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Sample records for ni-nb-zr-h glassy alloys

  1. Room-temperature nonlinear transport phenomena in low-dimensional Ni-Nb-Zr-H glassy alloys and its device

    SciTech Connect

    Fukuhara, Mikio; Yoshida, Hajime

    2014-05-15

    We report the room-temperature switching and Coulomb blockade effects in three–terminal glassy alloy field effect transistor (GAFET), using the millimeter sized glassy alloy. By applying dc and ac voltages to a gate electrode, GAFET can be switched from a metallic conducting state to an insulating state with Coulomb oscillation at a period of 14 μV at room temperature. The transistor showed the three-dimensional Coulomb diamond structure. The fabrication of a low-energy controllable device throws a new light on cluster electronics without wiring.

  2. Proton nuclear magnetic resonance studies of hydrogen diffusion and electron tunneling in Ni-Nb-Zr-H glassy alloys

    SciTech Connect

    Niki, Haruo; Okuda, Hiroyuki; Oshiro, Morihito; Yogi, Mamoru; Seki, Ichiro; Fukuhara, Mikio

    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.

  3. Deformation and Fracture Behavior of Metallic Glassy Alloys and Glassy-Crystal Composites

    NASA Astrophysics Data System (ADS)

    Louzguine-Luzgin, D. V.; Vinogradov, A.; Li, S.; Kawashima, A.; Xie, G.; Yavari, A. R.; Inoue, A.

    2011-06-01

    The present work demonstrates the deformation behavior of Zr-Cu-Ni-Al bulk glassy alloys and Zr-Ni-Cu-Al-Pd glassy foils as well as Ni-Cu-Ti-Zr bulk crystal-glassy composites. Fracture of Zr60Cu16Ni14Al10 and Zr64.13Ni10.12Cu15.75Al10 bulk glassy alloys is featured by nearly equal fraction areas of cleavage-like and vein-type relief. The observed pattern of alternating cleavage-like and vein-type patterns illustrates a result of dynamically self-organizing shear propagation at the final catastrophic stage. The deformation behavior of Zr64.13Ni10.12Cu15.75Al10 alloy has also been tested at LN2 temperature. The strength of the sample decreases with temperature, and no clear serrated flow typical for bulk glassy samples tested at room temperature is observed in the case of the samples tested at LN2 temperature. We also studied the deformation behavior of Zr-Ni-Cu-Al-Pd glassy foils thinned to electron transparency in situ in tension in a transmission electron microscope. We also present a Ni-Cu-Ti-Zr crystal-glassy composite material having a superior strength paired with a considerable ductility exceeding 10 pct. The metastable cP2 crystalline phase promotes a strain-induced martensitic transformation leading to pseudoelastic behavior as well as enhanced plasticity at room temperature. Underlying mechanisms of plastic deformation are discussed in terms of the interplay between the dislocation slip in the crystalline phase and the shear deformation in the glassy matrix.

  4. Development of an Automatic Fabrication System for Cast Glassy Alloys

    NASA Astrophysics Data System (ADS)

    Yokoyama, Yoshihiko

    2015-04-01

    The developed automatic fabrication system comprised three component functions: weighing, alloying, and casting. The measurement error of automatic weighing specimen was about less 1 pct for Zr-based master alloys (approximately 30 g). Especially, sufficient stirrer effect of arc-melting ingot for homogeneity can be achieved by the development of sinusoidal arcing and applying magnetic field. In order to achieve superior homogeneity of the glass structure with no secondary phase ( i.e., an intermetallic compound with a high melting temperature), a prealloying process should be advisable. In this study, high reliability of the density and mechanical properties of automatic processed cast glassy alloys (CGAs) was successfully obtained. The developed automatic fabrication process has a potential to accelerate the industrial application of CGAs in the near future.

  5. Bulk glassy and nonequilibrium crystalline alloys by stabilization of supercooled liquid: fabrication, functional properties and applications (Part 2)

    NASA Astrophysics Data System (ADS)

    Inoue, A.

    The novel stabilization phenomenon of supercooled liquid in special multi-component metallic alloys that follow the three component rules has enabled us to fabricate a number of bulk glassy and nonequilibrium crystalline alloys exhibiting useful characteristics. Following the previous review (Part 1; Proc. Jpn. Acad. Ser. B 81, 156-171), this paper (Part 2) reviews our recent results on the physical, chemical, mechanical and magnetic properties of the resulting bulk nonequilibrium materials including glassy single phase alloys, nanocrystal-, nanoquasicrystal- and dendritic crystal-dispersed glassy alloys and nanocrystalline alloys. Finally, the application potential of bulk glassy alloys is addressed, taking account of their novel engineering properties and production processes.

  6. Dielectric relaxation studies in Se90Cd8Sb2 glassy alloy

    NASA Astrophysics Data System (ADS)

    Shukla, Nitesh; Rao, Vandita; Dwivedi, D. K.

    2016-05-01

    Se90Cd8Sb2 chalcogenide semiconducting alloy was prepared by melt quench technique. The prepared glassy alloy has been characterized by techniques such as scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX).Dielectric properties of Se90Cd8Sb2 chalcogenide semiconductor have been studied using impedance spectroscopic technique in the frequency range 5×102Hz - 1×105Hz and in temperature range 303-318K. It is found that dielectric constant ɛ' and dielectric loss factor ɛ″ are dependent on frequency and temperature.

  7. Room-temperature amorphous alloy field-effect transistor exhibiting particle and wave electronic transport

    SciTech Connect

    Fukuhara, M.; Kawarada, H.

    2015-02-28

    The realization of room-temperature macroscopic field effect transistors (FETs) will lead to new epoch-making possibilities for electronic applications. The I{sub d}-V{sub g} characteristics of the millimeter-sized aluminum-oxide amorphous alloy (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} FETs were measured at a gate-drain bias voltage of 0–60 μV in nonmagnetic conditions and under a magnetic fields at room temperature. Application of dc voltages to the gate electrode resulted in the transistor exhibiting one-electron Coulomb oscillation with a period of 0.28 mV, Fabry-Perot interference with a period of 2.35 μV under nonmagnetic conditions, and a Fano effect with a period of 0.26 mV for Vg and 0.2 T under a magnetic field. The realization of a low-energy controllable device made from millimeter-sized Ni-Nb-Zr-H amorphous alloy throws new light on cluster electronics.

  8. Room-temperature amorphous alloy field-effect transistor exhibiting particle and wave electronic transport

    NASA Astrophysics Data System (ADS)

    Fukuhara, M.; Kawarada, H.

    2015-02-01

    The realization of room-temperature macroscopic field effect transistors (FETs) will lead to new epoch-making possibilities for electronic applications. The Id-Vg characteristics of the millimeter-sized aluminum-oxide amorphous alloy (Ni0.36Nb0.24Zr0.40)90H10 FETs were measured at a gate-drain bias voltage of 0-60 μV in nonmagnetic conditions and under a magnetic fields at room temperature. Application of dc voltages to the gate electrode resulted in the transistor exhibiting one-electron Coulomb oscillation with a period of 0.28 mV, Fabry-Perot interference with a period of 2.35 μV under nonmagnetic conditions, and a Fano effect with a period of 0.26 mV for Vg and 0.2 T under a magnetic field. The realization of a low-energy controllable device made from millimeter-sized Ni-Nb-Zr-H amorphous alloy throws new light on cluster electronics.

  9. Thermal expansion of a glassy alloy studied using a real-space pair distribution function

    SciTech Connect

    Louzguine-Luzgin, Dmitri V.; Inoue, Akihisa; Yavari, Alain R.; Vaughan, Gavin

    2006-03-20

    Thermal expansion of a glassy Cu{sub 55}Hf{sub 25}Ti{sub 15}Pd{sub 5} alloy studied by using reciprocal space functions is verified using a real-space pair distribution function. The experimental results obtained by real-time diffraction during heating in a synchrotron beam and their Fourier transformation processing to derive radial distribution functions indicate that both reciprocal and real-space distribution functions give good agreement in the calculation of thermal expansion data. In addition to providing structural information, these findings indicate that the change in the average atomic nearest-neighbor distance evaluated from the variation of the position of the main broad diffraction maximum can provide good thermal expansion data for metallic glasses.

  10. Composition dependence of dielectric properties in Se{sub 100-x}Cu{sub x} glassy alloys

    SciTech Connect

    Sharma, J.; Shrotriya, D.; Kumar, S.

    2015-06-24

    In this paper we report the composition dependent of dielectric properties in Se{sub 100-x}Cu{sub x} (x = 0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constants and the dielectric losses in the above glassy systems in the frequency range (1k Hz-5 M Hz) and temperature range (300 K–350 K) have been measured. It has been found that dielectric constant and the dielectric loss both are highly dependent on frequency and temperature and also found to increase with increasing concentration of Cu in pure amorphous Se. The role of Cu, as an impurity in the pure a-Se glassy alloy, is also discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have been also correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.

  11. Role of Cu additive on the dielectric relaxation of Se75Te25 and Se85Te15 glassy alloys

    NASA Astrophysics Data System (ADS)

    Sharma, J.; Kumar, S.

    2010-07-01

    The effect of Cu additive on the dielectric relaxation of two binary Se-Te glassy systems, comparing the properties of a-Se75Te25, a-Se85Te15 and a-Se75Te15Cu10 alloys has been reported. The temperature and frequency dependence of dielectric parameters in Glassy Se75Te25, Se85Te15 and Se75Te15Cu10 alloys are studied by measuring capacitance and dissipation factor in the frequency range (1 kHz-5 MHz) and temperature range (300-350 K). A Debye like relaxation of dielectric behavior has been observed. A comprehensive study on the relaxation mechanism revealed that the presence of grains and grain boundaries across the pallet thickness is the basic relaxation process. A detailed analysis shows that the observed dielectric loss is in agreement with the Guintini's theory of dielectric dispersion based on two electron hopping over a potential barrier and is applicable in the present case. Dielectric constant (ɛ’), dielectric loss (ɛ”), loss tangent (δ) and capacitive reactance (Xc) are found highly frequency and temperature dependent. Dependence of these dielectric parameters over the metallic impurity Cu, has also been found in the present glassy system and has been discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system.

  12. Glass Forming Ability of Hard Magnetic Nd55Al20Fe25 Bulk Glassy Alloy with Distinct Glass Transition

    NASA Astrophysics Data System (ADS)

    Xia, L.; Jo, C. L.; Dong, Y. D.

    Nd55Al20Fe25 bulk sample was prepared in the shape of rods 3 mm in diameter by suction casting. The sample exhibits typical amorphous characters in XRD pattern, distinct glass transition in DSC traces and hard magnetic properties. The distinct glass transition, which is invisible in DSC traces of previously reported Nd—Al—Fe ternary BMGs, allows us to investigate the glass forming ability (GFA) of Nd55Al20Fe25 alloy using the reduced glass transition temperature Trg and the recently defined parameter γ. However, it is found that the obtained diameter of the Nd55Al20Fe25 glassy rod is much larger than the critical section thickness of the BMG predicted by either Trg or γ. The microstructure of Nd55Al20 Fe25 as-cast rod was studied and the apparent GFA of the alloy was supposed to be enhanced by the metastable nano-precipitates dispersed within the glassy matrix.

  13. Effect of Nb Concentration on Thermal Stability and Glass-Forming Ability of Soft Magnetic (Fe,Co)-Gd-Nb-B Glassy Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Jia, Fei; Zhang, Xingguo; Xie, Guoqiang; Inoue, Akihisa

    2010-07-01

    Addition of a small amount of Nb to the (Fe,Co)-Gd-B glassy alloy in (Fe0.9Co0.1)71.5- x Nb x Gd3.5B25 increased the stabilization of supercooled liquid. The largest supercooled liquid region of 104 K was obtained for the x = 2 alloy. A distinct two-stage-like glass transition was observed with further incresing Nb content. The nanoscale (Fe,Co)23B6 phase precipitated in the glassy matrix after annealing, while the two-stage-like glass transition disappeared, indicating that the anomalous glass transition behavior originates from the exothermic reaction for the formation of the (Fe,Co)23B6 phase in the supercooled liquid region. The glass-forming ability (GFA) also increased by addition of Nb, leading to formation of the bulk glass form for the Nb-doped alloys. The best GFA with a diameter of over 3 mm was achieved for the x = 4 alloy. The (Fe,Co)-Gd-Nb-B glassy alloys exhibited good magnetic properties, i.e., rather high saturation magnetization of 0.81 to 1.22 T, low coercive force of 2.5 to 5.8 A/m, and low saturated magnetostriction of 9 to 19 × 10-6. In addition, the glassy alloys also possessed very high compressive fracture strength of 3842 to 3916 MPa and high Vickers hardness of 1025 to 1076.

  14. Casting Atmosphere Effects on the Precipitates, Magnetism, and Corrosion Resistance of Fe78Si9B13 Glassy Alloys

    NASA Astrophysics Data System (ADS)

    Meng, L. L.; Li, X. Y.; Pang, J.; Wang, L.; An, B.; Yin, L. J.; Song, K. K.; Wang, W. M.

    2013-11-01

    The precipitates, magnetism, and corrosion resistance of Fe78Si9B13 glassy samples fabricated in vacuum and air atmospheres (labeled as VAC and AIR samples, respectively) were studied. The findings show that the fraction of the amorphous phase in VAC samples is lower than that in the AIR counterparts. The Fe phase in VAC samples grows preferentially along the <200> orientation. The distribution of magnetization M 4000 of VAC samples oriented parallel and orthogonal to the field ( H // and H ⊥) at H = 4000 Oe is more scattered than AIR samples. The corrosion resistance of VAC samples is lower than AIR counterparts, which can be attributed to the minor alloying effect of oxygen and the passive effect of silicon atoms supplied from the amorphous phase.

  15. Dual-phase glassy/nanoscale icosahedral phase materials in Cu–Zr–Ti–Pd system alloys

    SciTech Connect

    Louzguine-Luzgin, Dmitri V.; Churyumov, A.Yu.

    2014-10-15

    The present work is devoted to an investigation of the formation kinetics, stability and homogeneity area of the nanoscale icosahedral phase formed on heating in the dual-phase glassy/quasicrystalline phase Cu–Zr–Ti–Pd alloys. The data obtained indicate that the Cu–Zr–Ti–Pd icosahedral phase is not a Cu-rich part of the compositional homogeneity area of the Zr–Cu–Pd one. Moreover, Ti, as well as Pd, is found to be an important element stabilizing quasicrystalline phase in the Cu–Zr–Ti–Pd alloys. The formation criteria for Cu- and Zr/Hf-based icosahedral phases are discussed based on the quasilattice constant to average atomic diameter ratio. Deviation from a certain ratio leads to destabilization of the icosahedral phase. By using the isothermal calorimetry traces transformation kinetics above and below the glass-transition region was analyzed. Some difference in the transformation kinetics above and below the glass-transition region allows us to suggest that possible structure changes occur upon glass-transition. - Highlights: • Formation kinetics, stability and homogeneity area of nanoscale icosahedral phase • Cu–Zr–Ti–Pd icosahedral phase is not a Cu-rich part of Zr–Cu–Pd one. • Ti, as well as Pd, is an important element stabilizing quasicrystalline phase. • Difference in transformation kinetics above and below glass-transition region.

  16. CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Reverse Monte Carlo study on structural order in liquid and glassy AlFe alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Jing-Xiang; Li, Hui; Zhang, Jie; Song, Xi-Gui; Bian, Xiu-Fang

    2009-11-01

    This paper reports that anomalous local order in liquid and glassy AlFeCe alloy has been detected by x-ray diffraction measurements. The addition of the element Ce has a great effect on this local structural order. The element Ce favours interpenetration of the icosahedra by sharing a common face and edges. It argues that frustration between this short-range order and the long-range crystalline order controls the glass-forming ability of these liquids. The obtained results suggest that a system having a stronger tendency to show local icosahedral order should be a better glass-former. This scenario also naturally explains the close relationship between the local icosahedral order in a liquid, glass-forming ability, and the nucleation barrier. Such topological local order has also been analysed directly using the reverse Monte Carlo method. It also estimated the fraction of local ordered and disordered structural units in a glassy AlFeCe alloy.

  17. A Practical Anodic and Cathodic Curve Intersection Model to Understand Multiple Corrosion Potentials of Fe-Based Glassy Alloys in OH- Contained Solutions.

    PubMed

    Li, Y J; Wang, Y G; An, B; Xu, H; Liu, Y; Zhang, L C; Ma, H Y; Wang, W M

    2016-01-01

    A practical anodic and cathodic curve intersection model, which consisted of an apparent anodic curve and an imaginary cathodic line, was proposed to explain multiple corrosion potentials occurred in potentiodynamic polarization curves of Fe-based glassy alloys in alkaline solution. The apparent anodic curve was selected from the measured anodic curves. The imaginary cathodic line was obtained by linearly fitting the differences of anodic curves and can be moved evenly or rotated to predict the number and value of corrosion potentials.

  18. Enhanced glass-forming ability of FeCoBSiNb bulk glassy alloys prepared using commercial raw materials through the optimization of Nb content

    SciTech Connect

    Fu Ying; Shen Baolong; Kimura, Hisamichi; Makino, Akihiro; Inoue, Akihisa

    2010-05-15

    We optimized the alloy compositions by modifying the Nb content in [(Fe{sub 0.5}Co{sub 0.5}){sub 0.75}B{sub 0.20}Si{sub 0.05}]{sub 100-x}Nb{sub x}(x=3.6-4.4) alloy system. As a result, it was found that the Nb content of 4.3 at. % was effective for approaching alloy to a eutectic point. By copper mold casting, [(Fe{sub 0.5}Co{sub 0.5}){sub 0.75}B{sub 0.20}Si{sub 0.05}]{sub 95.7}Nb{sub 4.3} bulk glassy alloy rods with diameters up to 4 mm were successfully synthesized even using commercial raw materials. These glassy alloys exhibit a rather high saturation magnetization of 0.77 T and low coercive force of 2.5 A/m.

  19. Development of micro-beam NRA for hydrogen mapping: Observation of fatigue-fractured surface of glassy alloys

    NASA Astrophysics Data System (ADS)

    Sekiba, D.; Yonemura, H.; Ogura, S.; Matsumoto, M.; Kitaoka, Y.; Yokoyama, Y.; Matsuzaki, H.; Narusawa, T.; Fukutani, K.

    2011-04-01

    A micro-beam NRA system by means of a resonant nuclear reaction of 1H( 15N, αγ) 12C has been developed at the beam line in MALT, University of Tokyo. The beam optics was analyzed in terms of the phase diagram. By carefully suppressing the spherical aberration of the final quadrupole magnetic lens, the 15N beam at the energy of 6.4 MeV was focused on targets with a size of 17 μm × 30 μm. For the precise positioning of the sample and beam spot, a combination of the mirror and optical microscope was adopted, so that the hydrogen concentration can be measured at a desirable position of the sample. With this new system, the hydrogen concentrations of fatigue-fractured surfaces of glassy alloys were determined from the viewpoint of the hydrogen embrittlement: Zr 50Cu 37Al 10Pd 3 and Zr 50Cu 40Al 10. Depth-resolved two-dimensional (2D) mapping of hydrogen concentration was performed in the area of 3 mm × 3 mm with an in-plane resolution of 150 μm. The maps taken at three different depths revealed that the hydrogen concentration is higher in the fatigue-fractured regions in both samples.

  20. Spin Glassiness and Ferromagnetism in Disordered Nickel-Manganese and Gold-Iron Alloys.

    NASA Astrophysics Data System (ADS)

    Abdul-Razzaq, Wathiq Nafee

    An initial magnetic study of disordered Ni(,100 -x)Mn(,x) for x = 23, 25, 27 showed that the latter two alloys have typical spin-glass (SG) properties below their susceptibility-peak temperatures (T(,g) = 120 K and 95 K, respectively). The x = 23 alloy, however, becomes ferro - magnetic at T(,c) = 160 K, below which (at T(,fg) = 60 K) it goes into a reentrant SG state, where its time-independent magnetizations (M) in various fixed fields applied during cooling (H(,cool)) reveal the existance of a spontaneous ferromagnetic moment. Its reentrant state is therefore mixed ferro-spin-glass (FSG),. Further study of Ni(,77)Mn(,23) showed that the narrow displaced hysteresis loops obtained at 4.2 K for high H(,cool) can be interpreted in terms of a single SG domain with a net magnetization (M(,S)) and a unidirectional anisotropy field (H(,K)). Its narrow symmetrical loop at 4.2 K for H(,cool) = 0 is shown to be consistent with the existence of an ensemble of smaller but similar domains of randomly oriented (')H(,K), which are coupled together antiferromagnetically via a weak average exchange field H(,E). With several additional Ni(,100-x)Mn(,x) alloys between x = 23 and x = 27, a detailed two-fold magnetic study was made. First, from the tem- perature dependence of the low-field M of each alloy, the variations of the magnetic transition temperatures (T(,g), T(,fg), and T(,c)) with compo- sition were determined. In the resulting magnetic phase diagram, the curves for these three temperatures meet at a multi-critical point located at x very close to 24, from which the boundary line separa- ting the FSG and SG phases extends vertically down in temperature. Secondly, from the hysteresis loops at 4.2 K obtained for high H(,cool) and for H(,cool) = 0, considered respectively as single=domain and multidomain behavior, values were deduced for the domain -model parameters (M(,S), H(,K), H(,E)), whose variations with composition are discussed briefly in physical terms. A similar but

  1. Potential applications of cold sprayed Cu50Ti20Ni30 metallic glassy alloy powders for antibacterial protective coating in medical and food sectors.

    PubMed

    El-Eskandrany, M Sherif; Al-Azmi, Ahmed

    2016-03-01

    Mechanical alloying was utilized for synthesizing of metallic glassy Cu50Ti20Ni30 alloy powders, using a low energy ball milling technique. The metallic glassy powders obtained after 100 h of ball milling had an average particle size of 1.7 mm in diameter and possessed excellent thermal stability, indexed by a relatively high glass transition temperature (358.3 °C) with a wide supercooled liquid region (61 °C). This amorphous phase crystallized into Ti2Cu and CuTiNi2 ordered phases through two overlapped crystallization temperatures at 419.3 °C and 447.5 °C, respectively. The total enthalpy change of crystallization was -4.8 kJ/mol. The glassy powders were employed as feedstock materials to double-face coating the surface of SUS 304 substrate, using cold spraying process under helium gas pressure at 400 °C. This coating material had an extraordinary high nanohardness value of 3.1 GPa. Moreover, it showed a high resistance to wear with a low value of the coefficient of friction ranging from 0.45 to 0.45. Biofilms were grown on 20-mm(2) SUS304 sheets coated coupons inoculated with 1.5 × 10(8) CFU ml(-1)E. coli. Significant biofilm inhibition (p The inhibition of biofilm formation by nanocrystalline powders of Cu-based provides a practical approach to achieve the inhibition of biofilms formation. PMID:26703232

  2. Potential applications of cold sprayed Cu50Ti20Ni30 metallic glassy alloy powders for antibacterial protective coating in medical and food sectors.

    PubMed

    El-Eskandrany, M Sherif; Al-Azmi, Ahmed

    2016-03-01

    Mechanical alloying was utilized for synthesizing of metallic glassy Cu50Ti20Ni30 alloy powders, using a low energy ball milling technique. The metallic glassy powders obtained after 100 h of ball milling had an average particle size of 1.7 mm in diameter and possessed excellent thermal stability, indexed by a relatively high glass transition temperature (358.3 °C) with a wide supercooled liquid region (61 °C). This amorphous phase crystallized into Ti2Cu and CuTiNi2 ordered phases through two overlapped crystallization temperatures at 419.3 °C and 447.5 °C, respectively. The total enthalpy change of crystallization was -4.8 kJ/mol. The glassy powders were employed as feedstock materials to double-face coating the surface of SUS 304 substrate, using cold spraying process under helium gas pressure at 400 °C. This coating material had an extraordinary high nanohardness value of 3.1 GPa. Moreover, it showed a high resistance to wear with a low value of the coefficient of friction ranging from 0.45 to 0.45. Biofilms were grown on 20-mm(2) SUS304 sheets coated coupons inoculated with 1.5 × 10(8) CFU ml(-1)E. coli. Significant biofilm inhibition (p The inhibition of biofilm formation by nanocrystalline powders of Cu-based provides a practical approach to achieve the inhibition of biofilms formation.

  3. Determination of Anthracene on Ag-Au Alloy Nanoparticles/Overoxidized-Polypyrrole Composite Modified Glassy Carbon Electrodes

    PubMed Central

    Mailu, Stephen N.; Waryo, Tesfaye T.; Ndangili, Peter M.; Ngece, Fanelwa R.; Baleg, Abd A.; Baker, Priscilla G.; Iwuoha, Emmanuel I.

    2010-01-01

    A novel electrochemical sensor for the detection of anthracene was prepared by modifying a glassy carbon electrode (GCE) with over-oxidized polypyrrole (PPyox) and Ag-Au (1:3) bimetallic nanoparticles (Ag-AuNPs). The composite electrode (PPyox/Ag-AuNPs/GCE) was prepared by potentiodynamic polymerization of pyrrole on GCE followed by its overoxidation in 0.1 M NaOH. Ag-Au bimetallic nanoparticles were chemically prepared by the reduction of AgNO3 and HAuCl4 using C6H5O7Na3 as the reducing agent as well as the capping agent and then immobilized on the surface of the PPyox/GCE. The nanoparticles were characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the bimetallic alloy nanoparticles. Transmission electron microscopy showed that the synthesized bimetallic nanoparticles were in the range of 20–50 nm. The electrochemical behaviour of anthracene at the PPyox/Ag-AuNPs/GCE with Ag: Au atomic ratio 25:75 (1:3) exhibited a higher electrocatalytic effect compared to that observed when GCE was modified with each constituent of the composite (i.e., PPyox, Ag-AuNPs) and bare GCE. A linear relationship between anodic current and anthracene concentration was attained over the range of 3.0 × 10−6 to 3.56 × 10−4 M with a detection limit of 1.69 × 10−7 M. The proposed method was simple, less time consuming and showed a high sensitivity. PMID:22163419

  4. A Practical Anodic and Cathodic Curve Intersection Model to Understand Multiple Corrosion Potentials of Fe-Based Glassy Alloys in OH- Contained Solutions

    PubMed Central

    Li, Y. J.; Wang, Y. G.; An, B.; Xu, H.; Liu, Y.; Zhang, L. C.; Ma, H. Y.; Wang, W. M.

    2016-01-01

    A practical anodic and cathodic curve intersection model, which consisted of an apparent anodic curve and an imaginary cathodic line, was proposed to explain multiple corrosion potentials occurred in potentiodynamic polarization curves of Fe-based glassy alloys in alkaline solution. The apparent anodic curve was selected from the measured anodic curves. The imaginary cathodic line was obtained by linearly fitting the differences of anodic curves and can be moved evenly or rotated to predict the number and value of corrosion potentials. PMID:26771194

  5. Excellent soft-magnetic properties of (Fe,Co)-Mo-(P,C,B,Si) bulk glassy alloys with ductile deformation behavior

    NASA Astrophysics Data System (ADS)

    Li, Fushan; Shen, Baolong; Makino, Akihiro; Inoue, Akihisa

    2007-12-01

    High glass-forming ability and excellent soft-magnetic and mechanical properties were simultaneously achieved in (Fe,Co)-Mo-(P,C,B,Si) bulk glassy alloys (BGAs). The large BGA with a maximal diameter up to 6mm was formed by copper mold casting in the alloys, which is the largest size in FePC BGA system. The BGA with a proper content of Co exhibits superhigh initial effective permeability of over 360 90 at 1kHz and saturation magnetization of over 1.0T. The fracture strength of the BGA reaches 3370MPa. This bulk specimen undergoes a plastic strain exceeding 1%, which is the largest for such large ferromagnetic BGAs.

  6. Devitrification of Mechanically Alloyed Zr-Ti-Nb-Cu-Ni-Al Glassy Powders Studied by Time-Resolved X-ray Diffraction

    SciTech Connect

    Scudino, S.; Sordelet, D.J.; Eckert, J.

    2009-04-13

    The crystallization of mechanically alloyed Zr{sub 67}Ti{sub 6.14}Nb{sub 1.92}Cu{sub 10.67}Ni{sub 8.52}Al{sub 5.75} glassy powder is investigated by time-resolved X-ray diffraction. The powder displays a multi-step crystallization behavior characterized by the formation of a metastable nanoscale quasicrystalline phase during the first stage of the crystallization process. At higher temperatures, coinciding with the second crystallization event, the amorphous-to-quasicrystalline transformation is followed by the precipitation of the tetragonal Zr{sub 2}Cu phase (space group I4/mmm) and the tetragonal Zr{sub 2}Ni phase (space group I4/mcm). The transformations are gradual and the quasicrystals and the subsequent phases coexist over a temperature interval of about 25K.

  7. Glassy composition for hermetic seals

    DOEpatents

    Wilder, Jr., James A.

    1980-01-01

    The invention relates to a glassy composition adaptable for sealing to aluminum-based alloys to form a hermetically-sealed insulator body. The composition may either be employed as a glass or, after devitrifying heat treatment, as a glass-ceramic.

  8. Magnetic properties and glass formability of Fe61Co10Zr5W4B20 bulk metallic glassy alloy

    NASA Astrophysics Data System (ADS)

    Pawlik, P.; Davies, H. A.; Gibbs, M. R. J.

    2003-10-01

    Amorphous melt spun ribbon samples of Fe61Co10Zr5W4B20 alloy of various thicknesses up to ˜350 μm and suction cast 1 mm diameter rod and 2, 3, and 4 mm outside diameter tube samples of the same alloy were produced. The experimental results for the rod samples indicate a relatively high saturation polarization μ0Ms=0.8 T and a Curie temperature TC=615 K, as well as a very low coercive field Hc=1.4±0.5 A/m with high anisotropy that lowers the permeability of the samples. Thermal analysis by differential scanning calorimetry carried out on ribbon and rod samples revealed a large supercooled liquid region ΔTx of ˜60 K for this alloy.

  9. Glass forming abilities and magnetic properties of soft magnetic Fe Co Zr W B bulk glassy alloys

    NASA Astrophysics Data System (ADS)

    Pawlik, Piotr; Pawlik, Katarzyna; Davies, Hywel A.; Wysłocki, Jerzy J.; Kaszuwara, Waldemar; Leonowicz, Marcin

    2006-09-01

    Melt-spun ribbon samples of various thicknesses up to 350 μm and suction-cast 1 and 2 mm diameter rods of Fe61Co10+xZr5W4-xB20(x=0,2,3) alloys, were produced. The results obtained for rods indicate relatively large saturation polarization Js, with high anisotropy field that lowers the permeability of the samples. X-ray diffractometry was applied to confirm the amorphous structure of the processed alloys.

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

    SciTech Connect

    Sharma, Rita Sharma, Shaveta; Kumar, Praveen; Chander, Ravi; Thangaraj, R.; Mian, M.

    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.

  11. Evolution of structure and local magnetic fields during crystallization of HITPERM glassy alloys studied by in situ diffraction and nuclear forward scattering of synchrotron radiation.

    PubMed

    Miglierini, Marcel; Pavlovič, Márius; Procházka, Vít; Hatala, Tomáš; Schumacher, Gerhard; Rüffer, Rudolf

    2015-11-14

    Evolution of structure and local magnetic fields in (Fe(1-x)Co(x))76Mo8Cu1B15 (HITPERM) metallic glass ribbons with various amounts of Co (x = 0, 0.25, 0.5) were studied in situ using diffraction and nuclear forward scattering of synchrotron radiation. It was found that crystallization of all three glasses proceeds in two stages. In the first stage, bcc (Fe,Co) nanocrystals are formed, while in the second stage additional crystalline phases evolve. For all three glasses, the crystallization temperatures at the wheel side were found to be lower than at the air side of the ribbon. The crystallization temperatures were found to decrease with increasing Co content. The lattice parameters of the bcc nanocrystals decrease up to about 550 °C and then increase pointing to squeezing Mo atoms out of the nanograins or to interface effects between the nanocrystals and the glassy matrix. Nuclear forward scattering enabled separate evaluation of the contributions that stem from structurally different regions within the investigated samples including the newly formed nanocrystals and the residual amorphous matrix. Even minor Co content (x = 0.25) has a substantial effect not only upon the magnetic behaviour of the alloy but also upon its structure. Making use of hyperfine magnetic fields, it was possible to unveil structurally diverse positions of Fe atoms that reside in a nanocrystalline lattice with different numbers of Co nearest neighbours.

  12. Large bulk soft magnetic [(Fe{sub 0.5}Co{sub 0.5}){sub 0.75}B{sub 0.20}Si{sub 0.05}]{sub 96}Nb{sub 4} glassy alloy prepared by B{sub 2}O{sub 3} flux melting and water quenching

    SciTech Connect

    Bitoh, T.; Makino, A.; Inoue, A.; Greer, A.L.

    2006-05-01

    The large bulk soft magnetic glassy [(Fe{sub 0.5}Co{sub 0.5}){sub 0.75}B{sub 0.20}Si{sub 0.05}]{sub 96}Nb{sub 4} alloy specimens with the diameters up to 7.7 mm have been prepared by water quenching the melt immersed in the molten flux of B{sub 2}O{sub 3}. The maximum diameter of the obtained specimens is approximately 1.5 times as large as the previous result for copper mold casting. The bulk specimen with 7.7 mm in diameter exhibits the saturation magnetization of 1.13 T, the coercivity lower than 20 A/m at room temperature, and the Curie temperature of 732 K. This bulk specimen is the thickest of any soft magnetic glassy alloys formed until now.

  13. Impingement effect on the glass crystal transformation kinetics by using DSC under non-isothermal regime. Application to the crystallization of the several semiconducting alloys of the Sb As Se and Ge Sb Se glassy systems

    NASA Astrophysics Data System (ADS)

    Vázquez, J.; González-Palma, R.; López-Alemany, P. L.; Villares, P.; Jiménez-Garay, R.

    2005-07-01

    A procedure has been developed for analyzing the evolution with time of the actual volume fraction transformed, for calculating the kinetic parameters and for analyzing the glass crystal transformation mechanisms in solid systems involving formation and growth of nuclei. By defining an extended volume of transformed material and assuming spatially random transformed regions, a general expression of the extended volume fraction has been obtained as a function of the temperature. Considering the mutual interference of regions growing from separate nuclei (impingement effect) and from the above-mentioned expression, the actual volume fraction transformed has been deduced. The kinetic parameters have been obtained, assuming that the reaction rate constant is a time function through its Arrhenian temperature dependence. The theoretical method developed has been applied to the crystallization kinetics of a set semiconducting alloys, prepared in our laboratory, corresponding to the Sb As Se and Ge Sb Se glassy systems. The obtained values for the kinetic parameters agree satisfactorily with the calculated results by the Austin-Rickett kinetic equation, under non-isothermal regime. This fact allows to check the validity of the theoretical model developed.

  14. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  15. Glassy correlations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Goldbart, Paul; Mao, Xiaoming

    2009-03-01

    We address the physical properties of an isotropic melt or solution of nematogenic polymers that is then cross-linked beyond the vulcanization point. To do this, we construct a replica Landau theory involving a coupled pair of order- parameter fields: one describing vulcanization, the other describing local nematic order. Thermal nematic fluctuations, present at the time of cross-linking, are trapped by cross- linking into the vulcanized network. The resulting glassy nematic fluctuations are analyzed in the Gaussian approximation in two regimes. When the localization length is shorter than the thermal nematic correlation length, the nematic correlations are well captured as glassy correlations. In the opposite regime, fluctuations in the positions of the localized polymers partially wash out the glassy nematic correlations.

  16. Alloy

    NASA Astrophysics Data System (ADS)

    Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

    2014-07-01

    The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

  17. Glassy features of crystal plasticity

    NASA Astrophysics Data System (ADS)

    Lehtinen, Arttu; Costantini, Giulio; Alava, Mikko J.; Zapperi, Stefano; Laurson, Lasse

    2016-08-01

    Crystal plasticity occurs by deformation bursts due to the avalanchelike motion of dislocations. Here we perform extensive numerical simulations of a three-dimensional dislocation dynamics model under quasistatic stress-controlled loading. Our results show that avalanches are power-law distributed and display peculiar stress and sample size dependence: The average avalanche size grows exponentially with the applied stress, and the amount of slip increases with the system size. These results suggest that intermittent deformation processes in crystalline materials exhibit an extended critical-like phase in analogy to glassy systems instead of originating from a nonequilibrium phase transition critical point.

  18. Structural order in glassy water.

    PubMed

    Giovambattista, Nicolas; Debenedetti, Pablo G; Sciortino, Francesco; Stanley, H Eugene

    2005-06-01

    We investigate structural order in glassy water by performing classical molecular dynamics simulations using the extended simple point charge (SPC/E) model of water. We perform isochoric cooling simulations across the glass transition temperature at different cooling rates and densities. We quantify structural order by orientational and translational order metrics. Upon cooling the liquid into the glassy state, both the orientational order parameter Q and translational order parameter tau increase. At T=0 K, the glasses fall on a line in the Q-tau plane or order map. The position of this line depends only on density and coincides with the location in the order map of the inherent structures (IS) sampled upon cooling. We evaluate the energy of the IS, eIS(T), and find that both order parameters for the IS are proportional to eIS. We also study the structural order during the transformation of low-density amorphous ice (LDA) to high-density amorphous ice (HDA) upon isothermal compression and are able to identify distinct regions in the order map corresponding to these glasses. Comparison of the order parameters for LDA and HDA with those obtained upon isochoric cooling indicates major structural differences between glasses obtained by cooling and glasses obtained by compression. These structural differences are only weakly reflected in the pair correlation function. We also characterize the evolution of structural order upon isobaric annealing, leading at high pressure to very-high density amorphous ice (VHDA). PMID:16089741

  19. Ending Aging in Super Glassy Polymer Membranes

    SciTech Connect

    Lau, CH; Nguyen, PT; Hill, MR; Thornton, AW; Konstas, K; Doherty, CM; Mulder, RJ; Bourgeois, L; Liu, ACY; Sprouster, DJ; Sullivan, JP; Bastow, TJ; Hill, AJ; Gin, DL; Noble, RD

    2014-04-16

    Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N-2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.

  20. Atomic structure of Zr-Cu glassy alloys and detection of deviations from ideal solution behavior with Al addition by x-ray diffraction using synchrotron light in transmission

    NASA Astrophysics Data System (ADS)

    Georgarakis, K.; Yavari, A. R.; Louzguine-Luzgin, D. V.; Antonowicz, J.; Stoica, M.; Li, Y.; Satta, M.; LeMoulec, A.; Vaughan, G.; Inoue, A.

    2009-05-01

    The atomic structure of Zr-Cu binary amorphous alloys was studied using real space pair distribution functions derived from x-ray diffraction. The structure can be modeled by an ideal solution approximation because of relatively weak Cu-Zr atomic interactions. Addition of Al to Zr-Cu metallic glasses modifies the atomic structure in the short and medium range order because of the strongly attractive interaction between Al and Zr atoms. These interactions generate strong deviations from the ideal solution behavior.

  1. Cooperative strings and glassy interfaces.

    PubMed

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

    2015-07-01

    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. PMID:26100908

  2. Cooperative strings and glassy interfaces.

    PubMed

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

    2015-07-01

    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.

  3. Brittle metallic glass deforms plastically at room temperature in glassy multilayers

    NASA Astrophysics Data System (ADS)

    Sharma, Parmanand; Yubuta, Kunio; Kimura, Hisamichi; Inoue, Akihisa

    2009-07-01

    Bulk metallic glasses are emerging as a new class of materials that can have applications ranging from structural materials to materials for future nanotechnology. However, catastrophic mechanical failure is a serious issue hindering the use of these materials in engineering applications. Here we introduce an approach to understanding and solving the problem of brittleness of metallic glasses. We have shown that even a very brittle metallic glass (La based) can be forced to deform plastically at room temperature if it is made in the form of multilayers involving other metallic glasses, i.e., a two-phase glass. The mechanically soft glassy layer (La based) having a lower critical shear stress acts as a nucleation or an initiation site for shear bands and the mechanically hard glassy layer (Zr based) acts as an obstacle to the propagation of shear bands. This process results in the multiplication of shear bands. Since the shear bands are associated with a local rise in temperature, a large number of shear bands can raise the overall temperature of the soft layer and eventually can drive it to the supercooled liquid state, where deformation of metallic glass is very large and homogeneous. The results reported here not only clarify the mechanism of large plastic deformation in two-phase glassy alloys but also suggest the possibility of a different kind of two-phase bulk glassy alloys exhibiting large plastic deformation at room temperature.

  4. Thermal Barrier Coatings Resistant to Glassy Deposits

    NASA Astrophysics Data System (ADS)

    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

  5. Molecular mobility in glassy dispersions.

    PubMed

    Mehta, Mehak; McKenna, Gregory B; Suryanarayanan, Raj

    2016-05-28

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  6. Molecular mobility in glassy dispersions

    NASA Astrophysics Data System (ADS)

    Mehta, Mehak; McKenna, Gregory B.; Suryanarayanan, Raj

    2016-05-01

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  7. On the Marginal Stability of Glassy Systems

    NASA Astrophysics Data System (ADS)

    Yan, Le; Baity-Jesi, Marco; Müller, Markus; Wyart, Matthieu

    2015-03-01

    In various glassy systems that are out of equilibrium, like spin glasses and granular packings, the dynamics appears to be critical: avalanches involving almost the whole system could happen. A recent conceptual breakthrough argues that such glassy systems sample the ensemble of marginal stable states, which inevitably results into critical dynamics. However, it is unclear how the marginal stability is dynamically guaranteed. We investigate this marginal stability assumption by studying specifically the critical athermal dynamics of the Sherrington-Kirkpatrick model. We discuss how a pseudo-gap in the density distribution of local fields characterizing the marginal stability arises dynamically.

  8. Active cage model of glassy dynamics.

    PubMed

    Fodor, Étienne; Hayakawa, Hisao; Visco, Paolo; van Wijland, Frédéric

    2016-07-01

    We build up a phenomenological picture in terms of the effective dynamics of a tracer confined in a cage experiencing random hops to capture some characteristics of glassy systems. This minimal description exhibits scale invariance properties for the small-displacement distribution that echo experimental observations. We predict the existence of exponential tails as a crossover between two Gaussian regimes. Moreover, we demonstrate that the onset of glassy behavior is controlled only by two dimensionless numbers: the number of hops occurring during the relaxation of the particle within a local cage and the ratio of the hopping length to the cage size. PMID:27575182

  9. Active cage model of glassy dynamics

    NASA Astrophysics Data System (ADS)

    Fodor, Étienne; Hayakawa, Hisao; Visco, Paolo; van Wijland, Frédéric

    2016-07-01

    We build up a phenomenological picture in terms of the effective dynamics of a tracer confined in a cage experiencing random hops to capture some characteristics of glassy systems. This minimal description exhibits scale invariance properties for the small-displacement distribution that echo experimental observations. We predict the existence of exponential tails as a crossover between two Gaussian regimes. Moreover, we demonstrate that the onset of glassy behavior is controlled only by two dimensionless numbers: the number of hops occurring during the relaxation of the particle within a local cage and the ratio of the hopping length to the cage size.

  10. Large-size ultrahigh strength Ni-based bulk metallic glassy matrix composites with enhanced ductility fabricated by spark plasma sintering

    SciTech Connect

    Xie Guoqiang; Louzguine-Luzgin, Dmitri V.; Kimura, Hisamichi; Inoue, Akihisa; Wakai, Fumihiro

    2008-03-24

    Ni-based bulk glassy alloy composites (GACs) simultaneously with ultrahigh strength and enhanced ductility and satisfying large-size requirements were fabricated by spark plasma sintering of gas-atomized Ni{sub 52.5}Nb{sub 10}Zr{sub 15}Ti{sub 15}Pt{sub 7.5} glassy alloy powder blend with ceramic or metal powders. No crystallization of metallic glassy matrix and good bonding state between the particles are responsible for good mechanical properties of the fabricated bulk GACs. The improvement of plastic ductility of the fabricated bulk GACs originates from the structural inhomogeneity caused by the particles inclusion. The additional particulates act as a resisting media causing deviation, branching, and multiplication of shear bands.

  11. Large-size ultrahigh strength Ni-based bulk metallic glassy matrix composites with enhanced ductility fabricated by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Xie, Guoqiang; Louzguine-Luzgin, Dmitri V.; Kimura, Hisamichi; Inoue, Akihisa; Wakai, Fumihiro

    2008-03-01

    Ni-based bulk glassy alloy composites (GACs) simultaneously with ultrahigh strength and enhanced ductility and satisfying large-size requirements were fabricated by spark plasma sintering of gas-atomized Ni52.5Nb10Zr15Ti15Pt7.5 glassy alloy powder blend with ceramic or metal powders. No crystallization of metallic glassy matrix and good bonding state between the particles are responsible for good mechanical properties of the fabricated bulk GACs. The improvement of plastic ductility of the fabricated bulk GACs originates from the structural inhomogeneity caused by the particles inclusion. The additional particulates act as a resisting media causing deviation, branching, and multiplication of shear bands.

  12. Plastic flow modeling in glassy polymers

    SciTech Connect

    Clements, Brad

    2010-12-13

    Glassy amorphous and semi-crystalline polymers exhibit strong rate, temperature, and pressure dependent polymeric yield. As a rule of thumb, in uniaxial compression experiments the yield stress increases with the loading rate and applied pressure, and decreases as the temperature increases. Moreover, by varying the loading state itself complex yield behavior can be observed. One example that illustrates this complexity is that most polymers in their glassy regimes (i.e., when the temperature is below their characteristic glass transition temperature) exhibit very pronounced yield in their uniaxial stress stress-strain response but very nebulous yield in their uniaxial strain response. In uniaxial compression, a prototypical glassy-polymer stress-strain curve has a stress plateau, often followed by softening, and upon further straining, a hardening response. Uniaxial compression experiments of this type are typically done from rates of 10{sup -5} s{sup -1} up to about 1 s{sup -1}. At still higher rates, say at several thousands per second as determined from Split Hopkinson Pressure Bar experiments, the yield can again be measured and is consistent with the above rule of thumb. One might expect that that these two sets of experiments should allow for a successful extrapolation to yet higher rates. A standard means to probe high rates (on the order of 105-107 S-I) is to use a uniaxial strain plate impact experiment. It is well known that in plate impact experiments on metals that the yield stress is manifested in a well-defined Hugoniot Elastic Limit (HEL). In contrast however, when plate impact experiments are done on glassy polymers, the HEL is arguably not observed, let alone observed at the stress estimated by extrapolating from the lower strain rate experiments. One might argue that polymer yield is still active but somehow masked by the experiment. After reviewing relevant experiments, we attempt to address this issue. We begin by first presenting our recently

  13. Photoluminescence of silver in glassy matrices

    SciTech Connect

    Garcia, M.A.; Garcia-Heras, M.; Cano, E.; Bastidas, J.M.; Villegas, M.A.; Montero, E.; Llopis, J.; Sada, C.; Marchi, G. de; Battaglin, G.; Mazzoldi, P.

    2004-10-01

    This work studies the behavior of Ag{sup +} ions incorporated in different silica-based glassy matrices. To this end, Ag-doped silica coatings, prepared via sol-gel and deposited on pure silica and soda-lime glasses, are investigated by means of structural and optical spectroscopy techniques. Silver tends to segregate towards the interface during the annealing process, but in the case of soda-lime glassy substrates the exchange process favors its diffusion into the substrate. The environment of Ag{sup +} ions during the annealing process determines their final oxidation state. In the pure silica matrix, Ag{sup +} ions are found to be unstable and tend to reduce to Ag{sup 0}, with the subsequent formation of metallic nanoparticles. However, the presence of network formers and modifiers gives rise to the appearance of nonbridging oxygen, which allows the stabilization of Ag{sup +} ions in the matrix.

  14. Wafer-level microstructuring of glassy carbon

    NASA Astrophysics Data System (ADS)

    Hans, Loïc. E.; Prater, Karin; Kilchoer, Cédric; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-03-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. One application is glass molding that allows to realize high resolution diffractive optical elements on large areas and at affordable price appropriate for mass production. We study glassy carbon microstructuring for future precision compression molding of low and high glass-transition temperature. For applications in optics the uniformity, surface roughness, edge definition and lateral resolution are very important parameters for a stamp and the final product. We study different methods of microstructuring of glassy carbon by etching and milling. Reactive ion etching with different protection layers such as photoresists, aluminium and titanium hard masks have been performed and will be compare with Ion beam etching. We comment on the quality of the structure definition and give process details as well as drawbacks for the different methods. In our fabrications we were able to realize optically flat diffractive structures with slope angles of 80° at typical feature sizes of 5 micron and 700 nm depth qualified for high precision glass molding.

  15. Mo-Si alloy development

    SciTech Connect

    Liu, C.T.; Heatherly, L.; Wright, J.L.

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  16. Glassy aerosols heterogeneously nucleate cirrus ice particles

    NASA Astrophysics Data System (ADS)

    Wilson, Theodore W.; Murray, Benjamin J.; Dobbie, Steven; Cui, Zhiqiang; Al-Jumur, Sardar M. R. K.; Möhler, Ottmar; Schnaiter, Martin; Wagner, Robert; Benz, Stefan; Niemand, Monika; Saathoff, Harald; Ebert, Volker; Wagner, Steven; Kärcher, Bernd

    2010-05-01

    Ice clouds in the tropical tropopause layer (TTL, ~12-18 km, ~180-200 K) play a key role in dehydrating air entering the stratosphere. However, in-situ measurements show that air within these clouds is unexpectedly supersaturated(1); normally the growth of ice crystals rapidly quenches any supersaturation. A number of explanations for high in-cloud humidity have been put forward, but recent research suggests high humidity may be related to the low numbers of ice crystals found within these clouds(1). Low ice number densities can be produced through selective nucleation by a small subset of aerosol particles. This is inconsistent with homogeneous nucleation of ice in liquid aerosols. However, droplets rich in organic material, ubiquitous in the TTL, are known to become glassy (amorphous, non-crystalline solid) under TTL conditions(2,3). Here we show, using a large cloud simulation chamber, that glassy solution droplets nucleate ice heterogeneously at low supersaturations. Using a one-dimensional cirrus model we also show that nucleation by glassy aerosol in the TTL may explain low TTL ice number densities and high in-cloud humidity. Recent measurements of the composition of TTL cirrus residues are consistent with our findings(4). (1) Krämer, M. et al. Ice supersaturations and cirrus cloud crystal numbers. Atm. Chem. Phys. 9, 3505-3522 (2009). (2) Murray, B. J. Inhibition of ice crystallisation in highly viscous aqueous organic acid droplets. Atm. Chem. Phys. 8, 5423-5433 (2008). (3) Zobrist, B., Marcolli, C., Pedernera, D. A. & Koop, T. Do atmospheric aerosols form glasses? Atm. Chem. Phys. 8, 5221-5244 (2008). (4) Froyd, K. D., Murphy, D. M., Lawson, P., Baumgardner, D. & Herman, R. L. Aerosols that form subvisible cirrus at the tropical tropopause. Atmos. Chem. Phys. 10, 209-218 (2010).

  17. Water sorption and diffusion in glassy polymers

    NASA Astrophysics Data System (ADS)

    Davis, Eric Mikel

    Water sorption and diffusion in glassy polymers is important in many fields, including drug delivery, desalination, energy storage and delivery, and packaging. Accurately measuring and understanding the underlying transport mechanisms of water in these glassy polymers is often complex due to both the nonequilibrium state of the polymer and the self-associating nature of water (e.g., hydrogen bonding). In this work, water sorption and diffusion in a number of glassy polymers were measured using gravimetric and spectroscopic techniques, including quartz spring microbalance, quartz crystal microbalance, and in situ time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian diffusion was observed in all polymers studied, indicated by an initial stage of water uptake, followed by a second stage of continuous, gradual uptake of water at later experimental times. These phenomena were attributed to diffusion driven by a concentration gradient, as well as diffusion driven by slow polymer relaxation resulting in additional water ingress over time. In order to gain additional insight into these phenomena, which are a product of nonequilibrium state of the polymers, diffusion-relaxation models were developed and employed to determine the time scales for both diffusion and polymer relaxation, where the ratio of these values (Deborah number) confirmed the observed non-Fickian water diffusion. In addition, the solubility of water in these polymers was predicted using two nonequilibrium thermodynamic models: the nonequilibrium lattice fluid (NELF) model and the nonequilibrium statistical associating fluid theory (NE-SAFT), where excellent agreement between the NE-SAFT predictions and experimental data was obtained over the entire water vapor activity range explored. Furthermore, the states of water were analyzed using the Zimm-Lundberg clustering theory, as well as in situ FTIR-ATR spectroscopy, where the latter technique provides a

  18. How Glassy States Affect Brown Carbon Production?

    NASA Astrophysics Data System (ADS)

    Liu, P.; Li, Y.; Wang, Y.; Bateman, A. P.; Zhang, Y.; Gong, Z.; Gilles, M. K.; Martin, S. T.

    2015-12-01

    Secondary organic material (SOM) can become light-absorbing (i.e. brown carbon) via multiphase reactions with nitrogen-containing species such as ammonia and amines. The physical states of SOM, however, potentially slow the diffusion of reactant molecules in organic matrix under conditions that semisolids or solids prevail, thus inhibiting the browning reaction pathways. In this study, the physical states and the in-particle diffusivity were investigated by measuring the evaporation kinetics of both water and organics from aromatic-derived SOMs using a quartz-crystal-microbalance (QCM). The results indicate that the SOMs derived from aromatic precursors toluene and m-xylene became solid (glassy) and the in particle diffusion was significantly impeded for sufficiently low relative humidity ( < 20% RH) at 293 K. Optical properties and the AMS spectra were measured for toluene-derived SOM after ammonia exposure at varied RHs. The results suggest that the production of light-absorbing nitrogen-containing compounds from multiphase reactions with ammonia was kinetically limited in the glassy organic matrix, which otherwise produce brown carbon. The results of this study have significant implications for production and optical properties of brown carbon in urban atmospheres that ultimately influence the climate and tropospheric photochemistry.

  19. Deformation and failure of glassy materials

    NASA Astrophysics Data System (ADS)

    Rottler, Joerg Gerhard

    Elastoplastic deformation of disordered solids and the formation of polymer crazes in amorphous polymer glasses are studied using large-scale molecular dynamics simulations. It is shown that the pressure-modified von Mises criterion accurately describes the maximum shear yield stress under general loading conditions. The pressure coefficient is insensitive to most model parameters, but is related to the bead geometry in analogy to friction coefficients. The yield stress decreases linearly with rising temperature and the strain rate dependence can be described by a power-law, or in a limited range, by a logarithm. The rate dependence does not vary with temperature, which is inconsistent with simple rate-state models of thermal activation such as the Eyring model. An analysis of the dynamics of the local stress distribution as well as modern phenomenological theories of rheology of glassy materials are discussed in light of these findings. We then present a comprehensive investigation of the deformation of glassy polymeric systems into a dense load-bearing network of fibrils and voids called a craze at large strains. This expansion takes place in the form of a drawing process, where the strain rate is strongly localized in a narrow interface region between dense polymer and craze. The expansion is controlled by some polymer chain segments between entanglements that are stretched taut during crazing. We also find that the distribution of tension in the craze develops an exponential force tail in close analogy to compressed jammed systems such as granular media. This highly anisotropic stress distribution and the localization of large forces on relatively few chains indicate that earlier models of the crazing process that treat the polymer as a viscous fluid with hydrodynamic interactions are incorrect. Simulations and simple scaling arguments are presented that describe craze breakdown through disentanglement or chain scission. Glassy polymers exhibit an unusually

  20. Active fluidization in dense glassy systems.

    PubMed

    Mandal, Rituparno; Bhuyan, Pranab Jyoti; Rao, Madan; Dasgupta, Chandan

    2016-07-20

    Dense soft glasses show strong collective caging behavior at sufficiently low temperatures. Using molecular dynamics simulations of a model glass former, we show that the incorporation of activity or self-propulsion, f0, can induce cage breaking and fluidization, resulting in the disappearance of the glassy phase beyond a critical f0. The diffusion coefficient crosses over from being strongly to weakly temperature dependent as f0 is increased. In addition, we demonstrate that activity induces a crossover from a fragile to a strong glass and a tendency of active particles to cluster. Our results are of direct relevance to the collective dynamics of dense active colloidal glasses and to recent experiments on tagged particle diffusion in living cells. PMID:27380935

  1. NRA of hydrogen in glassy polymeric carbon

    NASA Astrophysics Data System (ADS)

    Zimmerman, R. L.; Ila, D.; Jenkins, G. M.; Hirvonen, J. K.; Maleki, H.

    1997-02-01

    Glassy Polymeric Carbon (GPC) is prepared from a precursor resin by careful heat treatment. Heat Treatment Temperatures (HTT) above 1500 °C are believed to expel all hydrogen and oxygen from the grafene structure of GPC. However, we have shown that significant amounts of oxygen remain sequestered in the pores of GPC even at HTT's above 1500 °C. In the present study we report the detection of similar amounts of hydrogen for various heat treatment temperatures up to 2500 °C. A Nuclear Reaction Analysis (NRA) method with the 1H(15N,αγ)12C reaction and a specifically designed coincidence array is used to detect the 4.43 MeV gamma ray whose yield is proportional to the hydrogen content in the GPC. The H:C atomic ratio decreases with increasing HTT and we show that it exceeds 1:100 even for a HTT of 2500 °C.

  2. Glassy Behavior in a Micellar Polyelectrolyte System

    NASA Astrophysics Data System (ADS)

    Bhatia, Surita; Crichton, Mark; Mourchid, Ahmed

    2003-03-01

    We present SANS and rheology for micellar solutions of polystyrene-poly(acrylic acid) block copolymers that can be regarded as attractive colloids. These systems form gels at high effective micellar volume fractions that are suggestive of disordered colloidal glasses. At the gel point, the solution rheology follows the scaling predicted by classical percolation theory. We argue that this scaling could be due either to formation of a percolated network or a pre-transitional glassy phase. The addition of cationic and anionic surfactants (DTAB and SDS) can be used to modify the intermicellar interactions and solution rheology. Addition of an anionic surfactant acts to screen attractive interactions and causes a monotonic decrease in the elastic modulus. However, the addition of a cationic surfactant appears to initially induce a stronger intermicellar attraction, leading to gels with a higher elastic modulus. At higher surfactant concentrations, the cationic surfactant begins to screen intermicellar association, leading to a decrease in elasticity.

  3. Plastic and glassy crystal states of caffeine.

    PubMed

    Descamps, Marc; Correia, Natalia T; Derollez, Patrick; Danede, Florence; Capet, Frédéric

    2005-08-25

    The present paper focuses on the high temperature form I of caffeine and on its low temperature metastable form. Structural, dynamic, and kinetic information has been obtained by X-ray, dielectric, and calorimetric investigations. This study shows the following features: (1) The high temperature phase (I) of caffeine is in a state of dynamically orientationally disordered crystalline state (so-called "plastic, or rotator, phase"). (2) This high-symmetry hexagonal phase can be maintained at low temperature in a metastable situation. (3) Under deep undercooling of form I a glass transition occurs in the disordered crystalline state near room temperature. It is associated with the orientational freezing in of the molecular motions. Otherwise stated, the metastable state I enters into a nonergodic unstable state, so-called "glassy crystal" state. These findings rationalize the difficulties seen with caffeine in pharmaceutical science.

  4. Biaxial stress relaxation in glassy polymers - Polymethylmethacrylate.

    NASA Technical Reports Server (NTRS)

    Sternstein, S. S.; Ho, T. C.

    1972-01-01

    Biaxial stress relaxation studies were performed on glassy polymethylmethacrylate in combined torsion-tension strain fields using a specially designed apparatus with exceptionally high stiffness and low cross talk between the torsional and tensile load measuring transducers. It was found that at low strain levels uniaxial tension relaxation is slower than pure torsion relaxation; tensile-component relaxation rates are unaffected by the level of torsional strain; torsional-component relaxation rates decrease as tensile strain is increased; uniaxial tension relaxation rates approach the pure torsion rates at higher strains (about 2%). A phenomenological treatment is presented which shows that relaxation rates can be coupled to the strain fields in which they are observed and yet be consistent with the concepts of linear viscoelasticity and the Boltzmann superposition integral.

  5. Glassy Dynamics, Cell Mechanics and Endothelial Permeability

    PubMed Central

    Hardin, Corey; Rajendran, Kavitha; Manomohan, Greeshma; Tambe, Dhananjay T.; Butler, James P.; Fredberg, Jeffrey J.; Martinelli, Roberta; Carman, Christopher V.; Krishnan, Ramaswamy

    2013-01-01

    A key feature of all inflammatory processes is disruption of the vascular endothelial barrier. Such disruption is initiated in part through active contraction of the cytoskeleton of the endothelial cell (EC). Because contractile forces are propagated from cell to cell across a great many cell-cell junctions, this contractile process is strongly cooperative and highly nonlocal. We show here that the characteristic length scale of propagation is modulated by agonists and antagonists that impact permeability of the endothelial barrier. In the presence of agonists including thrombin, histamine, and H202, force correlation length increases, whereas in the presence of antagonists including sphingosine-1-phosphate, hepatocyte growth factor, and the rho kinase inhibitor, Y27632, force correlation length decreases. Intercellular force chains and force clusters are also evident, both of which are reminiscent of soft glassy materials approaching a glass transition. PMID:23638866

  6. Shock-wave studies of anomalous compressibility of glassy carbon

    NASA Astrophysics Data System (ADS)

    Molodets, A. M.; Golyshev, A. A.; Savinykh, A. S.; Kim, V. V.

    2016-02-01

    The physico-mechanical properties of amorphous glassy carbon are investigated under shock compression up to 10 GPa. Experiments are carried out on the continuous recording of the mass velocity of compression pulses propagating in glassy carbon samples with initial densities of 1.502(5) g/cm3 and 1.55(2) g/cm3. It is shown that, in both cases, a compression wave in glassy carbon contains a leading precursor with amplitude of 0.135(5) GPa. It is established that, in the range of pressures up to 2 GPa, a shock discontinuity in glassy carbon is transformed into a broadened compression wave, and shock waves are formed in the release wave, which generally means the anomalous compressibility of the material in both the compression and release waves. It is shown that, at pressure higher than 3 GPa, anomalous behavior turns into normal behavior, accompanied by the formation of a shock compression wave. In the investigated area of pressure, possible structural changes in glassy carbon under shock compression have a reversible character. A physico-mechanical model of glassy carbon is proposed that involves the equation of state and a constitutive relation for Poisson's ratio and allows the numerical simulation of physico-mechanical and thermophysical properties of glassy carbon of different densities in the region of its anomalous compressibility.

  7. High temperature annealing studies of strontium ion implanted glassy carbon

    NASA Astrophysics Data System (ADS)

    Odutemowo, O. S.; Malherbe, J. B.; Prinsloo, L.; Langa, D. F.; Wendler, E.

    2016-03-01

    Glassy carbon samples were implanted with 200 keV strontium ions to a fluence of 2 × 1016 ions/cm2 at room temperature. Analysis with Raman spectroscopy showed that ion bombardment amorphises the glassy carbon structure. Partial recovery of the glassy carbon structure was achieved after the implanted sample was vacuum annealed at 900 °C for 1 h. Annealing the strontium ion bombarded sample at 2000 °C for 5 h resulted in recovery of the glassy carbon substrate with the intensity of the D peak becoming lower than that of the pristine glassy carbon. Rutherford backscattering spectroscopy (RBS) showed that the implanted strontium diffused towards the surface of the glassy carbon after annealing the sample at 900 °C. This diffusion was also accompanied by loss of the implanted strontium. Comparison between the as-implanted and 900 °C depth profiles showed that less than 30% of the strontium was retained in the glassy carbon after heat treatment at 900 °C. The RBS profile after annealing at 2000 °C indicated that no strontium ions were retained after heat treatment at this temperature.

  8. Anodic electrosynthesis of some peroxy compounds on glassy carbon electrodes

    SciTech Connect

    Khomutov, N.E.; Zakhodyakina, N.A.; Svirida, L.V.; Nesvat, N.V.

    1987-11-10

    The authors present the results of a study of the anodic electrosynthesis of hydrogen peroxide and its derivatives on glassy carbon in solutions of sodium carbonate and sodium carbonate with sodium borate. We studied the kinetics of anodic processes on glassy carbon with the aid of polarization measurements and a method for determining the concentrations of active oxygen in the anolyte and the current efficiency. The current efficiencies with respect to active oxygen obtained on glassy carbon in the mixed solution of sodium borate and sodium carbonate are close to the current efficiencies which are observed on platinum anodes in the industrial electrosynthesis of perborates.

  9. A structural approach to relaxation in glassy liquids

    NASA Astrophysics Data System (ADS)

    Schoenholz, S. S.; Cubuk, E. D.; Sussman, D. M.; Kaxiras, E.; Liu, A. J.

    2016-05-01

    In contrast with crystallization, there is no noticeable structural change at the glass transition. Characteristic features of glassy dynamics that appear below an onset temperature, T0 (refs ,,), are qualitatively captured by mean field theory, which assumes uniform local structure. Studies of more realistic systems have found only weak correlations between structure and dynamics. This raises the question: is structure important to glassy dynamics in three dimensions? We answer this question affirmatively, using machine learning to identify a new field, `softness' which characterizes local structure and is strongly correlated with dynamics. We find that the onset of glassy dynamics at T0 corresponds to the onset of correlations between softness (that is, structure) and dynamics. Moreover, we construct a simple model of relaxation that agrees well with our simulation results, showing that a theory of the evolution of softness in time would constitute a theory of glassy dynamics.

  10. Ductile mode electrochemical oxidation assisted micromachining for glassy carbon

    NASA Astrophysics Data System (ADS)

    Nam, Eunseok; Lee, Chan-Young; Jun, Martin B. G.; Min, Byung-Kwon

    2015-04-01

    Recently, a new mechanical machining process using electrochemical oxidation was reported. Electrochemical oxidation assisted micromachining was applied to the machining of glassy carbon. The material removal process of the electrochemical oxidation assisted micromachining consists of repeated cycles of oxidation followed by removal of the oxide layer. In this paper, we experimentally investigate and compare the critical chip thickness for ductile mode cutting in mechanical machining and electrochemical oxidation assisted micromachining of glassy carbon. The theoretical critical chip thickness is calculated for mechanical machining of glassy carbon and experimentally verified. The effect of electrochemical oxidation on the critical chip thickness for ductile mode micromachining is also studied for glassy carbon. It is found that the critical chip thickness is increased for the electrochemical oxidation assisted micromachining.

  11. Adhesion in hydrogels and model glassy polymers

    NASA Astrophysics Data System (ADS)

    Guvendiren, Murat

    Two main topics are addressed in this dissertation: (1) adhesion in hydrogels; (2) interfacial interactions between model glassy polymers. A self-assembly technique for the formation of hydrogels from acrylic triblock copolymer solutions was developed, based on vapor phase solvent exchange. Structure formation in the gels was characterized by small angle X-ray scattering, and swelling was measured in controlled pH buffer solutions. Strong gels are formed with polymer weight fractions between 0.01 and 0.15, and with shear moduli between 0.6 kPa and 3.5 kPa. Adhesive functionality, based on 3,4-dihydroxy-L-phenylalanine (DOPA) was also incorporated into the triblock copolymers. The effect of DOPA concentration on gel formation and swelling was investigated in detail. The adhesive properties of DOPA-functionalized hydrogels on TiO2 were investigated with an axisymmetric adhesion method. It was shown that the presence of DOPA enhances the adhesive properties of the hydrogels, but that the effect is minimized at pH values below 10, where the DOPA groups are hydrophobic. Thin film membranes were produced in order to study the specific interactions between DOPA and TiO2 and DOPA and tissue, using a membrane inflation method. The presence of DOPA in the membranes enhances the adhesion on TiO 2 and tissue, although adhesion to tissue requires that the DOPA groups be oxidized while in contact with the tissue of interest. Porous hydrogel scaffolds for tissue engineering applications were formed by adding salt crystals to the triblock copolymer solution prior to solvent exchange. Salt was then leached out by immersing the gel into water. Structures of the porous hydrogels were characterized by confocal laser scanning microscopy. These hydrogels were shown to be suitable for tissue regeneration and drug delivery applications. Diffusion-mediated adhesion between two component miscible polymer systems having very different glassy temperatures was also investigated. Axisymmetric

  12. Synthesis and characterization of novel glassy liquid crystals

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip

    As an emerging class of photonic and electronic materials, glassy liquid crystals are capable of preserving in the solid state molecular order characteristic of liquid crystals. Because of superior chemical purity and favorable rheological properties, glassy liquid crystals can be readily processed into large-area monodomain films. This thesis aimed at deterministic synthesis of glassy chiral nematics, photochromic glassy nematics, and glassy discotics. The most significant contributions are recapitulated as follows: (1) Through deterministic synthesis of multifunctional materials via enzymatic and chemical approaches, enantiomeric glassy chiral nematics were prepared efficiently and shown to possess a glass transition temperature over 60°C and a cholesteric fluid temperature range wider than 100°C. Device concepts were also demonstrated for high-performance circular polarizers, notch filters and reflectors in the ultraviolet, across the visible, and to the infrared region. (2) The first photochromic glassy nematic liquid crystal was successfully designed, synthesized and characterized to possess a glass transition temperature over 100°C and a clearing point over 200°C. A large-area solid film was prepared through melt processing to demonstrate high-speed switching of anisotropic refractive indices and optical birefringence as a novel approach to rewritable optical memory and photonic switching in solid films. (3) Glassy discotic liquid crystals were synthesized and characterized by x-ray diffraction, polarizing optical microscopy, differential scanning calorimetry, and dynamic mechanical analysis to reveal sub-freezing glass transition temperatures. However, the absence of recrystallization at room temperature over a period of over four years was a manifestation of morphological stability of the discotics.

  13. No inherent glassiness in a Penrose tiling quasicrystal

    SciTech Connect

    Strandburg, K.J.; Dressel, P.R.

    1988-11-01

    Consideration of the structure of the Penrose pattern has led to speculation that a system with a Penrose tiling ground state might be subject to inherent glassy behavior. Monte Carol simulations show, using a simple model of the energetics, that there is no inherent glassiness in the Penrose tiling. Thermodynamic quantities measured are completely reversible, displaying no observable hysterisis, and the system may be easily cooled from a highly disordered configuration into its lowest energy state. 11 refs., 7 figs.

  14. Structural Properties of Defects in Glassy Liquids.

    PubMed

    Cubuk, Ekin D; Schoenholz, Samuel S; Kaxiras, Efthimios; Liu, Andrea J

    2016-07-01

    At zero temperature a disordered solid corresponds to a local minimum in the energy landscape. As the temperature is raised or the system is driven with a mechanical load, the system explores different minima via dynamical events in which particles rearrange their relative positions. We have shown recently that the dynamics of particle rearrangements are strongly correlated with a structural quantity associated with each particle, "softness", which we can identify using supervised machine learning. Particles of a given softness have a well-defined energy scale that governs local rearrangements; because of this property, softness greatly simplifies our understanding of glassy dynamics. Here we investigate the correlation of softness with other commonly used structural quantities, such as coordination number and local potential energy. We show that although softness strongly correlates with these properties, its predictive power for rearrangement dynamics is much higher. We introduce a useful metric for quantifying the quality of structural quantities as predictors of dynamics. We hope that, in the future, authors introducing new structural measures of dynamics will compare their proposals quantitatively to softness using this metric. We also show how softness correlations give insight into rearrangements. Finally, we explore the physical meaning of softness using unsupervised dimensionality reduction and reduced curve-fitting models, and show that softness can be recast in a form that is amenable to analytical treatment.

  15. Lithium ion diffusion through glassy carbon plate

    SciTech Connect

    Inaba, M.; Nohmi, S.; Funabiki, A.; Abe, T.; Ogumi, Z.

    1998-07-01

    The electrochemical permeation method was applied to the determination of the diffusion coefficient of Li{sup +} ion (D{sub Li{sup +}}) in a glassy carbon (GC) plate. The cell was composed of two compartments, which were separated by the GC plate. Li{sup +} ions were inserted electrochemically from one face, and extracted from the other. The flux of the permeated Li{sup +} ions was monitored as an oxidation current at the latter face. The diffusion coefficient was determined by fitting the transient current curve with a theoretical one derived from Fick's law. When the potential was stepped between two potentials in the range of 0 to 0.5 V, transient curves were well fitted with the theoretical one, which gave D{sub Li{sup +}} values on the order of 10{sup {minus}8} cm{sup {minus}2} s{sup {minus}1}. In contrast, when the potential was stepped between two potentials across 0.5 V, significant deviation was observed. The deviation indicated the presence of trap sites as well as diffusion sites for Li{sup +} ions, the former of which is the origin of the irreversible capacity of GC.

  16. Understanding glass-forming ability through sluggish crystallization of atomically thin metallic glassy films

    SciTech Connect

    Sun, Y. T.; Cao, C. R.; Huang, K. Q.; Zhao, N. J.; Gu, L. E-mail: dzheng@iphy.ac.cn Zheng, D. N. E-mail: dzheng@iphy.ac.cn Wang, W. H. E-mail: dzheng@iphy.ac.cn

    2014-08-04

    The glass-forming ability (GFA) of an alloy, closely related to its ability to resist crystallization, is a crucial issue in condensed matter physics. So far, the studies on GFA are mostly statistical and empirical guides. Benefiting from the ultrahigh thermal stability of ultrathin metallic glassy film and high resolution spherical aberration-corrected transmission electron microscope, the crystallization of atomically thin ZrCu and its microalloyed ZrCuAl glasses with markedly different GFA was investigated at the atomic scale. We find the Zr diffusivity estimated from the density of nuclei is dramatically decreased by adding of Al, which is the major reason for the much better GFA of the ZrCuAl metallic glass.

  17. Catalytic applications of amorphous alloys: Expectations, achievements, and disappointments

    NASA Astrophysics Data System (ADS)

    Molnár, Árpád

    2011-07-01

    This review intends to summarize the major achievements in the application of amorphous alloys as precursors of catalyst materials. This non-traditional catalyst preparation method may provide supported catalysts with novel chemical and structural properties. Selected examples for both glassy alloy precursors and those fabricated by mechanochemistry include CO oxidation over binary and ternary alloys, dehydrogenation over Cu-M (M = Ti, Zr or Hf), one-step synthesis of methyl isobutyl ketone, and selective hydrogenation of unsaturated carbonyl compounds. Ni alloys for methanation developed for the project to solve global warming by recycling carbon dioxide are also discussed.

  18. Shear banding in soft glassy materials

    NASA Astrophysics Data System (ADS)

    Fielding, S. M.

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic ‘glassy’ features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  19. Magnetic properties of Cu70.9Al18.1Mn11 alloy

    NASA Astrophysics Data System (ADS)

    Chatterjee, S.; Majumdar, S.

    2013-02-01

    The ferromagnetic shape memory alloy of nominal composition Cu70.9Al18.1Mn11 has been investigated through dc and ac magnetization measurements. The studied alloy undergoes ferromagnetic to glassy transition below martensitic transition. Clear frequency shift in ac susceptibility measurement is observed, which actually indicates the spin glass freezing in the sample. The studied alloy also shows constricted hysteresis loop at 5 K.

  20. Optical speckles of blood proteins embedded in porous glassy substrate

    NASA Astrophysics Data System (ADS)

    Holden, T.; Dehipawala, S.; Kokkinos, D.; Berisha, A.; Cheung, E.; Nguyen, A.; Golebiewska, U.; Schneider, P.; Tremberger, G., Jr.; Lieberman, D.; Cheung, T.

    2012-03-01

    Blood protein molecules could be embedded in porous glassy substrate with 10-nm pores. The embedding principle is based on blood cell dehydration with the destruction of the cell membrane, and reconstitution and centrifuge could yield a suitable solution for doping into a porous glassy medium. The doped glassy substrate speckle pattern under laser illumination could be used to characterize the protein size distribution. Calibration with known protein embedded samples would result in an optical procedure for the characterization of a blood sample. Samples embedded with larger kilo-Dalton protein molecule show more variation in the speckle patterns, consistent with protein folding interaction inside a pore cavity. A regression model has been used to correlate the protein molecule sizes with speckle sizes. The use of diffusion mean free path information to study protein folding in the embedding process is briefly discussed.

  1. The Erevan howardite: Petrology of glassy clasts and mineral chemistry

    NASA Technical Reports Server (NTRS)

    Nazarov, M. A.; Ariskin, A. A.

    1993-01-01

    The Erevan howardite is a polymict regolith breccia containing xenoliths of carbonaceous chondrites. In this work, we studied glassy clasts, which could be considered as primary quenched melts, and mineral chemistry of the breccia. The study reveals that the Erevan howardite consists of common rocks of the HED suite. However, unique glassy clasts, which are present in some eucritic melts, were identified. The mineral chemistry and the simulation of crystallization of the melts suggest that the compositions of the melts reflect those of some primary lithologies of EPB.

  2. On the origin of bulk glass forming ability in Cu-Hf, Zr alloys

    NASA Astrophysics Data System (ADS)

    Ristić, Ramir; Zadro, Krešo; Pajić, Damir; Figueroa, Ignacio A.; Babić, Emil

    2016-04-01

    Understanding the formation of bulk metallic glasses (BMG) in metallic systems and finding a reliable criterion for selection of BMG compositions are among the most important issues in condensed-matter physics and material science. Using the results of magnetic susceptibility measurements performed on both amorphous and crystallized Cu-Hf alloys (30-70 at% Cu) we find a correlation between the difference in magnetic susceptibilities of corresponding glassy and crystalline alloys and the variation in the glass forming ability (GFA) in these alloys. Since the same correlation can be inferred from data for the properties associated with the electronic structure of Cu-Zr alloys, it seems quite general and may apply to other glassy alloys based on early and late transition metals. This correlation is plausible from the free-energy considerations and provides a simple way to select the compositions with high GFA.

  3. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    PubMed Central

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

    2016-01-01

    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. PMID:26985910

  4. The nonequilibrium glassy dynamics of self-propelled particles.

    PubMed

    Flenner, Elijah; Szamel, Grzegorz; Berthier, Ludovic

    2016-09-14

    We study the glassy dynamics taking place in dense assemblies of athermal active particles that are driven solely by a nonequilibrium self-propulsion mechanism. Active forces are modeled as an Ornstein-Uhlenbeck stochastic process, characterized by a persistence time and an effective temperature, and particles interact via a Lennard-Jones potential that yields well-studied glassy behavior in the Brownian limit, which is obtained as the persistence time vanishes. By increasing the persistence time, the system departs more strongly from thermal equilibrium and we provide a comprehensive numerical analysis of the structure and dynamics of the resulting active fluid. Finite persistence times profoundly affect the static structure of the fluid and give rise to nonequilibrium velocity correlations that are absent in thermal systems. Despite these nonequilibrium features, for any value of the persistence time we observe a nonequilibrium glass transition as the effective temperature is decreased. Surprisingly, increasing departure from thermal equilibrium is found to promote (rather than suppress) the glassy dynamics. Overall, our results suggest that with increasing persistence time, microscopic properties of the active fluid change quantitatively, but the general features of the nonequilibrium glassy dynamics observed with decreasing the effective temperature remain qualitatively similar to those of thermal glass-formers. PMID:27499055

  5. Introduction to the Glassy State in the Undergraduate Curriculum

    ERIC Educational Resources Information Center

    Johari, Gyan P.

    1974-01-01

    Presents fundamentals of the glassy state which can serve as an introductory, phenomenological, and nonmathematical exposure to undergraduates in at most two lectures. Suggests the use of the material following students' acquisition of an elementary knowledge of thermodynamics, liquids, and the crystalline state. (CC)

  6. Pressure-induced transformations in computer simulations of glassy water.

    PubMed

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

    2013-11-14

    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. PMID:24320281

  7. Loss of halogens from crystallized and glassy silicic volcanic rocks

    USGS Publications Warehouse

    Noble, D.C.; Smith, V.C.; Peck, L.C.

    1967-01-01

    One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

  8. Glassy correlations and thermal fluctuations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Xing, Xiangjun; Ye, Fangfu; Goldbart, Paul

    2010-03-01

    By means of the vulcanization theory framework we address the properties of nematic elastomers prepared in the isotropic liquid state and subsequently randomly cross-linked beyond the gelation point. We base our analysis on a model replica Landau free energy, in which the vulcanization order parameter is coupled to the order parameter describing the local degree of nematic ordering, retaining fluctuation terms to the Gaussian level. We explore how the cross-linking renormalizes the thermal correlations of the local nematic order, and also results in frozen-in, glassy nematic correlations. We examine these thermal and glassy correlations for two different preparation histories of the system: in the first, the cross-linking is done at temperatures close to the isotropic-nematic transition; in the other, the cross-linking is done at higher temperatures, but the system is subsequently cooled to near this transition temperature.

  9. Understanding soft glassy materials using an energy landscape approach

    NASA Astrophysics Data System (ADS)

    Hwang, Hyun Joo; Riggleman, Robert A.; Crocker, John C.

    2016-09-01

    Many seemingly different soft materials--such as soap foams, mayonnaise, toothpaste and living cells--display strikingly similar viscoelastic behaviour. A fundamental physical understanding of such soft glassy rheology and how it can manifest in such diverse materials, however, remains unknown. Here, by using a model soap foam consisting of compressible spherical bubbles, whose sizes slowly evolve and whose collective motion is simply dictated by energy minimization, we study the foam's dynamics as it corresponds to downhill motion on an energy landscape function spanning a high-dimensional configuration space. We find that these downhill paths, when viewed in this configuration space, are, surprisingly, fractal. The complex behaviour of our model, including power-law rheology and non-diffusive bubble motion and avalanches, stems directly from the fractal dimension and energy function of these paths. Our results suggest that ubiquitous soft glassy rheology may be a consequence of emergent fractal geometry in the energy landscapes of many complex fluids.

  10. 2H NMR studies of supercooled and glassy aspirin

    NASA Astrophysics Data System (ADS)

    Nath, R.; Nowaczyk, A.; Geil, B.; Bohmer, R.

    2007-11-01

    Acetyl salicylic acid, deuterated at the methyl group, was investigated using 2H-NMR in its supercooled and glassy states. Just above the glass transition temperature the molecular reorientations were studied using stimulated-echo spectroscopy and demonstrated a large degree of similarity with other glass formers. Deep in the glassy phase the NMR spectra look similar to those reported for the crystal [A. Detken, P. Focke, H. Zimmermann, U. Haeberlen, Z. Olejniczak, Z. T. Lalowicz, Z. Naturforsch. A 50 (1995) 95] and below 20 K they are indicative for rotational tunneling with a relatively large tunneling frequency. Measurements of the spin-lattice relaxation times for temperatures below 150 K reveal a broad distribution of correlation times in the glass. The dominant energy barrier characterizing the slow-down of the methyl group is significantly smaller than the well defined barrier in the crystal.

  11. Understanding soft glassy materials using an energy landscape approach.

    PubMed

    Hwang, Hyun Joo; Riggleman, Robert A; Crocker, John C

    2016-09-01

    Many seemingly different soft materials-such as soap foams, mayonnaise, toothpaste and living cells-display strikingly similar viscoelastic behaviour. A fundamental physical understanding of such soft glassy rheology and how it can manifest in such diverse materials, however, remains unknown. Here, by using a model soap foam consisting of compressible spherical bubbles, whose sizes slowly evolve and whose collective motion is simply dictated by energy minimization, we study the foam's dynamics as it corresponds to downhill motion on an energy landscape function spanning a high-dimensional configuration space. We find that these downhill paths, when viewed in this configuration space, are, surprisingly, fractal. The complex behaviour of our model, including power-law rheology and non-diffusive bubble motion and avalanches, stems directly from the fractal dimension and energy function of these paths. Our results suggest that ubiquitous soft glassy rheology may be a consequence of emergent fractal geometry in the energy landscapes of many complex fluids. PMID:27322823

  12. Glassy states in fermionic systems with strong disorder and interactions

    NASA Astrophysics Data System (ADS)

    Schwab, David J.; Chakravarty, Sudip

    2009-03-01

    We study the competition between interactions and disorder in two dimensions. Whereas a noninteracting system is always Anderson localized by disorder in two dimensions, a pure system can develop a Mott gap for sufficiently strong interactions. Within a simple model, with short-ranged repulsive interactions, we show that, even in the limit of strong interaction, the Mott gap is completely washed out by disorder for an infinite system for dimensions D≤2 , leading to a glassy state. Moreover, the Mott insulator cannot maintain a broken symmetry in the presence of disorder. We then show that the probability of a nonzero gap as a function of system size falls onto a universal curve, reflecting the glassy dynamics. An analytic calculation is also presented in one dimension that provides further insight into the nature of slow dynamics.

  13. Molecular dynamics study of structure and glass forming ability of Zr70Pd30 alloy

    NASA Astrophysics Data System (ADS)

    Celtek, Murat; Sengul, Sedat; Domekeli, Unal; Canan, Cem

    2016-03-01

    In this study, the temperature effects on the structural evolution of the Zr70Pd30 binary alloy in the glassy and liquid states were studied using the molecular dynamics simulations based on the many-body type tight-binding potential. We considered the following properties in detail: the temperature dependence of the volume, the partial and total pair distribution functions and the simulated glass transition temperature. The effects of the cooling rates on the glass transition temperature were examined. The Wendt-Abraham parameter was calculated to determine the glass transition temperature of Zr70Pd30 glassy alloy. The pair analysis technique of Honeycutt-Andersen was applied to define local atomic arrangements produced from molecular dynamics simulations. The results show that the icosahedral ordering in glassy state has been composed during quenching period, and the simulated glass transition temperature and the total pair distribution functions are in good agreement with the experimental data.

  14. Composition-dependent metallic glass alloys correlate atomic mobility with collective glass surface dynamics.

    PubMed

    Nguyen, Duc; Zhu, Zhi-Guang; Pringle, Brian; Lyding, Joseph; Wang, Wei-Hua; Gruebele, Martin

    2016-06-22

    Glassy metallic alloys are richly tunable model systems for surface glassy dynamics. Here we study the correlation between atomic mobility, and the hopping rate of surface regions (clusters) that rearrange collectively on a minute to hour time scale. Increasing the proportion of low-mobility copper atoms in La-Ni-Al-Cu alloys reduces the cluster hopping rate, thus establishing a microscopic connection between atomic mobility and dynamics of collective rearrangements at a glass surface made from freshly exposed bulk glass. One composition, La60Ni15Al15Cu10, has a surface resistant to re-crystallization after three heating cycles. When thermally cycled, surface clusters grow in size from about 5 glass-forming units to about 8 glass-forming units, evidence of surface aging without crystal formation, although its bulk clearly forms larger crystalline domains. Such kinetically stable glass surfaces may be of use in applications where glassy coatings stable against heating are needed.

  15. Localization and Glassy Dynamics in the Immune System

    NASA Astrophysics Data System (ADS)

    Sun, Jun; Earl, David J.; Deem, Michael W.

    We discuss use of the generalized NK model to examine evolutionary dynamics within the immune system. We describe how randomness and diversity play key roles in the immune response and how their effects are captured by this hierarchical spin glass model. We discuss analytical aspects of the model as well as practical applications to design of the annual influenza vaccine. We discuss the subtle role that the glassy evolutionary dynamics plays in suppressing autoimmune disease.

  16. Yield Stress Enhancement in Glassy-Polyethylene Block Copolymers

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Polyethylene (PE) has the highest annual production volume of all synthetic polymers worldwide, and is valuable across many applications due to its low cost, toughness, processability, and chemical resistance. However, PE is not well suited to certain applications due to its modest yield stress and Young's modulus (approximately 30 MPa and 1 GPa, respectively for linear, high-density PE). Irreversible deformation of PE results from dislocation of crystal stems and eventual crystal fragmentation under applied stress. The liquid-like amorphous fraction provides no useful mechanical support to the crystal fold surface in a PE homopolymer, so the only method to enhance the force required for crystal slip, and hence the yield stress, is crystal thickening via thermal treatment. An alternative route towards modifying the mechanical properties of PE involves copolymerization of a minority high-glass transition temperature block into a majority-PE block copolymer. In this work, we investigate a system of glassy/linear-PE block copolymers prepared via ring-opening metathesis polymerization of cyclopentene and substituted norbornene monomers followed by hydrogenation. We demonstrate that a large change in mechanical properties can be achieved with the addition of a short glassy block (e.g. a doubling of the yield stress and Young's modulus versus PE homopolymer with the addition of 25 percent glassy block). Furthermore, owing to the low interaction energy between PE and the substituted polynorbornene blocks employed, these high-yield PE block copolymers can exhibit single-phase melts for ease of processability.

  17. Non-Equilibrium Water-Glassy Polymer Dynamics

    NASA Astrophysics Data System (ADS)

    Davis, Eric; Minelli, Matteo; Baschetti, Marco; Sarti, Giulio; Elabd, Yossef

    2012-02-01

    For many applications (e.g., medical implants, packaging), an accurate assessment and fundamental understanding of the dynamics of water-glassy polymer interactions is of great interest. In this study, sorption and diffusion of pure water in several glassy polymers films, such as poly(styrene) (PS), poly(methyl methacrylate) (PMMA), poly(lactide) (PLA), were measured over a wide range of vapor activities and temperatures using several experimental techniques, including quartz spring microbalance (QSM), quartz crystal microbalance (QCM), and time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior (diffusion-relaxation phenomena) was observed by all three techniques, while FTIR-ATR spectroscopy also provides information about the distribution of the states of water and water transport mechanisms on a molecular-level. Specifically, the states of water are significantly different in PS compared to PMMA and PLA. Additionally, a purely predictive non-equilibrium lattice fluid (NELF) model was applied to predict the sorption isotherms of water in these glassy polymers.

  18. Exploration for facultative endosymbionts of glassy-wingedsharpshooter (Hemiptera: Cicadellidae)

    SciTech Connect

    Montllor-Curley, C.; Brodie, E.L.; Lechner, M.G.; Purcell, A.H.

    2006-07-01

    Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae),glassy-winged sharpshooter, was collected in California and severalstates in the southeastern United States in 2002 and 2003 and analyzedfor endosymbiotic bacteria. Hemolymph, eggs, and bacteriomes wereexamined for the presence of bacteria by polymerase chain reaction. Asubset of hemolymph and egg samples had their 16S rRNA gene ampliconscloned and sequenced or analyzed by restriction digest patterns ofsamples compared with known bacterial DNA. Baumannia cicadellinicola, oneof the primary symbionts of glassy-winged sharpshooter, was found in themajority of hemolymph samples, although it has been considered until nowto reside primarily inside the specialized host bacteriocytes. Wolbachiasp., a common secondary symbiont in many insect taxa investigated todate, was the second most frequently detected bacterium in hemolymphsamples. In addition, we detected bacteria that were most closely related(by 16S rRNA gene sequence) to Pseudomonas, Stenotrophomonas, andAcinetobacter in hemolymph samples of one and/or two glassy-wingedsharpshooters, but their origin is uncertain.

  19. Thermodynamics of Water Sorption in High Performance Glassy Thermoplastic Polymers

    NASA Astrophysics Data System (ADS)

    Mensitieri, Giuseppe; Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino

    2014-05-01

    Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging fro 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different’populations’ of water molecules present within the PEEK and a quantitative assessment of these ‘populations’ in the case of PEI.The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non equilibrium nature of glassy poymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data.

  20. Quantifying glassy and crystalline basalt partitioning in the oceanic crust

    NASA Astrophysics Data System (ADS)

    Moore, Rachael; Ménez, Bénédicte

    2016-04-01

    The upper layers of the oceanic crust are predominately basaltic rock, some of which hosts microbial life. Current studies of microbial life within the ocean crust mainly focus on the sedimentary rock fraction, or those organisms found within glassy basalts while the potential habitability of crystalline basalts are poorly explored. Recently, there has been recognition that microbial life develops within fractures and grain boundaries of crystalline basalts, therefore estimations of total biomass within the oceanic crust may be largely under evaluated. A deeper understanding of the bulk composition and fractionation of rocks within the oceanic crust is required before more accurate estimations of biomass can be made. To augment our understanding of glassy and crystalline basalts within the oceanic crust we created two end-member models describing basalt fractionation: a pillow basalt with massive, or sheet, flows crust and a pillow basalt with sheeted dike crust. Using known measurements of massive flow thickness, dike thickness, chilled margin thickness, pillow lava size, and pillow lava glass thickness, we have calculated the percentage of glassy versus crystalline basalts within the oceanic crust for each model. These models aid our understanding of textural fractionation within the oceanic crust, and can be applied with bioenergetics models to better constrain deep biomass estimates.

  1. Fast algorithms for glassy materials: methods and explorations

    NASA Astrophysics Data System (ADS)

    Middleton, A. Alan

    2014-03-01

    Glassy materials with frozen disorder, including random magnets such as spin glasses and interfaces in disordered materials, exhibit striking non-equilibrium behavior such as the ability to store a history of external parameters (memory). Precisely due to their glassy nature, direct simulation of models of these materials is very slow. In some fortunate cases, however, algorithms exist that exactly compute thermodynamic quantities. Such cases include spin glasses in two dimensions and interfaces and random field magnets in arbitrary dimensions at zero temperature. Using algorithms built using ideas developed by computer scientists and mathematicians, one can even directly sample equilibrium configurations in very large systems, as if one picked the configurations out of a ``hat'' of all configurations weighted by their Boltzmann factors. This talk will provide some of the background for these methods and discuss the connections between physics and computer science, as used by a number of groups. Recent applications of these methods to investigating phase transitions in glassy materials and to answering qualitative questions about the free energy landscape and memory effects will be discussed. This work was supported in part by NSF grant DMR-1006731. Creighton Thomas and David Huse also contributed to much of the work to be presented.

  2. Three-dimensional jamming and flows of soft glassy materials.

    PubMed

    Ovarlez, G; Barral, Q; Coussot, P

    2010-02-01

    Various disordered dense systems, such as foams, gels, emulsions and colloidal suspensions, undergo a jamming transition from a liquid state (they flow) to a solid state below a yield stress. Their structure, which has been thoroughly studied with powerful means of three-dimensional characterization, shows some analogy with that of glasses, which led to them being named soft glassy materials. However, despite its importance for geophysical and industrial applications, their rheological behaviour, and its microscopic origin, is still poorly known, in particular because of its nonlinear nature. Here we show from two original experiments that a simple three-dimensional continuum description of the behaviour of soft glassy materials can be built. We first show that when a flow is imposed in some direction there is no yield resistance to a secondary flow: these systems are always unjammed simultaneously in all directions of space. The three-dimensional jamming criterion seems to be the plasticity criterion encountered in most solids. We also find that they behave as simple liquids in the direction orthogonal to that of the main flow; their viscosity is inversely proportional to the main flow shear rate, as a signature of shear-induced structural relaxation, in close similarity to the structural relaxations driven by temperature and density in other glassy systems. PMID:20062046

  3. Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon

    SciTech Connect

    Baker, D.F.

    1983-02-01

    These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.

  4. Investigation of glassy state molecular motions in thermoset polymers

    NASA Astrophysics Data System (ADS)

    Tu, Jianwei

    This dissertation presents the investigation of the glassy state molecular motions in isomeric thermoset epoxies by means of solid-state deuterium (2H) NMR spectroscopy technique. The network structure of crosslinked epoxies was altered through monomer isomerism; specifically, diglycidyl ether of bisphenol A (DGEBA) was cured with isomeric amine curatives, i.e., the meta-substituted diaminodiphenylsulfone (33DDS) and para-substituted diaminodiphenylsulfone (44DDS). The use of structural isomerism provided a path way for altering macroscopic material properties while maintaining identical chemical composition within the crosslinked networks. The effects of structural isomerism on the glassy state molecular motions were studied using solid-state 2H NMR spectroscopy, which offers unrivaled power to monitor site-specific molecular motions. Three distinctive molecular groups on each isomeric network, i.e., the phenylene rings in the bisphenol A structure (BPA), the phenylene rings in the diaminodiphenylsulfone structure (DDS), and the hydroxypropoyl ether group (HPE) have been selectively deuterated for a comprehensive study of the structure-dynamics- property relationships in thermoset epoxies. Quadrupolar echo experiments and line shape simulations were employed as the main research approach to gain both qualitative and quantitative motional information of the epoxy networks in the glassy state. Quantitative information on the geometry and rate of the molecular motions allows the elucidation of the relationship between molecular motions and macro physical properties and the role of these motions in the mechanical relaxation. Specifically, it is revealed that both the BPA and HPE moieties in the isomeric networks have almost identical behaviors in the deep glassy state, which indicates that the molecular motions in the glassy state are localized, and the correlation length of the motions does not exceed the length of the DGEBA repeat unit. BPA ring motions contribute

  5. Alloy materials

    DOEpatents

    Hans Thieme, Cornelis Leo; Thompson, Elliott D.; Fritzemeier, Leslie G.; Cameron, Robert D.; Siegal, Edward J.

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  6. Crystallization of the glassy grain boundary phase in silicon nitride ceramics

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III

    1991-01-01

    The role was studied of the intergranular glassy phase in silicon nitride as-processed with yttria as a sintering aid. The microstructure, crystallization, and viscosity of the glassy phase were areas studied. Crystallization of the intergranular glassy phase to more refractory crystalline phases should improve the high temperature mechanical properties of the silicon nitride. The addition of a nucleating agent will increase the rate of crystallization. The measurement of the viscosity of the glassy phase will permit the estimation of the high temperature deformation of the silicon nitride.

  7. Some Recent Developments in Structure and Glassy Behavior of Proteins

    NASA Astrophysics Data System (ADS)

    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).

  8. Evidence for a glassy state in strongly driven carbon.

    PubMed

    Brown, C R D; Gericke, D O; Cammarata, M; Cho, B I; Döppner, T; Engelhorn, K; Förster, E; Fortmann, C; Fritz, D; Galtier, E; Glenzer, S H; Harmand, M; Heimann, P; Kugland, N L; Lamb, D Q; Lee, H J; Lee, R W; Lemke, H; Makita, M; Moinard, A; Murphy, C D; Nagler, B; Neumayer, P; Plagemann, K-U; Redmer, R; Riley, D; Rosmej, F B; Sperling, P; Toleikis, S; Vinko, S M; Vorberger, J; White, S; White, T G; Wünsch, K; Zastrau, U; Zhu, D; Tschentscher, T; Gregori, G

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  9. Microscale rheology of a soft glassy material close to yielding.

    PubMed

    Jop, Pierre; Mansard, Vincent; Chaudhuri, Pinaki; Bocquet, Lydéric; Colin, Annie

    2012-04-01

    Using confocal microscopy, we study the flow of a model soft glassy material: a concentrated emulsion. We demonstrate the micro-macro link between in situ measured movements of droplets during the flow and the macroscopic rheological response of a concentrated emulsion, in the form of scaling relationships connecting the rheological "fluidity" with local standard deviation of the strain-rate tensor. Furthermore, we measure correlations between these local fluctuations, thereby extracting a correlation length which increases while approaching the yielding transition, in accordance with recent theoretical predictions.

  10. Positronics of radiation-induced effects in chalcogenide glassy semiconductors

    SciTech Connect

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

    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.

  11. Anomalous glassy relaxation near the isotropic-nematic phase transition

    NASA Astrophysics Data System (ADS)

    Jose, Prasanth P.; Chakrabarti, Dwaipayan; Bagchi, Biman

    2005-03-01

    Dynamical heterogeneity in a system of Gay-Berne ellipsoids near its isotropic-nematic (I-N) transition, and also in an equimolar mixture of Lennard-Jones spheres and Gay-Berne ellipsoids in deeply supercooled regime, is probed by the time evolution of non-Gaussian parameters (NGP). The appearance of a dominant second peak in the rotational NGP near the I-N transition signals the growth of pseudonematic domains. Surprisingly, such a second peak is instead observed in the translational NGP for the glassy binary mixture. Localization of orientational motion near the I-N transition is found to be responsible for the observed anomalous orientational relaxation.

  12. Evidence for a glassy state in strongly driven carbon

    SciTech Connect

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Gwangju Inst. of Science and Technology, Gwangju; Inst. for Basic Science, Gwangju ; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K. -U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  13. Deformation in Thin Glassy Polymer Films from Surface towards Interior

    NASA Astrophysics Data System (ADS)

    Chowdhury, Mithun; de Silva, Johann P.; Cross, Graham L. W.

    Polymer thin glassy films occupy an important place in last two decades of condensed matter research, concerning its surprising surface mobility and spatially dependent structural relaxation. However, ranges of cleverly designed indirect measurements on confined polymer glassy films already probed its mechanical properties; it is still a challenging task to directly probe such small confined volume through conventional mechanical testing. We have designed confined layer compression testing with a precisely designed and aligned flat probe during nanoindentation, which was further accompanied with atomic force microscopy. Due to natural confinement from the surrounding material, we show that a state of `uniaxial strain' is created beneath the probe under small axial strains. By this methodology we are able to directly probe uniaxial flows under both anelastic and plastic conditions while doing controlled creep studies at different positions in the film starting from surface towards interior. Depending on the extent of deformation, we found ranges of effects, such as densification, anelastic yield, and plastic yield. Enhanced creep rate upon deformation supports the idea of `deformation induced mobility'. Work performed at Trinity College Dublin.

  14. Electrical studies on silver based fast ion conducting glassy materials

    SciTech Connect

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

    2014-04-24

    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{sub 2}O−[(1−x)B{sub 2}O{sub 3}−xTeO{sub 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{sub 2} as well as with temperature. The conductivity of the present glass system is found to be of the order of 10{sup −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.

  15. Dynamics of caged ions in glassy ionic conductors.

    PubMed

    Habasaki, J; Ngai, K L; Hiwatari, Y

    2004-05-01

    At sufficiently high frequency and low temperature, the dielectric responses of glassy, crystalline, and molten ionic conductors all invariably exhibit nearly constant loss. This ubiquitous characteristic occurs in the short-time regime when the ions are still caged, indicating that it could be a determining factor of the mobility of the ions in conduction at longer times. An improved understanding of its origin should benefit the research of ion conducting materials for portable energy source as well as the resolution of the fundamental problem of the dynamics of ions. We perform molecular dynamics simulations of glassy lithium metasilicate (Li2SiO3) and find that the length scales of the caged Li+ ions motions are distributed according to a Levy distribution that has a long tail. These results suggest that the nearly constant loss originates from "dynamic anharmonicity" experienced by the moving but caged Li+ ions and provided by the surrounding matrix atoms executing correlated movements. The results pave the way for rigorous treatments of caged ion dynamics by nonlinear Hamiltonian dynamics.

  16. Effects of glassy-winged sharpshooter feeding, size, and lipid content on egg maturation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed during the adult stage to produce eggs. While glassy-winged sharpshooter egg production is related to adult feeding, rates of egg production are variable. In this study, effects of lipid allocation to eggs and fema...

  17. Use of glassy carbon as a working electrode in controlled potential coulometry.

    PubMed

    Plock, C E; Vasquez, J

    1969-11-01

    Glassy carbon has been used as the working electrode in controlled potential coulometry. The results of coulometric investigations of chromium, copper, iron, uranium and neptunium are compared with results obtained with platinum or mercury working electrodes. The accuracy of results with the glassy carbon electrode compares favourably with the results obtainable with the other electrodes, but the precision is poorer.

  18. Use of glassy carbon as a working electrode in controlled potential coulometry.

    PubMed

    Plock, C E; Vasquez, J

    1969-11-01

    Glassy carbon has been used as the working electrode in controlled potential coulometry. The results of coulometric investigations of chromium, copper, iron, uranium and neptunium are compared with results obtained with platinum or mercury working electrodes. The accuracy of results with the glassy carbon electrode compares favourably with the results obtainable with the other electrodes, but the precision is poorer. PMID:18960665

  19. Silicon-tin oxynitride glassy composition and use as anode for lithium-ion battery

    DOEpatents

    Neudecker, Bernd J.; Bates, John B.

    2001-01-01

    Disclosed are silicon-tin oxynitride glassy compositions which are especially useful in the construction of anode material for thin-film electrochemical devices including rechargeable lithium-ion batteries, electrochromic mirrors, electrochromic windows, and actuators. Additional applications of silicon-tin oxynitride glassy compositions include optical fibers and optical waveguides.

  20. Evaluation of grapevine as a host for the glassy-winged sharpshooter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grapevine was evaluated as a feeding and oviposition host for the glassy-winged sharpshooter. Two sets of experiments were conducted. The first set compared performance and preference of glassy-winged sharpshooter females for grapevine (cv. Chardonnay) versus cowpea (Vigna unguiculata cultivar black...

  1. Effect of glassy modes on electron spin-lattice relaxation in solid ethanol

    NASA Astrophysics Data System (ADS)

    Merunka, Dalibor; Kveder, Marina; Jokić, Milan; Rakvin, Boris

    2013-03-01

    Electron spin-lattice relaxation (SLR) of TEMPO radical was measured in the crystalline and glassy states of deuterated ethanol in the temperature range 5-80 K using X-band electron paramagnetic resonance (EPR). The measured SLR rates are higher in the glassy than in crystalline state and the excess SLR rate in glassy state is much lower than in ethanol. This result suggests that extra modes in glassy state, i.e. glassy modes, produce the excess SLR rate via the electron-nuclear dipolar (END) interaction between the electron spin of radical and the matrix protons or deuterons. Using the soft-potential model and assuming the END interaction between the electron spin and the matrix protons, the contributions to SLR rate of various mechanisms of glassy modes were theoretically analyzed. The evaluations of SLR rates in glassy ethanol indicate two main mechanisms of glassy modes: thermally activated relaxation of double-well systems and phonon-induced relaxation of quasi-harmonic local modes. The SLR rates induced by these mechanisms correlate well with the experimental data.

  2. Surface treatment of Glassy Polymeric Carbon artifacts for medical applications

    SciTech Connect

    Rodrigues, M. G.; Zimmerman, R. L.; Rezende, M. C.

    1999-06-10

    Glassy Polymeric Carbon (GPC) has been used for mechanical cardiac valves. GCP valves are chemically biocompatible and durable, but less thromboresistant than biological valves. Enhanced thromboresistance of mechanical cardiac components with porous surface has been demonstrated. The endothelialized tissue blood-contacting surface adheres to the porous prosthetic component and decreases the formation of thrombus. Our experience has shown that the porosity of GPC can be increased and controlled by MeV ion bombardment. We report here that the surface roughness of heat-treated GPC bombarded with C, O, Si and Au is also enhanced. The surface roughness of the ion-bombarded samples is on a smaller scale than those roughened by sand blasting (measurements made with Perthomete S and P). The roughness decreases slightly after heat treatment, in linear proportion to the shrinkage of the test piece. Possible beneficial effects of the imbedded ions on tissue adherence and thromboresistance must be determined by in vivo animal experiments.

  3. Anomalous glassy relaxation near the isotropic-nematic phase transition.

    PubMed

    Jose, Prasanth P; Chakrabarti, Dwaipayan; Bagchi, Biman

    2005-03-01

    Dynamical heterogeneity in a system of Gay-Berne ellipsoids near its isotropic-nematic (I-N) transition, and also in an equimolar mixture of Lennard-Jones spheres and Gay-Berne ellipsoids in deeply supercooled regime, is probed by the time evolution of non-Gaussian parameters (NGP). The appearance of a dominant second peak in the rotational NGP near the I-N transition signals the growth of pseudonematic domains. Surprisingly, such a second peak is instead observed in the translational NGP for the glassy binary mixture. Localization of orientational motion near the I-N transition is found to be responsible for the observed anomalous orientational relaxation. PMID:15903399

  4. Manufacturing of glassy thin shell for adaptive optics: results achieved

    NASA Astrophysics Data System (ADS)

    Poutriquet, F.; Rinchet, A.; Carel, J.-L.; Leplan, H.; Ruch, E.; Geyl, R.; Marque, G.

    2012-07-01

    Glassy thin shells are key components for the development of adaptive optics and are part of future & innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects: E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

  5. Determination of Fracture Patterns in Glass and Glassy Polymers.

    PubMed

    Baca, Allison C; Thornton, John I; Tulleners, Frederic A

    2016-01-01

    The study of fractures of glass, glassy-type materials, and plastic has long been of interest to the forensic community. The focus of this interest has been the use of glass and polymer fractures to associate items of evidence under the assumption that each fracture is different. Generally, it is well-accepted that deviations exist; however, the emphasis has been on classifying and predicting fracture rather than determining that each fracture is different. This study documented the controlled fracture patterns of 60 glass panes, 60 glass bottles, and 60 plastic tail light lens covers using both dynamic impact and static pressure methods under closely controlled conditions. Each pattern was intercompared, and based on the limited specimens tested in this study, the results illustrate that the fracture patterns are different. Further repetitive studies, under controlled conditions, will be needed to provide more statistical significance to the theory that each fracture forms a nonreproducible fracture pattern. PMID:26524485

  6. Evidence for a glassy state in strongly driven carbon

    DOE PAGESBeta

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; et al

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen closemore » to their original positions in the fluid.« less

  7. Evidence for a glassy state in strongly driven carbon

    PubMed Central

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K.-U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. PMID:24909903

  8. Electroanalytical study of nifedipine using activated glassy carbon electrode.

    PubMed

    Sentürk, Z; Ozkan, S A; Ozkan, Y

    1998-01-01

    The electrochemical properties of nifedipine have been investigated in aqueous solution by linear sweep and cyclic voltammetry. The method is based both on the reduction and on the oxidation of the drug at a glassy carbon electrode activated by applying a new pre-treatment. The voltammograms of nifedipine on pH, concentration and scan rate have been carefully examined. Both the electroreduction and electrooxidation of nifedipine allow its determination at pH 1.5 in the concentration range of 2 x 10(-5)-6 x 10(-4) M and 8 x 10(-5)-1 x 10(-3) M, respectively. The method has been applied to commercial samples (tablets and capsules).

  9. Point-to-set lengths, local structure, and glassiness

    NASA Astrophysics Data System (ADS)

    Yaida, Sho; Berthier, Ludovic; Charbonneau, Patrick; Tarjus, Gilles

    2016-09-01

    The growing sluggishness of glass-forming liquids is thought to be accompanied by growing structural order. The nature of such order, however, remains hotly debated. A decade ago, point-to-set (PTS) correlation lengths were proposed as measures of amorphous order in glass formers, but recent results raise doubts as to their generality. Here, we extend the definition of PTS correlations to agnostically capture any type of growing order in liquids, be it local or amorphous. This advance enables the formulation of a clear distinction between slowing down due to conventional critical ordering and that due to glassiness, and provides a unified framework to assess the relative importance of specific local order and generic amorphous order in glass formation.

  10. Evidence for a glassy state in strongly driven carbon.

    PubMed

    Brown, C R D; Gericke, D O; Cammarata, M; Cho, B I; Döppner, T; Engelhorn, K; Förster, E; Fortmann, C; Fritz, D; Galtier, E; Glenzer, S H; Harmand, M; Heimann, P; Kugland, N L; Lamb, D Q; Lee, H J; Lee, R W; Lemke, H; Makita, M; Moinard, A; Murphy, C D; Nagler, B; Neumayer, P; Plagemann, K-U; Redmer, R; Riley, D; Rosmej, F B; Sperling, P; Toleikis, S; Vinko, S M; Vorberger, J; White, S; White, T G; Wünsch, K; Zastrau, U; Zhu, D; Tschentscher, T; Gregori, G

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. PMID:24909903

  11. Poly(4-vinylpyridine)-coated glassy carbon flow detectors

    SciTech Connect

    Wang, J.; Golden, T.; Tuzhi, P.

    1987-03-01

    The performance of a thin-layer flow detector with a glassy carbon electrode coated with a film of protonated poly(4-vinylpyridine) is described. Substantial improvement in the selectivity of amperometric detection for liquid chromatography and flow injection systems is observed as a result of excluding cationic species from the surface. The detector response was evaluated with respect to flow rate, solute concentration, coating scheme, film-to-film reproducibility, and other variables. Despite the increase in diffusional resistance, low detection limits of ca. 0.04 and 0.10 ng of ascorbic acid and uric acid, respectively, are maintained. Protection from organic surfactants can be coupled to the charge exclusion effect by using a bilayer coating, with a cellulose acetate film atop the poly(4-vinylpyridine) layer. Applicability to urine sample is demonstrated.

  12. Electroanalysis of trimethoprim on metalloporphyrin incorporated glassy carbon electrode.

    PubMed

    Rajith, Leena; Kumar, Krishnapillai Girish

    2010-09-01

    Trimethoprim (TMP) is a bacteriostatic antibiotic mainly used in the prophylaxis and treatment of urinary tract infections. It belongs to the class of chemotherapeutic agents known as dihydrofolate reductase inhibitors. Its use is associated with idiosyncratic reactions, including liver toxicity and agranulocytosis. In order to determine TMP electrochemically, a metalloporphyrin modified glassy carbon electrode was prepared by coating [5,10,15,20- tetrakis(4-methoxyphenyl) porphyrinato]Mn (III)chloride (TMOPPMn(III)Cl) solution on the surface of the electrode. The electrochemical behaviour of TMP in Phosphate buffer solution (PBS) on TMOPPMn(III)Cl modified glassy carbon electrode (TMOPPMn(III)Cl/GCE) was explored using differential pulse voltammetry (DPV). The voltammograms showed enhanced oxidation response at the TMOPPMn (III)Cl/GCE with respect to the bare GCE for TMP, attributable to the electrocatalytic activity of TMOPPMn(III)Cl. Electrochemical parameters of the oxidation of TMP on the modified electrode were analyzed. The electro-oxidation of TMP was found to be irreversible, pH dependent and adsorption controlled on the modified electrode. It is found that the oxidation peak current is proportional to the concentration of TMP over the range 6 × 10⁻⁸ - 1 × 10⁻⁶ M with a very low detection limit of 3 × 10⁻⁹ M at 2 min open circuit accumulation. The repeatability expressed as relative standard deviation (RSD) for n = 9 was 3.2% and the operational stability was found to be 20 days. Another striking feature is that equimolar concentration of sulfamethoxazole did not interfere in the determination of TMP. Applicability to assay the drug in urine and tablet samples has also been studied.

  13. Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

    2015-02-01

    Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL).

  14. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1963-02-26

    A brazing alloy which, in the molten state, is characterized by excellent wettability and flowability, said alloy being capable of forming a corrosion resistant brazed joint wherein at least one component of said joint is graphite and the other component is a corrosion resistant refractory metal, said alloy consisting essentially of 20 to 50 per cent by weight of gold, 20 to 50 per cent by weight of nickel, and 15 to 45 per cent by weight of molybdenum. (AEC)

  15. VANADIUM ALLOYS

    DOEpatents

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  16. URANIUM ALLOYS

    DOEpatents

    Seybolt, A.U.

    1958-04-15

    Uranium alloys containing from 0.1 to 10% by weight, but preferably at least 5%, of either zirconium, niobium, or molybdenum exhibit highly desirable nuclear and structural properties which may be improved by heating the alloy to about 900 d C for an extended period of time and then rapidly quenching it.

  17. ZIRCONIUM ALLOY

    DOEpatents

    Wilhelm, H.A.; Ames, D.P.

    1959-02-01

    A binary zirconiuin--antimony alloy is presented which is corrosion resistant and hard containing from 0.07% to 1.6% by weight of Sb. The alloys have good corrosion resistance and are useful in building equipment for the chemical industry.

  18. Nonswelling alloy

    DOEpatents

    Harkness, S.D.

    1975-12-23

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

  19. Surface micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-09-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. This makes it also a suitable candidate as mold material for precision compression molding of low and high glass-transition temperature materials. To fabricate molds for diffractive optics a highresolution structuring technique is needed. We introduce a process that allows the micro-structuring of glassy carbon by reactive ion etching. Key parameters such as uniformity, surface roughness, edge definition and lateral resolution are discussed. They are the most relevant parameters for a stamp in optical applications. The use of titanium as a hard mask makes it possible to achieve a reasonable selectivity of 4:1, which has so far been one of the main problems in microstructuring of glassy carbon. We investigate the titanium surface structure with its 5-10 nm thick layer of TiO2 grains and its influence on the shape of the hard mask. In our fabrication procedure we were able to realize optically flat diffractive structures with slope angles of more than 80° at typical feature sizes of 5 μm and at 700 nm depth. The fabricated glassy carbon molds were applied to thermal imprinting onto different glasses. Glassy carbon molds with 1 mm thickness were tested with binary optical structures. Our experiments show the suitability of glassy carbon as molds for cost efficient mass production with a high quality.

  20. Terbium induced glassy magnetism in La,Ca-based cobaltites

    SciTech Connect

    Maryško, M. Hejtmánek, J.; Jirák, Z.; Kaman, O.; Knížek, K.

    2014-05-07

    The La{sub 0.8–x}Tb{sub x}Ca{sub 0.2}CoO{sub 3} cobaltites of orthoperovskite Pbnm structure were investigated by the X-ray and neutron diffraction, specific heat, and magnetization measurements. The terbium doping has two important effects, it increases the size disorder on perovskite A-sites and influences the magnetic properties due to large Ising-type moments (∼8.9 Bohr magnetons per Tb). The compounds show a bulk magnetic moment below T{sub C} = 82 K, 53 K, and 30 K for x = 0.1, 0.2, and 0.3, respectively. The neutron diffraction evidences a long-range ferromagnetic arrangement of cobalt moments, combined below ∼20 K with ordering of terbium moments in a canted arrangement. A homogeneous magnetic phase is proved for the x = 0.1 sample, while x = 0.2 and 0.3 are in an intrinsically non-homogeneous magnetic state with long-range ordering only comprising 55% and 30% of the sample volumes. The ac susceptibility experiments prove a glassy character of the terbium doped samples and provide arguments for the short-range ordering above T{sub C} and wide distribution of relaxation times.

  1. Mechanics of particulate composites with glassy polymer binders in compression

    PubMed Central

    Jordan, J. L.; Spowart, J. E.; Kendall, M. J.; Woodworth, B.; Siviour, C. R.

    2014-01-01

    Whether used as structural components in design or matrix materials for composites, the mechanical properties of polymers are increasingly important. The compressive response of extruded polymethyl methacrylate (PMMA) rod with aligned polymer chains and Al–Ni–PMMA particulate composites are investigated across a range of strain rates and temperatures. The particulate composites were prepared using an injection-moulding technique resulting in highly anisotropic microstructures. The mechanics of these materials are discussed in the light of theories of deformation for glassy polymers. The experimental data from this study are compared with PMMA results from the literature as well as epoxy-based composites with identical particulates. The PMMA exhibited the expected strain rate and temperature dependence and brittle failure was observed at the highest strain rates and lowest temperatures. The Al–Ni–PMMA composites were found to have similar stress–strain response to the PMMA with reduced strain softening after yield. Increasing volume fraction of particulates in the composite resulted in decreased strength. PMID:24711495

  2. Glassy state and cryopreservation of mint shoot tips.

    PubMed

    Teixeira, Aline S; González-Benito, M Elena; Molina-García, Antonio D

    2013-01-01

    Vitrification refers to the physical process by which a liquid supercools to very low temperatures and finally solidifies into a metastable glass, without undergoing crystallization at a practical cooling rate. Thus, vitrification is an effective freeze-avoidance mechanism and living tissue cryopreservation is, in most cases, relying on it. As a glass is exceedingly viscous and stops all chemical reactions that require molecular diffusion, its formation leads to metabolic inactivity and stability over time. To investigate glassy state in cryopreserved plant material, mint shoot tips were submitted to the different stages of a frequently used cryopreservation protocol (droplet-vitrification) and evaluated for water content reduction and sucrose content, as determined by ion chromatography, frozen water fraction and glass transitions occurrence by differential scanning calorimetry, and investigated by low-temperature scanning electron microscopy, as a way to ascertain if their cellular content was vitrified. Results show how tissues at intermediate treatment steps develop ice crystals during liquid nitrogen cooling, while specimens whose treatment was completed become vitrified, with no evidence of ice formation. The agreement between calorimetric and microscopic observations was perfect. Besides finding a higher sucrose concentration in tissues at the more advanced protocol steps, this level was also higher in plants precultured at 25/-1°C than in plants cultivated at 25°C.

  3. Dielectric studies of molecular motions in glassy and liquid nicotine

    NASA Astrophysics Data System (ADS)

    Kaminski, K.; Paluch, M.; Ziolo, J.; Ngai, K. L.

    2006-06-01

    The dielectric permittivity and loss spectra of glassy and liquid states of nicotine have been measured over the frequency range 10-2-109 Hz. The relaxation spectra are similar to common small molecular glass-forming substances, showing the structural α-relaxation and its precursor, the Johari-Goldstein β-relaxation. The α-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 α-relaxation time measured over 11 orders of magnitude cannot be described by a single Vogel-Fulcher-Tamman-Hesse equation. The most probable Johari-Goldstein β-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 α-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.

  4. Glassy cell carcinoma of the cervix: a literature review.

    PubMed

    Zolciak-Siwinska, A; Jonska-Gmyrek, J

    2014-08-01

    Glassy cell carcinoma (GCC) is a histologically aggressive subtype of cervical cancer with rapid growth and early metastases. The prognosis for patients with GCC is poor. This article reviews the literature pertinent to the epidemiology, cytology, pathology, immunohistochemistry, treatment and prognosis of GCC. MEDLINE (PubMed) was searched for all articles or abstracts on patients diagnosed with GCC published (in English) since the original definition by Glucksmann and Cherry, Cancer 1956;9:971. Accurate diagnosis of GCC enables implementation of the correct treatment strategy. Early-stage GCC should be treated with hysterectomy and pelvic lymph node dissection, with adjuvant radiochemotherapy if at least one intermediate or high risk factor for cervical cancer is present. Advanced GCC should be treated with neoadjuvant radiochemotherapy or chemotherapy with the aim of making the disease operable. There is a need for retrospective evaluation of GCC treatment from several centres to explore knowledge about this rare entity. Future studies should explore the role of targeted therapies and the most efficient chemotherapy regimen for the management of GCC.

  5. Mathematical modeling of glassy-winged sharpshooter population.

    PubMed

    Yoon, Jeong-Mi; Hrynkiv, Volodymyr; Morano, Lisa; Nguyen, Anh Tuan; Wilder, Sara; Mitchell, Forrest

    2014-06-01

    Pierce's disease (PD) is a fatal disease of grapevines which results from an infection by the plant pathogen Xyllela fastidiosa. This bacterium grows in the xylem (water-conducting) vessels of the plant blocking movement of water. PD can kill vines in one year and poses a serious threat to both the California and the expanding Texas wine industries. Bacteria are vectored from one vine to the next by a number of xylem feeding insect species. Of these, the Glassy-winged Sharpshooter (GWSS) is considered to be the primary xylem feeding insect in Texas vineyards. An extensive database of the xylem-feeding population frequencies was collected by USDA-APHIS for Texas vineyards over multiple years. This project focused on a subset of data, GWSS frequencies within 25 vineyards in Edwards Plateau located in central Texas. The proposed model investigates the natural population dynamics and the decline in GWSS, likely the result of pest management campaigns on the insects within the region. The model is a delay Gompertz differential equation with harvesting and immigration terms, and we use the data to estimate the model parameters.

  6. Mathematical modeling of glassy-winged sharpshooter population.

    PubMed

    Yoon, Jeong-Mi; Hrynkiv, Volodymyr; Morano, Lisa; Nguyen, Anh Tuan; Wilder, Sara; Mitchell, Forrest

    2014-06-01

    Pierce's disease (PD) is a fatal disease of grapevines which results from an infection by the plant pathogen Xyllela fastidiosa. This bacterium grows in the xylem (water-conducting) vessels of the plant blocking movement of water. PD can kill vines in one year and poses a serious threat to both the California and the expanding Texas wine industries. Bacteria are vectored from one vine to the next by a number of xylem feeding insect species. Of these, the Glassy-winged Sharpshooter (GWSS) is considered to be the primary xylem feeding insect in Texas vineyards. An extensive database of the xylem-feeding population frequencies was collected by USDA-APHIS for Texas vineyards over multiple years. This project focused on a subset of data, GWSS frequencies within 25 vineyards in Edwards Plateau located in central Texas. The proposed model investigates the natural population dynamics and the decline in GWSS, likely the result of pest management campaigns on the insects within the region. The model is a delay Gompertz differential equation with harvesting and immigration terms, and we use the data to estimate the model parameters. PMID:24506556

  7. Structural origin of low temperature glassy relaxation in magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, Suvra; Regmi, Rajesh; Lawes, Gavin

    2013-03-01

    Magnetic nanoparticles often exhibit glass-like relaxation features at low temperatures. Here we discuss the effects of doping boron, cobalt, gadolinium and lanthanum on the low temperature magnetic properties of Fe3O4 nanoparticles. We investigated the structure of the nanoparticles using both X-ray diffraction and Raman studies, and find evidence for secondary phase formation in certain samples. We acquired Transmission Electron Microscopic images to give direct information on the morphology and microstructure of these doped nanoparticles. We measured the ac out-of-phase susceptibility (χ//) vs temperature (T) to parameterize the low temperature glassy magnetic relaxation. All samples show low temperature magnetic relaxation, but the amplitude of the signal increases dramatically for certain dopants. We attribute these low temperature frequency-dependent magnetic relaxation features to structural defects, which are enhanced in some of the doped Fe3O4 nanoparticles. These studies also confirm that the low temperature relaxation in nanoparticles arises from single particle effects and are not associated with interparticle interactions.

  8. Surface temperatures and glassy state investigations in tribology, part 1

    NASA Technical Reports Server (NTRS)

    Winer, W. O.; Sanborn, D. M.

    1978-01-01

    The research in this report is divided into two categories: (1) lubricant rheological behavior, and (2) thermal behavior of a simulated elastohydrodynamic contact. The studies of the lubricant rheological behavior consists of high pressure, low shear rate viscosity measurements, viscoelastic transition measurements, by volume dilatometry, dielectric transitions at atmospheric pressure and light scattering transitions. Lubricant shear stress-strain behavior in the amorphous glassy state was measured on several fluids. It appears clear from these investigations that many lubricants undergo viscoplastic transitions in typical EHD contacts and that the lubricant has a limiting maximum shear stress it can support which in turn will determine the traction in the contact except in cases of very low slide-roll ratio. Surface temperature measurements were made for a naphthenic mineral oil and a polyphenyl ether. The maximum surface temperature in these experiments was approximately symmetrical about the zero slide-roll ration except for absolute values of slide-roll ratio greater than about 0.9. Additional surface temperature measurements were made in contacts with rough surfaces where the composite surface roughness was approximately equal to the EHD film thickness. A regression analysis was done to obtain a predictive equation for surface temperatures as a function of pressure, sliding speed, and surface roughness. A correction factor for surface roughness effects to the typical flash temperature analysis was found.

  9. PLUTONIUM ALLOYS

    DOEpatents

    Chynoweth, W.

    1959-06-16

    The preparation of low-melting-point plutonium alloys is described. In a MgO crucible Pu is placed on top of the lighter alloying metal (Fe, Co, or Ni) and the temperature raised to 1000 or 1200 deg C. Upon cooling, the alloy slug is broke out of the crucible. With 14 at. % Ni the m.p. is 465 deg C; with 9.5 at. % Fe the m.p. is 410 deg C; and with 12.0 at. % Co the m.p. is 405 deg C. (T.R.H.) l6262 l6263 ((((((((Abstract unscannable))))))))

  10. Development of the glassy state of benzophenone and effect of heating rate from the glassy state on solidification

    SciTech Connect

    Thoma, P.E.; Boehm, J.J.

    1997-12-31

    Benzophenone supercools to a glass when cooled to {minus}100 C. In fact, it is difficult to freeze benzophenone on cooling. In this investigation, the effect of cooling rate and the minimum cooling rate to obtain benzophenone as a glass is determined. From the glassy state, the influence of heating rate on the solidification temperature of benzophenone is determined. When heated at 3 C/min., solidification starts at about {minus}29 C. Upon additional heating, melting usually starts at about +24 C, which is 23 C lower than the solid equilibrium structure melting temperature of 47 C. Occasionally the solid that forms at about {minus}29 C undergoes a solid state phase transformation at about +22 C, when heated at 3 C/min. If this solid state phase transformation occurs, then the solid benzophenone starts to melt at 47 C. When solid benzophenone with the equilibrium structure is cooled to {minus}100 C, no solid state phase transformation occurs. It appears that the structure that solidified at {minus}29 C is metastable.

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

    PubMed Central

    Pedano, M. L.; Rivas, G. A.

    2005-01-01

    In this work we present a critical study of the nucleic acid layer immobilized at glassy carbon electrodes. Different studies were performed in order to assess the nature of the interaction between DNA and the electrode surface. The adsorption and electrooxidation of DNA demonstrated to be highly dependent on the surface and nature of the glassy carbon electrode. The DNA layer immobilized at a freshly polished glassy carbon electrode was very stable even after applying highly negative potentials. The electron transfer of potassium ferricyanide, catechol and dopamine at glassy carbon surfaces modified with thin (obtained by adsorption under controlled potential conditions) and thick (obtained by casting the glassy carbon surface with highly concentrated DNA solutions) DNA layers was slower than that at the bare glassy carbon electrode, although this effect was dependent on the thickness of the layer and was not charge selective. Raman experiments showed 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 of oligo(dG)21 and oligo(dC)21 was evaluated from the guanine oxidation signal and the reduction of the redox indicator Co(phen)33+. In both cases the chronopotentiometric response indicated that the compromise of the bases in the interaction of DNA with the electrode surface is too strong, preventing further hybridization. In summary, glassy carbon is a useful electrode material to detect DNA in a direct and very sensitive way, but not to be used for the preparation of biorecognition layers by direct adsorption of the probe sequence on the electrode surface for detecting the hybridization event.

  12. How important are glassy SOA ice nuclei for the formation of cirrus clouds?

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Penner, J. E.; Lin, G.; Liu, X.; Wang, M.

    2014-12-01

    Extremely low ice numbers (i.e. 5 - 100 / L) have been observed in the tropical troposphere layer (TTL) in a variety of field campaigns. Various mechanisms have been proposed to explain these low numbers, including the effect of glassy secondary organic aerosol acting as heterogeneous ice nuclei (IN). In this study, we explored these effects using the CAM5.3 model. SOA fields were provided by an offline version of the University of Michigan-IMPACT model, which has a detailed process-based mechanism that describes aerosol microphysics and SOA formation through both gas phase and multiphase reactions. The transition criterion of SOA to glassy heterogeneous IN follows the parameterization developed by Wang et al. 2012. With this parameterization, glassy SOA IN form mainly when the temperature (T) is lower than 210K. In the default CAM5.3 set-up in which only the fraction of Aitken mode sulfate aerosols with diameter larger than 100nm participate in the ice nucleation (Liu and Penner 2005 parameterization), glassy SOA IN are shown to decrease the ice number (Ni) by suppressing some of the homogeneous freezing at low temperatures thereby leading to an improved representation of the relationship between Ni and T compared to the observations summarized by Kramer et al. 2009. However, when we allow the total number of the Aitken mode sulfate particles to participate in homogeneous freezing, glassy SOA IN have only a small impact on the relationship between Ni and T. If the subgrid updraft velocity is decreased to 0.1 m/s (compared to 0.2 m/s in the default set-up), there is a large decrease of Ni, since homogeneous freezing is more easily suppressed by glassy SOA IN at these updrafts. We also present the effects of glassy SOA IN using an alternative ice nucleation scheme (Barahona and Nenes, 2009).

  13. How fast is water uptake on glassy and amorphous aerosol?

    NASA Astrophysics Data System (ADS)

    Bones, D. L.; Lienhard, D. M.; Krieger, U.; Reid, J. P.

    2011-12-01

    Atmospheric aerosol particles are typically complex mixtures of organic and inorganic species with correspondingly complex behaviour in their response to changes in humidity. Indeed, it has been recently recognised that many aerosols exist as highly viscous solutions or as amorphous glasses, rather than a crystalline state, over a wide range of relative humidities (Virtanen, et al. 2010). In this work, we investigate the formation of glassy or highly viscous phases in aqueous sugar aerosols such as sucrose and levoglucosan and aerosols of mixtures of sugars and inorganic compounds, reporting the timescale for the mass transfer of water between the particle and the gas phase with variation in water activity. Optical tweezers are used to trap single aerosol particles and examine the time-dependent response in their size to stepwise changes in RH, which result in the evaporation or condensation of water. The evolving particle size and homogeneity in composition are estimated from the wavelengths of specific resonance modes of the cavity enhanced Raman scattering spectra, deducing size changes with an accuracy of better than 1 nm. The experimental data is compared with a kinetic model of diffusional limited size change (Zobrist, et al. 2011), in which the diffusion of water within the particle bulk limits the rate of water transport between the gas and condensed phases. We report measurements in which ternary mixtures, with varying mole ratios of sucrose and sodium chloride, have allowed us to examine the water transport and response time in particle size over a wide range of bulk viscosities. Changes in size are dramatically hindered at low RH, with time scales approaching 10000s, for both increasing and decreasing RH regimes (Tong, et al. 2011). We also observe a marked relative shift in resonance modes, suggesting initial formation of a layer of water on the surface of the glassy particle and subsequent establishment of a steep concentration gradient within the

  14. Charge transport and glassy dynamics in ionic liquids.

    PubMed

    Sangoro, Joshua R; Kremer, Friedrich

    2012-04-17

    Ionic liquids (ILs) exhibit unique features such as low melting points, low vapor pressures, wide liquidus temperature ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. As a result, they show promise for use in variety of applications: as reaction media, in batteries and supercapacitors, in solar and fuel cells, for electrochemical deposition of metals and semiconductors, for protein extraction and crystallization, and many others. Because of the ease with which they can be supercooled, ionic liquids offer new opportunities to investigate long-standing questions regarding the nature of the dynamic glass transition and its possible link to charge transport. Despite the significant steps achieved from experimental and theoretical studies, no generally accepted quantitative theory of dynamic glass transition to date has been capable of reproducing all the experimentally observed features. In this Account, we discuss recent studies of the interplay between charge transport and glassy dynamics in ionic liquids as investigated by a combination of several experimental techniques including broadband dielectric spectroscopy, pulsed field gradient nuclear magnetic resonance, dynamic mechanical spectroscopy, and differential scanning calorimetry. Based on Einstein-Smoluchowski relations, we use dielectric spectra of ionic liquids to determine diffusion coefficients in quantitative agreement with independent pulsed field gradient nuclear magnetic resonance measurements, but spanning a broader range of more than 10 orders of magnitude. This approach provides a novel opportunity to determine the electrical mobility and effective number density of charge carriers as well as their types of thermal activation from the measured dc conductivity separately. We also unravel the origin of the remarkable universality of charge transport in different classes of glass-forming ionic liquids.

  15. Charge Transport and Glassy Dynamics in Ionic Liquids

    SciTech Connect

    Sangoro, Joshua R; Kremer, Friedrich

    2012-01-01

    Ionic liquids (ILs) exhibit unique features such as low melting points, low vapor pressures, wide liquidus temperature ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. As a result, they show promise for use in variety of applications: as reaction media, in batteries and supercapacitors, in solar and fuel cells, for electrochemical deposition of metals and semiconductors, for protein extraction and crystallization, and many others. Because of the ease with which they can be supercooled, ionic liquids offer new opportunities to investigate long-standing questions regarding the nature of the dynamic glass transition and its possible link to charge transport. Despite the significant steps achieved from experimental and theoretical studies, no generally accepted quantitative theory of dynamic glass transition to date has been capable of reproducing all the experimentally observed features. In this Account, we discuss recent studies of the interplay between charge transport and glassy dynamics in ionic liquids as investigated by a combination of several experimental techniques including broadband dielectric spectroscopy, pulsed field gradient nuclear magnetic resonance, dynamic mechanical spectroscopy, and differential scanning calorimetry. Based on EinsteinSmoluchowski relations, we use dielectric spectra of ionic liquids to determine diffusion coefficients in quantitative agreement with independent pulsed field gradient nuclear magnetic resonance measurements, but spanning a broader range of more than 10 orders of magnitude. This approach provides a novel opportunity to determine the electrical mobility and effective number density of charge carriers as well as their types of thermal activation from the measured dc conductivity separately. We also unravel the origin of the remarkable universality of charge transport in different classes of glass-forming ionic liquids.

  16. Modeling mechanophore activation within a crosslinked glassy matrix

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Min, Kyoungmin; Cremar, Lee D.; Degen, Cassandra M.; Martinez, Todd J.; Aluru, Narayana R.; White, Scott R.; Sottos, Nancy R.

    2013-07-01

    Mechanically induced reactivity is a promising means for designing self-reporting materials. Mechanically sensitive chemical groups called mechanophores are covalently linked into polymers in order to trigger specific chemical reactions upon mechanical loading. These mechanophores can be linked either within the backbone or as crosslinks between backbone segments. Mechanophore response is sensitive to both the matrix properties and placement within the matrix, providing two avenues for material design. A model framework is developed to describe reactivity of mechanophores located as crosslinks in a glassy polymer matrix. Simulations are conducted at the molecular and macromolecular scales in order to develop macroscale constitutive relations. The model is developed specifically for the case of spiropyran (SP) in lightly crosslinked polymethylmethacrylate (PMMA). This optically trackable mechanophore (fluorescent when activated) allows the model to be assessed in terms of observed experimental behavior. The force modified potential energy surface (FMPES) framework is used in conjunction with ab initio steered molecular dynamics (MD) simulations of SP to determine the mechanophore kinetics. MD simulations of the crosslinked PMMA structure under shear deformation are used to determine the relationship between macroscale stress and local force on the crosslinks. A continuum model implemented in a finite element framework synthesizes these mechanochemical relations with the mechanical behavior. The continuum model with parameters taken directly from the FMPES and MD analyses under predicts stress-driven activation relative to experimental data. The continuum model, with the physically motivated modification of force fluctuations, provides an accurate prediction for monotonic loading across three decades of strain rate and creep loading, suggesting that the fundamental physics are captured.

  17. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1962-02-20

    A brazing alloy is described which, in the molten state, is characterized by excellent wettability and flowability and is capable of forming a corrosion-resistant brazed joint. At least one component of said joint is graphite and the other component is a corrosion-resistant refractory metal. The brazing alloy consists essentially of 40 to 90 wt % of gold, 5 to 35 wt% of nickel, and 1 to 45 wt% of tantalum. (AEC)

  18. Nanophase Nickel-Zirconium Alloys for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Whitacre, jay; Valdez, Thomas

    2008-01-01

    Nanophase nickel-zirconium alloys have been investigated for use as electrically conductive coatings and catalyst supports in fuel cells. Heretofore, noble metals have been used because they resist corrosion in the harsh, acidic fuel cell interior environments. However, the high cost of noble metals has prompted a search for less-costly substitutes. Nickel-zirconium alloys belong to a class of base metal alloys formed from transition elements of widely different d-electron configurations. These alloys generally exhibit unique physical, chemical, and metallurgical properties that can include corrosion resistance. Inasmuch as corrosion is accelerated by free-energy differences between bulk material and grain boundaries, it was conjectured that amorphous (glassy) and nanophase forms of these alloys could offer the desired corrosion resistance. For experiments to test the conjecture, thin alloy films containing various proportions of nickel and zirconium were deposited by magnetron and radiofrequency co-sputtering of nickel and zirconium. The results of x-ray diffraction studies of the deposited films suggested that the films had a nanophase and nearly amorphous character.

  19. Processing, Microstructure, and Properties of Multiphase Mo Silicide Alloys

    SciTech Connect

    Heatherly, L.; Liu, C.T.; Schneibel, J.H.

    1998-11-30

    Multiphase Mo silicide alloys containing T2 (Mo{sub 5}SiB{sub 2}), Mo{sub 3}Si and Mo phases where prepared by both melting and casting (M and C) and powder metallurgical (PM) processes. Glassy phases are observed in PM materials but not in M and C materials. Microstructural studies indicate that the primary phase is Mo-rich solid solution in alloys containing {le}(9.4Si+13.8B, at. %) and T2 in alloys with {ge}(9.8Si+14.6B). An eutectic composition is estimated to be close to Mo-9.6Si-14.2B. The mechanical properties of multiphase silicide alloys were determined by hardness, tensile and bending tests at room temperature. The multiphase alloy MSB-18 (Mo-9.4Si-13.8B) possesses a flexure strength distinctly higher than that of MoSi{sub 2} and other Mo{sub 5}Si{sub 3} silicide alloys containing no Mo particles. Also, MSB-18 is tougher than MoSi{sub 2} by a factor of 4.

  20. Universality of the glassy transitions in the two-dimensional ±J Ising model.

    PubMed

    Parisen Toldin, Francesco; Pelissetto, Andrea; Vicari, Ettore

    2010-08-01

    We investigate the zero-temperature glassy transitions in the square-lattice ±J Ising model, with bond distribution P(J{xy})=pδ(J{xy}-J)+(1-p)δ(J{xy}+J) ; p=1 and p=1/2 correspond to the pure Ising model and to the Ising spin glass with symmetric bimodal distribution, respectively. We present finite-temperature Monte Carlo simulations at p=4/5 , which is close to the low-temperature paramagnetic-ferromagnetic transition line located at p≈0.89 , and at p=1/2 . Their comparison provides a strong evidence that the glassy critical behavior that occurs for 1-p{0}glassy and magnetic modes are not coupled at the multicritical zero-temperature point where the paramagnetic-ferromagnetic transition line and the T=0 glassy transition line meet. On the theoretical side we discuss the validity of finite-size scaling in glassy systems with a zero-temperature transition and a discrete Hamiltonian spectrum. Because of a freezing phenomenon which occurs in a finite volume at sufficiently low temperatures, the standard finite-size scaling limit in terms of TL(1/ν) does not exist; the renormalization-group invariant quantity ξ/L should be used instead as basic variable.

  1. Amorphous phase formation in mechanically alloyed iron-based systems

    NASA Astrophysics Data System (ADS)

    Sharma, Satyajeet

    Bulk metallic glasses have interesting combination of physical, chemical, mechanical, and magnetic properties which make them attractive for a variety of applications. Consequently there has been a lot of interest in understanding the structure and properties of these materials. More varied applications can be sought if one understands the reasons for glass formation and the methods to control them. The glass-forming ability (GFA) of alloys can be substantially increased by a proper selection of alloying elements and the chemical composition of the alloy. High GFA will enable in obtaining large section thickness of amorphous alloys. Ability to produce glassy alloys in larger section thicknesses enables exploitation of these advanced materials for a variety of different applications. The technique of mechanical alloying (MA) is a powerful non-equilibrium processing technique and is known to produce glassy (or amorphous) alloys in several alloy systems. Metallic amorphous alloys have been produced by MA starting from either blended elemental metal powders or pre-alloyed powders. Subsequently, these amorphous alloy powders could be consolidated to full density in the temperature range between the glass transition and crystallization temperatures, where the amorphous phase has a very low viscosity. This Dissertation focuses on identifying the various Fe-based multicomponent alloy systems that can be amorphized using the MA technique, studying the GFA of alloys with emphasis on improving it, and also on analyzing the effect of extended milling time on the constitution of the amorphous alloy powder produced at earlier times. The Dissertation contains seven chapters, where the lead chapter deals with the background, history and introduction to bulk metallic glasses. The following four chapters are the published/to be published work, where the criterion for predicting glass formation, effect of Niobium addition on glass-forming ability (GFA), lattice contraction on

  2. Temporal disconnectivity of the energy landscape in glassy systems

    NASA Astrophysics Data System (ADS)

    Lempesis, Nikolaos; Boulougouris, Georgios C.; Theodorou, Doros N.

    2013-03-01

    An alternative graphical representation of the potential energy landscape (PEL) has been developed and applied to a binary Lennard-Jones glassy system, providing insight into the unique topology of the system's potential energy hypersurface. With the help of this representation one is able to monitor the different explored basins of the PEL, as well as how - and mainly when - subsets of basins communicate with each other via transitions in such a way that details of the prior temporal history have been erased, i.e., local equilibration between the basins in each subset has been achieved. In this way, apart from detailed information about the structure of the PEL, the system's temporal evolution on the PEL is described. In order to gather all necessary information about the identities of two or more basins that are connected with each other, we consider two different approaches. The first one is based on consideration of the time needed for two basins to mutually equilibrate their populations according to the transition rate between them, in the absence of any effect induced by the rest of the landscape. The second approach is based on an analytical solution of the master equation that explicitly takes into account the entire explored landscape. It is shown that both approaches lead to the same result concerning the topology of the PEL and dynamical evolution on it. Moreover, a "temporal disconnectivity graph" is introduced to represent a lumped system stemming from the initial one. The lumped system is obtained via a specially designed algorithm [N. Lempesis, D. G. Tsalikis, G. C. Boulougouris, and D. N. Theodorou, J. Chem. Phys. 135, 204507 (2011), 10.1063/1.3663207]. The temporal disconnectivity graph provides useful information about both the lumped and the initial systems, including the definition of "metabasins" as collections of basins that communicate with each other via transitions that are fast relative to the observation time. Finally, the two examined

  3. Evidence for the Powdered, Glassy Nature of the Mercurian Surface

    NASA Astrophysics Data System (ADS)

    Cooper, B. L.; Potter, A. E., Jr.; Killen, R. M.; Morgan, T. H.

    1998-09-01

    We have developed a technique to obtain thermal IR spectra of Mercury in the 8-13 micron region in daylight [1]. We observed a smooth spectral curve for Mercury, with the exception of minor features near 9.6 microns and 12.7 microns. There was no evidence of a Christiansen feature down to the 8-micron limit of our spectra. This is in general agreement with Mercury spectra reported by [2], who found Christiansen peaks just at, or slightly below, 8 microns. Features near 9.6 microns are due to incomplete compensation of the ozone absorption band. There appears to be a shallow dip in the spectrum around 12.7 microns. This may represent a transparency peak in emission. Features in the Mercury spectrum have been reported at this wavelength [2], but as a shallow elevation instead of a dip. Most acidic silicates have a feature at around 12.2 microns, whereas mafic minerals (such as hypersthene and olivine) show this feature at longer wavelengths--12.7 to 13.2 microns [3]. The 12.7 micron feature could be evidence for mafic material on the Mercurian surface. However, the lack of a Christiansen feature at 8.5 - 9.0 microns (typical of hypersthene or olivine) makes this doubtful. The smoothness of the spectra suggests that the spectral contrast of the reststrahlen bands from the Mercury surface is below the signal-to-noise level of our data. The spectral contrast of reststrahlen features is greatly reduced in powdered minerals under vacuum, requiring S/N ratios of the order of 1000 to be detected [4]. Glass formation further reduces spectral contrast by disordering the crystal lattice. Consequently, our results imply that the surface of Mercury is covered by a fine powder, which is probably also glassy as a result of intense meteoroid bombardment [5]. References [1] Cooper et al. (1998) EOS, 79, no. 24, W59 [abstract] [2] Sprague and Roush (1998) Icarus, 133, 174. [3] Salisbury et al. (1988) USGS Open-File Report 88-686, Reston, Virginia. [4] Salisbury et al. (1997) Icarus

  4. Effect of entanglements on mechanical properties of glassy polymers

    NASA Astrophysics Data System (ADS)

    Hoy, Robert Scott

    Glass forming polymers are of great industrial importance and scientific interest because of their unique mechanical properties, which arise from the connectivity and random-walk-like structure of the constituent chains. In this thesis I study the relation of entanglements to the mechanical properties of model polymer glasses and brushes using molecular dynamics simulations. We perform extensive studies of glassy strain hardening, which stabilizes polymers against strain localization and fracture. Fundamental inconsistencies in existing entropic models of strain hardening imply that our understanding of its microscopic origins is far from complete. The dependence of stress on strain and entanglement density is consistent with experiment and entropic models. However, many of the assumptions of these models are totally inconsistent with our simulation results. The dependence on temperature, rate and interaction strength can be understood as reflecting changes in the plastic flow stress rather than a network entropy. A substantial energetic contribution to the stress rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic arrangements. The deformation of the entanglement network is not affine to the macroscopic stretch. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain. The entropic back stress responsible for shape recovery arises from chain orientation rather than entanglement. We also present some other results unrelated to strain hardening. We analyze the entanglement of polymer brushes embedded in long-chain melts and in implicit good and theta solvents. The melt-embedded brushes are more self-entangled than those in the solvents. The degree of self-entanglement of the brushes in the solvents follows a simple

  5. Microscopic origin of the non-Gaussian behavior of dynamic structure factors of glassy matter

    NASA Astrophysics Data System (ADS)

    Cabrillo, C.; González, M. A.; Cuello, G. J.; Bermejo, F. J.; Saboungi, M. L.; Price, D. L.

    2004-04-01

    We consider the Lamb-Mössbauer factors corresponding to the structure factors of a material (ethyl alcohol) showing two glassy phases, one of those being an orientationally disordered crystal. The deviations from the idealized Gaussian behavior expected for an isotropic-harmonic vibrator within the amorphous phase and disordered crystal are found to be remarkably close. Such proximity enables us to take advantage of the crystal symmetry to gain access to specific details of the effective interparticle potential. Once this is done the treatment is extended to include the fully amorphous material. The results depict atomic motions within the glassy matrices as significantly anisotropic and highly anharmonic and thus provide a way to understand the microscopic origin of phenomena considered as fingerprints of glassy dynamics.

  6. Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film.

    PubMed

    Kundhikanjana, Worasom; Sheng, Zhigao; Yang, Yongliang; Lai, Keji; Ma, Eric Yue; Cui, Yong-Tao; Kelly, Michael A; Nakamura, Masao; Kawasaki, Masashi; Tokura, Yoshinori; Tang, Qiaochu; Zhang, Kun; Li, Xinxin; Shen, Zhi-Xun

    2015-12-31

    Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time. PMID:26765006

  7. Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Ming Philip; Tsai, Yun-Yen; Lin, Chi-Wen; Shieh, Han-Ping David

    2006-08-01

    A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 °C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 μm pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.

  8. InP synthesis by the synthesis, solute diffusion (SSD) method using glassy-carbon crucibles

    SciTech Connect

    Miskys, C.R.; Oliveira, C.E.M. de; Carvalho, M.M.G. de

    1996-12-31

    An Indium Phosphide (InP) Synthesis system by the Synthesis, Solute Diffusion (SSD) method has been built. It provides high purity InP charges with low carrier densities (3 {times} 10{sup 14} to 2 {times} 10{sup 15} cm{sup {minus}3}) to be used as starting material for InP single-crystal Liquid Encapsulated Czochralski (LEC) growth. Glassy-carbon is a refractory material with low vapor pressure that can be moulded in various forms and sizes. Indeed the glassy-carbon crucible is reusable after the synthesis because InP does not stick to its walls. Preliminary electrical characteristics measurements showed residual carrier concentration below 3 {times} 10{sup 15} cm{sup {minus}3}. These results are comparable with those achieved utilizing quartz crucibles. The features denoted makes glassy-carbon an interesting alternative in comparison with quartz and PBN crucibles.

  9. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    NASA Astrophysics Data System (ADS)

    Kojima, Seiji; Shibata, Tomohiko; Igawa, Hikaru; Mori, Tatsuya

    2014-03-01

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz.

  10. Glassiness and exotic entropy scaling induced by quantum fluctuations in a disorder-free frustrated magnet

    PubMed Central

    Klich, I.; Lee, S.-H.; Iida, K.

    2014-01-01

    When spins are arranged in a lattice of triangular motif, the phenomenon of frustration leads to numerous energetically equivalent ground states, and results in exotic states such as spin liquid and spin ice. Here we report an alternative situation: a system, classically a liquid, freezes in the clean limit into a glassy state induced by quantum fluctuations. We call such glassy state a spin jam. The case in point is a frustrated magnet, where spins are arranged in a triangular network of bipyramids. Quantum corrections break the classical degeneracy into a set of aperiodic spin configurations forming local minima in a rugged energy landscape. This is established by mapping the problem into tiling with hexagonal tiles. The number of tessellations scales with the boundary length rather than its volume, showing the absence of local zero-energy modes. Low-temperature thermodynamics is discussed to compare it with other glassy materials. PMID:24686398

  11. A magnetic glassy phase in Fe(1+y)Se(x)Te(1-x) single crystals.

    PubMed

    Lamura, G; Shiroka, T; Bonfà, P; Sanna, S; Bernardini, F; De Renzi, R; Viennois, R; Giannini, E; Piriou, A; Emery, N; Cimberle, M R; Putti, M

    2013-04-17

    The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content. At the same time all the tested samples manifest a marked glassy character that vanishes for high Se contents. The presence of local electronic/compositional inhomogeneities most likely favours the growth of clusters whose magnetic moment 'freezes' at low temperature. This glassy magnetic phase justifies both the coherent muon precession seen at short times in the asymmetry data, as well as the glassy behaviour evidenced by both dc and ac magnetometry.

  12. Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film

    NASA Astrophysics Data System (ADS)

    Kundhikanjana, Worasom; Sheng, Zhigao; Yang, Yongliang; Lai, Keji; Ma, Eric Yue; Cui, Yong-Tao; Kelly, Michael A.; Nakamura, Masao; Kawasaki, Masashi; Tokura, Yoshinori; Tang, Qiaochu; Zhang, Kun; Li, Xinxin; Shen, Zhi-Xun

    2015-12-01

    Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time.

  13. Self-Induced Glassiness and Pattern Formation in Spin Systems Subject to Long-Range Interactions

    NASA Astrophysics Data System (ADS)

    Principi, Alessandro; Katsnelson, Mikhail I.

    2016-09-01

    We study the glass formation in two- and three-dimensional Ising and Heisenberg spin systems subject to competing interactions and uniaxial anisotropy with a mean-field approach. In three dimensions, for sufficiently strong anisotropy the systems always modulate in a striped phase. Below a critical strength of the anisotropy, a glassy phase exists in a finite range of temperature, and it becomes more stable as the system becomes more isotropic. In two dimensions the criticality is always avoided and the glassy phase always exists.

  14. Electrochemical assembling of methionine-gold nanoparticles and catalysis on the surface of glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Song, Y. Z.; Wang, J. H.; Zhang, X. M.; Cao, W.; Ge, A.; Zhou, L.

    2014-12-01

    In this paper cyclic voltammetry was used for the synthesis of linear array spherical gold nanoparticles on the surface of glassy carbon electrode using methionine as a stable reagent. The methionine-gold nanoparticles on the surface of glassy electrode were obtained. The methionine-gold nanoparticles were characterized by cyclic voltammetry, scanning electron microscopy, energy dispersive spectrometry and powder X-ray diffraction. Electrochemical behavior of methionine at methionine-gold nanoparticle modified electrode was investigated. It was demonstrated that the methionine-gold nanoparticles can catalyze electrochemical transformations of methionine.

  15. A Thermodynamic Theory of Solid Viscoelasticity. Part 3: Nonlinear Glassy Viscoelasticity, Stability Constraints, Specifications

    NASA Technical Reports Server (NTRS)

    Freed, Alan; Leonov, Arkady I.

    2002-01-01

    This paper, the last in the series, continues developing the nonlinear constitutive relations for non-isothermal, compressible, solid viscoelasticity. We initially discuss a single integral approach, more suitable for the glassy state of rubber-like materials, with basic functionals involved in the thermodynamic description for this type of viscoelasticity. Then we switch our attention to analyzing stability constraints, imposed on the general formulation of the nonlinear theory of solid viscoelasticity. Finally, we discuss specific (known from the literature or new) expressions for material functions that are involved in the constitutive formulations of both the rubber-like and glassy-like, complementary parts of the theory.

  16. Elastic properties of aspirin in its crystalline and glassy phases studied by micro-Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Ko, Jae-Hyeon; Lee, Kwang-Sei; Ike, Yuji; Kojima, Seiji

    2008-11-01

    The acoustic waves propagating along the direction perpendicular to the (1 0 0) cleavage plane of aspirin crystal were investigated using micro-Brillouin spectroscopy from which C11, C55 and C66 were obtained. The temperature dependence of the longitudinal acoustic waves could be explained by normal anharmonic lattice models, while the transverse acoustic waves showed an abnormal increase in the hypersonic attenuation at low temperatures indicating their coupling to local remnant dynamics. The sound velocity as well as the attenuation of the longitudinal acoustic waves of glassy aspirin showed a substantial change at ˜235 K confirming a transition from glassy to supercooled liquid state in vitreous aspirin.

  17. Self-organization and the physics of glassy networks

    NASA Astrophysics Data System (ADS)

    Boolchand, P.; Lucovsky, G.; Phillips, J. C.; Thorpe, M. F.

    Network glasses are the physical prototype for many self-organized systems, ranging from proteins to computer science. Conventional theories of gases, liquids and crystals do not account for the strongly material-selective character of the glass-forming tendency, the phase diagrams of glasses or their optimizable properties. A new topological theory, only 25 years old, has succeeded where conventional theories have failed. It shows that (probably all slowly quenched) glasses, including network glasses, are the result of the combined effects of a few simple mechanisms. These glass-forming mechanisms are topological in nature and have already been identified for several important glasses, including chalcogenide alloys, silicates (window glass and computer chips) and proteins.

  18. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Effect of Yttrium Addition on Glass Forming Ability of ZrCuAlSi Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Bac-Qing; Zhang, Xin-Yu; Li, Gong; Sun, Bao-Ru; Fan, Chang-Zeng; Zhan, Zai-Ji; Liu, Ri-Ping; Wang, Wen-Kui

    2009-06-01

    The effect of yttrium addition on glass formation of a ZrCuAlSi alloy is investigated. The maximum diameter 8mm of the glassy rods for (Zr46.3Cu43.3Al8.9Si1.5)100-xYx alloy with x = 2.5 is obtained by copper mould casting. Apparent enhancement of the glass formation ability is found with addition of yttrium, mainly due to the purification of the alloy melt and the suppression of formation of the primary phases by yttrium.

  19. Fabrication of Glassy and Crystalline Ferroelectric Oxide by Containerless Processing

    NASA Astrophysics Data System (ADS)

    Yoda, Shinichi

    1. Instruction Much effort has been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic effects. However, they require a higher cooling rate than glass formed by conventional techniques. Therefore, only amorphous thin-films have been formed, using rapid quenching with a cooling rate >105 K/s. The containerless processing is an attractive synthesis technique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable phase and glassy material. Recently a new ferroelectric materiel, monoclinic BaTi2 O5 , with Currie temperature as 747 K was reported. In this study, we fabricated a bulk BaTi2 O5 glass from melt using containerless processing to study the phase relations and ferroelectric properties of BaTi2 O5 . To our knowledge, this was the first time that a bulk glass of ferroelectric material was fabricated from melt without adding any network-forming oxide. 2. Experiments BaTi2 O5 sphere glass with 2mm diameter was fabricated using containerless processing in an Aerodynamic Levitation Furnace (ALF). The containerless processing allowed the melt to achieve deep undercooling for glass forming. High purity commercial BaTiO3 and TiO2 powders were mixed with a mole ratio of 1:1 and compressed into rods and then sintered at 1427 K for 10 h. Bulk samples with a mass of about 20 mg were cut from the rod, levitated with the ALF, and then melted by a CO2 laser beam. After quenching with a cooling rate of about 1000 K/s, 2 mm diameter sphere glass could be obtained. To analyze the glass structure, a high-energy x-ray diffraction experiment was performed using an incident photon energy of 113.5 keV at the high-energy x-ray diffraction beamline BL04B2 of SPring-8

  20. Glassy-winged sharpshooter can use a mechanical mechanism to inoculate Xylella fastidiosa into grapevines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Xylem-feeding leafhoppers such as the glassy-winged sharpshooter, Homalodisca vitripennis (Cicadellidae: Cicadellinae), are thought to inoculate the bacterium Xylella fastidiosa (Xf) from colonies bound to cuticle of the sharpshooter’s functional foregut (precibarium and cibarium). The mechanism of ...

  1. Glassy-winged sharpshooter oviposition effects on foliar grapevine and red-tipped photinia terpenoid levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is an important vector of Xylella fastidiosa, the bacterium that causes Pierce's disease of grapevine and is a threat to grape production throughout the United States. Female GWSS deposit egg masses be...

  2. Substrate-borne vibrational signals in intraspecific communication of glassy-winged sharpshooters (GWSS)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Exploitation of vibrational signals for suppressing glassy-winged sharpshooter (GWSS) populations could prove to be a useful tool. However, existing knowledge on GWSS vibrational communication is insufficient to implement a management program for this pest in California. Therefore, the objective of ...

  3. Effects of feeding on glassy-winged sharpshooter lipid content and egg production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glassy-winged sharpshooter females emerge without mature eggs, and females must feed to produce mature eggs. As a result, allocation of incoming resources must be balanced between egg production and maintenance of other critical biological functions. Central to this process is allocation of lipids s...

  4. Glassy-winged sharpshooter oviposition effects on photinia volatile chemistry with implications on egg parasitoid effectiveness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An effective way to limit incidence of Pierce’s disease of grapevine is to reduce populations of glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), which transmit the causal bacterium, Xylella fastidiosa. One strategy is to utilize egg parasitoids such as ...

  5. Columbia River Basalt Chemistry, Degassing, and Eruption Dynamics: Insights From Quenched Glassy Lapilli and Tuffs

    NASA Astrophysics Data System (ADS)

    Davis, K.; Wolff, J.; Rowe, M. C.; Neill, O. K.

    2015-12-01

    Primary eruptive vent areas for several lavas in the Imnaha and Grande Ronde Formations of the Columbia River Basalt exhibit phreatomagmatic character, due to the interaction of rising flood basalt magma with groundwater and/or surface water. Vent constructional forms range from extensive (>1 km) maar complexes with abundant basement lithics to small (<<1 km), lithic-poor low-angle cones. Phreatomagmatic tephra is lithified and variably palagonitized, but glassy basaltic lapilli can be recovered from many locations. Many lapilli have experienced variable degrees of Na leaching but preserve magmatic abundances of most other elements; nonetheless in many cases pristine, unmodified glass is amenable to analysis. In addition, phenocrysts in lapilli have fully glassy melt inclusions. Glassy lapilli have highly variable S contents between ~100 and ~1300 ppm. This is consistent with quenching before degassing was complete, a common feature of phreatomagmatic eruptions. Melt inclusions have ≤2900 ppm S, ≤3400 ppm CO2 and ≤2.6 wt% H2O, allowing estimates of atmospheric input from the main phase of Columbia River volcanism. In addition, the lithophile trace element contents, and petrogenetically significant ratios such as Ba/Nb, of glassy lapilli exhibit differ from those in the equivalent 'stony' lava flows by up to a factor of 2. This suggests that processes in the flow and crystallization of lava serve to modify trace element abundances, and may place limits on the petrogenetic significance of trace element data from crystalline lava samples.

  6. THE ROLE OF GLASSY-WINGED SHARPSHOOTER SALIVARY ENZYMES IN INFECTION AND MOVEMENT OF X. FASTIDIOSA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this project is to determine whether a vector’s enzymatic saliva aids the establishment of the few ‘pioneer’ Xylella fastidiosa (Xf) cells that are inoculated into a plant; thus the bacteria would co-localize with the saliva. Previous work showed that watery saliva of glassy-winged ...

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

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-04-01

    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 aerosols that have re-vitrified in contact with the

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

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-09-01

    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-vitrified in contact

  9. Glassy slags for minimum additive waste stabilization. Interim progress report, May 1993--February 1994

    SciTech Connect

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

    1994-05-01

    Glassy slag waste forms are being developed to complement glass waste forms in implementing Minimum Additive Waste Stabilization (MAWS) for supporting DOE`s environmental restoration efforts. The glassy slag waste form is composed of various crystalline and metal oxide phases embedded in a silicate glass phase. The MAWS approach was adopted by blending multiple waste streams to achieve up to 100% waste loadings. The crystalline phases, such as spinels, are very durable and contain hazardous and radioactive elements in their lattice structures. These crystalline phases may account for up to 80% of the total volume of slags having over 80% metal loading. The structural bond strength model was used to quantify the correlation between glassy slag composition and chemical durability so that optimized slag compositions were obtained with limited crucible melting and testing. Slag compositions developed through crucible melts were also successfully generated in a pilot-scale Retech plasma centrifugal furnace at Ukiah, California. Utilization of glassy slag waste forms allows the MAWS approach to be applied to a much wider range of waste streams than glass waste forms. The initial work at ANL has indicated that glassy slags are good final waste forms because of (1) their high chemical durability; (2) their ability to incorporate large amounts of metal oxides; (3) their ability to incorporate waste streams having low contents of flux components; (4) their less stringent requirements on processing parameters, compared to glass waste forms; and (5) their low requirements for purchased additives, which means greater waste volume reduction and treatment cost savings.

  10. Alloy softening in binary molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

  11. Effects of molecular architecture on fluid ingress behavior of glassy polymer networks

    NASA Astrophysics Data System (ADS)

    Jaskson, Matthew Blaine

    This manuscript demonstrates the synthesis of glassy polymer network isomers to control morphological variations and study solvent ingress behavior independent of chemical affinity. Well-controlled network architectures with varying free volume average hole-sizes have been shown to substantially influence solvent ingress within glassy polymer networks. Bisphenol-A diglycidyl ether (DGEBA), bisphenol-F diglycidyl ether (DGEBF), Triglycidyl p-aminophenol (pAP, MY0510), Triglycidyl maminophenol (mAP, MY0610), and tetraglydicyl-4,4'-diamino-diphenyl methane (TGDDM, MY721) were cured with 3,3'- and 4,4'-diaminodiphenyl sulfone (DDS) at a stoichiometric ratio of 1:1 oxirane to amine active hydrogen to generate a series of network architectures with an average free volume hole-size (Vh) ranging between 54-82 A3. Polymer networks were exposed to water and a broad range of organic solvents ranging in van der Waals (vdW) volumes from 18-88 A3 for up to 10,000h time. A clear relationship between glassy polymer network Vh and fluid penetration has been established. As penetrant vdW volume approached Vh, uptake kinetics significantly decreased, and as penetrant vdW volume exceeded Vh, a blocking mechanism dominated ingress and prevented penetrant transport. These results suggest that reducing the free volume hole-size is a reasonable approach to control solvent properties for glassy polymer networks. New techniques to monitor and predict the diffusion behavior of liquids through glassy networks are also presented. Digital Image Correlation (DIC) was employed to accurately measure the strain developed during case II diffusion. This technique also presented a new theory for a relationship between sample topology and irreversible macroscopic brittle failure induced by solvent absorption. A new modeling technique has been developed which can accurately predict the chemical and physical interactions a solvent may have with a glassy network. This new model can be used as a

  12. Host plant effects on development and reproduction of the glassy-winged sharpshooter, Homalodisca vitripennis (Homoptera: Cicadellidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development, survivorship, longevity, reproduction and life table parameters of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar), were examined in the laboratory using three host plants, sunflower (Helianthus annuus L.), Chrysanthemum morifolium L. and euonymus (Euonymus japonica Thu...

  13. Elastic Properties of 4-6 nm-thick Glassy Carbon Thin Films

    NASA Astrophysics Data System (ADS)

    Manoharan, M. P.; Lee, H.; Rajagopalan, R.; Foley, H. C.; Haque, M. A.

    2010-01-01

    Glassy carbon is a disordered, nanoporous form of carbon with superior thermal and chemical stability in extreme environments. Freestanding glassy carbon specimens with 4-6 nm thickness and 0.5 nm average pore size were synthesized and fabricated from polyfurfuryl alcohol precursors. Elastic properties of the specimens were measured in situ inside a scanning electron microscope using a custom-built micro-electro-mechanical system. The Young’s modulus, fracture stress and strain values were measured to be about 62 GPa, 870 MPa and 1.3%, respectively; showing strong size effects compared to a modulus value of 30 GPa at the bulk scale. This size effect is explained on the basis of the increased significance of surface elastic properties at the nanometer length-scale.

  14. Age-dependent modes of extensional necking instability in soft glassy materials.

    PubMed

    Hoyle, David M; Fielding, Suzanne M

    2015-04-17

    We study the instability to necking of an initially cylindrical filament of soft glassy material subject to extensional stretching. By numerical simulation of the soft glassy rheology model and a simplified fluidity model, and by analytical predictions within a highly generic toy description, we show that the mode of instability is set by the age of the sample relative to the inverse of the applied extensional strain rate. Young samples neck gradually via a liquidlike mode, the onset of which is determined by both the elastic loading and plastic relaxation terms in the stress constitutive equation. Older samples fail at smaller draw ratios via a more rapid mode, the onset of which is determined only by the solidlike elastic loading terms (though plastic effects arise later, once appreciable necking develops). We show this solidlike mode to be the counterpart, for elastoplastic materials, of the Considère mode of necking in strain-rate-independent solids. PMID:25933343

  15. Relaxation of enthalpy fluctuations during sub-T(g) annealing of glassy selenium.

    PubMed

    Gulbiten, Ozgur; Mauro, John C; Lucas, Pierre

    2013-06-28

    The relaxation behavior of glass is influenced by the presence of dynamical heterogeneities, which lead to an intrinsically non-monotonic decay of fluctuations in density and enthalpy during isothermal annealing. This is apparently a universal feature of fragile glass forming systems associated with localized spatial variations in relaxation time. Here we present direct experimental observation of the nonmonotonic evolution of enthalpy fluctuations in glassy selenium annealed near room temperature. The nonmonotonic change in the distribution of enthalpy fluctuations measured by heat capacity spectroscopy offers direct evidence for the presence of dynamical heterogeneity in this glass. An enthalpy landscape model of selenium is then used to simulate annealing under identical conditions. The simulation results closely follow the evolution of enthalpy fluctuations observed experimentally. The close match between model and experiment demonstrate that enthalpy and density fluctuations are sources of dynamical heterogeneities in glassy materials.

  16. Mechanical properties of thin glassy polymer films filled with spherical polymer-grafted nanoparticles.

    PubMed

    Maillard, Damien; Kumar, Sanat K; Fragneaud, Benjamin; Kysar, Jeffrey W; Rungta, Atri; Benicewicz, Brian C; Deng, Hua; Brinson, L Cate; Douglas, Jack F

    2012-08-01

    It is commonly accepted that the addition of spherical nanoparticles (NPs) cannot simultaneously improve the elastic modulus, the yield stress, and the ductility of an amorphous glassy polymer matrix. In contrast to this conventional wisdom, we show that ductility can be substantially increased, while maintaining gains in the elastic modulus and yield stress, in glassy nanocomposite films composed of spherical silica NPs grafted with polystyrene (PS) chains in a PS matrix. The key to these improvements are (i) uniform NP spatial dispersion and (ii) strong interfacial binding between NPs and the matrix, by making the grafted chains sufficiently long relative to the matrix. Strikingly, the optimal conditions for the mechanical reinforcement of the same nanocomposite material in the melt state is completely different, requiring the presence of spatially extended NP clusters. Evidently, NP spatial dispersions that optimize material properties are crucially sensitive to the state (melt versus glass) of the polymeric material.

  17. Glassy states and super-relaxation in populations of coupled phase oscillators.

    PubMed

    Iatsenko, D; McClintock, P V E; Stefanovska, A

    2014-01-01

    Large networks of coupled oscillators appear in many branches of science, so that the kinds of phenomena they exhibit are not only of intrinsic interest but also of very wide importance. In 1975, Kuramoto proposed an analytically tractable model to describe these systems, which has since been successfully applied in many contexts and remains a subject of intensive research. Some related problems, however, remain unclarified for decades, such as the existence and properties of the oscillator glass state. Here we present a detailed analysis of a very general form of the Kuramoto model. In particular, we find the conditions when it can exhibit glassy behaviour, which represents a kind of synchronous disorder in the present case. Furthermore, we discover a new and intriguing phenomenon that we refer to as super-relaxation where the oscillators feel no interaction at all while relaxing to incoherence. Our findings offer the possibility of creating glassy states and observing super-relaxation in real systems.

  18. Low substrate temperature deposition of diamond coatings derived from glassy carbon

    DOEpatents

    Holcombe, C.E. Jr.; Seals, R.D.

    1995-09-26

    A process is disclosed for depositing a diamond coating on a substrate at temperatures less than about 550 C. A powder mixture of glassy carbon and diamond particles is passed through a high velocity oxy-flame apparatus whereupon the powders are heated prior to impingement at high velocity against the substrate. The powder mixture contains between 5 and 50 powder volume percent of the diamond particles, and preferably between 5 and 15 powder volume percent. The particles have a size from about 5 to about 100 micrometers, with the diamond particles being about 5 to about 30 micrometers. The flame of the apparatus provides a velocity of about 350 to about 1000 meters per second, with the result that upon impingement upon the substrate, the glassy carbon is phase transformed to diamond as coaxed by the diamond content of the powder mixture. 2 figs.

  19. High-resolution images of Pd particles supported on highly oriented pyrolytic graphite and glassy carbon

    SciTech Connect

    Murakami, Yasushi; Naoi, Katsuo; Yahikozawa, Kiyochika; Takasu, Yoshio . Dept. of Fine Materials Engineering)

    1994-09-01

    Ultrafine metal particles dispersed on supporting materials have been developed as catalysts for the oxidation of automobile exhaust gas, the hydrogenation of carbon monoxide, and electrodes of fuel cells. Both activities and selectivities of these reactions depend on the morphology of the dispersed metal. The morphology of palladium particles supported on both highly oriented pyrolytic graphite (HOPG) and glassy carbon was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The particles on the HOPG were linked with neighboring particles to agglomerate, while the particles on the glassy carbon were circular. AFM data with tapping mode for the palladium particles on HOPG were consistent with the high-resolution SEM image. Although the lateral resolution of the AFM image was lower than that for the high-resolution SEM data, the AFM image clearly indicated the height distribution of the agglomerates.

  20. Low substrate temperature deposition of diamond coatings derived from glassy carbon

    DOEpatents

    Holcombe, Jr., Cressie E.; Seals, Roland D.

    1995-01-01

    A process for depositing a diamond coating on a substrate at temperatures less than about 550.degree. C. A powder mixture of glassy carbon and diamond particles is passed through a high velocity oxy-flame apparatus whereupon the powders are heated prior to impingement at high velocity against the substrate. The powder mixture contains between 5 and 50 powder volume percent of the diamond particles, and preferably between 5 and 15 powder volume percent. The particles have a size from about 5 to about 100 micrometers, with the diamond particles being about 5 to about 30 micrometers. The flame of the apparatus provides a velocity of about 350 to about 1000 meters per second, with the result that upon impingement upon the substrate, the glassy carbon is phase transformed to diamond as coaxed by the diamond content of the powder mixture.

  1. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

    DOE PAGESBeta

    Cheng, Shiwang; Bocharova, Vera; Belianinov, Alex; Xiong, Shaomin; Kisliuk, Alexander; Somnath, Suhas; Holt, Adam P.; Ovchinnikova, Olga S.; Jesse, Stephen; Martin, Halie J.; et al

    2016-05-20

    The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively researched. However, not much is known about the origin of this effect below Tg. In this paper, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the "glassy" Young's modulus in the interfacial polymer layer of PNCs is two-times higher than in the bulk polymer, which results in significant reinforcement below Tg. We ascribe this phenomenon to a high stretchingmore » of the chains within the interfacial layer. Since the interfacial chain packing is essentially temperature independent, these findings provide a new insight into the mechanical reinforcement of PNCs also above Tg.« less

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

    SciTech Connect

    Kim, K.H.

    1995-11-01

    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.

  3. Growth of InP single crystals by liquid encapsulated Czochralski (LEC) using glassy-carbon crucibles

    SciTech Connect

    Oliveira, C.E.M. de; Miskys, C.R.; Carvalho, M.M.G. de

    1996-12-31

    Using a high pressure puller and Glassy-Carbon crucibles, undoped InP single crystals weighing 100g and with 25 mm diameter were grown in the <100> direction. The residual carrier concentration of samples, measure by the Van der Pauw method at 300K, was about 5 {times} 10{sup 15}cm{sup {minus}3}, result as good as those obtained with Quartz crucibles with the advantage that Glassy-Carbon crucibles are fully reusable.

  4. Metal alloy identifier

    DOEpatents

    Riley, William D.; Brown, Jr., Robert D.

    1987-01-01

    To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

  5. Glassy Objects (Microtektites?) from Deep-Sea Sediments near the Ivory Coast.

    PubMed

    Glass, B P

    1968-08-30

    Glassy objects of spherical, oval, dumbbell, teardrop, and irregular shapes have been found in a deep-sea sediment core taken off the Ivory Coast. They occur in a layer of sediment that was apparently deposited about 800,000 years ago. Their geographic location, appearance, and physical properties suggest that they are microtektites and that they are related to the tektite-strewn field of the Ivory Coast.

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

    SciTech Connect

    Minelli, Matteo; Doghieri, Ferruccio

    2014-05-15

    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.

  7. The Influence of Ion Implantation on cell Attachment to Glassy Polymeric Carbon

    SciTech Connect

    Zimmerman, R.; Ila, D.; Gurhan, I.; Ozdal-Kurt, F.; Sen, B. H.; Rodrigues, M.

    2006-11-13

    In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that near surface implantation of silver in Glassy Polymeric Carbon (GPC) can completely inhibit cell attachment on implanted areas while leaving adjacent areas unaffected. Patterned ion implantation permits precise control of tissue growth on medical applications of GPC. We have shown that silver ion implantation or argon ion assisted surface deposition of silver inhibits cell growth on GPC, a desirable improvement of current cardiac implants.

  8. Crystallization of the glassy phase of grain boundaries in silicon nitride

    NASA Technical Reports Server (NTRS)

    Jefferson, D. A.; Thomas, J. M.; Wen, S.

    1984-01-01

    Three types of hot-pressed silicon nitride specimens (containing 5wt% Y2O3 and 2wt% Al2O3 additives) which were subjected to different temperature heat treatments were studied by X-ray diffraction, X-ray microanalysis and high resolution electron microscopy. The results indicated that there were phase changes in the grain boundaries after heat treatment and the glassy phase at the grain boundaries was crystallized by heat treatment.

  9. Highly Selective Membranes For The Separation Of Organic Vapors Using Super-Glassy Polymers

    DOEpatents

    Pinnau, Ingo; Lokhandwala, Kaaeid; Nguyen, Phuong; Segelke, Scott

    1997-11-18

    A process for separating hydrocarbon gases of low boiling point, particularly methane, ethane and ethylene, from nitrogen. The process is performed using a membrane made from a super-glassy material. The gases to be separated are mixed with a condensable gas, such as a C.sub.3+ hydrocarbon. In the presence of the condensable gas, improved selectivity for the low-boiling-point hydrocarbon gas over nitrogen is achieved.

  10. Radiation-induced intermediates in irradiated glassy ionic liquids at low temperature

    NASA Astrophysics Data System (ADS)

    Saenko, Elizaveta V.; Lukianova, Mariia A.; Shiryaeva, Ekaterina S.; Takahashi, Kenji; Feldman, Vladimir I.

    2016-07-01

    The primary radiation-induced processes in irradiated low-temperature pyrrolidinium- and piperidinium-type ionic liquids were investigated by EPR and optical absorption spectroscopy. A narrow singlet signal in the EPR spectra of irradiated ionic liquids was attributed to the physically stabilized electron. Broad absorption band in visible region was ascribed to "hole" species. Aromatic scavengers react with "hole" species in glassy irradiated ionic liquids at 77 K.

  11. A Novel Method for Electroplating Ultra-High-Strength Glassy Metals

    NASA Technical Reports Server (NTRS)

    Ramsey, Brian; Engelhaupt, Darell; Six, N. Frank (Technical Monitor)

    2002-01-01

    A novel method for electroplating ultra-high-strength glassy metals, nickel-phosphorous and nickel-cobalt-phosphorous, has been developed at NASA Marshall Space Flight Center, cooperatively with the University of Alabama in Huntsville. Traditionally, thin coatings of these metals are achieved via electroless deposition. Benefits of the new electrolytic process include thick, low-stress deposits, free standing shapes, lower plating temperature, low maintenance, and safer operation with substantially lower cost.

  12. Glassy Objects (Microtektites?) from Deep-Sea Sediments near the Ivory Coast.

    PubMed

    Glass, B P

    1968-08-30

    Glassy objects of spherical, oval, dumbbell, teardrop, and irregular shapes have been found in a deep-sea sediment core taken off the Ivory Coast. They occur in a layer of sediment that was apparently deposited about 800,000 years ago. Their geographic location, appearance, and physical properties suggest that they are microtektites and that they are related to the tektite-strewn field of the Ivory Coast. PMID:17812117

  13. Effects of Zr and Si on the Glass Forming Ability and Compressive Properties of Ti-Cu-Co-Sn Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Tan; Wu, Yidong; Si, Jiajia; Hui, Xidong

    2015-06-01

    To succeed in finding novel Ti-based bulk metallic glasses, which are free from Be, Ni, and noble metallic elements, a comprehensive study was performed on the effects of Zr and Si on the microstructural evolution, glass-forming ability (GFA), and mechanical properties of Ti46Cu44- x Zr x Co7Sn3 ( x = 0, 5, 10, 12.5, and 16 at. pct) and Ti46Cu31.5Zr12.5- x Co7Sn3Si x ( x = 0.5, 1, and 1.5 at. pct) alloys. It is shown that with the increase of Zr, the sequence of phase formation is β-Ti + α-Ti + (Ti, Zr)3Cu4 ⇒ β-Ti + α-Ti + TiCu ⇒ β-Ti + Ti2Cu + glass ⇒ glass ⇒ β-Ti + Ti2Cu + TiCuSn. The quinary Ti-Zr-Cu-Co-Sn alloy with 12.5 pct Zr exhibits the best GFA. The addition of 1 pct Si results in the improvement of the critical size of glassy rods up to 3 mm in diameter. The yield stress and Young's modulus of Z-series alloys increases, and the plastic strain decreases with the addition of Zr. The yield stress and ultimate compression stress of Ti46Zr11.5Cu31.5Co7Sn3Si1 glassy alloy reach 2477.9 and 2623.3 MPa, respectively. It was found that the addition of Si promotes the generation and multiplication of shear bands, resulting in certain plasticity in these kinds of glassy alloys.

  14. Spectroscopic ellipsometric and Raman spectroscopic investigations of pulsed laser treated glassy carbon surfaces

    NASA Astrophysics Data System (ADS)

    Csontos, J.; Pápa, Z.; Gárdián, A.; Füle, M.; Budai, J.; Toth, Z.

    2015-05-01

    In this study spectroscopic ellipsometry (SE) and Raman spectroscopy are applied to study structural modification of glassy carbon, due to high intensity laser ablation. Two KrF lasers with different pulse durations (480 fs and 18 ns), an ArF (20 ns), and a frequency doubled Nd:YAG laser (8 ns) were applied to irradiate the surface of glassy carbon targets. The main characteristics of the different laser treatments are compared by introducing the volumetric fluence which takes into account the different absorption values at different wavelengths. SE showed the appearance of a modified layer on the ablated surfaces. In the case of the ns lasers the thickness of this layer was in the range of 10-60 nm, while in the case of fs laser it was less than 20 nm. In all cases the average refractive index (n) of the modified layers slightly decreased compared to the refractive index of glassy carbon. Increase in extinction coefficient (k) was observed in the cases of ArF and fs KrF laser treatment, while the k values decreased significantly in the cases of nanosecond pulse duration KrF and Nd:YAG laser treatments. In the Raman spectra of the ablated areas the characteristic D and G peaks were widened due to appearance of an amorphous phase. Both Raman spectroscopy and SE indicate that the irradiated areas show carbon nanoparticle formation in all cases.

  15. Modelling multi-scale deformation of amorphous glassy polymers with experimentally motivated evolution of the microstructure

    NASA Astrophysics Data System (ADS)

    Engqvist, Jonas; Wallin, Mathias; Ristinmaa, Matti; Hall, Stephen A.; Plivelic, Tomás S.

    2016-11-01

    Novel experimental data, obtained recently using advanced multi-scale experiments, have been used to develop a micro-mechanically motivated constitutive model for amorphous glassy polymers. Taking advantage of the experiments, the model makes use of a microstructural deformation gradient to incorporate the experimentally obtained deformation of the microstructure, as well as its evolving orientation. By comparing results from the model to experimental data, it is shown that the proposed approach is able to accurately predict glassy polymer deformation over a wide range of length-scales, from the macroscopic response (mm range) down to the deformation of the microstructure (nm range). The proposed model is evaluated by comparing the numerical response to experimental results on multiple scales from an inhomogeneous cold drawing experiment of glassy polycarbonate. Besides the macroscopic force-displacement response, a qualitative comparison of the deformation field at the surface of the specimen is performed. Furthermore, the predicted evolution of the fabric orientation is compared to experimental results obtained from X-ray scattering experiments. The model shows very good agreement with the experimental data over a wide range of length scales.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    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 °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.

  17. Microwave enhanced electroanalysis of formulations: processes in micellar media at glassy carbon and at platinum electrodes.

    PubMed

    Ghanem, Mohamed A; Compton, Richard G; Coles, Barry A; Canals, Antonio; Marken, Frank

    2005-10-01

    The direct electroanalysis of complex formulations containing alpha-tocopherol (vitamin E) is possible in micellar solution and employing microwave-enhanced voltammetry. In the presence of microwave radiation substantial heating and current enhancement effects have been observed at 330 microm diameter glassy carbon electrodes placed into a micellar aqueous solution and both hydrophilic and highly hydrophobic redox systems are detected. For the water soluble Fe(CN)(6)(3-/4-) redox system in micellar aqueous solutions of 0.1 M NaCl and 0.1 M sodium dodecylsulfate (SDS) at low to intermediate microwave power, thermal effects and convection effects are observed. At higher microwave power, thermal cavitation is induced and dominates the mass transport at the electrode surface. For the micelle-soluble redox systems tert-butylferrocene and 2,5-di-tert-butyl-1,4-benzoquinone, strong and concentration dependent current responses are observed only in the presence of microwave radiation. For the oxidation of micelle-soluble alpha-tocopherol current responses at glassy carbon electrodes are affected by adsorption and desorption processes whereas at platinum electrodes, analytical limiting currents are obtained over a wide range of alpha-tocopherol concentrations. However, for the determination of alpha-tocopherol in a commercial formulation interference from proteins is observed at platinum electrodes and direct measurements are possible only over a limited concentration range and at glassy carbon electrodes.

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

    PubMed

    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. PMID:25939764

  19. A magnetic glassy phase in Fe1+ySexTe1-x single crystals

    NASA Astrophysics Data System (ADS)

    Lamura, G.; Shiroka, T.; Bonfà, P.; Sanna, S.; Bernardini, F.; De Renzi, R.; Viennois, R.; Giannini, E.; Piriou, A.; Emery, N.; Cimberle, M. R.; Putti, M.

    2013-04-01

    The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content. At the same time all the tested samples manifest a marked glassy character that vanishes for high Se contents. The presence of local electronic/compositional inhomogeneities most likely favours the growth of clusters whose magnetic moment ‘freezes’ at low temperature. This glassy magnetic phase justifies both the coherent muon precession seen at short times in the asymmetry data, as well as the glassy behaviour evidenced by both dc and ac magnetometry.

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

    SciTech Connect

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

    1994-03-01

    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.

  1. Glassy carbon as an absolute intensity calibration standard for small-angle scattering.

    SciTech Connect

    Zhang, F.; Ilavsky, J.; Long, G.; Allen, A.; Quintana, J.; Jemian, P.; NIST

    2010-05-01

    Absolute calibration of small-angle scattering (SAS) intensity data (measured in terms of the differential scattering cross section per unit sample volume per unit solid angle) is essential for many important aspects of quantitative SAS analysis, such as obtaining the number density, volume fraction, and specific surface area of the scatterers. It also enables scattering data from different instruments (light, X-ray, or neutron scattering) to be combined, and it can even be useful to detect the existence of artifacts in the experimental data. Different primary or secondary calibration methods are available. In the latter case, absolute intensity calibration requires a stable artifact with the necessary scattering profile. Glassy carbon has sometimes been selected as this intensity calibration standard. Here we review the spatial homogeneity and temporal stability of one type of commercially available glassy carbon that is being used as an intensity calibration standard at a number of SAS facilities. We demonstrate that glassy carbon is sufficiently homogeneous and stable during routine use to be relied upon as a suitable standard for absolute intensity calibration of SAS data.

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

    USGS Publications Warehouse

    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 (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.

  3. Microscopic theory of the glassy dynamics of passive and active network materials.

    PubMed

    Wang, Shenshen; Wolynes, Peter G

    2013-03-28

    Signatures of glassy dynamics have been identified experimentally for a rich variety of materials in which molecular networks provide rigidity. Here we present a theoretical framework to study the glassy behavior of both passive and active network materials. We construct a general microscopic network model that incorporates nonlinear elasticity of individual filaments and steric constraints due to crowding. Based on constructive analogies between structural glass forming liquids and random field Ising magnets implemented using a heterogeneous self-consistent phonon method, our scheme provides a microscopic approach to determine the mismatch surface tension and the configurational entropy, which compete in determining the barrier for structural rearrangements within the random first order transition theory of escape from a local energy minimum. The influence of crosslinking on the fragility of inorganic network glass formers is recapitulated by the model. For active network materials, the mapping, which correlates the glassy characteristics to the network architecture and properties of nonequilibrium motor processes, is shown to capture several key experimental observations on the cytoskeleton of living cells: Highly connected tense networks behave as strong glass formers; intense motor action promotes reconfiguration. The fact that our model assuming a negative motor susceptibility predicts the latter suggests that on average the motorized processes in living cells do resist the imposed mechanical load. Our calculations also identify a spinodal point where simultaneously the mismatch penalty vanishes and the mechanical stability of amorphous packing disappears.

  4. Influence of Cr on the nanoclusters formation and superferromagnetic behavior of Fe-Cr-Nb-B glassy alloys

    NASA Astrophysics Data System (ADS)

    Chiriac, H.; Whitmore, L.; Grigoras, M.; Ababei, G.; Stoian, G.; Lupu, N.

    2015-05-01

    High resolution imaging and electron diffraction confirm that in the as-quenched state the structure of Fe79.7-xCrxNb0.3B20 (x = 11-13 at. %) melt-spun ribbons is completely amorphous, independent of the Cr content. Energy-dispersive X-ray spectroscopy mapping emphasizes clearly the presence of Fe and Cr clusters varying from approximately 1 to 2-3 nm in size with the increase of Cr content from 11 to 13 at. %. The Fe and Cr atoms segregate the atomic scale to form nanometer sized clusters, influencing strongly the macroscopic magnetic behavior. The Curie temperature of the system, TCsystem, confirmed by the magnetic susceptibility versus temperature measurements, gives the strength of the magnetic interactions between clusters. The inter-cluster interactions are much stronger for lower contents of Cr, the microstructure is less uniform, and TCsystem increases from 290 K for 13 at. % Cr to 330 K for 11.5 at. % Cr. The whole system transforms to a ferromagnetic state through interactions between the clusters. Zero-field cooling and field cooling curves confirm the cluster behavior with a blocking temperature, Tb, of about 250 K. Above Tb, the ribbons behave as a superferromagnetic system, whilst below the blocking temperature a classical ferromagnetic behavior is observed.

  5. Influence of Cr on the nanoclusters formation and superferromagnetic behavior of Fe-Cr-Nb-B glassy alloys

    SciTech Connect

    Chiriac, H.; Whitmore, L.; Grigoras, M.; Ababei, G.; Stoian, G.; Lupu, N.

    2015-05-07

    High resolution imaging and electron diffraction confirm that in the as-quenched state the structure of Fe{sub 79.7−x}Cr{sub x}Nb{sub 0.3}B{sub 20} (x = 11–13 at. %) melt-spun ribbons is completely amorphous, independent of the Cr content. Energy-dispersive X-ray spectroscopy mapping emphasizes clearly the presence of Fe and Cr clusters varying from approximately 1 to 2–3 nm in size with the increase of Cr content from 11 to 13 at. %. The Fe and Cr atoms segregate the atomic scale to form nanometer sized clusters, influencing strongly the macroscopic magnetic behavior. The Curie temperature of the system, T{sub C}{sup system}, confirmed by the magnetic susceptibility versus temperature measurements, gives the strength of the magnetic interactions between clusters. The inter-cluster interactions are much stronger for lower contents of Cr, the microstructure is less uniform, and T{sub C}{sup system} increases from 290 K for 13 at. % Cr to 330 K for 11.5 at. % Cr. The whole system transforms to a ferromagnetic state through interactions between the clusters. Zero-field cooling and field cooling curves confirm the cluster behavior with a blocking temperature, T{sub b}, of about 250 K. Above T{sub b}, the ribbons behave as a superferromagnetic system, whilst below the blocking temperature a classical ferromagnetic behavior is observed.

  6. Dielectric study of equimolar acetaminophen-aspirin, acetaminophen-quinidine, and benzoic acid-progesterone molecular alloys in the glass and ultraviscous states and their relevance to solubility and stability.

    PubMed

    Johari, G P; Kim, S; Shanker, Ravi M

    2010-03-01

    Equimolar mixtures of acetaminophen-aspirin, acetaminophen-quinidine, and benzoic acid-progesterone have been vitrified and dielectric properties of their glassy and ultraviscous alloys have been studied. For 20 K/min heating rate, their T(g)s are 266, 330, and 263 K, respectively. The relaxation has an asymmetric distribution of times, and the distribution parameter increases with increase in temperature. The dielectric relaxation time varies with T according to the Vogel-Fulcher-Tammann equation, log(10)(tau(0)) = A(VFT) + [B(VFT)/(T - T(0))], where A(VFT), B(VFT), and T(0) are empirical constants. The equilibrium permittivity is highest for the aspirin-acetaminophen and lowest for the benzoic acid-progesterone alloy, indicating a substantial interpharmaceutical hydrogen bonding that makes the alloy more stable against crystallization than the pure components. The benzoic acid-progesterone alloy is thermodynamically the most nonideal. It showed cold crystallization on heating, which is attributed to its relatively greater magnitude of the JG relaxation in relation to its alpha-relaxation. It is argued that the difference between the free energy of an alloy and the pure components would have an effect on the solubility. Studies of solution thermodynamics of a glassy molecular alloy may be useful for optimizing choice of components and composition to form molecular alloys and to impact drug delivery. PMID:19780138

  7. Bulk metallic glass formation in Zr-Cu-Fe-Al alloys

    SciTech Connect

    Jin Kaifeng; Loeffler, Joerg F.

    2005-06-13

    We have discovered a series of bulk metallic glass-forming alloys of composition (Zr{sub x}Cu{sub 100-x}){sub 80}(Fe{sub 40}Al{sub 60}){sub 20} with x=68-77 and have investigated them by x-ray diffraction, small-angle neutron scattering, and differential scanning calorimetry. All of these alloys exhibit a calorimetric glass transition temperature of 670 Kalloy Zr{sub 58}Cu{sub 22}Fe{sub 8}Al{sub 12}. In rod shape this alloy has a critical casting thickness of 13 mm, as verified by detailed casting experiments, while alloys with x=68 and 77 can still be cast to a thickness of 5 mm. Furthermore, the region where glassy samples with a thickness of 0.5 mm can be prepared extends from x=62-81. The best glass-former, Zr{sub 58}Cu{sub 22}Fe{sub 8}Al{sub 12}, has a tensile yield strength of 1.71 GPa and shows an elastic limit of 2.25%. This new class of Ni-free Zr-based alloys is potentially very interesting for biomedical applications.

  8. Oxidation of electrodeposited lead-tin alloys in 5 M H 2SO 4

    NASA Astrophysics Data System (ADS)

    Petersson, I.; Ahlberg, E.

    By electroplating lead-tin alloys on a lightweight substrate material, such as glassy carbon, it is possible to obtain less dense electrodes with good contact between the active material and the substrate. The former is especially important for the lead-acid battery since it has relatively low energy density compared to many other battery systems. In order to obtain higher power densities for applications in, for example, electric or hybrid vehicles, the weight of the battery needs to be minimised. In the present investigation, the oxidation of electrodeposited lead-tin alloys in 5 M H 2SO 4 was studied as a function of tin concentration. The alloys were prepared by electrodeposition and the oxidation behaviour was studied by the means of cyclic voltammetry. Microstructural information on the deposited layer was obtained by scanning electron microscopy (SEM). The experimental results show that electrodeposited lead-tin alloys contain a supersaturated solid solution phase with up to 12 at.% Sn. Oxidation of this phase in 5 M H 2SO 4 leads to the formation of a PbO phase with increased conductivity compared to pure PbO. In addition, the amounts of PbO and PbO 2 decrease with increasing amounts of tin in the alloy and for high tin alloys, where a bulk tin phase is present, no PbO phase is observed.

  9. Designing new biocompatible glass-forming Ti75-x Zr10 Nbx Si15 (x = 0, 15) alloys: corrosion, passivity, and apatite formation.

    PubMed

    Abdi, Somayeh; Oswald, Steffen; Gostin, Petre Flaviu; Helth, Arne; Sort, Jordi; Baró, Maria Dolors; Calin, Mariana; Schultz, Ludwig; Eckert, Jürgen; Gebert, Annett

    2016-01-01

    Glass-forming Ti-based alloys are considered as potential new materials for implant applications. Ti75 Zr10 Si15 and Ti60 Zr10 Nb15 Si15 alloys (free of cytotoxic elements) can be produced as melt-spun ribbons with glassy matrix and embedded single β-type nanocrystals. The corrosion and passivation behavior of these alloys in their homogenized melt-spun states have been investigated in Ringer solution at 37°C in comparison to their cast multiphase crystalline counterparts and to cp-Ti and β-type Ti-40Nb. All tested materials showed very low corrosion rates as expressed in corrosion current densities icorr  < 50 nA/cm(2). Electrochemical and surface analytical studies revealed a high stability of the new alloys passive states in a wide potential range. This corresponds to low passive current densities ipass  = 2 ± 1 µA/cm(2) based on the growth of oxide films with thickness d <10 nm. A homogeneous constituent distribution in the melt-spun alloys is beneficial for stable surface passivity. The addition of Nb does not only improve the glass-forming ability and the mechanical properties but also supports a high pitting resistance even at extreme anodic polarization up to 4V versus SCE were oxide thickness values of d ∼35 nm are reached. With regard to the corrosion properties, the Nb-containing nearly single-phase glassy alloy can compete with the β-type Ti-40Nb alloy. SBF tests confirmed the ability for formation of hydroxyapatite on the melt-spun alloy surfaces. All these properties recommend the new glass-forming alloys for application as wear- and corrosion-resistant coating materials for implants. PMID:25611821

  10. Designing new biocompatible glass-forming Ti75-x Zr10 Nbx Si15 (x = 0, 15) alloys: corrosion, passivity, and apatite formation.

    PubMed

    Abdi, Somayeh; Oswald, Steffen; Gostin, Petre Flaviu; Helth, Arne; Sort, Jordi; Baró, Maria Dolors; Calin, Mariana; Schultz, Ludwig; Eckert, Jürgen; Gebert, Annett

    2016-01-01

    Glass-forming Ti-based alloys are considered as potential new materials for implant applications. Ti75 Zr10 Si15 and Ti60 Zr10 Nb15 Si15 alloys (free of cytotoxic elements) can be produced as melt-spun ribbons with glassy matrix and embedded single β-type nanocrystals. The corrosion and passivation behavior of these alloys in their homogenized melt-spun states have been investigated in Ringer solution at 37°C in comparison to their cast multiphase crystalline counterparts and to cp-Ti and β-type Ti-40Nb. All tested materials showed very low corrosion rates as expressed in corrosion current densities icorr  < 50 nA/cm(2). Electrochemical and surface analytical studies revealed a high stability of the new alloys passive states in a wide potential range. This corresponds to low passive current densities ipass  = 2 ± 1 µA/cm(2) based on the growth of oxide films with thickness d <10 nm. A homogeneous constituent distribution in the melt-spun alloys is beneficial for stable surface passivity. The addition of Nb does not only improve the glass-forming ability and the mechanical properties but also supports a high pitting resistance even at extreme anodic polarization up to 4V versus SCE were oxide thickness values of d ∼35 nm are reached. With regard to the corrosion properties, the Nb-containing nearly single-phase glassy alloy can compete with the β-type Ti-40Nb alloy. SBF tests confirmed the ability for formation of hydroxyapatite on the melt-spun alloy surfaces. All these properties recommend the new glass-forming alloys for application as wear- and corrosion-resistant coating materials for implants.

  11. Structure, phases, and mechanical response of Ti-alloy bioactive glass composite coatings.

    PubMed

    Nelson, G M; Nychka, J A; McDonald, A G

    2014-03-01

    Porous titanium alloy-bioactive glass composite coatings were manufactured via the flame spray deposition process. The porous coatings, targeted for orthodontic and bone-fixation applications, were made from bioactive glass (45S5) powder blended with either commercially pure titanium (Cp-Ti) or Ti-6Al-4V alloy powder. Two sets of spray conditions, two metallic particle size distributions, and two glass particle size distributions were used for this study. Negative control coatings consisting of pure Ti-6Al-4V alloy or Cp-Ti were sprayed under both conditions. The as-sprayed coatings were characterized through quantitative optical cross-sectional metallography, X-ray diffraction (XRD), and ASTM Standard C633 tensile adhesion testing. Determination of the porosity and glassy phase distribution was achieved by using image analysis in accordance with ASTM Standard E2109. Theoretical thermodynamic and heat transfer modeling was conducted to explain experimental observations. Thermodynamic modeling was performed to estimate the flame temperature and chemical environment for each spray condition and a lumped capacitance heat transfer model was developed to estimate the temperatures attained by each particle. These models were used to establish trends among the choice of alloy, spray condition, and particle size distribution. The deposition parameters, alloy composition, and alteration of the feedstock powder size distribution had a significant effect on the coating microstructure, porosity, phases present, mechanical response, and theoretical particle temperatures that were attained. The most promising coatings were the Ti-6Al-4V-based composite coatings, which had bond strength of 20±2MPa (n=5) and received reinforcement and strengthening from the inclusion of a glassy phase. It was shown that the use of the Ti-6Al-4V-bioactive glass composite coatings may be a superior choice due to the possible osteoproductivity from the bioactive glass, the potential ability to

  12. Turbine Blade Alloy

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca

    2001-01-01

    The High Speed Research Airfoil Alloy Program developed a fourth-generation alloy with up to an +85 F increase in creep rupture capability over current production airfoil alloys. Since improved strength is typically obtained when the limits of microstructural stability are exceeded slightly, it is not surprising that this alloy has a tendency to exhibit microstructural instabilities after high temperature exposures. This presentation will discuss recent results obtained on coated fourth-generation alloys for subsonic turbine blade applications under the NASA Ultra-Efficient Engine Technology (UEET) Program. Progress made in reducing microstructural instabilities in these alloys will be presented. In addition, plans will be presented for advanced alloy development and for computational modeling, which will aid future alloy development efforts.

  13. Laser micromilling of convex microfluidic channels onto glassy carbon for glass molding dies

    NASA Astrophysics Data System (ADS)

    Tseng, Shih-Feng; Chen, Ming-Fei; Hsiao, Wen-Tse; Huang, Chien-Yao; Yang, Chung-Heng; Chen, Yu-Sheng

    2014-06-01

    This study reports the fabrication of convex microfluidic channels on glassy carbon using an ultraviolet laser processing system to produce glass molding dies. The laser processing parameters, including various laser fluences and scanning speeds of galvanometers, were adjusted to mill a convex microchannel on a glassy carbon substrate to identify the effects of material removal. The machined glassy carbon substrate was then applied as a glass molding die to fabricate a glass-based microfluidic biochip. The surface morphology, milled width and depth, and surface roughness of the microchannel die after laser micromilling were examined using a three-dimensional confocal laser scanning microscope. This study also investigates the transcription rate of microchannels after the glass molding process. To produce a 180 μm high microchannel on the GC substrate, the optimal number of milled cycles, laser fluence, and scanning speed were 25, 4.9 J/cm2, and 200 mm/s, respectively. The width, height, and surface roughness of milled convex microchannels were 119.6±0.217 μm, 180.26±0.01 μm, and 0.672±0.08 μm, respectively. These measured values were close to the predicted values and suitable for a glass molding die. After the glass molding process, a typical glass-based microchannel chip was formed at a molding temperature of 660 °C and the molding force of 0.45 kN. The transcription rates of the microchannel width and depth were 100% and 99.6%, respectively. Thus, the proposed approach is suitable for performing in chemical, biochemical, or medical reactions.

  14. Methyl group dynamics in glassy, polycrystalline, and liquid coenzyme Q10 studied by quasielastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Smuda, Christoph; Busch, Sebastian; Wagner, Bernd; Unruh, Tobias

    2008-08-01

    The methyl group rotation of coenzyme Q10 confined in nanosized droplets was studied using quasielastic neutron scattering (QENS). Q10 as an oligoisoprene derivative with ten isoprene units can easily be supercooled in nanodroplets. Fixed window scans and QENS spectra at several temperatures of glassy Q10 were recorded to study the methyl group rotation which can be described by a logarithmic Gaussian distribution of hopping rates for temperatures below the glass transition temperature (Tg~200 K). A mean activation energy of 4.8 kJ/mol with a distribution width of 2.1 kJ/mol was obtained from the evaluation of the QENS spectra. A corresponding analysis of a fixed window scan yielded an average activation energy of 5.1 kJ/mol with a distribution width of 1.8 kJ/mol. The results are compared and discussed with those of chain deuterated polyisoprene-d5. For polycrystalline Q10, the QENS spectra could be described by the same model yielding a similar average activation energy as found for glassy Q10. However, no temperature dependence of the distribution width was observed. Based on the performed low-temperature measurements, the correlation times for the methyl group rotation were extrapolated to temperatures of liquid Q10. The complex dynamics of liquid Q10 could be described by a model yielding an apparent diffusion coefficient, the jump rate of the methyl groups, as well as an overall molecular rotational diffusion coefficient. The correlation times of the methyl group rotation in liquid Q10 at a given temperature T0 coincide with values determined in the glassy phase and extrapolated to T0.

  15. Permanent photoalignment of liquid crystals on nanostructured chalcogenide glassy thin films

    SciTech Connect

    Gelbaor, Miri; Abdulhalim, I.; Klebanov, Matvey; Lyubin, Victor

    2011-02-14

    Photoalignment of nematic liquid crystals is obtained on the chalcogenide glassy thin film of As{sub 2}S{sub 3} using irradiation with polarized blue light. A uniform homogeneously aligned device is obtained with high contrast and strong anchoring. The device alignment quality is permanent as checked by following its functionality over a period of few months. The origin of the observed photoalignment is attributed to the photoinduced anisotropy in chalcogenide glasses. No differences between the different As{sub 2}S{sub 3} film thicknesses observed, thus supporting the proposition that some orientational order is photoinduced on the surface of the glass and responsible for the photoalignment.

  16. A study on oxidized glassy carbon sheets for bipolar supercapacitor electrodes

    SciTech Connect

    Braun, A.; Baertsch, M.; Geiger, F.

    2000-07-01

    Electrochemical Double Layer Capacitors (EDLC) for high energy and power density applications, based on glassy carbon (GC) electrodes, are being developed in this laboratory. In the context of this project, GC sheets were oxidized and investigated with Small Angle X-ray Scattering (SAXS), Electrochemical Impedance Spectroscopy (EIS) and Nitrogen Gas Adsorption (BET). During oxidation on active film with open pores is built on the surface of the GC. Upon oxidation, the internal volumetric surface area of the active film decreases, whereas the volumetric electrochemical double layer capacitance increases. The authors show that this effect is correlated with the opening, the growth and the coalescence of the pores.

  17. Simple Model for the Deformation-Induced Relaxation of Glassy Polymers

    NASA Astrophysics Data System (ADS)

    Fielding, S. M.; Larson, R. G.; Cates, M. E.

    2012-01-01

    Glassy polymers show “strain hardening”: at constant extensional load, their flow first accelerates, then arrests. Recent experiments have found this to be accompanied by a striking and unexplained dip in the segmental relaxation time. Here we explain such behavior by combining a minimal model of flow-induced liquefaction of a glass with a description of the stress carried by strained polymers, creating a nonfactorable interplay between aging and strain-induced rejuvenation. Under constant load, liquefaction of segmental motion permits strong flow that creates polymer-borne stress. This slows the deformation enough for the segmental modes to revitrify, causing strain hardening.

  18. High-frequency collective excitations in molten and glassy Te studied by inelastic neutron scattering

    SciTech Connect

    Ruiz-Martin, M. D.; Jimenez-Ruiz, M.; Bermejo, F. J.

    2006-03-01

    The spectra of collective excitations of liquid and glassy tellurium have been studied by means of inelastic neutron scattering. Here we report on the dynamics of liquid Te as measured at two different temperatures, just above melting (T{sub m}=723 K) and at {approx}1000 K as well as the glass that is studied at room temperature. Estimates for the velocity of propagating excitations for both temperatures have been obtained from the experimental data, and a contrasting behavior is found with respect to anomalies shown by the adiabatic sound velocity measured by ultrasound methods. The origin of such differences is finally discussed.

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

    SciTech Connect

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

    2007-01-15

    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.

  20. Transmission of phage by glassy-winged sharpshooters, a vector of Xylella fastidiosa

    PubMed Central

    Bhowmick, Tushar Suvra; Das, Mayukh; Heinz, Kevin M.; Krauter, Peter C.; Gonzalez, Carlos F.

    2016-01-01

    ABSTRACT Xylella fastidiosa subsp. fastidiosa (Xff) is the causal agent of Pierce's Disease (PD) of grapevines and is vectored by the glassy-winged sharpshooter (GWSS, Homalodisca vitripennis). Previously we have reported the development of a bacteriophage (phage) based biocontrol system for PD, but no information on insect transmission of phages has been reported. Here we communicate that laboratory reared GWSSs fed on cowpea plants (Vigna unguiculata subsp. unguiculata) harboring the virulent phage Paz were able to uptake of phage efficiently when the phage was present in high concentration, but were inefficient in transfer to plants. PMID:27738554

  1. Separation in Binary Alloys

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Facemire, B. R.; Kaukler, W. F.; Witherow, W. K.; Fanning, U.

    1986-01-01

    Studies of monotectic alloys and alloy analogs reviewed. Report surveys research on liquid/liquid and solid/liquid separation in binary monotectic alloys. Emphasizes separation processes in low gravity, such as in outer space or in free fall in drop towers. Advances in methods of controlling separation in experiments highlighted.

  2. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

    A new vanadium-base alloy which possesses remarkable superconducting properties is presented. The alloy consists of approximately one atomic percent of palladium, the balance being vanadium. The alloy is stated to be useful in a cryotron in digital computer circuits.

  3. PLUTONIUM-THORIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.

    1959-09-15

    New plutonium-base binary alloys useful as liquid reactor fuel are described. The alloys consist of 50 to 98 at.% thorium with the remainder plutonium. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are easy fabrication, phase stability, and the accompanying advantuge of providing a means for converting Th/sup 232/ into U/sup 233/.

  4. DELTA PHASE PLUTONIUM ALLOYS

    DOEpatents

    Cramer, E.M.; Ellinger, F.H.; Land. C.C.

    1960-03-22

    Delta-phase plutonium alloys were developed suitable for use as reactor fuels. The alloys consist of from 1 to 4 at.% zinc and the balance plutonium. The alloys have good neutronic, corrosion, and fabrication characteristics snd possess good dimensional characteristics throughout an operating temperature range from 300 to 490 deg C.

  5. New alloys for electroformed replicated x-ray optics

    NASA Astrophysics Data System (ADS)

    Engelhaupt, Darell E.; Ramsey, Brian D.; O'Dell, Stephen L.; Jones, William D.; Russell, J. Kevin

    2000-11-01

    The process of electroforming nickel x-ray mirror shells from superpolished mandrels has been widely used. The recently launched XMM mission by the European Space Agency (ESA) is an excellent example, containing 174 such mirror shells of diameters ranging from 0.3 - 0.7 meters and with a thickness range of 0.47 - 1.07 mm. To continue to utilize this technique for the next generation of x-ray observatories, where larger collecting areas will be required within the constraints of tight weight budgets, demands that new alloys be developed that can withstand the large stresses imposed on very thin shells by the replication, handling and launch processes. Towards this end, we began a development program in late 1997 to produce a high-strength alloy suitable for electroforming very thin high-resolution x-ray optics for the proposed Constellation-X project. Requirements for this task are quite severe; not only must the electroformed deposit be very strong, it must also have very low residual stresses to prevent serious figure distortions in large thin-walled shells. Further, the processing must be done reasonably near room temperature, as large temperature changes will modify the figure of the mandrel. Also the environment must not be corrosive or otherwise damaging to the mandrel during the processing. The results of the development program are presented, showing the evolution of our plating processes and materials through to the present 'glassy' nickel alloy that satisfies the above requirements.

  6. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Ductile Bulk Aluminum-Based Alloy with Good Glass-Forming Ability and High Strength

    NASA Astrophysics Data System (ADS)

    Zhuo, Long-Chao; Pang, Shu-Jie; Wang, Hui; Zhang, Tao

    2009-06-01

    Based on a new approach for designing glassy alloy compositions, bulk Al-based alloys with good glass-forming ability (GFA) are synthesized. The cast Al86Si0.5Ni4.06Co2.94Y6Sc0.5 rod with a diameter of 1 mm shows almost fully amorphous structure besides about 5% fcc-Al nucleated in the center of the rod. The bulk alloy with high Al concentration exhibits an ultrahigh yield strength of 1.18 GPa and maximum strength of 1.27 GPa as well as an obvious plastic strain of about 2.4% during compressive deformation. This light Al-based alloy with good GFA and mechanical properties is promising as a new high specific strength material with good deformability.

  7. Geographic distribution and relative abundance of the invasive glassy-winged sharpshooter: effects of temperature and egg parasitoids.

    PubMed

    Gutierrez, Andrew Paul; Ponti, Luigi; Hoddle, Mark; Almeida, Rodrigo P P; Irvin, Nicola A

    2011-08-01

    The capacity to predict the geographic distribution and relative abundance of invasive species is pivotal to developing policy for eradication or control and management. Commonly used methods fall under the ambit of ecological niche models (ENMs). These methods were reviewed and shortcomings identified. Weather-driven physiologically based demographic models (PBDMs) are proposed that resolve many of the deficiencies of ENMs. The PBDM approach is used to analyze the invasiveness of the polyphagous glassy-winged sharpshooter (Homalodisca vitripennis [Germar]), a pest native to the southeastern United States and northeastern Mexico that extended its range into California in 1989. Glassy-winged sharpshooter vectors the pathogenic bacterium, Xylella fastidiosa (Wells) that causes Pierce's disease in grape and scorch-like diseases in other plants. PBDMs for glassy-winged sharpshooter and its egg parasitoids (Gonatocerus ashmeadi Girault and G. triguttatus Girault) were developed and linked to a PBDM for grape published by Wermelinger et al. (1991). Daily weather data from 108 locations across California for the period 1995-2006 were used to drive the PBDM system, and GRASS GIS was used to map the simulation results. The geographic distribution of glassy-winged sharpshooter, as observed, is predicted to be largely restricted to the warm areas of southern California, with the action of the two egg parasitoids reducing its abundance >90%. The average indispensable mortality contributed by G. triguttatus is <1%. A temperature-dependent developmental rate model for X. fastidiosa was developed that suggests its geographic range is also limited to the warm inland areas of southern California. Biological control of glassy-winged sharpshooter further decreases the pathogen's relative range. Climate warming scenarios of +2°C and +3°C suggest that the distribution and severity of glassy-winged sharpshooter and X. fastidiosa will increase in the agriculturally rich central valley

  8. High strength alloys

    DOEpatents

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  9. High strength alloys

    DOEpatents

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

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

    PubMed Central

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

    2015-01-01

    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. PMID:26263989

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

    PubMed Central

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

    2012-01-01

    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 ≫103 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 < 0.1 to > 1013 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. PMID:22753520

  12. Molecular dynamics simulation of rupture in glassy polymer bridges within filler aggregates

    NASA Astrophysics Data System (ADS)

    Froltsov, Vladimir A.; Klüppel, Manfred; Raos, Guido

    2012-10-01

    We present a series of nonequilibrium molecular dynamics simulations, investigating the rupture mechanisms in glassy polymer films confined between two solid surfaces. Such systems provide a useful model for the strong nonlinear reinforcement of rubber by colloidal filler particles. Depending on the degree of confinement three qualitatively different rupture modes have been found, which originate from the interplay of internal (polymer-polymer) and external (polymer-wall) interactions. In very thin films we observe the formation and stretching of many single-chain bridges between the confining surfaces. Progressing to thicker samples we observe fewer bridges, consisting of bundled polymer chains, and eventually just one large bridge in thick specimens. The yield stress and the elongational modulus of the polymer films have been calculated from the stress-strain curves at various temperatures and confinements and their behavior has been analyzed in terms of polymer-polymer and polymer-surface interaction energies. The thinnest films (5 monomer diameters) are always glassy in our simulations, while the others display a glass transition temperature around 0.50-0.55 (in units ɛ0/kB of the Lennard-Jones interaction energy), depending on their thickness. This range of values, which has been determined using both the nonequilibrium tensile simulations and equilibrium diffusion data, agrees with the transition temperature previously found by shear simulations [Baljon and Robbins, ScienceSCIEAS0036-807510.1126/science.271.5248.482 271, 482 (1996)].

  13. Analyzing aging under oscillatory strain field through the soft glassy rheology model.

    PubMed

    Kaushal, Manish; Joshi, Yogesh M

    2016-06-28

    In this work, we solve the Soft Glassy Rheology (SGR) model under application of oscillatory deformation field with varying magnitudes of strain as well as frequency for different noise temperatures. In the glassy domain, the SGR model undergoes time evolution of elastic modulus. Increase in strain magnitude beyond the linear regime is observed to enhance the rate of aging as manifested by a faster evolution of elastic modulus with increase in strain amplitude due to overaging. However at higher strain magnitudes, the rejuvenation effect starts dominating over the aging, thereby reducing the rate at which elastic modulus evolves. We also plot the aging phase diagram describing an occurrence of the linear, the overaging, and the rejuvenation regimes as a function of strain and frequency for different noise temperatures. The aging phase diagram suggests that while the linear regime remains unaffected by the changes in frequency and noise temperature, the width of the overaging regime increases with increase in frequency and noise temperature. We also study the time evolution of the shapes of relaxation time spectra as a function of strain amplitude, which renders further insight into the overaging and the rejuvenation behavior. While the phenomenon of overaging is observed to be an inherent character of the SGR model, experimentally not all the materials demonstrate overaging. Such a discrepancy suggests that the energy well depths before and after a yielding event may not be completely uncorrelated as assumed in the SGR formalism. PMID:27369524

  14. Multilevel micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-03-01

    A consumer market for diffractive optical elements in glass can only be created if high efficient elements are available at affordable prices. In diffractive optics the efficiency and optical properties increases with the number of levels used, but in the same way the costs are multiplied by the number if fabrication steps. Replication of multilevel diffractive optical elements in glass would allow cost efficient fabrication but a suitable mold material is needed. Glassy carbon shows a high mechanical strength, thermal stability and non-sticking adhesion properties, which makes it an excellent candidate as mold material for precision compression molding of low and high glass-transition temperature materials. We introduce an 8 level micro structuring process for glassy carbon molds with standard photolithography and a Ti layer as hard mask for reactive ion etching. The molds were applied to thermal imprinting onto low and high transition temperature glass. Optical performance was tested for the molded samples with different designs for laser beamsplitters. The results show a good agreement to the design specification. Our result allow us to show limitations of our fabrication technique and we discussed the suitability of precision glass molding for cost efficient mass production with a high quality.

  15. Gas-to-liquid permeation in silicon-containing, crosslinked, glassy copolymers of methyl methacrylate.

    PubMed

    Yang, W M; Peppas, N A

    1983-10-01

    Copolymers of methyl methacrylate with disiloxane derivatives have been proposed as biomaterials for contact lens applications. Although glassy, these copolymers exhibit high oxygen permeability and adequate wettability so that they can be used for manufacture of hard, extended wear lenses. Crosslinked copolymers of poly(methylmethacrylate-co-1,3-bis(methacryloxymethyl) -1,1,3,3-tetramethyl-disiloxane), P(MMA-co-BMTDS), containing from 0.085 to 0.53 mole fraction of BMTDS were prepared and tested for oxygen permeation using a novel apparatus which simulates the atmosphere/lens/cornea conditions. The gas-to-liquid dissolved oxygen permeability, P gd1 was determined and it was found to increase with BMTDS content. Permeability values for P(MMA-co-BMTDS) at 34 degrees C were significantly higher than for pure homopolymer PMMA, although these copolymers were glassy at this temperature. The increased oxygen permeation was attributed to increased oxygen solubility in the copolymers due to the presence of the -Si-O-bonds. PMID:6640054

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

    PubMed

    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. PMID:23381910

  17. Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes.

    PubMed

    Enache, Teodor Adrian; Fatibello-Filho, Orlando; Oliveira-Brett, Ana Maria

    2010-08-01

    The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was study by differential pulse voltammetry over a wide pH range. The hydrolysis products are 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA.

  18. Separating the ferromagnetic and glassy behavior within the metal-organic magnet Ni (TCNQ) 2

    NASA Astrophysics Data System (ADS)

    Berlie, Adam; Terry, Ian; Szablewski, Marek; Giblin, Sean R.

    2015-11-01

    An in-depth study of the metal-organic magnet Ni (TCNQ) 2 was conducted where the deuterated form was synthesised both to attempt to alter the magnetic properties of the material and to be advantageous in techniques such as neutron scattering and muon spectroscopy. Deuteration saw a 3 K increase in TC with magnetization and heat capacity measurements demonstrating a spin wave contribution at low temperatures confirming the 3D nature of the ferromagnetic state shown by Ni (TCNQ-D4)2 . AC susceptibility results suggest there is a glassy component associated with the magnetically ordered state, though muon spectroscopy measurements did not support the presence of a spin glass state. Instead muon spectroscopy at zero magnetic field indicated the presence of two magnetic transitions, one at 20 K and another below 6 K; the latter is likely due to the system entering a quasistatic regime, similar to what one might expect of a superspin or cluster glass. Neutron diffraction measurements further supported this by revealing very weak magnetic Bragg peaks suggesting that the magnetism may have a short coherence length and be confined to small grains or clusters. The separation of the ferromagnetic and glassy magnetic components of the material's properties suggest that this system may show promise as a metal-organic magnet which is easily modified to change its magnetic properties, providing larger grain sizes can be synthesized.

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

    NASA Astrophysics Data System (ADS)

    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.

    2013-10-01

    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.

  20. Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes.

    PubMed

    Enache, Teodor Adrian; Fatibello-Filho, Orlando; Oliveira-Brett, Ana Maria

    2010-08-01

    The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was study by differential pulse voltammetry over a wide pH range. The hydrolysis products are 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA. PMID:20402644

  1. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    PubMed

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification.

  2. Effect of water polyamorphism on the molecular vibrations of glycerol in its glassy aqueous solutions

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshiharu; Mishima, Osamu

    2016-07-01

    A glassy dilute glycerol-water solution undergoes a mutual polyamorphic transition relating to the transition between high- and low-density amorphous ices of solvent water. The polyamorphic transition behavior depends on the glycerol concentration, indicating that the glycerol affects the water polyamorphism. Here, we used the glassy dilute glycerol-water solution of the solute molar fraction of 0.07 and examined the effect of the polyamorphic change in solvent water on the molecular vibrations of glycerol via Raman spectroscopy. It is found that the molecular vibration of glycerol in high-density liquid like solvent water is different from that in the low-density liquid like solvent water and that the change in the molecular vibration of glycerol is synchronized with the polyamorphic transition of solvent water. The dynamical change of the solute molecule relates to the polyamorphic state of solvent water. This result suggests that the polyamorphic fluctuation of water structure emanated from the presumed liquid-liquid critical point plays an important role for the function of aqueous solution under an ambient condition such as the conformational stability of solute, the functional expression of solute, and so on.

  3. Effect of chemical substituents on the structure of glassy diphenyl polycarbonates.

    PubMed

    Sulatha, M S; Natarajan, Upendra

    2011-02-24

    Polycarbonates offer a wide variety of physical property behavior that is difficult to predict due to complexities at the molecular scale. Here, the physical structure of amorphous glassy polycarbonates having aliphatic and cycloaliphatic chemical groups is explored through atomistic simulations. The influence of chemical structure on solubility parameter, torsion distributions, radial distribution function, scattering structure factor, orientation distributions of phenylene rings and carbonate groups, and free volume distributions, leading to interchain packing effects, are shown. The effect of the cyclohexyl ring at the isopropylidene carbon as compared to the effect of the methyl groups positioned on the phenylene rings results in a larger reduction in the solubility parameter (δ). The interchain distance estimated for polycarbonates in this work is in the range of 5-5.8 Å. The o-methyl groups on the phenylene rings, as compared to a cyclohexyl ring, lead to higher interchain distances. The highest interchain distance is observed with a trimethylcyclohexylidene group at the isopropylidene carbon. Atomistic simulations reveal two different types of packing arrangement of nearest-neighbor chains in the glassy state, one type of which agrees with the NMR experimental data. The fundamental insights provided here can be utilized for design of chemical structures for tailored macroscopic properties.

  4. Molecular dynamics simulation of rupture in glassy polymer bridges within filler aggregates.

    PubMed

    Froltsov, Vladimir A; Klüppel, Manfred; Raos, Guido

    2012-10-01

    We present a series of nonequilibrium molecular dynamics simulations, investigating the rupture mechanisms in glassy polymer films confined between two solid surfaces. Such systems provide a useful model for the strong nonlinear reinforcement of rubber by colloidal filler particles. Depending on the degree of confinement three qualitatively different rupture modes have been found, which originate from the interplay of internal (polymer-polymer) and external (polymer-wall) interactions. In very thin films we observe the formation and stretching of many single-chain bridges between the confining surfaces. Progressing to thicker samples we observe fewer bridges, consisting of bundled polymer chains, and eventually just one large bridge in thick specimens. The yield stress and the elongational modulus of the polymer films have been calculated from the stress-strain curves at various temperatures and confinements and their behavior has been analyzed in terms of polymer-polymer and polymer-surface interaction energies. The thinnest films (5 monomer diameters) are always glassy in our simulations, while the others display a glass transition temperature around 0.50-0.55 (in units ε(0)/k(B) of the Lennard-Jones interaction energy), depending on their thickness. This range of values, which has been determined using both the nonequilibrium tensile simulations and equilibrium diffusion data, agrees with the transition temperature previously found by shear simulations [Baljon and Robbins, Science 271, 482 (1996)]. PMID:23214604

  5. Determination of trace amounts of lead and cadmium using a bismuth/glassy carbon composite electrode.

    PubMed

    Hwang, Gil-Ho; Han, Won-Kyu; Hong, Seok-Jun; Park, Joon-Shik; Kang, Sung-Goon

    2009-02-15

    We examined the use of a bismuth-glassy carbon (Bi/C) composite electrode for the determination of trace amounts of lead and cadmium. Incorporated bismuth powder in the composite electrode was electrochemically dissolved in 0.1M acetate buffer (pH 4.5) where nanosized bismuth particles were deposited on the glassy carbon at the reduction potential. The anodic stripping voltammetry on the Bi/C composite electrode exhibited well-defined, sharp and undistorted peaks with a favorable resolution for lead and cadmium. Comparing a non-oxidized Bi/C composite electrode with an in-situ plated bismuth film electrode, the Bi/C composite electrode exhibited superior performance due to its much larger surface area. The limit of detection was 0.41 microg/L for lead and 0.49 microg/L for cadmium. Based on this study, we are able to conclude that various types of composite electrodes for electroanalytical applications can be developed with a prudent combination of electrode materials.

  6. Incoherent chimera and glassy states in coupled oscillators with frustrated interactions

    NASA Astrophysics Data System (ADS)

    Choe, Chol-Ung; Ri, Ji-Song; Kim, Ryong-Son

    2016-09-01

    We suggest a site disorder model that describes the population of identical oscillators with quenched random interactions for both the coupling strength and coupling phase. We obtain the reduced equations for the suborder parameters, on the basis of Ott-Antonsen ansatz theory, and present a complete bifurcation analysis of the reduced system. New effects include the appearance of the incoherent chimera and glassy state, both of which are caused by heterogeneity of the coupling phases. In the incoherent chimera state, the system displays an exotic symmetry-breaking behavior in spite of the apparent structural symmetry where the oscillators for both of the two subpopulations are in a frustrated state, while the phase distribution for each subpopulation approaches a steady state that differs from each other. When the incoherent chimera undergoes Hopf bifurcation, the system displays a breathing incoherent chimera. The glassy state that occurs on a surface of three-dimensional parameter space exhibits a continuum of metastable states with zero value of the global order parameter. Explicit formulas are derived for the system's Hopf, saddle-node, and transcritical bifurcation curves, as well as the codimension-2 crossing points, including the Takens-Bogdanov point.

  7. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    PubMed

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification. PMID:26625272

  8. Sensitive Electrochemical Detection of Enzymatically-generated Thiocholine at Carbon Nanotube Modified Glassy Carbon Electrode

    SciTech Connect

    Liu, Guodong; Riechers, Shawn L.; Mellen, Maria C.; Lin, Yuehe

    2005-11-01

    A carbon nanotube modified glassy-carbon (CNT/GC) electrode was used for enhancing the sensitivity of electrochemical measurements of enzymatically-generated thiocholine. Cyclic voltammetric and amperometric characteristics of thiocholine at CNT/GC, glassy carbon, carbon paste, and gold electrodes were compared. The CNT layer leads to a greatly improved anodic detection of enzymatically generated thiocholine product including lower oxidation overpotential (0.15 V) and higher sensitivity because of its electrocatalytic activity, fast electron transfer and large surface area. The sensor performance was optimized with respect to the operating conditions. Under the optimal batch conditions, a detection limit of 5 ?10 -6 mol/L was obtained with good precision (RSD = 5.2%, n=10). Furthermore, the attractive response of thiocholine on a CNT/GC electrode has allowed it to be used for constant-potential flow injection analysis. The detection limit was greatly improved to 0.3 ?10-6 mol/L. The high sensitivity electrochemical detection of enzymatically generated thiocholine with a CNT sensing platform holds great promise to prepare an acetylcholinesterase biosensor for monitoring organophosphate pesticides and nerve agents.

  9. Mechanistic study of carvacrol processing and stabilization as glassy solid solution and microcapsule.

    PubMed

    Tackenberg, Markus W; Geisthövel, Carola; Marmann, Andreas; Schuchmann, Heike P; Kleinebudde, Peter; Thommes, Markus

    2015-01-30

    Essential oils and other liquid active pharmaceutical ingredients (APIs) are frequently microencapsulated to improve shelf life, handling, and for tailoring release. A glassy solid solution (GSS), a single-phase system, where the excipient is plasticized by the API, could be an alternative formulation system. Thus this study focuses on the investigation of two formulation strategies using carvacrol as a model compound, namely a microcapsule (MC) and a glassy solid solution (GSS). Applying the solubility parameter approach, polyvinylpyrrolidone (PVP) was chosen as a suitable matrix material for a GSS system, whereas maltodextrin and sucrose served as excipients for a microcapsule (MC) system. Differential scanning calorimetry (DSC) measurements of the excipients' glass transition temperatures and the melting point of carvacrol verified plasticizing properties of carvacrol on PVP. Batch mixing processes, as preliminary experiments for future extrusion processes, were performed to prepare GSSs and MCs with various amounts of carvacrol, followed by crushing and sieving. Maximally 4.5% carvacrol was encapsulated in the carbohydrate material, whereas up to 16.3% were stabilized as GSS, which is an outstanding amount. However, grinding of the samples led to a loss of up to 30% of carvacrol.

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

    PubMed

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

    2015-01-01

    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. PMID:26263989

  11. Relaxation phenomena in supercooled liquid and glassy acetaminophen studied by dielectric, photon correlation and Brillouin light scattering spectroscopies

    NASA Astrophysics Data System (ADS)

    Kwon, Hyun-Joung; Kim, Tae Hyun; Ko, Jae-Hyeon; Hwang, Yoon-Hwae

    2013-01-01

    Relaxation phenomena and acoustic properties of acetaminophen in the glassy and supercooled liquid phase were studied by dielectric, photon correlation and Brillouin spectroscopies. Dielectric and photon correlation studies revealed the structural relaxation process while a new relaxation process was found by dielectric measurement in a much lower frequency range. The acoustic anomalies clearly indicated a glass transition at 293 K and some remnant localized motions in the glassy phase that contributed to the acoustic damping. Partial crystallization in the supercooled liquid phase was signified at temperatures above 318 K by drastic changes in the Brillouin spectrum and decrease in the dielectric strength.

  12. Nucleation and growth of thin films of the organic conductor TTF-iodide over glassy carbon. Electrochemical and spectroelectrochemical study.

    PubMed

    Gómez, L; Rodríguez-Amaro, R

    2009-04-21

    On the basis of the electrochemical and spectroelectrochemical behavior of thin films of TTF over a glassy carbon electrode in iodide media, a new, more complete mechanism for the electrode processes involved is proposed. The voltammetric and chronoamperometric results for the films can be explained in light of a recently developed nucleation-growth model involving a layer-by-layer mechanism. Also, their in situ UV-vis spectral data expand the available knowledge about the overall mechanism and the nature of the compound formed over the glassy carbon electrode. PMID:19366229

  13. Nucleation and growth of thin films of the organic conductor TTF-iodide over glassy carbon. Electrochemical and spectroelectrochemical study.

    PubMed

    Gómez, L; Rodríguez-Amaro, R

    2009-04-21

    On the basis of the electrochemical and spectroelectrochemical behavior of thin films of TTF over a glassy carbon electrode in iodide media, a new, more complete mechanism for the electrode processes involved is proposed. The voltammetric and chronoamperometric results for the films can be explained in light of a recently developed nucleation-growth model involving a layer-by-layer mechanism. Also, their in situ UV-vis spectral data expand the available knowledge about the overall mechanism and the nature of the compound formed over the glassy carbon electrode.

  14. Electrochemical study of functionalization on the surface of a chitin/platinum-modified glassy carbon paste electrode.

    PubMed

    Sugawara, Kazuharu; Yugami, Asako; Terui, Norifumi; Kuramitz, Hideki

    2009-11-01

    To functionalize chitin surfaces using proteins, we developed a glucose oxidase (GOD)-chitin/platinum-modified glassy carbon paste electrode (GCPE) as a model. In a weakly acidic solution, negatively charged GOD were immobilized by the protonated acetylamide groups on chitin. When the electrode was immersed in a solution containing GOD, the enzyme was readily immobilized due to the electrostatic interaction. In addition, measurements were performed using electrodes made with powders of different sizes because sensor performance depends on the particle sizes of glassy carbon powder. PMID:19907096

  15. Creep Resistant Zinc Alloy

    SciTech Connect

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  16. Mechanochemical investigation of a glassy epoxy-amine thermoset subjected to fatigue

    NASA Astrophysics Data System (ADS)

    Foster, Stephen Finley

    Covalent bonds in organic molecules can be produced, altered, and broken through various sources of energy and processes. These include photochemical, thermochemical, chemical, and mechanochemical processes. Polymeric materials derive their physical properties from the time scale of motion, summation of intermolecular forces, and number of chain entanglements and crosslinks. Glassy thermoset polymers experience mechanical fatigue during dynamic stress loading and properties diminish with inevitable material failure at stress levels below the ultimate tensile strength (UTS). Damage modeling has been successful in predicting the number of cycles required to induce failure in a specimen due to stress. However, it does not directly provide an explanation of the origin of fatigue in polymers. It is hypothesized herein that mechanical failure at stress levels below the ultimate strength property is due to the accumulation of mechanically induced homolytic chain scission events throughout the glassy thermoset network. The goal of this research will be to quantify homolytic chain scission events with fatigue cycles with the ultimate goal of correlating mechanical property loss with degradation of covalent network structure. To accomplish this goal, stable free nitroxyl radicals were incorporated into an epoxy-amine matrix to detect homolytic chain scission resulting from fatigue. Chapter II discusses a successful synthesis and characterization of the nitroxyl radical molecule, a product of 4-hydroxy-2,2,5,5-tetramethylpiperdin-1-yl-oxyl (TEMPO) and isophorone diisocyanate designated as BT-IPDI. In Chapter III, the epoxy-amine reaction was determined to be unaffected by incorporation of up to 5 wt% of BT-IPDI. Although 50% UTS fatigue studies produced property degradation and fatigue failure as shown in Chapter IV, analysis of BT-IPDI through EPR did not detect homolytic chain scission. Chapter V reveals that mechano-radicals were produced from cryo-grinding the glassy

  17. Weldability of High Alloys

    SciTech Connect

    Maroef, I

    2003-01-22

    The purpose of this study was to investigate the effect of silicon and iron on the weldability of HAYNES HR-160{reg_sign} alloy. HR-I60 alloy is a solid solution strengthened Ni-Co-Cr-Si alloy. The alloy is designed to resist corrosion in sulfidizing and other aggressive high temperature environments. Silicon is added ({approx}2.75%) to promote the formation of a protective oxide scale in environments with low oxygen activity. HR-160 alloy has found applications in waste incinerators, calciners, pulp and paper recovery boilers, coal gasification systems, and fluidized bed combustion systems. HR-160 alloy has been successfully used in a wide range of welded applications. However, the alloy can be susceptible to solidification cracking under conditions of severe restraint. A previous study by DuPont, et al. [1] showed that silicon promoted solidification cracking in the commercial alloy. In earlier work conducted at Haynes, and also from published work by DuPont et al., it was recognized that silicon segregates to the terminal liquid, creating low melting point liquid films on solidification grain boundaries. Solidification cracking has been encountered when using the alloy as a weld overlay on steel, and when joining HR-160 plate in a thickness greater than19 millimeters (0.75 inches) with matching filler metal. The effect of silicon on the weldability of HR-160 alloy has been well documented, but the effect of iron is not well understood. Prior experience at Haynes has indicated that iron may be detrimental to the solidification cracking resistance of the alloy. Iron does not segregate to the terminal solidification product in nickel-base alloys, as does silicon [2], but iron may have an indirect or interactive influence on weldability. A set of alloys covering a range of silicon and iron contents was prepared and characterized to better understand the welding metallurgy of HR-160 alloy.

  18. Modelling and theories of alloy phase behavior

    SciTech Connect

    Watson, R.E.; Davenport, J.W.; Weinert, M.; Bennett, L.H.

    1987-01-01

    Many trends in alloy phase formation are readily understood in terms of physically plausible atomic parameters. This has led to the introduction of structural maps where two (or more) such atomic parameters are employed as the coordinates and well-defined regions are observed to be associated with particular crystalline phases. These coordinates sometimes involve the difference in atomic parameters and sometimes involve an average. An alternative approach to the emphasis on atomic parameters has been the consideration of how atoms are packed in some crystal structure and how this controls what the constituent atoms may be. Recently this has led to the utilization of Wigner-Seitz (sometimes called Voronoi or Dirichlet) constructs of the atomic cells in a crystal structure and to the observation that sometimes two crystals which are nominally considered to have the same crystal structure according to normal crystallographic designation should be considered to be different. The Wigner-Seitz cell constructs have also offered a framework for understanding trends in the magnetic and chemical properties of particular phases as well as making coordination between crystalline and glassy structures. Neither of the above approaches provides numerical estimates of quantities of thermodynamic interest such as heats of formation. Such heats are being calculated. 42 refs., 15 figs.

  19. Alloying of aluminum-beryllium alloys

    NASA Astrophysics Data System (ADS)

    Molchanova, L. V.; Ilyushin, V. N.

    2013-01-01

    The existing phase diagrams of Al-Be- X alloys, where X is an alloying element, are analyzed. Element X is noted to poorly dissolve in both aluminum and beryllium. It is shown that the absence of intermetallic compounds in the Al-Be system affects the phase equilibria in an Al-Be- X system. Possible phase equilibria involving phases based on aluminum, beryllium, and intermetallic compounds are proposed, and the types of strengthening of Al-Be alloys by an addition of a third element are classified.

  20. Rapidly solidified surface melts of Ni-B-Si-Cr brazing alloy

    NASA Astrophysics Data System (ADS)

    Tucker, T. R.; Ayers, J. D.

    1981-10-01

    Sintered powder layers of a Ni-based brazing alloy were consolidated by scanned electron beam radiation to produce a continuous fused coating. The surface of this coating was then remelted by laser and electron beams under differing conditions, resulting in a variety of resolidification structures. Alloy BNi2 was chosen for these studies because it exhibits substantial hardening on grain refinement and because it can be prepared in the glassy state relatively easily. Surface microhardness for BNi2 reaches a maximum of about 1200 DPH at a cooling rate approaching 105 K/s. For higher quench rates, hardness decreases and ductility increases. As the cooling rate approaches 107 k/s, overlapping beam scans produce an extended amorphous surface. A solidification rate higher than that needed to produce an amorphous structure in a single melt pass is necessary to avoid surface cracking or crystallization when overlapping melt passes are employed.

  1. Development of a novel high-entropy alloy with eminent efficiency of degrading azo dye solutions

    NASA Astrophysics Data System (ADS)

    Lv, Z. Y.; Liu, X. J.; Jia, B.; Wang, H.; Wu, Y.; Lu, Z. P.

    2016-09-01

    In addition to its scientific importance, the degradation of azo dyes is of practical significance from the perspective of environmental protection. Although encouraging progress has been made on developing degradation approaches and materials, it is still challenging to fully resolve this long-standing problem. Herein, we report that high entropy alloys, which have been emerging as a new class of metallic materials in the last decade, have excellent performance in degradation of azo dyes. In particular, the newly developed AlCoCrTiZn high-entropy alloy synthesized by mechanical alloying exhibits a prominent efficiency in degradation of the azo dye (Direct Blue 6: DB6), as high as that of the best metallic glass reported so far. The newly developed AlCoCrTiZn HEA powder has low activation energy barrier, i.e., 30 kJ/mol, for the degrading reaction and thus make the occurrence of reaction easier as compared with other materials such as the glassy Fe-based powders. The excellent capability of our high-entropy alloys in degrading azo dye is attributed to their unique atomic structure with severe lattice distortion, chemical composition effect, residual stress and high specific surface area. Our findings have important implications in developing novel high-entropy alloys for functional applications as catalyst materials.

  2. Development of a novel high-entropy alloy with eminent efficiency of degrading azo dye solutions

    PubMed Central

    Lv, Z. Y.; Liu, X. J.; Jia, B.; Wang, H.; Wu, Y.; Lu, Z. P.

    2016-01-01

    In addition to its scientific importance, the degradation of azo dyes is of practical significance from the perspective of environmental protection. Although encouraging progress has been made on developing degradation approaches and materials, it is still challenging to fully resolve this long-standing problem. Herein, we report that high entropy alloys, which have been emerging as a new class of metallic materials in the last decade, have excellent performance in degradation of azo dyes. In particular, the newly developed AlCoCrTiZn high-entropy alloy synthesized by mechanical alloying exhibits a prominent efficiency in degradation of the azo dye (Direct Blue 6: DB6), as high as that of the best metallic glass reported so far. The newly developed AlCoCrTiZn HEA powder has low activation energy barrier, i.e., 30 kJ/mol, for the degrading reaction and thus make the occurrence of reaction easier as compared with other materials such as the glassy Fe-based powders. The excellent capability of our high-entropy alloys in degrading azo dye is attributed to their unique atomic structure with severe lattice distortion, chemical composition effect, residual stress and high specific surface area. Our findings have important implications in developing novel high-entropy alloys for functional applications as catalyst materials. PMID:27677462

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Electrical and thermal conductivities of rapidly crystallized Cu-Zr alloys: The effect of anharmonicity

    NASA Astrophysics Data System (ADS)

    Uporov, S.; Bykov, V.; Estemirova, S.

    2016-10-01

    We present a comprehensive study of electrical and thermal conductivities, specific heat and magnetic susceptibility of rapidly crystallized Cu100-xZrx (x = 20-90) alloys. X-ray diffraction analysis has revealed that all the prepared compositions had strongly textured and distorted crystal structures. Different monoclinic and other non-equilibrium phases were detected in the case of glass-forming samples, whereas the alloys without a tendency to form glassy state show almost equilibrium phase content. Metallic type of electrical conductivity and the Kondo anomaly were observed for all the examined samples. It was found that the electrical resistance data cannot be adequately described within the standard Bloch-Grüneisen theory. We use the Debye characteristic temperature as a linear function to fit the electrical conductivity accurately. The composition dependence of the electron density of states at the Fermi level (DOS) has been extracted from room temperature magnetic susceptibility. We found that the glass-forming alloys are characterized by abnormally large values of DOS, which are comparable to those of glassy analogues. Noticeable anharmonic contribution in total specific heat has been revealed for all the studied compositions. In order to estimate the effect of anharmonicity in the system under consideration, we analyzed composition and temperature dependencies of the studied thermal characteristics related to the Grüneisen coefficient. Basing on the results obtained in this study we propose a phenomenological concept to explain abnormal behavior of physical properties of glass-forming Cu-Zr alloys within the standard solid state theory taking into account anharmonic effects.

  5. Glassy-winged sharpshooter Microbiota explored using deep 16S rRNA sequencing from individual insects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce’s disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where ...

  6. Exploring glassy-winged sharpshooter microbiota using deep 16S rRNA sequencing from individual insects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce’s disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where ...

  7. The Role of Olfactory Cues in Host-Plant Selection by the Glassy-Winged Sharpshooter, Homalodisca coagulata

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS) is a highly polyphagous and mobile vector of Pierce's disease of grapes. Trap captures in a multi-crop agricultural landscape under constant deficit irrigation suggest that adult GWSS movement is tied to irrigation schedules. To understand the observed patterns...

  8. Electrografting of 3-Aminopropyltriethoxysilane on a Glassy Carbon Electrode for the Improved Adhesion of Vertically Oriented Mesoporous Silica Thin Films.

    PubMed

    Nasir, Tauqir; Zhang, Lin; Vilà, Neus; Herzog, Grégoire; Walcarius, Alain

    2016-05-01

    Vertically oriented mesoporous silica has proven to be of interest for applications in a variety of fields (e.g., electroanalysis, energy, and nanotechnology). Although glassy carbon is widely used as an electrode material, the adherence of silica deposits is rather poor, causing mechanical instability. A solution to improve the adhesion of mesoporous silica films onto glassy carbon electrodes without compromising the vertical orientation and the order of the mesopores will greatly contribute to the use of this kind of modified carbon electrode. We propose here the electrografting of 3-aminopropyltriethoxysilane on glassy carbon as a molecular glue to improve the mechanical stability of the silica film on the electrode surface without disturbing the vertical orientation and the order of the mesoporous silica obtained by electrochemically assisted self-assembly. These findings are supported by a series of surface chemistry techniques such as X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and cyclic voltammetry. Finally, methylviologen was used as a model redox probe to investigate the cathodic potential region of both glassy carbon and indium tin oxide electrodes modified with mesoporous silica in order to demonstrate further the interest in the approach developed here. PMID:27065214

  9. Effect of host plant fertilization on the developmental biology and feeding preference of the glassy-winged sharpshooter.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The main objective of this research was to evaluate the effect of host plant fertilization on the survival, immature development, adult fecundity, and the feeding of the glassy-winged sharpshooter (GWSS), a primary vector of Xylella fastidiosa (Xf). The development biology of GWSS was studied on co...

  10. Salivary Secretions of the Glassy-winged Sharpshooter, Homalodisca vitripennis: Novel Method of Collection and Protein Profile

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter, Homalodisca vitripennis Takiya (Hemiptera: Cicadellidae) is a xylophagous leafhopper that efficiently transmits Xylella fastidiosa, causative agent of a variety of scorch diseases such as Pierce’s Disease of grapes. The transmission mechanism of X. fastidiosa by the ...

  11. Evaluation of a method to quantify glassy-winged sharpshooter (Hemiptera: Cicadellidae) egg maturation during a feeding assay

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methods to improve an assay relating adult feeding to egg maturation by the glassy-winged sharpshooter (Hemiptera: Cicadellidae) were evaluated. The assay consisted of confining adult females to cowpea stems in parafilm enclosures and quantifying adult feeding and egg maturation. Adult feeding was...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  13. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  14. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  15. Low activation ferritic alloys

    DOEpatents

    Gelles, David S.; Ghoniem, Nasr M.; Powell, Roger W.

    1986-01-01

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  16. Low activation ferritic alloys

    DOEpatents

    Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

    1985-02-07

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  17. PLUTONIUM-ZIRCONIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.; Waber, J.T.

    1960-08-30

    A series of nuclear reactor fuel alloys consisting of from about 5 to about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance plutonium, and having the structural composition of a plutonium are described. Zirconium is a satisfactory diluent because it alloys readily with plutonium and has desirable nuclear properties. Additional advantages are corrosion resistance, excellent fabrication propenties, an isotropie structure, and initial softness.

  18. Polymorphic ethyl alcohol as a model system for the quantitative study of glassy behavior

    NASA Astrophysics Data System (ADS)

    Fischer, H. E.; Bermejo, F. J.; Fayos, R.; Dawidowski, J.; Ramos, M. A.; Vieira, S.; Schober, H.; González, M. A.

    1997-02-01

    We have performed neutron diffraction experiments as well as neutron time-of-flight (TOF) and low-temperature specific heat ( Cp) measurements, on both hydrogenated and deuterated ethanol as functions of temperature. Ethanol appears to be unique in its ability to form a rotator-phase crystal and an orientational glass in the same temperature range where the amorphous phase can be produced. We find that these two orientationally disordered crystal phases have structures and dynamics which are very similar to those of the amorphous phase at the same temperature. These are therefore glassy systems which, due to the presence of an underlying lattice and a stoichiometry identical to the amorphous phase, are ideal for quantitative study.

  19. Characterization of anomalous movements of spherical living cells on a silicon dioxide glassy substrate

    PubMed Central

    Son, Myeonggu; Lee, Gyudo; Son, Jongsang; Choi, Seungyeop; Kim, Youngho; Lee, Sei-Young; Yoon, Young-Ro; Yoon, Dae Sung; Lee, Sang Woo

    2015-01-01

    The random walk of spherical living cells on a silicon dioxide glassy substrate was studied experimentally and numerically. This random walk trajectory exhibited erratic dancing, which seemingly obeyed anomalous diffusion (i.e., Lévy-like walk) rather than normal diffusion. Moreover, the angular distribution (−π to π) of the cells' trajectory followed a “U-shaped pattern” in comparison to the uniform distribution seen in the movements of negatively charged polystyrene microspheres. These effects could be attributable to the homeostasis-driven structural resilient character of cells and physical interactions derived from temporarily retained nonspecific binding due to weak forces between the cells and substrates. Our results provide new insights into the stochastic behavior of mesoscopic biological particles with respect to structural properties and physical interactions. PMID:25610514

  20. Amperometric biosensor based on glassy carbon electrode modified with long-length carbon nanotube and enzyme

    NASA Astrophysics Data System (ADS)

    Furutaka, Hajime; Nemoto, Kentaro; Inoue, Yuki; Hidaka, Hiroki; Muguruma, Hitoshi; Inoue, Hitoshi; Ohsawa, Tatsuya

    2016-05-01

    An amperometric biosensor based on a glassy carbon electrode modified with long-length multiwalled carbon nanotubes (MWCNTs) and enzyme nicotinamide-adenine-dinucleotide-dependent glucose dehydrogenase (GDH) is presented. We demonstrate the effect of the MWCNT length on the amperometric response of the enzyme biosensor. The long length of MWCNT is 200 µm (average), whereas the normal length of MWCNT is 1 µm (average). The response of the long MWCNT–GDH electrode is 2 times more sensitive than that of the normal-length MWCNT–GDH electrode in the concentration range from 0.25–35 mM. The result of electrochemical impedance spectroscopy measurements suggest that the long-length MWCNT–GDH electrode formed a better electron transfer network than the normal-length one.

  1. Voltammetric Determination of Flunixin on Molecularly Imprinted Polypyrrole Modified Glassy Carbon Electrode

    PubMed Central

    Radi, Abd-Elgawad; Abd El-Ghany, Nadia; Wahdan, Tarek

    2016-01-01

    A novel electrochemical sensing approach, based on electropolymerization of a molecularly imprinted polypyrrole (MIPpy) film onto a glassy carbon electrode (GCE) surface, was developed for the detection of flunixin (FXN). The sensing conditions and the performance of the constructed sensor were assessed by cyclic, differential pulse and (DPV) square wave voltammetry (SWV). The sensor exhibited high sensitivity, with linear responses in the range of 5.0 to 50.0 µM with detection limits of 1.5 and 1.0 µM for DPV and SWV, respectively. In addition, the sensor showed high selectivity towards FXN in comparison to other interferents. The sensor was successfully utilized for the direct determination of FXN in buffalo raw milk samples. PMID:27242945

  2. Electrocatalytic determination of paraquat using a nafion film coated glassy carbon electrode.

    PubMed

    Lu, T H; Sun, I W

    2000-11-01

    A nafion film coated glassy carbon electrode (NFGCE) was employed for the determination of paraquat. Paraquat was accumulated onto NFGCE by the cation-exchange feature of nafion at open circuit potential in basic medium followed by cathodic differential pulse voltammetric (CDPV) determination in a medium containing permanganate ions. The sensitivity for the determination of paraquat was improved through the electrocatalytic reduction of permanganate by the reduced paraquat. With 3-min accumulation, the analytical signal versus concentration dependence was linear from 1.0 to 100 ppb with a detection limit of 0.5 ppb. The interference from common metal ions was minimized by addition of ethylenediaminetetraacetate (EDTA) into the sample solution. The use of nafion also improves the resistance to interference from surfactants.

  3. Oxygen determination in organic fluorine compounds by means of a glassy-carbon pyrolysis tube.

    PubMed

    Imaeda, K; Kuriki, T; Ohsawa, K

    1977-07-01

    A conventional apparatus for determination of oxygen in organic compounds has been improved for application to organic fluorine compounds. A feature of the apparatus is the use of a pyrolysis tube made of glassy carbon instead of quartz, which eliminates effects due to hydrogen fluoride produced in pyrolysis of the sample. Ten analyses of dexamethasone with the apparatus gave a mean value of 20.44% for oxygen (theory, 20.38%), with a standard deviation of 0.16%. Oxygen in 9 organic fluorine compounds was accurately determined by using the apparatus, with an average error of +0.1%. One analysis by a gravimetric or a coulometric method took about 40 or 25 min, respectively.

  4. Synthesis of One-Dimensional SiC Nanostructures from a Glassy Buckypaper

    SciTech Connect

    Ding, Mengning; Star, Alexander

    2013-02-21

    A simple and scalable synthetic strategy was developed for the fabrication of one-dimensional SiC nanostructures - nanorods and nanowires. Thin sheets of single-walled carbon nanotubes (SWNTs) were prepared by vacuum filtration and were washed repeatedly with sodium silicate (Na₂SiO₃) solution. The resulting “glassy buckypaper” was heated at 1300 - 1500 °C under Ar/H₂ to allow a solid state reaction between C and Si precursors to form a variety of SiC nanostructures. The morphology and crystal structures of SiC nanorods and nanowires were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive xray spectroscopy (EDX), electron diffraction (ED) and x-ray diffraction (XRD) techniques. Furthermore, electrical conductance measurements were performed on SiC nanorods, demonstrating their potential applications in high-temperature sensors and control systems.

  5. Amperometric biosensor based on glassy carbon electrode modified with long-length carbon nanotube and enzyme

    NASA Astrophysics Data System (ADS)

    Furutaka, Hajime; Nemoto, Kentaro; Inoue, Yuki; Hidaka, Hiroki; Muguruma, Hitoshi; Inoue, Hitoshi; Ohsawa, Tatsuya

    2016-05-01

    An amperometric biosensor based on a glassy carbon electrode modified with long-length multiwalled carbon nanotubes (MWCNTs) and enzyme nicotinamide-adenine-dinucleotide-dependent glucose dehydrogenase (GDH) is presented. We demonstrate the effect of the MWCNT length on the amperometric response of the enzyme biosensor. The long length of MWCNT is 200 µm (average), whereas the normal length of MWCNT is 1 µm (average). The response of the long MWCNT-GDH electrode is 2 times more sensitive than that of the normal-length MWCNT-GDH electrode in the concentration range from 0.25-35 mM. The result of electrochemical impedance spectroscopy measurements suggest that the long-length MWCNT-GDH electrode formed a better electron transfer network than the normal-length one.

  6. Energy barriers, entropy barriers, and non-Arrhenius behavior in a minimal glassy model.

    PubMed

    Du, Xin; Weeks, Eric R

    2016-06-01

    We study glassy dynamics using a simulation of three soft Brownian particles confined to a two-dimensional circular region. If the circular region is large, the disks freely rearrange, but rearrangements are rarer for smaller system sizes. We directly measure a one-dimensional free-energy landscape characterizing the dynamics. This landscape has two local minima corresponding to the two distinct disk configurations, separated by a free-energy barrier that governs the rearrangement rate. We study several different interaction potentials and demonstrate that the free-energy barrier is composed of a potential-energy barrier and an entropic barrier. The heights of both of these barriers depend on temperature and system size, demonstrating how non-Arrhenius behavior can arise close to the glass transition. PMID:27415326

  7. Toward the Control of the Creation of Mixed Monolayers on Glassy Carbon Surfaces by Amine Oxidation.

    PubMed

    Groppi, Jessica; Bartlett, Philip N; Kilburn, Jeremy D

    2016-01-18

    A versatile and simple methodology for the creation of mixed monolayers on glassy carbon (GC) surfaces was developed, using an osmium-bipyridyl complex and anthraquinone as model redox probes. The work consisted in the electrochemical grafting on GC of a mixture of mono-protected diamine linkers in varying ratios which, after attachment to the surface, allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to remove one of the protecting groups selectively, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the resulting surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution.

  8. Electrochemistry of raloxifene on glassy carbon electrode and its determination in pharmaceutical formulations and human plasma.

    PubMed

    Bagheri, Akbar; Hosseini, Hadi

    2012-12-01

    The electrochemical behavior of raloxifene (RLX) on the surface of a glassy carbon electrode (GCE) has been studied by cyclic voltammetry (CV). The CV studies were performed in various supporting electrolytes, wide range of potential scan rates, and pHs. The results showed an adsorption-controlled and quasi-reversible process for the electrochemical reaction of RLX, and a probable redox mechanism was suggested. Under the optimum conditions, differential pulse voltammetry (DPV) was applied for quantitative determination of the RLX in pharmaceutical formulations. The DPV measurements showed that the anodic peak current of the RLX was linear to its concentration in the range of 0.2-50.0μM with a detection limit of 0.0750μM, relative standard deviation (RSD %) below 3.0%, and a good sensitivity. The proposed method was successfully applied for determination of the RLX in pharmaceutical and human plasma samples with a good selectivity and suitable recovery.

  9. Glassy phases and driven response of the phase-field-crystal model with random pinning.

    PubMed

    Granato, E; Ramos, J A P; Achim, C V; Lehikoinen, J; Ying, S C; Ala-Nissila, T; Elder, K R

    2011-09-01

    We study the structural correlations and the nonlinear response to a driving force of a two-dimensional phase-field-crystal model with random pinning. The model provides an effective continuous description of lattice systems in the presence of disordered external pinning centers, allowing for both elastic and plastic deformations. We find that the phase-field crystal with disorder assumes an amorphous glassy ground state, with only short-ranged positional and orientational correlations, even in the limit of weak disorder. Under increasing driving force, the pinned amorphous-glass phase evolves into a moving plastic-flow phase and then, finally, a moving smectic phase. The transverse response of the moving smectic phase shows a vanishing transverse critical force for increasing system sizes. PMID:22060323

  10. NMR evidence for inhomogeneous glassy behavior driven by nematic fluctuations in iron arsenide superconductors

    DOE PAGESBeta

    Dioguardi, A. P.; Lawson, M. M.; Bush, B. T.; Crocker, J.; Shirer, K. R.; Nisson, D. M.; Kissikov, T.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.; et al

    2015-10-16

    We present 75As nuclear magnetic resonance spin-lattice and spin-spin relaxation rate data in Ba(Fe1–xCox)2As2 and Ba(Fe1–xCux)2As2 as a function of temperature, doping, and magnetic field. The relaxation curves exhibit a broad distribution of relaxation rates, consistent with inhomogeneous glassy behavior up to 100 K. The doping and temperature response of the width of the dynamical heterogeneity is similar to that of the nematic susceptibility measured by elastoresistance measurements. In this study, we argue that quenched random fields which couple to the nematic order give rise to a nematic glass that is reflected in the spin dynamics.

  11. NMR evidence for inhomogeneous glassy behavior driven by nematic fluctuations in iron arsenide superconductors

    SciTech Connect

    Dioguardi, A. P.; Lawson, M. M.; Bush, B. T.; Crocker, J.; Shirer, K. R.; Nisson, D. M.; Kissikov, T.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.; Yuan, S.; Kuhns, P. L.; Reyes, A. P.; Grafe, H. -J.; Curro, N. J.

    2015-10-16

    We present 75As nuclear magnetic resonance spin-lattice and spin-spin relaxation rate data in Ba(Fe1–xCox)2As2 and Ba(Fe1–xCux)2As2 as a function of temperature, doping, and magnetic field. The relaxation curves exhibit a broad distribution of relaxation rates, consistent with inhomogeneous glassy behavior up to 100 K. The doping and temperature response of the width of the dynamical heterogeneity is similar to that of the nematic susceptibility measured by elastoresistance measurements. In this study, we argue that quenched random fields which couple to the nematic order give rise to a nematic glass that is reflected in the spin dynamics.

  12. Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects

    NASA Astrophysics Data System (ADS)

    Eisenbach, A.; Havdala, T.; Delahaye, J.; Grenet, T.; Amir, A.; Frydman, A.

    2016-09-01

    Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state.

  13. Amperometric sensing of hydrogen peroxide using glassy carbon electrode modified with copper nanoparticles

    SciTech Connect

    Sophia, J.; Muralidharan, G.

    2015-10-15

    In this paper, fabrication of glassy carbon electrode (GCE) modified with nano copper particles is discussed. The modified electrode has been tested for the non-enzymatic electrochemical detection of hydrogen peroxide (H{sub 2}O{sub 2}). The copper nanoparticles (Cu NPs) were prepared employing a simple chemical reduction method. The presence of Cu NPs was confirmed through UV–visible (UV–vis) absorption spectroscopy and X-ray diffraction (XRD) analysis. The size and morphology of the particles were investigated using transmission electron microscopy (TEM). The electrochemical properties of the fabricated sensor were studied via cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The electrochemical sensor displayed excellent performance features towards H{sub 2}O{sub 2} detection exhibiting wide linear range, low detection limit, swift response time, good reproducibility and stability.

  14. Thermomechanical processing of metallic glasses: extending the range of the glassy state

    NASA Astrophysics Data System (ADS)

    Sun, Yonghao; Concustell, Amadeu; Greer, A. Lindsay

    2016-09-01

    For crystalline metals, the science, technology and application of thermomechanical processing are established, but this is not true for glasses. Metallic glasses — because they can be plastically deformed — offer a unique opportunity to study the effects of thermomechanical treatments on the structure and properties of glasses. Depending on the rate of cooling, various glassy states can form from a liquid. Slower cooling gives states of lower enthalpy and smaller volume; such states might also be reached by annealing, which induces structural ‘relaxation’. A reduction in the degree of relaxation, or ‘rejuvenation’, is achievable through processes such as irradiation and mechanical deformation. In this Review, we explore the extent of relaxation and rejuvenation induced by thermomechanical processing (that is, elastic and plastic deformation, including cold and hot working, and cyclic loading). The issues that remain to be investigated and the prospects for further progress are discussed.

  15. Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects.

    PubMed

    Eisenbach, A; Havdala, T; Delahaye, J; Grenet, T; Amir, A; Frydman, A

    2016-09-01

    Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state. PMID:27661707

  16. Molecular motions in supercooled and glassy ibuprofen: deuteron magnetic resonance and high-resolution rheology study.

    PubMed

    Bauer, S; Storek, M; Gainaru, C; Zimmermann, H; Böhmer, R

    2015-04-16

    Using deuteron nuclear magnetic resonance, the molecular motions of specifically isotope-labeled ibuprofen were probed at the carboxylic group and at the methin group next to it. Spin relaxometry revealed slight differences between the molecular motions of the two isotopomers that are rationalized with reference to the hydrogen bonding of the COOH moiety. In the glassy state, a small-angle jump process among about four sites, related to the so-called γ-process, was identified using stimulated-echo spectroscopy. Indications for a Debye-like process, previously found to leave a weak signature in the dielectric loss, could not unambiguously be detected in magnetic resonance or shear mechanical experiments carried out for supercooled liquid ibuprofen.

  17. Determination of trimebutine in pharmaceuticals by differential pulse voltammetry at a glassy carbon electrode.

    PubMed

    Adhoum, Nafaâ; Monser, Lotfi

    2005-07-15

    The differential pulse voltammetric (DPV) determination of trimebutine (TMB) was achieved at a glassy carbon electrode in acetonitrile/0.1 M LiClO4. Trimebutine gave two irreversible, diffusion controlled peaks at 740 and 1318 mV versus Ag/AgCl reference electrode, respectively. The second oxidation peak was used to determine trimebutine concentrations in the range 1-50 microg ml(-1) with a detection limit (3sigmam) of 0.3 microg ml(-1). Precision of the method (RSD, n=6) within- and between-days obtained from six determinations at 5 microg ml(-1) was found to be 0.7 and 1.1%, respectively. The method was successfully applied to the quantitation of TMB in granule dosage form (Debridat) and recoveries between 98.4 and 101% were obtained. Excipients did not interfere with the assay and the results agreed well with those determined by previously established HPLC method. PMID:15967289

  18. Glassy behavior in a one-dimensional continuous-wave erbium-doped random fiber laser

    NASA Astrophysics Data System (ADS)

    Gomes, Anderson S. L.; Lima, Bismarck C.; Pincheira, Pablo I. R.; Moura, André L.; Gagné, Mathieu; Raposo, Ernesto P.; de Araújo, Cid B.; Kashyap, Raman

    2016-07-01

    The photonic analog of the paramagnetic to spin-glass phase transition in disordered magnetic systems, signaled by the phenomenon of replica symmetry breaking, has been reported using random lasers as the photonic platform. We report here a demonstration of replica symmetry breaking in a one-dimensional photonic system consisting of an erbium-doped random fiber laser operating in the continuous-wave regime. The system is based on a unique random fiber grating system which plays the role of random scattering, providing the disordered feedback mechanism. The clear transition from a photonic paramagnetic to a photonic spin-glass phase, characterized by the Parisi overlap parameter, was verified and indicates the glassy random-fiber-laser behavior.

  19. Toward the Control of the Creation of Mixed Monolayers on Glassy Carbon Surfaces by Amine Oxidation.

    PubMed

    Groppi, Jessica; Bartlett, Philip N; Kilburn, Jeremy D

    2016-01-18

    A versatile and simple methodology for the creation of mixed monolayers on glassy carbon (GC) surfaces was developed, using an osmium-bipyridyl complex and anthraquinone as model redox probes. The work consisted in the electrochemical grafting on GC of a mixture of mono-protected diamine linkers in varying ratios which, after attachment to the surface, allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to remove one of the protecting groups selectively, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the resulting surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution. PMID:26637108

  20. Survival of Staphylococcus aureus and enterotoxin A in glassy and rubbery states of gelatin.

    PubMed

    Bolton, K J; Dodd, C E; Gould, G W; Waites, W M

    1996-08-01

    About 1% of Staphylococcus aureus cells survived the production of gelatin sheets containing nutrient broth. Those cells which survived showed no evidence of injury. Growth occurred in rubbery state gelatin with a(w) values of 0.98 and 0.93 ; viability decreased during storage at a(w) values of 0.89, 0.62 and 0.36 but there was little loss of viability in gelatin at an aw of 0.25 over 27 d storage at 26 degrees C. Assays for enterotoxin A detected no synthesis of new toxin but no loss in pre-formed toxin. The results suggest that high levels of Staph. aureus and its toxins should be excluded from glassy and rubbery state food products in order to prevent illness. PMID:8760328

  1. Can Stress Relaxation Experiments be Used to Assess Deformation Induced Mobility in Glassy Polymers?

    NASA Astrophysics Data System (ADS)

    Kropka, Jamie; Long, Kevin

    The observance of an increase in glassy polymer relaxation rates under a mechanical deformation is often referred to as deformation induced mobility (DIM). It has been argued that stress relaxation experiments can provide indirect evidence of this phenomenon. Recently, stress relaxation experiments have been interpreted as demonstrating a mobility decrease with increased deformation when very slow strain rates, 1.2 x 10-5 s-1, are used to apply the deformation. This would suggest against generality of DIM and would have significant implications to constitutive models founded on this principle. Here, a mathematical exercise is performed to evaluate the implications of DIM on stress relaxation response. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  2. Electrochemical Determination of Glycoalkaloids Using a Carbon Nanotubes-Phenylboronic Acid Modified Glassy Carbon Electrode

    PubMed Central

    Wang, Huiying; Liu, Mingyue; Hu, Xinxi; Li, Mei; Xiong, Xingyao

    2013-01-01

    A versatile strategy for electrochemical determination of glycoalkaloids (GAs) was developed by using a carbon nanotubes-phenylboronic acid (CNTs-PBA) modified glassy carbon electrode. PBA reacts with α-solanine and α-chaconine to form a cyclic ester, which could be utilized to detect GAs. This method allowed GA detection from 1 μM to 28 μM and the detection limit was 0.3 μM. Affinity interaction of GAs and immobilized PBA caused an essential change of the peak current. The CNT-PBA modified electrodes were sensitive for detection of GAs, and the peak current values were in quite good agreement with those measured by the sensors. PMID:24287539

  3. Glassy phases and driven response of the phase-field-crystal model with random pinning.

    PubMed

    Granato, E; Ramos, J A P; Achim, C V; Lehikoinen, J; Ying, S C; Ala-Nissila, T; Elder, K R

    2011-09-01

    We study the structural correlations and the nonlinear response to a driving force of a two-dimensional phase-field-crystal model with random pinning. The model provides an effective continuous description of lattice systems in the presence of disordered external pinning centers, allowing for both elastic and plastic deformations. We find that the phase-field crystal with disorder assumes an amorphous glassy ground state, with only short-ranged positional and orientational correlations, even in the limit of weak disorder. Under increasing driving force, the pinned amorphous-glass phase evolves into a moving plastic-flow phase and then, finally, a moving smectic phase. The transverse response of the moving smectic phase shows a vanishing transverse critical force for increasing system sizes.

  4. Glassy and Metastable Crystalline BaTi2O5 by Containerless Processing

    NASA Astrophysics Data System (ADS)

    Yoda, Shinichi; Kentei Yu, Yu; Kumar, Vijaya; Kameko, Masashi

    Many efforts have been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic use. The containerless processing is an attractive synthesis tech-nique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable and glassy materials. We have fabricated a new ferroelectric materiel BaTi2 O5 [1] as bulk glass from melt by us-ing containerless processing and studied the phase relationship between microstructure and ferroelectric properties of BaTi2 O5 [2]. The structures of glassy and metastable crystalline BaTi2 O5 fabricated by the containerless pro-cessing were comprehensively investigated by combined X-ray and neutron diffractions, XANES analyses and computer simulations [3]. The 3-dimensional atomic structure of glassy BaTi2 O5 (g-BaTi2 O5 ), simulated by Reverse Monte Carlo (RMC) modelling on diffraction data, shows that extremely distorted TiO5 polyhedra interconnected with both corner-and edge-shared oxy-gen, formed a higher packing density structure than that of conventional silicate glass linked with only corner-sharing of SiO4 polyhedra. In addition, XANES measurement reveales that five-coordinated TiO5 polyhedra were formable in the crystallized metastable a-and b-BaTi2 O5 phases. The structure of metastable b-BaTi2 O5 was solved by ab initio calculation, and refined by Rietveld refinement as group Pnma with unit lattices a = 10.23784 ˚, b = 3.92715 ˚, c A A = 10.92757 A ˚. Our results show that the glass-forming ability enhanced by containerless pro-cessing, not by `strong glass former', fabricated new bulk oxide glasses with peculiar structures and properties. The intermediate-range structure of g-BaTi2 O5 and the crystalline structure of

  5. On the notion of ``1/f noise'' and data analysis for glassy water

    NASA Astrophysics Data System (ADS)

    Johari, G. P.

    2005-07-01

    It is argued that the measured dielectric loss is the sum of a background loss and a dipolar relaxation loss, and both should be considered in a dielectric spectrum analysis. The background loss can be determined by fitting a relaxation function to the spectral peak region. It is also shown that the dielectric loss tangent tanδ of glassy water, which has been rejected as "1/f noise" [A. Minoguchi, R. Richert, and C. A. Angell, Phys. Rev. Lett.93, 215703 (2004)], contains a large contribution from dipole relaxation loss, and its tanδ neither remains constant with change in f nor varies as 1/f. The incorrect attribution of water's tanδ of Minoguchi et al. puts into question the basis of their analysis.

  6. Amperometric determination of phenazopyridine hydrochloride in a flowing stream at the glassy carbon electrode.

    PubMed

    Belal, F

    1985-01-01

    A flow-injection method is described for the determination of phenazopyridine hydrochloride, based on electrochemical oxidation at the glassy carbon electrode. The suggested method is highly specific and can be used to determine phenazopyridine HCl in the presence of most drugs commonly found in pharmaceutical dosage forms or administered therapeutically. Applying a constant potential of +950 mV vs Ag/AgCl/3.5M KCl reference electrode, the calibration curve was linear in the 1-30 micrograms/mL range, with minimum detectability of 0.2 ng (signal-to-noise ratio 2). Good accuracy and precision were obtained when the method was applied to some dosage forms containing phenazopyridine HCl. Although automation was not used in this study, an automated system could be incorporated because the method uses the technique of continuous analysis in a flowing stream.

  7. Characterization of anomalous movements of spherical living cells on a silicon dioxide glassy substrate.

    PubMed

    Son, Myeonggu; Lee, Gyudo; Son, Jongsang; Choi, Seungyeop; Kim, Youngho; Lee, Sei-Young; Yoon, Young-Ro; Yoon, Dae Sung; Lee, Sang Woo

    2015-01-01

    The random walk of spherical living cells on a silicon dioxide glassy substrate was studied experimentally and numerically. This random walk trajectory exhibited erratic dancing, which seemingly obeyed anomalous diffusion (i.e., Lévy-like walk) rather than normal diffusion. Moreover, the angular distribution (-π to π) of the cells' trajectory followed a "U-shaped pattern" in comparison to the uniform distribution seen in the movements of negatively charged polystyrene microspheres. These effects could be attributable to the homeostasis-driven structural resilient character of cells and physical interactions derived from temporarily retained nonspecific binding due to weak forces between the cells and substrates. Our results provide new insights into the stochastic behavior of mesoscopic biological particles with respect to structural properties and physical interactions. PMID:25610514

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

    PubMed

    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

  9. NICKEL-BASE ALLOY

    DOEpatents

    Inouye, H.; Manly, W.D.; Roche, T.K.

    1960-01-19

    A nickel-base alloy was developed which is particularly useful for the containment of molten fluoride salts in reactors. The alloy is resistant to both salt corrosion and oxidation and may be used at temperatures as high as 1800 deg F. Basically, the alloy consists of 15 to 22 wt.% molybdenum, a small amount of carbon, and 6 to 8 wt.% chromium, the balance being nickel. Up to 4 wt.% of tungsten, tantalum, vanadium, or niobium may be added to strengthen the alloy.

  10. Effects of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Feeding, Size, and Lipid Content on Egg Maturation.

    PubMed

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

    2015-06-01

    The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed as an adult to produce eggs. Egg maturation rates depend on the host plant species provided to the adult female for feeding and are variable for females provided with the same host plant species. Here, the contribution of female size and lipid content to variation in egg maturation rates among females held on the same host plant species was assessed. To assess effects of female size and lipid content on egg maturation, feeding assays followed by measurements of egg load, female size, and lipid content were conducted. To accomplish this, females were field collected and held on cowpea until producing approximately 0, 12, 25, or 50 ml of excreta. After reaching prescribed excreta thresholds, females were dissected to determine egg load, hind tibia length, and head capsule width. Mature eggs were removed from the abdomen and dry weight of eggs and bodies (head, thorax, and abdomen) were obtained. Lipid content of eggs and bodies were determined using a quantitative colorimetric assay. Rates of body weight gain and body lipid gain were rapid with low levels of feeding (12 ml of excreta) but decelerated with additional feeding (>12 ml of excreta). In contrast, low levels of feeding (12 ml of excreta) resulted in little egg production, with rates of egg production accelerating with additional feeding (>12 ml of excreta). Accordingly, egg production was preceded by an increase in body dry weight and body lipid content. In agreement, probability that a female carried eggs increased with body lipid content in the 0-, 12-, and 25-ml feeding treatments. Across treatments, larger females carried more eggs than smaller females. Collectively, results suggest that variation in glassy-winged sharpshooter egg maturation rates partially may be explained by availability of lipid reserves at the start of a feeding bout and female size. PMID:26470224

  11. Permeability of Rubbery and Glassy Membranes of Ionic Liquid Filled Polymersome Nanoreactors in Water.

    PubMed

    So, Soonyong; Yao, Letitia J; Lodge, Timothy P

    2015-12-01

    Nanoemulsion-like polymer vesicles (polymersomes) having ionic liquid interiors dispersed in water are attractive for nanoreactor applications. In a previous study, we demonstrated that small molecules could pass through rubbery polybutadiene membranes on a time scale of seconds, which is practical for chemical transformations. It is of interest to determine how sensitive the rate of transport is to temperature, particularly for membranes in the vicinity of the glass transition (Tg). In this work, the molecular exchange rate of 1-butylimidazole through glassy polystyrene (PS) bilayer membranes is investigated via pulsed field gradient nuclear magnetic resonance (PFG-NMR) over the temperature range from 25 to 70 °C. The vesicles were prepared by the cosolvent method in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI]), and four different polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock polymers with varying PS molecular weights were examined. The vesicles were transferred from the ionic liquid to water at room temperature to form nanoemulsion solutions of polymer vesicles in water. The exchange rate of 1-butylimidazole added to the aqueous solutions was observed under equilibrium conditions at each temperature. The exchange rate decreased as the membrane thickness increased, and the exchange rate through the glassy membranes was three to four times slower than through the rubbery polybutadiene membranes under the same experimental conditions. These results demonstrate that the permeability through nanosized membranes depends on both the dimension and chemistry of membrane-forming blocks. Furthermore, the exchange rate was investigated as a function of temperature in the vicinity of the Tg of PS-PEO membranes. The exchange rate, however, is not a strong function of the temperature in the vicinity of the membrane Tg, due to a combination of the nanoscopic dimension of the membrane, and some degree of solvent

  12. Multilevel micro-structuring of glassy carbon molds for precision glass molding

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-09-01

    Replication techniques for diffractive optical elements (DOEs) in soft materials such as plastic injection molding are state of the art. For precision glass molding in glasses with high transition temperatures, molds with extreme thermal resistivity, low chemical reactivity and high mechanical strength are needed. Glassy Carbon can be operated up to 2000°C making it possible to mold almost all glasses including Fused Silica with a transition temperatures above 1060°C. For the structuring of Glassy Carbon wafers photolithography and a RIE process is used. We have developed a process using Si as a hard mask material. If the flow rates of the etching gases O2 and SF6 are chosen properly, high selectivity of GC to Si 19:1 can be achieved, which provides excellent conditions to realize high resolution elements with feature size down to 1 micron and fulfills requirements for optical applications. We fabricated several multilevel GC molds with 8 levels of structuring. Two different optical functionalities were implemented: 6x6 array beamsplitter and 1x4 linear beamsplitter. The molds were applied for precision glass molding of a low Tg glass L-BAL 42 (from Ohara) with a transition temperature of 565°C. Their optical performance was measured. A more detailed analysis of the impact of mold fabrication defects on optical performance is done. Rigorous coupled wave analysis simulations are performed, where we included fabrication constrains such as duty cycle, edge depth errors, wall verticality and misalignment errors. We will compare the results with the design specifications and discuss the influence of fabrication errors introduced during the different process steps.

  13. Permeability of Rubbery and Glassy Membranes of Ionic Liquid Filled Polymersome Nanoreactors in Water.

    PubMed

    So, Soonyong; Yao, Letitia J; Lodge, Timothy P

    2015-12-01

    Nanoemulsion-like polymer vesicles (polymersomes) having ionic liquid interiors dispersed in water are attractive for nanoreactor applications. In a previous study, we demonstrated that small molecules could pass through rubbery polybutadiene membranes on a time scale of seconds, which is practical for chemical transformations. It is of interest to determine how sensitive the rate of transport is to temperature, particularly for membranes in the vicinity of the glass transition (Tg). In this work, the molecular exchange rate of 1-butylimidazole through glassy polystyrene (PS) bilayer membranes is investigated via pulsed field gradient nuclear magnetic resonance (PFG-NMR) over the temperature range from 25 to 70 °C. The vesicles were prepared by the cosolvent method in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI]), and four different polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock polymers with varying PS molecular weights were examined. The vesicles were transferred from the ionic liquid to water at room temperature to form nanoemulsion solutions of polymer vesicles in water. The exchange rate of 1-butylimidazole added to the aqueous solutions was observed under equilibrium conditions at each temperature. The exchange rate decreased as the membrane thickness increased, and the exchange rate through the glassy membranes was three to four times slower than through the rubbery polybutadiene membranes under the same experimental conditions. These results demonstrate that the permeability through nanosized membranes depends on both the dimension and chemistry of membrane-forming blocks. Furthermore, the exchange rate was investigated as a function of temperature in the vicinity of the Tg of PS-PEO membranes. The exchange rate, however, is not a strong function of the temperature in the vicinity of the membrane Tg, due to a combination of the nanoscopic dimension of the membrane, and some degree of solvent

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

    SciTech Connect

    Dang, Nhan Chuong

    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 (Ic); and (3) water confined into poly(2-hydroxyethylmethacrylate) (poly-HEMA). In addition, results of photochemical hole burning (PHB) studies obtained for phthalocyanine tetrasulphonate (PcT) in HGW and free base phthalocyanine (Pc) 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 (Tg). 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/dynamics of water in confined space, which

  15. Effects of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) Feeding, Size, and Lipid Content on Egg Maturation.

    PubMed

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

    2015-06-01

    The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed as an adult to produce eggs. Egg maturation rates depend on the host plant species provided to the adult female for feeding and are variable for females provided with the same host plant species. Here, the contribution of female size and lipid content to variation in egg maturation rates among females held on the same host plant species was assessed. To assess effects of female size and lipid content on egg maturation, feeding assays followed by measurements of egg load, female size, and lipid content were conducted. To accomplish this, females were field collected and held on cowpea until producing approximately 0, 12, 25, or 50 ml of excreta. After reaching prescribed excreta thresholds, females were dissected to determine egg load, hind tibia length, and head capsule width. Mature eggs were removed from the abdomen and dry weight of eggs and bodies (head, thorax, and abdomen) were obtained. Lipid content of eggs and bodies were determined using a quantitative colorimetric assay. Rates of body weight gain and body lipid gain were rapid with low levels of feeding (12 ml of excreta) but decelerated with additional feeding (>12 ml of excreta). In contrast, low levels of feeding (12 ml of excreta) resulted in little egg production, with rates of egg production accelerating with additional feeding (>12 ml of excreta). Accordingly, egg production was preceded by an increase in body dry weight and body lipid content. In agreement, probability that a female carried eggs increased with body lipid content in the 0-, 12-, and 25-ml feeding treatments. Across treatments, larger females carried more eggs than smaller females. Collectively, results suggest that variation in glassy-winged sharpshooter egg maturation rates partially may be explained by availability of lipid reserves at the start of a feeding bout and female size.

  16. Chlorination treatment to improve the oxidation resistance of Nb-Mo-Si-B alloys

    NASA Astrophysics Data System (ADS)

    Behrani, Vikas; Thom, Andrew J.; Kramer, Matthew J.; Akinc, Mufit

    2005-03-01

    Recent studies have shown that the quaternary Nb-Mo-Si-B system is not oxidation resistant. The difference in oxidation resistance between Mo-Si-B and Nb-Mo-Si-B may be interpreted in terms of the volatility of the metal oxide that forms. MoO3 evaporates from the surface scale at about 650 °C, leaving a porous borosilicate glassy scale. Nb2O5 persists as a rapidly growing condensed phase that overwhelms the ability of the borosilicate glass to form a protective layer. In the present work, a novel chlorination process was employed to selectively remove Nb2O5 from the scale of the quaternary alloy as volatile NbCl5. A Nb-Mo-Si-B alloy was studied with a nominal composition of 63(Nb,Mo)-30Si-7B (at. pct) with Nb/Mo = 1:1. The alloy consisted of a three-phase microstructure of (Nb,Mo)5Si3B x (T1)-(Nb,Mo)5(Si,B)3 (T2)-(Nb,Mo)5Si3B x (D88). The oxidation behavior of these alloys in air was studied both before and after chlorination. Results showed that Nb2O5 can be selectively removed from the scale to leave a borosilicate-rich scale, which then forms a dense scale after heat treatment at 1100 °C in argon. The oxidation rate of the chlorinated alloy was about one-third that of the unchlorinated alloy under identical conditions. Alloy oxidation during heating to the test temperature was studied, and a plausible mechanism for the formation of porosity in the oxide scale has been offered.

  17. Copper-tantalum alloy

    DOEpatents

    Schmidt, Frederick A.; Verhoeven, John D.; Gibson, Edwin D.

    1986-07-15

    A tantalum-copper alloy can be made by preparing a consumable electrode consisting of an elongated copper billet containing at least two spaced apart tantalum rods extending longitudinally the length of the billet. The electrode is placed in a dc arc furnace and melted under conditions which co-melt the copper and tantalum to form the alloy.

  18. Cesium iodide alloys

    DOEpatents

    Kim, H.E.; Moorhead, A.J.

    1992-12-15

    A transparent, strong CsI alloy is described having additions of monovalent iodides. Although the preferred iodide is AgI, RbI and CuI additions also contribute to an improved polycrystalline CsI alloy with outstanding multispectral infrared transmittance properties. 6 figs.

  19. Ductile transplutonium metal alloys

    DOEpatents

    Conner, William V.

    1983-01-01

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  20. Nickel base coating alloy

    NASA Technical Reports Server (NTRS)

    Barrett, C. A. (Inventor); Lowell, C. E. (Inventor)

    1986-01-01

    Zirconium is added to a Ni-30 Al (beta) intermetallic alloy in the range of 0.05 w/o to 0.25 w/o. This addition is made during melting or by using metal powders. The addition of zirconium improves the cyclic oxidation resistance of the alloys at temperatures above 1100 C.

  1. PLUTONIUM-CERIUM ALLOY

    DOEpatents

    Coffinberry, A.S.

    1959-01-01

    An alloy is presented for use as a reactor fuel. The binary alloy consists essentially of from about 5 to 90 atomic per cent cerium and the balance being plutonium. A complete phase diagram for the cerium--plutonium system is given.

  2. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  3. Aluminum battery alloys

    DOEpatents

    Thompson, D.S.; Scott, D.H.

    1984-09-28

    Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  4. Aluminum battery alloys

    DOEpatents

    Thompson, David S.; Scott, Darwin H.

    1985-01-01

    Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  5. Ductile transplutonium metal alloys

    DOEpatents

    Conner, W.V.

    1981-10-09

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  6. Elevated Temperature Deformation of Cr3Si Alloyed with Mo

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Whittenberger, J. Daniel; Zeumer, B.; Sauthoff, G.

    1998-01-01

    Four-point bend, constant load compressive creep and constant engineering strain rate tests were conducted on arc-melted and powder-metallurgy (PM) processed Cr40Mo30Si30 specimens in the temperature range 1400 and 1700 K. This is a two phase alloy consisting of (CrMo)3Si and (Cr,Mo)5Si3 phases. The PM specimens, which were substantially weaker than the arc-melted materials, exhibited a stress exponent n, of about 2 and an apparent activation energy for creep, Q(sub 3), of 485 kJ/mol. The mechanism in these specimens appeared to be controlled by creep of a glassy phase. In the case of arc-melted specimens for which nis approximately 3 and Q(sub 3) is approximately 430 kJ/mol, the rate-controlling creep mechanism appeared to be that dominant in the (Cr,Mo)5Si3 phase. In this case, it is suggested that the Nabarro creep mechanism, where dislocation climb is controlled by Bardeen-Herring vacancy sources, is the dominant creep mechanism. Finally, an analysis of the present and literature data on Cr3Si alloyed with Mo appeared to suggest that the creep rate decreases sharply with an increase in the Mo/Si ratio.

  7. Ultrahigh temperature intermetallic alloys

    SciTech Connect

    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.; Walker, L.R.

    1997-12-01

    A new family of Cr-Cr{sub 2}X based alloys with fabricability, mechanical properties, and oxidation resistance superior to previously developed Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys has been identified. The new alloys can be arc-melted/cast without cracking, and exhibit excellent room temperature and high-temperature tensile strengths. Preliminary evaluation of oxidation behavior at 1100 C in air indicates that the new Cr-Cr{sub 2}X based alloys form an adherent chromia-based scale. Under similar conditions, Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys suffer from extensive scale spallation.

  8. Glassy ferromagnetism and magnetic phase separation in La1-xSrxCoO3

    NASA Astrophysics Data System (ADS)

    Wu, J.; Leighton, C.

    2003-05-01

    We present the results of a comprehensive investigation of the dc magnetization, ac susceptibility, and magnetotransport properties of the glassy ferromagnet La1-xSrxCoO3. The compositions studied span the range from the end-member LaCoO3 (x=0.0) through to x=0.7. These materials have attracted attention recently, primarily due to the spin-state transition phenomena in LaCoO3 and the unusual nature of the magnetic ground state for finite x. In this paper we present a consistent picture of the magnetic behavior of La1-xSrxCoO3 in terms of short-range ferromagnetic ordering and intrinsic phase separation. At high Sr doping (x>0.2) the system exhibits unconventional ferromagnetism (with a Curie temperature up to 250 K), which is interpreted in terms of the coalescence of short-range-ordered ferromagnetic clusters. Brillouin function fits to the temperature dependence of the magnetization as well as high-temperature Curie-Weiss behavior suggest that the Co3+ and Co4+ ions are both in the intermediate spin state. At lower Sr doping (x<0.18) the system enters a mixed phase that displays the characteristics of both a spin glass and a ferromagnet. A cusp in the zero-field-cooled dc magnetization, a frequency-dependent peak in the ac susceptibility and time-dependent effects in both dc and ac magnetic properties all point towards glassy behavior. On the other hand, field cooling results in a relatively large ferromagneticlike moment, with zero-field-cooled and field-cooled magnetizations bifurcating at an irreversibility point. Even in the region above x=0.2 the out-of-phase component of the ac susceptibility shows frequency-dependent peaks below the Curie temperature (indicative of glassy behavior) which have previously been interpreted in terms of the freezing of clusters. All of the results are consistent with the existence of a strong tendency towards magnetic phase separation in this material, a conclusion which is further reinforced by consideration of the electronic

  9. IUPAC-NIST Solubility Data Series 70. The Solubility of Gases in Glassy Polymers

    NASA Astrophysics Data System (ADS)

    Paterson, Russell; Yampol'Skii, Yuri P.; Fogg, Peter G. T.; Bokarev, Alexandre; Bondar, Valerii; Ilinich, Oleg; Shishatskii, Sergey

    1999-09-01

    Solubility of gases in polymers is an important property of polymeric materials relevant to many practical applications. Sorption of small molecules in polymers is a fundamental concern in such areas as food packaging, beverage storage, and polymer processing. However, by far the main interest in the solubility of gases in polymers, and especially in glassy polymers, is related to development of novel advanced materials for gas separation membranes. This is because the concentration gradient of a dissolved gas is the driving force of membrane processes. Development of these novel separation methods resulted in a rapid accumulation, in the recent literature, of thermodynamic data related to the solubility of gases in polymers at different temperatures and pressures. Polymers can be regarded as special cases of media intermediate between liquids and solids. As a consequence, modeling of gas sorption in polymers is very difficult and presents a permanent challenge to theoreticians and experimenters. The collection and critical evaluation of solubility data for various gas-polymer systems is relevant to both practical aspects of polymer applications and to fundamental studies of polymer behavior. This volume of the IUPAC-NIST Solubility Data Series summarizes the compilations and critical evaluations of the data on solubility of gases in glassy polymers. It is implied in this edition that "gases" are the components that are either permanent gases (supercitical fluids) or have saturated vapor pressure more than 1 atm at ambient conditions (298 K). The polymeric components of compilations and critical evaluations are primarily high molecular mass, amorphous, linear (noncross-linked) compounds that have the glass transition temperatures above ambient temperature. The data for each gas-polymer system have been evaluated, if the results of at least three independent and reliable studies have been reported. Where the data of sufficient accuracy and reliability are available

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

    PubMed

    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

  11. Voltammetric oxidation and determination of cinnarizine at glassy carbon electrode modified with multi-walled carbon nanotubes.

    PubMed

    Hegde, Rajesh N; Hosamani, Ragunatharaddi R; Nandibewoor, Sharanappa T

    2009-09-01

    The voltammetric oxidation of cinnarizine was investigated. In pH 2.5 Britton-Robinson buffer, cinnarizine shows an irreversible oxidation peak at about 1.20 V at a multi-walled carbon nanotube (MWCNT)-modified glassy carbon electrode. The cyclic voltammetric results indicate that MWCNT-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of cinnarizine. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the cinnarizine determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit are 9.0x10(-8) to 6.0x10(-6) M and 2.58x10(-9) M, respectively for cinnarizine. The proposed method was successfully applied to cinnarizine determination in pharmaceutical samples. The analytical performance of this sensor has been evaluated for the detection of analyte in urine as a real sample. PMID:19446444

  12. Prediction of physical aging in controlled-release coatings: the application of the relaxation coupling model to glassy cellulose acetate.

    PubMed

    Sinko, C M; Yee, A F; Amidon, G L

    1991-06-01

    The effect of physical aging on both the water transport properties and the mechanical properties of glassy cellulose acetate was investigated. Results indicate a reduction in the mechanical rate of relaxation as well as a reduction in the water permeability as the glass ages. A model which describes the low-frequency relaxation behavior of condensed, amorphous systems is used to quantitate the mechanical relaxation data. Systematic changes in key parameters from this model signify alterations in the microscopic or short-range structure as the glass physically ages. Predictions from this model correlate quite closely with the observed water permeability reductions and thus indicate that the transport properties of glassy polymers are dependent on the structure of the glass. This approach may provide further insight into the effects of nonequilibrium behavior on pharmaceutically important properties and may serve as a basis for predicting aging and permeability changes in controlled-release dosage forms.

  13. THORIUM-SILICON-BERYLLIUM ALLOYS

    DOEpatents

    Foote, F.G.

    1959-02-10

    Th, Si, anol Bt alloys where Be and Si are each present in anmounts between 0.1 and 3.5% by weight and the total weight per cent of the minor alloying elements is between 1.5 and 4.5% are discussed. These ternary alloys show increased hardness and greater resistant to aqueous corrosion than is found in pure Th, Th-Si alloys, or Th-Be alloys.

  14. The use of microelectrodes in the study of localized corrosion of aluminum 6111-like alloys

    NASA Astrophysics Data System (ADS)

    Abdullah, Aboubakr M.

    This thesis is classified into four chapters. While chapter 1 is only an introductory chapter that summarizes the two mechanisms that are trying to explain localized corrosion of metals and alloys, Chapter 4 is the conclusions and future work chapter that presents the new achievements that have been added to the field of corrosion science by this work besides the proposed work to be done in the future. In chapter 2, Crevice corrosion of an experimental Al 6111-like alloy with 0.68% Cu has been studied using potentiodynamic and potentiostatic techniques in different concentrations of sodium chloride and in 0.1M nitric acid solutions. Potentiodynamic experiments show that the alloy has an active/passive transition in a saturated sodium chloride solution at elevated temperatures (90 and 70°C). Also, a steep electrode potential gradient, E(x), within the crevice has been measured using a microprobe connected to a SCE and controlled by a 3-D manipulator, and the observed locations of corrosion on the crevice wall are similar to the locations seen previously for systems in which it was clear that the shift of E(x) into the active peak region of the polarization curve on the crevice wall stabilized the crevice corrosion process. In chapter 3, focuses on the corrosion of a peak aged aluminum 6111-like alloy of 1.47% copper using the artificial pit configuration (pencil electrode) with relatively larger specimens in the form of plates rather than wires. The sample which was flush with the surface of the epoxy resin mount was anodically polarized in neutral NaCl solutions of different concentrations and pH 6.9. The alloy dissolved uniformly at a certain rate to form a local cell with epoxy resin walls and the alloy surface as its bottom. The potential drop profile within the cavity was recorded on a daily basis. It showed that the total potential drop is in the order of 50 mV. The pH in the local cell was measured using a commercial mono pH microelectrode coupled with a

  15. Magnesium silicide intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Li, Gh.; Gill, H. S.; Varin, R. A.

    1993-11-01

    Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

  16. Behavior of nuclear waste elements during hydrothermal alteration of glassy rhyolite in an active geothermal system: Yellowstone National Park, Wyoming

    SciTech Connect

    Sturchio, N.C.; Seitz, M.G.

    1984-12-31

    The behavior of a group of nuclear waste elements (U, Th, Sr, Zr, Sb, Cs, Ba, and Sm) during hydrothermal alteration of glassy rhyolite is investigated through detailed geochemical analyses of whole rocks, glass and mineral separates, and thermal waters. Significant mobility of U, Sr, Sb, Cs, and Ba is found, and the role of sorption processes in their observed behavior is identified. Th, Zr, and Sm are relatively immobile, except on a microscopic scale. 9 references, 2 figures, 2 tables.

  17. Scanning Electron Microscopy and Petrography of Glassy Particles Produced by Lava Fountain Eruptions. Ph.D. Thesis - Final Report

    NASA Technical Reports Server (NTRS)

    Ladle, G. H.

    1978-01-01

    A conceptual model of a lava fountain consists of a vent, spatter ramparts, fountain column, downwind plume and associated pumice deposits. Glassy particles produced by lava fountain eruptions consist primarily of sideromelane glass and minor to moderate amounts of vesicles and crystals. Particles are classified on the basis of morphology as: (1) spherical, (2) elongate, (3) glass-coated mineral grain, (4) shard, (5) reticulite, (6) composite particle, and (7) lithic fragment.

  18. Attachment of gold nanoparticles to glassy carbon electrode and its application for the direct electrochemistry and electrocatalytic behavior of hemoglobin.

    PubMed

    Zhang, Lei; Jiang, Xiue; Wang, Erkang; Dong, Shaojun

    2005-08-15

    Gold nanoparticles have been attached onto glassy carbon electrode surface through sulfhydryl-terminated monolayer and characterized by X-ray photoelectron spectroscopy, atomic force microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The gold nanoparticles-attached glassy carbon electrodes have been applied to the immobilization/adsorption of hemoglobin, with a monolayer surface coverage of about 2.1 x 10(-10) mol cm(-2), and consequently obtained the direct electrochemistry of hemoglobin. Gold nanoparticles, acting as a bridge of electron transfer, can greatly promote the direct electron transfer between hemoglobin and the modified glassy carbon electrode without the aid of any electron mediator. In phosphate buffer solution with pH 6.8, hemoglobin shows a pair of well-defined redox waves with formal potential (E0') of about -0.085 V (versus Ag/AgCl/saturated KCl). The immobilized hemoglobin maintained its biological activity, showing a surface controlled electrode process with the apparent heterogeneous electron transfer rate constant (ks) of 1.05 s(-1) and charge-transfer coefficient (a) of 0.46, and displays the features of a peroxidase in the electrocatalytic reduction of hydrogen peroxide. A potential application of the hemoglobin-immobilized gold nanoparticles modified glassy carbon electrode as a biosensor to monitor hydrogen peroxide has been investigated. The steady-state current response increases linearly with hydrogen peroxide concentration from 2.0 x 10(-6) to 2.4 x 10(-4) M. The detection limit (3sigma) for hydrogen peroxide is 9.1 x 10(-7) M.

  19. TUNGSTEN BASE ALLOYS

    DOEpatents

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  20. High-Entropy Alloys with a Hexagonal Close-Packed Structure Designed by Equi-Atomic Alloy Strategy and Binary Phase Diagrams

    NASA Astrophysics Data System (ADS)

    Takeuchi, Akira; Amiya, Kenji; Wada, Takeshi; Yubuta, Kunio; Zhang, Wei

    2014-10-01

    High-entropy alloys (HEAs) with an atomic arrangement of a hexagonal close-packed (hcp) structure were found in YGdTbDyLu and GdTbDyTmLu alloys as a nearly single hcp phase. The equi-atomic alloy design for HEAs assisted by binary phase diagrams started with selecting constituent elements with the hcp structure at room temperature by permitting allotropic transformation at a high temperature. The binary phase diagrams comprising the elements thus selected were carefully examined for the characteristics of miscibility in both liquid and solid phases as well as in both solids due to allotropic transformation. The miscibility in interest was considerably narrow enough to prevent segregation from taking place during casting around the equi-atomic composition. The alloy design eventually gave candidates of quinary equi-atomic alloys comprising heavy lanthanides principally. The XRD analysis revealed that YGdTbDyLu and GdTbDyTmLu alloys thus designed are formed into the hcp structure in a nearly single phase. It was found that these YGdTbDyLu and GdTbDyTmLu HEAs with an hcp structure have delta parameter ( δ) values of 1.4 and 1.6, respectively, and mixing enthalpy (Δ H mix) = 0 kJ/mol for both alloys. These alloys were consistently plotted in zone S for disordered HEAs in a δ-Δ H mix diagram reported by Zhang et al. (Adv Eng Mater 10:534, 2008). The value of valence electron concentration of the alloys was evaluated to be 3 as the first report for HEAs with an hcp structure. The finding of HEAs with the hcp structure is significant in that HEAs have been extended to covering all three simple metallic crystalline structures ultimately followed by the body- and face-centered cubic (bcc and fcc) phases and to all four simple solid solutions that contain the glassy phase from high-entropy bulk metallic glasses.

  1. N.Q.R measurements of low energy Chiral structures in powdered glassy As2Se3

    NASA Astrophysics Data System (ADS)

    Nelson, Chris

    2012-02-01

    Experimental and theoretical work on the As-chalcogen glasses have shown that in the glassy state the local cylindrical symmetry associated with the elemental pyramidal unit is preserved. Here we introduce a local paracrystalline model of glassy As2Se3. This model is based on a tight binding calculation of the electric field gradient (EFG) at the core of an As atom located at the apex of the pyramidal structure. This EFG is shown to be hyper sensitive to the bond angles and bond lengths the As atom forms with the chalcogen nearest neighbors, as well as the hybrid angle formed with second neighbor As atoms. A continuous variation of the bonding parameters produces a unique set of these pyramidal units which are shown to fit the NQR data for powdered glassy samples. The best fit to the NQR data indicates that the pyramidal units organize themselves into Chiral structures in the glass. A plot of the electronic energy per molecular site shows that the chiral structures have on average a lower electronic energy than a random configuration.

  2. FTIR and Mössbauer spectroscopic study of sodium-aluminum-iron phosphate glassy materials for high level waste immobilization

    NASA Astrophysics Data System (ADS)

    Stefanovsky, S. V.; Stefanovsky, O. I.; Remizov, M. B.; Belanova, E. A.; Kozlov, P. V.; Glazkova, Ya. S.; Sobolev, A. V.; Presniakov, I. A.; Kalmykov, S. N.; Myasoedov, B. F.

    2015-11-01

    Complex sodium-aluminum-iron phosphate glassy materials with various Al2O3 to Fe2O3 ratio containing high level waste (HLW) surrogate were characterized by X-ray diffraction and scanning electron microscopy and studied in details by Fourier transform infrared (FTIR) spectroscopy. The samples with high Al2O3 content and not containing Fe2O3 were predominantly amorphous but subjected to devitrification under annealing. Addition of B2O3 and partial Fe2O3 substitution for Al2O3 in the materials increases their resistance to devitrification whereas further substitution and NiO incorporation significantly increase the tendency to devitrification. FTIR spectra demonstrate changes in the structure of glassy materials caused by both structural variations in the anionic motif and occurrence of crystalline phases in the materials. According to Mössbauer spectroscopy data, iron in the glassy samples is present as octahedrally coordinated Fe3+ ions while in the partly devitrified samples iron is partitioned among vitreous and crystalline phases entering the vitreous phase mainly as Fe3+O6 units and crystalline phases as major Fe3+ and minor Fe2+ ions in a magnetically ordered state and participating in a "fast" electronic exchange.

  3. Investigations into crazing in glassy amorphous polymers through molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Venkatesan, Sudarkodi; Basu, Sumit

    2015-04-01

    In many glassy amorphous polymers, localisation of deformation during loading leads to crazes. Crazes are crack like features whose faces are bridged either by fibrils or a cellular network of voids and fibrils. While formation of crazes is aided by the presence of surface imperfections and embedded dust particles, in this work, we focus on intrinsic crazes that form spontaneously in the volume of the material. We perform carefully designed molecular dynamics simulations on well equilibrated samples of a model polymer with a view to gaining insights into certain incompletely understood aspects of the crazing process. These include genesis of the early nanovoids leading to craze nucleation, mechanisms of stabilising the cellular or fibrillar structure and the competition between chain scission and chain disentanglement in causing the final breakdown of the craze. Additionally, we identify and enumerate clusters of entanglement points with high functionality as effective topological constraints on macromolecular chains. We show that regions with low density of entanglement clusters serve as sites for nanovoid nucleation under high mean stress. Growth occurs by the repeated triggering of cavitation instabilities above a growing void. The growth of the void is aided by disentanglement in and flow of entanglements away from the cavitating region. Finally, for the chain lengths chosen, scission serves to supply short chains to the growing craze but breakdown occurs by complete disentanglement of the chains. In fact, most of the energy supplied to the material seems to be used in causing disentanglements and very little energy is required to create a stable fibril.

  4. Bucky-gel coated glassy carbon electrodes, for voltammetric detection of femtomolar leveled lead ions.

    PubMed

    Wan, Qijin; Yu, Fen; Zhu, Lina; Wang, Xiaoxia; Yang, Nianjun

    2010-10-15

    Femtomolar (fM) leveled lead ions were electrochemically detected using a bucky-gel coated glassy carbon electrode and differential pulse anodic stripping voltammetry. The bucky-gel was composed of dithizone, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and multi-walled carbon nanotubes (MWCNTs). The fabrication of the bucky-gel coated electrode was optimized. The modified electrode was characterized with voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. After the accumulation of lead ions into the bucky-gel modified electrode at -1.2V vs. saturated calomel electrode (SCE) for 5 min in a pH 4.4 sodium acetate-acetate acid buffer solution, differential pulse anodic stripping voltammograms of the accumulated lead show an anodic wave at -0.58 V. The anodic peak current is detectable for lead ions in the concentration range from 1.0 μM down to 500 fM. The detection limit is calculated to be 100 fM. The proposed method was successfully applied for the detection of lead ions in lake water. PMID:20875583

  5. Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

    PubMed

    Li, Tianbao; Xu, Juan; Zhao, Lei; Shen, Shaofei; Yuan, Maosen; Liu, Wenming; Tu, Qin; Yu, Ruijin; Wang, Jinyi

    2016-10-01

    An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples. PMID:27474318

  6. Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

    PubMed

    Li, Tianbao; Xu, Juan; Zhao, Lei; Shen, Shaofei; Yuan, Maosen; Liu, Wenming; Tu, Qin; Yu, Ruijin; Wang, Jinyi

    2016-10-01

    An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples.

  7. Investigations of low-energy ion irradiation influence on glassy polymeric carbon

    NASA Astrophysics Data System (ADS)

    Abidzina, V.; Tereshko, I.; Elkin, I.; Muntele, I.; Muntele, C.; Minamisawa, R. A.; Ila, D.

    2007-04-01

    Glassy polymeric carbon (GPC), which is made from phenolic resins, has a high chemical inertness and is used as high temperature and radiation resistant coatings, as high temperature heat-exchangers, as well as a biomaterial in medicine for the manufacture of heart valves and prosthetic devices [G.M. Jenkins, D. Ila, H. Maleki, Mater. Res. Soc. Symp. Proc. 394 (1995) 181]. GPC is also used for the harsh environment of space, as well as for protective coating against extreme environments such as high temperature, highly ionizing radiation, as well as corrosive environments. In this work, we present the results of our investigation of the influence of the low-energy ion irradiation in glow-discharge plasma on GPC. Chemical changes in GPC prepared at 1000 °C were studied using FTIR, micro-Raman spectroscopy and Rutherford backscattering spectrometry (RBS). Porosity changes were monitored through introducing lithium from a molten LiCl salt into GPC and using the (p, α) nuclear reaction analysis (NRA) to measure Li concentration in treated GPC.

  8. An effective temperature theory coupling structural evolution and viscoplastic deformation of glassy polymers

    NASA Astrophysics Data System (ADS)

    Nguyen, Thao; Xiao, Rui

    Glassy polymers are amorphous polymers that have been driven out of equilibrium below the glass transition temperature. In the nonequilibrium state, the polymer chains continue to slowly rearrange towards a lower entropy state, which causes physical properties to change with time in a process referred to as physical aging. Physical aging can be reversed by plastic deformation, which moves the material further away from equilibrium. Though structural evolution and viscoplasticity are interdependent, they have been treated as separate processes and described by different theoretical approaches. Here, we introduce a new theory that strongly couples viscoplasticity and structural evolution through an effective temperature thermodynamic framework and a constitutive model for the dependence of the relaxation time on the configurational structure. The theory can describe a wide range of nonequilibrium behaviors, including viscoplasticity, physical aging, mechanical rejuvenation, and the glass transition, using a common set of parameters. We will show comparisons of theoretical predictions and experimental measurements of the effect of cold work and aging on the viscoplastic stress response and energy storage as measured by dynamic scanning calorimetry.

  9. Spinodals with Disorder: From Avalanches in Random Magnets to Glassy Dynamics

    NASA Astrophysics Data System (ADS)

    Nandi, Saroj Kumar; Biroli, Giulio; Tarjus, Gilles

    2016-04-01

    We revisit the phenomenon of spinodals in the presence of quenched disorder and develop a complete theory for it. We focus on the spinodal of an Ising model in a quenched random field (RFIM), which has applications in many areas from materials to social science. By working at zero temperature in the quasistatically driven RFIM, thermal fluctuations are eliminated and one can give a rigorous content to the notion of spinodal. We show that the latter is due to the depinning and the subsequent expansion of rare droplets. We work out the associated critical behavior, which, in any finite dimension, is very different from the mean-field one: the characteristic length diverges exponentially and the thermodynamic quantities display very mild nonanalyticities much like in a Griffith phenomenon. From the recently established connection between the spinodal of the RFIM and glassy dynamics, our results also allow us to conclusively assess the physical content and the status of the dynamical transition predicted by the mean-field theory of glass-forming liquids.

  10. Singular-potential random-matrix model arising in mean-field glassy systems

    NASA Astrophysics Data System (ADS)

    Akemann, Gernot; Villamaina, Dario; Vivo, Pierpaolo

    2014-06-01

    We consider an invariant random matrix ensemble where the standard Gaussian potential is distorted by an additional single pole of arbitrary fixed order. Potentials with first- and second-order poles have been considered previously and found applications in quantum chaos and number theory. Here we present an application to mean-field glassy systems. We derive and solve the loop equation in the planar limit for the corresponding class of potentials. We find that the resulting mean or macroscopic spectral density is generally supported on two disconnected intervals lying on the two sides of the repulsive pole, whose edge points can be completely determined imposing the additional constraint of traceless matrices on average. For an unbounded potential with an attractive pole, we also find a possible one-cut solution for certain values of the couplings, which is ruled out when the traceless condition is imposed. Motivated by the calculation of the distribution of the spin-glass susceptibility in the Sherrington-Kirkpatrick spin-glass model, we consider in detail a second-order pole for a zero-trace model and provide the most explicit solution in this case. In the limit of a vanishing pole, we recover the standard semicircle. Working in the planar limit, our results apply to matrices with orthogonal, unitary, and symplectic invariance. Numerical simulations and an independent analytical Coulomb fluid calculation for symmetric potentials provide an excellent confirmation of our results.

  11. Flow injection catalase activity measurement based on gold nanoparticles/carbon nanotubes modified glassy carbon electrode.

    PubMed

    El Nashar, Rasha Mohamed

    2012-07-15

    Amperometric flow injection method of hydrogen peroxide analysis was developed based on catalase enzyme (CAT) immobilization on a glassy carbon electrode (GC) modified with electrochemically deposited gold nanoparticles on a multiwalled carbon nanotubes/chitosan film. The resulting biosensor was applied to detect hydrogen peroxide with a linear response range 1.0×10(-7)-2.5×10(-3)M with a correlation coefficient 0.998 and response time less than 10s. The optimum conditions of film deposition such as potential applied, deposition time and pH were tested and the flow injection conditions were optimized to be: flow rate of 3ml/min, sample volume 75μl and saline phosphate buffer of pH 6.89. Catalase enzyme activity was successfully determined in liver homogenate samples of rats, raised under controlled dietary plan, using a flow injection analysis system involving the developed biosensor simultaneously with spectrophotometric detection, which is the common method of enzymatic assay.

  12. Electroanalysis of some common pesticides using conducting polymer/multiwalled carbon nanotubes modified glassy carbon electrode.

    PubMed

    Manisankar, P; Sundari, Pl Abirama; Sasikumar, R; Palaniappan, Sp

    2008-09-15

    The cyclic voltammetric behaviour of three common pesticides such as isoproturon (ISO), voltage (VOL) and dicofol (DCF) was investigated at glassy carbon electrode (GCE), multiwalled carbon nanotubes modified GCE (MWCNTs/GCE), polyaniline (PANI) and polypyrrole (PPY) deposited MWCNT/GCE. The modified electrode film was characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The electroactive behaviour of the pesticides was realized from the cyclic voltammetric studies. The differential pulse voltammetric principle was used to analyze the above-mentioned pesticides using MWCNT/GCE, PANI/MWCNT/GCE and PPY/MWCNT/GCE. Effects of accumulation potential, accumulation time, Initial scan potential, amplitude and pulse width were examined for the optimization of stripping conditions. The PANI/MWCNT/GCE performed well among the three electrode systems and the determination range obtained was 0.01-100 mgL(-1) for ISO, VOL and DCF respectively. The limit of detection (LOD) was 0.1 microgL(-1) for ISO, 0.01 microgL(-1) for VOL and 0.05 microgL(-1) for DCF on PANI/MWCNT/GCE modified system. It is significant to note that the PANI/MWCNT/GCE modified system results in the lowest LOD in comparison with the earlier reports. Suitability of this method for the trace determination of pesticide in spiked samples was also realized.

  13. Voltammetric determination of Δ9-THC in glassy carbon electrode: An important contribution to forensic electroanalysis.

    PubMed

    Balbino, Marco Antonio; de Menezes, Matheus Manoel Teles; Eleotério, Izabel Cristina; Saczk, Adelir Aparecida; Okumura, Leonardo Luiz; Tristão, Heloísa Maria; de Oliveira, Marcelo Firmino

    2012-09-10

    A new voltammetric method for the determination of Δ(9)-tetrahydrocannabinol (Δ(9)-THC) is described. The voltammetric experiments were accomplished in N-N dimethylformamide/water (9:1, v/v), using tetrabutylammonium tetrafluoroborate (TBATFB) 0.1mol/L as supporting electrolyte and a glassy carbon disk electrode as the working electrode. The anodic peak current was observed at 0.0V (vs. Ag/AgCl) after a 30s pre-concentration step under an applied potential of -1.2V (vs. Ag/AgCl). A linear dependence of Δ(9)-THC detection was obtained in the concentration range 2.4-11.3ng/mL, with a linear correlation coefficient of 0.999 and a detection limit of 0.34ng/mL. The voltammetric method was used to measure the content of Δ(9)-THC in samples (hemp and hashish) confiscated by the police. The elimination of chemical interferences from the samples was promptly achieved through prior purification using the TLC technique, by employing methanol/water (4:1, v/v) as the mobile phase. The results showed excellent correlation with results attained by HPLC.

  14. Behavior of the Ru-bda water oxidation catalyst covalently anchored on glassy carbon electrodes

    DOE PAGESBeta

    Matheu, Roc; Francàs, Laia; Chernev, Petko; Ertem, Mehmed Z.; Batista, Victor; Haumann, Michael; Sala, Xavier; Llobet, Antoni

    2015-05-07

    Electrochemical reduction of the dizaonium complex, [RuII(bda)(NO)(N–N2)2]3+, 23+ (N–N22+ is 4-(pyridin-4-yl) benzenediazonium and bda2– is [2,2'-bipyridine]-6,6'-dicarboxylate), in acetone produces the covalent grafting of this molecular complex onto glassy carbon (GC) electrodes. Multiple cycling voltammetric experiments on the GC electrode generates hybrid materials labeled as GC-4, with the corresponding Ru-aqua complex anchored on the graphite surface. GC-4 has been characterized at pH = 7.0 by electrochemical techniques and X-ray absorption spectroscopy (XAS) and has been shown to act as an active catalyst for the oxidation of water to dioxygen. This new hybrid material has a lower catalytic performance than its counterpartmore » in homogeneous phase and progressively decomposes to form RuO2 at the electrode surface. The resulting metal oxide attached at the GC electrode surface, GC-RuO2, is a very fast and rugged heterogeneous water oxidation catalyst with TOFis of 300 s–1 and TONs >45000. The observed performance is comparable to the best electrocatalysts reported so far, at neutral pH.« less

  15. Synthesis, network structure and morphology of s-triazine-organosilane glassy hybrid materials

    SciTech Connect

    Arafa, Isam; Shatnawi, Mazin; Saad, Heyam

    2009-08-15

    A series of five hybrid materials are synthesized by the reaction of cyanuric chloride (C{sub 3}N{sub 3}Cl{sub 3}) with different alkoxysilanes (R{sub x}Si(OC{sub 2}H{sub 5}){sub 4-x}, R=CH{sub 3}, C{sub 6}H{sub 5} and x=0, 1, 2) in ethanol using sol-gel technique. The resulting s-triazine-organosilane products were examined using spectroscopic (UV-visible, FT-IR), thermal (thermogravimetric analysis, TGA), powder X-ray diffraction (P-XRD), BET analysis and microscopic (scanning electron microscopy, SEM) techniques. These hybrid materials exhibit globular and two-dimensional morphological textures with varying degrees of crystalline microstructures. Depending on the functionality of the organosilane building blocks the obtained hybrid materials exhibit different material characteristics including their solid state, Vicat softening point (Vicat hardness), density and porosity. BET surface area measurements indicate that these materials possess small specific surface areas of 0.36-2.3 m{sup 2}/g with external surface area of approx0.02 m{sup 2}/g. The phenyl-containing hybrids exhibit pronounced hydrolytic stability compared to the methyl- and silica-based analogs. The DMSO and sulfolane solutions of the prepared hybrids are transparent to visible light whereas their cold-compressed discs are optically opaque. - Graphical abstract: Network structure of s-triazine-organosilane glassy hybrid materials.

  16. Pulse Laser Deposition Fabricating Gold Nanoclusters on a Glassy Carbon Surface for Nonenzymatic Glucose Sensing.

    PubMed

    Shu, Honghui; Chang, Gang; Wang, Zhiqiang; Li, Pai; Zhang, Yuting; He, Yunbin

    2015-01-01

    A One-step technique for depositing gold nanoclusters (GNCs) onto the surface of a glassy carbon (GC) plate was developed by using pulse laser deposition (PLD) with appropriate process parameters. The method is simple and clean without using any templates, surfactants, or stabilizers. The experimental factors (pulse laser number and the pressure of inert gas (Ar)) that affect the morphology and structure of GNCs, and thus affect the electrocatalytic oxidation performance towards glucose were systematically investigated by means of transmission electron microscopy (TEM) and electrochemical methods (cyclic voltammograms (CV) and chronoamperometry methods). The GC electrode modified by GNCs exhibited a rapid response time (about 2 s), a broad linear range (0.1 to 20 mM), and good stability. The sensitivity was estimated to be 31.18 μA cm(-2) mM(-1) (vs. geometric area), which is higher than that of the Au bulk electrode. It has a good resistance to the common interfering species, such as ascorbic acid (AA), uric acid (UA) and 4-acetaminophen (AP). Therefore, this work has demonstrated a simple and effective sensing platform for the nonenzymatic detection of glucose, and can be used as a new material for a novel non-enzymatic glucose sensor. PMID:26165282

  17. Graphene nanosheets modified glassy carbon electrode for simultaneous detection of heroine, morphine and noscapine.

    PubMed

    Navaee, Aso; Salimi, Abdollah; Teymourian, Hazhir

    2012-01-15

    In the present study, the graphene nanosheets (GNSs) modified glassy carbon (GC) electrode is employed for simultaneous determination of morphine, noscapine and heroin. To the best of our knowledge this is the first report of the simultaneous determination of these three important opiate drugs based on their direct electrochemical oxidation. Field emission scanning electron microscopy (FESEM) technique is utilized in order to study the surface morphology of the modified electrode. The modified electrode shows excellent electrocatalytic activity toward oxidation of morphine, noscapine and heroin at reduced overpotentials in wide pH range. In the performed experiments, differential pulse voltammetric determination of morphine, noscapine and heroin yields calibration curves with the following characteristics; linear dynamic range up to 65, 40 and 100 μM, sensitivity of 275, 500 and 217 nA μM(-1) cm(-2), and detection limits of 0.4, 0.2 and 0.5 μM at 3S(B), respectively. Fast response time, signal stability, high sensitivity, low cost and ease of preparation method without using any specific electron-transfer mediator or specific reagent are the advantageous of the proposed sensor. The modified electrode can be used for simultaneous or individual detection of three major narcotic components, heroin, noscapine and morphine at micromolar concentration without any separation or pretreatment steps.

  18. Glassy dynamics of model colloidal polymers: The effect of "monomer" size

    NASA Astrophysics Data System (ADS)

    Li, Jian; Zhang, Bo-kai; Li, Hui-shu; Chen, Kang; Tian, Wen-de; Tong, Pei-qing

    2016-05-01

    In recent years, attempts have been made to assemble colloidal particles into chains, which are termed "colloidal polymers." An apparent difference between molecular and colloidal polymers is the "monomer" size. Here, we propose a model to represent the variation from molecular polymer to colloidal polymer and study the quantitative differences in their glassy dynamics. For chains, two incompatible local length scales, i.e., monomer size and bond length, are manifested in the radial distribution function and intramolecular correlation function. The mean square displacement of monomers exhibits Rouse-like sub-diffusion at intermediate time/length scale and the corresponding exponent depends on the volume fraction and the monomer size. We find that the threshold volume fraction at which the caging regime emerges can be used as a rescaling unit so that the data of localization length versus volume fraction for different monomer sizes can gather close to an exponential curve. The increase of monomer size effectively increases the hardness of monomers and thus makes the colloidal polymers vitrify at lower volume fraction. Static and dynamic equivalences between colloidal polymers of different monomer sizes have been discussed. In the case of having the same peak time of the non-Gaussian parameter, the motion of monomers of larger size is much less non-Gaussian. The mode-coupling critical exponents for colloidal polymers are in agreement with that of flexible bead-spring chains.

  19. Glassy dynamics of model colloidal polymers: The effect of "monomer" size.

    PubMed

    Li, Jian; Zhang, Bo-Kai; Li, Hui-Shu; Chen, Kang; Tian, Wen-de; Tong, Pei-Qing

    2016-05-28

    In recent years, attempts have been made to assemble colloidal particles into chains, which are termed "colloidal polymers." An apparent difference between molecular and colloidal polymers is the "monomer" size. Here, we propose a model to represent the variation from molecular polymer to colloidal polymer and study the quantitative differences in their glassy dynamics. For chains, two incompatible local length scales, i.e., monomer size and bond length, are manifested in the radial distribution function and intramolecular correlation function. The mean square displacement of monomers exhibits Rouse-like sub-diffusion at intermediate time/length scale and the corresponding exponent depends on the volume fraction and the monomer size. We find that the threshold volume fraction at which the caging regime emerges can be used as a rescaling unit so that the data of localization length versus volume fraction for different monomer sizes can gather close to an exponential curve. The increase of monomer size effectively increases the hardness of monomers and thus makes the colloidal polymers vitrify at lower volume fraction. Static and dynamic equivalences between colloidal polymers of different monomer sizes have been discussed. In the case of having the same peak time of the non-Gaussian parameter, the motion of monomers of larger size is much less non-Gaussian. The mode-coupling critical exponents for colloidal polymers are in agreement with that of flexible bead-spring chains.

  20. A sensitive DNA biosensor fabricated from gold nanoparticles and graphene oxide on a glassy carbon electrode.

    PubMed

    Hajihosseini, Saeedeh; Nasirizadeh, Navid; Hejazi, Mohammad Saeid; Yaghmaei, Parichereh

    2016-04-01

    A sensitive electrochemical DNA biosensor was developed for Helicobacter pylori (H. pylori) detection using differential pulse voltammetry. Single-stranded DNA probe was immobilized on a graphene oxide/gold nanoparticles modified glassy carbon electrode (GO/AuNPs/GCE). A hybridization reaction was conducted with the target DNA and the immobilized DNA on the electrode surface. Oracet blue (OB) was selected for the first time as a redox indicator for amplifying the electrochemical signal of DNA. Enhanced sensitivity was achieved through combining the excellent electric conductivity of GO/AuNPs and the electroactivity of the OB. The DNA biosensor displayed excellent performance to demonstrate the differences between the voltammetric signals of the OB obtained from different hybridization samples (non-complementary, mismatch and complementary DNAs). The proposed biosensor has a linear range of 60.0-600.0 pM and a detection limit of 27.0 pM for detection of H. pylori. In addition, the biosensor have responded very well in the simulated real sample evaluations, signifying its potential to be used in future clinical detection of the H. pylori bacteria.

  1. Modified glassy carbon electrodes based on carbon nanostructures for ultrasensitive electrochemical determination of furazolidone.

    PubMed

    Shahrokhian, Saeed; Naderi, Leila; Ghalkhani, Masoumeh

    2016-04-01

    The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the glassy carbon electrode modified with different carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG), graphene oxide (GO), reduced graphene oxide (RGO) and RGO-CNT hybrids (various ratios) using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable increase in the cathodic peak current of Fu at the RGO modified GCE, compared to other modified electrodes and also bare GCE. The surface morphology and nature of the RGO film was thoroughly characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode showed two linear dynamic ranges of 0.001-2.0 μM and 2.0-10.0 μM with a detection limit of 0.3 nM for the voltammetric determination of Fu. This sensor was used successfully for Fu determination in pharmaceutical and clinical preparations.

  2. Voltammetric Determination of Codeine on Glassy Carbon Electrode Modified with Nafion/MWCNTs

    PubMed Central

    Piech, Robert; Rumin, Martyna; Paczosa-Bator, Beata

    2015-01-01

    A glassy carbon electrode modified with a Nafion/MWCNTs composite is shown to enable the determination of codeine using differential pulse voltammetry in phosphate buffer of pH 3.0. At a preconcentration time of 15 s, the calibration graph is linear in the 0.5 µM (0.15 mg·L−1) to 15 µM (4.5 mg·L−1) concentration range with a correlation coefficient of 0.998. The detection limit at a preconcentration time of 120 s is as low as 4.5 μg·L−1. The repeatability of the method at a 0.6 μg·L−1 concentration level, expressed as the RSD, is 3.7% (for n = 5). The method was successfully applied and validated by analyzing codeine in drug, human plasma, and urine samples. PMID:25741451

  3. Direct electrochemistry of glucose oxidase and glucose biosensing on a hydroxyl fullerenes modified glassy carbon electrode.

    PubMed

    Gao, Yun-Fei; Yang, Tian; Yang, Xiao-Lu; Zhang, Yu-Shuai; Xiao, Bao-Lin; Hong, Jun; Sheibani, Nader; Ghourchian, Hedayatollah; Hong, Tao; Moosavi-Movahedi, Ali Akbar

    2014-10-15

    Direct electrochemistry of glucose oxidase (GOD) was achieved when GOD-hydroxyl fullerenes (HFs) nano-complex was immobilized on a glassy carbon (GC) electrode and protected with a chitosan (Chit) membrane. The ultraviolet-visible absorption spectrometry (UV-vis), transmission electron microscopy (TEM), and circular dichroism spectropolarimeter (CD) methods were utilized for additional characterization of the GOD, GOD-HFs and Chit/GOD-HFs. Chit/HFs may preserve the secondary structure and catalytic properties of GOD. The cyclic voltammograms (CVs) of the modified GC electrode showed a pair of well-defined quasi-reversible redox peaks with the formal potential (E°') of 353 ± 2 mV versus Ag/AgCl at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant (ks) was calculated to be 2.7 ± 0.2s(-1). The modified electrode response to glucose was linear in the concentrations ranging from 0.05 to 1.0mM, with a detection limit of 5 ± 1 μM. The apparent Michaelis-Menten constant (Km(app)) was 694 ± 8 μM. Thus, the modified electrode could be applied as a third generation biosensor for glucose with high sensitivity, selectivity and low detection limit.

  4. Voltammetric determination of vitamin D3 with a rotating glassy carbon electrode.

    PubMed

    Hernández Méndez, J; Sánchez Pérez, A; Delgado Zamarreño, M; Hernández Garcia, M L

    1988-01-01

    A voltamperometric study (DC and DP) on the electroanalytical behaviour of vitamin D(3) in a methanolic solution using LiClO(4) as the supporting electrolyte and working with a glassy carbon electrode was carried out. Vitamin D(3) exhibits an oxidation wave (DC) or peak (DP) at potentials close to +1.1 V (versus SCE). The optimum experimental conditions for the best reproducibility of the voltamperometric signal were determined and the different parameters affecting the electrochemical process were studied. The electrochemical process was seen to be irreversible and, under certain conditions, adsorption of vitamin D(3) onto the electrode surface was observed. A voltamperometric procedure for the determination of vitamin D(3) in a concentration range of 2 x 10(-6) - 2 x 10(-4) M is proposed. The detection limit is of the order of 2 x 10(-6) M and the relative standard deviations are 1.1% (DC) and 2.6% (DP), respectively.

  5. Structure, texture, and properties of superconductive electrolytic niobium coatings on glassy carbon

    NASA Astrophysics Data System (ADS)

    Kolosov, V. N.; Shevyrev, A. A.

    2016-01-01

    Superconductive electrolytic niobium coatings 0.1-100 μm thick are prepared via electrochemical deposition onto SU-2000 glassy carbon substrates in (LiF + NaF + KF)eut-K2NbF7 molten salt. Their structure, texture, and residual stresses are investigated by X-ray diffraction methods. It is shown that, when depositing the coatings, the diffusion superconductive layer of niobium carbide is formed at the substrate-coating interface. The sequence of changes in the axis of the texture of niobium coating from <100> through <211> to a textureless state with an increase in their thickness is established. It is found that, in the interval 0.5-5 μm, the sign of the stress changes (compressive stresses change into tensile stresses) and it reaches its maximum value. With an increase in the coating thickness from 5 to 100 μm, tensile stresses decrease from 345 to 80 MPa. It is shown that the coatings formed can be used as the material for creating a working layer of a superconducting cryogenic gyroscope rotor.

  6. High-Fidelity Replica Molding of Glassy Liquid Crystalline Polymer Microstructures.

    PubMed

    Zhao, Hangbo; Wie, Jeong Jae; Copic, Davor; Oliver, C Ryan; Orbaek White, Alvin; Kim, Sanha; Hart, A John

    2016-03-01

    Liquid crystalline polymers have recently been engineered to exhibit complex macroscopic shape adaptivity, including optically- and thermally driven bending, self-sustaining oscillation, torsional motion, and three-dimensional folding. Miniaturization of these novel materials is of great interest for both fundamental study of processing conditions and for the development of shape-changing microdevices. Here, we present a scalable method for high-fidelity replica molding of glassy liquid crystalline polymer networks (LCNs), by vacuum-assisted replica molding, along with magnetic field-induced control of the molecular alignment. We find that an oxygen-free environment is essential to establish high-fidelity molding with low surface roughness. Identical arrays of homeotropic and polydomain LCN microstructures are fabricated to assess the influence of molecular alignment on the elastic modulus (E = 1.48 GPa compared to E = 0.54 GPa), and side-view imaging is used to quantify the reversible thermal actuation of individual LCN micropillars by high-resolution tracking of edge motion. The methods and results from this study will be synergistic with future advances in liquid crystalline polymer chemistry, and could enable the scalable manufacturing of stimuli-responsive surfaces for applications including microfluidics, tunable optics, and surfaces with switchable wetting and adhesion. PMID:26943057

  7. Behavior of the Ru-bda water oxidation catalyst covalently anchored on glassy carbon electrodes

    SciTech Connect

    Matheu, Roc; Francàs, Laia; Chernev, Petko; Ertem, Mehmed Z.; Batista, Victor; Haumann, Michael; Sala, Xavier; Llobet, Antoni

    2015-05-07

    Electrochemical reduction of the dizaonium complex, [RuII(bda)(NO)(N–N2)2]3+, 23+ (N–N22+ is 4-(pyridin-4-yl) benzenediazonium and bda2– is [2,2'-bipyridine]-6,6'-dicarboxylate), in acetone produces the covalent grafting of this molecular complex onto glassy carbon (GC) electrodes. Multiple cycling voltammetric experiments on the GC electrode generates hybrid materials labeled as GC-4, with the corresponding Ru-aqua complex anchored on the graphite surface. GC-4 has been characterized at pH = 7.0 by electrochemical techniques and X-ray absorption spectroscopy (XAS) and has been shown to act as an active catalyst for the oxidation of water to dioxygen. This new hybrid material has a lower catalytic performance than its counterpart in homogeneous phase and progressively decomposes to form RuO2 at the electrode surface. The resulting metal oxide attached at the GC electrode surface, GC-RuO2, is a very fast and rugged heterogeneous water oxidation catalyst with TOFis of 300 s–1 and TONs >45000. The observed performance is comparable to the best electrocatalysts reported so far, at neutral pH.

  8. Graphene modified glassy carbon sensor for the determination of aspirin metabolites in human biological samples.

    PubMed

    Purushotham, Meruva; Gupta, Pankaj; Goyal, Rajendra N

    2015-10-01

    A graphene modified glassy carbon (GR/GCE) sensor has been developed for the determination of aspirin metabolites 2,3- and 2,5-dihydroxybenzoic acids (2,3- and 2,5-DHB). The modified sensor was characterized by Field Emission Scanning Electron Microscopy and Electrochemical Impedance Spectroscopy. The electrochemical behavior of 2,3- and 2,5-DHB was investigated by cyclic and square wave voltammetry. The modified sensor exhibited excellent electrocatalytic activity for the oxidation of 2,3- and 2,5-DHB, leading to a remarkable enhancement in the peak current as compared to the bare sensor. The results were attributed to the enhanced surface area and high conductivity of GR. The anodic peak currents of 2,3- and 2,5-DHB were found to be linear in the concentration range of 1-150 µM and 1-200 µM with the detection limits of 47 nM and 51 nM, respectively. The sensor was capable to determine 2,5-DHB effectively without any interference from the uric acid and other metabolites present in the urine samples. The practical utility of GR/GCE has been successfully demonstrated for the determination of 2,5-DHB in the urine samples of persons undergoing treatment with aspirin. PMID:26078167

  9. Spinodals with Disorder: From Avalanches in Random Magnets to Glassy Dynamics.

    PubMed

    Nandi, Saroj Kumar; Biroli, Giulio; Tarjus, Gilles

    2016-04-01

    We revisit the phenomenon of spinodals in the presence of quenched disorder and develop a complete theory for it. We focus on the spinodal of an Ising model in a quenched random field (RFIM), which has applications in many areas from materials to social science. By working at zero temperature in the quasistatically driven RFIM, thermal fluctuations are eliminated and one can give a rigorous content to the notion of spinodal. We show that the latter is due to the depinning and the subsequent expansion of rare droplets. We work out the associated critical behavior, which, in any finite dimension, is very different from the mean-field one: the characteristic length diverges exponentially and the thermodynamic quantities display very mild nonanalyticities much like in a Griffith phenomenon. From the recently established connection between the spinodal of the RFIM and glassy dynamics, our results also allow us to conclusively assess the physical content and the status of the dynamical transition predicted by the mean-field theory of glass-forming liquids.

  10. Flow injection catalase activity measurement based on gold nanoparticles/carbon nanotubes modified glassy carbon electrode.

    PubMed

    El Nashar, Rasha Mohamed

    2012-07-15

    Amperometric flow injection method of hydrogen peroxide analysis was developed based on catalase enzyme (CAT) immobilization on a glassy carbon electrode (GC) modified with electrochemically deposited gold nanoparticles on a multiwalled carbon nanotubes/chitosan film. The resulting biosensor was applied to detect hydrogen peroxide with a linear response range 1.0×10(-7)-2.5×10(-3)M with a correlation coefficient 0.998 and response time less than 10s. The optimum conditions of film deposition such as potential applied, deposition time and pH were tested and the flow injection conditions were optimized to be: flow rate of 3ml/min, sample volume 75μl and saline phosphate buffer of pH 6.89. Catalase enzyme activity was successfully determined in liver homogenate samples of rats, raised under controlled dietary plan, using a flow injection analysis system involving the developed biosensor simultaneously with spectrophotometric detection, which is the common method of enzymatic assay. PMID:22817944

  11. Mechanisms of devitrification of grain boundary glassy phases in Si3N4 materials

    NASA Technical Reports Server (NTRS)

    Hench, L. L.

    1982-01-01

    Changes in the grain boundary (g.b.) phases of Si3N4 are analyzed, the effects of composition and thermal history on devitrification of the g.b. phases are determined, devitrification of the g.b. phases of Si3N are related to mechanical behavior and oxidation sensitivity of the material. The phase relationships that occur within the grain boundaries of Si3N4 containing various densification aids are reviewed. Comparisons of the effects of MgO, Y2O3, CeO2, and Y2O3 + AL2O3 are made in terms of the phase equilibria of the Si3N4 + SiO2 + additive compositional system. Two new equilibrium phase diagrams for the Si3N4-SiO2 and Y2O3 and Si3N4-SiO2-Ce2O3 systems are preented. The effects of Y2O3 vs CeO2 densification aids on the fracture surfaces of Si3N4 are compared. Auger electron spectroscopy shows that both oxides are concentrated within the fracture surface. Scanning electron microscopy shows evidence that Si3N4 with CeO2 formed an intergranular structure of fine grained oxynitride reaction products, as predicted by phase quilibria, whereas the Y2O3 containing sample shows evidence of an intergranular glassy phase.

  12. MIP-graphene-modified glassy carbon electrode for the determination of trimethoprim.

    PubMed

    da Silva, Hélder; Pacheco, João G; Magalhães, Júlia M C S; Viswanathan, Subramanian; Delerue-Matos, Cristina

    2014-02-15

    A novel sensitive electrochemical sensor was developed by electropolymerization of pyrrole (PY) and molecularly imprinted polymer (MIP) which was synthesized onto a glassy carbon electrode (GCE) in aqueous solution using cyclic voltammetry in the presence of Trimethoprim (TMP) as template molecules. Furthermore, a previous electrode modification was performed by deposition of a suspension of graphene on the electrode's surface. The performance of the imprinted and non-imprinted (NIP) films was evaluated by impedance spectroscopy (EIS) and cyclic voltammetry (CV) of a ferric solution. The molecularly imprinted film exhibited a high selectivity and sensitivity toward TMP. The sensor presented a linear range, between peak current intensity and logarithm of TMP concentration between 1.0 × 10(-6) and 1.0 × 10(-4)M. The results were accurate (with recoveries higher than 94%), precise (with standard deviations less than 5%) and the detection limit was 1.3 × 10(-7)M. The new sensor is selective, simple to construct and easy to operate. The MIP sensor was successfully applied to quantify TMP in urine samples.

  13. Self-Healing Glassy Thin Coating for High-Temperature Applications.

    PubMed

    Castanié, Sandra; Carlier, Thibault; Méar, François O; Saitzek, Sébastien; Blach, Jean-François; Podor, Renaud; Montagne, Lionel

    2016-02-17

    Glass thin films (with nanometer to micrometer thicknesses) are promising in numerous applications, both as passive coatings and as active components. Self-healing is a feature of many current technological developments as a means of increasing the lifetime of materials. In the context of these developments, we report on the elaboration of the first self-healing glassy thin-film coating developed specifically for high-temperature applications. This coating is obtained by pulsed laser deposition of alternating layers of vanadium boride (VB) and a multicomponent oxide glass. Self-healing is obtained through the oxidation of VB at the operating temperature. The investigation of the effect of elaboration parameters on the coating composition and morphology made it possible to obtain up to seven-layer coatings, with good homogeneity and perfect interfaces, and with a total thickness of less than 1 μm. The autonomic self-healing capacity of the coating has been demonstrated by an in situ experiment, which shows that a crack of nanometric dimension can be healed within a few minutes at 700 °C. PMID:26808059

  14. Short-Time Glassy Dynamics in Viscous Protein Solutions with Competing Interactions

    SciTech Connect

    Godfrin, P. Douglas; Hudson, Steven; Hong, Kunlun; Porcar, Lionel; Falus, Peter; Wagner, Norman; Liu, Yun

    2015-11-24

    Although there have been numerous investigations of the glass transition for colloidal dispersions with only a short-ranged attraction, less is understood for systems interacting with a long-ranged repulsion in addition to this attraction, which is ubiquitous in aqueous protein solutions at low ionic strength. Highly puri ed concentrated lysozyme solutions are used as a model system and investigated over a large range of protein concentrations at very low ionic strength. Newtonian liquid behavior is observed at all concentrations, even up to 480 mg/mL, where the zero shear viscosity increases by more than three orders of magnitude with increasing concentration. Remarkably, despite this macroscopic liquid-like behavior, the measurements of the dynamics in the short-time limit shows features typical of glassy colloidal systems. Investigation of the inter-protein structure indicates that the reduced short-time mobility of the protein is caused by localized regions of high density within a heterogeneous density distribution. This structural heterogeneity occurs on intermediate range length scale, driven by the competing potential features, and is distinct from commonly studied colloidal gel systems in which a heterogeneous density distribution tends to extend to the whole system. The presence of long-ranged repulsion also allows for more mobility over large length and long time scales resulting in the macroscopic relaxation of the structure. The experimental results provide evidence for the need to explicitly include intermediate range order in theories for the macroscopic properties of protein solutions interacting via competing potential features.

  15. Short-Time Glassy-like Dynamics Observed in Viscous Protein Solutions with Competing Potential Features

    NASA Astrophysics Data System (ADS)

    Wagner, Norman; Godfrin, Doug; Liu, Yun

    Structures in concentrated protein solutions caused by the combination of short-range attraction (SA) and long-range repulsion (LR) have been extensively studied due to their importance in understanding therapeutic protein formulations and the phase behavior in general. Despite extensive studies of kinetically arrested states in colloidal systems with short-range attraction, less is understood for the effect of an additional longer-range repulsion on model colloidal systems with a SA interaction. Highly purified lysozyme is used a model experimental system due to its stable globular structure and SALR interactions at low ionic strength that can be quantitatively modeled. The fluid microstructure and protein short time self diffusion are measured across a broad range of conditions by small angle neutron scattering (SANS) and neutron spin echo (NSE), respectively. Newtonian liquid behavior is observed at all concentrations, even with an increase of zero shear viscosity by almost four orders of magnitude with increasing concentration. However, dynamic measurements demonstrate a sub-diffusive regime at relatively short time scales for concentrated samples at low temperature. The formation of a heterogeneous density distribution is shown to produce localized regions of high density that reduce protein motion, giving it a glassy-like behavior at the short time scale. This heterogeneity occurs at the length scale associated with the intermediate range order driven by the competing potential features, distinguishable from heterogeneous colloidal gels.

  16. Structural Modifications And Mechanical Degradation Of Ion Irradiated Glassy Polymer Carbon

    NASA Astrophysics Data System (ADS)

    Abunaemeh, Malek; Seif, Mohamed; Elsamadicy, Abdalla; Muntele, Claudiu; Ila, Daryush

    2011-06-01

    The TRISO fuel has been used in some of the Generation IV nuclear reactor designs. It consists of a fuel kernel of UOx coated with several layers of materials with different functions. Pyrolytic carbon (PyC) is one of the materials in the layers. In this study we investigate the possibility of using Glassy Polymeric Carbon (GPC) as an alternative to PyC. GPC is used for artificial heart valves, heat-exchangers, and other high-tech products developed for the space and medical industries. This lightweight material can maintain dimensional and chemical stability in adverse environment and very high temperatures (up to 3000 °C). In this work, we are comparing the changes in physical and microstructure properties of GPC after exposure to irradiation fluence of 5 MeV Ag equivalent to a 1 displacement per atom (dpa) at samples prepared at 1000, 1500 and 2000 °C. The GPC material is manufactured and tested at the Center for Irradiation Materials (CIM) at Alabama A&M University. Transmission electron microscopy (TEM) and Raman spectroscopy were used for analysis.

  17. Low temperature glassy relaxation in rare earth doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, Suvra; Lawes, Gavin

    2012-10-01

    Magnetic nanoparticles typically exhibit glassy relaxation at low temperature, which can be affected by doping. Gadolinium and Lanthanum doped Fe3O4 nanoparticles were synthesized using a chemical co-precipitation method. The structural and optical properties of these nanoparticles were characterized by using Transmission Electron Microscope (TEM) and the Raman spectroscopy. The TEM images show the formation of nanoparticles of size ranging between 12-14 nm and Raman spectra are consistent with the formation of Fe3O4. AC magnetic measurements were also conducted on these nanoparticles. From the ac out-of-phase susceptibility (χ//) vs temperature (T) graphs, it is observed that the doped nanoparticles show larger amplitude relaxation peaks at low temperature as compared to the undoped particles. These magnetic relaxation features develop roughly between 25K to 35K and show frequency dependence. The increased magnetic relaxation at low temperatures can be attributed to structural defects which may arise due to the doping of lanthanides in Fe3O4 nanoparticles.

  18. Incorporating the effect of orientation hardening in an effective temperature nonequilibrium theory for glassy polymers

    NASA Astrophysics Data System (ADS)

    Guo, Jingkai; Xiao, Rui; Nguyen, Thao

    Amorphous polymers exhibit a wide range of time and temperature dependent behavior. Recently, Xiao and Nguyen developed an effective temperature theory that can capture a wide variety of nonequilibrium behaviors at moderate strains. At large strains, the stress response of glassy polymers is dominated by strain hardening as a result of chain alignment. The goal of this study was to extend the effective temperature theory to large deformation and make it capable of modeling strain hardening from deformation-induced molecular alignment. We compared two approaches. In the spirit of internal state variable thermodynamics theory, we introduced a series of stretch-like internal state variables to characterize the molecular resistance to plastic flow associated with each inelastic mechanism. The dependence of free energy on the internal state variables naturally gives rise to a deformation dependent back stress. The flow rule and the evolution of effective temperatures were derived in a thermodynamically consistent manner. In the second approach, we introduced a steady-state limit in the evolution of the effective temperature characterizing the nonequilibrium structure of the material. Both approaches can well capture the experimentally measured phenomena of orientation hardening, including the development of deformation-induced anisotropy in the yield strength and hardening modulus, the Bauschinger effect, and differences in the hardening moduli in tension and compression of pre-oriented specimens.

  19. Singular-potential random-matrix model arising in mean-field glassy systems.

    PubMed

    Akemann, Gernot; Villamaina, Dario; Vivo, Pierpaolo

    2014-06-01

    We consider an invariant random matrix ensemble where the standard Gaussian potential is distorted by an additional single pole of arbitrary fixed order. Potentials with first- and second-order poles have been considered previously and found applications in quantum chaos and number theory. Here we present an application to mean-field glassy systems. We derive and solve the loop equation in the planar limit for the corresponding class of potentials. We find that the resulting mean or macroscopic spectral density is generally supported on two disconnected intervals lying on the two sides of the repulsive pole, whose edge points can be completely determined imposing the additional constraint of traceless matrices on average. For an unbounded potential with an attractive pole, we also find a possible one-cut solution for certain values of the couplings, which is ruled out when the traceless condition is imposed. Motivated by the calculation of the distribution of the spin-glass susceptibility in the Sherrington-Kirkpatrick spin-glass model, we consider in detail a second-order pole for a zero-trace model and provide the most explicit solution in this case. In the limit of a vanishing pole, we recover the standard semicircle. Working in the planar limit, our results apply to matrices with orthogonal, unitary, and symplectic invariance. Numerical simulations and an independent analytical Coulomb fluid calculation for symmetric potentials provide an excellent confirmation of our results.

  20. Acoustic excitations in glassy sorbitol and their relation with the fragility and the boson peak

    NASA Astrophysics Data System (ADS)

    Ruta, B.; Baldi, G.; Scarponi, F.; Fioretto, D.; Giordano, V. M.; Monaco, G.

    2012-12-01

    We report a detailed analysis of the dynamic structure factor of glassy sorbitol by using inelastic X-ray scattering and previously measured light scattering data [B. Ruta, G. Monaco, F. Scarponi, and D. Fioretto, Philos. Mag. 88, 3939 (2008), 10.1080/14786430802317586]. The thus obtained knowledge on the density-density fluctuations at both the mesoscopic and macroscopic length scale has been used to address two debated topics concerning the vibrational properties of glasses. The relation between the acoustic modes and the universal boson peak (BP) appearing in the vibrational density of states of glasses has been investigated, also in relation with some recent theoretical models. Moreover, the connection between the elastic properties of glasses and the slowing down of the structural relaxation process in supercooled liquids has been scrutinized. For what concerns the first issue, it is here shown that the wave vector dependence of the acoustic excitations can be used, in sorbitol, to quantitatively reproduce the shape of the boson peak, supporting the relation between BP and acoustic modes. For what concerns the second issue, a proper study of elasticity over a wide spatial range is shown to be fundamental in order to investigate the relation between elastic properties and the slowing down of the dynamics in the corresponding supercooled liquid phase.

  1. Pulse Laser Deposition Fabricating Gold Nanoclusters on a Glassy Carbon Surface for Nonenzymatic Glucose Sensing.

    PubMed

    Shu, Honghui; Chang, Gang; Wang, Zhiqiang; Li, Pai; Zhang, Yuting; He, Yunbin

    2015-01-01

    A One-step technique for depositing gold nanoclusters (GNCs) onto the surface of a glassy carbon (GC) plate was developed by using pulse laser deposition (PLD) with appropriate process parameters. The method is simple and clean without using any templates, surfactants, or stabilizers. The experimental factors (pulse laser number and the pressure of inert gas (Ar)) that affect the morphology and structure of GNCs, and thus affect the electrocatalytic oxidation performance towards glucose were systematically investigated by means of transmission electron microscopy (TEM) and electrochemical methods (cyclic voltammograms (CV) and chronoamperometry methods). The GC electrode modified by GNCs exhibited a rapid response time (about 2 s), a broad linear range (0.1 to 20 mM), and good stability. The sensitivity was estimated to be 31.18 μA cm(-2) mM(-1) (vs. geometric area), which is higher than that of the Au bulk electrode. It has a good resistance to the common interfering species, such as ascorbic acid (AA), uric acid (UA) and 4-acetaminophen (AP). Therefore, this work has demonstrated a simple and effective sensing platform for the nonenzymatic detection of glucose, and can be used as a new material for a novel non-enzymatic glucose sensor.

  2. Electropolymerized molecular imprinting on glassy carbon electrode for voltammetric detection of dopamine in biological samples.

    PubMed

    Kiss, Laszlo; David, Vasile; David, Iulia Gabriela; Lazăr, Paul; Mihailciuc, Constantin; Stamatin, Ioan; Ciobanu, Adela; Ştefănescu, Cristian Dragoş; Nagy, Livia; Nagy, Géza; Ciucu, Anton Alexandru

    2016-11-01

    A simple and reliable method for preparing a selective dopamine (DA) sensor based on a molecularly imprinted polymer of ethacridine was proposed. The molecularly imprinted polymer electrode was prepared through electrodepositing polyethacridine-dopamine film on the glassy carbon electrode and then removing DA from the film via chemical induced elution. The molecular imprinted sensor was tested by cyclic voltammetry as well as by differential pulse voltammetry (DPV) to verify the changes in oxidative currents of DA. In optimized DPV conditions the oxidation peak current was well-proportional to the concentration of DA in the range from 2.0×10(-8)M up to 1×10(-6)M. The limit of detection (3σ) of DA was found to be as low as 4.4nM, by the proposed sensor that could be considered a sensitive marker of DA depletion in Parkinson's disease. Good reproducibility with relative standard deviation of 1.4% and long term stability within two weeks were also observed. The modified sensor was validated for the analysis of DA in deproteinized human serum samples using differential pulse voltammetric technique. PMID:27591643

  3. Application of low-temperature glassy carbon films in solid-phase microextraction.

    PubMed

    Giardina, M; Olesik, S V

    2001-12-15

    Low-temperature glassy carbon (LTGC) films were investigated as a sorbent coating for solid-phase microextraction because of its uniquely selective adsorptive characteristics. The selectivity of these coatings is primarily controlled by shape characteristics of the solute molecule and the final processing temperature used to form the LTGC, demonstrating unique adsorptive characteristics compared to commercial phases. The LTGC films were prepared by first coating porous silica particles with a diethylnyl oligomer precursor and then heat curing at temperatures between 300 and 1000 degrees C to form the LTGC. Then, using a sol-gel process, the LTGC-coated silica particles were immobilized onto stainless steel fibers and subsequently used for headspace and liquid extractions followed by GC-FID analysis. The selectivity of the LTGC is demonstrated by the extraction of a variety of aromatic hydrocarbons as well as the taste and odor contaminants geosmin, 2-methylisoborneol, and 2,4,6-trichloroanisole commonly found in water supplies. The data show that the LTGC coating has the highest affinity for molecules with the greatest cross-sectional surface area and polarizability and that this selective mechanism increases as a function of LTGC processing temperature. PMID:11791552

  4. Local Structure and Ion Transport in Glassy Poly(ethylene oxide styrene) Copolymers

    NASA Astrophysics Data System (ADS)

    Yang, Han-Chang; Mays, Jimmy; Sokolov, Alexei P.; Winey, Karen I.

    2014-03-01

    Polymer electrolytes have attracted attention for a wide variety of applications in energy production such as lithium-ion batteries and fuel cells. The concept of free volume provides important information about ion mobility and chain dynamics in the polymer matrix. Researchers have recently demonstrated that ion transport in glassy polymer can be improved by designing a system with high free volume. We have studied the effect of temperature and humidity on the intermolecular correlations of poly(ethylene oxide styrene-block-styrene) (PEOSt- b-St) block copolymer and poly(ethylene oxide styrene) (PEOSt) homopolymer using in situ multi-angle x-ray scattering across a wide range of scattering angles (q = 0.007-1.5 Å-1) . An increase in backbone-to-backbone distance is observed, indicating an increase in free volume between different polymer main chains. Structural characterization of the polymer segments will be discussed together with conductivity and dielectric results to better understand the ion transport mechanism in the local environment of the polymer system. Department of Chemistry, University of Tennessee.

  5. Confinement-Induced Glassy Dynamics in a Model for Chromosome Organization

    NASA Astrophysics Data System (ADS)

    Kang, Hongsuk; Yoon, Young-Gui; Thirumalai, D.; Hyeon, Changbong

    2015-11-01

    Recent experiments showing scaling of the intrachromosomal contact probability, P (s )˜s-1 with the genomic distance s , are interpreted to mean a self-similar fractal-like chromosome organization. However, scaling of P (s ) varies across organisms, requiring an explanation. We illustrate dynamical arrest in a highly confined space as a discriminating marker for genome organization, by modeling chromosomes inside a nucleus as a homopolymer confined to a sphere of varying sizes. Brownian dynamics simulations show that the chain dynamics slows down as the polymer volume fraction (ϕ ) inside the confinement approaches a critical value ϕc. The universal value of ϕc∞≈0.44 for a sufficiently long polymer (N ≫1 ) allows us to discuss genome dynamics using ϕ as the sole parameter. Our study shows that the onset of glassy dynamics is the reason for the segregated chromosome organization in humans (N ≈3 ×109, ϕ ≳ϕc∞), whereas chromosomes of budding yeast (N ≈108, ϕ <ϕc∞) are equilibrated with no clear signature of such organization.

  6. Quasi-elastic neutron scattering studies of the slow dynamics of supercooled and glassy aspirin

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Tyagi, Madhusudan; Mamontov, Eugene; Chen, Sow-Hsin

    2012-02-01

    Aspirin, also known as acetylsalicylic acid (ASA), is not only a wonderful drug, but also a good glass former. Therefore, it serves as an important molecular system to study the near-arrest and arrested phenomena. In this paper, a high-resolution quasi-elastic neutron scattering (QENS) technique is used to investigate the slow dynamics of supercooled liquid and glassy aspirin from 410 down to 350 K. The measured QENS spectra can be analyzed with a stretched exponential model. We find that (i) the stretched exponent β(Q) is independent of the wavevector transfer Q in the measured Q range and (ii) the structural relaxation time τ(Q) follows a power-law dependence on Q. Consequently, the Q-independent structural relaxation time τ0 can be extracted for each temperature to characterize the slow dynamics of aspirin. The temperature dependence of τ0 can be fitted with the mode-coupling power law, the Vogel-Fulcher-Tammann equation and a universal equation for fragile glass forming liquids recently proposed by Tokuyama in the measured temperature range. The calculated dynamic response function χT(Q, t) using the experimentally determined self-intermediate scattering function of the hydrogen atoms of aspirin shows direct evidence of the enhanced dynamic fluctuations as the aspirin is increasingly supercooled, in agreement with the fixed-time mean squared displacement langx2rang and the non-Gaussian parameter α2 extracted from the elastic scattering.

  7. Quasi-Elastic Neutron Scattering Studies of the Slow Dynamics of Supercooled and Glassy Aspirin

    SciTech Connect

    Zhang, Yang; Tyagi, M.; Mamontov, Eugene; Chen, Sow-hsin H

    2011-01-01

    Aspirin, also known as acetylsalicylic acid (ASA), is not only a wonderful drug, but also a good glass former. Therefore, it serves as an important molecular system to study the near-arrest and arrested phenomena. In this paper, a high-resolution quasi-elastic neutron scattering (QENS) technique is used to investigate the slow dynamics of supercooled liquid and glassy aspirin from 410 K down to 350 K. The measured QENS spectra can be analyzed with a stretched exponential model. We find that (i) the stretched exponent (Q) is independent of the wave vector transfer Q in the measured Q-range, and (ii) the structural relaxation time (Q) follows a power law dependence on Q. Consequently, the Q-independent structural relaxation time 0 can be extracted for each temperature to characterize the slow dynamics of aspirin. The temperature dependence of 0 can be fitted with the mode coupling power law, the Vogel-Fulcher-Tammann equation and a universal equation for fragile glass forming liquids recently proposed by M. Tokuyama in the measured temperature range. The calculated dynamic response function T(Q,t) using the experimentally determined self-intermediate scattering function of the hydrogen atoms of aspirin shows a direct evidence of the enhanced dynamic fluctuations as the aspirin is increasingly supercooled, in agreement with the fixed-time mean squared displacement x2 and non-Gaussian parameter 2 extracted from the elastic scattering.

  8. Spinodals with Disorder: From Avalanches in Random Magnets to Glassy Dynamics.

    PubMed

    Nandi, Saroj Kumar; Biroli, Giulio; Tarjus, Gilles

    2016-04-01

    We revisit the phenomenon of spinodals in the presence of quenched disorder and develop a complete theory for it. We focus on the spinodal of an Ising model in a quenched random field (RFIM), which has applications in many areas from materials to social science. By working at zero temperature in the quasistatically driven RFIM, thermal fluctuations are eliminated and one can give a rigorous content to the notion of spinodal. We show that the latter is due to the depinning and the subsequent expansion of rare droplets. We work out the associated critical behavior, which, in any finite dimension, is very different from the mean-field one: the characteristic length diverges exponentially and the thermodynamic quantities display very mild nonanalyticities much like in a Griffith phenomenon. From the recently established connection between the spinodal of the RFIM and glassy dynamics, our results also allow us to conclusively assess the physical content and the status of the dynamical transition predicted by the mean-field theory of glass-forming liquids. PMID:27104718

  9. Electron photoemission from platinum and palladium microdeposits on glassy carbon into the solution

    SciTech Connect

    Yakushev, V.V.; Bagotskii, V.S.; Skundin, A.M.

    1984-08-01

    It was of interest to the authors to compare the electrocatalytic and photoemission properties of microdeposits in other systems. Platinum and palladium microdeposits on glassy carbon were selected as such systems in the present work. The procedure used in the photoemission measurements has been previously described. All measurements were conducted in 1 N KOH. A mercury-mercuric oxide electrode served as reference electrode. The true surface areas of the platinum microdeposits were measured potentiodynamically in terms of hydrogen adsorption and oxygen desorption, while that of the palladium microdeposits was measured in terms of oxygen desorption. The results of the present work yield the important conclusion that the changes which occur in the density of electronic states in the microdeposits because of their contact with the support depend on potential, i.e., on the position of the Fermi level. It is found that the enhancement of the photoemission currents is attended by an increase, and the depression of the photoemission currents is attended by a decrease in electrocatalytic activity.

  10. Electroplating on titanium alloy

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1971-01-01

    Activation process forms adherent electrodeposits of copper, nickel, and chromium on titanium alloy. Good adhesion of electroplated deposits is obtained by using acetic-hydrofluoric acid anodic activation process.

  11. Alloy Selection System

    SciTech Connect

    2001-02-01

    Software will Predict Corrosion Rates to Improve Productivity in the Chemical Industry. Many aspects of equipment design and operation are influenced by the choice of the alloys used to fabricate process equipment.

  12. PLUTONIUM-URANIUM ALLOY

    DOEpatents

    Coffinberry, A.S.; Schonfeld, F.W.

    1959-09-01

    Pu-U-Fe and Pu-U-Co alloys suitable for use as fuel elements tn fast breeder reactors are described. The advantages of these alloys are ease of fabrication without microcracks, good corrosion restatance, and good resistance to radiation damage. These advantages are secured by limitation of the zeta phase of plutonium in favor of a tetragonal crystal structure of the U/sub 6/Mn type.

  13. Disk Alloy Development

    NASA Technical Reports Server (NTRS)

    Gabb, Tim; Gayda, John; Telesman, Jack

    2001-01-01

    The advanced powder metallurgy disk alloy ME3 was designed using statistical screening and optimization of composition and processing variables in the NASA HSR/EPM disk program to have extended durability at 1150 to 1250 "Fin large disks. Scaled-up disks of this alloy were produced at the conclusion of this program to demonstrate these properties in realistic disk shapes. The objective of the UEET disk program was to assess the mechanical properties of these ME3 disks as functions of temperature, in order to estimate the maximum temperature capabilities of this advanced alloy. Scaled-up disks processed in the HSR/EPM Compressor / Turbine Disk program were sectioned, machined into specimens, and tested in tensile, creep, fatigue, and fatigue crack growth tests by NASA Glenn Research Center, in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. Additional sub-scale disks and blanks were processed and tested to explore the effects of several processing variations on mechanical properties. Scaled-up disks of an advanced regional disk alloy, Alloy 10, were used to evaluate dual microstructure heat treatments. This allowed demonstration of an improved balance of properties in disks with higher strength and fatigue resistance in the bores and higher creep and dwell fatigue crack growth resistance in the rims. Results indicate the baseline ME3 alloy and process has 1300 to 1350 O F temperature capabilities, dependent on detailed disk and engine design property requirements. Chemistry and process enhancements show promise for further increasing temperature capabilities.

  14. Atomic structure of glassy Mg{sub 60}Cu{sub 30}Y{sub 10} investigated with EXAFS, x-ray and neutron diffraction, and reverse Monte Carlo simulations

    SciTech Connect

    Jovari, Pal; Saksl, Karel; Pryds, Nini; Lebech, Bente; Bailey, Nicholas P.; Mellerga ring rd, Anders; Delaplane, Robert G.; Franz, Hermann

    2007-08-01

    Short range order of amorphous Mg{sub 60}Cu{sub 30}Y{sub 10} 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 Mg{sub 2}Cu. The Cu-Y coordination number is 1.1{+-}0.2, and the Cu-Y distance is {approx}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 studied by differential scanning calorimetry and in situ x-ray powder diffraction. The alloy shows a glass transition and three crystallization events, the first and dominant one at 456 K corresponding to eutectic crystallization of at least three phases: Mg{sub 2}Cu and most likely cubic MgY and CuMgY.

  15. Correlation between diffusion barriers and alloying energy in binary alloys.

    PubMed

    Vej-Hansen, Ulrik Grønbjerg; Rossmeisl, Jan; Stephens, Ifan E L; Schiøtz, Jakob

    2016-01-28

    In this paper, we explore the notion that a negative alloying energy may act as a descriptor for long term stability of Pt-alloys as cathode catalysts in low temperature fuel cells. Using density functional theory calculations, we show that there is a correlation between the alloying energy of an alloy, and the diffusion barriers of the minority component. Alloys with a negative alloying energy may show improved long term stability, despite the fact that there is typically a greater thermodynamic driving force towards dissolution of the solute metal over alloying. In addition to Pt, we find that this trend also appears to hold for alloys based on Al and Pd. PMID:26750475

  16. Impeded ice nucleation in glassy and highly viscous aerosol particles: the role of water diffusion

    NASA Astrophysics Data System (ADS)

    Marcolli, C.; Peter, T.; Zobrist, B.; Krieger, U. K.; Luo, B. P.; Soonsin, V.; Pedernera, D. A.; Koop, T.

    2010-05-01

    are therefore likely to form glasses in the upper troposphere. If aerosol particles are highly viscous or glassy, the equality between relative humidity of an air mass and water activity of the contained particles is no longer fulfilled because water diffusion within the particles is too slow to follow RH changes in the atmosphere. There is a lack of literature data for water diffusion within organic glasses at low temperatures. We therefore measured hygroscopicity cycles of aerosol particles with an electrodynamic balance (EDB) at temperatures between 220 - 291 K and developed a microphysical model to calculate diffusion coefficients of water within the particles based on the EDB results together with available literature data. As model substance we chose sucrose, a substance that has been identified in biomass burning aerosols and may represent the high molecular weight constituents of the organic aerosol fraction. We indeed observed a hysteresis between water uptake and release for levitated sucrose particles that is due to slow water diffusion within the glassy particle and can be used to derive water diffusion coefficients at low temperatures with our microphysical model.

  17. Surface observation for seed-mediated growth attachment of gold nanoparticles on a glassy carbon substrate.

    PubMed

    Oyama, Munetaka; Yamaguchi, Shin-Ya; Zhang, Jingdong

    2009-02-01

    A seed-mediated growth method for surface modification was applied to the attachment of gold nanoparticles (AuNPs) to glassy carbon (GC) surfaces. By simply immersing a GC plate at first into a seed solution containing 4 nm Au nano-seed particles and then into a growth solution containing HAuCl(4), ascorbic acid and cetyltrimethyammonium bromide, AuNPs could be successfully attached to the GC surface via the growth of nanoparticles. A possible control of the size and density of AuNPs on GC was examined by observing surface images with a field-emission scanning electron microscope (FE-SEM) after several preparations with different immersion times. Compared with previous results on the growth of AuNPs on indium tin oxide (ITO) surfaces, it was characteristic that the AuNPs attached to GC surfaces exhibited smaller size and higher density as well as a flatter and non-crystal-like morphology. In addition, for performing the dense attachment of regular nano-sized AuNPs on GC surfaces, immersion for 2 h into the growth solution was sufficient. Longer immersion for 24 h caused an irregular growth of bold Au micro-crystals, while 24 h was necessary in the case of AuNPs on ITO surfaces. Shorter seeding and growth times were found to be effective for a sparse attachment of smaller Au nanoparticles whose size was ca. 20 nm. It was clarified that the seed-mediated growth method for surface modification was valid for fabricating a nanointerface composed of AuNPs on GC surfaces.

  18. Short-Time Glassy Dynamics in Viscous Protein Solutions with Competing Interactions

    DOE PAGESBeta

    Godfrin, P. Douglas; Hudson, Steven; Hong, Kunlun; Porcar, Lionel; Falus, Peter; Wagner, Norman; Liu, Yun

    2015-11-24

    Although there have been numerous investigations of the glass transition for colloidal dispersions with only a short-ranged attraction, less is understood for systems interacting with a long-ranged repulsion in addition to this attraction, which is ubiquitous in aqueous protein solutions at low ionic strength. Highly puri ed concentrated lysozyme solutions are used as a model system and investigated over a large range of protein concentrations at very low ionic strength. Newtonian liquid behavior is observed at all concentrations, even up to 480 mg/mL, where the zero shear viscosity increases by more than three orders of magnitude with increasing concentration. Remarkably,more » despite this macroscopic liquid-like behavior, the measurements of the dynamics in the short-time limit shows features typical of glassy colloidal systems. Investigation of the inter-protein structure indicates that the reduced short-time mobility of the protein is caused by localized regions of high density within a heterogeneous density distribution. This structural heterogeneity occurs on intermediate range length scale, driven by the competing potential features, and is distinct from commonly studied colloidal gel systems in which a heterogeneous density distribution tends to extend to the whole system. The presence of long-ranged repulsion also allows for more mobility over large length and long time scales resulting in the macroscopic relaxation of the structure. The experimental results provide evidence for the need to explicitly include intermediate range order in theories for the macroscopic properties of protein solutions interacting via competing potential features.« less

  19. A new Phytoreovirus infecting the glassy-winged sharpshooter (Homalodisca vitripennis)

    SciTech Connect

    Stenger, Drake C.; Sisterson, Mark S.; Krugner, Rodrigo; Backus, Elaine A.; Hunter, Wayne B.

    2009-04-10

    A new virus species of the genus Phytoreovirus was isolated from glassy-winged sharpshooter (GWSS), Homalodisca vitripennis Germar (Hemiptera: Cicadellidae), in California and designated here as Homalodisca vitripennis reovirus (HoVRV). Extraction of nucleic acid from GWSS adults collected from three Californian populations revealed an array of double-stranded (ds) RNA species that was soluble in 2 M LiCl and resistant to degradation upon exposure to S1 nuclease and DNase. Analysis of nucleic acid samples from single GWSS adults indicated that HoVRV dsRNA accumulated to high titer in individual insects. Double-shelled isometric virus particles purified from GWSS adults resembled those observed in thin sections of GWSS salivary glands by transmission electron microscopy. Purified HoVRV virions contained 12 dsRNA segments that, based on complete nucleotide sequences, ranged in size from 4475 to 1040 bp. Sequence comparisons indicated that the HoVRV dsRNA segments were most closely related (58.5 to 43.7% nt sequence identity) to the corresponding genome segments of Rice dwarf virus (RDV). Each HoVRV dsRNA segment encoded a single open reading frame (> 300 nts) except for segment 11, which appears to be dicistronic. Terminal nucleotide sequences of HoVRV positive-sense RNAs were similar to other phytoreoviruses (GGCG or GGCA at the 5'-end and UGAU or CGAU at the 3'-end) with adjacent imperfect inverted repeats potentially able to base pair. Phylogenetic analyses of the RNA-directed RNA polymerase (encoded by segment 1) and the outer capsid protein (encoded by segment 8) confirmed placement of HoVRV as a species of the genus Phytoreovirus sharing a most recent common ancestor with RDV. Reverse transcription-polymerase chain reaction assays revealed that HoVRV infection of GWSS in California was common and that the virus also occurred in GWSS populations from the Carolinas and Texas.

  20. Novel Cholesteric Glassy Liquid Crystals Comprising Benzene Functionalized with Hybrid Chiral-Nematic Mesogens

    SciTech Connect

    Kim, C; Marshall, K L; Wallace, J U; Ou, J J; Chen, S H

    2010-03-12

    With 4-cyanobiphenyl-4-yl benzoate nematogens chemically bonded to a benzene core via enantiomeric 2-methylpropyl spacers, a new series of cholesteric glassy liquid crystals has been synthesized for an investigation of structure-property relationships. Glass-forming ability, phase-transition temperatures, and stability against crystallization are affected by both the number and the position of substituent groups on the benzene ring with 1,3,5-trisubstituted system possessing the most favorable set of properties, Tg at 73 °C and Tc at 295 °C. With (S)-3-bromo-2-methylpropanol as the chiral precursor, left-handed helical stacking was observed for all the cholesteric GLCs reported herein. Films of the 1,3,5-trisubstituted and meta-disubstituted systems show a selective reflection wavelength, λR, at 413 and 422 nm, respectively, whereas that of the ortho-isomer exhibits a λR at 860 nm. Replacing one of the hybrid chiral-nematic mesogen in the 1,3,5-trisubstituted system by a nematogen loosens the helical pitch to yield a λR at 630 nm, still shorter than that of the ortho-isomer despite the dilution by a nematogen. This observation suggests the importance of regioisomerism to helical twisting. The difference in λR was interpreted in terms of molecular packing involving chiral spacers through computational chemistry. The susceptibility of cholesteric GLCs to photoalignment was tested using the ortho-isomer. The degree of photoalignment improves with an increasing rotational mobility of pendant coumarin monomers to an extent comparable to mechanical alignment on conventional rubbed polyimide films.

  1. Effect of a new bioactive fibrous glassy scaffold on bone repair.

    PubMed

    Gabbai-Armelin, P R; Souza, M T; Kido, H W; Tim, C R; Bossini, P S; Magri, A M P; Fernandes, K R; Pastor, F A C; Zanotto, E D; Parizotto, N A; Peitl, O; Renno, A C M

    2015-05-01

    Researchers have investigated several therapeutic approaches to treat non-union fractures. Among these, bioactive glasses and glass ceramics have been widely used as grafts. This class of biomaterial has the ability to integrate with living bone. Nevertheless, bioglass and bioactive materials have been used mainly as powder and blocks, compromising the filling of irregular bone defects. Considering this matter, our research group has developed a new bioactive glass composition that can originate malleable fibers, which can offer a more suitable material to be used as bone graft substitutes. Thus, the aim of this study was to assess the morphological structure (via scanning electron microscope) of these fibers upon incubation in phosphate buffered saline (PBS) after 1, 7 and 14 days and, also, evaluate the in vivo tissue response to the new biomaterial using implantation in rat tibial defects. The histopathological, immunohistochemistry and biomechanical analyzes after 15, 30 and 60 days of implantation were performed to investigate the effects of the material on bone repair. The PBS incubation indicated that the fibers of the glassy scaffold degraded over time. The histological analysis revealed a progressive degradation of the material with increasing implantation time and also its substitution by granulation tissue and woven bone. Histomorphometry showed a higher amount of newly formed bone area in the control group (CG) compared to the biomaterial group (BG) 15 days post-surgery. After 30 and 60 days, CG and BG showed a similar amount of newly formed bone. The novel biomaterial enhanced the expression of RUNX-2 and RANK-L, and also improved the mechanical properties of the tibial callus at day 15 after surgery. These results indicated a promising use of the new biomaterial for bone engineering. However, further long-term studies should be carried out to provide additional information concerning the material degradation in the later stages and the bone

  2. Effect of a new bioactive fibrous glassy scaffold on bone repair.

    PubMed

    Gabbai-Armelin, P R; Souza, M T; Kido, H W; Tim, C R; Bossini, P S; Magri, A M P; Fernandes, K R; Pastor, F A C; Zanotto, E D; Parizotto, N A; Peitl, O; Renno, A C M

    2015-05-01

    Researchers have investigated several therapeutic approaches to treat non-union fractures. Among these, bioactive glasses and glass ceramics have been widely used as grafts. This class of biomaterial has the ability to integrate with living bone. Nevertheless, bioglass and bioactive materials have been used mainly as powder and blocks, compromising the filling of irregular bone defects. Considering this matter, our research group has developed a new bioactive glass composition that can originate malleable fibers, which can offer a more suitable material to be used as bone graft substitutes. Thus, the aim of this study was to assess the morphological structure (via scanning electron microscope) of these fibers upon incubation in phosphate buffered saline (PBS) after 1, 7 and 14 days and, also, evaluate the in vivo tissue response to the new biomaterial using implantation in rat tibial defects. The histopathological, immunohistochemistry and biomechanical analyzes after 15, 30 and 60 days of implantation were performed to investigate the effects of the material on bone repair. The PBS incubation indicated that the fibers of the glassy scaffold degraded over time. The histological analysis revealed a progressive degradation of the material with increasing implantation time and also its substitution by granulation tissue and woven bone. Histomorphometry showed a higher amount of newly formed bone area in the control group (CG) compared to the biomaterial group (BG) 15 days post-surgery. After 30 and 60 days, CG and BG showed a similar amount of newly formed bone. The novel biomaterial enhanced the expression of RUNX-2 and RANK-L, and also improved the mechanical properties of the tibial callus at day 15 after surgery. These results indicated a promising use of the new biomaterial for bone engineering. However, further long-term studies should be carried out to provide additional information concerning the material degradation in the later stages and the bone

  3. Sequencing and De Novo Assembly of the Transcriptome of the Glassy-Winged Sharpshooter (Homalodisca vitripennis)

    PubMed Central

    Nandety, Raja Sekhar; Kamita, Shizuo G.; Hammock, Bruce D.; Falk, Bryce W.

    2013-01-01

    Background The glassy-winged sharpshooter Homalodisca vitripennis (Hemiptera: Cicadellidae), is a xylem-feeding leafhopper and important vector of the bacterium Xylella fastidiosa; the causal agent of Pierce’s disease of grapevines. The functional complexity of the transcriptome of H. vitripennis has not been elucidated thus far. It is a necessary blueprint for an understanding of the development of H. vitripennis and for designing efficient biorational control strategies including those based on RNA interference. Results Here we elucidate and explore the transcriptome of adult H. vitripennis using high-throughput paired end deep sequencing and de novo assembly. A total of 32,803,656 paired-end reads were obtained with an average transcript length of 624 nucleotides. We assembled 32.9 Mb of the transcriptome of H. vitripennis that spanned across 47,265 loci and 52,708 transcripts. Comparison of our non-redundant database showed that 45% of the deduced proteins of H. vitripennis exhibit identity (e-value ≤1−5) with known proteins. We assigned Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations, and potential Pfam domains to each transcript isoform. In order to gain insight into the molecular basis of key regulatory genes of H. vitripennis, we characterized predicted proteins involved in the metabolism of juvenile hormone, and biogenesis of small RNAs (Dicer and Piwi sequences) from the transcriptomic sequences. Analysis of transposable element sequences of H. vitripennis indicated that the genome is less expanded in comparison to many other insects with approximately 1% of the transcriptome carrying transposable elements. Conclusions Our data significantly enhance the molecular resources available for future study and control of this economically important hemipteran. This transcriptional information not only provides a more nuanced understanding of the underlying biological and physiological mechanisms that govern H

  4. Evidence for phase separation during the crystallization of hyperquenched glassy clathrate hydrate forming solutions

    NASA Astrophysics Data System (ADS)

    Tulk, C. A.; Ba, Y.; Klug, D. D.; McLaurin, G.; Ripmeester, J. A.

    1999-04-01

    Tetrahydrofuran, a water-soluble cyclic ether molecule, is well known for its ability to form clathrate hydrates (cubic structure II, melting point 277.5 K). An aqueous solution of THF (17:1 molecular ratio) was hyperquenched (cooled at a rate of 106Ks-1) to 77 K to give recoverable samples of ˜1 g of metastable amorphous material. The crystallization process was studied on three complementary length scales by x-ray powder diffraction, quadrupole echo double resonance (QEDOR) NMR spectroscopy, and Raman spectroscopy as the amorphous material was annealed at temperatures between 80 and 190 K. Results show that phase separation of the two components occurred predominantly during the annealing process, resulting in clusters of crystalline THF and ice Ic before clathrate hydrate crystallization was initiated. During the hyperquenching process, the decreasing molecular mobility of water molecules between room temperature and the fictive temperature (the temperature below which the solution becomes structurally immobilized upon hyperquenching) inhibits growth of the crystal nuclei that normally would result in crystalline clathrate hydrate formation. Annealing the samples between 110-140 K showed that the local hydrogen bonded O-H--O structure of the water molecules changed toward the arrangement characteristic of crystalline ice Ic. We propose that this process forces the THF out of the glassy solution, thus increasing the THF cluster size in the deposit so that these become visible to diffraction. Further annealing, above 150-160 K caused large-scale growth of crystalline clathrate hydrate material, which then could be associated with a reduction in the THF cluster size, and ice Ic.

  5. Glassy properties and viscous slowing down: An analysis of the correlation between nonergodicity factor and fragility.

    PubMed

    Niss, Kristine; Dalle-Ferrier, Cécile; Giordano, Valentina M; Monaco, Giulio; Frick, Bernhard; Alba-Simionesco, Christiane

    2008-11-21

    We present an extensive analysis of the proposed relationship [T. Scopigno et al., Science 302, 849 (2003)] between the fragility of glass-forming liquids and the nonergodicity factor as measured by inelastic x-ray scattering. We test the robustness of the correlation through the investigation of the relative change under pressure of the speed of sound, nonergodicity factor, and broadening of the acoustic exitations of a molecular glass former, cumene, and of a polymer, polyisobutylene. For polyisobutylene, we also perform a similar study by varying its molecular weight. Moreover, we have included new results on liquids presenting an exceptionally high fragility index m under ambient conditions. We show that the linear relation, proposed by Scopigno et al. [Science 302, 849 (2003)] between fragility, measured in the liquid state, and the slope alpha of the inverse nonergodicity factor as a function of T/T(g), measured in the glassy state, is not verified when increasing the data base. In particular, while there is still a trend in the suggested direction at atmospheric pressure, its consistency is not maintained by introducing pressure as an extra control parameter modifying the fragility: whatever is the variation in the isobaric fragility, the inverse nonergodicity factor increases or remains constant within the error bars, and one observes a systematic increase in the slope alpha when the temperature is scaled by T(g)(P). To avoid any particular aspects that might cause the relation to fail, we have replaced the fragility by other related properties often evoked, e.g., thermodynamic fragility, for the understanding of its concept. Moreover, we find, as previously proposed by two of us [K. Niss and C. Alba-Simionesco, Phys. Rev. B 74, 024205 (2006)], that the nonergodicity factor evaluated at the glass transition qualitatively reflects the effect of density on the relaxation time even though in this case no clear quantitative correlations appear. PMID:19026072

  6. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

    Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

    1987-01-01

    Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

  7. De-alloyed platinum nanoparticles

    DOEpatents

    Strasser, Peter; Koh, Shirlaine; Mani, Prasanna; Ratndeep, Srivastava

    2011-08-09

    A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

  8. PLUTONIUM-URANIUM-TITANIUM ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-07-28

    A plutonium-uranium alloy suitable for use as the fuel element in a fast breeder reactor is described. The alloy contains from 15 to 60 at.% titanium with the remainder uranium and plutonium in a specific ratio, thereby limiting the undesirable zeta phase and rendering the alloy relatively resistant to corrosion and giving it the essential characteristic of good mechanical workability.

  9. Sudden switchover between the polyamorphic phase separation and the glass-to-liquid transition in glassy LiCl aqueous solutions.

    PubMed

    Suzuki, Yoshiharu; Mishima, Osamu

    2013-02-28

    Lithium chloride aqueous solutions (LiClaq solutions) below 10 mol.% are vitrified by cooling from room temperature to 77 K at 0.3 GPa. We examine the solvent state of the glassy sample and its transformation by heating at 1 atm using low-temperature differential scanning calorimetry and Raman spectroscopy. This experimental study suggests strongly that the solvent state of the glassy LiClaq solution closely relates to the state of high-density amorphous ice. Moreover, we reconfirm that the separation into the low-density amorphous ice and the glassy highly concentrated LiClaq solution occurs in the glassy dilute LiClaq solution at ∼130 K, not the glass-to-liquid transition which is commonly observed in the glassy LiClaq solution above ∼10 mol.%. In order to interpret the sudden switchover between the glass-to-liquid transition and the phase separation at ∼10 mol.%, we propose a state diagram of LiClaq solution which connects with a polyamorphic state diagram of pure water and discuss a possibility that the electric field induces a polyamorphic transition of water. PMID:23464160

  10. Generation and Characterization of Anisotropic Microstructures in Rare Earth-Iron-Boron Alloys

    SciTech Connect

    Oster, Nathaniel

    2012-01-01

    The goal of this work is to investigate methods in which anisotropy could be induced in fine-grained alloys. We have identified two general processing routes to creating a fine, textured microstructure: form an amorphous precursor and devitrify in a manner that induces texture or form the fine, textured microstructure upon cooling directly from the liquid state. Since it is possible to form significant amounts of amorphous material in RE-Fe-B alloys, texture could be induced through biasing the orientationof the crystallites upon crystallization of the amorphous material. One method of creating this bias is to form glassy material and apply uniaxial pressure during crystallization. Experiments on this are presented. All of the work presented here utilizes melt-spinning, either to create precursor material, or to achieve a desired final microstructure. To obtain greater control of the system to process these materials, a study was done on the effects of heating the wheel and modifying the wheel’s surface finish on glass formation and phase selection. The second general approach—creating the desired microstructure directly from the liquid—can be done through directional rapid solidification. In particular, alloys melt-spun at low tangential wheel speeds often display directional columnar growth through a portion of the ribbon. By refining and stabilizing the columnar growth, a highly textured fine microstructure is achieved. The effects of adding a segregating element (Ag) on the columnar growth are characterized and presented.

  11. Glass-ceramic coated Mg-Ca alloys for biomedical implant applications.

    PubMed

    Rau, J V; Antoniac, I; Fosca, M; De Bonis, A; Blajan, A I; Cotrut, C; Graziani, V; Curcio, M; Cricenti, A; Niculescu, M; Ortenzi, M; Teghil, R

    2016-07-01

    Biodegradable metals and alloys are promising candidates for biomedical bone implant applications. However, due to the high rate of their biodegradation in human body environment, they should be coated with less reactive materials, such, for example, as bioactive glasses or glass-ceramics. Fort this scope, RKKP composition glass-ceramic coatings have been deposited on Mg-Ca(1.4wt%) alloy substrates by Pulsed Laser Deposition method, and their properties have been characterized by a number of techniques. The prepared coatings consist of hydroxyapatite and wollastonite phases, having composition close to that of the bulk target material used for depositions. The 100μm thick films are characterized by dense, compact and rough morphology. They are composed of a glassy matrix with various size (from micro- to nano-) granular inclusions. The average surface roughness is about 295±30nm due to the contribution of micrometric aggregates, while the roughness of the fine-texture particulates is approximately 47±4nm. The results of the electrochemical corrosion evaluation tests evidence that the RKKP coating improves the corrosion resistance of the Mg-Ca (1.4wt%) alloy in Simulated Body Fluid.

  12. Glass-ceramic coated Mg-Ca alloys for biomedical implant applications.

    PubMed

    Rau, J V; Antoniac, I; Fosca, M; De Bonis, A; Blajan, A I; Cotrut, C; Graziani, V; Curcio, M; Cricenti, A; Niculescu, M; Ortenzi, M; Teghil, R

    2016-07-01

    Biodegradable metals and alloys are promising candidates for biomedical bone implant applications. However, due to the high rate of their biodegradation in human body environment, they should be coated with less reactive materials, such, for example, as bioactive glasses or glass-ceramics. Fort this scope, RKKP composition glass-ceramic coatings have been deposited on Mg-Ca(1.4wt%) alloy substrates by Pulsed Laser Deposition method, and their properties have been characterized by a number of techniques. The prepared coatings consist of hydroxyapatite and wollastonite phases, having composition close to that of the bulk target material used for depositions. The 100μm thick films are characterized by dense, compact and rough morphology. They are composed of a glassy matrix with various size (from micro- to nano-) granular inclusions. The average surface roughness is about 295±30nm due to the contribution of micrometric aggregates, while the roughness of the fine-texture particulates is approximately 47±4nm. The results of the electrochemical corrosion evaluation tests evidence that the RKKP coating improves the corrosion resistance of the Mg-Ca (1.4wt%) alloy in Simulated Body Fluid. PMID:27127065

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

    PubMed

    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.

  14. Evolution of ferromagnetic interactions from cluster spin glass state in Co-Ga alloy

    NASA Astrophysics Data System (ADS)

    Mohammad Yasin, Sk.; Saha, Ritwik; Srinivas, V.; Kasiviswanathan, S.; Nigam, A. K.

    2016-11-01

    Low temperature magnetic properties of binary CoxGa100-x (x=54-57) alloy have been investigated. Analysis of frequency dependence of ac susceptibility provided a conclusive evidence for the existence of cluster spin glass like behavior with the freezing temperature ~8, 14 K for x=54, 55.5 respectively. The parameters for conventional 'slowing down' of the spin dynamics have been extracted from the acs data, which confirm the presence of glassy phase. The magnitude of Mydosh parameter obtained from the fits is larger than that reported for typical canonical spin glasses and smaller than those for non-interacting ideal superparamagnetic systems but comparable to those of known cluster-glass systems. Memory phenomena using specific cooling protocols also support the spin-glass features in Co55.5Ga44.5 composition. Further the development of ferromagnetic clusters from the cluster spin glass state has been observed in x=57 composition.

  15. Studies on the reactive melt infiltration of silicon and silicon-molybdenum alloys in porous carbon

    NASA Technical Reports Server (NTRS)

    Singh, M.; Behrendt, D. R.

    1992-01-01

    Investigations on the reactive melt infiltration of silicon and silicon-1.7 and 3.2 at percent molybdenum alloys into porous carbon preforms have been carried out by process modeling, differential thermal analysis (DTA) and melt infiltration experiments. These results indicate that the initial pore volume fraction of the porous carbon preform is a critical parameter in determining the final composition of the raction-formed silicon carbide and other residual phases. The pore size of the carbon preform is very detrimental to the exotherm temperatures due to liquid silicon-carbon reactions encountered during the reactive melt infiltration process. A possible mechanism for the liquid silicon-porous (glassy) carbon reaction has been proposed. The composition and microstructure of the reaction-formed silicon carbide has been discussed in terms of carbon preform microstructures, infiltration materials, and temperatures.

  16. Crystal nucleation in glass-forming alloy and pure metal melts under containerless and vibrationless conditions

    NASA Technical Reports Server (NTRS)

    Spaepen, F.; Turnbull, D.

    1982-01-01

    The undercooling behavior of large spheroids of Pd40Ni40P40 was investigated. By surface etching, supporting the specimens on a fused silica substrate, and successive heating and cooling, crystallization can be eliminated, presumable due to the removal of surface heterogeneities. By this method samples up to 3.2g with a 0.53 mm minor diameter, were made entirely glassy, except for some superficial crystals comprising less than 0.5% of the volume. These experiments show that a cooling rate of approximately 1 K/sec is adequate to avoid copious homogeneous nucleation in the alloy, and that by eliminating or reducing the effectiveness of heterogeneous nucleation sites, it is possible to form bulk samples of this metallic glass with virtually unlimited dimensions.

  17. Electrode-nanoparticle collisions: The measurement of the sticking coefficient of silver nanoparticles on a glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Zhou, Yi-Ge; Rees, Neil V.; Compton, Richard G.

    2011-10-01

    In this communication, we combine anodic particle coulometry (APC) with anodic stripping voltammetry, to find the proportion of NP impacts that result in adsorbed NPs, using AgNPs in collision with glassy carbon electrode. Sticking coefficients are reported for AgNP radii of 14, 29, and 45 nm, measured at electrode biases ranging from OCV to -0.2 to -1.2 V (vs. Ag/AgCl). No significant systematic trends were found in either case. We suggest that this methodology may be widely applicable to measuring the sticking coefficient of any oxidisable metal nanoparticle on an electrode surface in solution.

  18. A highly sensitive hydrogen peroxide sensor based on (Ag-Au NPs)/poly[o-phenylenediamine] modified glassy carbon electrode.

    PubMed

    Shamsipur, Mojtaba; Karimi, Ziba; Amouzadeh Tabrizi, Mahmoud

    2015-11-01

    Herein, the poly(o-phenylenediamine) decorated with gold-silver nanoparticle (Ag-Au NPs) nanocomposite modified glassy carbon was used for the determination of hydrogen peroxide. Electrochemical experiments indicated that the proposed sensor possesses an excellent sensitivity toward the reduction of hydrogen peroxide. The resulting sensor exhibited a good response to hydrogen peroxide over linear range from 0.2 to 60.0μM with a limit of detection of 0.08μM, good reproducibility, long-term stability and negligible interference from ascorbic acid, uric acid and dopamine. The proposed sensor was successfully applied to the determination of hydrogen peroxide in human serum sample.

  19. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

    A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

  20. Surface modification of high temperature iron alloys

    DOEpatents

    Park, J.H.

    1995-06-06

    A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

  1. Work function of binary alloys

    NASA Astrophysics Data System (ADS)

    Ishii, Ryusuke; Matsumura, Katsunori; Sakai, Akira; Sakata, Toyo

    2001-01-01

    By utilizing the field emission method, we have studied the composition dependence of work function in NiCu and PtRh alloys. In PtRh alloys, we find that the work function falls below the linear interpolation, in agreement with the experimental results on AgAu alloys [Fain and McDavid, Phys. Rev. B 9 (1974) 5099]. On the other hand, the work function of NiCu alloys is found to show little systematic deviation from the linear interpolation. The observed negative deviation in PtRh alloys is not compatible with a simple theoretical prediction based on the electronic density of states.

  2. Structural and mechanical characterization of ion-irradiated glassy polymeric carbon for TRISO fuel nuclear application

    NASA Astrophysics Data System (ADS)

    Abunaemeh, Malek; Seif, Mohamed; Elsamadicy, Abdalla; Ila, Daryush

    2012-08-01

    Tristructural isotropic (TRISO) fuel is considered as the fuel design of choice for the next generation of nuclear reactors (Generation IV). Its design consists of a fuel kernel of UO x coated with several layers having different functions. One of these functions is a containment shell/diffusion barrier for the fission fragments. Normally, the material of choice for this shell is pyrolytic carbon (PyC). The material does not offer a perfect barrier, due to its inherent crystalline structure, which is planar (like graphite) and therefore impossible to mold in one continuous sheet around the spherical fuel bead. Plane boundaries allow fragment diffusion at a much higher rate than through the plane. In this study, we investigate the possibility of replacing PyC with a different form of carbon, glassy polymeric carbon (GPC). We prepared samples of GPC and studied the evolution of their physical properties and structure as a function of the radiation environment that they were exposed to. The temperature at which the samples were held during irradiation was very similar to the Generation IV nuclear reactor (∼1000°C). During the fission of U235, the fission fragment mass distribution has two maxima around 98 and 137 amu, which would best correspond to elements Rb and Cs, respectively. However, both ions are hard to produce from our SNICS ion source at the Center for Irradiation of Materials; therefore, we used 107Ag and 197Au as best replacements. The irradiation sessions consisted in various fluences of 5 MeV Ag, and 5 MeV Au. For elemental sample analysis, we used transmission electron microscopy. For mechanical analysis, we used nano-indentation. It is of prime importance to measure the penetration of the implanted 107Ag.and 197Au and the evolution of mechanical properties of GPC irradiated with these ions. A procedure for manufacturing GPC with analysis is presented. This will show how the GPC structure differs as the temperature that it is prepared at increases

  3. Alloyed coatings for dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Wermuth, F. R.; Stetson, A. R.

    1971-01-01

    Processing techniques were developed for applying several diffusion barriers to TD-Ni and TD-NiCr. Barrier coated specimens of both substrates were clad with Ni-Cr-Al and Fe-Cr-Al alloys and diffusion annealed in argon. Measurement of the aluminum distribution after annealing showed that, of the readily applicable diffusion barriers, a slurry applied tungsten barrier most effectively inhibited the diffusion of aluminum from the Ni-Cr-Al clad into the TD-alloy substrates. No barrier effectively limited interdiffusion of the Fe-Cr-Al clad with the substrates. A duplex process was then developed for applying Ni-Cr-Al coating compositions to the tungsten barrier coated substrates. A Ni-(16 to 32)Cr-3Si modifier was applied by slurry spraying and firing in vacuum, and was then aluminized by a fusion slurry process. Cyclic oxidation tests at 2300 F resulted in early coating failure due to inadequate edge coverage and areas of coating porosity. EMP analysis showed that oxidation had consumed 70 to 80 percent of the aluminum in the coating in less than 50 hours.

  4. Shape Memory Alloy Actuator

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    2000-01-01

    The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

  5. Quinary metallic glass alloys

    DOEpatents

    Lin, X.; Johnson, W.L.

    1998-04-07

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3}K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf){sub a}(Al,Zn){sub b}(Ti,Nb){sub c}(Cu{sub x}Fe{sub y}(Ni,Co){sub z}){sub d} wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d{hor_ellipsis}y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  6. Quinary metallic glass alloys

    DOEpatents

    Lin, Xianghong; Johnson, William L.

    1998-01-01

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf).sub.a (Al,Zn).sub.b (Ti,Nb).sub.c (Cu.sub.x Fe.sub.y (Ni,Co).sub.z).sub.d wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d.multidot.y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  7. Importance of thiol-functionalized molecules for the structure and properties of compression-molded glassy wheat gluten bioplastics.

    PubMed

    Jansens, Koen J A; Lagrain, Bert; Brijs, Kristof; Goderis, Bart; Smet, Mario; Delcour, Jan A

    2013-11-01

    High-temperature compression molding of wheat gluten at low water levels yields a rigid plastic-like material. We performed a systematic study to determine the effect of additives with multiple thiol (SH) groups on gluten network formation during processing and investigate the impact of the resulting gluten network on the mechanical properties of the glassy end product. To this end, a fraction of the hydroxyl groups of different polyols was converted into SH functionalities by esterifying with 3-mercaptopropionic acid (MPA). The monofunctional additive MPA was evaluated as well. During low-temperature mixing SH-containing additives decreased the gluten molecular weight, whereas protein cross-linking occurred during high-temperature compression molding. The extent of both processes depended on the molecular architecture of the additives and their concentration. After molding, the material strength and failure strain increased without affecting the modulus, provided the additive concentration was low. The strength decreased again at too high concentrations for polyols with low SH functionalization. Attributing these effects solely to the interplay of plasticization and the SH-facilitated introduction of cross-links is inadequate, since an improvement in both strength and failure strain was also observed in the presence of high levels of MPA. It is hypothesized that, regardless of the molecular structure of the additive, the presence of SH-containing groups induces conformational changes which contribute to the mechanical properties of glassy gluten materials.

  8. Raman Spectroscopy of Isotopic Water Diffusion in Ultraviscous, Glassy, and Gel States in Aerosol by Use of Optical Tweezers.

    PubMed

    Davies, James F; Wilson, Kevin R

    2016-02-16

    The formation of ultraviscous, glassy, and amorphous gel states in aqueous aerosol following the loss of water results in nonequilibrium dynamics due to the extended time scales for diffusive mixing. Existing techniques for measuring water diffusion by isotopic exchange are limited by contact of samples with the substrate, and methods applied to infer diffusion coefficients from mass transport in levitated droplets requires analysis by complex coupled differential equations to derive diffusion coefficients. We present a new technique that combines contactless levitation with aerosol optical tweezers with isotopic exchange (D2O/H2O) to measure the water diffusion coefficient over a broad range (Dw ≈ 10(-12)-10(-17) m(2)·s(-1)) in viscous organic liquids (citric acid, sucrose, and shikimic acid) and inorganic gels (magnesium sulfate, MgSO4). For the organic liquids in binary and ternary mixtures, Dw depends on relative humidity and follows a simple compositional Vignes relationship. In MgSO4 droplets, water diffusivity decreases sharply with water activity and is consistent with predictions from percolation theory. These measurements show that, by combining micrometer-sized particle levitation (a contactless measurement with rapid mixing times) with an established probe of water diffusion, Dw can be simply and directly quantified for amorphous and glassy states that are inaccessible to existing methods. PMID:26751163

  9. Electroanalytical investigation and determination of pefloxacin in pharmaceuticals and serum at boron-doped diamond and glassy carbon electrodes.

    PubMed

    Uslu, Bengi; Topal, Burcu Dogan; Ozkan, Sibel A

    2008-02-15

    The anodic behavior and determination of pefloxacin on boron-doped diamond and glassy carbon electrodes were investigated using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. In cyclic voltammetry, pefloxacin shows one main irreversible oxidation peak and additional one irreversible ill-defined wave depending on pH values for both electrodes. The results indicate that the process of pefloxacin is irreversible and diffusion controlled on boron-doped diamond electrode and irreversible but adsorption controlled on glassy carbon electrode. The peak current is found to be linear over the range of concentration 2x10(-6) to 2x10(-4)M in 0.5M H(2)SO(4) at about +1.20V (versus Ag/AgCl) for differential pulse and square wave voltammetric technique using boron-doped diamond electrode. The repeatability, reproducibility, precision and accuracy of the methods in all media were investigated. Selectivity, precision and accuracy of the developed methods were also checked by recovery studies. The procedures were successfully applied to the determination of the drug in pharmaceutical dosage forms and humans serum samples with good recovery results. No electroactive interferences from the excipients and endogenous substances were found in the pharmaceutical dosage forms and biological samples, respectively.

  10. Dielectric relaxation and the conformer equilibrium in the liquid and glassy states of β- D-fructose

    NASA Astrophysics Data System (ADS)

    Tombari, E.; Cardelli, C.; Salvetti, G.; Johari, G. P.

    2001-01-01

    To investigate the ionic and molecular dynamics in the liquid and glassy states of β- D-fructose, its dielectric relaxation spectra (12 Hz-500 kHz) and dynamic heat capacity (3.33 mHz) have been measured from 5 K above its melting point through the vitrification range, by allowing sufficient time for attainment of the conformer (or chemical) equilibria. Effects of the change in the conformer population on thermal cycling has been further studied. The dielectric behavior of liquid β- D-fructose is characteristically different from that of other molecular liquids in three ways: (i) the contribution to orientation polarization associated with the fast relaxation process, which persists in the glassy state, is relatively high in the liquid state of β- D-fructose; (ii) this contribution decreases with temperature exceptionally rapidly on cooling; and (iii) the difference in the rates of the two process is exceptionally large. The dynamic heat capacity change through the vitrification region is ˜160 J/(mol K), and is spread over ˜20 K range, and the enthalpy relaxation time is ˜50 s at 383 K. Transformation of β-pyranose to other conformers and other conformer transformation equilibria change on thermal cycling with the result that the overall relaxation rate increases at T>315 K and decreases at T<315 K. The relaxation spectrum becomes broader, the dc conductivity increases and the rate of the Johari-Goldstein relaxation whose Arrhenius energy is 42.1 kJ/mol increases.

  11. Importance of thiol-functionalized molecules for the structure and properties of compression-molded glassy wheat gluten bioplastics.

    PubMed

    Jansens, Koen J A; Lagrain, Bert; Brijs, Kristof; Goderis, Bart; Smet, Mario; Delcour, Jan A

    2013-11-01

    High-temperature compression molding of wheat gluten at low water levels yields a rigid plastic-like material. We performed a systematic study to determine the effect of additives with multiple thiol (SH) groups on gluten network formation during processing and investigate the impact of the resulting gluten network on the mechanical properties of the glassy end product. To this end, a fraction of the hydroxyl groups of different polyols was converted into SH functionalities by esterifying with 3-mercaptopropionic acid (MPA). The monofunctional additive MPA was evaluated as well. During low-temperature mixing SH-containing additives decreased the gluten molecular weight, whereas protein cross-linking occurred during high-temperature compression molding. The extent of both processes depended on the molecular architecture of the additives and their concentration. After molding, the material strength and failure strain increased without affecting the modulus, provided the additive concentration was low. The strength decreased again at too high concentrations for polyols with low SH functionalization. Attributing these effects solely to the interplay of plasticization and the SH-facilitated introduction of cross-links is inadequate, since an improvement in both strength and failure strain was also observed in the presence of high levels of MPA. It is hypothesized that, regardless of the molecular structure of the additive, the presence of SH-containing groups induces conformational changes which contribute to the mechanical properties of glassy gluten materials. PMID:24131364

  12. A 3D Microfluidic Chip for Electrochemical Detection of Hydrolysed Nucleic Bases by a Modified Glassy Carbon Electrode

    PubMed Central

    Vlachova, Jana; Tmejova, Katerina; Kopel, Pavel; Korabik, Maria; Zitka, Jan; Hynek, David; Kynicky, Jindrich; Adam, Vojtech; Kizek, Rene

    2015-01-01

    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. PMID:25621613

  13. Boron doped diamond and glassy carbon electrodes comparative study of the oxidation behaviour of cysteine and methionine.

    PubMed

    Enache, T A; Oliveira-Brett, A M

    2011-04-01

    The electrochemical oxidation behaviour at boron doped diamond and glassy carbon electrodes of the sulphur-containing amino acids cysteine and methionine, using cyclic and differential pulse voltammetry over a wide pH range, was compared. The oxidation reactions of these amino acids are irreversible, diffusion-controlled pH dependent processes, and occur in a complex cascade mechanism. The amino acid cysteine undergoes similar three consecutive oxidation reactions at both electrodes. The first step involves the oxidation of the sulfhydryl group with radical formation, that undergoes nucleophilic attack by water to give an intermediate species that is oxidized in the second step to cysteic acid. The oxidation of the sulfhydryl group leads to a disulfide bridge between two similar cysteine moieties forming cysteine. The subsequent oxidation of cystine occurs at a higher potential, due to the strong disulfide bridge covalent bond. The electro-oxidation of methionine at a glassy carbon electrode occurs in two steps, corresponding to the formation of sulfoxide and sulfone, involving the adsorption and protonation/deprotonation of the thiol group, followed by electrochemical oxidation. Methionine undergoes a one-step oxidation reaction at boron doped diamond electrodes due to the negligible adsorption, and the oxidation also leads to the formation of methionine sulfone. PMID:21377428

  14. An Easily Fabricated Electrochemical Sensor Based on a Graphene-Modified Glassy Carbon Electrode for Determination of Octopamine and Tyramine

    PubMed Central

    Zhang, Yang; Zhang, Meiqin; Wei, Qianhui; Gao, Yongjie; Guo, Lijuan; Al-Ghanim, Khalid A.; Mahboob, Shahid; Zhang, Xueji

    2016-01-01

    A simple electrochemical sensor has been developed for highly sensitive detection of octopamine and tyramine by electrodepositing reduced graphene oxide (ERGO) nanosheets onto the surface of a glassy carbon electrode (GCE). The electrocatalytic oxidation of octopamine and tyramine is individually investigated at the surface of the ERGO modified glassy carbon electrode (ERGO/GCE) by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several essential factors including the deposition cycle of reduced graphene oxide nanosheets and the pH of the running buffer were investigated in order to determine the optimum conditions. Furthermore, the sensor was applied to the quantification of octopamine and tyramine by DPV in the concentration ranges from 0.5 to 40 μM and 0.1 to 25 μM, respectively. In addition, the limits of detection of octopamine and tyramine were calculated to be 0.1 μM and 0.03 μM (S/N = 3), respectively. The sensor showed good reproducibility, selectivity and stability. Finally, the sensor successfully detected octopamine and tyramine in commercially available beer with satisfactory recovery ranges which were 98.5%–104.7% and 102.2%–103.1%, respectively. These results indicate the ERGO/GCE based sensor is suitable for the detection of octopamine and tyramine. PMID:27089341

  15. Communication: Experimentally determined profile of local glass transition temperature across a glassy-rubbery polymer interface with a Tg difference of 80 K

    NASA Astrophysics Data System (ADS)

    Baglay, Roman R.; Roth, Connie B.

    2015-09-01

    Studying the local glass transition temperature Tg across a boundary, we investigate the characteristic length scales of cooperative dynamics. High molecular weight polymers have a large separation in time scales between cooperative segmental motion (α-relaxation) and chain diffusion allowing us to measure the local Tg(z) profile across a glassy-rubbery interface of polystyrene/poly(n-butyl methacrylate) using fluorescence. We find this profile in cooperative dynamics does not correlate with the 7-nm wide symmetric composition profile of the interface, but instead is very broad, spanning 350-400 nm from one bulk Tg value to another, and highly asymmetric, extending further into the glassy side.

  16. Advanced ordered intermetallic alloy deployment

    SciTech Connect

    Liu, C.T.; Maziasz, P.J.; Easton, D.S.

    1997-04-01

    The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

  17. Impact resistant glassy polymers: Pre-stress and mode II fracture

    NASA Astrophysics Data System (ADS)

    Archer, Jared Steven

    Model glassy polymers, polymethyl methacrylate (PMMA) and polycarbonate (PC) are used to experimentally probe several aspects of polymer fracture. In Chapter 1, the method of pre-stress is employed as a means of improving the fracture properites of brittle PMMA. Samples are tested under equi-biaxial compression, simple shear and a combination of biaxial compression and shear. Equi-biaxial compression is shown to increase the threshold stress level for projectile penetration whereas shear pre-stress has a large effect on the overall energy absorbed during an impact. There is also an apparent interaction observed between compression and shear to dramatically increase the threshold stress. Pre-stressed laminates of PMMA and PC show an increase in damage area because of the unique formation of a secondary cone. In Chapter 2, the effect of stress state on stress relaxation in PMMA and PC is investigated. Direct comparisons are made between uniaxial and biaxial loading conditions. The experimental methods used highlight the effect of hydrostatic stress on the relaxation process. The data shows an increase in relaxation time and increase in the breadth of the relaxation spectrum with increases in hydrostatic stress. This suggests that the stress state can have a significant effect on the useful lifetime of pre-stressed articles. In Chapter 3, Mode I and II fracture studies are performed from quasi-static to low velocity impact rates on PMMA and PC. Mode II testing utilizes an angled double-edge notched specimen loaded in compression. The shear banding response of PMMA is shown to be highly sensitive to rate, with diffuse shear bands forming at low rates and sharp distinct shear bands forming at high rates. As the rate increases, shear deformation becomes more localized to the point where Mode II fracture occurs. PC is much less rate dependent and stable shear band propagation is observed over the range of rates studied with lesser amounts of localization. A new theory is

  18. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    1998-01-01

    A filler metal alloy used as a filler for welding east nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and east in copper chill molds.

  19. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

    Santella, M.L.; Sikka, V.K.

    1998-03-10

    A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.

  20. Alternate alloying for environmental resistance

    SciTech Connect

    Smolik, G.R.; Banerji, S.K.

    1986-01-01

    The 35 papers contained in this collection detail efforts being made toward achieving environmental resistance of alloys and conserved usage of strategic and critical materials. An in-depth look is taken at the roles played by various alloying elements in providing desired microstructures, properties, and influences upon environmental attack. Also presented are applications and performances of alternate alloys in aqueous and high temperature gaseous and molten salt environments. The book is broken down into five key sections covering: 1) philosophies and status of programs designing alloys for resistance to various environmental and microstructural stability of some of these alloys systems, 2) applications in hot corrosion and sulfidizing environments, 3) applications in oxidizing conditions, 4) corrosion resistance in aqueous environments, and 5) other properties, such as physical and mechanical, which are necessary to evaluate overall alloy performance.

  1. Two phase titanium aluminide alloy

    DOEpatents

    Deevi, Seetharama C.; Liu, C. T.

    2001-01-01

    A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

  2. TERNARY ALLOY-CONTAINING PLUTONIUM

    DOEpatents

    Waber, J.T.

    1960-02-23

    Ternary alloys of uranium and plutonium containing as the third element either molybdenum or zirconium are reported. Such alloys are particularly useful as reactor fuels in fast breeder reactors. The alloy contains from 2 to 25 at.% of molybdenum or zirconium, the balance being a combination of uranium and plutonium in the ratio of from 1 to 9 atoms of uranlum for each atom of plutonium. These alloys are prepared by melting the constituent elements, treating them at an elevated temperature for homogenization, and cooling them to room temperature, the rate of cooling varying with the oomposition and the desired phase structure. The preferred embodiment contains 12 to 25 at.% of molybdenum and is treated by quenching to obtain a body centered cubic crystal structure. The most important advantage of these alloys over prior binary alloys of both plutonium and uranium is the lack of cracking during casting and their ready machinability.

  3. Alloy Interface Interdiffusion Modeled

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo H.; Garces, Jorge E.; Abel, Phillip B.

    2003-01-01

    With renewed interest in developing nuclear-powered deep space probes, attention will return to improving the metallurgical processing of potential nuclear fuels so that they remain dimensionally stable over the years required for a successful mission. Previous work on fuel alloys at the NASA Glenn Research Center was primarily empirical, with virtually no continuing research. Even when empirical studies are exacting, they often fail to provide enough insight to guide future research efforts. In addition, from a fundamental theoretical standpoint, the actinide metals (which include materials used for nuclear fuels) pose a severe challenge to modern electronic-structure theory. Recent advances in quantum approximate atomistic modeling, coupled with first-principles derivation of needed input parameters, can help researchers develop new alloys for nuclear propulsion.

  4. Amorphous metal alloy and composite

    DOEpatents

    Wang, Rong; Merz, Martin D.

    1985-01-01

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  5. Titanium-tantalum alloy development

    SciTech Connect

    Cotton, J.D.; Bingert, J.F.; Dunn, P.S.; Butt, D.P.; Margevicius, R.W.

    1996-04-01

    Research has been underway at Los Alamos National Laboratory for several years to develop an alloy capable of containing toxic materials in the event of a fire involving a nuclear weapon. Due to their high melting point, good oxidation resistance, and low solubility in molten plutonium, alloys based on the Ti-Ta binary system have been developed for this purpose. The course of the alloy development to-date, along with processing and property data, are presented in this overview.

  6. Heat Capacity And Structural Relaxation In Se{sub 80-x}Te{sub 20}Ag{sub x}(x = 3 and 9) Glassy Alloys

    SciTech Connect

    Naqvi, S. Faheem; Saxena, N. S.

    2011-10-20

    This paper reports the effects of annealing time and temperature on the thermodynamics of enthalpy relaxation of Se{sub 80-x}Te{sub 20}Ag{sub x} (x = 3,9) glasses. Differential Scanning Calorimetry (DSC) method is optimized for the measurement of enthalpy relaxation in the vicinity of glass transition. The recovery of excess enthalpy ({Delta}H{sub excess}) has been calculated from the knowledge of excess specific heat ({Delta}C{sub p}). It is found that excess enthalpy released ({Delta}H{sub excess}) increase with increase in annealing time (t{sub a}). From the knowledge of excess specific heat ({Delta}C{sub p}) and {Delta}H{sub excess}, it has been found that sub-T{sub g} annealing of glass leads to decrease in enthalpy of the system and thereby taking it to the more equilibrium state.

  7. Duct and cladding alloy

    DOEpatents

    Korenko, Michael K.

    1983-01-01

    An austenitic alloy having good thermal stability and resistance to sodium corrosion at 700.degree. C. consists essentially of 35-45% nickel 7.5-14% chromium 0.8-3.2% molybdenum 0.3-1.0% silicon 0.2-1.0% manganese 0-0.1% zirconium 2.0-3.5% titanium 1.0-2.0% aluminum 0.02-0.1% carbon 0-0.01% boron and the balance iron.

  8. Shape memory alloy actuator

    DOEpatents

    Varma, Venugopal K.

    2001-01-01

    An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

  9. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  10. Time course of colonization of the glassy-winged sharpshooter precibarium by Xylella fastidiosa provides evidence for two types of egestion during inoculation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction of the glassy-winged sharpshooter (GWSS) into California has caused an increase in incidence of Pierce’s Disease in grape-growing regions. Although host plant resistance to the causative bacterium, Xylella fastidiosa, and/or its GWSS vector is being sought, research is hampered by lack...

  11. Anterior foregut microbiota of the glassy-winged sharpshooter explored using deep 16S rRNA gene sequencing from individual insects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce’s disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where ...

  12. Covalent modification of glassy carbon spheres through ball milling under solvent free conditions: A novel electrochemical interface for mercury(II) quantification.

    PubMed

    Kempegowda, Raghu G; Malingappa, Pandurangappa

    2014-08-01

    A simple and green chemistry protocol has been proposed based on the covalent anchoring of benzamide molecule on glassy carbon spheres through ball milling under solvent free condition. The modification proceeds through the formation of an amide bond between carboxylic group of glassy carbon spheres and the amino group of modifier molecule. The formation of covalent bond was ascertained using X-ray photoelectron spectroscopy. Scanning electron microscopy was used to study the surface morphology of milled glassy carbon spheres. The aqueous colloidal solution of modified glassy carbon spheres was used in the preparation of thin film electrodes and subsequently used as a novel electrochemical interface in the quantification of mercury at trace level using a differential pulse anodic stripping voltammetric technique. The modified electrode showed good sensitivity and selectivity towards mercury with a detection limit of 1nM with least interference from most of the ions. The analytical utility of the proposed electrode has been validated by determining the mercury levels in number of sample matrices. PMID:24881534

  13. Evidence for the absence of enzymatic reactions in the glassy state. A case study of xanthophyll cycle pigments in the desiccation-tolerant moss Syntrichia ruralis.

    PubMed

    Fernández-Marín, Beatriz; Kranner, Ilse; San Sebastián, María; Artetxe, Unai; Laza, José Manuel; Vilas, José Luis; Pritchard, Hugh W; Nadajaran, Jayanthi; Míguez, Fátima; Becerril, José María; García-Plazaola, José Ignacio

    2013-07-01

    Desiccation-tolerant plants are able to withstand dehydration and resume normal metabolic functions upon rehydration. These plants can be dehydrated until their cytoplasm enters a 'glassy state' in which molecular mobility is severely reduced. In desiccation-tolerant seeds, longevity can be enhanced by drying and lowering storage temperature. In these conditions, they still deteriorate slowly, but it is not known if deteriorative processes include enzyme activity. The storage stability of photosynthetic organisms is less studied, and no reports are available on the glassy state in photosynthetic tissues. Here, the desiccation-tolerant moss Syntrichia ruralis was dehydrated at either 75% or <5% relative humidity, resulting in slow (SD) or rapid desiccation (RD), respectively, and different residual water content of the desiccated tissues. The molecular mobility within dry mosses was assessed through dynamic mechanical thermal analysis, showing that at room temperature only rapidly desiccated samples entered the glassy state, whereas slowly desiccated samples were in a 'rubbery' state. Violaxanthin cycle activity, accumulation of plastoglobules, and reorganization of thylakoids were observed upon SD, but not upon RD. Violaxanthin cycle activity critically depends on the activity of violaxanthin de-epoxidase (VDE). Hence, it is proposed that enzymatic activity occurred in the rubbery state (after SD), and that in the glassy state (after RD) no VDE activity was possible. Furthermore, evidence is provided that zeaxanthin has some role in recovery apparently independent of its role in non-photochemical quenching of chlorophyll fluorescence.

  14. Probing of structural relaxation times in the glassy state of sucrose and trehalose based on dynamical properties of two secondary relaxation processes

    SciTech Connect

    Kaminski, K.; Adrjanowicz, K.; Paluch, M.; Kaminska, E.

    2011-06-15

    Time-dependent isothermal dielectric measurements were carried out deeply in the glassy state on two very important saccharides: sucrose and trehalose. In both compounds two prominent secondary relaxation processes were identified. The faster one is an inherent feature of the whole family of carbohydrates. The slower one can also be detected in oligo- and polysaccharides. It was shown earlier that the {beta} process is the Johari-Goldstein (JG) relaxation coupled to motions of the glycosidic linkage, while the {gamma} relaxation originates from motions of the exocyclic hydroxymethyl unit. Recently, it was shown that the JG relaxation process can be used to determine structural relaxation times in the glassy state [R. Casalini and C. M. Roland, Phys. Rev. Lett. 102, 035701 (2009)]. In this paper we present the results of an analysis of the data obtained during aging using two independent approaches. The first was proposed by Casalini and Roland, and the second one is based on the variation of the dielectric strength of the secondary relaxation process during aging [J. K. Vij and G. Power, J. Non-Cryst. Solids 357, 783 (2011)]. Surprisingly, we found that the estimated structural relaxation times in the glassy state of both saccharides are almost the same, independent of the type of secondary mode. This finding calls into question the common view that secondary modes of intramolecular origin do not provide information about the dynamics of the glassy state.

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

    PubMed

    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. PMID:26652361

  16. Muscle movements that control inoculation of Xylella fastidiosa are revealed by head X-rays of feeding glassy-winged sharpshooters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mechanism of inoculation of the Pierce’s disease bacterium, Xylella fastidiosa (Xf), by vectors such as the glassy-winged sharpshooter (GWSS) is still unknown, despite nearly 70 years of study. Research in support of the egestion-salivation hypothesis for Xf inoculation is presented. Two impor...

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

    PubMed

    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.

  18. Effects of kaolin particle film and imidacloprid on glassy-winged sharpshooter (Homalodisca vitripennis) (Hemiptera: Cicadellidae)populations and the prevention of spread of Xylella fastidiosa in grape

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS), Homalodisca coagulata (Say), was introduced into California and soon became a major pest of important agronomic, horticultural, landscape, ornamental crops and native trees in California. This pest feeds readily on grape and, in doing so, transmits X. fastidio...

  19. Fluidisation and plastic activity in a model soft-glassy material flowing in micro-channels with rough walls

    NASA Astrophysics Data System (ADS)

    Scagliarini, A.; Lulli, M.; Sbragaglia, M.; Bernaschi, M.

    2016-06-01

    By means of mesoscopic numerical simulations of a model soft-glassy material, we investigate the role of boundary roughness on the flow behaviour of the material, probing the bulk/wall and global/local rheologies. We show that the roughness reduces the wall slip induced by wettability properties and acts as a source of fluidisation for the material. A direct inspection of the plastic events suggests that their rate of occurrence grows with the fluidity field, reconciling our simulations with kinetic elasto-plastic descriptions of jammed materials. Notwithstanding, we observe qualitative and quantitative differences in the scaling, depending on the distance from the rough wall and on the imposed shear. The impact of roughness on the orientational statistics is also studied.

  20. Electrocatalytic oxidation of hydrazine and hydroxylamine by graphene oxide-Pd nanoparticle-modified glassy carbon electrode.

    PubMed

    Lee, Eunhee; Kim, Daekun; You, Jung-Min; Kim, Seul Ki; Yun, Mira; Jeon, Seungwon

    2012-12-01

    Pd nanoparticle catalysts supported by thiolated graphene oxide (tGO) on a glassy carbon electrode (GCE), and denoted as tGO-Pd/GCE, are used in this study for the electrochemical determination of hydroxylamine and hydrazine. The physicochemical properties of tGO-Pd were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). They showed strong catalytic activity toward the oxidation of hydroxylamine and hydrazine. Cyclic voltammetry (CV) and amperometry were used to characterize the sensors' performances. The detection limits of hydroxylamine and hydrazine by tGO-Pd/GCE were 0.31 and 0.25 microM (s/n = 3), respectively. The sensors' sensitivity, selectivity, and stability were also investigated.

  1. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-03-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL‑1, with a detection limit of 0.1 ng·mL‑1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples.

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

    PubMed

    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.

  3. Interfacial electron transfer of glucose oxidase on poly(glutamic acid)-modified glassy carbon electrode and glucose sensing.

    PubMed

    Zhou, Xuechou; Tan, Bingcan; Zheng, Xinyu; Kong, Dexian; Li, Qinglu

    2015-11-15

    The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5-5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose. PMID:26278169

  4. Characterization of Au Irradiated Glassy Polymeric Carbon at 2,000°C for Nuclear Applications

    NASA Astrophysics Data System (ADS)

    Abunaemeh, M.; Seif, M.; Batra, A.; Elsamadicy, A.; Yang, Y.; Wang, L.; Muntele, C.; Ila, D.

    The TRISO fuel has been used in some of the Generation IV nuclear reactor designs [1]. It consists of a fuel kernel of UOx coated with several layers of materials with different functions. Pyrolytic carbon (PyC) is one of the materials in the layers. In this study we investigate the possibility of using Glassy Polymeric Carbon (GPC) as an alternative to PyC. In this work, we are comparing the changes in physical and microstructure properties of GPC after exposure to irradiation fluence of 5 MeV Au equivalent to a 1 displacement per atom (dpa) for GPC prepared at 2,000°C. The GPC material is manufactured and tested at the Center for Irradiation Materials (CIM) at Alabama A&M University using Transmission electron microscopy (TEM) and stopping range of ions in matter (SRIM) software.

  5. A glassy lava flow from Toconce volcano and its relation with the Altiplano-Puna Magma Body in Central Andes

    NASA Astrophysics Data System (ADS)

    Godoy, B.; Rodriguez, I.; Aguilera, F.

    2012-12-01

    Toconce is a composite stratovolcano located at the San Pedro - Linzor volcanic chain (SPLVC). This volcanic chain distributes within the Altiplano-Puna region (Central Andes) which is characterized by extensive rhyodacitic-to-rhyolitic ignimbritic fields, and voluminous domes of dacitic-to-rhyolitic composition (de Silva, 1989). The felsic melts that gave origin to ignimbrites and domes at this area were generated by mixing of mantle-derived magmas and anatectic melts assimilated during their ascent through the thick crust. Thus, partially molten layers exist in the upper crust below the APVC (de Silva et al., 2006). Evidence of large volumes of such melts has been also proposed by geophysical methods (i.e. the Altiplano-Puna Magma Body; Chmielowsky et al., 1999) In this work, petrography and whole rock, mineralogical and melt inclusions geochemistry of a glassy lava flow of Toconce volcano are presented. Petrographically, this lava flow shows a porphyric texture, with euhdral to subhedral plagioclase, ortho- and clino-pyroxene phenocrysts immersed in a glassy groundmass. Geochemically, the lava flow has 64.7% wt. SiO2. The glassy groundmass (~70% wt. SiO2) is more felsic than all the lavas in the volcanic chain (47-68% wt., Godoy et al., 2011). Analyzed orthopyroxene-hosted melt inclusions show an even higher SiO2 content (72-75% wt.), and a decreasing on Al2O3, Na2O, and CaO content with differentiation. Crystallization pressures of this lava flow, obtained using Putirka's two-pyroxene and clinopyroxene-liquid models (Putirka, 2008), range between 6 and 9 kbar. According to crystallization pressures, and major element composition, a felsic source located at shallow crustal pressures - where plagioclase is a stable mineralogical phase - originated the inclusions. This could be related to the presence of the Altiplano-Puna Magma Body (APMB) located below SPLVC. On the other hand, glassy groundmass, and disequilibrium textures in minerals of this lava flow could

  6. Nuclear quadrupole resonance study of local bonding in glassy As{sub x}Se{sub 1-x}

    SciTech Connect

    Ahn, Eungho; Williams, G. A.; Taylor, P. C.

    2006-11-01

    Nuclear quadrupole resonance (NQR) experiments were performed on glassy As{sub x}Se{sub 1-x} to study the local structural order. The bonding in As{sub x}Se{sub 1-x} is governed by preferential bonding (chemical ordering) between arsenic and selenium at arsenic concentrations x{<=}0.40; however, the bonding for higher arsenic concentrations is governed mostly by statistical considerations. At concentrations x{>=}0.45 the glasses are inhomogeneous with the presence of local regions of different composition. Measurements of the NQR spin echo intensity identify regions formed by arsenic atoms bonded to zero, one, two, or three selenium atoms. The NQR spectral line shapes and the longitudinal relaxation times suggest that these regions have a more ordered structure as compared to the homogeneous samples with low arsenic content. The existence of a small concentration of crystalline inclusions in amorphous As{sub 0.60}Se{sub 0.40} is also suggested.

  7. Segment Orientation and Optical Birefringence of Amorphous Polymers Under Tensile Deformation: Novel Computational Method applied to Different Glassy Polycarbonates

    NASA Astrophysics Data System (ADS)

    Natarajan, Upendra; Sulatha, M. S.

    2005-03-01

    Orientation dependent optical properties of Bisphenol A polycarbonate and two aliphatic substituted polycarbonates in glassy phase have been studied by atomistic modeling using molecular mechanics simulations under tensile deformation. Probability distributions and orientation functions show that phenylene rings and carbonate groups vectors along the main chain orient towards stretching direction following deformation. Interchain packing of rings and carbonates become ordered with strain. Efficient computational approach for calculation of optical birefringence of amorphous polymers is presented and applied to the polycarbonates in detail. Polarizability anisotropy of the polymer segments and chain as a function of deformation is calculated by combining information on the conformations and group polarizabilities, and used to estimate birefringence during deformation. Simulated and experimental values for segment orientation and bulk birefringence are in very good agreement. Effect of the optical properties of atomic groups on bulk birefringence is brought forth for the first time by molecular simulation for polymers other than polyethylene.

  8. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    PubMed Central

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-01-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL−1, with a detection limit of 0.1 ng·mL−1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples. PMID:27003798

  9. Interfacial electron transfer of glucose oxidase on poly(glutamic acid)-modified glassy carbon electrode and glucose sensing.

    PubMed

    Zhou, Xuechou; Tan, Bingcan; Zheng, Xinyu; Kong, Dexian; Li, Qinglu

    2015-11-15

    The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5-5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose.

  10. Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

    NASA Astrophysics Data System (ADS)

    Blacha-Grzechnik, Agata; Piwowar, Katarzyna; Krukiewicz, Katarzyna; Koscielniak, Piotr; Szuber, Jacek; Zak, Jerzy K.

    2016-05-01

    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 1O2 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.

  11. Glucose oxidase/colloidal gold nanoparticles immobilized in Nafion film on glassy carbon electrode: Direct electron transfer and electrocatalysis.

    PubMed

    Zhao, Shuang; Zhang, Kai; Bai, Yu; Yang, Weiwei; Sun, Changqing

    2006-10-01

    The direct electron transfer of glucose oxidase (GOD) was achieved based on the immobilization of GOD/colloidal gold nanoparticles on a glassy carbon electrode by a Nafion film. The immobilized GOD displayed a pair of well-defined and nearly reversible redox peaks with a formal potential (Eo ') of -0.434 V in 0.1 M pH 7.0 phosphate buffer solution and the response showed a surface-controlled electrode process. The dependence of Eo ' on solution pH indicated that the direct electron transfer reaction of GOD was a two-electron-transfer coupled with a two-proton-transfer reaction process. The experimental results also demonstrated that the immobilized GOD retained its electrocatalytic activity for the oxidation of glucose. So the resulting modified electrode can be used as a biosensor for detecting glucose. PMID:16556513

  12. Solid-State Constitutive Modelling of Glassy Polymers: Coupling the Rolie-Poly Equations for Melts with Anisotropic Viscoplastic Flow

    SciTech Connect

    De Focatiis, Davide S. A.; Buckley, C. Paul; Embery, John

    2008-07-07

    This paper investigates the behaviour of a well-characterised monodisperse grade of entangled atactic polystyrene across a very wide temperature and strain rate range through linear and non-linear melt rheology and solid-state deformation. In an effort to construct a constitutive model for large deformations able to describe rheological response right across this wide timescale, two well-established rheological models are combined: the well known RoliePoly (RP) conformational melt model and the Oxford glass-rubber constitutive model for glassy polymers. Comparisons between experimental data and simulations from a numerical implementation of the model illustrate that the model can cope well with the range of deformations in which orientation is limited to length-scales longer than an entanglement length. One approach in which the model can be expanded to incorporate the effects of orientation on shorter length scales using anisotropic viscoplastic flow is briefly discussed.

  13. Study of the voltammetric behavior of jatrorrhizine and its sensitive determination at electrochemical pretreatment glassy carbon electrode.

    PubMed

    Ye, Zhuo; Li, Yinfeng; Wen, Jianguo; Li, Kunjing; Ye, Baoxian

    2014-08-01

    A simple, inexpensive and highly sensitive electrochemical method for the determination of jatrorrhizine was developed using an electrochemically pretreated glassy carbon electrode (EPGCE). The electrochemical behavior of jatrorrhizine was systematically investigated in detail and some kinetic parameters were calculated for the first time. A reasonable reaction mechanism of jatrorrhizine on the EPGCE was also discussed and proposed, which could be a reference for the pharmacological action of jatrorrhizine in clinical study. And the first electroanalytical method of jatrorrhizine was established with a wide linear range from 7.0×10(-8) to 2.0×10(-5)mol L(-1) and a low detection limit of 5.0×10(-8)mol L(-1). The proposed method was successfully applied in determination of jatrorrhizine in pharmaceutical sample, Tinospora capillipes Gagnep (a traditional Chinese medicine), with satisfactory results. PMID:24881532

  14. Effect of Nitric Acid ``Washing'' Procedure on Electrochemical Behavior of Carbon Nanotubes and Glassy Carbon μ-Particles

    NASA Astrophysics Data System (ADS)

    Anik, Ülkü; Çevik, Serdar; Pumera, Martin

    2010-05-01

    The electroanalytic performances of glassy carbon paste electrode (GCPE), multi-walled carbon nanotube (MWCNT)-GCPE and double-walled carbon nanotube (DWCNT)-GCPE, which include HNO3 washed/unwashed materials, were compared by monitoring cyclic voltammograms of potassium ferricyanide and catechol. Electrodes were prepared by introducing proper amount of DWCNT and MWCNT into GCPE. First untreated materials (DWCNT, MWCNT, GC μ-particles) were used in the electrodes and then HNO3-treated materials were utilized for comparing difference in electrochemical performances. The effect of treatment procedure was also examined by applying Raman spectroscopy to treated and untreated materials. Moreover, TEM images were obtained for further investigation of MWCNT and DWCNT.

  15. Enhancement of electrogenerated chemiluminescence of luminol by ascorbic acid at gold nanoparticle/graphene modified glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Dong, Yongping; Gao, Tingting; Zhou, Ying; Chu, Xiangfeng; Wang, Chengming

    2015-01-01

    Gold nanoparticle/graphene (GNP/GR) nanocomposite was one-pot synthesized from water soluble graphene and HAuCl4 by hydrothermal method and characterized by TEM, Raman spectroscopy, XRD, XPS, UV-vis spectroscopy, and electrochemical impedance spectroscopy (EIS). Electrogenerated chemiluminescence (ECL) of luminol was investigated at the GNP/GR modified glassy carbon electrode (GNP/GR/GCE) and the GNP modified glassy carbon electrode (GNP/GCE) in aqueous solution respectively. The results revealed that one strong anodic ECL peak could be observed at ∼0.8 V at two modified electrodes compared with that at the bare electrode. The intensity of the anodic ECL at the GNP/GR/GCE is weaker than that at the GNP/GCE, which should be due to the synergic effect of the enhancing effect of gold nanoparticles and the inhibiting effect of graphene on anodic luminol ECL. One strong cathodic ECL peak located at ∼-0.8 V could be observed at the GNP/GR/GCE but not at the GNP/GCE, which should be result from the adsorbed oxygen at the graphene film. In the presence of ascorbic acid, the anodic ECL at the GNP/GR/GCE was enhanced more than 8-times, which is more apparent than that at the GNP/GCE. Whereas, the cathodic ECL peak was seriously inhibited at the GNP/GR/GCE. The enhanced ECL intensity at the GNP/GR/GCE varied linearly with the logarithm of ascorbic acid concentration in the range of 1.0 × 10-8 to 1.0 × 10-6 mol L-1 with a detection limit of 1.0 × 10-9 mol L-1. The possible ECL mechanism was also discussed.

  16. Evaluation in a Dog Model of Three Antimicrobial Glassy Coatings: Prevention of Bone Loss around Implants and Microbial Assessments

    PubMed Central

    López-Píriz, Roberto; Solá-Linares, Eva; Rodriguez-Portugal, Mercedes; Malpica, Beatriz; Díaz-Güemes, Idoia; Enciso, Silvia; Esteban-Tejeda, Leticia; Cabal, Belén; Granizo, Juan José; Moya, José Serafín; Torrecillas, Ramón

    2015-01-01

    Objectives The aim of the present study is to evaluate, in a ligature-induced peri-implantitis model, the efficacy of three antimicrobial glassy coatings in the prevention of biofilm formation, intrasulcular bacterial growth and the resulting peri-implant bone loss. Methods Mandibular premolars were bilaterally extracted from five beagle dogs. Four dental implants were inserted on each hemiarch. Eight weeks after, one control zirconia abutment and three with different bactericidal coatings (G1n-Ag, ZnO35, G3) were connected. After a plaque control period, bacterial accumulation was allowed and biofilm formation on abutments was observed by Scanning Electron Microscopy (SEM). Peri-implantitis was induced by cotton ligatures. Microbial samples and peri-implant crestal bone levels of all implant sites were obtained before, during and after the breakdown period. Results During experimental induce peri-implantitis: colony forming units counts from intrasulcular microbial samples at implants with G1n-Ag coated abutment remained close to the basal inoculum; G3 and ZnO35 coatings showed similar low counts; and anaerobic bacterias counts at control abutments exhibited a logarithmic increase by more than 2. Bone loss during passive breakdown period was no statistically significant. Additional bone loss occurred during ligature-induce breakdown: 0.71 (SD 0.48) at G3 coating, 0.57 (SD 0.36) at ZnO35 coating, 0.74 (SD 0.47) at G1n-Ag coating, and 1.29 (SD 0.45) at control abutments; and statistically significant differences (p<0.001) were found. The lowest bone loss at the end of the experiment was exhibited by implants dressing G3 coated abutments (mean 2.1; SD 0.42). Significance Antimicrobial glassy coatings could be a useful tool to ward off, diminish or delay peri-implantitis progression. PMID:26489088

  17. Radiation Effects in Refractory Alloys

    NASA Astrophysics Data System (ADS)

    Zinkle, Steven J.; Wiffen, F. W.

    2004-02-01

    In order to achieve the required low reactor mass per unit electrical power for space reactors, refractory alloys are essential due to their high operating temperature capability that in turn enables high thermal conversion efficiencies. One of the key issues associated with refractory alloys is their performance in a neutron irradiation environment. The available radiation effects data are reviewed for alloys based on Mo, W, Re, Nb and Ta. The largest database is associated with Mo alloys, whereas Re, W and Ta alloys have the least available information. Particular attention is focused on Nb-1Zr, which is a proposed cladding and structural material for the reactor in the Jupiter Icy Moons Orbiter (JIMO) project. All of the refractory alloys exhibit qualitatively similar temperature-dependent behavior. At low temperatures up to ~0.3TM, where TM is the melting temperature, the dominant effect of radiation is to produce pronounced radiation hardening and concomitant loss of ductility. The radiation hardening also causes a dramatic decrease in the fracture toughness of the refractory alloys. These low temperature radiation effects occur at relatively low damage levels of ~0.1 displacement per atom, dpa (~2×1024 n/m2, E>0.1 MeV). As a consequence, operation at low temperatures in the presence of neutron irradiation must be avoided for all refractory alloys. At intermediate temperatures (0.3 to 0.6 TM), void swelling and irradiation creep are the dominant effects of irradiation. The amount of volumetric swelling associated with void formation in refractory alloys is generally within engineering design limits (<5%) even for high neutron exposures (>>10 dpa). Very little experimental data exist on irradiation creep of refractory alloys, but data for other body centered cubic alloys suggest that the irradiation creep will produce negligible deformation for near-term space reactor applications.

  18. Directional Solidification of Monotectic Alloys

    NASA Technical Reports Server (NTRS)

    Hellawell, A.

    1983-01-01

    Cooling at certain rates produced fibrous composite structures. Alloy samples melted in alumina or graphite crucibles under argon and then chillcast into 33-mm-diameter rods or sucked directly into 3-mm-bore alumina or silica tubes. Alloying not automatic with immiscible components of different densities and widely different melting points.

  19. Directional Solidification Of Monotectic Alloys

    NASA Technical Reports Server (NTRS)

    Dhindaw, B. K.; Stefanescu, D. M.; Singh, A. K.; Curreri, P. A.

    1990-01-01

    Conditions promoting formation of aligned fibers sought. Report describes experiments in directional solidification of Cu/Pb and Bi/Ga monotectic alloys. Study motivated by need to understand physical mechanism governing formation of rodlike or fiberlike aligned structures in solidifying alloy and to determine process conditions favoring such structures.

  20. Shape memory alloy thaw sensors

    DOEpatents

    Shahinpoor, Mohsen; Martinez, David R.

    1998-01-01

    A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the Austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states.