Yazar "Tüzün, Fatma Nihal" seçeneğine göre listele

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    Comparison of the curing kinetic behavior for two epoxy resin systems containing EPIKOTE 828-EPIKURE 3090 and DURATEK KLM 606a-DURATEK KLM 606b
    (2007) Tüzün, Fatma Nihal; Gürü, Metin; Akyüz,Yüksel
    The aim of the study is to determine the optimum cure temperatures and kinetics for two different epoxy resin systems without using solvent. Two resin systems consist of EPIKOTE 828® epoxy resin-EPIKURE® 3090 polyamidoamine curing agent and DURATEK® KLM 606A epoxy resin-DURATEK®KLM 606B polyamide curing agent. The ratio of resin to curing agent was kept as 1:1 for both the systems. Curing temperatures of both the systems were determined and kinetic parameters were calculated with respect to the experimental results following nth-order kinetics. Then, a series of isothermal temperatures was applied to the resin systems in order to assess the cure process in terms of conversion, time, and temperature by using differential scanning calorimeter (DSC). The test results of both systems show that the rate of degree of cure for EPIKOTE 828® epoxy resin-EPIKURE® 3090 polyamidoamine curing agent system is approximately 10 times higher than that of DURATEK® KLM 606A epoxy resin-DURATEK® KLM 606B polyamide curing agent system at 230°C. © 2007 Society of Plastics Engineers.
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    Effect of the activator type and catalyst/activator ratio on physical and mechanical properties of cast PA-6
    (2008) Tüzün, Fatma Nihal
    The aim of the study is to produce suitable unfilled cast polyamide-6 composition exhibiting optimum mechanical, physical, thermal and electrical properties with anionic polymerization mechanism. Sodium lactamate was used as catalyst at all compositions. Activators used were varied as toluenediisocyanate (TDI), isophronediisocyanate (IPDI), hexamethylenediisocyanate (HMDI) and diphenylmethylenediamine (DPMD). Also, activator and catalyst content were varied between 0.4-0.8% and 1-4% respectively. The best mechanical properties were attained with using TDI as activator at 0.488%. Then, other properties of this composition were determined. Comparison of these properties with other plastics showed that it had the highest abrasion resistance, lower water absorption, higher tensile and flexural strength.
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    Oxidative desulfurization of cayirhan lignites by permanganate solution
    (2008) Gürü, Metin; Tüzün, Fatma Nihal; Selek Murathan, Ayşe; Asan, Abdurrahman; Kıyak, Tülin
    Unless important developments record new and renewable energy sources, the role of fossil fuels as an energy resource goes on. It is possible to detect sulfur, heavy metals, and tracer elements such as arsenic and selenium by decreasing calorific value of coals. Sulfur oxides, which are the main pollutants in atmosphere, are irritative to humans and plants, and erosion occurs on buildings. Although there are high lignite reservoirs, high sulfur content limits the efficient use of them. In this research, it is aimed to convert combustible sulfur in coal to non-combustible sulfur form in the ash by oxidizing it with permanganate solution. During this research, the effect of two different parameters of potassium permanganate concentration, processing time, and mean particle size were investigated at constant room temperature and shaking rate. The conversion of combustible sulfur to non-combustible sulfur form was achieved optimally with 0.14 M potassium permanganate solution, 0.1 mm mean particle size at 16 h of treatment time, and the combustible sulfur amount was decreased by 46.37% compared to undoped conditions.
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    Pore modification in porous ceramic membranes with sol-gel process and determination of gas permeability and selectivity
    (2010) Tüzün, Fatma Nihal; Arçevik, Ersel
    Summary: The aim of the study was to investigate the variation in total surface area, porosity, pore size, Knudsen and surface diffusion coefficients, gas permeability and selectivity before and after the application of sol-gel process to porous ceramic membrane in order to determine the effect of pore modification. In this study, three different sol-gel process were applied to the ceramic support separately; one was the silica sol-gel process which was applied to increase porosity, others were silica-sol dip coating and silica-sol processing methods which were applied to decrease pore size. As a result of this, total surface area, pore size and porosity of ceramic support and membranes were determined by using BET instrument. In addition to this, Knudsen and surface diffusion coefficients were also calculated. After then, ceramic support and membranes were exposed to gas permeation experiments by using the CO2 gas with different flow rates. Gas permeability and selectivity of those membranes were measured according to the data obtained. Thus, pore surface area, porosity, pore size and Knudsen diffusion coefficient of membrane treated with silica sol-gel process increased while total surface area was decreasing. Therefore, permeability of ceramic support and membrane treated with silica sol-gel process increased, and selectivity decreased with increasing the gas flow rate. Also, surface area, porosity, pore size, permeability, selectivity, Knudsen and surface diffusion coefficients of membranes treated with silica-sol dip coating and silica-sol processing methods were determined. As a result of this, porosity, pore size, Knudsen and surface diffusion coefficients decreased, total surface area increased in both methods. However, viscous flow and Knudsen flow permeability were detected as a consequence of gas permeability test and Knudsen flow was found to be a dominant transport mechanism in addition to surface diffusive flow owing to the small pore diameter in both methods. It was observed that silica-sol processing method had lower pore diameter and higher surface diffusion coefficient than silica-sol dip coating method. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Processing of urea-formaldehyde-based particleboard from hazelnut shell and improvement of its fire and water resistance
    (Wiley Blackwell, 2009) Gürü, Metin; Aruntaş, Yılmaz; Tüzün, Fatma Nihal; Bilici, İbrahim
    The purpose of this study was to manufacture urea-formaldehyde-based particleboard from hazelnut shell and eliminate its disadvantages such as flammability, water absorption, swelling thickness by using fly ash and phenol-formaldehyde. Synthesized urea-formaldehyde and grained hazelnut shells were blended at different ratios ranging from 0.8 to 3.2 hazelnut shell/urea-formaldehyde and dried at 70°Cinanoven until constant weight was reached. In addition, other parameters affecting polymer composite particleboard from hazelnut shell and urea-formaldehyde were investigated to be the amount of fly ash, amount of phenol formaldehyde and the effects of these parameters on bending stress, limit oxygen index, water absorption capacity and swelling in the thickness. The optimization results showed that the maximum bending strength was 4.1N/mm2, at urea-formaldehyde ratio of 1.0, reaction temperature of 70°C, reaction time of 25 min, hazelnut shell/urea- formaldehyde resin of 2.4 and mean particle size of 0.1 mm. Although the limited oxygen index and smoke density of composite particleboard without fly ash has 22.3 and 1.62, with fly ash of 16% (w/w) according to the filler has 38.2 and 1.47, respectively. Water absorption and increase in the swelling thickness exponentially decreased with increasing phenol formaldehyde. Copyright © 2009 John Wiley & Sons, Ltd.
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    The effect of aluminum and ammonium perchlorate content on temperature sensitivity, mechanical properties and performance of HTPB propellants
    (The Japan Society for Aeronautical and Space Sciences, 2007) Tüzün, Fatma Nihal
    This paper describes the effect of aluminum content variation of HTPB (hydroxyl terminated polybutadiene) propellants on temperature sensitivity, mechanical properties and performance values. Aluminum (Al) content was applied as 16, 18 and 20 percent to the propellant compositions and those compositions were tested at small test motors with three different propellant area ratios (K 1/4 200, 250 and 300) by keeping the propellant grain at three different temperatures (231, 258 and 323 K). As a result of this, a relationship such as P 1/4 aesT was determined with different coefficients for each of the three compositions and propellant area ratios. The lowest temperature sensitivity value was obtained for the composition containing 20% Al and 65% AP. The second relation as P 1/4 bKy was derived for three propellants and temperatures. The highest pressure was found with the K value of 300 for the propellant including 16% Al and 69% AP at 323 K. The third relationship such as r 1/4 cPn was also determined for three propellant compositions and temperatures. It was observed that the propellant having 16% Al and 69% AP had the highest burning rate at 323 K. The highest maximum tensile stress and elongation values were obtained for the propellants including 20% Al and 16% Al respectively. Evaluation of performance values for those propellants exhibits that the maximum characteristic velocity value is attained for the propellant containing 16% Al and 69% AP. © 2007 The Japan Society for Aeronautical and Space Sciences.
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    The effect of finely-divided fillers on the adhesion strengths of epoxy-based adhesives
    (Elsevier Ltd, 2015) Tüzün, Fatma Nihal; Tunalıoğlu, Mert Şafak
    It was aimed to investigate the effect of five different fillers on the adhesion strength of the metal parts used in different industries by using T-peel and lap-shear tests with respect to ASTM D 1876 and ASTM D 1002 respectively. EPIKOTE® 828 and DURATEK® epoxy resin types were used as adhesives with curing EPIKURE® 3090 modified polyamidoamine adduct and DURATEK® polyamide curing agents respectively. Curing temperatures were increased, while curing times were decreased. Five different fillers used are calcite with a mean particle diameter of 4.97 ?m, talc extra with an average particle diameter of 4.91 ?m, and barite extra with a mean particle diameter of 4.76 ?m supplied by ESEN MIKRONIZE, calcite with an average particle diameter of 0.7 ?m and coated calcite with a mean particle diameter of 0.9 ?m provided by ERCIYES MIKRON. The effect of five different fillers on adhesion strength was investigated with choosing the best regression model fitted to data by using two different epoxy resin systems. The best values in shear and peel tests were attained with calcite having the particle diameter of 0.7 ?m in both type of epoxy resins providing a good agreement between experimental and theoretical results.