Search results for: co-existence of high electrical conductivity and diamagnetism

Authors: Sutar Rani Ananda, M. V. Murugendrappa

Abstract:

To investigate electrical properties of conducting polypyrrole (PPy) and cobalt aluminum oxide (CAO) nanocomposites, impedance analyzer in frequency range of 100 Hz to 5 MHz is used. In this work, PPy/CAO nanocomposites were synthesized by chemical oxidation polymerization method in different weight percent of CAO in PPy. The dielectric properties and AC conductivity studies were carried out for different nanocomposites in temperature range of room temperature to 180 °C. With the increase in frequency, the dielectric constant for all the nanocomposites was observed to decrease. AC conductivity of PPy was improved by addition of CAO nanopowder.

Keywords: polypyrrole, dielectric constant, dielectric loss, AC conductivity

Procedia PDF Downloads 256

Authors: Rabah Bensaha, Badreeddine Toubal

Abstract:

Un-doped TiO2, Co single doped TiO2 and (Cu-Co) co-doped TiO2 thin films have been growth on silicon substrates by the sol-gel dip coating technique. We mainly investigated both effects of the dopants and annealing temperature on the structural, optical and electrical properties of TiO2 films using X-ray diffraction (XRD), Raman and FTIR spectroscopy, Atomic force microscopy (AFM), Scanning electron microscopy (SEM), UV–Vis spectroscopy. The chemical compositions of Co-doped and (Cu-Co) co-doped TiO2 films were confirmed by XRD, Raman and FTIR studies. The average grain sizes of CoTiO3-TiO2 nanocomposites were increased with annealing temperature. AFM and SEM reveal a completely the various nanostructures of CoTiO3-TiO2 nanocomposites thin films. The films exhibit a high optical reflectance with a large band gap. The highest electrical conductivity was obtained for the (Cu-Co) co-doped TiO2 films. The polyhedral surface morphology might possibly improve the surface contact between particle sizes and then contribute to better electron mobility as well as conductivity. The obtained results suggest that the prepared TiO2 films can be used for optoelectronic applications.

Keywords: sol-gel, TiO2 thin films, CoTiO3-TiO2 nanocomposites films, Electrical conductivity

Procedia PDF Downloads 418

Authors: Wiqar Hussain Shah

Abstract:

The electrical and thermal properties of the doped Tellurium Telluride (Tl10Te6) chalcogenide nano-particles are mainly characterized by a competition between metallic (hole doped concentration) and semi-conducting state. We have studied the effects of Sn doping on the electrical and thermoelectric properties of Tl10-xSnxTe6 (1.00 ≤x≤ 2.00), nano-particles, prepared by solid state reactions in sealed silica tubes and ball milling method. Structurally, all these compounds were found to be phase pure as confirmed by the x-rays diffractometery (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis. Additionally crystal structure data were used to model the data and support the findings. The particles size was calculated from the XRD data by Scherrer’s formula. The EDS was used for an elemental analysis of the sample and declares the percentage of elements present in the system. The thermo-power or Seebeck co-efficient (S) was measured for all these compounds which show that S increases with increasing temperature from 295 to 550 K. The Seebeck coefficient is positive for the whole temperature range, showing p-type semiconductor characteristics. The electrical conductivity was investigated by four probe resistivity techniques revealed that the electrical conductivity decreases with increasing temperature, and also simultaneously with increasing Sn concentration. While for Seebeck coefficient the trend is opposite which is increases with increasing temperature. These increasing behavior of Seebeck coefficient leads to high power factor which are increases with increasing temperature and Sn concentration except For Tl8Sn2Te6 because of lowest electrical conductivity but its power factor increases well with increasing temperature.

Keywords: Sn doping in Tellurium Telluride nano-materials, electron holes competition, Seebeck co-efficient, effects of Sn doping on Electrical conductivity, effects on Power factor

Procedia PDF Downloads 22

Authors: Saeid Mehvari, Yolanda Sanchez-Vicente, Sergio González Sánchez, Khalid Lafdi

Abstract:

Abstract- Materials with a combination of transparency, electrical conductivity, and flexibility are required in the ‎growing electronic sector. In this research, electrically conductive and flexible films have been prepared. These ‎composite films consist of dispersing micro-copper particles into polyurethane (PU) matrix. Two sets of samples were ‎made using both spin coating technique (sample thickness lower than 30 μm) and materials casting (sample thickness ‎lower than 100 μm). Copper concentrations in the PU matrix varied from 0.5 to 20% by volume. The dispersion of ‎micro-copper particles into polyurethane (PU) matrix were characterised using optical microscope and scanning electron ‎microscope. The electrical conductivity measurement was carried out using home-made multimeter set up under ‎pressures from 1 to 20 kPa through thickness and in plane direction. It seems that samples made by casting were not ‎conductive. However, the sample made by spin coating shows through-thickness conductivity when they are under ‎pressure. The results showed that spin-coated films with higher concentration of 2 vol. % of copper displayed a ‎significant increase in the conductivity value, known as percolation threshold. The maximum conductivity of 7.2 × 10-1 ‎S∙m-1 was reached at concentrations of filler with 20 vol. % at 20kPa. A semi-empirical model with adjustable ‎coefficients was used to fit and predict the electrical behaviour of composites. For the first time, the finite element ‎method based on the representative volume element (FE-RVE) was successfully used to predict their electrical ‎behaviour under applied pressures. ‎

Keywords: electrical conductivity, micro copper, numerical simulation, percolation threshold, polyurethane, RVE model

Procedia PDF Downloads 161

Authors: Jian Yang, Atsushi Yagi

Abstract:

Tree-grass coexistence system is of great importance for forest ecology. Mathematical models are being proposed to study the dynamics of tree-grass coexistence and the stability of the systems. However, few of the models concentrates on spatial dynamics of the tree-grass coexistence. In this study, we modified an age-structured continuous-space population model for forests, obtaining an age-structured continuous-space population model for the tree-grass competition model. In the model, for thermal competitions, adult trees can out-compete grass, and grass can out-compete seedlings. We mathematically studied the model to make sure tree-grass coexistence solutions exist. Numerical experiments demonstrated that a fraction of area that trees or grass occupies can affect whether the coexistence is stable or not. We also tried regulating the mortality of adult trees with other parameters and the fraction of area trees and grass occupies were fixed; results show that the mortality of adult trees is also a factor affecting the stability of the tree-grass coexistence in this model.

Keywords: population-structured models, stabilities of ecosystems, thermal competitions, tree-grass coexistence systems

Procedia PDF Downloads 123

Authors: Angelos Evangelou, Katerina Loizou, Loukas Koutsokeras, Orestes Marangos, Giorgos Constantinides, Stylianos Yiatros, Katerina Sofocleous, Vasileios Drakonakis

Abstract:

Owing to their outstanding strength to weight properties, carbon fiber reinforced polymer (CFRPs) composites have attracted significant attention finding use in various fields (sports, automotive, transportation, etc.). The current momentum indicates that there is an increasing demand for their employment in high value bespoke applications such as avionics and electronic casings, damage sensing structures, EMI (electromagnetic interference) structures that dictate the use of materials with increased electrical conductivity both in-plane and through the thickness. Several efforts by research groups have focused on enhancing the through-thickness electrical conductivity of FRPs, in an attempt to combine the intrinsically high relative strengths exhibited with improved z-axis electrical response as well. However, only a limited number of studies deal with printing of nano-enhanced polymer inks to produce a pattern on dry fabric level that could be used to fabricate CFRPs with improved through thickness electrical conductivity. The present study investigates the employment of screen-printing process on technical dry fabrics using nano-reinforced polymer-based inks to achieve the required through thickness conductivity, opening new pathways for the application of fiber reinforced composites in niche products. Commercially available inks and in-house prepared inks reinforced with electrically conductive nanoparticles are employed, printed in different patterns. The aim of the present study is to investigate both the effect of the nanoparticle concentration as well as the droplet patterns (diameter, inter-droplet distance and coverage) to optimize printing for the desired level of conductivity enhancement in the lamina level. The electrical conductivity is measured initially at ink level to pinpoint the optimum concentrations to be employed using a “four-probe” configuration. Upon printing of the different patterns, the coverage of the dry fabric area is assessed along with the permeability of the resulting dry fabrics, in alignment with the fabrication of CFRPs that requires adequate wetting by the epoxy matrix. Results demonstrated increased electrical conductivities of the printed droplets, with increase of the conductivity from the benchmark value of 0.1 S/M to between 8 and 10 S/m. Printability of dense and dispersed patterns has exhibited promising results in terms of increasing the z-axis conductivity without inhibiting the penetration of the epoxy matrix at the processing stage of fiber reinforced composites. The high value and niche prospect of the resulting applications that can stem from CFRPs with increased through thickness electrical conductivities highlights the potential of the presented endeavor, signifying screen printing as the process to to nano-enable z-axis electrical conductivity in composite laminas. This work was co-funded by the European Regional Development Fund and the Republic of Cyprus through the Research and Innovation Foundation (Project: ENTERPRISES/0618/0013).

Keywords: CFRPs, conductivity, nano-reinforcement, screen-printing

Procedia PDF Downloads 128

Authors: Yasin Polat, Yılmaz Dağdemir, Mehmet Arı

Abstract:

Samarium (III) oxide and Ytterbium (III) oxide doped Bismuth trioxide solid solutions, the nano ceramic (Bi2O3)1-x-y(Sm2O3)x(Yb2O3)y ternary system were obtained with x=5, 20 mol %, and y=5, 20 mol % dopant concentrations have been synthesized in air atmosphere with solid state reaction. Temperature dependent electrical conductivity of the samples have been investigated by 4-point probe technique by heating and cooling process. Doped-Bi2O3 materials of solid electrolyte systems are good oxygen anions O2-conductors which have collected much attention as potential solid ceramic electrolytes for solid oxide fuel cells (SOFCs) because of their relatively high oxygen ionic conductivity at lower temperatures.(Bi2O3)-based electrolytes have also wide other technological applications in devices with high economical interest such as oxygen sensors, ceramic membranes for oxygen separation, oxygen pumps, catalyzing of some heterogeneous reactions, partial oxidation of the hydrocarbons, and additive material in paints. In recent years, many experimental researches have mostly focused on improving of the Bi-based electrolytes which have high oxide ionic conductivity at low temperatures and better performance as alternatives to traditional stabilized zirconia has taken place. Generally, these systems are much better solid electrolytes than well-known stabilized zirconia, because some of the bismuth trioxide phases exhibit higher ion conductivity than other oxide ionic conductors. Crystal structure of the Nano ceramic (Bi2O3)1-x-y(Sm2O3)x(Yb2O3)y has been determined by X-Ray powder diffractions (XRD) measurements before and after electrical conductivity measurements of the samples. Surface and grain structure properties of the samples were determined by SEM analysis. The samples which synthesized in this study can be used in industrial applications such as electrolytes of the solid oxide fuel cells (SOFC).

Keywords: 4-point probe technique, bismuth trioxide, solid state reaction, solid oxide fuel cell

Procedia PDF Downloads 260

Authors: Siham Mezher Yousif, Intisar Yahiya Mohammed, Salma Nagem Mouhy

Abstract:

Low Density Polyethylene is a thermoplastic resin extracted from petroleum based, whereas the wax is an oily organic component that is contains of alkanes, ester, polyester, and hydroxyl ester. The purpose of this research is to find out the optimum conditions of the wax produced by inducing with LDPE. The experiments were carried out by mixing different percentages of wax and LDPE to produce different polymer/wax compositions, in which lower values of the penetration, thickness, and electrical conductivity are obtained with increasing of mixing ratio of LDPE/wax which showed results of 19 mm penetration, 692 micron thickness and 5.9 mA electrical conductivity for 90 wt % of LDPE/wax) maximum mixing ratio (. It’s found that the optimum results regarding penetration, enamel thickness, and electrical conductivity “according to the enamel hardness, insulation properties, and economic aspects” are 20 mm, 276 micron, and 6.2 mA respectively.

Keywords: paraffin wax, low density polyethylene, blending, mixing ratio, bleaching

Procedia PDF Downloads 82

Authors: M. Z. Shazana, R. Rosazley, M. A. Izzati, A. W. Fareezal, I. Rushdan, A. B. Suriani, S. Zakaria

Abstract:

There is an increasing interest in the development of flexible energy storage for application of Carbon Nanotubes and nanofibrillated cellulose (NFC). In this study, nanocomposite is consisting of Carbon Nanotube (CNT) mixed with suspension of nanofibrillated cellulose (NFC) from Oil Palm Empty Fruit Bunch (OPEFB). The use of Carbon Nanotube (CNT) as additive nanocomposite was improved the conductivity and mechanical properties of nanocomposite from nanofibrillated cellulose (NFC). The nanocomposite were characterized for electrical conductivity and mechanical properties in uniaxial tension, which were tensile to measure the bond of fibers in nanocomposite. The processing route is environmental friendly which leads to well-mixed structures and good results as well.

Keywords: carbon nanotube (CNT), nanofibrillated cellulose (NFC), mechanical properties, electrical conductivity

Procedia PDF Downloads 301

Authors: Divyanka Sontakke, Arpit Thakre, D. K Shinde, Sujata Parmeshwaran

Abstract:

Electrospinning is the most widely utilized method to create nanofibers because of the direct setup, the capacity to mass-deliver consistent nanofibers from different polymers, and the ability to produce ultrathin fibers with controllable diameters. Smooth and much arranged ultrafine Polyacrylonitrile (PAN) nanofibers with diameters going from submicron to nanometer were delivered utilizing Electrospinning technique. PAN powder was used as a precursor to prepare the solution utilized as a part of this process. At the point when the electrostatic repulsion contradicted surface tension, a charged stream of polymer solution was shot out from the head of the spinneret and along these lines ultrathin nonwoven fibers were created. The effect of electrospinning parameter such as applied voltage, feed rate, concentration of polymer solution and tip to collector distance on the morphology of electrospun PAN nanofibers were investigated. The nanofibers were heat treated for carbonization to examine the changes in properties and composition to make for electrical application. Scanning Electron Microscopy (SEM) was performed before and after carbonization to study electrical conductivity and morphological characterization. The SEM images have shown the uniform fiber diameter and no beads formation. The average diameter of the PAN fiber observed 365nm and 280nm for flat plat and rotating drum collector respectively. The four probe strategy was utilized to inspect the electrical conductivity of the nanofibers and the electrical conductivity is significantly improved with increase in oxidation temperature exposed.

Keywords: electrospinning, polyacrylonitrile carbon nanofibres, heat treatment, electrical conductivity

Procedia PDF Downloads 117

Authors: Jae-Ho Kim, Ryosuke Yokochi, Miho Fuzihashi, Susumu Yonezawa

Abstract:

The use of silver nanoparticles in conductive inks and their printing by injecting technology has been known for years. However, the very high cost of silver limits wide industrial applications. Since copper is much cheaper but possesses a very high conductivity (only 6% less than that of Ag), Cu nanoparticles can be considered as a replacement for silver nanoparticles. However, a major problem in utilizing their copper nanoparticles is their inherent tendency to oxidize in ambient conditions. In conductive printing applications, the presence of copper oxide on the surface of nanoparticles has two negative consequences: it increases the required sintering temperature and reduces the electrical conductivity. Only a limited number of reports have attempted to address the oxidation problem, which in general is based on minimizing the exposure of the copper nanoparticles to oxygen by a protective layer composed of a second material at the surface of the particles. To form the protective layer on the surface, carbon-based materials, surfactants, metals, and so on. In this study, we tried to modify the oxide on Cu particles using fluorine gas. And the creation effects of oxyfluorides or fluorides on the oxidation resistance of Cu particles were investigated. Compared with untreated sample (a), the fluorinated samples can restrain the weight increase even at 200℃ from the TG-DTA results. It might be considered that the substantial oxyfluorides on the surface play a role in protecting metal oxidation.

Keywords: copper metal, electrical conductivity, oxidation resistance, surface fluorination

Procedia PDF Downloads 80

Authors: H. Ben Khlifa, W. Cheikhrouhou, R. M'nassri

Abstract:

The Orthorhombic Pr0.8Na0.2MnO3 ceramic was prepared in Polycrystalline form by a Pechini sol–gel method and its structural, magnetic, electrical, and dielectric properties were investigated experimentally. A structural study confirms that the sample is a single phase. Magnetic measurements show that the sample is a charge ordered Manganite. The sample undergoes two successive magnetic phase transitions with the variation of temperature: a charge ordering transition occurred at TCO = 212 K followed by a Paramagnetic (PM) to ferromagnetic (FM) transition around TC = 115 K. From an electrical point of view, a saturation region was marked in the conductivity as a function of Temperature s(T) curves at a specific temperature. The dc-conductivity (sdc) reaches a maximum value at 240 K. The obtained results are in good agreement with the temperature dependence of the average normalized change (ANC). We found that the conduction mechanism was governed by small polaron hopping (SPH) in the high-temperature region and by variable range hopping (VRH) in the low-temperature region. Complex impedance analysis indicates the presence of a non-Debye relaxation phenomenon in the system. Also, the compound was modeled by an electrical equivalent circuit. Then, the contribution of the grain boundary in the transport properties was confirmed.

Keywords: manganites, preparation methods, magnetization, magnetocaloric effect, electrical and dielectric

Procedia PDF Downloads 132

Authors: Chompunut Jantarasorn, Chutima Prommak

Abstract:

This paper presents an intensive measurement studying of the network performance analysis when IEEE 802.11g Wireless Local Area Networks (WLAN) coexisting with IEEE 802.15.4 Wireless Personal Area Network (WPAN). The measurement results show that the coexistence between both networks could increase the Frame Error Rate (FER) of the IEEE 802.15.4 networks up to 60% and it could decrease the throughputs of the IEEE 802.11g networks up to 55%.

Keywords: wireless performance analysis, coexistence analysis, IEEE 802.11g, IEEE 802.15.4

Procedia PDF Downloads 518

Authors: P. Rutkowski, G. Górny, L. Stobierski, D. Zientara, W. Piekarczyk, K. Tran

Abstract:

The polycrystalline dense alumina shows thermal conductivity about 30 W/mK and very high electrical resistivity. These last two properties can be modified by introducing commercial relatively cheap graphene nanoparticles which, as two-dimensional flakes show very high thermal and electrical properties. The aim of this work is to show that it is possible to manufacture the anisotropic alumina-graphene material with directed multilayer graphene particles. Such materials can show the anisotropic properties mentioned before.

Keywords: alumina, composite, hot-pressed, graphene, properties

Procedia PDF Downloads 239

Authors: Evgen Prokhorov, Gabriel Luna-Barcenas

Abstract:

The polysaccharide chitosan (CS) is an attractive biopolymer for the stabilization of several nanoparticles in acidic aqueous media. This is due in part to the presence of abundant primary NH2 and OH groups which may lead to steric or chemical stabilization. Applications of most CS nanocomposites are based upon the interaction of high surface area nanoparticles (NPs) with different substance. Therefore, agglomeration of NPs leads to decreasing effective surface area such that it may decrease the efficiency of nanocomposites. The aim of this work is to measure nanocomposite’s electrical conductivity phenomena that will allow one to formulate optimal concentrations of conductivity NPs in CS-based nanocomposites. Additionally, by comparing the efficiency of such nanocomposites, one can guide applications in the biomedical (antibacterial properties and tissue regeneration) and sensor fields (detection of copper and nitrate ions in aqueous solutions). It was shown that the best antibacterial (CS-AgNPs, CS-AgNPs-carbon nanotubes) and would healing properties (CS-AuNPs) are observed in nanocomposites with concentrations of NPs near the percolation threshold. In this regard, the best detection limit in potentiometric and impedimetric sensors for detection of copper ions (using CS-AuNPs membrane) and nitrate ions (using CS-clay membrane) in aqueous solutions have been observed for membranes with concentrations of NPs near percolation threshold. It is well known that at the percolation concentration of NPs an abrupt increasing of conductivity is observed due to the presence of physical contacts between NPs; above this concentration, agglomeration of NPs takes place such that a decrease in the effective surface and performance of nanocomposite appear. The obtained relationship between electrical percolation threshold and performance of polymer nanocomposites with conductivity NPs is important for the design and optimization of polymer-based nanocomposites for different applications.

Keywords: chitosan, conductivity nanoparticles, percolation threshold, polymer nanocomposites

Procedia PDF Downloads 186

Authors: Jeevan Jyoti, Bhanu Pratap Singh, S. R. Dhakate

Abstract:

In the present study, multiwalled carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) were synthesized by chemical vapor deposition and Improved Hummer’s method, respectively and their composite with acrylonitrile butadiene styrene (ABS) were prepared by twin screw co rotating extrusion technique. The electromagnetic interference (EMI) shielding effectiveness of graphene oxide carbon nanotube (GCNTs) hybrid composites was investigated and the results were compared with EMI shielding of carbon nanotube (CNTs) and reduced graphene oxide (RGO) in the frequency range of 12.4-18 GHz (Ku-band). The experimental results indicate that the EMI shielding effectiveness of these composites is achieved up to –21 dB for 10 wt. % loading of GCNT loading. The mechanism of improvement in EMI shielding effectiveness is discussed by resolving their contribution in absorption and reflection loss. The main reason for such a high improved shielding effectiveness has been attributed to the significant improvement in the electrical conductivity of the composites. The electrical conductivity of these GCNT/ABS composites was increased from 10-13 S/cm to 10-7 S/cm showing the improvement of the 6 order of the magnitude. Scanning electron microscopic (SEM) and high resolution transmission electron microscopic (HRTEM) studies showed that the GCNTs were uniformly dispersed in the ABS polymer matrix. GCNTs form a network throughout the polymer matrix and promote the reinforcement.

Keywords: ABS, EMI shielding, multiwalled carbon nanotubes, reduced graphene oxide, graphene, oxide-carbon nanotube (GCNTs), twin screw extruder, multiwall carbon nanotube, electrical conductivity

Procedia PDF Downloads 328

Authors: Vaishnavi Patil, K. M. Kurundkar

Abstract:

Electrical Drives play a vital role in industry development and applications. Drives have an inevitable part in the needs of various fields such as industry, commercial, and domestic applications. The development of material technology, Power Electronics devices, and accompanying applications led to the focus of industry and researchers on high-speed electrical drives. Numerous articles charted the applications of electrical machines and various converters for high-speed applications. The choice depends on the application under study. This paper goals to highlight high-speed applications, main challenges, and some applications of electrical drives in the field.

Keywords: high-speed, electrical machines, drives, applications

Procedia PDF Downloads 27

Authors: Jiri Primas, Michal Malik, Darina Jasikova, Michal Kotek, Vaclav Kopecky

Abstract:

Authors of this paper discuss the measuring of volume ratio of two immiscible liquids in the homogenous mixture using the industrial Electrical Impedance Tomography (EIT) system ITS p2+. In the first part of the paper, the principle of EIT and the basic theory of conductivity of mixture of two components are stated. In the next part, the experiment with water and olive oil mixed with Rushton turbine is described, and the measured results are used to verify the theory. In the conclusion, the results are discussed in detail, and the accuracy of the measuring method and its advantages are also mentioned.

Keywords: conductivity, electrical impedance tomography, homogenous mixture, mixing process

Procedia PDF Downloads 368

Authors: Francis Mugabi, Kevin Duffy, Joseph J. Y. T Mugisha, Obiora Collins

Abstract:

Bluetongue virus (BTV) has 27 serotypes, with some of them coexisting in patchy (different) environments, which make its control difficult. Wind-aided midge movement is a known mechanism in the spread of BTV. However, its effects on the probability of coexistence of multiple BTV serotypes are not clear. Deterministic and stochastic models for r BTV serotypes in n discrete patches connected by midge and/or cattle movement are formulated and analyzed. For the deterministic model without midge and cattle movement, using the comparison principle, it is shown that if the patch reproduction number R0 < 1, i=1,2,...,n, j=1,2,...,r, all serotypes go extinct. If R^j_i0>1, competitive exclusion takes place. Using numerical simulations, it is shown that when the n patches are connected by midge movement, coexistence takes place. To account for demographic and movement variability, the deterministic model is transformed into a continuous-time Markov chain stochastic model. Utilizing a multitype branching process, it is shown that the midge movement can have a large effect on the probability of coexistence of multiple BTV serotypes. The probability of coexistence can be brought to zero when the control interventions that directly kill the adult midges are applied. These results indicate the significance of wind-aided midge movement and vector control interventions on the coexistence and control of multiple BTV serotypes in patchy environments.

Keywords: bluetongue virus, coexistence, multiple serotypes, midge movement, branching process

Procedia PDF Downloads 118

Authors: Wei Quan, Liu Chao, Mohammed N. Afsar

Abstract:

The dielectric properties and ionic conductivity of novel "ceramic state" polymer electrolytes for high capacity lithium battery are characterized by radio-frequency and Microwave methods in two broad frequency ranges from 50 Hz to 20 KHz and 4 GHz to 40 GHz. This innovative solid polymer electrolyte which is highly ionic conductive (10-3 S/cm at room temperature) from -40 oC to +150 oC and can be used in any battery application. Such polymer exhibits properties more like a ceramic rather than polymer. The various applied measurement methods produced accurate dielectric results for comprehensive analysis of electrochemical properties and ion transportation mechanism of this newly invented polymer electrolyte. Two techniques and instruments employing air gap measurement by capacitance bridge and inwave guide measurement by vector network analyzer are applied to measure the complex dielectric spectra. The complex dielectric spectra are used to determine the complex alternating current electrical conductivity and thus the ionic conductivity.

Keywords: polymer electrolyte, dielectric permittivity, lithium battery, ionic relaxation, microwave measurement

Procedia PDF Downloads 450

Authors: B. Roostaii, H. Kazeminejad, S. Khakshournia

Abstract:

The evolution of volume porosity previously obtained by using the existing low temperature high burn-up gaseous swelling model with progressive recrystallization for UO₂ fuel is utilized to study the degradation of irradiated UO₂ thermal conductivity calculated by the FRAPCON model of thermal conductivity. A porosity correction factor is developed based on the assumption that the fuel morphology is a three-phase type, consisting of the as-fabricated pores and pores due to intergranular bubbles whitin UO₂ matrix and solid fission products. The predicted thermal conductivity demonstrates an additional degradation of 27% due to porosity formation at burn-up levels around 120 MWd/kgU which would cause an increase in the fuel temperature accordingly. Results of the calculations are compared with available data.

Keywords: irradiation-induced recrystallization, matrix swelling, porosity evolution, UO₂ thermal conductivity

Procedia PDF Downloads 270

Authors: Abdelmalek Ammari

Abstract:

This paper represents an experimental study to determine the effect between thermal conductivity of Compressed Earth Block Stabilized (CEBs) by cement and the mineralogical and chemical analyses of soil, all the samples of CEB in the dry state and with different content of cement, the samples made by soil stabilized by Portland Cement. The soil used collected from fez city in Morocco. That determination of the thermal conductivity of CEBs plays an important role when considering its suitability for energy saving insulation. The measurement technique used to determine thermal conductivity is called hot ring method, the thermal conductivity of the tested samples is strongly affected by the quantity of the cement added. The soil of Fez, mainly composed of calcite, quartz, and dolomite, improved the behaviour of the material by the addition of cement. The findings suggest that to manufacture lightweight samples with high thermal insulation properties, it is advisable to use clays that contain quartz. . In addition, quartz has high thermal conductivity.

Keywords: compressed earth blocks, thermal conductivity, mineralogical, chemical, temperature

Procedia PDF Downloads 124

Authors: Issam Derkaoui, Mohammed Khenfouch, Bakang M. Mothudi, Malik Maaza, Izeddine Zorkani, Anouar Jorio

Abstract:

Transition metal oxides nanoparticles with different morphologies have attracted a lot of attention recently owning to their distinctive geometries, and demonstrated promising electrical properties for various applications. In this paper, we discuss the time and annealing effects on the structural and electrical properties of vanadium oxides nanoparticles (VO-NPs) prepared by microwave method. In this sense, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman Spectroscopy, Ultraviolet-visible absorbance spectra (Uv-Vis) and electrical conductivity were investigated. Hence, the annealing state and the time are two crucial parameters for the improvement of the optoelectronic properties. The use of these nanostructures is promising way for the development of technological applications especially for energy storage devices.

Keywords: Vanadium oxide, Microwave, Electrical conductivity, Optoelectronic properties

Procedia PDF Downloads 166

Authors: J. Marx, D. Smazna, R. Adelung, B. Fiedler

Abstract:

Aerographite is a 3D interconnected carbon foam. Its tetrapodal morphology is based on the zinc oxide (ZnO) template structure, which is replicated in the chemical vapour deposition (CVD) into a hollow carbon structure. This replication process is analyzed in ex-situ studies via interrupted synthesis and the observation of the reaction progress by using scanning electron (SEM), transmission electron microscopy (TEM) and Raman spectroscopy techniques. Based on the epitaxial growth process, with a layer-by-layer growth behaviour of the wall thickness or number of layers and the catalytical graphitization of the deposited amorphous carbon into graphitic carbon by zinc, a growth model is created. The properties of aerographite, such as the electrical conductivity is dependent on the graphitization and number of layer (wall thickness). Wall thicknesses between 3 nm and 22 nm are achieved by a controlled stepwise reduction of the synthesis time on the basis of the developed growth model, and by a further thermal treatment at 1800 °C the graphitization of the presented carbon foam is modified. The variation of the wall thickness leads to an optimum defect density (ID/IG ratio) and the graphitization to an improvement in the electrical conductivity. Furthermore, a metallic conducting behaviour of untreated and 1800 °C treated aerographite can be observed. Due to these structural and defective modifications, a fundamental structural-property equation for the description of their influences on the electrical conductivity is developed.

Keywords: electrical conductivity, electron microscopy (SEM/TEM), graphitization, wall thickness

Procedia PDF Downloads 127

Authors: S. Yakut, D. Deger, K. Ulutas, D. Bozoglu

Abstract:

Plasma poly(ethylene oxide) (pPEO) thin films were deposited between Aluminum (Al) electrodes on glass substrates by plasma assisted physical vapor deposition (PAPVD). The deposition was operated inside Argon plasma under 10⁻³ Torr and the thicknesses of samples were determined as 20, 100, 250, 500 nm. The plasma was produced at 5 W by magnetron connected to RF power supply. The capacitance C and dielectric loss factor tan δ were measured by Novovontrol Alpha-A high frequency empedance analyzer at freqquency and temperature intervals of 0,1 Hz and 1MHz, 193-353K, respectively. AC conductivity was derived from these values. AC conductivity results exhibited three different conductivity regions except for 20 nm. These regions can be classified as low, mid and high frequency regions. Low frequency region is observed at around 10 Hz and 300 K while mid frequency region is observed at around 1 kHz and 300 K. The last one, high frequency region, is observed at around 1 kHz and 200 K. There are some coinciding definitions for conduction regions, because these regions shift depending on temperature. Low frequency region behaves as DC-like conductivity while mid and high frequency regions show conductivities corresponding to mechanisms such as classical hopping, tunneling, etc. which are observed for amorphous materials. Unlike other thicknesses, for 20 nm sample low frequency region can not be detected in the investigated freuency range. It is thought that this is arised because of the presence of dead layer behavior.

Keywords: plasma polymers, dead layer, dielectric spectroscopy, AC conductivity

Procedia PDF Downloads 181

Authors: Nuray Uçar, Mervin Ölmez, Özge Alptoğa, Nilgün K. Yavuz, Ayşen Önen

Abstract:

In recent years, research on continuous graphene oxide fibers has been intensified. Therefore, many factors of production stages are being studied. In this study, the effect of exfoliation time and presence of activated carbon particle (ACP) on graphene oxide fiber’s properties has been analyzed. It has been seen that cross-sectional appearance of sample with ACP is harsh and porous because of ACP. The addition of ACP did not change the electrical conductivity. However, ACP results in an enormous decrease of mechanical properties. Longer exfoliation time results to higher crystallinity degree, C/O ratio and less d space between layers. The breaking strength and electrical conductivity of sample with less exfoliation time is some higher than sample with high exfoliation time.

Keywords: activated carbon, coagulation by wet spinning, exfoliation, graphene oxide fiber

Procedia PDF Downloads 315

Authors: Fatih Kılıç, Burak Birol, Necmettin Maraşlı

Abstract:

The directional solidification process is generally used for homogeneous compound production, single crystal growth, and refining (zone refining), etc. processes. The most important two parameters that control eutectic structures are temperature gradient and grain growth rate which are called as solidification parameters The solidification behavior and microstructure characteristics is an interesting topic due to their effects on the properties and performance of the alloys containing eutectic compositions. The solidification behavior of multicomponent and multiphase systems is an important parameter for determining various properties of these materials. The researches have been conducted mostly on the solidification of pure materials or alloys containing two phases. However, there are very few studies on the literature about multiphase reactions and microstructure formation of multicomponent alloys during solidification. Because of this situation, it is important to study the microstructure formation and the thermodynamical, thermophysical and microstructural properties of these alloys. The production process is difficult due to easy oxidation of magnesium and therefore, there is not a comprehensive study concerning alloys containing high Mg (> 30 wt.% Mg). With the increasing amount of Mg inside Al alloys, the specific weight decreases, and the strength shows a slight increase, while due to formation of β-Al8Mg5 phase, ductility lowers. For this reason, production, examination and development of high Mg containing alloys will initiate the production of new advanced engineering materials. The original value of this research can be described as obtaining high Mg containing (> 30% Mg) Al based multicomponent alloys by melting under vacuum; controlled directional solidification with various growth rates at a constant temperature gradient; and establishing relationship between solidification rate and microstructural, mechanical, electrical and thermal properties. Therefore, within the scope of this research, some > 30% Mg containing ternary or quaternary Al alloy compositions were determined, and it was planned to investigate the effects of directional solidification rate on the mechanical, electrical and thermal properties of these alloys. Within the scope of the research, the influence of the growth rate on microstructure parameters, microhardness, tensile strength, electrical conductivity and thermal conductivity of directionally solidified high Mg containing Al-32,2Mg-0,37Si; Al-30Mg-12Zn; Al-32Mg-1,7Ni; Al-32,2Mg-0,37Fe; Al-32Mg-1,7Ni-0,4Si; Al-33,3Mg-0,35Si-0,11Fe (wt.%) alloys with wide range of growth rate (50-2500 µm/s) and fixed temperature gradient, will be investigated. The work can be planned as; (a) directional solidification of Al-Mg based Al-Mg-Si, Al-Mg-Zn, Al-Mg-Ni, Al-Mg-Fe, Al-Mg-Ni-Si, Al-Mg-Si-Fe within wide range of growth rates (50-2500 µm/s) at a constant temperature gradient by Bridgman type solidification system, (b) analysis of microstructure parameters of directionally solidified alloys by using an optical light microscopy and Scanning Electron Microscopy (SEM), (c) measurement of microhardness and tensile strength of directionally solidified alloys, (d) measurement of electrical conductivity by four point probe technique at room temperature (e) measurement of thermal conductivity by linear heat flow method at room temperature.

Keywords: directional solidification, electrical conductivity, high Mg containing multicomponent Al alloys, microhardness, microstructure, tensile strength, thermal conductivity

Procedia PDF Downloads 239

Authors: Riccardo Pasquali, Keith Harlin, Mark Muller

Abstract:

The ShallowTherm project is focussed on developing and applying a methodology for extrapolating relatively sparsely sampled thermal conductivity measurements across Ireland using mapped Litho-Electrical (LE) units. The primary data used consist of electrical resistivities derived from the Geological Survey Ireland Tellus airborne electromagnetic dataset, GIS-based maps of Irish geology, and rock thermal conductivities derived from both the current Irish Ground Thermal Properties (IGTP) database and a new programme of sampling and laboratory measurement. The workflow has been developed across three case-study areas that sample a range of different calcareous, arenaceous, argillaceous, and volcanic lithologies. Statistical analysis of resistivity data from individual geological formations has been assessed and integrated with detailed lithological descriptions to define distinct LE units. Thermal conductivity measurements from core and hand samples have been acquired for every geological formation within each study area. The variability and consistency of thermal conductivity measurements within each LE unit is examined with the aim of defining a characteristic thermal conductivity (or range of thermal conductivities) for each LE unit. Mapping of LE units, coupled with characteristic thermal conductivities, provides a method of defining thermal conductivity properties at a regional scale and facilitating the design of ground source heat pump closed-loop collectors.

Keywords: thermal conductivity, ground source heat pumps, resistivity, heat exchange, shallow geothermal, Ireland

Procedia PDF Downloads 146

Authors: Deniz Bozoglu, Deniz Deger, Kemal Ulutas, Sahin Yakut

Abstract:

In recent years, silica aerogels have attracted great attention due to their outstanding properties, and their wide variety of potential applications such as microelectronics, nuclear and high-energy physics, optics and acoustics, superconductivity, space-physics. Hydrophobic silica aerogels were successfully synthesized in one-step by surface modification at ambient pressure. FT-IR result confirmed that Si-OH groups were successfully converted into hydrophobic and non-polar Si-CH3 groups by surface modification using trimethylchloro silane (TMCS) as co-precursor. Using Alpha-A High-Resolution Dielectric, Conductivity and Impedance Analyzer, AC conductivity of samples were examined at temperature range 293-423 K and measured over frequency range between 1-106 Hz. The characteristic relaxation time decreases with increasing temperature. The AC conductivity follows σ_AC (ω)=σ_t-σ_DC=Aω^s relation at frequencies higher than 10 Hz, and the dominant conduction mechanism is found to obey the Correlated Barrier Hopping (CBH) mechanism. At frequencies lower than 10 Hz, the electrical conduction is found to be in accordance with DC conduction mechanism. The activation energies obtained from AC conductivity results and it was observed two relaxation regions.

Keywords: aerogel, synthesis, dielectric constant, dielectric loss, relaxation time

Procedia PDF Downloads 170

Authors: Mahdi Almaky, Reda Hassanin, Benjamin Horrocks, Andrew Houlton

Abstract:

DNA-templated poly(N-substituted pyrrole)bipyridinium nanowires were synthesised at room temperature using the chemical oxidation method. The resulting CPs/DNA hybrids have been characterised using electronic and vibrational spectroscopic methods especially Ultraviolet-Visible (UV-Vis) spectroscopy and FTIR spectroscpy. The nanowires morphology was characterised using Atomic Force Microscopy (AFM). The electrical properties of the prepared nanowires were characterised using Electrostatic Force Microscopy (EFM), and measured using conductive AFM (c-AFM) and two terminal I/V technique, where the temperature dependence of the conductivity was probed. The conductivities of the prepared CPs/DNA nanowires are generally lower than PPy/DNA nanowires showingthe large effect on N-alkylation in decreasing the conductivity of the polymer, butthese are higher than the conductivity of their corresponding bulk films.This enhancement in conductivity could be attributed to the ordering of the polymer chains on DNA during the templating process. The prepared CPs/DNA nanowires were used as templates for the growth of copper nanowires at room temperature using aqueous solution of Cu(NO3)2as a source of Cu2+ and ascorbic acid as reducing agent. AFM images showed that these nanowires were uniform and continuous compared to copper nanowires prepared using the templating method directly onto DNA. Electrical characterization of the nanowires by c AFM revealed slight improvement in conductivity of these nanowires (Cu-CPs/DNA) compared to CPs/DNA nanowires before metallisation.

Keywords: templating, copper nanowires, polymer/DNA hybrid, chemical oxidation method

Procedia PDF Downloads 334