scholarly journals Theoretical Description of Carbon Felt Electrical Properties Affected by Compression

2019 ◽  
Vol 9 (19) ◽  
pp. 4030 ◽  
Author(s):  
Moshe Averbukh ◽  
Svetlana Lugovskoy
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Close Contact ◽  
Internal Surface ◽  
Theoretical Models ◽  
Theoretical Description ◽  
Carbon Felt ◽  
Long Carbon Fibers ◽  
Carbon Filaments ◽  
The Impact

Electro-conductive carbon felt (CF) material is composed by bonding together different lengths of carbon filaments resulting in a porous structure with a significant internal surface that facilitates enhanced electrochemical reactions. Owing to its excellent electrical properties, CF is found in numerous electrochemical applications, such as electrodes in redox flow batteries, fuel cells, and electrochemical desalination apparatus. CF electro-conductivity mostly arises from the close contact between the surface of two electrodes and the long carbon fibers located between them. Electrical conductivity can be improved by a moderate pressing of the CF between conducting electrodes. There exist large amounts of experimental data regarding CF electro-conductivity. However, there is a lack of analytical theoretical models explaining the CF electrical characteristics and the effects of compression. Moreover, CF electrodes in electrochemical cells are immersed in different electrolytes that affect the interconnections of fibers and their contacts with electrodes, which in turn influence conductivity. In this paper, we investigated both the role of CF compression, as well as the impact of electrolyte characteristics on electro-conductivity. The article presents results of measurements, mathematical analysis of CF electrical properties, and a theoretical analytical explanation of the CF electrical conductivity which was done by a stochastic description of carbon filaments disposition inside a CF frame.

scholarly journals Transport Properties of Natural and Artificial Smart Fabrics Impregnated by Graphite Nanomaterial Stacks

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1018
Author(s):  
Carola Esposito Corcione ◽  
Francesca Ferrari ◽  
Raffaella Striani ◽  
Antonio Greco
Keyword(s):  
Electrical Conductivity ◽  
Transport Properties ◽  
Low Cost ◽  
Empirical Relationship ◽  
Theoretical Models ◽  
Expandable Graphite ◽  
Easy Method ◽  
Textile Materials ◽  
Fabric Materials ◽  
The Impact

In this work, we studied the transport properties (thermal and electrical conductivity) of smart fabric materials treated with graphite nanomaterial stacks–acetone suspensions. An innovative and easy method to produce graphite nanomaterial stacks–acetone-based formulations, starting from a low-cost expandable graphite, is proposed. An original, economical, fast, and easy method to increase the thermal and electrical conductivity of textile materials was also employed for the first time. The proposed method allows the impregnation of smart fabric materials, avoiding pre-coating of the fibers, thus reducing costs and processing time, while obtaining a great increase in the transport properties. Two kinds of textiles, cotton and Lycra®, were selected as they represent the most used natural and artificial fabrics, respectively. The impact of the dimensions of the produced graphite nanomaterial stacks–acetone-based suspensions on both the uniformity of the treatment and the transport properties of the selected textile materials was accurately evaluated using several experimental techniques. An empirical relationship between the two transport properties was also successfully identified. Finally, several theoretical models were applied to predict the transport properties of the developed smart fabric materials, evidencing a good agreement with the experimental data.

scholarly journals A mechanistic model for electrical conduction in soil–root continuum: a virtual rhizotron study

2018 ◽  
Author(s):  
Sathyanarayan Rao ◽  
Félicien Meunier ◽  
Solomon Ehosioke ◽  
Nolwenn Lesparre ◽  
Andreas Kemna ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Root Growth ◽  
Water Content ◽  
Soil Water ◽  
Water Uptake ◽  
Numerical Study ◽  
Root Segments ◽  
Bulk Electrical Conductivity ◽  
The Impact

Abstract. Electrical Resistivity Tomography (ERT) has become an important tool to study soil water fluxes in cropped field. ERT results translates to water content via empirical pedophysical relations that take soil physical properties into account, usually ignoring the impact of roots. Studies shows high root dense soils behaves quite differently than less root dense soils in terms of bulk electrical conductivity. Yet, we do not completely understand the impact of root segments on the ERT measurements. In this numerical study, we coupled an electrical model with a plant-soil water flow model to investigate the impact of plant root growth and water uptake on the ERT virtual experiment. The electrical properties of roots were explicitly accounted in the finite element mesh and we obtained the electrical conductivities of root segments by conducting specific experiments on real maize plants. The contrast between electrical conductivity of roots and soil depends on factors such as root density, irrigation, root age, and root water uptake pattern. Root growth and water uptake processes thus affect this contrast together with the soil electrical properties. Model results indicate a non-negligible anisotropy in bulk electrical conductivity induced by root processes. We see a greater anisotropy in a sandy medium when compared to a loamy medium. We find that the water uptake process dominates the bulk electrical properties. The Gauss-Newton type ERT inversion of virtual rhizotron data demonstrate that, when root-soil electrical conductivity contrasts are high, it can lead to error in water content estimates since the electrical conductivity is partly due to root. Thus, incorporating the impact of root in the pedophysical relations is very important to interpret ERT results directly as water content.

scholarly journals Long-term heat treatment of collector bars for aluminium electrolysis: impact on microstructure and electrical properties

2020 ◽  
Vol 2 (9) ◽  
Author(s):  
Jonas Hankel ◽  
Sandra Kernebeck ◽  
Friederike Deuerler ◽  
Sebastian Weber
Keyword(s):  
Electrical Conductivity ◽  
Energy Efficiency ◽  
Cast Iron ◽  
Electrical Properties ◽  
Phase Transformations ◽  
Diffusion Processes ◽  
Electrolysis Cell ◽  
Service Temperature ◽  
Aluminium Electrolysis ◽  
The Impact

Abstract In order to identify possible optimizations regarding the electrical energy efficiency of an aluminium electrolysis cell, the impact of service temperature on microstructure and electrical properties of the cell cathode was investigated. The investigations include experiments regarding the chemical composition, especially the content of carbon, the electrical conductivity and the microstructure at selected positions. Thermodynamic calculations were used to estimate local service temperatures and explain phase transformations and formations. It was found that due to the increased service temperature diffusion processes of carbon took place to a particular extent between cast iron and collector bar. As a result, the carbon content in the collector bar changed from 0.06 to 1.05–1.4 wt%, while in the cast iron a reduction from 3.47 to < 1.50 wt% took place. These processes led to isothermal phase transformations and formations, that changed the matrix of the collector bar from austenitic with low content of ferrite to an austenitic matrix accompanied by precipitation of secondary, predominantly allotriomorphic cementite at service temperature. It was then shown that this has a negative effect on collector bar and decreases the electrical conductivity by up to 26 %. It was also discovered that graphite spheroidization within the grey cast iron has a positive effect on its electrical conductivity, which has increased by 52 %. The results provide the basis to gain an understanding of the carbon diffusion related processes within the cathode of an electrolysis cell and reveal further potential to increase the energy efficiency of primary aluminium production.

Effects of Functionalization MWCNTs on the Mechanical and Electrical Properties of nylon-6 Composites

2013 ◽  
Vol 750-752 ◽  
pp. 127-131 ◽  
Author(s):  
Xiang Dong Zhu ◽  
Qing Jie Jiao ◽  
Chong Guang Zang ◽  
Xian Peng Cao
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Volume Ratio ◽  
Nylon 6 ◽  
Coupling Process ◽  
Mechanical And Electrical Properties ◽  
Multi Walled Carbon Nanotube ◽  
The Matrix ◽  
The Impact ◽  
Coupling Treatment

Chemically coupling functionalization multi-walled carbon nanotube (MWCNTs)/nylon-6 (PA6) composites were prepared. The nanotubes were first treated by a volume ratio of 3:1 mixture of concentrated H2SO4/HNO3, and then the γ-aminopropyl-triethoxysilane (KH-550) was carried onto the surface of MWCNTs. Effect of MWCNTs coupling treatment on the mechanical and electrical properties of the MWCNTs/PA6 composites were investigated. The impact strength, tensile strength and modulus of p-MWCNTs (coupling process)/PA6 composites increase by 115.9%, 27.2% and 167.7%, respectively, compared with those of the pure nylon-6 resin. A significant increase of the electrical conductivity of the p-MWCNTs/PA6 composites with respect to the original-MWCNTs and a-MWCNTs/PA6 composites due to the increased compatibility with the matrix due to the formation of an inter face with stronger interconnections.

scholarly journals Influence of reduction conditions of NiO on its mechanical and electrical properties

2016 ◽  
Vol 6 (1) ◽  
pp. 113 ◽  
Author(s):  
Yehor Brodnikovskyi ◽  
Bogdan Vasyliv ◽  
Viktoriya Podhurska ◽  
Mariusz Andrzejczuk ◽  
Nikkia McDonald ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Structural Changes ◽  
Reduction Stage ◽  
Mechanical And Electrical Properties ◽  
Before And After ◽  
Mechanical Durability ◽  
And Performance ◽  
The Impact ◽  
Volume Decrease

<p class="PaperAbstract"><span lang="EN-GB">Yttria stabilized zirconia with a nickel catalyst (Ni-YSZ) is the most developed, widely used cermet anode for manufacturing Solid Oxide Fuel Cells (SOFCs). Its electro-catalytic properties, mechanical durability and performance stability in hydrogen-rich environ­ments makes it the state of the art fuel electrode for SOFCs. During the reduction stage in initial SOFC operation, the virgin anode material, a NiO-YSZ mixture, is reduced to Ni-YSZ. The volume decrease associated with the change from NiO-YSZ to Ni-YSZ creates voids and causes structural changes, which can influence the physical properties of the anode. In this work, the structural, mechanical and electrical properties of NiO samples before and after reduction in pure H<sub>2</sub> and a mixture of 5 vol. % H<sub>2</sub>-Ar were studied. The NiO to Ni phase transformations that occur in the anode under reducing and Reduction-Oxidation (RedOx) cycling conditions and the impact on cell microstruc­ture, strength and electrical conductivity have been examined. Results show that the RedOx treatment of the NiO samples influence on their properties controversially, due to structural transfor­mation (formation of large amount of fine pores) of the reduced Ni. It strengthened the treated samples yielding the highest mechanical strength values of 25.7 MPa, but from another side it is resulting in lowest electrical conductivity value of 1.9×10<sup>5</sup> S m<sup>-1</sup> among all reduced samples. The results of this investigation shows that reduction conditions of NiO is a powerful tool for influence on properties of the anode substrate.</span></p>

The Effects of Employment Protection legislationon Personnel Policies: A Review of Theoretical Modelsand Empirical results

2014 ◽  
pp. 126-140
Author(s):  
O. Mironenko
Keyword(s):  
Personnel Selection ◽  
Selection Criteria ◽  
Theoretical Models ◽  
Employment Protection ◽  
Empirical Results ◽  
Protection Legislation ◽  
Labour Contracts ◽  
Hiring And Firing ◽  
The Impact ◽  
Personnel Policies

Employers incur costs while fulfilling the requirements of employment protection legislation. The article contains a review of the core theoretical models and empirical results concerning the impact of these costs on firms’ practices in hiring, firing, training and remuneration. Overall, if wages are flexible or enforcement is weak, employment protection does not significantly influence employers’ behavior. Otherwise, stringent employment protection results in the reduction of hiring and firing rates, changes in personnel selection criteria, types of labour contracts and dismissal procedures, and, in some cases, it may lead to the growth of wages and firms’ investments to human capital.

Effect of Gamma Radiation on Structural, Optical and Electrical Properties of nanostructured CdHgTe Thin Films

2018 ◽  
Vol 1 (1) ◽  
pp. 26-31 ◽  
Author(s):  
B Babu ◽  
K Mohanraj ◽  
S Chandrasekar ◽  
N Senthil Kumar ◽  
B Mohanbabu
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Electrical Properties ◽  
Gamma Radiation ◽  
Glass Substrate ◽  
Gamma Ray ◽  
Optical And Electrical Properties ◽  
Deposition Technique ◽  
Polycrystalline Structure ◽  
Dc Electrical Conductivity

CdHgTe thin films were grown onto glass substrate via the Chemical bath deposition technique. XRD results indicate that a CdHgTe formed with a cubic polycrystalline structure. The crystallinity of CdHgTe thin films is gradually deteriorate with increasing the gamma irradiation. EDS spectrums confirms the presence of Cd, Hg and Te elements. DC electrical conductivity results depicted the conductivity of CdHgTe increase with increasing a gamma ray dosage

Effect of the structure of cellulose acetate membranes on their permeability, electrical conductivity and rejection

1990 ◽  
Vol 55 (12) ◽  
pp. 2933-2939 ◽  
Author(s):  
Hans-Hartmut Schwarz ◽  
Vlastimil Kůdela ◽  
Klaus Richau
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Cellulose Acetate ◽  
Reverse Osmosis ◽  
Water Flux ◽  
Cellulose Acetate Membrane ◽  
Structure Parameters ◽  
Dc Electrical Conductivity ◽  
Cellulose Acetate Membranes

Ultrafiltration cellulose acetate membrane can be transformed by annealing into reverse osmosis membranes (RO type). Annealing brings about changes in structural properties of the membranes, accompanied by changes in their permeability behaviour and electrical properties. Correlations between structure parameters and electrochemical properties are shown for the temperature range 20-90 °C. Relations have been derived which explain the role played by the dc electrical conductivity in the characterization of rejection ability of the membranes in the reverse osmosis, i.e. rRO = (1 + exp (A-B))-1, where exp A and exp B are statistically significant correlation functions of electrical conductivity and salt permeation, or of electrical conductivity and water flux through the membrane, respectively.

scholarly journals Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

2021 ◽  
Author(s):  
Istebreq A. Saeedi ◽  
Sunny Chaudhary ◽  
Thomas Andritsch ◽  
Alun S. Vaughan
Keyword(s):  
Glass Transition ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Epoxy Resins ◽  
Functional Network ◽  
Cross Linking ◽  
Network Modifier ◽  
Epoxy Resin System ◽  
The Cross ◽  
The Impact

AbstractReactive molecular additives have often been employed to tailor the mechanical properties of epoxy resins. In addition, several studies have reported improved electrical properties in such systems, where the network architecture and included function groups have been modified through the use of so-called functional network modifier (FNM) molecules. The study reported here set out to investigate the effect of a glycidyl polyhedral oligomeric silsesquioxane (GPOSS) FNM on the cross-linking reactions, glass transition, breakdown strength and dielectric properties of an amine-cured epoxy resin system. Since many previous studies have considered POSS to act as an inorganic filler, a key aim was to consider the impact of GPOSS addition on the stoichiometry of curing. Fourier transform infrared spectroscopy revealed significant changes in the cross-linking reactions that occur if appropriate stoichiometric compensation is not made for the additional epoxide groups present on the GPOSS. These changes, in concert with the direct effect of the GPOSS itself, influence the glass transition temperature, dielectric breakdown behaviour and dielectric response of the system. Specifically, the work shows that the inclusion of GPOSS can result in beneficial changes in electrical properties, but that these gains are easily lost if consequential changes in the matrix polymer are not appropriately counteracted. Nevertheless, if the system is appropriately optimized, materials with pronounced improvements in technologically important characteristics can be designed.

scholarly journals Effect of SWCNT-Tuball Paper on the Lightning Strike Protection of CFRPs and Their Selected Mechanical Properties

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3140
Author(s):  
Kamil Dydek ◽  
Anna Boczkowska ◽  
Rafał Kozera ◽  
Paweł Durałek ◽  
Łukasz Sarniak ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Copper Foil ◽  
Impact Resistance ◽  
Mechanical Analysis ◽  
Lightning Strike ◽  
Single Wall Carbon Nanotubes ◽  
Carbon Fibre Reinforced Polymer ◽  
The Impact

The main aim of this work was the investigation of the possibility of replacing the heavy metallic meshes applied onto the composite structure in airplanes for lightning strike protection with a thin film of Tuball single-wall carbon nanotubes in the form of ultra-light, conductive paper. The Tuball paper studied contained 75 wt% or 90 wt% of carbon nanotubes and was applied on the top of carbon fibre reinforced polymer before fabrication of flat panels. First, the electrical conductivity, impact resistance and thermo-mechanical properties of modified laminates were measured and compared with the reference values. Then, flat panels with selected Tuball paper, expanded copper foil and reference panels were fabricated for lightning strike tests. The effectiveness of lightning strike protection was evaluated by using the ultrasonic phased-array technique. It was found that the introduction of Tuball paper on the laminates surface improved both the surface and the volume electrical conductivity by 8800% and 300%, respectively. The impact resistance was tested in two directions, perpendicular and parallel to the carbon fibres, and the values increased by 9.8% and 44%, respectively. The dynamic thermo-mechanical analysis showed higher stiffness and a slight increase in glass transition temperature of the modified laminates. Ultrasonic investigation after lightning strike tests showed that the effectiveness of Tuball paper is comparable to expanded copper foil.

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