Electric Permittivity Measurements Research Articles

Qualitative and quantitative evaluation of solvent systems for countercurrent separation

Rational solvent system selection for countercurrent chromatography and centrifugal partition chromatography technology (collectively known as countercurrent separation) studies continues to be a scientific challenge as the fundamental questions of comparing polarity range and selectivity within a solvent system family and between putative orthogonal solvent systems remain unanswered. The current emphasis on metabolomic investigations and analysis of complex mixtures necessitates the use of successive orthogonal countercurrent separation (CS) steps as part of complex fractionation protocols. Addressing the broad range of metabolite polarities demands development of new CS solvent systems with appropriate composition, polarity (π), selectivity (σ), and suitability. In this study, a mixture of twenty commercially available natural products, called the GUESSmix, was utilized to evaluate both solvent system polarity and selectively characteristics. Comparisons of GUESSmix analyte partition coefficient (K) values give rise to a measure of solvent system polarity range called the GUESSmix polarity index (GUPI). Solvatochromic dye and electrical permittivity measurements were also evaluated in quantitatively assessing solvent system polarity. The relative selectivity of solvent systems were evaluated with the GUESSmix by calculating the pairwise resolution (αip), the number of analytes found in the sweet spot (Nsw), and the pairwise resolution of those sweet spot analytes (αsw). The combination of these parameters allowed for both intra- and inter-family comparison of solvent system selectivity. Finally, 2-dimensional reciprocal shifted symmetry plots (ReSS2) were created to visually compare both the polarities and selectivities of solvent system pairs. This study helps to pave the way to the development of new solvent systems that are amenable to successive orthogonal CS protocols employed in metabolomic studies.

Electrical characterization of a new enamel insulation

Investigations of dielectric properties of a newly developed enamel wire insulation created by adding chromium (III) oxide (Cr2O3) filler to polyamide-imide enamel base are presented. Results of measurements of electrical conductivity and complex permittivity at various temperatures as well as surface potential decay are discussed and compared with corresponding properties of standard enamel insulation. Contributions of different polarization relaxation processes in both enamels are examined based on the obtained master curves of dielectric response. In addition, the properties of chromium oxide filler are characterized separately and utilized further for analyzing its impact on the performance of enamel wire insulation by means of computer simulations. The experimental and simulated results demonstrate that the introduction of chromium oxide yields changes in the electrical properties that allow for mitigating the voltage stress in a wound insulation system. Furthermore, a correlation between the obtained results and the earlier described improved resistance to partial discharge activity of the chromium oxide filled enamel is discussed.

Thermal and dielectric properties of K3Nd(PO4)2 prepared by Pechini and solid state method

• The K 3 Nd(PO 4 ) 2 powders built of nanometric sized crystals have been obtained. • The polymorphic transition β/α depends strongly on preparation method. • The activation energy of active dipoles in K 3 Nd(PO 4 ) 2 has been determined. The binary neodymium–potassium phosphate β-K 3 Nd(PO 4 ) 2 was obtained by the ceramic and modified Pechini methods. The obtained powders were studied using TGA/DSC, XRD, FTIR and BET techniques. The materials obtained by the Pechini method show a strong tendency towards agglomeration. The average crystallite size of β-K 3 Nd(PO 4 ) 2 obtained at 480 °C amounts to about 30 nm. The temperature and enthalpy of the β/α-K 3 Nd(PO 4 ) 2 polymorphic transition were determined. In the case of the materials obtained by the Pechini method, the polymorphic transition occurs at 1181 °C and it is assisted by one endothermic effect with the Δ H ph.tr. = 58 ± 9 kJ mol −1 . For powders obtained by ceramic technique the β/α polymorphic transition takes place in a temperature range of 1148–1180 °C and is accompanied by two endothermic effects with the total enthalpy change of 53 ± 15 kJ mol −1 . The effect of the synthesis method and that of the size of the phosphate crystallites on the mechanism of polymorphic transition have been discussed. The electric permittivity and dielectric loss measurements were carried out, too. The activation energy of active dipoles in K 3 Nd(PO 4 ) 2 was determined on the basis of the electric permittivity and the dielectric dispersion and absorption measurements. The activation energy amounts to 149.8 kJ mol −1 .

Experimental Proof of an Anomalous Behavior in the Nematic Phase of the Liquid Crystal E7

Experimental proof about a no reported anomalous behavior in the nematic phase of the Liquid Crystal E7 (Merck) are demonstrated by means of optical, electrical and density measurements. Optical measurements were made by use of polarized light transmittance, electrical measurements were obtained using impedance spectroscopy and density measurements were made using a precision density meter. Evidence of a temperature range in which is contained a not related anomalous behavior in the nematic phase of the Liquid Crystal E7 is observed in optical measurements performed on a PDLC sample at different temperatures, and proven by electrical permittivity and volumetric density measurements. The temperature range of anomalous observation occurs between 23°C and 43°C and present a peak at about 32°C, coincidentally close to 35 °C, the N-I temperature of the liquid crystal 5CB, major constituent of the mixture that composing the eutectic liquid crystal E7 [1]. With regard to the application of this liquid crystal, it is clear the need to consider the existence of a temperature range in which the electro optical responses of E7 features a behavior, unknown until then.

Dielectric relaxation and electronic spectroscopy of double potassium yttrium tetraoxophosphate(V) K3Y(PO4)2 doped by neodymium and europium ions

The paper presents the results of our investigation on electric properties of double potassium yttrium tetraoxophosphate(V) doped by lanthanide ions K3Y(1−x)Lnx(PO4)2 (x = 0.01, 0.05, Ln = Eu3+, Nd3+). Electric permittivity and dielectric loss measurements have been performed on polycrystalline samples in the temperature range −50 °C to +120 °C and frequency range 1 kHz–1 MHz by means of HP 4282A impedance meter. The frequency and temperature dependence of electric properties were analyzed by theoretical models of dielectric relaxation in order to obtain information abut molecular dynamic of our solids in external electric field.

Dielectric relaxation in double potassium yttrium orthophosphate K3Y(PO4)2 doped by praseodymium and dysprosium ions

We report the paper presents the results of electric properties of double potassium yttrium orthophosphates doped by lanthanide ions K 3 Y( 1− x ) Ln x (PO 4 ) 2 ( x = 0.01, 0.05, Ln = Pr 3+ , Dy 3+ ). Electric permittivity and dielectric loss measurements have been performed on polycrystalline samples in the temperature range −50–120 °C and frequency range 1 kHz–1 MHz by means of HP 4282A impedance meter. The frequency and temperature dependence of electric properties were analyzed by theoretical models of dielectric relaxation in order to obtain information abut molecular dynamic of our solids in external electric field.

Combined estimation of effective electrical conductivity and permittivity for soil monitoring

The mapping of moisture content, composition, and texture of soils is attracting a growing interest, in particular with the goal of evaluating threats to soil quality, such as soil salinization. Fast noninvasive geophysical surveys are often used in this context. The aim of this work was to study constitutive models that can be used to parameterize electrical conductivity and permittivity starting from a unifying conceptual approach, and to evaluate whether the information carried by one measurement type can be used to identify soil parameters that are then used to predict the other geophysical quantity. To this end, a recently developed constitutive model was extended and modified to consider the grain surface conductivity, a critical component in most natural situations. The extended model was successfully tested against laboratory measurements. In addition, the new model was compared against five other equations that use similar soil parameterizations. It was concluded that only three out of the five selected models yield similar predictions, while the remaining two predict a different geophysical response for the same soil texture. Following this analysis, a methodology was developed to estimate soil salinity starting from the simultaneous measurements of bulk electrical conductivity and permittivity and validating this methodology against laboratory experiments. The method is valid in situations where the conductivity of the pore water remains approximately constant during the measurement period. Key features of the approach proposed to map soil salinization are (1) simplicity, (2) absence of fitting parameters, and (3) the fact that moisture content does not need to be measured or estimated independently. The methodology was tested on a large number of soil samples and proved robust and accurate.

Dielectric relaxation in double potassium yttrium orthophosphate K 3Y(PO 4) 2 doped by ytterbium ions

Electric properties were examined in double potassium yttrium orthophosphates K 3Y( 1− x )Yb x (PO 4) 2 ( x = 0.01, 0.05). Electric permittivity and dielectric loss measurements have been performed on polycrystalline samples in the temperature range −50 °C to 120 °C and frequency range 1 kHz–1 MHz by means of HP 4282A impedance meter. The frequency and temperature dependence of electric properties were analyzed by theoretical models of dielectric relaxation in order to obtain information about molecular dynamic of our solids in external electric field.

Magnetoelectric Contribution to Magnetoelastic Coupling in Pb(Fe1/2Nb1/2)O3 Multiferroics Ceramics

In this work, electrical permittivity, magnetic and anelastic measurements in lead iron niobate ceramics (PFN) were performed in the frequency and temperature range from 1 kHz to 10 MHz and from 15 K to 400 K, respectively. Anelastic results characterized unambiguously the magnetoelectric effect in the PFN, demonstrating that ME coupling arises indirectly via strain contribution rather than a direct coupling between electrical and magnetic order parameters.

Optimal requirements of a data acquisition system for a quadrupolar probe used in resistivity and permittivity surveys

This paper discusses the development and engineering of electrical spectroscopy for simultaneous and non invasive measurement of electrical resistivity and dielectric permittivity. A suitable quadrupolar probe is able to perform measurements on a subsurface with inaccuracies below a fixed limit (10%) in a bandwidth of low (LF) frequency (100kHz). The quadrupole probe should be connected to an appropriate analogical digital converter (ADC) which samples in phase and quadrature (IQ) or in uniform mode. If the quadrupole is characterized by a galvanic contact with the surface, the inaccuracies in the measurement of resistivity and permittivity, due to the IQ or uniform sampling ADC, are analytically expressed. A large number of numerical simulations proves that the performances of the probe depend on the selected sampler and that the IQ is better compared to the uniform mode under the same operating conditions, i.e. bit resolution and medium.

ChemInform Abstract: Native Oxide Films of In0.53Ga0.47As Formed Using Plasma Anodization.

This paper reports on DC plasma anodization that has been used to form insulating native oxide films on IN{sub 0.53}Ga{sub 0.47}As epitaxial layers supported on semi-insulting and conducting InP substrates. Anodizations at constant current density have been compared with those which were limited by a preset voltage. Rutherford back scattering showed that the composition was In{sub 0.46}(Ga + As){sub 1.47}O{sub 6.0} for both anodization processes. There was a loss of about 11% In in comparison with the aggregate of the Ga and As fractions. The absolute losses of In and (Ga + As) were 20 and 6%, respectively. The volume increase on oxidation was imperceptible. Auger electron spectroscopy showed that the oxide-semiconductor interface width was less than 40 {Angstrom}. When current limited growth was used, the composition within 200 {Angstrom} of the interface was particularly uniform. Measurements of electrical resistivity, breakdown field, permittivity, and etch rate are reported and point to the usefulness of the plasma native oxide as a device insulator material.

Inaccuracy assessment for simultaneous measurement of resistivity and permittivity applying sensitivity and transfer function approaches

Normal.dotm 0 0 1 188 1075 INGV BO 8 2 1320 12.0 0 false 14 18 pt 18 pt 0 0 false false false The present study proposes a theoretical modeling of simultaneous and noninvasive measurements of electrical resistivity and dielectric permittivity using a quadrupole probe on a subjacent medium. A mathematical–physical model is applied to the propagation of errors in the measurement of resistivity and permittivity based on a sensitivity functions tool. The findings are also compared with results of the classical method of analysis in the frequency domain, which is useful for determining the behavior of zero and pole frequencies in the linear time invariant circuit of the quadrupole. This study underlines that average values of electrical resistivity and dielectric permittivity can be used to estimate complex impedance over various terrains and concretes, especially when they are characterized by low levels of water saturation (content), and are analyzed within a bandwidth ranging only from low to middle frequencies. To meet the design specifications, that ensure satisfactory performances of the probe (inaccuracies of no more than 10%), the forecasts provided by the sensitivity functions approach are discussed in comparison with those foreseen by the transfer functions method (in terms of both the band of frequency f and the measurable range of resistivity ρ, or permittivity er).

Kapazitäts-Gittersensor: Prinzip und AnwendungCapacitance Wire-Mesh Sensor: Principle and Application

Zusammenfassung Gittersensoren ermöglichen räumlich und zeitlich hochaufgelöste Untersuchungen von Mehrphasenströmungen und können für viele strömungsdiagnostische Probleme eingesetzt werden. Dieser Beitrag beschreibt den neu entwickelten Kapazitäts-Gittersensor, welcher auf der Messung der elektrischen Permittivität (Kapazität) basiert. Neben der Beschreibung des Messprinzips und der dazugehörigen Messelektronik sowie Datenanalyse wird auch ein ausgewähltes Anwendungsbeispiel präsentiert. Der Gittersensor wurde bei der Untersuchung einer zweiphasigen Öl-Gas-Rohrströmung eingesetzt, wobei die Strömungsregime visualisiert und einige wichtige quantitative Strömungsparameter aus den gemessenen Rohdaten extrahiert wurden.

Spatially resolved inline measurement of liquid velocity in trickle bed reactors

The flow pattern in trickle bed reactors is of an inhomogeneous nature due to a random packing structure. Thus, the local values for liquid phase ratio and velocity are spread over the whole cross-section and a global determination of these values ignores the fact that local phenomena dominate mass and heat transfer and eventually the reactor efficiency. Only if both parameters can be locally quantified, can a realistic picture of the flow fields be drawn. A new wire-mesh sensor (WMS) setup based on the measurement of electrical permittivity of fluids was used, which can be applied to the packings of porous catalyst particles. A calibration method is proposed to get access to the liquid saturation. Axial velocity distributions are measured via a method based on the spatial tracer pulse time-of-flight between sensing points of two WMSs installed at a distance of few millimeters. The effects of gas and liquid flow rates on local liquid velocities were analyzed. The proposed technique was validated against liquid collector data, which showed very good agreement. For this purpose, distributions of the volumetric flow rate were calculated by applying the continuity equation to the saturation and velocity data obtained from WMS.

Dielectric relaxation in double potassium yttrium orthophosphate K 3Y(PO 4) 2 and sodium yttrium orthophosphate Na 3Y(PO 4) 2

This paper presents the results of our investigations on electric properties of double alkali metal yttrium orthophosphates M 3 IY(PO 4) 2 (M I = Na, K). Electric permittivity measurements have been performed on polycrystalline samples of potassium yttrium orthophosphate K 3Y(PO 4) 2 and sodium yttrium orthophosphate Na 3Y(PO 4) 2 in the temperature range from −20 °C to +120 °C and frequency range from 1 kHz to 1 MHz. Measurement of the frequency and temperature dependence of dielectric properties give information about dynamical reorientation of molecules with permanent or long lasting induced electric dipole moment μ.

Contribution to molecular mechanism of optical nonlinearity and electric conductivity of 3-nitroaniline single crystals by dielectric, electric and quantum chemical studies

The measurements of electric permittivities, of electric DC conductivity, and of the current–voltage characteristics at various temperatures and field frequencies were performed for the single crystals of 3-nitroaniline (m-NA). The 1.77 eV energy gap in the band structure, calculated by quantum chemical methods, is compared with the electronic transitions energies known from literature and with the experimentally found 0.40 eV activation energy of conductivity. The sign reversal of the current during the switch-on/off of the 980 nm diode laser beam and of the applied voltage seems to originate from the electrooptic Pockels effect and to be connected with the dynamical disorder in the crystal. The appearance of the current confirm the generation and detrapping of charge carriers (polarons) by near IR (NIR) radiation. These data indicate the electret features of the crystal. The mechanisms of electric conductivity and optical nonlinearity in the solid m-NA are proposed.

The Positive Temperature Coefficient of Resistivity Effect in the Pb(Fe1/2Nb1/2)O3Ceramics Admixed with Lithium

In the paper technological conditions were looked for to obtain the Pb(Fe1/2Nb1/2)O3 (PFN) ceramics and the PFN ceramics with the lithium admixture with the highest electric conduction and conditions appropriate for the PTC-R effect formation. Measurements of dc electrical resistivity, dielectric permittivity and dielectric loss were made as functions of temperature from room temperature to 190◦C, at 1 kHz. The best set of values of dielectric loss and dielectric constant, from the ferroelectricity point of view, were obtained when the precursor with orthorhombic structure was employed. By creating appropriate technological conditions in the PFN ceramics the PTC-R effect can occur above the Curie temperature. Their electric properties are determined by presence of a basic phase of the potential barrier on the grain boundaries.

Design and air–water calibration of a waveguide connector for TDR measurements of soil electric permittivity in stony soils

Time Domain Reflectometry (TDR) is one of the most widely used methods for measuring soil water content. TDR determines water content by measuring the apparent relative electric permittivity of the soil or relative permittivity ( ɛ ra ), which is directly related to soil water. For TDR waveguides used in stony soils, the connection between the Trase TDR probe head (Model Trase System 6051X1, Soilmoisture Equipment Co., USA) and the waveguides can be difficult because of the lack of parallelism between the waveguides. Such a lack of parallelism is caused by the occurrence of a large amount of rock fragments in the soil profile, which produces air gaps and compression zones around the waveguides causing errors in the estimation of ɛ ra when the Trase TDR probe head is connected to the waveguides. For this reason, a new type of flexible connector that minimises the existing problems has been designed. The signal travel time correction factor t 0 , which accounts for signal travel in the designed flexible waveguide connector, and the electrical path length of the waveguide L e have been calibrated. In addition, a software for analysing the waveform obtained using the Trase TDR system has been developed. The calibration results were considered to be good and the sensitivity of soil water content values to the estimates of t 0 was low. Higher values of soil apparent electric permittivity were found when the waveform was measured with the flexible connector than when the Trase connector was used; mainly with the waveguides 150 mm long and when the soil water content in the superficial layer was high.

Investigation of Magnetoelectric Coupling in Single-Phase Multiferroic Ceramics

In this work, electrical permittivity measurements in lead iron niobate ceramics (PFN) were performed in the frequency and temperature range from 10 kHz to 1.2 GHz and from 15 K to 450 K, respectively. The microwave dielectric results revealed unambiguously the magnetoelectric effect in the PFN and demonstrated that the nature of such coupling arises indirectly via ferroelastic contribution rather than a direct coupling between electrical and magnetic order parameters. Moreover, it was also verified that such coupling can be enhanced or suppressed depending on the relative orientation between the probing electric field and the macroscopic polarization.

Nature of the magnetoelectric coupling in multiferroicPb(Fe1/2Nb1/2)O3ceramics

In this work, electrical permittivity measurements in lead iron niobate (PFN) ceramics were performed in the frequency and temperature ranges from 10 kHz to 1.2 GHz and from 15 to 450 K, respectively. The microwave dielectric results characterized unambiguously the magnetoelectric effect in PFN and demonstrated that the nature of such coupling arises indirectly via ferroelastic contribution rather than a direct coupling between electrical and magnetic order parameters. Moreover, it was also verified that such coupling can be enhanced or suppressed depending on the relative orientation between the probing electric field and the macroscopic ferroelectric polarization.