İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı Tez Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/420

Browse

Now showing 1 - 7 of 7

EVALUATION OF MATERIAL OPTIONS FOR ELECTRICAL POWER SUPPLYING AND PROTECTIVE WEARABLE EQUIPMENT
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2020) KAAN, Murat; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Ballistic vests used in military applications are usually made out of layers of various materials and then combined to form a solitary conservative vest. Contrasted with bygone eras, functionality and productivity of ballistic vests have improved to a critical sum. ANSYS was explicitly used to compute such finite element analysis and the initial segment of the postulation dealt with the determination of material used for the first/front layer of the vest. Since nowadays all ballistic vests almost use Kevlar and epoxy layers in the material formation of the vest, the similar material candidates were chosen for this research as well. Practically, the only choice of material that had to be decided is for the front layer of the vest since many different materials can be used in that regard. Silicon Carbide (SiC) was picked on the grounds that it demonstrated the least deformation and least stress compared to other materials that were tested in ANSYS. In total; three materials were tested and evaluated respectively were Silicon Carbide, Boron Carbide (BC) and Alumina (Al2O3). In order to prove the protection of the ballistic vest design and its reliability in the ballistic sense, 6 (six) flawless shots were fired at certain points on the vest, based on American NIJ standards. In short, the thesis examines the protection of ballistic protective vests from serious military injuries during combat and the development of a hybrid solution that will provide the vest with a new function to provide the power needs of the equipment the soldier will need during combat. In addition, a novel idea is proposed to the literature by adding the fourth layer into the FEA based examined ballistic vest.
Experimental investigation and optimization of cutting parameters to minimize the burr formation in milling of S2-glass fiber-reinforced plastics
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2024) Sayın, Ahmed Çağrı; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Composite materials have a wide range of application areas due to their high mechanical properties, low density and versatility. Milling is an important process for the composite materials to shape them according to the needs of the application area. Burrs are often created during the milling process and result in rejection of parts in the desired usage area. This study focuses on the experimental and statistical analysis of the burrs during the milling process of S2-Glass Fiber Reinforced Plastics (S2-GFRP) and Basalt Fiber Reinforced Plastics (BFRP) composites. Damages occurring during the milling process were analyzed to evaluate the mechanical performance and surface quality of composite materials. Surface quality is determined by the area and length of the burrs that were produced during the milling operations. Optimum processing parameters have been determined to ensure minimum burr area and burr length. It is determined that there are multiple optimum parameters according to the processed material and cutting direction. Burr area and burr length are measured with image analysis. The total area of burrs is calculated, and the longest burr in each sample is measured. The effect of tool material, tool coating, spindle speed and feed rate on burr area and burr length is observed. Based on the experimental results, it was determined that the tool material is the only parameter that consistently affects burr area and bur length. The data obtained aims to ensure the more reliable and efficient use of these materials in engineering applications and makes significant contributions to sustainable production processes.
IMPROVING THE FLAME RETARDANCY USING NANOPARTICLES IN CABLE INSULATION
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2021) YILDIZ, Uğur; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Al(OH)3 (ATH) and Mg(OH)2 (MDH) like materials are frequently used as flame retardants due to their ability to form water and oxide-based substances under the influence of heat. In this study, it is aimed to produce cable insulations with improved flame retardant properties by synthesizing nano-sized Mg(OH)2 and using this material together with EVA (ethylene-vinyl-acetate) copolymer and micro-sized Al(OH)3 and Mg(OH)2 . The study can be divided into four parts. In the first part, the flame retardant properties of ATH and MDH were compared. In the second part, different raw materials were used for the synthesis of Mg(OH)2 nanoparticles; in the third part, the synthesis was carried out at factory scale and compared with the commercial product. The samples were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), X-Ray diffraction analysis (XRD), X-Ray fluorescence analysis (XRF) and Thermogravimetric analysis (TGA). In the last part, different amounts of nano-sized Mg(OH)2 particles were added to the formulas using both ATH and MDH; the effects on flame retardant performances were investigated by the Limiting Oxygen Index (LOI) test and the vertical burning test. Mechanical properties such as elongation and tensile strength were also studied. It has been observed that the synthesized Mg(OH)2 particles with a thickness of 5- 10 nm and lengths reaching 900 nm, mixed in ATH based samples at a maximum rate of 9% and in MDH based samples at a maximum rate of 10%; LOI values increased by 26% for ATH based samples and 38% for MDH based samples. However, considering the losses in mechanical properties with the increase of nanoparticle additive, it has been seen that a maximum rate of 5% nano-sized Mg(OH)2 can be added. Even in this case, the LOI values increased by 8.6% in ATH based samples and 26% in MDH based samples.
INVESTIGATION OF HYDROGEN EMBRITTLEMENT BY A MULTI-SCALE MODELLING APPROACH
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2021) KAPÇI, Mehmet Fazıl; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Hydrogen exposure of metallic materials during their service times or during the application of processes e.g. machining, welding, electroplating leads to degradation of the mechanical properties which is a phenomenon known as hydrogen embrittlement. Diffused hydrogen into metal can accumulate in crystal defects and alter the mechanical behavior under loading. In this thesis, diffusion of the hydrogen as well as the atomistic mechanisms of dislocation mobility depending on the presence of hydrogen were investigated for two edge dislocation systems that are active in the plasticity of α-Fe, specifically ½<111>{110} and ½<111>{112}. In particular, the glide of the dislocation pile-ups through a single crystal, as well as transmission of the pile-ups across the grain boundary were evaluated in bcc iron crystals that contain hydrogen concentrations in different amounts. Additionally, the uniaxial tensile response under a constant strain rate was analyzed for the aforementioned structures. Lastly, diffusion and backdiffusion of the hydrogen into bcc, fcc, and hcp crystal structures were investigated with numerical models. The results reveal that the presence of hydrogen decreases the velocity of the dislocations – in contrast to the commonly invoked HELP (Hydrogenenhanced localized plasticity) mechanism -, although some localization was observed near the grain boundary where dislocations were pinned by elastic stress fields. In the presence of pre-exisiting dislocations, hydrogen-induced hardening was observed as a consequence of the restriction of the dislocation mobility under uniaxial tension. Furthermore, it was observed that hydrogen accumulation in the grain boundary suppresses the formation of new grains that leads to a hardening response in the stressstrain behaviour which can initiate brittle fracture points
Investigation of interaction between nanocrystal quantum dot films and escherichia coli
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) Ünlü, Miray; 0000-0001-8165-6164; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Semiconductor nanocrytals also known as quantum dots (QD) with high photoluminesce quantum yield (PLQY), size tunability and favorable optical characteristics occupy a significant area in display technology, solar energy conversion and biotechnology. Size tuning feature of QDs allows peak emission wavelength ranging from ultraviolet to infrared spectral region. In literature, QD based studies have been performed in visible spectral range by employing mostly cadmium, being a toxic heavy metal. Recently, the search for less toxic alternatives revealed the cadmium free compounds, particularly InP. Cadmium free semiconductor nanocrytals' potential to be used as fluorescent probes in biodetection and biolabeling area has been proved over the past decades. Pathogens threaten life particularly via water sources like rivers, reservoirs and groundwater. Increasing demand for managing the 'contamination of drinkable water by pathogenic bacteria' problem needs a broad perspective about pathogens and their membrane characteristics which are integral part of microorganism detection platforms. Bacteria are categorized mainly upon their membrane properties which are gram negative and gram positive. Extra wall called as peptidoglycan layer in gram positive bacteria makes them more resistant to external forces. Gram negative bacteria with wavy wall is relatively more prone to their environment. One of the most known pathogenic bacteria, E. Coli, have damaged and destroyed many lives throughout the world. High growth rate enables this microorganism to spread around large areas in short time. Therefore, accurate and definite detection of this bacteria in water is crucial. The main frame of this research depends on QD based biodetection of bacteria. First of all, organic based QDs (50% PLQY) containing triocytlyphosphine-sulfur ligand were synthesized and via successful phase transfer, QDs in aqueous solvent with 20% PLQY were achieved. Although surface is damaged during ligand exchange procedure, QDs in aqueous solvent with high PLQY were obtained. SiO2 was covered with QDs thanks to the attraction between their NH2 group and carboxylic ends, respectively. In the final step, this hybrid structure was encapsulated with SiO2 and silica coated QDs (SCQD) were formed. In order to utilize SCQDs in bacteria detection, fluorescent agents were embeded in polymeric films which were formed by spin coating. As a result, SCQD facilitates the attachment of negatively charged bacteria onto the surface of the films. Appropriately grown DH5 alpha (E. Coli strain) expressing green fluorescent protein (GFP) was used as pathogen in the detection part. SCQD thin films were treated with water containing E.Coli DH5 alpha. Positively charged SCQD attracted negatively charged bacteria and the conjugation between them was analysed with time resolved spectroscopy and monitored with fluorescence microscope. Thus, usage of QDs as biosensor in pathogen detection could provide an insight in the future studies. Keywords: biodetection, E.coli, quantum dots, semiconductors, silica coated quantum dots, indium phosphate, InP QD
Nanoparticle reinforced hybrid composite material production process optimization / Nano-parçacık takviyeli hibrit kompozit üretimi için reçine geçişli kalıplama prosesi optimizasyonu
(Abdullah Gül Üniversitesi, 2017) DOĞUŞ KAÇMAZ, AZER; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı; DOĞUŞ KAÇMAZ, AZER
Composite materials have increasing application areas in today's industry and daily life due to their low density structure and high mechanical properties. Also, thermalstability and electrical conductivity can be improved by particle inclusion. Composite materials consist of preform, matrix and particles in matrix. Various production methods have been developed to bring these components together. Among these production methods, liquid composite molding methods are the most widely used methods for producing parts having advanced properties. A different method logic has been tried to obtain more homogeneous product than traditional resin Transfer Molding method in order to produce composite parts with superior mechanical properties. Since the Resin Transfer Molding (RTM) method is expensive and time-consuming, simulation is the fastest and economical method for optimization of the process. In this study, COMSOL software was used for numeric analysis. As a result, when production of hybrid composite materials with highly different permeable components performed with Resin Transfer Molding Method, Compression Resin Transfer Molding (CRTM) logic works much more precisely in terms of avoiding voids and providing homogeneity through preform when filling is performed from the top.
QUANTUM DOT BASED BIOSENSING
(Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2017) ÜNLÜ, Miray; AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı
Semiconductor nanocrytals also known as quantum dots (QD) with high photoluminesce quantum yield (PLQY), size tunability and favorable optical characteristics occupy a significant area in display technology, solar energy conversion and bioapplications. Size tuning feature of QDs allows emission wavelength ranging from ultraviolet to infrared spectral region. In literature, QD based studies have been performed in visible spectral range by employing mostly cadmium, being a toxic heavy metal. Recently, the search for less toxic alternatives revealed the cadmium free compounds, particularly InP. Cadmium free semiconductor nanocrytals’ potential to be used as fluorescent probes in biodetection and biolabeling area has been proved over the past decades. Pathogens threaten life particularly via water sources like rivers, reservoirs and groundwater. Increasing demand for managing the ‘contamination of drinkable water by pathogenic bacteria’ problem needs a broad perspective about pathogens and their membrane characteristics which are integral part of microorganism detection platforms. Bacteria are categorized mainly upon their membrane properties which are gram negative and gram positive. Extra wall called as peptidoglycan layer in gram positive bacteria makes them more resistant to external forces. Gram negative bacteria with wavy wall is relatively more prone to their environment. One of the most known pathogenic bacteria, E. Coli, have damaged and destroyed many lives throughout the world. High growth rate enables this microorganism to spread around large areas in short time. Therefore, accurate and definite detection of this bacteria in water is crucial. The main frame of this research depends on QD based biodetection of bacteria. First of all, organic based QDs (50% PLQY) containing triocytlyphosphine-sulfur ligand were synthesized and via successful phase transfer, aqueous QDs with 20% PLQY were achieved. Although surface is damaged during ligand exchange procedure, aqueous QDs with high PLQY were obtained. SiO2 was covered with QDs thanks to the attraction between their NH2 group and carboxylic ends, respectively. In the final step, this hybrid structure was covered with SiO2 and silica coated QDs (SCQD) were formed. In order to utilize SCQDs in bacteria detection, fluorescent agents were embeded in polymeric films which were formed by spin coating. As a result, SCQD facilitates the attachment of negatively charged bacteria onto the surface of the films. Appropriately grown DH5 alpha (E. Coli strain) expressing green fluorescent protein (GFP) was used as pathogen in the detection part. SCQD thin films were treated with water containing E.Coli DH5 alpha. Positively charged SCQD attracted negatively charged bacteria and the conjugation between them was analysed with time resolved spectroscopy and monitored with fluorescence microscope. Thus, usage of QDs as biosensor in pathogen detection could provide an insight in the future studies.

Browse

Browsing İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı Tez Koleksiyonu by Author "AGÜ, Fen Bilimleri Enstitüsü, İleri Malzemeler ve Nanoteknoloji Ana Bilim Dalı"