On the A.C. electrical conductivity of a Lorentz gas

1968 ◽  
Vol 2 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J. H. M. Fu ◽  
R. S. B. Ong
Keyword(s):  
Electrical Conductivity ◽  
Magnitude Estimate ◽  
Lorentz Gas ◽  
Collision Term ◽  
Homogeneous Case ◽  
Spatial Gradients ◽  
Effective Collision Frequency ◽  
Higher Order Terms ◽  
Order Of Magnitude ◽  
Effective Collision

Often one is interested in the electrical conductivity of a plasma for frequencies of the applied electric field comparable to or greater than the effective collision frequency. For the purpose of obtaining an order of magnitude estimate of the conductivity a Lorentz gas model with a Fokker–Planck collision term is used. For this simple model a formula for the a.c. electrical conductivity for two limiting cases is derived in closed form. The first term of the expression for the conductivity in the case where w/k is very large agrees with that obtained by Bernstein & Trehan (1960) for the spatially homogeneous case, while the effect of the spatial gradients is indicated in the higher order terms. In the case where w and k are both equal to zero the expression for the d.c. electrical conductivity of Spitzer (1962) is recovered.

Electromagnetic damping of elastic waves: a simple theory

1970 ◽  
Vol 7 (5) ◽  
pp. 1304-1307 ◽  
Author(s):  
F. E. M. Lilley ◽  
C. M. Carmichael
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Analytical Solution ◽  
Applied Magnetic Field ◽  
Elastic Waves ◽  
Magnetic Field Gradient ◽  
Magnitude Estimate ◽  
Simple Expression ◽  
Electromagnetic Damping ◽  
Order Of Magnitude

An order-of-magnitude estimate is made to check the effect observed in previously described experiments in which vibrations in a metal bar were damped by an applied magnetic field that was strongly non-uniform. Though the awkward geometry of the experiment has prevented an accurate analytical solution of the problem, some reasonable assumptions allow a simple expression for the effect to be obtained directly. This expression is in agreement with the experimental results regarding the dependence of the effect upon frequency, bar dimensions, density, electrical conductivity, and magnetic field gradient.

Structure and Conductivity of Iodine-Doped C60 Thin Films

1994 ◽  
Vol 359 ◽  
Author(s):  
Jun Chen ◽  
Haiyan Zhang ◽  
Baoqiong Chen ◽  
Shaoqi Peng ◽  
Ning Ke ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Room Temperature ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
X Ray ◽  
Thermally Activated ◽  
Order Of Magnitude

ABSTRACTWe report here the results of our study on the properties of iodine-doped C60 thin films by IR and optical absorption, X-ray diffraction, and electrical conductivity measurements. The results show that there is no apparent structural change in the iodine-doped samples at room temperature in comparison with that of the undoped films. However, in the electrical conductivity measurements, an increase of more that one order of magnitude in the room temperature conductivity has been observed in the iodine-doped samples. In addition, while the conductivity of the undoped films shows thermally activated temperature dependence, the conductivity of the iodine-doped films was found to be constant over a fairly wide temperature range (from 20°C to 70°C) exhibiting a metallic feature.

Electrical Properties of Additively Manufactured Acrylonitrile Butadiene Styrene/Carbon Nanotube Nanocomposite

2018 ◽  
Author(s):  
Dominic Thaler ◽  
Nahal Aliheidari ◽  
Amir Ameli
Keyword(s):  
Electrical Conductivity ◽  
Additive Manufacturing ◽  
Fused Deposition Modeling ◽  
Functional Materials ◽  
Acrylonitrile Butadiene Styrene ◽  
Extrusion Process ◽  
Print Quality ◽  
Fused Deposition ◽  
Order Of Magnitude ◽  
Butadiene Styrene

Additive manufacturing is an emerging method to produce customized parts with functional materials without big investments. As one of the common additive manufacturing methods, fused deposition modeling (FDM) uses thermoplastic-based feedstock. It has been recently adapted to fabricate composite materials too. Acrylonitrile butadiene styrene (ABS) is the most widely used material as FDM feedstock. However, it is an electrically insulating polymer. Carbon Nanotubes (CNTs) on the other hand are highly conductive. They are attractive fillers because of their high aspect ratio, and excellent mechanical and physical properties. Therefore, a nanocomposite of these two materials can give an electrically conductive material that is potentially compatible with FDM printing. This work focuses on the investigation of the relationships between the FDM process parameters and the electrical conductivity of the printed ABS/CNT nanocomposites. Nanocomposite filaments with CNT contents up to 10wt% were produced using a twin-screw extruder followed by 3D printing using FDM method. The starting material was pellets from a masterbatch containing 15 wt% CNT. Compression-molded samples of ABS/CNT were also prepared as the bulk baselines. The effects of CNT content and nozzle size on the through-layer and in-layer electrical conductivity of the printed nanocomposites were analyzed. Overall, a higher percolation threshold was observed in the printed samples, compared to that of the compression-molded counterparts. This resulted in the conductivity of the printed samples that is at least one order of magnitude lower. Moreover, at CNT contents up to 5 wt%, the in-layer conductivity of the printed samples was almost two orders of magnitudes higher than that in the through-layer direction. In ABS/3 wt% CNT samples, the through-layer conductivity continuously decreased as the nozzle diameter was decreased from 0.8 mm to 0.35 mm. These variations in the electrical conductivity were explained in terms of the CNT alignment, caused by the extrusion process during the print, quality of interlayer bonding during deposition, and the voids created due to the discrete nature of the printing process.

scholarly journals SYNTHESIS AND ELECTRICAL CONDUCTIVITY OF SOLID SOLUTIONS OF THE SYSTEM RbF-PbF2-SnF2

2019 ◽  
Vol 85 (5) ◽  
pp. 60-68
Author(s):  
Yuliay Pogorenko ◽  
Anatoliy Omel’chuk ◽  
Roman Pshenichny ◽  
Anton Nagornyi
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Temperature Dependence ◽  
Solid Solutions ◽  
Basic Structure ◽  
Elementary Cell ◽  
Initial Structure ◽  
Fluoride Ions ◽  
Temperature Range ◽  
Order Of Magnitude

In the system RbF–PbF2–SnF2 are formed solid solutions of the heterovalent substitution RbxPb0,86‑xSn1,14F4-x (0 < x ≤ 0,2) with structure of β–PbSnF4. At x > 0,2 on the X-ray diffractograms, in addition to the basic structure, additional peaks are recorded that do not correspond to the reflexes of the individual fluorides and can indicate the formation of a mixture of solid solutions of different composition. For single-phase solid solutions, the calculated parameters of the crystal lattice are satisfactorily described by the Vegard rule. The introduction of ions of Rb+ into the initial structure leads to an increase in the parameter a of the elementary cell from 5.967 for x = 0 to 5.970 for x = 0.20. The replacement of a part of leads ions to rubium ions an increase in electrical conductivity compared with β–PbSnF4 and Pb0.86Sn1.14F4. Insignificant substitution (up to 3.0 mol%) of ions Pb2+ at Rb+ at T<500 K per order of magnitude reduces the conductivity of the samples obtained, while the nature of its temperature dependence is similar to the temperature dependence of the conductivity of the sample β-PbSnF4. By replacing 5 mol. % of ions with Pb2+ on Rb+, the fluoride ion conductivity at T> 450 K is higher than the conductivity of the initial sample Pb0,86Sn1,14F4 and at temperatures below 450 K by an order of magnitude smaller. With further increase in the content of RbF the electrical conductivity of the samples increases throughout the temperature range, reaching the maximum values at x≥0.15 (σ573 = 0.34–0.41 S/cm, Ea = 0.16 eV and σ373 = (5.34–8.16)•10-2 S/cm, Ea = 0.48–0.51 eV, respectively). In the general case, the replacement of a part of the ions of Pb2+ with Rb+ to an increase in the electrical conductivity of the samples throughout the temperature range. The activation energy of conductivity with an increase in the content of RbF in the low-temperature region in the general case increases, and at temperatures above 400 K is inversely proportional decreasing. The nature of the dependence of the activation energy on the concentration of the heterovalent substituent and its value indicate that the conductivity of the samples obtained increases with an increase in the vacancies of fluoride ions in the structure of the solid solutions.

Absolutmessung der Leistungseinkopplung in ein Deuterium-Plasma bei der unteren Hybrid-Resonanz / Absolute Measurement of Power Transfer to a Deuterium Plasma Near the Lower Hybrid Resonance

1975 ◽  
Vol 30 (2) ◽  
pp. 204-211
Author(s):  
B. Lammers ◽  
U. Oberlack ◽  
H. Schlüter
Keyword(s):  
Absolute Measurement ◽  
Lower Hybrid ◽  
Power Transfer ◽  
Deuterium Plasma ◽  
Hybrid Resonance ◽  
Effective Collision Frequency ◽  
Bounded Plasma ◽  
Effective Collision ◽  
Lower Hybrid Resonance ◽  
Good Agreement

Abstract Absolute Measurement of Power Transfer to a Deuterium Plasma Near the Lower Hybrid Resonance The power transfer to a deuterium plasma generated by a high frequency discharge near the lower hybrid resonance is investigated in the range of several hundred watts. The results are compared with linear theories. Reasonable agreement is found between measurements and the linear theory of a bounded plasma as far as the wings of the resonance are concerned. But the dominant radial modes predicted by theory are not observed. Introduction of an empirical effective collision frequency ν* = 0.2 ωpe, however, results in good agreement between measurements and theory in the domain of these radial modes.

scholarly journals Influence of crystallinity on the thermoelectric power factor of P3HT vapour-doped with F4TCNQ

RSC Advances ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 1593-1599 ◽  
Author(s):  
Jonna Hynynen ◽  
David Kiefer ◽  
Christian Müller
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Thermoelectric Power Factor ◽  
Order Of Magnitude

The crystallinity of P3HT strongly benefits the electrical conductivity but not Seebeck coefficient, leading to an increase in power factor by one order of magnitude.

scholarly journals Development of Pressure-Responsive PolyPropylene and Biochar-Based Materials

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 339 ◽  
Author(s):  
Amir Noori ◽  
Mattia Bartoli ◽  
Alberto Frache ◽  
Erik Piatti ◽  
Mauro Giorcelli ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Electrical Conductivity ◽  
Differential Scanning Calorimetry ◽  
Plastic Deformation ◽  
Electrical Properties ◽  
Tea Leaves ◽  
Scanning Calorimetry ◽  
A Value ◽  
Wide Range ◽  
Order Of Magnitude

In this research paper, we reported the synthesis of biochar-based composites using biochar derived from exhausted tea leaves and polypropylene. The resulting materials were deeply characterized investigating mechanical (dynamic mechanical thermal analysis), thermal (thermogravimetrical analysis and differential scanning calorimetry), morphological (field emission scanning microscopy) and electrical properties vs. temperature. Furthermore, electrical conductivity was studied for a wide range of pressures showing an irreversible plastic deformation. An increment of one order of magnitude in the conductivity was observed in the case of 40 wt% biochar loading, reaching a value of 0.2 S/m. The material produced exhibited the properties of an irreversible pressure sensor.

scholarly journals Community Composition and Functioning of Denitrifying Bacteria from Adjacent Meadow and Forest Soils

2003 ◽  
Vol 69 (10) ◽  
pp. 5974-5982 ◽  
Author(s):  
J. J. Rich ◽  
R. S. Heichen ◽  
P. J. Bottomley ◽  
K. Cromack ◽  
D. D. Myrold
Keyword(s):  
Community Composition ◽  
Forest Soils ◽  
Vegetation Type ◽  
Denitrifying Bacteria ◽  
Nitrous Oxide Reductase ◽  
Soil C ◽  
Spatial Gradients ◽  
Order Of Magnitude ◽  
Denitrifier Communities ◽  
Dominant Genotype

ABSTRACT We investigated communities of denitrifying bacteria from adjacent meadow and forest soils. Our objectives were to explore spatial gradients in denitrifier communities from meadow to forest, examine whether community composition was related to ecological properties (such as vegetation type and process rates), and determine phylogenetic relationships among denitrifiers. nosZ, a key gene in the denitrification pathway for nitrous oxide reductase, served as a marker for denitrifying bacteria. Denitrifying enzyme activity (DEA) was measured as a proxy for function. Other variables, such as nitrification potential and soil C/N ratio, were also measured. Soil samples were taken along transects that spanned meadow-forest boundaries at two sites in the H. J. Andrews Experimental Forest in the Western Cascade Mountains of Oregon. Results indicated strong functional and structural community differences between the meadow and forest soils. Levels of DEA were an order of magnitude higher in the meadow soils. Denitrifying community composition was related to process rates and vegetation type as determined on the basis of multivariate analyses of nosZ terminal restriction fragment length polymorphism profiles. Denitrifier communities formed distinct groups according to vegetation type and site. Screening 225 nosZ clones yielded 47 unique denitrifying genotypes; the most dominant genotype occurred 31 times, and half the genotypes occurred once. Several dominant and less-dominant denitrifying genotypes were more characteristic of either meadow or forest soils. The majority of nosZ fragments sequenced from meadow or forest soils were most similar to nosZ from the Rhizobiaceae group in α-Proteobacteria species. Denitrifying community composition, as well as environmental factors, may contribute to the variability of denitrification rates in these systems.

scholarly journals The Electrical Conductivity of a Partially Ionized Argon-Potassium Plasma in a Magnetic Field

1966 ◽  
Vol 21 (9) ◽  
pp. 1468-1470 ◽  
Author(s):  
W. Feneberg
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Laguerre Polynomials ◽  
Lorentz Gas ◽  
Small Deviations ◽  
Starting Point ◽  
Potassium Plasma ◽  
Partially Ionized ◽  
Ramsauer Effect ◽  
The Magnetic Field

In the case of small deviations from thermal equilibrium the second ENSKOG approximation is used as a starting point for solving the BOLTZMANN equation of the electrons in a partially ionized plasma. The distribution function is expanded according to LAGUERRE polynomials up to the order of 3. In this order the electrical conductivity of a LORENTZ gas, which is known exactly, is obtained to an accuracy of roughly 5%. The approximation tested in this way was then used to calculate the conductivity of an argon-potassium mixture at electron temperatures between 2000°K and 3500°K.If only he collisions between electrons and argon atoms were to be considered, the electrical conductivity in the absence of a magnetic field would, in view of the RAMSAUER effect, be greater by a factor of 2.8 than that obtained with an infinitely strong magnetic field. When the interaction with the potassium atoms and the COULOMB interaction are taken into account as well the conductivity in the magnetic field varies by about 20%.

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