Electrochemically synthesized amorphous and crystalline nanowires: dissimilar nanomechanical behavior in comparison with homologous flat films

Science.gov (United States)

Zeeshan, M. A.; Esqué-de Los Ojos, D.; Castro-Hartmann, P.; Guerrero, M.; Nogués, J.; Suriñach, S.; Baró, M. D.; Nelson, B. J.; Pané, S.; Pellicer, E.; Sort, J.

2016-01-01

The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires requires taking the curved geometry of the indented surface and sink-in effects into account. These findings are of high relevance for optimizing the performance of new, mechanically-robust, nanoscale materials for increasingly complex miniaturized devices.The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires

Thermodynamics of Crystalline States

CERN Document Server

Fujimoto, Minoru

2013-01-01

Thermodynamics is a well-established discipline of physics for properties of matter in thermal equilibrium with the surroundings. Applying to crystals, however, the laws encounter undefined properties of crystal lattice, which therefore need to be determined for a clear and well-defined description of crystalline states. Thermodynamics of Crystalline States explores the roles played by order variables and dynamic lattices in crystals in a wholly new way. The book begins by clarifying basic concepts for stable crystals. Next, binary phase transitions are discussed to study collective motion of order variables, as described mostly as classical phenomena. New to this edition is the examination of magnetic crystals, where magnetic symmetry is essential for magnetic phase transitions. The multi-electron system is also discussed  theoretically, as a quantum-mechanical example, for superconductivity in metallic crystals. Throughout the book, the role played by the lattice is emphasized and studied in-depth. Thermod...

Glassy slag: A complementary waste form to homogeneous glass for the implementation of MAWS in treating DOE low level/mixed wastes

International Nuclear Information System (INIS)

Feng, X.; Ordaz, G.; Krumrine, P.

1994-01-01

Glassy slag waste forms are being developed to complement glass waste forms in implementing the Minimum Additive Waste Stabilization (MAWS) Program for supporting DOE's environmental restoration efforts. These glassy slags are composed of various metal oxide crystalline phases embedded in an alumino-silicate glass phase. The slags are appropriate final waste forms for waste streams that contain large amounts of scrap metals and elements with low solubilities in glass, and that have low-flux contents. Homogeneous glass waste forms are appropriate for wastes with sufficient fluxes and low metal contents. Therefore, utilization of both glass and glassy slag waste forms will make vitrification technology applicable to the treatment of a much larger range of radioactive and mixed wastes. The MAWS approach was a plied to glassy slags by blending multiple waste streams to produce the final waste form, minimizing overall waste form volume and reducing costs. The crystalline oxide phases formed in the glassy slags can be specially formulated so that they are very durable and contain hazardous and radioactive elements in their lattice structures. The Structural Bond Strength (SBS) Model was used to predict the chemical durability of the product from the slag composition so that optimized slag compositions could be obtain with a limited number of crucible melts and testing

New model system in radiation cryochemistry:. hyperquenched glassy water

Science.gov (United States)

Bednarek, Janusz; Plonka, Andrzej; Hallbrucker, Andreas; Mayer, Erwin

1999-08-01

Radicals generated by high-energy irradiation of liquid water, short-lived at ambient temperature, can be studied at cryogenic temperatures after irradiating water and dilute aqueous solutions in their glassy states which can be obtained by so-called hyperquenching of the liquids at cooling rates of ˜10 6-10 7 K s -1. In the glassy states of hyperquenched dilute aqueous solutions there is no problem with phase separation and radiolysis of glassy water is quite distinct from radiolysis of polycrystalline ice obtained from liquid water on slow-cooling in liquid nitrogen.

Irradiation-induced dimensional changes of poorly crystalline carbons

International Nuclear Information System (INIS)

Bullock, R.E.

1979-01-01

Data are presented on irradiation-induced changes of poorly crystalline carbons at high temperatures(>900 0 C). The materials surveyed include: (1) carbon fibers, (2) glassy carbons, (3) carbonaceous matrix materials for HTGR fuel rods and (4) pyrocarbons. The materials are listed in order of increasing stability, with maximum strains ranging from more than 50% for fibers to less than 10% for pyrocarbons. Dimensional changes of highly anisotropic carbon fibers appear to be sensitive to irradiation temperature, as slightly anisotropic pyrocarbons are, whereas temperature seems to have little influence on the behavior of isotropic glassy carbons over the range from 600 to 1350 0 C. Dimensional changes for graphite-filled matrix materials were roughly isotropic on the average and did not seem to be strongly temperature dependent for the lower fluences investigated. Increased graphite filler lowered volumetric dimensional changes of the matrix in agreement with a rule-of-mixtures relationship between change components for the filler and the less-stable binder phases. Instabilities of all of the poorly crystalline materials were generally greater than those for more crystalline carbons under the same conditions, including highly orientated graphites that approximate single-crystal behavior. (author)

Crystalline beam ground state

International Nuclear Information System (INIS)

Wei, Jie; Li, Xiao-Ping; Sessler, A.M.

1993-01-01

In order to employ Molecular Dynamics method, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing

Crystalline beam ground state

International Nuclear Information System (INIS)

Wei, J.; Li, X.P.

1993-01-01

In order to employ the Molecular Dynamics method, commonly used in condensed matter physics, the authors have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. They include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing

Deformation-induced amorphization of crystalline particles in a Cu-Ti metallic glass

International Nuclear Information System (INIS)

Kamentzky, E.A.; Askenazy, P.D.; Johnson, W.L.; Tanner, L.E.

1987-01-01

Crystalline particles and grains embedded in Cu 35 Ti 65 glass ribbons have been amorphized by isothermal cold rolling. The structural evolution has been studied by X-ray diffraction and TEM techniques. Initial particle morphologies are spherulitic and spherical, the latter with sizes ranging between 10 and 100 nm. The new amorphous phase seems to nucleate at crystalline-amorphous matrix interfaces. Initially there is a well defined interface between the new and the existing amorphous phases but it disappears as rolling progresses. Crystallites on a nanoscale still present in the final stages of particle amorphization have been observed by convergent beam electron diffraction. After sufficient deformation the consolidated ribbon becomes a completely glassy. A morphological description of the transformation process in terms of crystal destabilization and solid- state particle melting is presented

New model system in radiation cryochemistry. Hyperquenched glassy water

International Nuclear Information System (INIS)

Plonka, A.

1998-01-01

Complete text of publication follows. Since the radical generated by high-energy irradiation of liquid water are short-lived at ambient temperature, they are often studied at cryogenic temperatures after irradiating either crystalline ice or highly concentrated aqueous electrolyte solution glasses. While these studies provided a wealth of information, they also bear disadvantages in that further reactions of these radicals may not be those occurring in liquid water because of formation of other radicals from the solute in the case of the electrolyte solution glass and/or perturbation of the water structure by the solute. Furthermore, in slow-cooled aqueous solutions where ice is formed and phase separation of the solute occurs, the radicals trapped in the ice compartments are unable to interact with solutes because these are dissolved in the 'freeze-concentration' regions. These problems can in principle be overcome by investigating water and dilute aqueous solutions in their glassy states which can be obtained by rapid quenching of the liquids. Glassy water can now routinely be made in gram-quantities by so-called 'hyperquenching' of micrometer-sized water droplets on a solid cryoplate. The cooling rates are of the order of 10 6 - 10 7 K s -1 . Our results show that indeed in the hyperquenched dilute aqueous solutions there is no problem with phase separation and radiolysis of hyperquenched water is quite distinct from radiolysis of polycrystalline ice obtained from liquid water quenched in the liquid nitrogen

Structural characterization and aging of glassy pharmaceuticals made using acoustic levitation.

Science.gov (United States)

Benmore, Chris J; Weber, J K R; Tailor, Amit N; Cherry, Brian R; Yarger, Jeffery L; Mou, Qiushi; Weber, Warner; Neuefeind, Joerg; Byrn, Stephen R

2013-04-01

Here, we report the structural characterization of several amorphous drugs made using the method of quenching molten droplets suspended in an acoustic levitator. (13) C NMR, X-ray, and neutron diffraction results are discussed for glassy cinnarizine, carbamazepine, miconazole nitrate, probucol, and clotrimazole. The (13) C NMR results did not find any change in chemical bonding induced by the amorphization process. High-energy X-ray diffraction results were used to characterize the ratio of crystalline to amorphous material present in the glasses over a period of 8 months. All the glasses were stable for at least 6 months except carbamazepine, which has a strong tendency to crystallize within a few months. Neutron and X-ray pair distribution function analyses were applied to the glassy materials, and the results were compared with their crystalline counterparts. The two diffraction techniques yielded similar results in most cases and identified distinct intramolecular and intermolecular correlations. The intramolecular scattering was calculated based on the crystal structure and fit to the measured X-ray structure factor. The resulting intermolecular pair distribution functions revealed broad-nearest and next-nearest neighbor molecule-molecule correlations. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1290-1300, 2013. Copyright © 2013 Wiley Periodicals, Inc.

Glassy slags as novel waste forms for remediating mixed wastes with high metal contents

International Nuclear Information System (INIS)

Feng, X.; Wronkiewicz, D.J.; Bates, J.K.; Brown, N.R.; Buck, E.C.; Gong, M.; Ebert, W.L.

1994-01-01

Argonne National Laboratory (ANL) is developing a glassy slag final waste form for the remediation of low-level radioactive and mixed wastes with high metal contents. This waste form is composed of various crystalline and metal oxide phases embedded in a silicate glass phase. This work indicates that glassy slag shows promise as final waste form because (1) it has similar or better chemical durability than high-level nuclear waste (HLW) glasses, (2) it can incorporate large amounts of metal wastes, (3) it can incorporate waste streams having low contents of flux components (boron and alkalis), (4) it has less stringent processing requirements (e.g., viscosity and electric conductivity) than glass waste forms, (5) its production can require little or no purchased additives, which can result in greater reduction in waste volume and overall treatment costs. By using glassy slag waste forms, minimum additive waste stabilization approach can be applied to a much wider range of waste streams than those amenable only to glass waste forms

On the solubility advantage of a pharmaceutical’s glassy state over the crystal state, and of its crystal polymorphs

International Nuclear Information System (INIS)

Johari, G.P.; Shanker, Ravi M.

2014-01-01

Highlights: • Heat capacity data do not yield the solubility advantage of amorphous and metastable crystal pharmaceuticals. • There is no reversible equilibrium of an amorphous solid with its saturated solution. • Solubility advantage of an amorphous solid depends upon the solvent and other interactions. - Abstract: At equilibrium, the saturation solubility and vapor pressure of a material in a state of high free energy are greater than in its state of low free energy. This knowledge from classical thermodynamics is currently used for increasing the solubility of crystalline pharmaceuticals by producing them in their glassy state, or in other solid states of high free energy. The ratio of the apparent saturation solubility of these solids to that of a crystal, calculated from the thermodynamic data of the pure solute, ϕ cal , is called the solubility advantage, and it is used as a guide for increasing the solubility of a pharmaceutical. We argue that the ϕ cal differs from the measured solubility ratio, ϕ meas , because, (i) ϕ cal is independent of the solvent, but ϕ meas is not so, (ii) ϕ cal would increase with the dissolution time monotonically to a constant value, but ϕ meas would first reach a maximum and then decrease, and (iii) approximations are made in estimating ϕ cal and the effect of thermal history on high free energy solids is ignored. On the other hand, ϕ meas is affected by, (a) another chemical equilibrium in the solution, e.g., hydrogen-bond formation and ionic dissociation, (b) the production method and thermal history of a glass or an amorphous samples, and (c) mutarotation in the solution, isomerization or tautomeric conversion in the solid. We also discuss the effects of structural relaxation and crystallization on ϕ meas . The ϕ meas value of a (crystal) polymorph would be affected by all the three, and further if the polymorph is orientationally disordered. We provide evidence for these effects from analysis of the known

Crystal-like nature of acoustic excitations in glassy ethanol

International Nuclear Information System (INIS)

Matic, A.; Engberg, D.; Boerjesson, L.; Masciovecchio, C.; Santucci, S.C.; Monaco, G.; Verbeni, R.

2004-01-01

We report on inelastic x-ray scattering experiments on crystalline and glassy phases of ethanol in order to directly compare the influence of disorder on high frequency acoustic excitations. We find that both the dispersion and the line-width of the longitudinal acoustic excitations in the glass are the same as in the polycrystal in the reciprocal space portion covering the 1st and 2nd Brillouin zones. The structural disorder is found to play little role apart from an intrinsic angular averaging, and the nature of these excitations must essentially be the same in both glass and poly crystal

Glassy selenium at high pressure: Le Chatelier's principle still works

Science.gov (United States)

Brazhkin, V. V.; Tsiok, O. B.

2017-10-01

Selenium is the only easily vitrified elementary substance. Numerous experimental studies of glassy Se (g -Se) at high pressures show a large spread in the data on the compressibility and electrical resistivity of g -Se. Furthermore, H. Liu et al. [Proc. Natl. Acad. Sci. USA 105, 13229 (2008), 10.1073/pnas.0806857105] have arrived at the surprising conclusion that the volume of glass increases during pressure-induced crystallization. We have performed high-precision measurements of the specific volume and electrical resistivity of glassy selenium (g -Se) at high hydrostatic pressures up to 9 GPa. The measured bulk modulus at normal pressure is B =(9.0 5 ±0.15 ) GPa and its pressure derivative is BP'=6.4 ±0.2 . In the pressure range P <3 GPa, glassy selenium has an anomalously large negative second derivative of the bulk modulus. The electrical resistivity of g -Se decreases almost exponentially with increasing pressure and reaches 20 Ω cm at a pressure of 8.75 GPa. The inelastic behavior and weak relaxation of the volume for g -Se begin at pressures above 3.5 GPa; the volume and logarithm of the electrical resistivity relax significantly (logarithmically with the time) at pressures above 8 GPa. Bulk measurements certainly indicate that the volume of g -Se glass in the crystallization pressure range is larger than the volumes of both appearing crystalline phases (by 2% and 4%). Therefore, the "volume expansion phenomenon" suggested in [H. Liu et al., Proc. Natl. Acad. Sci. USA 105, 13229 (2008), 10.1073/pnas.0806857105] is not observed, and the pressure-induced crystallization of glassy selenium is consistent with the laws of thermodynamics.

Moessbauer effect study of oxidation and coordination states of iron in some sodium borate glasse:;

International Nuclear Information System (INIS)

Eissa, N.A.; Sanad, A.M.; Youssef, S.M.; El-Henawii, S.A.; Gomaa, S.Sh.; Mostafa, A.G.

1980-01-01

A structural study of some sodium borate glasses containing iron was carried out applying ME spectroscopy. Both oxidation and coordination states of iron were investigated under the effect of gradual replacing of sodium carbonate by sodium nitrate in the glass batches. The glasses were melted in porcelain crucibles using an electrically heated furnace at 1000+-10 deg C, then were quenched on a steel plate at room temperature (R.T.). The ME source was 20 mCi radioactive Co-57 in chromium. The obtained ME spectra indicated that at lower sodium nitrate content both Fe 2+ and Fe 3+ are present in these glasses. At moderate concentrations some Fe 3+ ions were separated in a crystalline phase and the rest of the iron ions appeared as ferric ions in glassy state. At high sodium nitrate content only Fe 3+ ions in glassy state were detected. The values of the ME parameters for all iron ions indicated that all of them are in the octahedral coordination state. The density measurements confirm the separation of a crystalline phase at moderate sodium nitrate content. (author)

Time evolution of quenched state and correlation to glassy effects

International Nuclear Information System (INIS)

Kilic, K.; Kilic, A.; Altinkok, A.; Yetis, H.; Cetin, O.; Durust, Y.

2005-01-01

In this work, dynamic changes generated by the driving current were studied in superconducting bulk polycrystalline YBCO sample via transport relaxation measurements (V-t curves). The evolution of nonlinear V-t curves was interpreted in terms of the formation of resistive and nonresistive flow channels and the spatial reorganization of the transport current in a multiply connected network of weak-link structure. The dynamic re-organization of driving current could cause an enhancement or suppression in the superconducting order parameter due to the magnitude of the driving current and coupling strength of weak-link structure along with the chemical and anisotropic states of the sample as the time proceeds. A nonzero voltage decaying with time, correlated to the quenched state, was recorded when the magnitude of initial driving current is reduced to a finite value. It was found that, after sufficiently long waiting time, the evolution of the quenched state could result in a superconducting state, depending on the magnitude of the driving current and temperature. We showed that the decays in voltage over time are consistent with an exponential time dependence which is related to the glassy state. Further, the effect of doping of organic material Bis dimethyl-glyoximato Copper (II) to YBCO could be monitored apparently via the comparison of the V-t curves corresponding to doped and undoped YBCO samples

Solid State Characterization of Commercial Crystalline and Amorphous Atorvastatin Calcium Samples

OpenAIRE

Shete, Ganesh; Puri, Vibha; Kumar, Lokesh; Bansal, Arvind K.

2010-01-01

Atorvastatin calcium (ATC), an anti-lipid BCS class II drug, is marketed in crystalline and amorphous solid forms. The objective of this study was to perform solid state characterization of commercial crystalline and amorphous ATC drug samples available in the Indian market. Six samples each of crystalline and amorphous ATC were characterized using X-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis, Karl Fisher titrimetry, microscopy (hot s...

Solid state characterization of commercial crystalline and amorphous atorvastatin calcium samples.

Science.gov (United States)

Shete, Ganesh; Puri, Vibha; Kumar, Lokesh; Bansal, Arvind K

2010-06-01

Atorvastatin calcium (ATC), an anti-lipid BCS class II drug, is marketed in crystalline and amorphous solid forms. The objective of this study was to perform solid state characterization of commercial crystalline and amorphous ATC drug samples available in the Indian market. Six samples each of crystalline and amorphous ATC were characterized using X-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis, Karl Fisher titrimetry, microscopy (hot stage microscopy, scanning electron microscopy), contact angle, and intrinsic dissolution rate (IDR). All crystalline ATC samples were found to be stable form I, however one sample possessed polymorphic impurity, evidenced in XRPD and DSC analysis. Amongst the amorphous ATC samples, XRPD demonstrated five samples to be amorphous 'form 27', while, one matched amorphous 'form 23'. Thermal behavior of amorphous ATC samples was compared to amorphous ATC generated by melt quenching in DSC. ATC was found to be an excellent glass former with T(g)/T(m) of 0.95. Residual crystallinity was detected in two of the amorphous samples by complementary use of conventional and modulated DSC techniques. The wettability and IDR of all amorphous samples was found to be higher than the crystalline samples. In conclusion, commercial ATC samples exhibited diverse solid state behavior that can impact the performance and stability of the dosage forms.

27Al nuclear magnetic resonance of glassy and crystalline Zr(1-x)AlxO(2-x/2) materials prepared from solution precursors

International Nuclear Information System (INIS)

Balmer, M.L.; Eckert, H.; Das, N.; Lange, F.F.

1996-01-01

The local environment of the aluminum atoms in a series of metastable Zr (1-x) Al x O (2-x/2) crystalline materials (0.08 ≤ x ≤ 0.57), prepared by diffusion-limited crystallization of amorphous precursors, has been determined by 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR). Results show the existence of aluminum in 4-, 5-, and 6-fold coordination in both the amorphous and crystalline states. Although the relative amounts of each type of coordination show no compositional dependence in the amorphous state, the results for the crystalline materials show a systematic decrease in the average aluminum coordination number with increasing aluminum content. Comparisons of MAS NMR results between pure Al 2 O 3 precursors and Zr (1-x) Al x O (2-x/2) crystalline materials processed under similar conditions show a profound effect of ZrO 2 on the coordination environment of the aluminum atom. Both a random distribution model and a model that assumes small-scale clustering of aluminum ions are considered to explain the trends in the type of aluminum coordination as a function of composition

Au55, a stable glassy cluster: results of ab initio calculations

Directory of Open Access Journals (Sweden)

Dieter Vollath

2017-10-01

Full Text Available Structure and properties of small nanoparticles are still under discussion. Moreover, some thermodynamic properties and the structural behavior still remain partially unknown. One of the best investigated nanoparticles is the Au55 cluster, which has been analyzed experimentally and theoretically. However, up to now, the results of these studies are still inconsistent. Consequently, we have carried out the present ab initio study of the Au55 cluster, using up-to-date computational concepts, in order to clarify these issues. Our calculations have confirmed the experimental result that the thermodynamically most stable structure is not crystalline, but it is glassy. The non-crystalline structure of this cluster was validated by comparison of the coordination numbers with those of a crystalline cluster. It was found that, in contrast to bulk materials, glass formation is connected to an energy release that is close to the melting enthalpy of bulk gold. Additionally, the surface energy of this cluster was calculated using two different theoretical approaches resulting in values close to the surface energy for bulk gold. It shall be emphasized that it is now possible to give a confidence interval for the value of the surface energy.

Glassy slag from rotary hearth vitrification

International Nuclear Information System (INIS)

Eschenbach, R.C.; Simpson, M.D.; Paulson, W.S.; Whitworth, C.G.

1995-01-01

Use of a Plasma Arc Centrifugal Treatment (PACT) system for treating mixed wastes containing significant quantities of soil results in formation of a glassy slag which melts at significantly higher temperatures than the borosilicate glasses. The slag typically contains mostly crystalline material, frequently in an amorphous matrix, thus the appellation open-quotes glassy slag.close quotes Details of the PACT process are given. The process will be used for treating buried wastes from Pit 9 at the Idaho National Engineering Laboratory and low-level mixed wastes from nuclear power plants in Switzerland. Properties of the slag after cooling to room temperature are reported, in particular the Product Consistency Test, for a number of different feedstocks. In almost all cases, the results compare favorably with conventional borosilicate glasses. In the PACT system, a transferred arc carries current from the plasma torch to a rotating molten bed of slag, which is the material being heated. Thus this transferred arc adds energy where it is needed - at and near the surface of the molten bath. Material is fed into the furnace through a sealed feeder, and falls into a rotating tub which is heated by the arc. Any organic material is quickly vaporized into the space above the slag bed and burned by the oxygen in the furnace. Metal oxides in the charge are melted into the slag. Metal in the feed tends to melt and collect as a separate phase underneath the slag, but can be oxidized if desired. When oxidized, it unites with other constituents forming a homogeneous slag

Atomic structure of glassy Mg60Cu30Y10 investigated with EXAFS, x-ray and neutron diffraction, and reverse Monte Carlo simulations

DEFF Research Database (Denmark)

Jovari, P.; Saksl, K.; Pryds, Nini

2007-01-01

Short range order of amorphous Mg60Cu30Y10 was investigated by x-ray and neutron diffraction, Cu and Y K-edge x-ray absorption fine structure measurements, and the reverse Monte Carlo simulation technique. We found that Mg-Mg and Mg-Cu nearest neighbor distances are very similar to values found...... in crystalline Mg2Cu. The Cu-Y coordination number is 1.1 +/- 0.2, and the Cu-Y distance is similar to 4% shorter than the sum of atomic radii, suggesting that attraction between Cu and Y plays an important role in stabilizing the glassy state. Thermal stability and structure evolution upon annealing were also...

Effect of high-order multicomponent on formation and properties of Zr-based bulk glassy alloys

Energy Technology Data Exchange (ETDEWEB)

Inoue, A., E-mail: ainouebmg@yahoo.co.jp [International Institute of Green Materials, Josai International University, Togane 283-8555 (Japan); School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Department of Physics, King Abdulaziz University, Jeddah 22254 (Saudi Arabia); Wang, Z.; Louzguine-Luzgin, D.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Han, Y. [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Kong, F.L. [International Institute of Green Materials, Josai International University, Togane 283-8555 (Japan); Shalaan, E.; Al-Marzouki, F. [Department of Physics, King Abdulaziz University, Jeddah 22254 (Saudi Arabia)

2015-07-25

Highlights: • A multicomponent Zr{sub 55}Al{sub 10}Fe{sub 6}Co{sub 6}Ni{sub 6}Cu{sub 6}Pd{sub 6}Ag{sub 5} bulk glassy alloy was formed. • The high-order multiplication suppression of the decrease in mechanical strength. • The BGAs show good corrosion resistance and slow growth rate of primary precipitates. - Abstract: We examined the formation, thermal stability, mechanical properties and corrosion behavior of a multicomponent Zr{sub 55}Al{sub 10}Fe{sub 6}Co{sub 6}Ni{sub 6}Cu{sub 6}Pd{sub 6}Ag{sub 5} bulk glassy alloy, with the aim of clarifying the effect of high-order multiplication of the number of components on their properties. The bulk glassy alloy rods of 2 and 6 mm in diameter were formed by suction casting even at the low total content of typical glass-forming 3-d late transition metals like Co, Ni and Cu. The Vickers hardness is different in the center region and in the outer surface region. The difference seems to reflect the relaxation level of glassy structure. The Young’s modulus and the compressive fracture strength are nearly the same for the base Zr{sub 55}Al{sub 10}Ni{sub 5}Cu{sub 30} alloy in spite of the existence of immiscible atomic pairs. Moreover, the multicomponent alloy exhibits better corrosion resistance than that for the base alloy. The glassy phase changes to a supercooled liquid state at 720 K and then starts to crystallize at 754 K with a single exothermic peak, in contrast to the appearance of a wide supercooled liquid region for the base alloy. The primary crystalline phase precipitates with very short incubation time and very low growth rate, which are different from those for the base alloy. The extremely low growth rate of the crystallites is presumably due to the reduction of diffusivity of late transition metal elements resulting from multiplication. Thus, the high-order multiplication has the features of (1) the maintenance of high glass-forming ability even at the lower Co, Ni and Cu content and in the absence of

New Scenario of Dynamical Heterogeneity in Supercooled Liquid and Glassy States of 2D Monatomic System.

Science.gov (United States)

Van Hoang, Vo; Teboul, Victor; Odagaki, Takashi

2015-12-24

Via analysis of spatiotemporal arrangements of atoms based on their dynamics in supercooled liquid and glassy states of a 2D monatomic system with a double-well Lennard-Jones-Gauss (LJG) interaction potential, we find a new scenario of dynamical heterogeneity. Atoms with the same or very close mobility have a tendency to aggregate into clusters. The number of atoms with high mobility (and size of their clusters) increases with decreasing temperature passing over a maximum before decreasing down to zero. Position of the peak moves toward a lower temperature if mobility of atoms in clusters is lower together with an enhancement of height of the peak. In contrast, the number of atoms with very low mobility or solidlike atoms (and size of their clusters) has a tendency to increase with decreasing temperature and then it suddenly increases in the vicinity of the glass transition temperature leading to the formation of a glassy state. A sudden increase in the number of strongly correlated solidlike atoms in the vicinity of a glass transition temperature (Tg) may be an origin of a drastical increase in viscosity of the glass-forming systems approaching the glass transition. In fact, we find that the diffusion coefficient decays exponentially with a fraction of solidlike atoms exhibiting a sudden decrease in the vicinity of the glass transition region.

Molecular dynamics in supercooled liquid and glassy states of antibiotics: azithromycin, clarithromycin and roxithromycin studied by dielectric spectroscopy. Advantages given by the amorphous state.

Science.gov (United States)

Adrjanowicz, K; Zakowiecki, D; Kaminski, K; Hawelek, L; Grzybowska, K; Tarnacka, M; Paluch, M; Cal, K

2012-06-04

Antibiotics are chemical compounds of extremely important medical role. Their history can be traced back more than one hundred years. Despite the passing time and significant progress made in pharmacy and medicine, treatment of many bacterial infections without antibiotics would be completely impossible. This makes them particularly unique substances and explains the unflagging popularity of antibiotics within the medical community. Herein, using dielectric spectroscopy we have studied the molecular mobility in the supercooled liquid and glassy states of three well-known antibiotic agents: azithromycin, clarithromycin and roxithromycin. Dielectric studies revealed a number of relaxation processes of different molecular origin. Besides the primary α-relaxation, observed above the respective glass transition temperatures of antibiotics, two secondary relaxations in the glassy state were identified. Interestingly, the fragility index as well as activation energies of the secondary processes turned out to be practically the same for all three compounds, indicating probably much the same molecular dynamics. Long-term stability of amorphous antibiotics at room temperature was confirmed by X-ray diffraction technique, and calorimetric studies were performed to evaluate the basic thermodynamic parameters. Finally, we have also checked the experimental solubility advantages given by the amorphous form of the examined antibiotics.

Glassy aerosols with a range of compositions nucleate ice heterogeneously at cirrus temperatures

Directory of Open Access Journals (Sweden)

T. W. Wilson

2012-09-01

Full Text Available Atmospheric secondary organic aerosol (SOA is likely to exist in a semi-solid or glassy state, particularly at low temperatures and humidities. Previously, it has been shown that glassy aqueous citric acid aerosol is able to nucleate ice heterogeneously under conditions relevant to cirrus in the tropical tropopause layer (TTL. In this study we test if glassy aerosol distributions with a range of chemical compositions heterogeneously nucleate ice under cirrus conditions. Three single component aqueous solution aerosols (raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA and levoglucosan and one multi component aqueous solution aerosol (raffinose mixed with five dicarboxylic acids and ammonium sulphate were studied in both the liquid and glassy states at a large cloud simulation chamber. The investigated organic compounds have similar functionality to oxidised organic material found in atmospheric aerosol and have estimated temperature/humidity induced glass transition thresholds that fall within the range predicted for atmospheric SOA. A small fraction of aerosol particles of all compositions were found to nucleate ice heterogeneously in the deposition mode at temperatures relevant to the TTL (<200 K. Raffinose and HMMA, which form glasses at higher temperatures, nucleated ice heterogeneously at temperatures as high as 214.6 and 218.5 K respectively. We present the calculated ice active surface site density, n_s, of the aerosols tested here and also of glassy citric acid aerosol as a function of relative humidity with respect to ice (RH_i. We also propose a parameterisation which can be used to estimate heterogeneous ice nucleation by glassy aerosol for use in cirrus cloud models up to ~220 K. Finally, we show that heterogeneous nucleation by glassy aerosol may compete with ice nucleation on mineral dust particles in mid-latitudes cirrus.

Ferromagnetic bulk glassy alloys

International Nuclear Information System (INIS)

Inoue, Akihisa; Makino, Akihiro; Mizushima, Takao

2000-01-01

This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

Formation and Applications of Bulk Glassy Alloys in Late Transition Metal Base System

International Nuclear Information System (INIS)

Inoue, Akihisa; Shen Baolong

2006-01-01

This paper reviews our recent results of the formation, fundamental properties, workability and applications of late transition metal (LTM) base bulk glassy alloys (BGAs) developed since 1995. The BGAs were obtained in Fe-(Al,Ga)-(P,C,B,Si), Fe-(Cr,Mo)-(C,B), Fe-(Zr,Hf,Nb,Ta)-B, Fe-Ln-B(Ln=lanthanide metal), Fe-B-Si-Nb and Fe-Nd-Al for Fe-based alloys, Co-(Ta,Mo)-B and Co-B-Si-Nb for Co-based alloys, Ni-Nb-(Ti,Zr)-(Co,Ni) for Ni-based alloys, and Cu-Ti-(Zr,Hf), Cu-Al-(Zr,Hf), Cu-Ti-(Zr,Hf)-(Ni,Co) and Cu-Al-(Zr,Hf)-(Ag,Pd) for Cu-based alloys. These BGAs exhibit useful properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based glassy alloys have good soft magnetic properties which cannot be obtained for amorphous and crystalline type magnetic alloys. The Fe- and Ni-based BGAs have already been used in some application fields. These LTM base BGAs are promising as new metallic engineering materials

How mechanical behavior of glassy polymers enables us to characterize melt deformation: elastic yielding in glassy state after melt stretching?

Science.gov (United States)

Wang, Shi-Qing; Zhao, Zhichen; Tsige, Mesfin; Zheng, Yexin

Fast melt deformation well above the glass transition temperature Tg is known to produce elastic stress in an entangled polymer due to the chain entropy loss at the length scale of the network mesh size. Here chains of high molecular weight are assumed to form an entanglement network so that such a polymer behaves transiently like vulcanized rubber capable of affine deformation. We consider quenching a melt-deformed glassy polymer to well below Tg to preserve the elastic stress. Upon heating such a sample to Tg, the sample can return to the shape it took before melt deformation. This is the basic principle behind the design of all polymer-based shape-memory materials. This work presents intriguing evidence based on both experiment and computer simulation that the chain network, deformed well above Tg, can drive the glassy polymer to undergo elastic yielding. Our experimental systems include polystyrene, poly(methyl methacrylate) and polycarbonate; the molecular dynamics simulation is based on Kremer-Grest bead-spring model. National Science Foundation (DMR-1444859 and DMR-1609977).

Determining the structural relaxation times deep in the glassy state of the pharmaceutical Telmisartan

Energy Technology Data Exchange (ETDEWEB)

Adrjanowicz, K; Paluch, M [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Ngai, K L [Naval Research Laboratory, Washington, DC 20375-5320 (United States)

2010-03-31

By using the dielectric relaxation method proposed recently by Casalini and Roland (2009 Phys. Rev. Lett. 102 035701), we were able to determine the structural alpha-relaxation times deep in the glassy state of the pharmaceutical, Telmisartan. Normally, deep in the glassy state tau{sub a}lpha is so long that it cannot be measured but tau{sub b}eta, which is usually much shorter, can be directly determined. The method basically takes advantage of the connection between the alpha-relaxation and the secondary beta-relaxation of the Johari-Goldstein kind, including a relation between their relaxation times tau{sub a}lpha and tau{sub b}eta, respectively. Thus, tau{sub a}lpha of Telmisartan were determined by monitoring the change of the dielectric beta-loss, epsilon'', with physical aging time at temperatures well below the vitrification temperature. The values of tau{sub a}lpha were compared with those expected by the coupling model (CM). Unequivocal comparison cannot be made in the case of Telmisartan because its beta-loss peak is extremely broad, and the CM predicts only an order of magnitude agreement between the primitive relaxation frequency and the beta-peak frequency. We also made an attempt to analyze all isothermal and aging susceptibility data after transformation into the electric modulus representation. The tau{sub a}lpha found in the glass state by using the method of Casalini and Roland in the modulus representation are similar to those obtained in the susceptibility representation. However, it is remarkable that the stretching parameter beta{sub KWWM} = 0.51 in the electric modulus representation gives more precise fits to the aging data than in the susceptibility representation with beta{sub KWW} = 0.61. Our results suggest that the electric modulus representation may be useful as an alternative to analyze aging data, especially in the case of highly polar glassformers having a large ratio of low frequency and high frequency dielectric

Pseudobinary glassy compositions (AsSex)1-y(AsTex)y

International Nuclear Information System (INIS)

El Mously, M.K.; El Dem, M.B.

1987-09-01

The ternery glassy composition of the general formula (AsSe x ) 1-y (AsTe x ) y can be considered as a pseudobinary system at x=1, 3/2 and 5/2 and 0 ≤ y ≤ 1. The results of DTA, electrical conductivity measurements, density of such glasses as well as the X-ray diffraction of the crystallized samples have been used to confirm this point of view and to explain the presence of new phases not shown in the simple binary systems As-Se and As-Te. The possibility of transformation of the glassy network from partially polymerized state MCN (molecular cluster network) to completely polymerized state CRN (continuous random network) by mixing two structural units was also discussed. (author). 12 refs, 7 figs, 2 tabs

Glassy behavior in the layered perovskites La2−xSrxCoO4(1.1≤x≤1.3)

International Nuclear Information System (INIS)

Mukherjee, S.; Mukherjee, Rajarshi; Banerjee, S.; Ranganathan, R.; Kumar, Uday

2012-01-01

The glassy behavior of the phase segregated state in the layered cobaltite La 2−x Sr x CoO 4 has been studied. The role of the inter-cluster interactions as well as the disordered spins at the paramagnetic–ferromagnetic interface, behind the observed glassy behavior have been investigated. The disordered spins at the interface appear to be strongly pinned, and they contribute little to the observed glassy behavior. On the other hand, the inter-cluster interactions play the key role. Both the Co 4+ and Co 3+ ions are in the intermediate spin state. - Highlights: ► Phase segregated state of cobaltite La 2−x Sr x CoO 4 for (1.1≤x≤1.3) to find the origin of the observed glassy behavior. ► Result of the frequency dependent ac susceptibility measurement excludes the possibility of any spin glass phase, hints strong inter-cluster interactions. ► Relaxation experiments confirm the system to be a collection of clusters with two preferred sizes. ► The glassy behavior originates from strong inter-cluster interactions.

Dynamical structure analysis of crystalline-state reaction and elucidation of chemical reactivity in crystalline environment

International Nuclear Information System (INIS)

Ohashi, Yuji

2010-01-01

It was found that a chiral alkyl group bonded to the cobalt atom in a cobalt complex crystal was racemized with retention of the single crystal form on exposure to visible light. Such reactions, which are called crystalline-state reactions, have been found in a variety of cobalt complex crystals. The concept of reaction cavity was introduced to explain the reaction rate quantitatively and the chirality of the photo-product. The new diffractometers and detectors were made for rapid data collection. The reaction mechanism was also elucidated using neutron diffraction analysis. The unstable reaction intermediates were analyzed using cryo-trapping method. The excited-state structures were obtained at the equilibrium state between ground and excited states. (author)

Permeation of Mixed Penetrants through Glassy Polymer Membranes.

Science.gov (United States)

1985-03-15

and LOPE. Also, ESCA was used in conjunction with plasma etching to determine the effects of the gas phase fluorine concentration and fluorination...at 35 3C. ARD-AISS5 65 PERMEATION OF MIXED PENETRANTS THROUGH GLASSY POLYMER 213 MENBRANES (U) NORTH CAROLINA STATE UNIV AT RALEIGH R T CHERN ET AL. 15

Study of crystallization kinetics and structural relaxation behavior in phase separated Ag{sub 33}Ge{sub 17}Se{sub 50} glassy alloys

Energy Technology Data Exchange (ETDEWEB)

Kumar, Praveen, E-mail: prafiziks@gmail.com [Semiconductors Laboratory, Department of Physics, GND University, Amritsar 143005 (India); Nanotechnology Research Centre, DAV Institute of Engineering and Technology, Kabir Nagar, Jalandhar 144008 (India); Yannopoulos, S.N. [Foundation for Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH/ICE-HT), P.O. Box 1414, GR-26 504, Rio-Patras (Greece); Sathiaraj, T.S. [Department of Physics, University of Botswana, Gaborone (Botswana); Thangaraj, R., E-mail: rthangaraj@rediffmail.com [Semiconductors Laboratory, Department of Physics, GND University, Amritsar 143005 (India)

2012-07-16

We report on the crystallization processes and structure (crystal phases) of Ag{sub 33}Ge{sub 17}Se{sub 50} glassy alloy using differential scanning calorimetry and x-ray diffraction techniques, respectively. The devitrification that gives rise to the first exothermic peak results in the crystallization of Ag{sub 2}Se and Ag{sub 8}GeSe{sub 6} phases, while the growth of GeSe{sub 2} accompanied by the transformation of Ag{sub 8}GeSe{sub 6} to Ag{sub 2}Se phase occurs during the second crystallization process. Different theoretical models are used to elucidate various kinetic parameters for the crystallization transformation process in this phase separated system. With annealing below the glass transition temperature, an inverse behavior between the variation of the optical gap and the band tailing parameter is observed for the thermally evaporated films. These results are explained as the mixing of different clusters/species in the amorphous state and/or changes caused by structural relaxation of the glassy network for the thermally evaporated films. - Highlights: Black-Right-Pointing-Pointer Phase separation in Ag{sub 33}Ge{sub 17}Se{sub 50} glassy alloy bordering two glass forming regions. Black-Right-Pointing-Pointer Transformation of Ag{sub 8}GeSe{sub 6} {yields} Ag{sub 2}Se along with crystallization GeSe{sub 2} phase. Black-Right-Pointing-Pointer Elucidation of various kinetic parameters for the crystalline transformation. Black-Right-Pointing-Pointer Structural relaxation in thermally evaporated films by optical spectroscopy.

Glassy carbon coated graphite for nuclear applications

International Nuclear Information System (INIS)

Delpeux S; Cacciaguerra T; Duclaux L

2005-01-01

Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF 2 , ThF 4 , and UF 4 ) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin or polyvinyl chloride precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm 3 and closed pores with nano-metric size (∼ 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons, in good agreement with the proposed texture model for glassy carbon. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry of the graphite substrate. The deposit regions where

Glassy carbon coated graphite for nuclear applications

Energy Technology Data Exchange (ETDEWEB)

Delpeux, S.; Cacciaguerra, T.; Duclaux, L. [Orleans Univ., CRMD, CNRS, 45 (France)

2005-07-01

Taking into account the problems caused by the treatment of nuclear wastes, the molten salts breeder reactors are expected to a great development. They use a molten fluorinated salt (mixture of LiF, BeF{sub 2}, ThF{sub 4}, and UF{sub 4}) as fuel and coolant. The reactor core, made of graphite, is used as a neutrons moderator. Despite of its compatibility with nuclear environment, it appears crucial to improve the stability and inertness of graphite against the diffusion of chemicals species leading to its corrosion. One way is to cover the graphite surface by a protective impermeable deposit made of glassy carbon obtained by the pyrolysis of phenolic resin [1,2] or polyvinyl chloride [3] precursors. The main difficulty in the synthesis of glassy carbon is to create exclusively, in the primary pyrolysis product, a micro-porosity of about twenty Angstroms which closes later at higher temperature. Therefore, the evacuation of the volatile products occurring mainly between 330 and 600 C, must progress slowly to avoid the material to crack. In this study, the optimal parameters for the synthesis of glassy carbon as well as glassy carbon deposits on nuclear-type graphite pieces are discussed. Both thermal treatment of phenolic and PVC resins have been performed. The structure and micro-texture of glassy carbon have been investigated by X-ray diffraction, scanning and transmission electron microscopies and helium pycno-metry. Glassy carbon samples (obtained at 1200 C) show densities ranging from 1.3 to 1.55 g/cm{sup 3} and closed pores with nano-metric size ({approx} 5 to 10 nm) appear clearly on the TEM micrographs. Then, a thermal treatment to 2700 C leads to the shrinkage of the entangled graphene ribbons (Fig 1), in good agreement with the proposed texture model for glassy carbon (Fig 2) [4]. Glassy carbon deposits on nuclear graphite have been developed by an impregnation method. The uniformity of the deposit depends clearly on the surface texture and the chemistry

Shear-transformation-zone theory of linear glassy dynamics.

Science.gov (United States)

Bouchbinder, Eran; Langer, J S

2011-06-01

We present a linearized shear-transformation-zone (STZ) theory of glassy dynamics in which the internal STZ transition rates are characterized by a broad distribution of activation barriers. For slowly aging or fully aged systems, the main features of the barrier-height distribution are determined by the effective temperature and other near-equilibrium properties of the configurational degrees of freedom. Our theory accounts for the wide range of relaxation rates observed in both metallic glasses and soft glassy materials such as colloidal suspensions. We find that the frequency-dependent loss modulus is not just a superposition of Maxwell modes. Rather, it exhibits an α peak that rises near the viscous relaxation rate and, for nearly jammed, glassy systems, extends to much higher frequencies in accord with experimental observations. We also use this theory to compute strain recovery following a period of large, persistent deformation and then abrupt unloading. We find that strain recovery is determined in part by the initial barrier-height distribution, but that true structural aging also occurs during this process and determines the system's response to subsequent perturbations. In particular, we find by comparison with experimental data that the initial deformation produces a highly disordered state with a large population of low activation barriers, and that this state relaxes quickly toward one in which the distribution is dominated by the high barriers predicted by the near-equilibrium analysis. The nonequilibrium dynamics of the barrier-height distribution is the most important of the issues raised and left unresolved in this paper.

Pressure-induced transformations in computer simulations of glassy water

Science.gov (United States)

Chiu, Janet; Starr, Francis W.; Giovambattista, Nicolas

2013-11-01

Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and high-density amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-induced LDA-to-HDA, (ii) decompression-induced HDA-to-LDA, and (iii) compression-induced hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a low-density and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative pressures, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high pressure to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water.

The factor that determines photo-induced crystalline-state reaction

International Nuclear Information System (INIS)

Takenaka, Y.

1995-01-01

The photo-induced crystalline-state reaction of cobaloxime complexes were investigated by X-ray diffraction method. The reactivity or the reaction rate is dependent only on the volume of the reaction cavity. The hydrogen bond formation of the reactive group and the difference of the base ligand have no effect. (author)

The Effect of PtRuIr Nanoparticle Crystallinity in Electrocatalytic Methanol Oxidation

Directory of Open Access Journals (Sweden)

Vladimir Linkov

2013-04-01

Full Text Available Two structural forms of a ternary alloy PtRuIr/C catalyst, one amorphous and one highly crystalline, were synthesized and compared to determine the effect of their respective structures on their activity and stability as anodic catalysts in methanol oxidation. Characterization techniques included TEM, XRD, and EDX. Electrochemical analysis using a glassy carbon disk electrode for cyclic voltammogram and chronoamperometry were tested in a solution of 0.5 mol L−1 CH3OH and 0.5 mol L−1 H2SO4. Amorphous PtRuIr/C catalyst was found to have a larger electrochemical surface area, while the crystalline PtRuIr/C catalyst had both a higher activity in methanol oxidation and increased CO poisoning rate. Crystallinity of the active alloy nanoparticles has a big impact on both methanol oxidation activity and in the CO poisoning rate.

Response to state comments on the draft regional characterization reports for the Crystalline Repository Project

International Nuclear Information System (INIS)

1984-11-01

In May, 1983, the US Department of Energy (DOE) Crystalline Repository Project Office (CPO) issued six draft Regional Characterization Reports (RCRs) for review and comment to the 17 Crystalline States comprising the Northeastern, Southeastern, and North Central crystalline regions. Comment letters were received from 13 of the 17 states. The more than 2000 comments generally focused on the quality and content of the characterization reports and on their intended use in region-to-area screening. These comments were paraphrased and grouped into 23 subjects within the following four topical areas: (1) General and Programmatic; (2) Geologic; (3) Environmental and Socioeconomic; and (4) Editorial. This document provides responses to the comments submitted by the states

Positron annihilation study of graphite, glassy carbon and C60/C70 fullerene

International Nuclear Information System (INIS)

Hasegawa, Masayuki; Kajino, Masahiro; Yamaguchi, Sadae; Iwata, Tadao; Kuramoto, Eiichi; Takenaka, Minoru.

1992-01-01

ACAR (Angular Correlation of Annihilation Radiation) and positron lifetime measurements have been made on, HOPG (Highly Oriented Pyrolytic Graphite), isotropic fine-grained graphite, glassy carbons and C 60 /C 70 powder. HOPG showed marked bimodality along the c-axis and anisotropy in ACAR momentum distribution, which stem from characteristic annihilation between 'interlayer' positrons and π-electrons in graphite. ACAR curves of the isotropic graphite and glassy carbons are even narrower than that of HOPG perpendicular to the c-axis. Positron lifetime of 420 and 390 - 480 psec, much longer than that of 221 psec in HOPG, were observed for the isotropic graphite and glassy carbons respectively, which are due to positron trapping in structural voids in them. Positron lifetime and ACAR width (FWHM) can be well correlated to void sizes (1.7 to 5.0 nm) of glassy carbons which have been determined by small angle neutron (SAN) scattering measurements. ACAR curves and positron lifetime of C 60 /C 70 powder agree well with those of glassy carbons. This shows that positron wave functions extend, as in the voids of glassy carbons, much wider than open spaces of the octahedral interstices of the face-centered cubic (FCC) structure of C 60 crystal and strongly suggests positron trapping in the 'soccer ball' vacancy. Possible positron states in the carbon materials are discussed with a simple model of void volume-trapping. Preliminary results on neutron irradiation damage in HOPG are also presented. (author)

Mechanics of amorphous solids—identification and constitutive modelling

NARCIS (Netherlands)

van Dommelen, J.A.W.; Estevez, R.

2018-01-01

Both polymers and metals can be in an organised crystalline or amorphous glassy state, where for polymers usually at least a part of the structure is amorphous and metals are in a glassy state only when processed under special conditions. At the 15th European Mechanics of Materials Conference in

Electrical resistivity in Zr48Nb8Cu12Fe8Be24 glassy and crystallized alloys

Science.gov (United States)

Bai, H. Y.; Tong, C. Z.; Zheng, P.

2004-02-01

The electrical resistivity of Zr48Nb8Cu12Fe8Be24 bulk metallic glassy and crystallized alloys in the temperature range of 4.2-293 K is investigated. It is found that the resistivity in glassy and crystallized states shows opposite temperature coefficients. For the metallic glass, the resistivity shows a negative logarithmic dependence at temperatures below 16 K, whereas it has more normal behavior for the crystallized alloy. At higher temperatures, the resistivity in both glassy and crystallized alloys shows dependence upon both T and T2, but the signs of the T and T2 terms are opposite. The results are interpreted in terms of scattering from two-level tunneling states in glasses and the generalized Ziman diffraction model.

Multiscale simulations of PS-SiO2 nanocomposites: from melt to glassy state.

Science.gov (United States)

Mathioudakis, I G; Vogiatzis, G G; Tzoumanekas, C; Theodorou, D N

2016-09-28

The interaction energetics, molecular packing, entanglement network properties, segmental dynamics, and elastic constants of atactic polystyrene-amorphous silica nanocomposites in the molten and the glassy state are studied via molecular simulations using two interconnected levels of representation: (a) a coarse-grained one, wherein each polystyrene repeat unit is mapped onto a single "superatom" and the silica nanoparticle is viewed as a solid sphere. Equilibration at all length scales at this level is achieved via connectivity-altering Monte Carlo simulations. (b) A united-atom (UA) level, wherein the polymer chains are represented in terms of a united-atom forcefield and the silica nanoparticle is represented in terms of a simplified, fully atomistic model. Initial configurations for UA molecular dynamics (MD) simulations are obtained by reverse mapping well-equilibrated coarse-grained configurations. By analysing microcanonical UA MD trajectories, the polymer density profile is studied and the polymer is found to exhibit layering in the vicinity of the nanoparticle surface. An estimate of the enthalpy of mixing between polymer and nanoparticles, derived from the UA simulations, compares favourably against available experimental values. The dynamical behaviour of polystyrene (in neat and filled melt systems) is characterized in terms of bond orientation and dihedral angle time autocorrelation functions. At low concentration in the molten polymer matrix, silica nanoparticles are found to cause a slight deceleration of the segmental dynamics close to their surface compared to the bulk polymer. Well-equilibrated coarse-grained long-chain configurations are reduced to entanglement networks via topological analysis with the CReTA algorithm, yielding a slightly lower density of entanglements in the filled than in the neat systems. UA melt configurations are glassified by MD cooling. The elastic moduli of the resulting glassy nanocomposites are computed through an

Time effects and glassy state behaviour in superconducting Y1Ba2Cu3O7-x

International Nuclear Information System (INIS)

Altinkok, A.; Yetis, H.; Olutas, M.; Kilic, K.; Kilic, A.

2007-01-01

The quenched disorder in the moving entity is investigated in a polycrystalline bulk sample of Y 1 Ba 2 Cu 3 O 7-x (YBCO) by slow transport relaxation measurements (V-t curves) on long time scales. The time evolution of sample voltage (V-t curve) are correlated to spatial reorganization of the driving current together with increasing or decreasing of resistive and non-resistive flow channels in a multiple connected network. In addition, it is shown that the voltage decays appearing in V-t curves are characterized by an exponential time dependence which is analogous to the glassy state relaxation

Crystalline state photoreactions direct observation of reaction processes and metastable intermediates

CERN Document Server

Ohashi, Yuji

2014-01-01

Offering some 300 references, this book focuses on chemical reactions in the crystalline state. The reactions span many fields in inorganic and organic chemistry, making this a useful resource for inorganic, organic and physical chemists and graduate students.

Glassy behavior in the layered perovskites La{sub 2-x}Sr{sub x}CoO{sub 4}(1.1{<=}x{<=}1.3)

Energy Technology Data Exchange (ETDEWEB)

Mukherjee, S., E-mail: sanseb68@yahoo.co.in [Department of Physics, University of Burdwan, Burdwan 713104 (India); Mukherjee, Rajarshi [Department .of Physics, University of Burdwan, Burdwan 713104 (India); Banerjee, S.; Ranganathan, R. [Saha Institute of Nuclear Physics, Kolkata 700 064 (India); Kumar, Uday [Department of Physical Sciences, Indian Institute of Science Education and Research - Kolkata, Mohonpur 741252 (India)

2012-03-15

The glassy behavior of the phase segregated state in the layered cobaltite La{sub 2-x}Sr{sub x}CoO{sub 4} has been studied. The role of the inter-cluster interactions as well as the disordered spins at the paramagnetic-ferromagnetic interface, behind the observed glassy behavior have been investigated. The disordered spins at the interface appear to be strongly pinned, and they contribute little to the observed glassy behavior. On the other hand, the inter-cluster interactions play the key role. Both the Co{sup 4+} and Co{sup 3+} ions are in the intermediate spin state. - Highlights: Black-Right-Pointing-Pointer Phase segregated state of cobaltite La{sub 2-x}Sr{sub x}CoO{sub 4} for (1.1{<=}x{<=}1.3) to find the origin of the observed glassy behavior. Black-Right-Pointing-Pointer Result of the frequency dependent ac susceptibility measurement excludes the possibility of any spin glass phase, hints strong inter-cluster interactions. Black-Right-Pointing-Pointer Relaxation experiments confirm the system to be a collection of clusters with two preferred sizes. Black-Right-Pointing-Pointer The glassy behavior originates from strong inter-cluster interactions.

Tuning the size-dependent He-irradiated tolerance and strengthening behavior of crystalline/amorphous Cu/Ta nanostructured multilayers

Energy Technology Data Exchange (ETDEWEB)

Liang, X.Q.; Zhang, J.Y., E-mail: jinyuzhang1002@mail.xjtu.edu.cn; Wang, Y.Q.; Wu, S.H.; Zeng, F.; Wu, K.; Liu, G., E-mail: lgsammer@mail.xjtu.edu.cn; Zhang, G.J.; Sun, J.

2016-08-30

Nanoindentation methodology was used to measure the hardness of Cu/Ta crystalline/amorphous nanostructured multilayers (CANMs) before and after He ion-implantation at room temperature. These CANMs have a constant modulation period (λ=25 nm) but different modulation ratios (η=h{sub Ta} / h{sub Cu}) spanning from 0.11 to 1.0. It is found that in sharp contrast to previously reported Cu/Cu-Zr CANMs by Zhang et al. [9], the He-irradiated Cu/Ta samples exhibit much greater microstructure stability without radiation-induced devitrification (RID) of glassy Ta nanolayers at smaller η (except the sample at η=1.0). Both the as-deposited and irradiated Cu/Ta CANMs manifest the monotonically increased hardness with decreasing η, however, there is an unexpected transition from size-dependent irradiation hardening at η<1.0 to softening at η≥1.0 caused by a competition between dislocation-bubble interactions in crystalline nanolayers and RID in glassy nanolayers. These findings not only provide fundamental understanding of the radiation-induced defect effect on plastic characteristics of CANMs, but also offer guidance for their microstructure sensitive design for performance optimization at a critical modulation ratio under extreme conditions.

NATO Advanced Study Institute on the Physics of Structurally Disordered Solids

CERN Document Server

1976-01-01

Structurally disordered solids are characterized by their lack of spatial order that is evidenced by the great variety of ordered solids. The former class of materials is commonly termed amorphous or glassy, the latter crystalline. However, both classes share, many of the other physical properties of solids, e. g. , me­ chanical stability, resistance to shear stress, etc. The traditional macroscopic distinction between the crystalline and the glassy states is that while the former has a fixed melting point, the latter does not. However, with the availability and production of a large number of materials in both crystalline and amorphous states, and their easy inter-convertability, simple de­ finitions are not possible or at best imprecise. For the present purpose, it is sufficient to say that in contrast to the crystalline state, in which the posi­ tions of atoms are fixed into adefinite structure, ex­ cept for small thermal vibrations, the amorphous state of the same material displays varying degrees of ...

Dielectric relaxation studies in super-cooled liquid and glassy phases of anti-cancerous alkaloid: Brucine

Science.gov (United States)

Afzal, Aboothahir; Shahin Thayyil, M.; Sulaiman, M. K.; Kulkarni, A. R.

2018-05-01

Brucine has good anti-tumor effects, on both liver cancer and breast cancer. It has bioavailability of 40.83%. Since the bioavailability of the drug is low, an alternative method to increase its bioavailability and solubility is by changing the drug into glassy form. We used Differential Scanning Calorimetry (DSC) for studying the glass forming ability of the drug. Brucine was found to be a very good glass former glass transition temperature 365 K. Based on the DSC analysis we have used broadband dielectric spectroscopy (BDS) for studying the drug in the super cooled and glassy state. BDS is an effective tool to probe the molecular dynamics in the super cooled and glassy state. Molecular mobility is found to be present even in the glassy state of this active pharmaceutical ingredient (API) which is responsible for the instability. Our aim is to study the factors responsible for instability of this API in amorphous form. Cooling curves for dielectric permittivity and dielectric loss revealed the presence of structural (α) and secondary relaxations (β and γ). Temperature dependence of relaxation time is fitted by Vogel-Fulcher-Tammann equation and found the values of activation energy of the α relaxation, fragility and glass transition temperature. Paluch's anti correlation is also verified, that the width of the α-loss peak at or near the glass transition temperature Tg is strongly anticorrelated with the polarity of the molecule. The larger the dielectric relaxation strength Δɛ (Tg) of the system, the narrower is the α-loss peak (higher value of βKWW).

Low temperature thermal conductivities of glassy carbons

International Nuclear Information System (INIS)

Anderson, A.C.

1979-01-01

The thermal conductivity of glassy carbon in the temperature range 0.1 to 100 0 K appears to depend only on the temperature at which the material was pyrolyzed. The thermal conductivity can be related to the microscopic structure of glassy carbon. The reticulated structure is especially useful for thermal isolation at cryogenic temperatures

Polymer and Polymer Gel of Liquid Crystalline Semiconductors

Institute of Scientific and Technical Information of China (English)

Teppei Shimakawa; Naoki Yoshimoto; Jun-ichi Hanna

2004-01-01

It prepared a polymer and polymer gel of a liquid crystalline (LC) semiconductor having a 2-phenylnaphthalene moiety and studied their charge carrier transport properties by the time-of-flight technique. It is found that polyacrylate having the mesogenic core moiety of 2-phenylnaphtalene (PNP-acrylate) exhibited a comparable mobility of 10-4cm2/Vs in smectic A phase to those in smectic A (SmA) phase of small molecular liquid crystals with the same core moiety, e.g., 6-(4'-octylphenyl)- 2-dodecyloxynaphthalene (8-PNP-O12), and an enhanced mobility up to 10-3cm2/Vs in the LC-glassy phase at room temperature, when mixed with a small amount of 8-PNP-O12. On the other hand, the polymer gel consisting of 20 wt %-hexamethylenediacrylate (HDA)-based cross-linked polymer and 8-PNP-O12 exhibited no degraded mobility when cross-linked at the mesophase. These results indicate that the polymer and polymer composite of liquid crystalline semiconductors provide us with an easy way to realize a quality organic semiconductor thin film for the immediate device applications.

Treatment of early glassy cell carcinoma of uterine cervix

International Nuclear Information System (INIS)

Kim, Ok Bae; Kim, Jin Hee; Choi, Tae Jin

2006-01-01

The purpose of this study was to investigate the clinical findings, treatment, and outcome of patients with glassy cell carcinoma of cervix. We reviewed all cases of glassy cell carcinoma of the uterine cervix confirmed and treated at the Dongsan Medical Center, Keimyung University, between January 1993 and December 2005. There were 7 cases with histopathologically confirmed gassy cell carcinoma. A tumor was diagnosed as glassy cell carcinoma if over 50% of the tumor cell type displayed glassy cell features. Six patients with stage IB had radical hysterectomy and bilateral pelvic node dissection, and 2 of them received adjuvant external pelvic irradiation with concurrent chemotherapy. Remaining one patient with stage IIA had curative concurrent chemoradiotherapy with external pelvic irradiation and brachytherapy. There were 7 patients diagnosed as glassy cell carcinoma among the 3,745 (0.2%) patients of carcinoma of uterine cervix. The mean age of 7 patients was 44 years with range of 35 to 53 years of age. The most frequent symptom was vaginal bleeding (86%). By the punch biopsy undertaken before treatment of 7 cases, 2 only cases could diagnose as glassy cell carcinoma of uterine cervix, but remaining of them confirmed by surgical pathological examination. The mean follow up duration was 73 months with range of 13 to 150 months. All 7 patients were alive without disease after treatment. Glassy cell carcinoma of the uterine cervix is a distinct clinicopathologic entity that demonstrates an aggressive biologic behavior. However for early-stage disease, we may have more favorable clinical outcome with radical surgery followed by chemoradiotherapy

EDTA modified glassy carbon electrode: Preparation and characterization

International Nuclear Information System (INIS)

Ustuendag, Zafer; Solak, Ali Osman

2009-01-01

EDTA-phenoxyamide modified glassy carbon electrode (EDTA-GC) was prepared at a glassy carbon electrode by surface synthesis. In the first step, nitrophenyl was grafted to the glassy carbon (GC) surface via the electrochemical reduction of its tetraflouroborate diazonium salt. In the second step, nitrophenyl-modified electrode (NP-GC) was subjected to the cathodic potential scan to reduce the nitro to amine group. p-Aminophenyl modified glassy carbon electrode (AP-GC) was dipped into a EDTA solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide (EDC) as an activating agent. Thus formed ((2-anilino-2-oxoethyl){2-[bis(carboxymethyl)amino]-ethyl}amino)acetic acid modified GC electrode was denoted as EDTA-GC and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry and X-ray photoelectron spectroscopy (XPS). Complexation of the EDTA-GC surface with Pb 2+ ions was investigated if this electrode could be used as a metal sensor.

Boron ion irradiation induced structural and surface modification of glassy carbon

International Nuclear Information System (INIS)

Kalijadis, Ana; Jovanović, Zoran; Cvijović-Alagić, Ivana; Laušević, Zoran

2013-01-01

The incorporation of boron into glassy carbon was achieved by irradiating two different types of targets: glassy carbon polymer precursor and carbonized glassy carbon. Targets were irradiated with a 45 keV B 3+ ion beam in the fluence range of 5 × 10 15 –5 × 10 16 ions cm −2 . For both types of targets, the implanted boron was located in a narrow region under the surface. Following irradiation, the polymer was carbonized under the same condition as the glassy carbon samples (at 1273 K) and examined by Raman spectroscopy, temperature programmed desorption, hardness and cyclic voltammetry measurements. Structural analysis showed that during the carbonization process of the irradiated polymers, boron is substitutionally incorporated into the glassy carbon structure, while for irradiated carbonized glassy carbon samples, boron irradiation caused an increase of the sp 3 carbon fraction, which is most pronounced for the highest fluence irradiation. Further analyses showed that different nature of boron incorporation, and thus changed structural parameters, are crucial for obtaining glassy carbon samples with modified mechanical, chemical and electrochemical properties over a wide range

Irradiation-induced defects in graphite and glassy carbon studied by positron annihilation

International Nuclear Information System (INIS)

Hasegawa, M.; Kajino, M.; Kuwahara, H.; Yamaguchi, S.; Kuramoto, E.; Takenaka, M.

1992-01-01

ACAR and positron lifetime measurements have been made on, HOPG, isotropic fine-grained graphites, glassy carbons and C 60 /C 70 . HOPG showed a marked bimodal ACAR distribution along the c-axis. By irradiation of 1.0 X 10 19 fast neutrons/cm 2 remarkable narrowing in the ACAR curves and disappearance of the bimodal distribution were observed. Lifetime in HOPG increased from 225 psec to 289 psec (positron-lifetime in vacancies and their small clusters) by the irradiation. The irradiation on isotropic graphites and glassy carbons, however, gave slight narrowing in ACAR curves and decrease in lifetimes (360 psec → 300psec). This suggests irradiation-induced vacancy trapping in crystallites. In C 60 /C 70 powder two lifetime components were detected: τ 1 =177psec, τ 2 =403psec (I 2 =58%). The former is less than the bulk lifetime of HOPG, while the latter being very close to lifetimes in the isotropic graphites and glassy carbons. This and recent 2D-ACAR study of HOPG surface [15] strongly suggest free and defect surface states around ''soccer ball'' cages

Interpretation of the Raman spectra of the glassy states of SixS1−x and SixSe1−x

International Nuclear Information System (INIS)

Devi, V. Radhika; Zabidi, Noriza Ahmad; Shrivastava, Keshav N.

2013-01-01

We use the density-functional theory to make models of Si x S y and Si x Se y for the values of x,y = 1–6. The vibrational frequencies are calculated for each model. The stable clusters are selected on the basis of positive vibrational frequencies. In the case of Si x S 1−x , the values of the vibrational frequencies calculated from the first principles for Si 2 S(triangular)cluster of atoms, 364.1 cm −1 and 380.8 cm −1 , agree with the experimentally measured values of 367 cm −1 and 381 cm −1 , indicating that Si 2 S clusters occur in the glassy state of SiS. The calculated values of the vibrational frequencies of SiSe 4 (pyramidal) which agree with the experimental Raman frequencies of glassy Si x Se 1−x are 114, 166 and 361 cm −1 . The calculated values for Si 2 Se 4 (bipyramidal) which agree with the experimental data of Si x Se 1−x are 166 and 464 cm −1 . In Si 4 Se (pyramidal) the values 246 and 304 cm −1 agree with the measured values. In Si 4 Se 2 (bipyramidal), the calculated values 162, 196 and 304 cm −1 agree with the measured values. The calculated values of 473 cm −1 for Si 6 Se 2 (bipyramidal) also agree with the experimentally measured values. We thus find that pyramidal structures are present in the amorphous Si x Se 1−x glassy state. - Highlights: • A first principles calculation is performed to calculate the vibrational frequencies. • The calculated frequencies of clusters agree with measured Raman values. • The structures, bond lengths and symmetries are determined. • The importance of Jahn–Teller effect in SiS and in SiSe is clearly seen. • The clusters of SiS and SiSe are found to stabilize in different symmetries

EDTA modified glassy carbon electrode: Preparation and characterization

Energy Technology Data Exchange (ETDEWEB)

Ustuendag, Zafer [Dumlupinar University, Faculty of Arts and Sciences, Department of Chemistry, Kuetahya (Turkey); Solak, Ali Osman [Ankara University, Faculty of Science, Department of Chemistry, Degol Street, Tandogan, 06100 Ankara (Turkey)], E-mail: osolak@science.ankara.edu.tr

2009-11-01

EDTA-phenoxyamide modified glassy carbon electrode (EDTA-GC) was prepared at a glassy carbon electrode by surface synthesis. In the first step, nitrophenyl was grafted to the glassy carbon (GC) surface via the electrochemical reduction of its tetraflouroborate diazonium salt. In the second step, nitrophenyl-modified electrode (NP-GC) was subjected to the cathodic potential scan to reduce the nitro to amine group. p-Aminophenyl modified glassy carbon electrode (AP-GC) was dipped into a EDTA solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide (EDC) as an activating agent. Thus formed ((2-anilino-2-oxoethyl){l_brace}2-[bis(carboxymethyl)amino]-ethyl{r_brace}amino)acetic acid modified GC electrode was denoted as EDTA-GC and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry and X-ray photoelectron spectroscopy (XPS). Complexation of the EDTA-GC surface with Pb{sup 2+} ions was investigated if this electrode could be used as a metal sensor.

United States Crystalline Repository Project - key research areas

International Nuclear Information System (INIS)

Patera, E.S.

1986-01-01

The Crystalline Repository Project is responsible for siting the second high-level nuclear waste repository in crystalline rock for the US Department of Energy. A methodology is being developed to define data and information needs and a way to evaluate that information. The areas of research the Crystalline Repository Project is involved in include fluid flow in a fractured network, coupled thermal, chemical and flow processes and cooperation in other nations and OECD research programs

Investigation of electrochemical behaviour and structure of oxide films on Ni60Nb40 alloy in amorphous and crystalline states

International Nuclear Information System (INIS)

Tomashov, N.D.; Skvortsova, I.B.; Gorodetskij, A.E.; Bogomolov, D.B.

1987-01-01

Electrochemical properties of Ni 60 Nb 40 alloy in amorphous and crystalline states as well as structure of oxide films forming during anode polarization in electrolytes on the surface of this alloy in both its states are investigated. It is stated that increased passive ability of Ni 60 Nb 40 alloys in amorphous state and high efficiency of chlorine evolution (2 n NaCl+HCl up to pH=0) anode process in comparison with crystalline state are defined by increased homogeneity and uniformity of passive films forming on amorphous alloy and their increased electron conductivity, that is in direct dependence on different structure of passive films forming on alloys in amorphous and crystalline states

Alpha B- and βA3-crystallins containing d-aspartic acids exist in a monomeric state.

Science.gov (United States)

Sakaue, Hiroaki; Takata, Takumi; Fujii, Norihiko; Sasaki, Hiroshi; Fujii, Noriko

2015-01-01

Crystallin stability and subunit-subunit interaction are essential for eye lens transparency. There are three types of crystallins in lens, designated as α-, β-, and γ-crystallins. Alpha-crystallin is a hetero-polymer of about 800kDa, consisting of 35-40 subunits of two different αA- and αB-subunits, each of 20kDa. The β/γ-crystallin superfamily comprises oligomeric β-crystallin (2-6 subunits) and monomeric γ-crystallin. Since lens proteins have very long half-lives, they undergo numerous post-translational modifications including racemization, isomerization, deamidation, oxidation, glycation, and truncation, which may decrease crystallin solubility and ultimately cause cataract formation. Racemization and isomerization of aspartyl (Asp) residues have been detected only in polymeric α- and oligomeric β-crystallin, while the situation in monomeric γ-crystallin has not been studied. Here, we investigated the racemization and isomerization of Asp in the γ-crystallin fraction of elderly donors. The results show that Asp residues of γS-, γD- and γC-crystallins were not racemized and isomerized. However, strikingly, we found that a portion of αB-crystallin and βA3-crystallin moved to the lower molecular weight fraction which is the same size of γ-crystallin. In those fractions, Asp-96 of αB-crystallin and Asp-37 of βA3-crystallin were highly inverted, which do not occur in the native lens higher molecular weight fraction. Our results indicate the possibility that the inversion of Asp residues may induce dissociation of αB- and βA3-crystallins from the polymeric and oligomeric states. This is the first report that stereoinversion of amino acids disturbs lens protein assembly in aged human lens. Copyright © 2014 Elsevier B.V. All rights reserved.

Some Recent Developments in Structure and Glassy Behavior of Proteins

Science.gov (United States)

Hu, Chin-Kun

2012-02-01

We have used ARVO developed by us to find that the ratio of volume and surface area of proteins in Protein Data Bank distributed in a very narrow region [1]. Such result is useful for the determination of protein 3D structures. It has been widely known that a spin glass model can be used to understand the slow relaxation behavior of a glass at low temperatures [2]. We have used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that polymer chains with neighboring monomers connected by rigid bonds can relax very slowly and show glassy behavior [3]. We have also found that native collagen fibrils show glassy behavior at room temperatures [4]. The results of [3] and [4] about the glassy behavior of polymers or proteins are useful for understanding the mechanism for a biological system to maintain in a non-equilibrium state, including the ancient seed [5], which can maintain in a non-equilibrium state for a very long time. (1) M.-C. Wu, M. S. Li, W.-J. Ma, M. Kouza, and C.-K. Hu, EPL, in press (2011); (2) C. Dasgupta, S.-K. Ma, and C.-K. Hu. Phys. Rev. B 20, 3837-3849 (1979); (3) W.-J. Ma and C.-K. Hu, J. Phys. Soc. Japan 79, 024005, 024006, 054001, and 104002 (2010), C.-K. Hu and W.-J. Ma, Prog. Theor. Phys. Supp. 184, 369 (2010); S. G. Gevorkian, A. E. Allahverdyan, D. S. Gevorgyan and C.-K. Hu, EPL 95, 23001 (2011); S. Sallon, et al. Science 320, 1464 (2008).

Glassy carbon based supercapacitor stacks

Energy Technology Data Exchange (ETDEWEB)

Baertsch, M; Braun, A; Koetz, R; Haas, O [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Considerable effort is being made to develop electrochemical double layer capacitors (EDLC) that store relatively large quantities of electrical energy and possess at the same time a high power density. Our previous work has shown that glassy carbon is suitable as a material for capacitor electrodes concerning low resistance and high capacity requirements. We present the development of bipolar electrochemical glassy carbon capacitor stacks of up to 3 V. Bipolar stacks are an efficient way to meet the high voltage and high power density requirements for traction applications. Impedance and cyclic voltammogram measurements are reported here and show the frequency response of a 1, 2, and 3 V stack. (author) 3 figs., 1 ref..

Formation of a glassy phase in ceramic-like coatings

International Nuclear Information System (INIS)

Sazonova, M.V.; Gorbatova, G.N.

1986-01-01

The authors investigate the synthesis directly in coatings of a borosilicate melt that could fill the role of glassy matrix, thereby avoiding fusion and processing of the glassy material. The effect of added boron on the formation of coatings based on molybdenum disilicide and tungsten disilicide in air at 900 degrees C is presented. Without an additive no coating forms; there is no adhesion to the graphite and a continuous film does not form. As a result of boron oxidation an easily fused glassy matrix forms, which bonds the molybdenum disilicide or tungsten disilicide particles together and ensures adhesion to the graphite

Structural and spectroscopic features of proton hydrates in the crystalline state. Solid-state DFT study on HCl and triflic acid hydrates

Science.gov (United States)

Vener, M. V.; Chernyshov, I. Yu.; Rykounov, A. A.; Filarowski, A.

2018-01-01

Crystalline HCl and CF3SO3H hydrates serve as excellent model systems for protonated water and perfluorosulphonic acid membranes, respectively. They contain characteristic H3O+, H5О+2, H7О+3 and H3O+(H2O)3 (the Eigen cation) structures. The properties of these cations in the crystalline hydrates of strong monobasic acids are studied by solid-state density function theory (DFT). Simultaneous consideration of the HCl and CF3SO3H hydrates reveals the impact of the size of a counter ion and the crystalline environment on the structure and infrared active bands of the simplest proton hydrates. The H7O+3 structure is very sensitive to the size of the counter ion and symmetry of the local environment. This makes it virtually impossible to identify the specific features of H7O+3 in molecular crystals. The H3O+ ion can be treated as the Eigen-like cation in the crystalline state. Structural, infrared and electron-density features of H5О+2 and the Eigen cation are virtually insensitive to the size of the counter ion and the symmetry of the local crystalline environment. These cations can be considered as the simplest stable proton hydrates in the condensed phase. Finally, the influence of the Grimme correction on the structure and harmonic frequencies of the molecular crystals with short (strong) intermolecular O-H···O bonds is discussed.

Structural state diagram of concentrated suspensions of jammed soft particles in oscillatory shear flow

Science.gov (United States)

Khabaz, Fardin; Cloitre, Michel; Bonnecaze, Roger T.

2018-03-01

In a recent study [Khabaz et al., Phys. Rev. Fluids 2, 093301 (2017), 10.1103/PhysRevFluids.2.093301], we showed that jammed soft particle glasses (SPGs) crystallize and order in steady shear flow. Here we investigate the rheology and microstructures of these suspensions in oscillatory shear flow using particle-dynamics simulations. The microstructures in both types of flows are similar, but their evolutions are very different. In both cases the monodisperse and polydisperse suspensions form crystalline and layered structures, respectively, at high shear rates. The crystals obtained in the oscillatory shear flow show fewer defects compared to those in the steady shear. SPGs remain glassy for maximum oscillatory strains less than about the yield strain of the material. For maximum strains greater than the yield strain, microstructural and rheological transitions occur for SPGs. Polydisperse SPGs rearrange into a layered structure parallel to the flow-vorticity plane for sufficiently high maximum shear rates and maximum strains about 10 times greater than the yield strain. Monodisperse suspensions form a face-centered cubic (FCC) structure when the maximum shear rate is low and hexagonal close-packed (HCP) structure when the maximum shear rate is high. In steady shear, the transition from a glassy state to a layered one for polydisperse suspensions included a significant induction strain before the transformation. In oscillatory shear, the transformation begins to occur immediately and with different microstructural changes. A state diagram for suspensions in large amplitude oscillatory shear flow is found to be in close but not exact agreement with the state diagram for steady shear flow. For more modest amplitudes of around one to five times the yield strain, there is a transition from a glassy structure to FCC and HCP crystals, at low and high frequencies, respectively, for monodisperse suspensions. At moderate frequencies, the transition is from glassy to HCP via

Enzymatic biofuel cell based on electrodes modified with lipid liquid-crystalline cubic phases

Science.gov (United States)

Nazaruk, Ewa; Smoliński, Sławomir; Swatko-Ossor, Marta; Ginalska, Grażyna; Fiedurek, Jan; Rogalski, Jerzy; Bilewicz, Renata

Two glassy carbon electrodes modified with enzymes embedded in lyotropic liquid-crystalline cubic phase were used for the biofuel cell construction. The monoolein liquid-crystalline film allowed to avoid separators in the biofuel cell. Glucose and oxygen as fuels, and glucose oxidase and laccase as anode and cathode biocatalysts, respectively were used. The biofuel cell parameters were examined in McIlvaine buffer, pH 7 solution containing 15 mM of glucose and saturated with dioxygen. A series of mediators were tested taking into account their formal potentials, stability in the cubic phase and efficiency of mediation. Most stable was the biofuel cell based on tetrathiafulvalene (TTF) and 2,2‧-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as anode and cathode mediators, respectively. The open-circuit voltage was equal to 450 ± 40 mV. The power densities and current densities were measured for all the systems studied.

Atmospheric pressure plasma treatment of glassy carbon for adhesion improvement

DEFF Research Database (Denmark)

Kusano, Yukihiro; Mortensen, Henrik Junge; Stenum, Bjarne

2007-01-01

density increased with the plasma treatments. Adhesion test of the treated glassy carbon covered with cured epoxy showed cohesive failure, indicating strong bonding after the treatments. This is in contrast to the adhesion tests of untreated samples where the epoxy readily peeled off the glassy carbon....

Ultrasensitive Determination of Piroxicam at Diflunisal-Derived Gold Nanoparticle-Modified Glassy Carbon Electrode

Science.gov (United States)

Shaikh, Tayyaba; uddin, SiraJ; Talpur, Farah N.; Khaskeli, Abdul R.; Agheem, Muhammad H.; Shah, Muhammad R.; Sherazi, Tufail H.; Siddiqui, Samia

2017-10-01

We present a simple and green approach for synthesis of gold nanoparticles (AuNps) using analgesic drug diflunisal (DF) as capping and stabilizing agent in aqueous solution. Characterization of the synthesized diflunisal-derived gold nanoparticles (DF-AuNps) was performed by ultraviolet-visible (UV-Vis) spectroscopy, revealing the surface plasmon absorption band at 520 nm under optimized experimental conditions. Fourier-transform infrared (FTIR) spectroscopy established the effective interaction of the capping agent with the AuNps. Topographical features of the synthesized DF-AuNps were assessed by atomic force microscopy (AFM), revealing average particle height of 29 nm to 32 nm. X-ray diffractometry was used to study the crystalline nature, revealing that the synthesized DF-AuNps possessed excellent crystalline properties. The synthesized DF-AuNps were employed to modify the surface of glassy carbon electrode (GCE) for selective determination of piroxicam (PX) using differential pulse voltammetry technique. The fabricated Nafion/DF-AuNps/GCE sensor exhibited high sensitivity compared with bare GCE. The current response of the fabricated sensor was found to be linear in the PX concentration range of 0.5 μM to 50 μM, with limit of detection (LOD) and limit of quantification (LOQ) of 50 nM and 150 nM, respectively. The proposed sensor was successfully utilized for sensitive and rapid determination of PX in human serum, urine, and pharmaceutical samples.

The quest for crystalline ion beams

CERN Document Server

Schramm, U; Bussmann, M; Habs, D

2002-01-01

The phase transition of an ion beam into its crystalline state has long been expected to dramatically influence beam dynamics beyond the limitations of standard accelerator physics. Yet, although considerable improvement in beam cooling techniques has been made, strong heating mechanisms inherent to existing high-energy storage rings have prohibited the formation of the crystalline state in these machines up to now. Only recently, laser cooling of low-energy beams in the table-top rf quadrupole storage ring PAaul Laser cooLing Acceleration System (PALLAS) has lead to the experimental realization of crystalline beams. In this article, the quest for crystalline beams as well as their unique properties as experienced in PALLAS will be reviewed.

Nonequilibrium steady state and induced currents of a mesoscopically glassy system: interplay of resistor-network theory and Sinai physics.

Science.gov (United States)

Hurowitz, Daniel; Rahav, Saar; Cohen, Doron

2013-12-01

We introduce an explicit solution for the nonequilibrium steady state (NESS) of a ring that is coupled to a thermal bath, and is driven by an external hot source with log-wide distribution of couplings. Having time scales that stretch over several decades is similar to glassy systems. Consequently there is a wide range of driving intensities where the NESS is like that of a random walker in a biased Brownian landscape. We investigate the resulting statistics of the induced current I. For a single ring we discuss how sign of I fluctuates as the intensity of the driving is increased, while for an ensemble of rings we highlight the fingerprints of Sinai physics on the distribution of the absolute value of I.

Relationship between low-temperature boson heat capacity peak and high-temperature shear modulus relaxation in a metallic glass

International Nuclear Information System (INIS)

Vasiliev, A. N.; Voloshok, T. N.; Granato, A. V.; Joncich, D. M.; Mitrofanov, Yu. P.; Khonik, V. A.

2009-01-01

Low-temperature (2 K≤T≤350 K) heat capacity and room-temperature shear modulus measurements (ν=1.4 MHz) have been performed on bulk Pd 41.25 Cu 41.25 P 17.5 in the initial glassy, relaxed glassy, and crystallized states. It has been found that the height of the low-temperature Boson heat capacity peak strongly correlates with the changes in the shear modulus upon high-temperature annealing. It is this behavior that was earlier predicted by the interstitialcy theory, according to which dumbbell interstitialcy defects are responsible for a number of thermodynamic and kinetic properties of crystalline, (supercooled) liquid, and solid glassy states.

Liquid crystalline order in polymers

CERN Document Server

Blumstein, Alexandre

1978-01-01

Liquid Crystalline Order in Polymers examines the topic of liquid crystalline order in systems containing rigid synthetic macromolecular chains. Each chapter of the book provides a review of one important area of the field. Chapter 1 discusses scattering in polymer systems with liquid crystalline order. It also introduces the field of liquid crystals. Chapter 2 treats the origin of liquid crystalline order in macromolecules by describing the in-depth study of conformation of such macromolecules in their unassociated state. The chapters that follow describe successively the liquid crystalli

Quasi-equilibrium in glassy dynamics: an algebraic view

International Nuclear Information System (INIS)

Franz, Silvio; Parisi, Giorgio

2013-01-01

We study a chain of identical glassy systems in a constrained equilibrium, where each bond of the chain is forced to remain at a preassigned distance to the previous one. We apply this description to mean-field glassy systems in the limit of a long chain where each bond is close to the previous one. We show that this construction defines a pseudo-dynamic process that in specific conditions can formally describe real relaxational dynamics for long times. In particular, in mean-field spin glass models we can recover in this way the equations of Langevin dynamics in the long time limit at the dynamical transition temperature and below. We interpret the formal identity as evidence that in these situations the configuration space is explored in a quasi-equilibrium fashion. Our general formalism, which relates dynamics to equilibrium, puts slow dynamics in a new perspective and opens the way to the computation of new dynamical quantities in glassy systems. (paper)

Time effects and glassy state behaviour in superconducting Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x}

Energy Technology Data Exchange (ETDEWEB)

Altinkok, A.; Yetis, H.; Olutas, M.; Kilic, K. [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory, 14280 Bolu (Turkey); Kilic, A. [Abant Izzet Baysal University, Department of Physics, Turgut Gulez Research Laboratory, 14280 Bolu (Turkey)], E-mail: kilic_a@ibu.edu.tr

2007-10-01

The quenched disorder in the moving entity is investigated in a polycrystalline bulk sample of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) by slow transport relaxation measurements (V-t curves) on long time scales. The time evolution of sample voltage (V-t curve) are correlated to spatial reorganization of the driving current together with increasing or decreasing of resistive and non-resistive flow channels in a multiple connected network. In addition, it is shown that the voltage decays appearing in V-t curves are characterized by an exponential time dependence which is analogous to the glassy state relaxation.

Intrinsic localized gap states in IGZO and its parent single crystalline TCOs

Energy Technology Data Exchange (ETDEWEB)

Schmeißer, D.; Haeberle, J.

2016-03-31

We report on the X-ray absorption data for Indium–Gallium–Zink–Oxide thin films, amorphous ZnO films, amorphous SnO{sub x} films, and single crystalline In{sub 2}O{sub 3}, Ga{sub 2}O{sub 3}, ZnO, and SnO{sub 2} data. These absorption data probe the empty conduction band states explicitly. Also they allow for an elemental assignment using resonant excitation to derive the contributions of each metal ion. We find that the lowest states appear right at the Fermi energy and result from configuration interaction induced charge transfer states which we consider as intrinsic gap states. - Highlights: • We identify contributions of localized configuration interaction induced gap states. • Auger profiles taken on metal absorption edges show metallic density of states around E{sub F}. • D-shell opening leads to a charge-transfer state involving metallic d-states.

Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors.

Science.gov (United States)

Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T; Evoy, Stephane

2016-03-14

Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

Directory of Open Access Journals (Sweden)

Wei Zheng

2016-03-01

Full Text Available Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

Laser irradiation and thermal treatment inducing selective crystallization in Sb2O3-Sb2S3 glassy films

Science.gov (United States)

Avila, L. F.; Pradel, A.; Ribeiro, S. J. L.; Messaddeq, Y.; Nalin, M.

2015-02-01

The influence of both thermal treatment and laser irradiation on the structural and optical properties of films in the Sb2O3-Sb2S3 system was investigated. The films were prepared by RF-sputtering using glass compositions as raw materials. Irreversible photodarkening effect was observed after exposure the films to a 458 nm solid state laser. It is shown, for the first time, the use of holographic technique to measure "in situ", simultaneously and independently, the phase and amplitude modulations in glassy films. The films were also photo-crystallized and analysed "in situ" using a laser coupled to a micro-Raman equipment. Results showed that Sb2S3 crystalline phase was obtained after irradiation. The effect of thermal annealing on the structure of the films was carried out. Different from the result obtained by irradiation, thermal annealing induces the crystallization of the Sb2O3 phase. Photo and thermal induced effects on films were studied using UV-Vis and Raman spectroscopy, atomic force microscopy (AFM), thermal analysis (DSC), X-ray diffraction, scanning electron microscopy (MEV) and energy-dispersive X-ray spectroscopy (EDX).

Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

Directory of Open Access Journals (Sweden)

R. Wagner

2012-09-01

Full Text Available The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA, levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosol particles that have re

Diffusion coefficients of tracers in glassy polymer systems prepared by gamma radiolysis

International Nuclear Information System (INIS)

Tonge, M.P.; Gilbert, R.G.

1996-01-01

Diffusion-controlled reactions are common in free radical polymerisation reactions, especially in glassy polymer matrices. Such reactions commonly have an important influence on the polymerisation process and final polymer properties. For example, the dominant growth-stopping event (bimolecular termination) is generally diffusion-controlled. In glassy polymer systems, where molecular mobility is very low, the chain growth mechanism (propagation) may become diffusion-controlled. At present, the mechanism for propagation in glassy polymers is poorly understood, but it is expected by the Smoluchowski expression applied to propagation to depend strongly on the diffusion coefficient of monomer. The objective of this study is to measure reliable diffusion coefficients of small tracer molecules in glassy polymers, and compare these with propagation rate coefficients in similar systems, by the prediction above. Samples were initially prepared in a sealed sampled cell containing monomer, inert diluent, and tracer dye. After irradiation for several days, complete conversion of monomer to polymer can be obtained. The diffusion coefficients for two tracer dyes have been measured as a function of weight fraction polymer glassy poly(methyl methacrylate) samples

Role of Disorder in the Thermodynamics and Atomic Dynamics of Glasses

DEFF Research Database (Denmark)

Chumakov, A.I.; Monaco, G.; Fontana, A.

2014-01-01

We measured the density of vibrational states (DOS) and the specific heat of various glassy and crystalline polymorphs of SiO2. The typical (ambient) glass shows a well-known excess of specific heat relative to the typical crystal (α-quartz). This, however, holds when comparing a lower......-density glass to a higherdensity crystal. For glassy and crystalline polymorphs with matched densities, the DOS of the glass appears as the smoothed counterpart of the DOS of the corresponding crystal; it reveals the same number of the excess states relative to the Debye model, the same number of all states...... in the low-energy region, and it provides the same specific heat. This shows that glasses have higher specific heat than crystals not due to disorder, but because the typical glass has lower density than the typical crystal....

Structure and Dynamics of the Metal Site of Cadmium-Substituted Carboxypeptidase A in Solution and Crystalline States and under Steady-State peptide Catalysis

DEFF Research Database (Denmark)

Bauer, R.; Danielsen, E.; Hemmingsen, L.

1997-01-01

are consistent with an intact scissile peptide bond in the enzyme-substrate complex of Bz-Gly-L-Phe and Bz-Gly-Gly-L-Phe. A single nuclear quadrupole interaction (NQI) is observed for the crystalline state of the enzyme between pH 5.7 and pH 9.4. This NQI agrees with calculations based on the metal coordination...... geometry for cadmium in crystalline CPD derived from X-ray diffraction studies. A single broad distribution of NQIs is observed for CPD in sucrose solutions and 0.1 M NaCl at pH values below 6.5. This NQI (NQI-1') has parameters very close to those for the crystalline state. The enzyme metal site......, characterized by this NQI, is converted into two new enzyme metal sites over the pH range of 6.5-8.3. The metal coordination sphere of one of these has a NQI (NQI-1) with parameters similar to those at lower pH values (NQI-1') while the other NQI (NQI-2) is characterized by markedly different NQI parameters...

Crystalline color superconductivity

International Nuclear Information System (INIS)

Alford, Mark; Bowers, Jeffrey A.; Rajagopal, Krishna

2001-01-01

In any context in which color superconductivity arises in nature, it is likely to involve pairing between species of quarks with differing chemical potentials. For suitable values of the differences between chemical potentials, Cooper pairs with nonzero total momentum are favored, as was first realized by Larkin, Ovchinnikov, Fulde, and Ferrell (LOFF). Condensates of this sort spontaneously break translational and rotational invariance, leading to gaps which vary periodically in a crystalline pattern. Unlike the original LOFF state, these crystalline quark matter condensates include both spin-zero and spin-one Cooper pairs. We explore the range of parameters for which crystalline color superconductivity arises in the QCD phase diagram. If in some shell within the quark matter core of a neutron star (or within a strange quark star) the quark number densities are such that crystalline color superconductivity arises, rotational vortices may be pinned in this shell, making it a locus for glitch phenomena

Electrochemical and microstructural characterization of platinum supported on glassy carbon

Directory of Open Access Journals (Sweden)

Terzić Sanja

2007-01-01

Full Text Available The effect of the electrochemical oxidation of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on oxidized glassy carbon were studied for methanol oxidation in H2SO4 solution. Platinum was potentiostatically deposited from H2SO4 + 6mM H2PtCl6 solution. Glassy carbon was anodically polarized in 1 M NaOH at 1.41 V (SCE for 35 and 95 s and in 0.5 M H2SO4 at 2V (SCE for 35; 95 s and 2.25 V for 35 and 95 s. Electrochemical treatment of the GC support leads to a better distribution of platinum on the substrate and has remarkable effect on the activity. The activity of the Pt/GCox electrode for methanol oxidation is larger than that of polycrystalline Pt and by more than one order of magnitude larger than that of a Pt/GC electrode. This increase in activity indicates the pronounced role of the organic residues of the GC support on the properties of Pt particles deposited on glassy carbon.

Raman non-coincidence effect of boroxol ring: The interplay between repulsion and attraction forces in the glassy, supercooled and liquid state

Science.gov (United States)

Kalampounias, Angelos G.; Papatheodorou, George N.

2018-06-01

Temperature dependent Raman spectra of boric oxide have been measured in a temperature range covering the glassy, supercooled and liquid state. The shift of the isotropic band assigned to boroxol rings relative to the anisotropic component upon heating the glass is measured and attributed to the Raman non-coincidence effect. The measured shift is associated with the competition between attraction and repulsion forces with increasing temperature. The relation of dephasing and orientational relaxation times to the non-coincidence effect of the condensed phases has been examined. We discuss our results in the framework of the current phenomenological status of the field in an attempt to separate the attraction and repulsion contributions corresponding to the observed non-coincidence effect.

Generation and extinction of crystal nuclei in an extremely non-equilibrium glassy state of salol

CERN Document Server

Paladi, F

2003-01-01

Strange generation and subsequent extinction of crystal nuclei were observed in the glassy state of salol (phenyl salicylate) during the course of ageing at very low constant-temperatures. The presence/absence of crystal nuclei within the glass were judged, by using a differential scanning calorimeter (DSC), from whether the crystal growth and fusion phenomena were observed in the following heating process or not. The liquid sample was cooled rapidly at 200 K min sup - sup 1 from 333 K above the fusion temperature down to a desired ageing temperature (T sub a) below the glass transition temperature (T sub g = 220 K), aged there for different periods (t sub a), and then heated up to 213 K at 200 K min sup - sup 1. The DSC measurement was carried out at 10 K min sup - sup 1 from 213 to 333 K. The ageing periods were taken in a range between 30 s and 316 min. At T sub a = 213 K, crystal nucleation was found to proceed for ageing longer than 100 min. No crystal nucleation was found at T sub a in between 123 and 1...

Electrical properties of carbon nanotubes modified GaSe glassy system

Science.gov (United States)

Khan, Hana; Khan, Zubair M. S. H.; Islam, Shama; Rahman, Raja Saifu; Husain, M.; Zulfequar, M.

2018-05-01

In this paper we report the investigation of the effect of Carbon Nanotubes (CNT) addition on the electrical properties of GaSe Glassy system. Dielectric constant and dielectric loss of GaSe glassy system are found to increase on CNT addition. The conductivity of GaSe glasy systems is also found to increase on CNT addition. This behavior is attributed to the excellent conduction properties of Carbon Nanotube.

Influence of radiation-damages on parameters of lattice oscillations in crystalline and vitreous SiO2

International Nuclear Information System (INIS)

Abdukadyrova, I.Kh.

2008-01-01

Using IR reflection spectroscopy, the influence of radiation-induced disturbances on a number of parameters of lattice oscillations in two SiO 2 modifications was investigated. Radiation kinetics of changes in spectral characteristics of fundamental oscillations in SiO 2 crystalline and glassy states was determined. Dose dependences of both reflectivity and degenerate mode vibrational frequency were found to show minima whose locations were governed by a type of a sample. Under higher doses of neutron radiation (10 21 cm -2 ), certain characteristics of bands were observed to be of the same values for the both materials modified. The features of radiation kinetics were found for dynamic parameters of the samples. It was deduced that specific character of radiation-induced changes observed in spectral and dynamic parameters of oscillations in the region of degenerate modes was due to both the accumulation of radiation damages and a change in the force field surrounding bridge-type bonds which was related with the change in the SiO 2 structure. (authors)

Grain-boundary, glassy-phase identification and possible artifacts

International Nuclear Information System (INIS)

Simpson, Y.K.; Carter, C.B.; Sklad, P.; Bentley, J.

1985-01-01

Specimen artifacts such as grain boundary grooving, surface damage of the specimen, and Si contamination are shown experimentally to arise from the ion milling used in the preparation of transmission electron microscopy specimens. These artifacts in polycrystalline, ceramic specimens can cause clean grain boundaries to appear to contain a glassy phase when the dark-field diffuse scattering technique, the Fresnel fringe technique, and analytical electron microscopy (energy dispersive spectroscopy) are used to identify glassy phases at a grain boundary. The ambiguity in interpreting each of these techniques due to the ion milling artifacts will be discussed from a theoretical view point and compared to experimental results obtained for alumina

Amorphous and Crystalline Particulates: Challenges and Perspectives in Drug Delivery.

Science.gov (United States)

Al-Obaidi, Hisham; Majumder, Mridul; Bari, Fiza

2017-01-01

Crystalline and amorphous dispersions have been the focus of academic and industrial research due to their potential role in formulating poorly water-soluble drugs. This review looks at the progress made starting with crystalline carriers in the form of eutectics moving towards more complex crystalline mixtures. It also covers using glassy polymers to maintain the drug as amorphous exhibiting higher energy and entropy. However, the amorphous form tends to recrystallize on storage, which limits the benefits of this approach. Specific interactions between the drug and the polymer may retard this spontaneous conversion of the amorphous drug. Some studies have shown that it is possible to maintain the drug in the amorphous form for extended periods of time. For the drug and the polymer to form a stable mixture they have to be miscible on a molecular basis. Another form of solid dispersions is pharmaceutical co-crystals, for which research has focused on understanding the chemistry, crystal engineering and physico-chemical properties. USFDA has issued a guidance in April 2013 suggesting that the co-crystals as a pharmaceutical product may be a reality; but just not yet! While some of the research is still oriented towards application of these carriers, understanding the mechanism by which drug-carrier miscibility occurs is also covered. Within this context is the use of thermodynamic models such as Flory-Huggins model with some examples of studies used to predict miscibility. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Fine kinetics of natural physical ageing in glassy As10Se90

International Nuclear Information System (INIS)

Balitska, V.; Golovchak, R.; Kozdras, A.; Shpotyuk, O.

2014-01-01

Sigmoid behavior of natural physical ageing in glassy As 10 Se 90 reveals multi-step-wise growing kinetics of enthalpy losses. Phenomenological description of this kinetics can be adequately developed in terms of first-order relaxation processes, tending atomic structure from initial towards more thermodynamically equilibrium state. This kinetics is shown to obey characteristic stretched exponential behavior originated from a number of growing steps, attributed to the interconnected processes of chalcogen chain alignment and cooperative shrinkage of glass network

RNA aptamers targeted for human αA-crystallin do not bind αB-crystallin, and spare the α-crystallin domain.

Science.gov (United States)

Mallik, Prabhat K; Shi, Hua; Pande, Jayanti

2017-09-16

The molecular chaperones, α-crystallins, belong to the small heat shock protein (sHSP) family and prevent the aggregation and insolubilization of client proteins. Studies in vivo have shown that the chaperone activity of the α-crystallins is raised or lowered in various disease states. Therefore, the development of tools to control chaperone activity may provide avenues for therapeutic intervention, as well as enable a molecular understanding of chaperone function. The major human lens α-crystallins, αA- (HAA) and αB- (HAB), share 57% sequence identity and show similar activity towards some clients, but differing activities towards others. Notably, both crystallins contain the "α-crystallin domain" (ACD, the primary client binding site), like all other members of the sHSP family. Here we show that RNA aptamers selected for HAA, in vitro, exhibit specific affinity to HAA but do not bind HAB. Significantly, these aptamers also exclude the ACD. This study thus demonstrates that RNA aptamers against sHSPs can be designed that show high affinity and specificity - yet exclude the primary client binding region - thereby facilitating the development of RNA aptamer-based therapeutic intervention strategies. Copyright © 2017 Elsevier Inc. All rights reserved.

EXPERIMENTAL ANALYSIS OF BIOLOGICAL PARAMETERS AND VECTOR ABILITY OF GLASSY-WINGED SHARPSHOOTERS FROM ALLOPATRIC POPULATIONS IN CALIFORNIA

Science.gov (United States)

The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar), is native to the southeastern United States and northeastern Mexico. It was detected in southern California in the late 1980s and in the San Joaquin Valley in 1999, where it transmits the bacterium Xylella fastidiosa to grapev...

A neutron-X-ray, NMR and calorimetric study of glassy Probucol synthesized using containerless techniques

International Nuclear Information System (INIS)

Weber, J.K.R.; Benmore, C.J.; Tailor, A.N.; Tumber, S.K.; Neuefeind, J.; Cherry, B.; Yarger, J.L.; Mou, Q.; Weber, W.; Byrn, S.R.

2013-01-01

Highlights: • Acoustic levitation was used to make phase-pure glassy forms of pharmaceutical compounds. • Neutrons, X-rays and NMR were used to characterize the glasses. • The glass comprised of slightly distorted molecules packed in a random network. • Potential for new drug synthesis routes is discussed. - Abstract: Acoustic levitation was used to trap 1–3 mm diameter drops of Probucol and other pharmaceutical materials in containerless conditions. Samples were studied in situ using X-ray diffraction and ex situ using neutron diffraction, NMR and DSC techniques. The materials were brought into non-equilibrium states by supersaturating solutions or by supercooling melts. The glass transition and crystallization temperatures of glassy Probucol were 29 ± 1 and 71 ± 1 °C respectively. The glassy form was stable with a shelf life of at least 8 months. A neutron/X-ray difference function of the glass showed that while molecular sub-groups remain rigid, many of the hydrogen correlations observed in the crystal become smeared out in the disordered material. The glass is principally comprised of slightly distorted Form I Probucol molecules with disordered packing rather than large changes in the individual molecular structure. Avoiding surface contact-induced nucleation provided access to highly non-equilibrium phases and enabled synthesis of phase-pure glasses

A neutron-X-ray, NMR and calorimetric study of glassy Probucol synthesized using containerless techniques

Energy Technology Data Exchange (ETDEWEB)

Weber, J.K.R., E-mail: rweber@anl.gov [Materials Development, Inc., Arlington Heights, IL 60004 (United States); Argonne National Laboratory, Argonne, IL 60439 (United States); Benmore, C.J. [Argonne National Laboratory, Argonne, IL 60439 (United States); Department of Physics, Arizona State University, AZ 85287 (United States); Tailor, A.N.; Tumber, S.K. [Materials Development, Inc., Arlington Heights, IL 60004 (United States); Neuefeind, J. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Cherry, B. [Magnetic Resonance Research Center, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Yarger, J.L. [Department of Physics, Arizona State University, AZ 85287 (United States); Magnetic Resonance Research Center, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Mou, Q. [Magnetic Resonance Research Center, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Weber, W. [Department of Physics, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Byrn, S.R. [Department of Industrial and Physical Pharmacy, Purdue University, IN 47907 (United States)

2013-10-16

Highlights: • Acoustic levitation was used to make phase-pure glassy forms of pharmaceutical compounds. • Neutrons, X-rays and NMR were used to characterize the glasses. • The glass comprised of slightly distorted molecules packed in a random network. • Potential for new drug synthesis routes is discussed. - Abstract: Acoustic levitation was used to trap 1–3 mm diameter drops of Probucol and other pharmaceutical materials in containerless conditions. Samples were studied in situ using X-ray diffraction and ex situ using neutron diffraction, NMR and DSC techniques. The materials were brought into non-equilibrium states by supersaturating solutions or by supercooling melts. The glass transition and crystallization temperatures of glassy Probucol were 29 ± 1 and 71 ± 1 °C respectively. The glassy form was stable with a shelf life of at least 8 months. A neutron/X-ray difference function of the glass showed that while molecular sub-groups remain rigid, many of the hydrogen correlations observed in the crystal become smeared out in the disordered material. The glass is principally comprised of slightly distorted Form I Probucol molecules with disordered packing rather than large changes in the individual molecular structure. Avoiding surface contact-induced nucleation provided access to highly non-equilibrium phases and enabled synthesis of phase-pure glasses.

Comparative studies on the pest reactions of single- and poly- crystalline MoSi2

International Nuclear Information System (INIS)

Chou, T.C.; Nieh, T.G.

1992-01-01

Molybdenum disilicide (MoSi 2 ) has many attractive properties, e.g., high melting point (2020 degrees C), relatively low density (6.28 g/cm 3 ), good thermal stability and thermal shock resistance, and excellent oxidation resistance, for potential high temperature applications. Specifically, it is oxidation resistant at temperatures up to about 1900 degrees C, resulting from the formation of a self-healing, glassy silica (SiO 2 ) surface layer. Because of its suitability for use as a high temperature coating and as heating elements, the oxidation properties of MoSi 2 have been extensively studied in the past 30 years, but mainly in the high temperature regimes. In this paper, the authors investigate the evolution and morphological characteristics of the oxidation products of both MoSi 2 single crystals and cast polycrystals. Special attention is given to addressing the nucleation of pest in single crystalline material. The results from both the single- and poly-crystalline samples are correlated with an effort to resolve the origin of MoSi 2 pest. Their implications to the early-stage formation (nucleation) of pest are discussed

Thermonuclear reactor materials composed of glassy carbons

International Nuclear Information System (INIS)

Kazumata, Yukio.

1979-01-01

Purpose: To improve the durability to plasma radiation by the use of glassy carbon as the structural materials for the first wall and the blanket in thermonuclear devices. Constitution: The glassy carbon (glass-like carbon) is obtained by forming specific organic substances into a predetermined configuration and carbonizing them by heat decomposition under special conditions. They are impermeable carbon material of 1.40 - 1.70 specific gravity, less graphitizable and being almost in isotropic crystal forms in which isotropic structure such as in graphite is scarcely observed. They have an extremely high hardness, are less likely to be damaged when exposed to radiation and have great strength and corrosion resistance. Accordingly, the service life of the reactor walls and the likes can remarkably be increased by using the materials. (Horiuchi, T.)

Polyamorphism in Water: Amorphous Ices and their Glassy States

Science.gov (United States)

Amann-Winkel, K.; Boehmer, R.; Fujara, F.; Gainaru, C.; Geil, B.; Loerting, T.

2015-12-01

Water is ubiquitous and of general importance for our environment. But it is also known as the most anomalous liquid. The fundamental origin of the numerous anomalies of water is still under debate. An understanding of these anomalous properties of water is closely linked to an understanding of the phase diagram of the metastable non-crystalline states of ice. The process of pressure induced amorphization of ice was first observed by Mishima et al. [1]. The authors pressurized hexagonal ice at 77 K up to a pressure of 1.6 GPa to form high density amorphous ice (HDA). So far three distinct structural states of amorphous water are known [2], they are called low- (LDA), high- (HDA) and very high density amorphous ice (VHDA). Since the discovery of multiple distinct amorphous states it is controversy discussed whether this phenomenon of polyamorphism at high pressures is connected to the occurrence of more than one supercooled liquid phase [3]. Alternatively, amorphous ices have been suggested to be of nanocrystalline nature, unrelated to liquids. Indeed inelastic X-ray scattering measurements indicate sharp crystal-like phonons in the amorphous ices [4]. In case of LDA the connection to the low-density liquid (LDL) was inferred from several experiments including the observation of a calorimetric glass-to-liquid transition at 136 K and ambient pressure [5]. Recently also the glass transition in HDA was observed at 116 K at ambient pressure [6] and at 140 K at elevated pressure of 1 GPa [7], using calorimetric measurements as well as dielectric spectroscopy. We discuss here the general importance of amorphous ices and their liquid counterparts and present calorimetric and dielectric measurements on LDA and HDA. The good agreement between dielectric and calorimetric results convey for a clearer picture of water's vitrification phenomenon. [1] O. Mishima, L. D. Calvert, and E. Whalley, Nature 314, 76, 1985 [2] D.T. Bowron, J. L. Finney, A. Hallbrucker, et al., J. Chem

Voltammetric quantitation of nitazoxanide by glassy carbon electrode

Directory of Open Access Journals (Sweden)

Rajeev Jain

2013-12-01

Full Text Available The present study reports voltammetric reduction of nitazoxanide in Britton–Robinson (B–R buffer by cyclic and square-wave voltammetry at glassy carbon electrode. A versatile fully validated voltammetric method for quantitative determination of nitazoxanide in pharmaceutical formulation has been proposed. A squrewave peak current was linear over the nitazoxanide concentration in the range of 20–140 µg/mL. The limit of detection (LOD and limit of quantification (LOQ was calculated to be 5.23 μg/mL and 17.45 μg/mL, respectively. Keywords: Nitazoxanide, Squarewave voltammetry, Glassy carbon electrode, Pharmaceutical formulation

Fabrication and nano-imprintabilities of Zr-, Pd- and Cu-based glassy alloy thin films

International Nuclear Information System (INIS)

Takenaka, Kana; Saidoh, Noriko; Nishiyama, Nobuyuki; Inoue, Akihisa

2011-01-01

With the aim of investigating nano-imprintability of glassy alloys in a film form, Zr 49 Al 11 Ni 8 Cu 32 , Pd 39 Cu 29 Ni 13 P 19 and Cu 38 Zr 47 Al 9 Ag 6 glassy alloy thin films were fabricated on Si substrate by a magnetron sputtering method. These films exhibit a very smooth surface, a distinct glass transition phenomenon and a large supercooled liquid region of about 80 K, which are suitable for imprinting materials. Moreover, thermal nano-imprintability of these obtained films is demonstrated by using a dot array mold with a dot diameter of 90 nm. Surface observations revealed that periodic nano-hole arrays with a hole diameter of 90 nm were successfully imprinted on the surface of these films. Among them, Pd-based glassy alloy thin film indicated more precise pattern imprintability, namely, flatter residual surface plane and sharper hole edge. It is said that these glassy alloy thin films, especially Pd-based glassy alloy thin film, are one of the promising materials for fabricating micro-machines and nano-devices by thermal imprinting.

Ideal solution behaviour of glassy Cu–Ti, Zr, Hf alloys and properties of amorphous copper

International Nuclear Information System (INIS)

Ristić, R.; Cooper, J.R.; Zadro, K.; Pajić, D.; Ivkov, J.; Babić, E.

2015-01-01

Highlights: • Ideal solution behaviour (ISB) is established in all Cu–Ti, Zr, Hf glassy alloys. • ISB enables reliable estimates for various properties of amorphous Cu. • ISB also impacts glass forming ability in these and probably other similar alloys. - Abstract: A comprehensive study of selected properties of amorphous (a) Cu–TE alloys (TE = Ti, Zr and Hf) has been performed. Data for average atomic volumes of a-Cu–Hf, Ti alloys combined with literature data show that ideal solution behaviour (Vegard’s law) extends over the whole glass forming range (GFR) in all a-Cu–TE alloys. This enables one to obtain an insight into some properties and probable atomic arrangements for both, a-TEs (Ristić et al., 2010) and a-Cu by extrapolation of the data for alloys. Indeed the atomic volumes and other properties studied for all a-Cu–TE alloys extrapolate to the same values for a-Cu. Depending on the property, these values are either close to those of crystalline (c) Cu, or are close to those for liquid (L) Cu. In particular, the electronic transport properties of a-Cu seem close to those of L-Cu, whereas the static properties, such as the density of states, and Young’s modulus, converge to those of c-Cu. The possible impact of these results on our understanding of a-Cu–TE alloys, including glass forming ability, is discussed

Immobilization of DNA at Glassy Ccarbon Electrodes: A Critical Study of Adsorbed Layer

Directory of Open Access Journals (Sweden)

G. A. Rivas

2005-11-01

Full Text Available In this work we present a critical study of the nucleic acid layer immobilized atglassy carbon electrodes. Different studies were performed in order to assess the nature of theinteraction between DNA and the electrode surface. The adsorption and electrooxidation of DNAdemonstrated to be highly dependent on the surface and nature of the glassy carbon electrode. TheDNA layer immobilized at a freshly polished glassy carbon electrode was very stable even afterapplying highly negative potentials. The electron transfer of potassium ferricyanide, catechol anddopamine at glassy carbon surfaces modified with thin (obtained by adsorption under controlledpotential conditions and thick (obtained by casting the glassy carbon surface with highly concentratedDNA solutions DNA layers was slower than that at the bare glassy carbon electrode, although thiseffect was dependent on the thickness of the layer and was not charge selective. Raman experimentsshowed an important decrease of the vibrational modes assigned to the nucleobases residues,suggesting a strong interaction of these residues with the electrode surface. The hybridization ofoligo(dG21 and oligo(dC21 was evaluated from the guanine oxidation signal and the reduction of theredox indicator Co(phen33+ . In both cases the chronopotentiometric response indicated that thecompromise of the bases in the interaction of DNA with the electrode surface is too strong, preventingfurther hybridization. In summary, glassy carbon is a useful electrode material to detect DNA in adirect and very sensitive way, but not to be used for the preparation of biorecognition layers by directadsorption of the probe sequence on the electrode surface for detecting the hybridization event.

Modeling of Disordered Binary Alloys Under Thermal Forcing: Effect of Nanocrystallite Dissociation on Thermal Expansion of AuCu3

Science.gov (United States)

Kim, Y. W.; Cress, R. P.

2016-11-01

Disordered binary alloys are modeled as a randomly close-packed assembly of nanocrystallites intermixed with randomly positioned atoms, i.e., glassy-state matter. The nanocrystallite size distribution is measured in a simulated macroscopic medium in two dimensions. We have also defined, and measured, the degree of crystallinity as the probability of a particle being a member of nanocrystallites. Both the distribution function and the degree of crystallinity are found to be determined by alloy composition. When heated, the nanocrystallites become smaller in size due to increasing thermal fluctuation. We have modeled this phenomenon as a case of thermal dissociation by means of the law of mass action. The crystallite size distribution function is computed for AuCu3 as a function of temperature by solving some 12 000 coupled algebraic equations for the alloy. The results show that linear thermal expansion of the specimen has contributions from the temperature dependence of the degree of crystallinity, in addition to respective thermal expansions of the nanocrystallites and glassy-state matter.

Solid state dewetting and stress relaxation in a thin single crystalline Ni film on sapphire

International Nuclear Information System (INIS)

Rabkin, E.; Amram, D.; Alster, E.

2014-01-01

In this study, we deposited a 80 nm thick single crystalline Ni film on a sapphire substrate. Heat treatment of this film at 1000 °C followed by slow cooling resulted in the formation of faceted holes, star-like channel instabilities and faceted microwires. The ridges at the rims of faceted holes and channels exhibited a twinning orientation relationship with the rest of the film. A sub-nanometer-high hexagonal topography pattern on the surface of the unperturbed film was observed by atomic force microscopy. No such pattern was observed on the top facets of isolated Ni particles and hole ridges. We discuss the observed dewetting patterns in terms of the effects of Ni surface anisotropy and faceting on solid state dewetting. The hexagonal pattern on the surface of the unperturbed film was attributed to thermal stress relaxation in the film via dislocations glide. This work demonstrates that solid state dewetting of single crystalline metal films can be utilized for film patterning and for producing hierarchical surface topographies

On the spherical nanoindentation creep of metallic glassy thin films at room temperature

Energy Technology Data Exchange (ETDEWEB)

Zhang, T.H.; Ye, J.H. [Institution of Micro/Nano-Mechanical Testing Technology & Application, College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014 (China); Feng, Y.H. [State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Ma, Y., E-mail: may@zjut.edu.cn [Institution of Micro/Nano-Mechanical Testing Technology & Application, College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014 (China)

2017-02-08

Metallic glassy thin films with eight kind of compositions were successfully prepared on Si substrate by magnetron sputtering. The room-temperature creep tests were performed at plastic regions for each sample relying on spherical nanoindetation. The creep deformations were studied by recording the total creep displacement and strain after 2000 s holding. More pronounced creep deformation was observed in the sample with lower glass transition temperature (T{sub g}). Strain rate sensitivity (SRS) was then calculated from the steady-state creep and exhibited a negative correlation with increasing T{sub g}. It is suggested that creep mechanism of the nano-sized metallic glass was T{sub g}-dependent, according to the demarcation of SRS values. Based on the obtained SRS, shear transformation zone (STZ) size in each sample could be estimated. The results indicated that an STZ involves about 25–60 atoms for the employed eight samples and is strongly tied to T{sub g}. The characteristic of STZ size in metallic glassy thin films was discussed in terms of applied method and deformation modes.

Spatially heterogeneous ages in glassy dynamics

International Nuclear Information System (INIS)

Castillo, Horacio E.; Chamon, Claudio Chamon; Cugliandolo, Leticia F.; Iguain, Jose Luis; Kennett, Malcolm P.

2003-09-01

We construct a framework for the study of fluctuations in the nonequilibrium relaxation of glassy systems with and without quenched disorder. We study two types of two-time local correlators with the aim of characterizing the heterogeneous evolution in these systems: in one case we average the local correlators over histories of the thermal noise, in the other case we simply coarse-grain the local correlators obtained for a given noise realization. We explain why the noise-averaged correlators describe the fingerprint of quenched disorder when it exists, while the coarse-grained correlators are linked to noise-induced mesoscopic fluctuations. We predict constraints on the distribution of the fluctuations of the coarse-grained quantities. In particular, we show that locally defined correlations and responses are connected by a generalized local out-of-equilibrium fluctuation-dissipation relation. We argue that large size heterogeneities in the age of the system survive in the long-time limit. A symmetry of the underlying theory, namely invariance under reparametrizations of the time coordinates, underlies these results. We establish a connection between the probabilities of spatial distributions of local coarse-grained quantities and the theory of dynamic random manifolds. We define, and discuss the behavior of, a two-time dependent correlation length from the spatial decay of the fluctuations in the two-time local functions. We characterize the fluctuations in the system in terms of their fractal properties. For concreteness, we present numerical tests performed on disordered spin models in finite and infinite dimensions. Finally, we explain how these ideas can be applied to the analysis of the dynamics of other glassy systems that can be either spin models without disorder or atomic and molecular glassy systems. (author)

The peculiarities of spectral manifestations of high-voltage electric discharge in different phase states of ion systems.

Science.gov (United States)

Gafurov, M M; Aliev, A R; Ataev, M B; Rabadanov, K Sh

2013-10-01

The effects of high-voltage pulsed discharge (HVPD activation) on vibrational spectra of ion salt systems have been studied. The peculiarities of spectral display of HVPD in ion melts and aqueous solutions of electrolytes, in ion-conducting phases of crystalline and glassy salt systems have been investigated. After HVPD a salt system is in non-equilibrium activated state. In the activated state of a salt system, the relaxation time of the vibrational excited states of molecular ions is shorter than in the equilibrium state if the vibrational relaxation rate increases with temperature in the system. For those systems for which the relaxation rate decreases at elevated temperatures, the relaxation time of the vibrational excited states of molecular ions is longer than in the equilibrium state. HVPD activation of a salt system can change the configuration of the electron shell of molecular ions. Therefore, the lifetime values of activated state of salt systems are abnormally large. Copyright © 2013 Elsevier B.V. All rights reserved.

Dielectric relaxation in glassy Se75In25− xPbx alloys

Indian Academy of Sciences (India)

In this paper we report the effect of Pb incorporation in the dielectric properties of a-Se75In25 glassy alloy. The temperature and frequency dependence of the dielectric constants and the dielectric losses in glassy Se75In25−Pb ( = 0, 5, 10 and 15) alloys in the frequency range (1 kHz–5 MHz) and temperature range ...

Metamict state radiation damage in crystalline materials

International Nuclear Information System (INIS)

Haaker, R.F.; Ewing, R.C.

1979-01-01

Metamict minerals provide an excellent basis for the evaluation of long-term radiation damage effects, particularly such changes in physical and chemical properties as microfracturing, hydrothermal alteration, and solubility. This paper summarizes pertinent literature on metamictization and proposes experiments that are critical to the elucidation of structural controls on radiation damage in crystalline phases

Interpretation of the Raman spectra of the glassy states of Si{sub x}S{sub 1−x} and Si{sub x}Se{sub 1−x}

Energy Technology Data Exchange (ETDEWEB)

Devi, V. Radhika [M.L.R. Institute of Technology, Affiliated to Jawaharlal Nehru Technological University, Dundigal, Hyderabad 500043 (India); Zabidi, Noriza Ahmad [Department of Physics, Centre for Defence Foundation Studies, National Defence University of Malaysia, Kem Sungai Besi, Kuala Lumpur 57000 (Malaysia); Shrivastava, Keshav N., E-mail: keshav1001@yahoo.com [School of Physics, University of Hyderabad, Hyderabad 50046 (India); Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia)

2013-09-16

We use the density-functional theory to make models of Si{sub x}S{sub y} and Si{sub x}Se{sub y} for the values of x,y = 1–6. The vibrational frequencies are calculated for each model. The stable clusters are selected on the basis of positive vibrational frequencies. In the case of Si{sub x}S{sub 1−x}, the values of the vibrational frequencies calculated from the first principles for Si{sub 2}S(triangular)cluster of atoms, 364.1 cm{sup −1} and 380.8 cm{sup −1}, agree with the experimentally measured values of 367 cm{sup −1} and 381 cm{sup −1}, indicating that Si{sub 2}S clusters occur in the glassy state of SiS. The calculated values of the vibrational frequencies of SiSe{sub 4} (pyramidal) which agree with the experimental Raman frequencies of glassy Si{sub x}Se{sub 1−x} are 114, 166 and 361 cm{sup −1}. The calculated values for Si{sub 2}Se{sub 4} (bipyramidal) which agree with the experimental data of Si{sub x}Se{sub 1−x} are 166 and 464 cm{sup −1}. In Si{sub 4}Se (pyramidal) the values 246 and 304 cm{sup −1} agree with the measured values. In Si{sub 4}Se{sub 2} (bipyramidal), the calculated values 162, 196 and 304 cm{sup −1} agree with the measured values. The calculated values of 473 cm{sup −1} for Si{sub 6}Se{sub 2} (bipyramidal) also agree with the experimentally measured values. We thus find that pyramidal structures are present in the amorphous Si{sub x}Se{sub 1−x} glassy state. - Highlights: • A first principles calculation is performed to calculate the vibrational frequencies. • The calculated frequencies of clusters agree with measured Raman values. • The structures, bond lengths and symmetries are determined. • The importance of Jahn–Teller effect in SiS and in SiSe is clearly seen. • The clusters of SiS and SiSe are found to stabilize in different symmetries.

"Non-equilibrium" block copolymer micelles with glassy cores: a predictive approach based on theory of equilibrium micelles.

Science.gov (United States)

Nagarajan, Ramanathan

2015-07-01

Micelles generated in water from most amphiphilic block copolymers are widely recognized to be non-equilibrium structures. Typically, the micelles are prepared by a kinetic process, first allowing molecular scale dissolution of the block copolymer in a common solvent that likes both the blocks and then gradually replacing the common solvent by water to promote the hydrophobic blocks to aggregate and create the micelles. The non-equilibrium nature of the micelle originates from the fact that dynamic exchange between the block copolymer molecules in the micelle and the singly dispersed block copolymer molecules in water is suppressed, because of the glassy nature of the core forming polymer block and/or its very large hydrophobicity. Although most amphiphilic block copolymers generate such non-equilibrium micelles, no theoretical approach to a priori predict the micelle characteristics currently exists. In this work, we propose a predictive approach for non-equilibrium micelles with glassy cores by applying the equilibrium theory of micelles in two steps. In the first, we calculate the properties of micelles formed in the mixed solvent while true equilibrium prevails, until the micelle core becomes glassy. In the second step, we freeze the micelle aggregation number at this glassy state and calculate the corona dimension from the equilibrium theory of micelles. The condition when the micelle core becomes glassy is independently determined from a statistical thermodynamic treatment of diluent effect on polymer glass transition temperature. The predictions based on this "non-equilibrium" model compare reasonably well with experimental data for polystyrene-polyethylene oxide diblock copolymer, which is the most extensively studied system in the literature. In contrast, the application of the equilibrium model to describe such a system significantly overpredicts the micelle core and corona dimensions and the aggregation number. The non-equilibrium model suggests ways to

Potentiometric application of boron- and phosphorus-doped glassy carbon electrodes

Directory of Open Access Journals (Sweden)

ZORAN V. LAUSEVIC

2001-03-01

Full Text Available Acomparative study was carried out of the potentiometric application of boronand phosphorus-doped and undoped glassy carbon samples prepared at the same heat treatment temperature (HTT 1000°C. The electrochemical activities of the obtained electrode materials were investigated on the example of argentometric titrations. It was found that the electrochemical behaviour of the doped glassy carbon samples are very similar to a Sigri (undoped glassy carbon sample (HTT 2400°C. The experiments showed that the potentiometric response depends on the polarization mode, the nature of the sample, the pretreatment of the electrode surface, and the nature of the supporting electrolyte. The amounts of iodide, bromide, and of chloridewere determined to be 1.27 mg, 0.80 mg and 0.54 mg, respectively, with a maximum relative standard deviation of less than 1.1%. The obtained results are in good agreement with the results of comparative potentiometric titrations using a silver indicator electrode. The titrationmethod was applied to the indirect determination of pyridoxine hydrochloride, i.e., vitamin B6.

mwnts composite film modified glassy carbon electrode

African Journals Online (AJOL)

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ABSTRACT: A poly p-aminosalicylic acid (Poly(p-ASA)) and multiwall carbon nanotubes. (MWCNTs) composite modified glassy carbon (GC) electrode was constructed by casting the MWNTs on the GC electrode surface followed by electropolymerization of the p-ASA on the MWCNTs/GCE. The electrochemical behaviours ...

Electron beam-induced Fries rearrangement of arylsulfonamides and arylsulfonates in the crystalline state

International Nuclear Information System (INIS)

Kato, Jun; Yuasa, Kanako; Yamashita, Takashi; Maekawa, Yasunari; Yoshida, Masaru

2003-01-01

Electron beam (EB)-induced reactions of organic crystals containing a carbonyl or a sulfonyl group have been investigated. The EB irradiation of benzenesulfonanilide (BSA) in the crystalline state induced the Fries rearrangement to yield o- and p-aminodiphenylsulfones as the major and minor products, respectively. Several BSA derivatives also had the same reactivity, while benzanilide as the corresponding carbonyl compound did not rearrange under the same conditions. These results showed that the S-N bond could be cleaved selectively by EB irradiation but the C-N bond couldn't, which could take place only by the use of EB. The EB irradiation of phenyl p-toluenesulfonate (PTS) crystals gave not only Fries-type products but also the oxidation product. By comparing with the reactivity of liquid phenyl benzenesulfonate, the EB-induced Fries rearrangement was suggested to proceed under crystalline lattice restrictions. The G-values of arylsulfonamides and arylsulfonates were in the range of ca. 1-2 molecules per 100 eV of absorbed energy. This is the first Fries rearrangement via direct excitation by EB irradiation. (author)

Voltammetric pH sensing using carbon electrodes: glassy carbon behaves similarly to EPPG.

Science.gov (United States)

Lu, Min; Compton, Richard G

2014-09-21

Developing and building on recent work based on a simple sensor for pH determination using unmodified edge plane pyrolytic graphite (EPPG) electrodes, we present a voltammetric method for pH determination using a bare unmodified glassy carbon (GC) electrode. By exploiting the pH sensitive nature of quinones present on carbon edge-plane like sites within the GC, we show how GC electrodes can be used to measure pH. The electro-reduction of surface quinone groups on the glassy carbon electrode was characterised using cyclic voltammetry (CV) and optimised with square-wave voltammetry (SWV) at 298 K and 310 K. At both temperatures, a linear correlation was observed, corresponding to a 2 electron, 2 proton Nernstian response over the aqueous pH range 1.0 to 13.1. As such, unmodified glassy carbon electrodes are seen to be pH dependent, and the Nernstian response suggests its facile use for pH sensing. Given the widespread use of glassy carbon electrodes in electroanalysis, the approach offers a method for the near-simultaneous measurement and monitoring of pH during such analyses.

Structure of Cu-Ti brazing filler metal in amorphous and crystalline states

Energy Technology Data Exchange (ETDEWEB)

Maksymova, S; Khorunov, V [Paton Electric Welding Institute, NASU, 11 Bozhenko Str., Kyiv, 03680 (Ukraine); Zelinskaya, G [G.V. Kurdyumov Institute of Metal Physics, NASU, Kyiv, 03142 (Ukraine)], E-mail: maksymova@paton.kiev.ua

2008-02-15

Structure, chemical homogeneity and phase composition of rapidly quenched ribbons of brazing filler metal Ti{sub 57}Cu{sub 43} were investigated. The ribbons were found to be amorphous. The alloy components are uniformly distributed along the thickness of the strip. High-temperature differential thermal analysis was used to determine temperature ranges of the ribbons crystallization. X-ray diffraction analysis was performed to study phase composition of the rapidly quenched ribbons in the initial state and after their isothermal annealing. Two crystalline phases - {gamma}-CuTi and CuTi{sub 3} being identified in the latter case.

Irradiation effects on polymer-model compounds

International Nuclear Information System (INIS)

Seguchi, Tadao; Hayakawa, Naohiro; Tamura, Naoyuki; Katsumura, Yosuke; Hayashi, Nariyuki; Tabata, Yoneho

1991-01-01

Irradiation effects on n-paraffins and squalane, used as models of polymers, were investigated by product analysis. Four n-paraffins, C 20 H 42 , C 21 H 44 , C 23 H 48 and C 24 H 50 , and squalane (C 30 H 62 ) were γ-irradiated under vacuum in liquid, crystalline and glassy states. The evolved gases were analyzed by gas chromatography and changes in molecular weight were analyzed by liquid chromatography and mass spectroscopy. G-values for crosslinking of n-paraffins were 1.2 for crystalline states (at 25 0 C) and 1.7 for liquid states (at 55 0 C), and showed no difference between odd and even carbon numbers. The G-value of liquid squalane was 1.7; it was 1.3 for the glassy state at low temperature (-77 0 C). Double bonds were common in the crosslinked products, especially after liquid-phase irradiation. The probability of chain scission was estimated as being negligible, though a small number of chain-scission products (which were products of scission at chain-ends or side chains) were observed by gas analysis. (author)

Location of radiation-induced grafted chains in polymers studied by solid-state NMR

International Nuclear Information System (INIS)

Whittacker, A.; Liu, H.

1998-01-01

In this study styrene and N-phenyl maleimide monomers were grafted onto poly(ethylene) (PE) chains using gamma radiation. Of main interest is the distribution of grafted chains within the polymer matrix, as this will determine the efficacy of mixing with the glassy polymers. It is expected that grafting will occur within the amorphous regions, and especially near the interface of the crystalline and amorphous regions. A suitable method for characterising the location of the grafted chains is solid-state 13 C NMR spectroscopy. The 13 C CPMAS spectrum of the blend of PE and N-phenyl maleimide mixed in the melt at 150 deg C , prior to reaction, is shown above. The spectrum shows the typical peaks for poly(ethylene) due to the amorphous and crystalline phase at 30.5 and 32.5 ppm, respectively. Peaks are also seen in the aromatic and carbonyl region due to the maleimide (not plotted). Experiments will be described where the NMR magnetisation is prepared in either the crystalline and amorphous regions of the poly(ethylene) prior to spin diffusion to the maleimide and styrene fractions. The location of the grafted monomers can then be determined by monitoring the changes in signal of polymer and graft with time

Thermodynamic Modeling of Gas Transport in Glassy Polymeric Membranes.

Science.gov (United States)

Minelli, Matteo; Sarti, Giulio Cesare

2017-08-19

Solubility and permeability of gases in glassy polymers have been considered with the aim of illustrating the applicability of thermodynamically-based models for their description and prediction. The solubility isotherms are described by using the nonequilibrium lattice fluid (NELF) (model, already known to be appropriate for nonequilibrium glassy polymers, while the permeability isotherms are described through a general transport model in which diffusivity is the product of a purely kinetic factor, the mobility coefficient, and a thermodynamic factor. The latter is calculated from the NELF model and mobility is considered concentration-dependent through an exponential relationship containing two parameters only. The models are tested explicitly considering solubility and permeability data of various penetrants in three glassy polymers, PSf, PPh and 6FDA-6FpDA, selected as the reference for different behaviors. It is shown that the models are able to calculate the different behaviors observed, and in particular the permeability dependence on upstream pressure, both when it is decreasing as well as when it is increasing, with no need to invoke the onset of additional plasticization phenomena. The correlations found between polymer and penetrant properties with the two parameters of the mobility coefficient also lead to the predictive ability of the transport model.

Nonresonant Faraday rotation in glassy semiconductors

Science.gov (United States)

van den Keybus, P.; Grevendonk, W.

1986-06-01

Nonresonant interband Faraday rotation in amorphous semiconductors, as a function of photon energy, may be described by an equation derived for direct transitions in crystalline semiconductors. In this paper it is shown how this equation may be obtained for the former case also, assuming a parabolic density of states function N(E) and a correlation between valence- and conduction-band states. The analysis of experiments on chalcogenide glasses reveals a Faraday-rotation energy gap EFRg that is significantly larger than the optical gap Eoptg. The effect is attributed to transitions between extended states, so that it is meaningful to compare EFRg with the mobility gap Eμg. For oxide glasses both gaps are comparable but for chalcogenide glasses EFRg is too large by a few tenths of 1 eV.

''Glassy'' low temperature thermal properties in crystalline solids

International Nuclear Information System (INIS)

Nathan, B.D.

1976-05-01

Amorphous dielectrics are known to exhibit anomalous low temperature properties. An extensive review of these properties is presented with an eye toward an understanding of low-lying excitation modes thought to exist in glasses. Work on these systems is described in which a Zr-20 percent Nb samplewhich would be expected to reduce and redistribute the proposed tunneling states. Indeed, the thermal conductivity becomes similar to that of a quenched Zr-8 percent Nb sample and the ''excess'' specific heat linear in temperature dependence is reduced to half the value found in quenched Zr-20 percent Nb. The coefficient of the T 3 term in the specific heat unexpectedly increased from 23.3 to 56.9 erg/gm K 4 and this is attributed to a softening of the lattice due to annealing. The specific heat of this sample was remeasured after it had been dunked in liquid nitrogen. The cubic term was then found to be 19.5 erg/g K 4 , smaller than that in quenched Zr-20 percent Nb, an effect which had been expected due to the chemical diffusion during annealing. Further study of this phenomenon is suggested. Among other relevant measurements performed were the specific heat of a sample of amorphous B 2 O 3 (presented by Stephens (1976)); thermal conductivities of phase-separated unleached Vycor glass and Pyrex; thermal conductivities above 1.2 0 K of polycrystalline MgO, heat-treated Pyroceram and porous Vycor (presented by Tait (1975)) and of mixed crystal KBr-KI (presented by Nathan, Lou and Tait (1976)). The last sample exhibited density fluctuations on a scale of 1000 A but exhibited thermal properties typical of dielectric crystal. Speed of sound measurements were made on both unleached and porous Vycor

Diverse topics in crystalline beams

International Nuclear Information System (INIS)

Wei, Jie; Draeseke, A.; Sessler, A.M.; Li, Xiao-Ping

1995-01-01

Equations of motion are presented, appropriate to interacting charged particles of diverse charge and mass, subject to the external forces produced by various kinds of magnetic fields and radio-frequency (rf) electric fields in storage rings. These equations are employed in the molecular dynamics simulations to study the properties of crystalline beams. The two necessary conditions for the formation and maintenance of crystalline beams are summarized. The transition from ID to 2D, and from 2D to 3D is explored, and the scaling behavior of the heating rates is discussed especially in the high temperature limit. The effectiveness of various cooling techniques in achieving crystalline states has been investigated. Crystalline beams made of two different species of ions via sympathetic cooling are presented, as well as circulating ''crystal balls'' bunched in all directions by magnetic focusing and rf field. By numerically reconstructing the original experimental conditions of the NAP-M ring, it is found that only at extremely low beam intensities, outside of the range of the original measurement, proton particles can form occasionally-passing disks. The proposed New ASTRID ring is shown to be suitable for the formation and maintenance of crystalline beams of all dimensions

Relation between time-temperature transformation and continuous heating transformation diagrams of metallic glassy alloys

International Nuclear Information System (INIS)

Louzguine-Luzgin, Dmitri V.; Inoue, Akihisa

2005-01-01

The time-temperature transformation (TTT) diagrams for the onset of devitrification of the Ge-Ni-La and Cu-Hf-Ti glassy alloys were calculated from the isothermal differential calorimetry data using an Arrhenius equation. The continuous heating transformation (CHT) diagrams for the onset of devitrification of the glassy alloys were subsequently recalculated from TTT diagrams. The recalculation method used for conversion of the TTT into CHT diagrams produces reasonable results and is not sensitive to the type of the devitrification reaction (polymorphous or primary transformation). The diagrams allow to perform a comparison of the stabilities of glassy alloys on a long-term scale. The relationship between these diagrams is discussed

Playback interference of glassy-winged sharp shooter communication

Science.gov (United States)

Animal communication is vital to reproduction, particularly for securing a mate. Insects commonly communicate by exchanging vibrational signals that are transmitted through host plants. The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is an important vector of Xylella fastidiosa, a pl...

Crystallization and evaluation of hen egg-white lysozyme crystals for protein pH titration in the crystalline state.

Science.gov (United States)

Iwai, Wakari; Yagi, Daichi; Ishikawa, Takuya; Ohnishi, Yuki; Tanaka, Ichiro; Niimura, Nobuo

2008-05-01

To observe the ionized status of the amino acid residues in proteins at different pH (protein pH titration in the crystalline state) by neutron diffraction, hen egg-white lysozyme was crystallized over a wide pH range (2.5-8.0). Crystallization phase diagrams at pH 2.5, 6.0 and 7.5 were determined. At pH diagram, and at pH > 4.5 the border shifted to the right (higher precipitant concentration). The qualities of these crystals were characterized using the Wilson plot method. The qualities of all crystals at different pH were more or less equivalent (B-factor values within 25-40). It is expected that neutron diffraction analysis of these crystals of different pH provides equivalent data in quality for discussions of protein pH titration in the crystalline state of hen egg-white lysozyme.

Fine kinetics of natural physical ageing in glassy As{sub 10}Se{sub 90}

Energy Technology Data Exchange (ETDEWEB)

Balitska, V. [Institute of Materials, Scientific Research Company “Carat”, 202 Stryjska Str., 79031 Lviv (Ukraine); Lviv State University of Vital Activity Safety, 35, Kleparivska Str., Lviv 79007 (Ukraine); Golovchak, R. [Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN 37044 (United States); Kozdras, A. [Faculty of Physics of Opole Technical University, 75, Ozimska Str., Opole 45370 (Poland); Shpotyuk, O., E-mail: shpotyuk@novas.lviv.ua [Institute of Materials, Scientific Research Company “Carat”, 202 Stryjska Str., 79031 Lviv (Ukraine); Institute of Physics, Jan Dlugosz University, Al. Armii Krajowej 13/15, Czestochowa 42201 (Poland)

2014-02-01

Sigmoid behavior of natural physical ageing in glassy As{sub 10}Se{sub 90} reveals multi-step-wise growing kinetics of enthalpy losses. Phenomenological description of this kinetics can be adequately developed in terms of first-order relaxation processes, tending atomic structure from initial towards more thermodynamically equilibrium state. This kinetics is shown to obey characteristic stretched exponential behavior originated from a number of growing steps, attributed to the interconnected processes of chalcogen chain alignment and cooperative shrinkage of glass network.

Annealing effects on the migration of ion-implanted cadmium in glassy carbon

Energy Technology Data Exchange (ETDEWEB)

Hlatshwayo, T.T., E-mail: thulani.hlatshwayo@up.ac.za [Physics Department, University of Pretoria, Pretoria (South Africa); Sebitla, L.D. [Physics Department, University of Pretoria, Pretoria (South Africa); Physics Department, University of Botswana, Gaborone (Botswana); Njoroge, E.G.; Mlambo, M.; Malherbe, J.B. [Physics Department, University of Pretoria, Pretoria (South Africa)

2017-03-15

The migration behaviour of cadmium (Cd) implanted into glassy carbon and the effects of annealing on radiation damage introduced by ion implantation were investigated. The glassy carbon substrates were implanted with Cd at a dose of 2 × 10{sup 16} ions/cm{sup 2} and energy of 360 keV. The implantation was performed at room temperature (RT), 430 °C and 600 °C. The RT implanted samples were isochronally annealed in vacuum at 350, 500 and 600 °C for 1 h and isothermally annealed at 350 °C up to 4 h. The as-implanted and annealed samples were characterized by Raman spectroscopy and Rutherford backscattering spectrometry (RBS). Raman results revealed that implantation at room temperature amorphized the glassy carbon structure while high temperature implantations resulted in slightly less radiation damage. Isochronal annealing of the RT implanted samples resulted in some recrystallization as a function of increasing temperature. The original glassy carbon structure was not achieved at the highest annealing temperature of 600 °C. Diffusion of Cd in glassy carbon was already taking place during implantation at 430 °C. This diffusion of Cd was accompanied by significant loss from the surface during implantation at 600 °C. Isochronal annealing of the room temperature implanted samples at 350 °C for 1 h caused Cd to diffuse towards the bulk while isothermal annealing at 500 and 600 °C resulted in the migration of implanted Cd toward the surface accompanied by a loss of Cd from the surface. Isothermal annealing at 350 °C for 1 h caused Cd to diffuse towards the bulk while for annealing time >1 h Cd diffused towards the surface. These results were interpreted in terms of trapping and de-trapping of implanted Cd by radiation damage.

Hysteresis, reentrance, and glassy dynamics in systems of self-propelled rods.

Science.gov (United States)

Kuan, Hui-Shun; Blackwell, Robert; Hough, Loren E; Glaser, Matthew A; Betterton, M D

2015-01-01

Nonequilibrium active matter made up of self-driven particles with short-range repulsive interactions is a useful minimal system to study active matter as the system exhibits collective motion and nonequilibrium order-disorder transitions. We studied high-aspect-ratio self-propelled rods over a wide range of packing fractions and driving to determine the nonequilibrium state diagram and dynamic properties. Flocking and nematic-laning states occupy much of the parameter space. In the flocking state, the average internal pressure is high and structural and mechanical relaxation times are long, suggesting that rods in flocks are in a translating glassy state despite overall flock motion. In contrast, the nematic-laning state shows fluidlike behavior. The flocking state occupies regions of the state diagram at both low and high packing fraction separated by nematic-laning at low driving and a history-dependent region at higher driving; the nematic-laning state transitions to the flocking state for both compression and expansion. We propose that the laning-flocking transitions are a type of glass transition that, in contrast to other glass-forming systems, can show fluidization as density increases. The fluid internal dynamics and ballistic transport of the nematic-laning state may promote collective dynamics of rod-shaped micro-organisms.

Electrochemical oxidation of niclosamide at a glassy carbon ...

African Journals Online (AJOL)

Cyclic voltammetry, square-wave voltammetry and controlled potential electrolysis have been used to study the electrochemical oxidation behaviour of niclosamide at a glassy carbon electrode. The number of electrons transferred, the wave characteristics, the diffusion coefficient and reversibility of the reactions have been ...

Glassy carbon supercapacitor: 100,000 cycles demonstrated

Energy Technology Data Exchange (ETDEWEB)

Baertsch, M; Braun, A; Schnyder, B; Koetz, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1999-08-01

A 5 V glassy carbon capacitor stack was built consisting of four bipolar and two end-plate electrodes. More than 100,000 charging/discharging cycles were applied to test the stability of the double-layer capacitor. Low and high frequency resistances were measured as a function of the number of cycles. (author) 2 figs., 1 ref.

SUPERNOVA SHOCK-WAVE-INDUCED CO-FORMATION OF GLASSY CARBON AND NANODIAMOND

Energy Technology Data Exchange (ETDEWEB)

Stroud, Rhonda [Naval Research Laboratory, Washington, D.C.; Chisholm, Matthew F [ORNL; Heck, Phillipp [The Field Museum, Chicago, IL; Alexander, Conel [Carnegie Institution of Washington; Nittler, Larry [Carnegie Institution of Washington

2011-01-01

Nanodiamond (ND) was the first extrasolar dust phase to be identified in meteorites. However, the 2 nm average size of the NDs precludes isotopic analysis of individual particles, and thus their origin(s) remains controversial. Using electron microscopy with subnanometer resolution, we show that ND separates from the Allende and Murchison meteorites are actually a two-phase mixture of ND and glassy carbon. This phase mixture is likely the product of supernova shock-wave transformation of pre-formed organics in the interstellar medium (ISM). The glassy carbon ND mixture is also a plausible contributor to the 2175 extinction feature in the diffuse ISM.

A wrinkling-based method for investigating glassy polymer film relaxation as a function of film thickness and temperature.

Science.gov (United States)

Chung, Jun Young; Douglas, Jack F; Stafford, Christopher M

2017-10-21

We investigate the relaxation dynamics of thin polymer films at temperatures below the bulk glass transition T g by first compressing polystyrene films supported on a polydimethylsiloxane substrate to create wrinkling patterns and then observing the slow relaxation of the wrinkled films back to their final equilibrium flat state by small angle light scattering. As with recent relaxation measurements on thin glassy films reported by Fakhraai and co-workers, we find the relaxation time of our wrinkled films to be strongly dependent on film thickness below an onset thickness on the order of 100 nm. By varying the temperature between room temperature and T g (≈100 °C), we find that the relaxation time follows an Arrhenius-type temperature dependence to a good approximation at all film thicknesses investigated, where both the activation energy and the relaxation time pre-factor depend appreciably on film thickness. The wrinkling relaxation curves tend to cross at a common temperature somewhat below T g , indicating an entropy-enthalpy compensation relation between the activation free energy parameters. This compensation effect has also been observed recently in simulated supported polymer films in the high temperature Arrhenius relaxation regime rather than the glassy state. In addition, we find that the film stress relaxation function, as well as the height of the wrinkle ridges, follows a stretched exponential time dependence and the short-time effective Young's modulus derived from our modeling decreases sigmoidally with increasing temperature-both characteristic features of glassy materials. The relatively facile nature of the wrinkling-based measurements in comparison to other film relaxation measurements makes our method attractive for practical materials development, as well as fundamental studies of glass formation.

The effect of crystallinity on cell growth in semi-crystalline microcellular foams by solid-state process: modeling and numerical simulation

Science.gov (United States)

Rezvanpanah, Elham; Ghaffarian Anbaran, S. Reza

2017-11-01

This study establishes a model and simulation scheme to describe the effect of crystallinity as one of the most effective parameters on cell growth phenomena in a solid batch foaming process. The governing model of cell growth dynamics, based on the well-known ‘Cell model’, is attained in details. To include the effect of crystallinity in the model, the properties of the polymer/gas mixtures (i.e. solubility, diffusivity, surface tension and viscosity) are estimated by modifying relations to consider the effect of crystallinity. A finite element-finite difference (FEFD) method is employed to solve the highly nonlinear and coupled equations of cell growth dynamics. The proposed simulation is able to evaluate all properties of the system at the given process condition and uses them to calculate the cell size, pressure and gas concentration gradient with time. A high-density polyethylene/nitrogen (HDPE/N2) system is used herein as a case study. Comparing the simulation results with the others works and experimental results verify the accuracy of the simulation scheme. The cell growth is a complicated combination of several phenomena. This study attempted to reach a better understanding of cell growth trend, driving and retarding forces and the effect of crystallinity on them.

Solvated electron structure in glassy matrices

International Nuclear Information System (INIS)

Kevan, L.

1981-01-01

Current knowledge of the detailed geometrical structure of solvated electrons in aqueous and organic media is summarized. The geometry of solvated electrons in glassy methanol, ethanol, and 2-methyltetrahydrofuran is discussed. Advanced electron magnetic resonance methods and development of new methods of analysis of electron spin echo modulation patterns, second moment line shapes, and forbidden photon spin-flip transitions for paramagnetic species in these disordered systems are discussed. 66 references are cited

The influence of the surface parameter changes onto the phonon states in ultrathin crystalline films

Science.gov (United States)

Šetrajčić, Jovan P.; Ilić, Dušan I.; Jaćimovski, Stevo K.

2018-04-01

In this paper, we have analytically investigated how the changes in boundary surface parameters influence the phonon dispersion law in ultrathin films of the simple cubic crystalline structure. Spectra of possible phonon states are analyzed using the method of two-time dependent Green's functions and for the diverse combination of boundary surface parameters, this problem was presented numerically and graphically. It turns out that for certain values and combinations of parameters, displacement of dispersion branches outside of bulk zone occurs, leading to the creation of localized phonon states. This fact is of great importance for the heat removal, electrical conductivity and superconducting properties of ultrathin films.

Crystalline and Crystalline International Disposal Activities

Energy Technology Data Exchange (ETDEWEB)

Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-03-06

This report presents the results of work conducted between September 2015 and July 2016 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program. Los Alamos focused on two main activities during this period: Discrete fracture network (DFN) modeling to describe flow and radionuclide transport in complex fracture networks that are typical of crystalline rock environments, and a comprehensive interpretation of three different colloid-facilitated radionuclide transport experiments conducted in a fractured granodiorite at the Grimsel Test Site in Switzerland between 2002 and 2013. Chapter 1 presents the results of the DFN work and is divided into three main sections: (1) we show results of our recent study on the correlation between fracture size and fracture transmissivity (2) we present an analysis and visualization prototype using the concept of a flow topology graph for characterization of discrete fracture networks, and (3) we describe the Crystalline International work in support of the Swedish Task Force. Chapter 2 presents interpretation of the colloidfacilitated radionuclide transport experiments in the crystalline rock at the Grimsel Test Site.

Graphene oxide-mediated electrochemistry of glucose oxidase on glassy carbon electrodes.

Science.gov (United States)

Castrignanò, Silvia; Valetti, Francesca; Gilardi, Gianfranco; Sadeghi, Sheila J

2016-01-01

Glucose oxidase (GOD) was immobilized on glassy carbon electrodes in the presence of graphene oxide (GO) as a model system for the interaction between GO and biological molecules. Lyotropic properties of didodecyldimethylammonium bromide (DDAB) were used to stabilize the enzymatic layer on the electrode surface resulting in a markedly improved electrochemical response of the immobilized GOD. Transmission electron microscopy images of the GO with DDAB confirmed the distribution of the GO in a two-dimensional manner as a foil-like material. Although it is known that glassy carbon surfaces are not ideal for hydrogen peroxide detection, successful chronoamperometric titrations of the GOD in the presence of GO with β-d-glucose were performed on glassy carbon electrodes, whereas no current response was detected upon β-d-glucose addition in the absence of GO. The GOD-DDAB-GO system displayed a high turnover efficiency and substrate affinity as a glucose biosensor. The simplicity and ease of the electrode preparation procedure of this GO/DDAB system make it a good candidate for immobilizing other biomolecules for fabrication of amperometric biosensors. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

Comparing the mechanism of water condensation and evaporation in glassy aerosol.

Science.gov (United States)

Bones, David L; Reid, Jonathan P; Lienhard, Daniel M; Krieger, Ulrich K

2012-07-17

Atmospheric models generally assume that aerosol particles are in equilibrium with the surrounding gas phase. However, recent observations that secondary organic aerosols can exist in a glassy state have highlighted the need to more fully understand the kinetic limitations that may control water partitioning in ambient particles. Here, we explore the influence of slow water diffusion in the condensed aerosol phase on the rates of both condensation and evaporation, demonstrating that significant inhibition in mass transfer occurs for ultraviscous aerosol, not just for glassy aerosol. Using coarse mode (3-4 um radius) ternary sucrose/sodium chloride/aqueous droplets as a proxy for multicomponent ambient aerosol, we demonstrate that the timescale for particle equilibration correlates with bulk viscosity and can be ≫10(3) s. Extrapolation of these timescales to particle sizes in the accumulation mode (e.g., approximately 100 nm) by applying the Stokes-Einstein equation suggests that the kinetic limitations imposed on mass transfer of water by slow bulk phase diffusion must be more fully investigated for atmospheric aerosol. Measurements have been made on particles covering a range in dynamic viscosity from  10(13) Pa s. We also retrieve the radial inhomogeneities apparent in particle composition during condensation and evaporation and contrast the dynamics of slow dissolution of a viscous core into a labile shell during condensation with the slow percolation of water during evaporation through a more homogeneous viscous particle bulk.

SUPERNOVA SHOCK-WAVE-INDUCED CO-FORMATION OF GLASSY CARBON AND NANODIAMOND

International Nuclear Information System (INIS)

Stroud, Rhonda M.; Chisholm, Matthew F.; Heck, Philipp R.; Alexander, Conel M. O'D.; Nittler, Larry R.

2011-01-01

Nanodiamond (ND) was the first extrasolar dust phase to be identified in meteorites. However, the 2 nm average size of the NDs precludes isotopic analysis of individual particles, and thus their origin(s) remains controversial. Using electron microscopy with subnanometer resolution, we show that ND separates from the Allende and Murchison meteorites are actually a two-phase mixture of ND and glassy carbon. This phase mixture is likely the product of supernova shock-wave transformation of pre-formed organics in the interstellar medium (ISM). The glassy carbon-ND mixture is also a plausible contributor to the 2175 A extinction feature in the diffuse ISM.

Electrochemical pre anodization of glassy carbon electrode and application to determine chloramphenicol

International Nuclear Information System (INIS)

Truc, Nguyen Minh; Mortensen, John; Anh, Nguyen Ba Hoai

2008-01-01

This paper suggested a method to enhance the performance of carbon electrodes for the determination of chloramphenicol (CAP). The sensitivity and the reproducibility of the carbon electrodes could be enhanced easily by electrochemical pretreatment. Some kinds of carbon material were studied including glassy carbon, graphite carbon and pyrolytic carbon. Numerous kinds of supporting electrolyte have been tried. For glassy carbon electrode, the acidic solution, H 2 SO 4 5 mM, resulted in best performance at pretreated voltage of +2.1V (vs. Ag/ AgCl) in duration of 250 second. However, for graphite and pyrolytic carbon electrodes, the phosphate buffer solution pH 6.0 gave the best performance at +1.7V (vs. Ag/ AgCl) in duration of 20 seconds. The detection limit could be at very low concentration of CAP: 0.8 ng/ ml for glassy carbon electrode, 3.5 ng/ ml for graphite carbon electrode. The method was successful applied to aqua-agriculture water sample and milk sample with simple extraction as well as direct ointment sample analysis. (author)

Crystalline and Crystalline International Disposal Activities

Energy Technology Data Exchange (ETDEWEB)

Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-12-21

This report presents the results of work conducted between September 2014 and July 2015 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program.

Theoretical study of the elasticity, mechanical behavior, electronic structure, interatomic bonding, and dielectric function of an intergranular glassy film model in prismatic β-Si3N4

International Nuclear Information System (INIS)

Ching, W. Y.; Rulis, Paul; Aryal, Sitaram; Ouyang, Lizhi; Misra, Anil

2010-01-01

Microstructures such as intergranular glassy films (IGFs) are ubiquitous in many structural ceramics. They control many of the important physical properties of polycrystalline ceramics and can be influenced during processing to modify the performance of devices that contain them. In recent years, there has been intense research, both experimentally and computationally, on the structure and properties of IGFs. Unlike grain boundaries or dislocations with well-defined crystalline planes, the atomic scale structure of IGFs, their fundamental electronic interactions, and their bonding characteristics are far more complicated and not well known. In this paper, we present the results of theoretical simulations using ab initio methods on an IGF model in β-Si 3 N 4 with prismatic crystalline planes. The 907-atom model has a dimension of 14.533 A x 15.225 A x 47.420 A . The IGF layer is perpendicular to the z axis, 16.4 A wide, and contains 72 Si, 32 N, and 124 O atoms. Based on this model, the mechanical and elastic properties, the electronic structure, the interatomic bonding, the localization of defective states, the distribution of electrostatic potential, and the optical dielectric function are evaluated and compared with crystalline β-Si 3 N 4 . We have also performed a theoretical tensile experiment on this model by incrementally extending the structure in the direction perpendicular to the IGF plane until the model fully separated. It is shown that fracture occurs at a strain of 9.42% with a maximum stress of 13.9 GPa. The fractured segments show plastic behavior and the formation of surfacial films on the β-Si 3 N 4 . These results are very different from those of a previously studied basal plane model [J. Chen et al., Phys. Rev. Lett. 95, 256103 (2005)] and add insights to the structure and behavior of IGFs in polycrystalline ceramics. The implications of these results and the need for further investigations are discussed.

Emergence of Griffiths phase and glassy mixed phase in Sm0.5Ca0.5MnO3 nanomanganites

International Nuclear Information System (INIS)

Giri, S.K.; Yusuf, S.M.; Mukadam, M.D.; Nath, T.K.

2014-01-01

Graphical abstract: A detailed investigation on the effect of grain size on formation of Griffiths phase, and glassy mixed phase in CE-type antiferromagnetic Sm 0.5 Ca 0.5 MnO 3 manganite are carried out. A rigorous measurement of linear and non-linear ac magnetic susceptibilities, time dependent relaxation and aging phenomena in Sm 0.5 Ca 0.5 MnO 3 nanomanganite confirm the existence of a glassy mixed phase in the low temperature regime. The signature of Griffiths phase in nanosized manganite has been confirmed from the detailed ac and dc magnetization studies. The existence of Griffiths phase is verified through the anomalous behavior of the low field temperature dependent an inverse ac and dc magnetic susceptibility. Based on experimental results, the glassy phase of nanomanganites has been attributed to the phase separation effect and interaction between the ferromagnetic clusters. A phenomenological core/shell model has also been proposed based on the surface disorder to explain the observed Griffiths phase in these nanosized manganites. Fig. 1: (Left) The plot of inverse of ac susceptibility χ ac -1 measured at f = 1 Hz and H ac = 2 Oe as a function of temperature for S750 sample. Inset shows the same for S550 sample. (Right) A schematic of the proposed model to describe the magnetic state of the Sm 0.5 Ca 0.5 MnO 3 system at different average sizes. Highlights: • Effect of grain size on Griffiths phase and glassy mixed phase is discussed. • GP is confirmed by dc, linear and non-linear ac magnetization in nanomanganites. • Glassy mixed phase is discussed by time dependent relaxation and aging phenomena. • The existence of GP is verified through an inverse ac and dc magnetic susceptibility. • A phenomenological core/shell model has been proposed based on surface disorder. -- Abstract: A detailed investigation on the effect of grain size on formation of Griffiths phase (GP), and glassy mixed phase in CE-type antiferromagnetic Sm 0.5 Ca 0.5 MnO 3

Irreducible tensor operators and crystalline potentials

International Nuclear Information System (INIS)

Boutron, F.; Saint-James, D.

1961-01-01

It is often accepted that the effects of its neighbourhood on the quantum state of an ion A may be obtained by the model of the crystalline effective field approximation. Within this assumption Stevens has developed a method which provides equivalent operators that facilitate the calculation of the matrix elements of the crystalline field in a given multiplicity. This method has been extended here. We demonstrate that in the expansion of the crystalline field in powers of the electrons coordinates of the ion A - for electrons of the same sub-shell of A - only even terms can contribute. Equivalent operators and matrix elements, in a given multiplicity, are given for these development terms - up to order 6 - and for potential invariant by the operations of one of the thirty-two point-groups. (author) [fr

Effects of nymphal diet and adult feeding on allocation of resources to glassy-winged sharpshooter egg production

Science.gov (United States)

The glassy-winged sharpshooter is an invasive insect capable of transmitting the bacterial pathogen Xylella fastidiosa. Pre-oviposition periods of laboratory reared glassy-winged sharpshooters are variable. Here, two questions were addressed: does nymphal diet affect pre-oviposition period and how d...

Formation of glassy carbon structure and its change under neutron irradiation

Energy Technology Data Exchange (ETDEWEB)

Kurolenkin, E.I.; Lopato, Yu.S.; Virgil' ev, Yu.S.; Khakimova, D.K.; Aksenov, S.I.

1981-01-01

The changes of glassy carbon structure, which is prepared of phenol-formaldehyde and furfurol-phenol-formaldehyde resins in the process of irradiation with 5.3x10/sup 20/ cm/sup -2/ neutron fluence with the energy E>0.18 MeV in the temperature range of 90-540 deg C are studied. It is established the irradiation results in the shrinkage of the samples. The compression of the samples increases with the irradiation temperature and neutron fluence. The thermal annealing does not result in the restoration of the volume of samples. The sample shrinkage, caused by more compact package of globular structures and the destruction of film structures, decrease gas permeability of glassy carbon.

Modification of dielectric function and electronic structure of the alloys at the phase transformation amorphous-crystalline state

International Nuclear Information System (INIS)

Belij, M.U.; Poperenko, L.V.; Shajkevich, I.A.; Karpusha, V.D.; Kravets, V.G.

1989-01-01

The relation between the features of the optical spectrum and the electronic structure parameters for non-crystalline nickel- and iron-based alloys is not yet precisely found. Therefore the main purpose of the study consists in investigation of the basic metal band structure modification at metalloid alloying. The density of electron states N(E) and structural parameters of amorphous alloys nickel-M, iron-M, Fe-TM-M (M - metalloid B,Si,C; TM - transition metal 3d (Ti,V,Cr,Mn,Co,Ni), 4d (Nb,Mo), 5d (Hf,Ta,W) and their transformation changes from amorphous (AS) to crystalline state (CS) have been determined. The methods of ellipsometry, Auger-spectroscopy and X-ray absorption spectroscopy are used. The function N(E) of the Ni- and Fe-based alloys has shown 4 density-of-states peaks, one of them located above the Fermi level E F and the others - below it. The observed features of the absorbed spectra of Ni-M (M = B,P) are related both to the interband transition from the levels falling into the occupied peaks of N(E) to the levels at E F , and to the 1-peak-states. When B increases the distance between 1-peak and E F decreases. With introduction of the TM atoms into Fe-B the impurities states related to them are formed above E F . From the X-ray data the cluster with nonhomogeneous electronic density for FeBSi (7.0 nm) and FeNbBSi (7.0 and 4.2 nm along and transverse to foil respectively) are estimated. The frequencies of relaxation and plasma oscillations are also calculated. (author)

Response to state comments on the revised draft northeastern regional characterization reports for the Crystalline Repository Project

International Nuclear Information System (INIS)

1985-08-01

The purpose of this document is to respond to the comments received from the States of the Northeastern Region on the revised draft Northeastern Regional Characterization Reports (RCRs). The responses in this document indicate the manner in which the suggestions or comments received have been considered in modifying the revised draft Northeastern RCRs. Both general comments related to the overall Crystalline Repository Project (CRP) and comments on specific sections of the RCRs are addressed. This document responds to Northeastern State comments on both the revised draft Northeastern Regional Geologic Characterization Report (RGCR) and the revised draft Northeastern Regional Environmental Characterization Report (RECR)

Response to state comments on the revised draft Southeastern Regional Characterization Reports for the Crystalline Repository Project

International Nuclear Information System (INIS)

1985-08-01

The purpose of this document is to respond to the comments received from the states of the Southeastern Region on the revised draft Southeastern Regional Characterization Reports (RCRs). The responses in this document indicate the manner in which the suggestions or comments received have been considered in modifying the revised draft Southeastern RCRs. Both general comments related to the overall Crystalline Repository Project (CRP) and comments on specific sections of the RCRs are addressed. This document responds to Southeastern State comments on both the revised draft Southeastern Regional Geologic Characterization Report (RGCR) and the revised draft Southeastern Regional Environmental Characterization Report (RECR)

Influence of thermal history on the photostructural changes in glassy As15S85 studied by Raman scattering and ab initio calculations

International Nuclear Information System (INIS)

Kolar, J.; Strizik, L.; Kohoutek, T.; Wagner, T.; Voyiatzis, G. A.; Chrissanthopoulos, A.; Yannopoulos, S. N.

2013-01-01

Photostructural changes—the hallmark of non-crystalline chalcogenides—are in essence the basis of a number of photoinduced effects, i.e., changes of their physical properties, which are exploited in a variety of applications, especially in photonics and optoelectronics. Despite the vast number of investigations of photostructural changes, there is currently lack of systematic studies on how the thermal history, which affects glass structure, modifies the extent of photostructural changes. In this article, we study the role of thermal history on photostructural changes in glassy As 15 S 85 . This particular sulfur-rich composition has been chosen based on the colossal photostructural response it exhibits under near-band gap light irradiation, which inherently originates from its nanoscale phase-separated nature. To control the thermal history, the glass was quenched to various temperatures and each of these quenched products was annealed under four different conditions. Off-resonant Raman scattering was used to study the equilibrium study of each product. Structural changes of interest involve changes of the sulfur atoms participating into S 8 rings and S n chains. Their ratio was found to depend on quenching/annealing conditions. Near-band gap light was used to perturb the rings-to-chain ratio and at the same time to record these changes through Raman scattering, revealing an intricate behavior of photostructural changes. Ab initio calculations were employed to determine the stability of various sulfur clusters/molecules thus aiding the correlation of the particular photo-response of glassy As 15 S 85 with its structural constituents

Crystalline Silica Primer

Science.gov (United States)

,

1992-01-01

Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated

Neutron-scattering study of low-energy excitations in triphenyl phosphite

CERN Document Server

Mayer, J; Massalska-Arodz, M; Janik, J A; Natkaniec, I; Steinsvoll, O

2002-01-01

The low-energy excitations in crystalline and glassy triphenyl phosphite were studied by inelastic incoherent neutron scattering with two different instruments. The results - the incoherent dynamic structure factor S(2 theta,omega) and the density of states G(omega) - were obtained using direct and inverted geometry time-of-flight spectrometers, respectively. The probable origin of the excess density of states in the glass (boson peak) is discussed. (orig.)

Neutron-scattering study of low-energy excitations in triphenyl phosphite

International Nuclear Information System (INIS)

Mayer, J.; Krawczyk, J.; Massalska-Arodz, M.; Janik, J.A.; Natkaniec, I.; Steinsvoll, O.

2002-01-01

The low-energy excitations in crystalline and glassy triphenyl phosphite were studied by inelastic incoherent neutron scattering with two different instruments. The results - the incoherent dynamic structure factor S(2θ,ω) and the density of states G(ω) - were obtained using direct and inverted geometry time-of-flight spectrometers, respectively. The probable origin of the excess density of states in the glass (boson peak) is discussed. (orig.)

High Temperature NMR Studies of the Glass-Crystal Transition in the Cs2S2O7-V2O5 System

DEFF Research Database (Denmark)

Lapina, Olga B.; Terskikh, Viktor V.; Shubin, Aleksander A.

1997-01-01

133Cs and 51V NMR spectra have been recorded of Cs2S2O7 and the catalytically important Cs2S2O7-V2O5 mixtures in the temperature range 20 - 550 C. A high mobility of Cs+ in the solid Cs2S2O7 was observed. The transformation from glassy state to crystalline state was investigated for the compositi...

Topological Crystalline Superconductivity in Locally Noncentrosymmetric Multilayer Superconductors.

Science.gov (United States)

Yoshida, Tomohiro; Sigrist, Manfred; Yanase, Youichi

2015-07-10

Topological crystalline superconductivity in locally noncentrosymmetric multilayer superconductors (SCs) is proposed. We study the odd-parity pair-density wave (PDW) state induced by the spin-singlet pairing interaction through the spin-orbit coupling. It is shown that the PDW state is a topological crystalline SC protected by a mirror symmetry, although it is topologically trivial according to the classification based on the standard topological periodic table. The topological property of the mirror subsectors is intuitively explained by adiabatically changing the Bogoliubov-de Gennes Hamiltonian. A subsector of the bilayer PDW state reduces to the two-dimensional noncentrosymmetric SC, while a subsector of the trilayer PDW state is topologically equivalent to the spinless p-wave SC. Chiral Majorana edge modes in trilayers can be realized without Cooper pairs in the spin-triplet channel and chemical potential tuning.

Disorder-induced localization in crystalline phase-change materials.

Science.gov (United States)

Siegrist, T; Jost, P; Volker, H; Woda, M; Merkelbach, P; Schlockermann, C; Wuttig, M

2011-03-01

Localization of charge carriers in crystalline solids has been the subject of numerous investigations over more than half a century. Materials that show a metal-insulator transition without a structural change are therefore of interest. Mechanisms leading to metal-insulator transition include electron correlation (Mott transition) or disorder (Anderson localization), but a clear distinction is difficult. Here we report on a metal-insulator transition on increasing annealing temperature for a group of crystalline phase-change materials, where the metal-insulator transition is due to strong disorder usually associated only with amorphous solids. With pronounced disorder but weak electron correlation, these phase-change materials form an unparalleled quantum state of matter. Their universal electronic behaviour seems to be at the origin of the remarkable reproducibility of the resistance switching that is crucial to their applications in non-volatile-memory devices. Controlling the degree of disorder in crystalline phase-change materials might enable multilevel resistance states in upcoming storage devices.

Degradation of L-Ascorbic Acid in the Amorphous Solid State.

Science.gov (United States)

Sanchez, Juan O; Ismail, Yahya; Christina, Belinda; Mauer, Lisa J

2018-03-01

Ascorbic acid degradation in amorphous solid dispersions was compared to its degradation in the crystalline state. Physical blends and lyophiles of ascorbic acid and polymers (pectins and polyvinylpyrrolidone [PVP]) were prepared initially at 50:50 (w/w), with further studies using the polymer that best inhibited ascorbic acid crystallization in the lyophiles in 14 vitamin : PVP ratios. Samples were stored in controlled environments (25 to 60 °C, 0% to 23% RH) for 1 mo and analyzed periodically to track the physical appearance, change in moisture content, physical state (powder x-ray diffraction and polarized light microscopy), and vitamin loss (high performance liquid chromatography) over time. The glass transition temperatures of select samples were determined using differential scanning calorimetry, and moisture sorption profiles were generated. Ascorbic acid in the amorphous form, even in the glassy amorphous state, was more labile than in the crystalline form in some formulations at the highest storage temperature. Lyophiles stored at 25 and 40 °C and those in which ascorbic acid had crystallized at 60 °C (≥70% ascorbic acid : PVP) had no significant difference in vitamin loss (P > 0.05) relative to physical blend controls, and the length of storage had little effect. At 60 °C, amorphous ascorbic acid lyophiles (≤60% ascorbic acid : PVP) lost significantly more vitamin (P vitamin loss significantly increased over time. In these lyophiles, vitamin degradation also significantly increased (P vitamins are naturally present or added at low concentrations and production practices may promote amorphization of the vitamin. Vitamin C is one of the most unstable vitamins in foods. This study documents that amorphous ascorbic acid is less stable than crystalline ascorbic acid in some environments (for example, higher temperatures within 1 wk), especially when the vitamin is present at low concentrations in a product. These findings increase the understanding of

Photoswitchable molecular dipole antennas with tailored coherent coupling in glassy composite

DEFF Research Database (Denmark)

Elbahri, Mady; Zillohu, Ahnaf Usman; Gothe, Bastian

2015-01-01

. We also introduce the concept of 'tailored molecular photonic coupling' while highlighting the role of interferences for the design of optically active media by adjusting the photonic response of the medium with the real and imaginary refractive index of photoswitchable molecules in the 'ON' state...... alteration of photochromic molecular dipole antennas. We successfully demonstrate the concept of Brewster wavelength, which is based on the dipolar interaction between radiating dipoles and the surrounding matrix possessing a net dipole moment, as a key tool for highly localized sensing of matrix polarity....... Our results enhance our fundamental understanding of coherent dipole radiation and open a new vein of research based on glassy disordered dipolar composites that act as macroscopic antenna with cooperative action; furthermore, these results have important implications for new design rules of tailored...

Dielectric relaxation and AC conductivity studies of Se90Cd10−xInx glassy alloys

Directory of Open Access Journals (Sweden)

Nitesh Shukla

2016-06-01

Full Text Available Chalcogenide glassy alloys of Se90Cd10−xInx (x = 2, 4, 6, 8 are synthesized by melt quench technique. The prepared glassy alloys have been characterized by techniques such as differential scanning calorimetry (DSC, scanning electron microscopy (SEM and energy dispersive X-ray (EDAX. Dielectric properties of Se90Cd10−xInx (x = 2, 4, 6, 8 chalcogenide glassy system have been studied using impedance spectroscopic technique in the frequency range 42 Hz to 5 MHz at room temperature. It is found that the dielectric constants ɛ′, dielectric loss factor ɛ″ and loss angle Tan δ depend on frequency. ɛ′, ɛ″ and loss angle Tan δ are found to be decreasing with the In content in Se90Cd10−xInx glassy system. AC conductivity of the prepared sample has also been studied. It is found that AC conductivity increases with frequency where as it has decreasing trend with increasing In content in Se–Cd matrix. The semicircles observed in the Cole–Cole plots indicate a single relaxation process.

Study of crystalline morphology and phase structure in poly(styrene-b-ethylene oxide-b-styrene) triblock copolymers bu solid state RMN spin diffusion

International Nuclear Information System (INIS)

Mantovani, Gerson L.; Phan, Trang; Bertin, Denis; Azevedo, Eduardo R. de; Bonagamba, Tito J.

2009-01-01

The phase structure and crystalline morphology of a series of polystyrene-b-polyethylene oxide-b-polystyrene (PS-b- PEO-b-PS) triblock copolymers, with different compositions and molecular weights, has been studied by solid-state NMR. WAXS and DSC measurements were used to detect the presence of crystalline domains of polyethylene oxide (PEO) blocks at room temperature as a function of the copolymer composition. 1 H NMR spin diffusion analyses provided an estimation of the size of the dispersed phases of the nano structured copolymers. (author)

Effect of glassy carbon properties on the electrochemical deposition of platinum nano-catalyst and its activity for methanol oxidation

Directory of Open Access Journals (Sweden)

SANJA TERZIC

2007-02-01

Full Text Available The effects of the properties of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on glassy carbon (GC/Pt for methanol oxidation in alkaline and acidic solutions were studied. Platinum was potentiostatically deposited on two glassy carbon samples, thermally treated at different temperatures, which were either polished or anodicaly polarised in acid (GCOX-AC/Pt and in alkali (GCOX-AL/Pt. Anodic polarisation of glassy carbon, either in alkaline or acidic solution, enhances the activity of both types of GC/Pt electrodes for methanol oxidation. The activity of the catalysts follows the change in the properties of the glassy carbon support upon anodic treatment. The specific activity of the GCOX-AL/Pt electrode for this reaction in alkali is increased only a few times in comparison with the activity of the GC/Pt one. On the other hand, the specific activity of the GCOX-AC/Pt electrode for methanol oxidation in acid is about one order of magnitude higher than that of the GC/Pt electrode. The role of the substrate on the properties of catalyst is discussed in detail.

Connection between NMR and electrical conductivity in glassy chalcogenide fast ionic conductors

International Nuclear Information System (INIS)

Kim, K.H.

1995-01-01

The work documented in this thesis follows the traditional order. In this chapter a general discussion of ionic conduction and of glassy materials are followed by a brief outline of the experimental techniques for the investigation of fast ionic conduction in glassy materials, including NMR and impedance spectroscopy techniques. A summary of the previous and present studies is presented in the last section of this introductory chapter. The details of the background theory and models are found in the Chapter II, followed by the description of the experimental details in Chapter III. Chapter IV of the thesis describes the experimental results and the analysis of the experimental observations followed by the conclusions in chapter V

Generation of fine hydromagmatic ash by growth and disintegration of glassy rinds

Science.gov (United States)

Mastin, L.G.

2007-01-01

The deposits of mafic hydromagmatic eruptions are more fine grained and variable in vesicularity than dry magmatic deposits. Blocky, equant shapes of many hydromagmatic clasts also contrast with droplet, thread, and bubble wall morphology of dry magmatic fragments. Small (disintegration of glassy rinds on pyroclast surfaces as they deform within turbulent flows. This process, termed "turbulent shedding", may occur during the expansion phase of vapor explosions or during turbulent but nonexplosive mixing of magma with water, steam, or water sprays. The occurrence of turbulent shedding and the resulting fragment sizes depend on the timescale for rind growth and the timescale between disturbances that remove or disintegrate glassy rinds. Turbulent shedding is directly observable in some small littoral jets at Kilauea. Calculations suggest that, in the presence of liquid water or water sprays, glassy rinds having a thickness of microns to millimeters should form in milliseconds to seconds. This is similar to the timescale between turbulent velocity fluctuations that can shred lava globules and remove such rinds. The fraction of a deposit consisting of fine ash should increase with the duration of this process: Large-scale Surtseyan jets generate hundreds or thousands of shedding events; bubble bursts or tephra jets at Kilauea's coast may produce only a few.

Protection of nuclear graphite toward fluoride molten salt by glassy carbon deposit

International Nuclear Information System (INIS)

Bernardet, V.; Gomes, S.; Delpeux, S.; Dubois, M.; Guerin, K.; Avignant, D.; Renaudin, G.; Duclaux, L.

2009-01-01

Molten salt reactor represents one of the promising future Generation IV nuclear reactors families where the fuel, a liquid molten fluoride salt, is circulating through the graphite reactor core. The interactions between nuclear graphite and fluoride molten salt and also the graphite surface protection were investigated in this paper by powder X-ray diffraction, micro-Raman spectroscopy and scanning electron microscopy coupled with X-ray microanalysis. Nuclear graphite discs were covered by two kinds of protection deposit: a glassy carbon coating and a double coating of pyrolitic carbon/glassy carbon. Different behaviours have been highlighted according to the presence and the nature of the coated protection film. Intercalation of molten salt between the graphite layers did not occur. Nevertheless the molten salt adhered more or less to the surface of the graphite disc, filled more or less the graphite surface porosity and perturbed more or less the graphite stacking order at the disc surface. The behaviour of unprotected graphite was far to be satisfactory after two days of immersion of graphite in molten salt at 500 deg. C. The best protection of the graphite disc surface, with the maximum of inertness towards molten salt, has been obtained with the double coating of pyrolitic carbon/glassy carbon

Electrocatalytic Determination of Isoniazid by a Glassy Carbon Electrode Modified with Poly (Eriochrome Black T)

OpenAIRE

Karim Asadpour-Zeynali; Venus Baghalabadi

2017-01-01

In this work poly eriochrome black T (EBT) was electrochemically synthesized on the glassy carbon electrode as electrode modifier. On the modified electrode, voltammetric behavior of isoniazid (INH) was investigated. The poly (EBT)-modified glassy carbon electrode has excellent electrocatalytic ability for the electrooxidation of isoniazid. This fact was appeared as a reduced overpotential of INH oxidation in a wide operational pH range from 2 to 13. It has been found that the catalytic peak ...

Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode

OpenAIRE

Amare, Meareg; Aklog, Senait

2017-01-01

Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6 ? 10?6 to 100 ? 10?6?mol?L?1 with determination coefficient and method detection limit (LoD = 3?s/slope) of 0....

Impact of crystallization on the structure and chemical durability of borosilicate glass

International Nuclear Information System (INIS)

Nicoleau, Elodie

2016-01-01

This work describes a new approach to help understand the chemical durability of partially crystallized nuclear waste conditioning matrices. Among the studies carried out on nuclear waste deep geological disposal, long term behavior studies have so far been conducted on homogeneous glassy matrices. However, as the crystalline phases may generate modifications in the chemical composition and properties of such matrices, the description and a better understanding of their effects on the chemical durability of waste packages are of primary importance. A protocol to study the durability of heterogeneous model matrices of nuclear interest containing different types of crystalline phases was developed. It is based on a detailed description of the morphology, microstructure and structure of the glassy matrix and crystalline phases, and on the study of various alteration regimes. Three crystal phases that may form when higher concentrations of waste are immobilized in Uranium Oxide type conditioning glasses were studied: alkali and alkaline earth molybdates, rare earth silicates and ruthenium oxide. The results highlight the roles of the composition and the structure of the surrounding glassy matrix as the parameters piloting the alteration kinetics of the partially crystallized glassy matrices. This behavior is identical whatever the nature of the crystalline phases, as long as these phases do not lead to a composition gradient and do not percolate within the glassy matrix. Given these results, a methodology to study partially crystallized matrices with no composition gradient is then suggested. Its key development lies firstly in the evaluation of the behavior of partially crystallized matrices through the experimental study of the residual glassy matrix in various alteration regimes. This methodology may be adapted to the case of new glass formulations with more complex compositions (e.g. highly waste-loaded glass), which may contain crystals formed during cooling

Relook on fitting of viscosity with undercooling of glassy liquids

Indian Academy of Sciences (India)

Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur ... The present approach is on the modification of viscosity fitting of undercooled liquid as a function of ... behaviour of glassy alloys and organic and ionic compounds ...... the present method is applied to calculate the analytical solu-.

Optical, electrical and solid state properties of nano crystalline zinc ...

African Journals Online (AJOL)

Semiconducting Zinc Sulphide (ZnS) thin films were deposited on glass substrate using relatively simple Chemical Bath Deposition (CBD) technique. Nano crystalline ZnS thin films were fabricated in the study. Optical characterization of the films showed that the materials are transparent to visible light, opaque to ultraviolet ...

How different oxidation states of crystalline myoglobin are influenced by X-rays.

Science.gov (United States)

Hersleth, Hans-Petter; Andersson, K Kristoffer

2011-06-01

extent you can collect X-ray diffraction data on your crystal before it becomes too heavily influenced/reduced by X-rays. This article is part of a Special Issue entitled: Protein Structure and Function in the Crystalline State. Copyright © 2010 Elsevier B.V. All rights reserved.

Further study of the glassy low-temperature properties of irradiated crystalline quartz: neutron and electron irradiation

International Nuclear Information System (INIS)

Laermans, C.; Daudin, B.

1979-01-01

Recently it has been shown that a quartz crystal after light fast neutron irradiation shows low temperature hypersonic properties which are similar to those found in glasses although the sample was still crystalline. Additional measurements have been carried out in the neutron-irradiated sample and a sample irradiated with high energy electrons has also been investigated. (Fast neutron dose 6 x 10 18 n/cm 2 , 2 MeV electron dose 3 x 10 19 e/cm 2 ). A magnetic field up to 1.5 T was found to have no influence in the hypersonic saturation behaviour of the neutron-irradiated sample (9 GHz, 1.65 K) and thermal conductivity measurements are consistent with a number of two level systems (2 LS) an order of magnitude lower than in vitreous silica as found before. Low temperature hypersonic measurements as a function of acoustic intensity and temperature as well as thermal conductivity measurements give no evidence for the presence of 2 LS in the electron irradiated sample. Considering the damage created in both samples this indicates that 2 LS are probably not related to point defects

Comparison of the electronic structure of amorphous versus crystalline indium gallium zinc oxide semiconductor: structure, tail states and strain effects

International Nuclear Information System (INIS)

De Jamblinne de Meux, A; Genoe, J; Heremans, P; Pourtois, G

2015-01-01

We study the evolution of the structural and electronic properties of crystalline indium gallium zinc oxide (IGZO) upon amorphization by first-principles calculation. The bottom of the conduction band (BCB) is found to be constituted of a pseudo-band of molecular orbitals that resonate at the same energy on different atomic sites. They display a bonding character between the s orbitals of the metal sites and an anti-bonding character arising from the interaction between the oxygen and metal s orbitals. The energy level of the BCB shifts upon breaking of the crystal symmetry during the amorphization process, which may be attributed to the reduction of the coordination of the cationic centers. The top of the valence band (TVB) is constructed from anti-bonding oxygen p orbitals. In the amorphous state, they have random orientation, in contrast to the crystalline state. This results in the appearance of localized tail states in the forbidden gap above the TVB. Zinc is found to play a predominant role in the generation of these tail states, while gallium hinders their formation. Last, we study the dependence of the fundamental gap and effective mass of IGZO on mechanical strain. The variation of the gap under strain arises from the enhancement of the anti-bonding interaction in the BCB due to the modification of the length of the oxygen–metal bonds and/or to a variation of the cation coordination. This effect is less pronounced for the amorphous material compared to the crystalline material, making amorphous IGZO a semiconductor of choice for flexible electronics. Finally, the effective mass is found to increase upon strain, in contrast to regular materials. This counterintuitive variation is due to the reduction of the electrostatic shielding of the cationic centers by oxygen, leading to an increase of the overlaps between the metal orbitals at the origin of the delocalization of the BCB. For the range of strain typically met in flexible electronics, the induced

Electrochemical functionalization of glassy carbon electrode by reduction of diazonium cations in protic ionic liquid

International Nuclear Information System (INIS)

Shul, Galyna; Ruiz, Carlos Alberto Castro; Rochefort, Dominic; Brooksby, Paula A.; Bélanger, Daniel

2013-01-01

Protic ionic liquid based on 2-methoxypyridine and trifluoroacetic acid was used as electrolyte for the functionalization of a glassy carbon electrode surface by electrochemical reduction of in situ generated 4-chlorobenzene diazonium and 4-nitrobenzene diazonium cations. The diazonium cations were synthesized in an electrochemical cell by reaction of the corresponding amines with NaNO 2 dissolved in protic ionic liquid. The resulting electrografted organic layers exhibit similar properties to those layers obtained by the derivatization from isolated diazonium salts dissolved in protic ionic liquid. Functionalized glassy carbon electrode surfaces were characterized by cyclic voltammetry, Fourier transform infrared and X-ray photoelectron spectroscopies. Atomic force microscopy thickness measurements revealed that, in our experimental conditions, the use of protic ionic liquid led to the formation of film with a thickness of about 1.5 nm. It is also demonstrated that the nitrobenzene chemisorbed on glassy carbon electrode or dissolved in protic ionic liquid undergoes electrochemical conversion to hydroxyaminobenzene

Effects of crystalline state and self-nanoemulsifying drug delivery system (SNEDDS) on oral bioavailability of the novel anti-HIV compound 6-benzyl-1-benzyloxymethyl-5-iodouracil in rats.

Science.gov (United States)

Lu, Ying-Yuan; Dai, Wen-Bing; Wang, Xin; Wang, Xiao-Wei; Liu, Jun-Yi; Li, Pu; Lou, Ya-Qing; Lu, Chuang; Zhang, Qiang; Zhang, Guo-Liang

2018-02-01

The objective of this study was to investigate the effect of crystalline state and a formulation of self-nanoemulsifying drug delivery system (SNEDDS) on oral bioavailability of 6-benzyl-1-benzyloxymethyl-5-iodouracil (W-1), a novel non-nucleoside reverse transcriptase inhibitor, in rats. The crystalline states of W-1 were characterized by scanning electron microscope (SEM), differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD). The SNEDDS was formulated by medium-chain lipids, characterized by droplet particle size. The plasma concentrations of W-1 were measured by high performance liquid chromatography (HPLC). The results indicated that W-1 compound were presented as crystalline forms, A and B, the degree of crystallization in form B was higher than that in form A. The SNEDDS of W-1 displayed a significant increase in the dissolution rate than W-1 powder. Furthermore, after oral administration of W-1 (100 mg/kg), the pharmacokinetic parameters of form A, form B, and W-1 SNEDDS were as follows: AUC 0-t 526.4 ± 123.5, 305.1 ± 58.5 and 2297 ± 451 ng h/mL (p < .05, when W-1 SNEDDS were compared with either form A or form B), respectively. With SNEDDS formulation, the relative bioavailabilities were enhanced by 4.36-fold and 7.53-fold over the form A and form B of W-1, respectively. In conclusion, the present results suggested that the crystalline states of W-1 might lead to the lower oral bioavailability, and SNEDDS formulation is a promising strategy of improving bioavailability, in spite of that crystalline states usually carry small lot-to-lot variability.

Crystallization and evaluation of hen egg-white lysozyme crystals for protein pH titration in the crystalline state

International Nuclear Information System (INIS)

Iwai, Wakari; Yagi, Daichi; Ishikawa, Takuya; Ohnishi, Yuki; Tanaka, Ichiro; Niimura, Nobuo

2008-01-01

Hen egg-white lysozyme was crystallized over a wide pH range (2.5–8.0) and the quality of the crystals was characterized. Crystallization phase diagrams at pH 2.5, 6.0 and 7.5 were determined To observe the ionized status of the amino acid residues in proteins at different pH (protein pH titration in the crystalline state) by neutron diffraction, hen egg-white lysozyme was crystallized over a wide pH range (2.5–8.0). Crystallization phase diagrams at pH 2.5, 6.0 and 7.5 were determined. At pH < 4.5 the border between the metastable region and the nucleation region shifted to the left (lower precipitant concentration) in the phase diagram, and at pH > 4.5 the border shifted to the right (higher precipitant concentration). The qualities of these crystals were characterized using the Wilson plot method. The qualities of all crystals at different pH were more or less equivalent (B-factor values within 25–40). It is expected that neutron diffraction analysis of these crystals of different pH provides equivalent data in quality for discussions of protein pH titration in the crystalline state of hen egg-white lysozyme

Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with γ-Alumina Nanoparticles

Science.gov (United States)

Diez-Berart, Sergio; López, David O.; Salud, Josep; Diego, José Antonio; Sellarès, Jordi; Robles-Hernández, Beatriz; de la Fuente, María Rosario; Ros, María Blanca

2015-01-01

In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy)-ω-(1-pyrenimine-benzylidene-4′-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

Effects of the sintering temperature on the diffused phase transition and the spin-glassy behavior in Pb0.95La0.05(Fe2/3W1/3)0.65Ti0.35O3 ceramics

International Nuclear Information System (INIS)

Hong, Cheng-Shong; Chu, Sheng-Yuan; Hsu, Chi-Cheng

2010-01-01

In this paper, the effect of the sintering temperature on the low-field dielectric behavior of nonstoichiometric Pb 0.95 La 0.05 (Fe 2/3 W 1/3 ) 0.65 Ti 0.35 O 3 relaxor ferroelectrics is investigated. The x-ray patterns and the scanning electron microscope images are used to detect the pyrochlore phase and the perovskite structure. The electric properties of the resistivity, the space charge polarization, the temperature-dependent dielectric constant and dielectric loss are discussed. The diffused phase transition and the ordering state are fitted and discussed by using the empirical law and two ordering models. Furthermore, the glassy behavior is determined by using the Curie-Weiss law and the spin-glass model. According to the experimental data and fitting results, the dielectric picture is changed from the short range order relaxorlike behavior to the long range order normal ferroelectric state as increasing the sintering temperature and the glassy behavior is weakened at the lowest and highest sintering temperature at which the pyrochlore phase PWO 4 is induced. Therefore, it is suggested that the 1:1 ordered domain is enhanced by increasing the sintering temperature and the glassy behavior is related to not only the ordering degree also the polar defect pairs. For more ordering degree and polar defect pairs, the glassy is weakened and the correlation of neighboring polar microregions is enhanced.

Equation-free dynamic renormalization in a glassy compaction model

International Nuclear Information System (INIS)

Chen, L.; Kevrekidis, I. G.; Kevrekidis, P. G.

2006-01-01

Combining dynamic renormalization with equation-free computational tools, we study the apparently asymptotically self-similar evolution of void distribution dynamics in the diffusion-deposition problem proposed by Stinchcombe and Depken [Phys. Rev. Lett. 88, 125701 (2002)]. We illustrate fixed point and dynamic approaches, forward as well as backward in time; these can be used to accelerate simulators of glassy dynamic phenomena

Equation-free dynamic renormalization in a glassy compaction model

Science.gov (United States)

Chen, L.; Kevrekidis, I. G.; Kevrekidis, P. G.

2006-07-01

Combining dynamic renormalization with equation-free computational tools, we study the apparently asymptotically self-similar evolution of void distribution dynamics in the diffusion-deposition problem proposed by Stinchcombe and Depken [Phys. Rev. Lett. 88, 125701 (2002)]. We illustrate fixed point and dynamic approaches, forward as well as backward in time; these can be used to accelerate simulators of glassy dynamic phenomena.

Response to state comments on the revised draft North Central Regional characterization reports for the Crystalline Repository Project

International Nuclear Information System (INIS)

1985-08-01

The purpose of this document is to respond to the comments received from the states of the North Central Region on the revised draft North Central Regional Characterization Reports (RCRs). The responses in this document indicate the manner in which the suggestions or comments received have been considered in modifying the revised draft North Central RCRs. Both general comments related to the overall Crystalline Repository Project (CRP) and comments on specific sections of the RCRs are addressed. This document responds to North Central State comments on both the revised draft North Central Regional Geologic Characterization Report (RGCR) and the revised draft North Central Regional Environmental Characterization Report (RECR)

Luminescent properties of the potassium zinc phosphates of composition K1-xTlxZn(PO3)3

International Nuclear Information System (INIS)

El Abiad, A.; Mesnaoui, M.; Maazaz, M.; Parent, C.; Le Flem, G.

2003-01-01

Crystalline and glassy K 1-x Tl x Zn(PO 3 ) 3 polyphosphates have been synthesized and characterized. UV-visible spectroscopy was systematically used in order to analyze the optical properties of Tl + ions both in crystalline and glassy forms with the similar compositions. The investigated polyphosphates can be considered as a model system since the spectroscopic properties of Tl + ions in the glasses could be deduced by comparison with those in crystals. From structural point of view, in the crystalline forms the thallium ions are six-fold coordinated in a dissymmetrical oxygenated sites. Three luminescences (α, A X , A T ) have been then observed and were attributed to the isolated Tl + ions. In the glassy forms, an additional luminescence (D) has been detected in the low-energy range and was assigned to the Tl + pairs formation. The relationship between the Tl + site symmetry and its optical properties is discussed in the context of the Fukuda's model

A study of nanostructured gold modified glassy carbon electrode for ...

Indian Academy of Sciences (India)

A nanostructured gold modified glassy carbon electrode (Aunano/GCE) was employed for the determination of trace chromium(VI). To prepare Aunano/GCE, the GCE was immersed into KAuCl4 solution and electrodeposition was conducted at the potential of -0.4 V (vs Ag/AgCl) for 600 s. Scanning electron microscopy ...

Gold nanoparticles directly modified glassy carbon electrode for non-enzymatic detection of glucose

Energy Technology Data Exchange (ETDEWEB)

Chang, Gang; Shu, Honghui; Ji, Kai [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); Oyama, Munetaka [Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8520 (Japan); Liu, Xiong [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); He, Yunbin, E-mail: ybhe@hubu.edu.cn [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China)

2014-01-01

This work describes controllable preparation of gold nanoparticles on glassy carbon electrodes by using the seed mediated growth method, which contains two steps, namely, nanoseeds attachment and nanocrystals growth. The size and the dispersion of gold nanoparticles grown on glassy carbon electrodes could be easily tuned through the growth time based on results of field-emission scanning electron microscopy. Excellent electrochemical catalytic characteristics for glucose oxidation were observed for the gold nanoparticles modified glassy carbon electrodes (AuNPs/GC), resulting from the extended active surface area provided by the dense gold nanoparticles attached. It exhibited a wide linear range from 0.1 mM to 25 mM with the sensitivity of 87.5 μA cm{sup −2} mM{sup −1} and low detection limit down to 0.05 mM for the sensing of glucose. The common interfering species such as chloride ion, ascorbic acid, uric acid and 4-acetamidophenol were verified having no interference effect on the detection of glucose. It is demonstrated that the seed mediated method is one of the facile approaches for fabricating Au nanoparticles modified substrates, which could work as one kind of promising electrode materials for the glucose nonenzymatic sensing.

Electric resistivity and thermoelectricity of Ni-Nb-Zr and Ni-Nb-Zr-H glassy alloys

Science.gov (United States)

Fukuhara, Mikio; Inoue, Akihisa

2010-09-01

Electric resistivity ρ and thermoelectric power S of Ni 36Nb 24Zr 40 and (Ni 0.36Nb 0.24Zr 0.4) 90H 10 glassy alloys were investigated in temperature region between 1.5 and 300 K. After resistivity curves of both alloys increase gradually with decreasing temperature down to around 6 K, they dropped suddenly and then reached zero resistivity at 2.1 K, leading to superconductivity. Linear curve with negative TCR of ρ vs T2 and slight increase of S/ T in temperature region down to around 6 K clearly reveal Fermi-liquid phenomenon in electronic state for both alloys independent of hydrogen content.

Electric resistivity and thermoelectricity of Ni-Nb-Zr and Ni-Nb-Zr-H glassy alloys

International Nuclear Information System (INIS)

Fukuhara, Mikio; Inoue, Akihisa

2010-01-01

Electric resistivity ρ and thermoelectric power S of Ni 36 Nb 24 Zr 40 and (Ni 0.36 Nb 0.24 Zr 0.4 ) 90 H 10 glassy alloys were investigated in temperature region between 1.5 and 300 K. After resistivity curves of both alloys increase gradually with decreasing temperature down to around 6 K, they dropped suddenly and then reached zero resistivity at 2.1 K, leading to superconductivity. Linear curve with negative TCR of ρ vs T 2 and slight increase of S/T in temperature region down to around 6 K clearly reveal Fermi-liquid phenomenon in electronic state for both alloys independent of hydrogen content.

Free volume and elastic properties changes in Cu-Zr-Ti-Pd bulk glassy alloy on heating

International Nuclear Information System (INIS)

Louzguine-Luzgin, Dmitri V.; Yavari, Alain Reza; Fukuhara, Mikio; Ota, Katsumi; Xie, Guoqiang; Vaughan, Gavin; Inoue, Akihisa

2007-01-01

The variation of free volume and elastic properties of the Cu 55 Zr 30 Ti 10 Pd 5 glassy alloy on heating was studied. The structure changes on heating were studied by synchrotron X-ray diffraction, differential scanning and isothermal calorimetries. The studied glassy alloy shows a rather high Poisson's ratio exceeding 0.42 which is maintained after the structure relaxation and primary devitrification. Young's and Shear modules decrease upon primary devitrification while Bulk modulus exhibits a maximum after structural relaxation

Occurrence of particle debris field during focused Ga ion beam milling of glassy carbon

Energy Technology Data Exchange (ETDEWEB)

Hu Qin [Centre for Industrial Photonics, Institute for Manufacturing, Department of Engineering, University of Cambridge, Alan Reece Building, 17 Charles Babbage Road, Cambridge, CB3 0FS (United Kingdom); O' Neill, William, E-mail: wo207@eng.cam.ac.uk [Centre for Industrial Photonics, Institute for Manufacturing, Department of Engineering, University of Cambridge, Alan Reece Building, 17 Charles Babbage Road, Cambridge, CB3 0FS (United Kingdom)

2010-08-01

To explore the machining characteristics of glassy carbon by focused ion beam (FIB), particles induced by FIB milling on glassy carbon have been studied in the current work. Nano-sized particles in the range of tens of nanometers up to 400 nm can often be found around the area subject to FIB milling. Two ion beam scanning modes - slow single scan and fast repetitive scan - have been tested. Fewer particles are found in single patterns milled in fast repetitive scan mode. For a group of test patterns milled in a sequence, it was found that a greater number of particles were deposited around sites machined early in the sequence. In situ EDX analysis of the particles showed that they were composed of C and Ga. The formation of particles is related to the debris generated at the surrounding areas, the low melting point of gallium used as FIB ion source and the high contact angle of gallium on glassy carbon induces de-wetting of Ga and the subsequent formation of Ga particles. Ultrasonic cleaning can remove over 98% of visible particles. The surface roughness (R{sub a}) of FIB milled areas after cleaning is less than 2 nm.

Occurrence of particle debris field during focused Ga ion beam milling of glassy carbon

International Nuclear Information System (INIS)

Hu Qin; O'Neill, William

2010-01-01

To explore the machining characteristics of glassy carbon by focused ion beam (FIB), particles induced by FIB milling on glassy carbon have been studied in the current work. Nano-sized particles in the range of tens of nanometers up to 400 nm can often be found around the area subject to FIB milling. Two ion beam scanning modes - slow single scan and fast repetitive scan - have been tested. Fewer particles are found in single patterns milled in fast repetitive scan mode. For a group of test patterns milled in a sequence, it was found that a greater number of particles were deposited around sites machined early in the sequence. In situ EDX analysis of the particles showed that they were composed of C and Ga. The formation of particles is related to the debris generated at the surrounding areas, the low melting point of gallium used as FIB ion source and the high contact angle of gallium on glassy carbon induces de-wetting of Ga and the subsequent formation of Ga particles. Ultrasonic cleaning can remove over 98% of visible particles. The surface roughness (R a ) of FIB milled areas after cleaning is less than 2 nm.

Electrochemical investigations of Pu(IV)/Pu(III) redox reaction using graphene modified glassy carbon electrodes and a comparison to the performance of SWCNTs modified glassy carbon electrodes

International Nuclear Information System (INIS)

Gupta, Ruma; Gamare, Jayashree; Sharma, Manoj K.; Kamat, J.V.

2016-01-01

Highlights: • First report of aqueous electrochemistry of Plutonium on graphene modified electrode. • Graphene is best electrocatalytic material for Pu(IV)/Pu(III) redox couple among the reported modifiers viz. reduced graphene oxide (rGO) and SWCNT’s. • The electrochemical reversibility of Pu(IV)/Pu(III) redox couple improves significantly on graphene modified electrode compared to previously reported rGO & SWCNTs modified electrodes • Donnan interaction between plutonium species and graphene surface offers a possibility for designing a highly sensitive sensor for plutonium • Graphene modified electrode shows higher sensitivity for the determination of plutonium compared to glassy carbon and single walled carbon nanotube modified electrode - Abstract: The work reported in this paper demonstrates for the first time that graphene modified glassy carbon electrode (Gr/GC) show remarkable electrocatalysis towards Pu(IV)/Pu(III) redox reaction and the results were compared with that of single-walled carbon nanotubes modified GC (SWCNTs/GC) and glassy carbon (GC) electrodes. Graphene catalyzes the exchange of current of the Pu(IV)/Pu(III) couple by reducing both the anodic and cathodic overpotentials. The Gr/GC electrode shows higher peak currents (i p ) and smaller peak potential separation (ΔE p ) values than the SWCNTs/GC and GC electrodes. The heterogeneous electron transfer rate constants (k s ), charge transfer coefficients (α) and the diffusion coefficients (D) involved in the electrocatalytic redox reaction were determined. Our observations show that graphene is best electrocatalytic material among both the SWCNTs and GC to study Pu(IV)/Pu(III) redox reaction.

Determination of Volatility and Element Fractionation in Glassy Fallout Debris by SIMS

Energy Technology Data Exchange (ETDEWEB)

Williamson, Todd L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tenner, Travis Jay [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bonamici, Chloe Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kinman, William Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Pollington, Anthony Douglas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Steiner, Robert Ernest [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-05-10

The purpose of this report is to characterize glassy fallout debris using the Trinity Test and then characterize the U-isotopes of U₃O₈ reference materials that contain weaponized debris.

Physical ageing in the above-bandgap photoexposured glassy arsenic selenides

Energy Technology Data Exchange (ETDEWEB)

Kozdras, A [Faculty of Physics of Opole University of Technology, 75, Ozimska str., Opole, PL-45370 (Poland); Golovchak, R [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA-79031 (Ukraine); Shpotyuk, O [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA-79031 (Ukraine)

2007-08-15

Physical ageing induced by above-bandgap light illumination is studied in glassy As-Se using differential scanning calorimetry. It is shown that measurable effect like to known short-term physical ageing is observed only in Se-rich glasses. The kinetics of this effect is compared with that caused by natural storage in a dark.

Physical ageing in the above-bandgap photoexposured glassy arsenic selenides

International Nuclear Information System (INIS)

Kozdras, A; Golovchak, R; Shpotyuk, O

2007-01-01

Physical ageing induced by above-bandgap light illumination is studied in glassy As-Se using differential scanning calorimetry. It is shown that measurable effect like to known short-term physical ageing is observed only in Se-rich glasses. The kinetics of this effect is compared with that caused by natural storage in a dark

Co-based soft magnetic bulk glassy alloys optimized for glass ...

Indian Academy of Sciences (India)

diameter of 5 mm by conventional copper mould casting method. It reveals ... For example, Co43Fe20Ta5.5B31.5 glassy alloy with a ... coercive force (Hc) of 0.25 A m. −1 ..... [7] Lu Z P, Liu C T, Thompson J R and Porter W D 2004 Phys. Rev.

V6O13 films by control of the oxidation state from aqueous precursor to crystalline phase.

Science.gov (United States)

Peys, Nick; Ling, Yun; Dewulf, Daan; Gielis, Sven; De Dobbelaere, Christopher; Cuypers, Daniel; Adriaensens, Peter; Van Doorslaer, Sabine; De Gendt, Stefan; Hardy, An; Van Bael, Marlies K

2013-01-28

An aqueous deposition process for V(6)O(13) films is developed whereby the vanadium oxidation state is continuously controlled throughout the entire process. In the precursor stage, a controlled wet chemical reduction of the vanadium(V) source with oxalic acid is achieved and monitored by (51)Vanadium Nuclear Magnetic Resonance ((51)V-NMR) and Ultraviolet-Visible (UV-Vis) spectroscopy. The resulting vanadium(IV) species in the aqueous solution are identified as mononuclear citrato-oxovanadate(IV) complexes by Electron Paramagnetic Resonance (EPR) and Fourier Transform Infra-Red (FTIR) spectroscopy. This precursor is successfully employed for the deposition of uniform, thin films. The optimal deposition and annealing conditions for the formation of crystalline V(6)O(13), including the control of the vanadium oxidation state, are determined through an elaborate study of processing temperature and O(2) partial pressure. To ensure a sub 100 nm adjustable film thickness, a non-oxidative intermediate thermal treatment is carried out at the end of each deposition cycle, allowing maximal precursor decomposition while still avoiding V(IV) oxidation. The resulting surface hydrophilicity, indispensable for the homogeneous deposition of the next layer, is explained by an increased surface roughness and the increased availability of surface vanadyl groups. Crystalline V(6)O(13) with a preferential (002) orientation is obtained after a post deposition annealing in a 0.1% O(2) ambient for thin films with a thickness of 20 nm.

A crystalline cluster method for deep impurities in insulators

International Nuclear Information System (INIS)

Guimaraes, P.S.

1983-01-01

An 'ab initio' self-consistent-field crystalline-cluster approach to the study of deep impurity states in insulators is proposed. It is shown that, in spite of being a cluster calculation, the interaction of the impurity with the crystal environment is fully taken into account. It is also shown that the present representation of the impurity states is, at least, as precise as the crystalline cluster representation of the pure crystal electronic structure. The procedure has been tested by performing the calculation of the electronic structure of the U center in a sodium chloride crystal, and it has been observed that the calculated GAMMA 1 - GAMMA 15 absorption energy is in good agreement with experiment. (Author) [pt

Models of agglomeration and glass transition

CERN Document Server

Kerner, Richard

2007-01-01

This book is for any physicist interested in new vistas in the domain of non-crystalline condensed matter, aperiodic and quasi-crystalline networks and especially glass physics and chemistry. Students with an elementary background in thermodynamics and statistical physics will find the book accessible. The physics of glasses is extensively covered, focusing on their thermal and mechanical properties, as well as various models leading to the formation of the glassy states of matter from overcooled liquids. The models of agglomeration and growth are also applied to describe the formation of quasicrystals, fullerenes and, in biology, to describe virus assembly pathways.

Definition and preparation of glassy matrices by innovating processes to confine radioactive wastes and industrial toxic materials

International Nuclear Information System (INIS)

Moncouyoux, J.P.

1995-01-01

The confinement by vitrification of high-level radioactive wastes is studied in the CEA for fifteen years. These studies have lead to the preparation of glassy matrices by innovating processes. These processes can be applied to non-radioactive toxic materials treatment too. In this work are more particularly described the glassy matrix long-dated behaviour and the different vitrification processes used (by direct induction in cold crucible, by transferred arc plasma). (O.L.). 1 tab

Vapor-deposited non-crystalline phase vs ordinary glasses and supercooled liquids: Subtle thermodynamic and kinetic differences

International Nuclear Information System (INIS)

Bhattacharya, Deepanjan; Sadtchenko, Vlad

2015-01-01

Vapor deposition of molecules on a substrate often results in glassy materials of high kinetic stability and low enthalpy. The extraordinary properties of such glasses are attributed to high rates of surface diffusion during sample deposition, which makes it possible for constituents to find a configuration of much lower energy on a typical laboratory time scale. However, the exact nature of the resulting phase and the mechanism of its formation are not completely understood. Using fast scanning calorimetry technique, we show that out-of-equilibrium relaxation kinetics and possibly the enthalpy of vapor-deposited films of toluene and ethylbenzene, archetypical fragile glass formers, are distinct from those of ordinary supercooled phase even when the deposition takes place at temperatures above the ordinary glass softening transition temperatures. These observations along with the absolute enthalpy dependences on deposition temperatures support the conjecture that the vapor-deposition may result in formation of non-crystalline phase of unique structural, thermodynamic, and kinetic properties

Organic-inorganic hybrid perovskite quantum dots with high PLQY and enhanced carrier mobility through crystallinity control by solvent engineering and solid-state ligand exchange.

Science.gov (United States)

Woo Choi, Jin; Woo, Hee Chul; Huang, Xiaoguang; Jung, Wan-Gil; Kim, Bong-Joong; Jeon, Sie-Wook; Yim, Sang-Youp; Lee, Jae-Suk; Lee, Chang-Lyoul

2018-05-22

The photoluminescence quantum yield (PLQY) and charge carrier mobility of organic-inorganic perovskite QDs were enhanced by the optimization of crystallinity and surface passivation as well as solid-state ligand exchange. The crystallinity of perovskite QDs was determined by the Effective solvent field (Esol) of various solvents for precipitation. The solvent with high Esol could more quickly countervail the localized field generated by the polar solvent, and it causes fast crystallization of the dissolved precursor, which results in poor crystallinity. The post-ligand adding process (PLAP) and post-ligand exchange process (PLEP) increase the PLQY of perovskite QDs by reducing non-radiative recombination and the density of surface defect states through surface passivation. Particularly, the post ligand exchange process (PLEP) in the solid-state improved the charge carrier mobility of perovskite QDs in addition to the PLQY enhancement. The ligand exchange with short alkyl chain length ligands could improve the packing density of perovskite QDs in films by reducing the inter-particle distance between perovskite QDs. The maximum hole mobility of 6.2 × 10-3 cm2 V-1 s-1, one order higher than that of pristine QDs without the PLEP, is obtained at perovskite QDs with hexyl ligands. By using PLEP treatment, compared to the pristine device, a 2.5 times higher current efficiency in perovskite QD-LEDs was achieved due to the improved charge carrier mobility and PLQY.

Electrocatalytic oxidation of hydrazine at overoxidized polypyrrole film modified glassy carbon electrode

Energy Technology Data Exchange (ETDEWEB)

Majidi, Mir Reza [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51664 (Iran, Islamic Republic of); Jouyban, Abolghasem [Faculty of Pharmacy and Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz 51664 (Iran, Islamic Republic of); Asadpour-Zeynali, Karim [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51664 (Iran, Islamic Republic of)]. E-mail: asadpour@tabrizu.ac.ir

2007-06-20

Electrocatalytic oxidation of hydrazine (HZ) was studied on an overoxidized polypyrrole (OPPy) modified glassy carbon electrode using cyclic voltammetry and chronoamperometry techniques. The OPPy-modified glassy carbon electrode has very high catalytic ability for electrooxidation of HZ, which appeared as a reduced overpotential in a wide operational pH range of 5-10. The overall numbers of electrons involved in the catalytic oxidation of HZ, the number of electrons involved in the rate-determining and diffusion coefficient of HZ were estimated using cyclic voltammetry and chronoamperometry. It has been shown that using the OPPy-modified electrode, HZ can be determined by cyclic voltammetry and amperometry with limit of detection 36 and 3.7 {mu}M, respectively. The results of the analysis suggest that the proposed method promises accurate results and could be employed for the routine determination of HZ.

{sup 35}Cl NQR in glassy crystal, 3-chlorothiophene

Energy Technology Data Exchange (ETDEWEB)

Fujimori, H., E-mail: fujimori@chs.nihon-u.ac.jp; Kaneko, T.; Asaji, T. [Nihon University, Department of Chemistry, College of Humanities and Sciences (Japan)

2008-01-15

{sup 35}Cl NQR measurements were carried out between 77 and 209 K for 3-chlorothiophene, which has a glass transition in a stable crystalline state. An NQR signal with full widths of about 100 kHz at half maximum was observed in this temperature range. The spin-lattice relaxation time T{sub 1} was measured at the peak frequencies. The activation energy {Delta}{epsilon}{sub a} obtained from the results of the T{sub 1} measurements showed a good agreement with those estimated from calorimetric measurements.

Amorphous physics and materials: Interstitialcy theory of condensed matter states and its application to non-crystalline metallic materials

International Nuclear Information System (INIS)

Khonik, V A

2017-01-01

A comprehensive review of a novel promising framework for the understanding of non-crystalline metallic materials, i.e., interstitialcy theory of condensed matter states (ITCM), is presented. The background of the ITCM and its basic results for equilibrium/supercooled liquids and glasses are given. It is emphasized that the ITCM provides a new consistent, clear, and testable approach, which uncovers the generic relationship between the properties of the maternal crystal, equilibrium/supercooled liquid and glass obtained by melt quenching. (topical review)

Study of electrical properties of glassy Se100–xTex alloys

Indian Academy of Sciences (India)

Unknown

can be successfully explained by correlated barrier hopping (CBH) model. ... The results show that bipolaron hopping dominates over single-polaron hopping in this glassy system. This .... where ∆E is the activation energy and σ0 is called the.

Phase separation and structure formation in gadolinium based liquid and glassy metallic alloys

International Nuclear Information System (INIS)

Han, Junhee

2014-01-01

tailored both at microscopic and macroscopic length scales. This includes either droplet-like or interconnected microstructures at the microscopic level and glass-glass or glass-crystalline composites at the macroscopic level. Essential parameter for the quenched in microstructure is the temperature dependence of liquid-liquid phase separation, which is determined by the chemical composition of the alloy: on the one hand, earlier and/or later stages of spinodal decomposition or almost homogeneous glassy states are obtained if the critical temperature of miscibility gap T c is close to the glass transition temperature T g ; and on the one hand, coarsening and secondary precipitations of the liquids are obtained if T c is much higher than T g . Finally, the influence of the microstructure developed by phase separation on their magnetic properties had been investigated. The saturation magnetization σ S depends on the overall amount of Gd atoms in the alloys and is not remarkably affected by phase separation processes. The Curie temperature T Curie of the magnetic transition is influenced by the changed chemical composition of the Gd-rich glassy phases compared to that of monolithic Gd-Co-Al glasses.

Quantum coherent transport in SnTe topological crystalline insulator thin films

Energy Technology Data Exchange (ETDEWEB)

Assaf, B. A.; Heiman, D. [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Katmis, F.; Moodera, J. S. [Francis Bitter Magnet Laboratory, MIT, Cambridge, Massachusetts 02139 (United States); Department of Physics, MIT, Cambridge, Massachusetts 02139 (United States); Wei, P. [Department of Physics, MIT, Cambridge, Massachusetts 02139 (United States); Satpati, B. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Zhang, Z. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Bennett, S. P.; Harris, V. G. [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

2014-09-08

Topological crystalline insulators (TCI) are unique systems where a band inversion that is protected by crystalline mirror symmetry leads to a multiplicity of topological surface states. Binary SnTe is an attractive lead-free TCI compound; the present work on high-quality thin films provides a route for increasing the mobility and reducing the carrier density of SnTe without chemical doping. Results of quantum coherent magnetotransport measurements reveal a multiplicity of Dirac surface states that are unique to TCI. Modeling of the weak antilocalization shows variations in the extracted number of carrier valleys that reflect the role of coherent intervalley scattering in coupling different Dirac states on the degenerate TCI surface.

Cooperative strings and glassy interfaces.

Science.gov (United States)

Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

2015-07-07

We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.

Asphaltene-laden interfaces form soft glassy layers in contraction experiments: a mechanism for coalescence blocking.

Science.gov (United States)

Pauchard, Vincent; Rane, Jayant P; Banerjee, Sanjoy

2014-11-04

In previous studies, the adsorption kinetics of asphaltenes at the water-oil interface were interpreted utilizing a Langmuir equation of state (EOS) based on droplet expansion experiments.1-3 Long-term adsorption kinetics followed random sequential adsorption (RSA) theory predictions, asymptotically reaching ∼85% limiting surface coverage, which is similar to limiting random 2D close packing of disks. To extend this work beyond this slow adsorption process, we performed rapid contractions and contraction-expansions of asphaltene-laden interfaces using the pendant drop experiment to emulate a Langmuir trough. This simulates the rapid increase in interfacial asphaltene concentration that occurs during coalescence events. For the contraction of droplets aged in asphaltene solutions, deviation from the EOS consistently occurs at a surface pressure value ∼21 mN/m corresponding to a surface coverage ∼80%. At this point droplets lose the shape required for validity of the Laplace-Young equation, indicating solidlike surface behavior. On further contraction wrinkles appear, which disappear when the droplet is held at constant volume. Surface pressure also decreases down to an equilibrium value near that measured for slow adsorption experiments. This behavior appears to be due to a transition to a glassy interface on contraction past the packing limit, followed by relaxation toward equilibrium by desorption at constant volume. This hypothesis is supported by cycling experiments around the close-packed limit where the transition to and from a solidlike state appears to be both fast and reversible, with little hysteresis. Also, the soft glass rheology model of Sollich is shown to capture previously reported shear behavior during adsorption. The results suggest that the mechanism by which asphaltenes stabilize water-in-oil emulsions is by blocking coalescence due to rapid formation of a glassy interface, in turn caused by interfacial asphaltenes rapidly increasing in

Characterization of glassy phase at the surface of alumina ceramics substrate and its effect on laser cutting

Energy Technology Data Exchange (ETDEWEB)

Fu Renli [School of Mechanical-Electronic and Materials Engineering, China Univ. of Mining and Technology, Xuzhou, JS (China); Dept. of Ceramics and Glass Engineering, CICECO, Univ. of Aveiro, Aveiro (Portugal); Li Yanbo [School of Mechanical-Electronic and Materials Engineering, China Univ. of Mining and Technology, Xuzhou, JS (China); Xu Xin; Ferreira, J.M.F. [Dept. of Ceramics and Glass Engineering, CICECO, Univ. of Aveiro, Aveiro (Portugal)

2004-07-01

Nowadays alumina ceramic substrates are widely used for high precision applications in electronic devices, such as hybrid integrated circuits (HIC). Usually, the alumina ceramic substrates are shaped through tape casting method and sintered in continuous slab kilns. The sintering aids used to enhance densification during sintering give rise to the formation of an alumino-silicate liquid phase, which is of crucial importance in pressureless and low-temperature sintering (<1600 C) of alumina ceramics. The preferential migration of liquid phase to the surface of alumina substrates under the capillary action and its transformation into glassy phase during cooling affects the subsequent processing steps of HIC. A smoothening effect on surface with its enrichment in glassy phase is accompanied by a decrease of the surface toughness. On the other hand, the accumulated glassy phase onto the surface has a great effect on laser cutting. The high temperatures developed during laser cutting turn the superficial glassy phase into liquid again, while rapid solidification will occur after removing laser beam. The fast cooling of the liquid phase causes formation of extensive network of cracks on the surface of alumina substrate. Apparently, the presence of such faults degrades mechanical strength and thermal shock resistance of alumina substrates. Meanwhile, the recast layers and spatter deposits at the periphery of the hole has been observed. (orig.)

Modification of glassy carbon surfaces by atmospheric pressure cold plasma torch

DEFF Research Database (Denmark)

Mortensen, Henrik Junge; Kusano, Yukihiro; Leipold, Frank

2006-01-01

The effect of plasma treatment on glassy carbon (GC) surfaces was studied with adhesion improvement in mind. A newly constructed remote plasma source was used to treat GC plates. Pure He and a dilute NH3/He mixture were used as feed gases. Optical emission spectroscopy was performed for plasma to...

Direct electron transfer from glucose oxidase immobilized on a nano-porous glassy carbon electrode

International Nuclear Information System (INIS)

Haghighi, Behzad; Tabrizi, Mahmoud Amouzadeh

2011-01-01

Highlights: → A direct electron transfer reaction of glucose oxidase was observed on the surface of a nano-porous glassy carbon electrode. → A pair of well-defined and reversible redox peaks was observed at the formal potential of approximately -0.439 V. → The apparent electron transfer rate constant was measured to be 5.27 s -1 . → A mechanism for the observed direct electron transfer reaction was proposed, which consists of a two-electron and a two-proton transfer. - Abstract: A pair of well-defined and reversible redox peaks was observed for the direct electron transfer (DET) reaction of an immobilized glucose oxidase (GOx) on the surface of a nano-porous glassy carbon electrode at the formal potential (E o ') of -0.439 V versus Ag/AgCl/saturated KCl. The electron transfer rate constant (k s ) was calculated to be 5.27 s -1 . The dependence of E o ' on pH indicated that the direct electron transfer of the GOx was a two-electron transfer process, coupled with two-proton transfer. The results clearly demonstrate that the nano-porous glassy carbon electrode is a cost-effective and ready-to-use scaffold for the fabrication of a glucose biosensor.

Direct electron transfer from glucose oxidase immobilized on a nano-porous glassy carbon electrode

Energy Technology Data Exchange (ETDEWEB)

Haghighi, Behzad, E-mail: haghighi@iasbs.ac.ir [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of); Tabrizi, Mahmoud Amouzadeh [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of)

2011-11-30

Highlights: > A direct electron transfer reaction of glucose oxidase was observed on the surface of a nano-porous glassy carbon electrode. > A pair of well-defined and reversible redox peaks was observed at the formal potential of approximately -0.439 V. > The apparent electron transfer rate constant was measured to be 5.27 s{sup -1}. > A mechanism for the observed direct electron transfer reaction was proposed, which consists of a two-electron and a two-proton transfer. - Abstract: A pair of well-defined and reversible redox peaks was observed for the direct electron transfer (DET) reaction of an immobilized glucose oxidase (GOx) on the surface of a nano-porous glassy carbon electrode at the formal potential (E{sup o}') of -0.439 V versus Ag/AgCl/saturated KCl. The electron transfer rate constant (k{sub s}) was calculated to be 5.27 s{sup -1}. The dependence of E{sup o}' on pH indicated that the direct electron transfer of the GOx was a two-electron transfer process, coupled with two-proton transfer. The results clearly demonstrate that the nano-porous glassy carbon electrode is a cost-effective and ready-to-use scaffold for the fabrication of a glucose biosensor.

Voltammetric behavior of sedative drug midazolam at glassy carbon electrode in solubilized systems

Directory of Open Access Journals (Sweden)

Rajeev Jain

2012-04-01

Full Text Available Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems, supporting electrolytes and pH using differential pulse, square-wave and cyclic voltammetry. Based on its reduction behavior, a direct differential pulse voltammetric method has been developed and validated for the determination of midazolam in parenteral dosage. Three well-defined peaks were observed in 0.1% SLS, Britton–Robinson (BR buffer of pH 2.5. The effect of surfactants like sodium lauryl sulfate (SLS, cetyl trimethyl ammonium bromide (CTAB and Tween 20 was studied. Among these surfactants SLS showed significant enhancement in reduction peak. The cathodic peak currents were directly proportional to the concentration of midazolam with correlation coefficient of 0.99. Keywords: Midazolam, Voltammetry, Surfactant, Glassy carbon electrode, Parenteral dosage form

ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

Directory of Open Access Journals (Sweden)

A. Benchettara

2014-12-01

Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

Directory of Open Access Journals (Sweden)

A. Benchettara

2015-07-01

Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

Mechanisms of charge-state determination in hydrogen-based impurity complexes in crystalline germanium

International Nuclear Information System (INIS)

Oliva, J.

1984-01-01

Recent experiments suggest that hydrogen may become bound to, and then tunnel around, substitutional carbon, silicon, or oxygen impurities in crystalline germanium. All these complexes are electrically active; [H,C] and [H,Si] are shallow acceptors, while [H,O] is a shallow donor. This paper attempts to elucidate the basic physical mechanisms controlling the charge state of such complexes as a function of the choice of the substitutional atom. A minimal-basis Bethe-cluster approach is used with the cluster comprising the ten-atom tetrahedral cage (including the substitutional atom) and enclosed H site, the latter coupled to all ten atoms of the cage. The important local correlation effect which tends to favor single occupation of the H site is modeled with a Hubbard-type term at that site. The charge state of the [H,C], [H,Si], and [H,O] complexes is associated with double occupation of the H site. Four aspects of the model are involved in favoring double occupation: (1) a low value of the H-site energy, (2) a reduced local correlation effect at the H site, (3) small hybridization between the H site and cage, and (4) a low value of the substitutional-site energy relative to that of the host. Results for the charge state for H at the cage center and for H near the substitutional atom are discussed in detail. Several useful formal results for local self-energies and local Green's functions are presented

Crystalline to amorphous transformation in silicon

International Nuclear Information System (INIS)

Cheruvu, S.M.

1982-09-01

In the present investigation, an attempt was made to understand the fundamental mechanism of crystalline-to-amorphous transformation in arsenic implanted silicon using high resolution electron microscopy. A comparison of the gradual disappearance of simulated lattice fringes with increasing Frenkel pair concentration with the experimental observation of sharp interfaces between crystalline and amorphous regions was carried out leading to the conclusion that when the defect concentration reaches a critical value, the crystal does relax to an amorphous state. Optical diffraction experiments using atomic models also supported this hypothesis. Both crystalline and amorphous zones were found to co-exist with sharp interfaces at the atomic level. Growth of the amorphous fraction depends on the temperature, dose rate and the mass of the implanted ion. Preliminary results of high energy electron irradiation experiments at 1.2 MeV also suggested that clustering of point defects occurs near room temperature. An observation in a high resolution image of a small amorphous zone centered at the core of a dislocation is presented as evidence that the nucleation of an amorphous phase is heterogeneous in nature involving clustering or segregation of point defects near existing defects

Electrochemically modified sulfisoxazole nanofilm on glassy carbon for determination of cadmium(II) in water samples

International Nuclear Information System (INIS)

Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Atar, Necip; Solak, Ali Osman; Uzun, Lokman; Üstündağ, Zafer

2013-01-01

Highlights: • Sulfisoxazole was grafted onto glassy carbon electrode. • The electrode was characterized by spectroscopic and electrochemical methods. • It has been used for the determination of Cd(II) ions in real samples in very low concentrations. -- Abstract: Sulfisoxazole (SO) was grafted to glassy carbon electrode (GCE) via the electrochemical oxidation of SO in acetonitrile solution containing 0.1 M tetrabutylammoniumtetra-fluoroborate (TBATFB). The prepared electrode was characterized by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), reflection–absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). The ellipsometric thickness of SO nanofilm at the glassy carbon surface was obtained as 14.48 ± 0.11 nm. The stability of the SO modified GCE was studied. The SO modified GCE was also utilized for the determination of Cd(II) ions in water samples in the presence of Pb(II) and Fe(II) by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) ions were 1.0 × 10 −10 to 5.0 × 10 −8 M and 3.3 × 10 −11 M (S/N = 3), respectively

Electrochemical Glucose Oxidation Using Glassy Carbon Electrodes Modified with Au-Ag Nanoparticles: Influence of Ag Content

Directory of Open Access Journals (Sweden)

Nancy Gabriela García-Morales

2015-01-01

Full Text Available This paper describes the application of glassy carbon modified electrodes bearing Aux-Agy nanoparticles to catalyze the electrochemical oxidation of glucose. In particular, the paper shows the influence of the Ag content on this oxidation process. A simple method was applied to prepare the nanoparticles, which were characterized by transmission electron microscopy, Ultraviolet-Visible spectroscopy, X-ray diffraction spectroscopy, and cyclic voltammetry. These nanoparticles were used to modify glassy carbon electrodes. The effectiveness of these electrodes for electrochemical glucose oxidation was evaluated. The modified glassy carbon electrodes are highly sensitive to glucose oxidation in alkaline media, which could be attributed to the presence of Aux-Agy nanoparticles on the electrode surface. The voltammetric results suggest that the glucose oxidation speed is controlled by the glucose diffusion to the electrode surface. These results also show that the catalytic activity of the electrodes depends on the Ag content of the nanoparticles. Best results were obtained for the Au80-Ag20 nanoparticles modified electrode. This electrode could be used for Gluconic acid (GA production.

The effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding.

Science.gov (United States)

Hamada, Yoshito; Ono, Makoto; Ohara, Motomu; Yonemochi, Etsuo

2016-12-30

In this study, the effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding was evaluated. The crystallinity of sulfamethazine was not decreased when it was ground alone. However, when structurally related impurities with sulfonamide derivatives were blended, the crystallinity of sulfamethazine was decreased by grinding. Other materials without a sulfonamide moiety showed no such effect. The Raman spectra of sulfamethazine demonstrated that there was a difference between its crystalline and amorphous states within its sulfonamide structure. It was suggested that the sulfonamide structure of the impurities was important in causing the inhibition of recrystallization of sulfamethazine during grinding. Copyright © 2016 Elsevier B.V. All rights reserved.

Diazonium Chemistry for the Bio-Functionalization of Glassy Nanostring Resonator Arrays

Directory of Open Access Journals (Sweden)

Wei Zheng

2015-07-01

Full Text Available Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-based process providing strong chemical adhesion. In this work, diazonium-based linker chemistry was performed for the first time on glassy nanostrings, which enabled the bio-functionalization of such devices. Large arrays of nanostrings with ultra-narrow widths down to 10 nm were fabricated employing electron beam lithography. Diazonium modification was first developed on SiCN surfaces and validated by X-ray photoelectron spectroscopy. Similarly modified nanostrings were then covalently functionalized with anti-rabbit IgG as a molecular probe. Specific enumeration of rabbit IgG was successfully performed through observation of downshifts of resonant frequencies. The specificity of this enumeration was confirmed through proper negative control experiments. Helium ion microscopy further verified the successful functionalization of nanostrings.

Diazonium Chemistry for the Bio-Functionalization of Glassy Nanostring Resonator Arrays.

Science.gov (United States)

Zheng, Wei; Du, Rongbing; Cao, Yong; Mohammad, Mohammad A; Dew, Steven K; McDermott, Mark T; Evoy, Stephane

2015-07-30

Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-based process providing strong chemical adhesion. In this work, diazonium-based linker chemistry was performed for the first time on glassy nanostrings, which enabled the bio-functionalization of such devices. Large arrays of nanostrings with ultra-narrow widths down to 10 nm were fabricated employing electron beam lithography. Diazonium modification was first developed on SiCN surfaces and validated by X-ray photoelectron spectroscopy. Similarly modified nanostrings were then covalently functionalized with anti-rabbit IgG as a molecular probe. Specific enumeration of rabbit IgG was successfully performed through observation of downshifts of resonant frequencies. The specificity of this enumeration was confirmed through proper negative control experiments. Helium ion microscopy further verified the successful functionalization of nanostrings.

Isotopic geochronology of the Western Carpathian crystalline complex: the present state

International Nuclear Information System (INIS)

Cambel, B.; Kral, J.

1989-01-01

Main events in the Western Carpathian crystalline complex documented by the U-Th-Pb, Rb-Sr, K-Ar and FT methods are as follows: Regional metamorphism of sedimentary rocks from the Tatric unit documented by isotopic homogenization of the 87 Sr/ 86 Sr ratio took place 400 million years ago (Silurian-Devonian boundary). Subsequent metamorphism of these rocks is associated with intrusions of granitoid bodies. The age of rhyolite volcanism of Gelnica sequence in the Gemericum is identical with that of the first stage of regional metamorphism. Granitoid plutonism covers a long time interval ranging from 390 to 280 million years. The presence of late Alpine granites has not yet been proved. Cooling of rocks from the crystalline complex to a temperature of ca. 270 degC was attained in the Tatric rocks ca. 300 million years ago and in the Veporic (Gemeric) rocks ca. 90-120 million years ago. The latest post-orogenic uplift differs in the Tatricum (most often Miocene) and the Veporicum (Upper Cretaceous). (author). 8 fis., 1 tab., 51 refs

Co-grinding Effect on Crystalline Zaltoprofen with ?-cyclodextrin/Cucurbit[7]uril in Tablet Formulation

OpenAIRE

Li, Shanshan; Lin, Xiang; Xu, Kailin; He, Jiawei; Yang, Hongqin; Li, Hui

2017-01-01

This work aimed to investigate the co-grinding effects of ?-cyclodextrin (?-CD) and cucurbit[7]uril (CB[7]) on crystalline zaltoprofen (ZPF) in tablet formulation. Crystalline ZPF was prepared through anti-solvent recrystallization and fully analyzed through single-crystal X-ray diffraction. Co-ground dispersions and mono-ground ZPF were prepared using a ball grinding process. Results revealed that mono-ground ZPF slightly affected the solid state, solubility, and dissolution of crystalline Z...

A metastable liquid melted from a crystalline solid under decompression

Science.gov (United States)

Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

2017-01-01

A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid-solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure-temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.

Investigating tautomeric polymorphism in crystalline anthranilic acid using terahertz spectroscopy and solid-state density functional theory.

Science.gov (United States)

Delaney, Sean P; Witko, Ewelina M; Smith, Tiffany M; Korter, Timothy M

2012-08-02

Terahertz spectroscopy is sensitive to the interactions between molecules in the solid-state and recently has emerged as a new analytical tool for investigating polymorphism. Here, this technique is applied for the first time to the phenomenon of tautomeric polymorphism where the crystal structures of anthranilic acid (2-aminobenzoic acid) have been investigated. Three polymorphs of anthranilic acid (denoted Forms I, II and III) were studied using terahertz spectroscopy and the vibrational modes and relative polymorph stabilities analyzed using solid-state density functional theory calculations augmented with London dispersion force corrections. Form I consists of both neutral and zwitterionic molecules and was found to be the most stable polymorph as compared to Forms II and III (both containing only neutral molecules). The simulations suggest that a balance between steric interactions and electrostatic forces is responsible for the favoring of the mixed neutral/zwitterion solid over the all neutral or all zwitterion crystalline arrangements.

Dynamics and Geometry of Icosahedral Order in Liquid and Glassy Phases of Metallic Glasses

Directory of Open Access Journals (Sweden)

Masato Shimono

2015-07-01

Full Text Available The geometrical properties of the icosahedral ordered structure formed in liquid and glassy phases of metallic glasses are investigated by using molecular dynamics simulations. We investigate the Zr-Cu alloy system as well as a simple model for binary alloys, in which we can change the atomic size ratio between alloying components. In both cases, we found the same nature of icosahedral order in liquid and glassy phases. The icosahedral clusters are observed in liquid phases as well as in glassy phases. As the temperature approaches to the glass transition point Tg, the density of the clusters rapidly grows and the icosahedral clusters begin to connect to each other and form a medium-range network structure. By investigating the geometry of connection between clusters in the icosahedral network, we found that the dominant connecting pattern is the one sharing seven atoms which forms a pentagonal bicap with five-fold symmetry. From a geometrical point of view, we can understand the mechanism of the formation and growth of the icosahedral order by using the Regge calculus, which is originally employed to formulate a theory of gravity. The Regge calculus tells us that the distortion energy of the pentagonal bicap could be decreased by introducing an atomic size difference between alloying elements and that the icosahedral network would be stabilized by a considerably large atomic size difference.

Preference for occupany of axial positions by substituents bonded to the heterocyclic ring in penta-O-acetyl-(+)-catechin in the crystalline state

Science.gov (United States)

Frank R. Fronczek; Garret Gannuch; Wayne L. Mattice; Richard W. Hemingway; Giacomo Chiari; Fred L. Tobiason; Karl Houglum; Armen Shanafelt

1985-01-01

The structure of penta-O-acetyl-(+)-catechin has been determined in the crystalline state. Crystals are monoclinic, space group C2, a=2320.0(7), b=980.1 (2), c=1108.0(3) pm, β=100.64(2)., Z=4, Dc=1.342 g cm-3, R=0.058 for 1121 observations. One of the acetyl groups is disordered. Axial positions...

Supercooled and glassy water: Metastable liquid(s), amorphous solid(s), and a no-man's land

Science.gov (United States)

Handle, Philip H.; Loerting, Thomas; Sciortino, Francesco

2017-12-01

We review the recent research on supercooled and glassy water, focusing on the possible origins of its complex behavior. We stress the central role played by the strong directionality of the water-water interaction and by the competition between local energy, local entropy, and local density. In this context we discuss the phenomenon of polyamorphism (i.e., the existence of more than one disordered solid state), emphasizing both the role of the preparation protocols and the transformation between the different disordered ices. Finally, we present the ongoing debate on the possibility of linking polyamorphism with a liquid-liquid transition that could take place in the no-man's land, the temperature-pressure window in which homogeneous nucleation prevents the investigation of water in its metastable liquid form.

Violation of the fluctuation-dissipation theorem in glassy systems: basic notions and the numerical evidence

International Nuclear Information System (INIS)

Crisanti, A; Ritort, F

2003-01-01

This review reports on the research done during past years on violations of the fluctuation-dissipation theorem (FDT) in glassy systems. It is focused on the existence of a quasi-fluctuation-dissipation theorem (QFDT) in glassy systems and the current supporting knowledge gained from numerical simulation studies. It covers a broad range of non-stationary aging and stationary driven systems such as structural glasses, spin glasses, coarsening systems, ferromagnetic models at criticality, trap models, models with entropy barriers, kinetically constrained models, sheared systems and granular media. The review is divided into four main parts: (1) an introductory section explaining basic notions related to the existence of the FDT in equilibrium and its possible extension to the glassy regime (QFDT), (2) a description of the basic analytical tools and results derived in the framework of some exactly solvable models, (3) a detailed report of the current evidence in favour of the QFDT and (4) a brief digression on the experimental evidence in its favour. This review is intended for inexpert readers who want to learn about the basic notions and concepts related to the existence of the QFDT as well as for the more expert readers who may be interested in more specific results. (topical review)

Topological structure and mechanics of glassy polymer networks.

Science.gov (United States)

Elder, Robert M; Sirk, Timothy W

2017-11-22

The influence of chain-level network architecture (i.e., topology) on mechanics was explored for unentangled polymer networks using a blend of coarse-grained molecular simulations and graph-theoretic concepts. A simple extension of the Watts-Strogatz model is proposed to control the graph properties of the network such that the corresponding physical properties can be studied with simulations. The architecture of polymer networks assembled with a dynamic curing approach were compared with the extended Watts-Strogatz model, and found to agree surprisingly well. The final cured structures of the dynamically-assembled networks were nearly an intermediate between lattice and random connections due to restrictions imposed by the finite length of the chains. Further, the uni-axial stress response, character of the bond breaking, and non-affine displacements of fully-cured glassy networks were analyzed as a function of the degree of disorder in the network architecture. It is shown that the architecture strongly affects the network stability, flow stress, onset of bond breaking, and ultimate stress while leaving the modulus and yield point nearly unchanged. The results show that internal restrictions imposed by the network architecture alter the chain-level response through changes to the crosslink dynamics in the flow regime and through the degree of coordinated chain failure at the ultimate stress. The properties considered here are shown to be sensitive to even incremental changes to the architecture and, therefore, the overall network architecture, beyond simple defects, is predicted to be a meaningful physical parameter in the mechanics of glassy polymer networks.

Evolution of optical properties and band structure from amorphous to crystalline Ga2O3 films

Science.gov (United States)

Zhang, Fabi; Li, Haiou; Cui, Yi-Tao; Li, Guo-Ling; Guo, Qixin

2018-04-01

The optical properties and band structure evolution from amorphous to crystalline Ga2O3 films was investigated in this work. Amorphous and crystalline Ga2O3 films were obtained by changing the growth substrate temperatures of pulsed laser deposition and the crystallinity increase with the rising of substrate temperature. The bandgap value and ultraviolet emission intensity of the films increase with the rising of crystallinity as observed by means of spectrophotometer and cathodoluminescence spectroscopy. Abrupt bandgap value and CL emission variations were observed when amorphous to crystalline transition took place. X-ray photoelectron spectroscopy core level spectra reveal that more oxygen vacancies and disorders exist in amorphous Ga2O3 film grown at lower substrate temperature. The valence band spectra of hard X-ray photoelectron spectroscopy present the main contribution from Ga 4sp for crystalline film deposited at substrate temperature of 500 oC, while extra subgap states has been observed in amorphous film deposited at 300 oC. The oxygen vacancy and the extra subgap density of states are suggested to be the parts of origin of bandgap and CL spectra variations. The experimental data above yields a realistic picture of optical properties and band structure variation for the amorphous to crystalline transition of Ga2O3 films.

Read/write characteristics of a new type of bit-patterned-media using nano-patterned glassy alloy

International Nuclear Information System (INIS)

Takenaka, Kana; Saidoh, Noriko; Nishiyama, Nobuyuki; Ishimaru, Manabu; Futamoto, Masaaki; Inoue, Akihisa

2012-01-01

The paper reports a feasibility study of new type bit-patterned-media using a nano-patterned glassy alloy template for ultra-high density hard disk applications. The prototype bit-patterned-media was prepared using a nano-hole array pattern fabricated on a Pd-based glassy alloy thin film and a Co/Pd multilayered film filled in the nano-holes. The prepared prototype bit-patterned-media had a smooth surface and isolated Co/Pd multilayer magnetic dots, where the average dot diameter, the average dot pitch and the average dot height were 30, 60 and 19 nm, respectively. MFM (magnetic force microscope) observation revealed that each dot was magnetized in a perpendicular direction and the magnetization could reverse when an opposite magnetic field was applied. Static read/write tester measurements showed that repeated writing and reading on isolated magnetic dots were possible in combination with conventional magnetic heads and high-accuracy positioning technologies. The present study indicates that the new type of bit-patterned-media composed of nano-hole arrays fabricated on glassy alloy film template and Co/Pd multilayer magnetic dots are promising for applications to next generation ultra-high density hard disk drives. - Highlights: ► Prototype BPM using a nano-hole array pattern of imprinted Pd-based glassy alloy thin film and Co/Pd multilayered film was set. ► The prototype BPM has smooth surface and isolated Co/Pd multilayer magnetic dots with an average dot diameter of 30 nm. ► Dots acted as perpendicular magnetic dot and were able to read, erase and write in a row by a usual perpendicular magnetic head.

Crystalline beams: Theory, experiments, and proposals

International Nuclear Information System (INIS)

Ruggiero, A.G.

1995-01-01

Crystalline Beams are an ordered state of an ensemble of ions, circulating in a storage ring, with very small velocity fluctuations. They can be obtained from ordinary warm ion beams with the application of intense cooling techniques (stochastic, electron, laser). A phase transition occurs when sufficiently small velocity spreads are reached, freezing the particle-to-particle spacing in strings, Zigzags, and helices ... The properties and the feasibility of Crystalline Beams depend on the choice of the lattice of the Storage Ring. There are three issues closely related to the design of the Storage Ring; namely: the determination of Equilibrium Configurations, Confinement Conditions, and Stability Conditions. Of particular concern is the effect of the trajectory curvature and of the beam momentum spread, since they set the requirements on the amount of momentum cooling, on the focussing, and on the distribution of bending in the lattice of the storage ring. The practical demonstration of Crystalline Beams may create the basis for an advanced technology for particle accelerators, where the limitations due to Coulomb intrabeam scattering and space-charge forces would finally be brought under control, so that beams of ions, more dense than normal, can be achieved for a variety of new applications

Cap casting and enveloped casting techniques for Zr55Cu30Ni5Al10 glassy alloy rod with 32 mm in diameter

International Nuclear Information System (INIS)

Yokoyama, Yoshihiko; Inoue, Akihisa; Mund, Enrico; Schultz, Ludwig

2009-01-01

In order to produce centimetre-sized bulk glassy alloys (BMGs), various cast techniques have been developed. We succeed in the development of cap casting and enveloped casting technique to accomplish the fabrication of centimetre sized BMGs. The former has an advantage to increase cooling rate and the later has an advantage to joint another materials instead of welding. This paper presents the production of a glassy Zr 55 Cu 30 Ni 5 Al 10 alloy rod with a diameter of 32 mm and joined glassy Zr 55 Cu 30 Ni 5 Al 10 alloy parts with another materials for industrial applications.

Electrical studies on silver based fast ion conducting glassy materials

International Nuclear Information System (INIS)

Rao, B. Appa; Kumar, E. Ramesh; Kumari, K. Rajani; Bhikshamaiah, G.

2014-01-01

Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI−Ag 2 O−[(1−x)B 2 O 3 −xTeO 2 ] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO 2 as well as with temperature. The conductivity of the present glass system is found to be of the order of 10 −2 S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries

Dielectric relaxation in glassy Se75In25−xPbx alloys

Indian Academy of Sciences (India)

to their atomic percentages and were sealed in quartz ampoules (length ~5 cm and internal dia. ~8 mm) in vacuum ... samples were taken out by breaking the quartz ampoules. The glassy nature of the ... measured with the help of a calibrated copper–constantan thermocouple mounted very near to the sample, which could ...

Dynamical singularities of glassy systems in a quantum quench.

Science.gov (United States)

Obuchi, Tomoyuki; Takahashi, Kazutaka

2012-11-01

We present a prototype of behavior of glassy systems driven by quantum dynamics in a quenching protocol by analyzing the random energy model in a transverse field. We calculate several types of dynamical quantum amplitude and find a freezing transition at some critical time. The behavior is understood by the partition-function zeros in the complex temperature plane. We discuss the properties of the freezing phase as a dynamical chaotic phase, which are contrasted to those of the spin-glass phase in the static system.

Positron lifetime study of the devitrification process in a cordierite glass

International Nuclear Information System (INIS)

Pedrosa, M.A.; Pareja, R.

1985-01-01

The devitrification of the 13.3% MgO-32.0% Al 2 O 3 -52.7% SiO 2 -2.0% BaO ceramic-glass via isochronal heating up to a stable crystalline structure has been studied by the positron annihilation technique. The lifetime spectra showed two components. This devitrification results as a two-stage process. The long-lifetime tau 2 , attributed to the pick-off annihilation of ortho-Ps states, decreased on crystallization, but it was insensitive to the hexagonal-orthorhombic transformation of the crystalline cordierite. On the contrary, the effective lifetime of positrons annihilating in states that are not Ps, increased. This increase has been attributed to the Al/Si order process inherent to the hexagonal-orthorhombic transformation. Moreover, the Ps fraction in the crystalline phases was higher than in the glassy phase. However the free volume model might qualitatively explain the relationship observed between I 2 and tau 2 . (author)

Gas Permeation Related to the Moisture Sorption in Films of Glassy Hydrophilic Polymers

NARCIS (Netherlands)

Laksmana, F. L.; Kok, P. J. A. Hartman; Frijlink, H. W.; Vromans, H.; Maarschalk, K. Van Der Voort

2010-01-01

The purpose of this article is to elucidate the effect of integral sorption of moisture on gas permeation in glassy hydrophilic polymers. The oxygen and the simultaneous moisture sorption into various hydroxypropyl methylcellulose (HPMC) films were measured under a wide range of relative humidities

A TPD-MS study of glassy carbon surfaces oxidized by CO2 and O2

Directory of Open Access Journals (Sweden)

MILA D. LAUSEVIC

2002-11-01

Full Text Available The temperature-programmed desorption (TPD method combined with mass spectrometric (MS analysis has been applied to investigate the surface properties of carbon materials. The apparatus consisting of a temperature-programmed furnace and a quadrupole mass spectrometer was constructed in order to characterize the surface of differently treated glassy carbon samples. In this work, samples of glassy carbon exposed to air, CO2 and O2 were examined. The desorption of H2O, CO and CO2, as major products, indicated the presence of different oxide groups. The amount of these groups for all samples was calculated. It is concluded that oxidation affects the nature and the amount of the surface oxide groups and contributes to their increased stability.

The influence of glass composition on crystalline phase stability in glass-ceramic wasteforms

International Nuclear Information System (INIS)

Maddrell, Ewan; Thornber, Stephanie; Hyatt, Neil C.

2015-01-01

Highlights: • Crystalline phase formation shown to depend on glass matrix composition. • Zirconolite forms as the sole crystalline phase only for most aluminous glasses. • Thermodynamics indicate that low silica activity glasses stabilise zirconolite. - Abstract: Zirconolite glass-ceramic wasteforms were prepared using a suite of Na 2 O–Al 2 O 3 –B 2 O 3 –SiO 2 glass matrices with variable Al:B ratios. Zirconolite was the dominant crystalline phase only for the most alumina rich glass compositions. As the Al:B ratio decreased zirconolite was replaced by sphene, zircon and rutile. Thermodynamic data were used to calculate a silica activity in the glass melt below which zirconolite is the favoured crystalline phase. The concept of the crystalline reference state of glass melts is then utilised to provide a physical basis for why silica activity varies with the Al:B ratio

Novel electroanalysis of hydroxyurea at glassy carbon and gold electrode surfaces

Directory of Open Access Journals (Sweden)

Keerti M. Naik

2014-09-01

Full Text Available A simple and a novel electroanalysis of hydroxyurea (HU drug at glassy carbon and gold electrode was investigated for the first time using cyclic, linear sweep and differential pulse voltammetric techniques. The oxidation of HU was irreversible and exhibited a diffusion controlled process on both electrodes. The oxidation mechanism was proposed. The dependence of the current on pH, the concentration, nature of buffer, and scan rate was investigated to optimize the experimental conditions for the determination of HU. It was found that the optimum buffer pH was 7.0, a physiological pH. In the range of 0.01 to 1.0 mM, the current measured by differential pulse voltammetry showed a linear relationship with HU concentration with limit of detection of 0.46 µM for glassy carbon electrode and 0.92 µM for gold electrode. In addition, reproducibility, precision and accuracy of the method were checked as well. The developed method was successfully applied to HU determination in pharmaceutical formulation and human biological fluids. The method finds its applications in quality control laboratories and pharmacokinetics.

Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium.

Science.gov (United States)

Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

2016-02-01

A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03-200μmolL(-1). The lower detection limits were found to be 0.02μmolL(-1). The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrical transport in crystalline phase change materials

International Nuclear Information System (INIS)

Woda, Michael

2012-01-01

In this thesis, the electrical transport properties of crystalline phase change materials are discussed. Phase change materials (PCM) are a special class of semiconducting and metallic thin film alloys, typically with a high amount of the group five element antimony or the group six element tellurium, such as Ge 2 Sb 2 Te 5 . The unique property portfolio of this material class makes it suitable for memory applications. PCMs reveal fast switching between two stable room-temperature phases (amorphous and crystalline) realized by optical laser or electrical current pulses in memory devices. Additionally, a pronounced property contrast in form of optical reflectivity and electrical conductivity between the amorphous and crystalline phase is the characteristic fingerprint of PCMs. The emerging electrical solid state memory PCRAM is a very promising candidate to replace Flash memory in the near future or to even become a universal memory, which is non-volatile and shows the speed and cyclability of DRAM. One of the main technological challenges is the switching process into the amorphous state, which is the most power demanding step. In order to reduce the switching power, the crystalline resistivity needs to be increased at a given voltage. Thus understanding and tayloring of this property is mandatory. In this work, first the technological relevance, i.e. optical and electrical memory concepts based on PCMs are introduced. Subsequently a description of the physical properties of PCMs in four categories is given. Namely, structure, kinetics, optical properties and electrical properties are discussed. Then important recent developments such as the identification of resonant bonding in crystalline PCMs and a property predicting coordination scheme are briefly reviewed. The following chapter deals with the theoretical background of electrical transport, while the next chapter introduces the experimental techniques: Sputtering, XRR, XRD, DSC, thermal annealing

Studies on Photodarkening Effect in Glassy As2S3 Using High Field NMR

Science.gov (United States)

Hari, Parameswar; Su, Tining; Taylor, Craig; Reyes, Arneil; Kuhns, Phil; Moulton, William; Sullivan, N. S.

2001-03-01

Photodarkening, or the shift of the optical absorption edge to smaller energies after excitation with light whose energy is near that of the optical band edge, has been studied in many chalcogenide glasses for many years. Recently we have conducted nuclear magnetic resonance (NMR) studies of 75As in glassy As2S3 at 17T . We compared the 75As NMR lineshape in glassy As2S3 before and after irradiation at 77K. After irradiation at 514.5 nm for 230 hours with 170 mW/cm2 there is a subtle change in the NMR lineshape. This change is reversible on annealing at 200 C for 1.75 hours. We will discuss the implications of this result based on NMR lineshape analysis using an exact solution of the spin 3/2 Hamiltonian

Evolution of optical properties and band structure from amorphous to crystalline Ga2O3 films

Directory of Open Access Journals (Sweden)

Fabi Zhang

2018-04-01

Full Text Available The optical properties and band structure evolution from amorphous to crystalline Ga2O3 films was investigated in this work. Amorphous and crystalline Ga2O3 films were obtained by changing the growth substrate temperatures of pulsed laser deposition and the crystallinity increase with the rising of substrate temperature. The bandgap value and ultraviolet emission intensity of the films increase with the rising of crystallinity as observed by means of spectrophotometer and cathodoluminescence spectroscopy. Abrupt bandgap value and CL emission variations were observed when amorphous to crystalline transition took place. X-ray photoelectron spectroscopy core level spectra reveal that more oxygen vacancies and disorders exist in amorphous Ga2O3 film grown at lower substrate temperature. The valence band spectra of hard X-ray photoelectron spectroscopy present the main contribution from Ga 4sp for crystalline film deposited at substrate temperature of 500 oC, while extra subgap states has been observed in amorphous film deposited at 300 oC. The oxygen vacancy and the extra subgap density of states are suggested to be the parts of origin of bandgap and CL spectra variations. The experimental data above yields a realistic picture of optical properties and band structure variation for the amorphous to crystalline transition of Ga2O3 films.

Nitric Oxide Detection with Glassy Carbon Electrodes Coated with Charge-different Polymer Films

Directory of Open Access Journals (Sweden)

Jianping Lei

2005-04-01

Full Text Available Trace amounts of nitric oxide (NO have been determined in aqueous phosphate buffersolutions (pH=7.4 by using a glassy carbon electrode coated with three charge-different polymerfilms. The glassy carbon electrode was coated first with negatively charged Nafion film containingtetrakis(pentafluorophenylporphyrin iron(III chloride (Fe(IIITPFPP as the NO oxidation catalyst,and then with positively charged poly(acrylamide-co-diallyldimethylammonium chloride (PADDAand with neutral poly(dimethylsiloxane (silicone at the outermost layer. This polymer-coatedelectrode showed an excellent selectivity towards NO against possible concomitants in blood such asnitrite, ascorbic acid, uric acid, and dopamine. All current ratios between each concomitant and NOat the cyclic voltammogram was in 10-3 ~ 10-4. This type of electrode showed a detection limit of80 nM for NO. It was speculated from the electrochemical study in methanol that high-valent oxoiron(IV of Fe(TPFPP participated in the catalytic oxidation of NO.

Calix[6]arene mono-diazonium salt synthesis and covalent immobilization onto glassy carbon electrodes

International Nuclear Information System (INIS)

Cannizzo, Caroline; Jasmin, Jean-Philippe; Vautrin-Ul, Christine; Chausse, Annie; Wagner, Mathieu; Doizi, Denis; Lamouroux, Christine

2014-01-01

This Letter describes the fast synthesis of a mono-aminated calix[6]arene. The immobilization of this macrocycle onto glassy carbon electrodes via diazonium salt chemistry and the electrochemical characterization of the grafted organic layer are also reported. (authors)

Contact mechanics in glassy polymers

NARCIS (Netherlands)

Breemen, van L.C.A.

2009-01-01

Polymers, primarily semi-crystalline, are widely used in applications where low friction is required; examples are cups in artificial hip joints, bearings and gears. Until now there is no clear indication why some polymers display low friction and others don’t. In this thesis a systematic

Positronics of radiation-induced effects in chalcogenide glassy semiconductors

International Nuclear Information System (INIS)

Shpotyuk, O.; Kozyukhin, S. A.; Shpotyuk, M.; Ingram, A.; Szatanik, R.

2015-01-01

Using As 2 S 3 and AsS 2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models

Positronics of radiation-induced effects in chalcogenide glassy semiconductors

Energy Technology Data Exchange (ETDEWEB)

Shpotyuk, O. [Scientific Research Company “Carat” (Ukraine); Kozyukhin, S. A., E-mail: sergkoz@igic.ras.ru [Russian Academy of Sciences, Kurnakov Institute of General and Inorganic Chemistry (Russian Federation); Shpotyuk, M. [Scientific Research Company “Carat” (Ukraine); Ingram, A. [Opole Technical University (Poland); Szatanik, R. [Opole University (Poland)

2015-03-15

Using As{sub 2}S{sub 3} and AsS{sub 2} glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.

Low-energy electron transmission and secondary-electron emission experiments on crystalline and molten long-chain alkanes

International Nuclear Information System (INIS)

Ueno, N.; Sugita, K.; Seki, K.; Inokuchi, H.

1986-01-01

This paper describes the results of low-energy electron transmission and secondary-electron emission experiments on thin films of long-chain alkanes deposited on metal substrates. The spectral changes due to crystal-melt phase transition were measured in situ in both experiments. The ground-state energy V 0 of the quasifree electron in crystalline state was determined to be 0.5 +- 0.1 eV. The value of V 0 for the molten state was found to be negative. Further, in the crystalline state evidence is found for a direct correspondence between the transmission maxima and the high value of the density of states in the conduction bands

Matrix formulation of the particle motion in crystalline beams

International Nuclear Information System (INIS)

Haffmans, A.F.; Maletic, D.; Ruggiero, A.G.

1994-01-01

To investigate the properties of Crystalline Beams in their ground state, the equations of motion of a single ion and the envelope equations are derived. It is possible to express the status of motion with a set of transfer matrices associated to each of the magnet elements of the storage ring. By inspection of the eigenvalues of the total transfer matrix one then determines the onset of crystalline structures and the stability limits. An analytical approach is also possible, based on the estimate of the shifting of the frequencies of oscillation, betatron and longitudinal, and on the approaching of a major half-integral stopband resonance driven by the space charge

120 mm Single-crystalline perovskite and wafers: towards viable applications

Institute of Scientific and Technical Information of China (English)

Yucheng Liu; Bo Wang; Qingbo Wei; Fengwei Xiao; Haibo Fan; Hao Deng; Liangping Deng; Shengzhong (Frank) Liu; Xiaodong Ren; Jing Zhang; Zhou Yang; Dong Yang; Fengyang Yu; Jiankun Sun; Changming Zhao; Zhun Yao

2017-01-01

As the large single-crystalline silicon wafers have revolutionized many industries including electronics and solar cells,it is envisioned that the availability of large single-crystalline perovskite crystals and wafers will revolutionize its broad applications in photovoltaics,optoelectronics,lasers,photodetectors,light emitting diodes (LEDs),etc.Here we report a method to grow large single-crystalline perovskites including single-halide crystals:CH3NH3PbX3 (X=Ⅰ,Br,Cl),and dual-halide ones:CH3NH3Pb(ClxBr1-x)3 and CH3NH3Pb(BrxI1-x)3,with the largest crystal being 120 mm in length.Meanwhile,we have advanced a process to slice the large perovskite crystals into thin wafers.It is found that the wafers exhibit remarkable features:(1) its trap-state density is a million times smaller than that in the microcrystalline perovskite thin films (MPTF);(2) its carrier mobility is 410 times higher than its most popular organic counterpart P3HT;(3) its optical absorption is expanded to as high as 910 nm comparing to 797 nm for the MPTF;(4) while MPTF decomposes at 150 ℃,the wafer is stable at high temperature up to 270 ℃;(5) when exposed to high humidity (75％ RH),MPTF decomposes in 5 h while the wafer shows no change for overnight;(6) its photocurrent response is 250 times higher than its MPTF counterpart.A few electronic devices have been fabricated using the crystalline wafers.Among them,the Hall test gives low carrier concentration with high mobility.The trap-state density is measured much lower than common semiconductors.Moreover,the large SC-wafer is found particularly useful for mass production of integrated circuits.By adjusting the halide composition,both the optical absorption and the light emission can be fine-tuned across the entire visible spectrum from 400 nm to 800 nm.It is envisioned that a range of visible lasers and LEDs may be developed using the dual-halide perovskites.With fewer trap states,high mobility,broader absorption,and humidity resistance,it is

Crystallinity and compositional changes in carbonated apatites: Evidence from 31P solid-state NMR, Raman, and AFM analysis

Science.gov (United States)

McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M. Banaszak; Tecklenburg, Mary M. J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

2013-10-01

Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and 31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse 31P NMR linewidth and inverse Raman PO43-ν1 bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3-10.3 wt% CO32- range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the 31P NMR chemical shift frequency and the Raman phosphate ν1 band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals.

Code Optimization, Frozen Glassy Phase and Improved Decoding Algorithms for Low-Density Parity-Check Codes

International Nuclear Information System (INIS)

Huang Hai-Ping

2015-01-01

The statistical physics properties of low-density parity-check codes for the binary symmetric channel are investigated as a spin glass problem with multi-spin interactions and quenched random fields by the cavity method. By evaluating the entropy function at the Nishimori temperature, we find that irregular constructions with heterogeneous degree distribution of check (bit) nodes have higher decoding thresholds compared to regular counterparts with homogeneous degree distribution. We also show that the instability of the mean-field calculation takes place only after the entropy crisis, suggesting the presence of a frozen glassy phase at low temperatures. When no prior knowledge of channel noise is assumed (searching for the ground state), we find that a reinforced strategy on normal belief propagation will boost the decoding threshold to a higher value than the normal belief propagation. This value is close to the dynamical transition where all local search heuristics fail to identify the true message (codeword or the ferromagnetic state). After the dynamical transition, the number of metastable states with larger energy density (than the ferromagnetic state) becomes exponentially numerous. When the noise level of the transmission channel approaches the static transition point, there starts to exist exponentially numerous codewords sharing the identical ferromagnetic energy. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Li ion transport in sputter deposited LiCoO{sub 2} thin films and glassy borate membranes

Energy Technology Data Exchange (ETDEWEB)

Stockhoff, Tobias; Gallasch, Tobias; Schmitz, Guido [Westfaelische Wilhelms-Universitaet Muenster, Institut fuer Materialphysik, Muenster (Germany)

2010-07-01

LiCoO{sub 2} membranes are key components of current battery technology. We investigate sputter-deposited thin films of these materials aiming at the application in all-solid-state thin film batteries. For this, LiCoO{sub 2} films (10-200 nm) were deposited onto ITO-coated glass substrates by ion beam sputtering. In addition, a part of these films are coated by an ion-conductive membrane of Li{sub 2}O-B{sub 2}O{sub 3} glasses in the thickness range of 50 to 300 nm. Structural, chemical and electrical properties of the layers are studied by means of TEM(EELS) and various electrical methods (cyclic voltammetry, chrono-amperometry/-potentiometry). Since the color of the LiCoO{sub 2} films changes from red-brown to grey during de-intercalation of Li and the substrate as well as the glassy membrane deposited on top are optical transparent, reversible Li de- and intercalation can be directly demonstrated and quantified by a measurement of light transmission through the layered system. Samples coated with an ion-conductive membrane reveal a characteristic delay in switching optical transparency which is due to the slower transport across the membrane. Varying the thickness of the glassy membrane, the d.c. ion-conductivity and permeation through the membrane is determined quantitatively. Using thin membranes in the range of a few tens of nanometers the critical current densities are way sufficient for battery applications.

Probing Properties of Glassy Water and Other Liquids with Site Selective Spectroscopies

Energy Technology Data Exchange (ETDEWEB)

Dang, Nhan Chuong [Iowa State Univ., Ames, IA (United States)

2005-01-01

The standard non-photochemical hole burning (NPHB) mechanism, which involves phonon-assisted tunneling in the electronically excited state, was originally proposed to explain the light-induced frequency change of chemically stable molecules in glassy solids at liquid helium temperatures by this research group more than two decades ago. The NPHB mechanism was then further elucidated and the concept of intrinsic to glass configurational relaxation processes as pre-mediating step to the hole burning process was introduced. The latter provided the theoretical basis for NPHB to evolve into a powerful tool probing the dynamics and nature of amorphous media, which aside from ''simple'' inorganic glasses may include also ''complex'' biological systems such as living cells and cancerous/normal tissues. Presented in this dissertation are the experimental and theoretical results of hole burning properties of aluminum phthalocyanine tetrasulphonate (APT) in several different matrices: (1) hyperquenched glassy water (HGW); (2) cubic ice (I_c); and (3) water confined into poly(2-hydroxyethylmethacrylate) (poly-HEMA). In addition, results of photochemical hole burning (PHB) studies obtained for phthalocyanine tetrasulphonate (P_cT) in HGW and free base phthalocyanine (P_c) in ortho-dichlorobenzene (DCB) glass are reported. The goal of this dissertation was to provide further evidence supporting the NPHB mechanism and to provide more insight that leads to a better understanding of the kinetic events (dynamics) in glasses, and various dynamical processes of different fluorescent chromorphores in various amorphous solids and the liquid that exist above the glass transition temperature (T_g). The following issues are addressed in detail: (1) time evolution of hole being burned under different conditions and in different hole burning systems; (2) temperature dependent hole profile; and (3) the structure

Mode coupling theory for nonequilibrium glassy dynamics of thermal self-propelled particles.

Science.gov (United States)

Feng, Mengkai; Hou, Zhonghuai

2017-06-28

We present a mode coupling theory study for the relaxation and glassy dynamics of a system of strongly interacting self-propelled particles, wherein the self-propulsion force is described by Ornstein-Uhlenbeck colored noise and thermal noises are included. Our starting point is an effective Smoluchowski equation governing the distribution function of particle positions, from which we derive a memory function equation for the time dependence of density fluctuations in nonequilibrium steady states. With the basic assumption of the absence of macroscopic currents and standard mode coupling approximation, we can obtain expressions for the irreducible memory function and other relevant dynamic terms, wherein the nonequilibrium character of the active system is manifested through an averaged diffusion coefficient D[combining macron] and a nontrivial structural function S 2 (q) with q being the magnitude of wave vector q. D[combining macron] and S 2 (q) enter the frequency term and the vertex term for the memory function, and thus influence both the short time and the long time dynamics of the system. With these equations obtained, we study the glassy dynamics of this thermal self-propelled particle system by investigating the Debye-Waller factor f q and relaxation time τ α as functions of the persistence time τ p of self-propulsion, the single particle effective temperature T eff as well as the number density ρ. Consequently, we find the critical density ρ c for given τ p shifts to larger values with increasing magnitude of propulsion force or effective temperature, in good accordance with previously reported simulation work. In addition, the theory facilitates us to study the critical effective temperature T for fixed ρ as well as its dependence on τ p . We find that T increases with τ p and in the limit τ p → 0, it approaches the value for a simple passive Brownian system as expected. Our theory also well recovers the results for passive systems and can be

Development of orodispersible polymer films with focus on the solid state characterization of crystalline loperamide.

Science.gov (United States)

Woertz, Christina; Kleinebudde, Peter

2015-08-01

The formulation of active pharmaceutical ingredients (API) as orodispersible films is gaining interest among novel oral drug delivery systems due to their small size, enhanced flexibility and improved patient compliance. The aim of this work was the preparation and characterization of orodispersible films containing loperamide hydrochloride (LPH) as model drug. As loperamide hydrochloride is poorly soluble in water it was used in crystalline form with a loading of 2mg/6cm(2) film. Hydroxypropyl methylcellulose (HPMC) and different types of hydroxypropyl cellulose (HPC) in different concentrations were used as film forming polymers whereas arabic gum, xanthan gum and tragacanth served as thickening agents. Films were characterized with respect to the content uniformity, morphology, thermal behavior and crystallinity. Suspensions were investigated regarding their viscosity using a rotational rheometer and the crystal structure of the Active Pharmaceutical Ingredient (API) was analyzed using polarized light microscopy. The development of flexible, non-brittle and homogeneous films of LPH was feasible. Two polymorphic forms of LPH appeared in the film formulations dependent on the utilized polymer. While in presence of HPMC the original polymorphic form I remained stable in suspension and films, the polymorphic form II occurred in presence of HPC. Both polymorphic forms were prepared separately and a solid state characterization was performed. Polymorph I showed isometric crystals whereas polymorph II showed needle shaped crystals. Tragacanth was able to prevent the transformation to polymorph II, if it was dissolved first before HPC. When HPC was added first to the suspension, the conversion to form II occurred irreversibly also after further addition of tragacanth. Copyright © 2015 Elsevier B.V. All rights reserved.

Egg maturation by the glassy-winged sharpshooter (Hemiptera: Cicadellidae); a vector of Xylella fastidiosa

Science.gov (United States)

Rates of spread of insect-transmitted plant pathogens are a function of vector abundance. Despite this, factors affecting population growth rates of insects that transmit plant pathogens have received limited attention. The glassy-winged sharpshooter (Homalodisca vitripennis) feeds on xylem-sap and ...

Determining the critical relative humidity at which the glassy to rubbery transition occurs in polydextrose using an automatic water vapor sorption instrument.

Science.gov (United States)

Yuan, Xiaoda; Carter, Brady P; Schmidt, Shelly J

2011-01-01

Similar to an increase in temperature at constant moisture content, water vapor sorption by an amorphous glassy material at constant temperature causes the material to transition into the rubbery state. However, comparatively little research has investigated the measurement of the critical relative humidity (RHc) at which the glass transition occurs at constant temperature. Thus, the central objective of this study was to investigate the relationship between the glass transition temperature (Tg), determined using thermal methods, and the RHc obtained using an automatic water vapor sorption instrument. Dynamic dewpoint isotherms were obtained for amorphous polydextrose from 15 to 40 °C. RHc was determined using an optimized 2nd-derivative method; however, 2 simpler RHc determination methods were also tested as a secondary objective. No statistical difference was found between the 3 RHc methods. Differential scanning calorimetry (DSC) Tg values were determined using polydextrose equilibrated from 11.3% to 57.6% RH. Both standard DSC and modulated DSC (MDSC) methods were employed, since some of the polydextrose thermograms exhibited a physical aging peak. Thus, a tertiary objective was to compare Tg values obtained using 3 different methods (DSC first scan, DSC rescan, and MDSC), to determine which method(s) yielded the most accurate Tg values. In general, onset and midpoint DSC first scan and MDSC Tg values were similar, whereas onset and midpoint DSC rescan values were different. State diagrams of RHc and experimental temperature and Tg and %RH were compared. These state diagrams, though obtained via very different methods, showed relatively good agreement, confirming our hypothesis that water vapor sorption isotherms can be used to directly detect the glassy to rubbery transition. Practical Application: The food polymer science (FPS) approach, pioneered by Slade and Levine, is being successfully applied in the food industry for understanding, improving, and

Semiclassical and quantum polarons in crystalline acetanilide

Science.gov (United States)

Hamm, P.; Tsironis, G. P.

2007-08-01

Crystalline acetanilide is a an organic solid with peptide bond structure similar to that of proteins. Two states appear in the amide I spectral region having drastically different properties: one is strongly temperature dependent and disappears at high temperatures while the other is stable at all temperatures. Experimental and theoretical work over the past twenty five years has assigned the former to a selftrapped state while the latter to an extended free exciton state. In this article we review the experimental and theoretical developments on acetanilide paying particular attention to issues that are still pending. Although the interpretation of the states is experimentally sound, we find that specific theoretical comprehension is still lacking. Among the issues that that appear not well understood is the effective dimensionality of the selftrapped polaron and free exciton states.

Case histories of roller cone core bit application in crystalline rock

International Nuclear Information System (INIS)

Dahlem, J.S.

1988-01-01

The increased interest in deep crystalline rock drilling projects has resulted in a requirement for premium coring bits which are effective in such a harsh and abrasive environment. Hard formation roller cone insert bits have traditionally and constantly performed well in crystalline rock. As a result, the application of state of the art roller cone rock bit technology to the design and development of core bits has made crystalline coring projects more viable than ever before. This paper follows the development of roller cone core bits by examining their use on project such as HDR (Hot Dry Rock, Los Alamos); NAGRA (Nuclear Waste Disposal Wells in Switzerland); Camborne School of Mines Geothermal Project in Cornwall, UK; Deep Gas Project in Sweden; and the KTB Deep Drilling Project in West Germany

Casimir Force Contrast Between Amorphous and Crystalline Phases of AIST

NARCIS (Netherlands)

Torricelli, Gauthier; van Zwol, Peter J.; Shpak, Olex; Palasantzas, George; Svetovoy, Vitaly B.; Binns, Chris; Kooi, Bart J.; Jost, Peter; Wuttig, Matthias

2012-01-01

Phase change materials (PCMs) can be rapidly and reversibly switched between the amorphous and crystalline state. The structural transformation is accompanied by a significant change of optical and electronic properties rendering PCMs suitable for rewritable optical data storage and non-volatile

Casimir Force Contrast Between Amorphous and Crystalline Phases of AIST

NARCIS (Netherlands)

Torrichelli, G.; van Zwol, P.J.; Shpak, O.; Palasantzas, G.; Svetovoy, Vitaly; Binns, C.; Kooi, B.J.; Jost, P.; Wittig, M.

2012-01-01

Phase change materials (PCMs) can be rapidly and reversibly switched between the amorphous and crystalline state. The structural transformation is accompanied by a signifi cant change of optical and electronic properties rendering PCMs suitable for rewritable optical data storage and nonvolatile

Do cracks melt their way through solids?

International Nuclear Information System (INIS)

Okamoto, P. R.

1998-01-01

Real-time, in situ fracture studies in the high-voltage electron microscope (HVEM) show that microscopically thin regions of amorphous NiTi form ahead of moving crack tips in the B2-NiTi intermetallic compound during tensile straining at temperatures equal to or below 600K. The upper cutoff temperature of 600K for this stress-induced melting (or amorphization) is identical to the upper cutoff temperatures reported in the literature for both heavy-ion-induced amorphization of the intermetallic NiTi and ion-beam-mixing-induced amorphization of Ni and Ti multilayer. These results, together with the fact that the higher crystallization temperatures (∼800K)of unrelaxed amorphous NiTi alloys obtained by rapid quenching can also be reduced to, but not lower than 600K, by heavy-ion irradiation, strongly suggest that structural relaxation processes enhanced or induced by dynamic atomic disordering allow the formation of a unique, fully-relaxed glassy state which is characterized by a unique isothermal crystallization temperature. We believe that this unique temperature is the Kauzmann glass-transition temperature, corresponding to the ideal glass having the same entropy as the crystalline state. As the glassy state with the lowest global free energy, the preferential formation of this ideal glass by disorder-induced amorphization processes can be understood as the most energetically-favored, kinetically-constrained melting response of crystalline materials driven far from equilibrium at low temperatures

Heavy ion irradiation of crystalline water ice. Cosmic ray amorphisation cross-section and sputtering yield

Science.gov (United States)

Dartois, E.; Augé, B.; Boduch, P.; Brunetto, R.; Chabot, M.; Domaracka, A.; Ding, J. J.; Kamalou, O.; Lv, X. Y.; Rothard, H.; da Silveira, E. F.; Thomas, J. C.

2015-04-01

Context. Under cosmic irradiation, the interstellar water ice mantles evolve towards a compact amorphous state. Crystalline ice amorphisation was previously monitored mainly in the keV to hundreds of keV ion energies. Aims: We experimentally investigate heavy ion irradiation amorphisation of crystalline ice, at high energies closer to true cosmic rays, and explore the water-ice sputtering yield. Methods: We irradiated thin crystalline ice films with MeV to GeV swift ion beams, produced at the GANIL accelerator. The ice infrared spectral evolution as a function of fluence is monitored with in-situ infrared spectroscopy (induced amorphisation of the initial crystalline state into a compact amorphous phase). Results: The crystalline ice amorphisation cross-section is measured in the high electronic stopping-power range for different temperatures. At large fluence, the ice sputtering is measured on the infrared spectra, and the fitted sputtering-yield dependence, combined with previous measurements, is quadratic over three decades of electronic stopping power. Conclusions: The final state of cosmic ray irradiation for porous amorphous and crystalline ice, as monitored by infrared spectroscopy, is the same, but with a large difference in cross-section, hence in time scale in an astrophysical context. The cosmic ray water-ice sputtering rates compete with the UV photodesorption yields reported in the literature. The prevalence of direct cosmic ray sputtering over cosmic-ray induced photons photodesorption may be particularly true for ices strongly bonded to the ice mantles surfaces, such as hydrogen-bonded ice structures or more generally the so-called polar ices. Experiments performed at the Grand Accélérateur National d'Ions Lourds (GANIL) Caen, France. Part of this work has been financed by the French INSU-CNRS programme "Physique et Chimie du Milieu Interstellaire" (PCMI) and the ANR IGLIAS.

http://ntv.ifmo.ru/file/article/10373.pdf

Directory of Open Access Journals (Sweden)

S. N. Zhukov

2014-07-01

Full Text Available Comparative analysis of spectral and luminescent properties for glasses SiO2-Al2O3-MgO-K2O-TiO2 doped with chromium ions and forsterite nano-glass ceramic have been done. Initial glasses were obtained by using a conventional melt quenching method. Glass ceramics were produced by the two-stage secondary heat treatment of initial glasses. At the first step of the heat treatment nucleation centers were formed at 700º C. At the second step there was an increase of Mg2SiO4: Cr crystalline phase. Crystalline phase composition and the crystals size were determined by X-ray diffractometer. It is shown that the crystalline phase of Mg2SiO4 (forsterite is precipitated during the heat treatment. Valency state and the chromium ion position in a forsterite or a glassy matrix are determined according to luminescence and absorption spectra. Identification of absorption and luminescence bands in initial and heat-treated samples is carried out. The dependence between spectral and luminescent properties of chromium and heat treatment modes is examined. The results demonstrate that ions of the trivalent and tetravalent chromium are transforming to the forsterite crystalline phase during the heat treatment, and a part of them remains in the glassy phase. Presented research results can be used for the development of glasses and nanoscale glassceramic for fiber tunable lasers and broadband optical amplifiers of a near infrared range which are used in information and telecommunication technologies.

Effect of the UV modification of α-crystallin on its ability to suppress nonspecific aggregation

International Nuclear Information System (INIS)

Ellozy, A.R.; Ceger, Patricia; Wang, R.H.; Dillon, James

1996-01-01

Recent studies have shown that structural modifications of α-crystallin during lens aging decrease it's effectiveness as a molecular chaperone. Some of these post-translational modifications have been linked to UV radiation, and this study was undertaken to investigate the effect of UV irradiation on the ability of α-crystallin to suppress nonspecific aggregation. The effect of 3-hydroxykynurenine (3-HK) was also investigated as a model for its glucoside (3-HKG), a main lens chromophore that has been linked to photochemical changes in the human lens. Alpha- and γ-crystallin solutions (1 mg/mL, 1:0.125 wt/wt) were photolyzed (transmission above 295nm) for various time intervals. Thermal denaturation of γ-crystallin with or without α-crystallin was carried out at 70 o C and increases in light scattering were measured at 360 nm. We found that (1) irradiation of γ-crystallin increased its susceptibility to heat-induced scattering. The addition of α-crystallin protects it against thermal denaturation, although its ability to do so decreases the longer γ-crystallin is irradiated and (2) irradiation of α-crystallin decreases its ability to suppress nonspecific aggregation and the presence of 3-HK during irradiation decreases its further. Our results indicate that post-translational modifications of α-crystallin due to UV irradiation affect the sites and mechanisms by which it interacts with γ-crystallin. The kinetics of γ-crystallin unfolding during thermal denaturation were also analyzed. We found that a simple two state model applied for nonirradiated γ-crystallin. This model does not hold when γ-crystallin is irradiated in the prescence or absence of α-crystallin. In these cases, two step or multistep mechanisms are more likely. (Author)

Modified positron annihilation model for glassy-like As2Se3

International Nuclear Information System (INIS)

Kozdras, A.; Shpotyuk, O.; Kovalskiy, A.; Filipecki, J.

2005-01-01

An approach to structural characterization of chalcogenide glasses based on the study of void distribution is discussed. The results of positron annihilation lifetime spectra measurements for glassy As 2 Se 3 are compared with nano-void distribution data obtained from Monte Carlo simulation. In this consideration perspectives to involve the parameters of nano-voids calculated from the first sharp diffraction peak in the frame work of known Elliott's model are analyzed. (author)

Electrical transport in crystalline phase change materials

Energy Technology Data Exchange (ETDEWEB)

Woda, Michael

2012-01-06

In this thesis, the electrical transport properties of crystalline phase change materials are discussed. Phase change materials (PCM) are a special class of semiconducting and metallic thin film alloys, typically with a high amount of the group five element antimony or the group six element tellurium, such as Ge{sub 2}Sb{sub 2}Te{sub 5}. The unique property portfolio of this material class makes it suitable for memory applications. PCMs reveal fast switching between two stable room-temperature phases (amorphous and crystalline) realized by optical laser or electrical current pulses in memory devices. Additionally, a pronounced property contrast in form of optical reflectivity and electrical conductivity between the amorphous and crystalline phase is the characteristic fingerprint of PCMs. The emerging electrical solid state memory PCRAM is a very promising candidate to replace Flash memory in the near future or to even become a universal memory, which is non-volatile and shows the speed and cyclability of DRAM. One of the main technological challenges is the switching process into the amorphous state, which is the most power demanding step. In order to reduce the switching power, the crystalline resistivity needs to be increased at a given voltage. Thus understanding and tayloring of this property is mandatory. In this work, first the technological relevance, i.e. optical and electrical memory concepts based on PCMs are introduced. Subsequently a description of the physical properties of PCMs in four categories is given. Namely, structure, kinetics, optical properties and electrical properties are discussed. Then important recent developments such as the identification of resonant bonding in crystalline PCMs and a property predicting coordination scheme are briefly reviewed. The following chapter deals with the theoretical background of electrical transport, while the next chapter introduces the experimental techniques: Sputtering, XRR, XRD, DSC, thermal annealing

Thermal Barrier Coatings Resistant to Glassy Deposits

Science.gov (United States)

Drexler, Julie Marie

Engineering of alloys has for years allowed aircraft turbine engines to become more efficient and operate at higher temperatures. As advancements in these alloy systems have become more difficult, ceramic thermal barrier coatings (TBCs), often yttria (7 wt %) stabilized zirconia (7YSZ), have been utilized for thermal protection. TBCs have allowed for higher engine operating temperatures and better fuel efficiency but have also created new engineering problems. Specifically, silica based particles such as sand and volcanic ash that enter the engine during operation form glassy deposits on the TBCs. These deposits can cause the current industrial 7YSZ thermal barrier coatings to fail since the glass formed penetrates and chemically interacts with the TBC. When this occurs, coating failure may occur due to a loss of strain tolerance, which can lead to fracture, and phase changes of the TBC material. There have been several approaches used to stop calcium-magnesium aluminio-silcate (CMAS) glasses (molten sand) from destroying the entire TBC, but overall there is still limited knowledge. In this thesis, 7YSZ and new TBC materials will be examined for thermochemical and thermomechanical performance in the presence of molten CMAS and volcanic ash. Two air plasma sprayed TBCs will be shown to be resistant to volcanic ash and CMAS. The first type of coating is a modified 7YSZ coating with 20 mol% Al2O3 and 5 mol% TiO2 in solid solution (YSZ+20Al+5Ti). The second TBC is made of gadolinium zirconate. These novel TBCs impede CMAS and ash penetration by interacting with the molten CMAS or ash and drastically changing the chemistry. The chemically modified CMAS or ash will crystallize into an apatite or anorthite phase, blocking the CMAS or ash from further destroying the coating. A presented mechanism study will show these coatings are effective due to the large amount of solute (Gd, Al) in the zirconia structure, which is the key to creating the crystalline apatite or

The electrocatalytical reduction of m-nitrophenol on palladium nanoparticles modified glassy carbon electrodes

International Nuclear Information System (INIS)

Shi Qiaofang; Diao Guowang

2011-01-01

Highlights: ► The deposition of palladium on a GC electrode was performed by cyclic voltammetry. ► SEM images showed palladium nanoparticles deposited on a glassy carbon (GC) electrode. ► The Pd/GC electrode can effectively catalyze m-nitrophenol in aqueous media. ► The reduction of m-nitrophenol on the Pd/GC electrode depended on potential and pH. ► XPS spectra of the Pd/GC electrodes demonstrated the presence of palladium. - Abstract: Palladium nanoparticles modified glassy carbon electrodes (Pd/GC) were prepared via the electrodeposition of palladium on a glassy carbon (GC) electrode using cyclic voltammetry in different sweeping potential ranges. The scanning electron microscope images of palladium particles on the GC electrodes indicate that palladium particles with diameters of 20–50 nm were homogeneously dispersed on the GC electrode at the optimal deposition conditions, which can effectively catalyze the reduction of m-nitrophenol in aqueous solutions, but their catalytic activities are strongly related to the deposition conditions of Pd. The X-ray photoelectron spectroscopy spectra of the Pd/GC electrode confirmed that 37.1% Pd was contained in the surface composition of the Pd/GC electrode. The cyclic voltammograms of the Pd/GC electrode in the solution of m-nitrophenol show that the reduction peak of m-nitrophenol shifts towards the more positive potentials, accompanied with an increase in the peak current compared to the bare GC electrode. The electrocatalytic activity of the Pd/GC electrode is affected by pH values of the solution. In addition, the electrolysis of m-nitrophenol under a constant potential indicates that the reduction current of m-nitrophenol on the Pd/GC electrode is approximately 20 times larger than that on the bare GC electrode.

Melt processing of Bi-Ca-Sr-Cu-O superconductors

International Nuclear Information System (INIS)

Zanotto, E.D.; Cronin, J.P.; Dutta, B.

1988-01-01

Several Bi-Ca-Sr-Cu-O compositions were melted in Al/sub 2/O/sub 3/ or Pt crucibles at temperatures between 1050C and 1200C. As-quenched specimens crystallized from the upper surfaces, while the bottom layers were glassy. Glass formation was improved for higher Bi/sub 2/O/sub 3/ concentrations. The crystalline portions were highly conductive, while the glassy layers were insulating. Both did not show superconductivity down to 10K. Thermal treatment in air caused a dramatic effect on the electronic properties; and annealing at 865C for long periods converted the two types of specimens (previously glassy or crystalline) to superconductors, at least for one composition. Aluminum impurity (up to 8.6 atom. pct.) had no detectable effect on the transition temperatures, i.e., T/sub c/ 85K for all superconducting samples. The flake-like (Bi/sub 2/Ca/sub 1/Sr/sub 2/Cu/sub 2/) phase, reported by other authors, was responsible for superconductivity

A nanoscale characterisation of extended defects in glassy-like As2Se3 semiconductors with PAL technique

International Nuclear Information System (INIS)

Shpotyuk, O.; Kovalskiy, A.; Filipecki, J.; Hyla, M.; Kozdras, A.

2003-01-01

A meaningful interpretation of positron lifetime characteristics for glassy-like g-As 2 Se 3 is developed taking into account calculations of Jensen et al. (J. Non-Cryst. Solids 170 (1994) 57) for positrons trapped by free-volume extended defects in orthorhombic As 2 Se 3 and void volume distribution for 146-atoms layer-biased model of amorphous As 2 Se 3 presented by Popescu (J. Non-Cryst. Solids 35-36 (1980) 549). The obtained results are compared for samples having different thermal pre-history. Two groups of experimental results with close lifetime characteristics are distinguished for each of the investigated samples. This feature is explained in terms of average positron lifetime by applying two-state positron trapping model for mathematical treatment of the obtained spectra

Liquid Crystalline Semiconductors Materials, properties and applications

CERN Document Server

Kelly, Stephen; O'Neill, Mary

2013-01-01

This is an exciting stage in the development of organic electronics. It is no longer an area of purely academic interest as increasingly real applications are being developed, some of which are beginning to come on-stream. Areas that have already been commercially developed or which are under intensive development include organic light emitting diodes (for flat panel displays and solid state lighting), organic photovoltaic cells, organic thin film transistors (for smart tags and flat panel displays) and sensors. Within the family of organic electronic materials, liquid crystals are relative newcomers. The first electronically conducting liquid crystals were reported in 1988 but already a substantial literature has developed. The advantage of liquid crystalline semiconductors is that they have the easy processability of amorphous and polymeric semiconductors but they usually have higher charge carrier mobilities. Their mobilities do not reach the levels seen in crystalline organics but they circumvent all of t...

Structural analysis of quaternary Se{sub 85−x}Sb{sub 10}In{sub 5}Ag{sub x} bulk glassy alloys

Energy Technology Data Exchange (ETDEWEB)

Sharma, Rita, E-mail: reetasharma2012@gmail.com; Sharma, Shaveta; Kumar, Praveen; Chander, Ravi; Thangaraj, R.; Mian, M. [Semiconductors Laboratory, Department of Physics, GND University, Amritsar (India)

2015-08-28

The physical properties of chalcogenide semiconductor have attracted much attention recently due to their applications in optical recording media and inorganic resist due to photo induced structural transformations observed in these materials. The bulk samples of Se{sub 85-x}Sb{sub 10}In{sub 5}Ag{sub x} system are prepared by melt-quenching technique. X-ray diffraction technique and RAMAN spectroscopy have been used to study the role of Ag additive on the amorphous/crystalline nature and molecular structure of Se{sub 85}Sb{sub 10}In{sub 5} glassy alloys. The phases Sb{sub 2}Se{sub 3}, In-Sb and In{sub 2}Se{sub 3} has been observed by X-ray diffraction. The formation of AgInSe{sub 2} phase along with the enhancement in intensity has been observed with the Ag addition.Three bands observed by raman spectroscopy for Se85Sb10In5 are at 70 cm-1, 212cm-1 and 252cm-1. The formation of small bands up to wavenumber 188cm{sup -1} and shifting in second band along with the increase in intensity up to sample x=5 has been observed with the Ag addition. The enhancement in intensity in third band with Ag content has been observed.

Playback of natural vibrational signals in vineyard trellis for mating disruption of glassy-winged sharpshooter

Science.gov (United States)

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is a vector of Xylella fastidiosa, an important bacterial pathogen of several crops in the Americas and Europe. Mating communication of this and many other cicadellid pests involves the exchange of substrate-...

Selective detection of crystalline cellulose in plant cell walls with sum-frequency-generation (SFG) vibration spectroscopy.

Science.gov (United States)

Barnette, Anna L; Bradley, Laura C; Veres, Brandon D; Schreiner, Edward P; Park, Yong Bum; Park, Junyeong; Park, Sunkyu; Kim, Seong H

2011-07-11

The selective detection of crystalline cellulose in biomass was demonstrated with sum-frequency-generation (SFG) vibration spectroscopy. SFG is a second-order nonlinear optical response from a system where the optical centrosymmetry is broken. In secondary plant cell walls that contain mostly cellulose, hemicellulose, and lignin with varying concentrations, only certain vibration modes in the crystalline cellulose structure can meet the noninversion symmetry requirements. Thus, SFG can be used to detect and analyze crystalline cellulose selectively in lignocellulosic biomass without extraction of noncellulosic species from biomass or deconvolution of amorphous spectra. The selective detection of crystalline cellulose in lignocellulosic biomass is not readily achievable with other techniques such as XRD, solid-state NMR, IR, and Raman analyses. Therefore, the SFG analysis presents a unique opportunity to reveal the cellulose crystalline structure in lignocellulosic biomass.

Structural and mechanical properties of glassy water in nanoscale confinement.

Science.gov (United States)

Lombardo, Thomas G; Giovambattista, Nicolás; Debenedetti, Pablo G

2009-01-01

We investigate the structure and mechanical properties of glassy water confined between silica-based surfaces with continuously tunable hydrophobicity and hydrophilicity by computing and analyzing minimum energy, mechanically stable configurations (inherent structures). The structured silica substrate imposes long-range order on the first layer of water molecules under hydrophobic confinement at high density (p > or = 1.0 g cm(-3)). This proximal layer is also structured in hydrophilic confinement at very low density (p approximately 0.4 g cm(-3)). The ordering of water next to the hydrophobic surface greatly enhances the mechanical strength of thin films (0.8 nm). This leads to a substantial stress anisotropy; the transverse strength of the film exceeds the normal strength by 500 MPa. The large transverse strength results in a minimum in the equation of state of the energy landscape that does not correspond to a mechanical instability, but represents disruption of the ordered layer of water next to the wall. In addition, we find that the mode of mechanical failure is dependent on the type of confinement. Under large lateral strain, water confined by hydrophilic surfaces preferentially forms voids in the middle of the film and fails cohesively. In contrast, water under hydrophobic confinement tends to form voids near the walls and fails by loss of adhesion.

Dielectric studies of molecular motions in glassy and liquid nicotine

Energy Technology Data Exchange (ETDEWEB)

Kaminski, K [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Paluch, M [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Ziolo, J [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Ngai, K L [Naval Research Laboratory, Washington DC 20375-5320 (United States)

2006-06-21

The dielectric permittivity and loss spectra of glassy and liquid states of nicotine have been measured over the frequency range 10{sup -2}-10{sup 9} Hz. The relaxation spectra are similar to common small molecular glass-forming substances, showing the structural {alpha}-relaxation and its precursor, the Johari-Goldstein {beta}-relaxation. The {alpha}-relaxation is well described by the Fourier transform of the Kohlrausch-Williams-Watts stretched exponential function with an approximately constant stretch exponent that is equal to 0.70 as the glass transition temperature is approached. The dielectric {alpha}-relaxation time measured over 11 orders of magnitude cannot be described by a single Vogel-Fulcher-Tamman-Hesse equation. The most probable Johari-Goldstein {beta}-relaxation time determined from the dielectric spectra is in good agreement with the primitive relaxation time of the coupling model calculated from parameters of the structural {alpha}-relaxation. The shape of the dielectric spectra of nicotine is compared with that of other glass-formers having about the same stretch exponent, and they are shown to be nearly isomorphic. The results indicate that the molecular dynamics of nicotine conform to the general pattern found in other glass-formers, and the presence of the universal Johari-Goldstein secondary relaxation, which plays a role in the crystallization of amorphous pharmaceuticals.

Blending crystalline/liquid crystalline small molecule semiconductors: A strategy towards high performance organic thin film transistors

Science.gov (United States)

He, Chao; He, Yaowu; Li, Aiyuan; Zhang, Dongwei; Meng, Hong

2016-10-01

Solution processed small molecule polycrystalline thin films often suffer from the problems of inhomogeneity and discontinuity. Here, we describe a strategy to solve these problems through deposition of the active layer from a blended solution of crystalline (2-phenyl[1]benzothieno[3,2-b][1]benzothiophene, Ph-BTBT) and liquid crystalline (2-(4-dodecylphenyl) [1]benzothieno[3,2-b]benzothiophene, C12-Ph-BTBT) small molecule semiconductors with the hot spin-coating method. Organic thin film transistors with average hole mobility approaching 1 cm2/V s, much higher than that of single component devices, have been demonstrated, mainly due to the improved uniformity, continuity, crystallinity, and stronger intermolecular π-π stacking in blend thin films. Our results indicate that the crystalline/liquid crystalline semiconductor blend method is an effective way to enhance the performance of organic transistors.

Saline groundwater in crystalline bedrock

International Nuclear Information System (INIS)

Lampen, P.

1992-11-01

The State-of-art report describes research made on deep saline groundwaters and brines found in crystalline bedrock, mainly in site studies for nuclear waste disposal. The occurrence, definitions and classifications of saline groundwaters are reviewed with a special emphasis on the different theories concerning the origins of saline groundwaters. Studies of the saline groundwaters in Finland and Sweden have been reviewed more thoroughly. Also the mixing of different bodies of groundwaters, observations of the contact of saline groundwaters and permafrost, and the geochemical modelling of saline groundwaters as well as the future trends of research have been discussed. (orig.)

Silicon Monoxide at 1 atm and Elevated Pressures: Crystalline or Amorphous?

KAUST Repository

AlKaabi, Khalid

2014-03-05

The absence of a crystalline SiO phase under ordinary conditions is an anomaly in the sequence of group 14 monoxides. We explore theoretically ordered ground-state and amorphous structures for SiO at P = 1 atm, and crystalline phases also at pressures up to 200 GPa. Several competitive ground-state P = 1 atm structures are found, perforce with Si-Si bonds, and possessing Si-O-Si bridges similar to those in silica (SiO2) polymorphs. The most stable of these static structures is enthalpically just a little more stable than a calculated random bond model of amorphous SiO. In that model we find no segregation into regions of amorphous Si and amorphous SiO2. The P = 1 atm structures are all semiconducting. As the pressure is increased, intriguing new crystalline structures evolve, incorporating Si triangular nets or strips and stishovite-like regions. A heat of formation of crystalline SiO is computed; it is found to be the most negative of all the group 14 monoxides. Yet, given the stability of SiO2, the disproportionation 2SiO (s) → Si(s)+SiO2(s) is exothermic, falling right into the series of group 14 monoxides, and ranging from a highly negative ΔH of disproportionation for CO to highly positive for PbO. There is no major change in the heat of disproportionation with pressure, i.e., no range of stability of SiO with respect to SiO2. The high-pressure SiO phases are metallic. © 2014 American Chemical Society.

Effect of Ultrasonic Vibration on Mechanical Properties of 3D Printing Non-Crystalline and Semi-Crystalline Polymers.

Science.gov (United States)

Li, Guiwei; Zhao, Ji; Wu, Wenzheng; Jiang, Jili; Wang, Bofan; Jiang, Hao; Fuh, Jerry Ying Hsi

2018-05-17

Fused deposition modeling 3D printing has become the most widely used additive manufacturing technology because of its low manufacturing cost and simple manufacturing process. However, the mechanical properties of the 3D printing parts are not satisfactory. Certain pressure and ultrasonic vibration were applied to 3D printed samples to study the effect on the mechanical properties of 3D printed non-crystalline and semi-crystalline polymers. The tensile strength of the semi-crystalline polymer polylactic acid was increased by 22.83% and the bending strength was increased by 49.05%, which were almost twice the percentage increase in the tensile strength and five times the percentage increase in the bending strength of the non-crystalline polymer acrylonitrile butadiene styrene with ultrasonic strengthening. The dynamic mechanical properties of the non-crystalline and semi-crystalline polymers were both improved after ultrasonic enhancement. Employing ultrasonic energy can significantly improve the mechanical properties of samples without modifying the 3D printed material or adjusting the forming process parameters.

Photoluminescence and excited state structure in Bi3+-doped Y2SiO5 single crystalline films

International Nuclear Information System (INIS)

Babin, V.; Gorbenko, V.; Krasnikov, A.; Mihokova, E.; Nikl, M.; Zazubovich, S.; Zorenko, Yu.

2013-01-01

Single crystalline films of Bi-doped Y 2 SiO 5 are studied at 4.2–350 K by the time-resolved luminescence methods under excitation in the 3.8–6.2 eV energy range. Ultraviolet luminescence of Y 2 SiO 5 :Bi (≈3.6 eV) is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi 3+ centers which are related to the 3 P 0 and 3 P 1 levels of a free Bi 3+ ion, respectively. The lowest-energy excitation band of this emission, located at ≈4.5 eV, is assigned to the 1 S 0 → 3 P 1 transitions of a free Bi 3+ ion. The phenomenological model is proposed to describe the excited-state dynamics of Bi 3+ centers in Y 2 SiO 5 :Bi, and parameters of the triplet RES are determined. -- Highlights: •Luminescence of Y 2 SiO 5 :Bi is investigated for the first time. •Ultraviolet emission arises from Bi 3+ ions located in Y lattice sites. •The triplet relaxed excited states parameters of Bi 3+ centers are determined

University Crystalline Silicon Photovoltaics Research and Development

Energy Technology Data Exchange (ETDEWEB)

Ajeet Rohatgi; Vijay Yelundur; Abasifreke Ebong; Dong Seop Kim

2008-08-18

The overall goal of the program is to advance the current state of crystalline silicon solar cell technology to make photovoltaics more competitive with conventional energy sources. This program emphasizes fundamental and applied research that results in low-cost, high-efficiency cells on commercial silicon substrates with strong involvement of the PV industry, and support a very strong photovoltaics education program in the US based on classroom education and hands-on training in the laboratory.

Effect of. gamma. -irradiation on the crystalline structure of silk fibroin and silk sericin

Energy Technology Data Exchange (ETDEWEB)

Tsukada, Masuhiro; Aoki, Akira

1985-02-01

Changes in the crystalline structure of silk sericin and silk fibroin induced by gamma-irradiation in the atmosphere described. The crystalline structure of silk sericin which had been subjected to gamma-irradiation remained unchanged. However the decomposition temperature of the specimen decreased to about 230 deg C, when the total dose of ..gamma.. rays exceeded 4.6 Mrad. The structure of the silk 1 type crystal of silk fibroin in the solid state, with a low degree of molecular orientation, changed into the silk 2 type crystal, when the total dose of ..gamma.. rays exceeded 4.6 Mrad. No changes in the crystalline structure were observed in the solid state of the silk 2 type crystal regardless of gamma-irradiation. The decrease in the decomposition temperature of the specimen was attributed to the decrease in the molecular orientation. However, the molecular conformation of silk fibroin with a randomly coiled structure remained unchanged even after gamma-irradiation.

Amorphous-crystalline transition in thermoelectric NbO2

International Nuclear Information System (INIS)

Music, Denis; Chen, Yen-Ting; Bliem, Pascal; Geyer, Richard W

2015-01-01

Density functional theory was employed to design enhanced amorphous NbO 2 thermoelectrics. The covalent-ionic nature of Nb–O bonding is identical in amorphous NbO 2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO 2 , which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO 2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO 2 possesses enhanced transport properties at all temperatures. Amorphous NbO 2 , reaching  −173 μV K −1 , exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions. (paper)

Detection and typing of Xylella fastidiosa from glassy-winged sharpshooter for Pierce’s disease epidemiology

Science.gov (United States)

Epidemiology of Pierce’s disease of grape, caused by the bacterial pathogen Xylella fastidiosa (Xf), is largely dependent on populations of insect vectors such as the invasive glassy-winged sharpshooter (GWSS) (Homalodisca vitripennis). In the grape-growing regions of the southern San Joaquin Valley...

Dissolution of crystalline ceramics

International Nuclear Information System (INIS)

White, W.B.

1982-01-01

The present program objectives are to lay out the fundamentals of crystalline waste form dissolution. Nuclear waste ceramics are polycrystalline. An assumption of the work is that to the first order, the release rate of a particular radionuclide is the surface-weighted sum of the release rates of the radionuclide from each crystalline form that contains it. In the second order, of course, there will be synergistic effects. There will be also grain boundary and other microstructural influences. As a first approximation, we have selected crystalline phases one at a time. The sequence of investigations and measurements is: (i) Identification of the actual chemical reactions of dissolution including identification of the solid reaction products if such occur. (ii) The rates of these reactions are then determined empirically to give what may be called macroscopic kinetics. (iii) Determination of the rate-controlling mechanisms. (iv) If the rate is controlled by surface reactions, the final step would be to determine the atomic kinetics, that is the specific atomic reactions that occur at the dissolving interface. Our concern with the crystalline forms are in two areas: The crystalline components of the reference ceramic waste form and related ceramics and the alumino-silicate phases that appear in some experimental waste forms and as waste-rock interaction products. Specific compounds are: (1) Reference Ceramic Phases (zirconolite, magnetoplumbite, spinel, Tc-bearing spinel and perovskite); (2) Aluminosilicate phases (nepheline, pollucite, CsAlSi 5 O 12 , Sr-feldspar). 5 figures, 1 table

Synthesis and characterization of manganese diselenide nanoparticles (MnSeNPs): Determination of capsaicin by using MnSeNP-modified glassy carbon electrode.

Science.gov (United States)

Sukanya, Ramaraj; Sakthivel, Mani; Chen, Shen-Ming; Chen, Tse-Wei; Al-Hemaid, Fahad M A; Ajmal Ali, M; Elshikh, Mohamed Soliman

2018-06-02

A new type of manganese diselenide nanoparticles (MnSeNPs) was synthesized by using a hydrothermal method. Their surface morphology, crystallinity and elemental distribution were characterized by using transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy which scrutinize the formation of the NPs. The NPs were coated on a glassy carbon electrode (GCE), and electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were applied to study the electroanalytical properties towards the oxidation of the food additive capsaicin. The modified GCE displays lower charge transfer resistance (R ct  = 29.52 Ω), a larger active surface area (0.089 cm 2 /g, and more efficient electrochemical oxidation of capsaicin compared to a MnS 2 /GCE and a bare GCE. The oxidation peak potential is 0.43 V (vs. Ag/AgCl) which is lower than that of previously reported GCEs. The sensor has a detection limit as low as 0.05 μM and an electrochemical sensitivity of 2.41 μA μM -1  cm -2 . The method was applied to the determination of capsaicin in pepper samples. Graphical abstract Electrochemical determination of capsaicin in pepper extract by using MnSeNPs modified electrode.

Implicit implementation and consistent tangent modulus of a viscoplastic model for polymers

OpenAIRE

ACHOUR-RENAULT, Nadia; CHATZIGEORGIOU, George; MERAGHNI, Fodil; CHEMISKY, Yves; FITOUSSI, Joseph

2015-01-01

In this work, the phenomenological viscoplastic DSGZ model[Duan, Y., Saigal, A., Greif, R., Zimmerman, M. A., 2001. A Uniform Phenomenological Constitutive Model for Glassy and Semicrystalline Polymers. Polymer Engineering and Science 41 (8), 1322-1328], developed for glassy or semi-crystalline polymers, is numerically implemented in a three dimensional framework, following an implicit formulation. The computational methodology is based on the radial return mapping algorithm. This implicit fo...

High-Efficiency Solid-State Dye-Sensitized Solar Cells: Fast Charge Extraction through Self-Assembled 3D Fibrous Network of Crystalline TiO 2 Nanowires

KAUST Repository

Tétreault, Nicolas

2010-12-28

Herein, we present a novel morphology for solid-state dye-sensitized solar cells based on the simple and straightforward self-assembly of nanorods into a 3D fibrous network of fused single-crystalline anatase nanowires. This architecture offers a high roughness factor, significant light scattering, and up to several orders of magnitude faster electron transport to reach a near-record-breaking conversion efficiency of 4.9%. © 2010 American Chemical Society.

Annealing effect on thermal conductivity and microhardness of carbon nanotube containing Se80Te16Cu4 glassy composites

Science.gov (United States)

Upadhyay, A. N.; Tiwari, R. S.; Singh, Kedar

2018-02-01

This study deals with the effect of thermal annealing on structural/microstructural, thermal and mechanical behavior of pristine Se80Te16Cu4 and carbon nanotubes (CNTs) containing Se80Te16Cu4 glassy composites. Pristine Se80Te16Cu4, 3 and 5 wt%CNTs-Se80Te16Cu4 glassy composites are annealed in the vicinity of glass transition temperature to onset crystallization temperature (340-380 K). X-ray diffraction (XRD) pattern revealed formation of polycrystalline phases of hexagonal CuSe and trigonal selenium. The indexed d-values in XRD patterns are in well conformity with the d-values obtained after the indexing of the ring pattern of selected area electron diffraction pattern of TEM images. The SEM investigation exhibited that the grain size of the CNTs containing Se80Te16Cu4 glassy composites increased with increasing annealing temperature and decreased at further higher annealing temperature. Thermal conductivity, microhardness exhibited a substantial increase with increasing annealing temperature of 340-360 K and slightly decreases for 380 K. The variation of thermal conductivity and microhardness can be explained by cross-linking formation and voids reduction.

EIS study of the redox reaction of Fe(CN)63-/4- at glassy carbon electrode via diazonium reduction in aqueous and acetonitrile solutions

Energy Technology Data Exchange (ETDEWEB)

Khoshroo, M.; Rostami, A. [Mazandaran Univ., Babolsar (Iran, Islamic Republic of). Dept. of Physical Chemistry

2008-07-01

This paper reported on a study that characterized soluble electroactive species by cyclic voltammetry to investigate the presence of grafted films and their blocking properties. In particular, the authority of the glassy carbon electrode modification conditions on the cyclic voltammetric response of Fe(CN)63-/4- oxido-reduction was examined for 2 layers grafted by electrochemical reduction of diazonium salts in acetonitrile and aqueous solutions. PAA and Fast Black K modified glassy carbon electrodes exhibited a significant blocking behaviour for oxidation and reduction reactions of the Fe(CN)63-/4- redox system in aqueous and acetonitrile solutions. The study showed that the blocking effect increased which changes in time and concentration of diazonium salts in acetonitrile solution. Electrochemical impedance spectroscopy (EIS) measurements showed that the physical barrier of grafted layers prevent the access of Fe(CN)63-/4- to the underlying glassy carbon electrode. Therefore the RCT resistance increases during the modification treatment. The substituted phenyl layers are much more compact and less permeable in a nonaqueous solvent than with an aqueous solvent. Electrochemical impedance measurements indicate that the kinetics of electron transfer slow down when the time and the concentration used to modify the glassy carbon electrode increase. 4 refs., 1 fig.

Interim rock mass properties and conditions for analyses of a repository in crystalline rock

International Nuclear Information System (INIS)

Tammemagi, H.Y.; Chieslar, J.D.

1985-03-01

A summary of rock properties for generic crystalline rock is compiled from literature sources to provide the input data for analyses of a conceptual repository in crystalline rock. Frequency histograms, mean values and ranges of physical, mechanical, thermal, and thermomechanical properties, and the dependence of these properties on temperature are described. A description of the hydrogeologic properties of a crystalline rock mass and their dependence on depth is provided. In addition, the temperature gradients, mean annual surface temperature, and in situ stress conditions are summarized for the three regions of the United States currently under consideration to host a crystalline repository; i.e., the North Central, Northeastern, and Southeastern. Brief descriptions of the regional geology are also presented. Large-scale underground experiments in crystalline rock at Stripa, Sweden, and in Climax Stock in Nevada, are reviewed to assess whether the rock properties presented in this report are representative of in situ conditions. The suitability of each rock property and the sufficiency of its data base are described. 110 refs., 27 figs., 4 tabs

Understanding the Composition Dependence of the Fragility of AgI-Ag2O-MxOy Glassy Systems

International Nuclear Information System (INIS)

Aniya, M

2011-01-01

It has been reported that the fragility in the AgI-Ag 2 O-M x O y (M = B, Ge, P, Mo) system is determined by Ag 2 O-M x O y and does not depend on the amount of AgI. This is an interesting result and provides a hint to understand the nature of the glassy state of these materials. However, the origin of such behavior has not been sufficiently discussed. In the present report a model for the above behavior is presented. According to the model, the behavior arises from the solid like nature of the network formed by Ag 2 O-M x O y and the liquid like AgI which flow between the networks. The model is consistent with the structural model of superionic glasses proposed previously.

Oxygen transport as a structure probe for heterogeneous polymeric systems

Science.gov (United States)

Hu, Yushan

Although permeability of small molecules is often measured as an important performance property, deeper analysis of the transport characteristics provides insight into polymer structure, especially if used in combination with other characterization techniques. Transport of small gas molecules senses the permeable amorphous structure and probes the nature of free volume. This work focuses on oxygen transport, supplemented with other methods of physical analysis, as a probe for: (1) the nature of free volume and crystalline morphology in the crystallized glassy state, (2) the nature of free volume and hierarchical structure in liquid crystalline polymers, and (3) the role of dispersed polyamide phase geometry on oxygen barrier properties of poly(ethylene terephthalate) (PET)/polyamide blends. In the first part, the improvement in oxygen-barrier properties of glassy polyesters by crystallization was examined. Examples included poly(ethylene naphthalate) (PEN), and a copolymer based on PET in which 55 mol% terephthalate was replaced with 4,4'-bibenzoate. Explanation of the unexpectedly high solubility of crystallized PEN required a two-phase transport model consisting of an impermeable crystalline phase of constant density and a permeable amorphous phase of variable density. The resulting relationship between oxygen solubility and amorphous phase density was consistent with free volume concepts of gas sorption. In the second part, oxygen barrier properties of liquid crystalline (LC) polyesters based on poly(diethylene glycol 4,4'-bibenzoate) (PDEGBB) were studied. This study extended the 2-phase transport model for oxygen transport of non-LC crystalline polymers to a smectic LCP. It was possible to systematically vary the solid state structure of (PDEGBB) from LC glass to crystallized LC glass. The results were consistent with a liquid crystalline state intermediate between the permeable amorphous glass and the impermeable 3-dimensional crystal. In this interpretation

Statistics of energy levels and zero temperature dynamics for deterministic spin models with glassy behaviour

NARCIS (Netherlands)

Degli Esposti, M.; Giardinà, C.; Graffi, S.; Isola, S.

2001-01-01

We consider the zero-temperature dynamics for the infinite-range, non translation invariant one-dimensional spin model introduced by Marinari, Parisi and Ritort to generate glassy behaviour out of a deterministic interaction. It is argued that there can be a large number of metastable (i.e.,

Reactions and Interactions in Liquid Crystalline Media

Science.gov (United States)

1991-10-30

nematic lyophases of potassium laurate, myristyl tri methylammonium bromide or sodium decylsulfate with 1-decanol and 23 water. A strong retardation of the...crystalline polyacrylate crosslinked elastomers were synthesized. 198c 0 0 96 0 0 0O-(CH12 ) 2 -0O(k 97 Crosslinking, up to 10% of structural units produced...in their isotropic state and they work as the transporting phase for the azo-crown ether molecules. The permeation of K+ from a potassium p

Molecular reorientations in a substance with liquid-crystalline and plastic-crystalline phases

International Nuclear Information System (INIS)

Nguyen, Xuan Phuc.

1986-05-01

Results of dielectric relaxation (DR), quasielastic neutron scattering (QNS), far infrared absorption (FIR), proton magnetic resonance (PMR), differential scanning calorimetry (DSC) and preliminary X-ray diffraction measurements on the di-n-pentyloxyazoxybenzene (5.OAOB) are presented. The measurements carried out by all these methods showed that 5.OAOB exhibits a nontypical for liquid-crystalline materials phase diagram. It has two mesophases: a nematic (N) and an ''intermediate'' crystalline phase just below it. A complex interpretation of results obtained is given. All suggestions concerning the character of reorientational motions of the molecule as a whole as well as of its segments in mesomorphic phases are analyzed. From comparison of the DR and QNS studies one can conclude that in the N phase the molecule as a whole performs rotational diffusion around the long axis (τ DR ∼ 100 ps) and at the same time the two moieties perform faster independent reorientations around N - benzene rings bonds withτ QNS ∼ 5 ps. On the basis of various experimental data it is shown that the CrI phase is a plastic-crystalline phase for which the molecule and its segments perform fast stochastic unaxial reorientations. This is the first case where the existence of such a phase in liquid-crystalline materials has been experimentally confirmed. (author)

Neutron transmission through crystalline Fe

International Nuclear Information System (INIS)

Adib, M.; Habib, N.; Kilany, M.; El-Mesiry, M.S.

2004-01-01

The neutron transmission through crystalline Fe has been calculated for neutron energies in the range 10 4 < E<10 eV using an additive formula. The formula permits calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-section as a function of temperature and crystalline form. The obtained agreement between the calculated values and available experimental ones justifies the applicability of the used formula. A feasibility study on using poly-crystalline Fe as a cold neutron filter and a large Fe single crystal as a thermal one is given

Glass-forming ability and crystallization behavior of some binary and ternary Ni-based glassy alloys

International Nuclear Information System (INIS)

Louzguine-Luzgin, Dmitri V.; Louzguina-Luzgina, Larissa V.; Xie Guoqiang; Li Song; Zhang Wei; Inoue, Akihisa

2008-01-01

The purpose of the current paper is to study the influence of Ti, V, Nb, Al, Sn and Pd additions on the glass-forming ability, formation of a supercooled liquid region and a devitrification process of some Ni-Zr glassy alloys as well as to compare the results with those obtained for similar Cu-based alloys studied earlier. The Ni-based glassy alloys were investigated by using X-ray diffraction, differential scanning and isothermal calorimetries. Although the studied Ni-based alloys showed high values of the reduced glass-transition temperature of about 0.6, their glass-forming ability is quite low. This fact may be explained by low stability of the supercooled liquid against crystallization and formation of the equilibrium intermetallic compounds with a high growth rate compared to those observed in similar Cu-based alloys studied earlier. Relatively low thermal conductivity of Ni-based alloys is also found to be another factor limiting their glass-forming ability

Destruction-polymerization transformations as a source of radiation-induced extended defects in chalcogenide glassy semiconductors

International Nuclear Information System (INIS)

Shpotyuk, Oleh; Filipecki, Jacek; Shpotyuk, Mykhaylo

2013-01-01

Long-wave shift of the optical transmission spectrum in the region of fundamental optical absorption edge is registered for As 2 S 3 chalcogenide glassy semiconductors after γ-irradiation. This effect is explained in the frameworks of the destruction-polymerization transformations concept by accepting the switching of the heteropolar As-S covalent bonds into homopolar As-As ones. It is assumed that (As 4 + ; S 1 - ) defect pairs are created under such switching. Formula to calculate content of the induced defects in chalcogenide glassy semiconductors is proposed. It is assumed that defects concentration depends on energy of broken covalent bond, bond-switching energy balance, correlation energy, optical band-gap and energy of excitation light. It is shown that theoretically calculated maximally possible content of radiation-induced defects in As 2 S 3 is about 1.6% while concentration of native defects is negligible. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Amorphous and crystalline aerosol particles interacting with water vapor: conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations

Directory of Open Access Journals (Sweden)

T. Koop

2009-12-01

Full Text Available Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we present a conceptual framework for the interaction of amorphous aerosol particles with water vapor, outlining characteristic features and differences in comparison to crystalline particles. We used a hygroscopicity tandem differential mobility analyzer (H-TDMA to characterize the hydration and dehydration of crystalline ammonium sulfate, amorphous oxalic acid and amorphous levoglucosan particles (diameter ~100 nm, relative humidity 5–95% at 298 K. The experimental data and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following conclusions:

(1 Many organic substances, including carboxylic acids, carbohydrates and proteins, tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids.

(2 Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at lower relative humidity than their crystalline counterparts.

(3 In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supramolecular networks and undergo transitions between swollen and collapsed network structures.

(4 Organic gels or (semi-solid amorphous shells (glassy, rubbery, ultra-viscous with low molecular diffusivity can kinetically limit the uptake and release of water and may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN and ice nuclei (IN. Moreover, (semi-solid amorphous phases may influence the uptake of gaseous photo

Precise Ab-initio prediction of terahertz vibrational modes in crystalline systems

DEFF Research Database (Denmark)

Jepsen, Peter Uhd; Clark, Stewart J.

2007-01-01

We use a combination of experimental THz time-domain spectroscopy and ab-initio density functional perturbative theory to accurately predict the terahertz vibrational spectrum of molecules in the crystalline phase. Our calculations show that distinct vibrational modes found in solid-state materials...

Solute induced relaxation in glassy polymers: Experimental measurements and nonequilibrium thermodynamic model

International Nuclear Information System (INIS)

Minelli, Matteo; Doghieri, Ferruccio

2014-01-01

Data for kinetics of mass uptake from vapor sorption experiments in thin glassy polymer samples are here interpreted in terms of relaxation times for volume dilation. To this result, both models from non-equilibrium thermodynamics and from mechanics of volume relaxation contribute. Different kind of sorption experiments have been considered in order to facilitate the direct comparison between kinetics of solute induced volume dilation and corresponding data from process driven by pressure or temperature jumps

Structural aspects of fish skin collagen which forms ordered arrays via liquid crystalline states.

Science.gov (United States)

Giraud-Guille, M M; Besseau, L; Chopin, C; Durand, P; Herbage, D

2000-05-01

The ability of acid-soluble type I collagen extracts from Soleidae flat fish to form ordered arrays in condensed phases has been compared with data for calf skin collagen. Liquid crystalline assemblies in vitro are optimized by preliminary treatment of the molecular population with ultrasounds. This treatment requires the stability of the fish collagen triple helicity to be controlled by X-ray diffraction and differential scanning calorimetry and the effect of sonication to be evaluated by viscosity measurements and gel electrophoresis. The collagen solution in concentrations of at least 40 mg ml(-1) showed in polarized light microscopy birefringent patterns typical of precholesteric phases indicating long-range order within the fluid collagen phase. Ultrastructural data, obtained after stabilization of the liquid crystalline collagen into a gelated matrix, showed that neutralized acid-soluble fish collagen forms cross-striated fibrils, typical of type I collagen, following sine wave-like undulations in precholesteric domains. These ordered geometries, approximating in vivo situations, give interesting mechanical properties to the material.

The make up of crystalline bedrock - crystalline body and blocks

International Nuclear Information System (INIS)

Huber, M.; Huber, A.

1986-01-01

Statements of a geological nature can be made on the basis of investigations of the bedrock exposed in southern Black Forest and these can, in the form of prognoses, be applied to the crystalline Basement of northern Switzerland. Such statements relate to the average proportions of the main lithological groups at the bedrock surface and the surface area of the granite body. Some of the prognoses can be compared and checked with the results from the deep drilling programme in northern Switzerland. Further, analogical interferences from the situation in the southern Black Forest allow predictions to be made on the anticipated block structure of the crystalline Basement. (author)

Norepinephrine-modified glassy carbon electrode for the simultaneous determination of ascorbic acid and uric acid

International Nuclear Information System (INIS)

Zare, H.R.; Memarzadeh, F.; Ardakani, M. Mazloum; Namazian, M.; Golabi, S.M.

2005-01-01

The oxidation of norepinephrine (NE) on a preactivated glassy carbon electrode leads to the formation of a deposited layer of about 4.2 x 10 -10 mol cm -2 at the surface of the electrode. The electron transfer rate constant, k s , and charge transfer coefficient, α, for electron transfer between the electrode and immobilized NE film were calculated as 44 s -1 and 0.46, respectively. The NE-modified glassy carbon electrode exhibited good electrocatalytic properties towards ascorbic acid (AA) oxidation in phosphate buffer (pH 7.0) with an overpotential of about 475 mV lower than that of the bare electrode. The electrocatalytic response was evaluated by cyclic voltammetry, chronoamperometry, amperometry and rotating disk voltammetry. The overall number of electrons involved in the catalytic oxidation of AA and the number of electrons involved in the rate-determining step are 2 and 1, respectively. The rate constant for the catalytic oxidation of AA was evaluated by RDE voltammetry and an average value of k h was found to be 8.42 x 10 3 M -1 s -1 . Amperometric determination of AA in stirred solution exhibits a linear range of 2.0-1300.0 μM (correlation coefficient 0.9999) and a detection limit of 0.076 μM. The precision of amperometry was found to be 1.9% for replicate determination of a 49.0 μM solution of AA (n = 6). In differential pulse voltammetric measurements, the NE-modified glassy carbon electrode can separate the AA and uric acid (UA) signals. Ascorbic acid oxidizes at more negative potential than UA. Also, the simultaneous determination of UA and AA is achieved at the NE-modified electrode

Hard sphere-like glass transition in eye lens α-crystallin solutions.

Science.gov (United States)

Foffi, Giuseppe; Savin, Gabriela; Bucciarelli, Saskia; Dorsaz, Nicolas; Thurston, George M; Stradner, Anna; Schurtenberger, Peter

2014-11-25

We study the equilibrium liquid structure and dynamics of dilute and concentrated bovine eye lens α-crystallin solutions, using small-angle X-ray scattering, static and dynamic light scattering, viscometry, molecular dynamics simulations, and mode-coupling theory. We find that a polydisperse Percus-Yevick hard-sphere liquid-structure model accurately reproduces both static light scattering data and small-angle X-ray scattering liquid structure data from α-crystallin solutions over an extended range of protein concentrations up to 290 mg/mL or 49% vol fraction and up to ca. 330 mg/mL for static light scattering. The measured dynamic light scattering and viscosity properties are also consistent with those of hard-sphere colloids and show power laws characteristic of an approach toward a glass transition at α-crystallin volume fractions near 58%. Dynamic light scattering at a volume fraction beyond the glass transition indicates formation of an arrested state. We further perform event-driven molecular dynamics simulations of polydisperse hard-sphere systems and use mode-coupling theory to compare the measured dynamic power laws with those of hard-sphere models. The static and dynamic data, simulations, and analysis show that aqueous eye lens α-crystallin solutions exhibit a glass transition at high concentrations that is similar to those found in hard-sphere colloidal systems. The α-crystallin glass transition could have implications for the molecular basis of presbyopia and the kinetics of molecular change during cataractogenesis.

Design of a candidate vibrational signal for mating disruption against the glassy-winged sharpshooter, Homalodisca Vitripennis

Science.gov (United States)

The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is an important pest of grapevines due to its ability to transmit Xylella fastidiosa, the causal agent of Pierce’s disease. GWSS mating communication is based on vibrational signals; therefore, vibrational mating disruption could be an ...

Rationale for geological isolation of high-level radioactive waste, and assessment of the suitability of crystalline rocks

International Nuclear Information System (INIS)

Smedes, H.W.

1980-01-01

This report summarizes the disposal objective to be met and the requisite geotechnical criteria to meet that objective; evaluates our present ability to determine whether certain criteria can be met and to predict whether they will continue to be met; discusses the consequences of failure to meet certain criteria; assesses what is known about how crystalline rocks meet those criteria; lists important gaps in our knowledge that presently preclude final assessment of suitability; and suggests priority research to fill those gaps. The report presents an elaboration of the above-stated behavior and suitability of crystalline rocks, and a rationale of site-selection in support of the recommended prompt and intensive study of granite and other crystalline rocks as potentially highly suitable candidate media for radioactive waste disposal. An overview is presented on what the rocks are, where they are, and what the critical attributes are of various crystalline-rock terranes in the conterminous United States. This is intended to provide a basis to aid in selecting, first regions, and then sites within those regions, as candidate repository sites

Pengaruh Kecepatan Pendinginan Terhadap Perubahan Volume Leburan Polymer Crystalline dan Non-Crystalline

OpenAIRE

Fahrurrozi, Mohammad; Moristanto, Bagus Senowulung dan

2003-01-01

AbstractThe study was directed to develop a method to predict the influence of the rate of cooling to the degree of crystallittitv (DOC) and volume change of crystalline polymers. Crystalline polymer melts exhibit volume shrinkage on cooling below melting point due to crystallization. Crystallization and volunrc shrinkage will proceed with varies rate as long as the temperature is above the glass tansition temperatrre. DOC achieved by polymer is not only determined by the inherent crystallini...

In situ nanocalorimetry of thin glassy organic films

Science.gov (United States)

León-Gutierrez, E.; Garcia, G.; Lopeandía, A. F.; Fraxedas, J.; Clavaguera-Mora, M. T.; Rodríguez-Viejo, J.

2008-11-01

In this work, we describe the design and first experimental results of a new setup that combines evaporation of liquids in ultrahigh vacuum conditions with in situ high sensitivity thermal characterization of thin films. Organic compounds are deposited from the vapor directly onto a liquid nitrogen cooled substrate, permitting the preparation and characterization of glassy films. The substrate consists of a microfabricated, membrane-based nanocalorimeter that permits in situ measurements of heat capacity under ultrafast heating rates (up to 105 K/s) in the temperature range of 100-300 K. Three glass forming liquids—toluene, methanol, and acetic acid—are characterized. The spikes in heat capacity related to the glass-transition temperature, the fictive temperature and, in some cases, the onset temperature of crystallization are determined for several heating rates.

Crystalline Organic Pigment-Based Field-Effect Transistors.

Science.gov (United States)

Zhang, Haichang; Deng, Ruonan; Wang, Jing; Li, Xiang; Chen, Yu-Ming; Liu, Kewei; Taubert, Clinton J; Cheng, Stephen Z D; Zhu, Yu

2017-07-05

Three conjugated pigment molecules with fused hydrogen bonds, 3,7-diphenylpyrrolo[2,3-f]indole-2,6(1H,5H)-dione (BDP), (E)-6,6'-dibromo-[3,3'-biindolinylidene]-2,2'-dione (IIDG), and 3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo-[3,4-c]pyrrole-1,4-dione (TDPP), were studied in this work. The insoluble pigment molecules were functionalized with tert-butoxylcarbonyl (t-Boc) groups to form soluble pigment precursors (BDP-Boc, IIDG-Boc, and TDPP-Boc) with latent hydrogen bonding. The single crystals of soluble pigment precursors were obtained. Upon simple thermal annealing, the t-Boc groups were removed and the soluble pigment precursor molecules with latent hydrogen bonding were converted into the original pigment molecules with fused hydrogen bonding. Structural analysis indicated that the highly crystalline soluble precursors were directly converted into highly crystalline insoluble pigments, which are usually only achievable by gas-phase routes like physical vapor transport. The distinct crystal structure after the thermal annealing treatment suggests that fused hydrogen bonding is pivotal for the rearrangement of molecules to form a new crystal in solid state, which leads to over 2 orders of magnitude enhancement in charge mobility in organic field-effect transistor (OFET) devices. This work demonstrated that crystalline OFET devices with insoluble pigment molecules can be fabricated by their soluble precursors. The results indicated that a variety of commercially available conjugated pigments could be potential active materials for high-performance OFETs.

Effect of chain rigidity on network architecture and deformation behavior of glassy polymer networks

Science.gov (United States)

Knowles, Kyler Reser

Processing carbon fiber composite laminates creates molecular-level strains in the thermoset matrix upon curing and cooling which can lead to failures such as geometry deformations, micro-cracking, and other issues. It is known strain creation is attributed to the significant volume and physical state changes undergone by the polymer matrix throughout the curing process, though storage and relaxation of cure-induced strains remain poorly understood. This dissertation establishes two approaches to address the issue. The first establishes testing methods to simultaneously measure key volumetric properties of a carbon fiber composite laminate and its polymer matrix. The second approach considers the rigidity of the polymer matrix in regards to strain storage and relaxation mechanisms which ultimately control composite performance throughout manufacturing and use. Through the use of a non-contact, full-field strain measurement technique known as digital image correlation (DIC), we describe and implement useful experiments which quantify matrix and composite parameters necessary for simulation efforts and failure models. The methods are compared to more traditional techniques and show excellent correlation. Further, we established relationships which represent matrix-fiber compatibility in regards to critical processing constraints. The second approach involves a systematic study of epoxy-amine networks which are chemically-similar but differ in chain segment rigidity. Prior research has investigated the isomer effect of glassy polymers, showing sizeable differences in thermal, volumetric, physical, and mechanical properties. This work builds on these themes and shows the apparent isomer effect is rather an effect of chain rigidity. Indeed, it was found that structurally-dissimilar polymer networks exhibit very similar properties as a consequence of their shared average network rigidity. Differences in chain packing, as a consequence of chain rigidity, were shown to

Probing crystallinity of never-dried wood cellulose with Raman spectroscopy

Science.gov (United States)

Umesh P. Agarwal; Sally A. Ralph; Richard S. Reiner; Carlos Baez

2016-01-01

The structure of wood cell wall cellulose in its native state remains poorly understood, limiting the progress of research and development in numerous areas, including plant science, biofuels, and nanocellulose based materials. It is generally believed that cellulose in cell wall microfibrils has both crystalline and amorphous regions. However, there is evidence that...

Amorphous silicon crystalline silicon heterojunction solar cells

CERN Document Server

Fahrner, Wolfgang Rainer

2013-01-01

Amorphous Silicon/Crystalline Silicon Solar Cells deals with some typical properties of heterojunction solar cells, such as their history, the properties and the challenges of the cells, some important measurement tools, some simulation programs and a brief survey of the state of the art, aiming to provide an initial framework in this field and serve as a ready reference for all those interested in the subject. This book helps to "fill in the blanks" on heterojunction solar cells. Readers will receive a comprehensive overview of the principles, structures, processing techniques and the current developmental states of the devices. Prof. Dr. Wolfgang R. Fahrner is a professor at the University of Hagen, Germany and Nanchang University, China.

Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

International Nuclear Information System (INIS)

Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

2016-01-01

A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L −1 . The lower detection limits were found to be 0.02 μmol L −1 . The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

Energy Technology Data Exchange (ETDEWEB)

Afkhami, Abbas, E-mail: afkhami@basu.ac.ir; Bahiraei, Atousa; Madrakian, Tayyebeh

2016-02-01

A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L{sup −1}. The lower detection limits were found to be 0.02 μmol L{sup −1}. The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

In situ differential reflectance spectroscopy of thin crystalline films of PTCDA on different substrates

International Nuclear Information System (INIS)

Proehl, Holger; Nitsche, Robert; Dienel, Thomas; Leo, Karl; Fritz, Torsten

2005-01-01

We report an investigation of the excitonic properties of thin crystalline films of the archetypal organic semiconductor PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) grown on poly- and single crystalline surfaces. A sensitive setup capable of measuring the optical properties of ultrathin organic molecular crystals via differential reflectance spectroscopy (DRS) is presented. This tool allows to carry out measurements in situ, i.e., during the actual film growth, and over a wide spectral range, even on single crystalline surfaces with high symmetry or metallic surfaces, where widely used techniques like reflection anisotropy spectroscopy (RAS) or fluorescence excitation spectroscopy fail. The spectra obtained by DRS resemble mainly the absorption of the films if transparent substrates are used, which simplifies the analysis. In the case of mono- to multilayer films of PTCDA on single crystalline muscovite mica(0001) and Au(111) substrates, the formation of the solid state absorption from monomer to dimer and further to crystal-like absorption spectra can be monitored

Review of New Technology for Preparing Crystalline Silicon Solar Cell Materials by Metallurgical Method

Science.gov (United States)

Li, Man; Dai, Yongnian; Ma, Wenhui; Yang, Bin; Chu, Qingmei

2017-11-01

The goals of greatly reducing the photovoltaic power cost and making it less than that of thermal power to realize photovoltaic power grid parity without state subsidies are focused on in this paper. The research status, key technologies and development of the new technology for preparing crystalline silicon solar cell materials by metallurgical method at home and abroad are reviewed. The important effects of impurities and defects in crystalline silicon on its properties are analysed. The importance of new technology on reducing production costs and improving its quality to increase the cell conversion efficiency are emphasized. The previous research results show that the raw materials of crystalline silicon are extremely abundant. The product of crystalline silicon can meet the quality requirements of solar cell materials: Si ≥ 6 N, P 1 Ω cm, minority carrier life > 25 μs cell conversion efficiency of about 19.3%, the product costs energy consumption energy consumption, low carbon and sustainable development are prospected.

Liquid crystalline dihydroazulene photoswitches

DEFF Research Database (Denmark)

Petersen, Anne Ugleholdt; Jevric, Martyn; Mandle, Richard J.

2015-01-01

A large selection of photochromic dihydroazulene (DHA) molecules incorporating various substituents at position 2 of the DHA core was prepared and investigated for their ability to form liquid crystalline phases. Incorporation of an octyloxy-substituted biphenyl substituent resulted in nematic...... phase behavior and it was possible to convert one such compound partly into its vinylheptafulvene (VHF) isomer upon irradiation with light when in the liquid crystalline phase. This conversion resulted in an increase in the molecular alignment of the phase. In time, the meta-stable VHF returns...... to the DHA where the alignment is maintained. The systematic structural variation has revealed that a biaryl spacer between the DHA and the alkyl chain is needed for liquid crystallinity and that the one aromatic ring in the spacer cannot be substituted by a triazole. This work presents an important step...

Encoding Gaussian Curvature in Glassy and Elastomeric Liquid Crystal Solids (Postprint)

Science.gov (United States)

2016-05-04

attention to director fields of the form n = cosψ(x2) ê1 + sinψ(x2) ê2, whose alignment angle field varies only with respect to one of the...λ−2 − λ2ν)/L2 < 0. (Online version in colour .) For a fixed two-dimensional metric, the problem of identifying equilibrium configurations that...length of 10 mm. (b) Positive (left) and negative (right) Gaussian curvature in 15µm thick glassy LC solid film at 175◦C. (Online version in colour .) (b

Optical properties of crystalline semiconductors and dielectrics

International Nuclear Information System (INIS)

Forouhi, A.R.; Bloomer, I.

1988-01-01

A new formulation for the complex index of refraction, N(E) = n(E)-ik(E), as a function of photon energy E, for crystalline semiconductors and dielectrics is developed based on our previous derivation of N(E) for amorphous materials. The extinction coefficient k(E) is deduced from a one-electron model with finite lifetime for the excited electron state. The refractive index n(E) is then derived from the Kramers-Kronig relation as the Hilbert transform of k(E). It is shown that n(∞)>1. Excellent agreement is found between our equations for n(E) and k(E) and published measured values for crystalline Si, Ge, GaP, GaAs, GaSb, InP, InAs, InSb, SiC, cubic C, and α-SiO 2 , over a wide range of energies (∼0--20 eV). Far fewer parameters, all of which have physical significance, are required and they can be determined for a particular material from the position and strength of the peaks in the k spectrum

Trapped electron decay by the thermally-assisted tunnelling to electron acceptors in glassy matrices. A computer simulation study

International Nuclear Information System (INIS)

Feret, B.; Bartczak, W.M.; Kroh, J.

1991-01-01

The Redi-Hopefield quantum mechanical model of the thermally-assisted electron transfer has been applied to simulate the decay of trapped electrons by tunnelling to electron acceptor molecules added to the glassy matrix. It was assumed that the electron energy levels in donors and acceptors are statistically distributed and the electron excess energy after transfer is dissipated in the medium by the electron-phonon coupling. The electron decay curves were obtained by the method of computer simulation. It was found that for a given medium there exists a certain preferred value of the electronic excess energy which can be effectively converted into the matrix vibrations. If the mismatch of the electron states on the donor and acceptor coincides with the ''resonance'' energy the overall kinetics of electron transfer is accelerated. (author)

Cytochrome C Dynamics at Gold and Glassy Carbon Surfaces Monitored by in Situ Scanning Tunnel Microscopy

DEFF Research Database (Denmark)

Andersen, Jens Enevold Thaulov; Møller, Per; Pedersen, Marianne Vind

1995-01-01

We have investigated the absorption of cytochrome c on gold and glassy carbon substrates by in situ scanning tunnel microscopy under potentiostatic control of both substrate and tip. Low ionic strength and potential ranges where no Faradaic current flows were used. Cyt c aggregates into flat...

Effects of stoichiometry on the transport properties of crystalline phase-change materials.

Science.gov (United States)

Zhang, Wei; Wuttig, Matthias; Mazzarello, Riccardo

2015-09-03

It has recently been shown that a metal-insulator transition due to disorder occurs in the crystalline state of the GeSb2Te4 phase-change compound. The transition is triggered by the ordering of the vacancies upon thermal annealing. In this work, we investigate the localization properties of the electronic states in selected crystalline (GeTe)x-(Sb2Te3)y compounds with varying GeTe content by large-scale density functional theory simulations. In our models, we also include excess vacancies, which are needed to account for the large carrier concentrations determined experimentally. We show that the models containing a high concentration of stoichiometric vacancies possess states at the Fermi energy localized inside vacancy clusters, as occurs for GeSb2Te4. On the other hand, the GeTe-rich models display metallic behavior, which stems from two facts: a) the tail of localized states shrinks due to the low probability of having sizable vacancy clusters, b) the excess vacancies shift the Fermi energy to the region of extended states. Hence, a stoichiometry-controlled metal-insulator transition occurs. In addition, we show that the localization properties obtained by scalar-relativistic calculations with gradient-corrected functionals are unaffected by the inclusion of spin-orbit coupling or the use of hybrid functionals.

Femtosecond Study of Self-Trapped Vibrational Excitons in Crystalline Acetanilide

Science.gov (United States)

Edler, J.; Hamm, P.; Scott, A. C.

2002-02-01

Femtosecond IR spectroscopy of delocalized NH excitations of crystalline acetanilide confirms that self-trapping in hydrogen-bonded peptide units exists and does stabilize the excitation. Two phonons with frequencies of 48 and 76 cm -1 are identified as the major degrees of freedom that mediate self-trapping. After selective excitation of the free exciton, self-trapping occurs within a few 100 fs. Excitation of the self-trapped states disappears from the spectral window of this investigation on a 1 ps time scale, followed by a slow ground state recovery of the hot ground state within 18 ps.

Improved crystalline quality of AlN epitaxial layer on sapphire by introducing TMGa pulse flow into the nucleation stage

Science.gov (United States)

Wu, Hualong; Wang, Hailong; Chen, Yingda; Zhang, Lingxia; Chen, Zimin; Wu, Zhisheng; Wang, Gang; Jiang, Hao

2018-05-01

The crystalline quality of AlN epitaxial layers on sapphire substrates was improved by introducing trimethylgallium (TMGa) pulse flow into the growth of AlN nucleation layers. It was found that the density of both screw- and edge-type threading dislocations could be significantly reduced by introducing the TMGa pulse flow. With increasing TMGa pulse flow times, the lateral correlation length (i.e. the grain size) increases and the strain in the AlN epilayers changes from tensile state to compressive state. Unstrained AlN with the least dislocations and a smooth surface was obtained by introducing 2-times TMGa pulse flow. The crystalline improvement is attributed to enhanced lateral growth and improved crystalline orientation by the TMGa pulse flow.

Functionalization of glassy carbon surface by means of aliphatic and aromatic amino acids. An experimental and theoretical integrated approach

International Nuclear Information System (INIS)

Vanossi, Davide; Benassi, Rois; Parenti, Francesca; Tassinari, Francesco; Giovanardi, Roberto; Florini, Nicola; De Renzi, Valentina; Arnaud, Gaelle; Fontanesi, Claudio

2012-01-01

Highlights: ► Glassy carbon is functionalized via electrochemical assisted grafting of amino acids. ► The grafting mechanism is suggested to involve the “zwitterionic” species. ► DFT calculations allowed to determine the electroactive species. ► An original grafting mechanism is proposed. - Abstract: Glassy carbon (GC) electrode surfaces are functionalized through electrochemical assisted grafting, in oxidation regime, of six amino acids (AA): β-alanine (β-Ala), L-aspartic acid (Asp), 11-aminoundecanoic acid (UA), 4-aminobenzoic acid (PABA), 4-(4-amino-phenyl)-butyric acid (PFB), 3-(4-amino-phenyl)-propionic acid (PFP). Thus, a GC/AA interface is produced featuring carboxylic groups facing the solution. Electrochemical (cyclic voltammetry and electrochemical impedance spectroscopy) and XPS techniques are used to experimentally characterize the grafting process and the surface state. The theoretical results are compared with the experimental evidence to determine, at a molecular level, the overall grafting mechanism. Ionization potentials, standard oxidation potentials, HOMO and electron spin distributions are calculated at the CCD/6-31G* level of the theory. The comparison of experimental and theoretical data suggests that the main electroactive species is the “zwitterionic” form for the three aliphatic amino acids, while the amino acids featuring the amino group bound to the phenyl aromatic moiety show a different behaviour. The comparison between experimental and theoretical results suggests that both the neutral and the zwitterionic forms are present in the acetonitrile solution in the case of 4-(4-amino-phenyl)-butyric acid (PFB) and 3-(4-amino-phenyl)-propionic acid.

Resistivity and Passivity Characterization of Ni-Base Glassy Alloys in NaOH Media

Directory of Open Access Journals (Sweden)

Khadijah M. Emran

2018-01-01

Full Text Available Resistivity and passivation behavior of two Ni-base bulk metallic glasses, with the nominal composition of Ni70Cr21Si0.5B0.5P8C ≤ 0.1Co ≤ 1Fe ≤ 1 (VZ1 and Ni72.65Cr7.3-Si6.7B2.15C ≤ 0.06Fe8.2Mo3 (VZ2, in various concentrations of NaOH solutions were studied. The investigations involved cyclic polarization (CP, electrochemical impedance spectroscopy (EIS, and electrochemical frequency modulation (EFM methods. Cyclic polarization measurements showed spontaneous passivation for both Ni-base glassy alloys at all alkaline concentrations, due to the presence of chromium as an alloying element that formed an oxide film on the alloy surface. The EIS analysis showed that the passive layers grown on the two Ni-base glassy alloy surfaces are formed by a double oxide layer structure. Scanning electron microscope (SEM examinations of the electrode surface showed Cr, Ni, Fe, and O rich corrosion products that reduced the extent of corrosion damage. Atomic force microscopy (AFM imaging technique was used to evaluate the topographic and morphologic features of surface layers formed on the surface of the alloys.

Lateral topological crystalline insulator heterostructure

Science.gov (United States)

Sun, Qilong; Dai, Ying; Niu, Chengwang; Ma, Yandong; Wei, Wei; Yu, Lin; Huang, Baibiao

2017-06-01

The emergence of lateral heterostructures fabricated by two-dimensional building blocks brings many exciting realms in material science and device physics. Enriching available nanomaterials for creating such heterostructures and enabling the underlying new physics is highly coveted for the integration of next-generation devices. Here, we report a breakthrough in lateral heterostructure based on the monolayer square transition-metal dichalcogenides MX2 (M  =  W, X  =  S/Se) modules. Our results reveal that the MX2 lateral heterostructure (1S-MX2 LHS) can possess excellent thermal and dynamical stability. Remarkably, the highly desired two-dimensional topological crystalline insulator phase is confirmed by the calculated mirror Chern number {{n}\\text{M}}=-1 . A nontrivial band gap of 65 meV is obtained with SOC, indicating the potential for room-temperature observation and applications. The topologically protected edge states emerge at the edges of two different nanoribbons between the bulk band gap, which is consistent with the mirror Chern number. In addition, a strain-induced topological phase transition in 1S-MX2 LHS is also revealed, endowing the potential utilities in electronics and spintronics. Our predictions not only introduce new member and vitality into the studies of lateral heterostructures, but also highlight the promise of lateral heterostructure as appealing topological crystalline insulator platforms with excellent stability for future devices.

Electrochemical behavior of cysteine at a CuGeO3 nanowires modified glassy carbon electrode

International Nuclear Information System (INIS)

Dong Yongping; Pei Lizhai; Chu Xiangfeng; Zhang Wangbing; Zhang Qianfeng

2010-01-01

A CuGeO 3 nanowire modified glassy carbon electrode was fabricated and characterized by scanning electron microscopy. The results of electrochemical impedance spectroscopy reveal that electron transfer through nanowire film is facile compared with that of bare glassy carbon electrode. The modified electrode exhibited a novel electrocatalytic behavior to the electrochemical reactions of L-cysteine in neutral solution, which was not reported previously. Two pairs of semi-reversible electrochemical peaks were observed and assigned to the processes of oxidation/reduction and adsorption/desorption of cysteine at the modified electrode, respectively. The electrochemical response of cysteine is poor in alkaline condition and is enhanced greatly in acidic solution, suggesting that hydrogen ions participate in the electrochemical oxidation process of cysteine. The intensities of two anodic peaks varied linearly with the concentration of cysteine in the range of 1 x 10 -6 to 1 x 10 -3 mol L -1 , which make it possible to sensitive detection of cysteine with the CuGeO 3 nanowire modified electrode. Furthermore, the modified electrode exhibited good reproducibility and stability.

Elastic properties of Pd40Cu30Ni10P20 bulk glass in supercooled liquid region

DEFF Research Database (Denmark)

Nishiyama, N.; Inoue, A.; Jiang, Jianzhong

2001-01-01

In situ ultrasonic measurements for the Pd40Cu30Ni10P20 bulk glass in three states: Glassy solid, supercooled liquid, and crystalline, have been performed. It is found that velocities of both longitudinal and transverse waves and elastic moduli (shear modulus, bulk modulus, Young's modulus......, and Lame parameter), together with Debye temperature, gradually decrease with increasing temperature through the glass transition temperature as the Poisson's ratio increases. The behavior of the velocity of transverse wave vs. temperature in the supercooled liquid region could be explained by viscosity...

An interatomic potential for studying CuZr bulk metallic glasses

DEFF Research Database (Denmark)

Paduraru, Anca; Kenoufi, Abdel; Bailey, Nicholas

2007-01-01

-scale deformation events and may furthermore involve localization through formation of shear bands. In this paper, an Effective Medium Theory (EMT) potential optimized for modeling the mechanical and thermodynamic properties of CuZr bulk metallic glass is studied. The late transition metals crystallizing in close......The mechanical properties of BMGs are remarkably different from the ones of ordinary metallic alloys due to the atomic level disorder in the glassy state. Unlike crystalline materials plastic deformation in metallic glasses cannot be caused by lattice defects but takes place through atomic...

Bulk metallic glasses and high entropy alloys for reprocessing applications

International Nuclear Information System (INIS)

Kamachi Mudali, U.; Jayaraj, J.

2016-01-01

Recent breakthroughs in materials engineering have generated complex alloys that retain a glassy state in bulk form (bulk metallic glasses or BMGs) via ingot casting. High corrosion resistance is expected for BMGs (amorphous) as they are free from defects associated with the crystalline state such as grain boundaries, dislocations and stacking faults. Compared with conventional alloys containing one or two principal elements, the recently developed HEAs are usually composed of five or more elements with equimolar or near equimolar elemental fractions, which forms single solid solution phase. These HEAs exhibit excellent microstructural stability with better mechanical, wear and corrosion resistance properties as they are essentially single phase. Reprocessing of spent fuel from the fast breeder reactor involves the use of high concentration of (11.5 M) nitric acid under boiling conditions for the dissolution of the fuel. Conventional AISI type 304LSS and nitric acid grade 304L stainless steel would undergo inter-granular corrosion under these conditions and cannot be used for the fabrication of dissolver vessel. Currently titanium is used and zirconium alloys are proposed for future dissolver applications. Thus searching for newer materials with higher corrosion resistance suggests metallic glasses and HEAs for critical components of the dissolver application. Several Zr-based glassy alloys with different microstructural states and Ni-Nb based glassy alloys and TiZrHfNbTa HEA were cast and characterized for microstructure and corrosion resistance in nitric acid medium. From these studies, factors such as the corrosive environment (nitric acid, chloride and fluoride), and the presence of passivating elements in the alloy were emphasized for better corrosion resistance of BMGs and HEA. Attempts were also made to prepare coatings of Zr-and Ni-based glassy alloys on 304LSS by laser based deposition technique and their corrosion properties were evaluated. (author)

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

Directory of Open Access Journals (Sweden)

M. S. Conconi

2014-12-01

Full Text Available The firing transformations of traditional (clay based ceramics are of technological and archeological interest, and are usually reported qualitatively or semiquantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite, the low crystalline (metakaolinite and/or spinel type pre-mullite and glassy phases evolution of a triaxial (clay-quartz-feldspar ceramic fired in a wide temperature range between 900 and 1300 ºC. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 ºC spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

International Nuclear Information System (INIS)

Conconi, M.S.; Gauna, M.R.; Serra, M.F.; Suarez, G.; Aglietti, E.F.; Rendtorff, N.M.

2014-01-01

The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

Energy Technology Data Exchange (ETDEWEB)

Conconi, M.S.; Gauna, M.R.; Serra, M.F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC), Buenos Aires (Argentina); Suarez, G.; Aglietti, E.F.; Rendtorff, N.M., E-mail: rendtorff@cetmic.unlp.edu.ar [Universidad Nacional de La Plata (UNLP), Buenos Aires (Argentina). Fac. de Ciencias Exactas. Dept. de Quimica

2014-10-15

The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

Effects of Xylem-Sap Composition on Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Egg Maturation on High- and Low-Quality Host Plants.

Science.gov (United States)

Sisterson, Mark S; Wallis, Christopher M; Stenger, Drake C

2017-04-01

Glassy-winged sharpshooters must feed as adults to produce mature eggs. Cowpea and sunflower are both readily accepted by the glassy-winged sharpshooter for feeding, but egg production on sunflower was reported to be lower than egg production on cowpea. To better understand the role of adult diet in egg production, effects of xylem-sap chemistry on glassy-winged sharpshooter egg maturation was compared for females confined to cowpea and sunflower. Females confined to cowpea consumed more xylem-sap than females held on sunflower. In response, females held on cowpea produced more eggs, had heavier bodies, and greater lipid content than females held on sunflower. Analysis of cowpea and sunflower xylem-sap found that 17 of 19 amino acids were more concentrated in cowpea xylem-sap than in sunflower xylem-sap. Thus, decreased consumption of sunflower xylem-sap was likely owing to perceived lower quality, with decreased egg production owing to a combination of decreased feeding and lower return per unit volume of xylem-sap consumed. Examination of pairwise correlation coefficients among amino acids indicated that concentrations of several amino acids within a plant species were correlated. Principal component analyses identified latent variables describing amino acid composition of xylem-sap. For females held on cowpea, egg maturation was affected by test date, volume of excreta produced, and principal components describing amino acid composition of xylem-sap. Principal component analyses aided in identifying amino acids that were positively or negatively associated with egg production, although determining causality with respect to key nutritional requirements for glassy-winged sharpshooter egg production will require additional testing. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

Electrochemical evaluation and determination of antiretroviral drug fosamprenavir using boron-doped diamond and glassy carbon electrodes.

Science.gov (United States)

Gumustas, Mehmet; Ozkan, Sibel A

2010-05-01

Fosamprenavir is a pro-drug of the antiretroviral protease inhibitor amprenavir and is oxidizable at solid electrodes. The anodic oxidation behavior of fosamprenavir was investigated using cyclic and linear sweep voltammetry at boron-doped diamond and glassy carbon electrodes. In cyclic voltammetry, depending on pH values, fosamprenavir showed one sharp irreversible oxidation peak or wave depending on the working electrode. The mechanism of the oxidation process was discussed. The voltammetric study of some model compounds allowed elucidation of the possible oxidation mechanism of fosamprenavir. The aim of this study was to determine fosamprenavir levels in pharmaceutical formulations and biological samples by means of electrochemical methods. Using the sharp oxidation response, two voltammetric methods were described for the determination of fosamprenavir by differential pulse and square-wave voltammetry at the boron-doped diamond and glassy carbon electrodes. These two voltammetric techniques are 0.1 M H(2)SO(4) and phosphate buffer at pH 2.0 which allow quantitation over a 4 x 10(-6) to 8 x 10(-5) M range using boron-doped diamond and a 1 x 10(-5) to 1 x 10(-4) M range using glassy carbon electrodes, respectively, in supporting electrolyte. All necessary validation parameters were investigated and calculated. These methods were successfully applied for the analysis of fosamprenavir pharmaceutical dosage forms, human serum and urine samples. The standard addition method was used in biological media using boron-doped diamond electrode. No electroactive interferences from the tablet excipients or endogenous substances from biological material were found. The results were statistically compared with those obtained through an established HPLC-UV technique; no significant differences were found between the voltammetric and HPLC methods.

Role of transport band edge variation on delocalized charge transport in high-mobility crystalline organic semiconductors

Science.gov (United States)

Kadashchuk, Andrey; Tong, Fei; Janneck, Robby; Fishchuk, Ivan I.; Mityashin, Alexander; Pavlica, Egon; Köhler, Anna; Heremans, Paul; Rolin, Cedric; Bratina, Gvido; Genoe, Jan

2017-09-01

We demonstrate that the degree of charge delocalization has a strong impact on polarization energy and thereby on the position of the transport band edge in organic semiconductors. This gives rise to long-range potential fluctuations, which govern the electronic transport through delocalized states in organic crystalline layers. This concept is employed to formulate an analytic model that explains a negative field dependence coupled with a positive temperature dependence of the charge mobility observed by a lateral time-of-flight technique in a high-mobility crystalline organic layer. This has important implications for the further understanding of the charge transport via delocalized states in organic semiconductors.

neutron transmission through crystalline materials

International Nuclear Information System (INIS)

El Mesiry, M.S.

2011-01-01

The aim of the present work is to study the neutron transmission through crystalline materials. Therefore a study of pyrolytic graphite (PG) as a highly efficient selective thermal neutron filter and Iron single crystal as a whole one, as well as the applicability of using their polycrystalline powders as a selective cold neutron filters is given. Moreover, the use of PG and iron single crystal as an efficient neutron monochromator is also investigated. An additive formula is given which allows calculating the contribution of the total neutron cross-section including the Bragg scattering from different )(hkl planes to the neutron transmission through crystalline iron and graphite. The formula takes into account their crystalline form. A computer CFe program was developed in order to provide the required calculations for both poly- and single-crystalline iron. The validity of the CFe program was approved from the comparison of the calculated iron cross-section data with the available experimental ones. The CFe program was also adapted to calculate the reflectivity from iron single crystal when it used as a neutron monochromator The computer package GRAPHITE, developed in Neutron Physics laboratory, Nuclear Research Center, has been used in order to provide the required calculations for crystalline graphite in the neutron energy range from 0.1 meV to 10 eV. A Mono-PG code was added to the computer package GRAPHITE in order to calculate the reflectivity from PG crystal when it used as a neutron monochromator.

Fine crystalline powders. Analysis of scientific and technical literature

International Nuclear Information System (INIS)

Denisenko, Eh.T.; Kulik, O.P.; Eremina, T.V.

1983-01-01

The state of development and studies of fine crystalline powders for recent five years is reviewed in the paper. Based on data available in literature, the most significant methods for fine metal and alloy powder production are considered and physicochemical properties of ultrafine particles are discussed from the standpoint of their interrelation with promising techniques for powder production. It is stated that the most important feature of ultrafine powder production technique at the present stage is a transition from the stage of data accumulation to that of controlled production of ultrafine structures of various metals and alloys under controllable conditions

Non-Gaussian nature of glassy dynamics by cage to cage motion

International Nuclear Information System (INIS)

Vorselaars, Bart; Lyulin, Alexey V.; Michels, M. A. J.; Karatasos, K.

2007-01-01

A model based on a single Brownian particle moving in a periodic effective field is used to understand the non-Gaussian dynamics in glassy systems of cage escape and subsequent recaging, often thought to be caused by a heterogeneous glass structure. The results are compared to molecular-dynamics simulations of systems with varying complexity: quasi-two-dimensional colloidlike particles, atactic polystyrene, and a dendritic glass. The model nicely describes generic features of all three topologically different systems, in particular around the maximum of the non-Gaussian parameter. This maximum is a measure for the average distance between cages

In-Vivo Characterization of Glassy Carbon Micro-Electrode Arrays for Neural Applications and Histological Analysis of the Brain Tissue

Science.gov (United States)

Vomero, Maria

The aim of this work is to fabricate and characterize glassy carbon Microelectrode Arrays (MEAs) for sensing and stimulating neural activity, and conduct histological analysis of the brain tissue after the implant to determine long-term performance. Neural applications often require robust electrical and electrochemical response over a long period of time, and for those applications we propose to replace the commonly used noble metals like platinum, gold and iridium with glassy carbon. We submit that such material has the potential to improve the performances of traditional neural prostheses, thanks to better charge transfer capabilities and higher electrochemical stability. Great interest and attention is given in this work, in particular, to the investigation of tissue response after several weeks of implants in rodents' brain motor cortex and the associated materials degradation. As part of this work, a new set of devices for Electrocorticography (ECoG) has been designed and fabricated to improve durability and quality of the previous generation of devices, designed and manufactured by the same research group in 2014. In-vivo long-term impedance measurements and brain activity recordings were performed to test the functionality of the neural devices. In-vitro electrical characterization of the carbon electrodes, as well as the study of the adhesion mechanisms between glassy carbon and different substrates is also part of the research described in this book.

Bio-based liquid crystalline polyesters

Science.gov (United States)

Wilsens, Carolus; Rastogi, Sanjay; Dutch Collaboration

2013-03-01

The reported thin-film polymerization has been used as a screening method in order to find bio-based liquid crystalline polyesters with convenient melting temperatures for melt-processing purposes. An in depth study of the structural, morphological and chemical changes occurring during the ongoing polycondensation reactions of these polymers have been performed. Structural and conformational changes during polymerization for different compositions have been followed by time resolved X-ray and Infrared spectroscopy. In this study, bio-based monomers such as vanillic acid and 2,5-furandicarboxylic acid are successfully incorporated in liquid crystalline polyesters and it is shown that bio-based liquid crystalline polymers with high aromatic content and convenient processing temperatures can be synthesized. Special thanks to the Dutch Polymer Institute for financial support

Crystallinity in starch plastics: consequences for material properties

NARCIS (Netherlands)

Soest, van J.J.G.; Vliegenthart, J.F.G.

1997-01-01

The processing of starches with biodegradable additives has made biodegradable plastics suitable for a number of applications. Starch plastics are partially crystalline as a result of residual crystallinity and the recrystallization of amylose and amylopectin. Such crystallinity is a key determinant

Technology needs for selecting and evaluating high-level waste repository sites in crystalline rock

International Nuclear Information System (INIS)

1988-12-01

This report describes properties and processes that govern the performance of the geological barrier in a nuclear waste isolation system in crystalline rock and the state-of-the-art in the understanding of these properties and processes. Areas and topics that require further research and development as well as technology needs for investigating and selecting repository sites are presented. Experiences from the Swedish site selection program are discussed, and a general investigation strategy is presented for an area characterization phase of an exploratory program in crystalline rocks. 255 refs., 65 figs., 10 tabs

Magnetocaloric effect of polycrystalline Sm0.5Ca0.5MnO3 compound: Investigation of low temperature magnetic state

Science.gov (United States)

Das, Kalipada; Banu, Nasrin; Das, I.; Dev, B. N.

2018-06-01

An attempt has been made to probe low temperature magnetic state of the polycrystalline Sm0.5Ca0.5MnO3 compound via magnetization and magnetocaloric studies. In the context of the earlier debatable reports on the above mentioned compound between the existence of glassy magnetic state and small ferromagnetic domains from the 'ac' susceptibility measurements, our experimental observation from magnetocaloric effect study clearly indicates the existence of ferromagnetic droplets along with certain amount of superparamagnetic component at low temperature (magnetization (even at H = 0.01 T) data do not exhibit the spin freezing nature at the low temperature which is almost a generic tendency of glassy magnetic state. Our study also highlights the competence of magnetocaloric effect as a tool to distinguish between different magnetic states of a compound.

A nanoscale characterisation of extended defects in glassy-like As{sub 2}Se{sub 3} semiconductors with PAL technique

Energy Technology Data Exchange (ETDEWEB)

Shpotyuk, O.; Kovalskiy, A.; Filipecki, J.; Hyla, M.; Kozdras, A

2003-12-31

A meaningful interpretation of positron lifetime characteristics for glassy-like g-As{sub 2}Se{sub 3} is developed taking into account calculations of Jensen et al. (J. Non-Cryst. Solids 170 (1994) 57) for positrons trapped by free-volume extended defects in orthorhombic As{sub 2}Se{sub 3} and void volume distribution for 146-atoms layer-biased model of amorphous As{sub 2}Se{sub 3} presented by Popescu (J. Non-Cryst. Solids 35-36 (1980) 549). The obtained results are compared for samples having different thermal pre-history. Two groups of experimental results with close lifetime characteristics are distinguished for each of the investigated samples. This feature is explained in terms of average positron lifetime by applying two-state positron trapping model for mathematical treatment of the obtained spectra.

Concentration and electrode material dependence of the voltammetric response of iodide on platinum, glassy carbon and boron-doped diamond in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide

International Nuclear Information System (INIS)

Bentley, Cameron L.; Bond, Alan M.; Hollenkamp, Anthony F.; Mahon, Peter J.; Zhang, Jie

2013-01-01

The electro-oxidation of iodide has been investigated as a function of concentration using steady-state microelectrode voltammetry, transient cyclic voltammetry and linear-sweep semi-integral voltammetry on platinum, glassy carbon and boron-doped diamond electrodes in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. Two oxidation processes are observed on all of the investigated electrode materials, with the first being assigned to the oxidation of iodide to triiodide (confirmed by UV/visible spectroscopy) and the second being attributed to the oxidation of triiodide to iodine. Iodide oxidation is kinetically more facile on platinum compared to glassy carbon or boron-doped diamond. At elevated bulk iodide concentrations, the nucleation and growth of sparingly soluble electrogenerated iodine at the electrode surface was observed and imaged in situ using optical microscopy. The diffusion coefficient of iodide was determined to be 2.59 (±0.04) × 10 −7 cm 2 s −1 and independent of the bulk concentration of iodide. The steady-state iodide oxidation current measured at a platinum microelectrode was found to be a linear function of iodide concentration, as expected if there are no contributions from non-Stokesian mass-transport processes (electron hopping and/or Grotthuss-type exchange) under the investigated conditions

Groundwater quality in the Piedmont and Blue Ridge crystalline-rock aquifers, eastern United States

Science.gov (United States)

Lindsey, Bruce

2017-12-07

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Piedmont and Blue Ridge crystalline-rock aquifers constitute one of the important areas being evaluated.

Voltammetric behavior of sedative drug midazolam at glassy carbon electrode in solubilized systems

OpenAIRE

Jain, Rajeev; Yadav, Rajeev Kumar

2012-01-01

Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems, supporting electrolytes and pH using differential pulse, square-wave and cyclic voltammetry. Based on its reduction behavior, a direct differential pulse voltammetric method has been developed and validated for the determination of midazolam in parenteral dosage. Three well-defined peaks were observed in 0.1% SLS, BrittonâRobinson (BR) buffer of pH 2.5. The effect of surfactants like sodium lauryl ...

Voltammetric behavior of sedative drug midazolam at glassy carbon electrode in solubilized systems

OpenAIRE

Jain, Rajeev; Yadav, Rajeev Kumar

2011-01-01

Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems, supporting electrolytes and pH using differential pulse, square-wave and cyclic voltammetry. Based on its reduction behavior, a direct differential pulse voltammetric method has been developed and validated for the determination of midazolam in parenteral dosage. Three well-defined peaks were observed in 0.1% SLS, Britton–Robinson (BR) buffer of pH 2.5. The effect of surfactants like sodium lauryl ...

Equation of State and Damage in Polyethylene

Energy Technology Data Exchange (ETDEWEB)

Coe, Joshua Damon [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Brown, Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Cady, Carl Mcelhinney [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carlson, Carl A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Clements, Bradford Edwin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dattelbaum, Dana Mcgraw [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Fezzaa, K. [Argonne National Lab. (ANL), Argonne, IL (United States); Gustavsen, Richard L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hooks, Daniel Edwin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Iverson, Adam Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Jensen, Brian J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Jordan, Jennifer Lynn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Jones, David Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Junghans, Sylvia Ann [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lang, John Michael Jr. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); LeBrun, Thomas John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lewis, Matthew W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Maerzke, Katie A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Pierce, Timothy Henry [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramos, Kyle James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rigg, Paulo [Washington State Univ., Pullman, WA (United States); Schilling, Benjamin Fritz [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sinclair, N. [Washington State Univ., Pullman, WA (United States); Stull, Jamie Ann [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Watkins, Erik Benjamin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Welch, Cynthia F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Welch, Paul Michael Jr. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-10-10

The dynamic response of polymers differs significantly from those of metals, upon which many of the National Laboratories' deformation, damage, and failure models are based. Their moduli, yield strength, and damage characteristics are highly strain rate-, temperature-, and phase-dependent, requiring models that encompass a wide range of phenomena including some not in equilibrium. Recently, Los Alamos developed the Glassy Amorphous Polymer (GAP)¹ model [1] to address limitations in existing models of polymer deformation. GAP captures both volumetric (equation of state) and deviatoric (shear) response, including a non-equilibrium component to the former (a feature determined to be crucial in capturing the low-pressure, viscoelastic response to impact loading). GAP has already been applied to polymers such as PMMA, PTFE, epoxy, and Kel-F 800, but with an emphasis on impact response as opposed to damage or failure. The current effort was launched to address this gap in predictive capability. For reasons that will be made clear, semi-crystalline polyethylene (PE) was chosen to serve as a model system for parameterization and validation. PE (-C₂H_4-)n is one of the most widely used polymers in industrial and engineering contexts, chiey due to the versatility of its mechanical response. This response can be tuned through network and chain structure, degree of crystallinity, and molecular weight. PE is found in several forms including low density (LDPE), high density (HDPE), and ultra-high molecular weight (UHMWPE). The focus here was on HDPE and UHMWPE, of pedigree described in the following section. Materials were well-characterized prior to study and are representative of semi-crystalline polymers of interest to DOE and DoD. Semi-crystalline PE undergoes a glass transition at low temperature (-35°C) and melts across a range of moderate temperatures (~80-180°C), depending on its structure. It is typically inert chemically, has low

Superacid Passivation of Crystalline Silicon Surfaces.

Science.gov (United States)

Bullock, James; Kiriya, Daisuke; Grant, Nicholas; Azcatl, Angelica; Hettick, Mark; Kho, Teng; Phang, Pheng; Sio, Hang C; Yan, Di; Macdonald, Daniel; Quevedo-Lopez, Manuel A; Wallace, Robert M; Cuevas, Andres; Javey, Ali

2016-09-14

The reduction of parasitic recombination processes commonly occurring within the silicon crystal and at its surfaces is of primary importance in crystalline silicon devices, particularly in photovoltaics. Here we explore a simple, room temperature treatment, involving a nonaqueous solution of the superacid bis(trifluoromethane)sulfonimide, to temporarily deactivate recombination centers at the surface. We show that this treatment leads to a significant enhancement in optoelectronic properties of the silicon wafer, attaining a level of surface passivation in line with state-of-the-art dielectric passivation films. Finally, we demonstrate its advantage as a bulk lifetime and process cleanliness monitor, establishing its compatibility with large area photoluminescence imaging in the process.

Nanoscale crystallinity modulates cell proliferation on plasma sprayed surfaces

Energy Technology Data Exchange (ETDEWEB)

Smith, Alan M. [School of Applied Sciences, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom); Paxton, Jennifer Z.; Hung, Yi-Pei; Hadley, Martin J.; Bowen, James; Williams, Richard L. [School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT (United Kingdom); Grover, Liam M., E-mail: l.m.grover@bham.ac.uk [School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT (United Kingdom)

2015-03-01

Calcium phosphate coatings have been applied to the surface of metallic prostheses to mediate hard and soft tissue attachment for more than 40 years. Most coatings are formed of high purity hydroxyapatite, and coating methods are often designed to produce highly crystalline surfaces. It is likely however, that coatings of lower crystallinity can facilitate more rapid tissue attachment since the surface will exhibit a higher specific surface area and will be considerably more reactive than a comparable highly crystalline surface. Here we test this hypothesis by growing a population of MC3T3 osteoblast-like cells on the surface of two types of hip prosthesis with similar composition, but with differing crystallinity. The surfaces with lower crystallinity facilitated more rapid cell attachment and increased proliferation rate, despite having a less heterogeneous surface topography. This work highlights that the influence of the crystallinity of HA at the nano-scale is dominant over macro-scale topography for cell adhesion and growth. Furthermore, crystallinity could be easily adjusted by without compromising coating purity. These findings could facilitate designing novel coated calcium phosphate surfaces that more rapidly bond tissue following implantation. - Highlights: • Crystallinity of HA at the nano-scale was dominant over macro-scale topography. • Lower crystallinity caused rapid cell attachment and proliferation rate. • Crystallinity could be easily adjusted by without compromising coating purity.

Nanoscale crystallinity modulates cell proliferation on plasma sprayed surfaces

International Nuclear Information System (INIS)

Smith, Alan M.; Paxton, Jennifer Z.; Hung, Yi-Pei; Hadley, Martin J.; Bowen, James; Williams, Richard L.; Grover, Liam M.

2015-01-01

Calcium phosphate coatings have been applied to the surface of metallic prostheses to mediate hard and soft tissue attachment for more than 40 years. Most coatings are formed of high purity hydroxyapatite, and coating methods are often designed to produce highly crystalline surfaces. It is likely however, that coatings of lower crystallinity can facilitate more rapid tissue attachment since the surface will exhibit a higher specific surface area and will be considerably more reactive than a comparable highly crystalline surface. Here we test this hypothesis by growing a population of MC3T3 osteoblast-like cells on the surface of two types of hip prosthesis with similar composition, but with differing crystallinity. The surfaces with lower crystallinity facilitated more rapid cell attachment and increased proliferation rate, despite having a less heterogeneous surface topography. This work highlights that the influence of the crystallinity of HA at the nano-scale is dominant over macro-scale topography for cell adhesion and growth. Furthermore, crystallinity could be easily adjusted by without compromising coating purity. These findings could facilitate designing novel coated calcium phosphate surfaces that more rapidly bond tissue following implantation. - Highlights: • Crystallinity of HA at the nano-scale was dominant over macro-scale topography. • Lower crystallinity caused rapid cell attachment and proliferation rate. • Crystallinity could be easily adjusted by without compromising coating purity

Local structure and influence of bonding on the phase-change behavior of the chalcogenide compounds K{sub 1-} {sub x} Rb {sub x} Sb{sub 5}S{sub 8}

Energy Technology Data Exchange (ETDEWEB)

Wachter, J B [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Chrissafis, K [Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Petkov, V [Department of Physics, Central Michigan University, Mount Pleasant, MI 48859 (United States); Malliakas, C D [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Bilc, D [Department of Physics, Central Michigan University, Mount Pleasant, MI 48859 (United States); Kyratsi, Th [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Paraskevopoulos, K M [Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Mahanti, S D [Department of Physics, Michigan State University, East Lansing, MI 48824 (United States); Torbruegge, T [Institut fuer Physikalische Chemie, Westf. Wilhelms-Universitaet Muenster (Germany); Eckert, H [Institut fuer Physikalische Chemie, Westf. Wilhelms-Universitaet Muenster (Germany); Kanatzidis, M.G. [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States)], E-mail: m-kanatzidis@northwestern.edu

2007-02-15

KSb{sub 5}S{sub 8} and its solid solution analogs with Rb and Tl were found to exhibit a reversible and tunable glass{sup {yields}}crystal{sup {yields}}glass phase transition. Selected members of this series were analyzed by differential scanning calorimetry to measure the effect of the substitution on the thermal properties. The solid solutions K{sub 1-} {sub x} Rb {sub x} Sb{sub 5}S{sub 8} exhibited clear deviations in melting and crystallization behavior and temperatures from the parent structure. The crystallization process of the glassy KSb{sub 5}S{sub 8} as a function of temperature could clearly be followed with Raman spectroscopy. The thermal conductivity of both glassy and crystalline KSb{sub 5}S{sub 8} at room temperature is {approx}0.40 W/m K, among the lowest known values for any dense solid-state material. Electronic band structure calculations carried out on KSb{sub 5}S{sub 8} and TlSb{sub 5}S{sub 8} show the presence of large indirect band-gaps and confirm the coexistence of covalent Sb-S bonding and predominantly ionic K(Tl)...S bonding. Pair distribution function analyses based on total X-ray scattering data on both crystalline and glassy K{sub 1-} {sub x} Rb {sub x} Sb{sub 5}S{sub 8} showed that the basic structure-defining unit is the same and it involves a distorted polyhedron of 'SbS{sub 7}' fragment of {approx}7 A diameter. The similarity of local structure between the glassy and crystalline phases accounts for the facile crystallization rate in this system. - Graphical abstract: The KSb{sub 5}S{sub 8} is a good example of a phase-change material with a mixed ionic/covalent bonding. The members of the K{sub 1-} {sub x} Rb {sub x} Sb{sub 5}S{sub 8} series exhibit phase-change properties with greater glass forming ability (GFA) than KSb{sub 5}S{sub 8}. The GFA increases with increasing Rb content. In this case, the random alloy disorder in the alkali metal sublattice seems to predominate over the increased degree of ionicity in going from K

Water-Protein Hydrogen Exchange in the Micro-Crystalline Protein Crh as Observed by Solid State NMR Spectroscopy

International Nuclear Information System (INIS)

Boeckmann, Anja; Juy, Michel; Bettler, Emmanuel; Emsley, Lyndon; Galinier, Anne; Penin, Francois; Lesage, Anne

2005-01-01

We report site-resolved observation of hydrogen exchange in the micro-crystalline protein Crh. Our approach is based on the use of proton T 2 ' -selective 1 H- 13 C- 13 C correlation spectra for site-specific assignments of carbons nearby labile protein protons. We compare the proton T 2 ' selective scheme to frequency selective water observation in deuterated proteins, and discuss the impacts of deuteration on 13 C linewidths in Crh. We observe that in micro-crystalline proteins, solvent accessible hydroxyl and amino protons show comparable exchange rates with water protons as for proteins in solution, and that structural constraints, such as hydrogen bonding or solvent accessibility, more significantly reduce exchange rates

Liquid crystalline order of carbon nanotubes

Science.gov (United States)

Georgiev, Georgi; Ahlawat, Aditya; Mulkern, Brian; Doyle, Robert; Mongeau, Jennifer; Ogilvie, Alex

2007-03-01

Topological defects formed during phase transitions in liquid crystals provide a direct proof of the standard Cosmological model and are direct links to the Early Universe. On the other hand in Nanotechnology, carbon nanotubes can be manipulated and oriented directly by changing the liquid crystalline state of the nanotubes, in combination with organic liquid crystals. Currently there are no nano-assemblers, which makes the liquid crystal state of the nanotubes, one of the few ways of controlling them. We show the design of a fast and efficient polarized light ellipsometric system (a new modification of previous optical systems) that can provide fast quantitative real time measurements in two dimensions of the formation of topological defects in liquid crystals during phase transitions in lab settings. Our aim is to provide fundamental information about the formation of optically anisotropic structures in liquid crystals and the orientation of carbon nanotubes in electric field.

Mechanical dispersion in fractured crystalline rock systems

International Nuclear Information System (INIS)

Lafleur, D.W.; Raven, K.G.

1986-12-01

This report compiles and evaluates the hydrogeologic parameters describing the flow of groundwater and transport of solutes in fractured crystalline rocks. This report describes the processes of mechanical dispersion in fractured crystalline rocks, and compiles and evaluates the dispersion parameters determined from both laboratory and field tracer experiments. The compiled data show that extrapolation of the reliable test results performed over intermediate scales (10's of m and 10's to 100's of hours) to larger spatial and temporal scales required for performance assessment of a nuclear waste repository in crystalline rock is not justified. The reliable measures of longitudinal dispersivity of fractured crystalline rock are found to range between 0.4 and 7.8 m

Crystallinity and mechanical effects from annealing Parylene thin films

Energy Technology Data Exchange (ETDEWEB)

Jackson, Nathan, E-mail: Nathan.Jackson@tyndall.ie [Tyndall National Institute, University College Cork, Cork (Ireland); Stam, Frank; O' Brien, Joe [Tyndall National Institute, University College Cork, Cork (Ireland); Kailas, Lekshmi [University of Limerick, Limerick (Ireland); Mathewson, Alan; O' Murchu, Cian [Tyndall National Institute, University College Cork, Cork (Ireland)

2016-03-31

Parylene is commonly used as thin film polymer for MEMS devices and smart materials. This paper investigates the impact on bulk properties due to annealing various types of Parylene films. A thin film of Parylene N, C and a hybrid material consisting of Parylene N and C were deposited using a standard Gorham process. The thin film samples were annealed at varying temperatures from room temperature up to 300 °C. The films were analyzed to determine the mechanical and crystallinity effects due to different annealing temperatures. The results demonstrate that the percentage of crystallinity and the full-width-half-maximum value on the 2θ X-ray diffraction scan increases as the annealing temperature increases until the melting temperature of the Parylene films was achieved. Highly crystalline films of 85% and 92% crystallinity were achieved for Parylene C and N respectively. Investigation of the hybrid film showed that the individual Parylene films behave independently to each other, and the crystallinity of one film had no significant impact to the other film. Mechanical testing showed that the elastic modulus and yield strength increase as a function of annealing, whereas the elongation-to-break parameter decreases. The change in elastic modulus was more significant for Parylene C than Parylene N and this is attributed to the larger change in crystallinity that was observed. Parylene C had a 112% increase in crystallinity compared to a 61% increase for Parylene N, because the original Parylene N material was more crystalline than Parylene C so the change of crystallinity was greater for Parylene C. - Highlights: • A hybrid material consisting of Parylene N and C was developed. • Parylene N has greater crystallinity than Parylene C. • Phase transition of Parylene N due to annealing results in increased crystallinity. • Annealing caused increased crystallinity and elastic modulus in Parylene films. • Annealed hybrid Parylene films crystallinity behave

NATO Advanced Study Institute on Engineering of Crystalline Materials Properties : State of the Art in Modeling Design and Applications. New Materials for better Defence and Security

CERN Document Server

Braga, Dario; Addadi, Lia

2008-01-01

This volume collects the lecture notes (ordered alphabetically according to the first author surname) of the talks delivered by the main speakers at the Erice 2007 International School of Crystallography, generously selected by NATO as an Advanced Study Institute (# 982582). The aim of the school was to discuss the state-of-the-art in molecular materials design, that is, the rational analysis and fabrication of crystalline solids showing a predefined structural organization of their component molecules and ions, which results in the manifestation of a specific collective property of technological interest. The School was held on June 7–17, 2007, in Erice (an old town, over 3000 years, located on the top of a Sicilian hill that oversees the sea near Trapani). The school developed following two parallel lines. First we established “where we are” in terms of modelling, design, synthesis and applications of crystalline solids with predefined properties. Second, we attempted to define current and possible fu...

Dynamics of polymers in the bulk state by neutron scattering

International Nuclear Information System (INIS)

Kanaya, Toshiji; Kaji, Keisuke; Kawaguchi, Tatsuya; Inoue, Kazuhiko.

1992-01-01

Dynamics of polymers in the bulk state was studied by quasi- and inelastic neutron scattering techniques in the time range of 10 -13 to 10 -10 s. The present work can be classified into three parts: (i) dynamics in the glassy, state, (ii) dynamics near the glass transition and (iii) dynamics in the molten state. In the first section, we discuss the low energy excitation in glassy polymers, which is an origin of anomalous thermal properties of amorphous materials at low temperatures. In the next section, we study dynamics of amorphous polymers near the glass transition which is one of the current topics of solid state physics as well as polymer physics. It was found that two modes of motion appear near the glass transition in the energy ranges near 1 meV and of 10-30μeV. These fast and slow modes arising ca. 50K below T g and just above T g , respectively, are discussed from viewpoints of molecular basis. In the last section, dynamics in the molten state is investigated by focusing on the mechanism of local conformational transition of polymer chains. The results are analyzed in terms of jump diffusion model with damped vibrational motions and compared with the Kramers' rate theory. (author)

Structure and function of small heat shock/alpha-crystallin proteins: established concepts and emerging ideas.

Science.gov (United States)

MacRae, T H

2000-06-01

Small heat shock/alpha-crystallin proteins are defined by conserved sequence of approximately 90 amino acid residues, termed the alpha-crystallin domain, which is bounded by variable amino- and carboxy-terminal extensions. These proteins form oligomers, most of uncertain quaternary structure, and oligomerization is prerequisite to their function as molecular chaperones. Sequence modelling and physical analyses show that the secondary structure of small heat shock/alpha-crystallin proteins is predominately beta-pleated sheet. Crystallography, site-directed spin-labelling and yeast two-hybrid selection demonstrate regions of secondary structure within the alpha-crystallin domain that interact during oligomer assembly, a process also dependent on the amino terminus. Oligomers are dynamic, exhibiting subunit exchange and organizational plasticity, perhaps leading to functional diversity. Exposure of hydrophobic residues by structural modification facilitates chaperoning where denaturing proteins in the molten globule state associate with oligomers. The flexible carboxy-terminal extension contributes to chaperone activity by enhancing the solubility of small heat shock/alpha-crystallin proteins. Site-directed mutagenesis has yielded proteins where the effect of the change on structure and function depends upon the residue modified, the organism under study and the analytical techniques used. Most revealing, substitution of a conserved arginine residue within the alpha-crystallin domain has a major impact on quaternary structure and chaperone action probably through realignment of beta-sheets. These mutations are linked to inherited diseases. Oligomer size is regulated by a stress-responsive cascade including MAPKAP kinase 2/3 and p38. Phosphorylation of small heat shock/alpha-crystallin proteins has important consequences within stressed cells, especially for microfilaments.

Crystalline-to-amorphous phase transition in irradiated silicon

International Nuclear Information System (INIS)

Seidman, D.N.; Averback, R.S.; Okamoto, P.R.; Baily, A.C.

1986-01-01

The amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e - ) and/or ion irradiated silicon (Si). The irradiations were performed in situ in the Argonne High Voltage Microscope-Tandem Facility. The irradiation of Si, at 0 K, with 1-MeV e - to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at 0 K, with 1.0 or 1.5-MeV Kr+ ions induced the c-to-a transition by a fluence of approx.0.37 dpa. Alternatively a dual irradiation, at 10 0 K, with 1.0-MeV e - and 1.0 or 1.5-MeV Kr+ to a Kr+ fluence of 1.5 dpa - where the ratio of the displacement rates for e - to ions was approx.0.5 - resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of damage and the mobilities of point defects

Structural and surface changes in glassy carbon due to strontium implantation and heat treatment

Science.gov (United States)

Odutemowo, O. S.; Malherbe, J. B.; Prinsloo, L. C.; Njoroge, E. G.; Erasmus, R.; Wendler, E.; Undisz, A.; Rettenmayr, M.

2018-01-01

There are still questions around the microstructure of glassy carbon (GC), like the observation of the micropores. These were proposed to explain the low density of GC. This paper explains the effect of ion bombardment (200 keV Sr+, 1 × 1016 Sr+/cm2 at RT) on the microstructure of GC. TEM and AFM show that micropores in pristine GC are destroyed leading to densification of GC from 1.42 g/cm3 to 2.03 g/cm3. The amorphisation of glassy carbon was also not complete with graphitic strands embedded within the GC. These were relatively few, as Raman analysis showed that the Sr implantation resulted in a typical amorphous Raman spectrum. Annealing of the sample at 900 °C only resulted in a slight recovery of the GC structure. AFM and SEM analysis showed that the surface of the sample became rougher after Sr implantation. The roughness increased after the sample was annealed at 600 °C due to segregation of Sr towards the surface of the GC. SEM measurements of a sample with both implanted and un-implanted edges after annealing at 900 °C, showed that the high temperature heat treatment did not affect the surface topography of un-irradiated GC.

Temperature and frequency response of conductivity in Ag2S doped chalcogenide glassy semiconductor

Science.gov (United States)

Ojha, Swarupa; Das, Anindya Sundar; Roy, Madhab; Bhattacharya, Sanjib

2018-06-01

The electric conductivity of chalcogenide glassy semiconductor xAg2S-(1-x)(0.5S-0.5Te) has been presented here as a function of temperature and frequency. Formation of different nanocrystallites has been confirmed from X-ray diffraction study. It is also noteworthy that average size of nanocrystallites decreases with the increase of dislocation density. Dc conductivity data have been interpreted using Mott's model and Greaves's model in low and high temperature regions respectively. Ac conductivity above the room temperature has been analyzed using Meyer-Neldel (MN) conduction rule. It is interestingly noted that Correlated Barrier Hopping (CBH) model is the most appropriate conduction mechanism for x = 0.35, where pairs of charge carrier are considered to hop over the potential barrier between the sites via thermal activation. To interpret experimental data for x = 0.45, modified non-overlapping small polaron tunnelling (NSPT) model is supposed to be appropriate model due to tunnelling through grain boundary. The conductivity spectra at various temperatures have been analyzed using Almond-West Formalism (power law model). Scaling of conductivity spectra reveals that electrical relaxation process of charge carriers (polaron) is temperature independent but depends upon the composition of the present chalcogenide glassy system.

Glycine phases formed from frozen aqueous solutions: Revisited

Energy Technology Data Exchange (ETDEWEB)

Surovtsev, N. V. [Institute of Automation and Electrometry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Adichtchev, S. V.; Malinovsky, V. K. [Institute of Automation and Electrometry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Ogienko, A. G.; Manakov, A. Yu. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Drebushchak, V. A. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Ancharov, A. I.; Boldyreva, E. V. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Institute of Solid Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Yunoshev, A. S. [Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Lavrentiev Institute of Hydrodynamics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation)

2012-08-14

Glycine phases formed when aqueous solutions were frozen and subsequently heated under different conditions were studied by Raman scattering, x-ray diffraction, and differential scanning calorimetry (DSC) techniques. Crystallization of ice I{sub h} was observed in all the cases. On cooling at the rates of 0.5 K/min and 5 K/min, glassy glycine was formed as an intermediate phase which lived about 1 min or less only, and then transformed into {beta}-polymorph of glycine. Quench cooling of glycine solutions (15% w/w) in liquid nitrogen resulted in the formation of a mixture of crystalline water ice I{sub h} and a glassy glycine, which could be preserved at cryogenic temperatures (80 K) for an indefinitely long time. This mixture remained also quite stable for some time after heating above the cryogenic temperature. Subsequent heating under various conditions resulted in the transformation of the glycine glass into an unknown crystalline phase (glycine 'X-phase') at 209-216 K, which at 218-226 K transformed into {beta}-polymorph of glycine. The 'X-phase' was characterized by Raman spectroscopy; it could be obtained in noticeable amounts using a special preparation technique and tentatively characterized by x-ray powder diffraction (P2, a= 6.648 A, b= 25.867 A, c= 5.610 A, {beta}= 113.12 Masculine-Ordinal-Indicator ); the formation of 'X-phase' from the glycine glassy phase and its transformation into {beta}-polymorph were followed by DSC. Raman scattering technique with its power for unambiguous identification of the crystalline and glassy polymorphs without limitation on the crystallite size helped us to follow the phase transformations during quenching, heating, and annealing. The experimental findings are considered in relation to the problem of control of glycine polymorphism on crystallization.

Glycine phases formed from frozen aqueous solutions: Revisited

Science.gov (United States)

Surovtsev, N. V.; Adichtchev, S. V.; Malinovsky, V. K.; Ogienko, A. G.; Drebushchak, V. A.; Manakov, A. Yu.; Ancharov, A. I.; Yunoshev, A. S.; Boldyreva, E. V.

2012-08-01

Glycine phases formed when aqueous solutions were frozen and subsequently heated under different conditions were studied by Raman scattering, x-ray diffraction, and differential scanning calorimetry (DSC) techniques. Crystallization of ice Ih was observed in all the cases. On cooling at the rates of 0.5 K/min and 5 K/min, glassy glycine was formed as an intermediate phase which lived about 1 min or less only, and then transformed into β-polymorph of glycine. Quench cooling of glycine solutions (15% w/w) in liquid nitrogen resulted in the formation of a mixture of crystalline water ice Ih and a glassy glycine, which could be preserved at cryogenic temperatures (80 K) for an indefinitely long time. This mixture remained also quite stable for some time after heating above the cryogenic temperature. Subsequent heating under various conditions resulted in the transformation of the glycine glass into an unknown crystalline phase (glycine "X-phase") at 209-216 K, which at 218-226 K transformed into β-polymorph of glycine. The "X-phase" was characterized by Raman spectroscopy; it could be obtained in noticeable amounts using a special preparation technique and tentatively characterized by x-ray powder diffraction (P2, a = 6.648 Å, b = 25.867 Å, c = 5.610 Å, β = 113.12°); the formation of "X-phase" from the glycine glassy phase and its transformation into β-polymorph were followed by DSC. Raman scattering technique with its power for unambiguous identification of the crystalline and glassy polymorphs without limitation on the crystallite size helped us to follow the phase transformations during quenching, heating, and annealing. The experimental findings are considered in relation to the problem of control of glycine polymorphism on crystallization.

Determination of crystallinity of ceramic materials from the Ruland Method

International Nuclear Information System (INIS)

Kniess, C.T.; Prates, P.B.; Gomes Junior, J.C.; Lima, J.C. de; Riella, H.G.; Kuhnen, N.C.

2011-01-01

Some methods found in literature approach the different characteristics between crystalline and amorphous phases by X ray diffraction technique. These methods use the relation between the intensities of the crystalline peaks and background amorphous or the absolute intensity of one of these to determine the relative amount of crystalline and amorphous material. However, a crystalline substance presents shows coherent diffuse scattering and a loss in the intensity of the peaks of diffraction in function of thermal vibrations of atoms and imperfections in the crystalline structure. A correct method for the determination of the crystallinity must take in account these effects. This work has as objective to determine the crystallinity of ceramic materials obtained with the addition of mineral coal bottom ashes, using the X ray diffraction technique and the Ruland Method, that considers the diminution of the intensity of the crystalline peak because of the disorder affects. The Ruland Method shows adequate for the determination of the crystallinity of the ceramic materials. (author)

Generic Crystalline Disposal Reference Case

Energy Technology Data Exchange (ETDEWEB)

Painter, Scott Leroy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harp, Dylan Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Perry, Frank Vinton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-02-20

A generic reference case for disposal of spent nuclear fuel and high-level radioactive waste in crystalline rock is outlined. The generic cases are intended to support development of disposal system modeling capability by establishing relevant baseline conditions and parameters. Establishment of a generic reference case requires that the emplacement concept, waste inventory, waste form, waste package, backfill/buffer properties, EBS failure scenarios, host rock properties, and biosphere be specified. The focus in this report is on those elements that are unique to crystalline disposal, especially the geosphere representation. Three emplacement concepts are suggested for further analyses: a waste packages containing 4 PWR assemblies emplaced in boreholes in the floors of tunnels (KBS-3 concept), a 12-assembly waste package emplaced in tunnels, and a 32-assembly dual purpose canister emplaced in tunnels. In addition, three failure scenarios were suggested for future use: a nominal scenario involving corrosion of the waste package in the tunnel emplacement concepts, a manufacturing defect scenario applicable to the KBS-3 concept, and a disruptive glaciation scenario applicable to both emplacement concepts. The computational approaches required to analyze EBS failure and transport processes in a crystalline rock repository are similar to those of argillite/shale, with the most significant difference being that the EBS in a crystalline rock repository will likely experience highly heterogeneous flow rates, which should be represented in the model. The computational approaches required to analyze radionuclide transport in the natural system are very different because of the highly channelized nature of fracture flow. Computational workflows tailored to crystalline rock based on discrete transport pathways extracted from discrete fracture network models are recommended.

Porosity measurements of crystalline rocks by laboratory and geophysical methods

International Nuclear Information System (INIS)

Alexander, J.; Hall, D.H.; Storey, B.C.

1981-12-01

Porosity values of igneous and metamorphic crystalline rocks have been determined from core samples taken at specific depths from Altnabreac, by a combination of laboratory and geophysical techniques. Using resaturation and mercury injection methods in three laboratories within I.G.S., porosity values have been derived and the effect of variations in the measuring techniques and results obtained have been compared. Comparison of inter-laboratory porosity values illustrates that systematic errors are present, resulting in higher porosity values for samples subjected to re-testing. This is considered to be caused by the variable nature of the initial samples combined with the inability to completely dry or resaturate samples during a second testing. Geophysical techniques for determining in situ porosity using the neutron log have been carried out in borehole ALA. The neutron log has been calibrated with laboratory derived porosity values and an empirical formula derived enabling porosity values to be ascribed throughout the logged borehole ALA. Comparison of the porosity results from Altnabreac with crystalline samples elsewhere in America, Europe and the U.K. suggest that porosities at Altnabreac are lower than average. However, very few publications concerned with water movement in crystalline areas actually state the method used. (author)

Proton nuclear magnetic resonance studies of hydrogen diffusion and electron tunneling in Ni-Nb-Zr-H glassy alloys

Energy Technology Data Exchange (ETDEWEB)

Niki, Haruo; Okuda, Hiroyuki; Oshiro, Morihito; Yogi, Mamoru [Department of Physics, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa 903-0213 (Japan); Seki, Ichiro; Fukuhara, Mikio [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2012-06-15

Using the Fourier transform of the echo envelope, the proton line shapes, spin-lattice relaxation time, and spin-spin relaxation time have been measured in a (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} glassy alloy at 1.83 T ({approx}78 MHz) and at temperatures between 1.8 and 300 K. First, the spectral line width decreases abruptly between 1.8 and 2.1 K. Next, it remains almost constant at 13 kHz up to {approx}150 K. Finally, the line width decreases as the temperature increases from {approx}150 to 300 K. The initial decrease in the spectral line width is ascribed to the distribution of the external field, which is caused by the penetration of vortices in the superconducting state. The subsequent leveling off in the spectral line width is ascribed to the dipole-dipole interaction between protons when hydrogen atoms are trapped into vacancies among the Zr-centered icosahedral Zr{sub 5}Ni{sub 5}Nb{sub 3} clusters. The final decrease in the spectral line width is ascribed to the motional narrowing of the width that is caused by the movement of hydrogen atoms. The temperature dependences of the spin-lattice and spin-spin relaxation time showed that at temperature above 150 K and the activation energy of 8.7 kJ/mol allowed the hydrogen atoms to migrate among the clusters. The distance between the hydrogen atoms is estimated to be 2.75 A. Hydrogen occupancies among clusters in the (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} glassy alloy play an important role in the diffusion behavior and in the electronic properties of this alloy.

Raw data from orientation studies in crystalline rock areas of the southeastern United States

International Nuclear Information System (INIS)

Price, V.

1976-03-01

Raw data are presented on orientation studies conducted in crystalline rock areas of the Southeast which were chosen because of published references to uranium mineralization. Preliminary data for four orientation study areas are included. These areas are Lamar County, Georgia; Oconee County, South Carolina; Brush Creek, North Carolina; and North Harper, North Carolina. Sample locality maps, tables of field data, and tables of analytical data are included for each study area

Quantum vibrational polarons: Crystalline acetanilide revisited

Science.gov (United States)

Hamm, Peter; Edler, Julian

2006-03-01

We discuss a refined theoretical description of the peculiar spectroscopy of crystalline acetanilide (ACN). Acetanilide is a molecular crystal with quasi-one-dimensional chains of hydrogen-bonded units, which is often regarded as a model system for the vibrational spectroscopy of proteins. In linear spectroscopy, the CO stretching (amide I) band of ACN features a double-peak structure, the lower of which shows a pronounced temperature dependence which has been discussed in the context of polaron theory. In nonlinear spectroscopy, both of these peaks respond distinctly differently. The lower-frequency band exhibits the anharmonicity expected from polaron theory, while the higher-frequency band responds as if it were quasiharmonic. We have recently related the response of the higher-frequency band to that of a free exciton [J. Edler and P. Hamm, J. Chem. Phys. 117, 2415 (2002)]. However, as discussed in the present paper, the free exciton is not an eigenstate of the full quantum version of the Holstein polaron Hamiltonian, which is commonly used to describe these phenomena. In order to resolve this issue, we present a numerically exact solution of the Holstein polaron Hamiltonian in one dimension (1D) and 3D. In 1D, we find that the commonly used displaced oscillator picture remains qualitatively correct, even for relatively large exciton coupling. However, the result is not in agreement with the experiment, as it fails to explain the free-exciton band. In contrast, when taking into account the 3D nature of crystalline acetanilide, certain parameter regimes exist where the displaced oscillator picture breaks down and states appear in the spectrum that indeed exhibit the characteristics of a free exciton. The appearance of these states is a speciality of vibrational polarons, whose source of exciton coupling is transition dipole coupling which is expected to have opposite signs of interchain and intrachain coupling.

Effects of alkaline or liquid-ammonia treatment on crystalline cellulose: changes in crystalline structure and effects on enzymatic digestibility

Directory of Open Access Journals (Sweden)

Himmel Michael E

2011-10-01

Full Text Available Abstract Background In converting biomass to bioethanol, pretreatment is a key step intended to render cellulose more amenable and accessible to cellulase enzymes and thus increase glucose yields. In this study, four cellulose samples with different degrees of polymerization and crystallinity indexes were subjected to aqueous sodium hydroxide and anhydrous liquid ammonia treatments. The effects of the treatments on cellulose crystalline structure were studied, in addition to the effects on the digestibility of the celluloses by a cellulase complex. Results From X-ray diffractograms and nuclear magnetic resonance spectra, it was revealed that treatment with liquid ammonia produced the cellulose IIII allomorph; however, crystallinity depended on treatment conditions. Treatment at a low temperature (25°C resulted in a less crystalline product, whereas treatment at elevated temperatures (130°C or 140°C gave a more crystalline product. Treatment of cellulose I with aqueous sodium hydroxide (16.5 percent by weight resulted in formation of cellulose II, but also produced a much less crystalline cellulose. The relative digestibilities of the different cellulose allomorphs were tested by exposing the treated and untreated cellulose samples to a commercial enzyme mixture (Genencor-Danisco; GC 220. The digestibility results showed that the starting cellulose I samples were the least digestible (except for corn stover cellulose, which had a high amorphous content. Treatment with sodium hydroxide produced the most digestible cellulose, followed by treatment with liquid ammonia at a low temperature. Factor analysis indicated that initial rates of digestion (up to 24 hours were most strongly correlated with amorphous content. Correlation of allomorph type with digestibility was weak, but was strongest with cellulose conversion at later times. The cellulose IIII samples produced at higher temperatures had comparable crystallinities to the initial cellulose I

Alpha-crystallin-type heat shock proteins: socializing minichaperones in the context of a multichaperone network.

Science.gov (United States)

Narberhaus, Franz

2002-03-01

Alpha-crystallins were originally recognized as proteins contributing to the transparency of the mammalian eye lens. Subsequently, they have been found in many, but not all, members of the Archaea, Bacteria, and Eucarya. Most members of the diverse alpha-crystallin family have four common structural and functional features: (i) a small monomeric molecular mass between 12 and 43 kDa; (ii) the formation of large oligomeric complexes; (iii) the presence of a moderately conserved central region, the so-called alpha-crystallin domain; and (iv) molecular chaperone activity. Since alpha-crystallins are induced by a temperature upshift in many organisms, they are often referred to as small heat shock proteins (sHsps) or, more accurately, alpha-Hsps. Alpha-crystallins are integrated into a highly flexible and synergistic multichaperone network evolved to secure protein quality control in the cell. Their chaperone activity is limited to the binding of unfolding intermediates in order to protect them from irreversible aggregation. Productive release and refolding of captured proteins into the native state requires close cooperation with other cellular chaperones. In addition, alpha-Hsps seem to play an important role in membrane stabilization. The review compiles information on the abundance, sequence conservation, regulation, structure, and function of alpha-Hsps with an emphasis on the microbial members of this chaperone family.

Microstructure examination of the interface of the glass-ceramic insulator of the molybdenum frame of a vacuum tube

International Nuclear Information System (INIS)

Spears, R.K.

1980-01-01

A common technique used in examining the structural integrity of a glass-ceramic insulator-molybdenum cylinder bond in a vacuum tube subassembly is to slit the outer molybdenum cylinder and separate it from the glass-ceramic insulator. Typically, a black glassy layer (0.001 to 0.002 in. thick) remains on the cylinder. This layer has been interpreted as a requirement for an adequate seal. A subassembly was found that did not exhibit this feature. Further investigation of approximately 100 subassemblies revealed four more parts lacking a black glassy layer. These parts were found to be from two production runs and from three glass-ceramic lots. A microstructural analysis showed that on those parts having a black glassy layer, the crystalline phase in the glass-ceramic grew to within one to two microns of the metal interface and then terminated. A dark region existed in the insulator between the interface and the termination of the crystalline phase. This was attributed to molybdenum oxide dissolved in the glass. On those parts where the glass-ceramic broke clean from the cylinder, the crystalline phase extended up to the metal. Also observed on these parts was the appearance of a dark region adjacent to the metal that extended approximately one to two microns into the glass-ceramic. This was assumed to be an oxide of molybdenum. This report presents information concerning the microstructure of the interface

Performance of conversion efficiency of a crystalline silicon solar cell with base doping density

Directory of Open Access Journals (Sweden)

Gokhan Sahin

Full Text Available In this study, we investigate theoretically the electrical parameters of a crystalline silicon solar cell in steady state. Based on a one-dimensional modeling of the cell, the short circuit current density, the open circuit voltage, the shunt and series resistances and the conversion efficiency are calculated, taking into account the base doping density. Either the I-V characteristic, series resistance, shunt resistance and conversion efficiency are determined and studied versus base doping density. The effects applied of base doping density on these parameters have been studied. The aim of this work is to show how short circuit current density, open circuit voltage and parasitic resistances are related to the base doping density and to exhibit the role played by those parasitic resistances on the conversion efficiency of the crystalline silicon solar. Keywords: Crystalline silicon solar cell, Base doping density, Series resistance, Shunt resistance, Conversion efficiency

A consequence of local equilibration and heterogeneity in glassy materials

International Nuclear Information System (INIS)

Berthier, Ludovic

2003-01-01

The existence of a generalized fluctuation-dissipation theorem observed in simulations and experiments performed in various glassy materials is related to the concepts of local equilibration and heterogeneity in space. Assuming the existence of a dynamic coherence length scale up to which the system is locally equilibrated, we extend previous generalizations of the FDT relating static to dynamic quantities to the physically relevant domain where asymptotic limits of large times and sizes are not reached. The formulation relies on a simple scaling argument and thus does not have the character of a theorem. Extensive numerical simulations support this proposition. Our results quite generally apply to systems with slow dynamics, independently of the space dimensionality, the chosen dynamics or the presence of disorder

Effect of solid phase on the selectivity of alkyl radical formation by gamma-irradiation of branched alkanes

International Nuclear Information System (INIS)

Koizumi, Hitoshi; Hashino, Masatoshi; Ichikawa, Tsuneki; Yoshida, Hiroshi

1992-01-01

ESR and electron spin echo measurements of alkyl radicals generated by γ-irradiation of glassy and crystalline branched alkanes C 10 ∼ C 13 have been carried out to elucidate the effect of molecular structure and solid phase on the selectivity of alkyl radical formation. Alkyl radicals generated and stabilized at 77 K in the glassy alkanes are secondary penultimate radicals. Tertiary radicals and secondary radicals other than the penultimate one are not generated either by hydrogen abstraction or from ionized or excited molecules. In the crystalline alkanes, however, a small amount of secondary internal radicals are generated in addition to the predominant formation of the secondary penultimate radicals. It is concluded that the detachment of C-H hydrogen preferentially takes place at the location where the motion of carbon atoms assisting the detachment of the C-H hydrogen easily occurs. (author)

Molecular imprinted polypyrrole modified glassy carbon electrode for the determination of tobramycin

International Nuclear Information System (INIS)

Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Özaltın, Nuran; Atar, Necip; Üstündağ, Zafer; Uzun, Lokman

2013-01-01

Graphical abstract: Atomic force microscopic images of (A) bare GCE and (B) TOB imprinted PPy/GCE surface. - Highlights: • Glassy carbon electrode based on molecularly imprinted polypyrrole was prepared. • The developed surfaces were characterized by AFM, FTIR, EIS and CV. • The developed nanosensor was applied to egg and milk samples. - Abstract: Over the past two decades, molecular imprinted polymers have attracted a broad interest from scientists in sensor development. In the preparation of molecular imprinted polymers the desired molecule (template) induces the creation of specific recognition sites in the polymer. In this study, the glassy carbon electrode (GCE) based on molecularly imprinted polypyrrole (PPy) was fabricated for the determination of tobramycin (TOB). The developed electrode was prepared by incorporation of a template molecule (TOB) during the electropolymerization of pyrrole on GCE in aqueous solution using cyclic voltammetry (CV) method. The performance of the imprinted and non-imprinted electrodes was evaluated by square wave voltammetry (SWV). The effect of pH, monomer and template concentrations, electropolymerization cycles on the performance of the imprinted and non-imprinted electrodes was investigated and optimized. The non-modified and TOB-imprinted surfaces were characterized by using atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and CV. The linearity range of TOB was 5.0 × 10 −10 –1.0 × 10 −8 M with the detection limit of 1.4 × 10 −10 M. The developed nanosensor was applied successfully for the determination of TOB in egg and milk

Voltammetric Determination of Acetaminophen in the Presence of Codeine and Ascorbic Acid at Layer-by-Layer MWCNT/Hydroquinone Sulfonic Acid-Overoxidized Polypyrrole Modified Glassy Carbon Electrode

OpenAIRE

Shahrokhian, Saeed; Saberi, Reyhaneh-Sadat

2011-01-01

A very sensitive electrochemical sensor constructed of a glassy carbon electrode modified with a layer-by-layer MWCNT/doped-overoxidized polypyrrole (oppy/MWCNT /GCE) was used for the determination of acetaminophen (AC) in the presence of codeine and ascorbic acid (AA). In comparison to the bare glassy carbon electrode, a considerable shift in the peak potential together with an increase in the peak current was observed for AC on the surface of oppy/MWCNT/GCE, which can be related to the enla...

Glassy-state stabilization of a dominant negative inhibitor anthrax vaccine containing aluminum hydroxide and glycopyranoside lipid A adjuvants.

Science.gov (United States)

Hassett, Kimberly J; Vance, David J; Jain, Nishant K; Sahni, Neha; Rabia, Lilia A; Cousins, Megan C; Joshi, Sangeeta; Volkin, David B; Middaugh, C Russell; Mantis, Nicholas J; Carpenter, John F; Randolph, Theodore W

2015-02-01

During transport and storage, vaccines may be exposed to temperatures outside of the range recommended for storage, potentially causing efficacy losses. To better understand and prevent such losses, dominant negative inhibitor (DNI), a recombinant protein antigen for a candidate vaccine against anthrax, was formulated as a liquid and as a glassy lyophilized powder with the adjuvants aluminum hydroxide and glycopyranoside lipid A (GLA). Freeze-thawing of the liquid vaccine caused the adjuvants to aggregate and decreased its immunogenicity in mice. Immunogenicity of liquid vaccines also decreased when stored at 40°C for 8 weeks, as measured by decreases in neutralizing antibody titers in vaccinated mice. Concomitant with efficacy losses at elevated temperatures, changes in DNI structure were detected by fluorescence spectroscopy and increased deamidation was observed by capillary isoelectric focusing (cIEF) after only 1 week of storage of the liquid formulation at 40°C. In contrast, upon lyophilization, no additional deamidation after 4 weeks at 40°C and no detectable changes in DNI structure or reduction in immunogenicity after 16 weeks at 40°C were observed. Vaccines containing aluminum hydroxide and GLA elicited higher immune responses than vaccines adjuvanted with only aluminum hydroxide, with more mice responding to a single dose. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Autokinase activity of alpha-crystallin inhibits its specific interaction with the DOTIS element in the murine gamma D/E/F-crystallin promoter in vitro.

Science.gov (United States)

Pietrowski, D; Graw, J

1997-10-01

In a previous report we demonstrated the in vitro interaction of alpha-crystallin with an element downstream of the transcriptional initiation site (DOTIS) of the murine gamma E-crystallin promoter (Pietrowski et al., 1994, Gene 144, 171-178). The aim of the present study was to investigate the influence of phosphorylation on this particular interaction. We could demonstrate that the autophosphorylation of alpha-crystallin leads to a complete loss of interaction with the DOTIS element, however, PKA-dependent phosphorylation of alpha-crystallin is without effect on the interaction. It is hypothesized that the autophosphorylation of alpha-crystallin might be involved in regulatory mechanisms of the murine gamma D/E/F-crystallin gene expression.

Microscopic theory of singlet exciton fission. III. Crystalline pentacene

International Nuclear Information System (INIS)

Berkelbach, Timothy C.; Reichman, David R.; Hybertsen, Mark S.

2014-01-01

We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singlet fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems

Microscopic theory of singlet exciton fission. III. Crystalline pentacene

Energy Technology Data Exchange (ETDEWEB)

Berkelbach, Timothy C., E-mail: tcb2112@columbia.edu; Reichman, David R., E-mail: drr2103@columbia.edu [Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 (United States); Hybertsen, Mark S., E-mail: mhyberts@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States)

2014-08-21

We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singlet fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems.

Impedance aspect of charge storage at graphite and glassy carbon electrodes in potassium hexacyanoferrate (II redox active electrolyte

Directory of Open Access Journals (Sweden)

Katja Magdić

2016-04-01

Full Text Available Different types of charge storage mechanisms at unmodified graphite vs. glassy carbon electrodes in acid sulphate supporting solution containing potassium hexacyanoferrate (II redox active electrolyte, have been revealed by electrochemical impedance spectroscopy and supported by cyclic voltammetry experiments. Reversible charge transfer of Fe(CN63-/4- redox reaction detected by assessment of CVs of glassy carbon electrode, is in impedance spectra indicated by presence of bulk diffusion impedance and constant double-layer/pseudocapacitive electrode impedance compared to that measured in the pure supporting electrolyte. Some surface retention of redox species detected by assessment of CVs of graphite electrode is in impedance spectra indicated by diffusion impedance coupled in this case by diminishing of double-layer/pseudo­capacitive impedance compared to that measured in the pure supporting electrolyte. This phenomenon is ascribed to contribution of additional pseudocapacitive impedance generated by redox reaction of species confined at the electrode surface.

Electrochemical deposition of gold nanoparticles on carbon nanotube coated glassy carbon electrode for the improved sensing of tinidazole

International Nuclear Information System (INIS)

Shahrokhian, Saeed; Rastgar, Shokoufeh

2012-01-01

The electrochemical reduction of tinidazole (TNZ) is studied on gold-nanoparticle/carbon-nanotubes (AuNP/CNT) modified glassy carbon electrodes using the linear sweep voltammetry. An electrochemical procedure was used for the deposition of gold nanoparticles onto the carbon nanotube film pre-cast on a glassy carbon electrode surface. The resulting nanoparticles were characterized by scanning electron microscopy and cyclic voltammetry. The effect of the electrodeposition conditions, e.g., salt concentration and deposition time on the response of the electrode was studied. Also, the effect of experimental parameters, e.g., potential and time of accumulation, pH of the buffered solutions and the potential sweep rate on the response is examined. Under the optimal conditions, the modified electrode showed a wide linear response toward the concentration of TNZ in the range of 0.1–50 μM with a detection limit of 10 nM. The prepared electrode was successfully applied for the determination of TNZ in pharmaceutical and clinical samples.

A 3D Microfluidic Chip for Electrochemical Detection of Hydrolysed Nucleic Bases by a Modified Glassy Carbon Electrode

Directory of Open Access Journals (Sweden)

Jana Vlachova

2015-01-01

Full Text Available Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur containing compounds and Nafion for detection of nucleobases in hydrolysed samples (HCl pH = 2.9, 100 °C, 1 h, neutralization by NaOH. It was found out that modification, especially with trithiocyanuric acid, increased the sensitivity of detection in comparison with pure GCE. All processes were finally implemented in a microfluidic chip formed with a 3D printer by fused deposition modelling technology. As a material for chip fabrication, acrylonitrile butadiene styrene was chosen because of its mechanical and chemical stability. The chip contained the one chamber for the hydrolysis of the nucleic acid and another for the electrochemical detection by the modified GCE. This chamber was fabricated to allow for replacement of the GCE.

A 3D microfluidic chip for electrochemical detection of hydrolysed nucleic bases by a modified glassy carbon electrode.

Science.gov (United States)

Vlachova, Jana; Tmejova, Katerina; Kopel, Pavel; Korabik, Maria; Zitka, Jan; Hynek, David; Kynicky, Jindrich; Adam, Vojtech; Kizek, Rene

2015-01-22

Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE) modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur containing compounds and Nafion) for detection of nucleobases in hydrolysed samples (HCl pH = 2.9, 100 °C, 1 h, neutralization by NaOH). It was found out that modification, especially with trithiocyanuric acid, increased the sensitivity of detection in comparison with pure GCE. All processes were finally implemented in a microfluidic chip formed with a 3D printer by fused deposition modelling technology. As a material for chip fabrication, acrylonitrile butadiene styrene was chosen because of its mechanical and chemical stability. The chip contained the one chamber for the hydrolysis of the nucleic acid and another for the electrochemical detection by the modified GCE. This chamber was fabricated to allow for replacement of the GCE.

In situ surface and interface study of crystalline (3×1)-O on InAs

Energy Technology Data Exchange (ETDEWEB)

Qin, Xiaoye, E-mail: xxq102020@utdallas.edu; Wallace, Robert M., E-mail: rmwallace@utdallas.edu [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Wang, Wei-E.; Rodder, Mark S. [Advanced Logic Lab, Samsung Semiconductor, Inc., Austin, Texas 78754 (United States)

2016-07-25

The oxidation behavior of de-capped InAs (100) exposed to O{sub 2} gas at different temperatures is investigated in situ with high resolution of monochromatic x-ray photoelectron spectroscopy and low energy electron diffraction. The oxide chemical states and structure change dramatically with the substrate temperature. A (3 × 1) crystalline oxide layer on InAs is generated in a temperature range of 290–330 °C with a coexistence of In{sub 2}O and As{sub 2}O{sub 3}. The stability of the crystalline oxide upon the atomic layer deposition (ALD) of HfO{sub 2} is studied as well. It is found that the generated (3 × 1) crystalline oxide is stable upon ALD HfO{sub 2} growth at 100 °C.

In-Vitro Enzymatic Degradation of γ-irradiated Porous Chitosan Scaffold: Crystallinity and degree of deacetylation

International Nuclear Information System (INIS)

Ismail Zainol; Azreena Mastor; Suhaida Md Ghani; Ahmad Fuad Yahya; Hazizan Md Akil

2009-01-01

Full text: Enzymatic degradation behavior of porous chitosan membrane was carried out in vitro by using enzymatic hydrolysis of chitosan in lysozyme solution. Chitosan was first modified by reducing its molecular weight by gamma (γ) radiation in the solid state. The chitosan powder was irradiated with gamma Co 60 source with various doses of 10, 25, 50 and 100 kGy. The molecular weight of irradiated chitosan was measured using visco metric method. The modified chitosan was transform into a porous membrane by lyophilization method. Degree of deacetylation (DD) and crystallinity of samples were measured using FTIR and XRD respectively on both gamma irradiated and enzymatic degradation samples. The results suggested that the irradiated chitosan become less crystalline without changes in DD. The enzymatic degradation of chitosan however shows an increment in DD and crystallinity. (author)

Glycation precedes lens crystallin aggregation

International Nuclear Information System (INIS)

Swamy, M.S.; Perry, R.E.; Abraham, E.C.

1987-01-01

Non-enzymatic glycosylation (glycation) seems to have the potential to alter the structure of crystallins and make them susceptible to thiol oxidation leading to disulfide-linked high molecular weight (HMW) aggregate formation. They used streptozotocin diabetic rats during precataract and cataract stages and long-term cell-free glycation of bovine lens crystallins to study the relationship between glycation and lens crystallin aggregation. HMW aggregates and other protein components of the water-soluble (WS) and urea-soluble (US) fractions were separated by molecular sieve high performance liquid chromatography. Glycation was estimated by both [ 3 H]NaBH 4 reduction and phenylboronate agarose affinity chromatography. Levels of total glycated protein (GP) in the US fractions were about 2-fold higher than in the WS fractions and there was a linear increase in GP in both WS and US fractions. This increase was parallelled by a corresponding increase in HMW aggregates. Total GP extracted by the affinity method from the US fraction showed a predominance of HMW aggregates and vice versa. Cell-free glycation studies with bovine crystallins confirmed the results of the animals studies. Increasing glycation caused a corresponding increase in protein insolubilization and the insoluble fraction thus formed also contained more glycated protein. It appears that lens protein glycation, HMW aggregate formation, and protein insolubilization are interrelated

XRD and solid state 13C-NMR evaluation of the crystallinity enhancement of 13C-labeled bacterial cellulose biosynthesized by Komagataeibacter xylinus under different stimuli: A comparative strategy of analyses.

Science.gov (United States)

Meza-Contreras, Juan C; Manriquez-Gonzalez, Ricardo; Gutiérrez-Ortega, José A; Gonzalez-Garcia, Yolanda

2018-05-22

The production and crystallinity of 13 C bacterial cellulose (BC) was examined in static culture of Komagataeibacter xylinus with different chemical and physical stimuli: the addition of NaCl or cloramphenicol as well as exposure to a magnetic field or to UV light. Crystalline BC biosynthesized under each stimulus was studied by XRD and solid state 13 C NMR analyses. All treatments produced BC with enhanced crystallinity over 90% (XRD) and 80% (NMR) compared to the control (83 and 76%, respectively) or to Avicel (77 and 62%, respectively). The XRD data indicated that the crystallite size was 80-85 Å. Furthermore, changes on the allomorphs (I α and I β ) ratio tendency of BC samples addressed to the stimuli were estimated using the C4 signal from 13 C NMR data. These results showed a decrease of the allomorph I α (3%) when BC was biosynthesized with UV light and chloramphenicol compared to control (58.79%). In contrast, the BC obtained with NaCl increased up to 60.31% of the I α allomorph ratio. Copyright © 2018 Elsevier Ltd. All rights reserved.

The molecular chaperone α-crystallin inhibits UV-induced protein aggregation

International Nuclear Information System (INIS)

Borkman, R.F.; Knight, Grady; Obi, Bettie

1996-01-01

Solutions of γ-crystallin, and various enzymes, at neutral pH and 24-26 o C, became turbid upon exposure to UV radiation at 295 or 308 nm. SDS-PAGE analysis revealed interchain cross-linking and aggregate formation compared to dark control solutions as reported previously. When α-crystallin was added to the protein solutions in stoichiometric amounts. UV irradiation resulted in significantly less turbidity than in the absence of α-crystallin. For example, addition of 0.5 mg of α-crystallin to 0.5 mg of γ-crystallin in 1.0 ml solution yielded only 25% of the turbidity seen in the absence of α-crystallin. Addition of 2.0 mg of α-crystallin resulted in 20% of the turbidity. Given the molecular weights of α- and γ-crystallin (about 800 kDa and 20 kDa, respectively), A γ/α 1:1 weight ratio corresponds to a 40:1 molar ratio, and a γ-/α 1:4 weight ratio corresponds to a 10:1 molar ratio. Hence, the molar ratio of α-crystallin needed to effectively protect γ-crystallin from photochemical opacification was γ/α = n:1, where n was in the range 10-40. In terms of subunits, this ratio is γ/α = 1:m, where m = 1-4. Thus, each γ-crystallin molecule needs 1-4 α subunits for protection. Similar stoichiometries were observed for protection of the other proteins studied. The protection stems in part from screening of UV radiation by α-crystallin but more importantly from a chaperone effect analogous to that seen in thermal aggregation experiments. (author)

Impact of the Formulation Pathway on the Colloidal State and Crystallinity of Poly-ε-caprolactone Particles Prepared by Solvent Displacement.

Science.gov (United States)

Pucci, Carlotta; Cousin, Fabrice; Dole, François; Chapel, Jean-Paul; Schatz, Christophe

2018-02-20

The formulation pathway and/or the mixing method are known to be relevant in many out-of-equilibrium processes. In this work, we studied the effect of the mixing conditions on the physicochemical properties of poly-ε-caprolactone (PCL) particles prepared by solvent displacement. More specifically, water was added in one shot (fast addition) or drop by drop to PCL solution in tetrahydrofuran (THF) to study the impact of the mixing process on particle properties including size, stability, and crystallinity. Two distinct composition maps representing the Ouzo domain characteristic of the presence of metastable nanoparticles have been established for each mixing method. Polymer nanoparticles are formed in the Ouzo domain according to a nucleation and growth (or aggregation) mechanism. The fast addition promotes a larger nucleation rate, thus favoring the formation of small and uniform particles. For the drop-by-drop addition, for which the polymer solubility gradually decreases, the composition trajectories systematically cross an intermediate unstable region between the solubility limit of the polymer and the Ouzo domain. This leads to heterogeneous nucleation as shown by the formation of larger and less stable particles. Particles formed in the Ouzo domain have semi-crystalline properties. The PCL melting point is decreased with the THF fraction trapped in particles in accordance with Flory's theory for melt crystallization. On the other hand, the degree of crystallinity is constant, around 20% regardless of the THF fraction. No difference between fast and slow addition could be detected on the semi-crystalline properties of the particles which emphasize that thermodynamic rather than kinetic factors drive the polymer crystallization in particles. The recovery of bulk PCL crystallinity after the removal of THF from particles tends to confirm this hypothesis.

Dangling bonds and crystalline inclusions in amorphous materials

Energy Technology Data Exchange (ETDEWEB)

Ferrari, L [Ferrara Univ. (Italy). Ist. di Matematica; Russo, G [Bologna Univ. (Italy). Ist. di Fisica

1981-02-07

It is suggested that on the surface of crystalline inclusions dangling bond formation is favoured due to unbalanced local stresses. The energy for bond tearings is probably originated from the exothermic process leading to the crystalline inclusion configuration which is more stable than the original amorphous one. A thermodynamical calculation is performed giving the ratio nsub(k) of crystalline inclusions having k dangling bonds on their surface.

A crystalline cluster method for deep impurities in insulators

International Nuclear Information System (INIS)

Guimaraes, P.S.

1983-01-01

An ''ab initio'' self-consistent-field crysttalline-cluster approach to the study of deep impurity states in insulators is proposed. It is shown that, in spite of being a cluster calculation, the interaction of the impurity with the crystal environment is fully taken into account. It is also shown that the present representation of the impurity states is, at least, as precise as the crystalline cluster representation of the pure crystal electronic structure. The procedure has been tested by performing the calculation of the electronic structure of the U center in a sodium chloride crystal, and it has been observed that the calculated γ 1 - γ 15 absorption energy is in good agreement with experiment. (author) [pt

Quenching of orbital momentum by crystalline fields in a multichannel Kondo impurity

International Nuclear Information System (INIS)

Schlottmann, P.; Lee, K.

1995-01-01

We consider an impurity of spin S interacting via an isotropic spin exchange with conduction electrons of spin 1/2. The conduction electrons can be in n different orbital channels. We assume that crystalline fields split the orbital degrees of freedom into two multiplets, the one with lower energy consisting of n * orbitals and the one of higher energy of n-n * orbitals. The exchange coupling is the same for all channels. We derive the thermodynamic Bethe ansatz equations for this model and discuss the ground-state properties of the impurity as a function of the spin S and the magnetic field. The solution of the ground-state Bethe ansatz equations is obtained numerically. Three situations have to be distinguished when the magnetic field is small compared to the Kondo temperature: (i) If S=n/2 or S=n * /2 the conduction electrons exactly compensate the impurity spin into a singlet ground state, (ii) if S>n/2 the impurity is undercompensated, i.e., only partially compensated leaving an effective spin S-n/2 at low temperatures, and (iii) in all other cases the impurity spin is overcompensated giving rise to critical behavior. The quenching of the orbits by the crystalline field dramatically affects the cases S * /2

Area Recommendation Report for the Crystalline Repository Project: Volume 1, Draft

International Nuclear Information System (INIS)

1986-01-01

This Draft Area Recommendation Report for the Crystalline Repository Project identifies portions of crystalline rock bodies as proposed potentially acceptable sites for consideration in the second high-level radioactive waste repository program. The US Department of Energy evaluated available geologic and environmental data for 235 crystalline rock bodies in the North Central, Northeastern, and Southeastern regions to identify preliminary candidate areas. Further evaluation of these preliminary candidate areas resulted in the selection of 12 as proposed potentially acceptable sites. The 12 proposed potentially acceptable sites are located in the States of Georgia (1), Maine (2), Minnesota (3), New Hampshire (1), North Carolina (2), Virginia (2), and Wisconsin (1). The data, analyses, and rationale with which the 12 proposed potentially acceptable sites were selected are presented in this draft report. The analyses presented demonstrate that the evidence available for each proposed potentially acceptable site supports (1) a finding that the site is not disqualified in accordance with the application requirements of Appendix III of the siting guidelines and (2) a decision to proceed with the continued investigation of the site on the basis of the favorable and potentially adverse conditions identified to date. Once this report is finalized, potentially acceptable sites in crystalline rock will be formally identified by the Secretary of Energy, in accordance with the DOE siting guidelines. These potentially acceptable sites will be investigated and evaluated in more detail during the area phase of the siting process. An additional eight areas, which meet the requirements for identification as potentially acceptable sites, will retain their designation as candidate areas

Molecular origins of anisotropic shock propagation in crystalline and amorphous polyethylene

Science.gov (United States)

O'Connor, Thomas C.; Elder, Robert M.; Sliozberg, Yelena R.; Sirk, Timothy W.; Andzelm, Jan W.; Robbins, Mark O.

2018-03-01

Molecular dynamics simulations are used to analyze shock propagation in amorphous and crystalline polyethylene. Results for the shock velocity Us are compared to predictions from Pastine's equation of state and hydrostatic theory. The results agree with Pastine at high impact velocities. At low velocities the yield stress becomes important, increasing the shock velocity and leading to anisotropy in the crystalline response. Detailed analysis of changes in atomic order reveals the origin of the anisotropic response. For shock along the polymer backbone, an elastic front is followed by a plastic front where chains buckle with a characteristic wavelength. Shock perpendicular to the chain backbone can produce plastic deformation or transitions to different orthorhombic or monoclinic structures, depending on the impact speed and direction. Tensile loading does not produce stable shocks: Amorphous systems craze and fracture while for crystals the front broadens linearly with time.

Crystalline Symmetry-Protected Majorana Mode in Number-Conserving Dirac Semimetal Nanowires

Science.gov (United States)

Zhang, Rui-Xing; Liu, Chao-Xing

2018-04-01

One of the cornerstones for topological quantum computations is the Majorana zero mode, which has been intensively searched in fractional quantum Hall systems and topological superconductors. Several recent works suggest that such an exotic mode can also exist in a one-dimensional (1D) interacting double-wire setup even without long-range superconductivity. A notable instability in these proposals comes from interchannel single-particle tunneling that spoils the topological ground state degeneracy. Here we show that a 1D Dirac semimetal (DSM) nanowire is an ideal number-conserving platform to realize such Majorana physics. By inserting magnetic flux, a DSM nanowire is driven into a 1D crystalline-symmetry-protected semimetallic phase. Interaction enables the emergence of boundary Majorana zero modes, which is robust as a result of crystalline symmetry protection. We also explore several experimental consequences of Majorana signals.

Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

Energy Technology Data Exchange (ETDEWEB)

Blacha-Grzechnik, Agata, E-mail: agata.blacha@polsl.pl [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Piwowar, Katarzyna; Krukiewicz, Katarzyna [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Koscielniak, Piotr; Szuber, Jacek [Institute of Electronics, Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Zak, Jerzy K. [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland)

2016-05-15

Highlights: • The selected group of four NH{sub 2}-derivatives of phenothiazine was grafted to Glassy Carbon (GC) surface. • The grafted phenothiazines are able to generate {sup 1}O{sub 2} when activated by the radiation. • Such modified solid surfaces may find their application in the wastewater treatment. - Abstract: The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate {sup 1}O{sub 2} when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals’ synthesis or in the wastewater treatment.

Carrier loss mechanisms in textured crystalline Si-based solar cells

OpenAIRE

Nakane, Akihiro; Fujimoto, Shohei; Fujiwara, Hiroyuki

2017-01-01

A quite general device analysis method that allows the direct evaluation of optical and recombination losses in crystalline silicon (c-Si)-based solar cells has been developed. By applying this technique, the optical and physical limiting factors of the state-of-the-art solar cells with ~20% efficiencies have been revealed. In the established method, the carrier loss mechanisms are characterized from the external quantum efficiency (EQE) analysis with very low computational cost. In particula...

Electrocatalytic Determination of Isoniazid by a Glassy Carbon Electrode Modified with Poly (Eriochrome Black T

Directory of Open Access Journals (Sweden)

Karim Asadpour-Zeynali

2017-06-01

Full Text Available In this work poly eriochrome black T (EBT was electrochemically synthesized on the glassy carbon electrode as electrode modifier. On the modified electrode, voltammetric behavior of isoniazid (INH was investigated. The poly (EBT-modified glassy carbon electrode has excellent electrocatalytic ability for the electrooxidation of isoniazid. This fact was appeared as a reduced overpotential of INH oxidation in a wide operational pH range from 2 to 13. It has been found that the catalytic peak current depends on the concentration of INH and solution pH. The number of electrons involved in the rate determining step was found 1. The diffusion coefficient of isoniazid was also estimated using chronoamperometry technique. The experimental results showed that the mediated oxidation peak current of isoniazid is linearly dependent on the concentration of isoniazid in the ranges of 8.0 × 10-6 – 1.18 × 10-3 M and 2.90 × 10-5 M – 1.67× 10-3 M with differential pulse voltammetry (DPV and amperometry methods, respectively. The detection limits (S/N = 3 were found to be 6.0 μM and 16.4 μM by DPV and amperometry methods, respectively. This developed method was applied to the determination of isoniazid in tablet samples with satisfactory results.

Age and petrogenetic constraints on the Lower Glassy Ignimbrite of the Mount Somers Volcanic Group, New Zealand

DEFF Research Database (Denmark)

van der Meer, Quinten; Waight, Tod Earle; Whitehouse, Martin

2017-01-01

The Mount Somers Volcanic Group (MSVG) forms a large (~18000 km2) calc-alkaline volcanic complex on New Zealand’s Eastern Province. U-Pb SIMS spot ages on zircon from the lower glassy ignimbrite in Rakaia Gorge reveal a bimodal distribution of 99.0 ± 0.5 and 96.3 ± 0.5 Ma (2σ). These ages...

What Is Crystalline Silica?

Science.gov (United States)

... and ceramic manufacturing and the tool and die, steel and foundry industries. Crystalline silica is used in manufacturing, household abrasives, adhesives, paints, soaps, and glass. Additionally, ...

Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantification of antihistamine drug pheniramine in solubilized systems

Directory of Open Access Journals (Sweden)

Rajeev Jain

2012-02-01

Full Text Available A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate. The experimental results suggest that the pheniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response. Peak current response is linearly dependent on the concentration of pheniramine in the range 200–1500 μg/mL with correlation coefficient 0.9987. The limit of detection is 58.31 μg/mL. The modified electrode shows good sensitivity and repeatability. Keywords: Pheniramine, Sodium lauryl sulfate (SLS, Glassy carbon electrode modified with multi-walled carbon nanotubes (GCE-MWCNTs, Solubilized systems, Voltammetric quantification

Lens proteome map and alpha-crystallin profile of the catfish Rita rita.

Science.gov (United States)

Mohanty, Bimal Prasanna; Bhattacharjee, Soma; Das, Manas Kumar

2011-02-01

Crystallins are a diverse group of proteins that constitute nearly 90% of the total soluble proteins of the vertebrate eye lens and these tightly packed crystallins are responsible for transparency of the lens. These proteins have been studied in different model and non-model species for understanding the modifications they undergo with ageing that lead to cataract, a disease of protein aggregation. In the present investigation, we studied the lens crystallin profile of the tropical freshwater catfish Rita rita. Profiles of lens crystallins were analyzed and crystallin proteome maps of Rita rita were generated for the first time. alphaA-crystallins, member of the alpha-crystallin family, which are molecular chaperons and play crucial role in maintaining lens transparency were identified by 1- and 2-D immunoblot analysis with anti-alphaA-crystallin antibody. Two protein bands of 19-20 kDa were identified as alphaA-crystallins on 1-D immunoblots and these bands separated into 10 discrete spots on 2-D immunoblot. However, anti-alphaB-crystallin and antiphospho-alphaB-crystallin antibodies were not able to detect any immunoreactive bands on 1- and 2-D immunoblots, indicating alphaB-crystallin was either absent or present in extremely low concentration in Rita rita lens. Thus, Rita rita alpha-crystallins are more like that of the catfish Clarias batrachus and the mammal kangaroo in its alphaA- and alphaB-crystallin content (contain low amount from 5-9% of alphaB-crystallin) and unlike the dogfish, zebrafish, human, bovine and mouse alpha-crystallins (contain higher amount of alphaB-crystallin from 25% in mouse and bovine to 85% in dogfish). Results of the present study can be the baseline information for stimulating further investigation on Rita rita lens crystallins for comparative lens proteomics. Comparing and contrasting the alpha-crystallins of the dogfish and Rita rita may provide valuable information on the functional attributes of alphaA- and alphaB-isoforms, as

Momentum-dependent excitation processes in crystalline and amorphous films of conjugated oligomers

International Nuclear Information System (INIS)

Zojer, E.; Knupfer, M.; Shuai, Z.; Fink, J.; Bredas, J.L.; Hoerhold, H.-H.; Grimme, J.; Scherf, U.; Benincori, T.; Leising, G.

2000-01-01

The electronic structure of periodic materials is usually described on the basis of band-structure models, in which each state is not only characterized by its energy but also by the corresponding electron momentum. In this paper we present investigations of momentum-dependent excitation processes in a number of molecular crystals and amorphous thin films. For our studies we have chosen ladder-type quinquephenyl (5LP), distyrylbenzene (3PV), a substituted quinquephenylenevinylene (5PV), and a bridged quarterthienyl (4TB). These substances are representative for several classes of conjugated organic materials. Their physical properties are dominated by the molecular building blocks. The investigated films, however, also allow us to study differences in the characteristics of crystalline (3PV and 4TB), partly amorphous (5LP) and fully amorphous (5PV) systems. Momentum-dependent excitations are induced by inelastic electron scattering in electron-energy-loss spectroscopy (EELS) experiments. The experimental data are compared to molecule based post-Hartree-Fock quantum-chemical simulations performed with the intermediate neglect of differential overlap (INDO) approach coupled to a configuration interaction (CI) technique applying the proper momentum-dependent transition matrix elements. Our results show that even in relatively small systems the molecular electronic states can be characterized by an associated range in momentum space. In addition, differences between inelastic electron scattering spectra for low values of momentum transfer and the optical data obtained for the crystalline samples underline the strong impact of light propagation on the absorption characteristics of highly anisotropic crystalline materials

Identification of crystalline structures using Moessbauer parameters and artificial neural network

International Nuclear Information System (INIS)

Salles, E.O.T.; Souza Junior, P.A. De; Garg, V.K.

1995-01-01

Moessbauer spectroscopy is a useful technique for characterizing the valences, electronic and magnetic states, coordination symmetric and site occupancies of Fe cations. The Moessbauer parameters of Isomer Shift (I.S.) and Quadrupole Splitting (Q.S.) are useful to distinguish paramagnetic ferrous and ferric ions in several substances, while the internal magnetic field provides information on the crystallinity. A correlation is being sought between Moessbauer parameters and several structure properties of some iron-containing minerals using Artificial Neural Networks (ANN). Distinct regions of crystalline structures are defined when any two parameters are plotted, but in several cases superposition of these regions leads to erroneous conclusions. We have tried to eliminate this difficulty by using convenient axes. These axes form n-dimensional vectors as input to our ANN. In recent years ANN has shown to be a powerful technique to solve problems as pattern recognition, optimization, preview ups and downs in stock market, automatic control and identification of a mineral from a Moessbauer spectrum of Moessbauer data bank. Using ANN we have been successful in identification of crystalline structures from plots of Moessbauer spectral parameters of I.S., Q.S., and structure using Moessbauer parameters of I.S., Q.S., and polyhedral volume of a coordination site are presented. (author) 28 refs.; 4 figs.; 2 tabs

Characterization of crystalline structures in Opuntia ficus-indica

OpenAIRE

Contreras-Padilla, Margarita; Rivera-Muñoz, Eric M.; Gutiérrez-Cortez, Elsa; del López, Alicia Real; Rodríguez-García, Mario Enrique

2014-01-01

This research studies the crystalline compounds present in nopal (Opuntia ficus-indica) cladodes. The identification of the crystalline structures was performed using X-ray diffraction, scanning electron microscopy, mass spectrometry, and Fourier transform infrared spectroscopy. The crystalline structures identified were calcium carbonate (calcite) [CaCO3], calcium-magnesium bicarbonate [CaMg(CO3)2], magnesium oxide [MgO], calcium oxalate monohydrate [Ca(C2O4)•(H2O)], potassium peroxydiphosph...

Electrocatalytic reduction of nitrite on tetraruthenated metalloporphyrins/Nafion glassy carbon modified electrode

Energy Technology Data Exchange (ETDEWEB)

Calfuman, Karla [Facultad de Ciencias, Departamento de Quimica, Universidad de Chile, Las Palmeras 3425, Casilla 653, Nunoa, Santiago (Chile); Aguirre, Maria Jesus [Facultad de Quimica y Biologia, Departamento de Quimica de los Materiales, Universidad de Santiago de Chile, Santiago (Chile); Canete-Rosales, Paulina; Bollo, Soledad [Facultad de Ciencias Quimicas y Farmaceuticas, Departamento de Quimica Farmacologica y Toxicologica, Universidad de Chile, Santiago (Chile); Llusar, Rosa [Departamento de Quimica Fisica y Analitica, Universidad de Jaume I, Castellon (Spain); Isaacs, Mauricio, E-mail: misaacs@uchile.cl [Facultad de Ciencias, Departamento de Quimica, Universidad de Chile, Las Palmeras 3425, Casilla 653, Nunoa, Santiago (Chile)

2011-10-01

Highlights: > Preparation and characterization of modified electrodes with M(II) Tetraruthenated porphyrins onto a Nafion film. > The electrodes were characterized by SEM, TEM, AFM and SECM techniques. > The modified electrodes are active in the electrochemical reduction of nitrite at -660 mV vs Ag/AgCl. > GC/Nf/CoTRP modified electrode is more electrochemically active than their Ni and Zn analogues. - Abstract: This paper describes the electrochemical reduction of nitrite ion in neutral aqueous solution mediated by tetraruthenated metalloporphyrins (Co(II), Ni(II) and Zn(II)) electrostatically assembled onto a Nafion film previously adsorbed on glassy carbon or ITO electrodes. Scanning electron microscope (SEM-EDX) and transmission electron microscopy (TEM) results have shown that on ITO electrodes the macrocycles forms multiple layers with a disordered stacking orientation over the Nafion film occupying hydrophobic and hydrophilic sites in the polyelectrolyte. Atomic force microscopy (AFM) results demonstrated that the Nafion film is 35 nm thick and tetraruthenated metalloporphyrins layers 190 nm thick presenting a thin but compacted morphology. Scanning electrochemical microscopy (SECM) images shows that the Co(II) tetraruthenated porphyrins/Nf/GC modified electrode is more electrochemically active than their Ni and Zn analogues. These modified electrodes are able to reduce nitrite at -660 mV showing enhanced reduction current and a decrease in the required overpotential compared to bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine at potentials where reduction of solvent is plausible demonstrating some selectivity toward the nitrite ion. Rotating disc electrode voltammetry shows that the factor that governs the kinetics of nitrite reduction is the charge propagation in the film.

Harvesting solar light with crystalline carbon nitrides for efficient photocatalytic hydrogen evolution

KAUST Repository

Bhunia, Manas Kumar

2014-08-14

Described herein is the photocatalytic hydrogen evolution using crystalline carbon nitrides (CNs) obtained by supramolecular aggregation followed by ionic melt polycondensation (IMP) using melamine and 2,4,6-triaminopyrimidine as a dopant. The solid state NMR spectrum of 15N-enriched CN confirms the triazine as a building unit. Controlling the amount and arrangements of dopants in the CN structure can dramatically enhance the photocatalytic performance for H2 evolution. The polytriazine imide (PTI) exhibits the apparent quantum efficiency (AQE) of 15% at 400 nm. This method successfully enables a substantial amount of visible light to be harvested for H2 evolution, and provides a promising route for the rational design of a variety of highly active crystalline CN photocatalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Applications of high resolution NMR to geochemistry: crystalline, glass, and molten silicates

International Nuclear Information System (INIS)

Schneider, E.

1985-11-01

The nuclear spin interactions and the associated quantum mechanical dynamics which are present in solid state NMR are introduced. A brief overview of aluminosilicate structure is presented and crystalline structure is then reviewed, with emphasis on the contributions made by 29 Si NMR spectroscopy. The local structure of glass aluminosilicates as observed by NMR, is presented with analysis of the information content of 29 Si spectra. A high-temperature (to 1300 0 C) NMR spectroscopic investigation of the local environment and dynamics of molecular motion in molten aluminosilicates is described. A comparison is made of silicate liquid, glass, and crystalline local structure. The atomic and molecular motions present in a melt are investigated through relaxation time (T 1 and T 2 ) measurements as a function of composition and temperature for 23 Na and 29 Si

Raman spectra of zinc phthalocyanine monolayers absorbed on glassy carbon and gold electrodes by application of a confocal Raman microspectrometer

NARCIS (Netherlands)

Palys-Staron, B.J.; Palys, B.J.; Puppels, G.J.; Puppels, G.J.; van den Ham, D.M.W.; van den Ham, D.M.W.; Feil, D.; Feil, D.

1992-01-01

Raman spectra of zinc phthalocyanine monolayers, adsorbed on gold and on glassy carbon surfaces (electrodes), are presented. These spectra have been recorded with the electrodes inside and outside an electrochemical cell filled with an aqueous electrolyte. A confocal Raman microspectrometer was

Polyether based segmented copolymers with uniform aramid units

NARCIS (Netherlands)

Niesten, M.C.E.J.

2000-01-01

Segmented copolymers with short, glassy or crystalline hard segments and long, amorphous soft segments (multi-block copolymers) are thermoplastic elastomers (TPE’s). The hard segments form physical crosslinks for the amorphous (rubbery) soft segments. As a result, this type of materials combines

Role of atomic bonding for compound and glass formation in Ni-Si, Pd-Si, and Ni-B systems

Science.gov (United States)

Tanaka, K.; Saito, T.; Suzuki, K.; Hasegawa, R.

1985-11-01

Valence electronic structures of crystalline compounds and glassy alloys of Ni silicides, Pd silicides, and Ni borides are studied by soft-x-ray spectroscopy over wide ranges of Si and B concentrations. The samples prepared include bulk compounds, glassy ribbons, and amorphous sputtered films. Silicon Kβ emissions of Ni and Pd silicides generally consist of a prominent peak fixed at ~=4.5 and ~=5.8 eV below the Fermi level EF, respectively, with a shoulder near EF which grows and shifts toward lower energy with increasing Si concentration. The former is identified as due to Si p-like states forming Si 3p-Ni 3d or Si 3p-Pd 4d bonding states while the latter as due to the corresponding antibonding states. Ni L3 and Pd L3 emissions of these silicides indicate that Ni 3d and Pd 4d states lie between the above two states. These local electronic configurations are consistent with partial-density-of-states (PDOS) calculations performed by Bisi and Calandra. Similar electronic configurations are suggested for Ni borides from B Kα and Ni L3 emissions. Differences of emission spectra between compounds and glasses of similar compositions are rather small, but some enhancement of the contribution of antibonding states to the PDOS near EF is suggested for certain glasses over that of the corresponding compounds. These features are discussed in connection with the compound stability and glass formability.

Evidence of icosahedral short-range order in Zr70Cu30 and Zr70Cu29Pd1 metallic glasses

DEFF Research Database (Denmark)

Saksl, K.; Franz, H.; Jovari, P.

2003-01-01

Change in local atomic environment during crystallization of Zr-based glassy alloys was studied by extended x-ray absorption fine structure (EXAFS) spectroscopy. The formation of icosahedral quasicrystalline phase followed by crystallization of tetragonal CuZr2 has been observed in the Zr70Cu29Pd1...... glassy alloy during annealing up to 850 K. On the other hand, the binary Zr70Cu30 alloy shows a single glassy to crystalline CuZr2 phase transformation. The local atomic environment of as-quenched Zr70Cu30 alloy is matched to an icosahedral local atomic configuration, which is similar to that of the as......-quenched Zr70Cu29Pd1 alloy and the alloy annealed at 593 K containing icosahedral phase. Considering that the supercooled liquid region appears prior to crystallization in the Zr70Cu30 glassy alloy, the observed results support the theory claiming a strong correlation between the existence of local...

Activation of glassy carbon electrodes by photocatalytic pretreatment

Energy Technology Data Exchange (ETDEWEB)

Dumanli, Onur [Department of Chemistry, Faculty of Science and Art, Ondokuz Mayis University, Kurupelit, 55139 Samsun (Turkey); Onar, A. Nur [Department of Chemistry, Faculty of Science and Art, Ondokuz Mayis University, Kurupelit, 55139 Samsun (Turkey)], E-mail: nonar@omu.edu.tr

2009-11-01

This paper describes a simple and rapid photocatalytic pretreatment procedure that removes contaminants from glassy carbon (GC) surfaces. The effectiveness of TiO{sub 2} mediated photocatalytic pretreatment procedure was compared to commonly used alumina polishing procedure. Cyclic voltammetric and chronocoulometric measurements were carried out to assess the changes in electrode reactivity by using four redox systems. Electrochemical measurements obtained on photocatalytically treated GC electrodes showed a more active surface relative to polished GC. In cyclic voltammograms of epinephrine, Fe(CN){sub 6}{sup 3-/4-} and ferrocene redox systems, higher oxidation and reduction currents were observed. The heterogeneous electron transfer rate constants (k{sup o}) were calculated for Fe(CN){sub 6}{sup 3-/4-} and ferrocene which were greater for photocatalytic pretreatment. Chronocoulometry was performed in order to find the amount of adsorbed methylene blue onto the electrode and was calculated as 0.34 pmol cm{sup -2} for photocatalytically pretreated GC. The proposed photocatalytic GC electrode cleansing and activating pretreatment procedure was more effective than classical alumina polishing.

Simulations of tensile failure in glassy polymers: effect of cross-link density

International Nuclear Information System (INIS)

Panico, M; Narayanan, S; Brinson, L C

2010-01-01

Molecular dynamics simulations are adopted to investigate the failure mechanisms of glassy polymers, particularly with respect to increasing density of cross-links. In our simulations thermosetting polymers, which are cross-linked, exhibit an embrittlement compared with uncross-linked thermoplastics in a similar fashion to several experimental investigations (Levita et al 1991 J. Mater. Sci. 26 2348; Sambasivam et al 1997 J. Appl. Polym. Sci. 65 1001; Iijima et al 1992 Eur. Polym. J. 28 573). We perform a detailed analysis of this phenomenon and propose an interpretation based on the predominance of chain scission process over disentanglement in thermosetting polymers. We also elucidate the brittle fracture response of the thermosetting polymers

Apatite layer growth on glassy Zr{sub 48}Cu{sub 36}Al{sub 8}Ag{sub 8} sputtered titanium for potential biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Thanka Rajan, S.; Karthika, M. [Electrochemical Materials Science Division, CSIR-Central Electrochemical Research Institute, Karaikudi 630003 (India); Bendavid, Avi [Plasma Processing & Deposition Team, CSIRO Manufacturing Flagship, LindField, 2070, Sydney (Australia); Subramanian, B., E-mail: subramanianb3@gmail.com [Plasma Processing & Deposition Team, CSIRO Manufacturing Flagship, LindField, 2070, Sydney (Australia); Electrochemical Materials Science Division, CSIR-Central Electrochemical Research Institute, Karaikudi 630003 (India)

2016-04-30

Graphical abstract: - Highlights: • Metallic biomaterials are surface modified by Zr based TFMGs. • A bone-like apatite layer was grown on a Ni-free Zr-based TFMG in vitro. • Apatite layer growth confirmed by XRD and XPS analysis indicates its bioactivity. • Electrochemical response of the TFMGs in SBF possesses good corrosion resistance. - Abstract: The bioactivity of magnetron sputtered thin film metallic glasses (TFMGs) of Zr{sub 48}Cu{sub 36}Al{sub 8}Ag{sub 8} (at.%) on titanium substrates was tested for bio implant applications. The structural and elemental compositions of TFMGs were analyzed by XRD, XPS and EDAX. X-ray diffraction analysis displayed a broad hump around the incident angle of 30–50°, suggesting that the coatings possess a glassy structure. An in situ crystal growth of hydroxyapatite was observed by soaking the sputtered specimen in simulated body fluid (SBF). The nucleation and growth of a calcium phosphate (Ca–P) bone-like hydroxyapatite on Zr{sub 48}Cu{sub 36}Al{sub 8}Ag{sub 8} (at.%) TFMG from SBF was investigated by using XRD, AFM and SEM. The presence of calcium and phosphorus elements was confirmed by EDAX and XPS. In vitro electrochemical corrosion studies indicated that the Zr-based TFMG coating sustain in the stimulated body-fluid (SBF), exhibiting superior corrosion resistance with a lower corrosion penetration rate and electrochemical stability than the bare crystalline titanium substrate.

Crystalline morphology of the matrix of PEEK-carbon fiber aromatic polymer composites. I. Assessment of crystallinity

International Nuclear Information System (INIS)

Blundell, D.J.; Chalmers, J.M.; Mackenzie, M.W.; Gaskin, W.F.

1985-01-01

The crystallinity of the polyetheretherketone (PEEK) matrix polymer in the Aromatic Polymer Composite APC-2 has been estimated using a combination of techniques based on wide angle x-ray diffraction and infrared reflection spectroscopy. Crystallinity varies systematically with cooling rate and annealing time over the range 20 to 40%. The occurrence of oriented crystal growth of the PEEK relative to the carbon fiber can be monitored by x-ray diffraction. 8 references, 10 figures, 1 table

Irradiation sterilization of semi-crystalline polymers

International Nuclear Information System (INIS)

Williams, J.; Dunn, T.; Stannett, V.

1978-01-01

A semi-crystalline polymer such as polypropylene, is sterilized by high energy irradiation, with the polymer containing a non-crystalline mobilizing additive which increases the free volume of the polymer, to prevent embrittlement of the polymer during and subsequent to the irradiation. The additive has a density of from 0.6 to 1.9 g/cm 3 and a molecular weight from 100 to 10,000 g/mole

Performance comparison between crystalline and co-amorphous salts of indomethacin-lysine

DEFF Research Database (Denmark)

Kasten, Georgia; Nouri, Khatera; Grohganz, Holger

2017-01-01

The introduction of a highly water soluble amino acid as co-amorphous co-former has previously been shown to significantly improve the dissolution rate of poorly water soluble drugs. In this work, dry ball milling (DBM) and liquid assisted grinding (LAG) were used to prepare different physical...... forms of salts of indomethacin (IND) with the amino acid lysine (LYS), allowing the direct comparison of their solid-state properties to their in vitro performance. X-ray powder diffraction and Fourier-transformed infrared spectroscopy showed that DBM experiments led to the formation of a fully co......-amorphous salt, while LAG resulted in a crystalline salt. Differential scanning calorimetry showed that the samples prepared by DBM had a single glass transition temperature (Tg) of approx. 100°C for the co-amorphous salt, while a new melting point (223°C) was obtained for the crystalline salt prepared by LAG...

Crystalline structure of metals

International Nuclear Information System (INIS)

Holas, A.

1972-01-01

An attempt is made to find the crystalline structure of metals on the basis of the existing theory of metals. The considerations are limited to the case of free crystals, that is, not subjected to any stresses and with T=0. The energy of the crystal lattice has been defined and the dependence of each term on structures and other properties of metals has been described. The energy has been used to find the values of crystalline structure parameters as the values at which the energy has an absolute minimum. The stability of the structure has been considered in cases of volume changes and shearing deformations. A semiqualitative description has been obtained which explains characteristic properties of one-electron metals. (S.B.)

Role of αA-crystallin-derived αA66-80 peptide in guinea pig lens crystallin aggregation and insolubilization.

Science.gov (United States)

Raju, Murugesan; Mooney, Brian P; Thakkar, Kavi M; Giblin, Frank J; Schey, Kevin L; Sharma, K Krishna

2015-03-01

Earlier we reported that low molecular weight (LMW) peptides accumulate in aging human lens tissue and that among the LMW peptides, the chaperone inhibitor peptide αA66-80, derived from α-crystallin protein, is one of the predominant peptides. We showed that in vitro αA66-80 induces protein aggregation. The current study was undertaken to determine whether LMW peptides are also present in guinea pig lens tissue subjected to hyperbaric oxygen (HBO) in vivo. The nuclear opacity induced by HBO in guinea pig lens is the closest animal model for studying age-related cataract formation in humans. A LMW peptide profile by mass spectrometry showed the presence of an increased amount of LMW peptides in HBO-treated guinea pig lenses compared to age-matched controls. Interestingly, the mass spectrometric data also showed that the chaperone inhibitor peptide αA66-80 accumulates in HBO-treated guinea pig lens. Following incubation of synthetic chaperone inhibitor peptide αA66-80 with α-crystallin from guinea pig lens extracts, we observed a decreased ability of α-crystallin to inhibit the amorphous aggregation of the target protein alcohol dehydrogenase and the formation of large light scattering aggregates, similar to those we have observed with human α-crystallin and αA66-80 peptide. Further, time-lapse recordings showed that a preformed complex of α-crystallin and αA66-80 attracted additional crystallin molecules to form even larger aggregates. These results demonstrate that LMW peptide-mediated cataract development in aged human lens and in HBO-induced lens opacity in the guinea pig may have common molecular pathways. Copyright © 2015 Elsevier Ltd. All rights reserved.

A novel highly selective and sensitive detection of serotonin based on Ag/polypyrrole/Cu2O nanocomposite modified glassy carbon electrode.

Science.gov (United States)

Selvarajan, S; Suganthi, A; Rajarajan, M

2018-06-01

A silver/polypyrrole/copper oxide (Ag/PPy/Cu 2 O) ternary nanocomposite was prepared by sonochemical and oxidative polymerization simple way, in which Cu 2 O was decorated with Ag nanoparticles, and covered by polyprrole (PPy) layer. The as prepared materials was characterized by UV-vis-spectroscopy (UV-vis), FT-IR, X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) with EDX, high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Sensing of serotonin (5HT) was evaluated electrocatalyst using polypyrrole/glassy carbon electrode (PPy/GCE), polypyrrole/copper oxide/glassy carbon electrode (PPy/Cu 2 O/GCE) and silver/polypyrrole/copper oxide/glassy carbon electrode (Ag/PPy/Cu 2 O/GCE). The Ag/PPy/Cu 2 O/GCE was electrochemically treated in 0.1MPBS solution through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The peak current response increases linearly with 5-HT concentration from 0.01 to 250 µmol L -1 and the detection limit was found to be 0.0124 μmol L -1 . It exhibits high electrocatalytic activity, satisfactory repeatability, stability, fast response and good selectivity against potentially interfering species, which suggests its potential in the development of sensitive, selective, easy-operation and low-cost serotonin sensor for practical routine analyses. The proposed method is potential to expand the possible applied range of the nanocomposite material for detection of various concerned electro active substances. Copyright © 2018 Elsevier B.V. All rights reserved.

Local atomic and electronic structure in glassy metallic alloys. Final report, March 1, 1979-May 31, 1982

International Nuclear Information System (INIS)

Messmer, R.P.; Wong, J.

1982-01-01

The research results reported, represent the first coordinated experimental-theoretical effort to arrive at important local atomic and electronic structure information in glassy alloys. During the three years covered by the contract, significant experimental and theoretical developments have taken place both in the general technical community and at General Electric which have had an important impact on the approach to this problem. This is particularly true in the theoretical area where two important advances, the development of a general Xα-LCAO approach, and the development of a general and accurate effective potential approach for density functional methods, have allowed us to construct a new computational capability which combines these two advances. Two subsections briefly review the experimental and theoretical technical developments, respectively. These developments have changed initial perspectives regarding research on local atomic and electronic structure in glassy metallic alloys. Section II presents a synopsis of our accomplishments during the contract period and Section III contains a more detailed discussion of some of these accomplishments, namely those portions of the work which have been published or submitted for publication at the time of writing this final report

Multi-crystalline II-VI based multijunction solar cells and modules

Science.gov (United States)

Hardin, Brian E.; Connor, Stephen T.; Groves, James R.; Peters, Craig H.

2015-06-30

Multi-crystalline group II-VI solar cells and methods for fabrication of same are disclosed herein. A multi-crystalline group II-VI solar cell includes a first photovoltaic sub-cell comprising silicon, a tunnel junction, and a multi-crystalline second photovoltaic sub-cell. A plurality of the multi-crystalline group II-VI solar cells can be interconnected to form low cost, high throughput flat panel, low light concentration, and/or medium light concentration photovoltaic modules or devices.

Applications of high resolution NMR to geochemistry: crystalline, glass, and molten silicates

Energy Technology Data Exchange (ETDEWEB)

Schneider, E.

1985-11-01

The nuclear spin interactions and the associated quantum mechanical dynamics which are present in solid state NMR are introduced. A brief overview of aluminosilicate structure is presented and crystalline structure is then reviewed, with emphasis on the contributions made by /sup 29/Si NMR spectroscopy. The local structure of glass aluminosilicates as observed by NMR, is presented with analysis of the information content of /sup 29/Si spectra. A high-temperature (to 1300/sup 0/C) NMR spectroscopic investigation of the local environment and dynamics of molecular motion in molten aluminosilicates is described. A comparison is made of silicate liquid, glass, and crystalline local structure. The atomic and molecular motions present in a melt are investigated through relaxation time (T/sub 1/ and T/sub 2/) measurements as a function of composition and temperature for /sup 23/Na and /sup 29/Si.

Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

International Nuclear Information System (INIS)

Liu, F. B.; Jing, B.; Cui, Y.; Di, J. J.; Qu, M.

2015-01-01

The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed

Region-to-area screening methodology for the Crystalline Repository Project

International Nuclear Information System (INIS)

1985-04-01

The purpose of this document is to describe the Crystalline Repository Project's (CRP) process for region-to-area screening of exposed and near-surface crystalline rock bodies in the three regions of the conterminous United States where crystalline rock is being evaluated as a potential host for the second nuclear waste repository (i.e., in the North Central, Northeastern, and Southeastern Regions). This document indicates how the US Department of Energy's (DOE) General Guidelines for the Recommendation of Sites for Nuclear Waste Repositories (10 CFR 960) were used to select and apply factors and variables for the region-to-area screening, explains how these factors and variable are to be applied in the region-to-area screening, and indicates how this methodology relates to the decision process leading to the selection of candidate areas. A brief general discussion of the screening process from the national survey through area screening and site recommendation is presented. This discussion sets the scene for detailed discussions which follow concerning the region-to-area screening process, the guidance provided by the DOE Siting Guidelines for establishing disqualifying factors and variables for screening, and application of the disqualifying factors and variables in the screening process. This document is complementary to the regional geologic and environmental characterization reports to be issued in the summer of 1985 as final documents. These reports will contain the geologic and environmental data base that will be used in conjunction with the methodology to conduct region-to-area screening

Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode

Directory of Open Access Journals (Sweden)

Meareg Amare

2017-01-01

Full Text Available Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6×10-6 to 100×10-6 mol L−1 with determination coefficient and method detection limit (LoD = 3 s/slope of 0.99925 and 8.37×10-7 mol L−1, respectively, supplemented by recovery results of 93.79–102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w% of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users’ highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode.

Science.gov (United States)

Amare, Meareg; Aklog, Senait

2017-01-01

Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6 × 10 -6 to 100 × 10 -6  mol L -1 with determination coefficient and method detection limit (LoD = 3 s/slope) of 0.99925 and 8.37 × 10 -7  mol L -1 , respectively, supplemented by recovery results of 93.79-102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie) and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w%) of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users' highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

Controlling the morphology of side chain liquid crystalline block copolymer thin films through variations in liquid crystalline content.

Science.gov (United States)

Verploegen, Eric; Zhang, Tejia; Jung, Yeon Sik; Ross, Caroline; Hammond, Paula T

2008-10-01

In this paper, we describe methods for manipulating the morphology of side-chain liquid crystalline block copolymers through variations in the liquid crystalline content. By systematically controlling the covalent attachment of side chain liquid crystals to a block copolymer (BCP) backbone, the morphology of both the liquid crystalline (LC) mesophase and the phase-segregated BCP microstructures can be precisely manipulated. Increases in LC functionalization lead to stronger preferences for the anchoring of the LC mesophase relative to the substrate and the intermaterial dividing surface. By manipulating the strength of these interactions, the arrangement and ordering of the ultrathin film block copolymer nanostructures can be controlled, yielding a range of morphologies that includes perpendicular and parallel cylinders, as well as both perpendicular and parallel lamellae. Additionally, we demonstrate the utilization of selective etching to create a nanoporous liquid crystalline polymer thin film. The unique control over the orientation and order of the self-assembled morphologies with respect to the substrate will allow for the custom design of thin films for specific nanopatterning applications without manipulation of the surface chemistry or the application of external fields.

A study of the electro-catalytic oxidation of methanol on a cobalt hydroxide modified glassy carbon electrode

International Nuclear Information System (INIS)

Jafarian, M.; Mahjani, M.G.; Heli, H.; Gobal, F.; Khajehsharifi, H.; Hamedi, M.H.

2003-01-01

Cobalt hydroxide modified glassy carbon electrodes (CHM/GC) prepared by the anodic deposition in presence of tartrate ions have been used for the electro-catalytic oxidation of methanol in alkaline solutions where the methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (IS) have been employed. In CV studies, in the presence of methanol the peak current of the oxidation of cobalt hydroxide increase is followed by a decrease in the corresponding cathodic current. This suggests that the oxidation of methanol is being catalysed through the mediated electron transfer across the cobalt hydroxide layer comprising of cobalt ions of various valence states. A mechanism based on the electro-chemical generation of Co(IV) active sites and their subsequent consumptions by methanol have been discussed and the corresponding rate law under the control of charge transfer has been developed and kinetic parameters have been derived. In this context the charge transfer resistance accessible both theoretically and through the IS studies have been used as a criteria. Under the CA regimes the reaction followed a Cottrellian behaviour

Gamma crystallins of the human eye lens.

Science.gov (United States)

Vendra, Venkata Pulla Rao; Khan, Ismail; Chandani, Sushil; Muniyandi, Anbukkarasi; Balasubramanian, Dorairajan

2016-01-01

Protein crystallins co me in three types (α, β and γ) and are found predominantly in the eye, and particularly in the lens, where they are packed into a compact, plastic, elastic, and transparent globule of proper refractive power range that aids in focusing incoming light on to the retina. Of these, the γ-crystallins are found largely in the nuclear region of the lens at very high concentrations (>400 mg/ml). The connection between their structure and inter-molecular interactions and lens transparency is an issue of particular interest. We review the origin and phylogeny of the gamma crystallins, their special structure involving the use of Greek key supersecondary structural motif, and how they aid in offering the appropriate refractive index gradient, intermolecular short range attractive interactions (aiding in packing them into a transparent ball), the role that several of the constituent amino acid residues play in this process, the thermodynamic and kinetic stability and how even single point mutations can upset this delicate balance and lead to intermolecular aggregation, forming light-scattering particles which compromise transparency. We cite several examples of this, and illustrate this by cloning, expressing, isolating and comparing the properties of the mutant protein S39C of human γS-crystallin (associated with congenital cataract-microcornea), with those of the wild type molecule. In addition, we note that human γ-crystallins are also present in other parts of the eye (e.g., retina), where their functions are yet to be understood. There are several 'crucial' residues in and around the Greek key motifs which are essential to maintain the compact architecture of the crystallin molecules. We find that a mutation that replaces even one of these residues can lead to reduction in solubility, formation of light-scattering particles and loss of transparency in the molecular assembly. Such a molecular understanding of the process helps us construct the

[Representation and mathematical analysis of human crystalline lens].

Science.gov (United States)

Tălu, Stefan; Giovanzana, Stefano; Tălu, Mihai

2011-01-01

The surface of human crystalline lens can be described and analyzed using mathematical models based on parametric representations, used in biomechanical studies and 3D solid modeling of the lens. The mathematical models used in lens biomechanics allow the study and the behavior of crystalline lens on variables and complex dynamic loads. Also, the lens biomechanics has the potential to improve the results in the development of intraocular lenses and cataract surgery. The paper presents the most representative mathematical models currently used for the modeling of human crystalline lens, both optically and biomechanically.

Co-grinding Effect on Crystalline Zaltoprofen with β-cyclodextrin/Cucurbit[7]uril in Tablet Formulation

Science.gov (United States)

Li, Shanshan; Lin, Xiang; Xu, Kailin; He, Jiawei; Yang, Hongqin; Li, Hui

2017-04-01

This work aimed to investigate the co-grinding effects of β-cyclodextrin (β-CD) and cucurbit[7]uril (CB[7]) on crystalline zaltoprofen (ZPF) in tablet formulation. Crystalline ZPF was prepared through anti-solvent recrystallization and fully analyzed through single-crystal X-ray diffraction. Co-ground dispersions and mono-ground ZPF were prepared using a ball grinding process. Results revealed that mono-ground ZPF slightly affected the solid state, solubility, and dissolution of crystalline ZPF. Co-ground dispersions exhibited completely amorphous states and elicited a significant reinforcing effect on drug solubility. UV-vis spectroscopy, XRPD, FT-IR, DSC, ssNMR, and molecular docking demonstrated the interactions in the amorphous product. Hardness tests on blank tablets with different β-CD and CB[7] contents suggested the addition of β-CD or CB[7] could enhance the compressibility of the powder mixture. Disintegration tests showed that CB[7] could efficiently shorten the disintegrating time. Dissolution tests indicated that β-CD and CB[7] could accelerate the drug dissolution rate via different mechanisms. Specifically, CB[7] could accelerate the dissolution rate by improving disintegration and β-CD showed a distinct advantage in solubility enhancement. Based on the comparative study on β-CD and CB[7] for tablet formulation combined with co-grinding, we found that CB[7] could be considered a promising drug delivery, which acted as a disintegrant.

Co-grinding Effect on Crystalline Zaltoprofen with β-cyclodextrin/Cucurbit[7]uril in Tablet Formulation

Science.gov (United States)

Li, Shanshan; Lin, Xiang; Xu, Kailin; He, Jiawei; Yang, Hongqin; Li, Hui

2017-01-01

This work aimed to investigate the co-grinding effects of β-cyclodextrin (β-CD) and cucurbit[7]uril (CB[7]) on crystalline zaltoprofen (ZPF) in tablet formulation. Crystalline ZPF was prepared through anti-solvent recrystallization and fully analyzed through single-crystal X-ray diffraction. Co-ground dispersions and mono-ground ZPF were prepared using a ball grinding process. Results revealed that mono-ground ZPF slightly affected the solid state, solubility, and dissolution of crystalline ZPF. Co-ground dispersions exhibited completely amorphous states and elicited a significant reinforcing effect on drug solubility. UV-vis spectroscopy, XRPD, FT-IR, DSC, ssNMR, and molecular docking demonstrated the interactions in the amorphous product. Hardness tests on blank tablets with different β-CD and CB[7] contents suggested the addition of β-CD or CB[7] could enhance the compressibility of the powder mixture. Disintegration tests showed that CB[7] could efficiently shorten the disintegrating time. Dissolution tests indicated that β-CD and CB[7] could accelerate the drug dissolution rate via different mechanisms. Specifically, CB[7] could accelerate the dissolution rate by improving disintegration and β-CD showed a distinct advantage in solubility enhancement. Based on the comparative study on β-CD and CB[7] for tablet formulation combined with co-grinding, we found that CB[7] could be considered a promising drug delivery, which acted as a disintegrant. PMID:28368030

Crystallinity and flux pinning properties of MgB2 bulks

International Nuclear Information System (INIS)

Yamamoto, A.; Shimoyama, J.; Ueda, S.; Katsura, Y.; Iwayama, I.; Horii, S.; Kishio, K.

2006-01-01

The relationship between flux pinning properties and crystallinity of MgB 2 bulks was systematically studied. Improved flux pinning properties under high fields were observed for samples with low crystallinity. Increased impurity scattering due to strain and defects in lattice corresponding to the degraded crystallinity was considered to enhance flux pinning strength at grain boundaries. Low-temperature synthesis and carbon substitution were confirmed to be effective for degrading crystallinity of MgB 2 bulks, resulting in high critical current properties under high fields

Liquid-Crystalline Ionic Liquids as Ordered Reaction Media for the Diels-Alder Reaction.

Science.gov (United States)

Bruce, Duncan W; Gao, Yanan; Canongia Lopes, José Nuno; Shimizu, Karina; Slattery, John M

2016-11-02

Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels-Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo:exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solution processed nanogap organic diodes based on liquid crystalline materials

Science.gov (United States)

Wang, Yi-Fei; Iino, Hiroaki; Hanna, Jun-ichi

2017-09-01

Co-planar nanogap organic diodes were fabricated with smectic liquid crystalline materials of the benzothienobenzothiophene (BTBT) derivative by a spin-coating technique. A high rectification ratio of the order of 106 at ±3 V was achieved when a liquid crystalline material of 2,7-didecyl benzothieno[3,2-b][1]benzothiophene (10-BTBT-10) was used in a device configuration of Al/10-BTBT-10/pentafluorobenzenethiol-treated Au on a glass substrate, which was 4 orders higher than that of the device based on non-liquid crystalline materials of 2,7-dibutyl benzothieno[3,2-b][1]benzothiophene (4-BTBT-4) and BTBT. Similar results were also observed when another liquid crystalline material of ω, ω'-dioctylterthiophene (8-TTP-8) and a non-liquid crystalline material of terthiophene (TTP) were used. These improved rectifications can be ascribed to the self-assembly properties and controllable molecular orientation of liquid crystalline materials, which made uniform perpendicular oriented polycrystalline films favorable for superior charge transport in nano-channels.

Biocompatibility of crystalline opal nanoparticles.

Science.gov (United States)

Hernández-Ortiz, Marlen; Acosta-Torres, Laura S; Hernández-Padrón, Genoveva; Mendieta, Alicia I; Bernal, Rodolfo; Cruz-Vázquez, Catalina; Castaño, Victor M

2012-10-22

Silica nanoparticles are being developed as a host of biomedical and biotechnological applications. For this reason, there are more studies about biocompatibility of silica with amorphous and crystalline structure. Except hydrated silica (opal), despite is presents directly and indirectly in humans. Two sizes of crystalline opal nanoparticles were investigated in this work under criteria of toxicology. In particular, cytotoxic and genotoxic effects caused by opal nanoparticles (80 and 120 nm) were evaluated in cultured mouse cells via a set of bioassays, methylthiazolyldiphenyl-tetrazolium-bromide (MTT) and 5-bromo-2'-deoxyuridine (BrdU). 3T3-NIH cells were incubated for 24 and 72 h in contact with nanocrystalline opal particles, not presented significant statistically difference in the results of cytotoxicity. Genotoxicity tests of crystalline opal nanoparticles were performed by the BrdU assay on the same cultured cells for 24 h incubation. The reduction of BrdU-incorporated cells indicates that nanocrystalline opal exposure did not caused unrepairable damage DNA. There is no relationship between that particles size and MTT reduction, as well as BrdU incorporation, such that the opal particles did not induce cytotoxic effect and genotoxicity in cultured mouse cells.

Graphene on insulating crystalline substrates

International Nuclear Information System (INIS)

Akcoeltekin, S; El Kharrazi, M; Koehler, B; Lorke, A; Schleberger, M

2009-01-01

We show that it is possible to prepare and identify ultra-thin sheets of graphene on crystalline substrates such as SrTiO 3 , TiO 2 , Al 2 O 3 and CaF 2 by standard techniques (mechanical exfoliation, optical and atomic force microscopy). On the substrates under consideration we find a similar distribution of single layer, bilayer and few-layer graphene and graphite flakes as with conventional SiO 2 substrates. The optical contrast C of a single graphene layer on any of those substrates is determined by calculating the optical properties of a two-dimensional metallic sheet on the surface of a dielectric, which yields values between C = -1.5% (G/TiO 2 ) and C = -8.8% (G/CaF 2 ). This contrast is in reasonable agreement with experimental data and is sufficient to make identification by an optical microscope possible. The graphene layers cover the crystalline substrate in a carpet-like mode and the height of single layer graphene on any of the crystalline substrates as determined by atomic force microscopy is d SLG = 0.34 nm and thus much smaller than on SiO 2 .

Highly tilted liquid crystalline materials possessing a direct phase transition from antiferroelectric to isotropic phase

Energy Technology Data Exchange (ETDEWEB)

Milewska, K.; Drzewiński, W. [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland); Czerwiński, M., E-mail: mczerwinski@wat.edu.pl [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland); Dąbrowski, R. [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland); Piecek, W. [Institute of Applied Physics, Military University of Technology, 00-908 Warsaw (Poland)

2016-03-01

Pure compounds and multicomponent mixtures with a broad temperature range of high tilted liquid crystalline antiferroelectric phase and a direct phase transition from antiferroelectric to isotropic phase, were obtained. X-ray diffraction analysis confirms these kinds of materials form a high tilted anticlinic phase, with a fixed layer spacing and very weak dependency upon temperature, after the transition from the isotropic phase. Due to this, not only pure orthoconic antiferroelectric liquid crystals but also those with a moderate tilt should generate a good dark state. Furthermore, due to the increased potential for forming anticlinic forces, such materials could minimize a commonly observed asymmetry of a rise and fall switching times at a surface stabilized geometry. - Highlights: • The new class of liquid crystalline materials with the direct SmC{sub A}*. • Iso phase transition were obtained. • Materials possess the layer spacing fixed and very weak dependent upon temperature. • Smectic layers without shrinkage are observed. • A good dark state can be generate in SSAFLC.

Colloidal glasses

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Colloidal glasses. Glassy state is attained when system fails to reach equilibrium due to crowding of constituent particles. In molecular glasses, glassy state is reached by rapidly lowering the temperature. In colloidal glasses, glassy state is reached by increasing the ...

Diffractometric method for determining the degree of crystallinity of materials

Energy Technology Data Exchange (ETDEWEB)

Chukhchin, D. G., E-mail: dimatsch@mail.ru; Malkov, A. V.; Tyshkunova, I. V.; Mayer, L. V.; Novozhilov, E. V. [Lomonosov Northen (Arctic) Federal University (Russian Federation)

2016-05-15

A new method for determining the degree of crystallinity of a material from X-ray diffraction data has been developed. The method is based on estimating the rate of change in function I = f(2θ) in the entire range of scattering angles. A calculation is performed using the ratio of the integral modulus of the first derivative of intensity with respect to angle 2θ to the integral area under the diffraction pattern curve. The method was tested on two substances with known amorphous and crystalline components. A linear relationship is revealed between the specified ratio of crystalline and amorphous parts and the calculated crystallinity index. The proposed method allows one to estimate impartially and compare the degree of crystallinity for samples of different nature.

Early hydration of portland cement with crystalline mineral additions

International Nuclear Information System (INIS)

Rahhal, V.; Talero, R.

2005-01-01

This research presents the effects of finely divided crystalline mineral additions (quartz and limestone), commonly known as filler, on the early hydration of portland cements with very different mineralogical composition. The used techniques to study the early hydration of blended cements were conduction calorimeter, hydraulicity (Fratini's test), non-evaporable water and X-ray diffraction. Results showed that the stimulation and the dilution effects increase when the percentage of crystalline mineral additions used is increased. Depending on the replacement proportion, the mineralogical cement composition and the type of crystalline addition, at 2 days, the prevalence of the dilution effect or the stimulation effect shows that crystalline mineral additions could act as sites of heat dissipation or heat stimulation, respectively

Hydrogen passivation of multi-crystalline silicon solar cells

Institute of Scientific and Technical Information of China (English)

胡志华; 廖显伯; 刘祖明; 夏朝凤; 陈庭金

2003-01-01

The effects of hydrogen passivation on multi-crystalline silicon (mc-Si) solar cells are reported in this paper.Hydrogen plasma was generated by means of ac glow discharge in a hydrogen atmosphere. Hydrogen passivation was carried out with three different groups of mc-Si solar cells after finishing contacts. The experimental results demonstrated that the photovoltaic performances of the solar cell samples have been improved after hydrogen plasma treatment, with a relative increase in conversion efficiency up to 10.6%. A calculation modelling has been performed to interpret the experimental results using the model for analysis of microelectronic and photonic structures developed at Pennsylvania State University.

Impact of change of matrix crystallinity and polymorphism on ovalbumin release from lipid-based implants.

Science.gov (United States)

Duque, Luisa; Körber, Martin; Bodmeier, Roland

2018-05-30

The objectives of this study were to prepare lipid-based implants by hot melt extrusion (HME) for the prolonged release of ovalbumin (OVA), and to relate protein release to crystallinity and polymorphic changes of the lipid matrix. Two lipids, glycerol tristearate and hydrogenated palm oil, with different composition and degree of crystallinity were studied. Solid OVA was dispersed within the lipid matrixes, which preserved its stability during extrusion. This was partially attributed to a protective effect of the lipidic matrix. The incorporation of OVA decreased the mechanical strength of the implants prepared with the more crystalline matrix, glycerol tristearate, whereas it remained comparable for the hydrogenated palm oil because of stronger physical and non-covalent interactions between the protein and this lipid. This was also the reason for the faster release of OVA from the glycerol tristearate matrix when compared to the hydrogenated palm oil (8 vs. 28 weeks). Curing induced and increased crystallinity, and changes in the release rate, especially for the more crystalline matrix. In this case, both an increase and a decrease in release, were observed depending on the tempering condition. Curing at higher temperatures induced a melt-mediated crystallization and solid state transformation of the glycerol tristearate matrix and led to rearrangements of the inner structure with the formation of larger pores, which accelerated the release. In contrast, changes in the hydrogenated palm oil under the same curing conditions were less noticeable leading to a more robust formulation, because of less polymorphic changes over time. This study helps to understand the effect of lipid matrix composition and crystallinity degree on the performance of protein-loaded implants, and to establish criteria for the selection of a lipid carrier depending on the release profile desired. Copyright © 2018. Published by Elsevier B.V.

Terahertz and direct current losses and the origin of non-Drude terahertz conductivity in the crystalline states of phase change materials

Energy Technology Data Exchange (ETDEWEB)

Shimakawa, Koichi [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice (Czech Republic); Department of Electrical Engineering, Gifu University (Japan); Wagner, Tomas; Frumar, Miloslav [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice (Czech Republic); Kadlec, Filip; Kadlec, Christelle [Institute of Physics, Academy of Sciences of the Czech Republic, Prague (Czech Republic); Kasap, Safa [Department of Electrical Engineering, University of Saskatchewan, Saskatoon SK S7N 5A9 (Canada)

2013-12-21

THz and DC losses in crystalline states of GeSbTe and AgInSbTe phase-change material systems are re-examined and discussed. Although a simple free carrier transport has been assumed so far in the GeSbTe (GST) system, it is shown through recent experimental results that a series sequence of intragrain and intergrain (tunneling) transport, as recently formulated in Shimakawa et al., “The origin of non-Drude terahertz conductivity in nanomaterials,” Appl. Phys. Lett. 100, 132102 (2012) may dominate the electronic transport in the commercially utilized GST system, producing a non-Drude THz conductivity. The extracted physical parameters such as the free-carrier density and mobility are significantly different from those obtained from the Drude law. These physical parameters are consistent with those obtained from the DC loss data, and provide further support for the model. Negative temperature coefficient of resistivity is found even in the metallic state, similar to amorphous metals, when the mean free path is short. It is shown that the concept of minimum metallic conductivity, often used in the metal-insulator transition, cannot be applied to electronic transport in these materials.

Quantitative aspects of crystalline lactose in milk products

NARCIS (Netherlands)

Roetman, K.

1982-01-01

The occurrence of crystalline lactose in milk products and its influence on their physical properties are briefly reviewed. The importance of the quantitive determination of crystalline lactose for scientific and industrial purposes is indicated, and a summary is given of our earlier work. This

Attenuation of Thermal Neutrons by Crystalline Silicon

International Nuclear Information System (INIS)

Adib, M.; Habib, N.; Ashry, A.; Fathalla, M.

2002-01-01

A simple formula is given which allows to calculate the contribution of the total neutron cross - section including the Bragg scattering from different (hkt) planes to the neutron * transmission through a solid crystalline silicon. The formula takes into account the silicon form of poly or mono crystals and its parameters. A computer program DSIC was developed to provide the required calculations. The calculated values of the total neutron cross-section of perfect silicon crystal at room and liquid nitrogen temperatures were compared with the experimental ones. The obtained agreement shows that the simple formula fits the experimental data with sufficient accuracy .A good agreement was also obtained between the calculated and measured values of polycrystalline silicon in the energy range from 5 eV to 500μ eV. The feasibility study on using a poly-crystalline silicon as a cold neutron filter and mono-crystalline as a thermal neutron one is given. The optimum crystal thickness, mosaic spread, temperature and cutting plane for efficiently transmitting the thermal reactor neutrons, while rejecting both fast neutrons and gamma rays accompanying the thermal ones for the mono crystalline silicon are also given

Low-dose radiation effects on the evolution of chronic dystrophical processes in cornea and clouding of crystalline lens

International Nuclear Information System (INIS)

Gajdaj, Yu.V.; Gajdaj, V.M.

1993-01-01

Low-dose radiation effects on the course of chronic dystrophical processes in cornea and the dynamics of crystalline lens clouding of involution age genesis are investigated in the patients participated in Chernobyl accident response. Examples of the concrete pathological cases are considered. It was stated that the above dose effects led to exacerbation of the chronic slack dystrophical processes in cornea and intensification of the development of cornea primary dystrophy. In a number of cases the intensification of development of crystalline lens clouding takes place resulted in the cataract for 2-3 years

A Hybrid Solid-State NMR and Electron Microscopy Structure-Determination Protocol for Engineering Advanced para-Crystalline Optical Materials

NARCIS (Netherlands)

Thomas, Brijith; Rombouts, Jeroen; Oostergetel, Gert T.; Gupta, Karthick B.S.S.; Buda, Francesco; Lammertsma, Koop; Orru, Romano; de Groot, Huub J.M.

2017-01-01

Hybrid magic-angle spinning (MAS) NMR spectroscopy and TEM were demonstrated for de novo structure determination of para-crystalline materials with a bioinspired fused naphthalene diimide (NDI)–salphen–phenazine prototype light-harvesting compound. Starting from chiral building blocks with C2

Electrochemical parameters of ethamsylate at multi-walled carbon nanotube modified glassy carbon electrodes.

Science.gov (United States)

Wang, Sheng-Fu; Xu, Qiao

2007-05-01

In this paper, some electrochemical parameters of ethamsylate at a multi-walled carbon nanotube modified glassy carbon electrode, such as the charge number, exchange current density, standard heterogeneous rate constant and diffusion coefficient, were measured by cyclic voltammetry, chronoamperometry and chronocoulometry. The modified electrode exhibits good promotion of the electrochemical reaction of ethamsylate and increases the standard heterogeneous rate constant of ethamsylate greatly. The differential pulse voltammetry responses of ethamsylate were linearly dependent on its concentrations in a range from 2.0 x 10(-6) to 6.0 x 10(-5) mol L(-1), with a detection limit of 4.0 x 10(-7) mol L(-1).

Electronic Transport Behaviors due to Charge Density Waves in Ni-Nb-Zr-H Glassy Alloys

Science.gov (United States)

Fukuhara, Mikio; Umemori, Yoshimasa

2013-11-01

The amorphous Ni-Nb-Zr-H glassy alloy containing subnanometer-sized icosahedral Zr5 Nb5Ni3 clusters exhibited four types of electronic phenomena: a metal/insulator transition, an electric current-induced voltage oscillation (Coulomb oscillation), giant capacitor behavior and an electron avalanche with superior resistivity. These findings could be excluded by charge density waves that the low-dimensional component of clusters, in which the atoms are lined up in chains along the [130] direction, plays important roles in various electron transport phenomena.

Electrocatalytic performance of Pu(IV)/Pu(III) redox reaction at graphene modified glassy carbon electrode

International Nuclear Information System (INIS)

Gupta, Ruma; Gamare, J.S.; Kamat, J.V.; Aggarwal, S.K.

2014-01-01

In this paper we explore the analytical perspectives of graphene modified electrode utilising commercially available graphene, which is well characterised, completely free from surfactants and has not been purposely oxidised or treated. We compare and critically contrast the electro-analytical performance of graphene modified glassy carbon electrodes (Gr/GC) with that of unmodified GC electrode towards Pu(IV)/Pu(III) redox reaction, monitoring of which has considerable importance in a plethora of areas where electrochemistry is conveniently and beneficially utilised for determination of nuclear fuels

Nonlinear optical properties of TeO$_2$ crystalline phases from first principles

OpenAIRE

Berkaine, Nabil; Orhan, Emmanuelle; Masson, Olivier; Thomas, Philippe; Junquera, Javier

2010-01-01

We have computed second and third nonlinear optical susceptibilities of two crystalline bulk tellurium oxide polymorphs: $\\alpha$-TeO$_{2}$ (the most stable crystalline bulk phase) and $\\gamma$-TeO$_{2}$ (the crystalline phase that ressembles the more to the glass phase. Third order nonlinear susceptibilities of the crystalline phases are two orders of magnitude larger than $\\alpha$-SiO$_{2}$ cristoballite, thus extending the experimental observations on glasses to the case of crystalline com...

The temperature dependent amide I band of crystalline acetanilide

Energy Technology Data Exchange (ETDEWEB)

Cruzeiro, Leonor [CCMAR, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Physics Department, FCT, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Freedman, Holly [CCMAR, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)

2013-10-01

The temperature dependent anomalous peak in the amide I band of crystalline acetanilide is thought to be due to self-trapped states. On the contrary, according to the present model, the anomalous peak comes from the fraction of ACN molecules strongly hydrogen-bonded to a neighboring ACN molecule, and its intensity decreases because, on average, this fraction decreases as temperature increases. This model provides, for the first time, an integrated and theoretically consistent view of the temperature dependence of the full amide I band and a qualitative explanation of some of the features of nonlinear pump–probe experiments.

The temperature dependent amide I band of crystalline acetanilide

Science.gov (United States)

Cruzeiro, Leonor; Freedman, Holly

2013-10-01

The temperature dependent anomalous peak in the amide I band of crystalline acetanilide is thought to be due to self-trapped states. On the contrary, according to the present model, the anomalous peak comes from the fraction of ACN molecules strongly hydrogen-bonded to a neighboring ACN molecule, and its intensity decreases because, on average, this fraction decreases as temperature increases. This model provides, for the first time, an integrated and theoretically consistent view of the temperature dependence of the full amide I band and a qualitative explanation of some of the features of nonlinear pump-probe experiments.

The temperature dependent amide I band of crystalline acetanilide

International Nuclear Information System (INIS)

Cruzeiro, Leonor; Freedman, Holly

2013-01-01

The temperature dependent anomalous peak in the amide I band of crystalline acetanilide is thought to be due to self-trapped states. On the contrary, according to the present model, the anomalous peak comes from the fraction of ACN molecules strongly hydrogen-bonded to a neighboring ACN molecule, and its intensity decreases because, on average, this fraction decreases as temperature increases. This model provides, for the first time, an integrated and theoretically consistent view of the temperature dependence of the full amide I band and a qualitative explanation of some of the features of nonlinear pump–probe experiments.

Amplitude dependent damping in single crystalline high purity molybdenum

International Nuclear Information System (INIS)

Zelada-Lambri, G.I; Lambri, O.A; Garcia, J.A; Lomer, J.N

2004-01-01

Amplitude dependent damping measurements were performed on high purity single crystalline molybdenum at several different constant temperatures between room temperature and 1273K. The employed samples were single crystals with the orientation, having a residual resistivity ratio of about 8000. Previously to the amplitude dependent damping tests, the samples were subjected to different thermomechanical histories. Amplitude dependent damping effects appear only during the first heating run in temperature where the samples have the thermomechanical state of the deformation process at room temperature. In the subsequent run-ups in temperature, i.e, after subsequent annealings, amplitude dependent damping effects were not detected (au)

Influence of surface morphology on methanol oxidation at a glassy carbon-supported Pt catalyst

Directory of Open Access Journals (Sweden)

S. STEVANOVIC

2008-08-01

Full Text Available Platinum supported on glassy carbon (GC was used as a model system for studying the influence of the surface morphology of a Pt catalyst on methanol oxidation in alkaline and acidic solutions. Platinum was deposited by the potential step method on GC samples from H2SO4 + H2PtCl6 solution under the same conditions with loadings from 10 to 80 mg cm-2. AFM and STM images of the GC/Pt electrodes showed that the Pt was deposited in the form of 3D agglomerates composed of spherical particles. Longer deposition times resulted in increased growth of Pt forms and a decrease in the specific area of the Pt. The real surface area of Pt increased with loading but the changes were almost negligible at higher loadings. Nevertheless, both the specific and mass activity of platinum supported on glassy carbon for methanol oxidation in acidic and in alkaline solutions exhibit a volcanic dependence with respect to the platinum loading. The increase in the activity can be explained by the increasing the particle size with the loading and thus an increase in the contiguous Pt sites available for adsorption and decomposition of methanol. However, the decrease in the activity of the catalyst with further increase of loading and particle size after reaching the maximum is related to the decrease of active sites available for methanol adsorption and their accessibility as a result of more close proximity and pronounced coalescence of the Pt particles.

Novel polypyrrole films with excellent crystallinity and good thermal stability

International Nuclear Information System (INIS)

Jeeju, Pullarkat P.; Varma, Sreekanth J.; Francis Xavier, Puthampadath A.; Sajimol, Augustine M.; Jayalekshmi, Sankaran

2012-01-01

Polypyrrole has drawn a lot of interest due to its high thermal and environmental stability in addition to high electrical conductivity. The present work highlights the enhanced crystallinity of polypyrrole films prepared from the redoped sample solution. Initially hydrochloric acid doped polypyrrole was prepared by chemical oxidative polymerization of pyrrole using ammonium peroxidisulphate as oxidant. The doped polypyrrole was dedoped using ammonia solution and then redoped with camphor sulphonic acid. Films were coated on ultrasonically cleaned glass substrates from the redoped sample solution in meta-cresol. The enhanced crystallinity of the polypyrrole films has been established from X-ray diffraction (XRD) studies. The room temperature electrical conductivity of the redoped polypyrrole film is about 30 times higher than that of the hydrochloric acid doped pellet sample. The results of Raman spectroscopy, Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) of the samples support the enhancement in crystallinity. Percentage crystallinity of the samples is estimated from XRD and DSC data. The present work is significant, since crystallinity of films is an important parameter for selecting polymers for specific applications. - Highlights: ► Polypyrrole films redoped with CSA have been prepared from meta-cresol solution. ► The solution casted films exhibit semi-crystallinity and good thermal stability. ► Percentage crystallinity estimated using XRD and DSC analysis is about 65%. ► Raman studies support the enhancement in crystallinity based on XRD and DSC data. ► The conductivity of the film is 30 times higher than that of HCl doped sample.

Novel polypyrrole films with excellent crystallinity and good thermal stability

Energy Technology Data Exchange (ETDEWEB)

Jeeju, Pullarkat P., E-mail: jeejupp@gmail.com [Division for Research in Advanced Materials, Department of Physics, Cochin University of Science and Technology, Cochin-22, Kerala (India); Varma, Sreekanth J.; Francis Xavier, Puthampadath A.; Sajimol, Augustine M. [Division for Research in Advanced Materials, Department of Physics, Cochin University of Science and Technology, Cochin-22, Kerala (India); Jayalekshmi, Sankaran, E-mail: jayalekshmi@cusat.ac.in [Division for Research in Advanced Materials, Department of Physics, Cochin University of Science and Technology, Cochin-22, Kerala (India)

2012-06-15

Polypyrrole has drawn a lot of interest due to its high thermal and environmental stability in addition to high electrical conductivity. The present work highlights the enhanced crystallinity of polypyrrole films prepared from the redoped sample solution. Initially hydrochloric acid doped polypyrrole was prepared by chemical oxidative polymerization of pyrrole using ammonium peroxidisulphate as oxidant. The doped polypyrrole was dedoped using ammonia solution and then redoped with camphor sulphonic acid. Films were coated on ultrasonically cleaned glass substrates from the redoped sample solution in meta-cresol. The enhanced crystallinity of the polypyrrole films has been established from X-ray diffraction (XRD) studies. The room temperature electrical conductivity of the redoped polypyrrole film is about 30 times higher than that of the hydrochloric acid doped pellet sample. The results of Raman spectroscopy, Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) of the samples support the enhancement in crystallinity. Percentage crystallinity of the samples is estimated from XRD and DSC data. The present work is significant, since crystallinity of films is an important parameter for selecting polymers for specific applications. - Highlights: Black-Right-Pointing-Pointer Polypyrrole films redoped with CSA have been prepared from meta-cresol solution. Black-Right-Pointing-Pointer The solution casted films exhibit semi-crystallinity and good thermal stability. Black-Right-Pointing-Pointer Percentage crystallinity estimated using XRD and DSC analysis is about 65%. Black-Right-Pointing-Pointer Raman studies support the enhancement in crystallinity based on XRD and DSC data. Black-Right-Pointing-Pointer The conductivity of the film is 30 times higher than that of HCl doped sample.

The hydrocarbon accumulations mapping in crystalline rocks by mobile geophysical methods

Science.gov (United States)

Nesterenko, A.

2013-05-01

Sedimentary-migration origin theory of hydrocarbons dominates nowadays. However, a significant amount of hydrocarbon deposits were discovered in the crystalline rocks, which corroborates the theory of non-organic origin of hydrocarbons. During the solving of problems of oil and gas exploration in crystalline rocks and arrays so-called "direct" methods can be used. These methods include geoelectric methods of forming short-pulsed electromagnetic field (FSPEF) and vertical electric-resonance sounding (VERS) (FSPEF-VERS express-technology). Use of remote Earth sounding (RES) methods is also actual. These mobile technologies are extensively used during the exploration of hydrocarbon accumulations in crystalline rocks, including those within the Ukrainian crystalline shield. The results of explorations Four anomalous geoelectric zones of "gas condensate reservoir" type were quickly revealed as a result of reconnaissance prospecting works (Fig. 1). DTA "Obukhovychi". Anomaly was traced over a distance of 4 km. Approximate area is 12.0 km2. DTA"Korolevskaya". Preliminary established size of anomalous zone is 10.0 km2. The anomalous polarized layers of gas and gas-condensate type were determined. DTA "Olizarovskaya". Approximate size of anomaly is about 56.0 km2. This anomaly is the largest and the most intense. DTA "Druzhba". Preliminary estimated size of anomaly is 16.0 km2. Conclusions Long experience of a successful application of non-classical geoelectric methods for the solving of variety of practical tasks allow one to state their contribution to the development of a new paradigm of geophysical researches. Simultaneous usage of the remote sensing data processing and interpretation method and FSPEF and VERS technologies can essentially optimize and speed up geophysical work. References 1. S.P. Levashov. Detection and mapping of anomalies of "hydrocarbon deposit" type in the fault zones of crystalline arrays by geoelectric methods. / S.P. Levashov, N.A. Yakymchuk, I