Browsing by Author "Dogan, T"
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Item Characterization and thermoluminescence behavior of beta irradiated NaBaBO3 phosphor synthesized by combustion methodOglakci, M; Akça, S; Halefoglu, YZ; Dogan, T; Ayvacikli, M; Karabulut, Y; Topaksu, M; Can, NNaBaBO3 host material was synthesized using the combustion method. In order to optimize the performance of the material, effects of sintering temperatures varying from 600 degrees to 1000 degrees C were investigated. The sintering temperature and dwell time were found to have pronounced effects on the pure NaBaBO3 material. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to confirm the phase formation and examine the surface morphology of the prepared powder material, respectively. TL behavior of NaBaBO3 was studied at various beta doses. It is seen that the sample exhibits well resolved TL glow peak at a peak temperature about 175 degrees C and corresponding TL intensity increases with the increasing beta dose. However, TL glow peak slightly shifts to lower temperature with the increasing beta dose level. This is the first TL report of a phosphor with a NaBaBO3 host. The TL kinetic parameters were estimated by the peak shape (PS) method and CGCD software. TL glow curves of NaBaBO3 consist of several traps and exhibited second order kinetics. A possible TL mechanism was also discussed using the energy level model. The obtained results can provide valuable knowledge related to the investigation of the intrinsic nature characteristics of NaBaBO3 in research fields pertaining to dosimetry.Item Thermoluminescence of β-particle induced Bern-4M muscovitePortakal-Uçar, ZG; Akca, S; Balci-Yegen, S; Yüksel, M; Dogan, T; Souadi, GO; Parlak, O; Topaksua, M; Can, NBern-4M muscovite from Switzerland was investigated via X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and thermoluminescence (TL). Muscovite has the theoretical formula KAl2 (AlSi3O10)(FOH)(2), or (KF)(2)(Al2O3)(3)(SiO2)(6)(H2O). Chemical analysis of the muscovite sample was carried out using EDS for major oxides. The results indicate that muscovite includes oxygen (59.1%), silicon (18.86%), and aluminum (15.22%) as major elements and contains low concentrations of potassium, magnesium, and sodium. In standard muscovites potassium use to be 10% and oxygen 47%, probably the sample was strongly lixiviated before the analysis. The thermoluminescence spectrum exhibits a wide glow peak located at 250 degrees C with a shoulder peak at high temperature region. Trap depth and frequency factor were calculated using Hoogenstraaten's method and found to be 1.16 eV and 1.4 x 10(10) s(-1), respectively. Reproducibility test indicated that the values within +/- 5% were obtained after 15 cycles. The storage time experiments were performed for different time periods up to 1 week for dark fading.Item Effects of axial impacts at different temperatures on failure response of adhesively bonded woven fabric glass fiber/epoxy composite jointsSayman, O; Soykok, IF; Dogan, T; Dogan, A; Arikan, VEvaluating post-impact failure responses of single-lap adhesively bonded composite-to-composite joints in uniaxial static tensile loading was the main objective of the current experimental study. At first, axial tensile impacts having various energy levels (10, 15, 20, and 25J) were applied to the joints at different temperatures (-20, 0, room temperature, 50, and 80?). Afterward, the samples were secondarily subjected to static tensile loading at ambient temperature, so that reductions in joint strengths arising from the impacts performed under different loading conditions could be assessed. Consequently, it was definitely proved that each of the axial impacts performed in any loading case has a noticeable effect on ultimate joint strengths, proportionally to the acting condition. Besides, the combination of high energy and temperature sometimes appeared to be the reason of impact failure, which occurs instantly without being able to perform axial static tests. When applied energy and/or absolute difference from room temperature is increased, lower joint resistances could be measured during secondary tensile tests.Item Thermoluminescence behaviour of europium doped magnesium silicate after beta exposureUçar, ZGP; Kaynar, UH; Dogan, T; Souadi, GO; Ayvacikli, M; Canimoglu, A; Topaksu, M; Can, NThis article presents a detailed analysis of beta ray exposed thermoluminescence response of a series of Eu3+ doped (0.5-10 mol%) Mg2SiO4 nanocrystalline samples successfully synthesized through solid state reaction method. Optimizing the doping concentration of Eu3+ ion in Mg2SiO4 phosphor was found as 3 mol%. Two main peaks were seen at 246 degrees C and 374 degrees C and also low temperature peak at 78 degrees C. The intensities of these peaks were increased linearly with increasing beta absorbed dose. T-m-T-stop method was used to reveal trap levels. Variable heating rate and computerized glow curve deconvolution methods were also used to evaluate the number of peaks and kinetic parameters, namely activation energy and frequency factor. The results of a series of experiments carried out to investigate some fading characteristics of Mg2SiO4:Eu3+ were also presented. The findings suggest that thermoluminescence properties of Mg2SiO4:Eu(3+ )makes this material suitable and promising dosimetric phosphor material for medical applications.Item Cathodoluminescence and photoluminescence properties of Dy doped La2CaB10O19 phosphorAyvacikli, M; Kaynar, ÜH; Karabulut, Y; Guinea, JG; Dogan, T; Can, NIn this study, we report a detailed analysis of the photoluminescence (PL) and cathodoluminescence (CL) properties of La2CaB10O19 (LCB) doped with Dy ion. Dy doped LCB materials were successfully synthesized using a sol-gel combustion method. Dy doped LCB has the monoclinic structure with lattice parameters a = 11.02067 angstrom, b = 6.55755 angstrom, c = 9.10541 angstrom and alpha = gamma = 90.00, and 13 = 91.49?. Under the excitation by a low voltage electron beam and pulse laser at 349 nm, the LCB:Dy3+ phosphor produces the characteristic emission bands of Dy3+ due to intra-configuration transitions of F-4(9/2) -> H-6(15/2) (480 nm, blue), F-4(9/2) -> H-6(13/2) (574 nm, yellow), F-4(9/2) -> H-6(11/2) (662 nm, red) and F-4(9/2) -> H-6(9/2) (752 nm, red). The concentration quenching phenomenon was observed in both CL and PL measurements and optimum doping concentration was estimated to be 2%. We suggest that the concentration quenching mechanism of intense yellow emission at 574 nm was attributed to dipole-dipole interaction for both CL and PL.Item Comparative studies on thermoluminescence characteristics of non-doped Mg2SiO4 prepared via a solid-state reaction technique and wet-chemical method: An unusual heating rate dependenceDogan, T; Akça, S; Yüksel, M; Kucuk, N; Ayvacikli, M; Karabulut, Y; Canimoglu, A; Topaksu, M; Can, NMagnesium orthosilicate (Mg2SiO4) was synthesized via a traditional solid-state reaction and a wet chemical route. This study primarily reported the thermoluminescence (TL) behavior of Mg2SiO4 host. X-ray diffraction pattern revealed that Mg2SiO4 exhibits orthorhombic structure matched with JCPDS card 900-6398. Dose response, reproducibility and trap parameters of TL glow curves were evaluated to clearly reveal TL features. Two TL glow peaks situated at 81 degrees C and 192 degrees C were monitored at a heating rate of 2 degrees Cs-1. We observed anomalous heating rate effect for the peak centered at 192 degrees C whilst TL intensity of the peak at 81 degrees C decreases with elevating heating rate. Trap depths of the electrons within the trap centers were found to be 1.04 +/- 0.01eV and 1.37 +/- 0.01eV for both methods using peak shape (PS) method. Distribution of trap centers was examined using the T-max - T-stop method and this case indicated that the glow curves consist of single TL peaks. The intensity of TL glow curves exhibited a good linear dose response under total area up to 20 Gy. A comparison of the two preparation techniques revealed that TL characteristics of this phosphor are partly dependent and Mg2SiO4 could be a promising material for dosimetric application. (C) 2019 Elsevier B.V. All rights reserved.Item Cathodoluminescence and thermoluminescence of ZnB2O4:Eu3+ phosphors prepared via wet-chemical synthesisDogan, T; Tormo, L; Akca, S; Kucuk, N; Guinea, JG; Karabulut, Y; Ayvacikli, M; Oglakci, M; Topaksu, M; Can, NIn present work, a series of Eu doped zinc borate, ZnB2O4, phosphors prepared via wet chemical synthesis and their structural, surface morphology, cathodoluminescence (CL) and thermoluminescence (TL) properties have been studied. Phase purity and crystal structure of as-prepared samples are confirmed by X-ray diffraction measurements (XRD) and they were well consistent with PDF card No. 39-1126, indicating the formation of pure phase. The thermoluminescence (TL) behaviors of Eu activated ZnB2O4 host lattice are studied for various beta doses ranging from 0.1 to 10 Gy. The high-temperature peak of Eu activated sample located at 192 degrees C exhibited a linear dose response in the range of 0.1-10 Gy. Initial rise (IR) and peak shape (PS) methods were used to determine the activation energies of the trapping centres. The effects of the variable heating rate on TL behaviour of Eu activated ZnB2O4 were also studied. When excited using an electron beam induced light emission (i.e cathodoluminescence, CL) at room temperature (RT), the as-prepared phosphors generate reddish-orange color due to predominant emission peaks of Eu3+ ions located at 576-710 nm assigned to the D-5(0)-> F-7(J) (J=1,2,3, and 4) transitions. The maximum CL intensity for Eu3+ ions at 614 nm with transition D-5(0)-> F-7(2) was reached Eu3+ concentration of 5 mol%; quenching occurred at higher concentrations. Strong emission peak for Eu3+ ions at 614 nm with transition D-5(0)-> F-7(2) is observed. The CL experimental data indicate that ZnB2O4:Eu3+ phosphor as an orange-red emitting phosphor may be promising luminescence materials for the optoelectronic applications.Item Thermoluminescence properties of Tb doped Mg2SiO4 after beta irradiationAkça, S; Portakal, ZG; Dogan, T; Kucuk, N; Canimoglu, A; Topaksu, M; Can, NIn this study, we performed Thermoluminescence (TL) experiments to extract the trapping parameters and dosimetric properties of Tb-doped Mg2SiO4 phosphors. Glow peaks located at 193, 270, and 350 degrees C were observed in the glow curve but the peak at 193 degrees C was especially investigated as a dosimetric peak in this study. We also observed an anomalous heating rate effect in which the maximum TL intensity of the glow curve augmented with an increasing heating rate. The computerized glow curve deconvolution (CGCD) method, initial rise (IR) and Hoogenstraaten's method were used to determine the activation energies of associated trapping centers for both BSL-TL 365 nm and IRSL-TL wideband blue filters. The TL characteristics of this phosphor indicate that Mg2SiO4:Tb3+ could be a promising material for dosimetric applications. Efforts should be made to improve the fading behaviour by adding other activators as co-dopants.Item Characterization of thermoluminescence kinetic parameters of beta irradiated B doped Ca5(PO4)3OH powder obtained from eggshellDepci, T; Oglakci, M; Sezer, S; Yücel, A; Dogan, T; Souadi, G; Topaksu, M; Can, NIn this study, we have synthesized B doped Ca5(PO4)3OH (HAP) by a sonication chemical method. The thermoluminescence (TL) properties of the family of synthesized samples (B doped Ca5(PO4)3OH (HAP) were investigated using an IRSL-TL 565 nm filter. This gave the highest TL intensity of each phosphor after 2 Gy beta-irradiation. Three TL glow peaks of B doped Ca5(PO4)3OH (HAP) are centered at around 84, 208 and 324 degrees C (with a heating rate of 2 degrees Cs-1). The trapping parameters such as activation energy (E), order of kinetics (b), frequency factor (s) were calculated by using initial rise (IR), various heating rates (VHR) and computerized glow curve deconvolution (CGCD) method. The response of TL glow curves remained constant within +/- 5% deviation from the initial value after 9 cycles of reuse; but only at tenth cycle the deviation goes up to 6%.Item Comprehensive study of photoluminescence and cathodoluminescence of Eu and Tb doped Mg2SiO4 prepared via a solid-state reaction techniqueUcar, ZGP; Akca, S; Dogan, T; Halefoglu, YZ; Kaynar, UH; Ayvacikli, M; Guinea, JG; Topaksu, M; Can, NWe report narrow-band green-red emitting Mg2SiO4 phosphors successfully synthesized through solid-state reaction method, and the cathodoluminescence (CL) and photoluminescence (PL) properties of the samples were investigated in detail. Under electron beam and 275 nm excitation, Mg2SiO4 phosphors doped with various Eu3+ and Tb3+ concentrations in the range of 1 mol % up to 10 mol % exhibit typical green and red emissions, respectively. Tb doped samples were efficiently excited by a low voltage electron beam and UV light, yielding several emission peaks between 370 and 760 nm, and produced a bright green light peaking at 541 nm due to the D-5(4) -> F-7(5) transition. Eu3+ doped samples exhibited CL and PL emission spectra from D-5(0) to F-7(j) manifold transitions of Eu3+. A strong red-light emission peaking at 610 nm also supports the incorporation of Eu3+ ions. A concentration quenching effect was observed and discussed for both phosphors. The optimal doping concentration of Eu3+ and Tb3+ doped phosphors was 7 mol %. In view of the outstanding performance in the PL and CL, the Mg2SiO4:Eu3+, Tb3+ can be considered as a promising green and red phosphor in solid-state lighting applications.Item Safety of once-or twice-daily dosing of non-vitamin K antagonist oral anticoagulants (NOACs) in patients with nonvalvular atrial fibrillation: A NOAC-TR studyEmren, SV; Zoghi, M; Berilgen, R; Özdemir, IH; Çelik, O; Çetin, N; Enhos, A; Köseoglu, C; Akyüz, A; Dogan, V; Levent, F; Dereli, Y; Dogan, T; Basaran, Ö; Karaca, I; Karaca, Ö; Otlu, YÖ; Özmen, Ç; Cosar, S; Sümerkan, M; Gürsul, E; Inci, S; Onrat, E; Ergene, OOnce-daily dosing of non-vitamin K antagonist oral anticoagulants (NOACs) may increase patient adherence to treatment but may also be associated with a higher risk of bleeding. In this study, we investigated the adherence to once-or twice-daily dosing of NOACs and the risk of bleeding in nonvalvular atrial fibrillation (NVAF) patients. This multicenter cross-sectional study, conducted between 1 September 2015 and 28 February 2016, included 2214 patients receiving NOACs for at least 3 months, due to NVAF. Patients receiving once-daily or twice-daily NOAC doses were 1: 1 propensity score matched for baseline demographic characteristics and the presence of other diseases. The medication adherence was assessed by the 8-item Morisky Medication Adherence Scale. Risk factors were investigated in relation to minor and major bleeding. The mean age of patients was 71 +/- 10 years, and 53% of the patients were women. The medication adherence was lower in patients receiving twice-daily NOAC doses compared to once-daily-dose group (47% versus 53%, p = 0.001), and there was no difference between the groups in terms of minor (15% versus 16%, p = 0.292) and major bleeding (3% versus 3%, p = 0.796). Independent risk factors for bleeding were non-adherence to medication (OR: 1.62, 95% CI: 1.23-2.14, p = 0.001), presence of 3 or more other diseases (OR: 10.3, 95% CI: 5.3-20.3, p < 0.001), and HAS-BLED (Hypertension, Abnormal renal and liver function, Stroke, Bleeding, Labile INR, Elderly, Drugs or alcohol) score (OR: 4.84, 95% CI: 4.04-5.8, p < 0.001). In summary, the once-daily dose of NOACs was associated with increased patient adherence to medication, while it was not associated with bleeding complications.Item Enhancing the blue luminescence behaviour of the Li co -doped novel phosphor ZnB 2 O 4: Tm 3+Kucuk, N; Kaynar, ÜH; Akca, S; Alajlani, Y; Yin, L; Wang, Y; Guinea, JG; Bulcar, K; Dogan, T; Karabulut, Y; Ayvacikli, M; Canimoglu, A; Topaksu, M; Can, NItem Luminescence characteristics of Dy3+ incorporated zinc borate powdersPortakal, ZG; Dogan, T; Yegen, SB; Küçük, N; Ayvacikli, M; Guine, JG; Canimoglu, A; Karabulut, Y; Topaksu, M; Can, NWe have synthesized powder samples of Dy3+ doped zinc borates by nitric acid method. X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) techniques were utilized to examine the structure and morphological observation of the samples. Luminescence characteristics of the samples were investigated using room temperature (RT) cathodoluminescence (CL) and radioluminescence (RL) measurements under excitation with electron beam and X-rays, respectively. The presence of small amounts of Dy3+ incorporated in the host lattice does not affect the structure of the prepared samples remarkably. The CL and RL spectra showed the characteristic emissions of Dy3+ (magnetic dipole transition of F-4(9/2) -> H-6(11/2) Blue; forced electric dipole transition of F-4(9/2) > H-6(13/2) Yellow; F-4(9/2) -> H-6(1/2) Red; F-4(9/2) -> (H-6(9/2) + H-6(11/2)) infrared). Thermoluminescence (TL) method was also conducted to determine the effects of various concentrations of Dy3+ on the TL properties of ZnB2O4. The TL glow peak of beta irradiated ZnB2O4:Dy3+ phosphors is a well-defined and centered at around 96 degrees C with a constant heating rate of 2 degrees C/s. Initial rise method was employed to observed main TL glow curve for determining the activation energy (E-a) and the frequency factor (s).Item Doping Sm3+ into ZnB2O4 phosphors and their structural and cathodoluminescence propertiesKucuk, N; Bulcar, K; Dogan, T; Guinea, JG; Portakal, ZG; Karabulut, Y; Ayvacikli, M; Canimoglu, A; Topaksu, M; Can, NIn this study, ZnB2O4:xSm(3+) (0.01 <= x <= 0.05 mol) powder phosphors have been synthesized by low temperature chemical synthesis method. The structure and morphological observation of the phosphor samples were systematically monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF#39-1126). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). When excited with electron beam, CL spectral measurements of scrutinized phosphors exhibit orange-red luminescence at 572 nm, 606 nm and 658 nm due to various transition from ground state to H-6(5/2),H-6(7/2) and (4)G(5/2) states, respectively. The transition (4)G(5/2) -> H-6(7/2) located at 606 nm can occur as hypersensitive transition having the selection rule Delta J = +/- 1. The observed peaks are in the region of yellow reddish light of Sm3+. Experimental results verify that the optimum Sm3+ content in terms of intense luminescence for this series of phosphors was 2%. Beyond 2% of Sm3+ ions concentration, luminescence quenching occurs due to an enhanced probability of the energy transfer from one Sm3+ to another that matches in energy via cross-relaxation and dipole-dipole interactions according to Dexter theory. A suitable energy transfer model between two adjacent Sm3+ ions in the ZnB2O4 phosphors was accomplished by the electric dipole-dipole interaction. The critical transfer distance (R-c) for non-radiative energy transfer was found to be 21.52 angstrom at 2 mol % Sm3+ doped ZnB2O4. Additionally, thermoluminescence (TL) glow curves of undoped and Sm activated ZnB2O4 under beta irradiation of 10 Gy are also discussed here. (C) 2018 Elsevier B.V. All rights reserved.Item Thermoluminescence behavior of Sm3+ activated ZnB2O4 phosphors synthesized using low temperature chemical synthesis methodBulcar, K; Dogan, T; Akça, S; Yüksel, M; Ayvacikli, M; Karabulut, Y; Kucuk, N; Canimoglu, A; Can, N; Topaksu, MThis study is mainly centered on thermoluminescence (TL) behavior under beta excitation at room temperature (RT) of Sm3+ activated ZnB2O4 phosphors synthesized by low temperature chemical synthesis method. The prepared phosphors were characterized by the X-ray powder diffraction (XRD) method. The effects of dopant concentration, beta radiation dose (0.115-69 Gy) and heating rate (0. 5-10 degrees C/s) on TL intensity of Sm3+ doped ZnB2O4 phosphors and reproducibility are investigated using a lexsyg smart TL/OSL reader system. The activation energy values, E obtained from the analysis of the TL glow curve were calculated with initial rise (IR) method and peak shape (PS) method over the deconvoluted glow curves. The E-a-T-stop and CGCD methods indicated that the glow curve of this phosphor is the superposition of at least six components, which were called to as P1-P6, in the temperature range between RT and 400 degrees C. The results reveal that 2% Sm3+ doped ZnB2O4 gives optimum TL response, the relative intensity of the glow peak increases linearly with increase of beta dose and, the peaks of TL glow curves shift towards the higher temperature side with increase in heating rate as the total area under the glow peak remains the same. The maximum variation of reproducibility for ten successive irradiation cycles of 20.7 Gy is less than 3% from the average value and the sample doped 2% Sm3+ shows a good stability for the reusability. Additionally, the results obtained from IR and PS methods indicates that the complex glow curve is composed of six distinguishable peaks.Item Anomalous heating rate response of beta irradiated Sm3+ and Tb3+ doped BaAl2O4 phosphorsKaynar, ÜH; Guvener, E; Ayvacikli, M; Dogan, T; Balci-Yegen, S; Oglakci, M; Topaksu, M; Karabulut, Y; Canimoglu, A; Benourdja, S; Can, NThe stuffed derivative of the tridymite structure, the oxide BaAl2O4 has been regarded as a long persistent phosphor. Thermoluminescence (TL) glow curve peaks of thin pellet samples of undoped and, Sm3+ and Tb3+ doped BaAl2O4 prepared by combustion method was reported. The structure of the compounds was monitored by X-ray diffraction and found a single-phase compound with a hexagonal structure. Performing a series of TL measurements for the temperature range from room temperature to 400 degrees C, the effect of beta radiation dose on TL response, various TL heating rate (HR) properties of undoped and Sm3+ and Tb3+ doped BaAl2O4 phosphors were investigated. Peak shape method was also utilized to assess the trap parameters. The activation energy of the main peak at 128 degrees C was found to be 0.97 eV. TL glow curves obtained from undoped and Tb3+ doped BaAl2O4 decrease with increasing HR value (varying from 0.5 to 15 degrees C s(-1)) in a way matching with thermal quenching effect. Contrary to expectations, anomalous HR dependence was observed on Sm3+ doped BaAl2O4 sample and a semi-localized transition model has been used in order to explain such behaviour. (C) 2018 Elsevier B.V. All rights reserved.