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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.
- 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.
- ItemPrimarily tests of a optoelectronic in-canopy sensor for evaluation of vertical disease infection in cereals(New York, NY : Wiley, 2022) Dammer, Karl-Heinz; Schirrmann, MichaelBACKGROUND: Health scouting of crops by satellite, airplanes, unmanned aerial (UAV) and ground vehicles can only evaluate the crop from above. The visible leaves may show no disease symptoms, but lower, older leaves not visible from above can do. A mobile in-canopy sensor was developed, carried by a tractor to detect diseases in cereal crops. Photodiodes measure the reflected light in the red and infrared wavelength range at 10 different vertical heights in lateral directions. RESULTS: Significant differences occurred in the vegetation index NDVI of sensor levels operated inside and near the winter wheat canopy between infected (stripe rust: 2018, 2019 / leaf rust: 2020) and control plots. The differences were not significant at those sensor levels operated far above the canopy. CONCLUSIONS: Lateral reflectance measurements inside the crop canopy are able to distinguish between disease-infected and healthy crops. In future mobile in-canopy scouting could be an extension to the common above-canopy scouting praxis for making spraying decisions by the farmer or decision support systems. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
- ItemSubsequent treatment of leafy vegetables with low doses of UVB-radiation does not provoke cytotoxicity, genotoxicity, or oxidative stress in a human liver cell model(Amsterdam [u.a.] : Elsevier, 2021) Wiesner-Reinhold, Melanie; Dutra Gomes, João Victor; Herz, Corinna; Tran, Hoai Thi Thu; Baldermann, Susanne; Neugart, Susanne; Filler, Thomas; Glaab, Johannes; Einfeldt, Sven; Schreiner, Monika; Lamy, EvelynUltraviolet B (UVB) radiation in low but ecological-relevant doses acts as a regulator in the plant's secondary metabolism. This study investigates the effect of UVB radiation from light-emitting diodes (LEDs) [peak wavelength of (290 ± 2) nm] on the biosynthesis of health-promoting secondary plant metabolites (carotenoids, phenolic compounds, and glucosinolates) of green and red leafy vegetables of Lactuca sativa, Brassica campestris, and Brassica juncea followed by evaluation of potential adverse effects in a human liver cell model. UVB radiation led to a significant increase in individual secondary plant metabolites, especially of phenolic compounds and glucosinolates, e.g. alkenyl glucosinolate content. Kaempferol und quercetin glycoside concentrations were also significantly increased compared to untreated plants. The plant extracts from Lactuca sativa, Brassica campestris, and Brassica juncea were used to assess cytotoxicity (WST-1 assay and trypan blue staining), genotoxicity (Comet assay), and production of reactive oxygen species (EPR) using metabolically competent human-derived HepG2 liver cells. No adverse effects in terms of cytotoxicity, genotoxicity, or oxidative stress were detected in an extract concentration ranging from 3.125 to 100 μg ml−1. Notably, only at very high concentrations were marginal cytostatic effects observed in extracts from UVB-treated as well as untreated plants. In conclusion, the application of UVB radiation from LEDs changes structure-specific health-promoting secondary plant metabolites without damaging the plants. The treatment did not result in adverse effects at the human cell level. Based on these findings, UVB LEDs are a future alternative, promising light source to replace currently commonly used high-pressure sodium lamps in greenhouses.
- ItemThe potential of calcium hydroxide to reduce storage losses: A four months monitoring study of spruce wood chip piles at industrial scale(New York, NY [u.a.] : Elsevier, 2021) Dumfort, Sabrina; Pecenka, Ralf; Ascher-Jenull, Judith; Peintner, Ursula; Insam, Heribert; Lenz, HannesThe objective of this study was to investigate the effect of an alkaline additive on the storage of wood chips from Norway spruce forest residues. Piles of untreated and calcium hydroxide treated wood chips (250 m3) were set up and investigated for four months. It was demonstrated that adding Ca(OH)2 to moist wood chips decreased the dry matter loss by 6%. This was attributed to the increase of the pH to a level of 8, rendering the habitat less suitable for fungal colonisation. The results suggest the set-up storage strategy as a potential alternative method for preserving wood chips when long term storage is required.
- ItemGraphene transfer methods: A review(New York, NY [u.a.] : Springer, 2021) Ullah, Sami; Yang, Xiaoqin; Ta, Huy Q.; Hasan, Maria; Bachmatiuk, Alicja; Tokarska, Klaudia; Trzebicka, Barbara; Fu, Lei; Rummeli, Mark H.Graphene is a material with unique properties that can be exploited in electronics, catalysis, energy, and bio-related fields. Although, for maximal utilization of this material, high-quality graphene is required at both the growth process and after transfer of the graphene film to the application-compatible substrate. Chemical vapor deposition (CVD) is an important method for growing high-quality graphene on non-technological substrates (as, metal substrates, e.g., copper foil). Thus, there are also considerable efforts toward the efficient and non-damaging transfer of quality of graphene on to technologically relevant materials and systems. In this review article, a range of graphene current transfer techniques are reviewed from the standpoint of their impact on contamination control and structural integrity preservation of the as-produced graphene. In addition, their scalability, cost- and time-effectiveness are discussed. We summarize with a perspective on the transfer challenges, alternative options and future developments toward graphene technology.
- ItemThermal protection implementation of the contact overheadline based on bay controllers of electric transport traction substations in the mining industry(Sankt-Peterburg : Inst., 2021) Lantsev, Dmitry; Frolov, Vladimir; Zverev, Sergej; Uhrlandt, Dirk; Valenta, JiříThe article presents the principle of thermal protection of the contact overheadlineand substantiates the possibility of practical implementation of this principle for rail electric transport in the mining industry. The algorithm for the implementation of modern digital protection of the contact overhead line as one of the functions of the controller is described. A mathematical model of thermal protection is proposed, which follows from the solution of the heat balance equation. The model takes into account the coefficient of the electrical networktopology, as well as the coefficient of consumption of the current-carrying core of the cable, which determines the reduction in the conducting section from contact erosion and the growth of oxide films. Corrections for air flows are introduced when receiving data from an external anemometer, via telemechanics protocol. The mathematical model was tested by writing a real thermal protection program in the C programming language for the bay controller, based on the circuitry of which is the STM32F407IGT6 microcontroller for the microcontroller unit. Verification tests were carried out on a serial bay controller in 2020. The graphs for comparing the calculated and actual values of temperatures, with different flow rates of the current-carrying conductor of the DC cable, are given. To obtain data, telemechanics protocols IEC 60870-104 and Modbus TCP, PLC Segnetics SMH4 were used.
- ItemReactive plasma cleaning and restoration of transition metal dichalcogenide monolayers(London : Nature Publishing Group, 2021) Marinov, Daniil; de Marneffe, Jean-François; Smets, Quentin; Arutchelvan, Goutham; Bal, Kristof M.; Voronina, Ekaterina; Rakhimova, Tatyana; Mankelevich, Yuri; El Kazzi, Salim; Nalin Mehta, Ankit; Wyndaele, Pieter-Jan; Heyne, Markus Hartmut; Zhang, Jianran; With, Patrick C.; Banerjee, Sreetama; Neyts, Erik C.; Asselberghs, Inge; Lin, Dennis; De Gendt, StefanThe cleaning of two-dimensional (2D) materials is an essential step in the fabrication of future devices, leveraging their unique physical, optical, and chemical properties. Part of these emerging 2D materials are transition metal dichalcogenides (TMDs). So far there is limited understanding of the cleaning of “monolayer” TMD materials. In this study, we report on the use of downstream H2 plasma to clean the surface of monolayer WS2 grown by MOCVD. We demonstrate that high-temperature processing is essential, allowing to maximize the removal rate of polymers and to mitigate damage caused to the WS2 in the form of sulfur vacancies. We show that low temperature in situ carbonyl sulfide (OCS) soak is an efficient way to resulfurize the material, besides high-temperature H2S annealing. The cleaning processes and mechanisms elucidated in this work are tested on back-gated field-effect transistors, confirming that transport properties of WS2 devices can be maintained by the combination of H2 plasma cleaning and OCS restoration. The low-damage plasma cleaning based on H2 and OCS is very reproducible, fast (completed in a few minutes) and uses a 300 mm industrial plasma etch system qualified for standard semiconductor pilot production. This process is, therefore, expected to enable the industrial scale-up of 2D-based devices, co-integrated with silicon technology.
- ItemModeling Polycrystalline Electrode-electrolyte Interfaces: The Differential Capacitance(Bristol : IOP Publishing, 2020) Müller, Rüdiger; Fuhrmann, Jürgen; Landstorfer, ManuelWe present and analyze a model for polycrystalline electrode surfaces based on an improved continuum model that takes finite ion size and solvation into account. The numerical simulation of finite size facet patterns allows to study two limiting cases: While for facet size diameter dfacet →0 we get the typical capacitance of a spatially homogeneous but possible amorphous or liquid surface, in the limit 1[nm] < dfacet, an ensemble of non-interacting single crystal surfaces is approached. Already for moderate size of the facet diameters, the capacitance is remarkably well approximated by the classical approach of adding the single crystal capacities of the contributing facets weighted by their respective surface fraction. As a consequence, the potential of zero charge is not necessarily attained at a local minimum of capacitance, but might be located at a local capacitance maximum instead. Moreover, the results show that surface roughness can be accurately taken into account by multiplication of the ideally flat polycrystalline surface capacitance with a single factor. In particular, we find that the influence of the actual geometry of the facet pattern in negligible and our theory opens the way to a stochastic description of complex real polycrystal surfaces. © 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.
- ItemEvaluation of spectral induced polarization field measurements in time and frequency domain(Amsterdam [u.a.] : Elsevier Science, 2020) Martin, Tina; Günther, Thomas; Orozco, Adrian Flores; Dahlin, TorleifSpectral induced polarization (SIP) measurements have been demonstrated to correlate with important parameters in hydrogeological and environmental investigations. Although SIP measurements were often collected in the frequency domain (FDIP), recent developments have demonstrated the capabilities to solve for the frequency-dependence of the complex conductivity through measurements collected in the time domain (TDIP). Therefore, the aim of our field investigations is a comparison of the measured frequency-dependence at a broad frequency range resolved through FDIP and TDIP. In contrast to previous studies, we conducted measurements with different instruments and measuring technologies for both FDIP and TDIP. This allows for investigating the robustness of different measurements and assessing various sources of errors, for the assessment of the advantages and drawbacks from different measuring techniques. Our results demonstrate that data collected through different instruments are consistent. Apparent resistivity measurements as well as the inversion results revealed quantitatively the same values for all instruments. The measurements of the IP effect are also comparable, particularly FDIP readings in the low frequencies (< 10 Hz) revealed to be quantitatively the same for different instruments. TDIP measurements are consistent for data collected with both devices. As expected, the spatial distribution of the values is also consistent for low frequency data (in FDIP) and late times measurements in TDIP (> 0.1 s). However, data quality for higher frequencies in FDIP (i.e., early times in TDIP) show larger variations, which reflects the differences between the instruments to deal with the electromagnetic contamination of the IP data. Concluded in general, the different instruments and measuring techniques can provide consistent responses for varying signal-to-noise ratio and measuring configurations. © 2020 The Authors