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Öğe Anode performance of hydrothermally grown carbon nanostructures and their molybdenum chalcogenides for Li-ion batteries(Cambridge Univ Press, 2018) Simsir, Hamza; Eltugral, Nurettin; Frohnhoven, Robert; Ludwig, Tim; Gonullu, Yakup; Karagoz, Selhan; Mathur, SanjayThree different hydrothermally grown carbonaceous materials and their molybdenum chalcogenides derived from glucose (HTC, HTC-MoO2, HTC-MoS2) were investigated to evaluate their potential as Li-ion battery anodes. All tested materials exhibited good cycling performance at a current density of 100 mA/g and showed high coulombic efficiency, >98%, after the 50th cycle. Reversible charge capacities of HTC, HTC-MoO2, and HTC-MoS2 were 296, 266, and 484 mAh/g, respectively, after 50 successive cycles. This study demonstrated that the HTC-MoS2 showed the highest reversible charge capacity which promises to be a good candidate for an environmentally friendly anode material for Li-ion batteries.Öğe Anti-wear behaviour of silver nanoparticles on Al-Si alloy(Iop Publishing Ltd, 2021) Akgul, Yasin; Simsir, HamzaIn recent years, studies have shown that using nanoparticles (NPs) as lubricant additives lead to the enhancement of the anti-wear behaviour of oils. In this study, the anti-wear behaviour of silver (Ag) NPs which were capped with polyvinyl alcohol and sodium citrate were investigated for three different sliding speeds (2, 3 and 4 mm s(-1)) under two different loads (30 and 50 N). Results show that the AgNPs led to a decrease in friction and wear due to the formation of a tribofilm and a rolling effect. However, influence of the AgNPs declined at higher loads while increasing at higher speed test conditions. Also, both stabilising agents underwent disordering of AgNPs morphology and size successively under the applied loads.Öğe Effect of Shot-Peening Process and Nanoparticle-Added Lubricant on the Tribological Performance of Aluminium-Based Sliding Bearing Material(Wiley, 2024) Korkmaz, Seyma; Cetin, M. Huseyin; Simsir, Hamza; Unal, Okan; Temel, FarabiIn this study, it is aimed to increase the wear and fatigue performance of aluminium-based sliding bearing material by using silver nanoparticles (AgNPs) added lubricant and shot-peening process. The main purpose is to minimise the wear of the bearing material by penetrating AgNPs added lubricants into the rough surfaces formed by shot peening. Almen intensity, coverage and shot size parameters in the shot-peening process were analysed in terms of hardness, surface roughness and fatigue strength. The shot-peened aluminium bronze was subjected to wear experiments under dry, pure water and AgNPs added lubricant conditions. The wear test results were analysed in terms of friction coefficient, wear volume and surface roughness parameters, and the interaction of lubricant and shot-peening parameters was evaluated. According to the results of the shot-peening experiments, the Almen intensity was the most effective parameter in terms of hardness and surface roughness (91.62%). It was concluded that the hardness value was 8% higher at high Almen (12-14A) intensity compared with low Almen intensities, and the shot-peening process could increase the fatigue strength by similar to 21 times. According to the wear tests, the most effective parameters were 4-6 Almen intensity and AgNP-added lubricant.Öğe Effects of Acidic and Alkaline Metal Triflates on the Hydrothermal Carbonization of Glucose and Cellulose(Amer Chemical Soc, 2019) Simsir, Hamza; Eltugral, Nurettin; Karagoz, SelhanThe transformation of glucose and cellulose into carbon-rich solid materials was carried out in hydrothermal media at 200 degrees C for 48 h with and without the use of acidic (Al(OTf)(3)) and alkaline (NaOTf) catalysts. The effects of the catalyst type on the yield of hydrothermal carbons (HTCs) and their properties were investigated. The use of Al(OTf)(3) led to a decrease in the yields of HTCs for both feedstocks. This result was reversed for the runs with NaOTf. Glucose-derived solid product without the use of a catalyst produced carbon spheres of a diameter between 500 and 600 nm. The use of a catalyst (regardless of whether Al(OTf)(3) or NaOTf) produced larger particles. Scanning electron microscopy images of HTC from cellulose exhibited irregular morphology. Carbon spheres produced from cellulose without the use of a catalyst ranged between 200 nm and 2 mu m. HTC products from cellulose with Al(OTf)(3) yielded aggregated carbon spheres with a diameter ranging between 300 and 600 nm. The use of NaOTf inhibited the secondary char formation. Although a small number of carbon spheres were observed on the surface, the surface was mostly smooth, like raw cellulose. The final chemical structures of HTC products were further investigated using advanced C-13 solid-state nuclear magnetic resonance (NMR). NMR spectra demonstrated that glucose was completely transformed into HTCs with and without a catalyst, because there were no peaks identified with carbon atoms of glucose. However, the peaks identified with carbon atoms of cellulose were observed in the non catalytic and catalytic runs with NaOTf. Cellulose was completely transformed into HTCs with only Al(OTf)(3).Öğe Hydrothermal carbon effect on iron matrix composites produced by powder metallurgy(Elsevier Science Sa, 2020) Simsir, Hamza; Akgul, Yasin; Erden, Mehmet AkifIn this work, hydrothermal carbons (HTC) were obtained from glucose at 200 degrees C for 30 h. HTC and its calcinated product (HTC*) were added to pure iron powder with different ratios (0.25, 0.50 and 0.75 wt%) to obtained HTC reinforced iron composites by powder metallurgy. To our knowledge, this is the first study that investigates the effect of HTC on iron matrix composites. Microstructure, hardness, compression and corrosion behaviors of composites were investigated. According to the results, mechanical properties of composites were enhanced with the increasing of HTC/HTC* amount. However, high corrosion resistances were gained with the using of the low amount of HTC (0.25 and 0.50 wt%) and HTC* (0.25 wt%).Öğe Hydrothermal carbonization for the preparation of hydrochars from glucose, cellulose, chitin, chitosan and wood chips via low-temperature and their characterization(Elsevier Sci Ltd, 2017) Simsir, Hamza; Eltugral, Nurettin; Karagoz, SelhanIn this work, the hydrothermal carbonization of glucose, cellulose, chitin, chitosan and wood chips at 200 degrees C at processing times between 6 and 48 h was studied. The carbonization degree of wood chips, cellulose and chitosan obviously increases as function of time. The heating value of glucose increases to 88% upon carbonization for 48 h, while it is only 5% for chitin. It is calculated to be between 44 and 73% for wood chips, chitosan and cellulose. Glucose yielded complete formation of spherical hydrochar structures at a shorter processing time, as low as 12 h. However, carbon spheres with narrow size (similar to 560 nm) distribution were obtained upon 48 h of residence time. Cellulose and wood chips yielded a similar morphology with an irregular size distribution. Chitin seemed not to undergo hydrothermal carbonization, whereas densely aggregated spheres of a uniform size around 42 nm were obtained from chitosan after 18 h. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Hydrothermal carbonization of citrus peels and their electrochemical efficacy in double-layer supercapacitors(Taylor and Francis, 2025-01-07) Durmaz, Hasan; Simsir, HamzaThis work involved the fabrication of supercapacitors with rapid charge/discharge rates using waste biomass. Initially, hydrochars were produced using the hydrothermal carbonization of four distinct citrus peels. Subsequently, physical, acidic, and basic activation was employed to enhance surface area and induce porosity. They were analyzed using elemental analysis, FTIR spectroscopy, and SEM examination. The electrochemical performance of the electrodes was assessed using galvanostatic charge-discharge and cyclic voltammetry techniques. The maximum specific capacity recorded was 65.1 mF/cm2 at a current rate of 0.50 mA for the electrode produced through potassium hydroxide activation and calcination. Consequently, it was demonstrated that supercapacitors with comparable specific capacity values may be fabricated from these waste orange peels.Öğe Hydrothermal carbonization of lignocellulosic biomass and effects of combined Lewis and Bronsted acid catalysts(Elsevier Sci Ltd, 2020) Evcil, Tolgahan; Simsir, Hamza; Ucar, Suat; Tekin, Kubilay; Karagoz, SelhanThis study is the first to investigate the effect of combined Lewis and Bronsted acid catalysts on the hydrothermal carbonization of fir wood samples; here, hydrothermal carbonization of fir wood-with and without catalyst-was performed. In non-catalytic runs, the effects of temperature and residence time on hydrochar yields were investigated; temperature significantly affected hydrochar yields, whereas residence time had very little effect. A gradual increase in temperature resulted in a decrease in hydrochar yields while increasing the carbon content of hydrochars. At all tested temperatures, the use of a catalyst led to a decrease in hydrochar yields. The highest heating value of 29.12 MJ kg(-1) was obtained at the highest temperature (275 degrees C) and the longest residence time (24 h). The use of catalysts slightly decreased the heating values. The hydrochars were mainly in the class of lignite coal; hydrochar obtained at 275 degrees C and a residence time of 12 h-either with or without catalysts-was classified as bituminous coal. Irregular carbon sphere formation was observed at all temperatures tested in the catalytic runs; however, no carbon spheres were observed in the non-catalytic runs. XRD patterns of hydrochars from the non-catalytic runs were similar for temperatures of 225, 250 and 275 degrees C; the peak observed at 2 theta of 22 degrees broadened after HTC processing. In the catalytic runs, two new peaks at 2 theta of 38 degrees and 49 degrees were observed, in addition to broadened peaks (2 theta = 22 degrees). The use of catalysts led to the formation of the secondary char.Öğe Investigation of the mechanical, tribological, and corrosion properties of 316L SS-HTC composites(Taylor & Francis Ltd, 2023) Simsir, Hamza; Erden, Mehmet AkifMany different additives have been used to improve the mechanical properties of stainless steel (SS) matrix materials. However, few studies are using carbonaceous additives. Among them, hydrothermal carbons (HTC), produced from biomass with a very low production cost and without any harmful chemicals, have not yet been tried. In this study, SS-HTC composites were produced by powder metallurgy using HTC in three different ratios. The effects of HTC content in the metal matrix on the mechanical, tribological, and corrosion tests are compared and discussed. According to the results of these tests, the best results of approximately 22% hardness value, 8% ultimate compressive strength, and 5% wear resistance increase were obtained with low HTC (0.25 wt%) use. De nombreux additifs differents ont ete utilises pour ameliorer les proprietes mecaniques des materiaux a matrice d'acier inoxydable (SS). Cependant, peu d'etudes utilisent des additifs carbones. Parmi eux, les carbones hydrothermaux (HTC), produits a partir de la biomasse avec un cout de production tres bas et sans aucun produit chimique nocif, n'ont pas encore ete essayes. Dans cette etude, on a produit des composites SS-HTC par la metallurgie des poudres en utilisant les HTC en trois proportions differentes. Les effets de la teneur en HTC dans la matrice metallique sur les essais mecaniques, tribologiques et de corrosion sont compares et discutes. Selon les resultats de ces tests, on a obtenu les meilleurs resultats d'une augmentation d'environ 22% de la valeur de durete, 8% de la resistance ultime a la compression et 5% de la resistance a l'usure avec une faible utilisation (0.25% en poids) de HTC.Öğe Investigation of the properties of Al7075-HTC composites produced by powder metallurgy(Sage Publications Ltd, 2021) Arsun, Ozan; Akgul, Yasin; Simsir, HamzaEven though aluminium matrix composites have been used in many different application areas, the improvement of its mechanical, tribological, and corrosion properties is crucial for enlargement of its application areas. To achieve this, many ceramic-based and carbon-based additives have been used. However, eco-friendly and low production cost hydrothermal carbons (HTCs) have not been used, yet. In this study, three different amounts of HTCs (0.25, 0.50, and 1.00 wt.%) produced from cellulose were used as a reinforcement material in Al 7075 by powder metallurgy for the first time. According to the mechanical, tribological, and corrosion test results, all of the mentioned properties of Al 7075 alloy were improved by reinforcing with HTCs. As a consequence of this study, HTCs can be used as appropriate reinforcement materials for the aluminium matrix composites.Öğe Investigation of tribological performance of hydrothermal carbon by pin-on-disc test and warm deep drawing process(Iop Publishing Ltd, 2024) Yurt, Ozgur Erdem; Sen, Nuri; Simsir, Hamza; Kucuk, Yilmaz; Altas, Emre; Gok, M. Sabri; Civek, TolgahanIn this study, the synthesis of hydrothermal carbon (HTC) lubricant and its usability as a lubricant under hot industrial conditions were investigated. In this context, the characterization of HTC produced from organic sources at low cost and in a short time was performed, and its tribological performance was analysed in detail. HTC produced by the hydrothermal carbonization method was characterized through SEM images and EDS analysis. To determine the effect of HTC on friction at different temperatures, HTC was subjected to a pin-on-disc wear test with AA5754 material. The effect of various lubricants, temperatures, blank holder pressure, and forming speed parameters on the forming force for the analysis of the tribological effect of HTC on deep drawing processes were statistically analysed. The performance of HTC was compared with Teflon, fullerenes, graphene, and carbon nanotube (CNT) materials. According to the results obtained from wear tests, the lowest friction coefficient value was achieved in the presence of fullerenes as the lubricant, and as the temperature increased, the friction coefficient decreased. It was observed that HTC exhibited lower performance in the wear test compared to fullerenes due to oxidation. When the effect of deep drawing parameters on the forming force was analysed, it was concluded that the most effective parameters were temperature (72.32%) and lubricant (20.89%). According to the S/N analysis results, the minimum forming force was obtained under the conditions of solid Teflon lubricant, 250 degrees C temperature, 15-bar blank holder pressure, and 2 mm/s forming speed. The tribological performance difference between HTC and Teflon is at the 1% level. The results demonstrate the potential industrial usability of HTC as a lubricant.Öğe Mechanical, tribological, and biological properties of carbon fiber/hydroxyapatite reinforced hybrid composites(Wiley, 2020) Akgul, Yasin; Ahlatci, Hayrettin; Turan, Muhammet E.; Simsir, Hamza; Erden, Mehmet A.; Sun, Yavuz; Kilic, AliThe present study aims to investigate the effect of short carbon fiber (SCFs) and hydroxyapatite (HAp) content on mechanical, tribological, and biological properties of high-density polyethylene (HDPE) matrix composites. The proposed HDPE/SCFs-HAp hybrid composites with good mechanical-tribological behavior and biocompatibility might be used as novel implants in orthopedics. The composites were developed using twin-screw extrusion and compression molding methods. Hardness, tensile, and 3-point bending tests were performed to investigate the mechanical properties of hybrid composites. To evaluate wear performance of the samples, three different loads (10, 20, and 30 N) were applied in simulated body fluid. Biological activities of the hybrid composite samples were investigated. Results show that HDPE-10%SCFs-10%HAp sample provides optimum mechanical, tribological, and biological properties.Öğe The morphological effects of hydrothermal carbon on mechanical, tribological and corrosion properties of AlSi12 composite(Iop Publishing Ltd, 2021) Simsir, HamzaAlthough aluminum and its composites have been used in many applications, their mechanical properties should be improved for use in wider applications. Hence, specially nanosized and sub-micron sized carbonaceous additives were used. As far as is known, hydrothermal carbons (HTCs) have not yet been used in aluminum-silicon matrix composites. In this study, two different morphologies of HTCs were synthesized from cellulose and chitosan. With the use of chitosan, the particle morphology of HTCs was changed from hard spheres to smaller aggregated spheres. Both HTCs had a positive effect on mechanical (hardness >%18, and ultimate compression strength >%9) and tribological properties (wear rate >% 14) and they caused only limited decrement of corrosion resistance (corrosion rate <%13). The aggregated spheres possessed HTCs presented better mechanical, tribological and corrosive properties than those the hard spheres possessed.Öğe Prediction of Flow Behavior and Deformation Analysis of AA5754 Sheet Metal at Warm and Hot Temperatures(Springer, 2024) Sen, Nuri; Civek, Tolgahan; Ilhan, Omer; Yurt, Ozgur Erdem; Cetin, M. Huseyin; Simsir, HamzaThe utilization of lightweight materials such as AA5754 aluminum alloys in the inner body panel parts of vehicles has been significantly important for automotive manufacturers to minimize the high fuel consumption by reducing the overall weight. In this study, the flow behavior of AA5754 sheet metal has been discussed by conducting uniaxial tensile tests at five different temperatures (RT, 200, 250, 300, 350 degrees C) and three strain rates (0.001, 0.01, 0.05 s(-1)). Additionally, the capability of Fields and Backofen (F&B) and Voce hardening rules in describing the flow behavior of AA5754 at different temperatures and strain rates has been investigated by conducting uniaxial tensile tests in finite element analysis. It has been found that the main deformation mechanisms for the AA5754 are the strain hardening mechanism up to 250 degrees C, strain hardening and dynamic recovery mechanisms at 300 degrees C, dynamic recrystallization and strain hardening mechanisms at 350 degrees C. While the F&B hardening rule has been able to successfully capture the flow behavior of AA5754 up to 250 degrees C with a 14.36% error, its capability has significantly reduced after 250 degrees C due to its incapability of describing the effects of dynamic recovery and recrystallization. Voce hardening model has been better able to describe the flow behavior of AA5754 at all the temperature levels than F&B model due to its saturation behavior.Öğe Preparation of nano-silver-supported activated carbon using different ligands(Springer, 2016) Eltugral, Nurettin; Simsir, Hamza; Karagoz, SelhanIn this study, we investigated the effect of water soluble ligands [i.e., sodium borohydride (NaBH4), polyvinyl alcohol, glucose and galactose] on the preparation of nano-silver-supported activated carbon (AC). Ligand-stabilized Ag nanoparticle dispersion characteristics were also compared with those of ligand-free Ag nanoparticles. The nanoparticle distribution was investigated using a scanning electron microscope (SEM) which enabled a qualitative analysis of ligand-dependent nanoparticle adsorption onto AC. Silver nanoparticles with average sizes ranging from 7 to 20 nm were synthesized with different coatings. In particular, silver nanoparticles reduced and stabilized by NaBH4 were found to have a dense and homogenous dispersion of sizes in the range of 100-400 nm on the AC surface. These particles also seemed to remain on the AC surface after rinsing with water. The distribution of silver nanoparticles prepared in the presence of NaBH4/PVA was not as good as the one prepared with NaBH4. Their aggregate size varied from 300 to 600 nm on the AC surface and particles greater than 500 nm were eliminated from the AC surface upon rinsing with water. Glucose- and galactose-stabilized silver nanoparticles did not display an extensive adsorption and their adsorption seemed to be poor. However, glucose-stabilized silver nanoparticles could still be detectable to some extent after rinsing, while galactose-stabilized ones could not. Antimicrobial studies showed that all silver-containing carbons studied in this study inhibit bacterial growth and act as bacteriostatic agents.Öğe The role of capping agents in the fabrication of nano-silver-decorated hydrothermal carbons(Elsevier Sci Ltd, 2019) Simsir, Hamza; Eltugral, Nurettin; Karagoz, SelhanIn this work, silver-decorated hydrothermally grown carbons were fabricated by introducing either silver nitrate, or silver nanoparticles (Ag NPs) which were coated differently with polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), gelatin, and glucose. Hybrid nanostructures were prepared by methods which involve either in situ formation under hydrothermal conditions or mixing of as-prepared hydrothermal carbons (HTCs) with Ag NPs. With these approaches, hybrid nanostructures could be fabricated with some differences in their morphologies. Interestingly, a dense silver core at the center of the HTCs was observed after hydrothermal processing of glucose with gelatin-stabilized Ag NPs while particles were observed to attach to the HTCs surface under mixing conditions. PVP-stabilized Ag NPs were shown to form hybrid products where particles were attached to the surface rather than encapsulated at the center. On the other hand, PVA-stabilized ones were hardly observed on the HTCs upon mixing for 48 h, and they seemed not to produce any hybrid HTC-Ag under hydrothermal processing. Besides, glucose-stabilized Ag NPs were also subjected to the hydrothermal process and HTCs produced with interesting surface characteristics revealed that Ag NPs induce their morphology.Öğe Synthesis of bis[N-(p-aryl)-carbamoyloxy]alkanes as new low-molecular weight organogelators(Pergamon-Elsevier Science Ltd, 2015) Demir-Ordu, Oznur; Simsir, Hamza; Alper, KorayA series of bis-carbamate-based low-molecular-weight organogelators were synthesized, and their structure property relationships with respect to their gelation abilities in organic solvents were investigated. The self-aggregation behavior of the thermoreversible organogels was investigated by FTIR, temperature-dependent NMR, and SEM studies. The results revealed that the self-assembly into fibrous structures is driven by hydrogen bonding, it it stacking, and hydrophobic interactions. It was found that para-aryl substitution and the number of methylene units connecting two carbamate groups had a significant influence on gelation. The effect of temperature on gel formation was also investigated for all compounds. The most interesting feature was observed for p-hexyl derivative, which gels at -18 degrees C but not room temperature. Furthermore, thermal properties of the gels were studied by dropping ball experiments and DSC. para-Alkoxyphenyl derivatives were also found to be good organogelators for olive oil, sunflower oil, corn oil, and ethyl laurate, isopropyl myristate, n-butyl palmitate. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Using a new sustainable carbon reinforcement in magnesium matrix composites(Elsevier Science Sa, 2022) Simsir, Hamza; Akgul, YasinMagnesium is not only light but also biodegradable. However, mechanical, tribological and corrosion properties of magnesium need to be enhanced for industrial applications. One of the most effective ways to improve these properties is by adding reinforcement materials. In this study, in contrast to the common carbonaceous reinforcements, hydrothermal carbons (HTCs) were used in pure magnesium for the first time. Bio/eco-friendly HTCs reinforced magnesium matrix composites with three different weight fractions (0.25, 0.50, and 1.00 wt %) were fabricated via powder metallurgy. As the most interesting result, the adding of a low amount of HTC improved the mechanical and tribological properties of magnesium. Even though the corrosion resistance was decreased, this decrement equal with other carbonaceous reinforcements. According to the results, HTC can be used as a promising material for magnesium matrix composites.
