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Öğe Absorbing properties and structural design of PVB/Fe3O4 nanocomposite(Elsevier Science Sa, 2019) Akinay, Yuksel; Hayat, Fatih; Colak, BektasRecently, 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).Öğe Al2O3/SiO2 nanoparticles-coated TiO2 catalyst on the exhaust pollutants of a diesel engine(Springer Heidelberg, 2021) Ergani, Songul Kaskun; Kocaman, Ayhan; Akinay, YukselIn 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.Öğe Comparison of microwave absorption properties between BaTiO3/Epoxy and NiFe2O4/Epoxy composites(Wiley, 2018) Akinay, Yuksel; Hayat, Fatih; Kanbur, Yasin; Gokkaya, Hasan; Polat, SafaMicrowave absorption properties of Epoxy/Nickel Ferrite (NiFe2O4) and Epoxy/Barium Titanate (BaTiO3) composites were investigated and compared in the 1-14 GHz. Epoxy/filler particles (NiFe2O4 and BaTiO3) composites were prepared with 85/15 mixture ratios via Ultrasonic Probe Sonicator method in solution. The complex permittivity (e '-e '') and permeability (mu '-mu '') of the composites have been measured at different microwave frequencies in 1-14 GHz via vector network analyzer (Keysight N9926A). The reflection loss (R-L) of composites was calculated and evaluated from camplex permitivity and permeability. The obtained results show that both composites exhibit the large R-L and broadband within the frequency range from 1 to 14 GHz for different thickness. Epoxy/BaTiO3 showed a better microwave absorption at the range of 6-7.2 GHz for 7 and 6 mm, at the range of 7.4-9.1 GHz for 5 mm. However, the Epoxy/NiFe2O4 exhibits the largest R-L and the widest bandwidth than those obtained from Epoxy/BaTiO3 composite. POLYM. COMPOS., 39:E2143-E2148, 2018. (c) 2017 Society of Plastics EngineersÖğe Effect of Ni on the mechanical behavior of a high-Mn austenitic TWIP steel(Carl Hanser Verlag, 2016) Akinay, Yuksel; Hayat, FatihThe effect of Ni on the mechanical properties and microstructure of twinning induced plasticity (TWIP) steels were investigated in this study. TWIP 1 (0.6 C, 24 Mn) and TWIP 2 (0.6 C, 24 Mn, 1 Ni) steels were fabricated and annealed at 700, 800 and 900 degrees C for 150 minutes and then air-cooled. The results revealed that the Ni containing steel (TWIP 2) exhibits a higher yield strength and tensile strength than the steel TWIP 1. Carbide precipitations have been detected in the microstructure of TWIP 1 and TWIP 2 specimens annealed at 700 degrees C. However, the microstructure of the steel TWIP 1 annealed at 800 and 900 degrees C was fully austenitic and some grains included twins. It turned out that with the addition of Ni, the formation of twinning decreased in consequence of the annealing at 800 and 900 degrees C.Öğe 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 OguzIn 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.Öğe Enhancement of biogas production using SnO2 nanoparticle-doped mica catalyst(Springer Heidelberg, 2023) Kaskun, Songul; Calhan, Rahman; Akinay, YukselDifferent 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).Öğe 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, YukselIn 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.Öğe 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; Bayraktar, OmerIn 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.Öğe Improved hydrogen adsorption of ZnO doped multi-walled carbon nanotubes(Pergamon-Elsevier Science Ltd, 2020) Kaskun, Songul; Akinay, Yuksel; Kayfeci, MuhammetHydrogen 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.Öğe Investigation of resistance spot welds between DP450 steel and aluminum alloys(Walter De Gruyter Gmbh, 2016) Akinay, Yuksel; Hayat, FatihIn this study, the resistance spot weldability of DP450 steel and aluminum alloys (AA1050, AA6061 and AA7075) was investigated and the interfacial characteristics of fracture zones was examined via microanalysis, scanning electron microscopy and energy dispersive spectroscopy (EDX). In addition, tensile shear load tests and hardness tests were performed to determine the mechanical properties and fracture behavior of welded joints. These results suggest that the tensile shear strength of the DP450/AA1050 and DP450/AA7075 joints was not affected by the reaction layer formed at the welding interface. This indicates that the spot weldability of DP450/AA6061 is better than DP450/AA1050 and DP450/AA7075 Al alloys.Öğe Magnetic and microwave absorption properties of PVB/Fe3O4 and PVB/NiFe2O4 composites(Wiley, 2018) Akinay, Yuksel; Hayat, Fatih; Cakir, Mustafa; Akin, EmreElectromagnetic and microwave absorbing properties of Polyvinylbutyral (PVB)/Fe3O4 and PVB/NiFe2O4 composites were investigated in the 1-14 GHz. PVB/filler particles (Fe3O4 and NiFe2O4) composites were prepared with 90/10 mixture ratios via Ultrasonic Probe Sonicator method in solution. The complex permittivity (epsilon-j epsilon) and permeability (- j) of the composites have been measured at different microwave frequencies in 1-14 GHz employing vector network analyzer (Keysight N9926A). The reflection loss (R-L) of composites was calculated and evaluated using theory of the absorbing wall. It was found that, both composites exhibit the large reflection loss and broadband within the frequency range from 1 to 14 GHz for 3, 5, and 7 mm. However, the R-L results show that, when the thickness is 7 mm, the minimum R-L was found to be -22.9 dB (99% power absorption) at the frequency of 13.93 GHz. The Fe3O4/PVB and NiFe2O4/PVB composites have potential application for microwave and radar absorptions. POLYM. COMPOS., 39:3418-3423, 2018. (c) 2017 Society of Plastics EngineersÖğe Mechanical Properties of Pattern Welded 1075-15N20 Steels(Carl Hanser Verlag, 2014) Ozkan, Furkan; Kirdan, Hakan; Kara, Ismail Hakki; Husem, Fazil; Ozcelik, Sait; Akinay, Yuksel; Cug, HarunForged welded (damascus) steels are produced by traditional methods and mostly used in the design of decorative tools. These steels are well-known for their good mechanical properties. The process for making forged welded (damascus) steel consists of stacking alternating sheets of different kinds of steel on top of each other and then forge welding them together. In this study, the steels 1075 and 15N20 were used for the forging and folding procedure. The effect of fold numbers on the microstructure and mechanical behavior were investigated. The steel consisted of both materials, 54 and 250 layers, respectively, produced by forge welding. The pattern layers are homogeneous and regular, but after the process sections with up to 54 pattern layers were irregular. Steel 1075 has a pearlitic microstructure, while steel 15N20 has a ferritic microstructure. The impact toughness and tensile strength of the folded steels improved with increasing the number of folds.Öğe Surface Integrity of NiTi Shape Memory Alloy in Milling with Cryogenic Heat Treated Cutting Tools under Different Cutting Conditions(Springer, 2021) Altas, Emre; Altin Karatas, Meltem; Gokkaya, Hasan; Akinay, YukselIn this study, the surface integrity of nickel-titanium (NiTi) shape memory alloys (SMAs) was investigated after face milling processes with cryogenically treated/untreated cemented carbide cutting tools at the conditions of dry cutting and minimum quantity lubrication (MQL) of cutting fluids depending on the changing cutting parameters. The integrity of surface layer of the workpiece material was evaluated according to the mean surface roughness, microstructure and hardness, as well as according to the resultant cutting force and flank wear of inserts. Cutting tests were carried out at three different cutting speeds (20, 35 and 50 m/min), feed rates (0.03, 0.07 and 0.14 mm/tooth) and a constant axial cutting depth (0.7 mm). The influence of these parameters on the surface integrity was extensively investigated. The face milling tests of NiTi SMA at optimal cutting parameters show that the surface integrity enhanced at a cutting speed of 50 m/min and feed rate of 0.03 mm/tooth using boron-added cutting fluid (EG + %5BX) with deep cryogenic heat treated (- 196 degrees C) CVD coated S40T grade cutting tool. Under MQL conditions, the minimum mean surface roughness (0.278 mu m), resultant cutting force (268.2 N) and flank wear (0.18 mm) were obtained due to the high thermal conductivity and lubrication property of EG + %5BX cutting fluid. The highest hardness values (343 HV) were measured at the zone subjected to the highest deformation, while the lowest one (316 HV) was measured at the zone at the least deformation.Öğe Synthesis and microwave absorption enhancement of BaTiO3 nanoparticle/polyvinylbutyral composites(Sage Publications Ltd, 2019) Akinay, Yuksel; Hayat, FatihBarium titanate (BaTiO3)-polyvinyl butyral (PVB) composites at various weight concentrations were prepared via ultrasonic probe sonicator. The sonication was carried out at 20 kHz and 70% amplitude for about 2 h and BaTiO3 nanoparticles were dispersed well in the mixture of PVB/ethanol under probe sonication. As a microwave absorbent, the microwave absorbing properties of the BaTiO3 nanoparticle-PVB composites with different mixture ratios of 5 wt.% (RAM1), 10 wt.% (RAM2) and 15 wt.% (RAM3) BaTiO3 were investigated based on transmission line theory in the frequency range from 1 GHz to 14 GHz. The minimum reflection loss (R-L) of the RAM1 reaches -3.47 dB at 5.57 GHz with a matching thickness of only 7.0 mm. For RAM2 with 4 mm and 4.2 mm thickness (t(m)), the R-L values are less than -10 dB obtained in the frequency 10.3-13.4 GHz. The RAM3 composite with 15 wt.% BaTiO3 mixture ratio shows a minimum reflection loss of -43.8 dB at 11.01 GHz with a -15 dB bandwidth over the extended frequency range of 10.2-13.2 GHz for a thickness of 2.8 mm and -44.2 dB at 4.77 GHz for a thickness of 6.5 mm.Öğe Wear resistance and tribological properties of GNPs and MWCNT reinforced AlSi18CuNiMg alloys produced by stir casting(Elsevier Sci Ltd, 2021) Turan, Muhammet Emre; Aydin, Fatih; Sun, Yavuz; Zengin, Huseyin; Akinay, YukselThe present work aims to produce Multiwalled Carbon Nanotube (MWCNT) and Graphene Nanoplatelets (GNPs) reinforced AlSiCuNiMg alloy matrix composites via stir casting. The wear resistance and tribological performances of produced materials are examined by steel balls in dry sliding conditions under loads of 10 N, 20 N, and 40 N. The composites were produced by the combination of semi powder metallurgy and stir casting techniques and then a solid-solution + aging process was applied. The microstructures and phase-type of all specimens were examined by Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). The results of this study show that the wear rates of the matrix decreased significantly with the addition of GNPs and MWCNTs reinforcements. When sliding speed increased, wear rates for all produced samples decrease. Graphene reinforced composite exhibited the best tribological behavior among the prepared samples. The design of test conditions and the analysis of output responses were studied by statistical analysis of Taguchi array, analysis of variance (ANOVA) and regression models. ANOVA indicated that the wear rate was mainly affected by material content followed by sliding speed and applied load. The wear mechanisms were identified by characterizations of worn surface, wear debris and counterface material.
