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Browsing by Author "Can, N"

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Green Approach to Synthesis and Strain Studies of ZnO Nanoparticles
Florence, SS; Adam, H; Manna, C; Can, N
In this paper, a simple, facile and green approach to synthesis Gum Arabic (GA, a natural gum) assisted ZnO nanoparticles by using a wet chemical reaction method is reported. The synthesis of ZnO nanoparticles has been with the assistance of two different types of GA namely Acacia Senegal and Acacia Seyal. The effects of GA and the properties of Senegal and Seyal GA have been studied by using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM).
Effect of material nonlinearity on symmetric aluminum metal-matrix laminated composite beams under a bending moment
Sayman, O; Çallioglu, H; Meriç, C; Can, N
In this study, an elastic-plastic stress analysis is carried out on symmetric laminated composite beams subjected to a bending moment. The composite beam is to be strain hardening. The Tsai-Hill theory is used as a yield criterion in the solution. The Bernoulli and Euler hypotheses are assumed to be valid. The beam lay-up sequences are chosen as [90degrees/0degrees](s), [30degrees/-30degrees](s), [45degrees/-45degrees](s), and [60degrees/-60degrees](s). The bending moment starting plastic yielding is found to be highest for [30degrees/-30degrees](s) orientation. sigma(x) residual stress component is found to be highest at the upper and lower surfaces. However sigma(x), residual stress component becomes the highest at the elastic and plastic boundary for further expansion of the plastic region. The transverse displacement is obtained at the free end, numerically.
Novel Dy and Sm activated BaSi2O5 phosphors: Insights into the structure, intrinsic and extrinsic luminescence, and influence of doping concentration
Alajlani, Y; Can, N
Pure and a series of BaSi2O5:RE3+ (RE = Dy, Sm) phosphors varying with the substitution of Ba2+ were prepared using a gel-combustion method. X-ray diffraction results confirmed that all samples exhibited an orthorhombic structure. FT-IR spectra showed that the samples consist of BaCO3, SiO2 network and the presence of OH groups. The photoluminescence spectrum of non-doped BaSi2O5 showed a broad-band emission peak at 520 nm. The analysis of photoluminescence emission and comparison of the chromaticity diagrams of BaSi2O5:Dy3+ and BaSi2O5:Sm3+ phosphors were presented, and their implications are also discussed. The optimum quenching concentrations and critical distances of Dy3+ and Sm3+ ions in the BaSi2O5 were 2mol%, 22.57 angstrom and 1 mol%, 28.44 angstrom, respectively. The investigation of concentration quenching behaviour, fluorescence decay curves, and decay time indicates that the dominant mechanism type leading to concentration quenching was governed by electric dipole-dipole interactions. The concentration dependence of intensity ratio of yellow-blue emission indicated that the emission of BaSi2O5:Dy3+ phosphors fell in the white light region tuning the blue and yellow components. BaSi2O5:Sm3+ phosphors may allow one to consider as potential orange-red-emitting phosphors.
Oxalic acid assisted synthesis of ZnS nanoparticles and their optical properties
Florence, SS; Can, N
ZnS nanoparticles and Oxalic acid (OA) assisted Zinc sulfide nanoparticles were synthesized by an easy and low-cost aqueous method using double distilled water as a solvent. A phase change has been observed while increasing the concentration of OA. Morphological studies by Transmission Electron Microscopy (TEM), Optical studies from Ultra Violet Spectroscopy (UV) and Photoluminescence (PL) and structural studies from X-ray diffraction (XRD) have been done to characterize the samples. UV absorption spectrum confirmed the blue shift and formation of nanostructures. From the PL spectrum, it is observed that both ZnS nanoparticles and OA assisted ZnS nanoparticles excited about 370 nm exhibit a blue-green emission between 420 and 470 nm. It may be recognized to the recombination of the imperfection of ZnS nanoparticles. The spherical morphology of ZnS nanoparticles and OA assisted ZnS nanoparticles has been shown in TEM micrographs and the size of the particles was measured as 8-20 nm and it is in good agreement with XRD studies.
Thermoluminescence glow curve analysis and kinetic parameters of Dy-doped BaSi2O5 phosphor
Alajlani, Y; Can, N
In this paper, Dy3+ incorporated BaSi2O5 phosphors were synthesized by gel combustion method and characterized by X-ray diffraction (XRD). The effects of various heating rates on thermoluminescence (TL) kinetics and glow peak temperatures of Dy3+ incorporated BaSi2O5 phosphors exposed to beta irradiation at room temperature were investigated. The glow curves of the phosphor exposed to beta-irradiation (0.1-100 Gy) consist of four main peaks located at 87,130, 271, and 327 degrees C and exhibit a good linearity between 0.1 and 100 Gy. Three experimental techniques including variable heating rate (VHR), repeated initial rise (RIR), peak shape (PS) and computerized glow curve deconvolution (CGCD) were employed to determine TL kinetic parameters. Our findings indicate that the TL glow peaks of the phosphor obey first-order kinetics. Analysis of the main dosimetric peaks through the techniques mentioned above indicates that activation energies (E) and pre-exponential factor (s) are in the range of 0.80-1.50 eV and 1.15 x 10(8)-3.28 x 10(13) s(-1). Additionally, it is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases. The effect on the TL intensities and glow peak temperatures of the heating rate is discussed in terms of thermal quenching. (C) 2020 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.
Third-order optical nonlinearities of Cu and Tb nanoparticles in SrTiO3
Cetin, A; Kibar, R; Hatipoglu, M; Karabulut, Y; Can, N
Some results of optical and nonlinear-optical properties of Cu and Tb nanoparticles implanted in SrTiO3 (STO) crystal are presented. The non-resonant third-order optical nonlinearities have been investigated by degenerate four wave mixing (DFWM), pump-probe and Z-scan techniques using femtosecond laser pulses. (C) 2010 Elsevier B.V. All rights reserved.
Comparisons of tin depth profile analysis in float glass
Townsend, PD; Can, N; Chandler, PJ; Farmery, BW; Lopez-Heredero, R; Peto, A; Salvin, L; Underdown, D; Yang, B
Data are presented showing the profile of tin diffusion during the production of float glass, by measuring non-destructively the refractive index profiles in the diffused layer. The optical waveguide modes give unequivocal evidence for an anomaly in the tin depth distribution. The results are compared with those from sectioning techniques, used in depth profiles determined by ion beam analyses and cathodoluminescence (CL). There is agreement between these methods which confirm the presence of a maximum in the tin concentration below the surface which had been in contact with the tin bath (this had been linked by Mossbauer data to a rise in the Sn4+ concentration). The ion beam analyses record different depth profiles for Si, Na and Ca. The Sn4+ feature increases the refractive index, as does the diffusion of Sn2+. The index becomes constant at large tin concentrations. We suggest that Sn4+ is linked to CL emission at 2.68 eV and Sn2+ to the 1.97 eV CL emission. Iron impurities give a 1.73 eV signal. Contrary to earlier suggestions, we prc,pose that the luminescence associated with the presence of tin arises from intrinsic defects stabilised by the tin, not from tin acting directly as a luminescence site. (C) 1998 Elsevier Science B.V.
Synthesis and competitive luminescence quenching mechanism of Ca3Al2O6Ln3+(Ln: Dy and Sm) phosphors
Bakr, M; Kaynar, ÜH; Ayvacikli, M; Benourdja, S; Karabulut, Y; Hammoudeh, A; Can, N
Sm3+ and Dy3+ activated Ca3Al2O6 phosphors were produced through a gel combustion method using Urea + beta-Alanine, Urea, and Urea + Glycine as fuels. The crystal structure and the phase purity of the obtained materials were characterized by X-ray powder diffraction (XRD). Ca3Al2O6 :Sm3+ phosphor shows characteristic emission lines (565 nm, 602 nm, 649 nm, and 714 nm) in the orange red region assigned to (4)G(5/2) -> H- 6(J) (J = 5/2, 7/2, 9/2, 11/2) transitions of Sm3+. The strongest peak is located at 602 nm. Emission spectra of Ca3Al2O6 :Dy3+ show that there are two dominant peaks centered at 480 nm and 573 nm emitting blue and yellow light. Optimum doping concentrations of Sm(NO3)(3) and Dy(NO3)(3) are 0.01 % and 0.03 %, respectively. The concentration quenching mechanism is verified to be a dipole-dipole interaction as the type of energy transfer among Sm3+-Sm3+ and Dy3+-Dy3+ ions. The critical distance is also calculated to be 24.19 angstrom and 16.77 angstrom, respectively.
Spectral, electron microscopic and chemical investigations of gamma-induced purple color zonings in amethyst crystals from the Dursunbey-Balikesir region of Turkey
Hatipoglu, M; Kibar, R; Çetin, A; Can, N; Helvaci, C; Derin, H
Amethyst crystals on matrix specimens from the Dursunbey-Balikesir region in Turkey have five representative purple color zonings: dark purple, light purple, lilac, orchid, and violet. The purple color zonings have been analyzed with optical absorption spectra in the visible wavelength region, chemical full trace element analyses (inductively coupled plasma-atomic emission spectroscopy and inductively coupled plasma-mass spectroscopy), and scanning electron microscopic images with high magnification. It can be proposed that the production of the purple color in amethyst crystals is due to three dominant absorption bands centered at 375, 530, and 675 nm, respectively. In addition, the purple color zonings are also due to four minor absorption bands centered at 435, 480, 620, and 760 nm. X-ray diffraction graphics of the investigated amethyst crystals indicate that these crystals are composed of a nearly pure alpha-quartz phase and do not include any moganite silica phase and/or other mineral implications. Trace element analyses of the amethyst crystals show five representative purple color zonings, suggesting that the absorption bands can be mainly attributed to extrinsic defects (chemical impurities). However, another important factor that influences all structural defects in amethyst is likely to be the gamma irradiation that exists during amethyst crystallization and its inclusion in host materials. This gamma irradiation originates from the large underlying intrusive granitoid body in the region of amethyst formation. Irradiation modifies the valence values of the impurity elements in the amethyst crystals. It is observed that the violet-colored amethyst crystals have the most stable and the least reversible coloration when exposed to strong light sources. This situation can be related to the higher impurity content of Fe (2.50 ppm), Co (3.1 ppm), Ni (38 ppm), Cu (17.9 ppm), Zn (10 ppm), Zr (3.9 ppm), and Mo (21.8 ppm).
Phase transition and luminescence characteristics of dysprosium doped strontium stannate phosphor synthesized using hydrothermal method
Kaynar, H; Coban, MB; Madkhli, AY; Ayvacikli, M; Can, N
A series of strontium stannate (SrSnO3) doped with Dy3+ ions at various wt % concentrations (1, 2, 3 and 5) were synthesized via hydrothermal reaction and analysed using X-ray diffraction (XRD), energy dispersive spectros-copy (EDS), environmental electron scanning microscope (ESEM), photoluminescence (PL) and, cath-odoluminescence (CL). The XRD results confirmed that all samples were assigned to cubic perovskite-type SrSnO3 structured with the Pm3m space group. The PL emission spectrum of Dy3+ activated samples consisted of some characteristic peaks located at 481 nm, 572 nm, 660 nm and 753 nm, corresponding to (4F9/2 -> 6H15/2, blue), (4F9/2 -> 6H13/2, yellow), 660 nm (4F9/2 -> 6H11/2, red) and 753 nm (4F9/2 -> 6H9/2, red) transitions. The PL emission line intensity is gradually enhanced with an increase in doping concentration up to 3 wt %, followed by concentration quenching. The confinement effects of localized resonant energy transfer might cause higher concentration quenching. PL emission spectra were affected by the temperature range from 10 K to 300 K. PL emission anomalies at 270 K in SrSnO3:Dy3+ have been reported to be consistent with a structural phase tran-sition at this temperature. This work confirms Singh et al.'s observation, revealing that SrSnO3 has a phase transition at 270 K.
Dy3+and Eu3+co-activated gadolinium aluminate borate phosphor: Synthesis, enhanced luminescence, energy transfer and tunable color
Madkhali, O; Kaynar, UH; Kaynar, SC; Ayvacikli, M; Can, N
The synthesis of GdAl3(BO3)4 phosphors incorporated with activators of Dy3+ and Dy3+/ Eu3+was successful and achieved through the gel combustion method. Powder X-ray diffraction (XRD) was employed to identify phase purity and the effects of dopant concentration on the crystallographic structure. The results of Photo-luminescence (PL) measurements revealed that the intensity and lifetime of luminescence properties varied depending on the concentrations of Dy3+ and Eu3+ ions. The dependence of luminescence intensity on doping concentration is investigated with respect to the energy transfer process between Eu3+ and Dy3+ ions. A decrease in luminescence lifetime occurs with increasing concentrations of Eu3+ co-doping. The energy transfer was also investigated using decay curve analysis. The co-doping of Eu3+ significantly boosts the energy transfer efficiency from 26% to 84%. These findings make GdAl3(BO3)4: Dy3+, Eu3+ phosphors an ideal choice for LED applications in solid state lighting and displays.
Characterization and thermoluminescence behavior of beta irradiated NaBaBO3 phosphor synthesized by combustion method
Oglakci, M; Akça, S; Halefoglu, YZ; Dogan, T; Ayvacikli, M; Karabulut, Y; Topaksu, M; Can, N
NaBaBO3 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.
Thermoluminescence glow curve analysis of Ca3Y2B4O12 phosphor prepared using combustion method
Hakami, J; Sonsuz, M; Kaynar, UH; Ayvacikli, M; Oglakci, M; Yüksel, M; Topaksu, M; Can, N
Ca3Y2B4O12 (CBYO) phosphor was synthesized using a gel combustion method. X-ray diffraction (XRD) measurement confirmed a single-phase structure (space group Pnma (62)) of synthesized compound. TL measurements were conducted between room temperature (RT) and 450 degrees C at a heating rate of 2 degrees Cs-1. Significant glow peaks were observed at 64, 116, and 242 degrees C in CYBO phosphor sample exposed to different beta doses. In the range of 0.1-100 Gy, the TL intensity of the glow peak displayed good linearity. Different methods were employed to determine the number of peaks, the trap structure, and the kinetic parameters of the thermoluminescence glow curve of CBYO; the Hoogenstraaten method, various heating rates (VHR), and glow curve deconvolution method (CGCD) implemented through tgcd:An R package. Currently available findings confirm that CYBO host is a promising candidate for environmental studies because one exhibits adequate TL dose response coupled with a good sensitivity and linearity.
Thermoluminescence characterization and kinetic parameters of Dy3+ activated Ca3Y2B4O12
Hakami, J; Sonsuz, M; Kaynar, UH; Ayvacikli, M; Oglakci, M; Topaksu, M; Can, N
In this study, thermoluminescence (TL) characteristics of Ca3Y2B4O12:xDy (0 < x < 0.07) phosphor samples were studied. The samples were exposed to beta irradiation in the dose range from 0.1 Gy to 100 Gy to investigate TL dose response. The concentration of Dy3+ in Ca3Y2B4O12 phosphor was optimized and found to be 1 mass % in terms of TL signal quality. The TL glow curve appears to be consisted of three peaks which were discernible at 72 degrees C, 280 C and 376 degrees C. The trapping parameters (E, b, and s) were calculated using initial rise (IR), and variable heating rate (VHR) techniques. The trapping parameters, order of kinetics, frequency factor, and figure of merit have been all determined by means of the Glow Curve Deconvolution (GCD) method (tgcd:An R package). Ca3Y2B4O12:Dy phosphor displays efficient thermoluminescence properties.
Radioluminescence and thermoluminescence of albite at low temperature
Can, N; Garcia-Guinea, J; Kibar, R; Çetin, A; Ayvacikli, M; Townsend, PD
Feldspar as an archaeological and geological natural material for dating and retrospective dosimetry is receiving more and more attention because of its useful luminescence properties. In this study, the 25-280 K thermoluminescence (TL) and radioluminescence (RL) spectra in albite, which is a component of the two main feldspar series, the alkali feldspar (Na, K)AlSi(3)O(8) and the plagioclases (NaAlSi(3)O(8)-CaAl(2)Si(2)O(8)) have been presented for aliquots along (001) and (010) crystallographic orientations. There are four main emission bands that are considered to arise from complexes of intrinsic defects linked in larger complexes with impurities such as Na(+), Mn(2+) or Fe(3+) ions. The consequence of their association is to produce different luminescence efficiencies that produce wavelength sensitive TL curves. Radioluminescence data at low temperature for albites is distorted by contributions from the TL sites, even when the RL is run in a cooling cycle. This indicates the potential for a far more general problem for analysis of low temperature RL in insulating materials. (C) 2011 Elsevier Ltd. All rights reserved.
TL and EPR studies of Cu, Ag and P doped Li2B4O7 phosphor
Can, N; Karali, T; Townsend, PD; Yildiz, F
Key characteristics of a newly prepared tissue-equivalent, highly sensitive thermoluminescence dosimeter, Li2B4O7: Cu, Ag, P, are presented. The material was developed at the Institute of Nuclear Sciences, Belgrade, in the form of sintered pellets. A new preparation procedure has greatly increased the sensitivity of the basic copper activated lithium borate and the glow curve of Li2B4O7 : Cu, Ag, P consists of a well-defined main dosimetric peak situated at about 460-465K with a sensitivity which is about four to five times higher than that of LiF : Mg, Ti (TLD-100). The exceptionally good response features of Li2B4O7 : Cu, Ag, P are attributed to the incorporation of Cu as a dopant. Both low and high temperature emission spectra are presented and the origins of the various emission bands are considered. Additional data are provided from electron paramagnetic resonance measurements.
Thermally stimulated luminescence glow curve structure of β-irradiated CaB4O7:Dy
Akin, A; Ekdal, E; Arslanlar, YT; Ayvacikli, M; Karali, T; Can, N
Thermally stimulated luminescence glow curves of CaB4O7:Dy samples after beta-irradiation showed glow peaks at similar to 335, 530 and 675 K, with a heating rate of 2 K/s. The main peak at 530 K was analyzed using the T-max-T-stop method and was found to be composed of at least five overlapping glow peaks. A curve-fitting program was used to perform computerized glow curve deconvolution (CGCD) analysis of the complex peak of the dosimetric material of interest. The kinetic parameters, namely activation energy (E) and frequency factor (s), associated with the main glow peak of CaB4O7:Dy at 520 K were evaluated using peak shape (PS) and isothermal luminescence decay (ILD) methods. In addition, the kinetics was determined to be first order (b = 1) by applying the additive dose method. The activation energies and frequency factors obtained using PS and ILD methods are calculated to be 0.72 and 0.72 eV and 8.76 x 10(5) and 1.44 x 106/s, respectively. Copyright (C) 2014 John Wiley & Sons, Ltd.
Luminescence characteristics of Al-and Ca-doped BeO obtained via a sol-gel method
Altunal, V; Guckan, V; Ozdemir, A; Can, N; Yegingil, Z
BeO, BeO:Al-1%, BeO:Ca-1%, and BeO:Al-1%, Ca-0.1% ceramics were synthesized by the sol-gel method. The X-ray luminescence was studied, and broad emission peaks located at 230 nm (similar to 5.4 eV) and 300 nm (similar to 4.1 eV) were observed. We investigated thermoluminescence peaks contributing to optically stimulated luminescence (OSL) signals for the ceramics. The thermal quenching of the OSL signals was evaluated, and the quenching energies were estimated as between approximately 0.5 eV and approximately 0.7 eV. To check the feasibility for dosimetry purposes, the dose response, reusability, and dark storage fading of the OSL signals were investigated. The dose response was observed to be linear between 0.1 and 100 Gy. The minimum detectable doses of BeO, BeO:Al-1%, BeO:Ca-1%, and BeO:Al-1%, Ca-0.1% were estimated as approximately 0.9 mGy, approximately 4 mGy, approximately 0.5 mGy, and approximately 0.5 mGy, respectively. Very good reusability was observed over ten cycles, with a maximum deviation of 2%. The results obtained from BeO:Al-1%, Ca-0.1% could be useful for OSL dosimetry, particularly in medical applications.
Anomalous heating rate dependence and analyses of thermoluminescence glow curves in Gd doped ZnB2O4 phosphors
Atasoz, S; Topaksu, M; Souadi, G; Can, N
Here, we report the thermoluminescence (TL) characteristics and trapping parameters under beta ray excitations of pelletized Gd-incorporated ZnB2O4 synthesized through the gel combustion method. The chemical composition of the obtained Gd incorporated ZnB2O4 was confirmed using X-ray diffraction (XRD). The best doping concentration of Gd was 0.25 mass%, which resulted in the highest luminous efficiency. The glow curves of the pellet-formed samples exposed to beta-irradiation at various doses showed glow peaks at about 79 degrees C, 133 degrees C and 276 degrees C with a heating rate of 2 degrees Cs-1. An anomalous heating rate effect was observed for the peak centered at 276 degrees C, but the TL intensity of the peak at 79 degrees C and 133 degrees C decreased with an increasing heating rate. The TL glow peaks were studied using T-m-T-stop, initial rise (IR), and variable heating rate (VHR) and Computerized glow curve deconvolution (CGCD) methods. In the range of 0.1-50 Gy, the total integral values of TL output increased linearly with increased dose. A complex glow curves are composed of six distinguishable peaks as revealed by the results obtained from IR and CGCD methods. The current results indicate that the ZnB2O4:Gd3+ phosphor is a suitable option in radiation dosimetry for environmental monitoring.
Luminescence of undoped and Eu3+activated zinc gallate phosphor: Synthesis, unusual intense 5D0 → 7F4 red emission
Souadi, G; Kaynar, ÜH; Ayvacikli, M; Can, N
A series of Eu3+-doped ZnGa2O4 samples were synthesized via the urea-glycine combustion route. Powder X-ray diffraction (XRD) was used to investigate the crystallinity of the samples, energy dispersive spectroscopy (EDS) to explore the elemental composition, Fourier transform infrared (FTIR), to observe the vibrational modes of the samples, photoluminescence (PL) to determine the luminescence properties. The XRD data prove that the samples remain single cubic structure even at high concentrations of Eu3+, enabling the formation of a unique emission spectrum. The active ion concentration was varied to examine the influence of concentration on luminescent properties. This study revealed a 5D0 & RARR;7F4 transition located at 700 nm with unusual intensity that has not been documented in the literature, which suggests that the active ion concentration can influence the luminescent characteristics of the phosphors. The increasing Eu3+ content increases the number of Eu3+ ions in ZnGa2O4 host lattice, which enhances the luminescence efficiency of the phosphor. However, beyond a certain level of Eu3+content (i.e., 3 wt% Eu3+), the number of Eu3+ ions becomes excessive, resulting in a reduction in luminescence efficiency due to concentration quenching. The dipole dipole interaction is elucidated to play a prominent role in the mechanism of Eu3+ quenching in the ZnGa2O4. An assessment of color coordinates based on emission spectra reveals that the coordinates shift from blue to the white light region, and then to red as Eu3+ content increases. This suggests that there is a substantial relationship between the Eu3+ concentration and the measured color coordinates.

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