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Öğe Adsorption of uranium (VI) from aqueous solutions using boron nitride/polyindole composite adsorbent(Wiley, 2024) Emre, Deniz; Zorer, Özlem Selçuk; Bilici, Ali; Budak, Erhan; Yılmaz, Selehattin; Kılıç, Necla Calışkan; Söğüt, Eda GökırmakTurbostratic boron nitride (tBN) surface is modified with polyindole (PIn) by a facile polymerization technique and the uranyl adsorption efficiency of this mesoporous hybrid is investigated. The successful surface modification is confirmed by FT-IR, Raman, XRD, TEM, SEM, EDX, EDS mapping XPS, BET, and zeta potential techniques. The batch experiments are performed in various temperatures (T), contact times (t), pH, and initial solution concentrations (C-0) to evaluate its adsorption performance. The optimum adsorption performance is achieved at pH = 5.0-5.5, T = 307 K, t = 10 min, C-0 = 18 mg L-1. These experimental results are evaluated using Freundlich, Redlich-Peterson, and Langmuir isotherm models, which presents equivalent regression coefficients. Maximum adsorption capacity (q(m)) of the nanoadsorbent (tBN/PIn), determined by the Langmuir isotherm, is 315.29 mg g(-1). The adsorption kinetics of uranyl ions on tBN/PIn are in harmony with the pseudo-second order model. tBN/PIn nanoadsorbent provides high adsorption efficiency even at exceptionally low UO22+ concentration range (4-40 mg L-1) and low adsorbent mass (0.005 g). XPS analysis results show that 0.05% of uranium is adsorbed on tBN/PIn via mainly U-O coordination. The results of present study demonstrate that tBN/PIn can a potential adsorbent for removing uranium from aqueous solutions.Öğe Comparison of the effect of representative metal and transition metal salts on the formation of hexagonal boron nitride(Bolu Abant İzzet Baysal Üniversitesi, 2009) Budak, Erhan; Bozkurt, ÇetinBor nitrür, malzeme bilimleri alanında sıradışı konudur. Borun ve azotun özel bağlama davranışları nedeniyle, bor nitrür birçok farklı yapılarda bulunabilir. Grafit benzeri yapısı ve mükemmel özellikleriyle hekzagonal bor nitür son yirmi yılda bir çok araştırmaya çalışmaya konu olmuştur.Bu çalışmada, hekzagonal bor nitrür modifiye O'Connor metodu ile farklı metal tuzlarının varlığında sentezlenmiştir. Sentezlenen maddelerin yapısal özellikleri X-Isını Kırınım Ölçeri (XRD), Fourier Dönüsüm Kızılötesi Spektroskopisi (FTIR) ve Taramalı Elektron Mikroskobu (SEM) kullanılarak belirlenmiştir.FTIR sonuçları hekzagonal bor nitrür oluşumunu doğrulamakta ve XRD analizlerinde hekzagonal bor nitrürün ana pikleri görülmüştür. Örnekler için örgü parametreleri hesaplanmış ve orjinal hexagonal bor nitrüre çok yakın bulunmuştur. Ayrıca sentezlenen maddelerin nano ölçekte olduğu gözlenmiştir.Öğe Density functional theory study on the identification of 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol(Pergamon-Elsevier Science Ltd, 2011) Parlak, Cihan; Akdoğan, Mustafa; Yıldırım, Gürcan; Karagöz, Nurettin; Budak, Erhan; Terzioğlu, CabirThis study deals with the identification of a title compound, 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol by means of quantum chemical calculations. The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments, thermodynamic properties, charge analyses, nuclear magnetic resonance (NMR) chemical shifts and ultraviolet-visible (UV-vis) spectra of the title molecule in the ground state were evaluated using density functional theory (OFT) with the standard B3LYP/6-311++G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra of the title compound were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the obtained optimized geometric parameters (bond lengths, bond angles and bond dihedrals) and vibrational frequencies were observed to be in good agreement with the available experimental results. Moreover, the calculations of the electronic spectra, C-13 and H-1 chemical shifts were compared with the experimental ones. Furthermore, we not only simulated the frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition states and energy band gaps, as well. It was found that charge analyses supported the evidences of MEP. Infrared intensities and Raman activities were also reported. (C) 2011 Elsevier B.V. All rights reserved.Öğe Effect of Li2CO3 on formation temperature of hBN by modified O'Connor model(Wiley-V C H Verlag Gmbh, 2016) Öz, Muhammed; Sarıtekin, Namık Kemal; Bozkurt, Çetin; Budak, Erhan; Yıldırım, GürcanThis study is interested in the effect of lithium carbonate on the formation of hexagonal boron nitride (hBN) by means of the available experimental methods including TGA, XRD, FTIR, SEM and HR-TEM. hBN samples were synthesized at the 1450 degrees C with different molar ratios of lithium carbonate by modified O'Connor routine. The crystalline hBN formation tended to improve with the increment of the Li2CO3 concentration level (especially after more 20 %). The dopant quantity decreased the residual stresses due to the presence of possible relaxation mechanisms along with the nanocrystal structure, even favored by XRD experimental findings regarding the enhancement of crystal plane alignments, crystallite sizes and lattice parameters. As for the FTIR surveys, the Li2CO3 foreign impurities strengthened more and more the covalent bonds between boron and nitrogen atoms. At the same time, the samples with 40 % lithium carbonate were annealed at the varied temperatures of 1000, 1150, 1300 and 1450 degrees C to determine the optimum annealing temperature. The XRD+FTIR investigations indicated that the degree of hexagonality improved with the increased annealing temperature. Similarly, the surface morphology confirmed not only the formation of regularity and flaky hexagonal BN structures, but also the strengthening of covalent bonds between the atoms.Öğe The effect of transition metals on the structure of h-BN intercalation compounds(Academic Press Inc Elsevier Science, 2004) Budak, Erhan; Bozkurt, ÇetinIn this study, hexagonal boron nitride (h-BN) were synthesized by the modified O'Connor method in the presence of various metal nitrates [M(NO3)(x), M = Cr, Mn, Fe, Co, Ni, Cu, Zn, and Ag]. The composites were analyzed by FTIR, XRF, XRD, and SEM techniques. XRD results indicated a change in the interlayer spacing due to the intercalation of Cr, Mn, Fe and Ag. SEM analyses illustrated the grain growth upon metal intercalation even at a temperature of 1320 K.Öğe Effects of annealing temperature on electrical characteristics of sputtered Al/Al2O3/p-Si (MOS) capacitors(Scientific Technical Research Council Turkey-Tubitak, 2018) Kaya, Şenol; Budak, Erhan; Yılmaz, ErcanThe aim of this study is to investigate annealing effects on the electrical characteristics of aluminum oxide (Al2O3) MOS capacitors. Chemical changes after annealing have been characterized using the Fourier transform infrared spectroscopy prior to detailed electrical investigation. The influence of annealing temperature on electrical characteristics has been investigated by capacitance-voltage (C-V) and conductance-voltage (G/omega-V) curves. Effective oxide trap density (N-ox), border trap densities (N-bt), and interface trap densities (N-it) were calculated during the electrical analysis. Remarkable changes in the measurements were observed depending on the annealing temperatures. The obtained results demonstrate that the optimum annealing temperature is 450 degrees C for the Al2O3-based devices.Öğe Hekzagonal bor nitrür oluşumuna ve özelliklerine metal interkalasyonuna etkisinin incelenmesi(2006) Bozkurt, Çetin; Altintaş, Bahadır; Budak, Erhan-Öğe Influences of platinum doping concentrations and operation temperatures on oxygen sensitivity of Pt/SnO2/Pt resistive gas sensors(Springer, 2019) Öztel, Sinan; Kaya, Şenol; Budak, Erhan; Yılmaz, ErcanInfluences of surface platinum (Pt) doping concentrations and operation temperatures on oxygen sensing properties of Pt/SnO2/Pt metal-semiconductor-metal (MSM) resistive gas sensors were investigated incorporating structural and chemical variations. Although tetragonal phase dominated crystallographic structure of the virgin film, it was observed that the triclinic phase with minor peak intensities was also present. With increasing the doped Pt concentration, the triclinic phase of the SnO2 cannot be detected due to diffusion of the Pt into the SnO2 lattices. Surface particle sizes increased up to 200 nm and relative porosity of the film surface almost enhanced with increasing the Pt concentrations. Oxygen deficient and chemically metastable phase of the SnxOy was transformed to SnO2 with the Pt addition due to catalytic effects of the Pt. Different vibrational modes became active depending on the Pt content which was due to the stretching of the SnO2 bonds. In addition, the resistivity of the Pt-doped SnO2 films increased with the Pt additions. The oxygen sensitivity of the sensor increased with increasing both the Pt concentrations and operation temperatures. The optimum operation temperature was found to be 335 degrees C. Interestingly, as operation temperature exceeds to 225 degrees C, high Pt concentration decreased the sensor sensitivity. In addition, selectivity of the MSM sensor changes with the Pt additions. The obtained results have depicted that the parameters used in the sensor fabrication and operation should be carefully selected to increase sensing properties of the MSM resistive gas sensors.Öğe Investigation of parameters of new MAPD-3NM silicon photomultipliers(IOP Publishing Ltd, 2022) Ahmadov, F.; Ahmadov, G.; Akbarov, R.; Aktağ, Aliekber; Budak, Erhan; Doğancı, Emre; Gürer, Umutcan; Karaçalı, HüseyinIn the presented work, the parameters of a new MAPD-3NM-II photodiode with buried pixel structure manufactured in cooperation with Zecotek Company are investigated. The photon detection efficiency, gain, capacitance and gamma-ray detection performance of photodiodes are studied. The SPECTRIG MAPD is used to measure the parameters of the MAPD-3NM-II and scintillation detector based on it. The obtained results show that the newly developed MAPD3NM-II photodiode outperforms its counterparts in most parameters and it can be successfully applied in space application, medicine, high-energy physics and security.Öğe Low temperature synthesis of hexagonal boron nitride by solid state reaction in the presence of lithium salts(Elsevier Sci Ltd, 2018) Budak, ErhanIn the present study, high crystalline nano sized hexagonal boron nitride powder (h-BN) was synthesized by classical solid-state reaction at 1100 degrees C using a mixture of boron oxide, urea and lithium salt (Li2O, LiCl, LiNO3). The characterization of samples was done by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Lithium salts played a positive role by lowering the formation temperature. The average grain sizes (22-26 nm) and graphitization index (1.7-2.9) of h-BN samples were calculated from XRD pattern. TEM images illustrated that the products were needle-like and multi-layered nano-crystalline h-BN powders.Öğe Radiation response of zirconium silicate P-MOS capacitor(Pergamon-Elsevier Science Ltd, 2020) Lök, Ramazan; Budak, Erhan; Yılmaz, ErcanThe chemical bonding of zirconium silicate films were examined by FTIR. The capacitance-voltage (C-V) measurements before and after irradiation were performed at high frequency. Furthermore, significant changes were observed depending on the radiation dose of the oxide traps and the intensity of the interface state. The sensitivity of this MOS capacitor is 4.3, 31.3 and 15.6 times less sensitive compared to the same thickness as Sm2O3, Al2O3 and Gd2O3. Therefore, it can be used as radiation-resistant material in nuclear reactors and space applications due to its stable electrical characteristics compared to other defined dielectrics. Interface states, (Nit) Barrier potential (Phi(b)) and oxide traps (Not) have also been investigated depending on the radiation effects. Ob is one of these important electrical properties. Phi(b) values decreased with increasing in radiation dose. Besides, radiation and frequency dependent dielectric constant (epsilon'), dielectric loss (epsilon '') and dielectric loss tangent (tan delta) and conductivity (sigma(ac)) of zirconium silicate were investigated. It is concluded that high-k zirconium Silicate is suitable for electronics applications in radiation harsh environment.Öğe SPICE modeling of RADFETs with different gate oxide thicknesses(Institute of Electrical and Electronics Engineers Inc., 2023) Marjanovic, M.; Gürer, Umutcan; Mitrovic, N.; Yılmaz, Ozan; Dankovic, D.; Budak, Erhan; Yılmaz, ErcanThis paper will present guidelines for creating a SPICE model of RADFETs with different gate oxide thicknesses. Model parameters, such as threshold voltage and carrier mobility, were extracted from the transfer characteristics in the saturation region. The model was satisfactorily used to simulate RADFETs with oxide thicknesses ranging from 40 nm to 300 nm. © 2023 IEEE.Öğe Structural and electrical characterizations of BiFeO3 capacitors deposited by sol-gel dip coating technique(Elsevier Science Sa, 2015) Çetinkaya, Ali Osman; Kaya, Şenol; Aktağ, Aliekber; Budak, Erhan; Yılmaz, ErcanBismuth ferrite (BiFeO3) thin films were deposited by sol-gel dip coating (SGDC) technique on Si-P(100) and glass substrates to investigate the structural and electrical characteristics. The aluminum (Al) metal contacts were formed on the samples deposited on the Si-P(100) to fabricate metal-oxide-semiconductor (MOS) capacitors. The fabricated MOS structures were characterized electrically by capacitance-voltage (C-V) and conductance- voltage (G/omega-V) measurements. The structural characterizations were performed by X-ray diffraction technique and scanning electron microscopy. The compositions of the films were investigated by energydispersive X-ray spectroscopy. The results exhibit that pure rhombohedral perovskite phase films were fabricatedwithout any elemental contamination. Average grain sizes of the BiFeO3 deposited on silicon and glass wafers were found to be about 34,50 and 30,00 nm, respectively. In addition, while the thin films deposited on glass substrate exhibit porous surface, those deposited on Si-P(100) wafers exhibit dense microstructure with a homogenous surface. Moreover, the C-V and G/omega-V characteristics are sensitive to applied voltage frequency due to frequency dependent charges (N-ss) and series resistance (R-s). The peak values of R-s have been decreased from 2,6 k Omega to 40 Omega, while N-ss is varied from 6,57 x 10(12) to 3,68 x 10(12) eV(-1) cm(-2) with increasing in frequency. Consequently, pure phase polycrystalline BiFeO3 thin films were fabricated successfully by SGDC technique and BiFeO3 dielectric layer exhibits stable insulation characteristics. (C) 2015 Elsevier B.V. All rights reserved.Öğe Structural characterization and electrical properties of Nd2O3 by sol-gel method(Springer, 2020) Lök, Ramazan; Budak, Erhan; Yılmaz, ErcanIn the current study, Neodymium oxide (Nd2O3) was prepared by sol-gel method and deposited on P-type < 100 > silicon wafer. The chemical characterization of samples was done by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectra (EDS) and atomic force microscopy (AFM). Nd-O bond formation was proven by FTIR, also cubic- Nd2O3 (c-Nd2O3) phase was detected by XRD. According to EDS analysis, neodymium concentration was approximately 59.41% while oxygen concentration was calculated as 10.21%. The amount of excess oxygen was 9.45% was originated by cristobalite formation. In addition, electrical characterizations of Nd2O3/p-Si MOS capacitor was performed by capacitance-voltage (C-V), conductance-voltage G/omega-V measurements at different frequencies between 250 kHz and 1 MHz. The maximum value of measured capacitance-voltage (C-V) and conductance-voltage (G/omega-V) was increased with decreasing in the applied voltage frequencies and after series resistance (R-s) correction, the measured C-V and G/omega-V characteristics, G/omega behavior started to decrease with rising the frequencies. According to the observed frequency dispersion, the deposited Nd2O3 on P-type < 100 & rang; silicon exhibits stable insulation property for future microelectronic applications.Öğe Substrate effect on microstructure and optical performance of sputter-deposited TiO2 thin films(Wiley-V C H Verlag Gmbh, 2012) Yıldırım, Gürcan; Bal, S.; Gülen, M.; Varilci, Ahmet; Budak, Erhan; Akdoğan, MustafaThis study deals with the role of the different substrates on the microstructural, optical and electronical properties of TiO2 thin films produced by conventional direct current (DC) magnetron sputtering in a mixture of pure argon and oxygen using a Ti metal target with the aid of Xray diffractometer (XRD), ultra violet spectrometer (UVvis) and atomic force microscopy (AFM) measurements. Transparent TiO2 thin films are deposited on Soda lime glass, MgO(100), quartz and sitall substrates. Phase purity, surface morphology, optical and photocatalytic properties of the films are compared with each other. It is found that the amplitude of interference oscillation of the films is in a range of 77-89%. The transmittance of the film deposited on Soda lime glass is the smallest while the film produced on MgO(100) substrate obtains the maximum transmittance value. The refractive index and optical band gap of the TiO2 thin films are also inferred from the transmittance spectra. The results show that the film deposited on Soda lime glass has the better optical property while the film produced on MgO(100) substrate exhibits much better photoactivity than the other films because of the large optical energy band gap. As for the XRD results, the film prepared on MgO(100) substrate contains the anatase phase only; on the other hand, the other films contain both anatase and rutile phases. Furthermore, AFM images show that the regular structures are observed on the surface of all the films studied. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)Öğe Synthesis and modification of hexagonal boron nitride(Bolu Abant İzzet Baysal Üniversitesi, 1999) Budak, Erhan; Bozkurt, ÇetinÖZET HEKZAGONAL BOR NİTRÜRÜN SENTEZLENMESİ VE MODİFİKASYONU Budak, Erhan Yüksek Lisans, Kimya Bölümü Tez Danışmanı: Yrd.Doç.Dr. Çetin BOZKURT Eylül 1999, 54 sayfa Bu çalışmada, O'Connor'ın modifıye edilmiş sentez yöntemiyle hekzagonal bor nitrür sentezlenmiş ve karşılaştırmalar için çeşitli metallerin nitratları, Mtn(N03)m, (Mt: Cr, Mn, Fe, Co, Ni, Cu, Zn ve Ag) 1:100 w/w oranında karıştırılark Mt-BN kompozitleri sentezlenmiştir. Her bir kompozitin Fourier Transform Infrared Spectrometresi, (FTIR), X-lsinlan Floresans Spektroskopisi, (XRF), X-lsmlan Difraksiyonu, (XRD) ve Taramalı Elektron Mikroskop, (SEM) analizleri yapılmıştır. FTIR analizleri uyum içinde olup, XRF ile her bir metalin varlığı ispat edilmiştir.XRD sonuçları BN tabakalarının kullanılan metal türüne göre değiştiğini göstermiştir. Bu değişimin öncelikle metallerin valens elektronlarıyla (d-71 etkileşimi) ve ikinci olarak metallerin atom yarıçaplanyla bağlantılı olduğu bulunmuştur. SEM analizlerinde metallerin atom yarıçapı artmasıyla kristallerin büyüdüğü tespit edilmiştir. Anahtar Kelimeler: Hekzagonal bor nitrür, turbostratik bor nitrür, tabakalar arası uzaklık, d-7t etkileşimi.Öğe Synthesis of Aromatic Conjugated Main Chain Azobenzene Polymers and Their Properties(2019) Bilen, Zeynep; Budak, Erhan; Bayazit, Mustafa Kemal; Özarslan, ÖzdemirAzobenzene polymers have great potential and impact on fundamental and applied research. Howeverlittle is known about their thermal stability and degradation behavior. Herein, nine conjugated mainchain azobenzene polymers were synthesized using the nitroamine derivatives of some diphenylenecompounds such as 4-amino-4?-nitrobiphenyl 1, 4-amino-4?-nitrobiphenyl ether 2 and 4-amino-4?-nitrobiphenyl sulfide 3, and comonomers triphenylamine A, N-methyldiphenyl amine B andtriphenylphosphine C via a diazo coupling reaction. These heteroatom-containing polymers werecharacterized by 1H- and 31P-NMR, FTIR, UV–Vis and Raman spectroscopy. The thermal stability anddegradation behavior of these polymers were studied by means of TGA technique. Electronic spectra ofthe polymers recorded in DMF showed two strong maxima at ca. 280 and 380 nm. They were resistantto heat up to 270 °C and, produced 41-61% char under a nitrogen atmosphere at 800 °C. UL 94 burningtests performed for TPU Ravathane® (TPE-U) with added azobenzene polymer revealed that thesepolymers could be used as an intumescent reactive flame retardant additive, particularly forpolyurethanes and elastomers, due to their high char yield at relatively high temperatures (e.g 800 °C).The carbonized materials were further characterized by XRD and SEM/EDX.Öğe Synthesis of hexagonal boron nitride with the presence of representative metals(Elsevier, 2010) Budak, Erhan; Bozkurt, ÇetinHexagonal boron nitride (h-BN) samples were prepared using the modified O'Connor method with KNO3 and Ca(NO3)(2) at different temperatures (1050, 1250, and 1450 degrees C). The samples were characterized by FTIR, XRD, and SEM techniques. Usage of representative metals exhibited a positive effect on the crystallization of h-BN and they caused the formation of nano-scale products at relatively low temperature. XRD results indicated that there was an increase in interlayer spacing due to the d-pi interaction. The calculated lattice constants were very close to the reported value for h-BN. (C) 2010 Elsevier B.V. All rights reserved.
