This study investigates the effects of basalt powder (BP) as a filler in natural rubber (NR) and synthetic polychloroprene rubber (CR) composites, focusing on their structural, mechanical, and thermal properties before and after aging. The NR/BP and CR/BP composites were prepared with varying basalt content levels of 0, 5, 10, 15, 50, and 100 parts per hundred rubber (phr) and characterized accordingly. Mechanical properties such as tensile strength, Young's modulus, and abrasion resistance were evaluated, alongside thermal properties, using thermogravimetric analysis. The results showed that increasing the basalt content reduced dispersion quality and weakened the filler and matrix interaction, decreasing tensile strength and Young's modulus. The reduction in tensile strength is substantial, with a decrease of 71.7% in NR/BP composites and 64.1% in CR/BP composites at maximum additive ratios. Aging significantly improved the tensile strength and modulus of the materials, which are attributed to an increased crosslink density and the transformation of polysulfide bonds into disulfide bonds. Shore A hardness increased with basalt content, reaching 60.3 for NR/BP and 74.1 for CR/BP at 100 phr, while abrasion resistance decreased, with abrasion loss rising by 130% and 88% for NR/BP and CR/BP composites, respectively. Scanning electron microscopy (SEM) analysis revealed increased surface roughness and filler aggregation at higher basalt contents, contributing to reduced mechanical performance. Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX) analyses confirmed the presence and dispersion of basalt powder within the composites.
Lightweight and sustainable recycled cellulose based hybrid aerogels with enhanced electromagnetic interference shielding
(Springer, 2025) Haspulat Taymaz, Bircan; 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.
The influence of annealing temperature on the gas sensing properties of multifunctional hematite (α-Fe2O3) films
(Springer, 2025) Sarf, Fatma; Er, Irmak Karaduman; Yakar, Emin; Acar, Selim
In this study, hematite (alpha-Fe2O3) were prepared using direct solution spin coating and the changes of some physical properties with annealing temperature (400, 500 and 600 degrees C) for 2 h were investigated. The sensors annealed at 400 degrees C, 500 degrees C and 600 degrees C are referred to as F400, F500 and F600 respectively. The X-ray diffraction patterns of the prepared samples confirm the polycrystalline nature of the rhombohedral crystal structure of hematite (alpha-Fe2O3). The surface roughness parameters (SA-SQ) of the alpha-Fe2O3 films decreased drastically with increasing annealing temperature from 400 to 600 degrees C (57.47-68.08/13.63-17.13). The direct optical band gap values were estimated from absorption measurements and ranged from 2.77 to 2.52 eV. The electrical resistivity measurement at room temperature of the samples decreased with increasing annealing temperature from 400 to 600 degrees C. The response of the CO sensor of F400, F500 and F600 was found at 180 degrees C. The response to 1 ppm CO gas was calculated to be 1.45%, 8% and 10% for F400, F500 and F600 respectively. The wettability test of the samples showed a water contact angle (WCA) of less than 90 degrees, demonstrating the hydrophilic surface especially for the samples annealed at 500 degrees C.
Influence of strand size and morphology on the mechanical performance of recycled CF/PEKK composites: Harnessing waste for aerospace secondary load-bearing applications
(Elsevier Sci Ltd, 2025) Özbek, Yağız; Al-Nadhari, Abdulrahman; Eskizeybek, Volkan; Yıldız, Mehmet; Sas, Hatice Sinem
The flexibility and precision of automated fiber placement (AFP) have made it a standard methodology in the aviation industry. However, the use of continuous slit tapes along component lengths generates significant waste. This waste presents an opportunity for recycling into secondary load-bearing structures, particularly in applications where components are not subjected to extreme working conditions. In this study, carbon fiber-reinforced polyetherketoneketone (CF/PEKK) strands are recycled into randomly oriented strand (ROS) panels using a costeffective, vacuum-assisted hot press process while maintaining aerospace-quality standards. Both long and short strand lengths, as well as shredded strands mimicking real-life industrial waste, are analyzed for their mechanical performance and geometric stability. Mechanical properties of the recycled CF/PEKK composites are evaluated through tensile, shear, compression, Izod impact, and dynamic mechanical analysis (DMA), using digital image correlation (DIC) for precise measurements. Additionally, topological 3D scanning is used to assess the geometric stability of the panels. Results indicate that short strands offer superior mechanical properties, while shredded strands perform comparably. This study makes a unique contribution by demonstrating the effective recycling of slit tape waste into high-performance composite materials, advancing sustainable practices in aerospace applications.
3D printed structured catalyst supports for enhanced CO2 methanation
(Elsevier Sci Ltd, 2025) Kabakçı, Elif; Kostretsova, Natalia; Morales, Elena Martin; Diaz-Ruiz, Jesus; Tarancon, Albert; Guilera, Jordi; Torrell, Marc
This work presents the implementation of ceramic stereolithography 3D printing to generate catalytic supports to investigate the influence of the structured reactor design on its conversion efficiency for CO2 methanation. Alumina monolithic supports were fabricated by stereolithography using a non-linear channel geometry formed by an array of twisted elements, which was compared to the conventional monolith design. The catalytic performance of the 3D printed monoliths, functionalized with Ni as a catalyst material, was evaluated and complemented by CFD simulation, showing the strong correlation between the support design selection and CO2 conversion rates. A maximum CO2 conversion of 84 % at 400 degrees C was achieved owing to the three-dimensional monolith design, which increased the catalytic activity of the system under high gas flow rates by creating a nonuniform reactant flow distribution with higher turbulence kinetic energy. Therefore, this work demonstrates the potential of ceramic 3D printing technologies to boost the catalytic device efficiency by implementing novel designs, not reproducible by conventional ceramic manufacturing approaches.
Enhancing structural health monitoring of fiber-reinforced polymer composites using piezoresistive Ti3C2Tx MXene fibers
(Nature Portfolio, 2025) Haspulat Taymaz, Bircan; Kamış, Handan; Dziendzikowski, Michal; Kowalczyk, Kamil; Dragan, Krzysztof; Eskizeybek, Volkan
The anisotropic behavior of fiber-reinforced polymer composites, coupled with their susceptibility to various failure modes, poses challenges for their structural health monitoring (SHM) during service life. To address this, non-destructive testing techniques have been employed, but they often suffer from drawbacks such as high costs and suboptimal resolutions. Moreover, routine inspections fail to disclose incidents or failures occurring between successive assessments. As a result, there is a growing emphasis on SHM methods that enable continuous monitoring without grounding the aircraft. Our research focuses on advancing aerospace SHM through the utilization of piezoresistive MXene fibers. MXene, characterized by its 2D nanofiber architecture and exceptional properties, offers unique advantages for strain sensing applications. We successfully fabricate piezoresistive MXene fibers using wet spinning and integrate them into carbon fiber-reinforced epoxy laminates for in-situ strain sensing. Unlike previous studies focused on high strain levels, we adjust the strain levels to be comparable to those encountered in practical aerospace applications. Our results demonstrate remarkable sensitivity of MXene fibers within low strain ranges, with a maximum sensitivity of 0.9 at 0.13% strain. Additionally, MXene fibers exhibited high reliability for repetitive tensile deformations and low-velocity impact loading scenarios. This research contributes to the development of self-sensing composites, offering enhanced capabilities for early detection of damage and defects in aerospace structures, thereby improving safety and reducing maintenance expenses.
Discrimination accuracy of haploid and diploid maize seeds using NIR spectroscopy coupled with different machine learning algorithms and data pretreatment methods
(Taylor & Francis Inc, 2025) Kahrıman, Fatih; Polat, Adem; Tiryaki, Ali Murat; Eskizeybek, Volkan; Fidan, Sertuğ; Songur, Umut
Spectral data collected at the single seed level allows determination of the biochemical content of the seed sample, as well as to identify the seed class. NIR (Near Infrared) spectroscopy provides a more precise method for differentiating haploid and diploid seeds in maize than traditional visual examination. In this study, classification models that can be used in the separation of haploid and diploid maize seeds were developed using spectra collected between 900-1700 nm from a single maize seed. In the study, 427 diploid and 311 haploid samples obtained by crossing 10 donor materials and 3 inducer lines and separated by eye according to the Navajo marker were used. Spectral measurements were conducted over the wavelength range of 900 to 1700 nm for each sample. The robust PCA (Principal Component Analysis) method was used to detect spectral outliers. Spectral data were treated with none, FD (First Derivative), SD (Second Derivative), SNV (Standard Normal Variate), and their binary combinations. Logistic Regression, Support Vector Machine with a linear kernel (SVM-C), Random Forest, and XGBoost methods were employed as machine learning techniques. The performance of the developed machine learning models was assessed using metrics such as Sensitivity, Specificity, Recall, F1-Score, and Accuracy. The Boosting method demonstrated the best performance with 94.9% accuracy, 95.1% sensitivity, 94% specificity, and an F1 Score of 96%, particularly when using raw reflectance data. These results obtained from raw data show that high accuracy can be achieved in classification models without requiring additional preprocessing steps. D2 preprocessing was found to be unsuitable for intact seed spectra, whereas SNV and D1 applications improved the classification success of other modeling techniques. The study revealed that the Boosting-Raw combination is a powerful and feasible method for classifying haploid and diploid samples.
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; Haspulat Taymaz, Bircan; Eskizeybek, Volkan; Kamış, 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.
Effect of synthesis conditions on cristobalite crystallization in low-cost ceramic membranes
(Korean Assoc Crystal Growth, Inc, 2025) Zeren, Nevzat; Abalı, Serkan
The raw materials quartz, calcite, kaolin, and zeolite were used to fabricate /f-cristobalite-based ceramic membranes at low temperatures. The raw materials were divided into two groups: calcite and zeolite. Calcite and zeolite raw material mixtures were prepared in different proportions by weight. Quartz-calcite-kaolin and quartz-zeolite-kaolin raw material mixtures were subjected to grinding, drying and shaping processes and then sintered separately at temperatures of 1100 degrees C, 1150 degrees C, and 1200 degrees C in a 7-hour furnace regime. All samples were subjected to X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), density, and mechanical testing. The effects of various raw materials with different compositions and sintering temperatures on the characteristics of ceramic membranes were examined. The necessary conditions for sufficient cristobalite production were created by a sintering temperature of 1200 degrees C with zeolite as the raw material. These criteria are also suitable for homogeneous pore size distribution and crystal structure formation. The flexural strength of the membrane containing 10 wt.% zeolite sintered at 1200 degrees C was 34.75 N.mm-2. The average pore diameter of the membrane sintered at 1200 degrees C with an initial zeolite content of 25 wt.%, was 33.95 nm.
Effect of deposition charges on the wettability performance of electrochromic polymers
(Elsevier, 2015) Çağlar, Aysel; Cengiz, Uğur; Yıldırım, Mehmet; Kaya, İsmet
Electrochromic polymers have been designed as future candidates for electrochromic displays (ECDs) and smart windows. This class of conducting polymers has been studied with their several optical properties as well as spectroelectrochemical stabilities. In practical use their contamination and abrasion could be expected to be main problem as exposed to moisture and other possible pollutants. In this study, we present a perspective to well-known electrochromic polymers in the words of their durable use. For this aim, a series of electrochromic polymers are deposited on indium tin oxide (ITO) coated glass plates by bulk electrolysis. Polymeric films are deposited by varied deposition charges (Q(s)) ranging from 62 to 620 mC cm(-2) for comparison. Equilibrium water contact angle (theta(equ)(water)) measurements of the prepared surfaces are measured by Attention Theta Optical Tensiometer. Surface roughness parameters (RMS) are determined by atomic force microscopy (AFM) technique and used for interpretation of hydrophobic-hydrophilic characteristics. The results clearly indicate that; poly(ethylenedioxythiophene) (PEDOT) has a hydrophilic surface whose hydrophilicity is increased by applied deposition charge and becomes a superhydrophile at high deposition charges. Among the tested polymers polycarbazole (PCarb) is the most promising long lifetime candidate due to its relatively hydrophobic character. Also, the hydrophobicity of PCarb is linearly increased by increasing deposition charge and reaches an optimum point at a particular condition. (C) 2015 Elsevier B.V. All rights reserved.
Chemical oxidative polymerization, optical, electrochemical and kinetic studies of 8-amino-2-naphthol
(Springer, 2015) Doğan, Fatih; Kaya, İsmet; Bilici, Ali; Yıldırım, Mehmet
Here the polymerization of 8-amino-2-naphthol (AN) is reported without use of an additional external template, surfactants or functional dopants. For this, NaOCl and hydrochloride acid solution (1.0 M) were used as oxidant and reaction medium, respectively. The structure of oligomer was elucidated by FT-IR, UV-vis and H-1-NMR techniques. The number average molecular weight of oligomer was found to be 2200Da with a polydispersity index of 1.4 by size exclusion chromatography. This oligomer exhibited a multicolor emission behavior as it was excited at different wavelenghts. Redox states were clarified by cyclic voltammetry (CV) technique and the relationship between anodic/cathodic peak currents vs. scan rates was determined. Thermal analysis and XRD data assigned that the resulting oligomer was in a semi-crystalline form. The activation energy related to the solid state decomposition was calculated from differential and integral non-isothermal methods and the lowest value using Kissinger procedures was determined to be 79.53 kJ/mol in N-2 atmosphere.
High Temperature Mechanical Behavior of MgAl2O4-YAG Eutectic Ceramic In Situ Composites by Float Zone Method
(Walter De Gruyter Gmbh, 2017) Abalı, Serkan
The directionally solidified eutectic MgAl2O4-Y3Al5O12 crystal was prepared at a pressure of 0.4 MPa of ambient nitrogen gas by the high frequency induction heated floating zone furnace. In order to determine the high temperature characteristics, directionally solidified MgAl2O4-Y3Al5O12 eutectic phase has been analyzed with creep test, tensile strength, young modulus and fracture toughness at the various temperatures and the microstructural variations have been studied according to the analysis results. It has been seen that directionally solidified with zone melting MgAl2O4-YAG eutectic ceramic which has given the value of 168 MPa below 10(-6)/s strain rate at 1,700 degrees C temperature has revealed minimum stress.
A green light emitting polymer in a PMMA matrix: oligo(azomethine-ether) with benzothiazole moieties
(Tubitak Scientific & Technological Research Council Turkey, 2015) Yıldırım, Mehmet; Kaya, İsmet
This study aimed to synthesize an oligo(azomethine-ether) with benzothiazole moiety in organic medium by means of chemical oxidative polycondensation (OP). Optical properties were examined by photoluminescence (PL) and UV-Vis measurements both in solutions and solid film involved a poly (methyl methacrylate) (PMMA) matrix. Oligomer film in the PMMA matrix emitted a fine green light with a fluorescence quantum yield (QY) of 3.30%. Spectral and thermal observations showed a high rate of C-O-C coupling (cross-linking) for the oligomer. SEC results indicated low molecular weight (similar to 3200-4650 g mol(-1)) and the oligomer was soluble in organic solvents with high polarity. Electrochemical behavior was characterized by cyclic voltammetry (CV), morphological properties by scanning electron microscopy (SEM), and thermal characteristics by TG-DTA and DSC techniques.
Synthesis and characterizations of poly(ether)/poly(phenol)s including azomethine coupled benzothiazole side chains: the effect of reaction conditions on the structure, optical, electrochemical, electrical and thermal properties
(Springer, 2014) Yıldırım, Mehmet; Kaya, İsmet
A new Schiff base, 4-((6-ethoxybenzothiazole-2-ylimino)methyl)benzene-1,2-diol (3,4-HBAEBT) was synthesized by the condensation reaction of 3,4-dihydroxybenzaldehyde (3,4-HBA) and 2-amino-6-ethoxybenzothiazole. The Schiff base, then, was converted to its polymer derivatives by oxidative polycondensation reaction in both organic (P-1) and aqueous alkaline medium (P-2). Spectral observations indicated different structural properties for each polymerization condition. Organic and aqueous alkaline medium produced poly(ether) and poly(phenol) structures, respectively. The obtained polymers were separately studied with respect to optical, electrochemical, electrical and thermal properties. With exception of thermal degradation behaviors, the other investigated properties as well as morphological characteristics of both polymers were considerably different. In the fluorescence measurements a solvatochromic effect was recorded and the emission colors of the polymers could be changed as turquoise-green by solvent change.
Synthesis of Novel crosslinked Poly(azomethine-urethane)s: Photophysical and thermal properties
(Elsevier Science Sa, 2015) Avcı, Ali; Kamacı, Musa; Kaya, İsmet; Yıldırım, Mehmet
This paper describes synthesis, photophysical, electrochemical and thermal properties of some new flexible crosslinked poly(azomethine-urethane)s. Synthesis procedure includes two main steps: The first one is the synthesis of a polyurethane prepolymer (TP) using toluene-2,4-diisocyanate and 2,4-dihydroxy benzaldehyde, and the second step is the synthesis of resulting flexible crosslinked poly(azomethineurethane) derivatives by conventional polycondensation reaction of TP with different aliphatic diamines. Diamines with various chain lengths (6-12 methylene numbers) were used to obtain various resulting polymers with different physical properties. Photophysical properties of the flexible crosslinked poly(azomethine-urethane)s were investigated using photoluminescence (PL). PL results showed that the flexible crosslinked poly(azomethine-urethane)s exhibited multicolor emission behavior. A linear relationship was observed between the excitation energies and the obtained emission maxima. This characteristic enabled adjusting the PL color at the desired scale. Thermal and morphological properties of the polymers were also investigated using TG-DTA, DSC and AFM techniques. (C) 2015 Elsevier B.V. All rights reserved.
Effect of calcination and sintering temperature on porosity and microstructure of porcelain tiles
(Walter De Gruyter Gmbh, 2022) Durgun, Ramazan; Abalı, Serkan
Porcelain tiles are prepared from kaolin, silica sand, feldspar, clay raw materials, and various additives. Ceramic powders are calcined at different temperatures after grinding, drying, and sieving. After the powders are formed and dried, they are sintered at different temperatures. Firing shrinkage (FS), water absorption (WA), and three-point flexure tests of the samples are compared. The mineralogical definitions are completed by performing a phase analysis via X-ray diffraction (XRD). After the microstructural investigations, pore-sizes and distributions are examined by the Barrett-Joyner-Halenda (BJH) method. The powder sintering process increases the crystallization of the compact material. Low porosity and high strength structures are obtained for the samples with powder calcination temperatures of 800 and 900 degrees C and a compact sintering temperature of 1200 degrees C. The pore volume increases by increasing the powder calcination temperature in samples compact-sintered at 1200 degrees C. When the powder calcination temperature of these samples is increased to 1000 degrees C, the flexural strength decreases. Therefore, the powder sintering temperature of 900 degrees C is the critical value.
Azomethine coupled fluorene-thiophene-pyrrole based copolymers: Electrochromic applications
(Elsevier Science Bv, 2013) Yıldırım, Mehmet; Kaya, İsmet; Aydın, Aysel
Two new copolymers were synthesized via the electrochemical copolymerization of 4,4'-(9H-fluorene-9,9-diyl)bis(N-(thiophen-2-ylmethylene)aniline) (FTMA) with thiophene (Th) and pyrrole (Py). According to the X-ray Photoelectron Spectroscopy (XPS) measurements, the polymers FTMA-co-Th and FTMA-co-Py possessed monomer ratios of nearly 1/5 (FTMA/Th) and 1/2 (FTMA/Py). Spectroelectrochemical investigations showed that FTMA-co-Th was a red color at low potentials and a blue color at high potentials. FTMA-co-Py was purple at low potentials and dark gray at high potentials. Spectroelectrochemical monitoring showed good absorption recoveries over repeated potential scans. As a result, FTMA-co-Th and FTMA-co-Py may be good candidates for electrochromic devices (ECDs) and could be used as coloring agents in electrochromic layers in ECDs. (C) 2013 Elsevier Ltd. All rights reserved.
Multilayer electrochromic surfaces derived from conventional conducting polymers: Optical and surface properties
(Elsevier Science Bv, 2015) Demir, Gülizar Elif; Yıldırım, Mehmet; Cengiz, Uğur; Kaya, İsmet
In this study, some kinds of multilayer (double and triple) electrochromic (EC) surfaces were prepared using layer-by-layer (LBL) electrodeposition techniques. Polypyrrole (PPy) was deposited as the first layer and the upper layers were changed. EC characteristics were investigated by spectroelectrochemical measurements. Surface roughness parameters (Root Mean Square-RMS) were determined using atomic force microscopy (AFM) technique. The results showed that different color options may be obtained by altering LBL deposition of EC polymers. Equilibrium water contact angle (circle minus(equ)(water)) measurements showed that incorporation of hydrophilic poly(3,4-ethylenedioxythiophene) PEDOT in LBL EC surfaces resulted in a decrease in the contact angle. However, the circle minus(equ)(water) of multilayer films increased with the incorporation of the hydrophobic polycarbazole (PCarb) layer. (C) 2015 Elsevier B.V. All rights reserved.
Fabrication of superhydrophobic and highly oleophobic electrochromic composite surfaces
(Elsevier Science Sa, 2016) Yıldırım, Mehmet; Demir, Gülizar Elif; Çağlar, Aysel; Cengiz, Uğur; Kaya, İsmet
Mechanically stable, superhydrophobic and highly oleophobic polymeric electrochromic (EC) composite surfaces were prepared. Firstly, an acrylate-based terpolymer with perfluoroalkyl side chains was synthesized as surface tension reducing component of the composite surfaces. Before the use, pre-synthesized terpolymer was gelled to gain higher mechanical stability. Obtained conducting gel was added into the electropolymerization media including 3,4-ethylenedioxythiophene (EDOT) or pyrrole (Py) monomers dissolved in an electrolyte solution. Electrodeposition time was varied to optimize the surface wettability characteristics. Water contact angles (WCA) and salad oil contact angles (OCA) were determined by Attension Theta Optical Tensiometer. WCA and OCA of flat surfaces were quite lower than those of the EC composite surfaces with high surface roughness caused by poly (3,4-ethylenedioxythiophene) (PEDOT) component. PEDOT and PPy components have provided not only EC properties but also surface roughness that particularly increases WCA and OCA. (C) 2016 Elsevier B.V. All rights reserved.

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