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- ItemOptical, electrical and chemical properties of PEO:I2 complex composite films(Heidelberg [u.a.] : Springer, 2022) Telfah, Ahmad; Al-Bataineh, Qais M.; Tolstik, Elen; Ahmad, Ahmad A.; Alsaad, Ahmad M.; Ababneh, Riad; Tavares, Carlos J.; Hergenröder, RolandSynthesized PEO:I2 complex composite films with different I2 concentrations were deposited onto fused silica substrates using a dip-coating method. Incorporation of PEO films with I2 increases the electrical conductivity of the composite, reaching a maximum of 46 mS/cm for 7 wt% I2. The optical and optoelectronic properties of the complex composite films were studied using the transmittance and reflectance spectra in the UV-Vis region. The transmittance of PEO decreases with increasing I2 content. From this study, the optical bandgap energy decreases from 4.42 to 3.28 eV as I2 content increases from 0 to 7 wt%. In addition, the refractive index for PEO films are in the range of 1.66 and 2.00.1H NMR spectra of pure PEO film shows two major peaks at 3.224 ppm and 1.038 ppm, with different widths assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase, respectively. By adding I2 to the PEO, both peaks (amorphous and crystal) are shifted to lower NMR frequencies indicating that I2 is acting as a Lewis acid, and PEO is acting as Lewis base. Hence, molecular iodine reacts favorably with PEO molecules through a charge transfer mechanism, and the formation of triiodide (I3-), the iodite (IO2-) anion, I 2· · · PEO and I2+···PEO complexes. PEO:I2 complex composite films are expected to be suitable for optical, electrical, and optoelectronic applications.
- ItemGeophysical investigation of a freshwater lens on the island of Langeoog, Germany – Insights from combined HEM, TEM and MRS data(Amsterdam [u.a.] : Elsevier Science, 2017) Costabel, Stephan; Siemon, Bernhard; Houben, Georg; Günther, ThomasA multi-method geophysical survey, including helicopter-borne electromagnetics (HEM), transient electromagnetics (TEM), and magnetic resonance sounding (MRS), was conducted to investigate a freshwater lens on the North Sea island of Langeoog, Germany. The HEM survey covers the entire island and gives an overview of the extent of three freshwater lenses that reach depths of up to 45 m. Ground-based TEM and MRS were conducted particularly on the managed western lens to verify the HEM results and to complement the lithological information from existing boreholes. The results of HEM and TEM are in good agreement. Salt- and freshwater-bearing sediments can, as expected, clearly be distinguished due to their individual resistivity ranges. In the resistivity data, a large transition zone between fresh- and saltwater with a thickness of up to 20 m is identified, the existence of which is verified by borehole logging and sampling. Regarding lithological characterisation of the subsurface, the MRS method provides more accurate and reliable results than HEM and TEM. Using a lithological index derived from MRS water content and relaxation time, thin aquitard structures as well as fine and coarse sand aquifers can be distinguished. Complementing the existing borehole data with the lithology information estimated from MRS, we generate a map showing the occurrence of aquitard structures, which significantly improves the hydrogeological model of the island. Moreover, we demonstrate that the estimates of groundwater conductivity in the sand aquifers from geophysical data are in agreement with the fluid conductivity measured in the boreholes.
- ItemInvestigation of selenium retention in high redox glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Shelestak, Larry J.; Arbab, MehranLaboratory glass melting experiments were made to study the effect of glass redox on selenium retention. Initially, it was found that as expected selenium retention decreases as glass redox ratio increases. But, unexpectedly, selenium retention then levels off and reaches a minimum upon further increases in glass redox, before once again increasing for very high redox ratios of more than 0.60. Selenium concentrations in the furnace atmosphere at different locations in a commercial float glass furnace were also measured as an indicator of selenium volatility at different stages of glass melting. Α study of the effect of glass redox ratio on the spectral absorption of the major selenium containing coloring centers in float glass was also made.
- ItemAtomistic simulation of glasses - Strategic considerations and review of selective results(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Fotheringham, Ulrich; Binder, Kurt; Horbach, Jürgen; Kob, WalterWithin the seope of a ten year cooperation between SCHOTT AG and Mainz University, important contributions to the atomistic simulation of multicomponent glasses have been developed. They have made the state of the art come closer to the visionary goal of determining the properties of unknown glasses a priori by theoretical means.
- ItemSurface tension of amber glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wing, Douglas R.; Clare, Alexis G.; Jones, Linda E.; Luo, ShengchunThe surface tension of 0.1 Fe2O3, 15 Na2O, 11 CaO, 73.9 SiO2 glass melts (composition given in mol %) containing additions of 0.0, 0.2, 0.5, and 1.0 wt % sodium sulfate were measured using pendant drop technique at temperatures between 1200 and 1400°C. Surface tension measurements were carried out in reducing (96 %Ar/4 %H2), inert (Argon) oxidizing (Dry Air) and wet (Wet Air) atmospheres. The surface tension of the amber glass melts was found to decrease with increasing temperature, these increases were larger than those reported for similar glasses containing iron alone. Melt atmosphere had only a small effect on the surface tension of the sulfur containing melts at the flow rates used in this study suggesting that sulfur decomposition could be in a sulfur-rich local environment. The fact that for sulfur containing melts the surfaee tension in the reducing atmosphere was slightly lower than that in the oxidizing atmosphere imitates the behavior in oxidized iron melts which would be contrary to the observations of other workers. The surface tension of the melts was found to increase with increasing SO3 content up to 0.13 to 0.31 wt%, after which it levels off or decreases. This roughly correlates with the intensity of the amber chromophore concentration in the resulting glass. The amber chromophore contains ferric iron tetrahedrally coordinated with three oxygens and a sulfide ion but the amber glass melt contains ferrous iron and an oxide of sulfur. The amber chromophore is believed to be controlled more by the sulfur content than the iron content and therefore the fact that the isothermal surfaee tension tracks the amber chromophore intensity suggests that the surface tension, too, is controlled by the sulfur. Since the oxide of sulfur serves to decrease surface tension partitioning of that species to the surface could cause the observed "tearing" effect seen in amber glass melts and assist in the homogenization of those melts.
- ItemA discussion of the cell voltage during discharge of an intercalation electrode for various C-rates based on non-equilibrium thermodynamics and numerical simulations(Bristol : IOP Publishing, 2020) Landstorfer, ManuelIn this work we discuss the modeling procedure and validation of a non-porous intercalation half-cell during galvanostatic discharge. The modeling is based on continuum thermodynamics with non-equilibrium processes in the active intercalation particle, the electrolyte, and the common interface where the intercalation reaction Li+ + e- ↔ Li occurs. The model is in detail investigated and discussed in terms of scalings of the non-equilibrium parameters, i.e. the diffusion coefficients DA and DE of the active phase and the electrolyte, conductivity sA and sE of both phases, and the exchange current density e0L, with numerical solutions of the underlying PDE system. The current density i as well as all non-equilibrium parameters are scaled s with respect to the 1-C current density iC A of the intercalation electrode. We compute then numerically the cell voltage E as function of the capacity Q and the C-rate Ch. Within a hierarchy of approximations we provide computations of E(Q) for various scalings of the diffusion coefficients, the conductivities and the exchange current density. For the later we provide finally a discussion for possible concentration dependencies. © The Author(s) 2019. Published by ECS.
- ItemMethane prediction based on individual or groups of milk fatty acids for dairy cows fed rations with or without linseed(New York, NY [u.a.] : Elsevier, 2019) Engelke, Stefanie W.; Daş, Gürbüz; Derno, Michael; Tuchscherer, Armin; Wimmers, Klaus; Rychlik, Michael; Kienberger, Hermine; Berg, Werner; Kuhla, Björn; Metges, Cornelia C.Milk fatty acids (MFA) are a proxy for the prediction of CH4 emission from cows, and prediction differs with diet. Our objectives were (1) to compare the effect of diets on the relation between MFA profile and measured CH4 production, (2) to predict CH4 production based on 6 data sets differing in the number and type of MFA, and (3) to test whether additional inclusion of energy-corrected milk (ECM) yield or dry matter intake (DMI) as explanatory variables improves predictions. Twenty dairy cows were used. Four diets were used based on corn silage (CS) or grass silage (GS) without (L0) or with linseed (LS) supplementation. Ten cows were fed CS-L0 and CS-LS and the other 10 cows were fed GS-L0 and GS-LS in random order. In feeding wk 5 of each diet, CH4 production (L/d) was measured in respiration chambers for 48 h and milk was analyzed for MFA concentrations by gas chromatography. Specific CH4 prediction equations were obtained for L0-, LS-, GS-, and CS-based diets and for all 4 diets collectively and validated by an internal cross-validation. Models were developed containing either 43 identified MFA or a reduced set of 7 groups of biochemically related MFA plus C16:0 and C18:0. The CS and LS diets reduced CH4 production compared with GS and L0 diets, respectively. Methane yield (L/kg of DMI) reduction by LS was higher with CS than GS diets. The concentrations of C18:1 trans and n-3 MFA differed among GS and CS diets. The LS diets resulted in a higher proportion of unsaturated MFA at the expense of saturated MFA. When using the data set of 43 individual MFA to predict CH4 production (L/d), the cross-validation coefficient of determination (R2 CV) ranged from 0.47 to 0.92. When using groups of MFA variables, the R2 CV ranged from 0.31 to 0.84. The fit parameters of the latter models were improved by inclusion of ECM or DMI, but not when added to the data set of 43 MFA for all diets pooled. Models based on GS diets always had a lower prediction potential (R2 CV = 0.31 to 0.71) compared with data from CS diets (R2 CV = 0.56 to 0.92). Models based on LS diets produced lower prediction with data sets with reduced MFA variables (R2 CV = 0.62 to 0.68) compared with L0 diets (R2 CV = 0.67 to 0.80). The MFA C18:1 cis-9 and C24:0 and the monounsaturated FA occurred most often in models. In conclusion, models with a reduced number of MFA variables and ECM or DMI are suitable for CH4 prediction, and CH4 prediction equations based on diets containing linseed resulted in lower prediction accuracy. © 2019 American Dairy Science Association
- ItemTheoretical Prediction of a Giant Anisotropic Magnetoresistance in Carbon Nanoscrolls(Washington, DC : ACS Publ., 2017-4-12) Chang, Ching-Hao; Ortix, CarmineSnake orbits are trajectories of charge carriers curving back and forth that form at an interface where either the magnetic field direction or the charge carrier type are inverted. In ballistic samples, their presence is manifested in the appearance of magnetoconductance oscillations at small magnetic fields. Here we show that signatures of snake orbits can also be found in the opposite diffusive transport regime. We illustrate this by studying the classical magnetotransport properties of carbon tubular structures subject to relatively weak transversal magnetic fields where snake trajectories appear in close proximity to the zero radial field projections. In carbon nanoscrolls, the formation of snake orbits leads to a strongly directional dependent positive magnetoresistance with an anisotropy up to 80%.
- ItemThe influence of partial replacement of Cu with Ga on the corrosion behavior of Ti40Zr10Cu36PD14 metallic glasses(Bristol : IOP Publishing, 2019) Wei, Qi; Gostin, Petre Flaviu; Addison, Owen; Reed, Daniel; Calin, Mariana; Bera, Supriya; Ramasamy, Parthiban; Davenport, AlisonTiZrCuPdGa metallic glasses are under consideration for small dental biomedical implants. There is interest in replacing some of the Cu with Ga to improve the glass-forming ability and biocompatibility. Ti40Zr10Cu36-xPd14Gax (x = 0, 1, 2, 4, 8 and 10 at.%) metallic glasses in rod and ribbon forms were fabricated by mould casting and melt spinning, respectively, and electrochemically tested in a 0.9wt.% NaCl (0.154 M) solution. It has been shown that for both rod and ribbon samples Ga levels up to 8% have no significant effect on passive current density, pitting potential or cathodic reactivity in 0.9% NaCl at 37°C. Different pitting potential and corrosion potential values were found when ribbon and rod samples of the same composition were compared for all compositions apart from the one containing the highest Ga level (10%). This was attributed to structural relaxation occurring as a result of the slower cooling rates during casting rods compared with melt-spinning ribbons. Substitution of Ga for Cu in these metallic glasses therefore expected to have no significant effect on corrosion susceptibility. © The Author(s) 2019.
- ItemEffect of TiO2 , ZrO2 and ZnO addition on the hydrolytic durability, viscosity and crystallization behaviour of fibre glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Tauch, Diana; Wange, Peter; Rüssel, ChristianGlasses of the System Na2O-K2O-MgO-CaO-BaO-AI2O3-SiO2-B2O3 with additions of TiO2, ZrO2 and ZnO were melted from the raw materials. The glasses were characterized with respect to their hydrolytic durabilities, the working ranges (difference of temperatures attributed to viscosities of 10^2 and 10^4 dPa s), the temperatures attributed to the working point (η = 10^3.5 dPa s), and the crystal growth velocities. In the most cases, the additions led to an increase in viscosity and to a slight decrease in the workability range. The crystal growth velocities decreased with the addition of Ti02 and/or Zr02, while they increased if adding ZnO. The addition of ZnO or of TiO2 and ZrO2 resulted in better chemical durability.