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The paper proposes the analytic modelling of flexible textile shields made of fabrics with inserted conductive yarns and metallic plasma coating in order to calculate their electromagnetic shielding effectiveness (EMSE). This manufacturing process is highly innovative, since copper plasma coating improves EMSE on the fabrics with inserted conductive yarns of stainless steel and silver with 10–15 dB in the frequency range of 0.1–1000 MHz, as shown by the measured EMSE values determined according to the standard ASTM ES-07 via the Transverse Electromagnetic (TEM) cell. On the other hand, modelling of EMSE for such conductive flexible shields gives an insight on estimating EMSE in the design phase of manufacturing the shield, based on its geometric and electrical parameters. An analytic model was proposed based on the sum of EMSE of the fabric with inserted conductive yarns and EMSE of the copper coating. The measurement results show close values to the proposed analytic model, especially in case of fabric with conductive yarns having stainless steel content.

The characteristics of interaction between six transition-metal porphyrines and the Ag(111) surface are detailed here as resulted from DFT calculations. Van der Waals interactions as well as the strong correlation in 3d orbitals of transition metals were taken into account in all calculations, including the structural relaxation. For each system we investigate four relative positions of the metallic atom on top the surface. We show that the interaction between the transition metal and silver is the result of a combination between the dispersion interaction, charge transfer and weak chemical interaction. The detailed analysis of the physical properties, such as dipolar and magnetic moments and the molecule–surface charge transfer, analyzed for different geometric configurations allows us to propose qualitative models, relevant for the understanding of the self-assembly processes and related phenomena.

This paper presents a methodology to predict the evolution of state-of-health for lead-acid battery under controlled aging conditions. The results are based on the electrochemical impedance spectroscopy data. We show that by collecting impedance data for the battery for two states of charge (fully charged and at 75% SOC, respectively) it is possible to predict the lifetime of the battery with high accuracy. Our conclusion is based on the effect of linear decay for the values of constant phase element in the equivalent circuit of the battery during the aging. In order to validate our conclusions we perform analysis over three separate cells. We show that the linear decay as a function of cycle index is a robust feature, present for all samples. Potential application of our methodology include the rapid evaluation of the industrial products, the possibility to test the effect of technological changes over the battery quality as well as the development of optimized battery management systems.

Electromagnetic (EM) radiation may be harmful for human’s health and for functioning of electronic equipment. The field of Electromagnetic Compatibility approaches various solutions to tackle this problem, while shielding of the radiation is one of the main solutions. Since the development of spinning technology for producing conductive yarns for fabrics, textile electromagnetic shields have become a valuable alternative to metallic shields. Their main advantages are given by the flexibility, the low weight and the good mechanical resistance, as well as by the possibility to precisely design the shield. The scientific literature includes several analytic relations for estimating the electromagnetic shielding effectiveness (EMSE), in case of woven fabrics with conductive yarns, which may be modeled as a grid of electric conductors. This book chapter tackles three different analytic models for estimating EMSE, which are useful to predict this functionality in the design phase of fabrics. The analytic relations are subsequently comparatively validated by EMSE measurements via TEM cell equipment of two woven fabrics with conductive yarns out of stainless steel and silver with a grid of 4 mm. Results of validated analytic relations are used for the approach of designing textile shields with regard to final application requirements.

Acenes and azaacenes lie at the core of molecular materials' applications due to their important optical and electronic features. A critical aspect is provided by their heteroatom multiplicity, which can strongly affect their properties. Here we report pyrazinacenes containing the dihydro-decaazapentacene and dihydro-octaazatetracene chromophores and compare their properties/functions as a model case at an oxidizing metal substrate. We find a distinguished, oxidation-state-dependent conformational adaptation and self-assembly behaviour and discuss the analogies and differences of planar benzo-substituted decaazapentacene and octaazatetracene forms. Our broad experimental and theoretical study reveals that decaazapentacene is stable against oxidation but unstable against reduction, which is in contrast to pentacene, its C-H only analogue. Decaazapentacenes studied here combine a planar molecular backbone with conformationally flexible substituents. They provide a rich model case to understand the properties of a redox-switchable pi-electronic system in solution and at interfaces. Pyrazinacenes represent an unusual class of redox-active chromophores. Acenes are a promising class of organic materials with distinctive electronic and optical properties. Here decaazapentacene and octaazatetracenes are prepared and their self-assembly behaviour at different oxidation states is analysed. Práce se zabývá studiem pyrazinacenů obsahujících dihydro-dekaazapentacenové a dihydro-oktaazatetracenové chromofory a porovnáním jejich vlastností při modelovém chování na oxidačním kovovém substrátu. Byla nalezena odlišná, na oxidačním stavu závislá konformační adaptace a samouspořádající se chování. Byly připraveny dekaazapentaceny a oktaazatetraceny a analyzováno jejich samoorganizující se chování v různých oxidačních stavech.

International audience; The applicability of organic materials in conventional Li-ion batteries is challenging owing to the lack of lithium-containing and air-stable cathodes. A class of conjugated sulfonamides to be used as lithium-ion positive electrodes is now shown to exhibit reversible charge storage. The applicability of organic battery materials in conventional rocking-chair lithium (Li)-ion cells remains deeply challenged by the lack of Li-containing and air-stable organic positive electrode chemistries. Decades of experimental and theoretical research in the field has resulted in only a few recent examples of Li-reservoir materials, all of which rely on the archetypal conjugated carbonyl redox chemistry. Here we extend the chemical space of organic Li-ion positive electrode materials with a class of conjugated sulfonamides (CSAs) and show that the electron delocalization on the sulfonyl groups endows the resulting CSAs with intrinsic oxidation and hydrolysis resistance when handled in ambient air, and yet display reversible electrochemistry for charge storage. The formal redox potential of the uncovered CSA chemistries spans a wide range between 2.85 V and 3.45 V (versus Li+/Li-0), finely tunable through electrostatic or inductive molecular design. This class of organic Li-ion positive electrode materials challenges the realm of the inorganic battery cathode, as this first generation of CSA chemistries already displays gravimetric energy storage metrics comparable to those of the stereotypical LiFePO4.

Using first-principles calculations, we investigate the binding energy for six transition metal - phthalocyanine molecules adsorbed on Au(111). We focus on the effect of translation on molecule - surface physical properties; van der Waals interactions as well as the strong correlation in d orbitals of transition metals are taken into account in all calculations. We found that dispersion interaction and charge transfer have the dominant role in the molecule-surface interaction, while the interaction between the transition metal and gold has a rather indirect influence over the physics of the molecule-surface system. A detailed analysis of the physical properties of the adsorbates at different geometric configurations allows us to propose qualitative models to account for all values of interface dipole charge transfer and magnetic moment of metal-phthalocyanines adsorbed on Au(111).

Recent experimental studies have found that magnetic impurities deposited on superconducting monolayer NbSe$_2$ generate coupled Yu-Shiba-Rusinov bound states. Here we consider ferromagnetic chains of impurities which induce a Yu-Shiba-Rusinov band and harbor Majorana bound states at the chain edges. We show that these topological phases are stabilized by strong Ising spin-orbit coupling in the monolayer and examine the conditions under which Majorana phases appear as a function of distance between impurities, impurity spin projection, orientation of chains on the surface of the monolayer, and strength of magnetic exchange energy between impurity and superconductor., Comment: 21 pages

A variety of technological approaches of lead-acid batteries have been employed during the last decades, within distinguished fabrication features of electrode grid composition, electrolyte additives, or oxide paste additives embodiment. We proposed in this study, a particular path for improving the efficiency of positive grids by developing two novel geometry designs of lead-acid battery metallic grids. Our projection is based on a hierarchical approach that employed exclusively rectangular shapes for the structural configuration of grids. The intensity of current distribution was firstly evaluated by a numerical algorithm across the electrodes grid surface, thus allowing measuring the propagation of the electric charge emitted from each point inside of the grid. The novel fabricated prototypes were investigated by electrochemical impedance spectroscopy, following a controlled aging procedure. Two distinct parameters were investigated for evaluation of batteries lifetime: i) a time-dependent analysis of Constant Phase Element – Q parameter at 75% SoC partially discharged, and ii) the resonance frequency of the circuit. To confirm our improvements, we compared the data with the ones of an industrial grid model. An increment of battery lifetime was obtained for one prototype, with an estimation growth of 25% - 28% over the usual industrial electrode, while for the later a slightly improved lifetime efficiency of about 10% was resulted.

We present a theoretical investigation that addresses the most important aspects of the interaction between α-glycero-phosphatidyl-choline and Au(111) surface. For the density functional calculations we employed both traditional exchange-correlation functionals and newly developed vdW-D2 corrected one. The comparison between these functionals allows us to spot the role of van der Waals effects into the molecule– surface interaction. The effect of an external field applied to the molecule–surface system was also explicitly investigated. Our results reveal a complex picture where the molecular adsorption is dominated by the interplay between a weak molecule–surface interaction and a rather important deformation energy of the adsorbed molecule. In the presence of an external electric field, the choline moiety provided the strongest response in terms of binding energy as well as geometric configuration of the adsorbate.

We present in this work a new electrochemical impedance spectroscopy approach for lifetime prediction of lead-acid cells under imposed aging conditions. Frequency dependent impedance fluctuations are being monitored during charging and discharging sequences of battery for two distinct states of charges. We monitored the battery impedance behavior in two distinct states: at 100% state of charge, and secondly, at 75% state-of-charge. During the aging process, we encompassed the impedance plots vs frequency shifting diagrams, in the framework of a single parameter, we refer here to resonant frequency of the circuit. The validation of our model was demonstrated by comparing the resonance frequency values in three fabricated cells, thus emphasizing the changes that appear in the various physical details, depending on battery fabrication methodology. For State-of-Charge = 100% the degradation of the battery is leading to an important variation of its resonance frequency, while for State-of-Charge = 75%, the fluctuations of resonance frequency are significantly smaller. Monitoring just one parameter, we developed an accurate fitting model function capable to predict the lead-acid cells aging process. We can say that for the cell produced under controlled conditions, we get a larger lifetime and an inferior degradation speed to the cells manufactured in laboratory.

The molecular doping of graphene with π-stacked conjugated molecules has been widely studied during the last 10 years, both experimentally or using first-principle calculations, mainly with strongly acceptor or donor molecules. Macrocyclic metal complexes have been far less studied and their behavior on graphene is less clear-cut. The present density functional theory study of cobalt porphyrin and phthalocyanine adsorbed on monolayer or bilayer graphene allows to compare the outcomes of two models, either a finite-sized flake of graphene or an infinite 2D material using periodic calculations. The electronic structures yielded by both models are compared, with a focus on the density of states around the Fermi level. Apart from the crucial choice of calculation conditions, this investigation also shows that unlike strongly donating or accepting organic dopants, these macrocycles do not induce a significant doping of the graphene sheet and that a finite size model of graphene flake may be confidently used for most modeling purposes. © 2017 Wiley Periodicals, Inc.

We examine the ballistic conduction through Au-NiMnSb-Au heterostructures consisting of up to four units of NiMnSb in the scattering region. We investigate the dependence of the transmission function computed within the local spin density approximation (LSDA) of the density functional theory (DFT) on the number of half-metallic units in the scattering region. For a single NiMnSb unit the transmission function displays a spin polarization of around 50 % in a window of 1 eV centered around the Fermi level. By increasing the number of layers an almost complete spin polarization of the transmission is obtained in the same energy window. Supplementing the DFT-LSDA calculations with local electronic interactions, of Hubbard-type on the Mn sites, leads to a hybridization between the interface and many-body states. The significant reduction of the spin polarization seen in the density of states is not apparent in the spin-polarization of the conduction electron transmission, which suggests the localized nature of the hybridized interface and many-body induced states., 25 pages, 6 figures

International audience; In this paper, the simultaneous measurement of out-of-plane thermal diffusivity and effective infrared absorption coefficient of an IR semi-transparent GaAs wafer using infrared lock-in thermography technique (LIT) is presented. The method relies on analysis of the generated LIT phase images recorded at different modulation frequencies, using the thermal wave model in the transmission configuration. The out-of-plane thermal diffusivity and effective infrared absorption coefficient are estimated from the best fit of the theoretical model to the experimental data. The obtained values are in good agreement with those obtained by supplementary measurement using the modulated photothermal infrared radiometry technique (PTR) in the reflection mode, and also with data reported in the literature. In addition, simple modification of the LIT experiment set up allows one to determinate the in-plane thermal diffusivity of n-GaAs wafer. It was found that in-plane and out-of-plane thermal diffusivities of the GaAs wafer are very close, as expected, within the limit of measurement errors. The results show that the LIT technique in transmission configuration can provide spatial information about both the (effective) infrared absorption coefficient and thermal diffusivity of semiconductor crystals.

This work explores a qualitative appraisal of lead acid battery electrodes by Electrochemical Impedance Spectroscopy. Lead acid cells behavior has been examined by gathering data of impedance modifications in distinct electrolyte volumes, from a full one to a battery filled at about 20% of the total volume of acid. Since the current between electrodes is inhomogeneous around the collector by varying the quantity of the electrolyte, we have associated numerical values of the elements in the battery equivalent circuit, to the homogeneity of the current in the electrodes. Theoretical considerations dealing with modeling, equivalent circuits and corresponding equations are provided. As a function of the electrolyte quantity, we investigated the dependence of the values for components of the Randle circuit. A particular attention has been devoted to constant phase element (CPE) peculiarities, as this parameter was found essential for a good quality fit over an extended range of batteries. The stability depending on current homogeneity at a certain battery state of charge was analysed in order to assess the effect of electrolyte volumes, and thereby to provide new quality requirements for improvement of lead-acid battery performance.

Using first-principles calculations, we study the electronic and transport properties of rutheniumterpyridine molecules sandwiched between two Au(111) electrodes. We analyse both single and packed molecular devices, more amenable to scaling and realistic integration approaches. The devices display all together robust negative differential resistance features at low bias voltages. Remarkably, the electrical control of the spin transport in the studied systems implies a subtle distribution of the magnetisation density within the biased devices and highlights the key role of the Au(111) electrical contacts.

We have investigated the ballistic transport for Mn, Fe-porphyrin molecules in contact with Au(111) electrodes by using density functional theory. We show that the information resulted from the projected density of electronic states does not provide a complete picture of the transport mechanism. Instead, we propose a methodology based on the concept of the orbital projected transmissions for selected groups of atoms. We have found that the transmission channels for occupied states can be assigned to short range scattering processes at gold-molecule interface, while for the states above Fermi level the transmission takes place via long range scattering processes. The interplay between these two conduction mechanisms is responsible for the transport path in metal-porphyrin; our model is in qualitative agreement with the existing experimental data on transport pathway on single porphyrin molecules.

An experimental method for the investigation of the current distribution in the electrodes of lead-acid batteries has been developed. The information is extracted by analysing the heat dissipation in the electrode during the discharge by using a high-performance IR camera. The effect of the current in the metallic grid can be de-convoluted from the total heat produced in the electrode by numerical processing of the temperature distribution over the electrode surface. By its simplicity and effectiveness, the proposed method has the potential to become an important tool in optimising electrode geometry.