Malzeme Bilimi ve Mühendisliği Bölümü Koleksiyonu

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

Listeleniyor 1 - 20 / 41

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.
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 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.
Superhydrophobic-electrochromic PEDOT/PFHP bilayer surfaces
(Elsevier Science Sa, 2016) Çağlar, Aysel; Yıldırım, Mehmet; Cengiz, Uğur; Kaya, İsmet
Firstly, highly soluble perfluorohexyl substituted pyrrole polymer (PFHP) was synthesized by one-step reaction and characterized using spectral characterization techniques. Monolayer PFHP films were deposited on ITO-glass plates by dip and spin-coating techniques using the THF and DCM solutions. Bilayer PEDOT/PFHP films were prepared in two steps: 1) Electrochemical deposition of PEDOT layer on ITO-glass surface, 2) PFHP top layer coating on PEDOT layer by dip and spin-coating techniques. Experimental conditions in coatings were varied to optimize the surface properties like hydrophobicity. SEM-EDX analyses were carried out to determine the surface characteristics. Water and oil contact angles (WCA and OCA) were measured by Attention Theta contact angle meter. Deposition of PFHP solutions on ITO-glasses formed relatively flat surfaces having low WCA and OCA. Bilayer PEDOT/PFHP had highly porous surfaces and increased WCA values up to >170 degrees. The films prepared from DCM solutions had higher WCA values due to the formation of surface morphology. Electrochromic properties of superhydrophobic bilayer PEDOT/PFHPwere also examined by spectroelectrochemical analysis. 20-25% of transmittance changes were obtained at two different absorption bands between the neutral and doped states. (C) 2016 Elsevier B.V. All rights reserved.
Değişik odun artıklarından bakalit üretimi
(1999) Alma, Hakkı; As, Nusret; Ergenoğlu, Fuat; Kaya, İsmet
Bu projemizde, Ülkemize özgü birkaç iğne yapraklı (sarıçam (Pinus sylvestris L), kızılcam (Pinus brutia Henry), Toros sediri (Cedrus libani Richard)), çeşitli Yapraklı ağaç (Anadolu kestanesi (Cesfanea sativa Mill.), yalancı akasya (Robinia pseudoacacia L), okaliptüs (Eucalyptus camaldulensis Dehn.), aylantus (Ailanthus altisimma (Mill.)) ve orman gülü (Rhododendron ponticum) gibi ağaççık türlerine ait odunların diri kısımlarının öğüntüleri (20-80 mesh) 160°C'de 1 saat süreyle sülfürik asit kullanılarak başarılı bir şekilde fenol ile reaksiyona sokulmuşlardır. Bu şekilde fenollendirilmiş odun artıklarının fenolleştirmenin tipik parametrelerinden olan fenolleştirme sonucunda metanol içerisinde çözünmeden geriye kalan artık odun ve odun bileşikleri ile reaksiyona giren fenol miktarlarına bakılmıştır. Ayrıca, elde edilen bakalit gibi termoset materyallerin mekanik ve biyolojik bozunma özellikleri incelenmiştir. Elde edilen sonuçlar, bu çalışmada kullanılan söz konusu ağaç türlerine ait odunların birbirlerine çok yakın fenolleştirme parametre değerlerini verdikleri görülmüştür. Fenollendirilmiş değişik odun örnekleri ve bu örneklerden elde edilen termoset rijit materyallerinin sırasıyla termal bozunma ve mekanik özellikler bakımından birbirlerine yakın değerlere sahip oldukları saptanmıştır. Diğer taraftan, fenollendirilmiş odun örneklerinin termal ağırlık kayıplarının sentetik novalak reçinesininkinden daha az olduğu ve bu örneklerden yapılan termoset materyallerin mekanik özelliklerinin sentetik novalak reçinesinden yapılmış olanlarınki ile hemen hemen aynı oldukları saptanmıştır.
Schiff bazı sübstitüentli oligofenollerin sentezi ve karakterizasyonu
(2003) Kaya, İsmet; Şenol Bahçeci, Dilek; Koyuncu, Sermet; Özdemir, Eyüp
Bu çalışmada, 2-aminofenol, 3-aminofenol, 4-aminofenol ile benzaldehit'in reaksiyonundan Schiff bazları elde edildi. Daha sonra oligo fenollerle NaOCl, $H_2O_$2 ve hava oksijenin oksidatif polikondenzasyon reaksiyon şartlan ve onların ürünleri incelendi. Schiff bazı sübstitüentli oligo fenoller alkali ortamda 50-100°C arasında 2-aminofenol, 3-aminofenol, 4-aminofenol ile benzaldehit'in oksidadif polikondenzasyonundan sentezlendi. Sentezlenmiş ürünlerin yapıları element analizi, FT-IR, $^1H-NMR$, $^{13}C-NMR$ ve UV-Vis spektrumlarındaki verilerinden faydalanarak belirlendi. O-2-HFBA-I, O-2-HFBA-II, O-3-HFBA ve O-4-HFBA'mn büyüklükçe ayırma kromatografısi analizleri (SEÇ) göre, sayıca ortalama molekül ağırlığı $(M_n)$, ağırlıkça ortalama molekül ağırlığı $(M_w)$ ve polidispersiti indeksi (PDI) değerleri sırasıyla 2166 g $mol^{-1}$, 2591 g $mol^{-1}$, 1,196; 1736 g $mol^{-1}$, 2509 g $mol^{-1}$, 1,445; 2372 g $mol^{-1}$, 4722 g $mol^{-1}$, 1,990 ve 2155 g $mol^{-1}$, 4164 g $mol^{-1}$ ve 1,737 olarak bulundu. Ayrıca, DTA ve TG analizleri oligo-2-hidroksifenilbenzaldimin (O-2-HPBA),oligo-3-hidroksifenilbenzaldimin (O-3-HPBA) ve oligo-4-hidroksifenilbenzaldimin (O-4-HPBA) thermo-oksidatif bozunmaya karşı kararlı olduklarını gösterdi. O-2-HPBA. O-3-HPBA ve O-4-HPBA'nın 1000°C'deki kütle kayıpları sırasıyla %93,63, %59,46 ve %95,87 olarak bulundu. Buna ilaveten, epoksi-oligomer blend karışımlarının termal özellikleri incelendi. Epoksi-oligomer blend karışımının 1000°C'deki kütle kaybı %55 olarak bulundu.
Süper yağ itici, elektrokromik yüzey malzemelerinin sentez ve karakterizasyonu
(2016) Yıldırım, Mehmet; Cengiz, Uğur; Demir, Gülizar Elif; Çağlar, Aysel; Kaya, İsmet
Proje Grubu : KBAG Sayfa Sayısı : 107 Proje No : 113Z246 Proje Bitiş Tarihi : 15.02.2016
Significantly improved shear, dynamic-mechanical, and mode II fracture performance of seawater aged basalt/epoxy composites: The impact of halloysite nanotube reinforcement
(Elsevier B.V., 2021) Ulus, Hasan; Kaybal, Halil Burak; Eskizeybek, Volkan; Avcı, Ahmet
The primary concern of fiber-reinforced polymers (FRPs) subjected to seawater environment is losing their initial mechanical performance since water can diffuse into the composite and deteriorates the fiber-matrix interface. Recent studies related to aging performance in the seawater environment have shown that introducing halloysite nanotubes (HNTs) into the polymer matrix offers a combination of an efficient barrier effect and an improved fiber-matrix interface. Hereupon, the principal objective of this study was to experimentally investigate the impact of HNTs on shear and mode II fracture performances of the seawater aged basalt fiber (BF) reinforced epoxy (EP) composites. After six months of aging in seawater, the findings indicated that HNTs reinforced multi-scale composites exhibited 34 and 46% higher shear strength and mode II delamination toughness compared to the neat specimens. Moreover, according to the dynamic-mechanical analysis, higher glass transition temperatures (8%) were obtained for the multi-scale composites. The reduction in mechanical performances induced by fiber-matrix interfacial degradation was also confirmed by scanning electron microscopy analysis. Chemical deterioration of the polymer matrix was explored by Raman spectroscopy to reveal the efficiency of HNTs induced barrier effect. As a result of these investigations, HNT modified BF/EP multi-scale composites were offered for future advanced engineering applications.
An experimental study on low velocity impact performance of bolted composite joints-part 2: Influence of long-term seawater aging
(Elsevier Ltd, 2021) Kaybal, Halil Burak; Ulus, Hasan; Eskizeybek, Volkan; Avcı, Ahmet
In the first part of this two-part paper (Part 1), the low-velocity impact (LVI) response of bolted fiber-reinforced polymer joints was investigated considering with two scenarios based on the localized impact damage as the impactor hit on the top of the bolt (ToB) and the side of the washer (SoW). Moreover, the influence of halloysite nanotubes (HNTs) reinforcement of the epoxy matrix on the impact performance was also evaluated. As the second part of the research, this paper represents the effects of seawater aging on the LVI response of FRPs. For this, the composite joints were submerged in an artificial seawater environment for six months to accelerate aging. Afterward, as following the systematic experimental path exhibited in Part 1, LVI tests were conducted by dropping the impactor on ToB and SoW regions. The test results showed that the seawater aging impaired almost 30% of the composite joints' impact resistance, where HNTs reinforced multi-scale composite joints exhibited a 13% higher impact loading performance. The ToB impact scenario was considered as visually and quantitatively more detrimental than the SoW tests. The detrimental impact of seawater aging was validated by tracking the elemental evolution in the seawater environment. Based on the mechanical, morphological, and structural analyses, a novel damage mechanism was introduced to address seawater aging's progress, including the role of nanoreinforcements.
An experimental study on low velocity impact performance of bolted composite joints part 1: Influence of halloysite nanotubes on dynamic loading response
(Elsevier Ltd, 2021) Kaybal, Halil Burak; Ulus, Hasan; Eskizeybek, Volkan; Avcı, Ahmet
Mechanical joints are a widely utilized to assembly fiber reinforced polymer composites in marine applications. Impact is one of the most encountered unpredictable loading types which significantly diminishes the mechanical properties of structures. The goal of this study is to investigate the dynamic loading response of bolted basalt-epoxy composite laminates under different impact energies. Unlike the existing low velocity impact tests of bolted composite joints, to reveal the effect of localized impact damage, the low-velocity impact tests were conducted on two different regions as the top of bolt (ToB) and the side of washer (SoW). In addition, the effects of HNTs reinforcement on the impact response and the damage propagation were also evaluated. It was obtained that ToB damage was comparatively severe for the composite joints due to the propagation of the damage through the hole center. Moreover, HNTs improved the impact resistance about %15, especially at lower impact energies. However, the nanoreinforcement efficiency diminished with increasing impact energy levels. The obtained results were further supported with macro-size images and scanning electron microscopy (SEM). Together with Part II, this study reports an extensive work of impact tests of bolted composite joints utilized in the marine industry.
GaN/ZnO hybrid nanostructures for improved photocatalytic performance: One-step synthesis
(TUBITAK, 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.

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