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Oksijen ve sıcaklığın reaktif magnetik alan sıçratma yöntemiyle büyütülen çinko oksit ince filmlere etkisi
Çinko oksit (ZnO), yarı iletken endüstrisinde gösterdiği saydam iletken oksit (SİO) özelliği ile hızla gelişmekte olan optoelektronik teknolojisinde sıklıkla kullanılan bir malzemedir. Bu tez çalışmasında, reaktif radyo frekans magnetik alan sıçratma yöntemi ile büyütülen ZnO ince filmlerin büyütme esnasında ortamda bulunan oksijen ve alttaş sıcaklığına bağlılığı yapısal ve optik özellikleri açısından değerlendirilmiştir. Yapılan X-ışınları kırınım deseni analizleri sonucunda elde edilen bulgular incelendiğinde bütün filmlerin yüksek yönelime sahip hekzagonal wurtzite yapısında olduğu ve bunun O2 miktarına bağlı olmadığı sonucuna ulaşılmıştır. Ayrıca, Raman spektrumları da wurtzite yapısının varlığını doğrulamaktadır. Aynı zamanda tüm örneklerin yüksek geçirgenliğe sahip olduğu ve film kalınlıklarının sıcaklık artışı ile azaldığı tespit edilmiştir. Alan etkili taramalı elektron mikroskobu (FE-SEM) ve atomik kuvvet mikroskobu (AFM) sonuçları ise filmlerdeki taneciklerin oda sıcaklığında, 100 oC'de ve 200 oC'de çok değişmediği ancak 300 oC sıcaklıkta büyütülen filmlerin homojen olmayan tanecik büyümesi sergilediği tespit edilmiştir. Ancak, bu durum O2 arttıkça azalmaktadır. Bütün filmler için optik bant boşluğu ⁓3.25 eV olarak tespit edilmiştir. Yapılan bu çalışma, optoelektronikte oldukça sık kullanılan ince film çinko oksit yapılarına ilişkin kapsamlı bir optimizasyon sunmuştur.
Perovskite güneş hücreleri için metal oksit alttaşların üretimi ve tasarımı
Tez çalışmasında, düzlemsel mimariye sahip perovskite güneş hücrelerinde (PGH) kullanılmak üzere optimize edilmiş indiyum kalay oksit (ITO) ve flor katkılı kalay oksit (FTO) alttaşların üretimi, karakterizasyonu ve hücre uygulamaları gerçekleştirilmiştir. Bu çalışmanın amacı, ticari alttaşlara kıyasla daha üstün optoelektronik özellikler sunan metal oksit alttaşları üreterek perovskite hücrelerinin performansını artırmaktır. ITO ve FTO alttaşlar, magnetron saçtırma yöntemi kullanılarak RF ve DC güç kaynaklarıyla farklı güç değerlerinde (optimum değerler sırasıyla 320 W ve 137 W) ve sistem için ideal kabul edilen ~5 x 10⁻³ Torr basınç altında üretilmiştir. Düşük basınçta plazma yoğunluğundaki kararsızlık nedeniyle bu strateji tercih edilmiştir. Üretimler, ITO için oda sıcaklığında, FTO için ise 150 °C'de gerçekleştirilmiştir. FTO üretimi sırasında yapıda oluşabilecek oksijen eksiklikleri, ortama az miktarda oksijen verilerek azaltılmaya çalışılmıştır. Üretilen ITO ve FTO kaplı camların elektriksel dirençleri ölçülmüş, ardından farklı sıcaklıklarda tavlama işlemi uygulanmıştır. Karakterizasyon sonuçları, özellikle ITO alttaşların güneş hücreleri için umut verici özellikler sergilediğini göstermiştir. ITO ve FTO alttaşlar, elektrot/c-TiO₂/perovskite/spiro-OMeTAD/Au mimarisine sahip hücrelerde elektrot olarak kullanılmış ve fotovoltaik performansları ticari ITO (Sigma-Aldrich, Kintec) ve FTO (Sigma-Aldrich) alttaşlarla karşılaştırılmıştır. Sonuçlar, proje kapsamında geliştirilen ITO filmlerin ticari ITO'ya göre daha üstün optik ve elektriksel özellikler sergilediğini ve fotovoltaik verim açısından daha yüksek sonuçlar elde edildiğini ortaya koymuştur. Akım yoğunluğu-voltaj (J-V) karakteristiklerine göre, ticari ITO kullanılan en iyi hücrede %19.9 verim elde edilirken, tez çalışması kapsamında geliştirilen ITO kullanılan hücrede %20.2 verime ulaşılmıştır. Sonuç olarak, bu tez, optimize edilmiş ITO alttaşların güneş hücrelerinde verimliliği artırma potansiyeline sahip olduğunu ve gelecekte optoelektronik aygıt teknolojisinde daha geniş uygulama alanı bulabileceğini göstermektedir.
Fabrication and characterization of nickel oxide functionalized graphene oxide-polyacrylamide nanocomposites
Graphene oxide (GO) and its functionalized - modified - reduced derivatives take important place in a variety of technological applications because of their unique electrical conductivity properties and excellent mechanical properties which intrinsically come from two dimensional, sp2 bonded carbon honeycomb crystal structure of graphene and its high specific surface area (~2600 m2 g-1). Having this large surface area allow graphene to be homogenously dispersed in polymer matrix, thus it can be used to fabricate advanced nanocomposites which can be integrated in energy storage systems, physical and biological sensors, flexible electronics and many other applications. Generally, graphene oxide is produced using main three methods known as Hummer method, Brodie method or Staudenmaier method. All these three methods contain a familiar, incredibly cost-effective route; an oxidation reaction of graphite and then followed by exfoliation step to form graphene oxide. Widely accepted, oxygen functional groups on surface graphite oxide allow it to be exfoliated to form graphene oxide. However, oxygen based groups distort intrinsic graphene properties, thus reduction step is needed to yield much accurate graphene form. Several reduction routes have been studied and reported, including chemical treatment, thermal treatment, electrochemical treatment. Some of oxygen groups can be removed, but a portion will remain that can be eliminated by several reduction steps. Besides, the certain functional groups can be chemically anchored on graphene oxide surface in reduction steps. This process is described as functionalization of graphene oxide with like inorganic molecules(e.g., metal oxides) or organic molecules (e.g., polymers). Polymers have been used in many application and product because of being relatively cheaper and easily processed. However, their low mechanical and electrical properties limit their applications in some areas. Most of publication in literature has reported remarkable improvements in mechanical and electrical properties, compared to the bare polymers with a small portion of graphene filler, as crosslinker. But, an important point, the improvements intensely depend on distribution of graphene in polymer matrix and forming interfacial bondings between the graphene and host matrices. Hydrophilic polymer lead the graphene sheets to aggregate owing to interactions between the hydrophilic polymer chains and graphene layers. In contrast, graphene oxide, having oxygen based functional groups anchored on the surface, is more suitable with hydrophilic - organic polymers. However, oxygen based groups hinder intrinsic electrical properties of graphene. Hereby, grafting or intercalating of reduced - functionalized graphene oxide into polymer matrix is the most compatible option among all routes to improve its mechanical and electrical properties, simultaneously. This work has focused on fabrication of nickel oxide functionalized graphene oxide - polyacrylamide nanocomposites, (NiO/GO)n/PAAM, and investigation of their structural, mechanical, electrical properties and self-healing ability. The aim of this study is to observe the effect of nickel oxide functionalized graphene oxide (NiO/GO) amount on structural, mechanical, electrical properties and self-healing ability of nanocomposite samples and compare them with that of (BIS) crosslinked (PAAM) samples to determine the difference between (NiO/GO) and (BIS). In the first step, (NiO/GO)n/PAAM and (BIS)n/PAAM samples were fabricated by using in-situ polymerization of polyacrylamide in presence of (NiO/GO) and (BIS), seperately. Secondly, structural characterization of (NiO/GO)n/PAAM nanocomposite samples were investigated by FTIR analysis and XRD to confirm the nanocomposition and crystal structure occured. After structural correction, mechanical properties, electrical properties and self-healing abilities of (NiO/GO)n/PAAM nanocomposite samples were determined and discussed.
Construction and characterization of biomimetic cell membranes on the surface of electrospun conductive nanofiber mats
Cell membranes are utilized by every organism for separation and protection of their contents from external environment. For higher organisms, biological membranes are used for compartmentalization and organelle formation. Understanding the structure and function of the cell membrane is crucial for manipulation of cellular trafficking, signaling pathways, drug delivery/targeting systems and biosensor applications. Biomimetic cell membranes are developed for these purposes with various strategies. One of these strategies is utilization of lipid bilayer membranes. Since the 45-50 % of the cell membrane is composed of lipid structures, lipid bilayer membranes are well suited candidates for their studies. Despite the development of variety of biosensors by immobilization of globular proteins, biosensors based on membrane proteins containing large hydrophobic parts have not been easily produced. When these proteins are incorporated into biomimetic membranes, both their structural integrity and the functionality would be preserved. The objective of this work was to construct a lipid bilayer on a conductive nanofiber mat. Constructed structure was aimed to be used as a model biosensing platform. Polycaprolactone (PCL) nanofiber mats were produced by electrospinning process. These mats were then coated with polypyrrole (PPy) by in situ polymerization method using various monomer concentrations and polymerization durations. Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) and Raman Spectroscopy were used for the analysis of bare PCL and PPy coated PCL structures. Broad N-H bond peak at 3500-2700 cm-1 and N-H in plane deformation peak at 1100 cm-1 were attributed to the PPy structure and it was concluded that polymerization was successfully performed. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) techniques were used for the morphological characterization of nanofibers. Smooth Polycaprolactone fibers with 251.81 nm diameter were obtained by electrospinning. When in situ polymerization performed at low concentration of pyrrole monomer, nanofibers with cauliflower-like structures (453.20 nm) were produced. With the increased Py concentration, PPy layer seemed to cover both the PCL nanofiber surfaces and the pores in between. The thickness and coverage of PPy was increased with the increasing Py monomer concentration and the duration of polymerization process. PCL/PPy electrodes were coated with phosphatidyl choline (PC) liposomes (PCL/PPy/PC) by vesicle fusion method in Phosphate Buffered Saline (PBS). PC liposome covered PCL/PPy mats were observed with SEM micrographs. Electrochemical Impedance Spectroscopy (EIS) and Equivalent Circuit Modelling (ECM) methods were utilized for the determination of electrochemical properties of electrodes. Impedance measurements were carried out between 0.01 Hz and 100 kHz. The charge transfer resistance (Rct) of PCL was highest. Rct of PPy significantly reduced. With increased concentration of PPy, Rct was further reduced. Coverage with PC resulted in an increase in resistance and provides an insulating layer on surface of the electrodes. Total coverage of the electrode surface rather than coverage of only nanofiber surface with PC resulted in better electrochemical properties. The constructed system was aimed to be used for different applications such as integration of membrane proteins and/or detection of different compounds which interact with cell membranes. This system can be further improved by using binary mixture of PC and phosphatidyl serine (PS) lipid for vesicle production.
Design simualtion and analysis of piezoresistive microcantilever for biosensing applications
In the past decade, several research works demonstrated the ability of Biological Microelectromechanical System (Bio-MEMS) biosensors to detect of biomolecules such as Deoxyribonucleic Acid (DNA), proteins, Bacteria and Antigens. But due to the low concentration of the analytes that need to be detected in the samples,a minuscule signal results in the output of the sensor. In response to this, a need arisen for an optimized biosensor capable of giving high output signal in response the detection of few analytes in the sample; the ultimate goal is being able to convert the attachment of a single biomolecule into a measurable quantity. For this purpose, MEMS microcantilevers based biosensors have emerged as a promising sensing solution because it is simple, cheap, highly sensitive and more importantly does not need analytes optical labeling (Label-free). Among the different microcantilever transducing techniques, piezoresistive based microcantilever biosensors seem to be a more attractive solution being cheap, high sensitive, miniature, works well in liquid environments and having integrated readout system. Even though there are many publications in literature that concentrated on increasing the piezoresistive microcantilevers sensitivity, they only considered in optimizing few design and process parameters thus the resultant sensitivity enhancements are not good enough for practical applications. After the analyzation of the work found in literature, it was found that the parameters/approaches that be can be optimized/used to enhance the sensitivity of Piezoresistive microcantilever-based sensors are: Cantilever dimensions, Cantilever Material, Cantilever Shape, Piezoresistor's material, Piezoresistor's doping level, Piezoresistor's Dimensions, Piezoresistor's position, Stress concentration Region's (SCR) shape and position. In this study, after a systematic analyzation of the effect of each design and process parameters on the sensitivity, a step-wise optimization approach was developed in which almost all these parameters were variated one at each step while fixing the others to get the maximum possible sensitivity at the end. Throughout this work, COMSOL Multiphysics 5.0, a commercial Finite Element Analysis (FEA) tool, was used to simulate the sensor performance. At each optimization step, the goal was to optimize the parameter in such a way that it maximizes and concentrates the stress in piezoresistors region for the same applied force thus get the higher sensitivity. In total, almost 46 different simulations were done to get the final optimized sensor. Starting with a rectangular cantilever, the piezoresistor material and doping level were optimized in two steps. When the piezoresistor material was varied (single crystal silicon and Poly-silicon), it was found that the ΔR⁄R sensitivity is higher in the case of single crystal silicon. xxiv But for this sensor design, polysilicon has been chosen as the piezoresistor material because it's sensitivity does not depend on the crystal orientation, the sensor fabrication is easier, cheaper and can be realized in ITUnano laboratory. Next, by changing the doping level in the range between 1×1015 cm−3 to 1×1020 cm−3 and calculating the ∆R/R sensitivity, the doping level that will be used throughout the following simulations was determined. It was found that, 1×1018 cm−3 doping level is high enough to reduce the thermal noise effect, at the same time it does not be affected the sensitivity that much. Thus this doping level was chosen and used throughout the following simulations. Afterward, the cantilever material is varied to find the material that gives maximum stress and deflection for the same applied force. It was found that SiO2 resulted into almost 2.5x higher deflection and 1.7x higher sensitivity when compared to single crystal silicon (the starting cantilever material) case thus SiO2 has been selected as the cantilever material for this biosensor and it is used in the following optimization steps. Next, various cantilever shapes (Rectangular, Pi-shape, T-shape, Trapezoid, SteppedTrapezoid, and Triangular) were introduced, and for each shape, the dimensions were varied bearing in mind the process and device limits. The results from all these simulations were compared to find the optimized shape which gives the maximum sensitivity. During the rectangular shape microcantilever optimization step, it was found that the cantilever thickness has the highest effect on the sensor sensitivity when compared to the change in cantilever length and width. In addition to that, after the different rectangular microcantilever dimensions were optimized (length, width and thickness), the sensitivity increased 18.3x folds. Also, adding two side holes to the rectangular cantilever structure (T-shape) increased the sensitivity by 1.6 factor. Overall, for the same applied force, the trapezoid-shaped microcantilever design gave higher sensitivity (more than 46x times greater than the starting sensor sensitivity) whereas the stepped-trapezoid shaped gave the highest maximum deflection. Afterward, Stress Concentration Region (SCR) was introduced in the optimized trapezoid structure in different locations and orientations seeking for further sensitivity enhancement. From the simulations, it was found that adding a 30µ×10µm SCR rectangular hole to the optimized trapezoid structure 15µm away from the clamped cantilever edge, resulted in almost 1.6x times sensitivity enhancement which gave the best sensitivity value compared to the other positions. Regarding the normalized change in resistance to the applied force the final sensor's sensitivity equals to -1.5×10-8 Ω/Ω ⁄pN; this means that for each 1pN (10-10 g) biomolecules attach to this biosensor; the piezoresistor resistivity will decrease by 1.5×10-8 Ω. When compared to the starting sensor, the final sensor design gave 73.5x times better ΔR⁄R sensitivity and it is more sensitive than the other sensor designs previously reported in the literature. The fabrication sequence for this sensor was prepared, but due to technical problems in some of the devices found in ITUnano laboratory, the sensor has not been fabricated.
Aerosol filtration performance of nanofibrous webs produced via centrifugal spinning technique
Nanofibers are one of the important nano scale products. Owing to their large specific surface area and high porosity, they are widely investigated for filtration, energy and biomedical applications [1]. So far, electrospinning is by far the most common method for nanofiber production, but this method has some difficulties such as low production rate (~1 ml/h/nozzle) and high voltage necessity (up to 60 kV) [2]. However, the wide-spread commercial use of electrospinning is limited mainly due to its low production rate. Most other nanofiber production methods, such as melt-blowing, bicomponent fiber spinning, phase separation, template synthesis, and self-assembly, are complex and can only be used to make nanofibers from limited types of polymers. Centrifugal spinning is an alternative method for producing nanofibers from various materials at high speed and low cost. In this thesis, the centrifugal spinning method was reviewed thoroughly. An overview on the centrifugal spinning process was given, and it was compared with the conventional nanofiber production methods. In addition, the nanofiber filter media were produced via custom made lab scale centrifugal spinning machine. There are three experimental chapters presented in the thesis. At the beginning a custom made centrifugal spinning device was designed and manufactured. The system were introduced. After the manufacture, several experimental studies were performed using various polymer solutions. Especially, the studies were concentrated on thermoplastic polyurethane (TPU) nanofibers. After the morphology characterization, an optimization study on fiber diameter of TPU nanofibers was performed. The optimal process parameter levels were determined, and also the effects of these parameters on fiber diameter were demonstrated statistically. Then, the filtration performance of the produced webs were analyzed. A correlation between the fiber diameter and filtration quality has been established. It is expected that this study will leave a positive impression onto the forthcoming studies on nanofibers especially for the nanofibrous filter production.
Nano boyutta malzeme katkılarının betonun elektriksel direnç birim şekil değiştirme ilişkisine etkisi
Ülkemizde son yirmi yılda, depremlerin, malzeme bozulmalarının ve çevresel faktörlerin sebep olduğu hasarlar yüzünden yıkılan betonarme yapılar, binlerce insanın yaralanmasına veya hayatını kaybetmesine sebep olmuştur. Yapı sağlığının izlenmesi, can ve mal kaybının oluşmasını önlemek için hayati öneme sahiptir. Yapı sağlığını izlemek için kullanılan gerinim pulları noktasal ölçüm yaparlar, duyarlılıkları düşüktür, ömürleri kısadır, yüksek maliyetlidir. Bu çalışmada, kendi birim şekil değiştirmesini ve hasarını ölçen akıllı beton üretilmiştir. Akıllı betonu belirlemek için, farklı iletken malzemeleri farklı hacimsel oranlarda içeren karışımlar tasarlandı. Her karışımdan üretilen örneklere basınç testi uygulandı. Elektriksel direnç değişimi ile basınç birim şekil değiştirmesi arasındaki ilişki belirlendi. Basınç birim şekil değiştirmesine en duyarlı makro boyutta malzeme katkılı karışımlar ve nano boyutta malzeme katkılı karışımlar belirlendi. Bu karışımlara yarmada çekme testi ve eğilme testi uygulandı. Birim şekil değiştirmeye ve çatlak uzunluğuna en duyarlı karışım akıllı beton olarak seçildi. Akıllı beton farklı yükleme hızlarında test edildi. Sıcaklık ve nemin akıllı betona etkileri araştırıldı. Çevresel elektrot metodu ve alternatif akım etkileri araştırıldı. Elektrik akımının birim şekil değiştirmeye dik olduğu çapraz yüklemenin etkileri araştırıldı. Akıllı beton, elektriksel direnç değişimi ile birim şekil değiştirme arasında güçlü bir doğrusal ilişki verdi. Elektriksel direnç değişimi ile birim şekil değiştirme mekanizması, basınç, yarmada çekme ve çapraz yükleme testleri için tanımlandı. Gömülü elektrot metodunun çevresel elektrot metodundan daha iyi olduğu gözlemlendi. Akıllı beton doğru akım uygulamaları, alternatif akıma daha yüksek duyarlılık verdi. Uzun dönemde, birim şekil değiştirme duyarlılığı azaldı; uzun süre bekleyen ve nemi arttırmak için suya batırılmış akıllı beton, aynı yaş numunelerine göre daha yüksek bir birim şekil değiştirme duyarlılığına sahiptir. Büyük ölçekte akıllı beton numuneleri birim şekil değiştirme ile elektriksel direnç değişimi arasında güçlü doğrusal ilişki gösterdi. Akıllı beton yapı sağlığını izlemek için prefabrik ve önemli yapılarda kullanılabilir.
Development of nano-material based optical chemical sensors indicating oxygen levels in petrochemistry related workplaces
In workplaces, especially in refineries, volatile petroleum solvents are usually in the form of mixtures of alkanes, cyclic alkanes, alkenes and the aromatics. Such atmospheres which are deficient in oxygen may not provide adequate sensory warning of danger. Therefore correct and continuous monitoring of oxygen levels in such environments is quite important. On the other hand, ruthenium (II) derivatives are known as oxygen sensitive dyes and have intensively been used in the design of optical chemical sensors. Most of the ruthenium dyes suffer from leaching from host matrices due to the water solubilities. In order to provide the best host/dye compatibility we used the amphiphilic ruthenium derivatives in silicon based matrices. In this work, emission-based oxygen sensing properties of highly luminescent ruthenium (II) derivatives were tested in the presence and absence of some volatile organics. Newly synthesized two orange-red emitting alkyl branched ruthenium complexes were used along with silver nanoparticles (AgNPs) in two different silicon based matrices for oxygen sensing purposes. The sensing materials were fabricated in form of thin films and electrospun nanofibers. Ionic liquid and perfluorinated compounds were exploited as additives to enhance the response to oxygen. Oxygen induced spectral changes at 630 nm were followed for both gas phase and dissolved oxygen as the analytical signal. The oxygen sensitivities of the probes were also tested by lifetime based and kinetic mode measurements. Utilization of the amphiphilic Ru dyes in silicon along with AgNPs in the form of electrospun fibers resulted in many advantages such as enhanced long term stability, increased surface area, sensitivity and improvement in all sensor dynamics. Sensing characteristics of the offered design were tested and calibrated in the presence of vapors of benzene, toluene, ethylbenzene, hexane and xylene, which simulate refinery related work places.
Production and application of n- and p-type Si wafer using CVD method
Necessity for electricity is one of the most significant issues of present time. Rapid consume of most used underground resources made it necessary for researching the new kind of energy sources. After the increase of daily requirements and quality necessities, innovations in electric production technologies gained importance. Production of electricity from the sun is based on the principal of contacting the two sides of a semiconductor stimulated by sun and the returning of electrons which have been sent to conductivity level to their initiation locations after completing the entire circuit. Materials science which is a multidisciplinary branch could be defined as investigation and development of proper tools for providing sources for humanity. In this respect, in the scale of current thesis, production of solar cells for renewable energy obtainment using modified semiconductor silicon wafers was aimed and studied. Single crystal structured crystal wafers with semi-conductive character were modified and the stimulation of material with sun light was achieved. In order to enlighten the structures of the produced solar cells, SEM, XRD, XPS, UV-vis and profilometer calculations were carried out. In addition of structural analysis, electrical properties of the produced cells were determined. There are many remarkable factors in current study in order to benefit fully from the sunlight. By texturation, refraction of photons interacted with surface was prevented opposite to the angle they interacted. Optimum realization studies of electron-hole separation were achieved with diffusion time determination. With utilization of reflection blocker coating, absorption of rays interacted with the surface of solar cells was provided. In addition to the scientific results, with the support of İZ-KA to the current study, more attention to renewable energy in Dokuz Eylül University was gained. Thanks to the energy stations in university in scope of current project, charging the batteries of electrical devices was realized.
Antifungal hibrit kaplamaların hazırlanması ve karakterizasyonu
Bu çalışmada, polikarbonat (PC) ve polimetil metakrilat (PMMA) yüzeylere kekik yağı, karabiber yağı, kimyon yağı ve çay ağacı yağı katkılı 3-(Trimethoxsilyl)propyl methacrylate (TMSPM) ve tetraethyl orthosilicate (TEOS) bağlayıcı madde bazlı hibrit kaplamalar yapılmıştır. Hibrit kaplama yüzeyleri termal ve UV ile kürlenmiştir. Kaplanan PC ve PMMA polimer yüzeyleri Fourirer Dönüşümlü Kızılötesi (FTIR) Spektroskopisi analizi, dijital mikroskop görüntülemesi, temas açısı analizi ve antifungal duyarlılık ile karakterize edilmiştir. Kaplamasız PC için 87.84°, PMMA için 95.89° temas açısı verilmiştir. FTIR analizlerinde TEOS, kekik yağı, kimyon yağı, çay ağacı yağı ve karabiber yağı için karakteristik pikler elde edilmiştir. Dijital mikroskop görüntüleri için 2.059-49.322 µm aralığında kalınlık elde edilmiştir. Anrifungal duyarlılık testinde Aspergillus flavus küfü için ek etkili olanlar sırasıyla kekik yağı, çay ağacı yağı, kimyon yağı, TEOS ve karabiber yağı sırasını takip etmiştir. Anahtar Kelimeler: Antifungal, Silan, Esansiyel yağlar, Kaplama, Polimer
Investigation of corrosion properties of Ni matrix nanocomposite coatings produced by electrodeposition technique
This research aimed to investigate electrochemical corrosion behavior of Nickel matrix nanocomposite coatings produced by electrodeposition technique in a Watts bath containing titanium dioxide and Zinc doped titanium dioxide nanoparticles. In this study, titanium dioxide and Zinc doped titanium dioxide nanoparticles were prepared using a sol-gel method. Obtained results indicate that all synthesized nanoparticles and particle sizes were below 100 nm. Nickel matrix nanocomposite coatings were produced by using electrochemical deposition tecnique on stainless steel substrates. The Watts bath for production of nanocomposite coatings were prepared using the different amounts of titanium dioxide and Zinc doped titanium dioxide nanoparticles. Besides, applied current density on the coating performance were investigated in order to optimize the coating properties. Pure Nickel coatings were also deposited under the same experimental conditions for comparison. The structural, morphological, mechanical and corrosion properties of the Nickel matrix nanocomposite coatings were investigated. The surface morphology, elemental composition and phase structure of the nanocomposite coatings were examined by Scanning Electron Microscopy, Energy Dispersive Spectrometer and X-ray Diffraction, respectively. Obtained results show that Nickel-Titanium dioxide and Nickel- Zinc/Titanium dioxide nanocomposite coatings improved corrosion properties.
Nano malzeme içeren çimentolu kompozitlerin termal verimliliği
Her yıl buzlanma ve kar nedeniyle birçok trafik kazası olmakta, vatandaşlarımız hayatlarını kaybetmekte, maddi ve manevi büyük kayıplar yaşanmaktadır. Hava alanlarında pist buzlanması ve kar nedeniyle de kazalar olmakta, can ve mal güvenliği tehdit altında kalmaktadır. Buzlanmaya karşı yollara ve pistlere atılan tuz ve diğer kimyasallar, yol malzemesine, taşıtlara zarar vermektedir. Tuz-kimyasal atma veya küreme ile yollar-pistler sürekli ve zamanında açık tutulamamakta, buna karşın personel, araç, yakıt ve sarf maliyetleri oluşmaktadır. Ayrıca, trafiği durdurma veya yavaşlatma nedeniyle oluşan sefer iptalleri ve gecikmeler, maddi ve manevi kayıplar oluşturmaktadır. Elektrikle ısınan harcı belirlemek için, öncelikle iletken olan tüm malzemeler (13 mm çelik lif, 6 mm çelik lif, pirinç toz ve lif, bakır toz ve lif, karbon lif, çok duvarlı karbon nanotüp, nano tufal, nano grafen, nikel) kullanılarak doğru akım ile ısınma testi yapıldı. Bu sonuçlara göre en iyi ısınan iletkenler, harç içerisinde farklı hacimsel oranlarda olmak üzere 18 farklı harç karışımı tasarlandı. Her karışımdan 3 adet 5×5×2,5 cm³ prizma üretildi. Isınma testi uygulamak amacı ile referans karışımı dâhil toplam 18 farklı harç karışımı hazırlandı. 7. günde ve 35. günde elektrik verilerek ısınma testleri yapıldı. Isınma testinde elde edilen; sıcaklık artışı, sıcaklık artış hızı ve tüketilen enerji, performans parametreleri olarak kullanıldı ve puanlama sistemi geliştirildi. Elektriksel direnç değişimi ile sıcaklık artışı arasındaki ilişki belirlendi. En iyi ısınan makro ve nano boyutta malzeme katkılı karışımlar belirlendi. Elektrik ile ısınan harç, hava alanlarında, yollarda ve binaların ısıtılmasında kullanılabilir.
Fotovoltaik-termoelektrik hibrid sistemlerinin termoelektrik modüllerinin verimlerinin arttırılması
The consumption of fossil fuels outcomes to greenhouse gases that brings out global warming of the World's atmosphere and nearby to climate change. Under the surface are hidden costs such as security expenses, clean-up efforts, air pollution, environmental damage, war-related expenses and other additional hidden expenses. Sources of Renewable energy are especially very good energy sources to battle against global warming. Energy from Sun, is a shining renewable energy source, especially for the regions with high solar irradiance. After the Oil Crisis, happened in 1973, the researchers especially focuses on photovoltaics. Till now the scientists are focusing on improving the effieciency of solar cells and photovoltaic modules. PV-TE Hybrid Systems are especially one of the shining systems of new type of systems, to enhance the module efficiency. Combining photovoltaic (PV) and thermoelectric (TE) modules into PV-TE systems has shown great promise for maximizing the use of the sun's spectrum, boosting overall power output, and lowering the amount of area needed for PV power plants. With my thesis I focused on enhancing the efficiency of a practical PV-TE system model. Usually, a significant temperature differential is produced across the thermoelectric generator (TEG) module utilizing a variety of heat removal techniques in order to increase the power output of the TE component. These cooling systems makes increase, in performance of TEG module, however, concurrently, they rise the electrical performance of PV. In this thesis, I assessed the performance of PV-TE systems using seven different TEGs and monocrystalline silicon solar cells in four different scenarios. According to Standard Test Conditions EN/IEC 61215, the PV-TE hybrid systems are first tested at 25 °C without a cooling device. We then assess the systems using a passive cooling strategy, improving heat dissipation with aluminum heat sinks. Additional evaluations use an active cooling (AC) system with coolants of water and nanofluid in succession. The evaluations' findings are intended to set a standard for raising the effectiveness of upcoming PV-TE systems.
Theoretical investigation of CU based intermetallic compounds at nanoscale
Intermetallic compounds (IMCs), including transition metals and p-block metals, exhibit high resistance to oxidation and corrosion, low density, high conductivity, and magnetic polarizability. There is growing interest in intermetallic compounds (IMCs) consisting of transition metals and p-block elements, particularly aluminum (TM-Al IMCs). These alloys exhibit a unique combination of properties that make them well-suited for extreme thermal environments. Notably, they possess a favorable balance of low density and high melting temperatures, which contributes to their structural integrity and thermal stability. This thesis employs the first-principles computational approach grounded in Theory of Density Functional (DFT) to analyze the structural and electronic characteristics, charge density distribution, spin polarizability, and magnetic properties of Cu(3-x)MnxAl (x = 0, 1) intermetallic compounds. The study implemented the Perdew, Burke, Ernzerhof (PBE) exchange-correlation functional as part of the Approximation of Generalized Gradient (GGA) framework. The calculation of metallic and conductive nature and structural properties was performed simultaneously for all crystal lattices of Cu(3-x)MnxAl (L12, D03, and Heusler L21) with 221-Pm3m, 225-Fm3m space groups. Notably, the study clarifies the stoichiometric similarity and difference between L12 and D03 type structures by presenting a detailed discussion of the D03 structure and its targeted properties for the first time. The lattice constant values obtained by performing various optimizations shows remarkable consistency with previously reported theoretical and experimental measurements. Density Functional Theory-DFT calculations were utilized to analyze the electronic structurethe electronic structure, including band structure, total density and partial density of states, Major and minor spin state densities, map of charge density distribution, and Mulliken bond population. Additionally, the study investigated the chemical bonding characteristics and mechanical properties of intermetallic compounds (IMCs), such as elastic constants, elastic moduli, Pugh's ratio, elastic anisotropy, Poisson's ratio, and Cauchy pressure. The directional dependence of each mechanical property (young, bulk, shear modulus) and the corresponding mechanical properties were calculated. The electron density distribution and population analysis are consistent and reveal the dominant bonding type in each IMC. Furthermore, a Spin Polarizability analysis has been carried out to demonstrate the magnetic nature of the Cu2MnAl (L21) Full Heusler alloy upon the addition of the Mn atom.
Synthesis and characterization of carbon nanomaterial(S) by hydrothermal carbonization of various wastes
This research investigates a sustainable and resource-efficient approach to biomass waste management by synthesizing high-value carbon nanomaterials through hydrothermal carbonization (HTC). Three distinct biomass wastes: pomegranate peel waste (PPW), marigold flower waste (MFW), and cotton fabric waste (CFW), were subjected to HTC under varying conditions to explore their conversion into functional carbon-rich products. Among the tested feedstocks, PPW emerged as the most promising precursor for carbon nanomaterial production, yielding well- defined hydrothermal carbonaceous nanospheres (HCNs) with diameters ranging from 50 to 300 nm. In contrast, the carbon materials derived from MFW and CFW exhibited irregular and poorly defined morphologies. Additionally, carbon dots (CDs) displaying strong blue luminescence were successfully recovered from the liquid phase of the PPW-HTC process, demonstrating the feasibility of dual-phase valorization from a single waste stream. To assess the environmental viability of the process, a prospective life cycle assessment (LCA) was conducted. The analysis identified electricity consumption for reactor heating (75–79%) and drying (20–22%) as the dominant contributors to environmental impact. Scenario modeling indicated that replacing the current electricity mix with renewable sources could reduce abiotic depletion and global warming potential by up to 120%. Sensitivity analysis of wastewater disposal routes revealed that while switching to treatment plants offers only minor improvements at laboratory scale (<1%), the benefits become more pronounced at industrial scales. The scenario involving CD recovery (HTCa) exhibited comparatively higher environmental burdens due to full energy allocation but avoided reliance on high-purity chemical precursors commonly used in conventional CD synthesis. This strategy highlights the environmental potential of integrating biomass-based inputs and waste valorization into emerging nanomaterial production pathways, aligning with circular economy principles. HCNs demonstrated significant potential as green antioxidants. Results from DPPH and phosphomolybdenum assays revealed strong radical-scavenging activity, comparable to ascorbic acid, a standard antioxidant. These findings support the use of HCNs as a sustainable alternative to fossil-derived nanomaterials and synthetic antioxidants, offering both environmental and human health benefits. Under the assay conditions employed in this study, HCNs exhibited minimal antibacterial activity. While these results indicate limited antibacterial effectiveness at the tested concentrations, they also suggest that HCNs may be less cytotoxic, potentially supporting their use in biocompatible or non-disruptive applications. Future studies should explore their performance under varying experimental conditions or investigate modifications to enhance antibacterial efficacy. In addition, the study evaluated the application of HCNs in cement composites. Incorporating HCNs resulted in improved workability and enhanced flexural strength in certain samples, along with a reduction in density without significant compromise in compressive strength. The method of HCNs incorporation was found to significantly influence the final properties of the composites. Although the sustainability impact of low-dosage additions is limited, these findings show the potential of HCNs as a useful addition in cement-based systems, suggesting the need for further research and optimization—particularly when combined with other sustainability-enhancing materials.
Development of high temperature tribological features of electroless nib and NiB/Al2O3 nanocomposite coatings
This study examines the microstructural, mechanical, and tribological performance of electroless NiB and NiB-Al2O3 coatings applied to mild steel (St-37) substrates. In this dissertation, the electroless NiB and NiB-Al2O3 coatings were deposited onto the steel substrates to produce homogeneous microstructures using the electroless deposition method. The effects of electroless deposition parameters on the microstructure and the friction behaviours of the coatings were investigated in detail. A temperature-controlled wear testing setup was employed to evaluate their high-temperature tribological behavior. The investigation specifically explored the influence of Al2O3 nanoparticle concentration, the configuration of the wear test, and the testing temperature on the dominant wear mechanisms of the coatings. Tribological testing was carried out to assess the performance of the coatings under varying thermal conditions. The tests were conducted at four distinct temperatures: 25 °C (room temperature), 200 °C, 400 °C, and 600 °C to evaluate the influence of elevated temperatures on the friction and wear characteristics of the coatings. A ball-on-disk configuration was utilized for providing controlled and consistent test conditions. During the experiments, a constant applied load of 3 N was applied to simulate realistic contact pressures typically encountered in practical applications. By systematically increasing the temperature, the study aimed to observe and analyze how thermal effects, and changes in material properties, impacted the tribological behavior of the coatings. The results provided valuable insights into the coatings' ability to maintain wear resistance and frictional performance across a wide range of operating temperatures. The experimental findings revealed that the electroless NiB-Al2O3 nanocomposite coatings consistently demonstrated a lower wear rate across all tested temperatures compared to the electroless NiB coatings without Al2O3 reinforcement. This enhanced wear resistance was attributed to the incorporation of Al2O3 nanoparticles, which significantly improved the coatings' ability to withstand wear under varying tribological conditions. Detailed characterization of the microstructures of the coatings, worn surfaces, and wear mechanisms was carried out using advanced analytical techniques, including Scanning Electron Microscopy (SEM) for observing surface morphology, Energy Dispersive X-ray Spectroscopy (EDS) for elemental analysis, X-ray Diffraction (XRD) and Raman Spectroscopy for chemical and structural identification. These techniques provided a comprehensive understanding of the tribological behavior of the coatings and the role of Al2O3 in improving their performance under high-temperature conditions.
Preparation of polybenzoxazine-EPDM rubber based hydrophobic nanocomposite materials
The aim of this thesis is to prepare a hydrophobic nanocomposite with Polybenzoxazine (PBZ) and ethylene-propylene-diene-monomer rubber (EPDM) filled by nano titanium dioxide (TiO₂) and polytetrafluoroethylene (PTFE/Teflon). In this work, the first step in the process is to synthesize fluorine-containing PBZ. Fluorine is intended to contribute to hydrophobicity of the PBZ. PBZ was synthesized by ring-opening polymerization, catalyzed by dimethyl amino ethanol (DMAE) base catalyst using benzoxazine monomer obtained from 4-hydroxy benzaldehyde, 2-(trifluoromethyl)aniline and paraformaldehyde. In order for the PBZ polymer to be ring-opening polymerization to take place, the reactants were magnetically mixed in an oil bath at 100 °C for 24 hours. As a result of polymerization, a hard brittle, light-yellow color solid polymer was obtained. Since the synthesized PBZ is a hard and brittle polymer on its own, it is necessary to get help from another polymer to improve the elasticity for polymer nanocomposite samples. Thus, it was prepared a blend with PBZ and EPDM rubber. Polymer nanocomposite samples with weigh ratios of 40% EPDM and 40% PBZ blend matrix, 10% nano TiO2 and 10% PTFE additives were prepared. Since at least one of the fillers must be nano-sized in order to meet the condition of being a nanocomposite, 0-20 nanometer TiO2 additive is used. Both nano TiO2 and PTFE additives helped to prepare a hydrophobic polymer nanocomposite. Since one of the matrix components is EPDM rubber, some of the samples were cross-linked with 0.1% sulfur by weight to perform the vulcanization step, which is an important step in the use of rubber material. Polymer nanocomposite samples prepared with and without sulfur were heated and cured with temperatures of 25 °C, 100 °C, 150 °C and 180 °C, respectively. The effect of sulfur and curing temperature on the hydrophobicity of polymer nanocomposite samples was studied. The EPDM-PBZ nanocomposites were also characterized by UV-vis., TGA-DTA, SEM, SEM-EDX, FTIR, contact angle measurement characterizations. The contact angle was noted as 101.1° for PBZE1-EPDM-PTFE-Nano TiO2 nanocomposite sample. According to the UV results, the samples showed wide range abroad absorption peaks. According to all test results, the preparation of a hydrophobic polymer nanocomposite was successful. It was observed that the additives were homogeneously distributed in the matrix, there was no agglomeration. When the prepared polymer nanocomposites were compared to whether they were hydrophobic or not, it was clearly seen that the temperature and the curing process by cross-linking with sulfur increased the hydrophobicity in the samples. In particular, the EPDM-PBZ polymer nanocomposite sample with sulfur, vulcanized at 150 °C presented better hydrophobic features with a contact angle of 110°.
Computational investigation of battery materials using density functional theory
Lithium-ion rechargeable batteries have revolutionized the world of portable electronics and electric vehicles. However, as the demand for high-performance, sustainable energy storage solutions grows, there is an increasing need to explore and optimize the materials used in these batteries. The use of Density Functional Theory (DFT) first-principle calculations is pivotal in rechargeable battery research. DFT enables precise exploration of atomic and electronic interactions in battery materials, offering insights into properties, electrochemical behavior, and the design of new materials. It accelerates battery development, ultimately shaping the future of energy storage technology. This thesis represents a comprehensive invistigation into the application of first-principle calculations based on DFT to advance our understanding of two distinct classes of lithium rechargeable batteries: all-solid-state batteries (ASSBs) and Li-O2 batteries. The first major segment of this study is dedicated to investigating the intricacies of all-solid-state batteries, with a specific emphasis on LiAlTi(PO3)4 (LATP) and Sulfure doped LATP (S@LATP) as a solid electrolyte. Solid-state batteries hold immense promise as they offer a safer alternative to conventional liquid electrolyte batteries while potentially delivering higher energy densities. Solid electrolytes offer improved safety, higher energy density, and longer cycle life compared to liquid electrolytes. These electrolytes come in various forms, including ceramics, polymers, and composites, each with unique characteristics. Challenges like low ionic conductivity and complex manufacturing persist but are being addressed through computational modeling and material synthesis. Notable materials like (LATP) show potential in all-solid-state batteries due to their high ionic conductivity, stability, and safety. To unlock their full potential, a deep understanding of the solid electrolyte's properties is essential. Our inquiry begins with a meticulous examination of the structural properties of LATP and S@LATP. Our study provies an explanation about the effect of Sulfur doping on the lattice parameters, stability, and atomic bond length of LATP. Leveraging the first-principle calculations and the Nudged Elastic Band (NEB) method, we embark on a detailed exploration of lithium ion diffusion mechanisms within both LATP and sulfur-doped LATP. The results not only reveal the energetically favored diffusion paths but also provide insights into the activation energy barriers, critical information for optimizing ionic conductivity in solid electrolytes. Our results showed sulfure doping caused a locally inhance the ionic diffution in LATP. Beside the structural properties and lithium ion diffusion, We delve into the charge distribution and electrochemical environment within LATP. Employing techniques such as charge transfer analysis, Bader charge analysis, and core level shifting, we gain insights into the change in the electrochemical behavior of LATP solid electrolyte. These findings not only contribute to the fundamental understanding of LATP but also lay the groundwork for strategies aimed at improving the ionic diffution in LATP liked electrolytes, such as LAGP. The second pivotal segment of this thesis pivots towards the realm of Li-O2 batteries. Li-O2 batteries, or lithium-oxygen batteries, show potential for high-energy applications like electric vehicles and energy storage due to their high theoretical energy density. These batteries consist of a lithium metal anode, a Li+ conducting electrolyte, and a porous oxygen (O2) cathode. The choice of cathode materials is crucial. Common types include noble metals, carbon-based materials, transition metal compounds, and perovskite oxides. Researchers are actively exploring these materials and employing advanced techniques like density functional theory (DFT) simulations to optimize Li-O2 battery performance. This research focuses on TiMn2, a transition metal compound, and MnO2, a transition metal oxide, as potential carbon-free cathode materials for Li-O2 batteries. While carbon-based cathodes have been the norm, the transition to carbon-free alternatives is imperative for improving overall battery performance. Carbon-free cathodes play a pivotal role in the advancement of Li-O2 batteries due to their paramount importance in improving battery performance and sustainability. Two noteworthy candidates, Titanium Manganese (TiMn2) and Manganese Dioxide (MnO2) was selectedt as a carbon free cathod materials. In this thesis, TiMn2 was selecteted for the first time to be an exciting cathode material, and its examination in this thesis represents a promessing potential as a carbon free cathod. The study delves into the surface stability of TiMn2, analyzing different atomic surface terminations. Moreover, our investigations involve the oxgyen redaction/evoluation reactions ORR/OER mechanism to form the final product of li-O2 battery reaction, Li2O2. The Gibbs free energy diagram further elucidates the ORR/OER process, and the calculated overpotential values for ORR and OER demonstrate. We invistigate the With an overpotential of approximately 1.16 V, TiMn2 showcases promising results, making it a strong contender for future Li-O2 batteries. Manganese dioxide (MnO2) underwent a comprehensive investigation employing two distinct Density Functional Theory (DFT) methodologies, namely, the Generalized Gradient Approximation with Hubbard U term (GGA+U) and the Strongly Constrained and Appropriately Normed with Hubbard U term (SCAN+U). Both GGA+U and SCAN+U methodologies exhibited significant variations in lattice parameters and calculated band gap values. Furthermore, an examination of MnO2's surface stability was conducted to identify the most stable termination. This study also furnished insights into surface reactivity toward lithium (Li) and oxygen (O) atoms in the surrounding environment. Subsequently, the Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER) were investigated using both GGA+U and SCAN+U approaches. The results demonstrated that the selected computational approach significantly influenced adsorption energy values and the positions of adsorbed reaction intermediates. Additionally, Gibbs free energy diagrams were simulated, enabling the calculation of charge and discharge potentials as well as overpotential. Notably, the outcomes revealed that each approach, GGA+U and SCAN+U, provided distinct values. This comparative analysis not only facilitated the assessment of the accuracy of initial structural predictions but also yielded valuable insights into the surface properties of the material. Overall, this thesis demonstrates the use of first-principle calculations as a powerful tool for understanding and optimizing the performance of advanced lithium rechargeable batteries.
Development of lithium-oxygen battery nanostructured electrodes facilitated by M13 virus and plant extract
Lithium-oxygen (Li-O2) batteries are a promising candidate for next-generation rechargeable battery systems due to their superior theoretical energy densities (11,586 W h Kg-1), which is near to those of gasoline (11,860 W h Kg-1). The principle of Li-O2 cell is relied on the formation of Li2O2 by the interaction between Li cations and oxygen (from the air) during discharge at the cathode surface and decomposition of Li2O2 upon charging. Therefore, the highly stable and reversible electrochemical reactions in Li-O2 cell is dependent on accelerating formation and decomposition of Li2O2. One solution to solve this issue is selecting an appropriate cathode catalyst with high porosity, good electronic conductivity, chemical stability, and high catalytic activity. In this thesis, our purpose is to develop novel efficient cathode materials for Li-O2 batteries using non-aqueous electrolytes by utilizing bio-inspired materials such as plant extract and M13 viruses. The M13 virus is a phage that infects bacteria but is harmless to humans and serves as a bio-template due to its unique morphology. Plant extracts are a rich source of bioactive chemicals. They have been demonstrated to be promising as reducing and capping agents for the biosynthesis of a variety of metal/metal oxide nanoparticles. Therefore, TiO2 nanoparticles with a cauliflower morphology were synthesized by using chamomile extract. Bio-TiO2 electrode containing 5 wt.% carbon black, showed a large overpotential and 30 stable cycles at the limited capacity of 500 mAhg-1. Therefore, to increase the cycle life of the Bio TiO2, a core-shell-like structure was formed with α-MnO2 as a shell, and the content of the carbon black was increased from 5 wt.% to 10 wt.%. The obtained TiO2/α-MnO2 showed 60 stable cycles at the limited capacity of 600 mAh g-1. However, 10 wt% carbon black caused the formation of by-products and limited the cycling behavior of the cathodes. As a result, to increase the electrical conductivity and catalytic activity of metal oxides without using carbon additives, the unique one-dimensional α-manganese oxide nanowires incorporated with ruthenium nanoparticles were constructed with the assistance of M13 bacteriophage. The virus templated Ru/α-MnO2 nanowires offered a high porosity and an extensive surface area as a cathode material. This cathode demonstrated a high capacity of 14,383 mAh g-1 with 48 stable cycles at a limited capacity of 1000 mAh g-1. In conclusion, these biosynthesis methods could provide an eco-friendly and cost-effective approach to develop high-performance battery electrodes. The design strategy manufactured in this thesis could be applied not only to batteries but also to other applications, which require nanoscale materials.
M13 virus template as a new approach to electrochemical energy storage in Li-O2 breathing battery cathodes
Due to high potential energy densities of lithium-oxygen (Li-O2) batteries (11,140 Wh kg-1) have been explored as one of the most promising energy storage systems for the future generation of state-of-the-art batteries. During discharge, oxygen (from the atmosphere) is reduced at the cathode (Oxygen reduction reaction, ORR), where it reacts with lithium ions released from the lithium metal anode to generate Li2O2, and the discharge residue decomposes during charging (Oxygen evolution reaction, OER). Cathode catalysts significantly improve ORR/OER and the electrochemical stability of Li-O2 systems. To accelerate ORR and OER in Li-O2 cells, a suitable air cathode architecture must possess sufficiently porous distribution to allow oxygen diffusion, high conductivity to transfer lithium ions, chemically stable, and highly catalytic activity. Therefore, we first report metal nanoparticles (e.g., Pd and Ru) and α-manganese oxide nanowire supported by reduced graphene oxide. In the Li-O2 cathode, noble metals are used as oxygen evolution reaction (OER) electrocatalysts to minimise charge overpotential and provide stable cycling performance. MnO2 is an appealing, useful transition metal oxide catalyst in Li-O2 batteries due to its cost effective, high catalytic activity, and good oxygen reduction characteristics. In the first experiment, Ruthenium nanoparticles were incorporated on MnO2 surfaces, and then the mixture was applied to 50% graphene via ball milling. This electrode demonstrates the charge overpotential and stability up to 40 cycles at a limited capacity of 800 mAh g-1. The produced rGO@Pd@α-MnO2 hybrid nanocomposite cathode delivered a full discharge capacity of 7500 mAh g-1 and maintain cycle life upto 50 cycles with a low discharge/charge potential gap of 0.4 V. Our result shows higher stability of Pd despite Ru. Furthermore, graphene-based electrodes with different graphene content (e.g. 100%, 75%, 50%) were prepared, and by reducing graphene, the higher performance of Li-O2 cell was obtained due to preventing side reactions. On the other hand, plant extract and M13 virus were utilized for the reduction of graphene oxide and preparation of MnO2 nanowires, respectively. Using these biomaterials assist in designing advanced nanomaterials through a green and biocompatible process. Overall, the synergistically effects of α-MnO2 nanowires and metal nanoparticles are combined in this study by decorating graphene sheets to boost cyclability and capacity, resulting in highly efficient Li-O2 cell performance.
Lityum iyon piller için yüksek kapasiteli LiFePO4/C/rGO nanokompozit pozitif elektrot
The development of new electrode materials with superior electrochemical capabilities, primarily dictated by the cathode materials, is required for widespread and extended applications of Li-ion secondary batteries. Because of its excellent stability, availability, and environmental friendliness, LiFePO4 (LFP) is widely recognized as a viable cathode material. This study used a low-cost iron (III) as the base material to manufacture single-phase LFP material with submicron particles using a simple solution combustion process based on the glycine–nitrate technique. The optimal Glycine to LiFePO4 ratio was found to be as 1:4 to produce high purity LiFePO4 and produced LiFePO4 showed 102 mAh/g discharge capacity at the constant rate of C/20. Sucrose was utilized as a carbon source to obtain carbon-coated LiFePO4 powders. The discharge capacity of the as-prepared LiFePO4/C sample with 12% carbon content is around 157 mAh/g at a 0.1 C rate and 88 mAh/g at a 5 C rate. Furthermore, throughout the 50-cycle at varying current rates, the electrodes showed excellent cycling performance. To enhance the capacity of carbon-coated LiFePO4, different amount of Graphene was reinforced to the cathode material. The carbon-coated lithium iron phosphate with 4 wt.% graphene showed a specific capacity of 197 mAh/g. The highly conductive graphene flakes wrapped around carbon-coated lithium iron phosphate enhance electron migration during charge and discharge operations, decreasing irreversible capacity during the first cycle and resulting in a coulombic efficiency of 99% at varied C-rates.
Development of nanocomposite biodegradable film containing iron nanoparticles biosynthesized by Saccharomyces cerevisiae
The present study has sheds light on the synthesis of iron oxide nanoparticles (IONPs) by Saccharomyces cerevisiae yeast as a green method by using the components of yeast cell walls as reducing agents to promote more beneficial effects in life applications. The main objective of the study is to examine the antimicrobial and mechanical properties of whey protein based edible films contained IONPs. At the present study, IONPs were synthesized by using S. cerevisiae from iron chloride (FeCl3) precursor at three different concentrations (0.5, 1.0, and 1.5 mM). These iron oxide nanoparticles and lysed yeast cells residue (YSR) were used with whey protein concentrate and glycerine to prepare nanocomposite edible films contained 0, 0.25, 0.5 and 0.75 mM IONPs. The results have shown successful synthesis of IONPs as hematite (Fe2O3) according to the XRD analysis with crystal average size (24-35 nm), while FTIR spectrum indicated the presence of IONPs with the protein matrix of the films. The FESEM images have shown the presence of nanomaterials in range between 43 and 127 nm. The films have shown zero inhibitory effects against the growth of tested bacterial strains. Tensile strength (TS) of the films containing 0.5 mM and 0.75 mM IONPs increased significantly (P<0.05) compared to the control films (without IONPs). E% at break and water vapor permeability of the films with IONPs decreased significantly (P<0.05) when compared to WPC films with no IONPs. The colour change (∆) was increased significantly (P<0.05) in IONPs contained films as well as the whiting index and yellowing index. In conclusion, incorporative IONPs into whey protein film showed no influence as antibacterial agent. Yet, IONPs enhanced the mechanical properties of whey protein based edible films.
Nano silicon reinforced carbon anodes for high-capacity lithium ion battery: State of charge (SOC) and battery life time testing
The importance of active materials for anodes has gained significant attention in recent times. Carbonaceous materials are typically used as anode candidates in lithium-ion batteries (LIBs), but their low theoretical capacity of 372mAh/g restricts their applications in advanced LIBs. Therefore, Silicon (Si) is considered a prominent alternative anode material for LIBs to replace graphite. Since the theoretical capacity of Si is ten times higher than graphite; however, it suffers from massive mechanical deformations induced during cycling. For this purpose, composites of Si-graphite are proposed for better cycling performance and increased specific capacity. Herein, nano Si powder (<100nm) containing mesocarbon microbeads (MCMB) composites are prepared, and their rate capabilities as anode material for LIBs have been investigated at different current densities. Diverse compositions of the active anode materials (Si and MCMB), carbon black (CB), a binder sodium carboxymethylcellulose (CMC-Na), and distilled water as a solvent have been utilized for the fabrication of anodes, and the fabricated anodes have been morphologically and electrochemically characterized. Moreover, the state-of-charge (SOC) analysis has been evaluated by setting three different upper and lower cut-off voltages. Our analysis revealed that a composite comprising the lowest Si content (5wt%) exhibited better rate performance and retained a capacity of 455mAh/g after 60 cycles. 15wt% Si showed the worst rate capability performance. Similarly, in theSOCanalysis,a moderate voltage window between 1-0.05V was found optimalon the basis of rate capability results. Voltage window between 1-0.07V lead to quick capacity loss and large surface cracks confirmed in FESEM images. Additionally, in the SOC analysis, 5wt% Si showed the best cycling performance and lost only 10% of its capacity at 1C and 13% at C/2 after 200 cycles between 1-0.05V.
Nanoyapılı Pt ve Pt-Ag alaşımlarının üretimi, karakterizasyonu ve hidrojen gaz algılama özelliklerinin incelenmesi
This thesis presented hydrogen (H2) sensing properties of platinum (Pt) and platinum-silver (Pt-Ag) thin films. Pt and PtAg films were deposited on glass substrate by magnetron sputter technique. The Pt thin films with different thickness (2-50 nm) were prepared using RF sputtering method. The thicknesses of the films were controlled by a piezoelectric sensor placed in sputter system at the same time of coating process. On the other hand in this study, 3 nm PtxAg1-x (x: 0.95, 0.90, 0.80 and 0.50) thin films were coated by co-sputtering technique. The structural properties of Pt and PtAg alloy films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) techniques. Hydrogen sensing properties of the Pt and PtAg films were investigated depending on film thickness, temperature and concentration. Temperature dependent resistances and the gas measurements of the Pt and PtAg thin films were studied under a dry air flow and hydrogen ambient at a temperature range from 30 °C to 200 °C. Thus the best working performances of Pt and PtAg sensors were detected. The results showed that the resistance is directly proportional with temperature, and inversely proportional with the thickness of Pt thin film sensors. The H2 sensing properties of Pt thin film sensors were examined in the concentration range of 0.1 % - 1 % H2. Among the results for Pt thin films, it was revealed that the Pt thin film with 2 nm thickness exhibited the best sensing performance to H2 at 30 °C under dry air flow. The best response time was obtained at high temperatures for Pt thin film sensors. H2 sensitivity of PtAg sensors were also investigated in the concentration of 25 ppm - 1000 ppm H2. The resistances and the sensitivities of PtAg thin film sensors were increased with enhancing the temperature. Among the results for PtAg sensors, 3 nm Pt0.80Ag0.20 sensor showed the best sensitivity properties at 150 oC.
Dopamin tayini için moleküler baskılanmış nanosensör hazırlanması
Dopamine is a catecholamine class neurotransmitter found in the mammalian central nervous system and has a very important role in metabolic functions, cardiovascular, renal and hormonal systems. Rapid, easy, selective and low-cost analysis of dopamine can be achieved by the use of molecularly imprinted polymers, which are only dopamine-specific artificial receptors, in the preparation of nanobiosensors for dopamine determination for the early diagnosis of such diseases. Within the scope of this thesis, two separate sensitive, selective, inexpensive and miniaturizable sensor systems have been developed for dopamine determination by combining the advantages of nanotechnology with the selectivity of molecular imprinting technology and the sensitivity of biosensor systems. In the first system, an electrochemical impedance-based (EIS) sensor was designed by using molecularly imprinted fullerene modified pyrrole-pyrrole-3-carboxylic acid copolymers on a screen-printed carbon electrode. The performance parameters of the sensor system were determined by the calibration curve between 25- 250 ng/mL (R2= 0.9939) and the LOD and LOQ were found to be 8.77 ng/mL and 26.6 ng/mL, respectively. The results obtained with the developed sensor were compared with the ELISA method and good correlation with R2= 0.979 was observed between ELISA and developed sensor. In the second system, an EIS based sensor was prepared by using molecularly imprinted Cys-APBA-APBA modified Pyrrole-3-carboxylic acid copolymers on a screen-printed gold electrode. The performance parameters of the sensor system were determined by the calibration curve between 100- 600 pM (R2= 0.9517) and the LOD and LOQ were found to be 30.34 pM and 95.82 pM, respectively. In the third system, an EIS based sensor was prepared by using molecularly imprinted Cys-PAMAM modified Pyrrole-3-carboxylic acid polymer on a screen-printed gold electrode for A-42. The performance parameters of the sensor system were determined by the calibration curve between 0.5- 200 ng/ml (R2= 0.9837) and the LOD and LOQ were found to be 0.14 ng/ml and 0.42 ng/ml, respectively.
Optoelekrtonik uygulamalara yönelik nano malzeme destekli florofor, fosfor veya fosfor karışımlarının polimerik matriksler içerisinde incelenmesi
In this thesis we investigated the interactions between the commercially available LED phosphorus and nano-scale materials or dyes in terms of their emission abilities in polymers. In the first part of the thesis, photoluminescence of the Eu2+ doped Ca-α-Sialon (Ca-α-SiAlON:Eu2+), Ce3+ doped lutetium aluminum garnet (LuAG:Ce3+) and their binary blends with the quinine sulphate (QS) were investigated by steady-state and decay time measurements. The Ca-α-SiAlON:Eu2+ exhibited 44% increase in the intensity when blended with the QS. Similarly, the binary blend of QS-LuAG:Ce3+ exhibited 98% enhancement in the intensity. Excited state lifetimes of the phosphors were also studied in nanosecond and microsecond time scales, respectively. Spectral data presented some evidence for the donor-acceptor relationship of the QS/ Ca-α-SiAlON:Eu2+ and QS/LuAG:Ce3+ counterparts where the QS was the donor. The offered phosphor blends, exhibited enhancement in the optical brightness without any spectral shift. In the second part of the thesis, CO2 sensitive HPTS dye was used along with the bioactive glasses and ionic liquid. The bioactive glasses equipped with the rare earths of Er3+, Tb3+ and Er3+and Tb3+, were chosen due to their porous structure, optical transparency and intrinsic fluorescence. After spectral characterization steps we exposed the composites towards varying concentrations of the CO2 and recorded the intensity based response both in steady-state and kinetic mode. We also determined the decay times in the absence and presence of the CO2. We obtained promising results from the studies performed by using the bio-compatible bioactive glasses in terms of enhanced optical brightness and CO2 sensitivity.
Biyosensör uygulamaları için karbon nanotüplerin sentezi ve karakterizasyonu üzerine araştırmalar
In this thesis, production optimizations of CNTs were carried out with the CVD method, which is a practical and cost-effective method. In the CVD method, a cause-effect relationship was established between the properties and process parameters that determine the final morphology, such as substrate type, catalyst type, catalyst concentration, growth time, and processing temperature. In the first stage, five different catalysts, four different substrate types, three different growth times, three different catalyst concentrations, and three different growth times were applied. As a result, the most efficient tubular performance was obtained on the Si wafer substrate at one thousand degrees Celsius processing temperature by applying growth times of three, five, and seven minutes with the help of iron-based catalysts. Data from SEM samples showed that the lowest tube diameter was acceptable nanoscale. With EDX analysis, it has been shown that as the catalyst concentration increases, the carbon efficiency decreases, confirming the results of the SEM analysis. The highest carbon percentage was determined in the sample with the lowest catalyst concentration. The specific peak attributed to sp2 hybridization of CNT carbon in FT-IR analysis was observed in all sample. CNTs, which are targeted for use in biosensor applications, are desired in terms of their high defect structure and faster interaction with chemical and bioactive species. The Raman spectra confirmed that this goal was achieved with the I_D/I_G ratio of the obtained CVD-based CNTs. XRD graphs showed that the expected graphitic peak for an ideal CNT was obtained for all samples. In XPS spectra, it was observed that the sp3/sp2 ratio increased with increasing catalyst concentration. The current-voltage characterizations revealed that all measurements were close and consistent, as well as high potential in a biosensor application. As a result, it has been proven that the properties of CNTs, which are the output of this thesis, can be improved for use in biosensors by controlling the production parameters. In this thesis, production optimizations of CNTs were carried out with the CVD method, which is a practical and cost-effective method. In the CVD method, a cause-effect relationship was established between the properties and process parameters that determine the final morphology, such as substrate type, catalyst type, catalyst concentration, growth time, and processing temperature. In the first stage, five different catalysts, four different substrate types, three different growth times, three different catalyst concentrations, and three different growth times were applied. As a result, the most efficient tubular performance was obtained on the Si wafer substrate at one thousand degrees Celsius processing temperature by applying growth times of three, five, and seven minutes with the help of iron-based catalysts. Data from SEM samples showed that the lowest tube diameter was acceptable nanoscale. With EDX analysis, it has been shown that as the catalyst concentration increases, the carbon efficiency decreases, confirming the results of the SEM analysis. The highest carbon percentage was determined in the sample with the lowest catalyst concentration. The specific peak attributed to sp2 hybridization of CNT carbon in FT-IR analysis was observed in all sample. CNTs, which are targeted for use in biosensor applications, are desired in terms of their high defect structure and faster interaction with chemical and bioactive species. The Raman spectra confirmed that this goal was achieved with the I_D/I_G ratio of the obtained CVD-based CNTs. XRD graphs showed that the expected graphitic peak for an ideal CNT was obtained for all samples. In XPS spectra, it was observed that the sp3/sp2 ratio increased with increasing catalyst concentration. The current-voltage characterizations revealed that all measurements were close and consistent, as well as high potential in a biosensor application. As a result, it has been proven that the properties of CNTs, which are the output of this thesis, can be improved for use in biosensors by controlling the production parameters.
Organik-inorganik hibrit nanokompozit malzemenin hazırlanması, karakterizasyonu, optimizasyonu ve uygulaması
Kurkumin, zerdeçal (Curcuma longa) köklerinde bulunan ve antioksidan, antienflamatuar, antimikrobiyal ve antikanserojenik aktiviteler sergileyen doğal bir polifenoldur. Kurkumin sahip olduğu olağanüstü biyolojik özellikleri nedeniyle farmasötik açıdan ilgi çekici bir terapötik ajandır. Bu umut verici biyomedikal özelliklere rağmen, serbest kurkumin moleküllerinin sudaki çözünürlüğünün az olması nedeniyle klinik etki ve biyoyararlanımı düşüktür. Bu nedenle, çözünürlüğünü ve biyouyumluluğunu arttırmak için ilaca uygun bir dağıtım sistemi sağlamak esastır. Bu çalışmada, nanokompozit malzemelerin sahip oldukları üstün özellikler ile moleküler baskılanmış polimerlerin kompozitlere kattığı yüksek seçicilik, mekanik kararlılık, tekrar kullanılabilirlik gibi üstün özelliklerinden yararlanılarak kurkuminin spesifik bağlanması ve kontrollü salımı için karbon bazlı moleküler baskılanmış nanokompozit ilaç dağıtım sistemi geliştirilmesi hedeflenmektedir. Bu amaçla, fonksiyonel monomer olarak kitosan ve derin ötektik çözücü ve fulleren kullanılarak hazırlanan CTS-DES-FUL@MIP nanokompoziti, deneysel tasarım ile dizayn edilmiş ve miniemülsiyon polimerizasyonuna göre sentezlenmiştir. Sentez parametrelerini etkileyen sekiz değişkenin (kitosan miktarı, fulleren miktarı, SDS hacmi, karıştırma hızı, sıcaklık, çapraz bağlayıcı miktarı, hegzadekan miktarı ve DES miktarı) taranması Plackett-Burman tasarımı ile yapılarak kurkuminin adsorpsiyonu için önemli olan parametreler belirlenmiştir. Daha sonra bu parametreler, tepki yüzeyi metodolojisi ile optimize edilmiştir. Ayrıca, optimize koşullar altında sentezlenen CTS-DES-FUL@MIP nanokompozitinin spesifik bağlanmasının belirlenmesi amacıyla adsorpsiyon parametrelerinin optimizasyonu ve adsorpsiyon performansı incelenmiştir. CTS-DES-FUL@MIP nanokompozitinden kurkuminin kontrollü salımı, simüle edilmiş gastrointestinal sıvılarında inkübasyon yöntemiyle araştırılmıştır. CTS-DES-FUL@MIP nanokompozitinden 120 saatlik sürenin sonunda salım %96,90 oranında gerçekleşmiştir. Buna dayanarak, baskılama işlemine bağlı olarak kurkumin ile CTS-DES-FUL@MIP nanokompozitin fonksiyonel monomerleri arasındaki yüksek spesifik etkileşimler nedeniyle uzun sürede salımın gerçekleştiği söylenebilir. Sonuç olarak, sentezlenen kurkumin baskılanmış polimerin kurkumin için etkili bir taşıyıcı olabileceği söylenebilmektedir.
Epoksi termoset polimer sistemlerin mekanik karakteristiklerinin nanoyapılar kullanılarak geliştirilmesi
Epoxy thermoset polymer composites are extensively utilized in a variety of industries, including the automotive, aviation, space, marine and electrical-electronic industries due to their outstanding mechanical, chemical, thermal, and electrical properties. However, since the neat epoxy intrinsically has a brittle structure, it should be incorporated with various particles to improve the fracture resistance and toughness. In this study, silica particles varying with different particle sizes and filler contents were used to prepare diglycidyl ether of bisphenol-A (DGEBPA) epoxy composite cured with methyl tetra hydro phthalic anhydride (MTHPA) to examine the impact of filler content and particle size on the composite's fracture behaviour. In accordance with ASTM-D5045 standard, linear elastic fracture mechanics were used to describe the fracture behaviour of composite materials. It was concluded that the fracture toughness increases with increasing particle size at the micro dimension but decreases inversely when shifted towards the nano dimension. The fracture surfaces were examined by SEM imaging technique, and toughening mechanisms were defined depending on the silica particle size and content. Before the fracture mechanics test studies, a time temperature transformation (TTT) diagram was constructed for the existing epoxy composite system, which can be used as a tool for the optimization of the process parameters.
ZnO nanoyapıların üretilmesi, karakterizasyonu ve uygulama alanlarının araştırılması
It is common knowledge that zinc oxide (ZnO) as a substantial semiconductor material because of its broad band gap (3.37eV) and good seperation energy (60 meV). Anodic oxidation of ZnO molecules have drawn interest because of their cost-effective synthesis, high efficiency and simplicity of the process. Anodization parameters (voltage, time, ph, electrolyte) can influence the morphology of ZnO. Also, ZnO is widely used in several implementations such as photovoltaic cell, chemical sensor, antibacterial agent and photocatalysts. Structures and different morphologies of ZnO can exert influence on its photocatalytic activity. In this thesis, ZnO nanostructures were produced succesfully through anodic oxidation method. Before anodization, a large portion of bulk Zn was cut off into nine pieces with dimensions 3x3 cm2. These samples were sanded up to acquire the appropriate material surface. After that, samples sonicated in ethanol, acetone and deionized water in an ultrasonic bath for ten minutes separately. Produced ZnO samples were heat treated at 300 °C for one hour with the heating rate of 5 °C/minute. The synthesized ZnO nanostructures were characterized to investigate their structure, elemental composition, photocatalytic activity and morphology with aid of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and UV-Vis spectrophotometer. Concludes from this produced ZnO specimens can make use of as photocatalyst.
Termal analizler için mikro ve nano yapılı aygıtlar
The recent advent of micro and nano devices increased the interest in small scale material properties, such as elasticity, conductivity or heat capacity, which are considerably different from their bulk counterparts due to, primarily, increasing surface to volume ratios. These novel properties must be analyzed by using ultra-sensitive devices since characterization of these properties is not possible with conventional probing instrumentation due to their large mass or volume which decreases signal to noise ratio. Microelectromechanical systems (MEMS) with short response time and high sensitivity are suitable for such measurements, such as very small mass detection (zeptograms) and calorimetry of small volume materials (yoctocalories).In this thesis a MEMS cantilever was used for thermomechanical characterization of thin film amorphous semiconductors. 100 nm thick As2S3 and Ge-As-Se-Te glasses were thermally evaporated onto a bilayer microcantilever. The microcantilever was deflected and vibrated by electrothermal actuation. By monitoring deflection, amplitude and phase of the cantilever oscillation, multiple glass transition and melting points were identified; the effects of the variation of thermal expansion coefficients (CTE), reversible and irreversible heat capacities and Young?s modulus of the thin film samples were observed simultaneously. Hence the possibility of the integration of calorimetry, thermomechanical analysis (TMA) and dynamical mechanical thermal analysis (DMTA) in a single MEMS device was demonstrate
Nanomalzemelerin sentezi ve [Ru(bpy)3]2+ kompleksi ile birlikte sensör özelliklerinin araştırılması
In this study, optical properties of tris(2,2-bipyridyl)ruthenium (II) chloride ([Ru(bpy)3]2+), a ruthenium complex, together with various nanoparticles (TiO2 and core-shell TiO2@Ag nanoparticles) were investigated in the oxygen-permeable polymeric material. Plasticizer containing polymethylmethacrylate (PMMA) was shaped in form of thin film by applying the spin coating process and its optical properties and sensitivity towards oxygen were observed. It is known from previous studies that the [Ru(bpy)3]2+ complex exhibits extraordinary optical properties and high oxygen sensitivity when embedded in the above-mentioned matrix and used in combination with silver nanoparticles. In our thesis, the presented design is totally different from the earlier published literature. The porous and straight thin composite films were fabricated via the spin coating technique. Unlike the previous studies, the semiconductor TiO2 and core-shell TiO2@Ag nanoparticles were doped into these composite materials and the spectral properties of the prepared thin films were examined. Luminescence signal variations resulting from the application of oxygen sensor at 626 nm were recorded.
Çeşitli yöntemlerle magnetit nanotaneciklerin hazırlanması ve karakterizasyonu
Magnetite nanoparticles are used in various fields including iron-containing fluid, catalyst, pigments, magnetic recording media, medical diagnosis and treatment. Size of the particles and their morphology, electrical, optical and magnetic properties and limit their use. Synthesis methods determine the morphological homogeneity and size distribution of nanoparticles. Currently there are printing materials called toners that are imported for use in many printers of various brands and models. Iron-based inorganic minerals with different magnetic properties are used in these materials. The aim of this study is to prepare and characterize magnetite nanoparticles for use in printers and photocopiers. In this context, co-precipitation, thermal synthesis, sol-gel synthesis, reverse micelle synthesis, hydro-/solvo-thermal, sonochemical, microwave, and biosynthesis have been proposed. Magnetite nanoparticles were synthesized by co-precipitation and solvothermal/ hydrothermal methods. Stability of the nanoparticles stability is achieved by coating with oleic acid (OA), stearic acid (SA), sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), (3-aminopropyl)triethoxysilane (APTES), oleyl amine (OAm) and hexadecyltrimethoxysilane (HDTMS). Characterization of the prepared samples was performed by techniques such as XRD, FTIR, TGA, SEM, XPS and VSM.
Endüstri 4.0 kestirimci bakım süreçlerinde isteme özgü MEMS (mikro elektro-mekanik sistemler) tabanlı sensörlerin aksiyomatik tasarımla seçim problemi
Bu tez çalışmasının amacı endüstriyel alandaki makine v.b sistemlerin Endüstri 4.0 kestirimci bakım kapsamında ölçülmek istenen farklı parametrelerine özgü (ses, titreşim, akış v.b) olarak nanobilim alanındaki MEMS (Mikro Elektro-Mekanik Sistem) tabanlı sensörlerin aksiyomatik tasarım metodu uygun tasarımın bu metotla seçilmesinin araştırılmasıdır. Tez çalışması kapsamında ve devamında özel bir Ar-Ge merkezinde literatür taramasının ilerletilmesi, üniversite-sanayi işbirliği çalışmalar yapılması, bu çalışmalar ile uygulamalı bir projeye dönüştürülerek firmaların kestirimci bakım proseslerinde uygun MEMS tabanlı sensörün testlerinin yapılması hedeflenmektedir. MEMS tabanlı sensörlerin üretiminde kullanılan ve tasarımını/modellenmesini şekillendiren en uygun yöntemin (litografi v.b ) tespitinin yapılması için kavramsal araştırmalar yapılacaktır. Modelleme / desenleme sürecinden sonra, sensör tabanının/membranının boyutsal ve benzer parametreleri optimize edilecek ve aksiyomatik tasarım yöntemi ile en uygun tasarım seçilecektir. Son olarak MEMS tabanlı sensörler için yapılan seçimlerin nano ölçekteki NEMS (Nano Elektro-Mekanik Sistem) tabanlı sensörler için de uygun olup olmadığı değerlendirilecektir
Elektrokromik cihaz uygulamaları için metal oksit ince film katmanlarının mıknatıssal saçtırma tekniğiyle kaplanması
Electrochromism is the property of certain materials which involves a change from a bleaching state to a colored state as effect either by the action of an electrical voltage or current. Electrochromic devices (ECD) are formed by materials that are capable of continuously and reversibly modulating their color, usually from a bleaching state to a colored one, with the application of a small electric current. Among this electrochromic materials, WO3 and NiOx metal oxides are the dominant among the electrochromic metal oxides. The applied electric current induces in them a reaction of reduction (gain of electrons) or oxidation (loss of electrons) that modifies the range of energies in which the compound interacts with visible light. In this work WO3 and NiOx were deposited onto ITO coated glass by reactive DC magnetron sputtering in Ar/O2 mixing gas at room temperature. For the deposition process was employed off-axis sputtering method in which the substrate is positioned out of the high-energy particles. The electrochemical properties of the WO3 and NiOx series were measured by using conventional three-electrode configuration in 1 M LiClO4-PC electrolyte.Then with the aim to test the performance of the electrochromic metal oxide films, a five-layer battery-like structure ECD (ITO/WO3/electrolyte/NiOx/ITO) was assembled with an Li+ based liquid electrolyte.The results confirm that off-axis magnetron sputtering provides good feasibility to deposit metal oxide thin films with a good electrochromic performance.
Dijital radyografi sisteminin tasarımı, geliştirilmesi ve üretimi
The development of scintillation materials are important because of the ever-increasing need for materials in high-energy physics and digital radiography. The present composition of the scintillators consists of organic or inorganic materials, each of which is suitable for different applications. Inorganic crystal scintillators are widely used because of their superior energy solubility and stiffness for high energy radiation. In the scope of the thesis, inorganic Gd2O2SO4 phosphorescent nanoparticles which are doped with pure and rare earth elements (Dy3+, Ce3+, Eu3+, Ho3+, Pr3+, Tb3+) are optimized according to the density of the dopants. In line with this optimization, scintillator materials were produced by the sol-gel method and characterized. The characterization process was carried out separately in three different production stages, namely solution, gel, and final product. In this process, the pH and turbidity values of the solutions were determined. Slightly acidic (pH: 6.1) and fully dissolved solutions were obtained. FTIR analysis was performed to determine organic bonds to the sol-gel material, and DTA-TG thermal analyzes were performed to determine exothermic-endothermic reactions. The heat treatment temperature required to find the correct phase was determined at this stage. The final product was then obtained and characterization was completed using FTIR, XRD, XPS, SEM and PL devices, respectively. When the characterizations are evaluated in detail, it is seen that the produced Gd2O2SO4: RE3+ nanoparticles are successfully produced in the desired phase structure and nanostructure. In addition, the specific emission spectra and decay times of each of the nanoparticles activated with different rare earth elements have been determined. This clearly shows that the produced scintillators can also be used in different detectors for the intended purpose in digital imaging.
Piezoelektrik nanomalzemeler kullanılarak elektroaktif polimer üretimi ve uygulamaları
In this research by using barium titanate and carbon nanotube additives composites having silicone elastomer (PDMS) matrix were made to produce electroactive polymer composite. First different temperatures and durations were examined to cure the PDMS silicon elastomer to obtain the one which has higher dielectric constant. After that to measure the barium titanate particle size, appropriate dispersant and particle amount optimization was made. Different weight percent amounts of barium titanate powder were mixed with the PDMS to determine optimum dielectric constant by LCR meter. CNT layer was coated onto the PDMS by stamping. Its morphological and electrical properties were observed by digital microscope. SEM, FTIR and DTA measurement were made to compare the surface morphology and particle distribution, bonding property change by effect of additives and curing regime respectively.
Savunma sanayiinde aşırı koşullara maruz kalan hafif alaşımların yüzey modifikasyonu
Bu çalışmada, alüminyum oksit, silisyum oksit, wolfram-titanyum karbür ve titanyum karbür parçacıklar ilave edilerek hazırlanan çözeltilerde, plazma elektrolitik oksidasyon (PEO) yöntemiyle AA7075 alaşımı üzerine seramik kaplamalar geliştirilmiştir. Parçacıkların ilave edildiği ana çözeltinin kimyasal bileşimi, en düşük gözenekliliğe ve en yüksek sertliğe sahip kaplamayı elde etmek için yapılan optimizasyon çalışması sonucunda belirlenmiştir. Kaplamaların faz bileşimi x-ışını kırınımı (XRD) yöntemiyle incelenmiştir. Taramalı elektron mikroskobu (SEM) ile kaplamaların yüzey morfolojisi ve kesitin mikroyapısı incelenmiştir. Enerji dağılımlı x-ışını spektrometresi (EDX) sayesinde kaplamaların kimyasal analizi yapılmıştır. Kaplamaların sertlik değerleri mikroVickers sertlik test cihazıyla ölçülmüştür. Kaplama yapılan altlık alaşımların sürtünme ve aşınma davranışını incelemek amacıyla 100Cr6 çelik ve alüminyum oksit bilyelere karşı kuru kaymalı aşınma testleri yapılmıştır. Aşınma testi sonrası yüzey profilometresiyle aşınma profili çıkarılarak aşınan malzeme hacmi hesaplanmıştır. Yapılan testler sonucunda AA7075 alaşımın yüzey sertliği ve aşınma dayanımının üretilen PEO kaplamalarla önemli ölçüde arttığı gözlenmiştir. Kaplamalar yoğun iç tabaka ve gözenekli üst tabakadan oluşmaktadır. Kaplama sertliğinin altlık/kaplama arayüzeyine yakın bölgede yüksek, yüzeye doğru ilerledikçe gözenekliliğin artışından dolayı düştüğü belirlenmiştir. Silisyum oksit parçacık içeren çözeltilerde üretilen kaplamaların diğer kaplamalara göre daha kalın ve pürüzlü olduğu tespit edilmiştir. En düşük aşınma kaybı titanyum karbür içeren çözeltilerde üretilen kaplamada elde edilmiştir.
Doğrudan alkollü yakıt pilleri için yenilikçi katalizör sentezi
In this thesis work, non-precious nitrogen-doped iron-nickel and iron nanoparticles, supported on three-dimensional reduced graphene oxide, are prepared via a combination of sacrificial support method and wet impregnation method as alternative anode catalysts to precious metal catalysts of the direct methanol fuel cells for electro-oxidation of methanol. Graphene oxide was synthesized via an improved Hummers method. Nitrogen doping was carried out by the pyrolysis of urea, which also provided the reduction of graphene oxide support simultaneously. Electrocatalytic activities of the catalysts for methanol electro-oxidation in acidic media were obtained by cyclic voltammetry (CV). Morphologies of the synthesized materials were obtained using scanning electron microscopy (SEM). The presence and distribution properties of the nanosized iron and nickel particles were detected via scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). Quantitative analyses of iron and nickel were conducted by inductively coupled plasma-optical emission spectrometry (ICP-OES). X-ray photoelectron spectroscopy (XPS) analyses were executed to obtain the surface chemical composition and bonding of the synthesized materials and to prove the formation of the alloy. Crystal structures of the materials produced were determined by examining their X-ray diffraction (XRD) patterns. Thermogravimetric analyses (TGA) of the samples were done under a nitrogen atmosphere to obtain their thermal behaviors.
Memristans malzemelerin FPGA sistemlerde simülasyonu ve performansının incelenmesi
Günümüz teknolojisinde tümleşik devreler üzerindeki bileşen sayısı Moore yasası sınırlarına ulaşmış olup halihazırda kullanılmakta olan Complementary Metal Oxide Semiconductor (Cmos) teknolojisinin getirilerini arttıracak geleceğin teknolojileri araştırılmaktadır. Bu teknolojiler arasında memristör teknolojisinin düşük güç tüketimi, düşük alan işgali ve en önemlisi sistem gücü kesilse dahi veriyi tutabilmesi rakipleri arasında yıldızının parlamasına sebep olmuştur. Bu tezde, memristörler ile mantık tasarımları, memristörlerin Complementary Metal Oxide Semiconductor (Cmos) sistemlere melez yapılarda entegrasyonu, Complementary Metal Oxide Semiconductor (Cmos) uyumluluğu Virtuoso Cadence Design Envoriment programında simule edilmiş, Field Programmable Gate Array (FPGA) ve veri depolama sistemlerinde kullanılan çapraz çubuk (Crossbar) mimarilerinde memristör teknolojisinin getirdiği sinsi akım (sneakpath current) problemleri gibi sorunlar ve çözüm yöntemleri araştırılarak farklı çözüm yolları önerilmiştir. Bu tezde memristör teknolojisinin araştırılması, milli teknoloji atılımımızda yeni teknolojilere entegrasyonun daha kolay sağlanmasına ve bu konuda söz sahibi olunmasına yardımcı olacağı düşünülmektedir.
Sol-jel yöntemi ile sentezlenen nanopartiküllerin fotokatalitik özelliklerinin geliştirilmesi
Among the transition metal oxide semiconductors, titanium dioxide is the most suitable photocatalyst commonly used for photocatalysis applications. However, there are still many difficulties to enhance the photocatalytic performance of titanium dioxide. Various techniques have been applied to develop the photocatalytic properties of titanium dioxide nanoparticles, such as doping transition metal elements (Ag, Ni, Cu, Zn etc.) doping, rare earth metal elements (La, Ce, Eu etc.) doping to other metals and non-metals elements (F, C, S etc.). Titanium dioxide is compatible with transition metal cations such as chromium, which has a high absorption of visible light. Scientific research shows that the doping of a transition metal and a noble metal together into titanium dioxide structure may lead to the development of photoactivity. The present thesis involves, pure chromium doped, chromium and nitrogen codoped TiO2 nanoparticles production by a sol-gel method using titanium(IV) isopropoxide, chromium nitrate and urea as precursors. Structural characterization of the undoped and doped TiO2 nanoparticles was performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectrometry (XPS). Particle size measurements of nanoparticles were performed by using Zetasizer. XRD results show that the undoped, Cr doped and Cr/N codoped TiO2 nanoparticles have the anatase phase. The photocatalytic properties of synthesized nanoparticles were determined by degredation of methylene blue solution under UV illumination. Photocatalytic efficiency of undoped, doped and codoped TiO2 were compared. The best photocatalytic activity was observed in C/N codoped TiO2 nanoparticles.
Katkılı nanopartikül içeren kaplamaların yapısal özelliklerinin incelenmesi
Main purpose of this thesis is to synthesize doped nanoparticles with sol-gel method in order to use them for deposition of Ni based nanocomposite coatings by electrodeposition technique and to investigate its effect on structural properties of the nanocomposite coatings. At first, undoped, Mn doped and Mn-N codoped titanium dioxide nanoparticles were synthesized by sol-gel method. Titanium tetraisopropoxide were used as the precursor. Structural analysis and particle size measurements of the nanoparticles were conducted by using X-Ray Diffraction (XRD) and particle size analyzer, respectively. Subsequently, Ni and Ni based nanocomposite coatings were fabricated on steel substrate by electrodeposition method. XRD and Scanning Electron Microscope (SEM) analysis were done to investigate crystalline structure and surface morphology, respectively. Electrochemical measurements of Ni and Ni based nanocomposite coatings were performed using a Gamry potentiostat/galvanostat system controlled by Gamry Framework Software. It was observed that nanocomposite coatings with doped nanoparticles has shown enhanced surface properties, compared to the undoped nanoparticle coatings.
Proses iyileştirmede nano teknolojik yöntemlerin geçerliliğinin 6-sigma tekniğiyle test edilmesi
Bu çalışmanın amacı disiplinler arası bir bilim olan Nanoteknoloji Tekniğinin yüksek katma değer sağlayarak rekabet gücünü artırması, düşük enerji tüketimi, yüksek performansı ile Proses İyileştirmedeki geçerliliğini 6 sigma ile test etmektir. Bu amaç doğrultusunda, yüzde 99 saflığın üzerinde gümüş nitrat ve yüzde 99 saflıkta sodyum borhidrid kullanılarak nano gümüş solü sentezlenmiştir. Sonra elde edilen nano gümüş çözeltisinin homojenize olması için ultrasonik banyo da 10 dakika' lık sürelerde ultrasonifikasyon işlemine tabi tutulmuştur. Ardından nano gümüş solü, santrifüj de saflaştırma işlemine tabi tutulmuştur. Sentezlenen nano gümüş solü Hellma quartz küvetlere alınan örnekler UV/VIS spektrofotometre de ölçümleri yapılmıştır. Nano gümüş sollerin nano boyutunun karakterize edilmesi işlemi ise nano gümüş solünün tanecik boyutunun Zeta-Sizer nano tanecik boyut ölçüm cihazında ölçülmesi ve değerlendirilmesi ile gerçekleştirilmiştir. Biyouyumlu polimerik malzemelerin çözeltilerinin hazırlanması ve nano gümüş sollerin hazırlanan çözeltiye doplanması işlemi yapılmıştır. Selüloz hidrojen peroksit ile yükseltgenmiştir. Chitosan çözeltisinin ve Chitosan-Polivinilalkol çözeltisi hazırlanmıştır. Sonra hidrojen peroksit ile yükseltgenen selülozun deasetillenmiş Chitosan ile kaplanması işlemi yapılmıştır. Ardından gümüş doplanmış karboksimetilselüloz çözeltisi kumaş (selüloz) üzerine elektro eğirme metodu ile kaplanmıştır. Son ürün olan kaplanmış kumaşa Geniş Spektrumlu Antibakteriyel Testlerin Yapılması işlemi gerçekleştirilmiştir. Tüm bu deneysel çalışmaların kapsadığı nanoteknolojik yöntemlerin geçerliliği 6 sigma yöntemi ile test edilmiştir.
ZnO, CuO ve γ-Fe3O4 nanopartiküllerin yeşil sentezi ve buğday genotipleri üzerindeki etkilerinin doku kültüründe araştırılması
Yapılan bu tez çalışmasında; ZnO, CuO ve γ-Fe3O4 nanopartikül yapılarının yeşil sentez yoluyla sentezlenmesi, karakterize edilmesi, iki farklı buğday genotipi üzerine olgun embriyo kültür tekniği kullanılarak etkilerinin araştırılması amaç edinilmiştir. Nanopartikül yapılarını sentezlemek için Euphorbia (Euphorbia amygdaloides) bitkisi ekstraktından elde edilen peroksidaz enziminden faydalanılmıştır. Kısmi olarak saflaştırılan peroksidaz enziminin %60-80 amonyum sülfat çöktürme yöntemiyle Euphorbia (Euphorbia amygdaloides) bitkisinden 149.5 kat saflaştırıldığı belirlenmiştir. Peroksidaz enzimi kullanılarak ZnO, CuO ve γ-Fe3O4 nanopartikül (NP)'lerin yeşil sentezi gerçekleştirilmiştir. Bu amaçla; NP'lerin sentezi için pH, sıcaklık, zaman, metal iyonu konsantrasyonu gibi çeşitli biyokimyasal verilerin optimizasyon işlemleri yapılmıştır. Elde edilen bulgulara göre ZnO, CuO ve γ-Fe3O4 nanopartiküllerin sentezlenme süreleri sırasıyla 30 dk, 30 dk ve 15 dk olmuştur. Optimum sentezlenme pH'larının 7.5, 8.0 ve 11.0 olduğu saptanırken, 30°C, 25°C ve 20°C'ler optimum sentez sıcaklıkları olarak belirlenmiştir. Elde edilen nanopartikül yapılarının karakterizasyonu için FT-IR, XRD ve SEM spektrum analizleri yapılmıştır. ZnO NP yapıları 60-80 nm arasında boyutlara sahipken, CuO NP yapıları 50-120 nm arasında, γ-Fe3O4 NP yapılarının ise 30-80 nm arasında boyutları arasında olduğu belirlenmiştir. Çalışmanın devamında ZnO, CuO ve γ-Fe3O4 nanopartiküllerinin, Kırik ve ES-26 olmak üzere iki ayrı buğday (Triticum aestivum L.) genotipinin olgun embriyo kültüründe, mikro element olarak etkileri araştırılmıştır. Bu kapsamda NP yapılarının hem Murashige and Skoog besi ortamında var olan normal miktarıyla(1x), hem de bu miktarın iki(2x) ve üç(3x) katları şeklinde test edilmiştir. Çalışma negatif ve pozitif kontrollerle desteklenmiştir. Elde edilen bulgularda, nanopartikül içeren uygulamalarda gelişmeye bırakılan buğday embriyolarının nanopartikül yapılarından aktif bir biçimde yararlanamadığı düşünülmektedir. Sonuç olarak kontrole kıyasla nanopartikül içeren uygulamaların gelişimleri daha az olmuştur. Tüm uygulamalar arasında kallus oluşum oranı bakımından 3x CuO NP içeren ortamlar ile 3x ZnO NP içeren ortamların kontrollere kıyasla daha başarılı sonuç verdiği belirlenmiştir. Bitki oluşturma kabiliyeti bakımından en başarılı grup kontrol grubu olmuştur. Bu doğrultuda kontrole kıyasla bitki rejenerasyonunun nanopartikül uygulamalarıyla artış göstermediği görülmektedir. Ancak bu durumun temelde nanopartiküllerin bitki tarafından yararlanım süreciyle ilgili olduğu düşünülmektedir. Toksik bir etki oluşturup oluşturmadığı ise gelecek çalışmaların konusu olmaya adaydır. Bu çalışma, olgun embriyo kültüründe yeşil sentez yoluyla elde edilen NP yapılarının test edilmesi noktasında bir ilk olma özelliği taşımaktadır. Bu durum embriyoların doku kültürü gelişim aşamalarına NP'lerin oluşturacağı etkilerin belirlenmesi noktasında literatürde bir eksikliği giderecektir.
Stronsiyum florür-germanıum içeren ince film cam üretimi ve karektrizasyonu
Bu araştırmada RF kopartma yöntemi kullanılarak, özelbir tür camın ince filmleri üretilmiştir. Bu çalışmada, ilk başlangıçta belirli miktarlarda: SrF2, SiO2, SrO, Al2O3, Na2CO3 ve K2CO3 malzemelerin karışımları kullanlarak ince film camlar elde edilmiştir. Daha sonra bu karışıma %3, %5 ve %10 oranlarında Ge katksı yapılarak camların soğuruculuk özelliklerideğiştirlmiştir. İlk olarak kaplamalar 6, 8, 10, 12, 14 ve 16 saat'de adi cam alttaşın üzerine yapılmıştır. Numunelerin XRD ve görünür ışık bölgesindeki soğurmaları analiz edilmiş ve 16 saat süre ile yapılan numunenin soğurma analizinde pik değerlerini net bir şekilde gözlemlenmiştir. Bu çalışma boyunca Ge un %3, %5 ve %10 yüzdesinde katkısı olan targetlerinin ince filmi, birde kuvartz alttaş üzerindede 16 saatde yapıldı ve numunelerinin XRD analizlerinde düzenli kristal pikleri oluşumu gözlemlendi. Farklı oranlarda kuvartz üzerinde yapılan numuneler, faz ayırma prensibi için, 570C 580C, 590C, 600C ve 610C sıcaklıkta, 3 saat süre boyunca fırın içerisine bırakıldı ve XRD sonuçları düzenli bir kristal oluşumunu gösterdi. Bu numunelerden XRD, SEM, soğurma analizi, geçirgenlik ve elektrik iletkenliği analizleri alındı.
Linalool monomerinden plazma polimerizasyonu ile antibakteriyal ince film elde edilmesi
Bu çalışmada linalool monomerinin plazma polimerizasyon tekniği kullanarak cam alttaş yüzeyinde ince filmleri (ppLin) sentezlendi ve bu filmlerin antibakteriyal etkisi incelendi. Plazma polimerizasyon ünitesi, linalool monomerinin 20W ve 15W elektrik akımlarında 15 ve 30 dakika sürede ve 500mTorr basınçta cam alttaşların yüzeylerinde ince film oluşturmak için kullanıldı. Sentezlenen ppLin FTIR, SEM, AFM analizi yapıldı. İnce filmlerin hidrofilik karakteri temas açısı ölçümleri yapılarak belirlendi. ppLin'in fonksiyonel grupları, E.coli (ATCC25922) ve S. aureus'a (ATCC29213) karşı antibakteriyal özellikleri test edildi. Elde edilen sonuçta en iyi antibakteriyal adezyon etkiyi E. coli için 20W 15 dakikada üretilen ppLin ince filmleri ve S. aureus için 20W 30 dakikada üretilen ppLin ince filmleri gösterdi. ppLin ince filmleri antibakteriyal etkileri McFarland 0,5 standardına göre belirlendi. 20W 15 dakikada üretilen ppLin ince filmleri, E.coli sayısında ilk gün %6 azalma dördüncü gün sonunda %10 azalma sağladı. 20W 30 dakikada üretilen ppLin ince filmleri, S. aureus sayısında ilk gün %4 azalma dördüncü günün sonunda %87 azalma sağladı.
Sythesis and characterization of copper oxide (CuO) nanowires by VLS technique
In this study, CuO nanowires have been grown on the Cu bases with the technique of Vapor-Liquid-Solid (VLS) accomplishedly. After appraisal phrase with Cu base hydrothermal, it has been supplied to be oxidized in the atmosphere environment and within the tube oven by itself. In this technique, the growth features of nanowires depend upon the diffusion, the hydrothermal method, the facet, the differences of pressure and temperature in the system,the retention time in the system, the thermodynamic bahaviour of the droplet composed and whether the base has a celluar structure or not. For that reason, Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) and RAMAN have been used for the purpose that the composed nanowires are analyzed reciprocatively. Energy Dispersive X-Ray Spectrometer has been also used to be defined the nanostructure in the process of formation of these nanowires. According to experimental findings acquired, it has been observed that the number and size of nanowire have increased in temperature rise (350-400-500-600 centigrade degree), and the heights of the nanowires have increased during the rise of temperature (30-60-120-140 minutes). Consequently, the experimental findings acquired have been mainted that they are in compliance by comparison with other experimental findings and theoretical data.
ZnO, Fe3O4 ve ZnO/Fe3O4 nanopartikülleri immobilize luffa sponge lifleri kullanılarak atık sulardan direkt mavi 15 azo boyar maddelerin giderilmesi; kinetik ve denge modellemesi
Bu çalışmada Luffa sponge ve ZnO, Fe3O4 ve ZnO/Fe3O4 nanopartiküllerinin kullanımı ile oluşturulan membran formlarıyla (saf Luffa sponge, Luffa s.+ZnO, Luffa s.+Fe3O4, Luffa s.+ZnO/Fe3O4) Direkt Mavi 15 azo boyalarının sulardan uzaklaştırılması çalışılmıştır. Bu amaçla ilk olarak ZnO ve Fe3O4 nanopartikülleri yeşil sentez yöntemi ile Euphorbia amygdaloides'den kısmi olarak 149,5 kat ve 29,5 verimle saflaştırılan peroksidaz enzimi katalizörlüğünde elde edilmiştir. Sentezlenen nanopartiküllere yönelik karakterizasyon çalışmaları yapılmıştır. ZnO için 304 nm, Fe3O4 için 481 nm'de ölçüm alınmıştır. 30°C'de ZnO için pH 6,0 ortamı Fe3O4 için pH 8,0 ortamı optimum pH ortamları olarak belirlenmiştir. 5 mM ZnCl2 ve 1mM FeCl2-Fe2Cl3 konsantrasyonları ile maksimum nanopartikül sentezi sağlanmıştır. Nanopartiküllere ait SEM, FT-IR ve XRD ölçümleri alınmıştır. Acinetobacter calcoaceticus strain ve Pediococcus acidilactici bakterilerine karşı disk difüzyon metodu ile nanopartiküllerin antimikrobiyal aktivitesi bulunmuştur. Bu nanopartiküller kullanılarak saf Luffa sponge, Luffa s.+ZnO, Luffa s.+Fe3O4, Luffa s.+ZnO/Fe3O4 membran formları oluşturulmuştur ve SEM, FT-IR ve XRD karakterizasyonu yapılmıştır. Membran formları ile Direkt Mavi 15 azo boyasının adsorpsiyonu çalışılmıştır. Yapılan optimizasyon çalışmaları doğrultusunda optimum temas süresi 45 dk, optimum pH 8,0, optimum sıcaklık 20°C, optimum boya konsantrasyonu 200 mg/L, optimum Luffa sponge miktarı 0,025 gr olarak belirlenmiştir. Membran formları ile boyanın adsorpsiyonuna yönelik SEM, FT-IR ve XRD karakterizasyonu yapılmıştır. Her bir membran formu yapılan analizlerde farklı değerler sergilemekle birlikte birbirine yakın değerlerde sergilemişlerdir. Nanopartikül yüklü membran formları saf Luffa sponge membran formuna kıyasla avantaj sağlamıştır. Langmiur ve Freundlich adsorpsiyon izoterm, birinci ve ikinci dereceden reaksiyon kinetiği, termodinamik sabitlerin hesaplanması çalışmaları yapılmıştır. Anahtar Kelimeler: Remediasyon, Nanopartikül, Direkt Mavi 15, Luffa Sponge
Ag, Au ve Pt nanopartiküllerin bıldırcın yumurta sarısı kullanılarak yeşil sentez yöntemi ile eldesi, karakterizasyonu ve antimikrobiyal özelliklerinin belirlenmesi
Yapılan bu tez çalışması kapsamında; Ag, Au ve Pt nanopartiküllerin (NP'lerin) bıldırcın yumurtası kullanılarak yeşil sentezinin yapılması, optimizasyonu ve karakterize edilmesi amaçlanmıştır. Nanopartiküllerin sentezinde ilk kez, biyokimyasal olarak protein ve vitamin bakımından zengin olan bıldırcın yumurtasının sarısı kullanılmıştır. Ag, Au ve Pt NP'lerinin yeşil sentez optimizasyonunu yapmak amacıyla; pH, sıcaklık, zaman ve metal iyonu konsantrasyonu gibi parametrelerin sentez reaksiyonları üzerine etkileri incelenmiştir. Elde edilen bulgulara göre Ag, Au ve Pt NP'leri için optimum sentezlenme sürelerinin sırasıyla; 3 sa, 4 sa ve 4 sa olduğu belirlenmiştir. Ag, Au ve Pt NP'leri için optimum sentez pH'ları sırasıyla; 8.0, 7.0 ve 6.0 olduğu saptanırken, enerji gereksinimini en aza indirgememizi sağlayan oda sıcaklığı ise her bir NP için optimum sentez sıcaklığı olarak belirlenmiştir. Ag, Au ve Pt NP'lerin sentezi için gerekli optimum metal iyon konsantrasyonunun sırasıyla 5 mM, 0.5 mM ve 5 mM olduğu kurulan reaksiyon ortamları ile tespit edilmiştir. NP'lerin yeşil sentezi gerçekleştirildikten sonra kurutularak elde edilen Ag, Au ve Pt NP yapılarının karakterizasyonu için Fourier Dönüşüm Kızılötesi Spektrofotometresi, X Işını Kırınım Difraktometresi ve Taramalı Elektron Mikroskobu cihazları kullanılmış ve analizleri yapılmıştır. Ortalama boyutları sırasıyla 60 nm, 73 nm ve 27.3 nm olan Ag, Au ve Pt NP'lerinin 10 gün boyunca aglomerasyona uğramadan stabil kaldıkları belirlenmiştir. Elde edilen bulgulara göre bıldırcın yumurta sarısı kullanılarak yapılan Ag, Au ve Pt NP sentezinin, diğer biyolojik ve kimyasal yöntemlere oranla daha düşük enerjiye gereksinim duyarak yüksek verimde gerçekleştirilebileceği tespit edilmiştir. Buna ek olarak yapılan bu çalışma ile sentezlenen Ag, Au ve Pt NP'lerinin antimikrobiyal özellikleri Acinetobacter calcoaceticus, Pediococcus acidilactici, Staphylococcus aureus ve Aeribacillus pallidus (P26) bakterilerine karşı test edilmiştir.
Gümüş ve antibiyotik içeren montmorillonit nanokompozitlerin geliştirilmesi ve katı atık depolama alanlarında kullanılabilirliğinin araştırılması
Nano malzemelerin kullanım alanları her geçen gün artmaktadır. Spesifik mühendislik malzemelerinin üretilmesinde kullanılan kil zeminler aynı zamanda katı atık depolama alanlarında ve barajlarda geçirimsiz yapı elemanı olarak kullanılmaktadır. Katı atık depolama alanları sadece çöplerin biriktirilme alanları olmaktan daha çok çevre sağlığını korumada önemli fonksiyonları olan mühendislik yapılarıdır. Özellikle içme sulama sularının kirlenmesinin önlenmesinde bu yapı alanlarının üstlendiği görev büyüktür. Polimer/kil nanoparçacıklarının üretiminde en iyi yöntemlerden biri çeşitli fonksiyonel monomerlerin interkalasyon (ko)polimerizasyon yöntemidir. Bu çalışma kapsamında literatürde sınırlı sayıda çalışma olan gümüş montmorillonit nano kompozit malzemesinin mühendislik ve tıbbi özellikleri araştırılmıştır. Bu çalışmada kullanılan kilin doğası gereği bakterilerin sevmediği yapıya sahip olduğu görülmüştür. Bentonit türündeki bu killer %0,1, %1, %10 oranlarında gümüş tuzu ile katkılandırılarak nanokompozit malzeme üretilmiştir. Kil ile antibakteriyel özeliği bilinen siprofloksasin etken maddesi aynı oranlarda katkılandırılarak hem antibakteriyel özellikleri incelenmiş hem de kontrol numuneleri oluşturulmuştur. Deney sonuçlarından kilin %0,1, %1 ve %10 oranlarında gümüş ve siprofloksasin ile muamele edildiği ve nanokompozit üretildiği XPS, SEM ve EDS sonuçları ile gösterilmiştir. Yapılan mikrobiyal testler sonucunda gümüş ve siprofloksasin katkılı killerin konsantrasyonuna bağlı olarak antibakteriyel özelliğinin artığı görülmüştür. Antibakteriyel testlerde katı atık depolama alanlarındaki atık su depolama havuzlarına da prototip oluşturması amacıyla numuneler ile yüzey kaplaması yapılmıştır. Test sonuçlarından elde edilen numunelerin antibakteriyel yüzey kaplaması malzemesi olarak kullanılabileceği gösterilmiştir. Katı atık depolama alanlarında gümüş katkılı kilin kullanımı yeni bir konudur. Geosentetik membran üzeri kaplamada, geosentetik kil membran yapımında veya atık su depolama alanının yüzey kaplamasında gümüş katkılı nanokilin kullanımının toplanan atık sulardaki bakteri öldürüğü ve üremesini engellediği ve kirli suların ıslahı ve zararlı etkilerinin giderileceği sonuçlarına varılmıştır