Browsing by Author "Akinay, Yuksel"

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Absorbing Properties and Structural Design of Pvb/Fe3o4 Nanocomposite
(Elsevier Science Sa, 2019) Akinay, Yuksel; Hayat, Fatih; Colak, Bektas
Recently, a wide range of studies has been carried out on microwave absorber composites for use in telecommunications, electromagnetic pollution, stealth technology, and other applications. In this study, the microwave absorption properties of polyvinyl butyral (PVB)/polyaniline (PAM) coated-Fe3O4 (COM1) and PVB/Fe3O4 (COM2) nanocomposites with single and double layer were investigated in the 1-14 GHz for different thickness (t(m)) of composites. XRD, FT-IR, TEM, and SEM were used to determine the structure properties of the composites. The Coaxial transmission line method was used to obtain permittivity (epsilon', epsilon '') and permeability (mu', mu '')parameters of the composites. The reflection loss of the single and multilayers of different thicknesses was calculated. It was figured out that the higher value of reflection loss (R-L) (-51.5 dB at 11.9 GHz) was obtained with COM2 composite. However, using PANI has provided a wider absorption range in COM1 composites. It was found that multilayer composites (COM4) provide broadband absorption compared to COM2 and double-layer design (COM3).
Al2o3/Sio2 Nanoparticles-Coated Tio2 Catalyst on the Exhaust Pollutants of a Diesel Engine
(Springer Heidelberg, 2021) Ergani, Songul Kaskun; Kocaman, Ayhan; Akinay, Yuksel
In this study, the effect of the catalytic converter (cc) coated with Al2O3/SiO2/TiO2 catalyst on the exhaust emissions of CO, NOX and HC was measured at 0, 25, 50, 75 and 100% load conditions from the diesel engine. Al2O3/SiO2-coated TiO2 powders were prepared by wet impregnation method and then coated to 32 pieces of 11 x 11 cm aluminium wire mesh plate by calcination method. The synthesised catalyst characterization was performed by XRD, EDX, SEM analyses and UV spectrophotometer. The exhaust emissions of CO, HC and NOX from the diesel engine were measured by GA-4040 gas analyser with and without a catalytic convertor. The emission results were evaluated for statistical analysis by IBM SPSS 22 Statistic Data Editor. Hence, it was seen that the modified catalytic convertor represented 43.05% reduction of NOX emission as a maximum at 75% load. Moreover, 56.84% decrease was seen in HC emissions as a maximum at 25% load. Furthermore, CO emissions reduction was measured to be 66.7% as maximum at 25% load. Consequently, the results of this experimental study showed that the catalytic converter coated with Al2O3/SiO2/TiO2 catalyst greatly reduced the exhaust emissions from the diesel engine and the synthesised catalyst can be alternative to overwhelm air pollution problem emitted from transportation.
Anchoring Modified G-C3n4 With Bi5o7br: S-Scheme Photocatalysts With Boosted Activities in Elimination of Inorganic and Organic Pollutants
(Elsevier, 2023) Jalalat, Zahra; Habibi-Yangjeh, Aziz; Hemmati-Eslamlu, Paria; Akinay, Yuksel
In this research, modified g-C3N4 with hydrogen peroxide was decorated with Bi5O7Br nanoparticles (abbreviated as g-C3N4(M)/Bi5O7Br) via a facile precipitation procedure. The s-scheme g-C3N4(M)/Bi5O7Br (20 %) nanocomposite showed superior photocatalytic ability in degradation to tetracycline (TC), as a pharmaceutical pollutant, upon visible light. The maximal removal constant was 34.3 and 6.83-folds premier than g-C3N4 and g-C3N4 (M) systems, respectively. Interestingly, the g-C3N4(M)/Bi5O7Br (20 %) nanocomposite demonstrated excellent activity in visible-light elimination of amoxicillin (AMX) (an antibiotic), methyl orange (an anionic pollutant), rhodamine B and Fuchsine (cationic pollutants), and also photoconversion of Cr (VI) into Cr (III) upon visible light, that was about 15.5, 18.9, 22.4, 21.7, and 23.2-folds preferable than that of g-C3N4, respectively. The spectrophotometric, photoluminescence, and electrochemical studies approved the production of more charges upon visible light, and promoted segregation/movement of the generated charges within the binary g-C3N4(M)/Bi5O7Br (20 %) photocatalyst. The impressive segregation of charges was assigned to developing an s-scheme structure between Bi5O7Br and g-C3N4 (M) semiconductors. Scavenging tests revealed that superoxide anion radicals, holes, and hydroxide radicals were crucial species in the reactions. Eventually, the biocompatibility of the treated solution was confirmed via the successful growth of wheat seeds. In conclusion, the s-scheme g-C3N4(M)/Bi5O7Br system can be used as a suitable sample for environmental detoxification.
Binary Ceo2-x/Ag4v2o7 Photocatalysts: Impressive Performances in Detoxification of Organic and Inorganic Pollutants
(Elsevier, 2024) Zohari Moafi, Marzieh; Habibi Yangjeh, Aziz; Habibi, Meysam; Akinay, Yuksel
Considering the sever threat of dangerous pollutants to unbalance the environment, it is necessary to develop an efficient and appropriate method to control and reduce environmental issues. We combined CeO2-x with Ag4V2O7 to fabricate binary novel CeO2-x/Ag4V2O7 photocatalysts through a facile hydrothermal route. Among the CeO2- x/Ag4V2O7 photocatalysts, the nanocomposite with 20 % of Ag4V2O7 was more effective than CeO2-x nanoparticles in detoxification of tetracycline (9.48 times), azithromycin (3.80 times), methylene blue (3.42 times), Fuchsine (3.58 times), and Cr (IV) (1.34-times) solutions under visible light. The charges segregation and transfer efficacious studies exhibited effective collaborations of CeO2-x and Ag4V2O7 nanoparticles in the successful reaching of the produced electron/hole pairs to the catalyst surface, and an s-scheme pathway was suggested for the charge segregation between CeO2-x and Ag4V2O7 nanoparticles. Moreover, the biocompatibility and reusability of the CeO2-x/Ag4V2O7 (20 %) photocatalyst were tested respectively in the growth of lentil seeds and four repeated runs.
Characterized Nano-Size Curcumin and Rosemary Oil for the Limitation Microbial Spoilage of Rainbow Trout Fillets
(Elsevier, 2020) Ceylan, Zafer; Meral, Raciye; Kose, Senol; Sengor, Gulgun; Akinay, Yuksel; Durmus, Mustafa; Ucar, Yilmaz
Curcumin and rosemary oil nanoemulsions (CUR and RON), having 184.3 nm and 158.3 nm average diameters, were successfully produced by a single sonication technique. Effectiveness of nanoemulsions against P. aeruginosa, E. coli, and S. typhimurium were tested by agar diffusion method. Total mesophilic bacteria (TMABc) growth in fish fillets treated with RON and CUR nanoemulsions was acceptable for human consumption up to the 9th day. Total psychrophilic bacteria counts (TPBc) in the fish fillets treated with RON and CUR was found to be lower (26% and 17%) than the control group samples, respectively. While TMAB growth in fish fillets treated with RON was effectively declined from 5.59 to 3.48 log CFU/g, TMAB count of the fish fillets treated with CUR was decreased from 7.42 to 6.53 log CFU/g during the analysis period. Therefore, the obtained novel nanomaterial could be effectively used to limit the rapid increase in bacterial spoilage of fish meat in the food industry.
Computation and Modeling of Microwave Absorbing Cuo/Graphene Nanocomposites
(Wiley, 2020) Akinay, Yuksel; Kizilcay, Abdullah O.
In this study, the microwave absorption properties of single- and double-layer composites were investigated for experimental and numerical solution in the 8.2 to 12.4 GHz for different thickness (t(m)) of composites. Herein, the single-layer composites (R1: CuO and R2: CuO-containing graphene nanoparticle [GNP]) and double-layer composites that composed of R1 and R2 layers were fabricated. The first double-layer composite labeled as D1 contains R1 as a matching layer and R2 as an absorbing layer and the second double-layer composite labeled as D2 contains R2 as a matching layer and R1 as an absorbing layer. D1 and D2 produced composites were also designed numerically and denoted as M1 and M2, respectively. The measured and simulated reflection loss (R-L) of double-layer composites shows similar performance, and it was observed that the microwave absorbers obtained with experimental studies can be modeled using computer design. The M2 double-layer design based on 5 mm of the matching layer and 2 mm of the absorbing layer shows a minimum R-L value of -33.7 dB at 10.06 GHz and an absorption bandwidth of about 1.13 GHz below -10 dB compared to single-layer composites.
A Critical Mini-Review on Challenge of Gaseous O3 Toward Removal of Viral Bioaerosols From Indoor Air Based on Collision Theory
(Springer Heidelberg, 2023) Kakaei, Karim; Padervand, Mohsen; Akinay, Yuksel; Dawi, Elmuez; Ashames, Akram; Saleem, Lama; Wang, Chuanyi
COVID-19, a pandemic of acute respiratory syndrome diseases, led to significant social, economic, psychological, and public health impacts. It was not only uncontrolled but caused serious problems at the outbreak time. Physical contact and airborne transmission are the main routes of transmission for bioaerosols such as SARS-CoV-2. According to the Centers for Disease Control (CDC) and World Health Organization (WHO), surfaces should be disinfected with chlorine dioxide, sodium hypochlorite, and quaternary compounds, while wearing masks, maintaining social distance, and ventilating are strongly recommended to protect against viral aerosols. Ozone generators have gained much attention for purifying public places and workplaces' atmosphere, from airborne bioaerosols, with specific reference to the COVID-19 pandemic outbreak. Despite the scientific concern, some bioaerosols, such as SARS-CoV-2, are not inactivated by ozone under its standard tolerable concentrations for human. Previous reports did not consider the ratio of surface area to volume, relative humidity, temperature, product of time in concentration, and half-life time simultaneously. Furthermore, the use of high doses of exposure can seriously threaten human health and safety since ozone is shown to have a high half-life at ambient conditions (several hours at 55% of relative humidity). Herein, making use of the reports on ozone physicochemical behavior in multiphase environments alongside the collision theory principles, we demonstrate that ozone is ineffective against a typical bioaerosol, SARS-CoV-2, at nonharmful concentrations for human beings in air. Ozone half-life and its durability in indoor air, as major concerns, are also highlighted in particular.
Cross-Linked Poly(styrene-Co Quartz and Kaolinite Proppants for Hydraulic Fracturing Applications
(Springer Heidelberg, 2025) Akkus, Ihsan Nuri; Akinay, Yuksel; Zengin, Adem; Kazici, Hilal celik
The hydraulic fracturing operation, used as a production process in shale gas and coalbed methane reservoirs in the oil and natural gas industry, consists of fracturing fluid, proppant, and many other chemicals. This study successfully produced hydraulic fracturing proppants based on quartz and kaolinite minerals using divinyl benzene cross-linked styrene polymer with an in situ suspension polymerization method. Morphological analysis of the prepared proppants confirmed their spherical structure and the sphericity of quartz and kaolinite proppants were determined as 0.9. The polymer shells of the prepared proppants showed thermal resistance up to 375 degrees C and then decomposed between 375 degrees C and 575 degrees C. As a result of mechanical tests, quartz proppants showed a crush resistance of 14.08% under a load of 18,000 psi. Similarly, a crush resistance of 14.28% for kaolinite proppants was determined under a load of 15,000 psi. The apparent densities of quartz and kaolinite proppants were determined as 1.635 g/cm3 and 1.365 g/cm3, respectively. However, quartz proppants mostly display brittle breakage behavior, while kaolinite proppants are plastically deformed under the applied load.
Cytotoxicity and Antibacterial Activity of Polyhedral Oligomeric Silsesquioxane Modified Ti3c2tx Mxene Films
(Nature Portfolio, 2025) Akinay, Yuksel; Karatas, Erkan; Ruzgar, Damla; Akbari, Ali; Baskin, Dilges; Cetin, Tayfun; Topuz, Mehmet
Bioactive antimicrobial films play important roles in various fields, such as biodegradable interfaces, tissue regeneration, and biomedical applications where preventing infection, biocompatibility, and immune rejection are important. In the present study, bioactive POSS-doped Ti3C2Tx MXene filled PLA composite film was prepared using the solution casting method for biomedical applications. The contact angle tests were investigated to reveal the usability of the thin films in biomedical applications. The angle decreased from 85.92 degrees degrees in pure PLA thin films to 72.23 degrees on POSS-doped Ti3C2Tx MXene films. The antibacterial performance, cytotoxicity and cell viability assessments of the prepared films have also been thoroughly investigated. Antibacterial tests revealed that the POSS-doped Ti3C2Tx MXene films effectively inhibited the growth of E. coli and S. aureus by 65.93% and 80.63%, respectively, within 4 h. These inhibition rates were observed as 58.32% and 54.97% for E. coli and S. aureus, respectively, after 24 h. Cytotoxicity assessments demonstrated that PMPs consistently showed higher cell viability due to the combination of POSS and Ti3C2Tx MXene. The obtained results suggest that the POSS-doped Ti3C2Tx MXene film is a promising candidate in cases where bacterial inhibition and high biocompatibility are of critical importance.
Design, Synthesis and Antimicrobial Activities of New Carbon Nanotubes Derivatives
(2021) Alma, M.hakki; Yiğit, Aybek; Akinay, Yuksel; Menges, Nurettin
Even though natural products or crops have been more common and popular in the recent, the chemicals without side-effects have been also addressed in various fields of industries due to possibility obtaining the large quantity and more bio-efficacy. In that context, many drugs have been developed for antibacterial activities but the over-uses of those relevant drugs have caused that microorganisms have adapted and evolved resistance against those drugs. Those lead to the researchers to focus on newly synthesized or functionalized molecules. In that context, nanotechnology, especially modified nanocarbon tubes (NCTs), are of the great interest of the various industries. Along with the current study, multi-walled carbon nanotubes (MWCNTs) were functionalized with three steps. Firstly, the carbon nanotube with a carboxylic acid tip on its surface was commercially purchased and then converted into acyl chloride, and later converted into a more reactive group. Then, the nucleophilic amino group such as diethylene triamine is bonded onto the carbon nanotube. Finally, after the carbon nanotube material with amine groups was functionalized with boric acid, carbon nanotube molecules carrying boric acid molecules were synthesized. Following modification and functionalization of MWCNTs, the newly synthesized molecules were characterized using FT-IR, SEM, TEM and XPS. After chemical characterization, the relevant molecules were screened for their anti-bacterial activities in comparison to those of well-known antibiotics. For anti-bacterial assays, molecules were tested against K. pneumoniae, E. coli, P.aeruginosa, S. aureus and B. subtilis. Concerning the findings of the antibacterial assays, concentrations of 40 and 80 μg /mL exhibited a range of activities but in parallel with those of standard antibiotics whereas the lower concentration, viz. 5, 10 and 20 μg / mL did not exhibit any activities. The highest activity was noted for 80 μg / mL, in comparison to those of antibiotics and other concentrations, against B. subtilis, with a 23 mm inhibition zone.
An Efficient Supported Cu(I) Catalyst for the Amination of Aryl Halides With Sodium Azide
(Wiley-v C H verlag Gmbh, 2024) Fekri, Somayeh; Mansoori, Yagoub; Akinay, Yuksel; Cetin, Tayfun; John, Michael
We present the synthesis and characterization of a new Cu(I) complex supported on SBA-15 as a catalyst for preparing anilines from the reaction of aryl halides with sodium azide. The SBA-15 support was modified by treating it sequentially with (3-aminopropyl) triethoxysilane (APTES), cyanuric chloride, and 2-aminothiazole (AT). The modified mesoporous silica, SBA-15@BAT, was then treated with a CuI solution in acetonitrile to give SBA-15@BAT-Cu(I). The catalyst underwent thorough characterization using conventional methods. X-Ray photoelectron spectroscopy (XPS) analysis corroborated the presence of copper in the +1 oxidation state in the catalyst. The supported Cu(I) complex sufficiently catalyzed the amination reaction of iodo-, bromo-, and chloroarenes with NaN3. The catalyst was centrifuged, washed, and applied in the subsequent run. We investigated the effects of various reaction components and parameters to determine the optimal conditions for the reaction. The heterogeneous catalyst exhibited noticeable stability and was reused over seven runs with slight deactivation. Supporting and characterization of a new Cu(I) catalyst catalyst based on 2-aminothiazole-Cu(I) on SBA-15. Optimization of the reaction conditions for the supported catalyst in the amination of haloarens with sodium azide. Preparation of a wide range of anilines from chloro-, bromo-, and iodoarens. image
The Electromagnetic Wave Absorption Properties of Woven Glass Fiber Composites Filled With Sb2o3 and Sno2 Nanoparticles Doped Mica Pigments
(Wiley, 2022) Akinay, Yuksel; Colak, Bektas; Turan, Muhammet Emre; Akkus, Ihsan Nuri; Kazici, Hilal Celik; Kizilcay, Abdullah Oguz
In this study, the electromagnetic wave absorption properties of woven glass fiber reinforced epoxy composites with Sb2O3 and SnO2 nanoparticles doped mica pigments were investigated. Herein, we synthesized SnO2/mica, Sb2O3/mica, and Sb2O3:SnO2/mica pigments using the sol-gel method. Subsequently, mica pigments filled glass fiber/epoxy composite panels were fabricated with a vacuum assisted resin mold. The phase, crystal, and morphological examinations of particles confirm the deposition of SnO2 and Sb2O3 nanoparticles on the mica surfaces. The electromagnetic wave absorption properties of samples were measured using the S parameters and obtained dielectric data. Sb2O3:SnO2/mica particles display higher complex permittivity and dielectric loss values due to the strong interfacial polarization between conductive nano metal-oxide shells and mica surfaces. According to the calculated reflection loss values, Sb2O3:SnO2/mica particles exhibit superior electromagnetic wave absorption performance with a minimum reflection loss of -25.62 dB for 2.4 mm thicknesses with effective bandwidth between 9.3 and 12.4 GHz. The S parameters of the prepared structural composites with the size of 30 cm x 30 cm x 3 mm was determined by the free-space technique using the transmission line technique. According to the S-12 parameters, filled glass fiber/epoxy composite containing 25 wt% Sb2O3:SnO2/mica show a minimum reflection loss of -20.426 dB at 8.2 GHz with effective bandwidth between 8.2 and 9.67 GHz. These results indicate that Sb2O3:SnO2/mica-filled fiber/epoxy composite is an excellent candidate for the practical application of electromagnetic wave absorbers.
Enhancement of Biogas Production Using Sno2 Nanoparticle-Doped Mica Catalyst
(Springer Heidelberg, 2023) Kaskun, Songul; Calhan, Rahman; Akinay, Yuksel
Different additives are used to enhance the microbial activity and ensure the suitable environment for anaerobic microorganisms in anaerobic digestion (AD) process. This study aims to investigate biogas production activity by adding mica particles (MP) and SnO2 nanoparticles (NPs)-doped mica (MSnO2) preparing by co-precipitation. The morphological and structural investigations of particles prove that the SnO2 NPs have been successfully embedded on mica surface. The deposition of SnO2 on the mica surfaces contributes the catalytic performance which in turn improves biogas production. The concentration of MP and MSnO2 was adjusted to be 0.03 mg/L and 0.06 mg/L for the biogas production experiment. In batch experiments, the highest biogas production, biogas yield, and methane yield were obtained at MSnO2-1 (0.03 mg/L) with 6890.2 mL, 245.4 ml/gVS, and 162.3 mL CH4/gVS, respectively. The addition of 0.03 mg/L MSnO2 increased biogas yield by 18.1% and methane yield by 33%, in the light of the data acquired from this experimental study that MSnO2 and pristine mica can be used effectively to enhance biogas production from cattle manure (CM).
Equivalent Analytical Model of Plain Weave Composite Fabric for Electromagnetic Shielding Applications
(Taylor & Francis inc, 2020) Kizilcay, Abdullah Oguz; Akinay, Yuksel
In this paper, the electromagnetic shielding effectiveness results of the plain weave composite fabric and the analytical solution of metal mesh were investigated. The composite fabric made of cotton yarns twisted with 50 mu m copper filaments was used in the experiment. As the fabric was weaved and stretched, it had square shaped apertures which had length of 1.2 mm. The electromagnetic shielding effectiveness of these fabrics was measured in the frequency range of 1.7-2.6 GHz via WR430 waveguide system. In order to model the shielding results of the aforementioned fabric, an analytical solution which facilitates to calculate shielding effectiveness of metal mesh, was taken into consideration. Due to the physical similarity between the fabric geometry and metal mesh structure, the values of fabric characteristics were substituted in analytical solution. A statistical approach showed that the measured SE results of plain weave composite fabric fitted in the analytical solution for metal mesh in 1.82-2.6 GHz frequency range with strength of 30-36 dB. Thus, depending on desired shielding efficiency the physical texture of shielding fabric can be determined analytically.
Experimental Investigation of the Effects of Aging and Cryogenic Treatments on the Mechanical Properties of Superelastic Nickel-Titanium Shape-Memory Alloys
(Sage Publications Ltd, 2022) Guven, Sedat; Altin Karatas, Meltem; Gokkaya, Hasan; Akinay, Yuksel
In this study, electropolishing and two different heat treatments were applied to wires made of superelastic nickel-titanium (NiTi) shape-memory alloy (SMA) and their mechanical properties and stress-induced deformations were investigated. In experimental studies, cryogenic and aging heat treatments were applied to NiTi SMA wire samples and tensile test experiments were carried out to determine the effect of the heat treatments on their mechanical properties. Following the tensile test experiments conducted at room temperature (23 degrees C), the study investigated changes in the elemental composition, fracture modes, micro cracks, and phase structures and in the mechanical properties formed in the fracture region. Intermetallic phase structures (Ti2Ni, Ni3Ti, and Ni4Ti3) were observed in the X-ray diffraction (XRD) analyses. It was concluded that the aging heat treatment had directly affected the reduction in hardness. In particular, in samples without the aging heat treatment, a stress-induced decrease in the Ni and Ti ratios and an increase in the carbon (C) ratio were observed in the chemical composition of the fracture surface of the superelastic NiTi SMA wires. It was determined that the changes in the chemical composition caused by stress had affected the mechanical properties negatively. In the fractography of the NiTi SMA wires, the samples exhibited mostly ductile fracture behavior with small dimples.
Facile Synthesis of Zno/Ceo2 Photocatalysts Sensitive To Visible Light With Tandem N-N Heterojunctions and Improved Performance Towards Tetracycline and Dye Effluent Removals
(Elsevier Science Sa, 2024) Andish-Lifshagerd, Fatemeh; Habibi-Yangjeh, Aziz; Habibi, Meysam; Akinay, Yuksel
Nowadays, ZnO-based photocatalysts are very effective in wastewater treatment. Herein, CeO2 and CeFeO3 nanoparticles were anchored on ZnO through a coprecipitation-calcination procedure. The fabricated materials were studied by TEM, EDX, SEM, XRD, HRTEM, XPS, PL, UV-vis DRS, BET, BJH, FTIR, and EIS analyses. The optimized ZnO/CeO2/CeFeO3 nanocomposite showed significant performance for the degradation of tetracycline hydrochloride, amoxicillin, Congo red, and Fuchsine with rate constants of 313 x 10-4 , 104 x 10-4 , 204 x 10-4 , and 163 x 10-4 min-1 , which was 24.1, 1.44, 20.4, and 2.03 times higher than ZnO, respectively. Moreover, the reduction of Cr(VI) to Cr(III) (189 x 10-4 min-1) over the ZnO/CeO2/CeFeO3 photocatalyst was almost 2.12 times faster than the ZnO photocatalyst (88.7 x 10-4 min-1). Besides, the photocatalyst presented remarkable stability after four cycles in the photodegradation of tetracycline hydrochloride contaminant. The purified solution over the photocatalyst was also tested in terms of biocompatibility. The optical, electrochemical, and textural analyses attributed the enhanced activity to the effective production and separation of charge carriers, facile transfer of electron/hole pairs, and promoted textural characteristics. The enhanced charge segregation was ascribed to the developing tandem n-n heterojunctions among ZnO, CeO2 , and CeFeO3.
Finite Element Simulation and Experimental Investigation on the Effect of Temperature on Pseudoelastic Behavior of Perforated Ni-Ti Shape Memory Alloy Strips
(Iop Publishing Ltd, 2022) Altas, Emre; Khosravi, Farshid; Gokkaya, Hasan; Arab Maleki, Vahid; Akinay, Yuksel; Ozdemir, Okan; Kandas, Halis
In the present study, the temperature-dependent pseudoelastic behavior of shape memory alloy (SMA) sheets is studied experimentally and by finite element (FE) modeling. For this purpose, temperature-dependent mechanical properties for Ni-Ti alloy materials are first obtained by using direct tensile and three-point bending experiments at 23 degrees C, 50 degrees C, and 80 degrees C temperatures, respectively. The structure of these materials is examined at different temperatures using SEM images and the XRD test. Furthermore, using the FE model, the pseudoelastic behavior and the effect of temperature on the residual deflection of the prose-shape memory strips with a circular hole under three-point bending loads are studied. After validating the results of the FE model with the results of experimental tests, the effects of various parameters such as the diameter and number of holes on residual deformation and residual strains are investigated. The results show that with increasing temperature, the mechanical properties including the tensile strength, Young's modulus, yield stress, and flexural strength of SMA strips increase significantly. For solid strips, although increasing the temperature increases the maximum flexural force, in contrast, it reduces the flexural stiffness. In solid strips, flexural stiffness decreases by 5.5% with increasing temperature from 23 degrees C to 80 degrees C.
Improved Hydrogen Adsorption of Zno Doped Multi-Walled Carbon Nanotubes
(Pergamon-elsevier Science Ltd, 2020) Kaskun, Songul; Akinay, Yuksel; Kayfeci, Muhammet
Hydrogen storage is still one of the most important problems to improve hydrogen energy usage widespread. New materials capable of storing hydrogen with high efficiency must be introduced to overcome this problem. In recent years, addition of metals or inorganic compounds to multiwalled carbon nanotubes (MWCNTs) has been generally used for hydrogen uptake studies to enhance adsorption property of the nanotubes. In this study, Zinc oxide (ZnO) nanoparticles doped MWCNTs (ZnO-MWCNTs) have been produced as new reversible hydrogen storage materials, and we have investigated characterization of ZnO-MWCNTs by XRD, SEM, TGA, TEM and BET analyses. The functionalized MWCNTs and ZnO doped MWCNTs were subjected to hydrogenation step by dynamic gas sorption analyser under pressure of 5-50 bar. The hydrogen uptake capacities of the materials under different pressures were measured gravimetrically. It was indicated that by controlling the pressures for hydrogenation of ZnO-MWCNTs induces the spillover of ZnO nanoparticles in the layer of MWCNTs which in return with high hydrogen adsorption capacity. Consequently, the hydrogen adsorption of the functionalized MWCNTs (fMWCNTs) and the ZnO-MWCNTs were achieved to be 1.05 wt% and 2.7091 wt% under pressure of 50 bar as maximum. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
The Influence of Mwcnts on Microwave Absorption Properties of Co/C and Ba-Hexaferrite Hybrid Nanocomposites
(Elsevier Science Sa, 2020) Li Peibo; Sun Yize; Akinay, Yuksel
The microwave absorber composites as the combinations of MWCNTs, Ba-hexaferrite and Co/C particles were prepared. For Co/C synthesis, firstly, the Co-based MOF (ZIF-67) was synthesized through the solvothermal method and secondly, the ZIF-67calcined at 500 degrees C to obtain Co/C particles. In addition, the BaCoTiFe10O19 powder was synthesized via the hydrothermal method. The structural and morphological analysis were carried out by X-ray diffractometer (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The permeability and permittivity values of composites were investigated in the range of X band frequency (8.2-12.4 GHz). The electromagnetic (EM) wave absorption performance of composites was evaluated by using values of the permeability and permittivity values. It was demonstrated that the EM absorption performance of composites was enhanced by the loading MWCNTs. The combination of MWCNT with Ba-M and Co/C increased the magnetic and dielectric losses due to the enhance in both polarization and surface area. The minimum reflection loss (R-L) of CBM.70.29.1 reached -34 dB with effective bandwidth (< -10 dB) in the range of X band frequency for matching thicknesses of 3.1 mm.
Microstructure and Chemical Analysis in Pseudoexfoliation Syndrome
(Taylor & Francis inc, 2021) Yavuzer, Kamil; Akinay, Yuksel
Purpose: The aim of this study is to show the pseudoexfoliation syndrome (PES) material accumulated in the lens anterior capsule and the trace elements directly with using scanning electron microscopy (SEM) and to investigate the effect of PES materials on aqueous humor by chemical analyses. Methods: The study groups consisted of 30 patients with PES and 30 patients without PES. 0.1-0.3 mL of aqueous humor was aspirated from anterior chamber and anterior capsule sample was obtained by applying continuous curvilinear capsulorhexis. The level of selected elements (Zn, Cu, Se, Fe, Si, Al, Ca, K) were determined from aqueous humor samples via Inductively coupled plasma - optical emission spectrometry (ICP-OES) machine. The morphology and elemental distribution of anterior lens capsules were carried out via a Zeiss Sigma 300 scanning electron microscope with energy dispersive X-ray spectroscopy (semiquantitative EDX). Results: For aqueous humor, the ICP-OES results show that Cu and Zn levels is higher (p <.001, both of them) in PES group than that the obtained from control group. It was noticed that the ratio of Cu/Zn was higher (p =.008) in aqueous humor, while Cu/Se ratio was higher in both aqueous humor (p <.001) and anterior capsule (p <.001) for PES group. The SEM images show that different metal precipitates were obtained from anterior lens capsules with PES. However, there is no obvious element precipitates on the anterior lens capsules without PES. Conclusion: The results observed that the level of selected elements can be obtained at different level in both PES group and control group. Especially, if the oxidative behavior of these elements which is thought to play a role in PES formation can be clarified, new approaches will be done to evaluate the structure of PES.