Conductivity Of Such Materials Research Articles

ZnO sintering aid effect on proton conductivity of BaCe0.6Zr0.3Y0.1O3-δ electrolyte for hydrogen sensors

Proton-conducting solid-state electrolytes, including perovskite-type materials, hold promise for hydrogen sensor development. These sensors leverage the proton conductivity of such materials to detect hydrogen gas presence. However, achieving both high density for gas tightness and good protonic conductivity in these refractory materials can be challenging.In this study, we propose the preparation of dense pellets of BaCe0.6Zr0.3Y0.1O3-δ using ZnO as a sintering aid (BCZY-Zn). These pellets were extensively characterized using X-ray diffraction and electrochemical impedance spectroscopy and compared with pellets sintered without sintering aid (BCZY). Subsequently, BCZY-Zn electrolyte was utilized to fabricate amperometric sensors for hydrogen monitoring. Finally, amperometric measurements were conducted at 500 °C while maintaining a voltage of 150 mV between electrodes. The sensors' performance was evaluated for hydrogen partial pressures ranging from 12 to 100 Pa within an argon atmosphere. Additionally, response and recovery times were calculated.

Electric-field-aligned liquid crystal polymer for doubling anisotropic thermal conductivity

High thermal conductive polymers have become more important because equipment requires high performance, high-energy density, and high integration. There are different strategies to make high thermal conductive polymers, among which is the synthesis of polymers in the liquid crystal phase. However, the thermal conductivity of such material is rarely beyond 1 W m−1 K−1 because of the disordered molecular directionality. The disordered directionality between crystal zones limits the thermal conductivity in a specific direction. Here, we show a method for unifying the direction of crystal zones by applying an external electric field on the liquid crystal monomers. Meanwhile, by exposing the transparent equipment and specially designed photopolymerisable monomer in UV light, the liquid crystal monomer is in situ polymerised into a liquid crystal polymer with a high intrinsic thermal conductivity of 1.02 W m−1 K−1. The molecular alignment was characterised and resulted in the resultant high conductivity.

Molecular modelling of graphene nanoribbons on the effect of porosity and oxidation on the mechanical and thermal properties

Graphene is considered as the most promising nanomaterial of the recent decades given the huge amount of studies that have been performed to characterize its outstanding properties and in searching of novel applications. Following this tendency, this study covers the modelling of graphene nanoribbons (GNRs) with the aim of analyzing the effect of porosity and oxidation on the tensile mechanical properties and in-plane thermal conductivity through molecular dynamics (MD). Using quasi-static simulations the mechanical properties were evaluated in first place. A ‘hardening’ mechanism was observed for GNRs at porosities below 1%, i.e. perfect or near-perfect GNRs, by which the GNRs could withstand higher loading levels. This hardening effect was manifested in the carbon network by the generation of dislocation lines formed by pentagon-heptagon pairs (5–7 defects), which acted as a stress reliever. The failure of GNRs was produced as a tearing mechanism with cracks growing along the armchair or zigzag directions. The porosity affected all the analysed tensile mechanical properties (i.e., Young’s modulus, Poisson’s ratio, tensile strength and deformation at break), but with different tendency in the fracture properties due to the presence or absence of hardening behaviour in the GNRs. Nevertheless, the oxidation affected only the tensile modulus and Poisson’s ratio but not to the tensile strength and deformation at break. The thermal conductivity of the GNRs was affected either by the porosity and oxidation. Pores and oxidation groups acted as phonon scatterers since they disrupted the carbon network by the generation of vacancies or out-of-plane carbons, respectively, which decreased the phonon mean free path and thus the thermal conductivity. In conclusion, the porosity and oxidation of GNRs greatly determine the tensile mechanical properties and in-plane thermal conductivity of such materials and must be considered when tuning the synthetic pathways.Graphical abstractThe effect of porosity and oxidation on the tensile mechanical and thermal conductivity properties of graphene nanoribbons are evaluated through molecular dynamics simulations.

Composite membranes for fuel cells

The current ecological situation attracts particular attention to alternative energy sources with no detrimental impact on the ecosystem. In comparison with conventional energy sources, fuel cells exhibit the following advantages: small and compact size, light weight, lack of noise when working, and cost-effectiveness in terms of fuel consumption. Most importantly, fuel cells are environmentally friendly, since no harmful substances are released into the atmosphere during their operation. Their goal is to convert chemical energy from various sources into environmentally friendly electric power. At present, chemical sources of energy are used everywhere, including batteries for mobile phones, laptops, as well as cars and uninterruptible power supplies, to name a few. The main components of solid polymer fuel cells are proton-exchange membranes, the main function of which is to ensure the transfer of protons from the anode to the cathode. The proton conductivity of such materials is determined by the presence of hydrophilic channels that transport mobile protons. The proton-exchange membrane must meet the following requirements: electrochemical and chemical stability in aggressive chemical environments, mechanical and thermal strength, low permeability to reagent gases (fuel and oxidizer), high ion exchange capacity and electrical conductivity, as well as a relatively low cost. This paper considers perfluorinated sulfonic acid membranes, organic–inorganic and acid–base composite membranes, as well as hybrid membranes obtained by sol-gel process, which can contribute to the development of technologies related to fuel cells in the future.

Computational insights into ionic conductivity of transition metal electrode materials for metal-ion batteries - A review

Charge/discharge rates and low-temperature performance of metal-ion batteries are strongly affected by the ionic conductivity of transition metal intercalation materials used in electrodes. Computational methods, based on crystal chemistry empirical approaches and rigorous density functional theory have become indispensable for the evaluation of ionic conductivity in such materials. During the last decade, hundreds of computational studies of various intercalation materials accumulated considerable knowledge regarding ionic conductivity. This review covers the modern crystal chemistry methods and their application to transition metal intercalation materials, as well as systematizes the available information retrieved from mostly density functional theory studies related to mechanisms of ionic conductivity/diffusivity with the focus on elementary migration acts of alkali cations. We consider in detail how the diffusion channel size and dimension, coordination, cation size, anion and transition metal type, oxidation state, state of charge/discharge, and other factors affect elementary migration acts of alkali cations. The review collects the design principles of new intercalation materials with high ionic conductivity being helpful for advanced energy storage technologies development.

An anionic porphyrinylphosphonate-based hydrogen-bonded organic framework: optimization of proton conductivity through the exchange of counterions.

Hydrogen-bonded organic frameworks (HOFs) possessing high crystallinity, simple synthetic procedure and easy regeneration provide high efficiency as multifunctional systems, including applications as proton conductors. Porphyrinylphosphonates having acidic moieties, which can form multiple hydrogen bonds, together with tunable physical-chemical properties of a macrocycle may significantly improve the proton conductivity of such materials. Herein, the synthesis, characterization and proton-conducting properties of a novel anionic HOF based on a new complex of palladium(II) with meso-tetrakis(4-(phosphonatophenyl))porphyrin, HOF-IPCE-1Pd, are reported. Directed structural transformation of the framework by the exchange of dimethylammonium counterions for ammonium cations along with the absorption of ammonia and water molecules led to the formation of a more hydrolytically stable structure of HOF-IPCE-1Pd-NH3, demonstrating the proton conductivity of 1.27 × 10-3 S cm-1 at 85 °C and 85% RH, which is one of the highest among all known HOFs based on porphyrins. It is noteworthy that the reversible absorbance of water/ammonia molecules preserves the crystal structure of HOF-IPCE-1Pd-NH3.

ИССЛЕДОВАНИЕ ПОМЕХОВОГО ФОНА НА ВХОДЕ ПРИЕМНИКА СИСТЕМЫ БЛИЖНЕПОЛЬНОЙ МАГНИТНОЙ СВЯЗИ В ГОРОДСКИХ УСЛОВИЯХ

Near-field magnetic communication (NFMC) has unique characteristics, such as secrecy,communication channel security, the ability to pass a signal through the vast majority of obstacleswithout significant attenuation. NFMC can be used in such use cases where traditional radio isimpossible. One of the tasks in which the use of NFMC is relevant is to provide reliable wireless communication for rescuers, firefighters, employees of the Ministry of Emergency Situations whenperforming their professional activities in the conditions of blockages caused by various destructionsof urban buildings. It should be noted that under such conditions, the conductivity of buildingmaterials and soil can affect the propagation of not only electric, but also magnetic fields. The factis that due to the conductivity of such materials, when using radio coupling, eddy currents arise inthe materials, which leads to the appearance of a secondary magnetic field that is in antiphase.The system under consideration is not subject to the effects described above. This article presentsthe results of experimental studies aimed at studying the interference environment in the NFMCchannel. Field experiments were carried out to measure the interference environment. Based onthe data obtained, it was concluded that the use of NFMC systems in urban environments is a ratherdifficult task due to the nature of the interference propagating in the channel of this type ofcommunication. The effective use of NFMC requires the development of receiving devices thatprovide sufficiently strong filtering of signals outside the selected band. Narrow band and highorder filtering is key priority of observed communication system.

Towards Improved Humidity Sensing Nanomaterials via Combined Electron and NH3 Treatment of Carbon-Rich FEBID Deposits.

Focused Electron Beam Induced Deposition (FEBID) is a unique tool to produce nanoscale materials. The resulting deposits can be used, for instance, as humidity or strain sensors. The humidity sensing concept relies on the fact that FEBID using organometallic precursors often yields deposits which consist of metal nanoparticles embedded in a carbonaceous matrix. The electrical conductivity of such materials is altered in the presence of polar molecules such as water. Herein, we provide evidence that the interaction with water can be enhanced by incorporating nitrogen in the deposit through post-deposition electron irradiation in presence of ammonia (NH3). This opens the perspective to improve and tune the properties of humidity sensors fabricated by FEBID. As a proof-of-concept experiment, we have prepared carbonaceous deposits by electron irradiation of adsorbed layers of three different precursors, namely, the aliphatic hydrocarbon n-pentane, a simple alkene (2-methyl-2-butene), and the potential Ru FEBID precursor bis(ethylcyclopentadienyl)ruthenium(II). In a subsequent processing step, we incorporated C-N bonds in the deposit by electron irradiation of adsorbed NH3. To test the resulting material with respect to its potential humidity sensing capabilities, we condensed sub-monolayer quantities of water (H2O) on the deposit and evaluated their thermal desorption behavior. The results confirm that the desorption temperature of H2O decisively depends on the degree of N incorporation into the carbonaceous residue which, in turn, depends on the chemical nature of the precursor used for deposition of the carbonaceous layer. We thus anticipate that the sensitivity of a FEBID-based humidity sensor can be tuned by a precisely timed post-deposition electron and NH3 processing step.

Modeling investigation for energy storage system including mixture of paraffin and ZnO nano-powders considering porous media

In this work, air conditioning unit with involve of porous media has been presented. The duct has several five-lobed cylinders containing the paraffin (RT27) and for augmenting the conductivity of such material, it was mixed with nano-sized particles of ZnO. To include the related terms of porous media, wiremesh approach was applied and turbulent regime for air zone was considered. Owing to solar irradiation, air becomes warmer up to T = 311.15K outside the duct and with entering within the duct makes paraffin to convert to liquid. So, not only the solar energy can be stored, but also the needed cool air inside the building can be provided. Mixing nanoparticles with paraffin leads to higher level of conduction which decline the required time for full melting about 5.22% when Re = 7000, γ = 0.95. With utilizing porous media, the needed time will be decreased about 37.15% when Re = 7000, φ = 0.035. As power of blower augments, the period of melting decreases around 41.77% when γ = 0.95, φ = 0.035. Among the scrutinized cases, the minimum required time for achieving full melting is 7985s which can be attained if γ = 0.95, φ = 0.035, Re = 7000.

Tool electrode considerations in EDM of titanium alloys – A review

The machining of Titanium alloys is quite challenging; it produces heat during cutting operation which is difficult to release owing to low thermal conductivity of such materials. Difficulties in machining of titanium material arises because of high cutting temperatures attained, chemical reaction between tool- work piece interface, and low modulus of elasticity . Electrical discharge machining (EDM) has emerged as one of the most promising manufacturing processes for producing extremely accurate and complex components of any material which is electrically conductive. The different aspects of tool electrode play a vital role in machining of Titanium and its alloys. This research paper discusses the research trends on different aspects of tool electrodes are being used in machining of Titanium and its variants.

HALL CONDUCTIVITY ESTIMATES FROM MAGNETOTELLURIC SOUNDING DATA

Many minerals have semiconductor properties. It is known that petroleum reservoir rocks permeated with hydrocarbon fluids can sometimes behave as semiconductors. In the Earth’s magnetic field, the electrical conductivity of such materials becomes anisotropic, and the Hall effect is quite possible in rocks in natural conditions and detectable by magnetotelluric sounding. In the anisotropic medium, the field is subject to normal mode splitting, and its components show different attenuation coefficients and phase velocities. The modes differ due to polarization and rotation of the field vectors (clockwise in one mode, and counterclockwise in another). With account of the Hall effect, responses of the medium can be different when the medium is excited by a single normal wave. To detect the Hall effect in MTS surveys, we use the polarization analysis method and select the spectra of modes with right and left circular polarization. Special experiments were carried out to detect the contribution of the Hall effect during the MTS surveys. This article presents the first estimates of the Hall conductivity for the studied rocks.

About the Features of Electric Conductivity Models for Polymer Composite Nanomaterials Based on Cu(Cu2O)-LDPE

Polymer nanocomposites based on Cu(Cu2O)-LDPE with a volume fraction of 0.1–0.4 copper filler in the form of spherical nanoparticles with sizes from 10 to 25 nm were synthesized. The electrical conductivity of such composite nanomaterials was measured, which is 4.5–5 times higher than the electrical conductivity of a polyethylene matrix. To predict the electrical conductivity of such materials, an analysis of well-known mathematical models is carried out and models for predicting the electrical conductivity of such materials are selected that are adequate to the experimental data.

Determination of thermal conductivity of composites with dispersed spherical inclusions

The existing shortcomings of the models for determining the thermal conductivity of composite materials with dispersed spherical inclusions raise the issue of creating more advanced calculation methods. This paper proposes a model for determining the thermal conductivity of composite materials, taking into account influence of thermal resistance at the material-inclusion boundary. The analysis of numerical and theoretical calculations showed that the analytical dependence is consistent with the results of numerical modelling for relatively small values of thermal conductivity of the filler and inclusion diameter. This paper considers several models that have been recently developed and that allow calculating thermal conductivity of such materials. They are compared with the model that takes into account influence of thermal resistance of the phase boundary. Applicability intervals of the considered model for various ratios of the thermal conductivity of inclusion material and matrix material are given.

Numerical analysis of electrically conductive fillers of composites for aircraft lightning strike protection

Purpose This paper aims to present a numerical analysis and comparison of two types of conductive fillers of polymeric composites subjected to lightning strikes. Design/methodology/approach Two types of conductive fillers were considered in the developed numerical models of electrically conductive composites: carbon nanotubes and polyaniline. For these fillers, the representative volume elements were developed to consider distribution of the particles that ensures percolation and homogenization of the materials within the Eshelby-based semi-analytical mean-field homogenization approach. The performed numerical analyses allowed determination of effective volume fractions of conducting particles, resistivity and conductivity tensors, and finally the current density for the simulated materials subjected to lightning strike. Findings The obtained results allowed for comparison of electrical conductivity of two simulated materials. It was observed that besides fair results obtained in the previous studies for intrinsically conducting polymers as fillers of composites dedicated for lightning strike protection, the composites filled with carbon nanotubes reveal much better conductivity. Practical implications The presented simulation results can be considered as initial information for further experimental tests on electrical conductivity of such materials. Originality/value The originality of the paper lies in the proposed design and simulation procedures of conductive composites as well as the comparison of selected composites dedicated for lightning strike protection as the most intensively developed materials for this purpose.

Thermal co-evaporated MoOx:Au thin films and its application as anode modifier in perovskite solar cells

Molybdenum oxide (MoOx) has been used as a suitable interfacial modifier for emergent solar cells. However, the relatively low electrical conductivity of such material requires a thickness less than 10 nm of MoOx, which may lead to an uncovered surface and reduce the effect of interfacial modification. In this work, MoO3 and Au powder were co-evaporated and MoOx:Au composite coatings with a thickness of 10–20 nm were obtained. They are highly transparent, more compact and conductive, and contain a higher percentage of MoO2 compound than MoOx films without Au. The composite films were co-evaporated on top of the hole transport layer (Spiro-MMeOTAD) in perovskite solar cells (PSCs). The insertion of a MoOx:Au composite film, with a thickness of 14.3 nm and an atomic concentration of 34% of Au, improves photovoltaic performance and stability of PSCs after 1000 h of storage in ambient conditions. It is concluded that a relatively thick MoOx:Au layer can work as an interfacial modifier to reduce the humidity and oxygen diffusion into perovskite layer and, at the same time, improve the charge transport in PSCs.

Machine learning-assisted cross-domain prediction of ionic conductivity in sodium and lithium-based superionic conductors using facile descriptors

Solid state lithium- and sodium-ion batteries utilize solid ionically conducting compounds as electrolytes. However, the ionic conductivity of such materials tends to be lower than their liquid counterparts, necessitating research efforts into finding suitable alternatives. The process of electrolyte screening is often based on a mixture of domain expertise and trial-and-error, both of which are time and resource-intensive. In this work, we present a novel machine-learning based approach to predict the ionic conductivity of sodium and lithium-based SICON compounds. Using primarily theoretical elemental feature descriptors derivable from tabulated information on the unit cell and the atomic properties of the components of a target compound on a limited dataset of 70 NASICON-examples, we have designed a logistic regression-based model capable of distinguishing between poor and good superionic conductors with a validation accuracy of over 84%. Moreover, we demonstrate how such a system is capable of cross-domain classification on lithium-based examples with the same accuracy, despite being introduced to zero lithium-based compounds during training. Through a systematic permutation-based evaluation process, we reduced the number of considered features from 47 to 7, reduction of over 83%, while simultaneously improving model performance. The contributions of different electronic and structural features to overall ionic conductivity is also discussed, and contrasted with accepted theories in literature. Our results demonstrate the utility of such a facile tool in providing opportunities for initial screening of potential candidates as solid-state electrolytes through the use of existing data examples and simple tabulated or calculated features, reducing the time-to-market of such materials by helping to focus efforts on promising candidates. Given enough data utilizing suitable descriptors, high accurate cross-domain classifiers could be created for experimentalists, improving laboratory and computational efficiency.

Transient Nonlinear Response of Dynamically Decoupled Ionic Conductors.

The present study demonstrates that large electric fields progressively enhance the conductivity of ionic systems up to timescales corresponding to those on which their structural rearrangements take place. Yet, in many ionic materials, some regarded as candidates for electrical energy storage applications, the structural relaxation process can be tremendously slower than (or highly decoupled from) the charge fluctuations. Consequently, nonlinear dielectric spectroscopy may be employed to access rheological information in dynamically decoupled ionic conductors, whereas the combination of large electric power density and good mechanical stability, both technologically highly desired, imposes specific experimental constraints to reliably determine the steady-state conductivity of such materials.

Statistical modeling of thermal conductivity for cement-based foam

This paper presents the formulation of two multivariate regression models for predicting the thermal conductivity of cement-based foam through statistical analysis. The cement-based foam was produced by replacing Portland cement with fly ash, silica fume, and metakaolin, up to 20% by mass, for densities that ranged from 400 to 800 kg/m3. In the first model, the porosity, moisture content, and thermal conductivity of the solid cement paste were considered as independent variables. Results reveal the presence of multicollinearity among these independent variables. In the second formulation, the porosity, mass ratio of the pozzolanic admixture in the binder, and maturity (in days) were taken as independent variables. This model was found statistically significant and was validated against a range of independently determined experimental values for thermal conductivity of such materials.

CTAB-assisted growth of self-supported Zn2GeO4 nanosheet network on a conductive foam as a binder-free electrode for long-life lithium-ion batteries.

The Ge-based compounds show great potential as replacements for traditional graphite anode in lithium-ion batteries (LIBs). However, large volume changes and low conductivity of such materials result in a poor electrochemical cycling and rate performance. Herein, we fabricate a self-supported and three-dimensional (3D) sponge-like structure of interlinked Zn2GeO4 ultrathin nanosheets anchored vertically on a nickel foam (ZGO NSs@NF) via a simple hydrothermal process assisted by cetyltrimethyl ammonium bromide (CTAB). Such robust self-supported hybrid structures greatly improve the structural tolerance of the active materials and accommodate the volume variation that occurs during repeated electrochemical cycling. As expected, the self-supported ZGO NSs@NF composites demonstrate an excellent lithium storage with a high discharge capacity, a long cycling life, and a good rate capability when used as binder-free anodes for LIBs. A high reversible discharge capacity of 794 mA h g-1 is maintained after 500 cycles at 200 mA g-1, corresponding to 81% capacity retention of the second cycle. Further evaluation at a higher current density (2 A g-1) also delivers a reversible discharge capacity (537 mA h g-1) for this binder-free anode. This novel 3D structure of the self-supported ultrathin nanosheets on a conductive substrate, with its volume buffer effect and good interfacial contacts, can stimulate the progress of other energy-efficient technologies.

Elastomer Heat-Shielding Materials Containing Aluminosilicate Microspheres

The influence of hollow aluminosilicate microspheres on the efficiency of elastomeric thermoprotective materials based on ethylene—propylene rubber is considered. The introduction of hollow aluminosilicate microspheres, even in small quantities, decreases the density and heat conductivity of such materials, with no loss of physical and mechanical properties.