Nilgun (DOGAN) BAYDOGAN | Istanbul Technical University (original) (raw)

Papers by Nilgun (DOGAN) BAYDOGAN

Strengthened bonds by chemical development at surface of low dielectric PMMA/Borax composite for low reflection of broadband waves (500 MHz—50 GHz)

Journal of Polymer Research

Finned heat exchangers made of TiB2–SiC–graphene composites with enhanced heat transfer performance

Journal of the Brazilian Society of Mechanical Sciences and Engineering

$Research paper thumbnail of Optimizing performance and energy consumption in GaN(n)/In x Ga 1- x N/GaN/AlGaN/GaN(p) light emitting diodes by quantum-well number and mole fraction$

Light-emitting devices (LEDs) with higher performance, lower energy demand and minimal environmen... more Light-emitting devices (LEDs) with higher performance, lower energy demand and minimal environmental impact are needed. With wide-band gaps and high emission efficiencies, III-V nitride semiconductors are useful for LEDs in short-wavelength regions. A multiple quantum well (MQW LED), based on InGaN/GaN, is proposed. The structure involves GaN(n)/InxGa1−xN(i)/GaN(i)/AlGaN(p)/GaN(p), where GaN(n) and GaN(p) have different dopants to formulate the junction at which electric field occurs, InxGa1−xN(i) is a 3 nm-thick intrinsic quantum well with (x) as indium mole fraction, GaN(i) is barrier intrinsic layer and AlGaN(p) is a 15 nm-thick electron blocking layer (EBL). Simulation is performed by Tcad-Silvaco. Various characteristics such as current versus voltage (I-V) plots, luminosity power, band diagram, spectrum response, radiative recombination rate and electric field effect, have been investigated. By controlling the InxGa1−xN(i) number of quantum wells and their indium mole fraction...

Stability of magnetic susceptibility at poly (Methyl Methacrylate) /Multi-walled carbon nanotubes nanocomposite

Polymer-Plastics Technology and Materials

Current Insight into 3D Printing in Solid‐State Lithium‐Ion Batteries: A Perspective

Batteries & supercaps, Jun 7, 2022

Compared to the state‐of‐art lithium‐ion batteries, the all‐solid‐state batteries offer improved ... more Compared to the state‐of‐art lithium‐ion batteries, the all‐solid‐state batteries offer improved safety along with high energy and power density. Although considerable research has been conducted, the inherent problems arising from solid electrolytes and the lack of suitable electrolytes hinder their development in practical applications. Furthermore, traditional synthesis routes have drawbacks due to limited control to fabricate the solid electrolytes with desired shape and size, impeding their maximum performance. In recent years, additive manufacturing or three‐dimensional (3D) printing techniques have played a vital role in constructing solid‐state batteries because of the rational design of functional electrode and electrolyte materials for batteries with increased performance. 3D printing in batteries may provide a new technology solution for existing challenges and limitations in emerging electronic applications. This process boosts lithium‐ion batteries by creating geometry‐optimized 3D electrodes. 3D printing offers a range of advantages compared to traditional manufacturing methods, including designing and printing more active and passive components (cathodes, anodes, and electrolytes) of batteries. 3D printing offers desired thickness, shape, precise control, topological optimization of complex structure and composition, and a safe approach for preparing stable solid electrolytes, cost‐effective and environmentally friendly.

Chemical activation of biochar-supported metal oxides for degradation of organic/inorganic and microbial contaminants

Elsevier eBooks, 2023

Development of Cu Layer with Ultrahigh Speed Micrometalic Cu Particle Bombardment on Sol-Gel Derived Zno:Al Thin Film

Social Science Research Network, 2022

THE ANNEALING AND AGING EFFECT ON IRRADIATED ZnO:Al FILM BY Cs-137

Irradiation Effect on Ta₂O₅ Thin Films

Defect and Diffusion Forum, May 1, 2014

Long-term effects of time-dependent solarization behavior on optical density and optical band gap... more Long-term effects of time-dependent solarization behavior on optical density and optical band gap of the gamma and beta irradiated Ta2O5 thin films were investigated to examine the optical aging of films at different absorbed dose levels. Irradiation process caused to induce defect centres. The population inversion of the colour centres was increased by controlling the absorbed dose at certain radiation dose levels. The efficient absorption of photons in tantalum reduced transmittance. The grain boundaries of the Ta2O5 thin film decreased at the end of irradiation process. The average grain boundaries changed after the irradiation process at 4.5 kGy and average grain boundaries decreased from ~ 11.5 to 5.5 μm. The optical fading behavior of induced color centers addressed to the potential opportunities of Ta2O5 thin film by monitoring absorption of photons in optoelectronic technology. Optical fading of the Ta2O5 thin film presented an importance to investigate the material stored ionizing radiation dose in it with the increase of elapsed time after the irradiation treatment.

Low Cycle Fatigue Behaviour of Irradiated Stainless Steel as Shielding Material

In this study, low cycle fatigue behaviour of a 304 quality austenitic stainless steel irradiated... more In this study, low cycle fatigue behaviour of a 304 quality austenitic stainless steel irradiated with a â¶Â°Co radioisotope at 100-kGray-dose level was examined for the usage at the nuclear reactor vessel or a nuclear waste container. After irradiation, 1 % increment in thickness of the specimens was measured. During fatigue tests, irradiated specimens failed at earlier cycles than unirradiated specimens. The effect of irradiation on number of cycles to failure was more obvious at high strain range values. The difference in failure cycles of unirradiated and irradiated specimens is about 27 %, at 4 % total strain range. However, at 1 % total strain range, both unirradiated and irradiated specimens failed at almost the same cycle value. (authors)

Characterization of high performance randomly segmented poly(urethane siloxane) and poly(imide siloxane) block copolymers

Nucleation and Atmospheric Aerosols, 2016

Poly(imide siloxane) block copolymers with the same polydimethlysiloxane(APPS) were prepared by u... more Poly(imide siloxane) block copolymers with the same polydimethlysiloxane(APPS) were prepared by using 4,4’-oxydianiline (ODA) and Benzofenon-3,3,4,4-tetrakarboksilik dianhydride(BTDA) to compose the polyimide hard block. APPS and BTDA composed the polysiloxane soft block. The length of polysiloxane soft blocks increased with increasing the length of polyimide hard block. Copolymerization of soft and hard segments were determined by using this method. Copolymer structures could be obtained by holding constant hard block segments and by adjusting and increasing soft block segments. Thus, more flexible randomly segmented poly(imide siloxane) block copolymers can be obtained. These composed structure as flexible and high performance copolymers were characterized by FT-IR and evaluated. The structures were tested mechanically to detect their elastic recovery property as flexible material. The characterization of the samples enabled to examine flexible substrates in order to use in solar cell, aerospace applications and microelectronic devices.

Swelling modification by electron beam at chalcopyrite copper indium gallium diselenium thin-film controlled optical features

Current Applied Physics, Aug 1, 2023

High temperature performance adhesive derived from randomly segmented poly (imide siloxane) copolymer

Materials Science And Engineering: B, 2023

Research and reviews: journal of material sciences, Jan 29, 2019

P oly (methyl methacrylate) (PMMA) is a wiedly used thermoplastic polymer material because of its... more P oly (methyl methacrylate) (PMMA) is a wiedly used thermoplastic polymer material because of its advantages including light weight, easy processability, high impact resistance, chemical stability, high resistance to weathering and excellent heat resistance etc. PMMA is an ideal candidate for aerospace, automotive, marine applications. However, long-term durability and reliability of polymeric materials are still problematic when they serve for structural application. Hence, in this study we added several nanomaterials to improve the weak properties of PMMA. PMMA was synthesized by Atom Transfer Radical Polymerization (ATRP) technique; nanofillers are dispersed at 5 different concentration levels such as 0.1, 0.25, 0.5, 1.0 and 2.0 wt. % via in situ polymerization method. The changes in the properties of PMMA nanocomposites examined by SEM, TGA/DSC tensile, impact and hardness tests. PMMA nanocomposite with the low nanofiller loading ratio showed noticeable enhancements in their mechanical and thermal aspects. In this study, we also synthesised self-healing PMMA nanocomposite. Encapsulate GMA was served as self-healing agent. Emulsion polymerization was applied to encapsulate GMA with poly (melamine-formaldehyde) (PMF) as the wall substance. GMA was added to PMMA nanocomposite solutions via melt compounding method. Self-healing performance of the PMMA nanocomposites was evaluated via impact test.

The changes in optical absorbance of ZrO2 thin film with the rise of the absorbed dose

9TH INTERNATIONAL PHYSICS CONFERENCE OF THE BALKAN PHYSICAL UNION (BPU-9), 2016

In this study, zirconium oxide (ZrO2) thin film samples prepared by sol–gel method were irradiate... more In this study, zirconium oxide (ZrO2) thin film samples prepared by sol–gel method were irradiated using Co-60 radioisotope as gamma source. Then, it was investigated the ionizing effect on optical properties of ZrO2 thin film samples with the rise of the absorbed dose. The changes in the optical absorbance of ZrO2 thin films were determined by using optical transmittance and the reflectance measurements in the range between 190 – 1100 nm obtained from PG Instruments T80 UV-Vis spectrophotometer.

Gama ışınları ile ışınlanmış kurşun-alkali-silika camın dozimetrik kullanımı

... Şekil 1. Görünür ışık için ışınlamadan önce ve sonra kurşun-alkali-silika camların geçirgenli... more ... Şekil 1. Görünür ışık için ışınlamadan önce ve sonra kurşun-alkali-silika camların geçirgenlik, yansıtıcılık ve soğurma eğrileri. ... Ezz-Eldin, FM, Abdel-Azim, F., Abdel-Azim, A. A. ve Ahmed, AA, (1994/b). Soda-lime-silica glass for radiation dosimetry, Medical Physics, 21, 7, 1085 ...

Effect of electron beam improved dielectric function on optical properties of sol-gel derived CuIn1-XGaXSe2 thin-film

Optical Materials, Dec 1, 2022

Synthesis of Poly(Methyl Methacrylate) Reinforced by Graphene Nanoplates

Key Engineering Materials, Aug 17, 2021

Graphene nanoplatelets (GNPs) was used as a nanofiller in Poly(methyl methacrylate) (PMMA) synthe... more Graphene nanoplatelets (GNPs) was used as a nanofiller in Poly(methyl methacrylate) (PMMA) synthesized by the Atom Transfer Radical Polymerization (ATRP) method. The first step in the synthesis of the PMMA/GNPs was the dispersion of GNPs in the PMMA liquid monomers by combining the solutions so that GNPs had superior mechanical properties, thermal stability, and electrical conductivity also lower density of mass. Then the crosslinked PMMA/GNPs nanocomposite samples were synthesized by using the in-situ polymerization method. However, there was a challenging technical problem in the application of GNPs (at a large amount) in the polymer. For the purpose of benefiting from the advantageous properties of GNPs (especially in bulk quantities) at PMMA, the major problem at the synthesis of PMMA/GNPs nanocomposite was the GNPs dispersion in the polymer matrix. This research has focused on solving that dispersion problem with the aim of enhancing the mechanical properties of the nanocomposite by utilizing the ATRP method as the effective production technic. The structural characterization of PMMA/GNPs nanocomposite was performed for the examination of the integration of GNPs in PMMA. The surface morphology of the nanocomposite was analyzed using SEM images. X-Ray Diffraction (XRD) as a non-destructive test method was used to examine the changes in the crystalline properties of the nanocomposite structure with the rise of the GNPs amount in PMMA. The bonding interactions with each other were investigated by using Raman analysis.

Procedia - Social and Behavioral Sciences, Jul 1, 2015

In this study, the changes in the linear attenuation coefficient for beta radiation of irradiated... more In this study, the changes in the linear attenuation coefficient for beta radiation of irradiated ZrO 2 thin film samples were determined using transmission method. The film samples irradiated by gamma radiation at 0.430Gy, 0.672Gy, 1.195Gy and 2.690Gy. The utilization of Co-60 radioisotope with the activity level of 0.018021 Ci was preferred to control the absorbed dose. The changes in the linear attenuation coefficient for beta radiation were investigated to evaluate the variations of the irradiated samples. The linear attenuation coefficients were determined by using two different Sr-90 radioisotopes. Hence the details in characteristic properties were assessed with respect to two different activity levels respectively, 2558 μCi and 0.0513 μCi. There were the changes in linear attenuation coefficient of the samples with the rise of the absorbed dose.