Makine Mühendisliği/Makale Koleksiyonu

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https://hdl.handle.net/20.500.12395/15594

Listeleniyor 1 - 20 / 48

Heat Transfer Effects on the Performance of an Air Standard Otto Cycle
(Selçuk Üniversitesi, 2011) Demirpolat, Havva; Ateş, Ali; Demirpolat, Süleyman Orkun; Kahraman, Ali
There are heat losses during the cycle of a real engine that are neglected in ideal air standard analysis. In this paper the performance of an air-standard Otto cycle with heat transfer loss and variable specific heats of working fluid is analyzed by using finite-time thermodynamics. Heat transfer from the unburned mixture to the cylinder walls has a negligible effect on the performance for the compression process. Additionally, the heat transfer rates to the cylinder walls during combustion are the highest and extremely important. Therefore, we assume that the compression and power processes proceed instantaneously so that they are reversible adiabatics, and the heat losses during the heat rejection process can be neglected. The heat loss through the cylinder wall is assumed to occur only during combustion and is further assumed to be proportional to the average temperature of both the working fluid and the cylinder wall. The results show that the effects of heat transfer loss and variable specific heats of working fluid on the cycle performance are obvious, and they should be considered in practice cycle analysis. Higher heat transfer to the combustion chamber walls lowers the peak temperature and pressure and reduces the work per cycle and the efficiency. The effects of other parameters, in conjunction with the heat transfer, including combustion constants and intake air temperature, are also reported. The results are of importance to provide good guidance for the performance evaluation and improvement of practical real engines.
Deniz suyu korozyon ortamında bazalt/epoksi kompozitlerin mekanik davranışlarının incelenmesi
(Selçuk Üniversitesi, 2017) Demirci, İbrahim; Avcı, Ahmet
Epoksi matrisli elyaf takviyeli kompozitler yüksek dayanım ve rijitliklerinden dolayı ileri teknoloji ürünleri olarak endüstride yaygın kullanılmaktadır. Son zamanlarda kullanım sahasının genişliği, yüksek dayanım ve rijitlik, korozyon direnci, gürültü, titreşim ve ısıl yalıtım özelliklerinin iyi olması ve maliyetinin karbon elyaflardan düşük olması nedeniyle, elyaf takviye malzemesi olarak kompozitlerde bazalt elyaflar tercih sebebi olmuştur. Dolayısıyla araştırmacılar bazalt elyaf takviyeli kompozitler ile ilgili çalışmalara yönlenmişlerdir. Yapılan çalışmada, vakum infüzyon yöntemi ile 6 tabakalı bazalt elyaf takviyeli (BTP) epoksi kompozit levhalar üretilmiştir. Üretilen bu levhalardan çekme numuneleri ASTM D 3039/D 3039M standartlarına uygun olarak hazırlanmış ve Akdeniz suyu korozyon ortamında 0, 10, 20 ve 40 gün sürelerinde bekletildikten sonra çekme deneyleri gerçekleştirilmiştir. Artan deniz suyu korozyon sürelerine göre çekme dayanımlarındaki % azalmalar tespit edilmiştir. 40 gün deniz suyu ortamında bekletilen BTP/Epoksi kompozitlerin çekme dayanımında %26.5’lik kaybın olduğu tespit edilmiştir.
Mermi namlu çıkış hızı ve enerjisini etkileyen parametrelerin optimizasyonu
(Selçuk Üniversitesi, 2020) Sürmeli, Dilara; Neşeli, Süleyman
Ateşli silahlarda merminin namluyu terk ediş hızını ve merminin enerjisini etkileyen birçok parametre mevcuttur. İç balistik enerjisinin sebep olduğu mermi hareketinin istenilen kararlılık ve performansta gerçekleşmesi, namlu twist/helis (yivset) oranına, namlu boyuna ve mermi çekirdeğinin ağırlığına doğrudan bağımlıdır. Bu maksatla yapılan çalışmada, kalite karakteristiğini (merminin namluyu terk ediş hızı ve merminin kinetik enerjisi) etkileyen parametrelerin en ideal kombinasyonunun tespiti amaçlanmıştır. Lapua Ballistics yazılımı vasıtasıyla .308 Winchester B466 kalibre 9.72 gram/150 grain, .308 Winchester B476 kalibre 11 gram/170 grain ve .308 Winchester B416 kalibre 13 gram/200 grain mermileri kullanılarak namlu boyu, namlu çapı ve çekirdek ağırlığı giriş parametrelerinin üçer seviyelerinde L9(313) Taguchi ortogonal tasarımına bağlı sanal atışlar gerçekleştirilmiştir. 1000 m mesafede yapılan atış simülasyonlarından elde edilen mermi çıkış hızı ve mermi çıkış enerjisi değerleri için Taguchi metodu kullanılarak analiz gerçekleştirilmiştir. Kullanılan giriş parametrelerinin sonuçlar üzerindeki etkililik seviyelerinin tespiti varyans analizi (ANOVA) ile yapılmıştır. Sonuçlar içerisinde hem merminin namluyu terk ediş hızını, hem de merminin enerjisini etkileyen en etkili parametrenin sırasıyla %70.07 ve %93.73 oranlarıyla çekirdek ağırlığı olduğu gözlemlenmiştir.
Parametric optimization for machinability parameters of S960QL structural steel during milling by finite elements
(Selçuk Üniversitesi, 2022) Binali, Rüstem; Yaldız, Süleyman; Neşeli, Süleyman
S960QL structural steel material is one of the materials used in armor and structural steel applications with its unique properties. However, the machinability of S960QL is difficult due to its high strength properties. Therefore, it is critical to determine the optimum machining parameters in milling to minimize the most influential machinability characteristics on cutting force, moment and temperature. In this study, three different feed rates (0.08-0.12-0.16 mm/tooth), three different radial depths (0.8-1.2-1.6 mm) and three different axial depths (4-6-8 mm) were applied and the finite element method was used milling experiments were carried out. ANOVA and statistical analyzes based on the “lowest and best” objective function were performed with the Minitab 18 program. It was determined that the optimum cutting parameters obtained as a result of the study were 0.8 mm radial depth, 4 mm axial depth and 0.08 mm/tooth feed rate. In addition, the lowest feed force value was obtained at A1B1D2 and the highest feed force value was obtained at A3B3D1 levels. In terms of moment and temperature values, the lowest value was determined at A1B1D1 and the highest value at A3B3D3 levels. Finally, according to the results of ANOVA analysis, the axial depth parameter was effective on the process feed force, and the axial depth parameter was effective on the moment and temperature.
Detailed Combustion Analysis of Gasohol at Low, Medium and High Loads in a Spark Ignition Engine
(Selçuk Üniversitesi, 2021) Ors, Ilker; Kul, Bahar Sayin; Yelbey, Savas; Ciniviz, Murat
In this study, detailed combustion analysis of gasoline and gasohol (90% gasoline + 10% bioethanol) as fuel at 2500 rpm engine speed, under 2 Nm, 3 Nm and 4 Nm engine loads was performed in a single cylinder, four stroke, air cooled spark ignition engine. According to the test results, it was determined that gasohol has a higher maximum in-cylinder pressure and heat release rate, the bioethanol in the gasohol increases the pressure rise rate, and gasohol has a higher knock density due to its lower compression ratio. However, it has been demonstrated that gasohol ignites earlier than gasoline and thus has a shorter ignition delay and a shorter combustion duration since it burns faster
Technical and economic assessment of liquid petroleum gas modification/conversion on a gasoline engine in Turkey for time interval between 2016-2020
(Selçuk Üniversitesi, 2021) Canli, Eyub
A 1.2-liter gasoline spark ignition internal combustion engine of a Renault Symbol sedan vehicle was adapted to Liquid Petroleum Gas (LPG) fuel system in 2016. The LPG system utilizes LPG and gasoline fuels according to the operational needs. After modification, fuel consumption of the engine, fuel prices per liter, travelled distance in kilometers, dates and some additional data were recorded till November 2020. Collected data is processed for derivation of performance and economy indicators. Literature and web have been reviewed in order to find related works. Providing a solid application example of LPG conversion is aimed in this work. Also, a snapshot of fuel prices between 2016 and 2020 is being presented by graphical resolution. Approximately 12 to 15 times of initial investment cost has been returned till November 2020 by the LPG system. Also, slightly less CO2, i.e., 6%, has been emitted by means of the utilization of the system. Time resolution of the data is provided by graphics and integral data is also given. LPG conversion is found beneficial in terms of fuel cost. Also, viewed four years period does not reveal any performance problems in terms of energy spending per kilometer. However, engine additional amortization due to LPG system is not considered and this should be kept in mind.
Tribological performance characterization of brake friction materials: What test? What coefficient of friction
(SAGE PUBLICATIONS LTD, 2019) Kchaou, Mohamed.; Sellami, Amira.; Fajoui, Jamal.; Kus, Recai.; Elleuch, Riadh.; Jacquemin, Frederic.
This article describes and explains the tribological tests and methods for the evaluation of the performance of the brake friction materials. It starts by discussing the particularities of these materials and the variation of characterization tests, which can experimentally simulate many aspects of brake situation but with a large field of tribo-test, from standard to specific protocol. Examples of preparation, procedures, instrumentation, and analysis results for the tribological aspect testing ranging from the scale of vehicle braking performance (by methods including inertia dynamometers, Krauss testing, friction assessment screening test, and Chase testing) to simplified test using reduced-scale prototypes for small-sample friction, are explained. A particular attention is attributed to the discussion of the viability of the friction coefficient report in relation to the material properties and brake compound performance. At the end of this article, the guarantee of the performance output or ranking evaluated by such experimental methods is discussed.
The investigation of the use of plant-based wild mustard and boron doped oil as engine lubrication oil in diesel engines
(PERGAMON-ELSEVIER SCIENCE LTD, 2019) Öğüt, H.; Oğuz, H.; Aydın, F.; Ciniviz, M.; Deveci, H.
In internal combustion engines, mineral engine oils which serve as lubricants between parts are not used alone due to technical reasons and various additives are made use of for better lubrication. In these additives, liquid boron serves to reduce friction. To reduce the environmental damage caused by engine lubrication oils, it is necessary to improve the properties of biological oils so that they can be used and compete with mineral oils technically. In the study, the use of liquid boron as an engine lubrication oil additive, together with wild mustard oil methyl ester, was investigated. Two diesel engines with the same characteristics were used. In the first engine, experiments were carried out using mineral lubrication oil, then the experiments were repeated using mineral oil with additives, and the results were compared for both situations. The study was conducted mainly in the fields of element analysis of endoscopic examination and lubricating oil (Al, Fe, Cu, Pb, Cr). As a result, it was found out that the engine in which mineral lubricating oil with boron and wild mustard oil methyl ester additive was used did not pose any risks in terms of wear and engine oil life, compared to the engine without additive lubricating oil. (C) 2019 Elsevier Ltd. All rights reserved.
The effects of the use of vegetable oil based as engine lubrication oil on engine performance and emissions in diesel engines
(TAYLOR & FRANCIS INC, 2020) Öğüt, Hüseyin.; Oğuz, Hidayet.; Aydın, Fatih.; Ciniviz, Murat.; Deveci, Hüseyin.
The boron occupies an important place on contributions and its usage is getting widespread. Although the use of boron-added mineral oils serves to reduce friction, environmental risks can not be totally removed. It is necessary to improve the properties of biological oils used for additives so that they can compete with mineral oils technically. In the study, the use of liquid boron as an additive for engine lubrication oil together with vegetable oil was investigated experimentally in two diesel engines. Experiments were first carried out using mineral lubrication oil in the engine, and then the experiments were repeated using mineral base oil with additives in the second engine with the same technical characteristics as the first engine. Basically, the study was performed in the fields of engine performance (torque, power, consumption per hour, specific fuel consumption) and exhaust emissions (CO, CO2, HC, O-2, SO2, NOx). As a result, it was concluded that the engine, in which boron and mineral oil with wild mustard oil were used, provided more significant fuel saving than in the engine with additive-free mineral oil, and no significant change was seen in the engine performance, also they showed similarities in terms of exhaust emissions.
Modern diffusers for interior design
(SELCUK UNIV, 2019) Demirpolat, Havva.
In this study; the elements of the new generation ventilation systems are explained with the general design principles of the HVAC systems. Nozzles and diffusers which are the last elements of HVAC systems are explained with examples. Latest decades, air distribution elements have become the decorative elements in the interior. Air distribution elements are the last elements which complex air conditioning system. In addition to providing air and particle movement control and thermal comfort in the interior, they are also extremely important technical equipment when considering the space design. Thanks to developing design and manufacturing technologies, the latest ventilation equipment has become extremely flexible and has aesthetic appearance. Different modern diffusers are presented with a sample application project in this study. The architectural structure considered as a case study is a complex consisting of showroom, office, sales and service departments serving in the automotive sector. The planer glass facade coating system is the determining element in architecture in general, while the interior stainless steel details and mounting elements form the basic style of the sample building. In the building which is an intensive human and vehicle movement, the glass facade provides maximum natural lighting and passive heating at the same time. For the summer months, mechanical ventilation is preferred, and the Cr-Ni ventilation equipment that provides harmony with the steel structure is the most noticeable interior detail. In this article, a wide interior analysis was carried out with installation plans and sample application visuals as well as mechanical ventilation details.
Investigation of progressive tool wear for determining of optimized machining parameters in turning
(ELSEVIER SCI LTD, 2019) Kuntoğlu, Mustafa.; Sağlam, Hacı.
On-line monitoring of tool wear and tool breakage are very important to reduce production costs through the optimization of machining parameters. Increasing cutting forces affect workpiece quality and tool condition that is the ultimate aim of production line and progressive tool wear which can trigger the tool breakage. Taguchi method is extensively used for determining number of experiment while variance analysis (ANOVA) deals with which parameter/s is/are effective on output. This study contains experiments and optimization processes during turning of AISI 1050 material with 3 input parameters (cutting speed, feed rate, tool tip) using Taguchi method. In order to determine the condition of the cutting tool, measurement of tangential cutting force and acoustic emission (AE) were carried out during metal removing. ANOVA results showed that cutting speed is the most effective about %45 and tool tip is the second about %35 on tool wear. On the other hand, the effect of feed rate on tangential cutting force (%88) and cutting speed on AE (%80) is remarkably higher than the other two parameters. In order to obtain the minimum tool wear value, the optimum cutting parameters have been selected as v(1) = 135 m/min, f(2) = 0,214 mm/rev, T-2 = P25. By implemented sensor system tool breakage can be successfully detected and used for producing high quality materials with low costs. (C) 2019 Elsevier Ltd. All rights reserved.
Investigation of engine performance and kit design for the usage of safflower oil as in diesel engine
(PERGAMON-ELSEVIER SCIENCE LTD, 2019) Oğuz, H.; Öğüt, H.; Aydın, F.; Ciniviz, M.; Eryılmaz, T.
In Turkey, the consumption of diesel oil is increasing both in transportation and in agricultural fields. In this study, the opportunities of the use of safflower oil, which grow originally in Turkey as a direct fuel in diesel engines, were researched to provide a new alternative for biofuel industry and to popularize the farming of oil crops. In this study, the kit design was completed first, and afterwards safflower oil was exposed to the process of neutralization and laundering, and then turned into standard fuel. For engine performance experiments, reference experiences were conducted by using diesel fuel by using safflower as a fuel in the engine with kit for 500 h; comparisons were made with regards to power, moment, diesel consumption, and exhaust emission. As a result, it was seen that when safflower was used as a fuel, there was a decrease in motor performance and emission, however specific fuel consumption increased. When safflower was used, there was not any residual on the engine that was found. The designed kit, which can be easily produced with national technology, did not cause any malfunction or negativity in the engine and it was successfully used. (C) 2019 Elsevier Ltd. All rights reserved.
Effect of plasma nitration process at various temperatures on wear behavior of aisi 4340 steel
(Gazi Univ, 2018) Basak, Hudayim; Duzcukoglu, Hayrettin; Senyurt, Muhammet Ali
In this study, AISI 4340 (34CrNiMo6) tempered steel was applied to the plasma nitration process at different temperatures and at different periods in order to increase the wear resistance of the outer surface without decreasing the hardness of the core under 40-44 HRC, and to prevent the component from distortion during heat treatment. The sufficient core strength and tensile stress of some mechanical elements such as mold, drill, U-Drill are required not to fall below a certain value. There were five different temperatures (450, 475, 500, 530 and 550 degrees C) and two different time values (18 and 32 hours) used with these temperatures utilized in the study. The study tried to identify the optimum nitriding temperature and time for the limit values determined by considering the wear value after nitriding. The wear characteristics of the samples in dry conditions were also investigated. It was observed that the ideal target values (core 40-44 HRC) in the nitrided components were reached at 450 degrees C in 32 hours.
Nanofiber tabakalı hava filtrelerinin partikül yakalama performanslarının incelenmesi
(2018) Dincer, Kevser; Önal, Gürol; Selbes, Mehmet; Akdemir, Ahmet
Bu çalışmada, 25-85 g/m2 gramaj arasındaki mikrofiber hava filtrelerininüzerine nanofiber kaplanarak çok küçük partikülleri yakalama performanslarıincelenmiştir. Filtrelerin performans tayini için basınç kaybı ve partikül yakalamatestleri yapılmıştır. Basınç kaybı deneylerinde filtrelere 0.3, 0.8, 1.3 m/s hızlarındahava, partikül yakalama testleri için ise 0.3 m/s hızında ortalama 100 nm çapındaformda toksik olmayan CaCO3 nanopartiküllü hava kullanılmıştır. Küçük fiberçapına sahip, kesit alanı büyük, rijit ve mukavim spunbond mikrofiber filtrelerinnanofiber tabaka kaplamaya elverişli olduğu ve optimum filtreleme sağladığıbelirlenmiştir. Küçük çaplı nanofiberlerin ince tabaka, büyük çaplı nanofiberlerinkalın tabakalı kaplanması filtreleme performansını arttırmaktadır. Nanofibertabaka kaplama ağırlığının artmasıyla performansın yükseldiği ve kritik birdeğerden sonra filtrenin tıkanarak ömrünü tamamladığı tespit edilmiştir.
Paslanmaz çeliklerde hidro-kesme yönteminin sonlu elemanlar yöntemi ile incelenmesi
(2018) Korkmaz, Habip Gökay; Toros, Serkan; Halkacı, Hüseyin Selçuk
Yapılan bu çalışmada kesme operasyonunun özellikle son yıllarda birçok alanda yaygın olarak kullanılmayabaşlanan hidro şekillendirme prosesine uyarlanabilirliğinin nümerik olarak değerlendirilmesi yapılmıştır.Nümerik çalışmalar kapsamında malzemenin kesilme yüzeyleri değerlendirilmiş ve çapak oluşum durumuzımbanın farklı hareketi için incelenmiştir. Modelleme çalışması kapsamında Johnson-Cook (J-C) pekleşme vehasar modeli kullanılarak, hedeflenen proses parametrelerinde kesme durumunun gerçekleşip gerçekleşmediğibelirlenmeye çalışılmıştır. Sonuç olarak hedef proses parametrelerinde 304 paslanmaz çeliğin bu proses ilekesilebilirliği gösterilmiştir.
Al 5754-O sac malzemenin şekillendirme sınır gerilme diyagramının elde edilmesi
(2018) Türköz, Mevlüt; Dilmeç, Murat; Halkacı, Hüseyin Selçuk
Sac şekillendirme proseslerinde, sacın istenen şekli alması bölgesel boyunlaşma ve yırtılma hasarlarıtarafından sınırlanır. Bu proseslerde malzeme davranışını tahmin etmek için bilgisayar modelleri geliştirilmiştir.Bu modellerin gerçek durumu temsil edebilmesi için malzeme parametrelerine ihtiyaç vardır. Bu parametrelergenellikle çekme deneyi ve şekillendirme sınırını belirten diyagramlar ile elde edilir. Şekillendirme sınırınıbelirten diyagramlar sınır birim şekil değiştirme değerlerini gösteren şekillendirme sınır diyagramı ve sınırgerilme değerlerini gösteren şekillendirme sınır gerilme diyagramıdır. Şekillendirme sınır diyagramının hasar tahminini karmaşık ve birden fazla kademeli şekillendirme işlemlerindedoğru olarak tahmin edemediği, şekillendirme sınır gerilme diyagramının ise bu durumlarda da başarılı hasartahminlerinde bulunduğu literatürde belirtilmektedir. Bu çalışmada Al 5754-O malzemeye ait şekillendirme sınırgerilme diyagramı hem teorik hem de sayısal yöntemle elde edilmiştir.
Surface roughness estimation for turning operation based on different regression models using vibration signals
(2018) Neşeli, Süleyman; Yalçın, Gökhan; Yaldız, Süleyman
On machined parts, major indication of surface quality is surface roughness and also surface quality is one of the most specifiedcustomer requirements. In the turning process, the importance of machining parameter choice is enhancing, as it controls the requiredsurface quality. To obtain the better surface quality, the most essential control parameters are tool overhang and tool geometry in turningoperations. The goal of this study was to develop an empirical multiple regression models for prediction of surface roughness (Ra) fromthe input variables in finishing turning of 42CrMo4 steel. The main input parameters of this model are tool overhang and tool geometrysuch as tool nose radius, approaching angle, and rake angle in negative direction. Regression analysis with linear, quadratic andexponential data transformation is applied so as to find the best suitable model. The best results according to comparison of modelsconsidering determination coefficient (R 2 ) are achieved with quadratic regression model. In addition, tool nose radius was determined asthe most effective parameter on turning by variance analysis (ANOVA). Cutting experiments and statistical analysis demonstrate that themodel developed in this work produces smaller errors than those from some of the existing models and have a satisfactory goodness in allthree models construction and verification.
The determination of the effect of mixture proportions and production parameters on density and porosity features of miscanthus reinforced brake pads by taguchi method
(2018) Ünaldı, Mahmut; Kuş, Recai
Brake pads are generally consisted of five different component groups. These groups are named as reinforcements, binders, abrasives, lubricants and fillers. Each of these groups has its own function such as to improve friction property, wear resistance, to increase strength, and to reduce porosity and noise. In this study, Miscanthus as reinforcement, cashew as lubricant, alumina as abrasive, calcite as filler, and phenolic resin as binder were used to produce composite ecological brake pad samples. Brake pads are usually developed through trial and error method and therefore, the evaluation process became complicated and time consuming due to the multiplicity of components, randomly selected mixing ratios, results obtained from the experiments, etc. and so Taguchi method is utilized to get rid of these difficulties of trial and error method. This study was made in order to determine the influence level of the brake pad ingredients and some production parameters to the density and porosity features of the brake pad samples. The ecological brake pad samples were manufactured and experiments were conducted to Taguchi Method L32 orthogonal array. According to the ANOVA (Analysis of Variance) tables and other graphical results obtained from Taguchi method, the density feature of brake pad samples are more influenced by the mixture proportion factors and moulding temperature, curing time and curing temperature factors have a minor effect on porosity feature of brake pad samples.
Alüminyum bal peteği yapılarda oluşan eğilme kuvvetlerinin çoklu regresyon ile incelenmesi
(2015) Akkuş, Harun; Düzcükoğlu, Hayrettin; Şahin, Ömer Sinan
Bu çalışmada, altıgen yapılı bal peteği kompozit yapıların çoklu regresyon tahmin modeli oluşturulmuştur. Saf epoksi ve %1 çok duvarlı karbon nano tüp (mwcnt) takviyeli yapıştırıcı ile farklı hücre genişliği ve farklı yükseklikteki numuneler yapıştırılarak üretilen alüminyum bal peteklerinin üç nokta eğilme deneyleri ASTM E1556-08 standardına göre gerçekleştirilmiştir. Deney sonucu eğilmeye sebep olan maksimum kuvvet(F) değerleri ölçülmüştür. Deney sonuçlarında hücre genişliği sabit tutulduğunda hücre yüksekliği arttırıldığında eğilme kuvvetinde artma olduğu gözlemlenmiştir. Aynı hücre yüksekliği için bakıldığında hücre genişliği arttıkça eğilme kuvvetinde azalma olduğu gözlemlenmiştir. %1 mwcnt ile takviye edilen yapıştırıcı eğilme kuvvetlerinde azalmaya sebep olmuştur. Fepoksi için en iyi sonuçlar logaritmik regresyon denklemiyle, FCNT için en iyi sonuçlar I. dereceden regresyon denklemiyle elde edilmiştir. Fepoksi ve FCNT bağımlı değişkenine en çok etkiye sahip olan bağımsız değişkenin hücre genişliği olduğu tespit edilmiştir
Preparation of the New Polyaniline/ZnO Nanocomposite and Its Photocatalytic Activity for Degradation of Methylene Blue and Malachite Green Dyes Under UV and Natural Sun Lights Irradiations
(ELSEVIER, 2012) Eskizeybek, Volkan; Sarı, Fahriye; Gülce, Handan; Gülce, Ahmet; Avcı, Ahmet
A new polyaniline (PANI) homopolymer and PANI/ZnO nanocomposite have been successfully synthesized in aqueous diethylene glycol solution medium via the chemical oxidative polymerization of aniline. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, FTIR spectra, UV-vis spectroscopy measurements were used to characterize the resulting PANI homopolymer and PANI/ZnO nanocomposite photocatalysts. The photocatalytic activities of PANI homopolymer and PANI/ZnO nanocomposites were investigated by the degradation of methylene blue (MB) and malachite green (MG) dyes in aqueous medium under natural sunlight and UV light irradiation and the efficiency of the catalysts have been discussed in detail. Results indicate that the addition of the ZnO nanoparticles to the PANI homopolymer enhance the photocatalytic efficiency under natural sunlight irradiation and a little amount of PANI/ZnO nanocomposite photocatalyst (0.4 g/L) degrades both of the dye solutions (MB or MG) with 99% efficiency after 5 h of irradiation under natural sunlight.

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