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Öğe A comprehensive statistical approach for determining the effect of two non-ionic surfactants on thermal conductivity and density of Al2O3–water-based nanofluids(Elsevier B.V., 2021) Altun, Aycan; Şara, Osman Nuri; Şimşek B.The purpose of this study was to evaluate the effect of surfactants on the density and thermal conductivity values of water, as well as to separately evaluate the variations in these values due to particle–surfactant interaction. To this end, Al2O3–water-based nanofluids with different particle volume concentrations (0.3–1.1%) were prepared, as were Tween 80 and Tergitol NP-10 surfactants at different weight ratios (0.2–0.8%). Density and thermal conductivity of obtained nanofluids were then measured at temperatures ranging from 298 to 338 K. Statistical evaluation was carried out to determine the effects of surfactant type, temperature, particle concentration, and surfactant concentration on density and thermal conductivity. Additionally, the sedimentation method, zeta potential, and particle size analysis were utilized to estimate the stability of nanofluids. Results showed that when base fluid (water and surfactant) density was determined, the use of surfactants had no additional impact on the density of the nanofluids. The highest observed improvement in thermal conductivity was 7.5%, obtained using 0.2 wt% Tween 80 and 1.1 vol% Al2O3 at 338 K. Although particle concentration was the most influential factor and surfactant type was not statistically significant for density ratio, the thermal conductivity ratio was affected by other factors in addition to particle concentration.Öğe Effects of dispersed and powdered silver nanoparticles on the mechanical, thermal, electrical and durability properties of cementitious composites(Elsevier Sci Ltd, 2019) Ceran, Ozge Bildi; Simsek, Baris; Doruk, Semahat; Uygunoglu, Tayfun; Şara, Osman NuriThis work aimed to analyze the thermal, electrical and mechanical properties of cementitious composites (CCs) modified with SNs in dispersed and powdered forms, using experimental design methods and image analysis techniques. It was concluded that SNs have smaller particle size increase thermal conductivity, ultrasonic pulse velocity and splitting tensile strength, and decrease electrical resistance, percentage of water absorption and porosity of CCs. It was found that the optimum usage level of powdered SNs in CCs is 2% by mass because of its tendency to agglomerate. However, it is more advantageous to use dispersed SNs when considering CC performance properties. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Heat transfer performance of water and Nanoencapsulated n-nonadecane based Nanofluids in a double pipe heat exchanger(Springer, 2017) Doruk, Semahat; Şara, Osman Nuri; Karaipekli, Ali; Yapici, SinanThe heat transfer and pressure drop characteristics for the flow of water, which is base fluid, and nanoencapsulated n-nonadecane based nanofluids in a double pipe heat exchanger were investigated. The results showed that no improvement in overall heat transfer coefficient was observed for the nanofluids containing 0.42% and 0.84% solid volume ratios with reference to the base fluid, while an improvement of about 10% was obtained for the nanofluids containing 1.68% solid volume ratio. It was found that the friction factors for the nanofluids exhibited a slight increase reference to the base fluid. A performance analysis based on constant pumping power was also performed.Öğe Nanomaterials Based Drinking Water Purification: Comparative Study with a Conventional Water Purification Process(Budapest Univ Technology Economics, 2019) Simsek, Baris; Sevgili, Inci; Ceran, Ozge Bildi; Korucu, Haluk; Şara, Osman NuriOne of the ways of fully securing the presence of fresh water is water treatment process. Nanomaterials and nanotechnology offers an innovative solution for water treatment. In this study, physical, chemical and microbiological improvement rates of raw water were analyzed after filtration with graphene oxide. Graphene oxide's water treatment performance; silver nanoparticles, silver nanoparticles & graphene oxide composites that are commonly used in water treatment were compared with a traditional treatment method. When compared to the traditional method, there were improvements of 50%, 40.7%, 86.8% and 45.5% for color, TIC, TOC and hardness properties, respectively in water treatment by GO-based filtration with solid liquid ratio of 0.7% (v/v). In water treatment with GO-Ag based filtration, 39.8%, 69.8%, 10.3% and 28.6% of improvements were obtained for TIC, TOC, hardness and LSI value compared to the conventional method. Both GO at 0.7% (v/v) solid-liquid ratio and GO-Ag nanocomposites were successful in the number of total viable microorganisms and inhibiting microorganisms such as Escherichia coil fecal (gaita-infected), Salmonella typhi, Enterococcus faecalis, Pseudomona aeruginosa and Staphylococcus aureus. Among the studied parameters GO-Ag nanocomposites found to be the most suitable for drinking water treatment.Öğe Preparation and characterization novel dioctyl terephthalate blended polyvinyl alcohol-composite films incorporated with the graphene oxide and silver nanoparticles(Elsevier Sci Ltd, 2020) Ceran, Ozge Bildi; Simsek, Baris; Şara, Osman NuriDioctyl terephthalate is of great interest as a replacement for the phthalate plasticizers such as dioctyl phthalate and diisononyl phthalate due to its orthophthalate-free and non-carcinogenic properties. This study focused on the production, characterization and optimization of the quality characteristics of its film properties, such as the mechanical, hydrophilic and thermal properties of dioctyl terephthalate-blended polyvinyl alcohol composites modified with graphene oxide and silver nanoparticles using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) based Taguchi Method. Dioctyl terephthalate has brought remarkable features, such as high elastic modulus, and hydrophilic and thermal stability to the polyvinyl alcohol matrix. The optimum Dioctyl terephthalate -blended polyvinyl alcohol films have a 2.26 times lower contact angle and a 13.41 times higher elastic modulus than the reference polyvinyl alcohol film. Dioctyl terephthalate should be preferentially used to manufacture more durable and hydrophilic composite films such as fibers, disposable underpad or industrial swab, instead of toxic phthalate plasticizers.Öğe PVC concrete composites: comparative study with other polymer concrete in terms of mechanical, thermal and electrical properties(Springer, 2019) Ceran, Ozge Bildi; Simsek, Baris; Uygunoglu, Tayfun; Şara, Osman NuriRecycling PVC wastes with conventional chemical recycling methods such as pyrolysis, gasification is not feasible due to the carbon dioxide and dioxin emmissions generated with these methods. PVC wastes can be disposed using in ready-mixed concrete which is the most commonly used building material. In this study, effects of waste PVC instead of fine aggregate and the effects of waste PVC on the concrete properties were analyzed using 0%, 30%, 35%, 40% and 45% (w/w) in the experiments. Effects of waste PVC in concrete were compared with the other waste polymer concrete in terms of mechanical, thermal and electrical properties. All waste polymers have reduced the mechanical strength of concrete as expected. Improvement rates for the splitting tensile strength for 28days are found to be 54.46%, 48.52% and 6.93% for PP, PET and rubberized concrete, respectively, in comparison with reference concrete. For thermal conductivity, improvement rates for 40% PC, 40% PP and 40% PVC concrete are found to be 52.56%, 44.87% and 42.31%, respectively. For electrical resistivity, the highest improvement rate was determined as 136.03%, 132.38% and 105.92% for PC, PVC and rubberized concrete, respectively.Öğe Response Surface Methodology Based Desirability Function Approach To Investigate Optimal Mixture Ratio of Silver Nanoparticles Synthesis Process(Amer Chemical Soc, 2017) Karhan, Oznur; Ceran, Ozge Bildi; Şara, Osman Nuri; Simsek, BarisSilver nanoparticles are known especially because their antimicrobial properties can be used as conductive ink or adhesives for different electronics in compliance with their unique electronic and optical properties. As they are well-known, these practices require smaller nanoparticle formation. A response surface methodology based desirability function approach has been first applied to achieve the desired size of silver nanoparticles with the green synthesis methods. It is notable that the improvement rates at 7.9% by the mean of particle size distribution in AgNPs manufacturing process have been obtained with the utilization of utilizing the proposed methodology. When these results are evaluated, it can be seen that an 89.3% lower standard deviation has been obtained in comparison with the studies in literature. The results also show that the minimization of the nanosilver production variance should be performed to obtain the high quality and large scale manufacturing process.Öğe Synthesis and Characterization of Polyvinyl Alcohol/Calcium Carbonate Composite Film(E-Journal of New World Sciences Academy, 2020) Şimşek, Barış; Ceran, Özge Bildi; Şara, Osman NuriCalcium carbonate is widely used as a filler material both in plastics and in the pharmaceutical industry in recent years. In this study, the synthesis and characterization of calcium carbonate reinforced polyvinyl alcohol composite film is provided. The synthesized composite film was characterized by FTIR and UV-VIS spectroscopy, the properties of the film were determined by measuring pH and film thickness. Finally, the morphology of the composite film was analyzed by optical microscope. The results show that the polyvinyl alcohol/calcium carbonate composite film was successfully synthesized. According to the results of the optical microscope the calcium carbonate was homogenously dispersed into the film matrix.Öğe Thermal Conductivity and Viscosity Correlations in Different Kinds of Aqueous Surfactant Solutions at Atmospheric Pressure as a Function of Temperature(Springer/Plenum Publishers, 2021) Altun, Aycan; Şara, Osman NuriSurfactants with a wide range of uses are often preferred to reduce particle aggregation in nanofluid and provide stability. However, added surfactants affect the properties of not only nanofluids but also base fluids. In this study, binary mixtures were prepared by using water and three different surfactants, namely, SDS, Tween 80, and NP 10, in four different concentrations of 0.2 % to 0.8 % by weight, separately. Density, thermal conductivity, and viscosity values of these prepared mixtures were measured experimentally at atmospheric pressure and the temperature of 298 to 338 K. Then, correlations were derived with respect to the data obtained for the studied parameter ranges. According to the result, a quadratic polynomial with coefficients was fitted for the density equation and two models for viscosity behavior were derived. Moreover, Thermal conductivity correlations were developed as second-order polynomials of temperature and concentration function. The proposed correlations showed good agreement with our experimental results.
