WorldWideScience

Sample records for bulk optical properties

  1. Ultraviolet-visible bulk optical properties of randomly distributed soot.

    Science.gov (United States)

    Renard, J B; Hadamcik, E; Brogniez, C; Berthet, G; Worms, J C; Chartier, M; Pirre, M; Ovarlez, J; Ovarlez, H

    2001-12-20

    The presence of soot in the lower stratosphere was recently established by in situ measurements. To isolate their contribution to optical measurements from that of background aerosol, the soot's bulk optical properties must be determined. Laboratory measurements of extinction and polarization of randomly distributed soot were conducted. For all soot, measurements show a slight reddening extinction between 400 and 700 nm and exhibit a maximum of 100% polarization at a scattering angle of 75 +/- 5 degrees. Such results cannot be reproduced by use of Mie theory assumptions. The different optical properties of soot and background stratospheric aerosol could allow isolation of soot in future analyses of stratospheric measurements.

  2. Far Infrared Optical Properties of Bulk Wurtzite Zinc Oxide Semiconductor

    Institute of Scientific and Technical Information of China (English)

    Pohkok Ooi; Saicheong Lee; Shashiong Ng; Zainuriah Hassan; Haslan Abu Hassan

    2011-01-01

    Polarized far infrared (FIR) reflectance technique was applied to study the optical properties of a bulk wurtzite zinc oxide (ZnO) single crystal. Room temperature polarized FIR reflectance spectra were taken at various angles of incidence, from 20° to 70°. The theoretical polarized FIR reflectance spectra were simulated based on the anisotropic dielectric function model. Good agreement was achieved between the experimental and the theoretical FIR reflectance spectra. Through this work, a complete set of reststrahlen parameters of a bulk wurtzite ZnO at the Brillouin zone centre was obtained. Additionally, other FIR optical properties such as the real and the imaginary parts of the complex dielectric function, real and imaginary parts of the refractive index, the absorption coefficient and the reciprocal of the absorption coefficient were also obtained by using numerical calculation.

  3. Optical and scintillation properties of bulk ZnO crystal

    Energy Technology Data Exchange (ETDEWEB)

    Yanagida, Takayuki [Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu 808-0196 (Japan); Fujimoto, Yutaka; Kurosawa, Shunsuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Yamanoi, Kohei; Sarukura, Nobuhiko [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Kano, Masataka; Wakamiya, Akira [Daishinku Corporation, 1389 Shinzaike, Hiraoka-cho, Kakogawa, Hyogo 675-0194 (Japan)

    2012-12-15

    Single crystal bulk ZnO scintillator grown by the hydrothermal method was tested on its scintillation performances. In X-ray induced radio luminescence spectrum, it exhibited two intense emission peaks at 400 and 550 nm. The former was ascribed to the free and bound exciton related luminescence and the latter to oxygen vacancy related one, respectively. X-ray induced scintillation decay time of the exciton related emission measured by the pulse X-ray streak camera system resulted {proportional_to} 4 ns. Finally, the light yield under {sup 241}Am 5.5 MeV {alpha}-ray was examined and it resulted {proportional_to} 500 ph/5.5 MeV-{alpha}.(copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Visible and near-infrared bulk optical properties of raw milk.

    Science.gov (United States)

    Aernouts, B; Van Beers, R; Watté, R; Huybrechts, T; Lammertyn, J; Saeys, W

    2015-10-01

    The implementation of optical sensor technology to monitor the milk quality on dairy farms and milk processing plants would support the early detection of altering production processes. Basic visible and near-infrared spectroscopy is already widely used to measure the composition of agricultural and food products. However, to obtain maximal performance, the design of such optical sensors should be optimized with regard to the optical properties of the samples to be measured. Therefore, the aim of this study was to determine the visible and near-infrared bulk absorption coefficient, bulk scattering coefficient, and scattering anisotropy spectra for a diverse set of raw milk samples originating from individual cow milkings, representing the milk variability present on dairy farms. Accordingly, this database of bulk optical properties can be used in future simulation studies to efficiently optimize and validate the design of an optical milk quality sensor. In a next step of the current study, the relation between the obtained bulk optical properties and milk quality properties was analyzed in detail. The bulk absorption coefficient spectra were found to mainly contain information on the water, fat, and casein content, whereas the bulk scattering coefficient spectra were found to be primarily influenced by the quantity and the size of the fat globules. Moreover, a strong positive correlation (r ≥ 0.975) was found between the fat content in raw milk and the measured bulk scattering coefficients in the 1,300 to 1,400 nm wavelength range. Relative to the bulk scattering coefficient, the variability on the scattering anisotropy factor was found to be limited. This is because the milk scattering anisotropy is nearly independent of the fat globule and casein micelle quantity, while it is mainly determined by the size of the fat globules. As this study shows high correlations between the sample's bulk optical properties and the milk composition and fat globule size, a

  5. Vibrational and optical properties of MoS2: From monolayer to bulk

    Science.gov (United States)

    Molina-Sánchez, Alejandro; Hummer, Kerstin; Wirtz, Ludger

    2015-12-01

    Molybdenum disulfide, MoS2, has recently gained considerable attention as a layered material where neighboring layers are only weakly interacting and can easily slide against each other. Therefore, mechanical exfoliation allows the fabrication of single and multi-layers and opens the possibility to generate atomically thin crystals with outstanding properties. In contrast to graphene, it has an optical gap of ~1.9 eV. This makes it a prominent candidate for transistor and opto-electronic applications. Single-layer MoS2 exhibits remarkably different physical properties compared to bulk MoS2 due to the absence of interlayer hybridization. For instance, while the band gap of bulk and multi-layer MoS2 is indirect, it becomes direct with decreasing number of layers. In this review, we analyze from a theoretical point of view the electronic, optical, and vibrational properties of single-layer, few-layer and bulk MoS2. In particular, we focus on the effects of spin-orbit interaction, number of layers, and applied tensile strain on the vibrational and optical properties. We examine the results obtained by different methodologies, mainly ab initio approaches. We also discuss which approximations are suitable for MoS2 and layered materials. The effect of external strain on the band gap of single-layer MoS2 and the crossover from indirect to direct band gap is investigated. We analyze the excitonic effects on the absorption spectra. The main features, such as the double peak at the absorption threshold and the high-energy exciton are presented. Furthermore, we report on the the phonon dispersion relations of single-layer, few-layer and bulk MoS2. Based on the latter, we explain the behavior of the Raman-active A1g and E2g1 modes as a function of the number of layers. Finally, we compare theoretical and experimental results of Raman, photoluminescence, and optical-absorption spectroscopy.

  6. Near infrared to ultraviolet optical properties of bulk single crystal and nanocrystal thin film iron pyrite

    Science.gov (United States)

    Subedi, Indra; Bhandari, Khagendra P.; Ellingson, Randall J.; Podraza, Nikolas J.

    2016-07-01

    We report optical properties of iron pyrite (FeS2) determined from ex situ spectroscopic ellipsometry measurements made on both a commercially available bulk single crystal and nanocrystalline thin film over a spectral range of 0.735-5.887 eV. The complex dielectric function, ɛ (E) = ɛ 1 (E) + iɛ 2 (E), spectra have been determined by fitting a layered parametric model to the ellipsometric measurements. Spectra in ɛ are modeled using a Kramers-Kronig consistent critical point parabolic band model involving seven critical points for the bulk single crystal and four critical points for the nanocrystalline film. Absorption coefficient spectra for both types of samples are also determined from ɛ. Critical point features in the nanocrystalline films are broader, have lower amplitude and lower energy critical points detected having a small blue shift when compared to the single crystal sample.

  7. Electronic and optical properties of titanium nitride bulk and surfaces from first principles calculations

    Science.gov (United States)

    Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.

    2015-11-01

    Prediction of the frequency-dependent dielectric function of thin films poses computational challenges, and at the same time experimental characterization by spectroscopic ellipsometry remains difficult to interpret because of changes in stoichiometry and surface morphology, temperature, thickness of the film, or substrate. In this work, we report calculations for titanium nitride (TiN), a promising material for plasmonic applications because of less loss and other practical advantages compared to noble metals. We investigated structural, electronic, and optical properties of stoichiometric bulk TiN, as well as of the TiN(100), TiN(110), and TiN(111) outermost surfaces. Density functional theory (DFT) and many-body GW methods (Green's (G) function-based approximation with screened Coulomb interaction (W)) were used, ranging from G0W0, GW0 to partially self-consistent sc-GW0, as well as the GW-BSE (Bethe-Salpeter equation) and time-dependent DFT (TDDFT) methods for prediction of the optical properties. Structural parameters and the band structure for bulk TiN were shown to be consistent with previous work. Calculated dielectric functions, plasma frequencies, reflectivity, and the electron energy loss spectrum demonstrated consistency with experiment at the GW0-BSE level. Deviations from experimental data are expected due to varying experimental conditions. Comparison of our results to spectroscopic ellipsometry data for realistic nanostructures has shown that although TDDFT may provide a computationally feasible level of theory in evaluation of the dielectric function, application is subject to validation with GW-BSE calculations.

  8. Non equilibrium optical properties in semiconductors from first--principles: a combined theoretical and experimental study of bulk silicon

    CERN Document Server

    Sangalli, Davide; Manzoni, Cristian; Cerullo, Giulio; Marini, Andrea

    2016-01-01

    The calculation of the equilibrium optical properties of bulk silicon by using the Bethe--Salpeter equation solved in the Kohn--Sham basis represents a cornerstone in the development of an ab--initio approach to the optical and electronic properties of materials. Nevertheless calculations of the {\\em transient} optical spectrum using the same efficient and successful scheme are scarce. We report, here, a joint theoretical and experimental study of the transient reflectivity spectrum of bulk silicon. Femtosecond transient reflectivity is compared to a parameter--free calculation based on the non--equilibrium Bethe--Salpeter equation. By providing an accurate description of the experimental results we disclose the different phenomena that determine the transient optical response of a semiconductor. We give a parameter--free interpretation of concepts like bleaching, photo--induced absorption and stimulated emission, beyond the Fermi golden rule. We also introduce the concept of optical gap renormalization, as a...

  9. Effect of ultrasonic homogenization on the Vis/NIR bulk optical properties of milk.

    Science.gov (United States)

    Aernouts, Ben; Van Beers, Robbe; Watté, Rodrigo; Huybrechts, Tjebbe; Jordens, Jeroen; Vermeulen, Daniel; Van Gerven, Tom; Lammertyn, Jeroen; Saeys, Wouter

    2015-02-01

    The size of colloidal particles in food products has a considerable impact on the product's physicochemical, functional and sensory characteristics. Measurement techniques to monitor the size of suspended particles could, therefore, help to further reduce the variability in production processes and promote the development of new food products with improved properties. Visible and near-infrared (Vis/NIR) spectroscopy is already widely used to measure the composition of agricultural and food products. However, this technology can also be consulted to acquire microstructure-related scattering properties of food products. In this study, the effect of the fat globule size on the Vis/NIR bulk scattering properties of milk was investigated. Variability in fat globule size distribution was created using ultrasonic homogenization of raw milk. Reduction of the fat globule size resulted in a higher wavelength-dependency of both the Vis/NIR bulk scattering coefficient and the scattering anisotropy factor. Moreover, the anisotropy factor and the bulk scattering coefficients for wavelengths above 600 nm were reduced and were dominated by Rayleigh scattering. Additionally, the bulk scattering properties could be well (R(2) ≥ 0.990) estimated from measured particle size distributions by consulting an algorithm based on the Mie solution. Future research could aim at the inversion of this model to estimate the particle size distributions from Vis/NIR spectroscopic measurements.

  10. Bulk growth, structure, optical properties and laser damage threshold of organic nonlinear optical crystals of Imidazolium L-Ascorbate

    Science.gov (United States)

    Saripalli, Ravi Kiran; Bhat, H. L.; Elizabeth, Suja

    2016-09-01

    Bulk, transparent organic nonlinear optical (NLO) single-crystals of imidazolium L-Ascorbate (ImLA) were grown using slow-evaporation. Crystal structure was determined by single crystal X-ray diffraction analysis. Preliminary linear optical measurements through UV-Visible and infrared spectroscopy revealed good optical transmittance and a low near-UV cutoff wavelength at 256 nm. Kurtz and Perry powder test revealed that ImLA is a phase-matchable NLO material with a second harmonic generation (SHG) efficiency of 1.2 times larger than that of standard KH2PO4 (KDP). Laser damage thresholds were determined for ImLA.

  11. Impact of Bulk Aggregation on the Electronic Structure of Streptocyanines: Implications for the Solid-State Nonlinear Optical Properties and All-Optical Switching Applications

    KAUST Repository

    Gieseking, Rebecca L.

    2014-10-16

    Polymethine dyes in dilute solutions show many of the electronic and optical properties required for all-optical switching applications. However, in the form of thin films, their aggregation and interactions with counterions do generally strongly limit their utility. Here, we present a theoretical approach combining molecular-dynamics simulations and quantum-chemical calculations to describe the bulk molecular packing of streptocyanines (taken as representative of simple polymethines) with counterions of different hardness (Cl and BPh4 ) and understand the impact on the optical properties. The accuracy of the force field we use is verified by reproducing experimental crystal parameters as well as the configurations of polymethine/counterion complexes obtained from electronic-structure calculations. The aggregation characteristics can be understood in terms of both polymethinecounterion and polymethinepolymethine interactions. The counterions are found to localize near one end of the streptocyanine backbones, and the streptocyanines form a broad range of aggregates with significant electronic couplings between neighboring molecules. As a consequence, the linear and nonlinear optical properties are substantially modified in the bulk. By providing an understanding of the relationship between the molecular interactions and the bulk optical properties, our results point to a clear strategy for designing polymethine and counterion molecular structures and optimizing the materials properties for all-optical switching applications.

  12. Ab-initio investigation of structural, electronic and optical properties BSb compound in bulk and surface (110 states

    Directory of Open Access Journals (Sweden)

    H A Badehian

    2015-07-01

    Full Text Available In recent work the structural, electronic and optical properties of BSb compound in bulk and surface (110 states have been studied. Calculations have been performed using Full-Potential Augmented Plane Wave (FP-LAPW method by WIEN2k code in Density Functional Theory (DFT framework. The structural properties of the bulk such as lattice constant, bulk module and elastic constants have been investigated using four different approximations. The band gap energy of the bulk and the (110 surface of BSb were obtained about 1.082 and 0.38 eV respectively. Moreover the surface energy, the work function, the surface relaxation, surface state and the band structure of BSb (110 were investigated using symmetric and stoichiometric 15 layers slabs with the vacuum of 20 Bohr. In addition, the real and imaginary parts of the dielectric function of the bulk and the BSb (110 slab were calculated and compared to each other. Our obtained results have a good agreement with the available results.

  13. Potential of a spectroscopic measurement method using adding-doubling to retrieve the bulk optical properties of dense microalgal media.

    Science.gov (United States)

    Bellini, Sarah; Bendoula, Ryad; Latrille, Eric; Roger, Jean-Michel

    2014-01-01

    In the context of algal mass cultivation, current techniques used for the characterization of algal cells require time-consuming sample preparation and a large amount of costly, standard instrumentation. As the physical and chemical properties of the algal cells strongly affect their optical properties, the optical characterization is seen as a promising method to provide an early diagnosis in the context of mass cultivation monitoring. This article explores the potential of a spectroscopic measurement method coupled with the inversion of the radiative transfer theory for the retrieval of the bulk optical properties of dense algal samples. Total transmittance and total reflectance measurements were performed over the 380-1020 nm range on dense algal samples with a double integrating sphere setup. The bulk absorption and scattering coefficients were thus extracted over the 380-1020 nm range by inverting the radiative transfer theory using inverse-adding-doubling computations. The experimental results are presented and discussed; the configuration of the optical setup remains a critical point. The absorption coefficients obtained for the four samples of this study appear not to be more informative about pigment composition than would be classical methods in analytical spectroscopy; however, there is a real added value in measuring the reduced scattering coefficient, as it appears to be strongly correlated to the size distribution of the algal cells.

  14. Tuning Optical Properties of MoS2 Bulk and Monolayer Under Compressive and Tensile Strain: A First Principles Study

    Science.gov (United States)

    Kafi, Fariba; Pilevar Shahri, Raheleh; Benam, Mohammad Reza; Akhtar, Arsalan

    2017-06-01

    Knowledge of the optical properties under compressive and tensile strain is highly important in photoelectron devices and the semiconductor industry. In this work, optical properties of bulk and monolayer MoS2 under compressive and tensile strains are investigated by means of density functional theory. The dielectric tensor is derived within the random phase approximation. Calculations indicate that unstrained two-dimensional and bulk MoS2 lead to semiconductors with the gaps of 1.64 eV and 0.84 eV, respectively, whereas the change in the value of the gap by applying tensile or compressive strain depends on the nature of strains. Dielectric function, absorption coefficient, reflectivity, energy loss and the refraction index of the strained and unstrained systems are studied for both parallel (E||x) and perpendicular (E||z) applied electric field polarizations, which are very sensitive to the type and amount of strains. For instance, the reflectivity of a MoS2 monolayer exposed to visible light in the E||z polarization direction, can be tuned from 4% to 10% by introducing strain. Finally, the Abbe number is calculated to characterize the dispersion of the materials under compressive and tensile strain. Bulk MoS2 for E||x shows the highest value of the Abbe number, which shrinks twenty times under the influence of compressive strain.

  15. Tuning Optical Properties of MoS2 Bulk and Monolayer Under Compressive and Tensile Strain: A First Principles Study

    Science.gov (United States)

    Kafi, Fariba; Pilevar Shahri, Raheleh; Benam, Mohammad Reza; Akhtar, Arsalan

    2017-10-01

    Knowledge of the optical properties under compressive and tensile strain is highly important in photoelectron devices and the semiconductor industry. In this work, optical properties of bulk and monolayer MoS2 under compressive and tensile strains are investigated by means of density functional theory. The dielectric tensor is derived within the random phase approximation. Calculations indicate that unstrained two-dimensional and bulk MoS2 lead to semiconductors with the gaps of 1.64 eV and 0.84 eV, respectively, whereas the change in the value of the gap by applying tensile or compressive strain depends on the nature of strains. Dielectric function, absorption coefficient, reflectivity, energy loss and the refraction index of the strained and unstrained systems are studied for both parallel ( E||x) and perpendicular ( E||z) applied electric field polarizations, which are very sensitive to the type and amount of strains. For instance, the reflectivity of a MoS2 monolayer exposed to visible light in the E||z polarization direction, can be tuned from 4% to 10% by introducing strain. Finally, the Abbe number is calculated to characterize the dispersion of the materials under compressive and tensile strain. Bulk MoS2 for E||x shows the highest value of the Abbe number, which shrinks twenty times under the influence of compressive strain.

  16. Comparison of Electronic and Optical Properties of GaN Monolayer and Bulk Structure: a First Principle Study

    Science.gov (United States)

    Imran, Muhammad; Hussain, Fayyaz; Rashid, Muhammad; Ullah, Hafeez; Sattar, Atif; Iqbal, Faisal; Ahmad, Ejaz

    2016-03-01

    The semiconducting two-dimensional (2D) architectures materials have potential applications in electronics and optics. The design and search of new 2D materials have attracted extensive attention recently. In this study, first principle calculation has been done on 2D gallium nitride (GaN) monolayer with respect to its formation and binding energies. The electronic and optical properties are also investigated. It is found that the single isolated GaN sheet is forming mainly ionic GaN bonds despite a slightly weaker GaN interaction as compared with its bulk counterpart. The dielectric constant value of 2D GaN is smaller as compared to 3D GaN due to less effective electronic screening effect in the layer, which is accompanied by lesser optical adsorption range and suggested to be a promising candidate in electronic and optoelectronic devices.

  17. Investigation of Electrical and Optical Properties of Bulk III-V Ternary Semiconductors

    Science.gov (United States)

    2009-03-01

    attained. [7] Many devices, such as optical amplifiers, superluminescent diodes , optoelectronic integrated circuits, IR diodes and detectors, field...desired for tunable lasers, semiconductor optical amplifiers, and superluminescent diodes which require very flat and wide gain spectrums. [8] In

  18. Electrodynamic balance measurements of thermodynamic, kinetic, and optical aerosol properties inaccessible to bulk methods

    Directory of Open Access Journals (Sweden)

    S. S. Steimer

    2015-06-01

    Full Text Available Measurements of a single, levitated particle in an electrodynamic balance are an established tool for deriving thermodynamic and material data such as density, refractive index and activities of components of an aqueous solution under supersaturated conditions, where bulk measurements are not possible. The retrieval relies on combining mass-to-charge data and size data from light scattering. Here, we use a combination of low- and high-resolution Mie resonance spectroscopy to obtain radius data, enabling an accurate size determination not only when the particle is in equilibrium, but also when it is out of equilibrium due to kinetic limitation of mass transport. With the data measured under non-equilibrium conditions, it is possible to retrieve the water diffusivity. A challenge is that the radius retrieval by comparing measured light scattering with Mie theory requires the knowledge of refractive index as a function of concentration. Here, we show an iterative retrieval of refractive index and size for compounds for which data cannot be obtained in the bulk either due to lack of sufficient amounts of sample or limited solubility. We demonstrate the measurement strategy and the retrieval of water activity, density, refractive index and water diffusivity for aqueous shikimic acid. Water diffusivity in concentrated shikimic acid decreases by 6 orders of magnitude at 250 K compared to that at room temperature.

  19. Electrodynamic balance measurements of thermodynamic, kinetic, and optical aerosol properties inaccessible to bulk methods

    Directory of Open Access Journals (Sweden)

    S. S. Steimer

    2015-01-01

    Full Text Available Measurements of a single, levitated particle in an electrodynamic balance are an established tool for deriving thermodynamic and material data such as density, refractive index and activities of components of an aqueous solution under supersaturated conditions, where bulk measurements are not possible. The retrieval relies on combining mass-to-charge data and size data from light scattering. Here, we use a combination of low- and high-resolution Mie resonance spectroscopy to obtain radius data, enabling an accurate size determination not only when the particle is in equilibrium, but also when it is out of equilibrium due to kinetic limitation of mass transport. With the data measured under non-equilibrium conditions, it is possible to retrieve the water diffusivity. A challenge is that the radius retrieval by comparing measured light scattering with Mie theory requires the knowledge of refractive index as a function of concentration. Here, we show an iterative retrieval of refractive index and size for compounds for which data cannot be obtained in the bulk either due to lack of sufficient amounts of sample or limited solubility. We demonstrate the measurement strategy and the retrieval of water activity, density, refractive index and water diffusivity for aqueous shikimic acid. Water diffusivity in concentrated shikimic acid decreases by 6 orders of magnitude at 250 K compared to that at room temperature.

  20. Electrical and Optical Properties of Bulk ZnO Single Crystal Grown by Flux Bridgman Method

    Institute of Scientific and Technical Information of China (English)

    LI Xin-Hua; XU Jia-Yue; JIN Min; SHEN Hui; LI Xiao-Min

    2006-01-01

    Zinc oxide (ZnO) single crystals are grown by the modified vertical Bridgman method using a PbF2 flux. Themaximum size of the as-grown ZnO crystal is about φ25 mm× 5mm. The transmittance of the as-grown ZnOcrystal is more than 70% in the range of 600-800nm and the optical band gap is estimated to be 3.21 eV. Thephotoluminescence spectrum indicates that the as-grown ZnO crystal has a very low concentration of nativedefects and is much closed to its stoichiometry. The electrical measurement exhibits that the ZnO crystal haslow electrical resistivity of 0.02394Ωcm-1 and a high carrier concentration of 2.10 × 1018 cm-3

  1. Optical absorption and scattering properties of bulk porcine muscle phantoms from interstitial radiance measurements in 650-900 nm range

    Science.gov (United States)

    Grabtchak, Serge; Montgomery, Logan G.; Whelan, William M.

    2014-05-01

    We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ˜4 cm in diameter and ˜3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths tissues and organs for interstitial optical interrogation.

  2. Nonlinear optical properties of bulk cuprous oxide using single beam Z-scan at 790 nm

    Energy Technology Data Exchange (ETDEWEB)

    Serna, J.; Rueda, E. [Grupo de Óptica y Fotónica, Instituto de Física, Universidad de Antioquia U de A, Calle 70 No. 52-21, Medellín (Colombia); García, H., E-mail: hgarcia@siue.edu [Department of Physics, Southern Illinois University, Edwardsville, Illinois 60026 (United States)

    2014-11-10

    The two-photon absorption (TPA) coefficient β and the nonlinear index of refraction n{sub 2} for bulk cuprous oxide (Cu{sub 2}O) direct gap semiconductor single crystal have been measured by using a balance-detection Z-scan single beam technique, with an excellent signal to noise ratio. Both coefficients were measured at 790 nm using a 65 fs laser pulse at a repetition rate of 90.9 MHz, generated by a Ti:Sapphire laser oscillator. The experimental values for β were explained by using a model that includes allowed-allowed, forbidden-allowed, and forbidden-forbidden transitions. It was found that the forbidden-forbidden transition is the dominant mechanism, which is consistent with the band structure of Cu{sub 2}O. The low value for β found in bulk, as compared with respect to thin film, is explained in terms of the structural change in thin films that result in opposite parities of the conduction and valence band. The n{sub 2} is also theoretically calculated by using the TPA dispersion curve and the Kramers-Kronig relations for nonlinear optics.

  3. Tailoring Magnetic Properties in Bulk Nanostructured Solids

    Science.gov (United States)

    Morales, Jason Rolando

    Important magnetic properties and behaviors such as coercivity, remanence, susceptibility, energy product, and exchange coupling can be tailored by controlling the grain size, composition, and density of bulk magnetic materials. At nanometric length scales the grain size plays an increasingly important role since magnetic domain behavior and grain boundary concentration determine bulk magnetic behavior. This has spurred a significant amount of work devoted to developing magnetic materials with nanometric features (thickness, grain/crystallite size, inclusions or shells) in 0D (powder), 1D (wires), and 2D (thin films) materials. Large 3D nanocrystalline materials are more suitable for many applications such as permanent magnets, magneto-optical Faraday isolators etc. Yet there are relatively few successful demonstrations of 3D magnetic materials with nanoscale influenced properties available in the literature. Making dense 3D bulk materials with magnetic nanocrystalline microstructures is a challenge because many traditional densification techniques (HIP, pressureless sintering, etc.) move the microstructure out of the "nano" regime during densification. This dissertation shows that the Current Activated Pressure Assisted Densification (CAPAD) method, also known as spark plasma sintering, can be used to create dense, bulk, magnetic, nanocrystalline solids with varied compositions suited to fit many applications. The results of my research will first show important implications for the use of CAPAD for the production of exchange-coupled nanocomposite magnets. Decreases in grain size were shown to have a significant role in increasing the magnitude of exchange bias. Second, preferentially ordered bulk magnetic materials were produced with highly anisotropic material properties. The ordered microstructure resulted in changing magnetic property magnitudes (ex. change in coercivity by almost 10x) depending on the relative orientation (0° vs. 90°) of an externally

  4. Recent results on bulk laser damage threshold of optical glasses

    Science.gov (United States)

    Jedamzik, Ralf; Elsmann, Frank

    2013-02-01

    Modern pulsed laser applications cover a broad range of wavelength, power and pulse widths. Beam guiding optics in laser systems do not only have specific requirements on the imaging quality but also have to withstand high laser power. The laser damage threshold of an optical component depends on the surface (polishing, coating ...) and also on the bulk material properties. Actual values of bulk laser damage thresholds, particularly at pulse lengths less than 1 nanosecond (1 ns), of optical glasses are rarely found in literature, except for fused silica, which is known as a key optical material for components in high power laser. However, fused silica is rather expensive and limited in optical properties. That is the reason why customers often ask for laser damage threshold data of optical glasses. Therefore, SCHOTT has started a project for the characterization of the bulk laser damage threshold of optical glasses at the wavelengths 532 nm and 1064 nm with pulse lengths in the nano- and pico-second range. Bulk and surface laser damage testing has been performed by the Laser Zentrum Hannover in Germany according to the S-on-1 test of DIN EN ISO 11254-2 / DIN EN ISO 21254.

  5. Bulk crystal growth, optical, mechanical and ferroelectric properties of new semiorganic nonlinear optical and piezoelectric Lithium nitrate monohydrate oxalate single crystal

    Science.gov (United States)

    Dalal, Jyoti; Kumar, Binay

    2016-01-01

    New semiorganic nonlinear optical single crystals of Lithium nitrate oxalate monohydrate (LNO) were grown by slow evaporation solution technique. Single crystal X-ray diffraction study indicated that LNO crystal belongs to the triclinic system with space group P1. Various functional groups present in the material were identified by FTIR and Raman analysis. UV-vis study showed the high transparency of crystals with a wide band gap 5.01 eV. Various Optical constants i.e. Urbach energy (Eu), extinction coefficient (K), refractive index, optical conductivity, electric susceptibility with real and imaginary parts of dielectric constant were calculated using the transmittance data which have applications in optoelectronic devices. A sharp emission peak was found at 438 nm in photoluminescence measurement, which revealed suitability of crystal for fabricating violet lasers. In dielectric studies, a peak has been observed at 33 °C which is due to ferroelectric to paraelectric phase transition. Piezoelectric charge coefficients (d33 = 9.2 pC/N and g33) have been calculated, which make it a suitable for piezoelectric devices applications. In ferroelectric studies, a saturated loop was found in which the values of coercive field and remnant polarization were found to be 2.18 kV/cm and 0.39 μC/cm2, respectively. Thermal behavior was studied by TGA and DSC studies. The relative SHG efficiency of LNO was found to be 1.2 times that of KDP crystal. In microhardness study, Meyer's index value was found to be 1.78 which revealed its soft nature. These optical, dielectric, piezoelectric, ferroelectric, mechanical and non-linear optical properties of grown crystal establish the usefulness of this material for optoelectronics, non-volatile memory and piezoelectric devices applications.

  6. Ultrafast dynamics in semiconductor optical amplifiers and all-optical processing: Bulk versus quantum dot devices

    DEFF Research Database (Denmark)

    Mørk, Jesper; Berg, Tommy Winther; Magnúsdóttir, Ingibjörg

    2003-01-01

    We discuss the dynamical properties of semiconductor optical amplifiers and the importance for all-optical signal processing. In particular, the dynamics of quantum dot amplifiers is considered and it is suggested that these may be operated at very high bit-rates without significant patterning...... effects, as opposed to quantum well or bulk devices....

  7. New optical technique for bulk magnetostriction measurement

    CERN Document Server

    Samata, H; Uchida, T; Abe, S

    2000-01-01

    A new optical technique was applied to the measurement of magnetostriction in bulk samples. This technique utilizes an optical fiber bundle, AC-modulated light and lock-in detection. Deformation of the sample is determined from the ratio of the incident and reflected light intensities. Noise due to the instability of the light source is eliminated by obtaining the ratio of the incident and reflected light intensities, and the noise caused in the detector circuit can be reduced by lock-in detection. The performance of this method was characterized with a series of measurements using a gold film and crystal disks of pure iron and nickel. This technique offers a resolution of 0.5 nm and is sensitive enough to measure magnetostriction as small as 5x10 sup - sup 7 in 1 mm thick samples.

  8. Optical properties of advanced materials

    CERN Document Server

    Kajikawa, Kotaro

    2013-01-01

    In the last decade, optically functionalized materials have developed rapidly, from bulk matters to structured forms. Now we have a rich variety of attractive advanced materials. They are applied to optical and electrical devices that support the information communication technology in the mid 21-th century. Accordingly, it is quite important to have a broad knowledge of the optical properties of advanced materials for students, scientists and engineers working in optics and related fields. This book is designed to teach fundamental optical properties of such advanced materials effectively. These materials have their own peculiarities which are very interesting in modern optical physics and also for applications because the concepts of optical properties are quite different from those in conventional optical materials. Hence each chapter starts to review the basic concepts of the materials briefly and proceeds to the practical use. The important topics covered in this book include:  quantum structures of sem...

  9. Optical sensors of bulk refractive index using optical fiber resonators

    Science.gov (United States)

    Eryürek, M.; Karadag, Y.; Ghafoor, M.; Bavili, N.; Cicek, K.; Kiraz, A.

    2017-05-01

    Optical fiber resonator (OFR) sensor is presented for bulk liquid refractive index (RI) sensing. The sensing mechanism relies on the spectral shifts of whispering gallery modes (WGMs) of OFRs which are excited using a tapered fiber. OFR liquid RI sensor is fully characterized using water solutions of ethanol and ethylene glycol (EG). A good agreement is achieved between the analytical calculations and experimental results for both TE and TM polarizations. The detection limit for bulk RI is calculated to be between 2.7 - 4.7 × 10-5 refractive index unit (RIU). The OFR sensor provides a robust, easy-to-fabricate and sensitive liquid refractive index sensor which can be employed in lab-on-a-chip applications.

  10. Optical properties of bulk semiconductors and graphene/boron nitride: the Bethe-Salpeter equation with derivative discontinuity-corrected density functional energies

    DEFF Research Database (Denmark)

    Yan, Jun; Jacobsen, Karsten W.; Thygesen, Kristian S.

    2012-01-01

    We present an efficient implementation of the Bethe-Salpeter equation (BSE) for optical properties of materials in the projector augmented wave method Grid-based projector-augmented wave method (GPAW). Single-particle energies and wave functions are obtained from the Gritsenko, Leeuwen, Lenthe...

  11. Electronic states and optical properties of GaAs/AlAs and GaAs/vacuum superlattices by the linear combination of bulk bands method

    Energy Technology Data Exchange (ETDEWEB)

    Botti, S.; Andreani, L. C.

    2001-06-15

    The linear combination of bulk bands method recently introduced by Wang, Franceschetti, and Zunger [Phys. Rev. Lett. >78, 2819 (1997)] is applied to a calculation of energy bands and optical constants of (GaAs){sub n}/(AlAs){sub n} and (GaAs){sub n}/(vacuum){sub n} (001) superlattices with n ranging from 4 to 20. Empirical pseudopotentials are used for the calculation of the bulk energy bands. Quantum-confinement-induced shifts of critical point energies are calculated and are found to be larger for the GaAs/vacuum system. The E{sub 1} peak in the absorption spectra has a blueshift and splits into two peaks for decreasing superlattice period; the E{sub 2} transition instead is found to be split for large-period GaAs/AlAs superlattices. The band contribution to linear birefringence of GaAs/AlAs superlattices is calculated and compared with recent experimental results of Sirenko [Phys. Rev. B >60, 8253 (1999)]. The frequency-dependent part reproduces the observed increase with decreasing superlattice period, while the calculated zero-frequency birefringence does not account for the experimental results and points to the importance of local-field effects.

  12. Production, Properties and Applications of Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    Tao Zhang; Akihisa Inoue

    2000-01-01

    A review is given of recent work concerned with the production method, the characteristic properties(1) Bulk amorphous system; (2) Mechanical and magnetic properties of bulkamorphous alloys; (3)application of bulk amorphous alloys.

  13. Calculated Bulk Properties of the Actinide Metals

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Andersen, O. K.; Johansson, B.

    1978-01-01

    Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spin-density scheme. The theory explains...... the variation of the atomic volume and the bulk modulus through the 5f series in terms of an increasing 5f binding up to plutonium followed by a sudden localisation (through complete spin polarisation) in americium...

  14. Calculated Bulk Properties of the Actinide Metals

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Andersen, O. K.; Johansson, B.

    1978-01-01

    Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spin-density scheme. The theory explains t...... the variation of the atomic volume and the bulk modulus through the 5f series in terms of an increasing 5f binding up to plutonium followed by a sudden localisation (through complete spin polarisation) in americium...

  15. Optical properties of bulk semiconductors and graphene/boron nitride: The Bethe-Salpeter equation with derivative discontinuity-corrected density functional energies

    Science.gov (United States)

    Yan, Jun; Jacobsen, Karsten W.; Thygesen, Kristian S.

    2012-07-01

    We present an efficient implementation of the Bethe-Salpeter equation (BSE) for optical properties of materials in the projector augmented wave method Grid-based projector-augmented wave method (GPAW). Single-particle energies and wave functions are obtained from the Gritsenko, Leeuwen, Lenthe, and Baerends potential [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.51.1944 51, 1944 (1995)] with the modifications from Kuisma [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.82.115106 82, 115106 (2010)] GLLBSC functional which explicitly includes the derivative discontinuity, is computationally inexpensive, and yields excellent fundamental gaps. Electron-hole interactions are included through the BSE using the statically screened interaction evaluated in the random phase approximation. For a representative set of semiconductors and insulators we find excellent agreement with experiments for the dielectric functions, onset of absorption, and lowest excitonic features. For the two-dimensional systems of graphene and hexagonal boron-nitride (h-BN) we find good agreement with previous many-body calculations. For the graphene/h-BN interface we find that the fundamental and optical gaps of the h-BN layer are reduced by 2.0 and 0.7 eV, respectively, compared to freestanding h-BN. This reduction is due to image charge screening which shows up in the GLLBSC calculation as a reduction (vanishing) of the derivative discontinuity.

  16. Optical Properties of Metals.

    Science.gov (United States)

    1983-07-15

    Elementary theory of the optical properties of solids in Advances in solid state physics, Vol. 15. Seitz, F.; Turnbull, D., ed. New York, NY: Academic Press... Properties of Solids (Academic Press, New York, 1972). 2. H.E. Bennett and J.M. Bennett, Optical Properties and Elec- tronic Structure of Metals and...34*. . . . . . . . . . . . | *.**,. ..ś . REFERENCES 1. There are many texts and review papers in this field. An excellent modern reference is F. Wooten, Optical

  17. Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties

    Science.gov (United States)

    Semaltianos, N. G.; Friedt, J.-M.; Chassagnon, R.; Moutarlier, V.; Blondeau-Patissier, V.; Combe, G.; Assoul, M.; Monteil, G.

    2016-05-01

    Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO2) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter in the range of 4.3-5.3 nm. Nanoparticles synthesized in DI water have band gaps of 5.6 and 5.4 eV, in ethanol 5.72 and 5.65 eV (using low and high pulse energy), and in toluene 3 eV. The values for the relative permittivity in the range of 7.74-8.90 were measured for hafnia nanoparticles' thin films deposited on substrates by drop-casting (self-assembled layers) in parallel plate capacitor structures.

  18. Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Semaltianos, N. G., E-mail: nsemaltianos@yahoo.com [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Friedt, J.-M.; Blondeau-Patissier, V.; Combe, G. [Dépt. Temps-Fréquence, Femto-st, UMR CNRS 6174, Université de Franche-Comté, Besançon 25030 (France); Chassagnon, R. [Laboratoire Interdisciplinaire Carnot De Bourgogne, ICB UMR CNRS 6303, Université de Bourgogne Franche-Comté, Dijon 21078 (France); Moutarlier, V. [UTINAM, UMR CNRS 6213, Université de Franche-Comté, Besançon 25030 (France); Assoul, M.; Monteil, G. [Dépt. Mécanique Appliquée, Femto-st, UMR CNRS 6174, Université de Franche-Comté, Besançon 25030 (France)

    2016-05-28

    Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO{sub 2}) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter in the range of 4.3–5.3 nm. Nanoparticles synthesized in DI water have band gaps of 5.6 and 5.4 eV, in ethanol 5.72 and 5.65 eV (using low and high pulse energy), and in toluene 3 eV. The values for the relative permittivity in the range of 7.74–8.90 were measured for hafnia nanoparticles' thin films deposited on substrates by drop-casting (self-assembled layers) in parallel plate capacitor structures.

  19. Optical hyperpolarization of nitrogen donor spins in bulk diamond

    Science.gov (United States)

    Loretz, M.; Takahashi, H.; Segawa, T. F.; Boss, J. M.; Degen, C. L.

    2017-02-01

    We report hyperpolarization of the electronic spins associated with substitutional nitrogen defects in bulk diamond crystals. Hyperpolarization is achieved by optical pumping of nitrogen vacancy centers followed by rapid cross relaxation at the energy level matching condition in a 51 mT bias field. The maximum observed donor spin polarization is 0.9 % , corresponding to an enhancement of 25 compared to the thermal Boltzmann polarization. A further accumulation of polarization is impeded by an anomalous optical saturation effect that we attribute to charge state conversion processes. Hyperpolarized nitrogen donors may form a useful resource for increasing the efficiency of diamond-based dynamic nuclear polarization devices.

  20. Optical properties of solids

    CERN Document Server

    Wooten, Frederick

    1972-01-01

    Optical Properties of Solids covers the important concepts of intrinsic optical properties and photoelectric emission. The book starts by providing an introduction to the fundamental optical spectra of solids. The text then discusses Maxwell's equations and the dielectric function; absorption and dispersion; and the theory of free-electron metals. The quantum mechanical theory of direct and indirect transitions between bands; the applications of dispersion relations; and the derivation of an expression for the dielectric function in the self-consistent field approximation are also encompassed.

  1. Effect of wavelengths and excitation density on the optical properties of P3HT: SiNWs bulk heterojunction for photovoltaic applications

    Science.gov (United States)

    Hidouri, T.; Saidi, H.; Amri, C.; Saidi, F.; Bouazizi, A.

    2016-09-01

    In this work, hybrid nano-composite based on poly (3-hexylthiophène) P3HT and silicon nanowires (SiNWs) were prepared by Ag-assisted chemical etching method (MACE) on n-type (100) Si substrate. We study the influence of the power and wavelength excitation on photoluminescence (PL) properties. We note that charge transfer between poly (3-hexylthiophène) and SiNWs is more pronounced using an excitation of 488 nm than 514 nm. This result correlates with the penetration depth found. Luminescence keys as function of excitation density proves an explication of the charge behavior in hybrid structure. A red shift of the PL peak was noted with increasing the excitation density for 488 nm and 514 nm excitation due to the confinement effect.

  2. Optical characteristics of wet-thermally oxidized bulk and nanoporous GaN

    Science.gov (United States)

    Kim, Sinjae; Kadam, Mahadev; Kang, Jin-Ho; Ryu, Sang-Wan

    2016-09-01

    Gallium nitride (GaN) films deposited on sapphire substrates by metal organic chemical vapor deposition were successfully transformed into bulk and nanoporous gallium oxide (Ga2O3) using a wet thermal oxidation technique. Oxidation depth measurements confirmed that the oxide growth appeared to be faster in the case of nanoporous GaN than that of bulk GaN. Spectroscopic ellipsometry was used to evaluate and compare the optical properties of nanoporous and bulk Ga2O3 films, such as refractive index and extinction coefficient, which revealed improved optical properties for nanoporous Ga2O3 compared to the bulk. The simulations conducted on the ellipsometric spectra for bulk and nanoporous Ga2O3 using the Forouhi-Bloomer model and the Bruggeman effective medium approximation revealed the best fit with a low mean square error value. In the case of nanoporous Ga2O3, zero absorption was observed in the wavelength range of 300 nm to 840 nm, supporting the use of this material as a transparent coating in optoelectronic devices.

  3. Thermodynamic properties of bulk and confined water

    Energy Technology Data Exchange (ETDEWEB)

    Mallamace, Francesco, E-mail: francesco.mallamace@unime.it [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienza della Terra Università di Messina and CNISM, I-98168 Messina (Italy); Mallamace, Domenico [Dipartimento di Scienze dell' Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Università di Messina, I-98166 Messina (Italy); Vasi, Sebastiano; Vasi, Cirino [IPCF-CNR, I-98166 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States)

    2014-11-14

    The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T{sub L} ≃ 225 K). The second, T{sup *} ∼ 315 ± 5 K, is a special locus of the isothermal compressibility K{sub T}(T, P) and the thermal expansion coefficient α{sub P}(T, P) in the P–T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T{sub L}) and the onset of the unfolding process (T{sup *})

  4. Properties of Bulk Sintered Silver As a Function of Porosity

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A [ORNL; Vuono, Daniel J [ORNL; Wang, Hsin [ORNL; Ferber, Mattison K [ORNL; Liang, Zhenxian [ORNL

    2012-06-01

    This report summarizes a study where various properties of bulk-sintered silver were investigated over a range of porosity. This work was conducted within the National Transportation Research Center's Power Device Packaging project that is part of the DOE Vehicle Technologies Advanced Power Electronics and Electric Motors Program. Sintered silver, as an interconnect material in power electronics, inherently has porosity in its produced structure because of the way it is made. Therefore, interest existed in this study to examine if that porosity affected electrical properties, thermal properties, and mechanical properties because any dependencies could affect the intended function (e.g., thermal transfer, mechanical stress relief, etc.) or reliability of that interconnect layer and alter how its performance is modeled. Disks of bulk-sintered silver were fabricated using different starting silver pastes and different sintering conditions to promote different amounts of porosity. Test coupons were harvested out of the disks to measure electrical resistivity and electrical conductivity, thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and yield stress. The authors fully recognize that the microstructure of processed bulk silver coupons may indeed not be identical to the microstructure produced in thin (20-50 microns) layers of sintered silver. However, measuring these same properties with such a thin actual structure is very difficult, requires very specialized specimen preparation and unique testing instrumentation, is expensive, and has experimental shortfalls of its own, so the authors concluded that the herein measured responses using processed bulk sintered silver coupons would be sufficient to determine acceptable values of those properties. Almost all the investigated properties of bulk sintered silver changed with porosity content within a range of 3-38% porosity. Electrical resistivity, electrical conductivity

  5. Optical find of hypersonic surface acoustic waves in bulk transparent materials

    Science.gov (United States)

    Jiménez Riobóo, Rafael J.; Sánchez-Sánchez, Alberto; Prieto, Carlos

    2016-07-01

    It is shown that direct information from surface acoustic waves (SAWs) of bulk transparent materials can be obtained by using Brillouin light scattering (BLS). The study of surface phonons by means of an optical spectroscopy such as BLS has been historically constrained to nontransparent and highly reflecting bulk and film samples or even to very thin films deposited on reflecting substrates. Probably due to its low signal and to the narrow window in experimental conditions, it was assumed for years that bulk transparent samples were not suited for Brillouin spectroscopy in order to get information on SAWs, negating this optical technique in the search for SAW properties. The reported experiments on transparent glasses and single crystals (cubic MgO and trigonal sapphire) prove that there is no intrinsic physical reason not to collect SAW propagation velocity data from transparent bulk samples and opens a challenge to apply the Brillouin spectroscopy in a wider scenario to obtain direct information, in a nondestructive and contactless way, about SAWs in bulk materials.

  6. Determination of thermal properties of composting bulking materials.

    Science.gov (United States)

    Ahn, H K; Sauer, T J; Richard, T L; Glanville, T D

    2009-09-01

    Thermal properties of compost bulking materials affect temperature and biodegradation during the composting process. Well determined thermal properties of compost feedstocks will therefore contribute to practical thermodynamic approaches. Thermal conductivity, thermal diffusivity, and volumetric heat capacity of 12 compost bulking materials were determined in this study. Thermal properties were determined at varying bulk densities (1, 1.3, 1.7, 2.5, and 5 times uncompacted bulk density), particle sizes (ground and bulk), and water contents (0, 20, 50, 80% of water holding capacity and saturated condition). For the water content at 80% of water holding capacity, saw dust, soil compost blend, beef manure, and turkey litter showed the highest thermal conductivity (K) and volumetric heat capacity (C) (K: 0.12-0.81 W/m degrees C and C: 1.36-4.08 MJ/m(3) degrees C). Silage showed medium values at the same water content (K: 0.09-0.47 W/m degrees C and C: 0.93-3.09 MJ/m(3) degrees C). Wheat straw, oat straw, soybean straw, cornstalks, alfalfa hay, and wood shavings produced the lowest K and C values (K: 0.03-0.30 W/m degrees C and C: 0.26-3.45 MJ/m(3) degrees C). Thermal conductivity and volumetric heat capacity showed a linear relationship with moisture content and bulk density, while thermal diffusivity showed a nonlinear relationship. Since the water, air, and solid materials have their own specific thermal property values, thermal properties of compost bulking materials vary with the rate of those three components by changing water content, bulk density, and particle size. The degree of saturation was used to represent the interaction between volumes of water, air, and solids under the various combinations of moisture content, bulk density, and particle size. The first order regression models developed in this paper represent the relationship between degree of saturation and volumetric heat capacity (r=0.95-0.99) and thermal conductivity (r=0.84-0.99) well. Improved

  7. Optical properties of nanoparticles

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    At the NBI I am involved in projects relating to optical properties of metallic nanoparticles in particular with respect to plasmonic heating with direct applications to photothermal cancer therapy. For this purpose we have developed heating assays that can be used to measure the heating of any...... nanoscopic heat source like an irradiated nanoparticle...

  8. Noise and saturation properties of semiconductor quantum dot optical amplifiers

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2002-01-01

    We present a detailed theoretical analysis of quantum dot optical amplifiers. Due to the presence of a reservoir of wetting layer states, the saturation and noise properties differ markedly from bulk or QW amplifiers and may be significantly improved.......We present a detailed theoretical analysis of quantum dot optical amplifiers. Due to the presence of a reservoir of wetting layer states, the saturation and noise properties differ markedly from bulk or QW amplifiers and may be significantly improved....

  9. Optical cleaning owing to the bulk photovoltaic effect

    Science.gov (United States)

    Sturman, B.; Kösters, M.; Haertle, D.; Becher, C.; Buse, K.

    2009-12-01

    It is shown within the conventional photovoltaic charge-transport model that photoexcitable electrons, localized at deep impurity levels, can be effectively removed by light from the exposed area at sufficiently high temperatures. This allows to modify strongly the absorption and photoelectric properties of the material and, in particular, to suppress “optical damage” in LiNbO3 and LiTaO3 crystals. This optical cleaning method is applicable to numerous pyro- and piezo-electric optical materials. It employs the photovoltaic drift of electrons and ionic charge compensation at elevated temperatures. The physics of the optical cleaning is very rich; it has strong links to nonlinear dynamics and offers important handles for improvement of the cleaning performance. The use of properly moving light beams leads, e.g., to a strong enhancement of the cleaning rate and allows to reduce the electron concentration by several orders of magnitude. The theoretical predictions are supported by the data of our cleaning experiments with LiNbO3 crystals. In particular, the intensity threshold of optical damage is increased by three orders of magnitude.

  10. Universal properties of bulk viscosity near the QCD phase transition

    CERN Document Server

    Karsch, F; Tuchin, K

    2008-01-01

    We extract the bulk viscosity of hot quark-gluon matter in the presence of light quarks from the recent lattice data on the QCD equation of state. For that purpose we extend the sum rule analysis by including the contribution of light quarks. We also discuss the universal properties of bulk viscosity in the vicinity of a second order phase transition, as it might occur in the chiral limit of QCD at fixed strange quark mass and most likely does occur in two-flavor QCD. We point out that a chiral transition in the O(4) universality class at zero baryon density as well as the transition at the chiral critical point which belongs to the Z(2) universality class both lead to the critical behavior of bulk viscosity. In particular, the latter universality class implies the divergence of the bulk viscosity, which may be used as a signature of the critical point. We discuss the physical picture behind the dramatic increase of bulk viscosity seen in our analysis, and devise possible experimental tests of related phenome...

  11. Optical properties of stanene

    Science.gov (United States)

    Pratap Chaudhary, Raghvendra; Saxena, Sumit; Shukla, Shobha

    2016-12-01

    Successful synthesis of graphene has created a runaway effect in the exploration of other similar two-dimensional materials. These materials are important as they provide large surface areas and have led to the exploration of new physical phenomena. Even though graphene has exotic electronic properties, its spin-orbit coupling is very weak. Tin, being one of the heaviest elements in this group, is expected to have enhanced spin-orbit coupling in addition to other exotic properties of graphene. Here we report optical signatures of free standing stanene obtained using UV-vis absorption spectroscopy. Raman measurements were performed on a transmission electron microscope (TEM) grid. Interlayer spacing, phonon frequencies and the imaginary part of the complex dielectric function obtained using first principles methods are in good agreement with the experimental data. Occurrence of parallel bands suggests the possibility of the presence of excitonic effects in stanene.

  12. Facile synthesis of tin phosphite nanosheets via exfoliated bulk crystals: Electronic structure and piezoelectric property.

    Science.gov (United States)

    Song, Jun-Ling; Zhang, Xi-Rui; Lu, Rui-Feng

    2016-08-01

    Tin phosphite nanosheets were synthesized by a facile exfoliation method. SnHPO3 nanosheets with a thickness of ∼2.6nm readily form a stable colloidal suspension in ethanol using ultrasonic method. Structures and optical properties of the obtained nanosheets were investigated. The prepared SnHPO3 nanosheets exhibit an obvious blue-shift in UV absorbance compared with bulk SnHPO3 crystal materials. Moreover, the piezoelectric coefficients of SnHPO3 monolayer were calculated based on density functional theory, which are larger than that of h-BN monolayer, indicating this material could be a good candidate for designing electro-optical nano-devices.

  13. Bulk amorphous metallic alloys: Synthesis by fluxing techniques and properties

    Energy Technology Data Exchange (ETDEWEB)

    He, Yi; Shen, Tongde; Schwarz, R.B.

    1997-05-01

    Bulk amorphous alloys having dimensions of at least 1 cm diameter have been prepared in the Pd-Ni-P, Pd-Cu-P, Pd-Cu-Ni-P, and Pd-Ni-Fe-P systems using a fluxing and water quenching technique. The compositions for bulk glass formation have been determined in these systems. For these bulk metallic glasses, the difference between the crystallization temperature T{sub x}, and the glass transition temperature T{sub g}, {Delta}T = T{sub x} - T{sub g}, ranges from 60 to 1 10 K. These large values of {Delta}T open the possibility for the fabrication of amorphous near net-shape components using techniques such as injection molding. The thermal, elastic, and magnetic properties of these alloys have been studied, and we have found that bulk amorphous Pd{sub 40}Ni{sub 22.5}Fe{sub 17.5}P{sub 20} has spin glass behavior for temperatures below 30 K. 65 refs., 14 figs., 3 tabs.

  14. Fiber-optic tunable multiwavelength variable attenuator and routing module designs that use bulk acousto-optics.

    Science.gov (United States)

    Riza, Nabeel A; Mughal, M Junaid

    2005-02-10

    A compact fiber-coupled bulk acousto-optical multiwavelength variable optical attenuator module design that uses a retroreflective double-pass geometry within a single bulk acousto-optic tunable filter device is presented. The proposed attenuator module demonstrates a high 17-dB notch dynamic range at a low 100-mW drive power and uses a single bulk collinear-interaction acousto-optic tunable-filter device. Experiments show a low (design is extended to allow for efficient architectures for routing modules such as agile drop filters, analog hitless tap filters, and digital add-drop switches.

  15. Soy protein isolate molecular level contributions to bulk adhesive properties

    Science.gov (United States)

    Shera, Jeanne Norton

    Increasing environmental awareness and the recognized health hazards of formaldehyde-based resins has prompted a strong demand for environmentally-responsible adhesives for wood composites. Soy protein-based adhesives have been shown to be commercially viable with 90-day shelf stability and composite physical properties comparable to those of commercial formaldehyde-based particleboards. The main research focus is to isolate and characterize the molecular level features in soy protein isolate responsible for providing mechanical properties, storage stability, and water resistance during adhesive formulation, processing, and wood composite fabrication. Commercial composite board will be reviewed to enhance our understanding of the individual components and processes required for particleboard production. The levels of protein structure will be defined and an overview of current bio-based technology will be presented. In the process, the logic for utilizing soy protein as a sole binder in the adhesive will be reinforced. Variables such as adhesive components, pH, divalent ions, blend aging, protein molecular weight, formulation solids content, and soy protein functionalization will relate the bulk properties of soy protein adhesives to the molecular configuration of the soybean protein. This work has demonstrated that when intermolecular beta-sheet interactions and protein long-range order is disrupted, viscosity and mechanical properties decrease. Storage stability can be maintained through the stabilization of intermolecular beta-sheet interactions. When molecular weight is reduced through enzymatic digestion, long-range order is disrupted and viscosity and mechanical properties decrease accordingly. Processibility and physical properties must be balanced to increase solids while maintaining low viscosity, desirable mechanical properties, and adequate storage stability. The structure of the soybean protein must be related to the particleboard bulk mechanical

  16. Bulk Viscous Matter-dominated Universes: Asymptotic Properties

    CERN Document Server

    Avelino, Arturo; Gonzalez, Tame; Nucamendi, Ulises; Quiros, Israel

    2013-01-01

    By means of a combined study of the type Ia supernovae test,together with a study of the asymptotic properties in the equivalent phase space -- through the use of the dynamical systems tools -- we demonstrate that the bulk viscous matter-dominated scenario is not a good model to explain the accepted cosmological paradigm, at least, under the parametrization of bulk viscosity considered in this paper. The main objection against such scenarios is the absence of conventional radiation and matter-dominated critical points in the phase space of the model. This entails that radiation and matter dominance are not generic solutions of the cosmological equations, so that these stages can be implemented only by means of very particular solutions. Such a behavior is in marked contradiction with the accepted cosmological paradigm which requires of an earlier stage dominated by relativistic species, followed by a period of conventional non-relativistic matter domination, during which the cosmic structure we see was formed...

  17. Tissue Papers in Turkey and Some Physical and Optical Properties

    Directory of Open Access Journals (Sweden)

    Ahmet TUTUŞ

    2016-04-01

    Full Text Available The objective of study was to determine some properties of tissue papers and identify the position in Turkey. Napkins, toilet papers and paper towels used in this study were supplied from 5 different companies. Physical and optical properties of these papers were investigated and compared them to each other. Grammage, moisture content, crepe, bulk, density, tensile strength, thickness, water retention value and water absorption time were determined as physical properties and brightness and whiteness values were measured as optical properties. According to obtained results, the best results in physical and optical properties of napkins, toilet papers and paper towels belong to C, E and A Company, respectively.

  18. Bulk viscous matter-dominated Universes: asymptotic properties

    Energy Technology Data Exchange (ETDEWEB)

    Avelino, Arturo [Departamento de Física, Campus León, Universidad de Guanajuato, León, Guanajuato (Mexico); García-Salcedo, Ricardo [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada - Legaria del IPN, México D.F. (Mexico); Gonzalez, Tame [Departamento de Ingeniería Civil, División de Ingeniería, Universidad de Guanajuato, Guanajuato (Mexico); Nucamendi, Ulises [Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Ciudad Universitaria, CP. 58040 Morelia, Michoacán (Mexico); Quiros, Israel, E-mail: avelino@fisica.ugto.mx, E-mail: rigarcias@ipn.mx, E-mail: tamegc72@gmail.com, E-mail: ulises@ifm.umich.mx, E-mail: iquiros6403@gmail.com [Departamento de Matemáticas, Centro Universitario de Ciencias Exactas e Ingenierías (CUCEI), Corregidora 500 S.R., Universidad de Guadalajara, 44420 Guadalajara, Jalisco (Mexico)

    2013-08-01

    By means of a combined use of the type Ia supernovae and H(z) data tests, together with the study of the asymptotic properties in the equivalent phase space — through the use of the dynamical systems tools — we demonstrate that the bulk viscous matter-dominated scenario is not a good model to explain the accepted cosmological paradigm, at least, under the parametrization of bulk viscosity considered in this paper. The main objection against such scenarios is the absence of conventional radiation and matter-dominated critical points in the phase space of the model. This entails that radiation and matter dominance are not generic solutions of the cosmological equations, so that these stages can be implemented only by means of unique and very specific initial conditions, i. e., of very unstable particular solutions. Such a behavior is in marked contradiction with the accepted cosmological paradigm which requires of an earlier stage dominated by relativistic species, followed by a period of conventional non-relativistic matter domination, during which the cosmic structure we see was formed. Also, we found that the bulk viscosity is positive just until very late times in the cosmic evolution, around z < 1. For earlier epochs it is negative, been in tension with the local second law of thermodynamics.

  19. Limits on hadron spectrum from bulk medium properties

    CERN Document Server

    Broniowski, Wojciech

    2016-01-01

    We bring up the fact that the bulk thermal properties of the hadron gas, as measured on the lattice, preclude a very fast rising of the number of resonance states in the QCD spectrum, as assumed by the Hagedorn hypothesis, unless a substantial repulsion between hadronic resonances is present. If the Hagedorn growth continued above masses ~1.8 GeV, then the thermodynamic functions would noticeably depart from the measured lattice values at temperatures above 140 MeV, just below the transition temperature to quark-gluon plasma.

  20. The Metal-Hydrogen System Basic Bulk Properties

    CERN Document Server

    Fukai, Yuh

    2005-01-01

    Metal hydrides are of inestimable importance for the future of hydrogen energy. This unique monograph presents a clear and comprehensive description of the bulk properties of the metal-hydrogen system. The statistical thermodynamics is treated over a very wide range of pressure, temperature and composition. Another prominent feature of the book is its elucidation of the quantum mechanical behavior of interstitial hydrogen atoms, including their states and motion. The important topic of hydrogen interaction with lattice defects and its materials-science implications are also discussed thoroughly. This second edition has been substantially revised and updated.

  1. The influence of fibrous bed bulk density on the bed properties

    Directory of Open Access Journals (Sweden)

    Šećerov-Sokolović Radmila M.

    2003-01-01

    Full Text Available The mean properties of seven different fibrous materials and the properties of their different bed bulk densities were investigated. The morphology of the surface, size and geometry were measured by optical microscopy. The bed porosity was measured by the weighing method. The experimental bed permeability, in a high range of bulk density, was calculated from the values of the sanitary water pressure drop at a constant temperature of 15°C, since the data followed Darcy's law. The Reynolds number for a fibrous bed was calculated using a relation from the literature. The Reynolds number was less than 1 for all ranges of fluid velocity. Three empirical relations for fibrous bed permeability were used and compared with the experimental data. It was determined that the empirical data depended on the fiber diameter and fraction of solid in the bed. The relative error linearly increased with increasing fiber diameter.

  2. Bulk Universality and Related Properties of Hermitian Matrix Models

    CERN Document Server

    Pastur, L

    2007-01-01

    We give a new proof of universality properties in the bulk of spectrum of the hermitian matrix models, assuming that the potential that determines the model is globally $C^{2}$ and locally $C^{3}$ function (see Theorem \\ref{t:U.t1}). The proof as our previous proof in \\cite{Pa-Sh:97} is based on the orthogonal polynomial techniques but does not use asymptotics of orthogonal polynomials. Rather, we obtain the $sin$-kernel as a unique solution of a certain non-linear integro-differential equation that follows from the determinant formulas for the correlation functions of the model. We also give a simplified and strengthened version of paper \\cite{BPS:95} on the existence and properties of the limiting Normalized Counting Measure of eigenvalues. We use these results in the proof of universality and we believe that they are of independent interest.

  3. Optical properties of photochromic and thermochromic materials

    Science.gov (United States)

    Mo, Yeon-Gon

    The optical properties of some thin film materials can be altered by an external stimulus. Photochromic and thermochromic materials, including inorganic and organic substances, have optical properties that can be changed in a reversible manner by irradiation and temperature respectively. These materials can be used in applications such as radiation or thermal sensors, information storage devices and smart window applications in buildings and cars. In this work, major effort was concentrated on passive thermal control coatings based on photochromic and thermochromic materials. The inorganic photochromic materials were based on tungsten and molybdenum oxide films and the organic photochromic materials included spiropyrans and spirooxazines. In addition, photochromic composite organic-inorganic films and thermochromic vanadium oxide films were prepared. The samples were synthesized using sputtering, sol-gel process, and thermal oxidation. The optical properties were investigated for the first time by ultraviolet/visible/infrared (UV/VIS/IR) spectroscopic ellipsometry, attenuated total reflection (ATR) infrared ellipsometry, spectrophotometry, and X-ray diffraction (XRD). For amorphous oxide films, the oxygen deficiency was important in determining the photochromic properties of the films. In the mid-infrared region, no photochromism was observed for the films. The optical properties of organic-inorganic composite films changed in the VIS/NIR wavelength region markedly in a reversible process, with UV irradiation. The composite films containing tungsten heteropolyoxometalate (HPOM) showed faster coloration and bleaching than pure tungsten oxide films. The composite films with molybdenum HPOM showed faster coloration and much slower bleaching than tungsten HPOM. The spiropyran and spirooxazine doped polymeric films were investigated for the first time using infrared and ATR ellipsometry. The infrared optical functions obtained by ATR measurements were a little smaller

  4. From molecule to bulk material: optical properties of hydrogen-bonded dimers [C12H12N4O2AgPF6]2 and [C28H28N6O3AgPF6]2 depend on the arrangement of the oxime moieties.

    Science.gov (United States)

    Cheng, Wen-Dan; Wu, Dong-Sheng; Shen, Juan; Huang, Shu-Ping; Xie, Zhi; Zhang, Hao; Gong, Ya-Jing

    2007-01-01

    The dependence of the optical properties of [C(12)H(12)N(4)O(2)AgPF(6)](2) (dimer-1) and [C(28)H(28)N(6)O(3)AgPF(6)](2) (dimer-2) on the arrangement of the oxime moieties in the molecule and in bulk crystals was investigated by means of time-dependent density functional theory. Dimer-1 with simple pyridine oxime ligands and a wavy arrangement has a smaller dipole moment and larger transition energy between the two states, and thus smaller third-order polarizabilities and two-photon absorption cross sections. Dimer-2 with extended pyridine oxime ligands and a ladder arrangement has a larger dipole moment and smaller transition energy between the two states, and thus larger third-order polarizabilities and two-photon absorption cross sections. The lowest energy absorption band is red-shifted for dimer-2 as compared with dimer-1, due to more pronounced pi-pi delocalization interactions and weaker hydrogen bonding in dimer-2. The electronic absorption spectra, frequency-dependent third-order polarizabilities, and two-photon absorption cross sections involve significant contributions from charge transfers from pi/pi* orbitals of the pyridine oxime ligands but no contribution from PF(6) (-) ions or H(2)O molecules in the wavelength range studied for the monomers and dimers of the C(12)H(12)N(4)O(2)AgPF(6) and C(28)H(28)N(6)O(3)AgPF(6) molecules. The third-order susceptibilities and two-photon absorption coefficients of bulk solids were estimated on the basis of the optical properties of the corresponding dimers, and the bulk material constructed from dimer-2 has the larger optical parameters of the two.

  5. Quantum-Confined and Enhanced Optical Absorption of Colloidal PbS Quantum Dots at Wavelengths with Expected Bulk Behavior.

    Science.gov (United States)

    Debellis, Doriana; Gigli, Giuseppe; Ten Brinck, Stephanie; Infante, Ivan; Giansante, Carlo

    2017-02-08

    Nowadays it is well-accepted to attribute bulk-like optical absorption properties to colloidal PbS quantum dots (QDs) at wavelengths above 400 nm. This assumption permits to describe PbS QD light absorption by using bulk optical constants and to determine QD concentration in colloidal solutions from simple spectrophotometric measurements. Here we demonstrate that PbS QDs experience the quantum confinement regime across the entire near UV-vis-NIR spectral range, therefore also between 350 and 400 nm already proposed to be sufficiently far above the band gap to suppress quantum confinement. This effect is particularly relevant for small PbS QDs (with diameter of ≤4 nm) leading to absorption coefficients that largely differ from bulk values (up to ∼40% less). As a result of the broadband quantum confinement and of the high surface-to-volume ratio peculiar of nanocrystals, suitable surface chemical modification of PbS QDs is exploited to achieve a marked, size-dependent enhancement of the absorption coefficients compared to bulk values (up to ∼250%). We provide empirical relations to determine the absorption coefficients at 400 nm of as-synthesized and ligand-exchanged PbS QDs, accounting for the broadband quantum confinement and suggesting a heuristic approach to qualitatively predict the ligand effects on the optical absorption properties of PbS QDs. Our findings go beyond formalisms derived from Maxwell Garnett effective medium theory to describe QD optical properties and permit to spectrophotometrically calculate the concentration of PbS QD solutions avoiding underestimation due to deviations from the bulk. In perspective, we envisage the use of extended π-conjugated ligands bearing electronically active substituents to enhance light-harvesting in QD solids and suggest the inadequacy of the representation of ligands at the QD surface as mere electric dipoles.

  6. Mechanical and thermal properties of bulk ZrB2

    Science.gov (United States)

    Nakamori, Fumihiro; Ohishi, Yuji; Muta, Hiroaki; Kurosaki, Ken; Fukumoto, Ken-ichi; Yamanaka, Shinsuke

    2015-12-01

    ZrB2 appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B4C. Since ZrB2 has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB2, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB2 bulk sample with 93.1% theoretical density by sintering ZrB2 powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB2 by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13-23 GPa and 1.8-2.8 MPa m0.5, respectively. The relationships between these properties were carefully examined in the present study.

  7. Thermo-optical properties of embedded silver nanoparticles

    Science.gov (United States)

    Rashidi Huyeh, M.; Shirdel Havar, M.; Palpant, B.

    2012-11-01

    Thermo-optical properties of nanocomposite materials consisting of noble metal nanoparticles dispersed in a dielectric medium are appropriate for many applications as imaging, nonlinear optics, or optical monitoring of local thermal exchanges. Here, we analyze the thermo-optical response of silver nanoparticles. The contribution of inter- and intraband transitions to the thermo-optical index of bulk silver is first extracted using experimental results reported earlier in the literature. The influence of these two contributions on the thermo-optical properties of silver nanoparticles embedded in glass is then investigated. The results show that these properties are essentially due to the intraband thermo-optical contribution in the vicinity of the surface plasmon resonance of the nanoparticles, while they are dominated by the interband contribution close to the interband transition threshold.

  8. Measurements of optical parameters of phantom solution and bulk animal tissues ex vivo at 650 nm

    Science.gov (United States)

    Sun, Ping; Wang, Yu; Liu, Jian

    2008-12-01

    Optical parameters of biological tissues, including absorption coefficient (μa), reduced scattering coefficient (μs') or scattering coefficient (μs), anisotropy factor (g) and refractive index (n) are investigated extensively and systemically at wavelength of 650 nm. Intralipid solution was selected to be the tissue phantom in order to test the validity of measurements. Considering the factors of fiber orientation and haemoglobin content, we chose some fresh bulk animal tissues in vitro which were bovine adipose, bovine muscle, porcine adipose, porcine muscle, porcine kidney, porcine liver, mutton and chicken breast. The basic assumption is that in vitro samples are a reasonable representation of the in vivo situation. We have gained numbers of experimental data of Intralipid and some tissues. Particularly, we have set up the close relationships among six optical parameters involving μa, μs', μs, g, n and μt. The experimental results show that for animal tissues, μa, μs' or μs and n rely deeply on muscle fiber orientations. Both of μs and μt range from 10mm-1 to 20mm-1. μa ranges from 10-2 mm-1 to 10-3 mm-1 and g from 0.95 to 0.99. The results of this study will be helpful in further understanding of optical properties of tissues.

  9. Optical properties of polymer nanocomposites

    Indian Academy of Sciences (India)

    S Srivastava; M Haridas; J K Basu

    2008-06-01

    Nanomaterials have emerged as an area of interest motivated by potential applications of these materials in light emitting diodes, solar cells, polarizers, light – stable colour filters, optical sensors, optical data communication and optical data storage. Nanomaterials are of particular interest as they combine the properties of two or more different materials with the possibility of possessing novel mechanical, electronic or chemical behaviour. Understanding and tuning such effects could lead to hybrid devices based on these nanocomposites with improved optical properties. We have prepared polymer nanocomposites of well-defined compositions and studied the optical properties of powders and their thin films. UV-vis absorption spectroscopy on nanocomposite powders and spectroscopic ellipsometry measurements on thin films was used to study the effect of interfacial morphology, interparticle spacing and finite size effects on optical properties of nanocomposites. Systematic shift in the imaginary part of the dielectric function can be seen with variation in size and fraction of the gold nanoparticle. The thickness of the film also plays a significant role in the tunability of the optical spectra.

  10. Variability of structural and electronic properties of bulk and monolayer Si2Te3

    Science.gov (United States)

    Shen, X.; Puzyrev, Y. S.; Combs, C.; Pantelides, S. T.

    2016-09-01

    Silicon telluride has diverse properties for potential applications in Si-based devices ranging from fully integrated thermoelectrics to optoelectronics to chemical sensors. This material has a unique layered structure: it has a hexagonal closed-packed Te sublattice, with Si dimers occupying octahedral intercalation sites. Here, we report a theoretical study of this material in both bulk and monolayer form, unveiling an array of diverse properties arising from reorientations of the silicon dimers between planes of Te atoms. The band gap varies up to 30% depending on dimer orientations. The variation of dimer orientations gives rise to thermal contraction, arising from more dimers aligning out of the plane as the material is heated. Strain also affects the dimer orientations and provides a degree of control of the materials properties, making Si2Te3 a promising candidate for nanoscale mechanical, optical, and memristive devices.

  11. Optical Properties of Photonic Crystals

    CERN Document Server

    Sakoda, Kazuaki

    2005-01-01

    This is the first comprehensive textbook on the optical properties of photonic crystals. It deals not only with the properties of the radiation modes inside the crystals but also with their peculiar optical response to external fields. A general theory of linear and nonlinear optical response is developed in a clear and detailed fashion using the Green's function method. The symmetry of the eigenmodes is treated systematically using group theory to show how it affects the optical properties of photonic crystals. Important recent developments such as the enhancement of stimulated emission, second harmonic generation, quadrature-phase squeezing, and low-threshold lasing are also treated in detail and made understandable. Numerical methods are also emphasized. Thus this book provides both an introduction for graduate and undergraduate students and also key information for researchers in this field. This second edition has been updated and includes a new chapter on superfluorescence.

  12. Characterization of a-SiNx:H layer. Bulk properties, interface with Si and solar cell efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Lamers, M.; Weeber, A. [ECN Solar Energy, P.O. Box 1, 1755 ZG Petten (Netherlands); Butler, K.; Harding, J. [University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Vullum, P.E. [SINTEF, Box 4760 Sluppen, 7465 Trondheim (Norway)

    2013-04-15

    In this paper two front-side a-SiNx:H layers that can be used in the solar cell industry are extensively characterized and related to solar cell efficiency. Variations in layer build up, atomic density, optical properties, bulk passivation and surface passivation are discussed. The build up of these two layers are considered against a background of over 80 SiNx:H layers. These layers differ in stoichiometry, atomic content, optical properties and surface passivation, as the refractive index is varied between 1.8 and 3.0. Additionally, comparable data output of different characterization equipment is discussed on validity. On solar cells, the effect of different layer build up is investigated and it is found that a wide process window is allowed for similar cell efficiencies regarding the optical transmission, bulk and surface passivation.

  13. Optical far-field super-resolution microscopy using nitrogen vacancy center ensemble in bulk diamond

    OpenAIRE

    Li, Shen; Chen, Xiang-Dong; Zhao, Bo-Wen; Dong, Yang; Zou, Chong-Wen; Guo, Guang-Can; Sun, Fang-Wen

    2016-01-01

    We demonstrate an optical far-field super-resolution microscopy using array of nitrogen vacancy centers in bulk diamond as near-field optical probes. The local optical field, which transmits through the nanostructures on the diamond surface, is measured by detecting the charge state conversion of nitrogen vacancy center. And the locating of nitrogen vacancy center with spatial resolution of 6.1 nm is realized with the charge state depletion nanoscopy. The nanostructures on the surface of diam...

  14. Optical Properties of Fluorescent Dyes

    Institute of Scientific and Technical Information of China (English)

    李戎; 陈东辉

    2001-01-01

    Fluorescent dyes have been widely used these years.Because of the special optical performance, conventional CCM systems seem to be unable to predict the recipes of fabrics dyed with fluorescent dyes. In order to enhance the functions of CCM systems, the optical properties of fluorescent dyes in their absorption region were investigated. It has been found that there was a fixed maximum absorption wavelength for each fluorescent dyes whatever its concentration is. Both absorption region and maximum absorption wavelength of the dyes in solution are the same to those in fabric, and that the absorption is directly proportional to the concentration of the dye. So the optical properties obtained in solutions cna be applied for describing the optics performance of fluorescent dyes in fabrics.

  15. Bulk Mechanical Properties of Single Walled Carbon Nanotube Electrodes

    Science.gov (United States)

    Giarra, Matthew; Landi, Brian; Cress, Cory; Raffaelle, Ryne

    2007-03-01

    The unique properties of single walled carbon nanotubes (SWNTs) make them especially well suited for use as electrodes in power devices such as lithium ion batteries, hydrogen fuel cells, solar cells, and supercapacitors. The performances of such devices are expected to be influenced, at least in part, by the mechanical properties of the SWNTs used in composites or in stand alone ``papers.'' Therefore, the elastic moduli and ultimate tensile strengths of SWNT papers were measured as functions of temperature, SWNT purity, SWNT length, and SWNT bundling. The SWNTs used to produce the papers were synthesized in an alexandrite laser vaporization reactor at 1100^oC and purified using conventional acid-reflux conditions. Characterization of the SWNTs was performed using SEM, BET, TGA, and optical and Raman spectroscopy. The purified material was filtered and dried to yield papers of bundled SWNTs which were analyzed using dynamic mechanical analysis (DMA). It was observed that the mechanical properties of acid-refluxed SWNT papers were significantly improved by controlled thermal oxidation and strain-hardening. Elastic moduli of SWNT papers were measured between 3 and 6 GPa. Ultimate (breaking) tensile stresses were measured between 45 and 90 MPa at 1-3% strain. These results and their implications in regard to potential applications in power devices will be discussed.

  16. Optical properties of flyash

    Energy Technology Data Exchange (ETDEWEB)

    Self, S.A.

    1990-04-01

    In this research program, we have adopted the approach that by measuring fundamental properties (i.e, the complex refractive index, m) of the fly ash which participates in the radiation transfer, we can use well established theoretical principles (Mie theory) to compute the radiative properties of dispersions of fly ash as found in coal combustors. With this approach one can, understand the underlying principles that affect the radiative properties of an ash dispersion and more confidently predict how variations in the characteristics of the ash dispersion cause variations in its radiative properties. An important criterion in this approach is that the fly ash particles be spherical, homogeneous, and isotropic. Fortunately, fly ash particles are formed at high temperatures at which most of them are molten, leading primarily to spherical particles. Furthermore, one should expect that molten particles will be reasonably homogeneous and isotropic. On cooling, most fly ash particles form glassy spheres which are homogeneous and isotropic. Some ash particles form hollow shells (cenospheres) while others form as particles with bubbles'' or voids, but most fly ash particles are well approximated as homogeneous isotropic spheres. In the following sections we review some of the underlying principles that affect the radiative properties of fly ash dispersions and report on progress that has been made during the past quarter.

  17. Augmentation of the In Vivo Elastic Properties Measurement System to Include Bulk Properties

    Science.gov (United States)

    2014-09-30

    estimates based on measured displacement magnitudes. APPROACH The bulk properties measurement methods are intended to run concurrently with the...to better understand biomechanics of sound reception and production in cetaceans, and 2) to understand and hopefully mitigate any harmful effects of

  18. Nonlinear optical properties of semiconductor nanocrystals

    Science.gov (United States)

    Ricard, Gianpiero Banfi Vittorio Degiorgio Daniel

    1998-05-01

    This review is devoted to the description of recent experimental results concerning the nonlinear optical properties of semiconductor-doped glasses SDGs with particular emphasis on the regime in which the energy of the incident photon is smaller than the energy gap. A considerable theoretical and experimental effort has been devoted in the last 10years to the fundamental aspects of quantumconfined structures, which have properties somewhat intermediate between the bulk crystals and atoms or molecules. From this point of view, SDGs represent an easily available test system, and optical techniques have been a major diagnostic tool. Luminescence and absorption spectroscopy were extensively used to characterize the electronic states. The experiments aimed at the measurement of the real and imaginary parts of the third-order optical susceptibility of SDGs below the bandgap are described in some detail, and the results obtained with different techniques are compared. Besides the intrinsic fast nonlinearity due to bound electrons, SDGs may present a larger but much slower nonlinearity due to the free carriers generated by two-photon absorption. This implies that experiments have to be properly designed for separation of the two effects. In this article we stress the importance of a detailed structural characterization of the samples. Knowledge of the volume fraction occupied by the nanocrystals is necessary in order to derive from the experimental data the intrinsic nonlinearity and to compare it with the bulk nonlinearity. We discuss recent experiments in which the dependence of the intrinsic nonlinearity on the crystal size is derived by performing, on the samples, measurements of the real part and imaginary part of the nonlinear optical susceptibility and measurements of crystal size and volume fraction. Structural characterization is of interest also for a better understanding of the physical processes underlying the growth of crystallites in SDGs. The average size of

  19. Bulk and integrated acousto-optic spectrometers for radio astronomy

    Science.gov (United States)

    Chin, G.; Buhl, D.; Florez, J. M.

    1981-01-01

    The development of sensitive heterodyne receivers (front end) in the centimeter and millimeter range, and the construction of sensitive RF spectrometers (back end) enable the spectral lines of interstellar molecules to be detected and identified. A technique was developed which combines acoustic bending of a collimated coherent light beam by a Bragg cell followed by detection by a sensitive array of photodetectors (thus forming an RF acousto-optic spectrometer (AOS). An AOS has wide bandwidth, large number of channels, and high resolution, and is compact, lightweight, and energy efficient. The thrust of receiver development is towards high frequency heterodyne systems, particularly in the millimeter, submillimeter, far infrared, and 10 micron spectral ranges.

  20. Recent Advances in Optically Controlled Bulk Semiconductor Switches

    Science.gov (United States)

    1985-06-01

    REO!NT AIJifl,NCES IN (FTICALIX ~1Ra.LW IILK SHttiaHlOCIOR swrrams L. Bovino , T. Burke, R. Youmans, M. Weiner, J. Carter U.S. Ar~ Electronics...fabrication of all of our optically activated switches. B.e.fer.enc.es. 1. L. Bovino , R. Youmans, T. Burke, M.Weiner, "Modulator Circuits Using Q...tically Activated Switches", Record of 16th Power Modulator SYJll>o- siurn, pp 235-239, June 1984. 2. M. Weiner, T. Burke, R. Youmans, L. Bovino , J

  1. Existence of the transverse relaxation time in optically excited bulk semiconductors

    Institute of Scientific and Technical Information of China (English)

    Zhang Hai-Chao; Lin Wei-Zhu; Wang Yu-Zhu

    2006-01-01

    Two basic types of depolarization mechanisms,carrier-carrier (CC) and carrier-phonon (CP) scattering,are investigated in optically excited bulk semiconductors (3D),in which the existence of the transverse relaxation time is proven based on the vector property of the interband transition matrix elements.The dephasing rates for both CC and CP scattering are determined to be equal to one half of the total scattering-rate-integrals weighted by the factors (1-COSx),wherex are the scattering angles.Analytical expressions of the polarization dephasing due to CC scattering are established by using an uncertainty broadening approach,and analytical ones due to both the polar optical-phonon and non-polar deformation potential scattering (including inter-valley scattering) are also presented by using the sharp spectral functions in the dephasing rate calculations.These formulas,which reveal the trivial role of the Coulomb screening effect in the depolarization processes,are used to explain the experimental results at hand and provide a clear physical picture that is difficult to extract from numerical treatments.

  2. A robust and tuneable mid-infrared optical switch enabled by bulk Dirac fermions

    Science.gov (United States)

    Zhu, Chunhui; Wang, Fengqiu; Meng, Yafei; Yuan, Xiang; Xiu, Faxian; Luo, Hongyu; Wang, Yazhou; Li, Jianfeng; Lv, Xinjie; He, Liang; Xu, Yongbing; Liu, Junfeng; Zhang, Chao; Shi, Yi; Zhang, Rong; Zhu, Shining

    2017-01-01

    Pulsed lasers operating in the mid-infrared (3-20 μm) are important for a wide range of applications in sensing, spectroscopy, imaging and communications. Despite recent advances with mid-infrared gain platforms, the lack of a capable pulse generation mechanism remains a significant technological challenge. Here we show that bulk Dirac fermions in molecular beam epitaxy grown crystalline Cd3As2, a three-dimensional topological Dirac semimetal, constitutes an exceptional ultrafast optical switching mechanism for the mid-infrared. Significantly, we show robust and effective tuning of the scattering channels of Dirac fermions via an element doping approach, where photocarrier relaxation times are found flexibly controlled over an order of magnitude (from 8 ps to 800 fs at 4.5 μm). Our findings reveal the strong impact of Cr doping on ultrafast optical properties in Cd3As2 and open up the long sought parameter space crucial for the development of compact and high-performance mid-infrared ultrafast sources.

  3. Optical properties of geometrically optimized graphene quantum dots

    Science.gov (United States)

    Bugajny, Paweł; Szulakowska, Ludmiła; Jaworowski, Błazej; Potasz, Paweł

    2017-01-01

    We derive effective tight-binding model for geometrically optimized graphene quantum dots and based on it we investigate corresponding changes in their optical properties in comparison to ideal structures. We consider hexagonal and triangular dots with zigzag and armchair edges. Using density functional theory methods we show that displacement of lattice sites leads to changes in atomic distances and in consequence modifies their energy spectrum. We derive appropriate model within tight-binding method with edge-modified hopping integrals. Using group theoretical analysis, we determine allowed optical transitions and investigate oscillatory strength between bulk-bulk, bulk-edge and edge-edge transitions. We compare optical joint density of states for ideal and geometry optimized structures. We also investigate an enhanced effect of sites displacement which can be designed in artificial graphene-like nanostructures. A shift of absorption peaks is found for small structures, vanishing with increasing system size.

  4. Bulk and integrated acousto-optic spectrometers for molecular astronomy with heterodyne spectrometers

    Science.gov (United States)

    Chin, G.; Buhl, D.; Florez, J. M.

    1981-01-01

    A survey of acousto-optic spectrometers for molecular astronomy is presented, noting a technique of combining the acoustic bending of a collimated coherent light beam with a Bragg cell followed by an array of sensitive photodetectors. This acousto-optic spectrometer has a large bandwidth, a large number of channels, high resolution, and is energy efficient. Receiver development has concentrated on high-frequency heterodyne systems for the study of the chemical composition of the interstellar medium. RF spectrometers employing acousto-optic diffraction cells are described. Acousto-optic techniques have been suggested for applications to electronic warfare, electronic countermeasures and electronic support systems. Plans to use integrated optics for the further miniaturization of acousto-optic spectrometers are described. Bulk acousto-optic spectrometers with 300 MHz and 1 GHz bandwidths are being developed for use in the back-end of high-frequency heterodyne receivers for astronomical research.

  5. OPTICAL AND DYNAMIC PROPERTIES OF UNDOPED AND DOPED SEMICONDUCTOR NANOSTRUCTURES

    Energy Technology Data Exchange (ETDEWEB)

    Grant, C D; Zhang, J Z

    2007-09-28

    This chapter provides an overview of some recent research activities on the study of optical and dynamic properties of semiconductor nanomaterials. The emphasis is on unique aspects of these properties in nanostructures as compared to bulk materials. Linear, including absorption and luminescence, and nonlinear optical as well as dynamic properties of semiconductor nanoparticles are discussed with focus on their dependence on particle size, shape, and surface characteristics. Both doped and undoped semiconductor nanomaterials are highlighted and contrasted to illustrate the use of doping to effectively alter and probe nanomaterial properties. Some emerging applications of optical nanomaterials are discussed towards the end of the chapter, including solar energy conversion, optical sensing of chemicals and biochemicals, solid state lighting, photocatalysis, and photoelectrochemistry.

  6. Optical properties of sea ice in Liaodong Bay, China

    Science.gov (United States)

    Xu, Zhantang; Yang, Yuezhong; Wang, Guifen; Cao, Wenxi; Li, Zhijun; Sun, Zhaohua

    2012-03-01

    Many industrial, agricultural, and residential areas surrounding Liaodong Bay are responsible for much of the particulate matter (PM) and colored dissolved organic matter (CDOM) found in the sea ice in the bay. Understanding the optical properties of "dirty" sea ice is important for analyzing remote sensing data and calculating energy balances. We designed a hyperspectral radiation instrument to observe the optical properties of sea ice. The results show that albedo peaks ranged from 0.3 to 0.85 and that the peaks shifted to a longer wavelength for high PM and CDOM concentrations. The absorption and scattering coefficients for sea ice were obtained. The bulk absorption coefficient shows that bulk absorption is primarily determined by PM and CDOM at shorter wavelengths, while pure ice and brine pockets become more important at longer wavelengths. Scattering coefficients for sea ice ranged from 197 to 1072 m-1, and showed consistent variations with gas bubble and brine pocket concentrations. The effects of PM and CDOM on the bulk absorption coefficient of sea ice were studied. At 440 nm, particulates accounted for 55-98% and CDOM accounted for 2-37% of the bulk absorption. Ratios between particulate absorption and bulk absorption for sea ice were almost constant from 400 to 550 nm, and began to decrease sharply for wavelengths >550 nm. Ratios between CDOM and bulk absorption decreased almost linearly with increasing wavelength.

  7. Investigations on growth morphology, bulk growth and crystalline perfection of L-threonine, an organic nonlinear optical material

    Energy Technology Data Exchange (ETDEWEB)

    Linet, J. Mary [Department of Physics, Loyola College, Nungambakkam, Chennai 600 034 (India); Das, S. Jerome, E-mail: sjeromedas2004@yahoo.co [Department of Physics, Loyola College, Nungambakkam, Chennai 600 034 (India)

    2010-09-15

    L-threonine single crystal was successfully grown from aqueous solution. The morphology of the grown crystal was compared with the predicted morphology using Bravais-Friedel-Donnay-Harker law and was found to be in good agreement with the predicted morphology. Good optical quality bulk single crystal of enhanced size has been grown using unidirectional crystal growth method. High-resolution X-ray analysis study resulted in a rocking curve with a full width half maximum of 20 arc sec exhibiting the good crystalline quality of the grown crystal. The optical transmission study shows 90% of transmission in the entire visible region that exhibits the good optical quality of the grown crystal. The mechanical properties were analyzed by Vicker's microhardness method.

  8. Combined optical and electrical modeling of polymer : fullerene bulk heterojunction solar cells

    NARCIS (Netherlands)

    Kotlarski, Jan D.; Blom, Paul W. M.; Koster, Lambert. J. A.; Lenes, Martijn; Slooff, Lenneke H.

    2008-01-01

    Optical interference effects are important for the total absorption as well as the profile of the exciton generation rate in polymer:fullerene bulk heterojunction solar cells. For solar cells with an active layer of poly[2-methoxy-5-(3('),7(')-dimethyloctyloxy)-1,4-phenylenevinylene] as electron don

  9. Regression-based algorithm for bulk motion subtraction in optical coherence tomography angiography.

    Science.gov (United States)

    Camino, Acner; Jia, Yali; Liu, Gangjun; Wang, Jie; Huang, David

    2017-06-01

    We developed an algorithm to remove decorrelation noise due to bulk motion in optical coherence tomography angiography (OCTA) of the posterior eye. In this algorithm, OCTA B-frames were divided into segments within which the bulk motion velocity could be assumed to be constant. This velocity was recovered using linear regression of decorrelation versus the logarithm of reflectance in axial lines (A-lines) identified as bulk tissue by percentile analysis. The fitting parameters were used to calculate a reflectance-adjusted upper bound threshold for bulk motion decorrelation. Below this threshold, voxels are identified as non-flow tissue, their flow values are set to zeros. Above this threshold, the voxels are identified as flow voxels and bulk motion velocity is subtracted from each using a nonlinear decorrelation-velocity relationship previously established in laboratory flow phantoms. Compared to the simpler median-subtraction method, the regression-based bulk motion subtraction improved angiogram signal-to-noise ratio, contrast, vessel density repeatability, and bulk motion noise cleanup in the foveal avascular zone, while preserving the connectivity of the vascular networks in the angiogram.

  10. Bulk fabrication and properties of solar grade silicon microwires

    Directory of Open Access Journals (Sweden)

    F. A. Martinsen

    2014-11-01

    Full Text Available We demonstrate a substrate-free novel route for fabrication of solar grade silicon microwires for photovoltaic applications. The microwires are fabricated from low purity starting material via a bulk molten-core fibre drawing method. In-situ segregation of impurities during the directional solidification of the fibres yields solar grade silicon cores (microwires where the concentration of electrically detrimental transition metals has been reduced between one and two orders of magnitude. The microwires show bulk minority carrier diffusion lengths measuring ∼40 μm, and mobilities comparable to those of single-crystal silicon. Microwires passivated with amorphous silicon yield diffusion lengths comparable to those in the bulk.

  11. Augmentation of the In Vivo Elastic Properties Measurement System to Include Bulk Properties

    Science.gov (United States)

    2015-09-30

    vivo shear and bulk properties of cetacean soft tissues, including jaw fats and brain. The ultimate goal is to field a prototype system for...pattern. A second ultrasonic transducer monitors the tissue displacement along the ultrasound beam axis, and supports an enhanced embodiment of an...Figure 1. CFE concept. Color contour plots illustrate soft tissue displacements parallel to the transducer beam axes. (A) The annular force generation

  12. Ab initio calculation and spectral properties of nano- and bulk materials

    Energy Technology Data Exchange (ETDEWEB)

    Kulagin, N. A., E-mail: nkulagin@bestnet.kharkov.ua [Kharkov National University for Radioelectronics (Ukraine)

    2013-01-15

    This paper presents the development of ab initio calculation of the electronic structure of either clusters, nano-crystals, doped and unperfected bulk crystals. In addition, analysis of selected experimental data for {gamma}- or plasma irradiated pure and doped wide-band gap oxides such as sapphire, {alpha}-Al{sub 2}O{sub 3}, garnet, Y{sub 3}Al{sub 5}O{sub 12}, Gd{sub 3}Sc{sub 2}Al{sub 3}O{sub 12} and perovskites YAlO{sub 3}, SrTiO{sub 3} is presented. Change in the crystals surface morphology and spectroscopic properties of sapphire, perovskites, garnets as well as ion oxidation state in pure and doped {gamma}- and plasma irradiated crystals are discussed in detail using the optical and X ray spectroscopy experimental results.

  13. Optimization of parameters for the synthesis of Y2Cu2O5 nanoparticles by Taguchi method and comparison of their magnetic and optical properties with their bulk counterpart

    Science.gov (United States)

    Farbod, Mansoor; Rafati, Zahra; Shoushtari, Morteza Zargar

    2016-06-01

    Y2Cu2O5 nanoparticles were synthesized by sol-gel combustion method and effects of different factors on the size of nanoparticles were investigated. In order to reduce the experimental stages, Taguchi robust design method was employed. Acid citric:Cu+2 M ratio, pH, sintering temperature and time were chosen as the parameters for optimization. Among these factors the solution pH had the most influence and the others had nearly the same influence on the nanoparticles sizes. Based on the predicted conditions by Taguchi design, the sample with a minimum particle size of 47 nm was prepared. The magnetic behavior of Y2Cu2O5 nanoparticles were measured and found that at low fields they are soft ferromagnetic but at high fields they behave paramagnetically. The magnetic behavior of nanoparticles were compared to their bulk counterparts and found that the Mr of the samples was slightly different, but the Hc of the nanoparticles was 76% of the bulk sample. The maximum absorbance peak of UV-vis spectrum showed a blue shift for the smaller particles.

  14. Satellite material contaminant optical properties

    Science.gov (United States)

    Wood, B. E.; Bertrand, W. T.; Seiber, B. L.; Kiech, E. L.; Falco, P. M.; Holt, J. D.

    1990-03-01

    The Air Force Wright Research and Development Center and the Arnold Engineering Development Center are continuing a program for measuring optical effects of satellite material outgassing products on cryo-optic surfaces. Presented here are infrared (4000 to 700 cm(-1)) transmittance data for contaminant films condensed on a 77 K germanium window. From the transmittance data, the contaminant film refractive and absorptive indices (n, k) were derived using an analytical thin-film interference model with a nonlinear least-squares algorithm. To date 19 materials have been studied with the optical contents determined for 13 of those. The materials include adhesives, paints, composites, films, and lubricants. This program is continuing and properties for other materials will be available in the future.

  15. Ab-initio investigations of the electronic properties of bulk wurtzite Beryllia and its derived nanofilms

    KAUST Repository

    Goumri-Said, Souraya

    2010-08-01

    In this Letter we investigate the electronic properties of the bulk and the nanofilm BeO in wurtzite structure. We performed a first-principles pseudo-potential method within the generalized gradient approximation. We will give more importance to the changes in band structure and density of states between the bulk structure and its derived nanofilms. The bonding characterization will be investigated via the analysis Mulliken population and charge density contours. It is found that the nanofilm retains the same properties as its bulk structure with slight changes in electronic properties and band structure which may offer some unusual transport properties. © 2010 Elsevier B.V. All rights reserved.

  16. Optimization of parameters for the synthesis of Y{sub 2}Cu{sub 2}O{sub 5} nanoparticles by Taguchi method and comparison of their magnetic and optical properties with their bulk counterpart

    Energy Technology Data Exchange (ETDEWEB)

    Farbod, Mansoor, E-mail: farbod_m@scu.ac.ir; Rafati, Zahra; Shoushtari, Morteza Zargar

    2016-06-01

    Y{sub 2}Cu{sub 2}O{sub 5} nanoparticles were synthesized by sol–gel combustion method and effects of different factors on the size of nanoparticles were investigated. In order to reduce the experimental stages, Taguchi robust design method was employed. Acid citric:Cu{sup +2} M ratio, pH, sintering temperature and time were chosen as the parameters for optimization. Among these factors the solution pH had the most influence and the others had nearly the same influence on the nanoparticles sizes. Based on the predicted conditions by Taguchi design, the sample with a minimum particle size of 47 nm was prepared. The magnetic behavior of Y{sub 2}Cu{sub 2}O{sub 5} nanoparticles were measured and found that at low fields they are soft ferromagnetic but at high fields they behave paramagnetically. The magnetic behavior of nanoparticles were compared to their bulk counterparts and found that the M{sub r} of the samples was slightly different, but the H{sub c} of the nanoparticles was 76% of the bulk sample. The maximum absorbance peak of UV–vis spectrum showed a blue shift for the smaller particles. - Highlights: • Y{sub 2}Cu{sub 2}O{sub 5} nanoparticles (Y202) were synthesized by sol–gel combustion method. • To optimize the synthesis parameters Taguchi statistical method was used. • The solution pH had the most influence and the others had nearly the same effect. • The hysteresis loop of (Y202) nanoparticles showed a soft ferromagnetic behavior. • UV maximum absorbance peak showed a blue shift for the nanoparticle.

  17. Prediction of nonlinear optical properties of large organic molecules

    Science.gov (United States)

    Cardelino, Beatriz H.

    1992-01-01

    The preparation of materials with large nonlinear responses usually requires involved synthetic processes. Thus, it is very advantageous for materials scientists to have a means of predicting nonlinear optical properties. The prediction of nonlinear optical properties has to be addressed first at the molecular level and then as bulk material. For relatively large molecules, two types of calculations may be used, which are the sum-over-states and the finite-field approach. The finite-field method was selected for this research, because this approach is better suited for larger molecules.

  18. Optical far-field super-resolution microscopy using nitrogen vacancy center ensemble in bulk diamond

    Science.gov (United States)

    Li, Shen; Chen, Xiang-dong; Zhao, Bo-Wen; Dong, Yang; Zou, Chong-Wen; Guo, Guang-Can; Sun, Fang-Wen

    2016-09-01

    We demonstrate optical far-field super-resolution microscopy using an array of nitrogen vacancy centers in bulk diamond as near-field optical probes. The local optical field, which transmits through the nanostructures on the diamond surface, is measured by detecting the charge state conversion of the nitrogen vacancy center. Locating the nitrogen vacancy center with a spatial resolution of 6.1 nm is realized with charge state depletion nanoscopy. The nanostructures on the surface of a diamond are then imaged with a resolution below the optical diffraction limit. The results offer an approach to build a general-purpose optical super-resolution microscopy technique and a convenient platform for high spatial resolution quantum sensing with nitrogen vacancy centers.

  19. Optical far-field super-resolution microscopy using nitrogen vacancy center ensemble in bulk diamond

    CERN Document Server

    Li, Shen; Zhao, Bo-Wen; Dong, Yang; Zou, Chong-Wen; Guo, Guang-Can; Sun, Fang-Wen

    2016-01-01

    We demonstrate an optical far-field super-resolution microscopy using array of nitrogen vacancy centers in bulk diamond as near-field optical probes. The local optical field, which transmits through the nanostructures on the diamond surface, is measured by detecting the charge state conversion of nitrogen vacancy center. And the locating of nitrogen vacancy center with spatial resolution of 6.1 nm is realized with the charge state depletion nanoscopy. The nanostructures on the surface of diamond are then imaged with resolution below optical diffraction limit. The results offer an approach to built a general-purpose optical super-resolution microscopy and a convenient platform for high spatial resolution quantum sensing with nitrogen vacancy center.

  20. Structure and properties of nanocrystalline rare earth bulks prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    卢年端; 宋晓艳; 刘雪梅; 张久兴

    2009-01-01

    A series of rare earth bulks with the ultrafine nanocrystalline structure were prepared by applying an "oxygen-free" (an environmental oxygen concentration less than 0.5 ppm) in-situ synthesis system, where the inert-gas condensation was combined with the spark plasma sintering technology into an entirely closed system. The thermal and mechanical properties of the prepared ultrafine nanocrystalline bulks were characterized and compared with those of the raw polycrystalline bulks. It was found that the speci...

  1. Effects of Mass Fluctuation on Thermal Transport Properties in Bulk Bi2Te3

    Science.gov (United States)

    Huang, Ben; Zhai, Pengcheng; Yang, Xuqiu; Li, Guodong

    2016-10-01

    In this paper, we applied large-scale molecular dynamics and lattice dynamics to study the influence of mass fluctuation on thermal transport properties in bulk Bi2Te3, namely thermal conductivity (K), phonon density of state (PDOS), group velocity (v g), and mean free path (l). The results show that total atomic mass change can affect the relevant vibrational frequency on the micro level and heat transfer rate in the macro statistic, hence leading to the strength variation of the anharmonic phonon processes (Umklapp scattering) in the defect-free Bi2Te3 bulk. Moreover, it is interesting to find that the anharmonicity of Bi2Te3 can be also influenced by atomic differences of the structure such as the mass distribution in the primitive cell. Considering the asymmetry of the crystal structure and interatomic forces, it can be concluded by phonon frequency, lifetime, and velocity calculation that acoustic-optical phonon scattering shows the structure-sensitivity to the mass distribution and complicates the heat transfer mechanism, hence resulting in the low lattice thermal conductivity of Bi2Te3. This study is helpful for designing the material with tailored thermal conductivity via atomic substitution.

  2. Structure and optical properties of CdSe chalcogenide semiconductors

    Science.gov (United States)

    Ganaie, Mohsin; Prince, Zulfequar, M.

    2015-08-01

    CdSe bulk sample has been prepared by melt-quenching technique and were characterized with XRD, SEM, FTIR, and electrical measurements. Thin films were deposited by thermal evaporation technique on ultra clean glass substrates under a high vacuum of 10-6 Torr. An XRD measurement reveals the coexistence of glassy and crystalline phase in bulk sample. SEM studies shows single phase, porous, and granular surface morphology of powder CdSe alloy. Optical properties (optical gap, absorption coefficient, extinction coefficient, refractive index) are calculated in the range of 190-1100nm. Analysis of the optical measurement shows that the non-direct transition is predominant and the band gap come outs to be 1.751eV. Dc conductivity measurement is thermally activated process which shows the semiconducting nature of the sample having activation energy 0.31eV.

  3. Structural and magnetic properties of bulk nanocrystalline Erbium metal

    Directory of Open Access Journals (Sweden)

    Ming Yue

    2011-06-01

    Full Text Available Bulk nanocrystalline Erbium metals were prepared via Spark Plasma Sintering (SPS and subsequent annealing process. The nanocrystalline Er metals have the same hexagonal close packed structure as that of coarse-grained sample. Decrease in grain size results in remarkable changes in the three magnetic ordering temperatures of the nanocrystalline Er metal. At 5 K, the magnetization drops by 10.9%, while the coercivity increases by 4 times for nanocrystalline Er compared with those of coarse-grained sample. These results indicate the remarkable influence of the nanostructure on the magnetism of Er due to finite size effect.

  4. Electric- and magnetic-field dependence of the electronic and optical properties of phosphorene quantum dots

    Science.gov (United States)

    Li, L. L.; Moldovan, D.; Xu, W.; Peeters, F. M.

    2017-02-01

    Recently, black phosphorus quantum dots were fabricated experimentally. Motivated by these experiments, we theoretically investigate the electronic and optical properties of rectangular phosphorene quantum dots (RPQDs) in the presence of an in-plane electric field and a perpendicular magnetic field. The energy spectra and wave functions of RPQDs are obtained numerically using the tight-binding approach. We find edge states within the band gap of the RPQD which are well separated from the bulk states. In an undoped RPQD and for in-plane polarized light, due to the presence of well-defined edge states, we find three types of optical transitions which are between the bulk states, between the edge and bulk states, and between the edge states. The electric and magnetic fields influence the bulk-to-bulk, edge-to-bulk, and edge-to-edge transitions differently due to the different responses of bulk and edge states to these fields.

  5. Comments on universal properties of entanglement entropy and bulk reconstruction

    CERN Document Server

    Haehl, Felix M

    2015-01-01

    Entanglement entropy of holographic CFTs is expected to play a crucial role in the reconstruction of semiclassical bulk gravity. We consider the entanglement entropy of spherical regions of vacuum, which is known to contain universal contributions. After perturbing the CFT with a relevant scalar operator, also the first order change of this quantity gives a universal term which only depends on a discrete set of basic CFT parameters. We show that in gravity this statement corresponds to the uniqueness of the ghost-free graviton propagator on an AdS background geometry. While the gravitational dynamics in this context contains little information about the structure of the bulk theory, there is a discrete set of dimensionless parameters of the theory which determines the entanglement entropy. We argue that for every (not necessarily holographic) CFT, any reasonable gravity model can be used to compute this particular entanglement entropy. We elucidate how this statement is consistent with AdS/CFT and also give v...

  6. Photoinduced nanocomposites—creation, modification, linear and nonlinear optical properties

    Science.gov (United States)

    Bityurin, N.; Alexandrov, A.; Afanasiev, A.; Agareva, N.; Pikulin, A.; Sapogova, N.; Soustov, L.; Salomatina, E.; Gorshkova, E.; Tsverova, N.; Smirnova, L.

    2013-07-01

    UV irradiation of materials consisting of a polymer matrix that possesses precursors of noble metals followed by annealing results in creation of metal nanoparticles within the irradiated domains. Such photoinduced nanocomposites are promising for photonics applications due to the strong alteration of their optical properties compared to initial nonirradiated materials. We report our results on the synthesis and investigation of two kinds of these materials: (a) Photoinduced Au nanocomposites based on PMMA matrices, including bulk materials prepared by means of the polymerization technique;

  7. Engineering optical properties of semiconductor metafilm superabsorbers

    Science.gov (United States)

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2016-04-01

    Light absorption in ultrathin layer of semiconductor has been considerable interests for many years due to its potential applications in various optical devices. In particular, there have been great efforts to engineer the optical properties of the film for the control of absorption spectrums. Whereas the isotropic thin films have intrinsic optical properties that are fixed by materials' properties, metafilm that are composed by deep subwavelength nano-building blocks provides significant flexibilities in controlling the optical properties of the designed effective layers. Here, we present the ultrathin semiconductor metafilm absorbers by arranging germanium (Ge) nanobeams in deep subwavelength scale. Resonant properties of high index semiconductor nanobeams play a key role in designing effective optical properties of the film. We demonstrate this in theory and experimental measurements to build a designing rule of efficient, controllable metafilm absorbers. The proposed strategy of engineering optical properties could open up wide range of applications from ultrathin photodetection and solar energy harvesting to the diverse flexible optoelectronics.

  8. Correlations between critical parameters and bulk properties of nuclear matter

    CERN Document Server

    Lourenço, O; Dutra, M; Delfino, A

    2016-01-01

    The present work starts by providing a clear identification of correlations between critical parameters ($T_c$, $P_c$, $\\rho_c$) and bulk quantities at zero temperature of relativistic mean-field models (RMF) presenting third and fourth order self-interactions in the scalar field $\\sigma$. Motivated by the nonrelativistic version of this RMF model, we show that effective nucleon mass ($M^*$) and incompressibility ($K_o$), at the saturation density, are correlated with $T_c$, $P_c$, and $\\rho_c$, as well as, binding energy and saturation density itself. We verify agreement of results with previous theoretical ones regarding different hadronic models. Concerning recent experimental data of the symmetric nuclear matter critical parameters, our study allows a prediction of $T_c$, $P_c$ and $\\rho_c$ compatible with such values, by combining them, through the correlations found, with previous constraints related to $M^*$ and $K_o$. An improved RMF parametrization, that better agrees with experimental values for $T_...

  9. Magnetic properties of Fe-Co-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Tiberto, Paola, E-mail: tiberto@inrim.i [INRIM, Electromagnetism Division, Strada delle Cacce 91, I-10135 Torino (Italy); Piccin, Rafael [Universita di Torino, Dipartimento di Chimica IFM and NIS, I-10125 Torino (Italy); Lupu, Nicoleta; Chiriac, Horia [National Institute of Research and Development for Technichal Physics, 700050 Iasi (Romania); Baricco, Marcello [Universita di Torino, Dipartimento di Chimica IFM and NIS, I-10125 Torino (Italy)

    2009-08-26

    Amorphous [(Fe{sub 1-x}Co{sub x}){sub 75}B{sub 20}Si{sub 5}]{sub 93}Nb{sub 4}Y{sub 3}(x=0, 0.2 and 0.4) have been produced by water-cooled Cu-mold injection casting technique in cylindrical shape. Amorphous ribbon having the same composition have been produced by rapid quenching technique. The presence of an amorphous structure have been checked by means of X-ray diffraction measurements and differential scanning calorimetry. Magnetic hysteresis loops have been measured by means of vibrating sample magnetometer at a maximum field of 10 kOe. In addition, to study the frequency dependence of magnetic losses, hysteresis loops have been measured by a digital wattmeter. A critical analysis of the results obtained on both ribbons and bulk cylinder will be presented. The obtained data will be compared with the ones of Fe-based materials conventionally exploited in applications.

  10. Quantum Electrostatic Model for Optical Properties of Nanoscale Gold Films

    Directory of Open Access Journals (Sweden)

    Qian Haoliang

    2015-11-01

    Full Text Available The optical properties of thin gold films with thickness varying from 2.5 nm to 30 nm are investigated. Due to the quantum size effect, the optical constants of the thin gold film deviate from the Drude model for bulk material as film thickness decreases, especially around 2.5 nm, where the electron energy level becomes discrete. A theory based on the self-consistent solution of the Schrödinger equation and the Poisson equation is proposed and its predictions agree well with experimental results.

  11. Melt growth and properties of bulk BaSnO3 single crystals

    Science.gov (United States)

    Galazka, Z.; Uecker, R.; Irmscher, K.; Klimm, D.; Bertram, R.; Kwasniewski, A.; Naumann, M.; Schewski, R.; Pietsch, M.; Juda, U.; Fiedler, A.; Albrecht, M.; Ganschow, S.; Markurt, T.; Guguschev, C.; Bickermann, M.

    2017-02-01

    We present the first-time growth of bulk BaSnO3 single crystals from the melt by direct solidification, their basic electrical and optical properties as well as their structural quality. Our measurement of the melting point (MP) of BaSnO3 amounts to 1855 °C  ±  25 K. At this temperature an intensive decomposition and non-stoichiometric evaporation takes place as the partial pressure of SnO(g) is about 90 times higher than that of BaO(g). X ray powder diffraction identified only the BaSnO3 perovskite phase, while narrow rocking curves having a full width at half maximum of 26 arcsec and etch pit densities below 106 cm-2 confirm a high degree of structural perfection of the single crystals. In this respect they surpass the structural properties of those single crystals that were reported in the literature. The electrical conductivity of nominally undoped crystals depends on the growth conditions and ranges from insulating to medium n-type conductivity. After post-growth annealing in an oxidizing atmosphere undoped crystals are generally insulating. Doping the crystals with lanthanum during growth results in a high n-type conductivity. For a La doping concentration of 0.123 wt.% we measured an electron concentration of 3.3  ×  1019 cm-3 and an electron mobility of 219 cm2 V-1 s-1. Based on optical absorption measurements we determined an energy of 3.17  ±  0.04 eV at 5 K and of 2.99  ±  0.04 eV at 297 K for the indirect band gap of BaSnO3.

  12. Melt growth and properties of bulk BaSnO3 single crystals.

    Science.gov (United States)

    Galazka, Z; Uecker, R; Irmscher, K; Klimm, D; Bertram, R; Kwasniewski, A; Naumann, M; Schewski, R; Pietsch, M; Juda, U; Fiedler, A; Albrecht, M; Ganschow, S; Markurt, T; Guguschev, C; Bickermann, M

    2017-02-22

    We present the first-time growth of bulk BaSnO3 single crystals from the melt by direct solidification, their basic electrical and optical properties as well as their structural quality. Our measurement of the melting point (MP) of BaSnO3 amounts to 1855 °C  ±  25 K. At this temperature an intensive decomposition and non-stoichiometric evaporation takes place as the partial pressure of SnO(g) is about 90 times higher than that of BaO(g). X ray powder diffraction identified only the BaSnO3 perovskite phase, while narrow rocking curves having a full width at half maximum of 26 arcsec and etch pit densities below 10(6) cm(-2) confirm a high degree of structural perfection of the single crystals. In this respect they surpass the structural properties of those single crystals that were reported in the literature. The electrical conductivity of nominally undoped crystals depends on the growth conditions and ranges from insulating to medium n-type conductivity. After post-growth annealing in an oxidizing atmosphere undoped crystals are generally insulating. Doping the crystals with lanthanum during growth results in a high n-type conductivity. For a La doping concentration of 0.123 wt.% we measured an electron concentration of 3.3  ×  10(19) cm(-3) and an electron mobility of 219 cm(2) V(-1) s(-1). Based on optical absorption measurements we determined an energy of 3.17  ±  0.04 eV at 5 K and of 2.99  ±  0.04 eV at 297 K for the indirect band gap of BaSnO3.

  13. Bulk and electrochemical properties of BiVO4

    NARCIS (Netherlands)

    Vinke, I.C.; Diepgrond, J.; Boukamp, B.A.; Vries, de K.J.; Burggraaf, A.J.

    1992-01-01

    The mixed (oxygen ionic-electronic) conductor bismuth vanadate (BiVO4) was studied with respect to its electrochemical properties. The ionic transference numbers, measured by the concentration cell method in the temperature range of 800 to 1000 K, vary from 0.7 to 0.3. The total conductivity of this

  14. Viscoelastic and optical properties of four different PDMS polymers

    Science.gov (United States)

    Deguchi, Shinji; Hotta, Junya; Yokoyama, Sho; Matsui, Tsubasa S.

    2015-09-01

    Polydimethylsiloxane (PDMS) is the most commonly used silicone elastomer with a wide range of applications including microfluidics and microcontact printing. Various types of PDMS are currently available, and their bulk material properties have been extensively investigated. However, because the properties are rarely compared in a single study, it is often unclear whether the large disparity of the reported data is attributable to the difference in methodology or to their intrinsic characteristics. Here we report on viscoelastic properties and optical properties of four different PDMS polymers, i.e. Sylgard-184, CY52-276, SIM-360, and KE-1606. Our results show that all the PDMSs are highly elastic rather than viscoelastic at the standard base/curing agent ratios, and their quantified elastic modulus, refractive index, and optical cleanness are similar but distinct in magnitude.

  15. Thermal and optical properties of porous silicon

    Directory of Open Access Journals (Sweden)

    Silva A. Ferreira da

    2001-01-01

    Full Text Available Thermal diffusivity and optical absorption have been investigated for porous silicon, at room temperature, using photoacoustic spectroscopy. The experimental results obtained conform well with the existing studies recently published. The value obtained for thermal diffusivity is 0.045 ± 0.002 cm²/s.The absorption onsets show energy structures, differing from the ordinary semiconductor of bulk type.

  16. Multi-beam-bulk model for electron transport during commutation in an optically triggered pseudospark thyratron

    Science.gov (United States)

    Pak, Hoyoung; Kushner, Mark J.

    1990-10-01

    The electron energy distribution in low-pressure pulsed power plasma switches is typically not in equilibrium with the local electric field. To simulate electron transport under these conditions a computer model has been developed and has been applied to the optically triggered pseudospark, or back-lit-thyratron (BLT). The model uses many groups of electrons divided into the ``bulk'' and the ``beam''. The bulk is represented by a fluid while the beam electrons are ballistic in nature and have not undergone significant energy-loss collisions after generation. To account for beam electrons being generated at arbitrary locations in the BLT, multiple beams are employed in the model. The commutation phase of switching in the BLT is investigated and the onset of a hollow cathode effect during switching is predicted.

  17. Fabrication of Bi2223 bulks with high critical current properties sintered in Ag tubes

    Science.gov (United States)

    Takeda, Yasuaki; Shimoyama, Jun-ichi; Motoki, Takanori; Kishio, Kohji; Nakashima, Takayoshi; Kagiyama, Tomohiro; Kobayashi, Shin-ichi; Hayashi, Kazuhiko

    2017-03-01

    Randomly grain oriented Bi2223 sintered bulks are one of the representative superconducting materials having weak-link problem due to very short coherence length particularly along the c-axis, resulting in poor intergrain Jc properties. In our previous studies, sintering and/or post-annealing under moderately reducing atmospheres were found to be effective for improving grain coupling in Bi2223 sintered bulks. Further optimizations of the synthesis process for Bi2223 sintered bulks were attempted in the present study to enhance their intergrain Jc. Effects of applied pressure of uniaxial pressing and sintering conditions on microstructure and superconducting properties have been systematically investigated. The best sample showed intergrain Jc of 2.0 kA cm-2 at 77 K and 8.2 kA cm-2 at 20 K, while its relative density was low ∼65%. These values are quite high as for a randomly oriented sintered bulk of cuprate superconductors.

  18. Bulk and electrochemical properties of BiVO4

    OpenAIRE

    Vinke, I.C.; Diepgrond, J. (Jan); Boukamp, B.A.; De, Vries, J.A.; Burggraaf, A.J.

    1992-01-01

    The mixed (oxygen ionic-electronic) conductor bismuth vanadate (BiVO4) was studied with respect to its electrochemical properties. The ionic transference numbers, measured by the concentration cell method in the temperature range of 800 to 1000 K, vary from 0.7 to 0.3. The total conductivity of this ceramic material isone order of magnitude lower than found for cubic yttria-stabilized zirconia (YSZ). The activation enthalpy for the electronic conductivity is high (193 kJ/mol) compared to the ...

  19. Optical properties of epitaxial YAG:Yb films

    Science.gov (United States)

    Ubizskii, S. B.; Matkovskii, A. O.; Melnyk, S. S.; Syvorotka, I. M.; Müller, V.; Peters, V.; Petermann, K.; Beyertt, A.; Giesen, A.

    2004-03-01

    This work deals with the investigation of the optical properties of epitaxial YAG:Yb films and their suitability as gain media for thin disk lasers. Epitaxial films of YAG:Yb were grown by the liquid phase epitaxy method in air on the (111)-oriented YAG substrates. The thickness of the grown layers was from 30 to 260 m. The melt composition was varied to obtain the desired doping level from 10 to 15% and to optimize the optical properties. The best epitaxial films were colourless and had an Yb3+ luminescence lifetime of more than 950 s, which is very close to the intrinsic lifetime of the Yb ions in the bulk YAG single crystals. These films were tested in a thin disk laser setup with 24 absorption passes of the 940 nm pumping beam. The maximum output power at 1.03 m wavelength in CW operation reached more than 60 W and the optical efficiency was close to 30%.

  20. Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

    Energy Technology Data Exchange (ETDEWEB)

    Lollobrigida, V. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Basso, V.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F. [Istituto Nazionale di Ricerca Metrologica (INRIM), I-10135 Torino (Italy); Borgatti, F. [CNR, Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), I-40129 Bologna (Italy); Torelli, P.; Panaccione, G. [CNR, Istituto Officina dei Materiali (IOM), Lab. TASC, I-34149 Trieste (Italy); Tortora, L. [Laboratorio di Analisi di Superficie, Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Ingegneria Meccanica, Università Tor Vergata, I-00133 Rome (Italy); Stefani, G.; Offi, F. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy)

    2014-05-28

    We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

  1. Sludge Bulking Property of Membrane Bio-reactor in Albumen Wqastewater Treatment

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    Albumen wastewater was treated by Membrane Bio-reactor. Sludge bulking property of Membrane Bio-Reactor was investigated in this study through contrast research. When the sludge bulking appeared, the removal efficiency of COD in Membrane Bio-reactor increased slightly under the function of filamentous bacteria. However, the negative effects of the higher net water-head differential pressures,the higher block rate of membrane pore and the great quantity of filamentous bacteria at the externalsurface pres...

  2. Bulk and electrochemical properties of BiVO[sub 4

    Energy Technology Data Exchange (ETDEWEB)

    Vinke, I.C.; Diepgrond, J.; Boukamp, B.A.; Vries, K.J. de; Burggraaf, A.J. (Lab. for Inorganic Chemistry, Materials Science and Catalysis, Univ. of Twente, Enschede (Netherlands))

    1992-09-01

    The mixed (oxygen ionic-electronic) conductor bismuth vanadate (BiVO[sub 4]) was studied with respect to its electrochemical properties. The ionic transference numbers, measured by the concentration cell method in the temperature range of 800 to 1000 K, vary from 0.7 to 0.3. The total conductivity of this ceramic material is one order of magnitude lower than found for cubic yttria-stabilized zirconia (YSZ). The activation enthalpy for the electronic conductivity is high (193 kJ/mol) compared to the ionic conductivity (71 kJ/mol). The P[sub O2] dependency of the conductivity data in combination with the Seebeck measurements showed electrons to be the majority charge carriers, indicating that BiVO[sub 4] is an n-type mixed conductor. (orig.).

  3. Modeling the material properties at the onset of damage initiation in bulk potassium dihydrogen phosphate crystals

    Science.gov (United States)

    Demos, Stavros G.; Feit, Michael D.; Duchateau, Guillaume

    2014-10-01

    A model simulating transient optical properties during laser damage in the bulk of KDP/DKDP crystals is presented. The model was developed and tested using as a benchmark its ability to reproduce the well-documented damage initiation behaviors but most importantly, the salient behavior of the wavelength dependence of the damage threshold. The model involves two phases. During phase I, the model assumes a moderate localized initial absorption that is strongly enhanced during the laser pulse via excited state absorption and thermally driven generation of additional point defects in the surrounding material. The model suggests that during a fraction of the pulse duration, the host material around the defect cluster is transformed into a strong absorber that leads to significant increase of the local temperature. During phase II, the model suggests that the excitation pathway consists mainly of one photon absorption events within a quasicontinuum of short-lived vibronic defect states spanning the band gap that was generated after the initial localized heating of the material due to thermal quenching of the excited state lifetimes. The width of the transition (steps) between different number of photons is governed by the instantaneous temperature, which was estimated using the experimental data. The model also suggests that the critical physical parameter prior to initiation of breakdown is the conduction band electron density. This model, employing very few free parameters, for the first time is able to quantitatively reproduce the wavelength dependence of the damage initiation threshold, and thus provides important insight into the physical processes involved.

  4. Synthesis and optical properties studies

    Directory of Open Access Journals (Sweden)

    N.A. El-Ghamaz

    2017-01-01

    Full Text Available 4-(4-Amino-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-ylideneamino-phenol (L1 and 4-(4-Amino-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-ylideneamino-benzoic acid (L2 have been synthesized by the condensation reaction of 4-aminoantipyrine (4-AAP and 4-aminophenol or 4-aminobenzoic acid in ethanolic solution and are characterized by various physico-chemical techniques. Thin films of L1 and L2 have been prepared by the conventional spin coating technique. X-ray diffraction patterns (XRD show an amorphous nature for both powder and thin films for L1 and L2 ligands. The optical absorption and refraction properties of L1 and L2 are investigated by spectrophotometric techniques at normal incidence of light in the wavelength range of 200–2500 nm. The absorption spectra show two peaks in the UV region which correspond to π → π∗ transition and a peak in UV–Vis region which may correspond to n → π∗ transition. The values of dispersion parameters Eo, Ed, εL, ε∞ and N/m* are calculated according to the single oscillator model. The presence of the OH group increases the value of ε∞ from 3.21 to 3.32 and the value of N/m* from 7.38 × 1053 to 2.08 × 1054 m−3Kg−1. The optical band transition is found to be indirect allowing fundamental energy gap values of 3.4 and 3.9 eV and onset energy gap values of 2.1 and 2.6 eV for L1 and L2, respectively.

  5. Optical Properties of Non-Crystalline Semiconductors.

    Science.gov (United States)

    1984-01-01

    Instruments, 1974, unpublished. 42. de Neufville, J.P., Photostructural transformations in amorphous solids, 0 in Optical Properties of Solids --New...semiconductors, in Optical Properties of Solids , Nudelman, S., and Mitra, S.S., eds., Plenum, N.Y., 1969, 123. 52. Cody, G.D., Brooks, B.G., and

  6. Measurements of optical parameters of phantom solution and bulk animal tissues in vitro at 650 nm

    Science.gov (United States)

    Sun, Ping; Wang, Yu

    2010-02-01

    Optical parameters of bulk animal tissue in vitro, including absorption coefficient ( μa), reduced scattering coefficient ( μ' s) or scattering coefficient ( μs), total attenuation coefficient ( μt), anisotropy factor ( g) and refractive index ( n) are measured at wavelength of 650 nm. Clinical Intralipid-10% is diluted in distilled water into different concentrations to use as tissue phantoms. Four types of animal tissues in vitro are studied. The relationships among the optical parameters are analyzed systemically. For animal tissues, μa, μ' s or μs and n rely on muscle fiber orientations. μs and μt range from 10 to 20 mm -1, μa from 10 -2 to 10 -3 mm -1 and g from 0.95 to 0.99.

  7. Short optical pulse generation at 40 GHz with a bulk electro-absorption modulator packaged device

    Science.gov (United States)

    Langlois, Patrick; Moore, Ronald; Prosyk, Kelvin; O'Keefe, Sean; Oosterom, Jill A.; Betty, Ian; Foster, Robert; Greenspan, Jonathan; Singh, Priti

    2003-12-01

    Short optical pulse generation at 40GHz and 1540nm wavelength is achieved using fully packaged bulk quaternary electro-absorption modulator modules. Experimental results obtained with broadband and narrowband optimized packaged modules are presented and compared against empirical model predictions. Pulse duty cycle, extinction ratio and chirp are studied as a function of sinusoidal drive voltage and detuning between operating wavelength and modulator absorption band edge. Design rules and performance trade-offs are discussed. Low-chirp pulses with a FWHM of ~12ps and sub-4ps at a rate of 40GHz are demonstrated. Optical time-domain demultiplexing of a 40GHz to a 10GHz pulse train is also demonstrated with better than 20dB extinction ratio.

  8. Contribution of the comonomers to the bulk and surface properties of methacrylate copolymers.

    Science.gov (United States)

    Hermitte, L; Thomas, F; Bougaran, R; Martelet, C

    2004-04-01

    Relationships between formulation, bulk properties, and surface properties are investigated on series of copolymers prepared with hydroxyethylmethacrylate (HEMA), methylmethacrylate (MMA), and ethylmethacrylate (EMA) monomers, and on the homopolymers PMMA and PHEMA. The bulk water content, swelling ratio, and static (sessile drop and captive bubble) and dynamic (Wilhelmy plate technique) contact angles and the electrokinetic potential (streaming potential) are measured. The bulk water content and swelling ratio of HEMA copolymers are proportional to the amount of HEMA and are linearly correlated to the contact angle hysteresis. Periodic instabilities in the wetting cycles, similar to Haines jumps, are observed with HEMA copolymers and support a bidirectional relaxation of the hydrophilic groups respectively towards external water and capillary water. The origin of the electrokinetic potential of these nonionizable polymers is attributed to specific adsorption of [Formula: see text] ions. Its dependence on surface hydrophobicity and statistical length of the side-chains is interpreted in terms of the properties of water molecules near the interface.

  9. Glass Formability and Soft Magnetic Properties of Bulk Y-Fe-B-Ti Metals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Ti effects on the glass forming ability and the magnetic properties of Y-Fe-B-Ti bulk metallic glasses have been investigated. Substituting 2 and 4 at% Ti for Fe or B in Y6Fe70B22 alloys decrease the saturation magnetization (σs) and deteriorate the glass forming ability, respectively. However, substitution of 2 at% Ti for Y in Y6Fe72B22 alloy induces larger supercooled region of 72.7℃, which not only makes the bulk glassy rod as large as 3mm in diameter, but also results in the superior soft magnetic properties of σ5=126emu/g,coercivity ( Hc ) = 0.2 Oe and Curie temperature (Tc) = 268℃. Among all Y-Fe-B-Ti bulk amorphous rods, Y4Fe72B22Ti2 displays the best glass forming ability and also the proper soft magnetic properties.

  10. Functional imaging in bulk tissue specimens using optical emission tomography: fluorescence preservation during optical clearing

    Science.gov (United States)

    Sakhalkar, H. S.; Dewhirst, M.; Oliver, T.; Cao, Y.; Oldham, M.

    2007-04-01

    Optical emission computed tomography (optical-ECT) is a technique for imaging the three-dimensional (3D) distribution of fluorescent probes in biological tissue specimens with high contrast and spatial resolution. In optical-ECT, functional information can be imaged by (i) systemic application of functional labels (e.g. fluorophore labelled proteins) and/or (ii) endogenous expression of fluorescent reporter proteins (e.g. red fluorescent protein (RFP), green fluorescent protein (GFP)) in vivo. An essential prerequisite for optical-ECT is optical clearing, a procedure where tissue specimens are made transparent to light by sequential perfusion with fixing, dehydrating and clearing agents. In this study, we investigate clearing protocols involving a selection of common fixing (4% buffered paraformaldehyde (PFA), methanol and ethanol), dehydrating (methanol and ethanol) and clearing agents (methyl salicylate and benzyl-alcohol-benzyl-benzoate (BABB)) in order to determine a 'fluorescence friendly' clearing procedure. Cell culture experiments were employed to optimize the sequence of chemical treatments that best preserve fluorescence. Texas red (TxRed), fluorescein isothiocyanate (FITC), RFP and GFP were tested as fluorophores and fluorescent reporter proteins of interest. Fluorescent and control cells were imaged on a microscope using a DSred2 and FITC filter set. The most promising clearing protocols of cell culture experiments were applied to whole xenograft tumour specimens, to test their effectiveness in large unsectioned samples. Fluorescence of TxRed/FITC fluorophores was not found to be significantly affected by any of the test clearing protocols. RFP and GFP fluorescence, however, was found to be significantly greater when cell fixation was in ethanol. Fixation in either PFA or methanol resulted in diminished fluorescence. After ethanol fixation, the RFP and GFP fluorescence proved remarkably robust to subsequent exposure to either methyl salicylate or BABB

  11. Microstructure-property relationship in magnetoelectric bulk composites

    Energy Technology Data Exchange (ETDEWEB)

    Sheikh, Arif D.; Fawzi, Abdulsamee [Novel Materials Research Laboratory, Department of Physics, University of Pune, Pune 411 007, M.S. (India); Mathe, V.L., E-mail: vlmathe@physics.unipune.ernet.i [Novel Materials Research Laboratory, Department of Physics, University of Pune, Pune 411 007, M.S. (India)

    2011-03-15

    We present systematic studies that comprise phase connectivity and dielectric, multiferroic (MF) and magnetoelectric (ME) properties of (x) Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4}+(1-x) Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.67}Ti{sub 0.33}O{sub 3} [where x=0.15, 0.30 and 0.45] ME composites prepared by conventional solid-state reaction method. Scanning electron microscopic images of the composites predict different types of connectivity schemes viz 3-0, 3-1 and 3-3. The phase transition temperature of PMN-PT is independent of Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4} content. Room temperature P-E and M-H loops indicate the simultaneous existence of ferroelectric/magnetic ordering. In order to study the possibility of monitoring electrical ordering by means of a magnetic field, ME measurements were carried out. The composition-dependent phase connectivity was well co-related to formation of percolation path and inturn magnetoelectric output. - Research highlights: > Synthesis of (x) Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4}+ (1-x) PMN-PT [where x=0.15, 0.30 and 0.45] ME composites. > Microstructure of the composites with x=0.15, 0.30 and 0.45, predicts different types of connectivity scheme viz 3-0, 3-1 and 3-3 respectively. > Dielectric behavior of the ME composites. > Room-temperature P-E and M-H loops indicate the existence of multiferroic ordering. > Co-relation of phase connectivity with magnetoelectric output.

  12. Structure and property evaluation of a vacuum plasma sprayed nanostructured tungsten-hafnium carbide bulk composite

    Energy Technology Data Exchange (ETDEWEB)

    Rea, K.E.; Viswanathan, V.; Kruize, A. [Surface Engineering and Nanotechnology Facility (SNF), University of Central Florida, Eng. 381, 4000 Central Florida Blvd., Orlando, FL 32816 (United States); AMPAC, Department of Mechanical, Materials, and Aerospace Engineering (MMAE), Nanoscience and Technology Center, University of Central Florida, Eng. 381, 4000 Central Florida Blvd., Orlando, FL 32816 (United States); Hosson, J.Th.M. de [Department of Applied Physics, University of Groningen, Nijenborgh 4, NL-9747 AG (Netherlands); O' Dell, S.; McKechnie, T. [Plasma Processes, Inc., 4914 Moores Mill Road, Huntsville, AL 35811 (United States); Rajagopalan, S.; Vaidyanathan, R. [AMPAC, Department of Mechanical, Materials, and Aerospace Engineering (MMAE), Nanoscience and Technology Center, University of Central Florida, Eng. 381, 4000 Central Florida Blvd., Orlando, FL 32816 (United States); Seal, S. [Surface Engineering and Nanotechnology Facility (SNF), University of Central Florida, Eng. 381, 4000 Central Florida Blvd., Orlando, FL 32816 (United States); AMPAC, Department of Mechanical, Materials, and Aerospace Engineering (MMAE), Nanoscience and Technology Center, University of Central Florida, Eng. 381, 4000 Central Florida Blvd., Orlando, FL 32816 (United States)], E-mail: sseal@mail.ucf.edu

    2008-03-25

    Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured thermo-mechanical components. Spray drying of powder feedstock appears to have a significant effect on the improved mechanical properties of the bulk nanocomposite. The reported elastic modulus of the nanocomposite nearly doubles due to the presence of HfC nano particulates in the W matrix. High resolution transmission electron microscopy (HRTEM) revealed the retention of nanostructures at the select process conditions and is correlated with the enhanced mechanical properties of the nanocomposite.

  13. Thermal, spectral, and surface properties of LED light-polymerized bulk fill resin composites.

    Science.gov (United States)

    Pişkin, Mehmet Burçin; Atalı, Pınar Yılmaz; Figen, Aysel Kantürk

    2015-02-01

    The aim of this study was to evaluate the thermal, spectral, and surface properties of four different bulk fill materials – SureFil SDR (SDR, Dentsplay DETREY), QuixFil (QF, Dentsplay DETREY), X-tra base (XB, Voco) X-tra fil (XF, Voco) – polymerized by light-emitting diode (LED). Resin matrix, filler type, size and amount, and photoinitiator types influence the degree of conversion. LED-cured bulk fill composites achieved sufficient polymerization. Scanning electron microscope (SEM) analysis revealed different patterns of surface roughness, depending on the composite material. Bulk fill materials showed surface characteristics similar to those of nanohybrid composites. Based on the thermal analysis results, glass transition (T(g)) and initial degradation (T(i)) temperatures changed depending on the bulk fill resin composites.

  14. Improvement of the mechanical properties of bulk superconductors; Jushiganshin niyoru baruku chodendotai no kikaitekitokusei no kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Tomita, M; Murakami, M [Superconductivity Research Laboratory, Tokyo (Japan)

    1999-11-25

    Large single-grain bulk rare earth element (RE)-Ba-Cu-O superconductors can trip large fields exceeding several teslas and thus can function as very strong quasi-permanent magnets. However, the maximum trapped field is essentially limited by the mechanical strength of the bulk superconductors. The stress produced by refrigeration sometimes causes cracking. A large electromagnetic force also acts on superconductors when they trap large magnetic fields, and this occasionally leads to device failure. We have recently found that epoxy resin can penetrate into bulk superconductors under certain conditions. Microstructural observation revealed that microcracks as well as porosities can be impregnated with epoxy resin, which greatly improves the mechanical properties of bulk RE-Ba-Cu-O and thus results in the improvement of field trapping capability. (author)

  15. Synthesis, characterization and optical properties of nanoparticles

    Science.gov (United States)

    Li, Shoutian

    ZnO, Si, silica, Ge, Ga oxide, W oxide and Mo oxide nanoparticles have been synthesized and characterized, and their optical properties have been investigated. These particles were synthesized by a Laser Vaporization and Controlled Condensation (LVCC) technique in a modified diffusion cloud chamber. The particles deposited on smooth substrates reveal highly organized web-like structures with uniform micrometer size pores. The effect of solvents on the web-like structures was also investigated. ZnO nanoparticles were also prepared by wet chemical methods such as the reversed micelle and sol solutions technique. The photoluminescence quantum yield is enhanced 10 times once the surfaces of the ZnO nanoparticles are coated with a layer of stearate molecules. Many techniques have been used to characterize the nanoparticles. SEM gives information about particle size and morphology; X-ray diffraction and Raman spectroscopy determine the crystallinity and crystal structure; XPS and FTIR reveal the surface chemical composition; UV-vis spectroscopy and photoluminescence measurements characterize the optical properties of nanoparticles. Silica nanoparticles, prepared in an amorphous phase, show bright blue photoluminescence upon irradiation with UV light, but the luminescence has a very short lifetime (less than 20 ns). Si nanoparticles, with a diamond-like crystal phase, acquire oxidized-surfaces on exposure to air. The surface-oxidized Si nanocrystals show a short- lived blue emission characteristic of the SiO2 coating and a longer-lived red emission at room temperature. The lifetime of the red emission depends on the emission wavelength. Some substituted benzene molecules and tungsten oxide nanoparticles can quench the red photoluminescence of the Si nanocrystals. Tungsten oxide and molybdenum oxide nanoparticles show photochromic properties: they change color to blue when irradiated. The photons drive a transition from one chemical state to another. The color change of

  16. Structure and physical properties of silicon clusters and of vacancy clusters in bulk silicon

    CERN Document Server

    Sieck, A

    2000-01-01

    different from the solid. The calculated stabilities and positron-lifetimes of vacancy clusters in bulk silicon indicate the positron-lifetimes of about 435 ps detected in irradiated silicon to be related to clusters of 9 or 10 vacancies. The vacancies in these clusters form neighboring hexa-rings and, therefore, minimize the number of dangling bonds. In this thesis the growth-pattern of free silicon clusters and vacancy clusters in bulk silicon is investigated. The aim is to describe and to better understand the cluster to bulk transition. Silicon structures in between clusters and solids feature new interesting physical properties. The structure and physical properties of silicon clusters can be revealed by a combination of theory and experiment, only. Low-energy clusters are determined with different optimization techniques and a density-functional based tight-binding method. Additionally, infrared and Raman spectra, and polarizabilities calculated within self-consistent field density-functional theory are...

  17. Calculation of the Bulk Electromagnetic Properties of Thunderclouds Using a Two-Space Scattering Formalism

    Science.gov (United States)

    Phanord, Dieudonne D.; Koshak, William J.; Solakiewicz, Richard J.; Blakeslee, Richard J.

    1998-01-01

    A two-space scatterer formalism and equivalent medium approach of Twersky are used to obtain formulae for the bulk electromagnetic parameters of a thundercloud medium that is illuminated by lightning optical emissions. A modified WKB approximation is applied to derive the two-space scattering amplitude. Optical constants of dry air, moist atmosphere, and water,.are inserted into the formulae to generate numerical values via iteration. The two-space scatterer formalism results are close to those obtained from free- or sin-le-space formalisms for the dilute case. The numerical values of the bulk parameters are required to successfully transform the scattering problem to that of an equivalent obstacle excited by an incident wave traveling in K - space but radiating in k(sub 1) -space.

  18. Relationship between material properties and transparent heater performance for both bulk-like and percolative nanostructured networks.

    Science.gov (United States)

    Sorel, Sophie; Bellet, Daniel; Coleman, Jonathan N

    2014-05-27

    Transparent heaters are important for many applications and in the future are likely to be fabricated from thin, conducting, nanostructured networks. However, the electrical properties of such networks are almost always controlled by percolative effects. The impact of percolation on heating effects has not been considered, and the material parameter combinations that lead to efficient performance are not known. In fact, figures of merit for transparent heaters have not been elucidated, either in bulk-like or percolative systems. Here, we develop a simple yet comprehensive model describing the operation of transparent heaters. By considering the balance of Joule heating versus power dissipated by both convection and radiation, we derive an expression for the time-dependent heater temperature as a function of both electrical and thermal parameters. This equation can be modified to describe the relationship between temperature, optical transmittance, and electrical/thermal parameters in both bulk-like and percolative systems. By performing experiments on silver nanowire networks, systems known to display both bulk-like and percolative regimes, we show the model to describe real systems extremely well. This work shows the performance of transparent heaters in the percolative regime to be significantly less efficient compared to the bulk-like regime, implying the diameter of the nanowires making up the network to be critical. The model allows the identification of figures of merit for networks in both bulk-like and percolative regimes. We show that metallic nanowire networks are most promising, closely followed by CVD graphene, with networks of solution-processed graphene and carbon nanotubes being much less efficient.

  19. Photorefractive optics materials, properties, and applications

    CERN Document Server

    Yu, Francis T S

    1999-01-01

    The advances of photorefractive optics have demonstrated many useful and practical applications, which include the development of photorefractive optic devices for computer communication needs. To name a couple significant applications: the large capacity optical memory, which can greatly improve the accessible high-speed CD-ROM and the dynamic photorefractive gratings, which can be used for all-optic switches for high-speed fiber optic networks. This book is an important reference both for technical and non-technical staffs who are interested in this field. * Covers the recent development in materials, phenomena, and applications * Includes growth, characterization, dynamic gratings, and liquid crystal PR effect * Includes applications to photonic devices such as large capacity optical memory, 3-D interconnections, and dynamic holograms * Provides the recent overall picture of current trends in photorefractive optics * Includes optical and electronic properties of the materials as applied to dynamic photoref...

  20. Phase transformation and magnetic properties of Fe-Pt based bulk alloys

    NARCIS (Netherlands)

    de Boer, F.R.; Xiao, Q.F.; Zhang, Z.D.; Buschow, K.H.J.; Bruck, E.H.

    2004-01-01

    The ordering transformation and magnetic properties of Fe59.75Pt39.5Nb0.75 bulk alloys have been investigated in detail by using different homogenization temperatures and different low-temperature annealing times to obtain samples with different microstructure and different atomically ordered states

  1. Surface and bulk dissolution properties, and selectivity of DNA-linked nanoparticle assemblies

    NARCIS (Netherlands)

    Lukatsky, D.B.; Frenkel, D.

    2005-01-01

    Using a simple mean-field model, we analyze the surface and bulk dissolution properties of DNA-linked nanoparticle assemblies. We find that the dissolution temperature and the sharpness of the dissolution profiles increase with the grafting density of the single-stranded DNA "probes" on the surface

  2. "Peak tracking chip" for label-free optical detection of bio-molecular interaction and bulk sensing.

    Science.gov (United States)

    Bougot-Robin, Kristelle; Li, Shunbo; Zhang, Yinghua; Hsing, I-Ming; Benisty, Henri; Wen, Weijia

    2012-10-21

    A novel imaging method for bulk refractive index sensing or label-free bio-molecular interaction sensing is presented. This method is based on specially designed "Peak tracking chip" (PTC) involving "tracks" of adjacent resonant waveguide gratings (RWG) "micropads" with slowly evolving resonance position. Using a simple camera the spatial information robustly retrieves the diffraction efficiency, which in turn transduces either the refractive index of the liquids on the tracks or the effective thickness of an immobilized biological layer. Our intrinsically multiplex chip combines tunability and versatility advantages of dielectric guided wave biochips without the need of costly hyperspectral instrumentation. The current success of surface plasmon imaging techniques suggests that our chip proposal could leverage an untapped potential to routinely extend such techniques in a convenient and sturdy optical configuration toward, for instance for large analytes detection. PTC design and fabrication are discussed with challenging process to control micropads properties by varying their period (step of 2 nm) or their duty cycle through the groove width (steps of 4 nm). Through monochromatic imaging of our PTC, we present experimental demonstration of bulk index sensing on the range [1.33-1.47] and of surface biomolecule detection of molecular weight 30 kDa in aqueous solution using different surface densities. A sensitivity of the order of 10(-5) RIU for bulk detection and a sensitivity of the order of ∼10 pg mm(-2) for label-free surface detection are expected, therefore opening a large range of application of our chip based imaging technique. Exploiting and chip design, we expect as well our chip to open new direction for multispectral studies through imaging.

  3. An overview of micro-optical components and system technology: bulk, planar, and thin-film for laser initiated devices

    Science.gov (United States)

    Lizotte, Todd

    2010-08-01

    There are a number of attractive micro optical elements or combinations of elements that are currently used or could be employed in optically initiated ordnance systems. When taking a broad-spectrum examination of optically initiated devices, the required key parameters become obviously straightforward for micro optics. Plainly stated, micro optics need to be simple, inexpensive, reliable, robust and compatible within their operational environment. This presentation focuses on the variety of optical elements and components available in the market place today that could be used to realize micro-optical beam shaping and delivery systems for optically initiated devices. A number of micro optical elements will be presented with specific bulk, planar optical and thin film optical devices, such as diffractive optics, micro prisms, axicons, waveguides, micro lenses, beam splitters and gratings. Further descriptions will be presented on the subject of coupling light from a laser beam into a multimode optical fiber. The use of micro optics for collimation of the laser source and conditioning of the laser beam to achieve the highest efficiency and matching the optical fiber NA will be explained. An emphasis on making these optical assemblies compact and rugged will be highlighted.

  4. Two Dimensional Organometal Halide Perovskite Nanorods with Tunable Optical Properties.

    Science.gov (United States)

    Aharon, Sigalit; Etgar, Lioz

    2016-05-11

    Organo-metal halide perovskite is an efficient light harvester in photovoltaic solar cells. Organometal halide perovskite is used mainly in its "bulk" form in the solar cell. Confined perovskite nanostructures could be a promising candidate for efficient optoelectronic devices, taking advantage of the superior bulk properties of organo-metal halide perovskite, as well as the nanoscale properties. In this paper, we present facile low-temperature synthesis of two-dimensional (2D) lead halide perovskite nanorods (NRs). These NRs show a shift to higher energies in the absorbance and in the photoluminescence compared to the bulk material, which supports their 2D structure. X-ray diffraction (XRD) analysis of the NRs demonstrates their 2D nature combined with the tetragonal 3D perovskite structure. In addition, by alternating the halide composition, we were able to tune the optical properties of the NRs. Fast Fourier transform, and electron diffraction show the tetragonal structure of these NRs. By varying the ligands ratio (e.g., octylammonium to oleic acid) in the synthesis, we were able to provide the formation mechanism of these novel 2D perovskite NRs. The 2D perovskite NRs are promising candidates for a variety of optoelectronic applications, such as light-emitting diodes, lasing, solar cells, and sensors.

  5. The CLASS blazar survey - II. Optical properties

    NARCIS (Netherlands)

    Caccianiga, A; Marcha, MJ; Anton, S; Mack, KH; Neeser, MJ

    2002-01-01

    This paper presents the optical properties of the objects selected in the CLASS blazar survey. Because an optical spectrum is now available for 70 per cent of the 325 sources present in the sample, a spectral classification, based on the appearance of the emission/absorption lines, is possible. A wi

  6. Handbook of the Properties of Optical Materials

    Science.gov (United States)

    1984-01-01

    EFFECTIVE MASS - - MOBILITY - - A-2 ARSEWIC SELENIOE (As2 Se3 ) OPTICAL PROPERTIES TRANSMISSION RANGE: 9 - 11n Optical Absorption Coefficient = 0.079...of 55 KRS-5 as a function of wavelength. A-2120 ZINC SELENIOE ZnSe 0 STRUCTURE CRYSTALLINE SYMMETRY = Cubic, 43m LATTICE CONSTANTS (A) = a = 5.667

  7. Optical properties of ALON (aluminum oxynitride)

    Science.gov (United States)

    Hartnett, T. M.; Bernstein, S. D.; Maguire, E. A.; Tustison, R. W.

    1998-06-01

    The optical properties of ALON (aluminum oxynitride) are presented. Optical scatter and index of refraction, and absorption of several different compositions of ALON are compared. The temperature dependence of emissivity of ALON was measured in the temperature range 46°C to 1200°C.

  8. The CLASS blazar survey - II. Optical properties

    NARCIS (Netherlands)

    Caccianiga, A; Marcha, MJ; Anton, S; Mack, KH; Neeser, MJ

    2002-01-01

    This paper presents the optical properties of the objects selected in the CLASS blazar survey. Because an optical spectrum is now available for 70 per cent of the 325 sources present in the sample, a spectral classification, based on the appearance of the emission/absorption lines, is possible. A

  9. Properties of Single Mode Polymer Optical Fiber

    Institute of Scientific and Technical Information of China (English)

    YANG Dong-xiao

    2003-01-01

    The density,dynamic modulus,Young's modulus,tensile strength,extension properties,Fourier transform infrared spectrum and differential scanning calorimetry have been measured and discussed for single mode polymethyl-methacrylate optical fiber.The results show that the fiber can provide large strain range for polymeric optical fiber Bragg gratings.

  10. Optical Properties of Rotationally Twinned Nanowire Superlattices

    DEFF Research Database (Denmark)

    Bao, Jiming; Bell, David C.; Capasso, Federico

    2008-01-01

    We have developed a technique so that both transmission electron microscopy and microphotoluminescence can be performed on the same semiconductor nanowire over a large range of optical power, thus allowing us to directly correlate structural and optical properties of rotationally twinned zinc ble...

  11. Growth of Ce:LiYF{sub 4} bulk single crystal with high Ce concentration by Cz method and the scintillation properties

    Energy Technology Data Exchange (ETDEWEB)

    Yokota, Yuui; Yamaji, Akihiro; Kurosawa, Shunsuke [Institute for Materials Research, Tohoku University, Sendai, 9808577 Miyagi (Japan); Kawaguchi, Noriaki; Fukuda, Kentaro [Tokuyama Corp., Sendai, 9893204 Miyagi (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, Sendai, 9808577 Miyagi (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai, 9893204 Miyagi (Japan)

    2012-12-15

    Ce 2% doped LiYF4 [Ce:LYF] bulk single crystal was grown by Czochralski method and the structural phase, crystallinity, optical properties and scintillation properties were investigated. Grown Ce:LYF bulk single crystal included some cracks in the initial part of crystal and meanwhile there were no visible cracks in the center and end parts. Full width of half maximum of X-ray rocking curve on the plate crystal in center part of Ce:LYF bulk single crystal was 81.4 arcsec. Alpha-ray position in the pulse-height spectra under alpha-ray irradiation was almost quarter that of Li-glass(GS20). Decay times of the crystals in center and end parts were 69.9 and 58.3 ns, respectively (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Nanomechanical properties of selected single pharmaceutical crystals as a predictor of their bulk behaviour.

    Science.gov (United States)

    Egart, Mateja; Janković, Biljana; Lah, Nina; Ilić, Ilija; Srčič, Stanko

    2015-02-01

    The main goal of this research was to assess the mechanical properties of APIs' polymorphic forms at the single-crystal level (piroxicam, famotidine, nifedipine, olanzapine) in order to predict their bulk deformational attributes, which are critical for some pharmaceutical technology processes. The mechanical properties of oriented single crystals were determined using instrumented nanoindentation (continuous stiffness measurement). All polymorphic forms investigated were previously identified using a combination of calorimetric and spectroscopic techniques. Mechanical properties such as Young's modulus and indentation hardness were consistent with the molecular packing of the polymorphic forms investigated with respect to crystal orientation. For mechanically interlocked structures, characteristic of most polymorphic forms, response of single crystals to indentation was isotropic. The material's bulk elastic properties can be successfully predicted by measuring Young's modulus of single crystals because a good linear correlation with a bulk parameter such as the tablets' elastic relaxation index was determined. The results confirm the idea that the intrinsic mechanical properties of pharmaceutical crystals (Young's modulus) largely control and anticipate their deformational behavior during tablet compression. Young's modulus and indentation hardness represent a very valuable and effective tool in preformulation studies for describing materials' mechanical attributes, which are important for technological processes in which materials are exposed to deformation.

  13. Effect of Density and Surface Roughness on Optical Properties of Silicon Carbide Optical Components

    Institute of Scientific and Technical Information of China (English)

    LIU Gui-Ling; HUANG Zheng-Ren; LIU Xue-Jian; JIANG Dong-Liang

    2008-01-01

    @@ The effect of density and surface roughness on the optical properties of silicon carbide optical components is investigated.The density is the major factor of the total reflectance while the surface roughness is the major factor of the diffuse reflectance.The specular reflectance of silicon carbide optical components can be improved by increasing the density and decreasing the surface roughness,in the form of reducing bulk absorption and surface-related scattering,respectively.The contribution of the surface roughness to the specular reflectance is much greater than that of the density.When the rms surface roughness decreases to 2.228nm,the specular reflectance decreases to less than 0.7% accordingly.

  14. High temperature superconductor bulk materials fundamentals, processing, properties control, applications aspects

    CERN Document Server

    Krabbes, Gernot; Canders, Wolf-Rüdiger; May, Hardo; Palka, Ryszard

    2005-01-01

    With its comprehensive review of the current knowledge and the future requirements in the field, this book presents all the features of bulk high temperature superconducting materials. Starting from physical and chemical fundamentals, the authors move on to portray methods and problems of materials processing, thoroughly working out the characteristic properties of bulk superconductors in contrast to long conductors and films. They provide a wide range of specific materials characteristics with respect to the latest developments and future applications guiding from fundamentals to practical engineering examples. The authors are all leading international specialists involved in the field of high TC superconductor bulk materials since the beginning. Of utmost interest to engineers, scientists, and PhD students working in this field

  15. Effects of cooling rates on the mechanical properties of a Ti-based bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Mechanical properties of the glassy specimens fabricated at different cooling rates with a composition of Ti40Zr25Cu12Ni3Be20 were systematically investigated. It was confirmed that faster cooling rates caused not only a larger amount of frozen-in free volume but also a higher glass transition temperature in the bulk glassy alloy. Increase in the free volume was found to favor plastic deformation and then to give rise to larger compressive plasticity, whilst the rise in the glass transition temperature seemed to be closely related to the higher yield strength. Moreover, the increase of yield strength and plasticity induced by fast cooling rates may also be associated with the residual stress generated during the fabrication process. Our results suggest that the deformation behavior of bulk metallic glasses is sensitive to various factors and influences from the other factors should be excluded as far as cooling-rate effects on bulk metallic glasses are considered.

  16. Results of potentiometric and optical properties of shabo terroir wines

    OpenAIRE

    Иукуридзе, Элдар Жораевич

    2015-01-01

    The RO-potential value is of particular importance in the production of dry and sparkling wines. Compliance of wine products with regulatory requirements characterizes the quality features and individual characteristics of different bulk wines. These include potentiometric and optical characteristics of bulk wines and wines.The purpose of the work is to conduct research for determining the potentiometric and optical characteristics of bulk wines, provided by the "PTK Shabo" LLC.For determinin...

  17. Effects of binder addition on the mechanical properties of bulk Y-Ba-Cu-O superconductors

    Science.gov (United States)

    Seki, H.; Wongsatanawarid, A.; Kobayashi, S.; Ikeda, Y.; Murakami, M.

    2010-11-01

    We studied the effects of binder addition on the mechanical properties of bulk Y-Ba-Cu-O superconductors. We prepared YBa2Cu3Oy, Y2BaCuO5 powders and polyvinyl alcohol mixed with water as a binder. These raw materials were mixed, and the binder-added powders were pressed into pellets. The hardness of the green compacts with binder is higher than that without the binder. However, the hardness of green compacts with 8% binder is the same as that with 4% binder. The maximum compression strength of the precursor with binder is higher than that without binder. Equally, the maximum strength of the green compacts with 8% binder is higher than that with 4% binder. The differential thermal analysis measurements showed that the exothermic reaction due to the decomposition of the organic binder started at 550 °C and gradually proceeded with further heating. After de-binder treatment, BaCO3 powders were produced on the green compacts. The green compacts were subjected to melt-processing. We also measured trapped magnetic fields of binder-added bulk Y-Ba-Cu-O superconductors with a Hall probe scanning device. Trapped magnetic field of the bulk added with 4% is higher than that of the binder-free bulk. Hence, Y-Ba-Cu-O bulk with suitable amount of binder shows good influence for mechanical strength and trapped magnetic field.

  18. Thermal properties measurement of dry bulk materials with a cylindrical three layers device

    Science.gov (United States)

    Jannot, Y.; Degiovanni, A.

    2013-09-01

    This paper presents a new method dedicated to thermal properties (conductivity and diffusivity) measurement of dry bulk materials including powders. The cylindrical three layers experimental device (brass/bulk material/stainless steel) and the principle of the measurement method based on a crenel thermal excitation are presented. The one-dimensional modeling of the system is used for a sensitivity analysis and to calculate the standard deviation of the estimation error. Experimental measurements are carried out on three bulk materials: glass beads, cork granules, and expanded polystyrene beads. The estimated thermal properties are compared with the values obtained by other measurement methods. Results are in good agreement with theoretical predictions: both thermal conductivity and diffusivity can be estimated with a good accuracy for low density material like cork granules or expanded polystyrene beads since only thermal diffusivity can be estimated for heavier materials like glass beads. It is finally shown that this method like all transient methods is not suited to the thermal characterization of wet bulk materials.

  19. Optical properties of a heated cornstarch mixture

    Science.gov (United States)

    Vazquez-Landaverde, Pedro A.; Morales Sánchez, Eduardo; Huerta-Ruelas, Jorge A.

    2007-03-01

    In this study, the objective was to evaluate optical properties of a corn starch-water mixture as descriptors of its behavior under processing conditions. A solution of corn starch in water was prepared and heated from 25 to 85°C in a temperature-controlled optical cell. For the measurement of optical properties, a polarized laser beam modulated through a photoelastic modulator and an analyzer, was used as optical probe. It was possible to measure transmitted light, along with optical rotation. Optical measurements showed changes related to temperature dependent phenomena such as starch granule swelling and gelatinization, in the ranges 25 to 60°C, 60 to 85°C. Above 80°C transmission values were higher, due to the solution clarification caused by corn starch gelatinization. Regarding optical rotation, it was difficult to obtain reliable measurements at low temperatures due to the high turbidity of the system. However, once gel was formed at higher temperatures, optical rotation and light transmission increased. This study demonstrated that optical techniques are suitable for the study of the behavior of water-starch mixtures under processing conditions such as heating, revealing a promising future for the monitoring of such phenomena in the production line to lower costs and improve product quality.

  20. Titania doping effect on superconducting properties of MgB2 bulk samples

    Science.gov (United States)

    Serrano, G.; Bridoux, G.; Serquis, A.

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB2 samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO2 nanotubes contents, annealed at different temperatures in the 750-900°C range. We discuss the Tc, Jc and Hc2 performance and their correlation with the different synthesis parameters.

  1. First principle investigation of structural and electronic properties of bulk ZnSe

    Energy Technology Data Exchange (ETDEWEB)

    Khatta, Swati; Tripathi, S. K., E-mail: surya@pu.ac.in; Prakash, Satya [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh-160 014 (India)

    2015-08-28

    Electronic and structural properties of ZnSe are investigated using plane-wave self-consistent field method within the framework of density functional theory. The pseudopotential method within the local density approximation is used for the exchange-correlation potential. The equilibrium lattice parameter, static bulk modulus and its pressure derivative are calculated. The electronic band structure, partial density of states and density of states are also obtained. The results are compared with available theoretical calculations and experimental results.

  2. Titania doping effect on superconducting properties of MgB{sub 2} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, G; Serquis, A [Institute Balseiro - Centra Atomico Bariloche and CONICET, (8400) S. C. de Bariloche, Rio Negro (Argentina); Bridoux, G, E-mail: serranog@ib.cnea.gov.a [Institute Balseiro - Centra Atomico Bariloche, (8400) S. C. de Bariloche, Rio Negro (Argentina)

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB{sub 2} samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO{sub 2} nanotubes contents, annealed at different temperatures in the 750-900 deg. C range. We discuss the T{sub c}, J{sub c} and H{sub c2} performance and their correlation with the different synthesis parameters.

  3. Optical properties of molecules chemisorbed on the Ni (111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Robota, H. J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Whitmore, P. M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Harris, C. B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

    1982-02-15

    The adsorption of a variety of molecules on Ni(111) is studied by UV/visible spectroscopic ellipsometry. The spectra were analyzed within a simple dielectric model. The absorption spectra of annealed, thin, condensed layers of pyrazine, pyridine, and naphthalene on the Ni(111) surface resemble bulk crystal spectra, indicating minimal perturbations due to the metal substrate. Chemisorption of molecules on the Ni(111) surface produced enhanced absorption between 2800Å and 3100Å. The wide range of adsorbate properties and surface chemistry suggest a modification of the optical response of the metal upon chemisorption. Furthermore, this enhanced optical absorption is attributed to nonvertical interband transitions made possible by loss of translational invariance at the surface.

  4. Hyperhoneycomb boron nitride with anisotropic mechanical, electronic, and optical properties

    Science.gov (United States)

    Yu, Jin; Qu, Lihua; van Veen, Edo; Katsnelson, Mikhail I.; Yuan, Shengjun

    2017-09-01

    Boron nitride structures have excellent thermal and chemical stabilities. Based on state-of-art theoretical calculations, we propose a wide-gap semiconducting BN crystal with a three-dimensional hyperhoneycomb structure (Hp-BN), which is both mechanically and thermodynamically stable. Our calculated results show that Hp-BN has a higher bulk modulus and a smaller energy gap as compared to c-BN. Moreover, due to the unique bonding structure, Hp-BN exhibits anisotropic electronic and optical properties. It has great adsorption in the ultraviolet region, but it is highly transparent in the visible and infrared region, suggesting that the Hp-BN crystal could have potential applications in electronic and optical devices.

  5. Giant magneto-optical response in non-magnetic semiconductor BiTeI driven by bulk Rashba spin splitting

    OpenAIRE

    Demkó, L.; Schober, G. A. H.; Kocsis, V.; Bahramy, M.S.; Murakawa, H.; Lee, J. S.; Kézsmárki, I.; Arita, R.; Nagaosa, N.; Tokura, Y.

    2012-01-01

    We study the magneto-optical (MO) response of polar semiconductor BiTeI with giant bulk Rashba spin splitting at various carrier densities. Despite being non-magnetic, the material is found to yield a huge MO activity in the infrared region under moderate magnetic fields (

  6. Optical Property Analyses of Plant Cells for Adaptive Optics Microscopy

    Science.gov (United States)

    Tamada, Yosuke; Murata, Takashi; Hattori, Masayuki; Oya, Shin; Hayano, Yutaka; Kamei, Yasuhiro; Hasebe, Mitsuyasu

    2014-04-01

    In astronomy, adaptive optics (AO) can be used to cancel aberrations caused by atmospheric turbulence and to perform diffraction-limited observation of astronomical objects from the ground. AO can also be applied to microscopy, to cancel aberrations caused by cellular structures and to perform high-resolution live imaging. As a step toward the application of AO to microscopy, here we analyzed the optical properties of plant cells. We used leaves of the moss Physcomitrella patens, which have a single layer of cells and are thus suitable for optical analysis. Observation of the cells with bright field and phase contrast microscopy, and image degradation analysis using fluorescent beads demonstrated that chloroplasts provide the main source of optical degradations. Unexpectedly, the cell wall, which was thought to be a major obstacle, has only a minor effect. Such information provides the basis for the application of AO to microscopy for the observation of plant cells.

  7. Optical properties of a scorpion (Centruroides limpidus)

    Science.gov (United States)

    Ullrich, Bruno; Duckworth, Robyn M.; Singh, Akhilesh K.; Barik, Puspendu; Mejía-Villanueva, Vicente O.; Garcia-Pérez, Alberto C.

    2016-04-01

    Scorpions, elusive by nature, tend to appear nocturnally and are usually not appreciated when encountered. The exoskeleton is capable of fluorescing allowing for their detection at night in order to prevent undesirable encounters. The specificity of their fluorescing suggests specialized optical features. However, despite the blue-green fluorescence, to the best of our knowledge, no further results have been published on the optical properties of scorpions. Their exoskeletal structure whose versatility provides them protection, camouflage, and flexibility has not been studied under laser excitation and monochromatic light. The experiments reveal the nonlinear optical properties, infrared photoluminescence, and photoconductivity of the epicuticle of scorpions, demonstrating that the scorpion’s outer-covering is a prototype of a semiconducting inherently integrated multifunctional polymeric film with appealing potential applications such as optical logics, photonic frequency converters, novel multiplexers handling electronic and photonic inputs, and lasers.

  8. Bulk magnetic properties of CdFe2O4 in nano-regime

    Indian Academy of Sciences (India)

    Rucha Desai; R V Mehta; R V Upadhyay; Amita Gupta; A Praneet; K V Rao

    2007-06-01

    Cadmium ferrite particles have been synthesized using co-precipitation technique followed by a low temperature (600°C) annealing in a time scale much shorter than reported in literature. Incorporation of sodium chloride during annealing helps to form a single phase spinel structure with a final particle size of around 50 nm. Even at such a short length scale we observe the overall magnetic properties to be similar to those of the bulk. The observed magnetic properties can be explained on the basis of an anti-ferromagnetic core with a shell containing ‘ferromagnetic-like’, but canted spin structure.

  9. Crystallization and thermophysical properties of Cu46Zr47Al6Co1 bulk metallic glass

    Directory of Open Access Journals (Sweden)

    Kang Wu

    2013-11-01

    Full Text Available Phase evolution of two-step crystallization and the subsequent B2-phase transformation was presented in Cu46Zr47Al6Co1 bulk metallic glass (BMG during heating process. Thermophysical properties, i.e. the thermal diffusivity and the specific heat capacity, of the BMG in amorphous solid state and supercooled liquid state as well as its crystalline counterparts were measured from room temperature to 1070 K. The thermal conductivity was also calculated through combination of the data of the thermal diffusivity and the specific heat capacity. The possible influence of the crystallization on the thermophysical properties was discussed.

  10. Optical properties of cluster plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Yasuaki; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment; Downer, M.C.

    1998-03-01

    It is shown that unlike a gas plasma or an electron plasma in a metal, an ionized clustered material (`cluster plasma`) permits propagation below the plasma cut-off of electromagnetic (EM) waves whose phase velocity is close to but below the speed of light. This results from the excitation of a plasma oscillation mode (and/or polarization mode) through the cluster surface which does not exist in usual gaseous plasma. The existence of this new optical mode, cluster mode, is confirmed via numerical simulation. (author)

  11. Anionic or Cationic S-Doping in Bulk Anatase TiO 2 : Insights on Optical Absorption from First Principles Calculations

    KAUST Repository

    Harb, Moussab

    2013-05-02

    Using first principles calculations, we investigate the structural, electronic, optical, and energetic properties of S-doped anatase TiO2 bulk systems. To ensure accurate band gap predictions, we use the HSE06 exchange correlation functional, and the absorption spectra are obtained with density functional perturbation (DFPT) theory by employing HSE06. Various oxidation states (anionic and cationic) of sulfur are considered depending on the location in bulk TiO2: in interstitial position or in substitution for either oxygen or titanium atoms. Among the explored structures, two anionic and one cationic configurations induce an improved optical absorption response in the visible region as observed experimentally. Moreover, we undertake a thermodynamic analysis as a function of the chemical potential of oxygen and considering three relevant sulfur chemical doping agents (S 2, H2S, and thiourea). It highlights that cationic configurations (S4+ and S6+) are strongly stabilized in a wide range of oxygen chemical potential (including standard conditions), whereas anionic species are stabilized only at very low chemical potential of oxygen. The metastable cationic Ti(1-2x)O2S2x system involving the presence of S4+ species in substitution for Ti 4+, with the formation of SO2 units, should offer the best compromise between the thermodynamic conditions and the expected optical properties. © 2013 American Chemical Society.

  12. Linear Optical Properties of Gold Colloid

    Directory of Open Access Journals (Sweden)

    Jingmin XIA

    2015-11-01

    Full Text Available Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9558

  13. Effective Optical Properties of Plasmonic Nanocomposites

    Directory of Open Access Journals (Sweden)

    Christoph Etrich

    2014-01-01

    Full Text Available Plasmonic nanocomposites find many applications, such as nanometric coatings in emerging fields, such as optotronics, photovoltaics or integrated optics. To make use of their ability to affect light propagation in an unprecedented manner, plasmonic nanocomposites should consist of densely packed metallic nanoparticles. This causes a major challenge for their theoretical description, since the reliable assignment of effective optical properties with established effective medium theories is no longer possible. Established theories, e.g., the Maxwell-Garnett formalism, are only applicable for strongly diluted nanocomposites. This effective description, however, is a prerequisite to consider plasmonic nanocomposites in the design of optical devices. Here, we mitigate this problem and use full wave optical simulations to assign effective properties to plasmonic nanocomposites with filling fractions close to the percolation threshold. We show that these effective properties can be used to properly predict the optical action of functional devices that contain nanocomposites in their design. With this contribution we pave the way to consider plasmonic nanocomposites comparably to ordinary materials in the design of optical elements.

  14. Electronic and optical properties of lead iodide

    DEFF Research Database (Denmark)

    Ahuja, R.; Arwin, H.; Ferreira da Silva, A.

    2002-01-01

    The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising...... detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given. ©2002 American Institute of Physics....

  15. Microfabrication with femtosecond laser processing : (A) laser ablation of ferrous alloys, (B) direct-write embedded optical waveguides and integrated optics in bulk glasses.

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Junpeng; McDaniel, Karen Lynn; Palmer, Jeremy Andrew; Yang, Pin; Griffith, Michelle Lynn; Vawter, Gregory Allen; Harris, Marc F.; Tallant, David Robert; Luk, Ting Shan; Burns, George Robert

    2004-11-01

    -write optical waveguides and integrated optics in bulk glass. The effects of laser and environmental parameters on such aspects as removal rate, feature size, feature definition, and ablation angle during the ablation process of metals were studied. In addition, the manufacturing requirements for component fabrication including precision and reproducibility were investigated. The effect of laser processing conditions on the optical properties of direct-written waveguides and an unusual laser-induced birefringence in an optically isotropic glass are reported. Several integrated optical devices, including a Y coupler, directional coupler, and Mach-Zehnder interferometer, were made to demonstrate the simplicity and flexibility of this technique in comparison to the conventional waveguide fabrication processes.

  16. Simultaneous description of bulk and interfacial properties of fluids by the Mie potential

    CERN Document Server

    Werth, Stephan; Horsch, Martin; Hasse, Hans

    2016-01-01

    The vapor-liquid equilibrium (VLE) of the Mie potential, where the dispersive exponent is constant (m = 6) while the repulsive exponent n is varied between 9 and 48, is systematically investigated by molecular simulation. For systems with planar vapor-liquid interfaces, long-range correction expressions are derived, so that interfacial and bulk properties can be computed accurately. The present simulation results are found to be consistent with the available body of literature on the Mie fluid which is substantially extended. On the basis of correlations for the considered thermodynamic properties, a multicriteria optimization becomes viable. Thereby, users can adjust the three parameters of the Mie potential to the properties of real fluids, weighting different thermodynamic properties according to their importance for a particular application scenario. In the present work, this is demonstrated for carbon dioxide for which different competing objective functions are studied which describe the accuracy of the...

  17. Optical properties of zinc oxide clusters encapsulated in a zeolite host

    OpenAIRE

    Türk, T.; Sabin, F.; Vogler, Arnd

    1992-01-01

    The optical properties of nanometer-sized semiconductor materials are of interest in areas such as photocatalysis and non-linear optics. Ultrasmall zinc oxide particles encapsulated in a porous zeolite (A) host were characterized by powder X-ray diffraction, reflectance, and luminescence spectra. Compared to bulk ZnO the particles show pronounced blue shifts of the reflectance as well as the luminescence bands owing to the quantum size effect.

  18. Optical Properties of Mineral Particles and Their Effect on Remote-Sensing Reflectance in Coastal Waters

    Science.gov (United States)

    2001-09-30

    1997. Photometric immersion refractometry : A method for determining the refractive index of marine microbial particles from beam attenuation...light is collected by the absorption meter due to geometry of instrument. In the previous report we described our effort to develop a method for...bulk optical properties in coastal waters, (2) develop reliable remote sensing algorithms for coastal waters, (3) develop improved methods for optical

  19. Nanostructuring and Thermoelectric Properties of Bulk N-type Mg2Si

    Institute of Scientific and Technical Information of China (English)

    YANG Meijun; ZHANG Lianmeng; SHEN Qiang

    2009-01-01

    Preparation and thermoelectric properties of nanostructured n-type Mg_2Si bulk ma-terials were reported.Nanosized Mg_2Si powder was obtained by mechanical milling of the microsized Mg_2Si powder prepared by solid-state reaction.The bulk materials with 30 nm and 5μm were prepared by spark plasma sintering of the nanosized and microsized Mg_2Si powder,respectively.Both the samples show n-type conduction and the Seebeck coefficient of the sintered samples increase deter-minately with the grain size decrease from 5μm to 30 nm.On the other hand,the electrical and thermal conductivity decrease with the decrease of grain size.Accordingly,decreasing their grain size in-creases their thermoelectric-figure-of-merit.A maximum thermoelectric figure of merit of 0.36 has been obtained for the nanostuctured Mg_2Si sample at 823 K,which is 38%higher than that of mi-crosized Mg_2Si bulk materials and higher than results of other literatures.It could be expected that the properties of the nanocomposites could be further improved by doping optimization.

  20. A robust, melting class bulk superhydrophobic material with heat-healing and self-cleaning properties

    Science.gov (United States)

    Ramakrishna, S.; Santhosh Kumar, K. S.; Mathew, Dona; Reghunadhan Nair, C. P.

    2015-01-01

    Superhydrophobic (SH) materials are essential for a myriad of applications such as anti-icing and self-cleaning due to their extreme water repellency. A single, robust material simultaneously possessing melt-coatability, bulk water repellency, self-cleanability, self-healability, self-refreshability, and adhesiveness has been remaining an elusive goal. We demonstrate a unique class of melt-processable, bulk SH coating by grafting long alkyl chains on silica nanoparticle surface by a facile one-step method. The well-defined nanomaterial shows SH property in the bulk and is found to heal macro-cracks on gentle heating. It retains wettability characteristics even after abrading with a sand paper. The surface regenerates SH features (due to reversible self-assembly of nano structures) quickly at ambient temperature even after cyclic water impalement, boiling water treatment and multiple finger rubbing tests. It exhibits self-cleaning properties on both fresh and cut surfaces. This kind of coating, hitherto undisclosed, is expected to be a breakthrough in the field of melt-processable SH coatings. PMID:26679096

  1. Macroscopic Properties of Restacked, Redox-Liquid Exfoliated Graphite and Graphite Mimics Produced in Bulk Quantities

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Vikram K [ORNL; Quinlan, Ronald [ORNL; Agapov, Alexander L [ORNL; Dunlap, John R [ORNL; Nelson, Kimberly M [ORNL; Duranty, Edward R [ORNL; Sokolov, Alexei P [ORNL; Bhat, Gajanan [ORNL; Mays, Jimmy [ORNL

    2014-01-01

    The excellent properties exhibited by monolayer graphene have spurred the development of exfoliation techniques using bulk graphite to produce large quantities of pristine monolayer sheets. Development of simple chemistry to exfoliate and intercalate graphite and graphite mimics in large quantities is required for numerous applications. To determine the macroscopic behavior of restacked, exfoliated bulk materials, a systematic approach is presented using a simple, redox-liquid sonication process along to obtain large quantities of 2D and 3D hexagonally layered graphite, molybdenum disulfi de, and boron nitride, which are subsequently characterized to observe chemical and structural changes. For MoS 2 sonicated with the antioxidant sodium bisulfi te, results from Raman spectroscopy, X-ray diffraction, and electron microscopy indicate the presence of distorted phases from different polymorphs, and apparent nanotube structures in the bulk, restacked powder. Furthermore, using thermograviemtric analysis, the antioxidant enhances the resistance to oxidative degradation of MoS 2 , upon thermal treatment up to 900 C. The addition of the ionic antioxidant decreased dispersion stability in non-polar solvent, suggesting decreased compatibility with non-polar systems. Using simple chemical methods, the ability to generate tailored multidimensional layered materials with unique macroscopic properties is critical for numerous applications, including electrical devices, reinforced polymer composites, lithium ion capacitors, and chemical sensing.

  2. Quick preparation and thermal transport properties of nanostructured β-FeSi2 bulk material

    Institute of Scientific and Technical Information of China (English)

    Li Han; Tang Xin-Feng; Cao Wei-Qiang; Zhang Qing-Jie

    2009-01-01

    This paper reports that the nanostructured β-FeSi2 bulk materials are prepared by a new synthesis process by combining melt spinning (MS) and subsequent spark plasma sintering (SPS). It investigates the influence of linear speed of the rolling copper wheel, injection pressure and SPS regime on microstructure and phase composition of the rapidly solidified ribbons after MS and bulk production respectively, and discusses the effects of the microstructure on Sis2 and ε-FeSi) in the rapidly solidified ribbons;thermal transport properties. There are two crystalline phases (α-Fe the crystal grains become smaller when the cooling rate increases (the 20 nm minimum crystal of ε-FeSi is obtained). Having been sintered for 1 min above 1123K and annealed for 5min at 923K, the single-phase nanostructured β- FeSi2 bulk materials with 200-500 nm grain size and 98% relative density are obtained. The microstructure of β-FeSi2has great effect on thermal transport properties. With decreasing sintering temperature, the grain size decreases, the thermal conductivity of β-FeSi2is reduced remarkably. The thermal conductivity of β-FeSi decreases notably (reduced 72% at room temperature) in comparison with the β-FeSi2prepared by traditional casting method.

  3. Electronic structure and optical properties of boron suboxide B6O system: First-principles investigations

    Science.gov (United States)

    Wang, Jinjin; Wang, Zhanyu; Jing, Yueyue; Wang, Songyou; Chou, Che-Fu; Hu, Han; Chiou, Shan-Haw; Tsoo, Chia-Chin; Su, Wan-Sheng

    2016-10-01

    The structural, mechanical, electronic, and optical properties of B6O were explored by means of first-principles calculations. Such a system is mechanically stable and also a relatively hard material which are derived from obtained elastic constants and bulk moduli. Bulk B6O is a direct-gap semiconductor with a bandgap of about 2.93 eV within G0W0 approximation. Furthermore, the optical properties, such as real and imaginary parts of dielectric functions, refractive index and extinction coefficient, and the comparison of optical properties between the density-functional theory (DFT) and G0W0 Bethe-Salpeter equation (G0W0-BSE) results, were computed and discussed. The results obtained from our calculations open a possibility for expanding its use in device applications.

  4. Optical properties of low-dimensional materials

    CERN Document Server

    Ogawa, T

    1998-01-01

    This book surveys recent theoretical and experimental studies of optical properties of low-dimensional materials. As an extended version of Optical Properties of Low-Dimensional Materials (Volume 1, published in 1995 by World Scientific), Volume 2 covers a wide range of interesting low-dimensional materials including both inorganic and organic systems, such as disordered polymers, deformable molecular crystals, dilute magnetic semiconductors, SiGe/Si short-period superlattices, GaAs quantum wires, semiconductor microcavities, and photonic crystals. There are excellent review articles by promis

  5. Ab initio calculation of the optical and magneto-optical properties of moderately correlated magnetic solids

    Energy Technology Data Exchange (ETDEWEB)

    Perlov, A. E-mail: alexander.perlov@cup.uni-muenchen.de; Chadov, S.; Ebert, H.; Chioncel, L.; Lichtenstein, A.I.; Katsnelson, M.I

    2004-05-01

    An approach for the calculation of the optical and magneto-optical properties of solids based on the one-particle Green function is introduced in the framework of the linear muffin-tin orbital (LMTO) method. The approach keeps all advantages of the more accurate Korringa-Kohn-Rostoker (KKR) scheme as the possibility to account for many-body effects in terms of the non-local energy-dependent self-energy but is numerically much more efficient. In particular an incorporation of the single-site self-energy coming from the dynamical mean-field theory (DMFT) is implemented. An application of the approach to bulk Ni and Fe showed rather good agreement with the experimental data, in contrast with the results of standard local spin density approximation (LSDA) computations.

  6. Improved ice particle optical property simulations in the ultraviolet to far-infrared regime

    Science.gov (United States)

    Bi, Lei; Yang, Ping

    2017-03-01

    To derive the bulk radiative properties of ice clouds, aircraft contrails and snow grains, which are fundamental to atmospheric radiative transfer calculations in downstream applications, it is necessary to accurately simulate the scattering of light by individual ice particles. An ice particle optical property database reported in 2013 (hereafter, TAMUice2013) is updated (hereafter, TAMUice2016) to incorporate recent advances in computation of the optical properties of nonspherical particles. Specifically, we employ the invariant imbedding T-matrix (II-TM) method to compute the optical properties of particles with small to moderate size parameters. Both versions use the Improved Geometric Optics Method (IGOM) to compute the optical properties of large ice crystals, but TAMUice2016 improves the treatment of inhomogeneous waves inside the scattering particles in the case where ice is absorptive such as at infrared wavelengths. To bridge the gap between the extinction efficiencies computed from the II-TM and the IGOM, TAMUice2016 includes spectrally dependent higher order terms of the edge effect in addition to the first order counterpart considered in TAMUice2013. Furthermore, the differences between TAMUice2013 and TAMUice2016 are quantified with respect to the computation of the bulk optical properties of ice clouds.

  7. Using molecular mechanics to predict bulk material properties of fibronectin fibers.

    Directory of Open Access Journals (Sweden)

    Mark J Bradshaw

    Full Text Available The structural proteins of the extracellular matrix (ECM form fibers with finely tuned mechanical properties matched to the time scales of cell traction forces. Several proteins such as fibronectin (Fn and fibrin undergo molecular conformational changes that extend the proteins and are believed to be a major contributor to the extensibility of bulk fibers. The dynamics of these conformational changes have been thoroughly explored since the advent of single molecule force spectroscopy and molecular dynamics simulations but remarkably, these data have not been rigorously applied to the understanding of the time dependent mechanics of bulk ECM fibers. Using measurements of protein density within fibers, we have examined the influence of dynamic molecular conformational changes and the intermolecular arrangement of Fn within fibers on the bulk mechanical properties of Fn fibers. Fibers were simulated as molecular strands with architectures that promote either equal or disparate molecular loading under conditions of constant extension rate. Measurements of protein concentration within micron scale fibers using deep ultraviolet transmission microscopy allowed the simulations to be scaled appropriately for comparison to in vitro measurements of fiber mechanics as well as providing estimates of fiber porosity and water content, suggesting Fn fibers are approximately 75% solute. Comparing the properties predicted by single molecule measurements to in vitro measurements of Fn fibers showed that domain unfolding is sufficient to predict the high extensibility and nonlinear stiffness of Fn fibers with surprising accuracy, with disparately loaded fibers providing the best fit to experiment. This work shows the promise of this microstructural modeling approach for understanding Fn fiber properties, which is generally applicable to other ECM fibers, and could be further expanded to tissue scale by incorporating these simulated fibers into three dimensional

  8. Linear and nonlinear optical properties of tellurite glasses

    Science.gov (United States)

    Jin, Zhian

    Tellurite glasses have been widely studied from bulk materials to structured devices, with the emphasis on the development of nonlinear optical fibers to demonstrate the functionalities of supercontinuum generation, erbium doped fiber amplifier and Raman amplifiers, etc. The new type tellurite-based optical fibers exhibit superior advantages over conventional silica ones, due to their high optical nonlinearity, broad transmission window, high rare earth element solubility and Raman gain intensity. Like silica fibers, tellurite fibers may also incorporate various fiber structures including solid core-cladding one and microstructure one (e.g. photonic crystal). The fiber loss was ever reported as low as ˜1dB/m using rod-in-tube fabrication process. Beyond all those progresses, little success has been made on improving the optical nonlinear property of tellurite glasses chi(3) ˜ 50 times bigger than fused silica). The challenge remains for tellurite glasses that their optical nonlinearity is more than 1 order smaller to compare with chalcogenides, although they are more stable chemically and structurally. In this work, after carefully reviewing the trend of optical nonlinearity for solid glasses, we adopted two strategies to potentially increase the linear and third-order optical nonlinear properties for tellurite glasses. A more polarizable electronic excitation may be achievable by introducing chalcogen elements (e.g. Sulfur or Selenium) into TeO2 vitreous network and synthesizing glasses with a linear helical chainlike structure. The ab initio computational results of microscopic hyper-polarizabilities of hypothetical mixed - 2 - tellurite chalcogenide glass molecular structure (TeO2(TeOX)n) confirmed the enhanced effect as Te-X (X=S or Se) bonds exist and the molecular size (n) grows. Quantitative estimates of the macroscopic linear and nonlinear properties for a mixed glass made from chains of n = 5 units leads to a conclusion that the extra Te-S (or Te

  9. Optical properties of graphene nanoribbons

    Science.gov (United States)

    Karimi, Farhad; Knezevic, Irena

    We calculate the dielectric function and optical conductivity of ultra-narrow armchair graphene nanoribbons (AGNRs) and zigzag graphene nanoribbons (ZGNRs) by a self- consistent-field approach within a Markovian master-equation formalism (SCF-MMEF) coupled with full-wave electromagnetic equations. Based on third-nearest-neighbor tight-binding, with appropriate modifications for AGNRs and ZGNRs, we calculate electron dispersions and Bloch wave functions in excellent agreement with the local spin-density approximation (LSDA) results. A generalized Markovian master equation of the Lindblad form, which maintains the positivity of the density matrix, is derived to describe the interaction of the electronic system with an external electromagnetic field (to first order) and with a dissipative environment (to second order). Not only does the SCF-MMEF capture the interband electron-hole-pair generation, but it also accurately accounts for concurrent interband and intraband electron scattering with phonons and impurities. We employ the SCF-MMEF to calculate the dielectric function, complex conductivity, and loss function for both suspended and supported AGNRs and ZGNRs with different widths. Then, we obtain the plasmon dispersion and propagation length from the loss-function maximum. Support by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0008712.

  10. Optical properties of substituted polyacetylenes

    Science.gov (United States)

    Gontia, Ilarie I.

    In this work we present continuous wave (CW) optical spectroscopies of sustituted polyacetylenes: poly-disabstituted-acetylene (PDPA-nBu) and polyphenylacetylene (PPA). We found that although PDPA-nBu is a degenerate ground state polymer, it shows strong photoluminescence (PL) with quantum efficiency larger than 60%. Polarized PL measurements show that PDPA-nBu emission originates from intrachain excitons rather than from the side groups of the polymer chain. The absorption bands were identified, correlating the experimental results with the model proposed in the literature. The CW photomodulation (PM) spectra of pristine unoxidized and oxidized PDPA-nBu films showed that both solitons and polarons are simultaneously photogenerated. On the contrary, the PM spectrum of PDPA-nBu in toluene solution showed only polaron photogeneration. Using the photoinduced absorption detected magnetic resonance (PADMR) spectroscopy and doping induced electron spin resonance (ESR) we identified the spin of the photogenerated species. For spin 1/2 resonance, polaron, neutral soliton, and charged soliton bands were observed in the lambda-PADMR spectrum. We also investigated the charge transfer (CT) process in the PDPA-nBu/ C60 composites. The absorption spectra in the visible and infrared ranges of PDPA-nBu/C60 blend do not show any evidence for CT in the ground state. Using PL, PM and PADMR spectroscopies we show that in the PDPA-nBu/C60 blends the charge transfer reaction takes place in the excited state. PL spectra measured in films with different C60 concentration showed exciton quenching that is due to the fast CT process. The PM spectrum showed the signature of CT, namely, a PA band that peaks at about 1.15 eV, which is associated with C60 ion resulting from the excitons separation into positively charged polaron on the polymer chain and negative C60 ion. PADMR spectra also showed the signature of the CT reaction. We observed two resonances that were identified in H

  11. Optical properties of epitaxial YAG:Yb films

    Energy Technology Data Exchange (ETDEWEB)

    Ubizskii, S.B. [Institute for Telecommunication, Radioelectronics and Electronic Engineering, Lviv Polytechnic National University, 12, Bandera St., Lviv, 79013 (Ukraine); Matkovskii, A.O. [Institute for Telecommunication, Radioelectronics and Electronic Engineering, Lviv Polytechnic National University, 12, Bandera St., Lviv, 79013 (Ukraine); Institute of Physics, University Rzezsow, 16 Rejtana St., Rzeszow, 35310 (Poland); Melnyk, S.S.; Syvorotka, I.M. [R and D Institute for Materials, Scientific Research Company ' ' Carat' ' , 202, Stryjska St., Lviv, 79031 (Ukraine); Mueller, V.; Peters, V.; Petermann, K. [Institut fuer Laser-Physik, Universitaet Hamburg, Jungiusstrasse 9a, 20355 Hamburg (Germany); Beyertt, A.; Giesen, A. [Institut fuer Strahlwerkzeuge, Universitaet Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart (Germany)

    2004-03-01

    This work deals with the investigation of the optical properties of epitaxial YAG:Yb films and their suitability as gain media for thin disk lasers. Epitaxial films of YAG:Yb were grown by the liquid phase epitaxy method in air on the (111)-oriented YAG substrates. The thickness of the grown layers was from 30 to 260 {mu}m. The melt composition was varied to obtain the desired doping level from 10 to 15% and to optimize the optical properties. The best epitaxial films were colourless and had an Yb{sup 3+} luminescence lifetime of more than 950 {mu}s, which is very close to the intrinsic lifetime of the Yb ions in the bulk YAG single crystals. These films were tested in a thin disk laser setup with 24 absorption passes of the 940 nm pumping beam. The maximum output power at 1.03 {mu}m wavelength in CW operation reached more than 60 W and the optical efficiency was close to 30%. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Optical properties of spherical gold mesoparticles

    DEFF Research Database (Denmark)

    Evlyukhin, A. B.; Kuznetsov, A. I.; Novikov, S. M.;

    2012-01-01

    Optical properties of spherical gold particles with diameters of 150-650 nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond the quadrup...

  13. Optical Properties of Nanoparticles and Nanocomposites

    CSIR Research Space (South Africa)

    Kumbhakar, P

    2014-01-01

    Full Text Available entitled “Optical properties and in vitro biological studies of oligonucleotide-modified quantum dots,” Gérard et al. have reported the synthesis and characterizations of a series of new oligonucleotide-modified CdTe quantum dots (QDs); also they have...

  14. Some optical properties of the spiral inflector

    CERN Document Server

    Toprek, D

    1999-01-01

    This paper compares some optical properties of different spiral inflectors using the program CASINO. The electric field distribution in the inflectors has been numerically calculated from an electric potential map produced by the program RELAX3D. The magnetic field is assumed to be constant. We have also made an effort to minimize the inflector fringe field using the RELAX3D program. (author)

  15. Optical Properties of Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Perinetti, U.

    2011-01-01

    This thesis presents different optical experiments performed on semiconductor quantum dots. These structures allow to confine a small number of electrons and holes to a tiny region of space, some nm across. The aim of this work was to study the basic properties of different types of quantum dots

  16. Comparative properties of optically clear epoxy encapsulants

    Science.gov (United States)

    Edwards, Maury; Zhou, Yan

    2001-12-01

    Three epoxy systems were evaluated for physical dn optical properties. The three systems chosen for the study were selected on the basis of their optical clarity, color and chemistry. Three distinctly different chemistries were chosen, aromatic epoxy-amine cured. Aromatic epoxy- anhydride cured and cycloaliphatic epoxy-anhydride cured. All three systems remained optically clear and water-white after full cure. The three selected systems were tested for physical properties, adhesion and light transmission properties. Light transmission was measured after thermal and humidity exposure. Adhesion was measured after humidity exposure only. Both of the epoxy-anhydride systems performed well in optical properties but poorer in adhesion as compared to the epoxy-amine system. The aromatic epoxy- amine system discolored badly during thermal exposure at 100 C. Data generated from this work will be used in selecting clear encapsulating materials for photonics applications. No single system offers optimal performance in all areas. The best compromise material is the aromatic epoxy-anhydride system.

  17. Optical Properties of Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Perinetti, U.

    2011-01-01

    This thesis presents different optical experiments performed on semiconductor quantum dots. These structures allow to confine a small number of electrons and holes to a tiny region of space, some nm across. The aim of this work was to study the basic properties of different types of quantum dots mad

  18. Emergent low-symmetry phases with large property enhancement in ferroelectric KNbO3 bulk crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lummen, Tom T. A.; Leung, J; Kumar, Amit; Wu, X; Ren, Y; Vanleeuwen, Brian K; Haislmaier, Ryan C.; Holt, Martin; Lai, Keji; Kalinin, Sergei V.; Gopalan, Venkatraman

    2017-08-18

    The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well-known materials, when their structural symmetry is deviated from equilibrium through a small local strain or field. Here, the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO3 is reported. This phase is found to coexist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network of ferroelectric domain walls. While the local microstructural shear strain involved is only approximate to 0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature. Moreover, the meandering walls of the low-symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m(-1). This discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals.

  19. Temperature dependence of the bulk and surface properties of liquid Zn-Cd alloys

    Energy Technology Data Exchange (ETDEWEB)

    Awe, O.E. [University of Ibadan, Department of Physics, Ibadan (Nigeria); Azeez, A.A. [African University of Science and Technology, Abuja (Nigeria)

    2017-05-15

    The effects of temperature on the bulk and surface properties of liquid Zn-Cd alloys have been theoretically investigated, using a combination of self association model, Darken's thermodynamic equation for diffusion, empirical model for viscosity and a statistical mechanics model. The results from this study show that change in temperature resulted in cross-over effects in bulk and surface properties. We also found that with an increase in temperature, a pronounced asymmetry of viscosity isotherm is significantly reduced, and viscosity isotherm exhibited anomalous behaviour. Our results reveal that the homocoordination tendency in Zn-Cd liquid alloys is not strong and reduces with increasing temperature. The study further suggests a pronounced segregation of Cd-atoms at the surface of Zn-Cd liquid alloys and the extent of segregation reduces with temperature. We as well found that, in addition to the reported understanding that size-factor determines the compositional location of asymmetry of the viscosity isotherm, temperature is an operating parameter that has effect, not only on the composition of asymmetry, but also on the magnitude of asymmetry. In all the properties investigated, the most pronounced effect of temperature (52.9 %) is on the viscosity while the least effect (7.1 %) is on the surface tension. (orig.)

  20. Connecting point defect parameters with bulk properties to describe diffusion in solids

    Science.gov (United States)

    Chroneos, A.

    2016-12-01

    Diffusion is a fundamental process that can have an impact on numerous technological applications, such as nanoelectronics, nuclear materials, fuel cells, and batteries, whereas its understanding is important across scientific fields including materials science and geophysics. In numerous systems, it is difficult to experimentally determine the diffusion properties over a range of temperatures and pressures. This gap can be bridged by the use of thermodynamic models that link point defect parameters to bulk properties, which are more easily accessible. The present review offers a discussion on the applicability of the cBΩ model, which assumes that the defect Gibbs energy is proportional to the isothermal bulk modulus and the mean volume per atom. This thermodynamic model was first introduced 40 years ago; however, consequent advances in computational modelling and experimental techniques have regenerated the interest of the community in using it to calculate diffusion properties, particularly under extreme conditions. This work examines recent characteristic examples, in which the model has been employed in semiconductor and nuclear materials. Finally, there is a discussion on future directions and systems that will possibly be the focus of studies in the decades to come.

  1. Mechanically flexible optically transparent silicon fabric with high thermal budget devices from bulk silicon (100)

    KAUST Repository

    Hussain, Muhammad Mustafa

    2013-05-30

    Today’s information age is driven by silicon based electronics. For nearly four decades semiconductor industry has perfected the fabrication process of continuingly scaled transistor – heart of modern day electronics. In future, silicon industry will be more pervasive, whose application will range from ultra-mobile computation to bio-integrated medical electronics. Emergence of flexible electronics opens up interesting opportunities to expand the horizon of electronics industry. However, silicon – industry’s darling material is rigid and brittle. Therefore, we report a generic batch fabrication process to convert nearly any silicon electronics into a flexible one without compromising its (i) performance; (ii) ultra-large-scale-integration complexity to integrate billions of transistors within small areas; (iii) state-of-the-art process compatibility, (iv) advanced materials used in modern semiconductor technology; (v) the most widely used and well-studied low-cost substrate mono-crystalline bulk silicon (100). In our process, we make trenches using anisotropic reactive ion etching (RIE) in the inactive areas (in between the devices) of a silicon substrate (after the devices have been fabricated following the regular CMOS process), followed by a dielectric based spacer formation to protect the sidewall of the trench and then performing an isotropic etch to create caves in silicon. When these caves meet with each other the top portion of the silicon with the devices is ready to be peeled off from the bottom silicon substrate. Release process does not need to use any external support. Released silicon fabric (25 μm thick) is mechanically flexible (5 mm bending radius) and the trenches make it semi-transparent (transparency of 7%). © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  2. Characterization of Aerogel's Optical Properties

    Science.gov (United States)

    Justen, Abigail; Young, Jonathan

    2013-10-01

    Aerogel is used in the kaon aerogel Cerenkov detector at Jefferson Lab. Kaons are identified by the number of photons created through Cerenkov radiation emitted as the kaon travels through the aerogel. Depending on the refractive index of the aerogel, kaons of different momenta can be detected and distinguished from protons. Therefore, a uniform refractive index in the detector is important to reduce uncertainty in the Cerenkov radiation. We found the refractive index of the aerogel by shining a red construction laser through it and measuring how far the beam refracted. The refractive index of aerogel is also directly related to the density of aerogel. The humidity in the air, if absorbed, could also affect the refractive index. To test the effect of humidity on aerogel we used a humidity controlled environment between 80 and 100 percent on aerogel from Matsushita Electric Works, Ltd, Japan Fine Ceramic Center, and Novosibirsk. Finally, we tested the transmittance of aerogel tiles with a UV/Vis photospectrometer to find the correlation between transmittance and the tile's properties. Tiles with the highest transmittance will allow for the most accurate count of the photons produced through Cerenkov radiation. The results from these experiments will be presented. Supported in Part by NSF Grant 1019521 and 1039446.

  3. Germanium quantum dots: Optical properties and synthesis

    Science.gov (United States)

    Heath, James R.; Shiang, J. J.; Alivisatos, A. P.

    1994-07-01

    Three different size distributions of Ge quantum dots (≳200, 110, and 60 Å) have been synthesized via the ultrasonic mediated reduction of mixtures of chlorogermanes and organochlorogermanes (or organochlorosilanes) by a colloidal sodium/potassium alloy in heptane, followed by annealing in a sealed pressure vessel at 270 °C. The quantum dots are characterized by transmission electron microscopy, x-ray powder diffraction, x-ray photoemission, infrared spectroscopy, and Raman spectroscopy. Colloidal suspensions of these quantum dots were prepared and their extinction spectra are measured with ultraviolet/visible (UV/Vis) and near infrared (IR) spectroscopy, in the regime from 0.6 to 5 eV. The optical spectra are correlated with a Mie theory extinction calculation utilizing bulk optical constants. This leads to an assignment of three optical features to the E(1), E(0'), and E(2) direct band gap transitions. The E(0') transitions exhibit a strong size dependence. The near IR spectra of the largest dots is dominated by E(0) direct gap absorptions. For the smallest dots the near IR spectrum is dominated by the Γ25→L indirect transitions.

  4. Quantum optical properties in plasmonic systems

    Science.gov (United States)

    Ooi, C. H. Raymond

    2015-04-01

    Plasmonic metallic particle (MP) can affect the optical properties of a quantum system (QS) in a remarkable way. We develop a general quantum nonlinear formalism with exact vectorial description for the scattered photons by the QS. The formalism enables us to study the variations of the dielectric function and photon spectrum of the QS with the particle distance between QS and MP, exciting laser direction, polarization and phase in the presence of surface plasmon resonance (SPR) in the MP. The quantum formalism also serves as a powerful tool for studying the effects of these parameters on the nonclassical properties of the scattered photons. The plasmonic effect of nanoparticles has promising possibilities as it provides a new way for manipulating quantum optical properties of light in nanophotonic systems.

  5. Optical Transmission Properties of Dielectric Aperture Arrays

    Science.gov (United States)

    Yang, Tao

    Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index

  6. 160 Gb/s all-optical AND gate using bulk SOA turbo-switched Mach-Zehnder interferometer

    Science.gov (United States)

    Rendón-Salgado, I.; Gutiérrez-Castrejón, R.

    2017-09-01

    A novel architecture to implement an all-optical AND gate that relies on the use of a bulk semiconductor optical amplifier-based active Mach-Zehnder interferometer and the turbo-switch effect is presented. Its performance is analyzed in terms of relevant physical parameters and its power consumption calculated. Error-free operation at 160 Gb/s is numerically demonstrated, thus becoming the fastest AND gate of its kind. Accurate simulations using a well-tested design suite predict a 2.7 dB improvement in terms of quality factor when compared to a conventional scheme. The performance advantages of the proposed architecture remain when combined with a turbo-switched XOR gate: the resulting all-optical half-adder also operates error-free at 160 Gb/s. Our research work boosts the potential of interferometric turbo-switched photonic structures as ultra-fast all-optical processing elements.

  7. Study on Surface and Bulk Properties of Ce-5 % Lanthanum Alloy

    Institute of Scientific and Technical Information of China (English)

    Luo Lizhu; Wang Xiaolin; Fu Xiaoguo; Zhang Yanzhi; Zhao Zhengping; Liu Chunrong

    2004-01-01

    The surface and bulk properties of Ce-5% La were studied with X-ray photoelectron spectroscopy (XPS)and X-ray diffraction (XRD), respectively.The XRD analysis shows that cerium in bulk is in γ-phase, and its lattice parameter is 0.516 nm.And we also find Ce2O3 in the bulk from the XRD figure but no existence of metal lanthanum because of its small quantity.The XPS analysis shows that there are always oxides existing in the surface.The O1s peak always exists at the binding energy of 530.3 eV, which may be attributed to Ce2O3 and La2O3, but no evidence was found for the existence of CeO2.It is concluded that there is a thick layer of Ce2O3 on the sample surface.And the Ce3d peak show multi-split in the figure, in which there are two peaks in each region, 3d5/2 and 3d3/2, and the binding energy of these peaks are 882.86, 887.70 eV for 3d5/2, and 901.44, 905.93 eV for 3d3/2.The special phenomena can be attributed to the changes of 4f electronic configuration, and the cerium in the sample exhibits properties similar to Ce2O3.But the influence of the addition of lanthanum to cerium is not visible, and further investigations are expected.

  8. Thermoelectric properties of Mg2X (X = Si, Ge) based bulk and quantum well systems

    Science.gov (United States)

    Yelgel, Övgü Ceyda

    2017-01-01

    Mg2X (X = Si, Ge) compounds are promising thermoelectric materials for middle temperature applications due to good thermoelectric properties, nontoxicity, and abundantly available constituent elements. So far, these materials used in applications have all been in bulk form. Herein we report a full theory of thermoelectric transport properties of 3D bulk and 2D quantum well systems. The main aim of this present work is to show the effect of quantum confinement on the enhancement of the thermoelectric figure of merit theoretically. Results are given for n-type Mg2 Si0.5 Ge0.5 solid solutions and n-type Mg2Si/Mg2Ge/Mg2Si quantum well systems where the values of well widths are taken as 10 nm, 15 nm, and 20 nm, respectively. The n-type doping is made by using Sb- and La-elements as dopants. Experimental results for solid solutions are included to provide demonstration of proof of principle for the theoretical model applied for 3D bulk structures. The maximum thermoelectric figure of merits of Lax Mg2 -x Si0.49 Ge0.5 Sb0.01 solid solutions are obtained to be 0.64 and 0.56 at 800 K for x = 0 and x = 0.01 sample, respectively. While, at the same temperature, due to the relatively low phonon thermal conductivity the state-of-the-art ZT values of 2.41 and 2.26 have been attained in the Mg2Si/Mg2Ge/Mg2Si quantum well samples with 0.01 wt. % Sb-doped and 0.01 wt. % Sb- and 0.01 wt. % La-doped, respectively.

  9. Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Marius

    2015-07-01

    Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

  10. Optical and Electrical Characterization of Melt-Grown Bulk Indium Gallium Arsenide and Indium Arsenic Phosphide Alloys

    Science.gov (United States)

    2011-03-01

    constant match and mismatch effects on the quality of crystal. Bulk crystal growth typically uses the Czochralski Method (melt). In this method , a...deviation and Michelson Fabry-Perot interferometry methods . The measured results of refractive indices, transport properties, bandgap energies, and...exhibit some random compositional fluctuations across the sample. A practical method of extracting bandgap energies directly from the FTIR

  11. Fast methods of computing bulk radiative properties of inhomogeneous clouds illuminated by solar radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gabriel, P. [Colorado State Univ., Fort Collins, CO (United States)

    1995-09-01

    The use of cloud fraction as a means of incorporating horizontal cloud inhomogeneity in radiative transfer calculations is widespread in the atmospheric science community. This research attempts to bypass the use of cloud fraction in radiative transfer modeling for two-dimensional media. Gabriel describes two approximation techniques useful in calculating the domain averaged bulk radiative properties such as albedo, flux divergence and mean radiance that dispense with the need to use cloud fraction as a specifier of cloud inhomogeneity. The results suggest that the variability of the medium can largely be accounted for through the pseudo-source term, offering hope of parameterizing the equation of transfer in terms of the statistical properties of the medium. 1 fig.

  12. Multifragmentation of a very heavy nuclear system (II): bulk properties and spinodal decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Frankland, J.D.; Rivet, M.F.; Borderie, B. [Paris-11 Univ., Inst. de Physique Nucleaire, 91 - Orsay (France)] [and others

    2000-07-01

    The properties of fragments and light charged particles emitted in multifragmentation of single sources formed in central 36 A.MeV Gd+U collisions are reviewed. Most of the products are isotropically distributed in the reaction c.m. Fragment kinetic energies reveal the onset of radial collective energy. A bulk effect is experimentally evidenced from the similarity of the charge distribution with that from the lighter 32 A.MeV Xe+Sn system. Spinodal decomposition of finite nuclear matter exhibits the same property in simulated central collisions for the two systems, and appears therefore as a possible mechanism at the origin of multifragmentation in this incident energy domain. (authors)

  13. Study of microstructure and electrical properties of bulk YBCO prepared by melt textured growth technique

    Energy Technology Data Exchange (ETDEWEB)

    Gonal, M. R.; Krishnan, Madangopal [Glass and Advanced Materials Division, Bhabha Atomic Research Centre, Mumbai, INDIA 400 085 (India); Tewari, R. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai, INDIA 400 085 (India); Tyagi, A. K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai, INDIA 400 085 (India); Gyore, A.; Vajda, I. [Department of Electric Power Engineering, Budapest Univ. of Technology & Economics, Budapest (Hungary)

    2015-06-24

    Bulk YBCO components were prepared using Melt Texture Growth (MTG) technique. Components were fabricated using MTG by addition of Y{sub 2}BaCuO{sub 5} (Y211) and Ag to YBCO, which leads to improved grain size without affecting superconducting properties. Green compacts prepared by cold isostatic pressing were pre-sintered at 930°C before subjecting melt texturing. Cooling rates lower than 1 °C.h{sup −1} was used, in between (peritectic) temperature of about 995 and 1025°C, to obtain large grained components. Microstructure studies in details were carried out by Scanning Electron Microscope (SEM), Electron Probe Micro Analysis (EPMA), Orientation Imaging Microscope (OIM) and TEM correlated with electrical properties like Critical current density (J{sub c})

  14. Optical properties of ZnS:Mn nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, F.; En Naciri, A. [Universite Paul Verlaine-Metz, Laboratoire LPMD, 1 Bd Arago, 57078 Metz (France); Grob, J.J. [InESS, 23 rue du Loess-B20, 67037 Strasbourg Cedex 2 (France)

    2010-02-15

    The optical properties of Mn-doped zinc sulfide (ZnS) nanocrystals embedded in SiO{sub 2} matrix are studied by spectroscopic ellipsometry (SE). The crystals are obtained by sequential multi-energy ion implantation of Zn, S, and Mn into a silica layer grown on Si(111) followed by a subsequent annealing for 30 min at 900 C. The formation of the nanocrystals is evidenced by transmission electron microscopy. The application of a critical-point based model for the analysis of the SE data yields die dielectric function (DF) between 0.6 and 6.5 eV. A pronounced shift of the absorption edge towards higher energies is detected for the nanocrystals In comparison to bulk ZnS (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Optical and Structural Properties of Ultra-thin Gold Films

    CERN Document Server

    Kossoy, Anna; Simakov, Denis; Leosson, Kristjan; Kéna-Cohen, Stéphane; Maier, Stefan A

    2014-01-01

    Realizing laterally continuous ultra-thin gold films on transparent substrates is a challenge of significant technological importance. In the present work, formation of ultra-thin gold films on fused silica is studied, demonstrating how suppression of island formation and reduction of plasmonic absorption can be achieved by treating substrates with (3-mercaptopropyl) trimethoxysilane prior to deposition. Void-free fi lms with deposition thickness as low as 5.4 nm are realized and remain structurally stable at room temperature. Based on detailed structural analysis of the fi lms by specular and diffuse X-ray reflectivity measurements, it is shown that optical transmission properties of continuous ultra-thin films can be accounted for using the bulk dielectric function of gold. However, it is important to take into account the non-abrupt transition zone between the metal and the surrounding dielectrics, which extends through several lattice constants for the laterally continuous ultra-thin films (film thickness...

  16. Optical Properties of Relativistic Plasma Mirrors

    CERN Document Server

    Vincenti, H; Kahaly, S; Martin, Ph; Quéré, F

    2013-01-01

    The advent of ultrahigh-power femtosecond lasers creates a need for optical components suitable to handle ultrahigh light intensities. Due to the unavoidable laser-induced ionization of matter, these components will have to be based on a plasma medium. An archetype of such optical elements is a plasma mirror, created when an intense femtosecond laser pulse impinges on a solid target. It consists of a dense plasma, formed by the laser field itself, which specularly reflects the main part of the pulse. Plasma mirrors have major potential applications as active optical elements to manipulate the temporal and spatial properties of intense laser beams, in particular for the generation of intense attosecond pulses of light. We investigate the basic physics involved in the deformation of a plasma mirror resulting from the light pressure exerted by the ultraintense laser during reflection, by deriving a simple model of this fundamental process, which we validate both numerically and experimentally. The understanding ...

  17. Engineering optical properties using plasmonic nanostructures

    Science.gov (United States)

    Tamma, Venkata Ananth

    Plasmonic nanostructures can be engineered to take on unusual optical properties not found in natural materials. The optical responses of plasmonic materials are functions of the structural parameters and symmetry of the nanostructures, material parameters of the nanostructure and its surroundings and the incidence angle, frequency and polarization state of light. The scattering and hence the visibility of an object could be reduced by coating it with a plasmonic material. In this thesis, presented is an optical frequency scattering cancelation device composed of a silicon nanorod coated by a plasmonic gold nanostructure. The principle of operation was theoretically analyzed using Mie theory and the device design was verified by extensive numerical simulations. The device was fabricated using a combination of nanofabrication techniques such as electron beam lithography and focused ion beam milling. The optical responses of the scattering cancelation device and a control sample of bare silicon rod were directly visualized using near-field microscopy coupled with heterodyne interferometric detection. The experimental results were analyzed and found to match very well with theoretical prediction from numerical simulations thereby validating the design principles and our implementation. Plasmonic nanostructures could be engineered to exhibit unique optical properties such as Fano resonance characterized by narrow asymmetrical lineshape. We present dynamic tuning and symmetry lowering of Fano resonances in plasmonic nanostructures fabricated on flexible substrates. The tuning of Fano resonance was achieved by application of uniaxial mechanical stress. The design of the nanostructures was facilitated by extensive numerical simulations and the symmetry lowering was analyzed using group theoretical methods. The nanostructures were fabricated using electron beam lithography and optically characterized for various mechanical stress. The experimental results were in good

  18. Optical properties of coumarins containing copolymers

    Science.gov (United States)

    Skowronski, L.; Krupka, O.; Smokal, V.; Grabowski, A.; Naparty, M.; Derkowska-Zielinska, B.

    2015-09-01

    We investigate the optical properties such as absorption coefficient, refractive index, real and imaginary parts of dielectric function and energy band gap of coumarin-containing copolymers thin films by means of spectroscopic ellipsometry (SE) combined with transmittance measurements (T) and atomic force microscopy (AFM). We found that the optical properties of coumarin-containing copolymers strongly depend from length of alkyl spacer as well as the type of substitution in coumarin moiety. In our case the refractive index as well as the energy band gap of coumarin-containing copolymer decrease with increase the length of alkyl spacer. Additionally, the lengthening of the alkyl spacer brings the bathochromic shifts of the absorption spectra towards longer wavelengths.

  19. Optical properties of stabilized copper nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mohindroo, Jeevan Jyoti, E-mail: jjmdav@gmail.com [Punjab Technical University, Kapurthala Punjab (India); Department of Chemistry, DAV College, Amritsar, Punjab India (India); Garg, Umesh Kumar, E-mail: Umeshkgarg@gmail.com [Punjab Technical University, Kapurthala Punjab (India); Guru Teg Bahadur Khalsa College of IT, Malout, Punjab (India); Sharma, Anshul Kumar [Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India)

    2016-05-06

    Optical studies involving calculation of Band Gap of the synthesized copper nanoparticles were carried out in the wavelength range of 500 to 650 nm at room temperature, the particles showed high absorption at 550 nm indicating their good absorptive properties. In this method water is used as the medium for reduction of copper ions in to copper Nanoparticles the stabilization of copper Nanoparticles was studied with starch both as a reductant and stabilizer,. The reaction mixture was heated using a kitchen microwave for about 5 minutes to attain the required temp for the reaction. The pH of the solution was adjusted to alkaline using 5% solution of NaOH. Formation of Copper Nanoparticles was indicated by change in color of the solution from blue to yellowish black which is supported by the UV absorption at 570 nm.the synthesized particles were washed with water and alcohol. The optical properties depend upon absorption of radiations which in turn depends upon ratio of electrons and holes present in the material and also on the shape of the nanoparticles. In the present investigation it was observed that optical absorption increases with increase in particle size. The optical band gap for the Nanoparticles was obtained from plots between hv vs. (αhv){sup 2} and hv vs. (αhv){sup 1/2}. The value of Band gap came out to be around 1.98–2.02 eV which is in close agreement with the earlier reported values.

  20. Polarimetric Properties of Optically Resonant Nanostructures

    Science.gov (United States)

    Theisen, Michael John

    Optically resonant nanostructures have been incorporated into a variety of devices used in a number of different fields. In this thesis, we explore optically resonant nanostructures in two forms. First we investigate a relatively new material, gallium implanted silicon (Si:Ga). We cover the fabrication process and experimentally find the optical properties as a function of both dose and wavelength. We then use the properties of this new material to create suspended arrays of Si:Ga nanowires, and determine their optical characteristics. In the second part of this thesis, we use more conventional materials and fabrication procedures to investigate the phase effects of guided mode resonators. We look at the spectral phase effects for a grating coupled silicon-on-insulator based guided mode resonator. We also look the angular phase effects of a surface plasmon polariton based guided mode resonator, comparing experimental results to theory calculated with rigorous coupled wave analysis for both cases. In addition, the guided mode resonance is modeled as a Fano resonance to gain insight into the functional form of the phase. Knowing the phase response of guided mode resonances may allow the creation of guided mode resonance based devices with higher sensitivity than traditional reflectance based devices.

  1. Preparation and Optical Properties of SnO2/SiO2 Nanocomposite

    Institute of Scientific and Technical Information of China (English)

    FENG Yi-Si; YAO Ri-Sheng; ZHANG Li-De

    2004-01-01

    SnO2/SiO2 nanocomposites have been prepared by the soaking-thermal-decomposing method, tin oxide nanoparticles are uniformly dispersed in the mesopores of silica. The optical absorption edge of the obtained nanocomposite presents a redshift compared with bulk tin oxide. With the increasing annealing temperature during the procedure of the sample preparation, the optical absorption edge of the sample moves to shorter wavelength (blueshift). These optical properties can be ascribed to the amorphous structure and band defects of surface lavers of the tin oxide nanoparticles.

  2. Optical Mapping of Release Properties in Synapses

    OpenAIRE

    Pablo Ariel; Ryan, Timothy A.

    2010-01-01

    Synapses are important functional units that determine how information flows through the brain. Understanding their biophysical properties and the molecules that underpin them is an important goal of cellular neuroscience. Thus, it is of interest to develop protocols that allow easy measurement of synaptic parameters in model systems that permit molecular manipulations. Here, we used a sensitive and high-time resolution optical approach that allowed us to characterize two functional parameter...

  3. Properties of an optical soliton gas

    Science.gov (United States)

    Schwache, A.; Mitschke, F.

    1997-06-01

    We consider light pulses propagating in an optical fiber ring resonator with anomalous dispersion. New pulses are fed into the resonator in synchronism with its round-trip time. We show that solitary pulse shaping leads to a formation of an ensemble of subpulses that are identified as solitons. All solitons in the ensemble are in perpetual relative motion like molecules in a fluid; thus we refer to the ensemble as a soliton gas. Properties of this soliton gas are determined numerically.

  4. Polymer based nanocomposites with tailorable optical properties

    Science.gov (United States)

    Colombo, Annalisa; Simonutti, Roberto

    2014-09-01

    Transparent polymers are extensively used in everyday life, from windows to computer displays, from food packaging to lenses. A possible approach for modulating their optical properties (refractive index, transparency, color and luminescence) is to change the chemical structure of the polymer, however this option is in many cases economically prohibitive. Our approach, instead, relies in the use of standard polymers with the supplement of specific nanostructured additives able to tune the final property of the material. Among others, the cases of luminescent solar concentrators based on poly(methylmethacrylate) containing luminescent quantum dots and highly transparent polymer nanocomposites with high refractive index will be presented.

  5. Climatology of Aerosol Optical Properties in Southern Africa

    Science.gov (United States)

    Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

    2011-01-01

    A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

  6. Climatology of Aerosol Optical Properties in Southern Africa

    Science.gov (United States)

    Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

    2011-01-01

    A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

  7. Optical properties of nasal septum cartilage

    Science.gov (United States)

    Bagratashvili, Nodar V.; Sviridov, Alexander P.; Sobol, Emil N.; Kitai, Moishe S.

    1998-05-01

    Optical parameters (scattering coefficient s, absorption coefficient k and scattering anisotropy coefficient g) of hyaline cartilage were studied for the first time. Optical properties of human and pig nasal septum cartilage, and of bovine ear cartilage were examined using a spectrophotometer with an integrating sphere, and an Optical Multi-Channel Analyser. We measured total transmission Tt, total reflection Rt, and on-axis transmission Ta for light propagating through cartilage sample, over the visible spectral range (14000 - 28000 cm-1). It is shown that transmission and reflection spectra of human, pig and bovine cartilage are rather similar. It allows us to conclude that the pig cartilage can be used for in-vivo studies instead of human cartilage. The data obtained were treated by means of the one-dimensional diffusion approximation solution of the optical transport equation. We have found scattering coefficient s, absorption coefficient k and scattering anisotropy coefficient g by the iterative comparison of measured and calculated Tt, Rt and Ta values for human and pig cartilage. We found, in particular, that for 500 nm irradiation s equals 37,6 plus or minus 3.5 cm-1, g equals 0,56 plus or minus 0.05, k approximately equals 0,5 plus or minus 0.3 cm-1. The above data were used in Monte Carlo simulation for spatial intensity profile of light scattered by a cartilage sample. The computed profile was very similar to the profile measured using an Optical Multi-Channel Analyzer (OMA).

  8. An investigation of electronic and optical properties of InN nanosheet by first principle study

    Science.gov (United States)

    Farzan, M.; Elahi, S. M.; Salehi, H.; Abolhassani, M. R.

    2017-07-01

    In this work, we investigated electronic and optical properties of InN nanosheet using density function theory (DFT) implemented in Wien2k code. We calculated the dielectric function, absorption coefficient, optical conductivity, refraction index, extinction index, reflectivity, and energy loss function of the InN nanosheet within GGA (PBE) and Engel-Vosko (E.V) approximation in two directions E||x (electric field parallel to nanosheet) and E||z (electric field perpendicular to nanosheet), we also calculated the band gap energy within GGA (PBE) and E.V approximations. Optical conductivity in directions to x and z shows that InN nanosheet has semiconductor properties. At the end, we calculated electronic and optical properties, and elastic constant of InN Bulk (wurtzite).

  9. The effect of curing intensity on mechanical properties of different bulk-fill composite resins.

    Science.gov (United States)

    Alkhudhairy, Fahad I

    2017-01-01

    The purpose of this study was to investigate the effects of two curing light intensities on the mechanical properties (Vickers microhardness, compressive strength, and diametral tensile strength) of bulk-fill resin-based composites (RBCs). Four commercially available bulk-fill RBCs (Tetric(®) N-Ceram, SonicFill™, Smart Dentin Replacement (SDR™) Posterior Flowable Material, and Filtek™ Posterior Restorative) were used in this study. A total of 72 cylindrical specimens of each RBC (n=288) were prepared and subjected to Vickers microhardness, compressive strength, and diametral tensile strength tests at high (1200 mW/cm(2)) and low (650 mW/cm(2)) curing light intensities (each n=12). Results were evaluated using independent and paired sample t-tests, one-way analysis of variance, and Tukey's post hoc test. All tests were performed at a significance level of Pintensity light. Although having the least mean microhardness values, a significant difference was observed between SDR cured using high-intensity light and that cured using low-intensity light (Pintensity light, and the least was measured for Tetric N-Ceram cured using low-intensity light (214.3 MPa). At high and low curing light intensities, diametral tensile strength for all RBCs except SonicFill was significant (Pintensity (1200 mW/cm(2)) had a positive influence on the compressive and tensile strength of the four bulk-fill RBCs and microhardness of two materials tested compared with lower curing light intensity (650 mW/cm(2)). SonicFill showed the greatest microhardness and compressive strength significantly for both curing light intensities and greater diametral tensile strength with high-intensity light, although not significant. SDR cured with high-intensity light showed the greatest diametral tensile strength among the four materials.

  10. Irradiating of Bulk Soybeans: Influence on Their Functional and Sensory Properties for Soyfood Processing

    Science.gov (United States)

    Chia, Chiew-Ling; Wilson, Lester A.; Boylston, Terri; Perchonok, Michele; French, Stephen

    2006-01-01

    Soybeans were chosen for lunar and planetary missions, where soybeans will be supplied in bulk or grown locally, due to their nutritive value and ability to produce oil and protein for further food applications. However, soybeans must be processed into foods prior to consumption. Radiation that soybeans would be exposed to during bulk storage prior to and during a Mars mission may influence their germination and functional properties. The influence of radiation includes the affect of surface pasteurization to ensure the astronauts safety from food-borne illnesses (HACCP, CCP), and the affect of the amount of radiation the soybeans receive during a Mars mission. Decreases in the amount of natural antioxidants free radical formation, and oxidation-induced changes in the soybean will influence the nutritional value, texture, color, and aroma of soyfoods. The objective of this study was to determine the influence of pasteurization and sterilization surface radiation on whole soybeans using gamma and electron beam radiation. The influence of 0, 1, 5, 10, and 30kGy on microbial load, germination rate, ease of processing, and quality of soymilk and tofu were determined. Surface radiation of whole dry soybeans using electron beam or gamma rays from 1-30kGy did provide microbial safety for the astronauts. However, the lower dose levels had surviving yeasts and molds. These doses caused oxidative changes that resulted in soymilk and tofu with rancid aromas. GC-MS of the aroma compounds using SPME Headspace confirmed the presence of lipid oxidation compounds. Soybean germination ability was reduced as radiation dosage increased. While lower doses may reduce these problems, the ability to insure microbial safety of bulk soybeans will be lost. Counter measures could include vacuum packaging, nitrogen flushing, added antioxidants, and radiating under freezing conditions. Doses below 1kGy need to be investigated further to determine the influence of the radiation encountered

  11. Theoretical investigation of magnetic and optical properties of semiconductor nanocrystals

    Science.gov (United States)

    Proshchenko, Vitaly

    This thesis presents the theoretical investigation of physical properties of pure and transition metal doped semiconductor nanostructures. First we study optical and energy (the density of states) spectra for Cd mSem clusters of various sizes and shapes, such as spheres, cubes, nanorods, and nanotubes. This work requires a careful computational analysis where a proper exchange-correlation functional has to be chosen to fit the experimental data. The next part of the thesis deals with the magnetic properties of manganese doped CdSe, ZnSe, ZnS, and CdS quantum dots (QDs). We theoretically explain the effect of dual luminescence and show that in the case with CdSe quantum dots the luminescence becomes tunable by a QD size. We also study the concentration dependence of magnetic order and optical transitions in Mn doped CdSe nanocrystals. Room temperature d0 ferromagnetism is studied in ZnS quantum dots and nanowires in Chapter 4. To find the magnetization of the medium and large size nanocrystals we introduce the surface-bulk (SB) model. We show that the condensation of Zn vacancies into a single droplet takes place which leads to the week d0 ferromagnetism in ZnS nanocrystals. In the last Chapter we study electronic, optical, and charge transport properties of two new holey 2D materials, ELH-g-C2N-H and ELH-g-C2N-Br with hydrogen and bromine side-groups, respectively. Since the two 2D crystals under study have not been synthesized yet, we provide the stability analysis and prove that the calculated crystal structures correspond to the global energy minimum criterion.

  12. Microstructure and mechanical properties of Zr-Cu-Al bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Zr49Cu46Al5 and Zr48.5Cu46.5Al5 bulk metallic glasses(BMGs) with diameter of 5 mm were prepared through water-cooled copper mold casting. The phase structures of the two alloys were identified by X-ray diffractometry(XRD). The thermal stability was examined by differential scanning calorimetry(DSC). Zr49Cu46Al5 alloy shows a glass transition temperature, Tg, of about 689 K, an crystallization temperature, Tx, of about 736 K. The Zr48.5Cu46.5Al5 alloy shows no obvious exothermic peak. The microstructure of the as-cast alloys was analyzed by transmission electron microscopy(TEM). The aggregations of CuZr and CuZr2 nanocrystals with grain size of about 20 nm are observed in Zr49Cu46Al5 nanocrystalline composite, while the Zr48.5Cu46.5Al5 alloy containing many CuZr rmartensite plates is crystallized seriously. Mechanical properties of bulk Zr49Cu46Al5 nanocrystalline composite and Zr48.5Cu46.5Al5 alloy measured by compression tests at room temperature show that the work hardening ability of Zr48.5Cu46.5Al5 alloy is larger than that of Zr49Cu46Al5 alloy.

  13. Thermal and mechanical properties of Cu-Zr-Al bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, T.L. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Shek, C.H. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)]. E-mail: apchshek@cityu.edu.hk

    2007-05-31

    The effects of adding small amount of aluminum to the binary Cu{sub 50}Zr{sub 50} bulk metallic glass (BMG) on the thermal and mechanical properties were investigated. The Al addition was limited to 3 {<=} x {<=} 10 at.% in order to form fully amorphous bulk samples. Glassy rods of 3 mm diameter of these alloys were prepared by copper mold suction casting. The (Cu{sub 50}Zr{sub 50}){sub 100-x}Al {sub x} BMGs (x = 0 and 3 {<=} x {<=} 10 at.%) were characterized with differential scanning calorimetry (DSC), X-ray diffraction (XRD), Vickers microhardness test and nanoindentation, respectively. The glass transition temperatures, crystallization temperatures and super-cooled liquid regions of the specimens increased with increasing Al content. The microhardness of the specimens also increases with increasing Al content. Room temperature nanoindentation was carried out on the cross-section of the rods. The results showed that the nanohardness and creep displacement were dependent on the Al content.

  14. Accurate Electronic, Transport, and Bulk Properties of Wurtzite Beryllium Oxide (BeO)

    Science.gov (United States)

    Bamba, Cheick Oumar; Malozovsky, Yuriy; Franklin, Lashounda; Bagayoko, Diola

    We present ab-initio, self-consistent density functional theory (DFT) description of electronic, transport, and bulk properties of wurtzite Beryllium oxide (w-BeO). We used a local density approximation potential (LDA) and the linear combination of atomic orbitals (LCOA) formalism. Our implementation of the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF), ensures the full, physical content of our local density approximation (LDA) calculations - as per the derivation of DFT [AIP Advances, 4, 127104 (2014) We report the band gap, density of states, partial density of state, effective masses, and the bulk modulus. Our calculated band gap of 10.29 eV, using an experimental, room temperature lattice constant of 2.6979 A at room temperature is in agreement with the experimental value of 10.6 eV. Acknowledgments:This work was funded in part the US National Science Foundation [NSF, Award Nos. EPS-1003897, NSF (2010-2015)-RII-SUBR, and HRD-1002541], the US Department of Energy, National Nuclear Security Administration (NNSA, Award No. DE-NA0002630), LaSPACE, and LONI-SUBR.

  15. Comparing near-surface and bulk densities of asteroids using radar scattering properties

    Science.gov (United States)

    Zambrano Marin, Luisa Fernanda; Nolan, Michael C.; Taylor, Patrick A.; Virkki, Anne

    2016-10-01

    Dual-polarization radar measurements of asteroids provide a joint constraint on the near-surface density and porosity, which can give insights on asteroid composition and evolution. Magri et al. (2001) used (433) Eros radar and spacecraft data as calibration for estimating the near-surface densities and porosities of 45 other radar-detected asteroids (36 main-belt and 9 near-Earth). At that time, only (433) Eros had both radar observations and a measured bulk density. Now that there have been spacecraft observations of several other asteroids and radar measurements of the densities of several binary near-Earth asteroids with various compositions, we can expand the calibration to include those objects. We begin by applying the method of Magri et al. to Ceres, Vesta, Itokawa, 1994 CC, 2001 SN263, 1998 QE2, and 2000 DP107 to explore the differences between the bulk density and the near-surface density measured with radar. We expect significant differences between Ceres and Vesta and the small near-Earth asteroids as the porosities of these objects are expected to be quite different. However, we expect that small binary objects likely have similar internal structures, so that any differences should depend on composition and perhaps surface weathering.Reference: Magri et al., "Radar constraints on asteroid Properties using 433 Eros as ground truth". Meteoritics & Planetary Science 36, 1697-1709, 2001.

  16. Bulk and surface properties of magnesium peroxide MgO2

    Science.gov (United States)

    Esch, Tobit R.; Bredow, Thomas

    2016-12-01

    Magnesium peroxide has been identified in Mg/air batteries as an intermediate in the oxygen reduction reaction (ORR) [1]. It is assumed that MgO2 is involved in the solid-electrolyte interphase on the cathode surface. Therefore its structure and stability play a crucial role in the performance of Mg/air batteries. In this work we present a theoretical study of the bulk and low-index surface properties of MgO2. All methods give a good account of the experimental lattice parameters for MgO2 and MgO bulk. The reaction energies, enthalpies and free energies for MgO2 formation from MgO are compared among the different DFT methods and with the local MP2 method. A pronounced dependence from the applied functional is found. At variance with a previous theoretical study but in agreement with recent experiments we find that the MgO2 formation reaction is endothermic (HSE06-D3BJ: ΔH = 51.9 kJ/mol). The stability of low-index surfaces MgO2 (001) (Es = 0.96 J/m2) and (011) (Es = 1.98 J/m2) is calculated and compared to the surface energy of MgO (001). The formation energy of neutral oxygen vacancies in the topmost layer of the MgO2 (001) surface is calculated and compared with defect formation energies for MgO (001).

  17. Improvements on effective permittivity measurements of powdered alumina: Implications for bulk permittivity properties of asteroid regoliths

    Science.gov (United States)

    Hickson, Dylan; Sotodeh, Shahroukh; Daly, Michael G.; Ghent, Rebecca; Nolan, Michael C.

    2017-01-01

    Accurate measurements of the dielectric properties of materials are essential in constraining interpretations of radar observations of planetary bodies. For bodies whose surfaces are comprised of regolith this requires an understanding of the behaviour of the bulk permittivity of powders. In this research we measure the effective permittivity of powdered aluminium oxide (or alumina, Al2O3) in a 7 mm and 14 mm (diameter) coaxial airline at 7.5 GHz for multiple samples with varying grain size. The dielectric constant of alumina is extracted from these measurements using the Bruggeman (Effective Medium Approximation) mixing equation. We develop a model to account for heterogeneity within the airline, specifically in regards to local variation in porosity. The results of the model show good correlation to experimental data and effectively correct for grain size effects on the measured bulk permittivity. We show that particle shape can have a significant impact on the output of the model and can be accounted for by modelling particles as ellipsoids rather than perfect spheres, where the depolarization factor must be measured and averaged for a specific sample batch.

  18. Microstructure and mechanical property of nano-SiCp reinforced high strength Mg bulk composites produced by friction stir processing

    Energy Technology Data Exchange (ETDEWEB)

    Sun, K., E-mail: greatsunkai@sina.com [Key Laboratory for Advanced Materials Processing Technology, Ministry of Education (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Shi, Q.Y.; Sun, Y.J.; Chen, G.Q. [Key Laboratory for Advanced Materials Processing Technology, Ministry of Education (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer Ultimate tensile strength of the bulk composite improved significantly. Black-Right-Pointing-Pointer Nanoparticles dispersed uniformly in the composites after friction stir process. Black-Right-Pointing-Pointer Strengthening mechanism of the composites has been studied. - Abstract: Friction stir processing has been applied to fabricate SiC-Mg bulk composites in this study. AZ63 magnesium alloy, a kind of commercial engineering materials, was selected as base metal. SiC nanoparticles with average size of 40 nm were selected as reinforced particles. After being ultrasonic dispersed in ethanol and friction stir processed with base metal, the SiC particles were uniformly dispersed. Friction stir processing without filling any particles was also applied to base metal as a comparison group. Microstructure evolution was observed by optical microscope and scanning electron microscope. Fine and uniform nugget zone were found both in comparison group and composite. The phases of the material were determined by X-ray diffraction. Transmission electron microscopy observation was conducted to study the condition of SiC nanoparticles. SiC particles were found both inside the grain and at the grain boundary. No micro-sized particle agglomeration was observed in the composite. Vicker hardness and tensile test were carried out to study the mechanical properties of the composite. The average Vicker hardness of the base metal, comparison group and composite were 80 Hv, 85 Hv and 109 Hv respectively. The ultimate tensile strength of the composite reached 312 MPa. Compared with 160 MPa of the as-casted Mg alloy, 263 MPa of the comparison group, the effect of nanoparticles on strength increase was significant.

  19. Quantum theory of the optical and electronic properties of semiconductors

    CERN Document Server

    Haug, Hartmut

    2009-01-01

    This invaluable textbook presents the basic elements needed to understand and research into semiconductor physics. It deals with elementary excitations in bulk and low-dimensional semiconductors, including quantum wells, quantum wires and quantum dots. The basic principles underlying optical nonlinearities are developed, including excitonic and many-body plasma effects. Fundamentals of optical bistability, semiconductor lasers, femtosecond excitation, the optical Stark effect, the semiconductor photon echo, magneto-optic effects, as well as bulk and quantum-confined Franz-Keldysh effects, are covered. The material is presented in sufficient detail for graduate students and researchers with a general background in quantum mechanics.This fifth edition includes an additional chapter on 'Quantum Optical Effects' where the theory of quantum optical effects in semiconductors is detailed. Besides deriving the 'semiconductor luminescence equations' and the expression for the stationary luminescence spectrum, the resu...

  20. Optical Properties of GaSb Nanofibers

    Directory of Open Access Journals (Sweden)

    Perez-Bergquist Alejandro

    2011-01-01

    Full Text Available Abstract Amorphous GaSb nanofibers were obtained by ion beam irradiation of bulk GaSb single-crystal wafers, resulting in fibers with diameters of ~20 nm. The Raman spectra and photoluminescence (PL of the ion irradiation-induced nanofibers before and after annealing were studied. Results show that the Raman intensity of the GaSb LO phonon mode decreased after ion beam irradiation as a result of the formation of the amorphous nanofibers. A new mode is observed at ~155 cm-1 both from the unannealed and annealed GaSb nanofiber samples related to the A1g mode of Sb–Sb bond vibration. Room temperature PL measurements of the annealed nanofibers present a wide feature band at ~1.4–1.6 eV. The room temperature PL properties of the irradiated samples presents a large blue shift compared to bulk GaSb. Annealed nanofibers and annealed nanofibers with Au nanodots present two different PL peaks (400 and 540 nm, both of which may originate from Ga or O vacancies in GaO. The enhanced PL and new band characteristics in nanostructured GaSb suggest that the nanostructured fibers may have unique applications in optoelectronic devices.

  1. Spectroscopic and Mechanical Properties of a New Generation of Bulk Fill Composites

    Science.gov (United States)

    Monterubbianesi, Riccardo; Orsini, Giovanna; Tosi, Giorgio; Conti, Carla; Librando, Vito; Procaccini, Maurizio; Putignano, Angelo

    2016-01-01

    Objectives: The aims of this study were to in vitro evaluate the degree of conversion and the microhardness properties of five bulk fill resin composites; in addition, the performance of two curing lamps, used for composites polymerization, was also analyzed. Materials and Methods: The following five resin-based bulk fill composites were tested: SureFil SDR®, Fill Up!™, Filtek™, SonicFill™, and SonicFill2™. Samples of 4 mm in thickness were prepared using Teflon molds filled in one increment and light-polymerized using two LED power units. Ten samples for each composite were cured using Elipar S10 and 10 using Demi Ultra. Additional samples of SonicFill2, (3 and 5 mm-thick) were also tested. The degree of conversion (DC) was determined by Raman spectroscopy, while the Vickers microhardness (VMH) was evaluated using a microhardness tester. The experimental evaluation was carried out on top and bottom sides, immediately after curing (t0), and, on bottom, after 24 h (t24). Two-ways analysis of variance was applied to evaluate DC and VMH-values. In all analyses, the level of significance was set at p < 0.05. Results: All bulk fill resin composites recorded satisfactory DCs on top and bottom sides. At t0, the top of SDR and SonicFill2 showed the highest DCs-values (85.56 ± 9.52 and 85.47 ± 1.90, respectively), when cured using Elipar S10; using Demi Ultra, SonicFill2 showed the highest DCs-values (90.53 ± 2.18). At t0, the highest DCs-values of bottom sides were recorded by SDR (84.64 ± 11.68), when cured using Elipar S10, and Filtek (81.52 ± 4.14), using Demi Ultra. On top sides, Demi Ultra lamp showed significant higher DCs compared to the Elipar S10 (p < 0.05). SonicFill2 reached suitable DCs also on bottom of 5 mm-thick samples. At t0, VMH-values ranged between 24.4 and 69.18 for Elipar S10, and between 26.5 and 67.3 for Demi Ultra. Using both lamps, the lowest VMH-values were shown by SDR, while the highest values by SonicFill2. At t24, all DC and VMH

  2. The effect of curing intensity on mechanical properties of different bulk-fill composite resins

    Directory of Open Access Journals (Sweden)

    Alkhudhairy FI

    2017-02-01

    Full Text Available Fahad I Alkhudhairy Restorative Dental Sciences Department, College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia Objective: The purpose of this study was to investigate the effects of two curing light intensities on the mechanical properties (Vickers microhardness, compressive strength, and diametral tensile strength of bulk-fill resin-based composites (RBCs.Materials and methods: Four commercially available bulk-fill RBCs (Tetric® N-Ceram, SonicFill™, Smart Dentin Replacement (SDR™ Posterior Flowable Material, and Filtek™ Posterior Restorative were used in this study. A total of 72 cylindrical specimens of each RBC (n=288 were prepared and subjected to Vickers microhardness, compressive strength, and diametral tensile strength tests at high (1200 mW/cm2 and low (650 mW/cm2 curing light intensities (each n=12. Results were evaluated using independent and paired sample t-tests, one-way analysis of variance, and Tukey’s post hoc test. All tests were performed at a significance level of P<0.05.Results: The highest mean microhardness was observed for SonicFill (58.3 Vickers hardness number [VHN] cured using high-intensity light. Although having the least mean microhardness values, a significant difference was observed between SDR cured using high-intensity light and that cured using low-intensity light (P<0.05. In the total sample, the highest mean compressive strength was obtained for SonicFill (262.6 MPa, followed by SDR (253.2 MPa, both cured using high-intensity light, and the least was measured for Tetric N-Ceram cured using low-intensity light (214.3 MPa. At high and low curing light intensities, diametral tensile strength for all RBCs except SonicFill was significant (P<0.001.Conclusion: A higher curing light intensity (1200 mW/cm2 had a positive influence on the compressive and tensile strength of the four bulk-fill RBCs and microhardness of two materials tested compared with lower curing light intensity

  3. Optical properties of polypropylene upon recycling.

    Science.gov (United States)

    De Santis, Felice; Pantani, Roberto

    2013-01-01

    In the last few years there has been an increasing interest in the possibility of recycling polymeric materials, using physical recycling. However, is it well known that polymers experience a depletion of all the properties upon recycling. These effects have been widely characterized in the literature for what concerns the mechanical or rheological properties. The changes of optical properties after recycling have been much less studied, even if, especially in food packaging, optical characteristics (above all the opacity) are of extreme importance, and thus it is quite significant to assess the effect of recycling on these properties. In this work, the influence of recycling steps on the opacity of films of a commercial grade of isotactic polypropylene (i-PP) was studied. The material was extruded several times to mimic the effect of recycling procedures. After extrusion, films were obtained by cooling samples of material at different cooling rates. The opacity of the obtained films was then measured and related to their crystallinity and morphology. It was found that opacity generally increases on increasing the amount of α phase and for the same amount of α phase on increasing the size of the spherulites.

  4. Optical Properties of Polypropylene upon Recycling

    Directory of Open Access Journals (Sweden)

    Felice De Santis

    2013-01-01

    Full Text Available In the last few years there has been an increasing interest in the possibility of recycling polymeric materials, using physical recycling. However, is it well known that polymers experience a depletion of all the properties upon recycling. These effects have been widely characterized in the literature for what concerns the mechanical or rheological properties. The changes of optical properties after recycling have been much less studied, even if, especially in food packaging, optical characteristics (above all the opacity are of extreme importance, and thus it is quite significant to assess the effect of recycling on these properties. In this work, the influence of recycling steps on the opacity of films of a commercial grade of isotactic polypropylene (i-PP was studied. The material was extruded several times to mimic the effect of recycling procedures. After extrusion, films were obtained by cooling samples of material at different cooling rates. The opacity of the obtained films was then measured and related to their crystallinity and morphology. It was found that opacity generally increases on increasing the amount of α phase and for the same amount of α phase on increasing the size of the spherulites.

  5. Membrane fouling in a submerged membrane bioreactor with focus on surface properties and interactions of cake sludge and bulk sludge.

    Science.gov (United States)

    Yu, Haiying; Lin, Hongjun; Zhang, Meijia; Hong, Huachang; He, Yiming; Wang, Fangyuan; Zhao, Leihong

    2014-10-01

    In this study, the fouling behaviors and surface properties of cake sludge and bulk sludge in a submerged membrane bioreactor (MBR) were investigated and compared. It was found that the specific filtration resistance (SFR) of cake sludge was about 5 times higher than that of bulk sludge. Two types of sludge possessed similar extracellular polymeric substances (EPS) content, particle size distribution (PSD) and zeta potential. However, their surface properties in terms of surface tensions were significantly different. Further analysis showed that cake sludge was more hydrophilic and had worse aggregation ability. Moreover, cake sludge surface possessed more hydrocarbon, less oxygen and nitrogen moieties than bulk sludge surface. It was suggested that, rather than EPS and PSD differences, the differences in the surface composition were the main cause of the great differences in SFR and adhesion ability between cake sludge and bulk sludge.

  6. Carrier transport and charge transfer properties in coumarin-doped bulk-heterojunction materials

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, T.; Maeda, T.; Yamashita, K. [Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto 606-8585 (Japan); Yanagi, H. [Graduate School of Materials Science, Nara Institute of Science and Technology, Nara 630-0192 (Japan)

    2012-12-15

    We have investigated photovoltaic properties of organic solar cells using polymer-fullerene bulk-heterojunction films doped with coumarin dyes. Whereas the coumarin molecules used in this study had similar absorption bands, evident difference was observed in the open-circuit voltage as well as in the short-circuit current. In particular, the doping of coumarin 307 was found to cause a distinct enhancement in the open-circuit voltage. On the other hand, the doping of coumarin 30 gave a serious degradation in the device performance. These results were strongly associated with calculated molecular energies of the doped dyes, especially with the highest occupied molecular orbital energy. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Bulk-Quantity Synthesis and Conductive Properties of Comb-Like Dendritic ZnO Nanostructures

    Institute of Scientific and Technical Information of China (English)

    LIAO Zhi-Min; ZHANG Hong-Zhou; XU Jun; YU Da-Peng

    2005-01-01

    @@ Adopting a simple low-temperature (~ 500℃) vapour process, we have synthesized bulk quantity comb-like dendritic ZnO nanostructures in large area.An atomic force microscope equipped with Au-coated probes was employed to elucidate the current-voltage characteristic of the individual ZnO nanocomb.The connection electrodes were defined by depositing Pt wires using focused ion beam (FIB).A rectification effect was observed,while it was slightly suppressed compared with that of the previous reports.The good conductive properties of the sample can be attributed to the Ga+ ions implantation through the FIB process of electrode definition.We suggest that the material and the FIB method can be developed to fabricate novel nanosized devices.

  8. Bulk and surface properties of ZnTe-ZnS system semiconductors

    Science.gov (United States)

    Kirovskaya, I. A.; Mironova, E. V.; Kosarev, B. A.; Nor, P. E.; Bukashkina, T. L.

    2016-10-01

    Physicochemical studies of a new ZnTe-ZnS semiconductor system are conducted. It is found that at certain ratios of binary components, substitutional solid solutions with a cubic sphalerite structure are formed in this system. Interrelated laws governing changes in the bulk (crystal chemical, structural) and surface (acid-base) properties with varying system composition are identified. It is assumed they can be attributed to the nature of the active (acid-base) sites. The presented data, observed patterns, and an interpretation of them are used not only to confirm earlier proposed mechanisms of atomic-molecular interaction on diamond-like semiconductors, but to search for promising materials for use in highly sensitive selective sensors for environmental and medical purposes as well.

  9. Thermoelectric properties of bulk MoSi2 synthesized by solid state microwave heating

    Science.gov (United States)

    Lan, Yu; Xie, Mianyu; Ouyang, Ting; Yue, Song

    2016-07-01

    In this research, single phase α-MoSi2 was prepared by solid state hybrid microwave heating within 90 min at relatively low temperature 1273 K. Such precursor powders were then ball milled and sintered by microwave heating at different temperatures. The thermoelectric (TE) properties of MoSi2 bulks were investigated in the temperature range of 300-673 K. When the sintering temperature increases from 973 K to 1273 K, the electrical resistivity decreases significantly and the Seebeck coefficients increase obviously, leading to the maximum TE powder factor of 6.2 × 10-6Wm-1K-2 at 673 K. These results demonstrate the feasibility of high efficient and economical synthesis of MoSi2 by microwave heating technique, with the final products having comparable TE performance in comparison to those from typical methods with long duration and energy-extensive consumption.

  10. Effects of densification of precursor pellets on microstructures and critical current properties of YBCO melt-textured bulks

    Science.gov (United States)

    Setoyama, Yui; Shimoyama, Jun-ichi; Motoki, Takanori; Kishio, Kohji; Awaji, Satoshi; Kon, Koichi; Ichikawa, Naoki; Inamori, Satoshi; Naito, Kyogo

    2016-12-01

    Effects of densification of precursor disks on the density of residual voids and critical current properties for YBCO melt-textured bulk superconductors were systematically investigated. Six YBCO bulks were prepared from precursor pellets with different initial particle sizes of YBa2Cu3Oy (Y123) powder and applied pressures for pelletization. It was revealed that use of finer Y123 powder and consolidation using cold-isostatic-pressing (CIP) with higher pressures result in reduction of residual voids at inner regions of bulks and enhance Jc especially under low fields below the second peak.

  11. Understanding and Revisiting Properties of EuTiO3 Bulk Material and Films from First Principles

    Science.gov (United States)

    Yang, Yurong; Ren, Wei; Wang, Dawei; Bellaiche, L.

    2012-12-01

    Ab initio computations are performed to investigate properties of bulk material and epitaxial films made of EuTiO3 (ETO). A whole family of nanoscale twinned phases, that present complex oxygen octahedra tilting (OOT) and unusual antiferroelectricity, is found to be degenerate in energy with simpler phases (all possessing typical OOT) in bulk ETO. Such degeneracy provides a successful explanation of recently observed anomalous phenomena. The calculations also lead to revisiting the (rich) phase diagram of ETO films.

  12. Particle Size-Specific Magnetic Measurements as a Tool for Enhancing Our Understanding of the Bulk Magnetic Properties of Sediments

    Directory of Open Access Journals (Sweden)

    Robert G. Hatfield

    2014-10-01

    Full Text Available Bulk magnetic properties of soils and sediments are often sensitive proxies for environmental change but commonly require interpretation in terms of the different sources of magnetic minerals (or components that combine to generate them. Discrimination of different components in the bulk magnetic record is often attempted through endmember unmixing and/or high resolution measurements that can require intensive measurement plans, assume linear additivity, and sometimes have difficulty in discriminating a large number of sources. As an alternative, magnetic measurements can be made on isolated sediment fractions that constitute the bulk sample. When these types of measurements are taken, heterogeneity is frequently observed between the magnetic properties of different fractions, suggesting different magnetic components often associate with different physical grain sizes. Using a particle size-specific methodology, individual components can be isolated and studied and bulk magnetic properties can be linked to, and isolated from, sedimentological variations. Deconvolving sedimentary and magnetic variability in this way has strong potential for increased understanding of how magnetic fragments are carried in natural systems, how they vary with different source(s, and allows for a better assessment of the effect environmental variability has in driving bulk magnetic properties. However, despite these benefits, very few studies exploit the information they can provide. Here, I present an overview of the different sources of magnetic minerals, why they might associate with different sediment fractions, how bulk magnetic measurements have been used to understand the contribution of different components to the bulk magnetic record, and outline how particle size-specific magnetic measurements can assist in their better understanding. Advantages and disadvantages of this methodology, their role alongside bulk magnetic measurements, and potential future

  13. Anisotropic Optical Properties of Layered Germanium Sulfide

    CERN Document Server

    Tan, Dezhi; Wang, Feijiu; Mohamed, Nur Baizura; Mouri, Shinichiro; Sandhaya, Koirala; Zhang, Wenjing; Miyauchi, Yuhei; Ohfuchi, Mari; Matsuda, Kazunari

    2016-01-01

    Two-dimensional (2D) layered materials, transition metal dichalcogenides and black phosphorus, have attracted much interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to their remarkable optical properties and prospects for new devices. Here, we report the anisotropic optical properties of layered 2D monochalcogenide of germanium sulfide (GeS). Three Raman scattering peaks corresponding to the B3g, A1g, and A2g modes with strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence (PL) is observed with a peak at around 1.66 eV that originates from the direct optical transition in GeS at room temperature. Moreover, determination of the polarization dependent characteristics of the PL and absorption reveals...

  14. Optical properties of quasiperiodically arranged semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Werchner, Marco

    2009-12-18

    This work consists of two parts which are entitled ''One-Dimensional Resonant Fibonacci Quasicrystals'' and ''Resonant Tunneling of Light in Silicon Nanostructures''. A microscopic theory has been applied to investigate the optical properties of the respective semiconductor nanostructures. The studied one-dimensional resonant Fibonacci quasicrystals consist of GaAs quantum wells (QW) that are separated by either a large spacer L or a small one S. These spacers are arranged according to the Fibonacci sequence LSLLSLSL.. The average spacing satisfies a generalized Bragg condition with respect to the 1s-exciton resonance of the QWs. A theory, that makes use of the transfer-matrix method and that allows for the microscopic description of many-body effects such as excitation-induced dephasing caused by the Coulomb scattering of carriers, has been applied to compute the optical spectra of such structures. A pronounced sharp reflectivity minimum is found in the vicinity of the heavy-hole resonance both in the measured as well as in the calculated linear 54-QW spectra. Specifically, the influence of the carrier density, of the QW arrangement, of a detuning away from the exact Bragg condition, of the average spacing as well as of the ratio of the optical path lengths of the large and small spacers L and S, respectively, and of the QW number on the optical properties of the samples have been studied. Additionally, self-similarity among reflection spectra corresponding to different QW numbers that exceed a Fibonacci number by one is observed, which identifies certain spectral features as true fingerprints of the Fibonacci spacing. In the second part, resonant tunneling of light in stacked structures consisting of alternating parallel layers of silicon and air have been studied theoretically.Light may tunnel through the air barrier due to the existence of evanescent waves inside the air layers if the neighboring silicon layer is close

  15. Low-power chip-level optical interconnects based on bulk-silicon single-chip photonic transceivers

    Science.gov (United States)

    Kim, Gyungock; Park, Hyundai; Joo, Jiho; Jang, Ki-Seok; Kwack, Myung-Joon; Kim, Sanghoon; Kim, In Gyoo; Kim, Sun Ae; Oh, Jin Hyuk; Park, Jaegyu; Kim, Sanggi

    2016-03-01

    We present new scheme for chip-level photonic I/Os, based on monolithically integrated vertical photonic devices on bulk silicon, which increases the integration level of PICs to a complete photonic transceiver (TRx) including chip-level light source. A prototype of the single-chip photonic TRx based on a bulk silicon substrate demonstrated 20 Gb/s low power chip-level optical interconnects between fabricated chips, proving that this scheme can offer compact low-cost chip-level I/O solutions and have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, 3D-IC, and LAN/SAN/data-center and network applications.

  16. Enhanced infrared magneto-optical response of the nonmagnetic semiconductor BiTeI driven by bulk Rashba splitting.

    Science.gov (United States)

    Demkó, L; Schober, G A H; Kocsis, V; Bahramy, M S; Murakawa, H; Lee, J S; Kézsmárki, I; Arita, R; Nagaosa, N; Tokura, Y

    2012-10-19

    We study the magneto-optical (MO) response of the polar semiconductor BiTeI with giant bulk Rashba spin splitting at various carrier densities. Despite being nonmagnetic, the material is found to yield a huge MO activity in the infrared region under moderate magnetic fields (up to 3 T). Our first-principles calculations show that the enhanced MO response of BiTeI comes mainly from the intraband transitions between the Rashba-split bulk conduction bands. These transitions connecting electronic states with opposite spin directions become active due to the presence of strong spin-orbit interaction and give rise to distinct features in the MO spectra with a systematic doping dependence. We predict an even more pronounced enhancement in the low-energy MO response and dc Hall effect near the crossing (Dirac) point of the conduction bands.

  17. Enhanced infrared magneto-optical response of the nonmagnetic semiconductor BiTeI driven by bulk Rashba splitting

    Energy Technology Data Exchange (ETDEWEB)

    Demko, L.; Tokura, Y. [Multiferroics Project, ERATO, JST, c/o Department of Applied Physics, University of Tokyo (Japan); Schober, G.A.H. [Institute for Theoretical Physics, University of Heidelberg (Germany); Kocsis, V.; Kezsmarki, I. [Department of Physics, Budapest University of Technology and Economics and Condensed Matter Research Group of the Hungarian Academy of Sciences (Hungary); Bahramy, M.S.; Murakawa, H. [CMRG and CERG, RIKEN ASI (Japan); Lee, J.S.; Arita, R.; Nagaosa, N. [Department of Applied Physics, University of Tokyo (Japan)

    2013-07-01

    We study the magneto-optical (MO) response of the polar semiconducting BiTeI with giant bulk Rashba spin splitting at various carrier densities. Despite being nonmagnetic, the material is found to yield a huge MO activity in the infrared region under moderate magnetic fields (up to 3 T). Our first-principles calculations show that the enhanced MO response of BiTeI comes mainly from the intraband transitions between the Rashba-split bulk conduction bands. These transitions connecting electronic states with opposite spin directions become active due to the presence of strong spin-orbit interaction and give rise to distinct features in the MO spectra with a systematic doping dependence. We predict an even more pronounced enhancement in the low-energy MO response and dc Hall effect near the crossing (Dirac) point of the conduction bands.

  18. Phosphate-based glass fiber vs. bulk glass: Change in fiber optical response to probe in vitro glass reactivity.

    Science.gov (United States)

    Massera, J; Ahmed, I; Petit, L; Aallos, V; Hupa, L

    2014-04-01

    This paper investigates the effect of fiber drawing on the thermal and structural properties as well as on the glass reactivity of a phosphate glass in tris(hydroxymethyl)aminomethane-buffered (TRIS) solution and simulated body fluid (SBF). The changes induced in the thermal properties suggest that the fiber drawing process leads to a weakening and probable re-orientation of the POP bonds. Whereas the fiber drawing did not significantly impact the release of P and Ca, an increase in the release of Na into the solution was noticed. This was probably due to small structural reorientations occurring during the fiber drawing process and to a slight diffusion of Na to the fiber surface. Both the powders from the bulk and the glass fibers formed a Ca-P surface layer when immersed in SBF and TRIS. The layer thickness was higher in the calcium and phosphate supersaturated SBF than in TRIS. This paper for the first time presents the in vitro reactivity and optical response of a phosphate-based bioactive glass (PBG) fiber when immersed in SBF. The light intensity remained constant for the first 48h after which a decrease with three distinct slopes was observed: the first decrease between 48 and 200h of immersion could be correlated to the formation of the Ca-P layer at the fiber surface. After this a faster decrease in light transmission was observed from 200 to ~425h in SBF. SEM analysis suggested that after 200h, the surface of the fiber was fully covered by a thin Ca-P layer which is likely to scatter light. For immersion times longer than ~425h, the thickness of the Ca-P layer increased and thus acted as a barrier to the dissolution process limiting further reduction in light transmission. The tracking of light transmission through the PBG fiber allowed monitoring of the fiber dissolution in vitro. These results are essential in developing new bioactive fiber sensors that can be used to monitor bioresponse in situ.

  19. Enhanced Photovoltaic Properties of Bulk Heterojunction Organic Photovoltaic Devices by an Addition of a Low Band Gap Conjugated Polymer

    Directory of Open Access Journals (Sweden)

    Eui Jin Lee

    2016-12-01

    Full Text Available In this study, we fabricated organic photovoltaics (OPVs by introducing the polymer additive HTh6BT into the photoactive layer of a poly(3-hexylthiophene:phenyl-C61-butyric acid methyl ester (P3HT:PCBM system. The HTh6BT had a relatively low band gap energy of 1.65 eV and a molecular and crystalline structure similar to that of P3HT. In the photoactive layer, the HTh6BT and P3HT can both act as donors. In such parallel-type bulk heterojunctions, each donor can form excitons and generate charges while being separated from the donor/acceptor interface. Changes in the photovoltaic property of the OPV device by the addition of HTh6BT were evaluated, and the optical characteristics of the photoactive layer, as well as the surface morphology, polymer ordering, and crystallinity of the P3HT:PCBM film were analyzed. Compared to a device without HTh6BT, all short-circuit current densities, open-circuit voltages, and fill factors were enhanced, leading to the enhancement of the power conversion efficiency by 36%.

  20. On the optical properties of plasmonic glasses

    Science.gov (United States)

    Antosiewicz, Tomasz J.; Langhammer, Christoph; Apell, S. Peter

    2014-12-01

    We report on the optical properties of plasmonic glasses which are metal-dielectric composites composed of metallic inclusions in a host dielectric medium. The investigated structures are of quasi-random nature, described by the pair correlation function, featuring a minimum center-to-center distance between metallic inclusions and long range randomness. Plasmonic glasses exhibiting short-range order only may be fabricated using bottom-up, self-assembly methods and have been utilized in a number of applications such as plasmonic sensing or plasmon-enhanced solar harvesting, and may be also employed for certain non-linear applications. It is therefore important to quantify their properties. Using theoretical methods we investigate optical of 1D, 2D, and 3D structures composed of amorphous distributions of metallic spheres. It is shown, that the response of the constituent element, i.e. the single sphere localized surface plasmon resonance, is modified by the scattered fields of the other spheres in such a way that its peak position, peak amplitude, and full-width at half-maximum exhibit damped oscillations. The oscillation amplitude is set by the particle density and for the peak position may vary by up to 0.3 eV in the optical regime. Using a modified coupled dipole approach we calculate the effective (average) polarizability of plasmonic glasses and discuss their spectra as a function of the dimensionality, angle of incidence and polarization, and the minimum center-to-center distance. The analytical model is complemented and validated by T-Matrix calculations of the optical cross-sections of amorphous arrays of metallic spheres obtained using a modification of the Random Sequential Adsorption algorithm for lines, surfaces, and volumes.

  1. Infrared optical properties of gold nanoantenna arrays

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Daniel; Neubrech, Frank; Pucci, Annemarie [Kirchhoff Institute for Physics, Heidelberg (Germany); Gui, Han; Enders, Dominik; Nagao, Tadaaki [National Institute for Materials Science, Tsukuba (Japan)

    2011-07-01

    Antenna-like gold nanoparticles are proven to be well-suited for spectroscopic applications due to their tuneable plasmonic properties. Excited resonantly by electromagnetic radiation, they are able to strongly enhance the local electromagnetic field. This effect can be exploited for example for surface-enhanced infrared (IR) spectroscopy, making the detection of very small amounts of molecules possible. Although the investigation of single particles is possible, well-arranged arrays of nanoantennas promise to have greater potential for possible sensor applications since the overall sensitivity can be increased if several nanoantennas interact. In this paper, we report on the IR optical properties of gold nanoantenna arrays and show the dependence of characteristic resonance parameters from the geometrical arrangement of the antennas on the substrate. The stripe-like, polycrystalline gold nanoantennas with rectangular cross-sections were produced by electron beam lithography on silicon wafers. The resonance characteristics were extracted from spectroscopic measurements with our IR microscope. Special focus herein is on interaction between nanoantennas in direction perpendicular to the long particle axis. It is shown that beginning from a crucial distance, the optical properties change dramatically if the gap between the nanoantennas is further decreased.

  2. Optical Properties and Biological Applications of Electromagnetically Coupled Metal Nanoparticles

    Science.gov (United States)

    Sheikholeslami, Sassan Nathan

    The optical properties of metallic particles change dramatically as the size shrinks to the nanoscale. The familiar mirror-like sheen of bulk metals is replaced by the bright, sharp, colorful plasmonic resonances of nanoparticles. The resonances of plasmonic metal nanoparticles are highly tunable throughout the visible spectrum, depending on the size, shape, local dielectric environment, and proximity to other optical resonances. Fundamental and applied research in the nanoscience community in the past few decades has sought to understand and exploit these phenomena for biological applications. In this work, discrete nanoparticle assemblies were produced through biomolecular interactions and studied at the single particle level with darkfield spectroscopy. Pairs of gold nanoparticles tethered by DNA were utilized as molecular rulers to study the dynamics of DNA bending by the restriction enzyme EcoRV. These results substantiated that nanoparticle rulers, deemed "plasmon rulers", could measure the dynamics of single biomolecules with high throughput, long lifetime, and high temporal resolution. To extend these concepts for live cell studies, a plasmon ruler comprised of peptide-linked gold nanoparticle satellites around a core particle was synthesized and utilized to optically follow cell signaling pathways in vivo at the single molecule level. The signal provided by these plasmon rulers allowed continuous observation of caspase-3 activation at the single molecule level in living cells for over 2 hours, unambiguously identifying early stage activation of caspase-3 in apoptotic cells. In the last section of this dissertation, an experimental and theoretical study of electomagnetic coupling in asymmetric metal nanoparticle dimers is presented. A "heterodimer" composed of a silver particle and a gold particle is observed to have a novel coupling between a plasmon mode (free electron oscillations) and an inter-band absorption process (bound electron transitions). The

  3. Magnetizing properties of the commercial bulk superconductors; Shihan yo koon chodendo baruku no jika tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, H.; Fujinuma, S.; Noto, K. [Iwate Univ., Iwate (Japan); Murakami, M.; Yoshioka, J. [International Superconductivity Tech. Center, Tokyo (Japan); Chiba, T.

    2000-05-29

    It carries out the research in the high-temperature superconductor by many researchers, and it expects the practical application in tape wire rod, thin film and bulk material in various fields mainly on electric power application. Especially, it markets the high-temperature superconductivity bulk material for the application in the bulk material. It recently develops superconductive permanent magnet, which realized the temperature range of which superconducting characteristic using the high-temperature superconductivity bulk material is excellent using small refrigerating machine. Then, we evaluated the magnetization characteristic on the high-temperature superconductivity bulk material marketed. (NEDO)

  4. Direct correlation of single-molecule properties with bulk mechanical performance for the biomimetic design of polymers.

    Science.gov (United States)

    Chung, Jaeyoon; Kushner, Aaron M; Weisman, Adam C; Guan, Zhibin

    2014-11-01

    For rational design of advanced polymeric materials, it is critical to establish a clear mechanistic link between the molecular structure of a polymer and the emergent bulk mechanical properties. Despite progress towards this goal, it remains a major challenge to directly correlate the bulk mechanical performance to the nanomechanical properties of individual constituent macromolecules. Here, we show a direct correlation between the single-molecule nanomechanical properties of a biomimetic modular polymer and the mechanical characteristics of the resulting bulk material. The multi-cyclic single-molecule force spectroscopy (SMFS) data enabled quantitative derivation of the asymmetric potential energy profile of individual module rupture and re-folding, in which a steep dissociative pathway accounted for the high plateau modulus, while a shallow associative well explained the energy-dissipative hysteresis and dynamic, adaptive recovery. These results demonstrate the potential for SMFS to serve as a guide for future rational design of advanced multifunctional materials.

  5. Magnetic properties and power losses in Fe-Co-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Piccin, R. [Dip. Chim. IFM and NIS, Universita di Torino, Via P. Giuria 9, Torino 10125 (Italy)], E-mail: rafael.piccin@unito.it; Tiberto, P. [Electromagnetism Division, INRIM, Strade delle Cacce 91, Torino 10135 (Italy); Chiriac, H. [National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., Iasi 700050 (Romania); Baricco, M. [Dip. Chim. IFM and NIS, Universita di Torino, Via P. Giuria 9, Torino 10125 (Italy)

    2008-10-15

    Magnetic properties of Fe-Co-based bulk metallic glasses have been experimentally investigated. Samples were prepared by water-cooled Cu-mold injection casting technique. The samples have cylindrical shapes with 0.8 mm diameter and 30 mm length. Amorphous structures were confirmed by the presence of a main halo in X-ray diffraction patterns and by the detection of crystallization signal around 650 deg. C using differential scanning calorimetry. Owing to their amorphous structure, these materials present good soft magnetic properties with coercivity below 100 A/m and magnetic induction around 1.0 T in quasi-static conditions. Hysteresis loops were measured using a digital wattmeter with controlled induction waveform. Power losses were analyzed for the following compositions: [(Fe{sub 1-x}Co{sub x}){sub 75}B{sub 20}Si{sub 5}]{sub 93}Nb{sub 4}Y{sub 3} (x=0, 0.2, 0.4, 0.5 and 0.6) over a range of frequencies from 1 to 400 Hz at selected fixed peak inductions. Co addition has shown to improve the soft magnetic properties when x=0.2, 0.4 and 0.5, decreasing coercive fields and power losses, while the magnetic induction is slightly increased (except for x=0.5). Further Co addition (x=0.6) is detrimental for the soft magnetic properties due to the presence of crystalline {alpha}-Fe-(Co) and boride phases. The frequency dependence of power losses was described using a separation theory. It has been observed that an f{sup 1/2} rule is in good agreement with the experimental data.

  6. Nonlinear optical properties of induced transmission filters.

    Science.gov (United States)

    Owens, Daniel T; Fuentes-Hernandez, Canek; Hales, Joel M; Perry, Joseph W; Kippelen, Bernard

    2010-08-30

    The nonlinear optical (NLO) properties of induced transmission filters (ITFs) based on Ag are experimentally determined using white light continuum pump-probe measurements. The experimental results are supported using simulations based on the matrix transfer method. The magnitude of the NLO response is shown to be 30 times that of an isolated Ag film of comparable thickness. The impacts of design variations on the linear and NLO response are simulated. It is shown that the design can be modified to enhance the NLO response of an ITF by a factor of 2 or more over a perfectly matched ITF structure.

  7. Investigation on the bulk growth of $\\alpha$-LiIO$_3$ single crystals and the influence of pH on its structural, morphological and optical characteristics

    Indian Academy of Sciences (India)

    A SILAMBARASAN; P RAJESH; P RAMASAMY; A K KARNAL; RAJEEV BHATT; INDRANIL BHAUMIK; P K GUPTA

    2017-08-01

    $\\alpha$-LiIO$_3$ is an excellent optical material exhibiting strong nonlinear optical, piezoelectric and elasto-opticproperties. However, its practical applications are limited by the insufficient reproducibility of the mentioned propertiescaused by the strong influence of the growth conditions, and, in particular, pH of the solution from which $\\alpha$-LiIO$_3$3 crystal is grown. Herein, we investigate to grow bulk size good quality crystals of $\\alpha$-LiIO$_3$ based on the observed problems during its crystallization process. A systematic investigation was carried out to find the effect of pH on solubility, crystal growth, structural, surface and laser damage properties of $\\alpha$-LiIO$_3$ single crystals. The structure and phase of LiIO$_3$ were confirmedby powder X-ray diffractometer analysis. The functional groups of the compound were identified using Fourier transforminfrared spectroscopy. Surface defects of the grown crystals were studied by etch patterns. The crystal grown at pH 10showed 10% optical transmission enhancement in comparison to the crystals grown at pH 2. The indirect optical bandgap ofthe crystal was reinvestigated using ultraviolet–Visible–near-infrared transmittance spectrum. The laser damage thresholdstudies of the crystals grown at pH 10 reveal the higher optical radiation stability against 532 nm laser. The second-ordernonlinear optical behaviour of $\\alpha$-LiIO$_3$ crystals grown at different pH conditions have been investigated by using Kurtz andPerry powder technique with Nd:YAG laser pulses at the wavelength of 1064 nm.

  8. Improving magnetic properties of MgB{sub 2} bulk superconductors by synthetic engine oil treatment

    Energy Technology Data Exchange (ETDEWEB)

    Taylan Koparan, E., E-mail: etaylan20@gmail.com [Department of Science Education, Eregli Faculty of Education, Bulent Ecevit University, TR-67300, Zonguldak (Turkey); Savaskan, B. [Energy Systems Engineering, Faculty of Technology, Karadeniz Technical University, 61830, Of, Trabzon (Turkey); Yanmaz, E. [Department of Mechatronics, Faculty of Engineering and Architecture, İstanbul Gelişim University, İstanbul (Turkey)

    2016-08-15

    Highlights: • The effects of synthetic engine oil treatment on magnetic properties of bulk MgB{sub 2} superconductors has been first time investigated and reported. • Synthetic engine oil used as a product which is cheap and a rich carbon source obviously has improved the superconducting magnetic properties of MgB{sub 2}. • The critical current density of all of MgB{sub 2} samples immersed at different standby time in engine oil in whole field range has been better than that of the pure MgB{sub 2} sample. • The MgB{sub 2} sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. - Abstract: The present study focuses on the effects of standby time of the MgB{sub 2} samples immersed in synthetic engine oil on the critical current density ( J{sub c}(H)), magnetic field dependence of the pinning force density f{sub p}(b) and T{sub c} performances of MgB{sub 2} bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB{sub 2} pellet samples were immersed at different standby time of 30 min, 120 min, 300 min and 1440 min in synthetic engine oil after the first heating process. Finally, MgB{sub 2} samples immersed in synthetic engine oil were sintered at 1000 °C and kept for 15 min in Ar atmosphere. The critical current density of all of MgB{sub 2} samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB{sub 2} sample because of the number of the pinning centers. The MgB{sub 2} sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. The J{sub c} value for the pure sample is 2.0 × 10{sup 3} A/cm{sup 2}, whereas for the MgB{sub 2} sample immersed at 300 min standby time in engine oil the J{sub c} is enhanced to 4.8 × 10{sup 3} A/cm{sup 2} at 5 K and 3 T. The superconducting transition temperature (T{sub c}) did not change

  9. Photoluminescence and electro-optic properties of small (25-35 nm diameter) quantum boxes

    Science.gov (United States)

    Davis, L.; Ko, K. K.; Li, W.-Q.; Sun, H. C.; Lam, Y.; Brock, T.; Pang, S. W.; Bhattacharya, P. K.; Rooks, M. J.

    1993-05-01

    The luminescence and electro-optic properties of buried 25-35 nm quantum boxes have been measured. The quantum boxes were defined by a combination of molecular beam epitaxial growth and regrowth, electron beam lithography, and dry etching. The photoluminescence from 35 nm boxes shows a blue shift of about 15 meV compared to the bulk luminescence and an enhancement, taking into account the fill factor. An enhanced effective linear electrooptic coefficient is observed for the quantum boxes.

  10. Assessing the dependence of bulk ice properties from probes with anti-shatter tips on environmental conditions

    Science.gov (United States)

    Jackson, Robert C.

    Ice clouds have significant impacts on the Earth's radiative budget. Their radiative impact highly depends on ice cloud microphysical properties. Climate and weather prediction models have to make certain assumptions about how the various processes are represented. Observations of how cloud properties vary with environmental conditions can help evaluate some parameterizations used in models. However, sufficient data are not available to characterize how ice crystal properties vary as a function of environmental conditions. Furthermore, many of these assumptions are derived from historical datasets collected by in situ probes, namely optical array probes that can be contaminated by shattered artifacts generated by large particles shattering on the probe tips and inlets. Therefore this study has two main objectives. Prior estimates of ice crystal size distributions derived from 2D Cloud Probes (2DCs) have been artificially amplified by small ice crystals generated from the shattering of large ice crystals on the probe tips. Although anti-shatter tips and algorithms exist, there is considerable uncertainty in their effectiveness. Therefore, this thesis first examines the differences in ice crystal size distributions, and bulk and optical properties from adjacent 2DCs with standard and anti-shatter tips, and processed with and without anti-shattering algorithms. The measurements were obtained from the National Research Council of Canada Convair-580 during the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) and the National Center for Atmospheric Research C-130 during the 2011 Instrumentation Development and Education in Airborne Science 2011 (IDEAS-2011). The 2DC size distributions are compared with those from the Holographic Detector for Clouds (HOLODEC), which has anti-shatter tips and allows for identification of shattering through spatial statistics. The ratio of the number concentration N of particles with maximum dimensions 125 to 500 mum from the 2DC with

  11. The Evolution of Microstructures and the Properties of Bulk Metallic Glass with Consubstantial Composition Laser Welding

    Directory of Open Access Journals (Sweden)

    Pingjun Tao

    2016-09-01

    Full Text Available A Zr55Cu30Ni5Al10 plate-like bulk metallic glass (BMG was prepared using copper mold suction casting. Additionally, alloy powders with the same nominal composition were synthesized. The alloy powders were welded or melted to the cleaned surface of the BMG with a laser beam acceleration voltage of 60 kV, a beam current range from 60 to 100 mA, a welding speed of 60 mm/s, as well as an impulse width of 3.0 ms. The effect of consubstantial composition welding on the microstructures and properties was investigated. The molten and subsequently solidified metallic mixtures remain an amorphous structure, but the enthalpy of the welded or melted position varies due to the combination of the micro-structural relaxation and nano-crystals precipitated during the energy inputs. The surface layers of the BMG can be significantly intensified after welding processes; however, the heat-affected zones (HAZs exhibit a slight degradation in mechanical properties with respect to the BMG matrix. This study has important reference value for specialists working on the promotion of applications of BMGs.

  12. Structural and electronic properties of bulk and low-index surfaces of zincblende PtC

    Science.gov (United States)

    Gokhan Sensoy, Mehmet; Toffoli, Daniele; Ustunel, Hande

    2017-03-01

    Transition metal carbides have been extensively used in diverse applications over the past decade. Their versatility is in part thanks to their unique bonding, which displays a mixture of ionic, metallic and covalent character. While the bulk structure of zincblende (ZB) PtC has been investigated several times, a detailed understanding of the electronic and structural properties of its low-index surfaces is lacking. In this work, we present an ab initio investigation of the properties of five crystallographic ZB PtC surfaces (Pt/C-terminated PtC(1 0 0), PtC(1 1 0) and Pt/C-terminated PtC(1 1 1)). Upon geometry optimization, both polar and nonpolar surfaces undergo a mild interlayer relaxation, without extensive reconstructions. Calculated vacancy formation energies indicate facile C removal on the (1 1 1) surface while Pt-vacancy formation is endothermic. Finally, atomic O adsorption energies on all surfaces reveal a high affinity of the C-terminated surfaces towards this species.

  13. The bulk elastic modulus and the reversible properties of cell walls in developing Quercus leaves.

    Science.gov (United States)

    Saito, Takami; Soga, Kouichi; Hoson, Takayuki; Terashima, Ichiro

    2006-06-01

    We examined the relationship between the bulk elastic modulus (epsilon) of an individual leaf obtained by the pressure-volume (P-V) technique and the mechanical properties of cell walls in the leaf. The plants used were Quercus glauca and Q. serrata, an evergreen and a deciduous broad-leaved tree species, respectively. We compared epsilon and Young's modulus of leaf specimens determined by the stretch technique at various stages of their leaf development. The results showed that epsilon increased from approximately 5 to 20 MPa during leaf development, although other potential determinants of epsilon such as the apoplastic water content in the leaf and the diameter of a palisade tissue cells remained almost constant. epsilon in these two species was similar at every developmental stages, although the apparent mechanical strength of the leaf lamina and thickness of mesophyll cell walls were greater in Q. glauca. There were significant linear relationships between Young's modulus and epsilon (P < 0.01; R (2) = 0.78 and 0.84 in Q. glauca and Q. serrata, respectively) with small y-intercepts. From these results, we conclude that epsilon is closely related to the reversible properties of the cell walls. From the estimation of epsilon based on a physical model, we suggest that the effective thickness of cell walls responsible for epsilon is smaller than the observed wall thickness.

  14. Structural and electronic properties of bulk and low-index surfaces of zincblende PtC.

    Science.gov (United States)

    Sensoy, Mehmet Gokhan; Toffoli, Daniele; Ustunel, Hande

    2017-03-29

    Transition metal carbides have been extensively used in diverse applications over the past decade. Their versatility is in part thanks to their unique bonding, which displays a mixture of ionic, metallic and covalent character. While the bulk structure of zincblende (ZB) PtC has been investigated several times, a detailed understanding of the electronic and structural properties of its low-index surfaces is lacking. In this work, we present an ab initio investigation of the properties of five crystallographic ZB PtC surfaces (Pt/C-terminated PtC(1 0 0), PtC(1 1 0) and Pt/C-terminated PtC(1 1 1)). Upon geometry optimization, both polar and nonpolar surfaces undergo a mild interlayer relaxation, without extensive reconstructions. Calculated vacancy formation energies indicate facile C removal on the (1 1 1) surface while Pt-vacancy formation is endothermic. Finally, atomic O adsorption energies on all surfaces reveal a high affinity of the C-terminated surfaces towards this species.

  15. Bulk electronic, elastic, structural, and dielectric properties of the Weyl semimetal TaAs

    Science.gov (United States)

    Buckeridge, J.; Jevdokimovs, D.; Catlow, C. R. A.; Sokol, A. A.

    2016-03-01

    We present results of electronic structure calculations of the bulk properties of the Weyl semimetal TaAs. The emergence of Weyl (massless) fermions in TaAs, due to its electronic band structure, is indicative of a new state of matter in the condensed phase that is of great interest for fundamental physics and possibly new applications. Many of the physical properties of the material, however, are unknown. We have calculated the structural parameters, dielectric function, elastic constants, phonon dispersion, electronic band structure, and Born effective charges using density functional theory within the generalized gradient approximation, including spin-orbit coupling where necessary. Our results provide essential information on the material; and our calculations agree well with the relatively small number of experimental data available. Moreover, we have determined the relative stability of the ground state body-centered tetragonal phase with respect to other common binary phases as a function of pressure at the athermal limit, predicting a transition to the CsCl cubic structure at 23.3 GPa. Finally, we have determined the band structure using an unbiased hybrid density functional that includes 25% exact exchange, in order to refine the previously determined positions in k space of the Weyl points.

  16. Structure–property relationships of oligothiophene–isoindigo polymers for efficient bulk-heterojunction solar cells

    KAUST Repository

    Ma, Zaifei

    2014-01-01

    A series of alternating oligothiophene (nT)-isoindigo (I) copolymers (PnTI) were synthesized to investigate the influence of the oligothiophene block length on the photovoltaic (PV) properties of PnTI:PCBM bulk-heterojunction blends. Our study indicates that the number of thiophene rings (n) in the repeating unit alters both polymer crystallinity and polymer-fullerene interfacial energetics, which results in a decreasing open-circuit voltage (Voc) of the solar cells with increasing n. The short-circuit current density (Jsc) of P1TI:PCBM devices is limited by the absence of a significant driving force for electron transfer. Instead, blends based on P5TI and P6TI feature large polymer domains, which limit charge generation and thus Jsc. The best PV performance with a power conversion efficiency of up to 6.9% was achieved with devices based on P3TI, where a combination of a favorable morphology and an optimal interfacial energy level offset ensures efficient exciton separation and charge generation. The structure-property relationship demonstrated in this work would be a valuable guideline for the design of high performance polymers with small energy losses during the charge generation process, allowing for the fabrication of efficient solar cells that combine a minimal loss in Voc with a high Jsc. © 2014 The Royal Society of Chemistry.

  17. The effect of curing intensity on mechanical properties of different bulk-fill composite resins

    Science.gov (United States)

    Alkhudhairy, Fahad I

    2017-01-01

    Objective The purpose of this study was to investigate the effects of two curing light intensities on the mechanical properties (Vickers microhardness, compressive strength, and diametral tensile strength) of bulk-fill resin-based composites (RBCs). Materials and methods Four commercially available bulk-fill RBCs (Tetric® N-Ceram, SonicFill™, Smart Dentin Replacement (SDR™) Posterior Flowable Material, and Filtek™ Posterior Restorative) were used in this study. A total of 72 cylindrical specimens of each RBC (n=288) were prepared and subjected to Vickers microhardness, compressive strength, and diametral tensile strength tests at high (1200 mW/cm2) and low (650 mW/cm2) curing light intensities (each n=12). Results were evaluated using independent and paired sample t-tests, one-way analysis of variance, and Tukey’s post hoc test. All tests were performed at a significance level of Pmicrohardness was observed for SonicFill (58.3 Vickers hardness number [VHN]) cured using high-intensity light. Although having the least mean microhardness values, a significant difference was observed between SDR cured using high-intensity light and that cured using low-intensity light (Pmicrohardness of two materials tested compared with lower curing light intensity (650 mW/cm2). SonicFill showed the greatest microhardness and compressive strength significantly for both curing light intensities and greater diametral tensile strength with high-intensity light, although not significant. SDR cured with high-intensity light showed the greatest diametral tensile strength among the four materials. PMID:28260947

  18. Superconducting Properties and Microstructure in MgB2 Bulks, Wires and Tapes

    Institute of Scientific and Technical Information of China (English)

    冯勇; 阎果; 赵勇; 吴晓京; 周廉; 张平祥

    2003-01-01

    We prepared a series of MgB2 bulk samples under different temperatures, holding time and increasing rates in temperature by the solid state reaction. The thermodynamic behavior and phase formation in the Mg-B system were studied by using DTA,XRD and SEM. The results indicate that the formation of the MgB2 phase is very fast and the high increasing rate in temperature is necessary to obtain high quality MgB2. In addition, the effects of the Zr-doping in Mg1-xZrxB2 bulk samples fabricated by the solid state reaction at ambient pressure on phase compositions, microstructure and flux pinning behavior were investigated by using XRD, SQUID magnetometer, SEM and TEM. Critical current density Jc can be significantly enhanced by the Zr-doping and the best data are achieved in Mg0.9Zr0.1B2. For this sample, Jc values are remarkably improved to 1.83×106 A/cm2 in self-field and 5.51×105 A/cm2 in 1 T at 20 K. Also, high quality MgB2/Ta/Cu wires and tapes with and without Ti-doping, MgB2/Fe wires and 18 filament MgB2/NbZr/Cu tapes were fabricated by the powder-in-tube (PIT) method at ambient pressure. The phase compositions, microstructure features and flux pinning properties were studied. The results suggest that Fe is thebest metal for these sheaths. MgB2/Fe wires exhibit very high Jc at high temperatures and high fields. Jc values reach as high as 1.43×105 A/cm2 (4.2 K, 4 T) and 3.72×104 A/cm2 (15 K, 4 T).

  19. Predicting bulk mechanical properties of cellularized collagen gels using multiphoton microscopy.

    Science.gov (United States)

    Raub, C B; Putnam, A J; Tromberg, B J; George, S C

    2010-12-01

    Cellularized collagen gels are a common model in tissue engineering, but the relationship between the microstructure and bulk mechanical properties is only partially understood. Multiphoton microscopy (MPM) is an ideal non-invasive tool for examining collagen microstructure, cellularity and crosslink content in these gels. In order to identify robust image parameters that characterize microstructural determinants of the bulk elastic modulus, we performed serial MPM and mechanical tests on acellular and cellularized (normal human lung fibroblasts) collagen hydrogels, before and after glutaraldehyde crosslinking. Following gel contraction over 16 days, cellularized collagen gel content approached that of native connective tissues (∼200 mg ml⁻¹). Young's modulus (E) measurements from acellular collagen gels (range 0.5-12 kPa) exhibited a power-law concentration dependence (range 3-9 mg ml⁻¹) with exponents from 2.1 to 2.2, similar to other semiflexible biopolymer networks such as fibrin and actin. In contrast, cellularized collagen gel stiffness (range 0.5-27 kPa) produced concentration-dependent exponents of 0.7 uncrosslinked and 1.1 crosslinked (range ∼5-200 mg ml⁻¹). The variation in E of cellularized collagen hydrogels can be explained by a power-law dependence on robust image parameters: either the second harmonic generation (SHG) and two-photon fluorescence (TPF) (matrix component) skewness (R²=0.75, exponents of -1.0 and -0.6, respectively); or alternatively the SHG and TPF (matrix component) speckle contrast (R²=0.83, exponents of -0.7 and -1.8, respectively). Image parameters based on the cellular component of TPF signal did not improve the fits. The concentration dependence of E suggests enhanced stress relaxation in cellularized vs. acellular gels. SHG and TPF image skewness and speckle contrast from cellularized collagen gels can predict E by capturing mechanically relevant information on collagen fiber, cell and crosslink density.

  20. Minority carrier bulk lifetimes through a large multicrystalline silicon ingot and related solar cell properties

    Science.gov (United States)

    Martinuzzi, S.; Gauthier, M.; Barakel, D.; Périchaud, I.; Le Quang, N.; Palais, O.; Goaer, G.

    2007-10-01

    The bulk lifetime τ n and diffusion length Ln of minority carriers vary through the height of a cast multicrystalline silicon (mc-Si) block. This variation is due to the segregation of metallic impurities during the directional solidification and the native impurity concentrations increase from the bottom to the top of the ingot, which is solidified last, while the ingot bottom, which is solidified first, is contaminated by the contact with the crucible floor. It is of interest to verify if a correlation exists between the bulk lifetime τ of as cut wafers and the conversion efficiency η of solar cells. In a very large ingot (>310 kg), it was found that τ0, in raw wafers, τdif in phosphorus diffused ones and Ln in diffused wafers are smaller in the top and in the bottom of the ingot. The same evolution is observed in solar cells, however the diffusion length values Lcel in the central part of the ingot are markedly higher than those found in diffused wafers, due to the in-diffusion of hydrogen from the SiN-H antireflection coating layer. The variations of η and those of τ 0, along the ingot height, are well correlated, suggesting that the evaluation of τ 0 can predict the properties of the devices. In addition, segregation phenomena around the grain boundaries are observed at the bottom of the ingots, due to a marked contamination by the crucible floor, and at its top where impurities are accumulated. These phenomena are linked to the long duration of the solidification process and the large amount of imperfect silicon used to cast the ingot.

  1. Electronic, elastic, and optical properties of monolayer BC2N

    Science.gov (United States)

    Jiao, Lina; Hu, Meng; Peng, Yusi; Luo, Yanting; Li, Chunmei; Chen, Zhiqian

    2016-12-01

    The structural stability, electronic structure, elasticity, and optical properties of four types of monolayer BC2N have been investigated from first principles using calculation based on density functional theory. The results show that the structural stability of BC2N increases with the number of C-C and B-N bonds. By calculating the two-dimensional Young's modulus, shear modulus, Poisson's ratio, and shear anisotropic factors in different directions, four structures present various anisotropies and the most stable structure is almost isotropic. For C-type BC2N, the values of two-dimensional Young's modulus, shear modulus, and bulk modulus (309, 128, 195 GPa m-1), are smaller than those of graphene (343, 151, 208) but bigger than those of h-BN (286, 185, 116). Furthermore, the dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss spectrum are also calculated to investigate the mechanism underpinning the optical transitions in BC2N, revealing monolayer BC2N as a candidate window material.

  2. Broadband optical characterization of material properties

    DEFF Research Database (Denmark)

    Nielsen, Otto Højager Attermann

    , as well as details of the absorption spectrum which relate to chemical composition. The thesis focuses on two production process from the food industry. The first process is from the dairy industry where discrimination between chemical and structural properties is of importance. To explore...... inspection system for spectrallyresolved Static Light Scattering (SLS). (II) Photon Time-of-Flight (PToF) spectroscopy, which is a state of the art technique for characterization of turbid media. (III) A new hyperspectral imaging system based on full-field illumination by diffuse laser light. This thesis...... the fermentation process. It has also been shown that the optical inspection methods sense changes to structural properties before any are detected by traditional mechanical rheology. Finally, the developed hyperspectral imaging system was used to quantify the content of astaxanthin in fish feed, and performed...

  3. Optical Properties of Topological Insulator Bragg Gratings

    CERN Document Server

    Crosse, J A

    2015-01-01

    Using the transfer matrix formalism, we study the transmission properties of a Bragg grating constructed from a layered axionic material. Such a material can be realized by a topological insulator subject to a time-symmetry breaking perturbation, such as an external magnetic field or surface magnetic impurities. Whilst the reflective properties of the structure are only negligibly changed by the presence of the axionic material, the grating induces Faraday and Kerr rotations in the transmitted and reflected light, respectively. These rotations are proportional to the number of layers and the strength of the time-symmetry breaking perturbation. In areas of low reflectivity the rotation angle of TE polarization decreases with increasing incidence angle while the TM polarization increases with increasing incidence angle with the converse occurring in areas of high reflectivity. The formalism and results will be useful in the development of optical and photonic devices based on topological insulators, devices whi...

  4. BOREAS TE-10 Leaf Optical Properties

    Science.gov (United States)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Chan, Stephen S.; Middleton, Elizabeth

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-10 (Terrestrial Ecology) team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, gas exchange, oxygen evolution, and biochemical properties of boreal vegetation. This data set describes the spectral optical properties (reflectance and transmittance) of boreal forest conifers and broadleaf tree leaves as measured with a Spectron Engineering SE590 spectroradiometer at the Southern Study Area Old Black Spruce (SSA OBS), Old Jack Pine (OJP), Young Jack Pine (YJP), Old Aspen (OA), Old Aspen Auxiliary (OA-AUX), Young Aspen Auxiliary (YA-AUX), and Young Aspen (YA) sites. The data were collected during the growing seasons of 1994 and 1996 and are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  5. Microwave processed bulk and nano NiMg ferrites: A comparative study on X-band electromagnetic interference shielding properties

    Energy Technology Data Exchange (ETDEWEB)

    Chandra Babu Naidu, K., E-mail: chandrababu954@gmail.com [Ceramic Composite Laboratory, Centre for Crystal Growth, SAS, VIT University, Vellore 632014, Tamilnadu (India); Madhuri, W., E-mail: madhuriw12@gmail.com [Ceramic Composite Laboratory, Centre for Crystal Growth, SAS, VIT University, Vellore 632014, Tamilnadu (India); IFW, Leibniz Institute for Solid State and Materials Research, Technische Universität Dresden, 01069 Dresden (Germany)

    2017-02-01

    Bulk and nano Ni{sub 1-x}Mg{sub x}Fe{sub 2}O{sub 4} (x = 0–1) samples were synthesized via microwave double sintering and microwave assisted hydrothermal techniques respectively. The diffraction pattern confirmed the formation of cubic spinel phases in case of both the ferrites. The larger bulk densities were achieved to the bulk than that of nano. In addition, a comparative study on X-band (8.4–12 GHz) electromagnetic interference shielding properties of current bulk and nanomaterials was elucidated. The results showed that the bulk Ni{sub 0.6}Mg{sub 0.4}Fe{sub 2}O{sub 4} composition revealed the highest total shielding efficiency (SE{sub T}) of ∼17 dB. In comparison, the shielding efficiency values of all bulk contents were higher than that of nano because of larger bulk densities. Moreover, the ac-electromagnetic parameters such as electrical conductivity (σ{sub ac}), the respective real (ε′ & μ′) and imaginary parts (ε″ & μ″) of complex permittivity and permeability were investigated as a function of gigahertz frequency. The bulk ferrites of x = 0.4 & 0.6 showed the high ε″ of 10.26 & 6.71 and μ″ of 3.65 & 3.09 respectively at 12 GHz which can work as promising microwave absorber materials. Interestingly, nanoferrites exhibited negative μ″ values at few frequencies due to geometrical effects which improves the microwave absorption. - Highlights: • Bulk and nano NiMg ferrites are prepared by microwave and hydrothermal method. • X-band EMI shielding properties are studied for both bulk and nano ferrites. • Bulk Ni{sub 0.6}Mg{sub 0.4}Fe{sub 2}O{sub 4} revealed the highest SE{sub T} of ∼17 dB at 8.4 GHz. • Bulk x = 0.4 & 0.6 showed the high ε″ and μ″ at 12 GHz for absorber applications.

  6. Optical properties of matrix confined species

    Science.gov (United States)

    Lezhnina, M. M.; Kynast, U. H.

    2010-11-01

    A majority of optically functional materials can be perceived as a liaison between ionic or molecular guests and a more or less rigid host. The guests exhibit an optical function, whereas the host provides suitable space, both of them synergistically complementing each other. The embracement of guests and hosts is often very intimate, as e.g. in typical phosphors, where luminescent ions even become part of the host. While the host-guest terminology usually is not applied to such marriages, the term becomes appropriate, if the host grants some degrees of spatial freedom, yet giving order and structure to its guests. Zeolites, clays and inverse opals are porous materials naturally providing hospitable cavities, channels or other compartments, and at the same time the guests are often demanded to occupy preassigned positions within these, or to structurally adapt to the interior host topology. Whereas zeolites and clays are merely patient providers of guest space, inverse opals, can actively turn the light on and off. The present article summarises and highlights recent experimental evidence, ongoing research and some envisaged merits resulting from the interaction of matrix confined luminescent ions, complexes and molecules with a focus on the optical properties of rare earth based materials.

  7. Optical properties of titanium dioxide nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Abdelmoula, Mohamed [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Department of Materials Science, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Sokoloff, Jeffrey; Lu, Wen-Tao; Menon, Latika [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Close, Thomas; Richter, Christiaan, E-mail: christiaan.richter@rit.edu [Department of Chemical Engineering, Rochester Institute of Technology, Rochester, New York, 14623 (United States)

    2014-01-07

    We present experimental measurements and a theoretical analysis of the near UV to NIR optical properties of free standing titania nanotube arrays. An improved understanding of the optical physics of this type of nanostructure is important to several next generation solar energy conversion technologies. We measured the transmission, reflection, and absorption of the electromagnetic spectrum from 300 nm to 1000 nm (UV to NIR) of titania nanotube arrays. We measured the total, specular, and diffuse reflection and transmission using both single point detection and an integrating sphere spectrometer. We find that the transmission, but not the reflection, of light (UV to NIR) through the nanotube array is well-explained by classic geometric optics using an effective medium model taking into account the conical geometry of the nanotubes. For wavelengths shorter than ∼500 nm, we find the surprising result that the reflection coefficient for light incident on the open side of the nanotube array is greater than the reflection coefficient for light incident on the closed “floor” of the nanotube array. We consider theoretical models based on the eikonal approximation, photonic crystal band theory, and a statistical treatment of scattering to explain the observed data. We attribute the fact that light with wavelengths shorter than 500 nm is more highly reflected from the open than the closed tube side as being due to disorder scattering inside the nanotube array.

  8. Physical and optical properties of binary amorphous selenium-antimony thin films

    Science.gov (United States)

    Sharma, Pankaj; Sharma, Ishu; Katyal, S. C.

    2009-03-01

    Amorphous thin films with compositions Se1-xSbx (x =0, 0.025, 0.05, 0.075, and 0.10 at. %) have been deposited by thermal evaporation (at ˜10-4 Pa) from bulk samples. The compositional dependence of their optical properties, refractive index, extinction coefficient, absorption coefficient, and optical band gap with increasing Sb content is investigated using transmission spectra in the range of 400-1200 nm. The refractive-index dispersion has been analyzed on the basis of the Wemple-DiDomenico single-oscillator approach. It has been found that the refractive index increases with increasing Sb content. The behavior of the optical band gap, when the composition of the material is varied, shows, as expected, just the opposite trends. The optical band gap decreases from 2.025 to 1.753 eV with ±0.001 eV uncertainty. Band gap calculated theoretically also shows a decrease with the increase in Sb content. The optical behavior is supported by physical properties, i.e., decrease in optical band gap is supported by the decrease in cohesive energy of the system. Some other physical properties, viz., coordination number, lone-pair electrons, and glass transition temperature, are also investigated theoretically. The optical results may lead to yield more sensitive detectors based on amorphous selenium, and physical properties may be useful in achieving more stable alloys which are favorable in x-ray imaging applications.

  9. Optical properties of nano-silicon

    Indian Academy of Sciences (India)

    S Tripathy; R K Soni; S K Ghoshal; K P Jain

    2001-06-01

    We investigated the optical properties of silicon clusters and Si nanocrystallites using photoluminescence (PL) and Raman scattering technique. Broad luminescence band in the red region was observed from Si-doped SiO2 thin films deposited by co-sputtering of Si and SiO2 on -type Si (100) substrates, annealed in Ar and O2 atmosphere. Nanocrystalline Si particles fabricated by pulsed plasma processing technique showed infrared luminescence from as grown film at room temperature. Raman spectra from these films consisted of broad band superimposed on a sharp line near 516 cm–1 whose intensity, frequency, and width depend on the particle sizes arising from the phonon confinement in the nanocrystalline silicon. We also performed PL, Raman and resonantly excited PL measurements on porous silicon film to compare the optical properties of Si nanostructures grown by different techniques. An extensive computer simulation using empirical pseudopotential method was carried out for 5–18 atoms Si clusters and the calculated gap energies were close to our PL data.

  10. Optical Properties of Black Silicon: An Analysis

    Science.gov (United States)

    Marthi, Sita Rajyalaxmi; Sekhri, Suramya; Ravindra, N. M.

    2015-09-01

    Silicon (Si) continues to be the dominant semiconducting material used in photovoltaic technology for the manufacture of solar cells. Si, an indirect band gap semiconducting material, has a reflectance of about 30% in the visible range of wavelengths. Standard Si solar cells are not entirely useful in the infrared spectrum region. In order to enhance the performance of silicon solar cells, reflectance losses must be minimized and absorption must be maximized. In the solar cell industry, anti-reflection (AR) coating is used to suppress reflection losses. AR coatings are limited in use because they only reduce the reflectance for a narrow range of wavelengths and incident angle since their functionality is based on a quarter-wavelength coating. Surface texturing is a technique, by which the reflectivity is reduced in a wide range of wavelengths. Black silicon (B-Si) is a material with surface roughness in the micron scale. B-Si, when used instead of crystalline Si (c-Si), offers the possibility to increase the absorption of light in the visible and infrared range of wavelengths. B-Si has a very low reflectivity in the visible range of wavelengths. It exhibits high absorptance in the visible and infrared region. The main objective of this paper is to study the optical properties of B-Si by simulation and compare them with the simulated and experimental optical properties of B-Si and c-Si.

  11. Solid, shape recovered 'Bulk' nitinol: Part II-Mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Saigal, Anil, E-mail: anil.saigal@tufts.edu [Department of Mechanical Engineering, Tufts University, Medford, MA 02155 (United States); Fonte, Matthew [Department of Mechanical Engineering, Tufts University, Medford, MA 02155 (United States)

    2011-06-25

    Highlights: {yields} Evaluate use of solid bulk Nitinol as a potential material for hip replacements. {yields} At 400 MPa, Nitinol has an endurance limit greater than 10 million cycles. {yields} Below 445 MPa [1 1 1] textured specimens last longer than [1 1 0] textured specimens. {yields} Above 445 MPa, it switches and both fail relatively quickly around 400,000 cycles. {yields} Impact toughness - Charpy: 4 ft-lbs {+-} 3%, CT: 20-31 MPa{radical}m. - Abstract: The use of Nitinol for medical purposes was first reported in the late 1960s. Today Nitinol is commonly used for the manufacture of stents, which are primarily used in peripheral and coronary bypass graft interventions. The application of NiTi in orthopedics is an exciting prospect but one that has yet to be realized. Nitinol's unique mechanical behavior is derived from the coordinated atomic movements manifesting in phase transformations from cubic austenite to monoclinic martensite. These phase transformations are solid-to-solid phase transformations that occur without diffusion or plasticity, potentially making them reversible. They involve changes in the crystalline structure that can be induced by changes in either temperature or stress. In addition to phase transformations, Nitinol's mechanical strength is strongly dependent on the alloy composition and the method in which the material is processed, i.e. rolled, drawn, extruded, or forged. The mechanical work, combined with the intermediate heat treatment steps, contribute to modify microstructure, transformation temperatures and mechanical properties. These manufacturing processing steps lead to texturing (crystallographic alignment) of the material. Alignment of the atomic planes from texture in the polycrystalline material have a marked influence on the mechanical properties by either limiting or promoting phase transformations and shape recovery strains. This paper focuses on the fatigue and fracture properties of Nitinol.

  12. Accurate simulation of optical properties in dyes.

    Science.gov (United States)

    Jacquemin, Denis; Perpète, Eric A; Ciofini, Ilaria; Adamo, Carlo

    2009-02-17

    Since Antiquity, humans have produced and commercialized dyes. To this day, extraction of natural dyes often requires lengthy and costly procedures. In the 19th century, global markets and new industrial products drove a significant effort to synthesize artificial dyes, characterized by low production costs, huge quantities, and new optical properties (colors). Dyes that encompass classes of molecules absorbing in the UV-visible part of the electromagnetic spectrum now have a wider range of applications, including coloring (textiles, food, paintings), energy production (photovoltaic cells, OLEDs), or pharmaceuticals (diagnostics, drugs). Parallel to the growth in dye applications, researchers have increased their efforts to design and synthesize new dyes to customize absorption and emission properties. In particular, dyes containing one or more metallic centers allow for the construction of fairly sophisticated systems capable of selectively reacting to light of a given wavelength and behaving as molecular devices (photochemical molecular devices, PMDs).Theoretical tools able to predict and interpret the excited-state properties of organic and inorganic dyes allow for an efficient screening of photochemical centers. In this Account, we report recent developments defining a quantitative ab initio protocol (based on time-dependent density functional theory) for modeling dye spectral properties. In particular, we discuss the importance of several parameters, such as the methods used for electronic structure calculations, solvent effects, and statistical treatments. In addition, we illustrate the performance of such simulation tools through case studies. We also comment on current weak points of these methods and ways to improve them.

  13. Study of the atypical formations in the corrosion bulks of an ancient bronze shield, by optical and electron microscopy.

    Science.gov (United States)

    Mircea, Otilia; Sandu, Ion; Vasilache, Viorica; Sandu, Andrei Victor

    2012-11-01

    This article presents the atypical formations in the structure of the corrosion crust and in the partially mineralized metallic core, which resulted during the underground stay of a bronze shield, dated between the 1st century B.C. and the 1st century A.D. For our study, we choose a representative fragment from the rim of the shield, which was analyzed by optical microscopy and by electron microscopy coupled with energy-dispersive X-ray spectroscopy, to study its morphology, its composition, and the location of chemical compounds on the surface and inside the bulk formed during the underground stay, by processes of chemical and physical alteration, assisted by contamination with structural elements from the site. Those processes, by monolithization and mineralization formed a series of structures consisting of congruent elements and phases with a complex composition. Those formations, defined as surface effects generated by exogenous factors and endogenous factors inside the bulk, are frequently found in ancient bronze objects (such as the exterior flat mole formations and the Liesegang effect in the stratigraphic structure of the bulk). Some of those structures have atypical characteristics as regards their structure, composition, and formation mechanism, which may be used in archeometry. Moreover, that includes the object in the category of special cases, in terms of artifact evolution during underground stay and of the atypical formations resulted from the action of pedological and environmental factors.

  14. Linear and nonlinear optical properties of chalcogenide microstructured optical fibers

    Science.gov (United States)

    Trolès, Johann; Brilland, Laurent; Caillaud, Celine; Renversez, Gilles; Mechin, David; Adam, Jean-Luc

    2015-03-01

    Chalcogenide glasses are known for their large transparency in the mid-infrared and their high linear refractive index (>2). They present also a high non-linear coefficient (n2), 100 to 1000 times larger than for silica, depending on the composition. we have developed a casting method to prepare the microstructured chalcogenide preform. This method allows optical losses as low as 0.4 dB/m at 1.55 µm and less than 0.05 dB/m in the mid IR. Various chalcogenide MOFs operating in the IR range has been fabricated in order to associate the high non-linear properties of these glasses and the original MOF properties. For example, small core fibers have been drawn to enhance the non linearities for telecom applications such as signal regeneration and generation of supercontinuum sources. On another hand, in the 3-12 µm window, single mode fibers and exposed core fibers have been realized for Gaussian beams propagation and sensors applications respectively.

  15. Improving magnetic properties of MgB2 bulk superconductors by synthetic engine oil treatment

    Science.gov (United States)

    Taylan Koparan, E.; Savaskan, B.; Yanmaz, E.

    2016-08-01

    The present study focuses on the effects of standby time of the MgB2 samples immersed in synthetic engine oil on the critical current density (Jc(H)), magnetic field dependence of the pinning force density fp(b) and Tc performances of MgB2 bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB2 pellet samples were immersed at different standby time of 30 min, 120 min, 300 min and 1440 min in synthetic engine oil after the first heating process. Finally, MgB2 samples immersed in synthetic engine oil were sintered at 1000 °C and kept for 15 min in Ar atmosphere. The critical current density of all of MgB2 samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB2 sample because of the number of the pinning centers. The MgB2 sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. The Jc value for the pure sample is 2.0 × 103 A/cm2, whereas for the MgB2 sample immersed at 300 min standby time in engine oil the Jc is enhanced to 4.8 × 103A/cm2 at 5 K and 3 T. The superconducting transition temperature (Tc) did not change with the increasing standby time of the samples in synthetic engine oil at all. The best diamagnetic property was obtained from the sample which kept in synthetic engine oil for 300 min. Synthetic engine oil treatment results in remarkable improvement of the critical current density and pinning force performances of MgB2 superconductors. It was found that all MgB2 samples have a different pinning property at different measuring temperatures. Using synthetic engine oil as a product which is cheap and a rich carbon source in MgB2 bulk superconductors makes MgB2 samples immersed in synthetic engine oil a good candidate for industrial applications.

  16. Evaluation of the physical properties, bulk density and aggregate stability of potential substrates in quarry restoration.

    Science.gov (United States)

    Jordan, M.; Garcia-Orenes, F.; Mataix-Solera, J.; Garcia-Sanchez, E.

    2012-04-01

    Quarrying activity entails significant environmental impact affecting the soil, water, plants, landscape, etc. One of the most important impacts is the loss of the productive layer of the soil and its vegetation cover. However, mining activities are absolutely necessary for human development; keeping them sustainable implicates looking for viable solutions for the restoration of these areas to prevent degradation during and after the exploitation period. The aim of this study was to evaluate different substrates obtained from different mixes of sewage sludge and different mine spoils, to check how they are effective in quarry restoration, and to establish good practises in mining restoration. Also, the study tried to approach two refuses, one deriving from mining activity, as are the mine spoils that need to be reused for their valorisation, and the other, sewage sludge, obtained in the water depuration process to acquire a cheap substrate for soil rehabilitation. This preliminary work, which is included in a larger study, shows the results obtained from two physical properties studied, bulk density and aggregate stability, as key properties in the substrate structure for use in mining area restoration. Two doses of composted sewage sludge (30 and 90 Tm/Ha), both very rich in calcium carbonate, were applied to two different mine spoils under lab conditions. The first material, of poor quality, originated from the acquisition of arid particles in crushed limestone (Z). It is characterized by stable ''coarse elements'' predominance (up to 75% of its weight), and by the presence of elevated percentages of sand. The other waste material tested comes from limestone extraction (basically formed by the levels of interspersed non-limestone materials and the remains of stripped soils (D)). The results show that the high dose of sewage sludge applied to a mix of the two mine spoils significantly increased the percentage of stable aggregates by more than 50% than the control

  17. Growth and characterization studies of sodium Di(L-Malato) borate bulk single crystal: A promising nonlinear optical material

    Science.gov (United States)

    Senthil, A.; Loganayaki, M.; Lenin, M.; Ramasamy, P.

    2012-06-01

    A semi-organic nonlinear optical material, sodium di(L-malato) borate (NaDMB) has been synthesized. Optically good quality bulk single crystal of NaDMB was successfully grown by slow evaporation solution technique (SEST) and Sankaranarayanan-Ramasamy (SR) method at 36 °C. Transparent, colourless crystal of size 22 mm X 8 mm X 6 mm with well defined morphology was grown by SEST and oriented unidirectional bulk single crystal of size 48 mm length and 16 mm diameter was grown by SR method. The grown crystals were subjected to single crystal X-ray diffraction studies. The crystal belongs to monoclinic structure with space group P21. The grown crystals were characterized by UV-vis studies. The structural perfection of the grown crystal has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The differential thermal (DTA) and thermogravimetric (TG) analysis traces reveal the thermal stability of the sample. The second-harmonic generation efficiency was estimated by Kurtz and Perry powder technique.

  18. Review on Optical and Electrical Properties of Conducting Polymers

    Directory of Open Access Journals (Sweden)

    Manisha Bajpai

    2016-01-01

    Full Text Available We reviewed optical and electrical properties of conjugated polymers. The charge transport models to describe the hole and electron transport mechanism are also included in the electrical properties of conjugated polymers. The effect of optical and electrical properties after doping is also indexed in this paper.

  19. Comparisons of Accurate Electronic, Transport, and Bulk Properties of XP (X = B, Al, Ga, In)

    Science.gov (United States)

    Malozovsky, Yuriy; Ejembi, John; Saliev, Azizjon; Franklin, Lashounda; Bagayoko, Diola

    We present comparisons of results from ab-initio,self-consistent local density approximation (LDA) calculations of accurate, electronic and related properties of zinc blende XP (X =B, Al, Ga, In) phosphides. We implemented the linear combination of atomic orbitals following the Bagayoko, Zhao, and Williams (BZW) method as enhanced by Ekuma and Franklin (BZW-EF). Consequently, our results have the full physical content of DFT and agree very well with corresponding experimental ones [AIP Advances, 4, 127104 (2014)]. Our calculated, indirect band gap of 2.02 eV for BP, 2.56 eV for AlP, and of 2.29 eV for GaP, from Γ to X-point, are in excellent agreement with experimental values. Our calculated direct band gap of 1.43 eV, at Γ, for InP is also in an excellent agreement with experimental value. We discuss calculated electron and hole effective masses, total (DOS) and partial (pDOS) densities of states, and the bulk modulus of these phosphides. Acknowledgments: NSF and the Louisiana Board of Regents, LASiGMA [Award Nos. EPS- 1003897, NSF (2010-15)-RII-SUBR] and NSF HRD-1002541, DOE - National, Nuclear Security Administration (NNSA) (Award Nos. DE-NA0001861 and DE- NA0002630), LaSPACE, and LONI-SUBR.

  20. Phase formation and mechanical properties of Cu-Zr-Ti bulk metallic glass composites

    Science.gov (United States)

    Kim, Byoung Jin; Yun, Young Su; Kim, Won Tae; Kim, Do Hyang

    2016-11-01

    The effect of the type of the crystalline phase and its volume fraction on the mechanical property of Cu50Zr50-xTix alloys (x = 0-10) bulk metallic glass composites has been investigated in this study. Up to 6 at% of Ti, B19' phase particles distributed in the glassy matrix, while at 8 and 10% of Ti, B2 phase particles are retained in the glass matrix due to suppression of the eutectoid transformation of B2 phase and by avoidance of martensitic transformation of B2 into B19'. The volume fraction of crystalline phase is strongly dependent on the cooling rate. The larger volume fraction of the crystalline phases results in the lower yield stress, the higher plastic strain, and the more pronounced work hardening behavior. At the crystalline volume fraction below 30%, the variation of the yield strength can be described by the rule of mixture model (ROM), while at the crystalline volume fraction higher than 50% by the load-bearing model (LBM). At the crystal fractions between 30 and 50%, there is a yield strength drop and a transition from the ROM to the LBM. This transition is due to the formation of the crystalline structural framework at higher crystal fraction.

  1. The effect of nanoparticle permeation on the bulk rheological properties of mucus from the small intestine.

    Science.gov (United States)

    Wilcox, M D; Van Rooij, L K; Chater, P I; Pereira de Sousa, I; Pearson, J P

    2015-10-01

    The effectiveness of delivering oral therapeutic peptides, proteins and nucleotides is often hindered by the protective mucus barrier that covers mucosal surfaces of the gastrointestinal (GI) tract. Encapsulation of active pharmaceutical ingredients (API) in nanocarriers is a potential strategy to protect the cargo but they still have to pass the mucus barrier. Decorating nanoparticles with proteolytic enzymes has been shown to increase the permeation through mucus. Here we investigate the effect of poly(acrylic acid) (PAA) nanoparticles decorated with bromelain (BRO), a proteolytic enzyme from pineapple stem, on the bulk rheology of mucus as well as non-decorated poly(lactic-co-glycolic acid) (PLGA) nanoparticles. Porcine intestinal mucus from the small intestine was incubated for 30min in the presence of PLGA nanoparticles or polyacrylic nanoparticles decorated with bromelain (PAA-BRO). The effect of nanoparticles on the rheological properties, weight of gel, released glycoprotein content from mucus as well as the viscosity of liquid removed was assessed. Treatment with nanoparticles decreased mucus gel strength with PAA-BRO reducing it the most. PAA-BRO nanoparticles resulted in the release of increased glycoprotein from the gel network whereas mucus remained a gel and exhibited a similar breakdown stress to control mucus. Therefore it would be possible to use bromelain to increase the permeability of nanoparticles through mucus without destroying the gel and leaving the underlying mucosa unprotected.

  2. Microstructural and Superconducting Properties of V-Doped MgB2 Bulk and Wires

    Science.gov (United States)

    Castillo, O. E.; Sastry, P. V. P. S. S.; Trociewitz, B.; Trociewitz, U. P.; Schwartz, J.

    2004-06-01

    Studies of the effects of doping MgB2 bulk and Fe-clad wires with V are presented. Samples of composition Mg1-xVxB2 (x = 0.0, 0.05, 0.10, 0.15) have been investigated to understand the role of V doping on the phase formation, microstructure and superconducting properties. Fe-clad wires were fabricated by groove rolling and cold drawing. The superconducting transition temperature remained constant at about 39 K for all the compositions studied. Energy dispersive x-ray (EDX) analysis confirmed the presence of V in the superconducting phase. Enhancement of magnetization hysteresis loop widths indicates an improvement in flux pinning for V-doped samples. Studies on the variation of maximum reaction temperatures suggest that the optimum reaction temperature varies with V content. The optimum reaction temperature also depended on the wire diameter with the larger wires requiring higher reaction temperature. The transport critical current densities measured for groove-rolled wires were in the range of 1.0 - 1.4 × 105 A/cm2.

  3. Simulation study of mechanical properties of bulk metallic glass systems: martensitic inclusions and twinned precipitates

    Science.gov (United States)

    Zaheri, A.; Abdeljawad, F.; Haataja, M.

    2014-12-01

    Monolithic bulk metallic glasses (BMGs) exhibit a unique combination of mechanical properties, such as high strength and large elasticity limits, but the lack of ductility is considered the main Achilles' heel of BMG systems. To increase the competitiveness of BMGs vis-à-vis conventional structural materials, the problem of catastrophic failure via intense plastic strain localization (‘shear banding’) has to be addressed. Recent experimental observations suggest that the addition of structural heterogeneities, in the form of crystalline particles, to BMG systems hinders the catastrophic propagation of shear bands and leads to enhanced ductility. These structural heterogeneities can be introduced by either forming BMG composites, where second-phase crystalline particles accommodate applied loads via martensitic transformation mechanisms, or developing glassy alloys that precipitate crystalline particles under deformation, a process by which further deformation can be sustained by twinning mechanisms in the crystalline phase. In this work, we present a non-linear continuum model capable of capturing the structural heterogeneity in the glassy phase and accounting for intrinsic work hardening via martensitic transformations in second-phase reinforcements in BMG composites and deformation twinning in precipitated crystalline particles. Simulation results reveal that in addition to intrinsic work hardening in the crystalline phase, particle size greatly affects the overall mechanical behavior of these BMG systems. The precipitation of crystalline particles in monolithic BMGs yields two-phase microstructures that promote more homogeneous deformation, delay the propagation of incipient shear bands, and ultimately result in improved ductility characteristics.

  4. AC Calorimetry and Thermophysical Properties of Bulk Glass-Forming Metallic Liquids

    Science.gov (United States)

    Johnson, William L.

    2000-01-01

    Thermo-physical properties of two bulk metallic glass forming alloys, Ti34Zr11Cu47Ni8 (VIT 101) and Zr57Nb5Ni12.6Al10CU15.4 (VIT 106), were investigated in the stable and undercooled melt. Our investigation focused on measurements of the specific heat in the stable and undercooled liquid using the method of AC modulation calorimetry. The VIT 106 exhibited a maximum undercooling of 140 K in free radiative cooling. Specific heat measurements could be performed in stable melt down to an undercooling of 80 K. Analysis of the specific heat data indicate an anomaly near the equilibrium liquidus temperature. This anomaly is also observed in y the temperature dependencies of the external relaxation time, the specific volume, and the surface tension; it is tentatively attributed to a phase separation in the liquid state. The VIT 101 specimen exhibited a small undercooling of about 50 K. Specific heat measurements were performed in the stable and undercooled melt. These various results will be combined with ground based work such as the measurement of T-T-T curves in the electrostatic levitator and low temperature viscosity and specific heat measurements for modeling the nucleation kinetics of these alloys.

  5. Correlation between structural, electrical and magnetic properties of GdMnO{sub 3} bulk ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Samantaray, S. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, D.K. [Department of Physics, Institute of Technical Education and Research, S ‘O’ A University, Bhubaneswar 751030, Odisha (India); Pradhan, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Mishra, P.; Sekhar, B.R. [Institue of Physics, Sachivalaya Marg, Bhubaneswar, Odisha (India); Behera, Debdhyan [Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, Odisha (India); Rout, P.P.; Das, S.K. [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India); Sahu, D.R. [School of Physics, University of the Witwatersrand, Johannesburg (South Africa); Roul, B.K., E-mail: ims@iopb.res.in [Institute of Materials Science, Planetarium Building, Bhubaneswar 751013, Odisha (India)

    2013-08-15

    This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO{sub 3} (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO{sub 3}. Room temperature dielectric constant (ε{sub r}) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO{sub 3} at room temperature as multifunctional materials. - Highlights: • Preparation of single-phasic polycrystalline GdMnO{sub 3} sample by the solid state sintering route. • Observation of square type P–E hysteresis loop with higher saturation and remnant polarization. • Observation of antiferromagnetic behavior at 40 K in polycrystalline GdMnO{sub 3}. • Possibility of room temperature application of GdMnO{sub 3} as multifunctional material.

  6. Structure–property relationships of oligothiophene–isoindigo polymers for efficient bulk-heterojunction solar cells

    DEFF Research Database (Denmark)

    Ma, Zaifei; Sun, Wenjun; Himmelberger, Scott

    2014-01-01

    A series of alternating oligothiophene (nT)–isoindigo (I) copolymers (PnTI) were synthesized to investigate the influence of the oligothiophene block length on the photovoltaic (PV) properties of PnTI:PCBM bulk-heterojunction blends. Our study indicates that the number of thiophene rings (n......) in the repeating unit alters both polymer crystallinity and polymer–fullerene interfacial energetics, which results in a decreasing open-circuit voltage (Voc) of the solar cells with increasing n. The short-circuit current density (Jsc) of P1TI:PCBM devices is limited by the absence of a significant driving force...... for electron transfer. Instead, blends based on P5TI and P6TI feature large polymer domains, which limit charge generation and thus Jsc. The best PV performance with a power conversion efficiency of up to 6.9% was achieved with devices based on P3TI, where a combination of a favorable morphology and an optimal...

  7. Wave optical simulation of the light trapping properties of black silicon surface textures.

    Science.gov (United States)

    Bett, Alexander Jürgen; Eisenlohr, Johannes; Höhn, Oliver; Repo, Päivikki; Savin, Hele; Bläsi, Benedikt; Goldschmidt, Jan Christoph

    2016-03-21

    Due to their low reflectivity and effective light trapping properties black silicon nanostructured surfaces are promising front side structures for thin crystalline silicon solar cells. For further optimization of the light trapping effect, particularly in combination with rear side structures, it is necessary to simulate the optical properties of black silicon. Especially, the angular distribution of light in the silicon bulk after passage through the front side structure is relevant. In this paper, a rigorous coupled wave analysis of black silicon is presented, where the black silicon needle shaped structure is approximated by a randomized cone structure. The simulated absorptance agrees well with measurement data. Furthermore, the simulated angular light distribution within the silicon bulk shows that about 70% of the light can be subjected to internal reflection, highlighting the good light trapping properties.

  8. Effect of transition metal dopants on the optical and magnetic properties of semiconductor nanocrystals

    Indian Academy of Sciences (India)

    Ranjani Viswanatha

    2015-06-01

    This review discusses the recent developments in doped semiconductor nanocrystals with a special emphasis on the effect of dopant on the electronic structure of the host nanocrystals. The review focusses on 3 transition metal dopants with unique electronic structure making them receptive for dramatic changes in magnetism, absorption and photoluminescence properties by the successful introduction of a small percentage of dopants into the nanocrystals. Many of these properties are shown to be qualitatively different from that of the bulk properties, leading to challenges in understanding the nature and effects of the confinement of the host. The optical and magnetic changes induced by Mn doping is first reviewed, followed by the use of Cu as a probe to understand the bulk and surface electronic structure of the host. The review concludes with a short section on photomagnetism induced by Cu on the host nanocrystal and a summary of the work with other transition metal ions.

  9. Workshop on Optical Properties of Mesoscopic Semiconductor Structures

    Science.gov (United States)

    1993-03-28

    TELEPHONE (include Area Code) 22c OFFICE SYMSO- Larry R. Cooper, Code 111455 1 0 DD FORM 1473. 84 MAR 83 APR ed,tion may be useo until ex’hausted SECURITY...Speaker: DI. Wolford , IBM Yorktown, Optical Spectra qf lnterfiwe Free GaAs Srructures- From Bulk to the Quantum Limit 2:30 Discussion Contributors: M...24 8:00 Discussion Leader: D. Wolford Invited Speaker: T. Kennedy Naval Research Laboratory, Recombination in Superlattlkes StudIdl through Optically

  10. Magnetic properties and microstructural homogeneity in NdFeAl bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Zempoalteca, R.; Valenzuela, R.; Betancourt, I. [Depto de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, UNAM, Avenida Universidad (Mexico)

    2011-11-15

    Bulk metallic glasses of nominal composition Nd{sub 60}Fe{sub 30}Al{sub 10} were prepared by copper mold casting in the form of rods of 3 mm in diameter and 50 mm in length. Preparation conditions were varied to assess the effects of the injection distance and the injection pressure of the melt. In order to determine their microstructure, disk-shaped samples were obtained from different cut zones along the axis rod. A non-homogeneous phase distribution was observed, which resulted from the heat transfer regime during the cooling of the melt in the copper mold. As expected, the nature, distribution and volumetric fraction of the various phases produced play an important role on the resulting magnetic properties. Among the main observed phases are Fe-rich rod-like crystals, Nd-rich dendritic crystals and a ''like-amorphous'' matrix. The hard magnetic properties of these materials can be associated with this matrix. In these cooling regimes, the coercive field increases as the cooling rate of the amorphous matrix increases. Hysteresis loops showed a high degree of coupling between phases with different magnetic order. Both the coercive field and the magnetization showed a significant variation along the rod axis; a maximum appeared as a function of the axis length. In order to gather more information about the coupling between the observed phases, {delta}M (or Henkel) plots were obtained, showing an exchange character for interactions (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. OM85. Basic Properties of Optical Materials Summaries of Papers.

    Science.gov (United States)

    1985-05-01

    Optical Properties of Solids (Academic, New York, 1972) Ch.3. 7. D.B. Tanner, A.J...12, (1973). 6. T. Fleisch and R. Abermann, Thin Solid FilffF-42, 255-263 (1977). 7. F. Wooten, Optical Properties of Solids (Academic Press, New York...resolve cp structure. Such mea- surements are still lacking for many common semiconducting materials. REFERENCES 1. D.E. Aspnes, in Optical Properties of Solids :

  12. Surface and Bulk Electronic Structure and Chemisorption Properties of Titanium and Vanadium Oxides

    Science.gov (United States)

    Smith, Kevin Eugene

    The unusual electronic properties of Ti _2O_3 and V _2O_3, in particular the metal-insulator transitions which they undergo, have produced widespread interest in the physics of these materials, while the use of titanium and vanadium oxides as catalysts and catalyst supports makes a detailed understanding of their surface properties of great importance. The electronic structure and gas adsorption properties of single crystal titanium and vanadium oxides have been studied here using ultraviolet and x-ray photoemission spectroscopy, synchrotron radiation, Auger electron spectroscopy and low energy electron diffraction. Spatially anisotropic resonant photoemission from 3d states in Ti_2O_3 and V_2O_3 was observed and shown to originate from localised molecular orbitals. This contrasts with an energy analysis of the photoemission data which revealed dispersing, delocalised d-bands in both oxides. A large resonance was observed in the O 2p emission at the cation 3p to 3d absorption edge in Ti_2O _3 which is inconsistent with hybridisation, indicating the possible existence of inter-atomic resonances. The first detailed photoemission observation of metal-insulator transitions in Cr-doped V_2O _3 is reported; large changes in the density of states at the Fermi level are seen at these transitions. The surface electronic structure of single crystal TiO_2, Ti_2O _3 and V_2O _3 was found to be indistinguishable from that of the bulk. The interaction of SO_2 with these oxides was extensively studied since sulfur is a notorious catalyst poison. SO_2 reacts vigorously with the titanium oxides, dissociating in the presence of Ti^{3+} cations to form TiO_2 and TiS _2; in their absence no reaction occurs. Surprisingly, SO_2 reacts very weakly with V _2O_3, adsorbing in both dissociated and molecular form. Additionally, only a weak reaction of H_2S and TiO _2 was found. The electronic structure of these oxides is shown to be extremely complex, displaying both localised and

  13. Electronic and optical properties of Praseodymium trifluoride

    Energy Technology Data Exchange (ETDEWEB)

    Saini, Sapan Mohan, E-mail: smsaini.phy@nitrr.ac.in [Department of Physics, National Institute of Technology, Raipur-492010, (CG) (India)

    2014-10-24

    We report the role of f- states on electronic and optical properties of Praseodymium trifluoride (PrF{sub 3}) compound. Full potential linearized augmented plane wave (FPLAPW) method with the inclusion of spin orbit coupling has been used. We employed the local spin density approximation (LSDA) and Coulomb-corrected local spin density approximation (LSDA+U). LSDA+U is known for treating the highly correlated 4f electrons properly. Our theoretical investigation shows that LSDA+U approximation reproduce the correct insulating ground state of PrF{sub 3}. On the other hand there is no significant difference of reflectivity calculated by LSDA and LSDA+U. We find that the reflectivity for PrF{sub 3} compound stays low till around 7 eV which is consistent with their large energy gaps. Our calculated reflectivity compares well with the experimental data. The results are analyzed in the light of transitions involved.

  14. Optical properties of thin polymer films

    Science.gov (United States)

    Kasarova, Stefka N.; Sultanova, Nina G.; Petrova, Tzveta; Dragostinova, Violeta; Nikolov, Ivan

    2009-10-01

    In this report three types of optical polymer thin films deposited on glass substrates are investigated. Transmission spectra of the polymer samples are obtained in the range from 400 nm to 1500 nm. A laser microrefractometer has been used to measure the refractive indices of the examined materials at 406, 656, 910 and 1320 nm. Dispersion properties of the polymer films are analyzed on the base of the Cauchy-Schott's and Sellmeier`s approximations. Dispersion coefficients are calculated and dispersion charts in the visible and near infrared spectral regions are presented and compared. Abbe numbers of mean and partial dispersion of the polymer films are obtained. Calculation of refractive indices at many laser emission wavelengths in the considered spectral range is accomplished.

  15. Tellurium quantum dots: Preparation and optical properties

    Science.gov (United States)

    Lu, Chaoyu; Li, Xueming; Tang, Libin; Lai, Sin Ki; Rogée, Lukas; Teng, Kar Seng; Qian, Fuli; Zhou, Liangliang; Lau, Shu Ping

    2017-08-01

    Herein, we report an effective and simple method for producing Tellurium Quantum dots (TeQDs), zero-dimensional nanomaterials with great prospects for biomedical applications. Their preparation is based on the ultrasonic exfoliation of Te powder dispersed in 1-methyl-2-pyrrolidone. Sonication causes the van der Waals forces between the structural hexagons of Te to break so that the relatively coarse powder breaks down into nanoscale particles. The TeQDs have an average size of about 4 nm. UV-Vis absorption spectra of the TeQDs showed an absorption peak at 288 nm. Photoluminescence excitation (PLE) and photoluminescence (PL) are used to study the optical properties of TeQDs. Both the PLE and PL peaks revealed a linear relationship against the emission and excitation energies, respectively. TeQDs have important potential applications in biological imaging and catalysis as well as optoelectronics.

  16. Optical mapping of release properties in synapses

    Directory of Open Access Journals (Sweden)

    Pablo Ariel

    2010-08-01

    Full Text Available Synapses are important functional units that determine how information flows through the brain. Understanding their biophysical properties and the molecules that underpin them is an important goal of cellular neuroscience. Thus, it is of interest to develop protocols that allow easy measurement of synaptic parameters in model systems that permit molecular manipulations. Here, we used a sensitive and high-time resolution optical approach that allowed us to characterize two functional parameters critical to presynaptic efficacy: vesicle fusion probability (Pv and readily releasable pool size (RRP. We implemented two different approaches to determine the RRP size that were in broad agreement: depletion of the RRP by high frequency stimulation and saturation of the calcium sensor during single action potential stimuli. Our methods are based on reporters that provide a robust, quantitative, purely presynaptic readout and present a new avenue to study molecules that affect synaptic vesicle exocytosis.

  17. Optical properties of thin nanosilicon films

    Science.gov (United States)

    Buchenko, Viktor V.; Rodionova, Tatiana V.; Sutyagina, Anastasia S.; Goloborodko, Andrey A.; Multian, Volodymyr V.; Uklein, Andrii V.; Gayvoronsky, Volodymyr Ya.

    2016-12-01

    Present paper is devoted to the investigation of the nanosilicon films internal structure effect on optical properties. Atomic force microscopy results reveal that the films with different thickness have fundamentally different grain size distribution (samples with the film thickness less than 50 nm have single-mode grain size distribution, while samples with the film thickness more than 50 nm have multi-mode distribution of grain size). The correlation between grain size of nanosilicon films, photoluminescence and scattering indicatrix was shown. Well-isolated vibronic structures were observed on the ultraviolet-visible photoluminescence spectrum from nanosilicon films with the thickness more than 10 nm. The photoluminescence spectra in the red range correlate with the nanosilicon grain size distribution due to the effect of the quantum confinement. However, due to the complex shape of the grains mathematical modeling of photoluminescence spectrum is complicated. Both scattering indicatrix and photoluminescence reveal the multi-mode grain size distribution of the films with thickness more than 50 nm. The comparative analysis of theoretical results of optical radiation scattering by nanosilicon films with experimental ones is illustrated. Mathematical modeling of the scattering indicatrix shows the correlation of average grain size from scattering and photoluminescence data.

  18. Electro-Optical Sensor Fabricated Using a Bulk Cleavage Technique and Its Characteristics for Near-Field Intra-Body Communication

    Science.gov (United States)

    Furuya, Akinori; Sasaki, Ai-ichiro; Morimura, Hiroki; Aihara, Kimihisa; Shinagawa, Mitsuru

    2013-09-01

    This paper describes how to obtain a low cost electro-optical (EO) sensor module for the mass production of near-field intra-body communication devices. In this study, we used a bulk cleavage technique to fabricate EO modulators without the need for any optical polishing or washing processes, and clarified the feasibility of assembling optical components using only a passive alignment technique with a compact housing.

  19. Diameter grouping in bulk samples of single-walled carbon nanotubes from optical absorption spectroscopy

    NARCIS (Netherlands)

    Golden, M.S.; Fink, J.; Dunsch, L.; Bauer, H.-D.; Reibold, M.; Knupfer, M.; Friedlein, R.; Pichler, T.; Jost, O.

    1999-01-01

    The influence of the synthesis parameters on the mean characteristics of single-wall carbon nanotubes in soot produced by the laser vaporization of graphite has been analyzed using optical absorption spectroscopy. The abundance and mean diameter of the nanotubes were found to be most influenced by

  20. Crystal growth and optical properties of 4-aminobenzophenone (ABP)

    Science.gov (United States)

    Li, Zhengdong; Wu, Baichang; Su, Genbo; Huang, Gongfan

    1997-02-01

    Bulk crystals of 4-aminobenzophenone (ABP) were grown from organic solution. The crystal structure was determined by X-ray analysis. The refractive indices were determined by the method of prism minimum deviation. Some effective nonlinear-optical coefficients deff were measured. A blue second-harmonic emission with wavelengths of 433 and 460 nm were observed during laser diode pumping.

  1. Size-dependent optical properties of 9,10-bis(phenylethynyl)anthracene crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yagita, Yoshimi; Matsui, Kazunori, E-mail: matsui@kanto-gakuin.ac.jp

    2015-05-15

    The optical properties of 9,10-bis(phenylethynyl)anthracene (BPEA) were studied for various states: nanoparticles (~100 nm), microcrystals (~1 μm), bulk crystals (~1 mm), and vacuum-deposited film. The absorption spectra showed a red shift from ethanol solution to bulk crystals with an increase in crystal size. The vacuum-deposited film seemed to have mixed spectral characteristics of nanoparticles and bulk crystals. The fluorescence of BPEA showed two peaks for the various crystals. The fluorescence of the shorter wavelength peak was shifted toward the blue from 556 to 527 nm from the bulk to nanoparticles. On the other hand, the position of the longest wavelength peak changed little, staying around 596 nm. The relative intensity of the former and latter increased with a decrease in the crystal size. The time-resolved fluorescence spectra clearly confirmed the existence of two emissive sites in the bulk crystals. These sites are probably located at the peripheral and inner positions of the crystals. Change in the relative proportions of the two sites could be the main reason for the size-dependent fluorescence. - Highlights: ●The optical properties of 9,10-bis(phenylethynyl)anthracene crystals were studied. ●The absorption spectra showed a red-shift with an increase in crystal size. ●The fluorescence spectra showed size-dependent and size-independent peaks. ●A size-dependent peak with a shorter decay is attributed to the surface molecules. ●A size-independent peak with a longer decay is attributed to the bulk crystals.

  2. Prediction of nonlinear optical properties of organic materials. General theoretical considerations

    Science.gov (United States)

    Cardelino, B.; Moore, C.; Zutaut, S.

    1993-01-01

    The prediction of nonlinear optical properties of organic materials is geared to assist materials scientists in the selection of good candidate molecules. A brief summary of the quantum mechanical methods used for estimating hyperpolarizabilities will be presented. The advantages and limitations of each technique will be discussed. Particular attention will be given to the finite-field method for calculating first and second order hyperpolarizabilities, since this method is better suited for large molecules. Corrections for dynamic fields and bulk effects will be discussed in detail, focusing on solvent effects, conformational isomerization, core effects, dispersion, and hydrogen bonding. Several results will be compared with data obtained from third-harmonic-generation (THG) and dc-induced second harmonic generation (EFISH) measurements. These comparisons will demonstrate the qualitative ability of the method to predict the relative strengths of hyperpolarizabilities of a class of compounds. The future application of molecular mechanics, as well as other techniques, in the study of bulk properties and solid state defects will be addressed. The relationship between large values for nonlinear optical properties and large conjugation lengths is well known, and is particularly important for third-order processes. For this reason, the materials with the largest observed nonresonant third-order properties are conjugated polymers. An example of this type of polymer is polydiacetylene. One of the problems in dealing with polydiacetylene is that substituents which may enhance its nonlinear properties may ultimately prevent it from polymerizing. A model which attempts to predict the likelihood of solid-state polymerization is considered, along with the implications of the assumptions that are used. Calculations of the third-order optical properties and their relationship to first-order properties and energy gaps will be discussed. The relationship between monomeric and

  3. Optical and electrical properties of electrochemically deposited polyaniline/CeO2 hybrid nanocomposite film

    Institute of Scientific and Technical Information of China (English)

    Anees A. Ansari; M. A. M. Khan; M. Naziruddin Khan; Salman A. Alrokayan; M. Alhoshan; M. S. Alsalhi

    2011-01-01

    This paper reports the optical and electrical properties of electrochemically deposited polyaniline (PANI)/cerium oxide (CeO2) hybrid nano-composite film onto indium-fin-oxide (ITO) glass substrate. UV-visible spectroscopy and I-V characteristic were performed to study the optical and electrical parameters of the electrochemically deposited film. The film exhibited a strong absorption below 400 nm (3.10 eV) with a well defined absorbance peak at around 285 nm (4.35 eV). The estimated band gap of the CeO2 sample was 3.44 eV, higher than bulk CeO2 powder (Eg = 3.19 eV) due to the quantum confinement effect. Optical and electrochemical characteristics indicated that the electrical properties of PANI/CeO2 hybrid nanocomposite film are dominated by PANI doping.

  4. The study of thermal and optical properties of Sn added Pb-Se-Ge chalcogenide glass

    Science.gov (United States)

    Modgil, Vivek; Kumar, Prashant; Nidhi, A. V.; Rangra, V. S.

    2014-04-01

    Compositional dependence of thermal and optical properties of Pb9Se71Ge20-xSnx (x = 8, 9,10,11,12 at. %) glass have been studied. Glass transition and crystallization kinetic has been investigated by DSC technique under non-isothermal conditions and at different heating rates. Phase separation in the material has been observed and present phases have been detected by examining the XRD of annealed bulk samples. Material possesses good glass forming ability, glass stability and high value glass transition temperature. Various optical constants such as refractive index, extinction coefficient and optical band gap have been determined by analyzing optical transmittance data in the wavelength range of 200-2500 nm.

  5. Lensed fiber probes designed as an alternative to bulk probes in optical coherence tomography.

    Science.gov (United States)

    Ryu, Seon Young; Choi, Hae Young; Na, Jihoon; Choi, Woo June; Lee, Byeong Ha

    2008-04-01

    We demonstrate a compact all-fiber sampling probe for an optical coherence tomography (OCT) system. By forming a focusing lens directly on the tip of an optical fiber, a compact sampling probe could be implemented. To simultaneously achieve a sufficiently long working distance and a good lateral resolution, we employed a large-mode area photonic crystal fiber (PCF) and a coreless silica fiber (CSF) of the same diameters. A working distance of up to 1270 microm, a 3 dB distance range of 2210 microm, and a transverse resolution of 14.2 microm were achieved with the implemented PCF lensed fiber; these values are comparable to those obtainable with a conventional objective lens having an NA of 0.25 (10 x). The performance of the OCT system equipped with the proposed PCF lensed fiber is presented by showing the OCT images of a rat finger as a biological sample and a pearl as an in-depth sample.

  6. Ab initio prediction of the electronic and optical excitations in polythiophene: Isolated chains versus bulk polymer

    Science.gov (United States)

    van der Horst, J.-W.; Bobbert, P. A.; de Jong, P. H. L.; Michels, M. A. J.; Brocks, G.; Kelly, P. J.

    2000-06-01

    We calculate the electronic and optical excitations of polythiophene using the GW (G stands for one-electron Green function, W for the screened Coulomb interaction) approximation for the electronic self-energy, and include excitonic effects by solving the electron-hole Bethe-Salpeter equation. Two different situations are studied: excitations on isolated chains and excitations on chains in crystalline polythiophene. The dielectric tensor for the crystalline situation is obtained by modeling the polymer chains as polarizable line objects, with a long-wavelength polarizability tensor obtained from the ab initio polarizability function of the isolated chain. With this model dielectric tensor we construct a screened interaction for the crystalline case, including both intra- and interchain screening. In the crystalline situation both the quasiparticle band gap and the exciton binding energies are drastically reduced in comparison with the isolated chain. However, the optical gap is hardly affected. We expect this result to be relevant for conjugated polymers in general.

  7. Intrinsic carrier multiplication efficiency in bulk Si crystals evaluated by optical-pump/terahertz-probe spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yamashita, G.; Nagai, M., E-mail: mnagai@mp.es.osaka-u.ac.jp, E-mail: ashida@mp.es.osaka-u.ac.jp; Ashida, M., E-mail: mnagai@mp.es.osaka-u.ac.jp, E-mail: ashida@mp.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, Osaka 560-8531 (Japan); Matsubara, E. [Graduate School of Engineering Science, Osaka University, Osaka 560-8531 (Japan); Department of Physics, Osaka Dental University, Hirakata, Osaka 573-1121 (Japan); Kanemitsu, Y. [Institute for Chemical Research, Kyoto University, Kyoto 611-0011 (Japan)

    2014-12-08

    We estimated the carrier multiplication efficiency in the most common solar-cell material, Si, by using optical-pump/terahertz-probe spectroscopy. Through close analysis of time-resolved data, we extracted the exact number of photoexcited carriers from the sheet carrier density 10 ps after photoexcitation, excluding the influences of spatial diffusion and surface recombination in the time domain. For incident photon energies greater than 4.0 eV, we observed enhanced internal quantum efficiency due to carrier multiplication. The evaluated value of internal quantum efficiency agrees well with the results of photocurrent measurements. This optical method allows us to estimate the carrier multiplication and surface recombination of carriers quantitatively, which are crucial for the design of the solar cells.

  8. Size-resolved and bulk activation properties of aerosols in the North China Plain

    Directory of Open Access Journals (Sweden)

    Z. Z. Deng

    2011-04-01

    Full Text Available Size-resolved and bulk activation properties of aerosols were measured at a regional/suburban site in the North China Plain (NCP, which is occasionally heavily polluted by anthropogenic aerosol particles and gases. A Cloud Condensation Nuclei (CCN closure study is conducted with bulk CCN number concentration (NCCN and calculated CCN number concentration based on the aerosol number size distribution and size-resolved activation properties.

    The observed CCN number concentration (NCCN-obs are higher than those observed in other locations than China, with average NCCN-obs of roughly 2000, 3000, 6000, 10 000 and 13 000 cm−3 at supersaturations of 0.056, 0.083, 0.17, 0.35 and 0.70%, respectively. An inferred critical dry diameter (Dm is calculated based on the NCCN-obs and aerosol number size distribution assuming homogeneous chemical composition. The inferred cut-off diameters are in the ranges of 190–280, 160–260, 95–180, 65–120 and 50–100 nm at supersaturations of 0.056, 0.083, 0.17, 0.35 and 0.7%, with their mean values 230.1, 198.4, 128.4, 86.4 and 69.2 nm, respectively.

    Size-resolved activation measurements show that most of the 300 nm particles are activated at the investigated supersaturations, while almost no particles of 30 nm are activated even at the highest supersaturation of 0.72%. The activation ratio increases with increasing supersaturation and particle size. The slopes of the activation curves for ambient aerosols are not as steep as those observed in calibrations with ammonium sulfate suggesting that the observed aerosols is an external mixture of more hygroscopic and hydrophobic particles.

    The calculated CCN number concentrations (NCCN-calc based on the size-resolved activation ratio and aerosol number size distribution correlate well with the NCCN-obs, and

  9. Estimation of the Crustal Bulk Properties Beneath Mainland Portugal from P-Wave Teleseismic Receiver Functions

    Science.gov (United States)

    Dündar, Süleyman; Dias, Nuno A.; Silveira, Graça; Kind, Rainer; Vinnik, Lev; Matias, Luís; Bianchi, Marcelo

    2016-06-01

    In this work, we present results from teleseismic P-wave receiver functions (PRFs) obtained in Portugal, Western Iberia. A dense seismic station deployment conducted between 2010 and 2012, in the scope of the WILAS project and covering the entire country, allowed the most spatially extensive probing on the bulk crustal seismic properties of Portugal up to date. The application of the H- κ stacking algorithm to the PRFs enabled us to estimate the crustal thickness ( H) and the average crustal ratio of the P- and S-waves velocities V p/ V s ( κ) for the region. Observations of Moho conversions indicate that this interface is relatively smooth with the crustal thickness ranging between 24 and 34 km, with an average of 30 km. The highest V p/ V s values are found on the Mesozoic-Cenozoic crust beneath the western and southern coastal domain of Portugal, whereas the lowest values correspond to Palaeozoic crust underlying the remaining part of the subject area. An average V p/ V s is found to be 1.72, ranging 1.63-1.86 across the study area, indicating a predominantly felsic composition. Overall, we systematically observe a decrease of V p/ V s with increasing crustal thickness. Taken as a whole, our results indicate a clear distinction between the geological zones of the Variscan Iberian Massif in Portugal, the overall shape of the anomalies conditioned by the shape of the Ibero-Armorican Arc, and associated Late Paleozoic suture zones, and the Meso-Cenozoic basin associated with Atlantic rifting stages. Thickened crust (30-34 km) across the studied region may be inherited from continental collision during the Paleozoic Variscan orogeny. An anomalous crustal thinning to around 28 km is observed beneath the central part of the Central Iberian Zone and the eastern part of South Portuguese Zone.

  10. Effect of Initial Bulk Material Composition on Thermoelectric Properties of Bi2Te3 Thin Films

    Science.gov (United States)

    Budnik, A. V.; Rogacheva, E. I.; Pinegin, V. I.; Sipatov, A. Yu.; Fedorov, A. G.

    2013-07-01

    V2VI3 compounds and solid solutions based on them are known to be the best low-temperature thermoelectric (TE) materials. The predicted possibility of enhancement of the TE figure of merit in two-dimensional (2D) structures has stimulated studies of the properties of these materials in the thin-film state. The goal of the present work is to study the dependences of the Seebeck coefficient S, electrical conductivity σ, Hall coefficient R H, charge carrier mobility μ H, and TE power factor P = S 2 σ of Bi2Te3 thin films on the composition of the initial bulk material used for preparing them. Thin films with thickness d = 200 nm to 250 nm were grown by thermal evaporation in vacuum of stoichiometric Bi2Te3 crystals (60.0 at.% Te) and of crystals with 62.8 at.% Te onto glass substrates at temperatures T S of 320 K to 500 K. It was established that the conductivity type of the initial material is reproduced in films fairly well. For both materials, an increase in T S leads to an increase in the thin-film structural perfection, better correspondence between the film composition and that of the initial material, and increase in S, R H, μ H, σ, and P. The room-temperature maximum values of P for the films grown from crystals with 60.0 at.% and 62.8 at.% Te are P = 7.5 × 10-4 W/K2 m and 35 × 10-4 W/K2 m, respectively. Thus, by using Bi2Te3 crystals with different stoichiometry as initial materials, one can control the conductivity type and TE parameters of the films, applying a simple and low-cost method of thermal evaporation from a single source.

  11. Properties of grain boundaries in bulk, melt processed Y-Ba-Cu-O fabricated using bridge-shaped seeds

    Science.gov (United States)

    Shi, Y.-H.; Durrell, J. H.; Dennis, A. R.; Babu, N. Hari; Mancini, C. E.; Cardwell, D. A.

    2012-04-01

    Single grain RE-Ba-Cu-O ((RE)BCO, where RE is a rare earth element or yttrium) bulk superconducting materials have significant potential for a variety of engineering applications due to their ability to trap high magnetic fields. However, it is well known that the presence of grain boundaries coupled with a high angle of misorientation (typically 5°) significantly reduces the critical current density, Jc, in all forms of high temperature superconducting materials. It is of considerable fundamental and technological interest, therefore, to investigate the grain boundary properties of bulk, film and tape (RE)BCO. We report a successful multi-seeding technique for the fabrication of fully aligned, artificial (0° misalignment) grain boundaries within large grain YBCO bulk superconductors using bridge-shaped seeds. The microstructure and critical current densities of the grain boundaries produced by this technique have been studied in detail.

  12. Optical Properties of Nanoscale Bismuth Selenide and Its Heterocrystals

    Science.gov (United States)

    Vargas, Anthony

    Over the past 12 years since the groundbreaking work on graphene, the field of 2D layered materials has grown by leaps and bounds as more materials are theoretically predicted and experimentically verified. These materials and their unique electronic, optical, and mechanical properties have inspired the scientific community to explore and investigate novel, fundamental physical phenomena as well create and refine technological devices which leverage the host of unique benefits which these materials possess. In the past few years, this burgeoning field has heavily moved towards combining layers of various materials into novel heterostructures. These heterostructures are an exciting area of research because of the plethora of exciting possibilities and results which arise due to the large number of heterostructure combinations and configurations. Particularly, the research into the optical properties of these layered materials and their heterostructures under confinement provides another exciting avenue for developing optoelectric devices. In this dissertation, I present work on the synthesis of Bi2Se 3 nanostructures via chemical vapor deposition (CVD) and the study of the optical properties of these nanostructures and their heterostructures with MoS2. The bulk of the current published work on Bi2Se 3 has focused on the exotic topological properties of its surface states, both interesting fundamental physics purposes as well as for studying avenues for spintronics. In contrast, the work presented here focuses on studying the optical properties of Bi2Se3 nanostructures and how these properties evolve when subjected to confinement. Specifically, the absorbance of singlecrystal Bi2Se3 with sizes tailored down to a few nanometers in diameter and a few quintuple layers (QLs) in thickness. We find a dramatically large bandgap, Eg ≥ 2.5 eV, in the smallest particles which is much higher than that seen in 1QL measurements taken with ARPES. Additionally, utilizing

  13. Influence of optical interference and carrier lifetime on the short circuit current density of organic bulk heterojunction solar cells

    Institute of Scientific and Technical Information of China (English)

    You Hai-Long; Zhang Chun-Fu

    2009-01-01

    Based on simple analytical equations, short circuit current density (Jsc) of the organic bulk heterojunction solar cells has been calculated. It is found that the optical interference effect plays a very important role in the determination of JSC;and obvious oscillatory behaviour of Jsc was observed as a function of thickness. At the same time, the influence of JSC only increases the carrier lifetime on JSC also cannot be neglected. When the carrier lifetime is relatively short, at the initial stage and then decreases rapidly with the increase of active layer thickness. However, for a relatively long carrier lifetime, the exciton dissociation probability must be considered, and Jsc behaves wave-like with the increase of active layer thickness. The validity of this model is confirmed by the experimental results.

  14. Optical and mechanical studies on unidirectional grown tri-nitrophenol methyl p-hydroxybenzoate bulk single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Uthrakumar, R. [Department of Physics, Loyola College, Chennai 600 034 (India); Vesta, C. [Department of Physics, SDNB Vaishnav College, Chennai 600 044 (India); Robert, R. [Department of Physics, Government Arts College (Men), Krishnagiri 635 001 (India); Mangalam, G. [Department of Physics, MGR University, Chennai 600 095 (India); Jerome Das, S., E-mail: jerome@loyolacollege.ed [Department of Physics, Loyola College, Chennai 600 034 (India)

    2010-10-15

    The bulk single crystal of tri-nitrophenol methyl p-hydroxybenzoate (TNMPHB) of length 90 mm and diameter 12 mm was obtained by employing unidirectional growth technique. Single crystal X-ray diffraction studies and powder XRD analysis have been carried out to confirm the identity of the crystal. The optical band gap of the grown crystal was calculated to be 4.91 eV from UV transmission spectrum. The mechanical strength of the grown crystal has been studied using Vicker's microhardness tester. Low dielectric loss shows that the grown crystal contains lesser defects authenticating the suitability of the crystal towards device applications. The surface morphology studies have been carried out on the grown crystal.

  15. The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.B. [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Uwani, Y., E-mail: gen422310@s.okayama-u.ac.jp [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Joo, J.H.; Kawamoto, R. [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Jo, Y.S. [Center for Applied Superconductivity Technology, Korea Electrotechnology Research Institute, Seongju-dong, Changwon 641-120 (Korea, Republic of)

    2011-11-15

    The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

  16. Effect of silver addition on the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductors

    CERN Document Server

    Nariki, S; Matsui, M; Murakami, M

    2002-01-01

    The effect of Ag addition on the microstructure and the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductor has been investigated. The single grain Gd-Ba-Cu-O bulk superconductors 32 mm in diameter were fabricated with 0-30 mass%Ag/sub 2/O additions by the melt growth method under controlled oxygen partial pressure of 1.0%. From microscopic observations, it was found that the macro- cracks in the a-b plane decreased with Ag addition. The three-point bending test showed that the average strength of Ag-free bulk was 69 MPa at room temperature, while the strength was dramatically improved to 110-115 MPa with 10-30 mass%Ag/sub 2/O additions. The trapped magnetic field of Ag-free bulk sample was 1.3 T at 77 K. The trapped field of bulk Gd-Ba-Cu-O samples with 10-20 mass%Ag/sub 2/O exhibited high values of 1.8-2.0 T at 77 K. However, the trapped field of the sample with 30 mass%Ag/sub 2/O addition was lowered to 1.1 T with decreasing the critical current density. The trapped field of Ag- adde...

  17. Structural and Optical Properties and Emerging Applications of Metal Nanomaterials

    Institute of Scientific and Technical Information of China (English)

    Tammy Y.Olson; Jin Z.Zhang

    2008-01-01

    Nanomaterials possess intriguing optical properties that depend sensitively on size, shape, and material content of the structures. Controlling such structural characteristics of the nanostructures allows the tailoring of their physical and chemical properties, e.9. optical, electronic, and catalytic, to achieve what is desired for specific applications of interest. This review will cover the development of various shapes for silver and gold nanomaterials with emphasis on their relation to optical properties. Examples of various modern synthetic methods and characterization techniques are highlighted. The influence of the metal nanomaterial's shape and optical absorption on surface enhanced Raman scattering (SERS) and a final note on new emerging applications of metal nanostructures are also discussed.

  18. Influence of bulk fibre properties of PAN-based carbon felts on their performance in vanadium redox flow batteries

    Science.gov (United States)

    Schweiss, Rüdiger

    2015-03-01

    Polyacrylonitrile (PAN)-based carbon felts with different fibre properties were studied in terms of their suitability as porous flow-through electrode materials in all vanadium redox flow batteries. The crystallinity and their bulk hetero element content (in particular nitrogen) of the carbon fibres was shown to produce a significant effect on the electrocatalytical properties of the electrodes towards vanadium species. Similar effects were seen on the capacity losses associated with concomitant hydrogen evolution. Adjustments of fibre properties offer the potential of manufacturing improved electrode materials, potentially without additional steps such as surface activation or decoration with catalytically active species.

  19. Optical properties and photoluminescence of tetrahexyl-sexithiophene allotropes

    NARCIS (Netherlands)

    Botta, C; Destri, S; Porzio, W; Bongiovanni, G; Loi, MA; Mura, A; Tubino, R

    2001-01-01

    The optical absorption, Raman scattering and photoluminescence of two phases of tetrahexyl-sexithiophene (4HT6) display properties coherently related to the different molecular conformations imposed by the chain packing. We analyse the temperature dependence of the optical properties of a sample in

  20. Optical properties and photoluminescence of tetrahexyl-sexithiophene allotropes

    NARCIS (Netherlands)

    Botta, C; Destri, S; Porzio, W; Bongiovanni, G; Loi, MA; Mura, A; Tubino, R

    2001-01-01

    The optical absorption, Raman scattering and photoluminescence of two phases of tetrahexyl-sexithiophene (4HT6) display properties coherently related to the different molecular conformations imposed by the chain packing. We analyse the temperature dependence of the optical properties of a sample in

  1. A Technique to Measure Focal Length of a Lens with no Bulk Motion using Tunable Optics and Optical MEMS Technology

    CERN Document Server

    Reza, Syed Azer

    2016-01-01

    This paper presents a motion-free technique for characterizing the focal length of any spherical convex or concave lens. The measurement system uses a Gaussian Beam from a Laser Source (LS), an Electronically Controlled Variable Focus Lens (ECVFL), a Digital Micromirror Device (DMD) and a Photo-Detector (PD). As the proposed method does not involve any motion-stages or other moving components, the focal length is measured without requiring any mechanical motion of bulk components. The method requires measuring the spot size of the Gaussian Beam at the DMD plane for various settings of the ECVFL focal length. These beam spot size measurements, are used to estimate the focal length of a lens sample by employing standard polynomial-fitting techniques. Due to the inherent motion-free nature of the proposed setup, the measurements are fast, repeatable, reliable and ideal for use in industrial lens production, manufacturing of imaging systems and sensitive laboratory experiments. Using a DMD and an ECVFL also allow...

  2. Effect of catalyst concentration on size, morphology and optical properties of silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Arora, Ekta; Ritu,; Kumar, Sacheen, E-mail: sacheen3@gmail.com [Department of Electronics science, Kurukshetra University, Kurukshetra, Haryana, India-136119 (India); Kumar, Dinesh

    2016-05-06

    Today, nanomaterials play a key role in various fields such as electronics, aerospace, pharmaceuticals and biomedical because of their unique physical, chemical and biological properties which are different from bulk materials. Nano sized silica particles have gained the prominent position in scientific research and have wide applications. The sol-gel method is the best method to synthesize silica nanoparticles because of its potential to produce monodispersed with narrow size distribution at mild conditions. The silica nanoparticles were obtained by hydrolysis of tetraethyl orthosilicate (TEOS) in ethanol act as solvent. The synthesized nanoparticles were characterized by Field Emission Scanning electron Microscope (FE-SEM), UV Spectrometer. The smallest size of silica particles is around 150nm examined by using FE-SEM. The optical properties and band structure was analyzed using UV-visible spectroscopy which is found to be increase by reducing the size of particles. Concentration effect of catalyst on the size, morphology and optical properties were analyzed.

  3. Effect of catalyst concentration on size, morphology and optical properties of silica nanoparticles

    Science.gov (United States)

    Arora, Ekta; Ritu, Kumar, Sacheen; Kumar, Dinesh

    2016-05-01

    Today, nanomaterials play a key role in various fields such as electronics, aerospace, pharmaceuticals and biomedical because of their unique physical, chemical and biological properties which are different from bulk materials. Nano sized silica particles have gained the prominent position in scientific research and have wide applications. The sol-gel method is the best method to synthesize silica nanoparticles because of its potential to produce monodispersed with narrow size distribution at mild conditions. The silica nanoparticles were obtained by hydrolysis of tetraethyl orthosilicate (TEOS) in ethanol act as solvent. The synthesized nanoparticles were characterized by Field Emission Scanning electron Microscope (FE-SEM), UV Spectrometer. The smallest size of silica particles is around 150nm examined by using FE-SEM. The optical properties and band structure was analyzed using UV-visible spectroscopy which is found to be increase by reducing the size of particles. Concentration effect of catalyst on the size, morphology and optical properties were analyzed.

  4. Assessing Uncertainties in Satellite Ocean Color Bio-Optical Properties

    Science.gov (United States)

    2012-10-01

    Uncertainties in retrievals of bio -optical properties from satellite ocean color imagery are related to a variety of factors, including errors...associated with sensor calibration and degradation, atmospheric correction, and the bio -optical inversion algorithms. Here we examine the impact of...water-leaving radiances (nLw) and downstream bio -optical properties, such as the absorption and backscattering coefficients and chlorophyll. We use a

  5. The effect of high energy concentration source irradiation on structure and properties of Fe-based bulk metallic glass

    Science.gov (United States)

    Pilarczyk, Wirginia

    2016-06-01

    Metallic glasses exhibit metastable structure and maintain this relatively stable amorphous state within certain temperature range. High intensity laser beam was used for the surface irradiation of Fe-Co-B-Si-Nb bulk metallic glasses. The variable parameter was laser beam pulse energy. For the analysis of structure and properties of bulk metallic glasses and their surface after laser remelting the X-ray analysis, microscopic observation and test of mechanical properties were carried out. Examination of the nanostructure of amorphous materials obtained by high pressure copper mold casting method and the irradiated with the use of TITAN 80-300 HRTEM was carried out. Nanohardness and reduced Young's modulus of particular amorphous and amorphous-crystalline material zone of the laser beam were examined with the use of Hysitron TI950 Triboindenter nanoindenter and with the use of Berkovich's indenter. The XRD and microscopic analysis showed that the test material is amorphous in its structure before irradiation. Microstructure observation with electron transmission microscopy gave information about alloy crystallization in the irradiated process. Identification of given crystal phases allows to determine the kind of crystal phases created in the first place and also further changes of phase composition of alloy. The main value of the nanohardness of the surface prepared by laser beam has the order of magnitude similar to bulk metallic glasses formed by casting process irrespective of the laser beam energy used. Research results analysis showed that the area between parent material and fusion zone is characterized by extraordinarily interesting structure which is and will be the subject of further analysis in the scope of bulk metallic glasses amorphous structure and high energy concentration source. The main goal of this work is the results' presentation of structure and chosen properties of the selected bulk metallic glasses after casting process and after irradiation

  6. A comparison study on the electronic structures, lattice dynamics and thermoelectric properties of bulk silicon and silicon nanotubes

    Science.gov (United States)

    Lu, Peng-Xian; Qu, Ling-Bo; Cheng, Qiao-Huan

    2013-11-01

    In order to investigate the mechanism of the electron and phonon transport in a silicon nanotube (SiNT), the electronic structures, the lattice dynamics, and the thermoelectric properties of bulk silicon (bulk Si) and a SiNT have been calculated in this work using density functional theory and Boltzmann transport theory. Our results suggest that the thermal conductivity of a SiNT is reduced by a factor of 1, while its electrical conductivity is improved significantly, although the Seebeck coefficient is increased slightly as compared to those of the bulk Si. As a consequence, the figure of merit (ZT) of a SiNT at 1200 K is enhanced by 12 times from 0.08 for bulk Si to 1.10. The large enhancement in electrical conductivity originates from the largely increased density of states at the Fermi energy level and the obviously narrowed band gap. The significant reduction in thermal conductivity is ascribed to the remarkably suppressed phonon thermal conductivity caused by a weakened covalent bonding, a decreased phonon density of states, a reduced phonon vibration frequency, as well as a shortened mean free path of phonons. The other factors influencing the thermoelectric properties have also been studied from the perspective of electronic structures and lattice dynamics.

  7. Recombination dynamics of optically excited charge carriers in bulk MoS2

    Science.gov (United States)

    Völzer, Tim; Lütgens, Matthias; Fennel, Franziska; Lochbrunner, Stefan

    2017-10-01

    Transition metal dichalcogenides (TMDCs), such as MoS2, are promising candidates for optoelectronic or catalytic applications. On that account, a detailed characterization of the electronic dynamics in these materials is of pivotal importance. Here, we investigate the temporal evolution of an excited carrier population by all-optical pump-probe spectroscopy. On the sub-picosecond time scale we observe thermal relaxation of the excited carriers by electron–phonon coupling. The dynamics on the nanosecond time scale can be understood in terms of defect-assisted Auger recombination over a broad carrier density regime spanning more than one order of magnitude. Hence, our results emphasize the importance of defect states for electronic processes in TMDCs at room temperature.

  8. OPTICAL PROPERTIES OF CARBAMIDE AQUEOUS SOLUTIONS

    Directory of Open Access Journals (Sweden)

    E. V. Avramenko

    2016-03-01

    Full Text Available Subject of Research. The paper presents the results of measurements of refractometric properties (refractive index n, its temperature factor dn/dt and the ultraviolet spectral absorption in carbonic acid diamide aqueous solutions (carbamide depending on solid residue mass fraction md = 0-50 % and on temperaturet = 10-70 °C.Method of Research. Laboratory methods ofliquid-phase medium refractometry and ultraviolet spectrophotometry were applied for the research. We carried out computational modeling of electronic states spectrum for the carbonic acid diamide molecule and theoretical calculation of the fundamental electronic absorption of the molecule in the ultraviolet wavelenght region.Main Results. We have established that the solution concentration md has a nonlinear character and may be represented by the quadratic polynomial with the error Δn= ± 0,0005. We have shown the refractive indexdependence on temperature n(t changes in linear fashion att = 10-70 °C.At that, the inclination of lines n(t increases at the increase of md; so, the temperature factor dn/dt may be approximated by the quadratic polynomial. Transmission spectra of solutions in the spectral region λ= 225-760 nm have no special features except for the sharp edge in the short-wavelength region; the fundamental electronic absorptionis responsible for it. We have established that dispersion dependences of the refraction index n(λ;md in aqueous solutions of carbamide at λ= 360-760 nm and at md = 0-50 % may be calculated with the satisfactory error without additional adjustable parameters from the ultraviolet absorption data in terms of the one-dimentional oscillator Lorentz model.PracticalRelevance. Representedmeasurements of carbonic acid diamide aqueous solutions optical properties may be applied for the adjustment and calibration of commercial refractometers at processing lines of the AdBlue reagent manufacture for the selective catalytic reduction (SCR of motor transport

  9. Physical characteristics and optical properties of PbS nanoclusters: DFT simulation and experimental study

    Science.gov (United States)

    Dong, Yanhua; Wen, Jianxiang; Sun, Xiaolan; Shang, Yana; Wang, Tingyun

    2015-08-01

    The physical characteristics and optical properties of PbS nanoclusters are investigated by using density functional theory (DFT) of first-principles. Microstructure models of (PbS)n (n=1-9) nanoclusters and bulk materials are built on Materials Studio platform, and its energy band structures, highest occupied molecular orbital-lowest unoccupied molecular orbital gap (HOMO-LUMO gap), density of state (DOS), and optical properties are calculated, respectively. Compared to PbS bulk materials, PbS nanoclusters show a discrete energy gap as well as the DOS, because of the quantum confinement effect. It is interesting that the HOMO-LUMO gap of (PbS)n (n=1-9) shows oscillates with the increasing of the n number. However, when its size is large enough, the HOMO-LUMO gap is gradually decrease with the increasing of size (>27 atoms). And, the HOMO-LUMO gap of PbS nanoclusters of different sizes is range from 2.575 to 0.58 eV, which covers the low loss communication band of optical communication. In addition, PbS nanomaterials (NMs) with small size are synthesized by using oleylamine as ligands. Sizes of PbS NMs can be accurately controlled through control of the reaction time as well as the growth temperature. The photoluminescence (PL) spectra show strong size dependence, which is large red shift with increasing size of the NMs. This trend is basically in agreement with the theoretical calculation above. Moreover, transmission electron microscopy (TEM) further reveals the morphology of PbS NMs. PbS NMs can be used in optical fiber amplifiers and fiber lasers because of its unique optical properties in optical communication bands.

  10. Computational Study of Linear and Nonlinear Optical Properties of Single Molecules and Clusters of Organic Electro-Optic Chromophores

    Science.gov (United States)

    Garrett, Kerry

    Organic electro-optic (OEO) materials integrated into silicon-organic hybrid (SOH) devices afford significant improvements in size, weight, power, and bandwidth (SWAP) performance of integrated electronic/photonic systems critical for current and next generation telecommunication, computer, sensor, transportation, and defense technologies. Improvement in molecular first hyperpolarizability, and in turn electro-optic activity, is crucial to further improvement in the performance of SOH devices. The timely preparation of new chromophores with improved molecular first hyperpolarizability requires theoretical guidance; however, common density functional theory (DFT) methods often perform poorly for optical properties in systems with substantial intramolecular charge transfer character. The first part of this dissertation describes the careful evaluation of popular long-range correction (LC) and range-separated hybrid (RSH) density functional theory (DFT) for definition of structure/function relationships crucial for the optimization of molecular first hyperpolarizability, beta. In particular, a benchmark set of well-characterized OEO chromophores is used to compare calculated results with the corresponding experimentally measured linear and nonlinear optical properties; respectively, the wavelength of the peak one-photon absorption energy, lambdamax, and beta. A goal of this work is to systematically determine the amount of exact exchange in LC/RSH-DFT methods required for accurately computing these properties for a variety OEO chromophores. High-level electron correlation (post-Hartree-Fock) methods are also investigated and compared with DFT. Included are results for the computation of beta using second-order Moller-Plesset perturbation theory (MP2) and the double-hybrid method, B2PLYP. The second part of this work transitions from single-molecule studies to computing bulk electronic and nonlinear optical properties of molecular crystals and isotropic ensembles of a

  11. Optical and Electrical Characterization of Bulk Grown Indium-Gallium-Arsenide Alloys

    Science.gov (United States)

    2010-03-01

    using the liquid encapsulated Czochralski (LEC) method but suffered from a large number of 13 misfits and some cracks [3]. In 1995, Suzuki et al...properties of samples grown through the vertical Bridgman (or multi-component zone melting growth) method have been investigated through...applications. 2 The InxGa1-xAs samples analyzed here were grown using the vertical Bridgman or multi-component zone melting growth method (MCZM) by

  12. Comparison of near surface and column-integrated atmospheric aerosol optical properties

    Science.gov (United States)

    Aryal, Rudra Prasad

    Optical and chemical properties of size-resolved aerosols in near-surface air at Tudor Hill, Bermuda were measured between July 2006 and June 2009. Vertical distributions of aerosol backscattering and column-averaged aerosol optical properties were characterized with a Micro-pulse lidar (MPL) and a CIMEL automated sun-sky radiometer. The chemical species in size-segregated aerosols in marine air were compared with the surface level aerosol optical properties. The aerosol concentration, along with chemical components, was compared with the surface level wind speed and showed a significant correlation with the sea salt components. The non-sea salt components such as non-sea salt sulfate and ammonium did not show a correlation with the surface level wind speed. A comparison between scattering data at surface level with the extinction coefficient at the lowest altitude bin (75m) from the lidar inversion shows a consistent correlation but is quantitatively different. This quantitative discrepancy was explained based on the hygroscopic growth due to differences in relative humidity in measurement conditions. Aerosol optical properties measured near the surface were often significantly correlated with those averaged over the column. These include scattering by near-surface bulk aerosol at 530 nm versus column aerosol optical depth (AOD), near-surface sub-microm scattering fraction versus column averaged sub-microm scattering fraction, and the average angstrom exponent over column and lidar ratio derived using column integrated size distribution and complex refractive index. We also found that the single scattering albedo (ω o) measured at the surface by combining daily averages of the aerosol absorption and aerosol light scattering were in the same range as the instantaneous ω o retrieved for the column. The relative contribution of submicron aerosol light scattering to total aerosol light scattering is slightly higher in the column relative to the surface. Surface

  13. Thermo-optical properties of optically stimulated luminescence in feldspars

    DEFF Research Database (Denmark)

    Poolton, N.R.J.; Bøtter-Jensen, L.; Johnsen, O.

    1995-01-01

    Optically stimulated luminescence processes in feldspars are subject to competing thermal enhancement and quenching processes: this article describes the thermal enhancement effects for orthoclase, albite and plagioclase feldspars. It is demonstrated that certain lattice vibrational modes can...

  14. Nonlinear optical properties of metal nanoparticle composites for optical applications

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Y. E-mail: takeda.yoshihiko@nims.go.jp; Kishimoto, N

    2003-05-01

    Optical absorption and nonlinear optical response were investigated for nanoparticle composites in amorphous SiO{sub 2} fabricated by negative Ta ion implantation at 60 keV. X-ray photoelectron spectroscopy was used to identify Ta and the oxide formation in the matrix. Optical absorption clearly indicated a surface plasmon peak at 2.2 eV and the peak resulted from formation of nanoparticles embedded in the matrix. The measured absorption was compared with calculated ones, evaluated by Maxwell-Garnett theory. Nonlinear absorption was measured with a pump-probe method using a femtosecond laser system. The pumping laser transiently bleached the surface plasmon band and lead to the nonlinearity. The transient response recovered in several picoseconds and behaved in terms of electron dynamics in metallic nanoparticles. The Ta nanoparticle composite is one of the promising candidates for nonlinear optical materials with good thermal stability.

  15. Optical properties of mouse biotissues and their optical phantoms

    Science.gov (United States)

    Krainov, A. D.; Mokeeva, A. M.; Sergeeva, E. A.; Agrba, P. D.; Kirillin, M. Yu.

    2013-08-01

    Based on spectrophotometric measurements in the range of 700-1100 nm performed with the use of an integrating sphere, we have obtained absorption and scattering spectra of internal organs of mouse, as well as of aqueous solutions of India ink and Lipofundin, which are basic model media for creating optical phantoms of biological tissues. To retrieve the spectra of optical characteristics, we have used original formulas that relate the parameters of the medium with measured spectrophotometric characteristics and that are constructed based on classical analytical models of propagation of light in turbid media. As a result of comparison of spectra of biotissues and model media, we have developed a mixture of Lipofundin and India ink serving as mouse optical phantoms for problems of optical medical diagnostics.

  16. Optical properties of marine waters and the development of bio-optical algorithms

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, E.

    This paper presents the primary optical variables used in the measurement of the optical properties of marine waters. How can in-situ measurements be used in the optical recognition of coastal and open ocean waters. We then look at bio...

  17. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata, E-mail: tsom@iopb.res.in [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India)

    2015-08-07

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼10{sup 20 }cm{sup −3}). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  18. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    Science.gov (United States)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2015-08-01

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (˜1020 cm-3). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  19. Inferring inherent optical properties and water constituent profiles from apparent optical properties.

    Science.gov (United States)

    Fan, Yongzhen; Li, Wei; Calzado, Violeta Sanjuan; Trees, Charles; Stamnes, Snorre; Fournier, Georges; McKee, David; Stamnes, Knut

    2015-07-27

    The BP09 experiment conducted by the Centre for Maritime Research and Experimentation in the Ligurian Sea in March 2009 provided paired vertical profiles of nadir-viewing radiances L(u)(z) and downward irradiances E(d)(z) and inherent optical properties (IOPs, absorption, scattering and backscattering coefficients). An inversion algorithm was implemented to retrieve IOPs from apparent optical properties (AOPs, radiance reflectance R(L), irradiance reflectance R(E) and diffuse attenuation coefficient K(d)) derived from the radiometric measurements. Then another inversion algorithm was developed to infer vertical profiles of water constituent concentrations, including chlorophyll-a concentration, non-algal particle concentration, and colored dissolved organic matter from the retrieved IOPs based on a bio-optical model. The algorithm was tested on a synthetic dataset and found to give reliable results with an accuracy better than 1%. When the algorithm was applied to the BP09 dataset it was found that good retrievals of IOPs could be obtained for sufficiently deep waters, i.e. for L(u)(z) and E(d)(z) measurements conducted to depths of 50 m or more. This requirement needs to be satisfied in order to obtain a good estimation of the backscattering coefficient. For such radiometric measurements a correlation of 0.88, 0.96 and 0.93 was found between retrieved and measured absorption, scattering and backscattering coefficients, respectively. A comparison between water constituent values derived from the measured IOPs and in-situ measured values, yielded a correlation of 0.80, 0.78, and 0.73 for chlorophyll-a concentration, non-algal particle concentration, and absorption coefficient of colored dissolved organic matter at 443 nm, respectively. This comparison indicates that adjustments to the bio-optical model are needed in order to obtain a better match between inferred and measured water constituent values in the Ligurian Sea using the methodology developed in this paper.

  20. Optical and Transport Properties of Organic Molecules: Methods and Applications

    Science.gov (United States)

    Strubbe, David Alan

    Organic molecules are versatile and tunable building blocks for technology, in nanoscale and bulk devices. In this dissertation, I will consider some important applications for organic molecules involving optical and transport properties, and develop methods and software appropriate for theoretical calculations of these properties. Specifically, we will consider second-harmonic generation, a nonlinear optical process; photoisomerization, in which absorption of light leads to mechanical motion; charge transport in junctions formed of single molecules; and optical excitations in pentacene, an organic semiconductor with applications in photovoltaics, optoelectronics, and flexible electronics. In the Introduction (Chapter 1), I will give an overview of some phenomenology about organic molecules and these application areas, and discuss the basics of the theoretical methodology I will use: density-functional theory (DFT), time-dependent density-functional theory (TDDFT), and many-body perturbation theory based on the GW approximation. In the subsequent chapters, I will further discuss, develop, and apply this methodology. 2. I will give a pedagogical derivation of the methods for calculating response properties in TDDFT, with particular focus on the Sternheimer equation, as will be used in subsequent chapters. I will review the many different response properties that can be calculated (dynamic and static) and the appropriate perturbations used to calculate them. 3. Standard techniques for calculating response use either integer occupations (as appropriate for a system with an energy gap) or fractional occupations due to a smearing function, used to improve convergence for metallic systems. I will present a generalization which can be used to compute response for a system with arbitrary fractional occupations. 4. Chloroform (CHCl3) is a small molecule commonly used as a solvent in measurements of nonlinear optics. I computed its hyperpolarizability for second

  1. Structure and property evaluation of a vacuum plasma sprayed nanostructured tungsten-hafnium carbide bulk composite

    NARCIS (Netherlands)

    Rea, K. E.; Viswanathan, V.; Kruize, A.; De Hosson, J. Th. M.; O'Dell, S.; McKechnie, T.; Rajagopalan, S.; Vaidyanathan, R.; Seal, S.; O’Dell, S.

    2008-01-01

    Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured then no-mechanical components. Spray drying of powder feedstock appears to have a significant effect on

  2. Effect of preheating and light-curing unit on physicochemical properties of a bulk fill composite.

    Science.gov (United States)

    Theobaldo, Jéssica Dias; Aguiar, Flávio Henrique Baggio; Pini, Núbia Inocencya Pavesi; Lima, Débora Alves Nunes Leite; Liporoni, Priscila Christiane Suzy; Catelan, Anderson

    2017-01-01

    The aim of this study is to evaluate the effect of composite preheating and polymerization mode on degree of conversion (DC), microhardness (KHN), plasticization (P), and depth of polymerization (DP) of a bulk fill composite. Forty disc-shaped samples (n = 5) of a bulk fill composite were prepared (5 × 4 mm thick) and randomly divided into 4 groups according to light-curing unit (quartz-tungsten-halogen [QTH] or light-emitting diode [LED]) and preheating temperature (23 or 54 °C). A control group was prepared with a flowable composite at room temperature. DC was determined using a Fourier transform infrared spectrometer, KHN was measured with a Knoop indenter, P was evaluated by percentage reduction of hardness after 24 h of ethanol storage, and DP was obtained by bottom/top ratio. Data were statistically analyzed by analysis of variance and Tukey's test (α = 0.05). Regardless of light-curing, the highest preheating temperature increased DC compared to room temperature on bottom surface. LED showed a higher DC compared to QTH. Overall, DC was higher on top surface than bottom. KHN, P, and DP were not affected by curing mode and temperature, and flowable composite showed similar KHN, and lower DC and P, compared to bulk fill. Composite preheating increased the polymerization degree of 4-mm-increment bulk fill, but it led to a higher plasticization compared to the conventional flowable composite evaluated.

  3. The microstructure network and thermoelectric properties of bulk (Bi,Sb)2Te3

    DEFF Research Database (Denmark)

    Xie, Wenjie; Hitchcock, Dale A.; Kang, Hye J.

    2012-01-01

    We report small-angle neutron scattering studies on the microstructure network in bulk (Bi,Sb)(2)Te-3 synthesized by the melt-spinning (MS) and the spark-plasma-sintering (SPS) process. We find that rough interfaces of multiscale microstructures generated by the MS are responsible for the large...

  4. Modeling the spectral optical properties of ammonium sulfate and biomass burning aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Grant, K.E.; Chuang, C.C.; Grossman, A.S.; Penner, J.E. [Michigan Univ., Ann Arbor, MI (United States)

    1997-09-01

    The importance of including the global and regional radiative effects of aerosols in climate models has increasingly been realized. Accurate modeling of solar radiative forcing due to aerosols from anthropogenic sulfate and biomass burning emissions requires adequate spectral resolution and treatment of spatial and temporal variability. The variation of aerosol spectral optical properties with local relative humidity and dry aerosol composition must be considered. Because the cost of directly including Mie calculations within a climate model is prohibitive, parameterizations from offline calculations must be used. Starting from a log-normal size distribution of dry ammonium sulfate, we developed optical properties for tropospheric sulfate aerosol at 15 relative humidities up to 99 percent. The resulting aerosol size distributions were then used to calculate bulk optical properties at wavelengths between 0.175 {micro}m and 4 {micro}m. Finally, functional fits of optical properties were made for each of 12 wavelength bands as a function of relative humidity. Significant variations in optical properties occurred across the total solar spectrum. Relative increases in specific extinction and asymmetry factor with increasing relative humidity became larger at longer wavelengths. Significant variation in single-scattering albedo was found only in the longest near-IR band. This is also the band with the lowest albedo. A similar treatment was done for aerosols from biomass burning. In this case, size distributions were taken as having two carbonaceous size modes and a larger dust mode. The two carbonaceous modes were considered to be humidity dependent. Equilibrium size distributions and compositions were calculated for 15 relative humidities and five black carbon fractions. Mie calculations and Chandrasekhar averages of optical properties were done for each of the resulting 75 cases. Finally, fits were made for each of 12 spectral bands as functions of relative humidity

  5. SMEX02 Atmospheric Aerosol Optical Properties Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of observations of atmospheric parameters including spectral aerosol optical depths, precipitable water, sky radiance distributions and...

  6. Electronic structure, bulk and magnetic properties of MB{sub 6} and MB{sub 12} borides

    Energy Technology Data Exchange (ETDEWEB)

    Baranovskiy, A.E. [Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103 (Ukraine)]. E-mail: baranovskiy@ilt.kharkov.ua; Grechnev, G.E. [Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103 (Ukraine); Fil, V.D. [Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103 (Ukraine); Ignatova, T.V. [Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103 (Ukraine); Logosha, A.V. [Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103 (Ukraine); Panfilov, A.S. [Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103 (Ukraine); Svechkarev, I.V. [Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103 (Ukraine); Shitsevalova, N.Yu. [Institute for Problems of Materials Science, NASU, Kiev 03680 (Ukraine); Filippov, V.B. [Institute for Problems of Materials Science, NASU, Kiev 03680 (Ukraine); Eriksson, O. [Department of Physics, University of Uppsala, S-751 21 Uppsala (Sweden)

    2007-09-13

    The bulk and magnetic properties of MB{sub 6} and MB{sub 12} were investigated on the basis of first principles electronic structure calculations. The elastic constants were measured for ZrB{sub 12}, HoB{sub 12}, ErB{sub 12}, TmB{sub 12}, LuB{sub 12}, YB{sub 6} and LaB{sub 6} compounds at low temperatures. The calculated equations of states and balanced crystal orbital overlap populations have allowed to analyse bonding and magnetic properties of MB{sub 6} and MB{sub 12}.

  7. Correlation of Bulk Dielectric and Piezoelectric Properties to the Local Scale Phase Transformations, Domain Morphology, and Crystal Structure Modified

    Energy Technology Data Exchange (ETDEWEB)

    Priya, Shashank [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Viehland, Dwight [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2014-12-14

    Three year program entitled “Correlation of bulk dielectric and piezoelectric properties to the local scale phase transformations, domain morphology, and crystal structure in modified lead-free grain-textured ceramics and single crystals” was supported by the Department of Energy. This was a joint research program between D. Viehland and S. Priya at Virginia Tech. Single crystal and textured ceramics have been synthesized and characterized. Our goals have been (i) to conduct investigations of lead-free piezoelectric systems to establish the local structural and domain morphologies that result in enhanced properties, and (ii) to synthesize polycrystalline and grain oriented ceramics for understanding the role of composition, microstructure, and anisotropy

  8. Independent control of adhesive and bulk properties of hybrid silica coatings on polycarbonate.

    Science.gov (United States)

    Lionti, Krystelle; Cui, Linying; Volksen, Willi; Dauskardt, Reinhold; Dubois, Geraud; Toury, Berangere

    2013-11-13

    excellent mechanical properties and exceptional adherence of this hybrid material to PC should lead to interesting new applications in diverse fields: optical eye-glasses, medical materials, packaging, and so forth.

  9. Effect of Ca substitution on some physical properties of nano-structured and bulk Ni-ferrite samples

    Energy Technology Data Exchange (ETDEWEB)

    Assar, S.T., E-mail: soha_talaat@yahoo.com; Abosheiasha, H.F.

    2015-01-15

    Nanoparticles of Ni{sub 1−x}Ca{sub x}Fe{sub 2}O{sub 4} (x=0.0, 0.02, 0.04, 0.06 and 0.10) were prepared by citrate precursor method. A part of these samples was sintered at 600 °C for 2 h in order to keep the particles within the nano-size while the other part was sintered at 1000 °C to let the particles to grow to the bulk size. The effect of Ca{sup 2+} ion substitution in nickel ferrite on some structural, magnetic, electrical and thermal properties was investigated. All samples were characterized by using X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). A two probe method was used to measure the dc electrical conductivity whereas the photoacoustic (PA) technique was used to determine the thermal diffusivity of the samples. To interpret different experimental results for nano and bulk samples some cation distributions were assumed based on the VSM and XRD data. These suggested cation distributions give logical explanations for other experimental results such as the observed values of the absorption bands in FTIR spectra and the dc conductivity results. Finally, in the thermal measurements it was found that increasing the Ca{sup 2+} ion content causes a decrease in the thermal diffusivity of both nano and bulk samples. The explanation of this behavior is ascribed to the phonon-phonon scattering. - Highlights: • The physical properties of both nano and bulk samples of Ni-Ca ferrites were investigated. • Cation distribution plays a vital role in tailoring the physical properties of all the samples. • The dc conductivity of the nanosamples is higher than their bulk counterparts. • Increasing Ca{sup 2+} content enhances M{sub s}, M{sub r}, and σ{sub dc} of the bulk samples over their nanocounterparts. • The behavior of thermal diffusivity of the samples attributed to the phonon-phonon scattering.

  10. First-principles calculations of the structural, electronic, optical and thermal properties of the BNxAs1-x alloys

    Science.gov (United States)

    Hamioud, L.; Boumaza, A.; Touam, S.; Meradji, H.; Ghemid, S.; El Haj Hassan, F.; Khenata, R.; Omran, S. Bin

    2016-06-01

    The present paper aims to study the structural, electronic, optical and thermal properties of the boron nitride (BN) and BAs bulk materials as well as the BNxAs1-x ternary alloys by employing the full-potential-linearised augmented plane wave method within the density functional theory. The structural properties are determined using the Wu-Cohen generalised gradient approximation that is based on the optimisation of the total energy. For band structure calculations, both the Wu-Cohen generalised gradient approximation and the modified Becke-Johnson of the exchange-correlation energy and potential, respectively, are used. We investigated the effect of composition on the lattice constants, bulk modulus and band gap. Deviations of the lattice constants and the bulk modulus from the Vegard's law and the linear concentration dependence, respectively, were observed for the alloys where this result allows us to explain some specific behaviours in the electronic properties of the alloys. For the optical properties, the calculated refractive indices and the optical dielectric constants were found to vary nonlinearly with the N composition. Finally, the thermal effect on some of the macroscopic properties was predicted using the quasi-harmonic Debye model in which the lattice vibrations are taken into account.

  11. Optical Properties of Nanoparticle Systems Mie and Beyond

    CERN Document Server

    Quinten, Michael

    2011-01-01

    Unlike other books who concentrate on metallic nanoparticles with sizes less than 100 nm, the author discusses optical properties of particles with (a) larger size and (b) of any material. The intention of this book is to fill the gap in the description of the optical properties of small particles with sizes less than 1000 nm and to provide a comprehensive overview on the spectral behavior of nanoparticulate matter. The author concentrates on the linear optical properties elastic light scattering and absorption of single nanoparticles and on reflectance and transmittance of nanoparticle matter

  12. Resonating properties of passive spherical optical microcavities

    Institute of Scientific and Technical Information of China (English)

    Wen Li(李文); Ruopeng Wang(王若鹏)

    2004-01-01

    As an optically pumped device, the lasing characteristics of a spherical microcavity laser depend on the optical pumping processes. These characteristics can be described in term of the Q factor and the optical field distribution in a microsphere. We derived analytical expressions and carried out numerical calculation for Q factor and optical field. The Q factor is found to be oscillatory functions of the radius of a microsphere and the pumping wavelength, and the pumping efficiency for a resonating microsphere is much higher than that for an anti-resonating microsphere. Using tunable lasers as pumping sources is suggested in order to achieve a higher pumping efficiency. Numerical calculation on optical field distribution in spherical microcavities shows that a well focused Gaussian beam is a suitable incident wave for cavity quantum electrodynamics experiments in which strong confinement of optical field in the center of a microsphere is requested, but higher order spherical wave should be used instead for exciting whispering-gallery-mode (WGM) microsphere lasers, for the purpose of favoring optical energy transferring to WGM in optical microspheres.

  13. Optical properties of graphene antidot lattices

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Flindt, Christian; Pedersen, Jesper Goor

    2008-01-01

    demonstrate that this artificial nanomaterial is a dipole-allowed direct-gap semiconductor with a very pronounced optical-absorption edge. Hence, optical infrared spectroscopy should be an ideal probe of the electronic structure. To address realistic experimental situations, we include effects due to disorder...

  14. Electronic Structure, Optical and Sensor Properties of ZnO Nanowires

    Directory of Open Access Journals (Sweden)

    O.V. Bovgyra

    2016-06-01

    Full Text Available Density functional theory calculations of structural, electronic and optical properties of nanowires ZnO were performed. The obtained results are showing that the band gap increase with the decrease of the ZnO nanowire size. The calculated ZnO nanowires dielectric function shows a significant blueshift with those of bulk ZnO. Our results give some reference to the thorough understanding of optical properties of ZnO, and also enable more precise monitoring and controlling during the growth of ZnO materials to be possible. Also theoretical calculations of adsorption of the different gases molecules on side of nanowires ZnO were performed. Their charge transfer to the nanowire sidewall is investigated in order to determine the donor or acceptor character of molecular adsorbing.

  15. Electronic and optical properties of RESn3 (RE=Pr & Nd) intermetallics: A first principles study

    Science.gov (United States)

    Pagare, G.; Abraham, Jisha A.; Sanyal, S. P.

    2015-06-01

    A theoretical study of structural, electronic and optical properties of RESn3 (RE = Pr & Nd) intermetallics have been investigated systematically using first principles density functional theory. The calculations are carried out within the PBE-GGA and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B') are calculated and the calculated lattice parameters show well agreement with the experimental results. We first time predict elastic constants for these compounds. From energy dispersion curves, it is found that these compounds are metallic in nature. The linear optical response of these compounds are also studied and the higher value of static dielectric constant shows the possibility to use them as good dielectric materials.

  16. Structural, electronic and optical properties of La{sub x}Sc{sub 1-x}Sb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ghezali, M. [Department of science and technology, University of bechar, BP 417 rue de kanadissa, 08000 bechar (Algeria); Microphysics and nanophysics laboratory (LaMiN), ENP-oran, BP 1523 ElM’Naouer, oran 31000, Algeria ghezali-mohamed75@yahoo.fr (Algeria)

    2015-03-30

    We present calculations of the structural, electronic and optic properties of LaxSc1-xSb ternary alloys for 0≤x≤1, by using the first principle full potential linear muffin-tin orbital (FPLMTO) method based on the local density approximation (LDA). the lattice constant, bulk modulus, electronic band structures, density of state and optical properties such as dielectric functions, refractive index and extinction coefficient are calculated and discussed for (x=0.25, 0.5 and 0.75). Our results agree well with the available data in the literature.

  17. Glass Formation, Chemical Properties and Surface Analysis of Cu-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Akihisa Inoue

    2011-04-01

    Full Text Available This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs. In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni and Cu–Zr–Ag–Al–(Nb bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance.

  18. Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

    Directory of Open Access Journals (Sweden)

    Nicola H. Perry

    2016-10-01

    Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

  19. Effect of preheating and light-curing unit on physicochemical properties of a bulk fill composite

    Directory of Open Access Journals (Sweden)

    Theobaldo JD

    2017-05-01

    Full Text Available Jéssica Dias Theobaldo,1 Flávio Henrique Baggio Aguiar,1 Núbia Inocencya Pavesi Pini,2 Débora Alves Nunes Leite Lima,1 Priscila Christiane Suzy Liporoni,3 Anderson Catelan3 1Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, Piracicaba, 2Ingá University Center, Maringá, 3Departament of Dentistry, University of Taubaté, Taubaté, Brazil Objective: The aim of this study is to evaluate the effect of composite preheating and polymerization mode on degree of conversion (DC, microhardness (KHN, plasticization (P, and depth of polymerization (DP of a bulk fill composite.Methods: Forty disc-shaped samples (n = 5 of a bulk fill composite were prepared (5 × 4 mm thick and randomly divided into 4 groups according to light-curing unit (quartz–tungsten–halogen [QTH] or light-emitting diode [LED] and preheating temperature (23 or 54 °C. A control group was prepared with a flowable composite at room temperature. DC was determined using a Fourier transform infrared spectrometer, KHN was measured with a Knoop indenter, P was evaluated by percentage reduction of hardness after 24 h of ethanol storage, and DP was obtained by bottom/top ratio. Data were statistically analyzed by analysis of variance and Tukey’s test (α = 0.05.Results: Regardless of light-curing, the highest preheating temperature increased DC compared to room temperature on bottom surface. LED showed a higher DC compared to QTH. Overall, DC was higher on top surface than bottom. KHN, P, and DP were not affected by curing mode and temperature, and flowable composite showed similar KHN, and lower DC and P, compared to bulk fill.Conclusion: Composite preheating increased the polymerization degree of 4-mm-increment bulk fill, but it led to a higher plasticization compared to the conventional flowable composite evaluated. Keywords: composite resins, physicochemical phenomena, polymerization, hardness, heating

  20. Optical properties of photoreceptor and retinal pigment epithelium cells investigated with adaptive optics optical coherence tomography

    Science.gov (United States)

    Liu, Zhuolin

    Human vision starts when photoreceptors collect and respond to light. Photoreceptors do not function in isolation though, but share close interdependence with neighboring photoreceptors and underlying retinal pigment epithelium (RPE) cells. These cellular interactions are essential for normal function of the photoreceptor-RPE complex, but methods to assess these in the living human eye are limited. One approach that has gained increased promise is high-resolution retinal imaging that has undergone tremendous technological advances over the last two decades to probe the living retina at the cellular level. Pivotal in these advances has been adaptive optics (AO) and optical coherence tomography (OCT) that together allow unprecedented spatial resolution of retinal structures in all three dimensions. Using these high-resolution systems, cone photoreceptor are now routinely imaged in healthy and diseased retina enabling fundamental structural properties of cones to be studied such as cell spacing, packing arrangement, and alignment. Other important cell properties, however, have remained elusive to investigation as even better imaging performance is required and thus has resulted in an incomplete understanding of how cells in the photoreceptor-RPE complex interact with light. To address this technical bottleneck, we expanded the imaging capability of AO-OCT to detect and quantify more accurately and completely the optical properties of cone photoreceptor and RPE cells at the cellular level in the living human retina. The first objective of this thesis was development of a new AO-OCT method that is more precise and sensitive, thus enabling a more detailed view of the 3D optical signature of the photoreceptor-RPE complex than was previously possible (Chapter 2). Using this new system, the second objective was quantifying the waveguide properties of individual cone photoreceptor inner and outer segments across the macula (Chapter 3). The third objective extended the AO

  1. Microstructures and mechanical properties of bulk nanocrystalline Fe{sub 3}Al materials with 5, 10 and 15 wt.% Cr prepared by aluminothermic reaction

    Energy Technology Data Exchange (ETDEWEB)

    La Peiqing, E-mail: pqla@lut.cn [State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China); Wang Hongding; Bai Yaping; Yang Yang; Wei Yupeng; Lu Xuefeng; Zhao Yang; Cheng Chunjie [State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China)

    2011-08-15

    Highlights: {yields} We prepare bulk nanocrystalline material by aluminothermic reaction. {yields} Microstructures keep bcc disordered structure of Fe{sub 3}Al. {yields} Materials have good plastic deformation and texture changes after compression. - Abstract: Bulk nanocrystalline Fe{sub 3}Al based materials with 5, 10 and 15 wt.% Cr were prepared by aluminothermic reaction, in which melts were superheated about 1500 K before solidification. Microstructures of the materials were investigated by optical microscope, electron probe microscope, X-ray diffraction and transmission electron microscope. It was shown that microstructure of the materials consist of nanocrystalline matrix phase, which was composed of Fe, Al and Cr elements, and a small amount of contamination. The nanocrystalline phase was disordered bcc structure, and which did not change with Cr content. Average grain sizes of the nanocrystalline phase of the materials with 5, 10 and 15 wt.% Cr were 33, 21 and 37 nm, respectively. Compressive properties and hardness of the materials were tested. It indicated that the materials had a considerable plastic deformation and were not fractured in compression. Yield strength of the materials were about three times higher but hardness were a little lower than those of Fe{sub 3}Al material with coarsen grain. The hardness and yield strength of the materials varied slightly with Cr content and that of the material with 10 wt.% Cr was slightly lower. Average grain sizes of the materials decreased and texture changes appeared after the compression.

  2. Bulk Properties of Transition Metals: A Challenge for the Design of Universal Density Functionals.

    Science.gov (United States)

    Janthon, Patanachai; Luo, Sijie Andy; Kozlov, Sergey M; Viñes, Francesc; Limtrakul, Jumras; Truhlar, Donald G; Illas, Francesc

    2014-09-09

    Systematic evaluation of the accuracy of exchange-correlation functionals is essential to guide scientists in their choice of an optimal method for a given problem when using density functional theory. In this work, accuracy of one Generalized Gradient Approximation (GGA) functional, three meta-GGA functionals, one Nonseparable Gradient Approximation (NGA) functional, one meta-NGA, and three hybrid GGA functionals was evaluated for calculations of the closest interatomic distances, cohesive energies, and bulk moduli of all 3d, 4d, and 5d bulk transition metals that have face centered cubic (fcc), hexagonal closed packed (hcp), or body centered cubic (bcc) structures (a total of 27 cases). Our results show that including the extra elements of kinetic energy density and Hartree-Fock exchange energy density into gradient approximation density functionals does not usually improve them. Nevertheless, the accuracies of the Tao-Perdew-Staroverov-Scuseria (TPSS) and M06-L meta-GGAs and the MN12-L meta-NGA approach the accuracy of the Perdew-Burke-Ernzerhof (PBE) GGA, so usage of these functionals may be advisable for systems containing both solid-state transition metals and molecular species. The N12 NGA functional is also shown to be almost as accurate as PBE for bulk transition metals, and thus it could be a good choice for studies of catalysis given its proven good performance for molecular species.

  3. Measurement of Optical Properties of Small Particles

    Energy Technology Data Exchange (ETDEWEB)

    Arakawa, E.T.; Tuminello, P.S. [Oak Ridge National Lab., TN (United States); Khare, B.N. [NASA Ames Research Center, Moffett Field, CA (United States); Millham, M.E. [USAMCCOM, Edgewood Research, Development, and Engineering Center, Aberdeen Proving Ground, MD (United States); Authier, S. [Ecole Superiere d`Optique, Orsay (France); Pierce, J. [University of Tennessee, Knoxville, TN (United States)

    1997-12-01

    We have measured the optical constants of montmorillonite and the separated coats and cores of B. subtilis spores over the wavelength interval from 200 nm to 2500 nm. The optical constants of kaolin were obtained over the wavelength interval from 130 nm to 2500 nm. Our results are applicable to the development of systems for detection of airborne biological contaminants. Future work will include measurement of the optical constants of B. cereus spores, B. sub tilts vegetative cells, egg albumin, illite, and a mixture (by weight) of one third kaolin, one third montmorillonite, and one third illite.

  4. Nonlinear optical properties of Au/PVP composite thin films

    Institute of Scientific and Technical Information of China (English)

    Shen Hong; Cheng Bo-Lin; Lu Guo-Wei; Wang Wei-Tian; Guan Dong-Yi; Chen Zheng-Hao; Yang Guo-Zhen

    2005-01-01

    Colloidal Au and poly(vinylpyrrolidone) (PVP) composite thin films are fabricated by spin-coating method. Linear optical absorption measurements of the Au/PVP composite films indicate an absorption peak around 530 nm due to the surface plasmon resonance of gold nanoparticles. Nonlinear optical properties are studied using standard Z-scan technique, and experimental results show large optical nonlinearities of the Au/PVP composite films. A large value of films.

  5. Optical and electrical characteristics of chromium- and iron-doped zinc selenide thin film and bulk materials for optically and electrically pumped lasers

    Science.gov (United States)

    Gallian, Andrew

    This work is devoted to evaluating new laser systems based upon chromium and iron doped ZnSe structures. These systems are based upon new materials and pumping schemes. These topics can be broken down into three major subgroups: new materials based upon Cr2+:ZnSe, Fe2+:ZnSe lasers and pump sources, and electrically pumped Cr2+:ZnSe systems. Both hot-pressed ceramic and thin film Cr2+:ZnSe samples were evaluated for their potential as laser gain media. This work entailed spectroscopic analysis of both their absorption and emission spectra as well as characterizing their lifetime of luminescence. For hot-pressed ceramic Cr2+:ZnSe the samples were tested in a laser cavity and proven to be the first laser system in the mid-IR to be demonstrated based upon hot-pressed Cr2+:ZnSe. Thin film Cr2+:ZnSe was determined to have different spectroscopic characteristics for luminescence compared to reference bulk samples. This difference is attributed to the location of all of the optical centers within a Fabry-Perot cavity formed by the film surface and the wafer on which it was deposited. Fe2+:ZnSe laser demonstration at room temperature is presented. This laser operates in a spectral region of great interest for spectroscopy. To develop this laser system new pumping systems were required. Such systems as passively Q-switched Er:YSGG and Stokes Stimulated Raman Scattering from a D2 cell are described in great depth. Electrically pumped Transition Metal 2+:II-VI systems are ideal for small portable spectroscopic and scientific tools. The elimination of an optical pump source removes many complications of other systems including, complications due to having a second laser. This work was approached by modeling electrically motivated transitions with sub-band optical excitation. Lasing of Cr 2+:ZnSe was achieved using a 532 nm pump source. This result, in combination with photo-current and photo-Hall measurements, led to the development of some theories explaining possible

  6. The microstructure of MX-80 clay with respect to its bulk physical properties under different environmental conditions

    Energy Technology Data Exchange (ETDEWEB)

    Pusch, R. [Geodevelopment AB, Lund (Sweden)

    2001-03-01

    A model of microstructural evolution of MX-80 buffer is presented in the report.Quantification of the microstructure is made by use of digitalized micrographs taken by transmission electron microscopy using suitably impregnated specimens with appropriate thickness. The model is termed MMM, a successor of the earlier GMM. Practically useful microstructural parameters refer to the fraction of a thin section that represents dense and soft parts of the clay matrix. The derived microstructural parameters are directly coupled to the most important bulk physical properties, i.e. the hydraulic conductivity, gas penetrability, swelling pressure and cation/anion diffusion capacities. The study has shown that even at very high densities, softer and more pervious zones exist in the form of interconnected 'external' voids filled with more or less dense clay gels. At bulk densities exceeding 2000 kg/m{sup 3} after water saturation, the gel density is also high but for low bulk densities it may be so much reduced that the gels do not remain stable at high electrolyte content of the pore water. The fact that the density variations are small for high bulk densities means that the separation of matrix components ('fracturing') that is required for letting gas through is on the same order of magnitude as the bulk swelling pressure. For lower bulk densities, displacement or consolidation of the clay gels in 'external' voids is concluded to take place in conjunction with gas penetration. At high densities the limited degree of continuity and constrictions of the channels leading to anion-excluding charge conditions mean that the anion diffusion capacity is very low, while cation diffusion may be extensive because it takes place not only through channels but also through the inter lamellar space and along the surfaces of stacks of lamellae, i.e. by surface diffusion. Two Pre-Quaternary clays that have been investigated and characterized with respect to the

  7. All-electron versus pseudopotential calculation of optical properties: the case of GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Monachesi, P.; Marini, A.; Onida, G.; Palummo, M.; Sole, R. del [Tor Vergata Univ., Rome (Italy). Dipt. di Fisica

    2001-03-16

    The reliability of the widespread practice of calculating the optical properties of solids using pseudo wavefunctions instead of the true electron wavefunctions has been tested in the case of bulk GaAs. Pseudopotential calculations of the imaginary part of the dielectric function - where the matrix elements of the momentum operator are calculated between pseudo wavefunctions - have been compared with all-electron full-potential linear muffin-tin orbital calculations where the true wavefunctions are used. No evidence has been found of differences due to the different sets of wavefunctions employed in the two approaches. (orig.)

  8. Sensitivity Study of Ice Crystal Optical Properties in the 874 GHz Submillimeter Band

    Science.gov (United States)

    Tang, Guanglin; Yang, Ping; Wu, Dong L.

    2015-01-01

    Testing of an 874 GHz submillimeter radiometer on meteorological satellites is being planned to improve ice water content retrievals. In this paper we study the optical properties of ice cloud particles in the 874 GHz band. The results show that the bulk scattering and absorption coefficients of an ensemble of ice cloud particles are sensitive to the particle shape and effective diameter, whereas the latter is also sensitive to temperature. The co-polar back scattering cross-section is not sensitive to particle shape, temperature, and the effective diameter in the range of 50200 m.

  9. Optical, elastic and thermal properties of ZB-AlN semiconductor from first-principle calculations

    Science.gov (United States)

    Kumar, V.; Singh, Bhanu P.; Chandra, Satish

    2016-12-01

    The optical, elastic and thermal properties of zincblende aluminium nitride have been studied. The refractive index, absorption coefficient, reflectivity, dielectric constant, extinction coefficient, and energy-loss spectrum have been calculated using the pseudo-potential method under density functional theory at different pressures. The heat capacity, Debye temperature and phonon frequencies have been calculated using CASTEP code at 0 GPa. The elastic stiffness constants, bulk modulus, Young's modulus, shear modulus and pressure derivatives of elastic constants have also been calculated. The calculated results are compared with the available experimental and theoretical data. Reasonably good agreement has been found between them.

  10. Measurement of inherent optical properties in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.; Desa, E.; Kurian, J.; Mascarenhas, A.A.M.Q.

    Inherent optical properties, absorption and began attenuation were measured in situ using a reflective tube absorption meter at nint wavelength, 412, 440, 488, 510, 555, 630, 650, 676 and 715 nm, in the Arabian Sea during March. Since inherent...

  11. Spectroscopic properties of rare earths in optical materials

    CERN Document Server

    Parisi, Jürgen; Osgood, R; Warlimont, Hans; Liu, Guokui; Jacquier, Bernard

    2005-01-01

    Aimed at researchers and graduate students, this book provides up-to-date information for understanding electronic interactions that impact the optical properties of rare earth ions in solids. Its goal is to establish a connection between fundamental principles and the materials properties of rare-earth activated luminescent and laser optical materials. The theoretical survey and introduction to spectroscopic properties include electronic energy level structure, intensities of optical transitions, ion-phonon interactions, line broadening, and energy transfer and up-conversion. An important aspect of the book lies in its deep and detailed discussions on materials properties and the potential of new applications such as optical storage, information processing, nanophotonics, and molecular probes that have been identified in recent experimental studies. This volume will be a valuable reference book on advanced topics of rare earth spectroscopy and materials science.

  12. Compact All Solid State Oceanic Inherent Optical Property Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This work concerns the development of a prototype of a Volume Scattering Function (VSF) sensor for measurement of this inherent optical property(IOP) of seawater....

  13. Compact All Solid State Oceanic Inherent Optical Property Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Light propagation in the sea and the consequent remote sensing signals seen by aircraft and spacecraft is fundamentally governed by the inherent optical properties...

  14. Tailored synthesis of superparamagnetic gold nanoshells with tunable optical properties.

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Q.; Ge, J.; Goebl, J.; Hu, Y.; Sun, Y.; Yin, Y.; Center for Nanoscale Materials; Univ. of California at Riverside

    2010-05-04

    Multifunctional Au nanoshells with tunable optical properties and fast magnetic response have been fabricated through a sequence of sol-gel, surface-protected etching, and seed-mediated growth processes. The use of a porous silica layer enhances the uniformity of nanoshell growth, the reproducibility of the synthesis, and the structural and optical stability of the products.

  15. Tuning of copper nanocrystals optical properties with their shapes.

    Science.gov (United States)

    Salzemann, C; Brioude, A; Pileni, M-P

    2006-04-13

    Copper nanocrystals are obtained by chemical reduction of copper ions in mixed reverse micelles. A large excess of reducing agent favors producing a new generation of shaped copper nanocrystals as nanodisks, elongated nanocrystals, and cubes. By using UV-Visible spectroscopy and numerical optical simulations we demonstrate that the optical properties are tuned by the relative proportions of spheres and nanodisks.

  16. Airborne LIDAR as a tool for estimating inherent optical properties

    Science.gov (United States)

    Trees, Charles; Arnone, Robert

    2012-06-01

    LIght Detection and Ranging (LIDAR) systems have been used most extensively to generate elevation maps of land, ice and coastal bathymetry. There has been space-, airborne- and land-based LIDAR systems. They have also been used in underwater communication. What have not been investigated are the capabilities of LIDARs to measure ocean temperature and optical properties vertically in the water column, individually or simultaneously. The practical use of bathymetric LIDAR as a tool for the estimation of inherent optical properties remains one of the most challenging problems in the field of optical oceanography. LIDARs can retrieve data as deep as 3-4 optical depths (e.g. optical properties can be measured through the thermocline for ~70% of the world's oceans). Similar to AUVs (gliders), UAV-based LIDAR systems will increase temporal and spatial measurements by several orders of magnitude. The LIDAR Observations of Optical and Physical Properties (LOOPP) Conference was held at NURC (2011) to review past, current and future LIDAR research efforts in retrieving water column optical/physical properties. This new observational platform/sensor system is ideally suited for ground truthing hyperspectral/geostationary satellite data in coastal regions and for model data assimilation.

  17. Optical properties of the fluid-fluid interface

    Science.gov (United States)

    Blokhuis, E. M.; Bedeaux, D.

    1990-04-01

    In this paper we derive formulae for the optical properties (reflection, transmission and ellipsometric coefficients) of a fluid-fluid interface. An expansion to the second order in the interfacial thickness is used. Deviations of the above-mentioned coefficients from the value found using a step function profile for the refractive index (Fresnel) are found to be the sum of three terms. The first follows from the so-called intrinsic profile using the standard theory for stratified media. The second is due to capillary waves and was already analyzed in two earlier papers [B.J.A. Zielinska, D. Bedeaux and J. Vlieger, Physica A 107 (1981) 91; 117 (1983) 28]. The third is due to the modification of the relevant correlation functions in the neigbourhood of the interface due to fluctuations with a wavelength comparable to or smaller than the bulk correlation length. A comparison is made with experimental results close to the critical point. We discuss how the introduction of the rigidity of the interface as suggested by Meunier [J. Phys. (Paris) 48 (1987) 1819] may reduce the contributions due to capillary waves to the reflection and the ellipsometric coefficients. Expressions for these coefficients are given explicitly contain both the rigidity as well as the large wavevector cutoff used by Sengers and van Leeuwen [Phys. Rev. A 39 (1989) 6346] in their analysis of the behaviour of the surface tension. The rigidity is found not to affect the scaling behaviour of these coefficients near the critical point. For zero rigidity the expressions for the capillary wave contributions reduce to those given in the two earlier papers while for an infinite cutoff wavevector they reduce to those given by Meunier.

  18. Using electron microscopy to calculate optical properties of biological samples

    OpenAIRE

    Wu, Wenli; Radosevich, Andrew J.; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K.; Szleifer, Igal; Backman, Vadim

    2016-01-01

    The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy...

  19. Optical properties of silicon germanium waveguides at telecommunication wavelengths.

    Science.gov (United States)

    Hammani, Kamal; Ettabib, Mohamed A; Bogris, Adonis; Kapsalis, Alexandros; Syvridis, Dimitris; Brun, Mickael; Labeye, Pierre; Nicoletti, Sergio; Richardson, David J; Petropoulos, Periklis

    2013-07-15

    We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.

  20. THE STRUCTURE AND OPTICAL PROPERTIES OF COPOLYMER OF CHOLESTERIC ESTER

    Institute of Scientific and Technical Information of China (English)

    Zhou Enle; Zhang Yongqing; Zhao Xiaoguang; Xu Yang; Zhou Xingmao

    1988-01-01

    The structure and switching properties of liquid crystalline side chain copolymers of cholesteric ester of1,2-hydroxypropyl 2,4-di-isocyanatoluene methylmethacrylate (PHCPM) have been studied in detail. The cholesteric mesophase of PHCPM is shown by polarizing microscopy, X-ray diffraction and selective light reflection. Solution of PHCPM in CHCl3 is optically anisotropic; its optical properties were determined by specific rotation [α], circular dichroism (CD) and wide-angle light scattering (WALS) methods.

  1. Structural, electronic, linear, and nonlinear optical properties of ZnCdTe{sub 2} chalcopyrite

    Energy Technology Data Exchange (ETDEWEB)

    Ouahrani, Tarik [Laboratoire de Physique Theorique, Universite de Tlemcen, B.P. 230, Tlemcen 13000 (Algeria); Reshak, Ali H. [Institute of Physical Biology, South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Microelectronic Engineering, University of Malaysia Perlis (UniMAP), Block A, Kompleks Pusat Pengajian, 02600 Arau Jejawi, Perlis (Malaysia); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Baltache, H.; Amrani, B. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Bouhemadou, A. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Faculty of Sciences, Department of Physics, University of Setif, Setif 19000 (Algeria)

    2011-03-15

    We report results of first-principles density functional calculations using the full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) and the Engel-Vosko-GGA (EV-GGA) formalism were used for the exchange-correlation energy to calculate the structural, electronic, linear, and nonlinear optical properties of the chalcopyrite ZnCdTe{sub 2} compound. The valence band maximum and the conduction band minimum are located at the {gamma}-point, resulting in a direct band gap of about 0.71 eV for GGA and 1.29 eV for EV-GGA. The results of bulk properties, such as lattice parameters (a, c, and u), bulk modulus B, and its pressure derivative B' are evaluated. The optical properties of this compound, namely the real and the imaginary parts of the dielectric function, reflectivity, and refractive index, show a considerable anisotropy as a consequence ZnCdTe{sub 2} posseses a strong birefringence. In addition, the extinction coefficient, the electron energy loss function, and the nonlinear susceptibility are calculated and their spectra are analyzed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Critical Analysis on the Structural and Magnetic Properties of Bulk and Nanocrystalline Cu-Fe-O

    Directory of Open Access Journals (Sweden)

    D. Paul Joseph

    2010-01-01

    Full Text Available Nanocrystalline and bulk samples of “Fe”-doped CuO were prepared by coprecipitation and ceramic methods. Structural and compositional analyses were performed using X-ray diffraction, SEM, and EDAX. Traces of secondary phases such as CuFe2O4, Fe3O4, and α-Fe2O3 having peaks very close to that of the host CuO were identified from the Rietveld profile analysis and the SAED pattern of bulk and nanocrystalline Cu0.98Fe0.02O samples. Vibrating Sample Magnetometer (VSM measurements show hysteresis at 300 K for all the samples. The ferrimagnetic Neel transition temperature ( was found to be around 465°C irrespective of the content of “Fe”, which is close to the value of cubic CuFe2O4. High-pressure X-Ray diffraction studies were performed on 2% “Fe”-doped bulk CuO using synchrotron radiation. From the absence of any strong new peaks at high pressure, it is evident that the secondary phases if present could be less than the level of detection. Cu2O, which is diamagnetic by nature, was also doped with 1% of “Fe” and was found to show paramagnetic behavior in contrast to the “Fe” doped CuO. Hence the possibility of intrinsic magnetization of “Fe”-doped CuO apart from the secondary phases is discussed based on the magnetization and charge state of “Fe” and the host into which it is substituted.

  3. Fatigue Properties and Morphology of Fatigue Fracture of Bulk Metallic Glass

    Science.gov (United States)

    Zhao, X. Y.; Chen, Z. H.; Wang, H. P.; Zhan, J.

    2016-11-01

    Changes in the amorphous structure and fatigue resistance of Zr57.5Cu27.3Al8.5Ni6.7 bulk metallic glass are studied. A copper-rich phase produced by cyclic stresses is discovered. This phase observed on the fracture surface may hinder crack propagation. The specimens after fatigue failure have a V shape (do not break into two completely) due to the high density of shear bands and multiple branching of the shear bands in the strained region.

  4. Optical Properties of Volcanic Ash: Improving Remote Sensing Observations

    Science.gov (United States)

    Whelley, P.; Colarco, P. R.; Aquila, V.; Krotkov, N. A.; Bleacher, J. E.; Garry, W. B.; Young, K. E.; Lima, A. R.; Martins, J. V.; Carn, S. A.

    2015-12-01

    Many times each year explosive volcanic eruptions loft ash into the atmosphere. Global travel and trade rely on aircraft vulnerable to encounters with airborne ash. Volcanic ash advisory centers (VAACs) rely on dispersion forecasts and satellite data to issue timely warnings. To improve ash forecasts model developers and satellite data providers need realistic information about volcanic ash microphysical and optical properties. In anticipation of future large eruptions we can study smaller events to improve our remote sensing and modeling skills so when the next Pinatubo 1991 or larger eruption occurs, ash can confidently be tracked in a quantitative way. At distances >100km from their sources, drifting ash plumes, often above meteorological clouds, are not easily detected from conventional remote sensing platforms, save deriving their quantitative characteristics, such as mass density. Quantitative interpretation of these observations depends on a priori knowledge of the spectral optical properties of the ash in UV (>0.3μm) and TIR wavelengths (>10μm). Incorrect assumptions about the optical properties result in large errors in inferred column mass loading and size distribution, which misguide operational ash forecasts. Similarly, simulating ash properties in global climate models also requires some knowledge of optical properties to improve aerosol speciation. Recent research has identified a wide range in volcanic ash optical properties among samples collected from the ground after different eruptions. The database of samples investigated remains relatively small, and measurements of optical properties at the relevant particle sizes and spectral channels are far from complete. Generalizing optical properties remains elusive, as does establishing relationships between ash composition and optical properties, which are essential for satellite retrievals. We are building a library of volcanic ash optical and microphysical properties. In this presentation we show

  5. Optical properties of a-Si:B films

    Energy Technology Data Exchange (ETDEWEB)

    Alias, M.F.A.; Al-Douri, A.A.J.; Hasoon, F.S. (Solar Energy Research Center, Scientific Research Council, Baghdad (IQ)); Al-Foadi, A.H. (Al-Mustansiryah Univ., Baghdad (IQ). Coll. of Science); Kazmerski, L.L. (Solar Energy Research Inst., Golden, CO (USA))

    1989-01-01

    The optical properties of p-type a-Si films prepared by thermal evaporation have been studied. The films were prepared under different conditions which include variation of substrate and annealing temperature and dopant percentage of boron. The properties actually studied include the optical absorption and the optical gap which increased as the film annealed at higher temperature. However it decreased for films deposited at higher substrate temperature and doping concentration, whereas the increased substrate and annealing temperatures caused decrease in energy of localized and recombination states. (author).

  6. Structural and optical properties of Si-doped Ag clusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-03-06

    The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

  7. Electro-optical properties of tetragonal KNbO3

    Indian Academy of Sciences (India)

    P U Sastry

    2007-06-01

    Linear electro-optical tensor coefficients and optical susceptibility of tetragonal KNbO3 are calculated using a formalism based on bond charge theory. Results are in close agreement with the experimental data. The covalent Nb–O bonding network comprising the distorted NbO6 octahedral groups in the structure is found to be a major contributor to the electro-optic coefficients making these groups more sensitive to these properties than the KO12 groups. The orientations of the chemical bonds play an important role in determining these properties.

  8. Structure and properties of Fe-Cr-Mo-C bulk metallic glasses obtained by die casting method

    Directory of Open Access Journals (Sweden)

    W. Pilarczyk

    2010-09-01

    Full Text Available urpose: The goal of this work is to investigate structure and properties of Fe54Cr16Mo12C18 alloy rods with different diameters obtained by the pressure die casting method.Design/methodology/approach: Master alloy ingot with compositions of Fe54Cr16Mo12C18 was prepared by induction melting of pure Fe, Cr, Mo, C elements in argon atmosphere. The investigated material were cast in form of rods with different diameters. Glassy and crystalline structures were examined by X-ray diffraction. The microscopic observation of the fracture morphology was carried out by the SEM with different magnification. The thermal properties of the studied alloy were examined by DTA and DSC method.Findings: These materials exhibit high glass-forming ability, excellent mechanical properties and corrosion resistance.Research limitations/implications: It is difficult to obtain a metallic glass of Fe54Cr16Mo12C18 alloy. The investigations carried out on the different samples of Fe54Cr16Mo12C18 bulk metallic alloy allowed to state that the studied ribbon was amorphous whereas rods were amorphous – crystalline.Originality/value: The formation and investigation of the casted Fe-Cr-Mo-C bulk materials and the study of glass-forming ability of this alloy.

  9. The sound velocity and bulk properties of sediments in the Bohai Sea and the Yellow Sea of China

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jiewen; LIU Baohua; KAN Guangming; LI Guanbao; PEI Yanliang; LIU Xiaolei

    2016-01-01

    In order to investigate the correlation between a sound velocity and sediment bulk properties and explore the influence of frequency dependence of the sound velocity on the prediction of the sediment properties by the sound velocity, a compressional wave velocity is measured at frequencies of 25–250 kHz on marine sediment samples collected from the Bohai Sea and the Yellow Sea in laboratory, together with the geotechnical parameters of sediments. The results indicate that the sound velocity ranges from 1.232 to 1.721 km/s for the collected sediment samples with a significant dispersion within the series measuring frequency. Poorly sorted sediments are highly dispersive nearly with a positive linear relationship. The porosity shows a better negative logarithmic correlation with the sound velocity compared with other geotechnical parameters. Generally, the sound velocity increases with the increasing of the average particle size, sand content, wet and dry bulk densities, and decreasing of the clay content, and water content. An important point should be demonstrated that the higher correlation can be obtained when the measuring frequency is low within the frequency ranges from 25 to 250 kHz since the inhomogeneity of sediment properties has a more remarkably influence on the laboratory sound velocity measurement at the high frequency.

  10. Microstructural and superconducting properties of C6H6 added bulk MgB2 superconductor

    Science.gov (United States)

    Babaoğlu, Meral G.; Safran, Serap; Çiçek, Özlem; Ağıl, Hasan; Ertekin, Ercan; Hossain, Md. Shahriar A.; Yanmaz, Ekrem; Gencer, Ali

    2012-10-01

    The effect of aromatic hydrocarbon (benzene, C6H6) addition on lattice parameters, microstructure, critical temperature (Tc), critical current density (Jc) of bulk MgB2 has been studied. In this work only 2 mol% C6H6 addition was found to be very effective in increasing the Jc values, while resulting in slight reduction of the Tc. Jc values of 2 mol% C6H6 added MgB2 bulks reached to 1.83×106 A/cm2 at 15 K and 0 T. Microstructural analyses suggest that Jc enhancement is associated with the substitution of carbon with boron and which also results in the smaller MgB2 grain size. The change in the lattice parameters or the lattice disorder is claimed as a cause of the slight reduction in the Tc by carbon addition. We note that our results show the advantages of C6H6 addition include homogeneous mixing of precursor powders, avoidance of expansive nanoadditives, production of highly reactive C, and significant enhancement in Jc of MgB2, compared to un-doped samples.

  11. Preparation and Properties of Mg-Cu-Y-Al bulk Amorphous Alloys

    DEFF Research Database (Denmark)

    Pryds, Nini; Eldrup, Morten Mostgaard; Ohnuma, M.

    2000-01-01

    Bulk amorphous (Mg(1-gamma)Al(gamma))(60)CU(30)Y(10) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs, time was recorded during the cooling and solidification process of the melt and compared with a spacial and tempo......Bulk amorphous (Mg(1-gamma)Al(gamma))(60)CU(30)Y(10) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs, time was recorded during the cooling and solidification process of the melt and compared with a spacial......-ray diffraction (XRD) and differential scanning calorimetry (DSC) for different alloy compositions and annealing temperatures. On annealing into the supercooled liquid state (441 K), specimens with no Al content remain basically amorphous while nanoparticles are formed and remain stable also at higher...... temperatures in specimens containing a few percent Al. The alloy with no Al crystallises apparently without the formation of nanoparticles. The critical cooling rate for the formation of an amorphous Mg(60)CU(30)Y(10) specimen was determined experimentally by a combination of DSC data and temperature vs, time...

  12. On the adsorption properties of magnetic fluids: Impact of bulk structure

    Science.gov (United States)

    Kubovcikova, Martina; Gapon, Igor V.; Zavisova, Vlasta; Koneracka, Martina; Petrenko, Viktor I.; Soltwedel, Olaf; Almasy, László; Avdeev, Mikhail V.; Kopcansky, Peter

    2017-04-01

    Adsorption of nanoparticles from magnetic fluids (MFs) on solid surface (crystalline silicon) was studied by neutron reflectometry (NR) and related to the bulk structural organization of MFs concluded from small-angle neutron scattering (SANS). The initial aqueous MF with nanomagnetite (co-precipitation reaction) stabilized by sodium oleate and MF modified by a biocompatible polymer, poly(ethylene glycol) (PEG), were considered. Regarding the bulk structure it was confirmed in the SANS experiment that comparatively small and compact (size 30 nm) aggregates of nanoparticle in the initial sample transfer to large and developed (size>130 nm, fractal dimension 2.7) associates in the PEG modified MF. This reorganization in the aggregates correlates with the changes in the neutron reflectivity that showed that a single adsorption layer of individual nanoparticles on the oxidized silicon surface for the initial MF disappears after the PEG modification. It is concluded that all particles in the modified fluid are in the aggregates that are not adsorbed by silicon.

  13. Hydrogen Desorption Properties of Bulk and Nanoconfined LiBH4-NaAlH4

    Directory of Open Access Journals (Sweden)

    Payam Javadian

    2016-06-01

    Full Text Available Nanoconfinement of 2LiBH4-NaAlH4 into a mesoporous carbon aerogel scaffold with a pore size, BET surface area and total pore volume of Dmax = 30 nm, SBET = 689 m2/g and Vtot = 1.21 mL/g, respectively is investigated. Nanoconfinement of 2LiBH4-NaAlH4 facilitates a reduction in the temperature of the hydrogen release by 132 °C, compared to that of bulk 2LiBH4-NaAlH4 and the onset of hydrogen release is below 100 °C. The reversible hydrogen storage capacity is also significantly improved for the nanoconfined sample, maintaining 83% of the initial hydrogen content after three cycles compared to 47% for that of the bulk sample. During nanoconfinement, LiBH4 and NaAlH4 reacts to form LiAlH4 and NaBH4 and the final dehydrogenation products, obtained at 481 °C are LiH, LiAl, AlB2 and Al. After rehydrogenation of the nanoconfined sample at T = 400 °C and p(H2 = 126 bar, amorphous NaBH4 is recovered along with unreacted LiH, AlB2 and Al and suggests that NaBH4 is the main compound that can reversibly release and uptake hydrogen.

  14. Optical properties of nanowire metamaterials with gain

    DEFF Research Database (Denmark)

    Isidio de Lima, Joaquim Junior; Adam, Jost; Rego, Davi

    2016-01-01

    The transmittance, reflectance and absorption of a nanowire metamaterial with optical gain are numerically simulated and investigated. It is assumed that the metamaterial is represented by aligned silver nanowires embedded into a semiconductor matrix, made of either silicon or gallium phosphide....... The gain in the matrix is modeled by adding a negative imaginary part to the dielectric function of the semiconductor. It is found that the optical coefficients of the metamaterial depend on the gain magnitude in a non-trivial way: they can both increase and decrease with gain depending on the lattice...... constant of the metamaterial. This peculiar behavior is explained by the field redistribution between the lossy metal nanowires and the amplifying matrix material. These findings are significant for a proper design of nanowire metamaterials with low optical losses for diverse applications....

  15. Nonlinear optical properties of ultrathin metal layers

    DEFF Research Database (Denmark)

    Lysenko, Oleg

    2016-01-01

    . The optical characterization of the plasmonic waveguides is performed using femtosecond and picosecond optical pulses. Two nonlinear optical effects in the strip plasmonic waveguides are experimentally observed and reported. The first effect is the nonlinear power transmission of the plasmonic mode......-order nonlinear susceptibility of the plasmonic mode in the gold strip waveguides significantly depends on the metal layer thickness and laser pulse duration. This dependence is explained in detail in terms of the free-electron temporal dynamics in gold. The third-order nonlinear susceptibility of the gold layer...... duration dependence of the third-order nonlinear susceptibility of gold is calculated in the broad range from tens of femtoseconds to tens of picoseconds using the two-temperature model of the free-electron temporal dynamics of gold, and shows the saturation of the thirdorder nonlinear susceptibility...

  16. Optical properties of nanowire metamaterials with gain

    Science.gov (United States)

    Lima, Joaquim; Adam, Jost; Rego, Davi; Esquerre, Vitaly; Bordo, Vladimir

    2016-11-01

    The transmittance, reflectance and absorption of a nanowire metamaterial with optical gain are numerically simulated and investigated. It is assumed that the metamaterial is represented by aligned silver nanowires embedded into a semiconductor matrix, made of either silicon or gallium phosphide. The gain in the matrix is modeled by adding a negative imaginary part to the dielectric function of the semiconductor. It is found that the optical coefficients of the metamaterial depend on the gain magnitude in a non-trivial way: they can both increase and decrease with gain depending on the lattice constant of the metamaterial. This peculiar behavior is explained by the field redistribution between the lossy metal nanowires and the amplifying matrix material. These findings are significant for a proper design of nanowire metamaterials with low optical losses for diverse applications.

  17. Optical properties and structure of beryllium lead silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Zhidkov, I. S., E-mail: i.s.zhidkov@urfu.ru [Ural Federal University, Mira Str. 19, Yekaterinburg, 620002, Russia and Institute of Metal Physics, Russian Academy of Sciences-Ural Division, S. Kovalevskoi Str. 18, 620990 Yekaterinburg (Russian Federation); Zatsepin, A. F.; Cholakh, S. O.; Kuznetsova, Yu. A. [Ural Federal University, Mira Str. 19, Yekaterinburg, 620002 (Russian Federation)

    2014-10-21

    Luminescence and optical properties and structural features of (BeO){sub x}(PbO⋅SiO{sub 2}){sub 1−x} glasses (x = 0 ÷ 0.3) are investigated by means of optical absorption and photoluminescence spectroscopy and X-ray diffraction. The regularities of the formation of the optical absorption edge and static disorder are studied. It is shown that the optical absorption and luminescence are determined by transitions between localized states of lead ions. The impact of beryllium oxide on optical and luminescence properties and electronic structure of bands tails is discussed. The presence of two different concentration ranges with various short-range order structure and band tails nature has been established.

  18. Optical properties and structure of beryllium lead silicate glasses

    Science.gov (United States)

    Zhidkov, I. S.; Zatsepin, A. F.; Cholakh, S. O.; Kuznetsova, Yu. A.

    2014-10-01

    Luminescence and optical properties and structural features of (BeO)x(PbOṡSiO2)1-x glasses (x = 0 ÷ 0.3) are investigated by means of optical absorption and photoluminescence spectroscopy and X-ray diffraction. The regularities of the formation of the optical absorption edge and static disorder are studied. It is shown that the optical absorption and luminescence are determined by transitions between localized states of lead ions. The impact of beryllium oxide on optical and luminescence properties and electronic structure of bands tails is discussed. The presence of two different concentration ranges with various short-range order structure and band tails nature has been established.

  19. Optical and dielectric properties of double helix DNA thin films

    Energy Technology Data Exchange (ETDEWEB)

    Soenmezoglu, Savas, E-mail: svssonmezoglu@kmu.edu.tr [Department of Physics, Faculty of Kamil Ozdag Science, Karamanoglu Mehmetbey University, 70100, Karaman (Turkey); Ates Soenmezoglu, Ozlem [Department of Biology, Faculty of Kamil Ozdag Science, Karamanoglu Mehmetbey University, 70100, Karaman (Turkey)

    2011-12-01

    In this work, the thin film of wheat DNA was deposited by spin-coating technique onto glass substrate, and the optical and dielectric properties of the double helix DNA thin film were investigated. The optical constants such as refractive index, extinction coefficient, dielectric constant, dissipation factor, relaxation time, and optical conductivity were determined from the measured transmittance spectra in the wavelength range 190-1100 nm. Meanwhile, the dispersion behavior of the refractive index was studied in terms of the single oscillator Wemple-DiDomenico (W-D) model, and the physical parameters of the average oscillator strength, average oscillator wavelength, average oscillator energy, the refractive index dispersion parameter and the dispersion energy were achieved. Furthermore, the optical band gap values were calculated by W-D model and Tauc model, respectively, and the values obtained from W-D model are in agreement with those determined from the Tauc model. The analysis of the optical absorption data indicates that the optical band gap E{sub g} was indirect transitions. These results provide some useful references for the potential application of the DNA thin films in fiber optic, solar cell and optoelectronic devices. Highlights: {yields} The optical constants of DNA in full UV-vis spectrum were determined. {yields} The change in optical and dielectric property demonstrates that this material has potential to be used as a novel technology. {yields} DNA shows promise to be more suitable material than other materials currently being used for photonic devices.

  20. Modeling Optical and Electronic Properties of Silica Nano-Clusters in Silicon Rich Oxide Films

    Directory of Open Access Journals (Sweden)

    N.D. Espinosa-Torres

    2013-07-01

    Full Text Available Quantum effects are very important in nano scale systems such as molecules and clusters constituted of particles from a few to hundreds or a few thousands of atoms. Their optical and electronic properties are often dependent on the size of the systems and the way in which the atoms in these molecules or clusters are bonded. Generally, these nano-structures display optical and electronic properties significantly different of the bulk materials. Silica agglomerates expected in Silicon Rich Oxide (SRO films have optical properties, which depend directly on size, and their rationalization can lead to new applications with a potential impact on many fields of science and technology. On the other hand, the room temperature photoluminescence (PL of Si : SiO2 or Si : SiOx structures usually found in SRO has recently generated an enormous interest due to their possible applications in optoelectronic devices. However, the understanding of the emission mechanism is still under debate. In this research, we employed the Density Functional Theory with a functional B3LYP and a basis set 6-31 G* to calculate the electronic and optical properties of molecules and clusters of silicon dioxide. With the theoretical calculation of the structural and optical properties of silicon dioxide clusters is possible to evaluate the contribution of silica in the luminescent emission mechanism experimentally found in thin SRO films. It was found that silica contribution to the luminescent phenomenon in SRO thin films is less important than that of the silicon monoxide agglomerates because the number of silica structures, which may show emission in the visible spectrum, is much lower [1], compared to the number of silicon monoxide structures which emit in this region.

  1. Evaluation of Trapped Magnetic Field Properties in Superconducting MgB2 Bulk Magnets of Various Shapes by Finite Element Method

    Science.gov (United States)

    Hiramatsu, Y.; Otabe, E. S.; Kiuchi, M.

    The trapped magnetic field properties of superconducting MgB2 bulk magnets with various shapes such as a triangular, a quadrangular, a hexangular bulk were calculated by the Finite Elements Method (FEM). The effect for the combination of several numbers of bulks was also investigated for several kinds of shapes to obtain large area of bulk surface in spite of one large bulk. In this calculation, the simple magnetization process replaced by the field-cool magnetization was used to obtain the equivalent distribution of the magnetic field, and the thermal equation in FEM was omitted. The trapped magnetic field for the triangular bulk by FEM was compared with the experimental result. It was found that the calculated results agreed well with the experimental result. The maximum trapped magnetic field was obtained in the cylindrical shape among several kinds of shapes. The trapped magnetic field was increased by the combination of multi-bulks. It was confirmed that the trapped magnetic field of the multi-bulks was larger than that of the single bulk. The trapped magnetic field increases with increasing the number of the bulks.

  2. Electronic, elastic, acoustic and optical properties of cubic TiO{sub 2}: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Mahmood, Tariq, E-mail: tariq_mahmood78@hotmail.com [Research Center of Materials Science, School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Centre for High Energy Physics, University of the Punjab, Lahore 54590 (Pakistan); Cao, Chuanbao, E-mail: cbcao@bit.edu.cn [Research Center of Materials Science, School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Tahir, Muhammad; Idrees, Faryal [Research Center of Materials Science, School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Ahmed, Maqsood [Centre for High Energy Physics, University of the Punjab, Lahore 54590 (Pakistan); Tanveer, M.; Aslam, Imran; Usman, Zahid; Ali, Zulfiqar; Hussain, Sajad [Research Center of Materials Science, School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)

    2013-07-01

    The electronic, elastic, acoustic and optical properties of cubic phases TiO{sub 2} fluorite and pyrite are investigated using the first principles calculations. We have employed five different exchange–correlation functions within the local density and generalized gradient approximations using the ultrasoft plane wave pseudopotential method. The calculated band structures of cubic-TiO{sub 2} elucidate that the TiO{sub 2} fluorite and pyrite are direct and indirect semiconductors in contrast to the previous findings. From our studied properties such as bulk and shear moduli, elastic constants C{sub 44} and Debye temperature for TiO{sub 2} fluorite and pyrite, we infer that both the cubic phases are not superhard materials and the pyrite phase is harder than fluorite. The longitudinal and transversal acoustic wave speeds for both phases in the directions [100], [110] and [111] are determined using the pre-calculated elastic constants. In addition, we also calculate the optical properties such as dielectric function, absorption spectrum, refractive index and energy loss function using the pre-optimized structure. On the observation of optical properties TiO{sub 2} fluorite phase turn out to be more photocatalytic than pyrite.

  3. Investigation of Nonlinear Optical Properties of Semiconductors.

    Science.gov (United States)

    1984-02-23

    optical studies of InSb NI. W. Goodwin" and D. G. Seiler Center jo .4pphed Quurntm Electronics, Department of Phytics , North 1exu.% State Unuvpieroty...lnSb, in zero magnetic field, is that of Pidgeon anJ data, aside from two-photon absorption, could be ab- co-workers,’ who give references to other

  4. Estimation of Korean paddy field soil properties using optical reflectance

    Science.gov (United States)

    An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applie...

  5. Ab initio calculation of the optical and magneto-optical properties of moderately correlated magnetic solids

    NARCIS (Netherlands)

    Perlov, A.; Chadov, S.; Ebert, H.; Chioncel, L.; Lichtenstein, A.I.; Katsnelson, M.I.

    2004-01-01

    An approach for the calculation of the optical and magneto-optical properties of solids based on the one-particle Green function is introduced in the framework of the linear muffin-tin orbital (LMTO) method. The approach keeps all advantages of the more accurate Korringa-Kohn-Rostoker (KKR) scheme a

  6. Measuring optical properties of a blood vessel model using optical coherence tomography

    Science.gov (United States)

    Levitz, David; Hinds, Monica T.; Tran, Noi; Vartanian, Keri; Hanson, Stephen R.; Jacques, Steven L.

    2006-02-01

    In this paper we develop the concept of a tissue-engineered optical phantom that uses engineered tissue as a phantom for calibration and optimization of biomedical optics instrumentation. With this method, the effects of biological processes on measured signals can be studied in a well controlled manner. To demonstrate this concept, we attempted to investigate how the cellular remodeling of a collagen matrix affected the optical properties extracted from optical coherence tomography (OCT) images of the samples. Tissue-engineered optical phantoms of the vascular system were created by seeding smooth muscle cells in a collagen matrix. Four different optical properties were evaluated by fitting the OCT signal to 2 different models: the sample reflectivity ρ and attenuation parameter μ were extracted from the single scattering model, and the scattering coefficient μ s and root-mean-square scattering angle θ rms were extracted from the extended Huygens-Fresnel model. We found that while contraction of the smooth muscle cells was clearly evident macroscopically, on the microscopic scale very few cells were actually embedded in the collagen. Consequently, no significant difference between the cellular and acellular samples in either set of measured optical properties was observed. We believe that further optimization of our tissue-engineering methods is needed in order to make the histology and biochemistry of the cellular samples sufficiently different from the acellular samples on the microscopic level. Once these methods are optimized, we can better verify whether the optical properties of the cellular and acellular collagen samples differ.

  7. Development of DPD coarse-grained models: From bulk to interfacial properties

    Science.gov (United States)

    Solano Canchaya, José G.; Dequidt, Alain; Goujon, Florent; Malfreyt, Patrice

    2016-08-01

    A new Bayesian method was recently introduced for developing coarse-grain (CG) force fields for molecular dynamics. The CG models designed for dissipative particle dynamics (DPD) are optimized based on trajectory matching. Here we extend this method to improve transferability across thermodynamic conditions. We demonstrate the capability of the method by developing a CG model of n-pentane from constant-NPT atomistic simulations of bulk liquid phases and we apply the CG-DPD model to the calculation of the surface tension of the liquid-vapor interface over a large range of temperatures. The coexisting densities, vapor pressures, and surface tensions calculated with different CG and atomistic models are compared to experiments. Depending on the database used for the development of the potentials, it is possible to build a CG model which performs very well in the reproduction of the surface tension on the orthobaric curve.

  8. Relationships between soil moisture-holding properties and soil texture, organic matter content, and bulk density

    Science.gov (United States)

    Riley, H. C. F.

    1981-01-01

    Specimens from the surface horizon and the subsoil of 62 soil horizons in Hedmark and Oppland were investigated to study how the mechanical composition of the soil, the organic matter content and the bulk density affect their porosity and air capacity and their total and available water content. Most of the specimens belonged to the loam group, and a smaller number was from sandy and silty types of soil. Equations were established to make it possible to calculate the water retention curves and the amount of available water from the above mentioned parameters. As a rule, errors derived from the equations are no greater than those which are found in similar research in other countries.

  9. Raman Spectroscopy and Magnetic Properties of Mn-Doped ZnO Bulk Single Crystal

    Institute of Scientific and Technical Information of China (English)

    HE Qing-Bo; XU Jia-Yue; LI Xin-Hua; A.Kamzin; L.Kamzina

    2007-01-01

    Mn doped ZnO bulk single crystals are grown by the modified Bridgman method.The as-grown crystals are red in colour.The additional Raman mode observed at 524 cm-1 is attributed to the Mn ions incorporating into ZnO crystal.The crystal exhibited paramagnetic under lower applied fleld below 2280 Oe.Then diamagnetism is observed in the crystal when the magnetic field rises up and becomes dorainant under applied field above 5270 Oe.The magnetic susceptibility dependence on the temperature follows a Curie law indicating a typical paramagnetic characteristic under an applied field of 2kOe.No ferromagnetic ordering is observed in the as-grown Mn-doped ZnO crystal.

  10. Microstructure and mechanical properties of a novel Zr-based bulk metallic glass composite

    Institute of Scientific and Technical Information of China (English)

    SUN Yufeng; WANG Yuren; GUO Jian; WEI Bingchen; LI Weihuo

    2005-01-01

    Zr48.5Cu46.5Al5 bulk metallic glass (BMG) composites with diameters of 3 and 4 mm were prepared through suction casting in an arc melting furnace by modulating the alloy composition around the monothetic BMG composition of the high glass forming ability. Microstructural characterization reveals that the composites contain micron-sized CuZr phase with martensite structure, as well as nano-sized Zr2Cu crystalline particles and Cu10Zr7 plate-like phase embedded in an amorphous matrix. Room temperature compression tests showed that the composites exhibited significant strain hardening and obvious plastic strain of 7.7% for 3 mm and 6.4% for 4 mm diameter samples, respectively.

  11. Lanthanide upconversion luminescence at the nanoscale: fundamentals and optical properties.

    Science.gov (United States)

    Nadort, Annemarie; Zhao, Jiangbo; Goldys, Ewa M

    2016-07-01

    Upconversion photoluminescence is a nonlinear effect where multiple lower energy excitation photons produce higher energy emission photons. This fundamentally interesting process has many applications in biomedical imaging, light source and display technology, and solar energy harvesting. In this review we discuss the underlying physical principles and their modelling using rate equations. We discuss how the understanding of photophysical processes enabled a strategic influence over the optical properties of upconversion especially in rationally designed materials. We subsequently present an overview of recent experimental strategies to control and optimize the optical properties of upconversion nanoparticles, focussing on their emission spectral properties and brightness.

  12. Lanthanide upconversion luminescence at the nanoscale: fundamentals and optical properties

    Science.gov (United States)

    Nadort, Annemarie; Zhao, Jiangbo; Goldys, Ewa M.

    2016-07-01

    Upconversion photoluminescence is a nonlinear effect where multiple lower energy excitation photons produce higher energy emission photons. This fundamentally interesting process has many applications in biomedical imaging, light source and display technology, and solar energy harvesting. In this review we discuss the underlying physical principles and their modelling using rate equations. We discuss how the understanding of photophysical processes enabled a strategic influence over the optical properties of upconversion especially in rationally designed materials. We subsequently present an overview of recent experimental strategies to control and optimize the optical properties of upconversion nanoparticles, focussing on their emission spectral properties and brightness.

  13. Microstructure and mechanical properties of bulk highly faulted fcc/hcp nanostructured cobalt microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Barry, Aliou Hamady [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Laboratoire Chimie des Matériaux, Département de Chimie, Faculté des Sciences et Technique, Université de Nouakchott (Mauritania, Islamic Republic of); Dirras, Guy, E-mail: dirras@unv-paris13.fr [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Schoenstein, Frederic; Tétard, Florent; Jouini, Noureddine [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France)

    2014-05-01

    Nanostructured cobalt powders with an average particle size of 50 nm were synthesized using a polyol method and subsequently consolidated by spark plasma sintering (SPS). SPS experiments performed at 650 °C with sintering times ranging from 5 to 45 min under a pressure of 100 MPa, yielded to dense bulk nanostructured cobalt (relative density greater than 97%). X-ray diffraction patterns of the as-prepared powders showed only a face centered cubic (fcc) crystalline phase, whereas the consolidated samples exhibited a mixture of both fcc and hexagonal close packed (hcp) phases. Transmission electron microscopy observations revealed a lamellar substructure with a high density of nanotwins and stacking faults in every grain of the sintered samples. Room temperature compression tests, carried out at a strain rate of 10{sup −3} s{sup −1}, yielded to highest strain to fracture values of up to 5% for sample of holding time of 15 min, which exhibited a yield strength of 1440 MPa, an ultimate strength as high as 1740 MPa and a Young's modulus of 205 GPa. The modulus of elasticity obtained from the nanoindentation tests, ranges from 181 to 218 GPa. The lowest modulus value of 181 GPa was obtained for the sample with the highest sintering time (45 min), which could be related to mass density loss as a consequence of trapped gases releasing. - Highlights: • Co nanopowder (50 nm) was prepared by reduction in polyol medium. • SPS was used to process bulk nanostructured Co specimens. • Microstructures were made of intricate fcc/hcp, along with nanotwins and SFs. • High strengths and moderate compressive ductility were obtained. • Deformation mechanisms related to complex interplay of different length scales.

  14. Chemical and Physical Properties of Bulk Aerosols within Four Sectors Observed during TRACE-P

    Science.gov (United States)

    Jordan, C. E.; Anderson, B. E.; Talbot, R. W.; Dibb, J. E.; Fuelberg, E.; Hudgins, C. H.; Kiley, C. M.; Russo, R.; Scheuer, E.; Seid, G.

    2003-01-01

    Chemical and physical aerosol data collected on the DC-8 during TRACE-P were grouped into four sectors based on back trajectories. The four sectors represent long-range transport from the west (WSW), regional circulation over the western Pacific and Southeast Asia (SE Asia), polluted transport from Northern Asia with substantial sea salt at low altitudes (NNW) and a substantial amount of dust (Channel). WSW has generally low mixing ratios at both middle and high altitudes, with the bulk of the aerosol mass due to non-sea-salt water-soluble inorganic species. Low altitude SE Asia also has low mean mixing ratios in general, with the majority of the aerosol mass comprised of non-sea-salts, however, soot is also relatively important m this region. "w had the highest mean sea salt mixing ratios, with the aerosol mass at low altitudes (a km) evenly divided between sea salts, mm-sea-salts, and dust. The highest mean mixing ratios of water-soluble ions and soot were observed at the lowest altitudes (a km) in the Channel sector. The bulk of the aerosol mass exported from Asia emanates h m Channel at both low and midaltitudes, due to the prevalence of dust compared to other sectors. Number densities show enhanced fine particles for Channel and NNW, while their volume distributions are enhanced due to sea salt and dust Low-altitude Channel exhibits the highest condensation nuclei ((34) number densities along with enhanced scattering coefficients, compared to the other sectors. At midaltitudes (2-7 km), low mean CN number densities coupled with a high proportion of nonvolatile particles (265%) observed in polluted sectors (Channel and NNW) are attributed to wet scavenging which removes hygroscopic CN particles. Low single scatter albedo m SE Asia reflects enhanced soot

  15. Optical and electrical properties of glycine manganese chloride crystal

    Science.gov (United States)

    Venkatesan, G.; Kathiravan, V.; Pari, S.

    2017-06-01

    The organo-metal material of Glycine Manganese Chloride has been grown by solvent evaporation solution growth method. Single crystal XRD study has been carried out to confirm the grown crystal. FT-IR was recorded to identify the functional groups present in the crystal. The linear optical property of the grown crystal was analyzed by UV-Vis spectrum. Third order nonlinear optical properties was measured by Z-scan technique using Nd:YAG laser at 532 nm. Fluorescence emission revealed that can serve as a photo active material. Impedance and dielectric studies were also carried out for the material. Thermal property of the sample was analyzed by TG and DTA studies. The predicted NLO properties, UV-Vis absorbance and Z-scan studies indicate that the attractive material for optical applications.

  16. A method for estimating optical properties of dusty cloud

    Institute of Scientific and Technical Information of China (English)

    Tianhe Wang; Jianping Huang

    2009-01-01

    Based on the scattering properties of nonspherical dust aerosol,a new method is developed for retrieving dust aerosol optical depths of dusty clouds.The dusty clouds are defined as the hybrid system of dust plume and cloud.The new method is based on transmittance measurements from surface-based instruments multi-filter rotating shadowband radiometer(MFRSR)and cloud parameters from lidar measurements.It uses the difference of absorption between dust aerosols and water droplets for distinguishing and estimating the optical properties of dusts and clouds,respectively.This new retrieval method is not sensitive to the retrieval error of cloud properties and the maximum absolute deviations of dust aerosol and total optical depths for thin dusty cloud retrieval algorithm are only 0.056 and 0.1.respectively,for given possible uncertainties.The retrieval error for thick dusty cloud mainly depends on lidar-based total dusty cloud properties.

  17. First-Principles Calculations of Structural, Electronic and Optical Properties of Ternary Semiconductor Alloys ZAs x Sb1- x ( Z = B, Al, Ga, In)

    Science.gov (United States)

    Bounab, S.; Bentabet, A.; Bouhadda, Y.; Belgoumri, Gh.; Fenineche, N.

    2017-08-01

    We have investigated the structural and electronic properties of the BAs x Sb 1- x , AlAs x Sb 1- x , GaAs x Sb 1- x and InAs x Sb 1- x semiconductor alloys using first-principles calculations under the virtual crystal approximation within both the density functional perturbation theory and the pseudopotential approach. In addition the optical properties have been calculated by using empirical methods. The ground state properties such as lattice constants, both bulk modulus and derivative of bulk modulus, energy gap, refractive index and optical dielectric constant have been calculated and discussed. The obtained results are in reasonable agreement with numerous experimental and theoretical data. The compositional dependence of the lattice constant, bulk modulus, energy gap and effective mass of electrons for ternary alloys show deviations from Vegard's law where our results are in agreement with the available data in the literature.

  18. Optical properties of organic semiconductor thin films. Static spectra and real-time growth studies

    Energy Technology Data Exchange (ETDEWEB)

    Heinemeyer, Ute

    2009-07-20

    The aim of this work was to establish the anisotropic dielectric function of organic thin films on silicon covered with native oxide and to study their optical properties during film growth. While the work focuses mainly on the optical properties of Diindenoperylene (DIP) films, also the optical response of Pentacene (PEN) films during growth is studied for comparison. Spectroscopic ellipsometry and differential reflectance spectroscopy are used to determine the dielectric function of the films ex-situ and in-situ, i.e. in air and in ultrahigh vacuum. Additionally, Raman- and fluorescence spectroscopy is utilized to characterize the DIP films serving also as a basis for spatially resolved optical measurements beyond the diffraction limit. Furthermore, X-ray reflectometry and atomic force microscopy are used to determine important structural and morphological film properties. The absorption spectrum of DIP in solution serves as a monomer reference. The observed vibronic progression of the HOMO-LUMO transition allows the determination of the Huang-Rhys parameter experimentally, which is a measure of the electronic vibrational coupling. The corresponding breathing modes are measured by Raman spectroscopy. The optical properties of DIP films on native oxide show significant differences compared to the monomer spectrum due to intermolecular interactions. First of all, the thin film spectra are highly anisotropic due to the structural order of the films. Furthermore the Frenkel exciton transfer is studied and the energy difference between Frenkel and charge transfer excitons is determined. Real-time measurements reveal optical differences between interfacial or surface molecules and bulk molecules that play an important role for device applications. They are not only performed for DIP films but also for PEN films. While for DIP films on glass the appearance of a new mode is visible, the spectra of PEN show a pronounced energy red-shift during growth. It is shown how the

  19. Bulk and surface properties of demixing liquid Al-Sn and Sn-Tl alloys

    Science.gov (United States)

    Odusote, Y. A.; Popoola, A. I.; Oluyamo, S. S.

    2016-02-01

    The energetics of mixing in Al-Sn and Sn-Tl-segregating binary alloys has been explained through the study of surface properties (surface concentrations and surface tension) and various concentration-dependent thermodynamic (free energy of mixing, entropy of mixing and enthalpy of mixing) and transport (chemical diffusion) properties as well as the microscopic functions (concentration fluctuations in the long-wavelength limits and chemical short-range order parameter) using a statistical mechanical theory in conjunction with the self-association model (SAM). The theoretical property values obtained by the SAM were compared to the corresponding experimental values available in literature.

  20. Dominance of interface chemistry over the bulk properties in determining the electronic structure of epitaxial metal/perovskite oxide heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, Scott A.; Du, Yingge; Gu, Meng; Droubay, Timothy C.; Hepplestone, Steven; Sushko, Petr

    2015-06-09

    We show that despite very similar crystallographic properties and work function values in the bulk, epitaxial Fe and Cr metallizations on Nb:SrTiO3(001) generate completely different heterojunction electronic properties. Cr is Ohmic whereas Fe forms a Schottky barrier with a barrier height of 0.50 eV. This contrast arises because of differences in interface chemistry. In contrast to Cr [Chambers, S. A. et al., Adv. Mater. 2013, 25, 4001.], Fe exhibits a +2 oxidation state and occupies Ti sites in the perovskite lattice, resulting in negligible charge transfer to Ti, upward band bending, and Schottky barrier formation. The differences between Cr and Fe are understood by performing first-principles calculations of the energetics of defect formation which corroborate the observed interface chemistry and structure.

  1. Designing Optical Properties in DNA-Programmed Nanoparticle Superlattices

    Science.gov (United States)

    Ross, Michael Brendan

    A grand challenge of modern science has been the ability to predict and design the properties of new materials. This approach to the a priori design of materials presents a number of challenges including: predictable properties of the material building blocks, a programmable means for arranging such building blocks into well understood architectures, and robust models that can predict the properties of these new materials. In this dissertation, we present a series of studies that describe how optical properties in DNA-programmed nanoparticle superlattices can be predicted prior to their synthesis. The first chapter provides a history and introduction to the study of metal nanoparticle arrays. Chapter 2 surveys and compares several geometric models and electrodynamics simulations with the measured optical properties of DNA-nanoparticle superlattices. Chapter 3 describes silver nanoparticle superlattices (rather than gold) and identifies their promise as plasmonic metamaterials. In chapter 4, the concept of plasmonic metallurgy is introduced, whereby it is demonstrated that concepts from materials science and metallurgy can be applied to the optical properties of mixed metallic plasmonic materials, unveiling rich and tunable optical properties such as color and asymmetric reflectivity. Chapter 5 presents a comprehensive theoretical exploration of anisotropy (non-spherical) in nanoparticle superlattice architectures. The role of anisotropy is discussed both on the nanoscale, where several desirable metamaterial properties can be tuned from the ultraviolet to near-infrared, and on the mesoscale, where the size and shape of a superlattice is demonstrated to have a pronounced effect on the observed far-field optical properties. Chapter 6 builds upon those theoretical data presented in chapter 5, including the experimental realization of size and shape dependent properties in DNA-programmed superlattices. Specifically, nanoparticle spacing is explored as a parameter that

  2. Magneto-optical properties of paramagnetic superrotors

    CERN Document Server

    Milner, A A; Floß, J; Averbukh, I Sh; Milner, V

    2014-01-01

    We study the dynamics of paramagnetic molecular superrotors in an external magnetic field. Optical centrifuge is used to create dense ensembles of oxygen molecules in ultra-high rotational states. In the presence of magnetic field, the gas of centrifuged molecules becomes optically birefringent, which indicates preferential alignment of molecular axes along the field direction. The experimental observations are supported by numerical calculations and explained by means of an intuitive qualitative model, in which the effect of the applied magnetic field on the distribution of molecular axes is mediated by the spin-rotation coupling. We show that the induced magneto-rotational birefringence is more robust with respect to collisions than the rotational coherence, and that this robustness increases with increasing angular momentum.

  3. Effects of varying surfactant chain lengths on the magnetic, optical and hyperthermia properties of ferrofluids

    Science.gov (United States)

    Rablau, Corneliu; Vaishnava, Prem; Regmi, Rajesh; Sudakar, Chandran; Black, Correy; Lawes, Gavin; Naik, Ratna; Lavoie, Melissa; Kahn, David

    2009-03-01

    We report studies of the structural, magnetic, magneto-thermal and magneto-optic properties of dextran, oleic acid, lauric acid and myristic acid surfacted Fe3O4 nanoparticles of hydrodynamic sizes ranging from 32 nm to 92 nm. All the samples showed saturation magnetization of ˜50 emu/g, significantly smaller than the bulk value for Fe3O4, together with superparamagnetic behavior. The ac magnetization measurements on the dextran coated nanoparticles showed frequency dependent blocking temperature, consistent with superparamgnetic blocking. The ferrofluid heating rates in a 250 Gauss, 100 kHz ac magnetic field varied with the chain lengths of the surfactants, with higher heating rates for longer chains. DC-magnetic-field-induced light scattering patterns produced by two orthogonal He-Ne laser beams passing through the ferrofluid sample revealed different optical signatures for different surfactants.

  4. Structure and optical properties of the Ge and Sn quantum-dots

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Embedded cluster samples Ge:CaF2 and Sn:CaF2 with different sizes less than 8nm were produced and their optical properties were examined. Electron diffraction reveals that the clusters' structures are crystallites and compared with the bulk Germanium and Stannum, lattice constants expand about 4.7% in the case of Ge:CaF2 and 5.2% of Sn:CaF2. Optical absorption and photoluminescence spectra of these samples show good agreement with the Quantum-Confinement-Effect(QCE) theory. With the decreasing of the cluster's size, the energy gap broadens and the absorption edge blueshift is observed, and the absorption edge also shifts with the changing of the fraction of Sn and Ge. The XPS results show that in the cluster state, the binding energy becomes higher.

  5. High pressure studies on nanometer sized clusters: Structural, optical, and cooperative properties

    Energy Technology Data Exchange (ETDEWEB)

    Tolbert, S.H.

    1995-05-01

    High-pressure Se EXAFS is used to study pressure-induced structural transformations in CdSe nanocrystals. The transformation is wurtzite to rock salt, at a pressure much higher than in bulk. High-pressure XRD is used to confirm the EXAFS results. Diffraction peak widths indicate that nanocrystals do not fragment upon transformation. Optical absorption correlates with structural transformations and is used to measure transition pressures; transformation pressure increases smoothly as nanocrystal size decreases. Thermodynamics of transformation is modeled using an elevated surface energy in the high-pressure phase. High-pressure study of Si nanocrystals show large increases in transformation pressure in crystallites to 500{angstrom} diameter, and an overall change in crystallite shape upon transformation is seen from XRD line widths. C{sub 60} single crystals were studied using Raman scattering; results provide information about the clusters` rotational state. Optical properties of high-pressure phase CdSe clusters were studied.

  6. Computational Approach for Studying Optical Properties of DNA Systems in Solution

    DEFF Research Database (Denmark)

    Nørby, Morten Steen; Svendsen, Casper Steinmann; Olsen, Jógvan Magnus Haugaard

    2016-01-01

    In this paper we present a study of the methodological aspects regarding calculations of optical properties for DNA systems in solution. Our computational approach will be built upon a fully polarizable QM/MM/Continuum model within a damped linear response theory framework. In this approach...... the environment is given a highly advanced description in terms of the electrostatic potential through the polarizable embedding model. Furthermore, bulk solvent effects are included in an efficient manner through a conductor-like screening model. With the aim of reducing the computational cost we develop a set...... of averaged partial charges and distributed isotropic dipole-dipole polarizabilities for DNA suitable for describing the classical region in ground-state and excited-state calculations. Calculations of the UV-spectrum of the 2-aminopurine optical probe embedded in a DNA double helical structure are presented...

  7. Fundamental Stellar Properties from Optical Interferometry

    CERN Document Server

    van Belle, Gerard T; Boyajian, Tabetha; Harper, Graham; Hummel, Christian; Pedretti, Ettore; Baines, Ellyn; White, Russel; Ravi, Vikram; Ridgway, Steve

    2010-01-01

    High-resolution observations by visible and near-infrared interferometers of both single stars and binaries have made significant contributions to the foundations that underpin many aspects of our knowledge of stellar structure and evolution for cool stars. The CS16 splinter on this topic reviewed contributions of optical interferometry to date, examined highlights of current research, and identified areas for contributions with new observational constraints in the near future.

  8. The optical, vibrational, structural and elasto-optic properties of Zn0.25Cd0.75SySe1-y quaternary alloys

    Science.gov (United States)

    Paliwal, U.; Swarkar, C. B.; Sharma, M. D.; Joshi, K. B.

    2016-05-01

    The optical, vibrational, structural and elasto-optic properties of quaternary II-VI alloys Zn0.25Cd0.75S0.25Se0.75, Zn0.25Cd0.75S0.50Se0.50 and Zn0.25Cd0.75S0.75Se0.25 are presented. Within the empirical pseudopotential method (EPM) the disorder effects are modeled via modified virtual crystal approximation (MVCA). The computed bandgaps and the refined form factors are utilized to evaluate optical, vibrational, structural and elasto-optic properties. The refractive index (n), static (ɛ0) and high frequency dielectric (ɛ∞) constants are calculated to reveal optical behavior of alloys. The longitudinal ωLO(0) and transverse ωTO(0) optical frequencies are obtained to see vibrational characteristics. Moreover, the elastic constants (cij) and bulk moduli (B) are computed by combining the EPM with Harrison bond orbital model. The elasto-optic nature of alloys is examined by computing the photo-elastic constants. These values are significant with regard to the opto-electronic applications especially when no experimental data are available on this system.

  9. Valence-EELS analysis of local electronic and optical properties of PMN-PT epitaxial film

    Energy Technology Data Exchange (ETDEWEB)

    Kiguchi, Takanori [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)], E-mail: tkiguchi@imr.tohoku.ac.jp; Wakiya, Naoki [Department of Materials Science, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561 (Japan); Shinozaki, Kazuo [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Konno, Toyohiko J. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2009-04-15

    This study investigated local electrical and optical properties of Pb(Mg{sub 0.39}Nb{sub 0.61})-0.34 mol%PbTiO{sub 3} solid solution (PMN-PT) film stacked on Si (0 0 1) wafer with (La,Sr)CoO{sub 3-x}/CeO{sub 2}/YSZ buffer layers. TEM-VEELS analysis of the PMN-PT thin film, which was grown epitaxially on the Si substrate with two coexisting phases of pseudocubic and tetragonal morphology, was firstly conducted using the TEM-VEELS method. The ELF has shown a bulk plasmon peak and two interband plasmon peaks. The interband transition has been interpreted in comparison with the joint density of state obtained from the measured dielectric function and the density of state calculated by the density functional theory. The interband transition from the O 2p band to Nb 4d/Ti 3d bands determines the optical properties around the band gap. The optical absorption of PMN-PT film has shown the band gap of 3.5 {+-} 0.2 V. The refractive index derived from the TEM-VEELS analysis in the nano-region of the film has agreed with that obtained with the conventional optical measurement from the macroscopic region.

  10. Optical Properties of Magnetron sputtered Nickel Thin Films

    Science.gov (United States)

    Twagirayezu, Fidele; Geerts, Wilhelmus J.; Cui, Yubo

    2015-03-01

    The study of optical properties of Nickel (Ni) is important, given the pivotal role it plays in the semiconductor and nano-electronics technology. Ni films were made by DC and RF magnetron sputtering in an ATC Orion sputtering system of AJA on various substrates. The optical properties were studied ex situ by variable angle spectroscopic (220-1000 nm) ellipsometry at room temperature. The data were modeled and analyzed using the Woollam CompleteEase Software fitting ellipsometric and transmission data. Films sputtered at low pressure have optical properties similar to that of Palik. Films sputtered at higher pressure however have a lower refraction index and extinction coefficient. It is expected from our results that the density of the sputtered films can be determined from the ellipsometric quantities. Our experiments also revealed that Ni is susceptible to a slow oxidation changing its optical properties over the course of several weeks. The optical properties of the native oxide differ from those of reactive sputtered NiO similar as found by. Furthermore the oxidation process of our samples is characterized by at least two different time constants.

  11. Controlling the coexistence of structural phases and the optical properties of gallium nanoparticles with optical excitation

    Science.gov (United States)

    MacDonald, K. F.; Fedotov, V. A.; Pochon, S.; Stevens, G.; Kusmartsev, F. V.; Emel'yanov, V. I.; Zheludev, N. I.

    2004-08-01

    We have observed reversible structural transformations, induced by optical excitation at 1.55 μm, between the β, γ and liquid phases of gallium in self-assembled gallium nanoparticles, with a narrow size distribution around 50 nm, on the tip of an optical fiber. Only a few tens of nanowatts of optical excitation per particle are required to control the transformations, which take the form of a dynamic phase coexistence and are accompanied by substantial changes in the optical properties of the nanoparticle film. The time needed to achieve phase equilibrium is in the microsecond range, and increases sharply near the transition temperatures.

  12. Optical and Electrical Properties of Nanostructured Metallic Electrical Contacts

    CERN Document Server

    Toranzos, Victor J; Mochán, W Luis; Zerbino, Jorge O

    2016-01-01

    We study the optical and electrical properties of silver films with a graded thickness obtained through metallic evaporation in vacuum on a tilted substrate to evaluate their use as semitransparent electrical contacts. We measure their ellipsometric coefficients, optical transmissions and electrical conductivity for different widths, and we employ an efficient recursive method to calculate their macroscopic dielectric function, their optical properties and their microscopic electric fields. The topology of very thin films corresponds to disconnected islands, while very wide films are simply connected. For intermediate widths the film becomes semicontinuous, multiply connected, and its microscopic electric field develops hotspots at optical resonances which appear near the percolation threshold of the conducting phase, yielding large ohmic losses that increase the absorptance above that of a corresponding homogeneous film. Optimizing the thickness of the film to maximize its transmittance above the percolation...

  13. Thermoelectric Properties of Mg2Si1-xSnx Synthesized by Bulk Mechanical Alloying

    Institute of Scientific and Technical Information of China (English)

    SONG Ren-bo; LIU Ya-zheng; Tatsuhiko AIZAWA

    2006-01-01

    Bulk mechanical alloying (BMA) has been successfully applied to solid-state synthesis of p-type and n-type thermoelectric materials Mg2Si1-xSnx (x = 0, 0.2, 0.4, 0.6, 0.8, 1) from element-powders at the room temperature in a relatively short time. The electrical conductivity, the Seebeck coefficient and the thermal conductivity of the Mg2Si1-xSnx are quite sensitive to the x-content. With the x-content rising, the electrical conductivity increases. When x = 0.6, it reaches the lowest and Mg2Si shows an n-type of semi-conducting. However, when x = 0.2 and T>525 K, the Seebeck coefficient of the samples will change the opposite way. While x≥0.4, the samples present a p-type of semi-conducting. The figure of merit, Z of Mg2Si1-xSnx will be obtained in the range from 300 K to 700 K. When x = 0.6, Z proves to be higher than that of other samples at 300 K≤T≤650 K.

  14. Preparation and Properties of Mg-Cu-Y-Al bulk Amorphous Alloys

    DEFF Research Database (Denmark)

    Pryds, Nini; Eldrup, Morten Mostgaard; Ohnuma, M.

    2000-01-01

    measurements to be 60-150 K/s, in agreement with estimates from the literature. The Vickers hardness (Hv) of the amorphous material for y = 2% is higher (similar to 360 kg/mm(2)) than for y = 0 (similar to 290 kg/mm(2)). On crystallisation the hardness of the latter material increases to the 400 kg/mm(2) level......Bulk amorphous (Mg(1-gamma)Al(gamma))(60)CU(30)Y(10) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs, time was recorded during the cooling and solidification process of the melt and compared with a spacial...... and temporal numerical simulation of that process. It is concluded that good thermal contact is maintained between the amorphous part of the solidified sample and the mould, while a rather poor contact develops between the crystalline part of the sample and the mould, probably due to the appearance of a narrow...

  15. Mechanical properties of high dense coal fly-ash bulk materials by plasma spark sintering (SPS)

    Energy Technology Data Exchange (ETDEWEB)

    Kaneko, G.; Hasezaki, K.; Nakashita, A.; Kakuda, H. [Shimane University, Shimane (Japan). Dept. of Material Science

    2008-10-15

    Coal fly-ash bulk materials were prepared by spark plasma sintering (SPS). The as-received coal fly ash produced by Misumi Power Station (The Chugoku Electric Power Co. Inc.), had an average particle size of 19 mm and contained about 2% carbon from unburned coal. The sintering temperature was 1273 K for 10 min. The mass density of the sintered compact was 2.4 x 103 kg/m{sup 3}. After three-point flexural testing of the compact, the average flexural strength and Young's modulus were 25.6 MPa and 23.0 GPa, respectively. From the flexural strength, the Weibull modulus was found to be m = 6.13, indicating that the compact was a typical ceramics. Fractographic examination indicated that in all specimens the fracture origin was located on the bottom surface and was not an intrinsic flaw. Vickers indentation test showed that the fracture toughness was 0.61 MPa.m{sup 0.5} and the calculated critical flaw size c{sub 0}, was 0.18 mm. This c{sub 0} value was larger than that of the voids and the unburned carbon at the fracture surface. It is noteworthy that the mechanical strength of the sintered compact was not affected by the voids and unburned carbon.

  16. Mechanical Properties, Damage and Fracture Mechanisms of Bulk Metallic Glass Materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The deformation, damage, fracture, plasticity and melting phenomenon induced by shear fracture were investigated and summarized for Zr-, Cu-, Ti- and Mg-based bulk metallic glasses (BMGs) and their composites. The shear fracture angles of these BMG materials often display obvious differences under compression and tension,and follow either the Mohr-Coulomb criterion or the unified tensile fracture criterion. The compressive plasticity of the composites is always higher than the tensile plasticity, leading to a significant inconsistency. The enhanced plasticity of BMG composites containing ductile dendrites compared to monolithic glasses strongly depends on the details of the microstructure of the composites. A deformation and damage mechanism of pseudo-plasticity, related to local cracking, is proposed to explain the inconsistency of plastic deformation under tension and compression. Besides, significant melting on the shear fracture surfaces was observed. It is suggested that melting is a common phenomenon in these materials with high strength and high elastic energy, as it is typical for BMGs and their composites failing under shear fracture. The melting mechanism can be explained by a combined effect of a significant temperature rise in the shear bands and the instantaneous release of the large amount of elastic energy stored in the material.

  17. STUDY ON THE POLING PROPERTIES OF NONLINEAR OPTICAL ACTIVE DERIVATIVE OF POLY (p-HYDROXYSTYRENE):(PS)O-DCV

    Institute of Scientific and Technical Information of China (English)

    YE Cheng; WANG Jiafu; FENG Zhiming

    1993-01-01

    In this paper,the poling properties of (PS)O-DCV,a derivative of poly (p-hydroxystyrene),was reported.The investigations showed that the thermochromism correction,which was neglected in the literatures,should be considered in the measurements of order parameter of poled films with electrochromism technique Here,another linear optical method,IR and polarized IR spectra for characterizing of poled films was suggested first time.The bulk second nonlinear optical coefficient d33 of poled films could be estimated by measured order parameter semi-qualitatively.

  18. Electrodeposited CdTe{emdash}optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Rakhshani, A.E. [Physics Department, Kuwait University, PO Box 5969, Safat 13060 (Kuwait)

    1997-06-01

    For the measurement of optical constants, the electrodeposited films of CdTe were lifted off their opaque substrates and transferred onto glass slides using a transparent liquid adhesive. This technique proved to give results more reliable than those obtained on samples in which CdTe is deposited on CdS-coated conducting glass. The measured optical dispersion in the photon energy range of E{lt}1.5eV is in excellent agreement with that for the single crystal. The optical absorption coefficient was determined in the E{lt}3.5eV range and was compared with that for the single crystal. The results revealed two direct allowed transitions at 1.50 eV [{Gamma}{sub 8}valenceband(VB){r_arrow}{Gamma}{sub 6}conductionband(CB)] and 2.43 eV [{Gamma}{sub 7}(VB){r_arrow}{Gamma}{sub 6}(CB)] and three indirect allowed transitions at 1.27 eV [L{sub 4,5}(VB){r_arrow}{Gamma}{sub d}], 1.83 eV [L{sub 6}(VB){r_arrow}{Gamma}{sub d}], and 2.84 eV [{Gamma}{sub 8}(VB){r_arrow}L{sub 6}(CB)]. The 1.27 and the 1.83 eV transitions, which have not been reported previously and were not detected in single-crystal data, are attributed to the transitions to a grain-boundary-related defect energy band {Gamma}{sub d}, 0.65 eV above {Gamma}{sub 8} (VB). The indirect transitions at 1.83 and 2.84 eV are assisted by phonons having energies of 80 and 84 meV, respectively. {copyright} {ital 1997 American Institute of Physics.}

  19. Electrodeposited CdTe—optical properties

    Science.gov (United States)

    Rakhshani, A. E.

    1997-06-01

    For the measurement of optical constants, the electrodeposited films of CdTe were lifted off their opaque substrates and transferred onto glass slides using a transparent liquid adhesive. This technique proved to give results more reliable than those obtained on samples in which CdTe is deposited on CdS-coated conducting glass. The measured optical dispersion in the photon energy range of E<1.5 eV is in excellent agreement with that for the single crystal. The optical absorption coefficient was determined in the E<3.5 eV range and was compared with that for the single crystal. The results revealed two direct allowed transitions at 1.50 eV [Γ8 valence band(VB)→Γ6 conduction band(CB)] and 2.43 eV [Γ7(VB)→Γ6(CB)] and three indirect allowed transitions at 1.27 eV [L4,5(VB)→Γd], 1.83 eV [L6(VB)→Γd], and 2.84 eV [Γ8(VB)→L6(CB)]. The 1.27 and the 1.83 eV transitions, which have not been reported previously and were not detected in single-crystal data, are attributed to the transitions to a grain-boundary-related defect energy band Γd, 0.65 eV above Γ8 (VB). The indirect transitions at 1.83 and 2.84 eV are assisted by phonons having energies of 80 and 84 meV, respectively.

  20. Numerical evaluation of bulk material properties of dental composites using two-phase finite element models.

    Science.gov (United States)

    Li, Jianying; Li, Haiyan; Fok, Alex S L; Watts, David C

    2012-09-01

    The aim of this study was to numerically evaluate the effects of filler contents and resin properties on the material properties of dental composites utilizing realistic 3D micromechanical finite element models. 3D micromechanical finite element models of dental composites containing irregular fillers with non-uniform sizes were created based on a large-scale, surrogate mixture fabricated from irregularly shaped stones and casting resin. The surrogate mixture was first scanned with a micro-CT scanner, and the images reassembled to produce a 3D finite element model. Different filler fractions were achieved by adjusting the matrix volume while keeping the fillers unchanged. Polymerization shrinkage, Young's modulus, Poisson's ratio and viscosity of the model composites were predicted using the finite element models, and their dependence on the filler fraction and material properties of the resin matrix were considered. Comparison of the numerical predictions with available experimental data and analytical models from the literature was performed. Increased filler fraction resulted in lower material shrinkage, higher Young's modulus, lower Poisson's ratio and higher viscosity in the composite. Predicted shrinkage and Young's modulus agreed well with the experimental data and analytical predictions. The McGee-McCullough model best fit the shrinkage and Young's modulus predicted by the finite element method. However, a new parameter, used as the exponent of the filler fraction, had to be introduced to the McGee-McCullough model to better match the predicted viscosity and Poisson's ratio with those from the finite element analysis. Realistic micro-structural finite element models were successfully applied to study the effects of filler fraction and matrix properties on a wide range of mechanical properties of dental composites with irregular fillers. The results can be used to direct the design of such materials to achieve the desired mechanical properties. Published by

  1. Optical Properties of Bismuth Tellurite Based Glass

    Directory of Open Access Journals (Sweden)

    Hooi Ming Oo

    2012-04-01

    Full Text Available A series of binary tellurite based glasses (Bi2O3x (TeO2100−x was prepared by melt quenching method. The density, molar volume and refractive index increase when bismuth ions Bi3+ increase, this is due to the increased polarization of the ions Bi3+ and the enhanced formation of non-bridging oxygen (NBO. The Fourier transform infrared spectroscopy (FTIR results show the bonding of the glass sample and the optical band gap, Eopt decreases while the refractive index increases when the ion Bi3+ content increases.

  2. Optical properties of bismuth tellurite based glass.

    Science.gov (United States)

    Oo, Hooi Ming; Mohamed-Kamari, Halimah; Wan-Yusoff, Wan Mohd Daud

    2012-01-01

    A series of binary tellurite based glasses (Bi(2)O(3))(x) (TeO(2))(100-) (x) was prepared by melt quenching method. The density, molar volume and refractive index increase when bismuth ions Bi(3+) increase, this is due to the increased polarization of the ions Bi(3+) and the enhanced formation of non-bridging oxygen (NBO). The Fourier transform infrared spectroscopy (FTIR) results show the bonding of the glass sample and the optical band gap, E(opt) decreases while the refractive index increases when the ion Bi(3+) content increases.

  3. Structural Stability and Optical Properties of Nanomaterials with Reconstructed Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Puzder, A; Williamson, A; Reboredo, F; Galli, G

    2003-10-24

    The authors present density functional and quantum Monte Carlo calculations of the stability and optical properties of semiconductor nanomaterials with reconstructed surfaces. they predict the relative stability of silicon nanostructures with reconstructed and unreconstructed surfaces, and show that surface step geometries unique to highly curved surfaces dramatically reduce the optical gaps and decrease excitonic lifetimes. These predictions provide an explanation of both the variations in the photoluminescence spectra of colloidally synthesized nanoparticles and observed deep gap levels in porous silicon.

  4. Nonlinear Optical Properties and Femtosecond Laser Micromachining of Special Glasses

    OpenAIRE

    Almeida,Juliana M. P.; Gustavo F. B. Almeida; Boni, Leonardo De; Cleber R. Mendonça

    2015-01-01

    Materials specially designed for photonics have been at the vanguard of chemistry, physics and materials science, driven by the development of new technologies. One particular class of materials investigated in this context are glasses, that in principle should exhibit high third order optical nonlinearities and fast response time, whose optical properties can be tailored by compositional changes, such as, for instance, the incorporation of metallic nanoparticles to explore plasmon resonances...

  5. Thin Film Solar Cells and their Optical Properties

    Directory of Open Access Journals (Sweden)

    Stanislav Jurecka

    2006-01-01

    Full Text Available In this work we report on the optical parameters of the semiconductor thin film for solar cell applications determination. The method is based on the dynamical modeling of the spectral reflectance function combined with the stochastic optimization of the initial reflectance model estimation. The spectral dependency of the thin film optical parameters computations is based on the optical transitions modeling. The combination of the dynamical modeling and the stochastic optimization of the initial theoretical model estimation enable comfortable analysis of the spectral dependencies of the optical parameters and incorporation of the microstructure effects on the solar cell properties. The results of the optical parameters ofthe i-a-Si thin film determination are presented.

  6. Optical properties of lead–bismuth cuprous glasses

    Indian Academy of Sciences (India)

    P T Deshmukh; D K Burghate; V S Deogaonkar; S P Yawale; S V Pakade

    2003-10-01

    The optical transmission and absorption spectra in UV–VIS were recorded in the wavelength range 350–800 nm for different glass compositions in the system (CuO)(PbO)50–(Bi2O3)50 ( = 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 20.0). Absorption coefficient (), optical energy gap (opt), refractive index (D), optical dielectric constant ($\\varepsilon_{\\infty}^{′}$), measure of extent of band tailing ( ), constant () and ratio of carrier concentration to the effective mass (/*) have been reported. The effects of compositions of glasses on these parameters have been discussed. It has been indicated that a small compositional modification of the glasses lead to an important change in all the optical properties including non-linear behaviour. The optical parameters were found to be almost the same for different glasses in the same family.

  7. An investigation of aerosol optical properties: Atmospheric implications and influences

    Science.gov (United States)

    Penaloza-Murillo, Marcos A.

    An experimental, observational, and theoretical investigation of aerosol optical properties has been made in this work to study their implications and influences on the atmosphere. In the laboratory the scientific and instrumental methodology consisted of three parts, namely, aerosol generation, optical and mass concentration measurements, and computational calculations. In particular the optical properties of ammonium sulfate and caffeine aerosol were derived from measurements made with a transmissometer cell-reciprocal- integrating nephelometer (TCRIN), equipped with a laser beam at 632.8 nm, and by applying a Mie theory computer code The aerosol generators, optical equipment and calibration procedures were reviewed. The aerosol shape and size distribution were studied by means of scanning electron microscopy and the Gumprecht- Sliepcevich/Lipofsky-Green extinction-sedimentation method. In particular the spherical and cylindrical shape were considered. During this investigation, an alternative method for obtaining the optical properties of monodisperse spherical non-absorbing aerosol using a cell-transmissometer, which is based on a linearisation of the Lambert-Beer law, was found. In addition, adapting the TCRIN to electrooptical aerosol studies, the optical properties of a circular-cylindrical aerosol of caffeine were undertaken under the condition of random orientation in relation with the laser beam, and perpendicular orientation to it. A theoretical study was conducted to assess the sensitivity of aerosol to a change of shape under different polarisation modes. The aerosol optical properties, obtained previously in the laboratory, were then used to simulate the direct radiative forcing. The calculations and results were obtained by applying a one- dimensional energy-balance box model. The influence of atmospheric aerosol on the sky brightness due to a total solar eclipse was studied using the photometric and meteorological observations made during the

  8. Structure property relationships for the nonlinear optical response of fullerenes

    Science.gov (United States)

    Rustagi, Kailash C.; Ramaniah, Lavanya M.; Nair, Selvakumar V.

    1994-11-01

    We present a phenomenological theory of nonlinear optical response of fullerenes. An empirical tight-binding model is used in conjunction with a classical electromagnetic picture for the screening. Since in bulk media such a picture of screening corresponds to the self- consistent field approach, the only additional approximation involved in our approach is the neglect of nonlocality. We obtain reliable estimates for the linear and nonlinear susceptibilities of C60, C70, C76 and other pure carbon fullerenes and also substituted fullerenes. The relatively large values of (beta) that we obtain for C76 and substituted fullerenes appear promising for the development of fullerene-based nonlinear optical materials. Our phenomenological picture of screening provides a good understanding of the linear absorption spectra of higher fullerenes and predicts that a comparison of the one-photon and multi-photon spectra will provide an insight into screening effects in these systems.

  9. Online single particle measurements of black carbon coatings, structure and optical properties

    Science.gov (United States)

    Allan, James; Liu, Dantong; Taylor, Jonathan; Flynn, Michael; Williams, Paul; Morgan, William; Whitehead, James; Alfarra, Rami; McFiggans, Gordon; Coe, Hugh

    2016-04-01

    The impacts of black carbon on meteorology and climate remain a major source of uncertainty, owing in part to the complex relationship between the bulk composition of the particulates and their optical properties. A particular complication stems from how light interacts with particles in response to the microphysical configuration and any 'coatings', i.e. non-black carbon material that is either co-emitted or subsequently obtained through atmospheric processing. This may cause the particle to more efficiently absorb or scatter light and may even change the sign of its radiative forcing potential. While much insight has been gained through measurements of bulk aerosol properties, either while suspended or after collection on a filter or impactor substrate, this does not provide a complete picture and thus may not adequately constrain the system. Here we present an overview of recent work to better constrain the properties of black carbon using online, in situ measurements of single particles, primarily using a Single Particle Soot Photometer (SP2). We have developed novel methods of inverting the data produced and combining the different metrics derived so as to give the most effective insights into black carbon sources, processes and properties. We have also used this measurement in conjunction with other instruments (sometimes in series) and used the data to challenge many commonly used models of optical properties such as core-shell Mie, Rayleigh-Debeye-Gans and effective medium. This work has been carried out in a variety of atmospheric environments and with laboratory-produced soots, e.g. from a diesel engine rig. Highlights include the finding that with real-world atmospheric aerosols, bulk optical measurements may be insufficient to derive brown carbon parameters without detailed morphological data. We also show that the enhancement of absorption for both ambient and laboratory generated particles only occurs after the coating mass fraction reaches a certain

  10. Using electron microscopy to calculate optical properties of biological samples.

    Science.gov (United States)

    Wu, Wenli; Radosevich, Andrew J; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K; Szleifer, Igal; Backman, Vadim

    2016-11-01

    The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy factor g, the phase function and the shape factor D of the nuclei are calculated. The results show strong agreement with an independent study. This method provides a new way to extract the true phase function of biological samples and provides an independent validation for optical property measurement techniques.

  11. Origin of Interplanetary Dust through Optical Properties of Zodiacal Light

    CERN Document Server

    Yang, Hongu

    2015-01-01

    This study investigates the origin of interplanetary dust particles (IDPs) through the optical properties, albedo and spectral gradient, of zodiacal light. The optical properties were compared with those of potential parent bodies in the solar system, which include D-type (as analogue of cometary nuclei), C-type, S-type, X-type, and B-type asteroids. We applied Bayesian inference on the mixture model made from the distribution of these sources, and found that >90% of the interplanetary dust particles originate from comets (or its spectral analogues, D-type asteroids). Although some classes of asteroids (C-type and X-type) may make a moderate contribution, ordinary chondrite-like particles from S-type asteroids occupy a negligible fraction of the interplanetary dust cloud complex. The overall optical properties of the zodiacal light were similar to those of chondritic porous IDPs, supporting the dominance of cometary particles in zodiacal cloud.

  12. Determination of optical properties by variation of boundary conditions

    Science.gov (United States)

    Nickell, Stephan; Essenpreis, Matthias; Kraemer, U.; Kohl-Bareis, Matthias; Boecker, Dirk

    1998-01-01

    Propagation of photons in multiple scattering media depends on absorbing and scattering properties as well as the boundary conditions of the semi-infinite medium. A new method is shown that makes use of differences in boundary conditions to determine the optical properties. Induced are these different conditions by varying the reflectivity of a sensor head. We describe the influence of the change in reflectivity with the common diffusion theory. By building a ratio between the spatially-resolved diffuse reflectance under different boundary conditions it is possible to calculate the optical properties of homogeneous phantoms. Due to optical heterogeneities in living tissue, limitations of the method was observed, which restricts the application to in vivo measurements.

  13. Measuring the optical properties of IceCube drill holes

    Directory of Open Access Journals (Sweden)

    Rongen Martin

    2016-01-01

    Full Text Available The IceCube Neutrino Observatory consists of 5160 digital optical modules (DOMs in a cubic kilometer of deep ice below the South Pole. The DOMs record the Cherenkov light from charged particles interacting in the ice. A good understanding of the optical properties of the ice is crucial to the quality of the event reconstruction. While the optical properties of the undisturbed ice are well understood, the properties of the refrozen drill holes still pose a challenge. A new data-acquisition and analysis approach using light originating from LEDs within one DOM detected by the photomultiplier of the same DOM will be described. This method allows us to explore the scattering length in the immediate vicinity of the considered DOMs.

  14. Photoconductive and nonlinear optical properties of composites based on metallophthalocyanines

    Science.gov (United States)

    Vannikov, A. V.; Grishina, A. D.; Gorbunova, Yu. G.; Tsivadze, A. Yu.

    2015-08-01

    The photoconductive, photorefractive and nonlinear optical properties of composites from polyvinylcarbazole or aromatic polyimide containing supramolecular ensembles of (tetra-15-crown-5) - phthalocyaninato gallium, indium, - phthalocyaninateacetato yttrium, - phthalocyaninato ruthenium with axially coordinated pyrazine molecules were investigated at 633, 1030 and 1064nmusing continuous and pulsed lasers. Supramolecular ensembles (SE) were prepared through dissolution of molecular metallophthalocyanines in tetrachloroethane (TCE) and subsequent treatment via three cycles of heating to 90∘C and slow cooling to room temperature. The zscan method in femtosecond and nanosecond regimeswas used for measuring nonlinear optical properties phthalocyaninato indium and yttrium in TCE solutions and polymer films. It was established that effect of heavy metallic atom is basic factor which determines the quantum yield, photorefractive amplification of laser object beam, dielectric susceptibility of third order and nonlinear optical properties of metallophthalocyanines.

  15. Dependence of optical properties of calcium bismuthates on synthesis conditions

    Science.gov (United States)

    Shtarev, D. S.; Shtareva, A. V.

    2016-08-01

    The article studies optical properties of calcium bismuthate nanoparticles of different composition. For the first time the synthesis of these compounds was produced by the pyrolysis of organic precursors using an organic solvent. Characterization of particles was made by scanning electron microscopy and X-ray analysis. The optical properties were investigated by diffuse reflectance spectroscopy (DRS). It is shown that the type of crystal lattice of the particles of calcium bismuthate determines the possibility to control the optical properties of nanoparticles by varying their composition. The conclusions about the production process and the composition of calcium bismuthate, the most promising for use as a photocatalyst of visible light and solar cells, were made.

  16. Comparing optical properties of different species of diatoms

    DEFF Research Database (Denmark)

    Maibohm, Christian; Friis, Søren Michael Mørk; Su, Y.;

    2015-01-01

    species dependent with huge variety in size, shape, and micro- structure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with commo n traits, effects and differences between the different...... frustules. We have observed, when incident light interacts w ith the micro-structured frustule it is multiple diffracted giving rise to wavelength dependent multiple focal points and other optical effects. Experimental results have been simulated and well confirmed by free space FFT propagation routine...... analysis software. The software uses parameters which are extracted from experimental im ages as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule...

  17. Preparation and optical and electrical evaluation of bulk SiO{sub 2} sonogel hybrid composites and vacuum thermal evaporated thin films prepared from molecular materials derived from (Fe, Co) metallic phthalocyanines and 1,8 dihydroxiantraquinone compounds

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Vergara, Maria Elena [Coordinacion de Ingenieria Mecatronica, Facultad de Ingenieria, Universidad Anahuac Mexico Norte. Avenida Universidad Anahuac 46, Col. Lomas Anahuac, 52786 Huixquilucan, Estado de Mexico (Mexico); Morales-Saavedra, Omar G. [Universidad Nacional Autonoma de Mexico, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, CCADET-UNAM, A.P. 70-186, Coyoacan, 04510 Mexico, D.F. (Mexico)], E-mail: omar.morales@ccadet.unam.mx; Ontiveros-Barrera, Fernando G.; Torres-Zuniga, Vicente; Ortega-Martinez, Roberto [Universidad Nacional Autonoma de Mexico, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, CCADET-UNAM, A.P. 70-186, Coyoacan, 04510 Mexico, D.F. (Mexico); Ortiz Rebollo, Armando [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, IIM-UNAM, A.P. 70-360, Coyoacan, 04510 Mexico, D.F. (Mexico)

    2009-02-25

    Semiconducting molecular material of PcFe(CN)L1 and PcCo(CN)L1 (L1 = 1,8 dihydroxianthraquinone), PcFe(CN)L2 and PcCo(CN)L2 (L2 = double potassium salt of 1,8 dihydroxianthraquinone) have been successfully used to prepare thin film and bulk sol-gel hybrid optical materials. These samples were developed according to the vacuum thermal evaporation technique and the catalyst-free sonogel route, respectively. Thin films samples were deposited on Corning glass substrates and crystalline silicon wafers and were characterized by infrared (FTIR), Raman and ultraviolet-visible (UV-vis) spectroscopies. IR-spectroscopy and Raman studies unambiguously confirmed that the molecular material thin films exhibit the same intra-molecular bonds, which suggests that the thermal evaporation process does not alter these bonds significantly. These results show that it is possible to deposit molecular materials of PcFe(CN)L2 and PcCo(CN)L2 on Corning glass substrates and silicon wafers. From the UV-vis studies the optical band gap (E{sub g}) was evaluated. The effect of temperature on conductivity was also evaluated in these samples. Finally, the studied molecular systems dissolved at different concentrations in tetrahydrofuran (THF) were successfully embedded into a highly pure SiO{sub 2} sonogel network generated via sonochemical reactions to form several solid state, optically active sol-gel hybrid glasses. By this method, homogeneous and stable hybrid monoliths suitable for optical characterization can be produced. The linear optical properties of these amorphous bulk structures were determined by the Brewster angle method and by absorption-, Raman- and photoluminescent (PL)-spectroscopies, respectively.

  18. Optical Properties Of Nanometer-Scale Structures

    CERN Document Server

    Kudykina, T A

    2016-01-01

    Two approaches (micro- and macro- investigations) are used to determine the dimension dependences of the optical parameters of the nanometer-scale layers of materials. It is shown that both an index of refraction and coefficient of absorption depend strongly on the thickness of the layer. In this region of thicknesses, the dimension resonance occurs, where an index of refraction has a maximum and a coefficient of absorption has a minimum. The numerical calculation of the optical parameters of some materials (Ag, Al, Fe, Ge, Si, Se, Te) have been carried out with the use of the experimental data of reflection and transparency of thin layers, obtained in a series of works, and with our formulas for the wave amplitudes and the laws of refractions. The analogues of the Fresnel formulas and the Snell law have been derived from the Maxwell boundary conditions where the absorption and conductivity of media were taken into account. The use of our formulas for the wave amplitudes leads to the fulfillment of the conser...

  19. Nonlinear optical properties of sodium copper chlorophyllin in aqueous solution.

    Science.gov (United States)

    Li, Jiangting; Peng, Yufeng; Han, Xueyun; Guo, Shaoshuai; Liang, Kunning; Zhang, Minggao

    2017-06-16

    Sodium copper chlorophyllin (SCC), as one of the derivatives of chlorophyll - with its inherent green features; good stability for heat, light, acids and alkalies; unique antimicrobial capability; and particular deodori zation performance - is widely applied in some fields such as the food industry, medicine and health care, daily cosmetic industry etc. SCC, as one of the metal porphyrins, has attracted much attention because of its unique electronic band structure and photon conversion performance. To promote the application of SCC in materials science; energy research and photonics, such as fast optical communications; and its use in nonlinear optical materials, solar photovoltaic cells, all-optical switches, optical limiters and saturable absorbers, great efforts should be dedicated to studying its nonlinear optical (NLO) properties. In this study, the absorption spectra and NLO properties of SCC in aqueous solution at different concentrations were measured. The Z-scan technique was used to determine NLO properties. The results indicated that the absorption spectra of SCC exhibit 2 characteristic absorption peaks located at the wavelengths 405 and 630 nm, and the values of the peaks increase with increasing SCC concentration. The results also showed that SCC exhibits reverse saturation absorption and negative nonlinear refraction (self-defocusing). It can be seen that SCC has good optical nonlinearity which will be convenient for applications in materials science, energy research and photonics.

  20. Nonlinear optical properties of manganese porphyrin-incorporated PVC film

    Directory of Open Access Journals (Sweden)

    Jeong-Hyon Ha

    2010-12-01

    Full Text Available We measured thermally originated solid phase nonlinear optical properties of manganese porphyrin-incorporated PVC polymer film using CW low-power Z-scan and optical power limiting methods. The nonlinear refractive index (n2 of this porphyrin film is estimated to have a negative value of 7.2 ⅹ10-5 cm2/W at 632.8 nm and to be larger than that of ZnTPP in the Nafion film. The photodegradation effect common in the solution phase appears to be minor in this solid phase system. The large nonlinear effect is thought to limit the optical power due to the aperture effect.

  1. Optical Writing of Magnetic Properties by Remanent Photostriction.

    Science.gov (United States)

    Iurchuk, V; Schick, D; Bran, J; Colson, D; Forget, A; Halley, D; Koc, A; Reinhardt, M; Kwamen, C; Morley, N A; Bargheer, M; Viret, M; Gumeniuk, R; Schmerber, G; Doudin, B; Kundys, B

    2016-09-02

    We present an optically induced remanent photostriction in BiFeO_{3}, resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO_{3}/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO_{3}. Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

  2. Optical Writing of Magnetic Properties by Remanent Photostriction

    Science.gov (United States)

    Iurchuk, V.; Schick, D.; Bran, J.; Colson, D.; Forget, A.; Halley, D.; Koc, A.; Reinhardt, M.; Kwamen, C.; Morley, N. A.; Bargheer, M.; Viret, M.; Gumeniuk, R.; Schmerber, G.; Doudin, B.; Kundys, B.

    2016-09-01

    We present an optically induced remanent photostriction in BiFeO3 , resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO3/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO3 . Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

  3. Direct observation of bulk second-harmonic generation inside a glass slide with tightly focused optical fields

    Science.gov (United States)

    Wang, Xianghui; Fardad, Shima; Das, Susobhan; Salandrino, Alessandro; Hui, Rongqing

    2016-04-01

    Bulk second-harmonic generation (SHG) inside glass slides is directly detected unambiguously without interference from surface contributions. This is enabled by tightly focused and highly localized ultrashort laser pulses. The theoretical calculations based on vector diffraction theory and the phenomenological model of SHG inside centrosymmetric materials agree well with the measured far-field SHG radiation patterns for different polarization states of the fundamental beam. The results indicate that the observed bulk SHG is predominantly related to the bulk parameter δ' and originates from the three-dimensional field gradient in the focal region.

  4. Chemical and physical properties of bulk aerosols within four sectors observed during TRACE-P

    Science.gov (United States)

    Jordan, C. E.; Anderson, B. E.; Talbot, R. W.; Dibb, J. E.; Fuelberg, H. E.; Hudgins, C. H.; Kiley, C. M.; Russo, R.; Scheuer, E.; Seid, G.; Thornhill, K. L.; Winstead, E.

    2003-11-01

    Chemical and physical aerosol data collected on the DC-8 during TRACE-P were grouped into four sectors based on back trajectories. The four sectors represent long-range transport from the west (WSW), regional circulation over the western Pacific and Southeast Asia (SE Asia), polluted transport from northern Asia with substantial sea salt at low altitudes (NNW) and a substantial amount of dust (Channel). WSW has generally low mixing ratios at both middle and high altitudes, with the bulk of the aerosol mass due to non-sea-salt water-soluble inorganic species. Low altitude SE Asia also has low mean mixing ratios in general, with the majority of the aerosol mass comprised of non-sea-salts, however, soot is also relatively important in this region. NNW had the highest mean sea salt mixing ratios, with the aerosol mass at low altitudes (Asia emanates from Channel at both low and midaltitudes, due to the prevalence of dust compared to other sectors. Number densities show enhanced fine particles for Channel and NNW, while their volume distributions are enhanced due to sea salt and dust. Low-altitude Channel exhibits the highest condensation nuclei (CN) number densities along with enhanced scattering coefficients, compared to the other sectors. At midaltitudes (2-7 km), low mean CN number densities coupled with a high proportion of nonvolatile particles (≥65%) observed in polluted sectors (Channel and NNW) are attributed to wet scavenging which removes hygroscopic CN particles. Low single scatter albedo in SE Asia reflects enhanced soot.

  5. Characterization of electrical and optical properties of silicon based materials

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Guobin

    2009-12-04

    In this work, the electrical and luminescence properties of a series of silicon based materials used for photovoltaics, microelectronics and nanoelectronics have been investigated by means of electron beam induced current (EBIC), cathodoluminescence (CL), photoluminescence (PL) and electroluminescence (EL) methods. Photovoltaic materials produced by block casting have been investigated by EBIC on wafers sliced from different parts of the ingot. Various solar cell processings have been compared in parallel wafers by means of EBIC collection efficiency measurements and contrast-temperature C(T) behaviors of the extended defects, i. e. dislocations and grain boundaries (GBs). It was found that the solar cell processing with phosphorus diffusion gettering (PDG) followed with a SiN firing greatly reduces the recombination activity of extended defects at room temperature, and improves the bulk property simultaneously. A remaining activity of the dislocations indicates the limitation of the PDG at extended defects. Abnormal behavior of the dislocation activity after certain solar cell processes was also observed in the region with high dislocation density, the dislocations are activated after certain solar cell processings. In order to evaluate the properties of a thin polycrystalline silicon layer prepared by Al-induced layer exchange (Alile) technique, epitaxially layer grown on silicon substrate with different orientations was used as a model system to investigate the impact by the process temperature and the substrates. EBIC energy dependent collection efficiency measurements reveal an improvement of the epilayer quality with increasing substrate temperature during the growth from 450 C to 650 C, and a decrease of epilayer quality at 700 C. PL measurements on the epitaxially grown Si layer on silicon substrates revealed no characteristic dislocation-related luminescence (DRL) lines at room temperature and 77 K, while in the samples prepared by Alile process, intense

  6. Structure and magnetic properties of bulk nanocrystalline Nd-Fe-B permanent magnets prepared by hot pressing and hot deformation

    Institute of Scientific and Technical Information of China (English)

    SONG Jie; YUE Ming; ZUO Jianhua; ZHANG Zirui; LIU Weiqiang; ZHANG Dongtao; ZHANG Jiuxing

    2013-01-01

    Structure and magnetic properties were studied for bulk nanocrystalline Nd-Fe-B permanent magnets that were prepared at 650 ℃ for 3 min under 300 MPa using the SPS-3.20-MK-V sintering machine and the hot pressed magnets were then submitted to hot deformation with height reduction of 50%,60%,70%,80%,and 85%.Effects of height reduction (HR) and deformation temperature on the structure and magnetic properties of the magnets were investigated.The crystal structure was evaluated by means of X-ray diffraction (XRD) and the microstructure was observed by transmission electron microscopy (TEM).The magnetic properties of the magnets were investigated by vibrating sample magnetometer (VSM).As the height reduction increased,the remanence (Br) of the magnets increased first,peaks at 1.3 T with HR=60%,then decreased again,and the coercivity (Hci) of the magnets decreased monotonically.On the other hand,as the deformation temperature increased,the Br of the magnets increased first,peaks at 1.36 T with HR=60%,then decreased again,and the Hci of the magnets decreased monotonically.Under optimal conditions,the hot deformed magnet possessed excellent magnetic properties as Br=l.36 T,Hci=1143 kA/m,and (BH)max=370 kJ/m3,suggesting the good potential of the magnets in practical applications.

  7. Optical properties of organic and semiconductor nanostructures

    NARCIS (Netherlands)

    Jeukens, C.R.L.P.N.

    2005-01-01

    Nanostructures have at least one of their dimensions in the range 1-100 nm. Fabricating new, well-defined nanoscale objects and studying their physical properties is of importance, because it can lead to the development of potentially useful materials, novel device applications, and the discovery of

  8. Tunable Quantum Dot Solids: Impact of Interparticle Interactions on Bulk Properties

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, Michael B. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Fan, Hongyou [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Brener, Igal [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Liu, Sheng [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Luk, Ting S. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Li, Binsong [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    QD-solids comprising self-assembled semiconductor nanocrystals such as CdSe are currently under investigation for use in a wide array of applications including light emitting diodes, solar cells, field effect transistors, photodetectors, and biosensors. The goal of this LDRD project was develop a fundamental understanding of the relationship between nanoparticle interactions and the different regimes of charge and energy transport in semiconductor quantum dot (QD) solids. Interparticle spacing was tuned through the application of hydrostatic pressure in a diamond anvil cell, and the impact on interparticle interactions was probed using x-ray scattering and a variety of static and transient optical spectroscopies. During the course of this LDRD, we discovered a new, previously unknown, route to synthesize semiconductor quantum wires using high pressure sintering of self-assembled quantum dot crystals. We believe that this new, pressure driven synthesis approach holds great potential as a new tool for nanomaterials synthesis and engineering.

  9. Nonlocal optical properties in periodic lattice of graphene layers.

    Science.gov (United States)

    Chern, Ruey-Lin; Han, Dezhuan

    2014-02-24

    Based on the effective medium model, nonlocal optical properties in periodic lattice of graphene layers with the period much less than the wavelength are investigated. Strong nonlocal effects are found in a broad frequency range for TM polarization, where the effective permittivity tensor exhibits the Lorentzian resonance. The resonance frequency varies with the wave vector and coincides well with the polaritonic mode. Nonlocal features are manifest on the emergence of additional wave and the occurrence of negative refraction. By examining the characters of the eigenmode, the nonlocal optical properties are attributed to the excitation of plasmons on the graphene surfaces.

  10. Liquid Xe scintillation calorimetry and Xe optical properties

    CERN Document Server

    Baldini, A; Cei, F; Doke, T; Grassi, M; Haruyama, T; Mihara, S; Mori, T; Nicolò, D; Nishiguchi, H; Ootani, W; Ozone, K; Papa, A; Pazzi, R; Sawada, R; Sergiampietri, F; Signorelli, G; Suzuki, S; Terasawa, K

    2004-01-01

    The optical properties of LXe in the vacuum ultra violet (VUV), determining the performance of a scintillation calorimeter, are discussed in detail. The available data, measured in a wider spectral region from visible to UV light, and in a large range of Xe densities, from gas to liquid, are examined. It is shown that this information can be used for deriving the LXe optical properties in the VUV. A comparison is made with the few direct measurements in LXe for VUV light resulting from the LXe excitation by ionizing particles. A useful relation is obtained which connects the Rayleigh scattering length to the refractive index in LXe.

  11. First principles studies of elastic, electronic and optical properties of chalcopyrite semiconductor ZnSnP{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sahin, S. [Gazi University, Department of Physics, Teknikokullar, 06500, Ankara (Turkey); Ciftci, Y.O., E-mail: yasemin@gazi.edu.tr [Gazi University, Department of Physics, Teknikokullar, 06500, Ankara (Turkey); Colakoglu, K. [Gazi University, Department of Physics, Teknikokullar, 06500, Ankara (Turkey); Korozlu, N. [Erzincan University, Department of Physics, Basbaglar, 24100, Erzincan (Turkey)

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer We have examined elastic, electronic and optic properties of ZnSnP{sub 2}. Black-Right-Pointing-Pointer All calculations are calculated in chalco pyrite (BCT) crsytal structures. Black-Right-Pointing-Pointer The calculated elastic constants satisfy mechanical stability conditions. - Abstract: The structural, elastic, electronic and optical properties of ZnSnP{sub 2} were investigated using first principles plane-wave pseudopotential method within local density approximation (LDA). The results on the basic physical parameters, such as the lattice constant, bulk modulus, pressure derivative of bulk modulus, Zener anisotropy factor, Poisson's ratio, Young's modulus and isotropic shear modulus were presented. Band structures and density of states were calculated and it was found that the crystal is a semiconductor with a direct energy band gap of about 1.06 eV for ZnSnP{sub 2}. We have analysed the basic optical properties, such as dielectric function refractive index, extinction coefficient, the absorption coefficient, optical reflectivity and electron energy loss spectrum in the energy range 0-20 eV. The obtained results are in agreement with the available experimental and other theoretical values.

  12. The application of the symmetry properties of optical second harmonic generation to studies of interfaces and gases

    Energy Technology Data Exchange (ETDEWEB)

    Feller, M.B.

    1991-11-01

    Optical second harmonic generation has proven to be a powerful tool for studying interfaces. The symmetry properties of the process allow for surface sensitivity not available with other optical methods. In this thesis, we take advantage of these symmetry properties SHG to study a variety of interesting systems not previously studied with this technique. We show that optical second harmonic generation is an effective surface probe with a submonolayer sensitivity for media without inversion symmetry. We demonstrate the technique at a gallium arsenide surface, exploiting the different symmetry properties of the bulk and surface of the crystal to isolate the surface contribution. We also demonstrate that optical second harmonic generation can be used to determine the anisotropic orientational distribution of a surface monolayer of molecules. We apply the technique to study homogeneously aligned liquid crystal cells. To further explore the LC-polymer interface, we used SHG to study the surface memory effect. The surface memory effect is the rendering of an isotropic interface anisotropic by putting it in contact with an anisotropic bulk. Last, we describe some preliminary measurements of a time-resolved spectroscopic study of the phenomenon of second harmonic generation in a gas. The construction of a 500 microjoule pulsed, tunable laser source is described.

  13. The application of the symmetry properties of optical second harmonic generation to studies of interfaces and gases

    Energy Technology Data Exchange (ETDEWEB)

    Feller, Marla Beth [Univ. of California, Berkeley, CA (United States)

    1991-11-01

    Optical second harmonic generation has proven to be a powerful tool for studying interfaces. The symmetry properties of the process allow for surface sensitivity not available with other optical methods. In this thesis, we take advantage of these symmetry properties SHG to study a variety of interesting systems not previously studied with this technique. We show that optical second harmonic generation is an effective surface probe with a submonolayer sensitivity for media without inversion symmetry. We demonstrate the technique at a gallium arsenide surface, exploiting the different symmetry properties of the bulk and surface of the crystal to isolate the surface contribution. We also demonstrate that optical second harmonic generation can be used to determine the anisotropic orientational distribution of a surface monolayer of molecules. We apply the technique to study homogeneously aligned liquid crystal cells. To further explore the LC-polymer interface, we used SHG to study the surface memory effect. The surface memory effect is the rendering of an isotropic interface anisotropic by putting it in contact with an anisotropic bulk. Last, we describe some preliminary measurements of a time-resolved spectroscopic study of the phenomenon of second harmonic generation in a gas. The construction of a 500 microjoule pulsed, tunable laser source is described.

  14. Simulation of integrated optical network (IPON) properties

    Science.gov (United States)

    Siska, Petr; Koudelka, Petr; Latal, Jan; Vitasek, Jan; Kepak, Stanislav; Vašinek, Vladimír.

    2014-09-01

    There is an increasing pressure nowadays on the efficient use of existing ICT infrastructure in order to provide the latest services for corporate customers or end users. With the increase in number of services, requirements for optical networks of all hierarchies are increasing as well. This increase in the requirements, however, involves risks which must be faced by Internet service providers. These include the maximum use of spectral range, bandwidth and reachable distance, suppression of dispersion effect, route planning efficiency, CAPEX and OPEX costs management, or successful combination of technologies of deployed networks. The aim of this article is to present the problems associated with interconnection of WDM-PON and ver.2 EPON (IEEE 802.3ah standard). The entire simulation is based on real parameters, which were provided by the manufacturers of the technologies and then measured in the laboratory. Then we were able to perform simulations based on more realistic features of these technologies.

  15. Synthesis, crystal growth and studies on non-linear optical property of new chalcones

    Science.gov (United States)

    Sarojini, B. K.; Narayana, B.; Ashalatha, B. V.; Indira, J.; Lobo, K. G.

    2006-09-01

    The synthesis, crystal growth and non-linear optical (NLO) property of new chalcone derivatives are reported. 4-Propyloxy and 4-butoxy benzaldehydes were made to under go Claisen-Schmidt condensation with 4-methoxy, 4-nitro and 4-phenoxy acetophenones to form corresponding chalcones. The newly synthesized compounds were characterized by analytical and spectral data. The Second harmonic generation (SHG) efficiency of these compounds was measured by powder technique using Nd:YAG laser. Among tested compounds three chalcones showed NLO property. The chalcone 1-(4-methoxyphenyl)-3-(4-propyloxy phenyl)-2-propen-1-one exhibited SHG conversion efficiency 2.7 times that of urea. The bulk crystal of 1-(4-methoxyphenyl)-3-(4-butoxyphenyl)-2-propen-1-one (crystal size 65×28×15 mm 3) was grown by slow-evaporation technique from acetone. Microhardness of the crystal was tested by Vicker's microhardness method.

  16. Preparation, Electrochemical Property and Application in Bulk-modified Electrode of Dawson-type Phosphomolybdate-doped Polypyrrole Composite Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A kind of inorganic-organic hybrid semiconductor composite nanoparticles: Dawson-type phosphomolybdatedoped polypyrrole (P2Mo18-PPy) was designed and prepared using microemulsion oxidation-polymerization at room temperature and characterized by TEM and IR. The P2Mo18-PPy was used as a bulk-modifier to fabricate a chemically modified carbon paste electrode(CPE) by direct mixing, which represents the example of polyoxometalates (POMs)-doped semiconductor polymer nanoparticles modified electrode. Both the advantage of POMs-doped polymer and the surface-renewal property of the CPE were fully utilized. The electrochemical behavior of the P2Mo18-PPy bulk-modified CPE(P2Mo18-PPy-CPE) was investigated with cyclic voltammetry. Three couples of reversible redox peaks were observed in the range from + 800 to 0 mV, which corresponded to the reduction and oxidation through two-, four- and six-electron processes, respectively. The P2Mo18-PPY-CPE showed a high electrocatalytic activity for the reduction of nitrite, which expanded the application of POMs-doped semiconductor polymer nanoparticles.

  17. THE EFFECT OF THE PHYSICAL PROPERTIES OF PARTICLES OF BULK-BLENDED FERTILIZERS ON SEGREGATION BY CONING

    Directory of Open Access Journals (Sweden)

    Silva G.A. da

    1997-01-01

    Full Text Available Bulk blending is a way to produce compound fertilizers in which the different nutrients are present in different particles. Due to the heterogeneous composition of bulk blends, particle segregation, when it occurs, is a serious problem to the fertilizer producer, as well as to the farmer. Free fall is one of the main types of particle movement to promote segregation. The physical properties of the particles that potentially affect the tendency to segregate the most are size, density and shape. The main objective of this work is to study the influence of size and density of particles and distance of fall on segregation due to free fall. It was found that particle size is the most important physical characteristic to affect segregation; the greater the difference in particle size, the greater the segregation. Free fall is an important mechanical factor affecting segregation; the greater the distance of fall, the greater the segregation. No evidence of the influence of particle density on segregation was found

  18. Assimilation of remotely-sensed optical properties to improve marine biogeochemistry modelling

    Science.gov (United States)

    Ciavatta, Stefano; Torres, Ricardo; Martinez-Vicente, Victor; Smyth, Timothy; Dall'Olmo, Giorgio; Polimene, Luca; Allen, J. Icarus

    2014-09-01

    In this paper we evaluate whether the assimilation of remotely-sensed optical data into a marine ecosystem model improves the simulation of biogeochemistry in a shelf sea. A localized Ensemble Kalman filter was used to assimilate weekly diffuse light attenuation coefficient data, Kd(443) from SeaWiFs, into an ecosystem model of the western English Channel. The spatial distributions of (unassimilated) surface chlorophyll from satellite, and a multivariate time series of eighteen biogeochemical and optical variables measured in situ at one long-term monitoring site were used to evaluate the system performance for the year 2006. Assimilation reduced the root mean square error and improved the correlation with the assimilated Kd(443) observations, for both the analysis and, to a lesser extent, the forecast estimates, when compared to the reference model simulation. Improvements in the simulation of (unassimilated) ocean colour chlorophyll were less evident, and in some parts of the Channel the simulation of this data deteriorated. The estimation errors for the (unassimilated) in situ data were reduced for most variables with some exceptions, e.g. dissolved nitrogen. Importantly, the assimilation adjusted the balance of ecosystem processes by shifting the simulated food web towards the microbial loop, thus improving the estimation of some properties, e.g. total particulate carbon. Assimilation of Kd(443) outperformed a comparative chlorophyll assimilation experiment, in both the estimation of ocean colour data and in the simulation of independent in situ data. These results are related to relatively low error in Kd(443) data, and because it is a bulk optical property of marine ecosystems. Assimilation of remotely-sensed optical properties is a promising approach to improve the simulation of biogeochemical and optical variables that are relevant for ecosystem functioning and climate change studies.

  19. Processing, properties, and applications of sol-gel silica optics

    Science.gov (United States)

    Nogues, Jean-Luc R.; LaPaglia, Anthony J.

    1989-12-01

    For many years the market share maintained by U.S. optics manufacturers has been declining continuously caused in part by intense competition principally from countries in the Far East, and in part by the lack of a highly trained cadre of opticians to replace the current generation. This fact could place in jeopardy the defense system of the United States in case of international war. For example, in 1987, optical glass component imports accounted for approximately 50 percent of the Department of Defense (DOD) consumption. GELTECH's sol-gel technology is a new process for making a high quality optical glass and components for commercial and military uses. This technology offers in addition to being a local source of optics, the possibility to create new materials for high-tech optical applications, and the elimination of the major part of grinding and polishing for which the skill moved off-shore. This paper presents a summary of the solgel technology for the manufacture of high quality optical glass and components. Properties of pure silica glass made by solgel process (Type V and Type VI silicas) are given and include: ultraviolet, visible and near infrared spectrophotometry, optical homogeneity and thermal expansion. Many applications such as near net shape casting or Fresnel lens surface replication are discussed. Several potential new applications offered by the solgel technology such as organic-inorganic composites for non linear optics or scintillation detection are also reported in this paper.

  20. Optical and magneto-optical properties of aligned Ni nanowires embedded in polydimethylsiloxane

    Energy Technology Data Exchange (ETDEWEB)

    Hamidi, S.M., E-mail: m_hamidi@sbu.ac.ir [Magneto-plasmonic lab, Laser and plasma Research Institute, G. C. Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Sobhani, A. [Magneto-plasmonic lab, Laser and plasma Research Institute, G. C. Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Aftabi, A. [Physics department, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Najafi, M. [Department of materials engineering, Hamedan university of technology, Hamedan (Iran, Islamic Republic of)

    2015-01-15

    We report the magnetic, optical and magneto-optical properties of aligned Nickel nanowires embedded in polydimethylsiloxane matrix. The NWs prepared by electrodeposition method in anodic alumina template and then dispersed in ethanol and placed in a heater to evaporate the ethanol and finally dispersed in PDMS matrix to reach to the composite. The used external magnetic field arranges the NWs and our aligned NWs were investigated by magnetic hysteresis loop, surface plasmon resonance and spectral magneto-optical techniques. Our results show that these aligned NWs have a sufficient squareness, a strong increase of the magneto-optical response in visible range and very good surface plasmon resonance. - Highlights: • Magnetic, optical and magneto-optical properties of aligned Nickel nanowires embedded in polydimethylsiloxane matrix have been investigated. • Magnetic hysteresis loop, surface plasmon resonance and spectral magneto-optical techniques have been measured. • Aligned NWs have a sufficient squareness. • Strong increase of the magneto-optical response takes place in the visible range. • Very good surface plasmon resonance has been occurred.