Dielectric Loss Angle Tangent Research Articles

Non-destructive detection of water adulteration level in fresh milk based on combination of dielectric spectrum technology and machine learning method

To rapidly realize the identification of fresh milk for water adulteration and to predict the amount of water adulteration, this study adopts a coaxial probe and a vector network analyzer to analyze the variation laws of dielectric constant ε', dielectric loss factor ε'' and dielectric loss angle tangent tanδ in the range of 2–20 GHz under 100 frequency points. Soft independent modeling of class analogy (SIMCA), Naive Bayes (NB), K-nearest neighbors (KNN), and support vector machine (SVM) models were built based on full dielectric spectra for qualitative testing of adulteration levels in milk. Feature variables of FDS were extracted by using the successive projections algorithm (SPA) and uninformative variables elimination (UVE). Partial least squares regression (PLSR), support vector regression (SVR), and particle swarm optimization least square support vector regression (PSO-LSSVR) models were built for quantitative testing of adulteration levels in milk. The results demonstrate an increasing trend of ε'' and tanδ with increasing frequency and a decreasing trend of ε'. The ε'-SIMCA model achieves the best effect in distinguishing water adulteration in milk, showing accuracy (ACC) of 1, Sensitivity (SNS) of 1, Specificity (SPC) precision (PRE) of 1, and an F1-score (F1) of 1. The tanδ-SPA-PSO-LSSVR model optimally predicts the optimal prediction effect of moisture content of milk, showing an RP2 of 0.994 and an RMSEP of 0.016 %. This study is conducive to building a more comprehensive knowledge system of water adulteration in fresh milk. Its results can provide a theoretical reference in the development of non-destructive detection instruments for natural milk.

Frequency dispersion of dielectric coefficients of MnGaInTe4 crystals

The frequency and temperature dependences of the tangent of dielectric loss angle as well as the real and imaginary part of the dielectric constant of MnGaInTe4 crystals are investigated in the frequency range of 102 to 106 Hz. The experimental values of the studied characteristics are determined. The real and imaginary parts of the permittivity are found to undergo significant dispersion, which has a relaxation nature. The main type of dielectric losses in MnGaInTe4 crystals in the frequency range of 102 to 106 Hz are the electrical conductivity losses. The conductivity is characterized by a zone-hopping mechanism. The activation energies of charge carriers are determined.

Multi-frequency composite wearable antenna for wireless communications

This paper proposes a multi-band composite wearable antenna for wireless communication, which uses a monopole structure as the radiating body and achieves multi-band characteristics through slit-loading and multi-branching methods. A polymer composite substrate with high dielectric constant and low dielectric loss was prepared using in situ polymerization, and the optimal dielectric constant and loss angle tangent were obtained by controlling the coating ratio of melamine formaldehyde resin to carbon nanotubes (MWCNTs) and the filler doping rate to achieve miniaturization of the antenna. Comparative experimental results show that the obtained composites have high flexibility and good dielectric properties. The antenna operates in the frequency bands of 2.21–2.52 GHz, 3.07–3.87 GHz, and 4.36–6.03 GHz, which cover the frequency bands of WLAN and WiMAX and 5G applications. The antenna was fabricated and tested, and its performance roughly matched the simulation results. Meanwhile, the antenna has passed the SAR safety test and maintained a stable performance under different curvatures, so it has potential applications in the wireless communication system.

PVDF/poly(3-methylthiophene)/MWCNT nanocomposites for EMI shielding in the microwave range

This work presents a new approach to enhance EMI shielding efficiency of nanocomposites of dielectric polymers, multiwalled carbon nanotubes (MWCNTs) and intrinsically conducting polymers for account of using core-shell morphology for conducting components. To realize this approach new ternary nanocomposites of poly(vinylidene fluoride) (PVDF), MWCNTs and poly(3-methylthiophene) doped by Cl− anions (P3MT) were prepared through synthesis of thermally stable core/shell nanocomposites PVDF/P3MT and MWCNT/P3MT. These binary nanocomposites were mixed with pure MWCNTs or PVDF followed by compression molding to prepare the ternary nanocomposites of different morphology to discriminate their EMI shielding properties in a wide frequency range (1–67 GHz). Values of the tangent of dielectric loss angle, the efficiency of transmission, reflection and absorption of microwave radiation, and shielding efficiency (SE) of the specified materials were found from analysis of spectral dependences of their complex dielectric constants. It was shown that while the melt mixing of the binary PVDF/P3MT nanocomposite with MWCNTs both in a pure state and in the binary nanocomposite (MWCNT/P3MT) expectedly strongly enhances SE of the former, this effect is non-linear and depends on presence/absence of the P3MT shell on the MWCNT core. The ternary nanocomposite PVDF/P3MT/MWCNT made of the binary polymer-polymer nanocomposite PVDF/P3MT and pure MWCNTs showed highest SE values at the frequencies above 4.5 GHz up to 68.4 dB at 67 GHz in the case of the 1 mm thickness sample. However, below 4.5 GHz the SE was higher in the case of the ternary nanocomposites containing core/shell MWCNT/P3MT nanocomposite instead of pure MWCNT.

Frequency domain spectroscopy analysis of superconducting cable during pre-cooling

A 1.2 km, 35 kV superconducting cable project has been built in Shanghai, China. In order to monitor the internal condition of the cable in real time, during the 15-day pre-cooling process, the Frequency Domain Spectroscopy (FDS) test at 0.1 Hz–1000 Hz was carried out, and the dielectric loss angle tangent (tanδ)-frequency curves at different temperatures were obtained. A special phenomenon is found: in the early stage of pre-cooling, tanδ is the largest at the lowest frequency and decreases with the increase of frequency; in the late stage of pre-cooling, it becomes that tanδ is the largest at the highest frequency and decreases with the decrease of frequency. According to the Dielectric Polarization Theory in the field of dielectric physics, it is believed that the above phenomenon occurs because the tanδ-frequency curve shifts to the low frequency direction with the decrease of temperature. The evaluation method of the pre-cooling process based on FDS is proposed. In the early stage of cooling, it is suitable to use high frequency tanδ to monitor, and in the late cooling stage, low frequency tanδ is suitable.

Broadband dielectric behaviour and structural characterization of PVDF/PMMA/OMMT polymer nanocomposites for promising performance nanodielectrics in flexible technology advances

Characterization of broadband dielectric behaviour of polymer nanocomposites (PNCs) is vital for the exploration of efficient nanodielectrics as energy storage, flexible dielectric substrates, and insulators in a wide range of advanced electronic device technologies. Accordingly, herein, PNC films based on poly(vinylidene fluoride) (PVDF)/ poly(methyl methacrylate) (PMMA) blend matrix (80/20 wt/wt%) dispersed with 0, 2.5, 5, and 10 wt% organo-modified montmorillonite (OMMT) nanoclay are developed by state-of-the-art homogenized solution casting method. These PVDF/PMMA/OMMT compositions based flexible PNC films are characterized in detail by employing a scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) device, x-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectrometer, differential scanning calorimeter (DSC), inductance-capacitance-resistance (LCR) meter, and impedance/material analyzer (IMA). The SEM microimages, XRD traces, and FTIR spectra evidenced appreciable homogeneity and surface morphology, intercalated and exfoliated OMMT structures, and the α, β and γ-phase crystallites of the PVDF in these complex semicrystalline PNCs. The DSC thermograms confirmed a significant alteration in the melting temperature and degree of crystallinity of the PVDF crystallites with the increased amount of OMMT in the 80PVDF/20PMMA blend host matrix. The broadband dielectric dispersion spectra over the frequency range of 20 Hz−1 GHz explained the contribution of interfacial polarization in the complex dielectric permittivity at lower experimental frequencies, whereas at higher frequencies permittivity is ruled by dipolar polarization in these composites at 27 °C. The dielectric loss angle tangent and electric modulus spectra revealed an intense structural dynamics relaxation process in the upper radio frequency region. The influence of OMMT concentration on the dielectric permittivity and electrical conductivity is explored. The detailed dielectric and electrical characterization of these innovative semicrystalline composites with important structural and thermal properties revealed their immense potential as high-performance nanodielectrics for highlighting current applications of broadband frequency range electrical and electronic device technologies.

Preparation of paraffin wax-modified floating aluminum powder and composite coating with infrared stealth and wave-transparent function

Low Infrared (IR) emissivity coatings in military aerospace need to meet both stealth and radar transmission. At present, there are few research on this aspect, therefore how to solve the compatibility problem of low infrared emissivity and high radar wave transmission rate of materials is an important direction for the development of infrared stealth materials. A multi-functional composite coating with low IR emissivity, dielectric loss, and antistatic properties was prepared using modified floating aluminum powder (Al@PW), short-cut carbon fiber, and ethylene propylene diene monomer (EPDM) as the binder. The coating's properties were investigated, highlighting the effect of PW. The results indicate that modifying floating Al powder with PW is an effective solution to the trade-off between low IR emissivity and high wave transparency. At a dosage of 11 g (about 12.5 wt% in Al@PW), the coating demonstrated the best overall performance, including the IR emissivity of 0.582, the surface resistivity of 9.5 MΩ/□, the dielectric constant of 5.15, the dielectric loss angle tangent of 0.052, the tensile strength of 11.75 MPa, and the elongation at break of 516.10%. The composite coating may be used as a multi-functional protective coating for airborne radomes.

Preparation of Discontinuous Cu/SiO2 Multilayers—AC Conduction and Determining the Measurement Uncertainty

This paper presents a test stand for testing alternating current electrical parameters of Cu-SiO2 multilayer nanocomposite structures obtained by the dual-source non-reactive magnetron sputtering method (resistance, capacitance, phase shift angle, and dielectric loss angle tangent δ). In order to confirm the dielectric nature of the test structure, measurements in the temperature range from room temperature to 373 K were carried out. The alternating current frequencies in which the measurements were made ranged from 4 Hz to 7.92 MHz. To improve the implementation of measurement processes, a program was written to control the impedance meter in the MATLAB environment. Structural studies by SEM were conducted to determine the effect of annealing on multilayer nanocomposite structures. Based on the static analysis of the 4-point method of measurements, the standard uncertainty of type A was determined, and taking into account the manufacturer's recommendations regarding the technical specification, the measurement uncertainty of type B.

The Investigation of the effect of laser radiation on the dielectric properties of polymethylmethacrylate

The problem of studying the interaction of laser radiation with polymer materials lies in the study of the effect of intense energy fluxes on matter. The effect of pulsed laser radiation on a high-molecular substance was studied from changes in the electrical parameters of the irradiated materials. Changes in ε’, tg δ depending on the frequency of the external field, the dose of laser irradiation, temperature and time were investigated by a highly sensitive physicochemical method -the method of dielectric losses. This article examined the impact of laser radiation on the dielectric properties of polymethylmethacrylate at frequency of 50 kHz within the temperature interval from 170 to 420 K. The authors showed that the processing of the samples with laser radiation leads to substantial changes in the dielectric constant and tangent of dielectric loss angle.

OBTAINING MANGANESE - DOPED BISMUTH FERRITE CERAMIC SAMPLES AND STUDYING THEIR PROPERTIES

A self-propagating high-temperature synthesis technology of manganese - doped bism¬u¬th ferrite has been developed. The best conditions for the preparation of the inital components mixture and synthesis are determined by X-ray phase analysis. The technological processes of obtaining ceramic samples and preparing ohmic contacts have been developed. Frequency dependence of dielectric permeability and loss angle tangent and volt-ampere characteristics are studied.

ANALYSIS OF STRUCTURAL CHANGES AND DIELECTRIC PROPERTIES UNDER THERMAL AGING OF CROSS-LINKED POLYETHYLENE USED AS POWER CABLES INSULATION

Cross-linked polyethylene polymer insulation is widely used as a raw material for insulation of cables. Polyethylene with added peroxide and silane is mostly used. Here, the mechanism of the change of the dielectric loss angle tangent was studied in the case of applying different voltages (in the range of 2-12 kV) to polyethylene samples with added silane and peroxide subjected to heat aging. Combined, i.e., the effect of both thermal aging and applied voltage on the tangent of the dielectric loss angle was investigated during measurements in the frequency range of 50-400 Hz. In the obtained results, it was observed that the value of the dielectric loss angle exceeds the effect of voltage, and the reasons for this increase are mentioned in the article. When we increase the aging period, peaks in the dielectric losses also appeared in the last periods. Also, in the article, the structural change of the insulation was studied by means of Fourier transform infrared spectra (FTIR).

Microstructure and gyromagnetic properties of low-sintered M-type barium hexagonal ferrite with various Ga3+ ions substitutions

The adjustment of crystal structures and properties by ion substitution has received increasing interest in recent years to solve issues related to the preparation of LTCC microwave devices. In this work, Fe3+ ions were substituted in BaFe12O19 sintered at a low temperature (920 °C). The changes in microstructures, dielectric characteristics, and magnetic properties were all examined. The ferromagnetic resonance linewidth (ΔH) of BaM ferrite was measured at magnetic fields from 6000 to 24,000 Oe. The results revealed well-grown microstructures of BaM ferrite grains at 920 °C to form typical hexagonal structures. The increase in substitution of Ga3+ ions decreased the lattice constant and cell volume of the crystals. More interestingly, the dielectric and magnetic properties depicted significant changes in the original dielectric and magnetic parameters of BaM after the substitution of Ga3+ ions. The permittivity (ε′) rose to a maximum of 16.36 at x = 0.4, while the dielectric loss angle tangent (tan δε) declined to 1.2 × 10^−3. As Ga3+ ions rose, the saturation magnetization 4πMs decreased from 3168.58 Gauss to 2571.18 Gauss. The remanence (Mr) reached a maximum value of 31.07 emu/g at x = 0.4. The ferromagnetic resonance linewidth (ΔH) of BaM ferrite sample at 31 GHz attained a minimum value of 4216.336 Oe at x = 0.8. In sum, these findings look promising for future fabrication of LTCC microwave RF devices.

Research on characteristic parameters for multi-factor aging of stator bar insulation of pumped storage generator

The real stator bars of an 18kV pumped storage generator were taken as research objects. The multi-factor sequential aging tests of thermal cycling, electrothermal and vibration were carried out. The dielectric loss angle tangent (tanδ), capacitance (C), Δtanδ, ΔC and maximum partial discharge of the samples at different aging periods were measured. The variation of these parameters with aging time was summarized, and the aging mechanism was analysed. The results show that tanδ, Δtanδ, and ΔC increase overall with aging time, while the capacitance decreases slightly with aging time. The maximum partial discharge decreases gradually at beginning of aging, and then increases after aging of 4 periods. All of tanδ, Δtanδ, ΔC and maximum partial discharge increase obviously in the later stages of aging. They can be used as characteristic parameters for multi-factor aging of stator bars insulation of pumped storage generators, to evaluate the aging state of the insulation with epoxy mica.

Influence of silicon carbide nanowires on the properties of Bi–B–Si–Zn–Al glass based low temperature co-fired ceramics

In this study, the performance of low-temperature sintered Bi–B–Si–Zn–Al glass/Al 2 O 3 /SiC nanowires composite fabricated by the tape casting method was systematically investigated. The thermal conductivity of the composite sintered at 900 °C for 2 h increased from 4.356 W/(mK) to 6.868 W/(mK) by incorporating 0.5 wt% SiC nanowires, and the dielectric constant and the dielectric loss angle tangent were 4.21 and 1.10 × 10 −2 at 25 GHz, respectively. The sintered sheet containing 0.5 wt% SiC nanowires had a low thermal expansion of 4.53 ppm/°C at 25 °C–200 °C. Microstructure and XRD analysis indicated the formation of ZnAl 2 O 4 crystal. The network model was introduced to analyze the enhancement of thermal conductivity when adding 1.25 wt% SiC nanowires. Such low-temperature co-fired ceramic (LTCC) may have a promising application in the field of electronic substrate.

Effect of sintering temperature on microstructure and magnetic and dielectric properties of M-type barium ferrites

In this study, the effect of sintering temperature on microstructure, magnetic properties and dielectric behavior of M-type barium ferrites (BaM) is systematically analyzed. BaBi0.45(CoTi)1.2Fe9.15O19 samples with a dense microstructure and typical hexagonal shape are obtained at the sintering temperature of 920 °C. Moreover, the permittivity (ε′) of BaM increases to 21.41 at 0.01 GHz and the permeability (μ′) increases to 10.82 at the optimized temperature of 920 °C. Based on mathematical fitting, the saturation magnetization (4πMs) of samples is calculated to be 3272.27 Gauss and the magnetocrystalline anisotropy constant K1 is found to be 4.18 × 106 erg cm−3. More interestingly, the magnetic loss angle tangent (tanδμ) is reduced to 2.7 × 10−1 and the dielectric loss angle tangent (tanδε) is reduced to 5.8 × 10−3. The optimized magnetic and dielectric properties, with low losses, enhance the suitability of BaM ferrites for miniaturized microstrip devices.

Пленочные полимерные композиционные пьезоматериалы для изготовления активных элементов звукопрозрачных конформных гидроакустических антенн

This paper describes manufacturing technology and main dielectric and electrophysical properties of a new polymeric composite piezomaterial, highlighting its advantages over conventional piezoceramics. The study also suggests a manufacturing technology for active elements of a long conformal emitter/receiver array. Polymeric composite piezomaterial discussed in this paper was based on polyvinyldenfluoride (PVDF) and piezoceramics of lead zirconate-titanate system (CTS). Its main properties given in this study are: frequency curves for dielectric (tangent of dielectric loss angle, relative dielectric constant, quality factor) ane electromechanic (tension piezomodulus, acoustic impedance) properties. Performance parameters of the active element given in this paper are: directional patterns at different frequencies, effective piezomodulus and frequency-piezosensitivity curve. The paper shows that this composite material is equal to conventional PVDF films in terms of its dielectric properties and compliance but offers better electromechanical parameters. Piezoconverter designs suggested in this study feature uniform frequencysensitivity diagram for both transmission and reception over the whole frequency band under investigation, as well as insensitivity to flow noise. New composite materials newly introduced to hydroacoustics also make these designs of receiving array elements insensitive to parasytic vibration of hull structures. The paper shows the advantages of the developed composite piezofilm as compared to conventional hydroacoustic piezoceramics. Piezofilms, including composite ones, are as sensitive as ceramics but more compact, less heavy and feature much greater specific area of reception. A promising approach would be to further increase piezomoduli of film-based materials keeping their acoustic impedance low, which would result in greater operational efficiency of receiving sonar arrays.

Effect of activated carbon/in situ synthesized magnetite hybrid fillers on the microwave properties of natural rubber composites

The purpose of the study is to synthesize nanosized magnetite in situ the nanosized porous texture of activated carbons and to examine the impact of the resulting hybrid filler upon the microwave properties and electromagnetic interference shielding effectiveness of composites based on natural rubber. The fillers have been characterized by X-ray diffraction and photoelectron spectroscopy establishing the influence of the magnetite layer on the texture characteristics. Studies have been carried out on the effect that the fillers synthesized have on the microwave properties, the real and imaginary part of the permittivity and permeability as well as on the dielectric and magnetic loss angle tangent of the composites. It has been found that filler comprising externally about 5% of magnetite phase is the most effective. The introduction of the magnetic phase contributes to the improvement in the microwave characteristics and expanding the frequency range in which the composites are of good microwave properties due to the combination of high dielectric and the high magnetic losses. Copyright © 2017 VBRI Press.

Effect of the cobalt ferrite and carbon fiber powder doping ratio on the electromagnetic properties of coated polyaniline-based polyester–cotton fabric

In this project, firstly, polyaniline-based polyester–cotton fabric was prepared by in situ polymerization using polyester–cotton fabric as the base fabric, aniline as the monomer, ammonium persulfate as the oxidizer, and camphor sulfonic acid as the dopant. Secondly, cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric was prepared by the textile coating process using polyaniline-based polyester–cotton fabric as the base fabric, PU2540-type polyurethane as the adhesive, and cobalt ferrite and carbon fiber powder as functional particles. Finally, the effect of the cobalt ferrite and carbon fiber powder doping ratio on the shielding effectiveness, reflection loss, dielectric constant real part, imaginary part, and loss angle tangent of cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric was studied by using the controlled variable method with emphasis on the cobalt ferrite/carbon fiber powder doping ratio. The results show that in the frequency range of 0.01–3.0 GHz, when the doping ratio of cobalt ferrite to carbon fiber powder is 0:3, the reflection loss of cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric reaches the minimum value at 1.49 GHz, the minimum reflection loss is –21.4 dB, and the effective absorption band is 1.25–1.94 GHz. In the test band, the shielding efficiency, reflection loss, the real part and imaginary part of the dielectric constant, and the loss angle tangent of the carbon fiber powder-coated polyaniline-based polyester–cotton fabric are larger than those of cobalt ferrite-coated polyaniline-based polyester–cotton fabric. The smaller the doping ratio of cobalt ferrite to carbon fiber powder, the larger value of the shielding efficiency, reflection loss, the real part and imaginary part of the dielectric constant, and loss angle tangent of the cobalt ferrite/carbon fiber powder-coated polyaniline-based polyester–cotton fabric.

Two-stage PVD method for protective coating formation

The CVD methods are typically used for the formation of aluminum oxide coatings since aluminum oxide is a dielectric. The adhesion between the protective coating and the substrate material is normally improved by growing thin intermediate layers based on titanium oxides and nitrides. These intermediate layers are mainly formed using the PVD methods. In this paper, we propose a two-stage PVD method for forming a layered structure on the titanium substrate. The formation of intermediate layers was carried out by the magnetron method (first stage), and the main protective layer was deposited at the second stage using a fore-vacuum electron source. The dense beam plasma generated during the electron beam transport in a fore-vacuum gas medium compensates for the negative electrical charge accumulating on the surface of the aluminum oxide target and facilitates its effective evaporation. The electrical properties of the intermediate layers and the resulting layered coatings have been investigated, including the tangent of dielectric loss angle, the real and imaginary parts of the conductivity and the dielectric constant dependencies on frequency.

Квантовые свойства диэлектрических потерь в нанометровых слоях твердых диэлектриков при сверхнизких температурах

Using the methods of quasi-classical kinetic theory, continuum electrodynamics, and non-relativistic quantum theory, we construct and study the quantum kinetic equation of proton relaxation, which, together with the Poisson operator equation describes the mechanism of diffusion tunneling transport of hydrogen ions (protons) in the potential field of a crystal lattice perturbed by a polarizing field (quantum diffusion polarization) in crystals with hydrogen bonds. Using the apparatus of the density matrix (statistical matrix), by complete quantum-mechanical averaging of the polarization operator, studies are carried out of the experimental value of the polarization of the dielectric, as a function of the parameters of the external electric field (amplitude, frequency of electromotive force) and temperature. When calculating the equilibrium density matrix for an ensemble of basic relaxers (hydrogen ions), the proton-proton and proton-phonon interactions are not taken into account, and the Hamilton operator for the phonon subsystem is assumed to be a numerical constant for a given crystal under given experimental conditions (calculated by computer method as a parameter for comparing the theory with the experiment). The influence of the phonon subsystem on the kinetics of the relaxation process is reduced to a weak spatially homogeneous force field acting on protons moving in the field of the main forces of hydrogen bonds. The Hamilton of the proton subsystem is constructed for the model of an ideal proton gas in equilibrium with the ionic subsystem of the crystal lattice, and the equilibrium statistical operator of the proton subsystem is written using the Boltzmann quantum statistics. Theoretically, the size effects are found to be manifested in shifts of the low-temperature (50–100 K) maxima of the dielectric loss angle tangent towards ultra-low temperatures (4–25 K) with a decrease in the amplitudes of the maxima by 3-4 orders of magnitude, with a reduction in the thickness of the crystal layer from 1–10 microns to 1–10 nm. The effect of anomalous displacements of low-temperature maxima, which is explained by the abnormally high quantum transparency of the potential barrier for protons (0.8-0.9) in thin films of a crystal with hydrogen bonds (1-10 nm), causes, near the temperatures of the shifted maxima of dielectric losses (4–25 K), a quasi-ferroelectric state, which is also characterized by abnormally high values of the real component of the complete dielectric permittivity (2.5–3.5millions).