Browsing by Subject "X ray diffraction analysis"

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Open Access
Anharmonicity in GaTe layered crystals
(Wiley-VCH Verlag GmbH & Co. KGaA, 2002) Aydınlı, Atilla; Gasanly, N. M.; Uka, A.; Efeoglu, H.
The temperature dependencies (10-300 K) of seven Raman-active mode frequencies in layered semiconductor gallium telluride have been measured in the frequency range from 25 to 300 cm -1. Softening and broadening of the optical phonon lines are observed with increasing temperature. Comparison between the experimental data and theories of the shift of the phonon lines during heating of the crystal showed that the experimental dependencies can be explained by contributions from thermal expansion and lattice anharmonicity. Lattice anharmonicity is determined to be due to three-phonon processes.
Open Access
The effect of gadolinium doping on the structural, magnetic and photoluminescence properties of electrospun bismuth ferrite nanofibers
(Elsevier Ltd, 2015) George Philip G.; Senthamizhan, A.; Srinivasan Natarajan, T.; Chandrasekaran G.; Annal Therese H.
Gadolinium (Gd) doped Bismuth ferrite (BFO) nanofibers (Bi1-xGdxFeO3 (x=0.0, 0.05, 0.10, 0.15 and 0.20)) were synthesized via electrospinning. Scanning Electron Microscope (SEM) analysis showed that the diameter of the nanofibers ranged from 150 to 250 nm. X-Ray Diffraction (XRD) analysis revealed a structural phase transition with varying 'x', the compositions with x≤0.10 have crystal structures with space group R3c, while the compositions with x > 0.10 have crystal structures with space group Pnma. Vibrating Sample Magnetometer (VSM) analysis exhibited the weak ferromagnetic nature of the BFO nanofibers. However an increase in the saturated magnetic moment with increase in Gd dopant concentration was observed. The Photoluminescence (PL) spectra of the Bi:1-x :x nanofibers show enhanced Near Band Emission (NBE) intensity at x=0.10 due to the passivation of oxygen vacancies by Gd doping. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Open Access
The effect of growth conditions on the optical and structural properties of InGaN/GaN MQW LED structures grown by MOCVD
(Gazi University Eti Mahallesi, 2014) Cetđn, S.; Sağlam, S.; Ozcelđk, S.; Özbay, Ekmel
Five period InGaN/GaN MQW LED wafers were grown by low pressure MOCVD on an AlN buffer layer, which was deposited on a c-plane (0001)-faced sapphire substrate. The effect of growth conditions, such as the well growth time, growth temperatures, and indium flow rate on the properties of MQW structures were investigated by using high resolution X-ray diffraction and room temperature photoluminescence. By increasing growth temperature, the emission wavelengths showed a blue-shift while it red-shifted via an increase in the indium flow rate. The emission wavelength can be tuned by way of changing the well growth time of the samples. ©2014 Gazi University Eti Mahallesi. All rights reserved.
Open Access
Examination of the temperature related structural defects of InGaN/GaN solar cells
(Academic Press, 2015) Durukan, İ. K.; Bayal, Ö.; Kurtuluş, G.; Baş, Y.; Gültekin, A.; Öztürk, M. K.; Çörekçi, S.; Tamer, M.; Özçelik, S.; Özbay, Ekmel
In this study the effects of the annealing temperature on the InGaN/GaN solar cells with different In-contents grown on sapphire substrate by the Metal Organic Chemical Vapor Deposition (MOCVD) are analyzed by High Resolution X-ray Diffraction (HRXRD) and an Atomic Force Microscope (AFM). The plane angles, mosaic crystal sizes, mixed stress, dislocation intensities of the structure of the GaN and InGaN layers are determined. According to the test results, there are no general characteristic trends observed due to temperature at both structures. There are fluctuating failures determined at both structures as of 350 °C. The defect density increased on the GaN layer starting from 350 °C and reaching above 400 °C. A similar trend is observed on the InGaN layer, too.
Open Access
Gold catalysts supported on ceria doped by rare earth metals for water gas shift reaction: influence of the preparation method
(2009) Andreeva, D.; Ivanov, I.; Ilieva, L.; Abrashev, M. V.; Zanella, R.; Sobczak, J. W.; Lisowski, W.; Kantcheva, M.; Avdeev, G.; Petrov, K.
Gold catalysts based on ceria, doped by various RE metals (La, Sm, Gd, Yb, Y) were studied. The influence of the preparation methods on structure, properties and catalytic activity in the WGS reaction was investigated. The catalysts' supports were prepared using two different methods: co-precipitation (CP) and mechanochemical activation (MA). The catalysts were tested in a wide temperature interval without and after reactivation. All samples were characterized using a combination of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS) and TPR. It was found that the catalytic activity of MA catalysts is higher than CP ones. The gold catalysts based on ceria doped by Yb and Sm exhibited the highest activity. After reactivation in air the MA samples almost kept the WGS activity same, while the CP catalysts increased it. The catalysts of a single- and double-phase structure are formed as a result of CP and MA preparation, respectively. There are no big differences in the gold particles size (2-3 nm) depending on dopants and on the preparation techniques. The RS spectra analysis indicates that most probably the oxygen vacancies are adjacent to Me3+ dopant and the ceria structure seems to be better ordered than in the case of alumina as a dopant. There is no distinct correlation between reducibility and WGS activity. The XPS analysis disclose positively charged gold particles in addition to metallic gold within a surface region of fresh samples and only metallic gold on the samples after catalytic processing. There is no simple correlation between the concentration of Ce3+ in the samples and their WGS activity.
Open Access
Increasing Ti-6Al-4V brazed joint strength equal to the base metal by Ti and Zr amorphous filler alloys
(2012) Ganjeh, E.; Sarkhosh H.; Bajgholi, M.E.; Khorsand H.; Ghaffari, M.
Microstructural features developed along with mechanical properties in furnace brazing of Ti-6Al-4V alloy using STEMET 1228 (Ti-26.8Zr-13Ni-13.9Cu, wt.%) and STEMET 1406 (Zr-9.7Ti-12.4Ni-11.2Cu, wt.%) amorphous filler alloys. Brazing temperatures employed were 900-950 °C for the titanium-based filler and 900-990 °C for the zirconium-based filler alloys, respectively. The brazing time durations were 600, 1200 and 1800 s. The brazed joints were evaluated by ultrasonic test, and their microstructures and phase constitutions analyzed by metallography, scanning electron microscopy and X-ray diffraction analysis. Since microstructural evolution across the furnace brazed joints primarily depends on their alloying elements such as Cu, Ni and Zr along the joint. Accordingly, existence of Zr 2Cu, Ti 2Cu and (Ti,Zr) 2Ni intermetallic compounds was identified in the brazed joints. The chemical composition of segregation region in the center of brazed joints was identical to virgin filler alloy content which greatly deteriorated the shear strength of the joints. Adequate brazing time (1800 s) and/or temperature (950 °C for Ti-based and 990 °C for Zr-based) resulted in an acicular Widmanstätten microstructure throughout the entire joint section due to eutectoid reaction. This microstructure increased the shear strength of the brazed joints up to the Ti-6Al-4V tensile strength level. Consequently, Ti-6Al-4V can be furnace brazed by Ti and Zr base foils produced excellent joint strengths. © 2012 Elsevier Inc. All rights reserved.
Open Access
Investigation on the formation of Cu-Fe nano crystalline super-saturated solid solution developed by mechanical alloying
(2013) Mojtahedi, M.; Goodarzi, M.; Aboutalebi, M.R.; Ghaffari, M.; Soleimanian V.
In this study, the formation of super saturated solid solution in the binary Cu-Fe system was investigated. Three powder blends with 30, 50 and 70 wt.% of Fe were milled for different times to 96 h. The variations of lattice parameter and inter-planar spacing were calculated and analyzed using X-ray diffraction analysis (XDA). The anisotropy of lattice deformation in the FCC phase was studied and the obtained results were compared to milled pure Cu powder. Furthermore, crystallite size was calculated using Scherer formula in comparison with Rietveld full profile refinement method. Considering the previous studies about the formation of non-equilibrium FCC and BCC phases, the phase evolution has been discussed and the proportion of each phase was calculated using Rietveld refinement method. Supplementary studies on the evolution of microstructure and formation of solid solution were carried out using high resolution transmission electron microscopy (HRTEM). Finally, high angle annular dark field (HAADF) imaging was utilized to find out the level of homogeneity in the resulting phases. While true alloying takes place in each phase, the final structure consists of both FCC and BCC nano-crystallites. © 2012 Elsevier B.V. All rights reserved.
Open Access
Liquid crystalline mesophases of pluronics (L64, P65, and P123) and transition metal nitrate salts ([M(H2O)6](NO 3)2)
(American Chemical Society, 2005) Demirörs, A. F.; Eser, B. E.; Dag, Ö.
The triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymers, Pluronics (L64, P65, and P123), form liquid crystalline (LC) mesophases with transition metal nitrate salts (TMS), [M(H2O) n] (NO3)2, in the presence and absence of free water in the media. In this assembly process, M-OH2 plays an important role as observed in a TMS:CnEOm (C nEOm is oligo(ethylene oxide) nonionic surfactants) system. The structure of the LC mesophases and interactions of the metal ion-nitrate ion and metal ion-Pluronic were investigated using microscopy (POM), diffraction (XRD), and spectroscopy (FTIR and micro-Raman) techniques. The TMS:L64 system requires a shear force for mesophase ordering to be observed using X-ray diffraction. However, TMS:P65 and TMS:P123 form well structured LC mesophases. Depending on the salt/Pluronic mole ratio, hexagonal LC mesophases are observed in the TMS:P65 systems and cubic and tetragonal LC mesophases in the TMS:P123 systems. The LC mesophase in the water/salt/Pluronic system is sensitive to the concentration of free (H2O) and coordinated water (M-OH2) molecules and demonstrates structural changes. As the free water is evaporated from the H2O:TMS:Pluronic LC mesophase (ternary mixture), the nitrate ion remains free in the media. However, complete evaporation of the free water molecules enforces the coordination of the nitrate ion to the metal ion in all TMS:Pluronic systems. © 2005 American Chemical Society.
Open Access
Lyotropic liquid-crystalline phase of oligo(ethylene oxide) surfactant/transition metal salt and the synthesis of mesostructured cadmium sulfide
(American Chemical Society, 2003) Dag, Ö.; Alayoǧlu, S.; Tura, C.; Çelik, Ö.
Lyotropic liquid-crystalline (LLC), transition metal salt: oligo(ethylene oxide) nonionic surfactant (CnH2n+1(CH2CH2O)mOH, denoted as CnEOm), systems have been studied by means of diffraction, microscopy, and spectroscopy to elucidate the structural, thermal, and templating properties. In the system, the lyotropic salts of transition metal aqua complexes, such as chlorides and sulfates, are insoluble and do not form a LC phase in CnEOm-type nonionic surfactants. However, the transition metal aqua complexes of nitrates and perchlorates are soluble and form 2D and 3D hexagonal and cubic mesophases. These phases are stable in a very broad range of salt:surfactant mole ratios (1.0 and 3.6). The nitrate salts form a hexagonal mesophase. However, in high nitrate salt concentrations (above 3.2 salt:surfactant mole ratio), the salt crystals are either insoluble or the salt:surfactant mixtures are in a cubic mesophase. The structure and thermal properties of the new system are determined by the solubility of the transition metal salts, the concentration of the salt, and the surfactant type. The LC [Cd(H2O)4](NO3)2: C12EO10 mesophase has been reacted with H2S gas to produce solid mesostructured CdS (meso-CdS). The meso-CdS particles are spherical in morphology and are made up of hierarchical organization of 2-4-nm CdS particles. The salt:surfactant LLC systems and the solid meso-CdS have been investigated using polarized optical microscopy, X-ray diffraction, Fourier transform infrared, Fourier transform Raman, and UV-vis absorption spectroscopy, scanning electron microscopy, and transmission electron microscopy.
Open Access
Nature of the Ti-Ba interactions on the BaO/TiO2/Al 2O3 NOx storage system
(2009) Andonova, S. M.; Şentürk, G. S.; Kayhan, E.; Ozensoy, E.
A ternary oxide-based NO* storage material in the form of BaOZTiO2Zy-Al2O3 was synthesized and characterized. Thermally induced structural changes occurring on the surfaces of the TiO2Zy-Al2O3 and BaOZ TiO 2Zy-Al2O3 systems were studied in a comparative manner within 300-1273 K via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and BET surface area analysis. The surface acidity of the studied oxide systems was also investigated via pyridine adsorption monitored by in-situ Fourier transform infrared (FTIR) spectroscopy. BaO/TiO2γ-Al 2O3 ternary oxide was synthesized by incorporating different loadings of (8-20 wt %) BaO onto the TiO2/γ Al 2O3 support material, which was originally prepared using the sol-gel method. In the TiO2Zy-Al2O3 binary oxide support material, anatase phase exhibited a relatively high thermal stability at T < 1073 K. The presence of TiO2 domains on the surface of the alumina particles was found to alter the surface acidity of alumina by providing new medium-strength Lewis acid sites. SEMZEDX results indicate that in the BaO/TiO2γ-Al2O3 system, TiO2 domains present a significant affinity toward BaO and/or Ba(NO3) 2 resulting in a strong Ti-Ba interaction and the formation of overlapping domains on the surface. The presence of TiO2 also leads to a decrease in the decomposition temperature of the Ba(N03) 2 phase with respect to the Ti-free Ba(N03) 2ZyAl2O3 system. Such a destabilization is likely to occur due to a weaker interaction between Ba(N03) 2 and y-Al203 domains in the ternary oxide as well as due to the change in the surface acidity in the presence of TiO 2. At relatively high temperatures (e.g., 873-1273 K) formation of complex structures in the form of BaTiO3, Ba1.23Al 2.46Ti5.54O16, BaTiO5, andor Ba x:AlyTizOn., were also observed. © 2009 American Chemical Society.
Open Access
Optical characteristics of nanocrystalline AlxGa1-xN thin films deposited by hollow cathode plasma-assisted atomic layer deposition
(AVS Science and Technology Society, 2014) Goldenberg, E.; Ozgit-Akgun, C.; Bıyıklı, Necmi; Kemal Okyay, A.
Gallium nitride (GaN), aluminum nitride (AlN), and AlxGa 1-xN films have been deposited by hollow cathode plasma-assisted atomic layer deposition at 200 °C on c-plane sapphire and Si substrates. The dependence of film structure, absorption edge, and refractive index on postdeposition annealing were examined by x-ray diffraction, spectrophotometry, and spectroscopic ellipsometry measurements, respectively. Well-adhered, uniform, and polycrystalline wurtzite (hexagonal) GaN, AlN, and Al xGa1-xN films were prepared at low deposition temperature. As revealed by the x-ray diffraction analyses, crystallite sizes of the films were between 11.7 and 25.2 nm. The crystallite size of as-deposited GaN film increased from 11.7 to 12.1 and 14.4 nm when the annealing duration increased from 30 min to 2 h (800 °C). For all films, the average optical transmission was ∼ 85% in the visible (VIS) and near infrared spectrum. The refractive indices of AlN and AlxGa1-xN were lower compared to GaN thin films. The refractive index of as-deposited films decreased from 2.33 to 2.02 (λ = 550 nm) with the increased Al content x (0 ≤ x ≤ 1), while the extinction coefficients (k) were approximately zero in the VIS spectrum (>400 nm). Postdeposition annealing at 900 °C for 2 h considerably lowered the refractive index value of GaN films (2.33-1.92), indicating a significant phase change. The optical bandgap of as-deposited GaN film was found to be 3.95 eV, and it decreased to 3.90 eV for films annealed at 800 °C for 30 min and 2 h. On the other hand, this value increased to 4.1 eV for GaN films annealed at 900 °C for 2 h. This might be caused by Ga 2O3 formation and following phase change. The optical bandgap value of as-deposited AlxGa1-xN films decreased from 5.75 to 5.25 eV when the x values decreased from 1 to 0.68. Furthermore, postdeposition annealing did not affect the bandgap of Al-rich films. © 2014 American Vacuum Society.
Open Access
Properties of high specific strength Al-4wt.% Al2O3/B4C nano-composite produced by accumulative roll bonding process
(Elsevier Ltd, 2013) Alizadeh, M.; beni H.A.; Ghaffari, M.; Amini, R.
The influence of nano-scale reinforcement on the mechanical and microstructural properties of ultrafine-grained composites was studied. Al matrix (pure aluminum) composites, with a grain size of 230nm and B4C and Al2O3 reinforcements with an average size of 50nm, were fabricated via the accumulative roll bonding (ARB) process. To evaluate structure and microstructure of the produced composites, X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) were applied. Mechanical properties of the specimens were investigated by tensile and hardness tests. The result revealed that in comparison with monolithic Al (ARBed Al without ceramic particles), the presence of nano-particles enhances specific strength of composites. Also, the results showed that with increasing ARB cycles, the microhardness of the composites increases. In addition, the specific strength and microhardness of the composite samples are higher than those of the monolithic Al. The density of the composite samples and monolithic Al was measured by the Archimedes method showing that the density decreases in presence of ceramic particles. © 2013 Elsevier Ltd.
Open Access
Raman and TEM studies of Ge nanocrystal formation in SiOx: Ge/SiOx multilayers
(Wiley, 2007) Dana, Aykutlu; Aǧan, S.; Tokay, S.; Aydınlı, Atilla; Finstad, T. G.
Alternating germanosilicate-siliconoxide layers of 10-30 nm thickness were grown on Si substrates by plasma enhanced chemically vapor deposition (PECVD). The compositions of the grown films were determined by X-ray photoelectron spectroscopy measurements. The films were annealed at temperatures varying from 670 to 1000°C for 5 to 45 minutes under nitrogen atmosphere. High resolution cross section TEM images, electron diffraction and electron energy-loss spectroscopy as well as energy-dispersive X-ray analysis (EDAX) data confirm presence of Ge nanocrystals in each layer. The effect of annealing on the Ge nanocrystal formation in multilayers was investigated by Raman spectroscopy and Transmission Electron Microscopy (TEM). As the annealing temperature is raised to 850°C, single layer of Ge nanocrystals observed at lower annealing temperatures is transformed into a double layer with the smaller sized nanocrystals closer to the substrate SiO2 interface.
Open Access
Solventless acid-free synthesis of mesostructured titania: nanovessels for metal complexes and metal nanoclusters
(Wiley - V C H Verlag GmbH & Co. KGaA, 2003) Dag, Ö.; Soten, I.; Çelik, Ö.; Polarz, S.; Coombs, N.; Ozin, G. A.
A new and highly reproducible method to obtain mesostructured titania materials is introduced in this contribution. The meso-structured titania is obtained by employing self-assembled structures of non-ionic alkyl-poly(ethylene oxide) surfactants as templates. The materials are produced without additional solvents such as alcohols, or even water. Only the titanium(iv) ethoxide and the surfactant (C12EO10) are needed. Water, in the form of that attached to the surfactant and from the atmosphere, induces growth of titania nanoclusters in the synthesis sol. It is indicated that these nanoclusters interact with the surfactant EO-head groups to form a new titanotropic amphiphile. The new amphiphiles self-assemble into titanium nanocluster-surfactant hybrid lyotropic phases, which are transformed to the final mesostructured materials by further condensation of the titania network. The titania materials can be obtained also with noble-metal particles immobilized in the mesostructured framework. It is seen that when different metal salts are used as the metal precursors, different interactions with the titania walls are found. The materials are characterized by X-ray diffraction (XRD), polarization optical microscopy (POM), transmission electron microscopy (TEM), UV-vis spectroscopy, and micro-Raman analysis.
Open Access
Spectroscopic investigation of nitrate-metal and metal-surfactant interactions in the solid AgNO3/C12EO10 and liquid-crystalline [M(H2O)n](NO3)2/C12EO10 systems
(American Chemical Society, 2003) Dag, Ö.; Samarskaya, O.; Tura, C.; Günay, A.; Çelik, Ö.
Interactions of the nitrate ions in various metal nitrate salts with CnH2n-1(CH2CH2O)mOH (CnEOm)-type nonionic surfactants have been investigated both in the solid and in the liquid-crystalline (LC) systems. In the ternary system, the mixture of salt/water/CnEOm has a mesophase up to a certain concentration of salt, and the nitrate ions in this phase are usually in a free-ion form. However, upon the evaporation of the water phase, the nitrate ion interacts with the metal center and coordinates as either a bidentate or unidentate ligand. It is this interaction that makes the AgNO3 ternary system undergo a phase separation by releasing solid Ag(CnEOm)xNO3 complex crystals. In contrast, the salt/surfactant systems maintain their stable LC phases for months. Note also that the salt/surfactant systems consist of transition-metal aqua complexes in which the coordinated water molecules play a significant role in the self-assembly and organization of the nonionic surfactant molecules into an LC mesophase. Throughout this work, Fourier transform infrared spectroscopy has been extensively used to investigate the interactions of the nitrate ions with a metal center and the metal ions with the surfactant molecules. Polarized optical microscopy and X-ray diffraction techniques have been applied to investigate the nature of the crystalline and LC phases.
Open Access
Structural analysis of an InGaN/GaN based light emitting diode by X-ray diffraction
(Springer, 2009-04-18) Öztürk, M. K.; Hongbo, Y.; SarIkavak, B.; Korçak, S.; Özçelik, S.; Özbay, Ekmel
The important structural characteristics of hexagonal GaN in an InGaN/GaN multi quantum well, which was aimed to make a light emitted diode and was grown by metalorganic chemical vapor deposition on c-plain sapphire, are determined by using nondestructive high-resolution X-ray diffraction in detail. The distorted GaN layers were described as mosaic crystals characterized by vertical and lateral coherence lengths, a mean tilt, twist, screw and edge type threading dislocation densities. The rocking curves of symmetric (00.l) reflections were used to determine the tilt angle, while the twist angle was an extrapolated grown ω-scan for an asymmetric (hk.l) Bragg reflection with an h or k nonzero. Moreover, it is an important result that the mosaic structure was analyzed from a different (10.l) crystal direction that was the angular inclined plane to the z-axis. The mosaic structure parameters were obtained in an approximately defined ratio depending on the inclination or polar angle of the sample.
Open Access
Synthesis of polybenzoxazine/clay nanocomposites by in situ thermal ring-opening polymerization using intercalated monomer
(2011) Demir, K.D.; Tasdelen, M.A.; Uyar, T.; Kawaguchi, A.W.; Sudo, A.; Endo, T.; Yagci, Y.
A new class of polybenzoxazine/montmorillonite (PBz/MMT) nanocomposites has been prepared by the in situ polymerization of the typical fluid benzoxazine monomer, 3-pentyl-5-ol-3,4-dihydro-1,3-benzoxazine, with intercalated benzoxazine MMT clay. A pyridine-substituted benzoxazine was first synthesized and quaternized by 11-bromo-1-undecanol and then used for ion exchange reaction with sodium ions in MMT to obtain intercalated benzoxazine clay. Finally, this organomodified clay was dispersed in the fluid benzoxazine monomers at different loading degrees to conduct the in situ thermal ring-opening polymerization. Polymerization through the interlayer galleries of the clay led to the PBz/MMT nanocomposite formation. The morphologies of the nanocomposites were investigated by both X-ray diffraction and transmission electron microscopic techniques, which suggested the partially exfoliated/intercalated structures in the PBz matrix. Results of thermogravimetric analysis confirmed that the thermal stability and char yield of PBz nanocomposites increased with the increase of clay content. © 2011 Wiley Periodicals, Inc.
Open Access
TL/OSL studies of Li2B4O7:Cu dosimetric phosphors
(2013) Aydin, T.; Demirtaş H.; Aydin, S.
Dosimetric phosphors of Cu-doped lithium tetraborate (Li2B 4O7:Cu) were produced using a sintering technique in a laboratory environment and characterized using Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD). The thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of powdered (Li2B 4O7) phosphor doped with copper at different concentrations (0.020-0.025 wt %) were studied. The Cu-doped Li 2B4O7 phosphor material has two dominant TL glow peaks, and the maximum TL responses of the peaks are at 115 C and 243 C in the range of 0 C-310 C. The TL response of the Cu-doped lithium tetraborate is approximately 900 times more sensitive than undoped lithium tetraborate. The TL and OSL signal intensities increase as the beta radiation doses increase up to approximately 150.00 Gy and 76.50 Gy, respectively. The OSL dose-response curve is linear up to a dose range of 12.00 Gy for Cu-doped Li2B 4O7 dosimetric phosphors. The time-dependent fading behavior of the Cu-doped lithium tetraborate was found to be quite stable over long time durations. In addition, the repeatability of the OSL dose measurements were determined to be 2/3 lower compared to the TL measurements. The reproducibility of the OSL measurements was approximately 5%. Based on the TL and OSL results, the prepared phosphors can be used to measure beta doses ranging from 10 μGy to 150.00 Gy and 76.50 Gy, respectively, by using the TL and OSL techniques, with confidence limits of approximately 7% and 3-4%, respectively. © 2013 Elsevier Ltd. All rights reserved.
Open Access
Zno nanostructures via hydrothermal synthesis on atomic layer deposited seed-layers
(IEEE, 2015) Orlov, A.; Ulianova, V.; Bogdan, O.; Pashkevich, G.; Bıyıklı, Necmi; Goldenberg, Eda; Haider, Ali
The original results of two different types of ZnO nanostructures grown via hydrothermal synthesis on ZnO seed-layers coated by atomic layer deposition process on Si substrates were presented. Scanning electron microscopy and X-ray diffractometry were used for the analysis of resulting nanostructured ZnO samples. The influence of annealing on crystal properties of the ZnO nanostructures was shown. It was ascertained that solution composition had a significant influence on the morphology of nanostructures and post-growth annealing modified the crystal properties of nanostructures. © 2015 IEEE.