Temperature Coefficient Of Electrical Conductivity Research Articles

Dynamics of changes in the temperature coefficient of electrical conductivity of distilled water in conductometric cells during heating and cooling

Dynamics of changes in the temperature coefficient of electrical conductivity of distilled water in conductometric cells during heating and cooling

Dynamics of changes in the temperature coefficient of electrical conductivity of distilled water in conductometric cells during heating and cooling

The problem of taking into account the influence of air on the properties of distilled water is considered, namely the lack of a single generally accepted method for calculating such an influence. The sensitivity of the structure of water to the influence of external factors is described and the possibility of recording and studying such factors by changes in the temperature coefficient of electrical conductivity of water is shown. The dependences of the temperature coefficient of electrical conductivity of distilled water on the rate of change in water temperature, the degree of filling of conductometric cells, as well as on the intensity of the exchange of carbon dioxide between water and air across their interface have been studied. It is noted that these metabolic processes are currently insufficiently studied. A hardware-software measuring complex has been developed and manufactured to study the temperature coefficient of electrical conductivity of water when its temperature changes within the range of 20–55 °C. The temperature coefficient of electrical conductivity of water in sealed conductometric cells was measured at different degrees of filling the cells with distilled water and the rate of heating and cooling of water. The degree of filling of the cells varied within the range of 10–100 %, the rate of change in water temperature varied within the range of 0.04–2.00 °C/min. With a constant heating and cooling time of 15 minutes in all experiments, the change in speed was achieved by changing the temperature of the heating element. The integral temperature coefficient of electrical conductivity is calculated based on the initial and final values of electrical conductivity and water temperature in each measurement cycle. The dependences of the temperature coefficient of electrical conductivity on the rate of change in water temperature at several constant degrees of cell filling were obtained. It has been shown that with a constant ratio of the volumes of water and air in the cell and an increase in the rate of heating of water, the temperature coefficient of electrical conductivity of water decreases by 19–22 %. It has been established that at a constant rate of water heating, with a decrease in the volume of water in the cell, the temperature coefficient of electrical conductivity of water decreases by 40–42 %. The results obtained can be used to quantify the dissociation coefficient of carbonic acid, the mobility of hydrogen ions, as well as the intensity of the gas exchange process under various external influences on water. Refinement of data on the electrical conductive properties of water and processes at the water/air interface is necessary for the development of models of atmospheric phenomena and climate change, as well as for the creation of sensors for weak changes in environmental parameters for the purposes of both environmental monitoring and medical diagnostics.

Sb2Te3 nanosheets: Topological insulators with extraordinary electromagnetic response behaviors

Topological insulators exhibit a new variety of unusual phenomena associated with topologically protected gapless surface states. Interestingly, most topological insulators are possibly outstanding electromagnetic shielding materials due to the easily adjustable electric transport performance, which can be controlled by regulating nanostructures based on conducting surface states. Herein, a series of Sb2Te3 nanosheets with different thicknesses were prepared by a hydrothermal method. The electrical conductivity increases as the thickness of the topological nanosheet decreases, so the nanosheet aggregates exhibit an extraordinary electromagnetic response behavior different from metallic materials, which is beneficial to achieving excellent electromagnetic shielding in applications of integrated circuit field. Moreover, Sb2Te3 nanosheet aggregates show a positive temperature coefficient of electrical conductivity that it increases monotonically with increasing temperature in the entire range of 313–573 K. The effect of positive temperature coefficient implies that the longitudinal conductance plays a dominant role in Sb2Te3 nanosheet aggregates. An equivalent circuit model was proposed to describe the unique electrical conductance behavior of nanosheet aggregates for topological insulators. The outstanding electromagnetic shielding performance and positive temperature correlation make Sb2Te3 nanosheets emerging in next-generation electronic equipments and aerospace applications in high-temperature environments.

The Initial Requirements for the Heat Exchanger for Gathering Phase Transition Energy

Production of heat power equipment and provision of agricultural production facilities with it is less than 40 percent, so it is important to conduct research on the development of domestic heat exchange equipment. (Research purpose) The research purpose is in developing the initial requirements for the heat exchanger of an experimental installation in order to gather the energy of the water-ice phase transition for its manufacture. (Materials and methods) Authors conduct patent search on the websites of the World Intellectual Property Organization, Rospatent, Google patents, the European Patent Office and the Eurasian Patent Organization. The article presents drawings using the COMPASS-3D V17 graphic editor. (Results and discussion) The article presents an energy-saving system for maintaining the microclimate of an agricultural facility using a heat pump. It was found that the thermal and physical parameters of the coolant (freezing point, thermal conductivity, solubility of salt, density) as water and salt solutions of various concentrations, as well as electrical and physical parameters (permittivity, tangent of the dielectric loss angle, electrical conductivity, temperature coefficient of electrical conductivity) change during external electrophysical treatment (exposure to an electric field, including electric freezing), magnetic field (including alternating magnetic field in the ultrahigh frequency range, low-frequency magnetic field, weak infra-low frequency magnetic field). (Conclusions) The energy-saving, eco-friendly heat exchange equipment with a heat pump unit is designed to maintain the microclimate of agricultural facilities. The article presents the initial requirements for the heat exchanger of the experimental installation for obtaining the energy of the water-ice phase transition, which will allow producing an experimental sample. Authors have developed a scheme for a heat exchanger of an experimental sample of heat exchange equipment with a heat pump unit for gathering energy of the water-ice phase transition.

Features of Measuring the Electrical Conductivity of Distilled Water in Contact with Air

The paper describes the results of experiments on measuring the electrical conductivity (specific conductance) of distilled water during prolonged contact with air. To carry out the experiments, a hardware-software complex was developed and manufactured that made it possible to measure the electrical conductivity of water with a relative error of the order of ±0.1% with a change in its temperature within 2–50°C, and a temperature error of ±0.06°C. It is shown that the time of diffusion and dissolution of carbon dioxide in water significantly affects the time dependence of the specific conductance of water when its temperature changes. The peculiarity of measuring the electrical conductivity of distilled water for open and closed systems is shown in the results of experiments with partially and completely filled conductometric cells. Thus, in a filled cell in the absence of gas exchange between water and air, the temperature coefficient of electrical conductivity of water is close to the known table value. In this case, in an empty cell, the gas exchange process significantly reduces the value of this coefficient, and the degree of decrease is proportional to the exposure time between the temperature setting and the moment of conductivity measurement. The experimental results are supplemented by theoretical dependences of the specific conductance of water on temperature for various gas exchange conditions between water and air. It is also shown that when measuring the temperature coefficient of electrical conductivity of distilled water in contact with air, it is necessary to take into account not only the time of dissolution of carbon dioxide in it, but also the design features of the electrolytic cell.

The temperature dependence of electron transport in a composite film of graphene oxide with single-wall carbon nanotubes: an analysis and comparison with a nanotube film

The work describes the results of low-temperature studies (5–291 K) of electron transport in composite films of graphene oxide with single-wall nanotubes (GO-SWNTs) obtained by vacuum filtration of their aqueous suspension. The emergence of conductivity in such films is shown to be related to nanotubes, since the GO film, unlike the nanotube film, has no conductivity. For a comparative analysis, the electrical conductivity of the SWNT film was also considered. The GO-SWNT and SWNT films exhibit a semiconductor behavior with a negative temperature coefficient of electrical conductivity. The temperature dependences of film resistance have been analyzed using the 3D Mott model that describes the motion of electrons (due to thermally activated tunneling through barriers) with variable-range hopping (the VRH model) in an interval of 5–240 K. The analysis of the dependences yielded estimates for the parameters of electron transport in the composite GO-SWNT film and SWNT nanotube film: the average hopping range and energy of the electron; their temperature dependences have been plotted. A comparison of these parameters for different films showed that nanotube contact with the GO surface hinders electron transport in the composite film. To describe the temperature dependence of film resistance at Т > 240 K, the Arrhenius model is used from which the potential barrier value has been obtained.

Temperature Coefficients of Electrical Conductivity and Conduction Mechanisms in Butyl Rubber-Carbon Black Composites

Electrical properties of butyl rubber filled with General Purpose Furnace (GPF) carbon black were studied. The carbon black concentration (X) in the compound was X = 40, 60, 70, 80, and 100 parts by weight per hundred parts by weight of rubber (phr). The corresponding volume fractions of GPF carbon black were 0.447 ± 0.022, 0.548 ± 0.027, 0.586 ± 0.029, 0.618 ± 0.031 and 0.669 ± 0.034, respectively. The concentration dependence of conductivity ( $$ \sigma $$ ) at constant temperature showed that $$ \sigma $$ follows a percolation theory; $$ \sigma \propto \left( {X - X_{o} } \right)^{\gamma } $$ , where X o is the concentration at percolation threshold. The exponent $$ \gamma $$ was found as 6.6 (at room temperature 30°C). This value agrees with other experimental values obtained by many authors for different rubber-carbon black systems. Electron tunneling between the aggregates, which are dispersed in the insulator rubber, was mainly the conduction process proposed at constant temperature in the butyl-GPF carbon black composites. Temperature dependence of conductivity was investigated in the temperature range from 30°C up to 120°C. All samples exhibit negative temperature coefficients of conductivity (NTCC). The values obtained are − 0.130°C−1, − 0.019°C−1, − 0.0082°C−1, − 0.0094°C−1, and − 0.072°C−1 for carbon black concentrations of 40 phr, 60 phr, 70 phr, 80 phr, and 100 phr, respectively. The samples of concentrations 40 phr and 60 phr have also positive temperature coefficients of conductivity (PTCC) of values + 0.031 and + 0.013, respectively. Electrical conduction at different temperatures showed various mechanisms depending on the carbon black concentration and/or the interval of temperature. The hopping conduction mechanism was noticed at the lower temperature region while carrier thermal activation mechanisms were recorded at the higher temperature range.

Influence of nanoparticle surface coating on electrical conductivity of LDPE/Al<inf>2</inf>O<inf>3</inf> nanocomposites for HVDC cable insulations

LDPE/metal oxide nanocomposites are promising materials for future high-voltage DC cable insulation. This paper presents data on the influence of the structure of the nanoparticle coating on the electrical conductivity of LDPE/Al 2 O 3 nanocomposites. Al 2 O 3 nanoparticles, 50 nm in size, were coated with a series of silanes with terminal alkyl groups of different lengths (methyl, w-octyl and n-octadecyl groups). The density of the coatings in vacuum was between 200 and 515 kg m−3, indicating substantial porosity in the coating. The dispersion of the nanoparticles in the LDPE matrix was assessed based on statistics for the nearest-neighbor particle distance. The electrical conductivity of the nanocomposites was determined at both 40 and 60 °C. The results show that an appropriate surface coating on the nanoparticles allowed uniform particle dispersion up to a filler loading of 10 wt.%, with a maximum reduction in the electrical conductivity by a factor of 35. The composites based on the most porous octyl-coated nanoparticles showed the greatest reduction in electrical conductivity and the lowest temperature coefficient of electrical conductivity of the composites studied.

Electrical and thermal studies on some acetylacetoneand benzoylacetone-arylhydrazones

The electrical and thermal properties of some acetylacetone-(I) and benzoylacetone-(II) arylhydrazone derivatives have been investigated. The results obtained show semiconductor behavior as evident from the positive temperature coefficient of electrical conductivity (dG/dT). Values of activation energy (ΔE) have been calculated in each case. The electrical conductivity increases with the introduction of either electron-donating or electron-withdrawing substituents to the phenyl ring. Differential thermal analysis curves showed sharp well-defined peaks at the melting point of the investigated compounds. The latent heats of fusion were calculated from these thermograms.

Technical Note: An Addendum to Electrical Conductivities in Shaly Sands— I. The Relation Between Hydrocarbon Saturation and Resistivity Index; II. The Temperature Coefficient of Electrical Conductivity

With regard to the article we published in 1974, "Electrical Conductivities in Shaly Sands—I. The Relation Between Hydrocarbon Saturation and Resistivity Index; II. The Temperature Coefficient of Electrical Conductivity," it has come to our attention that we inadvertently neglected to publish an updated version of Fig. 16. We apologize for this oversight on our part; we believed the revised Fig. 16 had been published. To remedy this oversight, we provide an update to the original 1974 version of Fig. 16 in the article. We thank the management of Shell International E&P, Inc. for permission to publish these data.

極性ゴムの交流導電度温度依存性の測定と理論的考察

It is important to understand temperature dependence of electrical conductivity for polar rubber, which is utilized for charging members of an electrophotographic apparatus. The temperature dependence measurements of AC conductivity were investigated for NBR compounds. The conditions for the measurements were as follows; the sample was fixed between the electrodes with 40kPa, AC voltage: ±70V at various constant frequencies, temperature: from - 50°C to 100°C at a heating rate of 4°C/min. in a dry N2 stream. AC conductivity was used the reciprocal of the real part of admittance. As a result the conductivity was in proportion to AC frequency around Tg, and direct current conductivity was shown above Tg, which conductivity and its temperature dependence increased with using the additive such as polyoxyethylene oleyl ether, 1, 8-diazabicyclo [5, 4, 0]-7-undecene (phenol resin mixture) and benzyltriethyl ammonium chloride. Furthermore, it was found that the thermal expansion coefficient of free volume fraction that assumed from time-temperature superposition principle of complex modulus gave as good correlation for the temperature coefficient of electrical conductivity defined by the theoretical equation of the jumping model.

Anomalous Behaviour of Electrical Conductivity Observed in Insulating Poly(methyl Methacrylate) Thin Films Cast under Humid Atmosphere

Electrical conductivity of the solution cast thin films of poly(methyl methacrylate) [PMMA] has been studied in the temperature range 290–359 K by using surface-type cells. Anomalous behaviour of electrical conductivity has been observed (during heating as well as cooling) at a particular temperature range higher than room temperature, showing a negative temperature coefficient of electrical conductivity in the thin films of PMMA prepared in a humid atmosphere with relative humidity greater than ∼90%. DSC measurements on such a thin film suggest the existence of two phase transitions in the film in the studied temperature range. Films prepared in a dry atmosphere or films prepared by incorporating water externally did not show any such anomalous behaviour in conductivity. The results related to anomalous behaviour in electrical conductivity of PMMA films have been discussed.

Size-Induced Metal to Semiconductor Transition in a Stabilized Gold Cluster Ensemble

A size-induced transition from a positive to a negative temperature coefficient of electrical conductivity is displayed by thin films of a series of six dodecanethiol-stabilized gold cluster complexes with the gold core diameter progressively increasing from 1.7 to 7.2 nm. The size of the gold core may influence both its intrinsic conductivity and the charging energy barrier for tunneling to an adjacent monolayer-encapsulated cluster.

Conductive composites prepared via a propagating polymerization front

AbstractA novel material, a conducting composite with variable temperature coefficient of electrical conductivity, was prepared in a propagating front of an addition polymerization. Graphite and zinc particles were incorporated into an acrylamide‐triethylene glycol dimethacrylate copolymer. Specific electric resistance values of the materials yielded were measured at room temperature and also conductivity measurements were performed in the range of 20–220°C. The basic recipe was modified by doping the conductive composite materials with microscopic‐scale‐size particles of several inorganic and organic compounds, resulting in significantly different conductivity features of the composite. Scanning electron microscopy was performed to study the morphology of materials yielded. No percolative patterns containing zinc particles were found to support the conductive behavior of the composite. In accordance with to the modifying effect of doping materials we suspect that the acrylamide‐triethylene glycol dimethacrylate copolymer plays a specific role in the electric conductivity behavior of the composite material.

Electrical, spectral and thermochromic properties of some hydrazone derivatives

The electrical and spectral properties of some ethyl cyanoacetate phenylhydrazone derivatives have been investigated. Results obtained show anomalous metallic-like and semiconducting behaviours corresponding to the low and higher temperature ranges. At high temperatures a positive temperature coefficient of electrical conductivity (dΣ/dT) provides evidence for the semiconducting character, and the linear correlation indicates metallic-like behaviour at a low temperature range. Values of activation energy (δE) were calculated in each case. In addition, the current-voltage dependence of the hydrazone derivatives was investigated. This showed that the compounds under study have ohmic conduction. The correlation between γmax and Σa Hammett constant was also investigated. The hydrazone derivatives are thermolabile and undergo thermochromic behaviour during heating.

Electrical and spectrophotometric properties of charge-transfer complexes of some anthracene derivatives

The solid charge-transfer (CT) complexes of some anthracene derivatives with nitroaromatic acceptors were prepared. The ionization potential IP, electron affinity EA and energy of the CT transition for the donors, acceptors and CT complexes respectively were determined from the spectrophotometric measurements. In addition, the electrical properties of the CT complexes were investigated. The positive temperature coefficient of electrical conductivity (dσ/d T) found for all samples provides evidence of their semiconducting properties. A correlation between the spectrophotometric and conductivity parameters was established. The mechanism of the conduction process in these complexes was also studied.

Electrical properties of charge transfer complexes of diaminonaphthalene donors with dinitro- and trinitrobenzene acceptors

The electrical properties of some charge transfer complexes, with stoichiometries 1:1 and 1:2 (donor : acceptor), of 1,5-diaminonaphthalene and 2,3-diaminonaphthalene with dinitro- and trinitrobenzenes have been investigated. The positive temperature coefficient of electrical conductivity (dσ/d T) is evidence for a semiconducting character. The energy gaps ( E g) for conduction and the charge transfer excitation energies ( E CT) have been discussed. The mechanism of the conduction process is also interpreted.

Applied potential tomography for non-invasive temperature mapping in hyperthermia.

In the field of hyperthermia for cancer treatment, much effort is being put into the development of non-invasive temperature monitoring so that the trauma of implanting thermocouple or thermistor probes in the patient can be avoided. Preliminary studies investigating the use of applied potential tomography (APT) for this purpose have been reported. APT has the advantages over other tomographic methods that the instrumentation is inexpensive, transportable, and could easily be accommodated in a hyperthermia treatment environment. Moreover, the temperature coefficient of electrical conductivity is large (2% degrees C-1) compared, for example, with the corresponding quantity in CT, the x-ray attenuation coefficient, which changes by only 0.04% degrees C-1. In our experimental system, 16 electrodes were fixed around a cylindrical block of agar simulating a human thigh. The system was driven with 5 mA at 50 kHz. The agar was heated using the 13.56 MHz capacitive system currently in clinical use in this hospital. By relating data sets recorded at different times during heating to a set recorded before heating, images of the temperature change in the agar with time were computed and are presented. The experiment was then repeated in vivo on the thigh of a volunteer.

The electrical properties of some 2-aminopyrimidine and 2-aminopyrazine schiff bases

The electrical properties of some Schiff bases of 2-aminopyrimidine and 2-aminopyrazine with benzaldehyde derivatives have been investigated. Such measurements have rarely been done on these compounds. The positive temperature coefficient of electrical conductivity (dσ/d T) found for all the samples investigated is evidence for the semiconducting character within the range of temperature studied. For the compounds studied, a correlation between the electrical properties and their chemical structure is established. The mechanism of the conduction process in these samples is also studied.

A comparison of the temperature coefficients of electrical conductivity of Atlantic and Pacific seawaters

The Practical Salinity Scale 1978 (PSS) defines the relationship among salinity, electrical conductivity, temperature, and pressure. Strictly speaking, the PSS is only applicable to waters with the same relative chemical composition as standard seawater. We have tested the predictions of the PSS for samples of Atlantic and Pacific waters. The results indicate that the PSS is valid for these natural seawaters over the defined temperature range of the scale.