Loss Angle Tangent Research Articles

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.

Rheological and Tribological Study of Polyethylsiloxane with SiO2 Nanoparticles Additive

Nowadays, much attention is paid to the creation of high-performance lubricants with improved properties through the use of ultrafine nanopowders. The paper shows the results of studying the viscoelastic properties of samples of silicon dioxide nanoparticle suspensions based on polyethylsiloxane (silicone oil) by the acoustic resonance method. The method is based on a study of the additional coupling effect on the resonance characteristics of the piezoelectric resonator. The values of the shear modulus and the tangent of the mechanical loss angle were calculated. The interaction between polymer molecules and nanoparticles was characterized by infrared spectroscopy. The influence of silicon dioxide nanoparticles (as a nano-additive) on the performance characteristics of polyethylsiloxane lubricant is presented. The results of determining the friction coefficient from the sliding speed show an increase in the tear strength of the lubricating film, leading to improved tribological properties.

Exothermic synthesis of ceramic materials based on the system Zn2SiO4‒RO (R ― Ba, Sr)‒Al2O3‒SiO2

The synthesis of ceramic materials in the Zn2SiO4‒RO (R ― Ba, Sr)‒Al2O3‒SiO2 system was carried out using the technology of exothermic synthesis from solutions including zinc, barium and strontium nitrates, silica and organic reducing agent (glycine and carbamide). It is shown that the implementation of an exothermic process followed by calcination at a temperature of 1000 °C contributes to the formation of crystalline phases of willemite (Zn2SiO4), barium aluminosilicates (BaAl2Si2O8) and strontium (SrAl2Si2O8). The dependence of the quantitative phase composition and parameters of the elementary cells of the crystalline phases is established. Sintering of synthesized materials occurs at a temperature of 1275 °C. The dielectric permittivity of sintered materials is 5,33‒6,06 and the tangent of the dielectric loss angle is 1,5·10‒3‒3,16·10‒3 at a frequency of 1 MHz, the minimum values correspond to ceramics based on the Zn2SiO4‒BaAl2Si2O8‒SrAl2Si2O8 triple system. Ill. 5. Ref. 19. Tab. 2.

DIELECTRIC PROPERTIES OF CERAMICS BASED ON BN–ZrB2 AND BN–ZrO2 PRODUCED BY SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS

Dielectric properties of ceramic materials based on BN–ZrB2 and BN–ZrO2 systems synthesized in the mode of self-propagating high-temperature synthesis (SHS) from a mixture of boron B powders, boron nitride BN and zirconium dioxide ZrO2 in an atmosphere of nitrogen N2 have been studied. The experimental results showed that ceramics synthesized from the initial mixture of (30B + 10ZrO2 + 60BN, wt. %) composition have permittivity (?) and tangent of the dielectric loss angle (tg) values of 2.63 and 0.006, respectively, at room temperature.

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.

Analysis of Thermomechanical Properties and the Influence of Machining Process on the Surface Structure of Composites Manufactured from Metal Chips with a Polymer Matrix.

Nowadays, the dynamic development of the entire market of composite materials is noticeable, which is very often associated with the need to use waste or recycled materials in their production. In the process of producing composites themselves, the easy possibility of shaping their mechanical and thermomechanical properties becomes apparent, which can be a big problem for materials with a homogeneous structure. For the tests, samples made of a combination of acrylic–phenolic resin with fine aluminum and brass chips were used. The tests were performed for composite samples produced by pressing. This paper presents the results of the DMTA method of the conservative modulus and the tangent of mechanical loss angle of the composite, a detailed stereometric analysis of the surface after machining, roughness parameters and volumetric functional parameters were performed. For the tested samples, changes in the values of the conservative modulus and the mechanical loss coefficient were recorded, which indicated significant differences for the composite with brass chips in relation to composites with aluminum chips. In the case of the composite with aluminum chips, slight changes in the conservative modulus were recorded in the glass transition phase and the elastic deformation phase at different frequencies. In contrast, for composites with brass, slight changes were recorded in the entire range of the course of the conservative module as a function of temperature when different excitation frequencies were applied. In relation to the polymer matrix, a significant increase in the value of the conservative modulus of composites was recorded in the entire temperature range of the test. Significant differences were recorded in the study of the surface of composites in the case of using different materials obtained after machining as fillers. The dependences of the amplitude parameters of the surface after machining the sample made of phenolic–acrylic resin prove the poor performance properties of the surface. The use of chips in the composite significantly changed the surface geometry.

Structure-dielectric property relations in (Al0.5Nb0.5)4+ co-doped Ca0.8Sr0.2TiO3 ceramics with excellent temperature stability

Ca0.8Sr0.2Ti1-x(Al0.5Nb0.5)xO3 (abbreviated as CSTANx) microwave dielectric ceramics were synthesized through the solid-state reaction. The effects of (Al0.5Nb0.5)4+ co-doping on the microstructure and dielectric behavior were systematically investigated, and the relationship between structure and property was discussed. All compositions exhibited a single orthorhombic phase with dense morphology. The doping of (Al0.5Nb0.5)4+ was beneficial to increasing the ordering at the B-site and inhibiting the reduction of Ti4+, which in turn reduced the dielectric loss. In addition, the temperature stability of relative permittivity and resonant frequency was significantly improved due to the limitation of relative permittivity as well as the distortion and tilting of BO6 octahedron. At 1 MHz, the variation of the relative permittivity (εr) for x = 0.6 composition was only 1% from 25 to 350 °C, and the loss angle tangent (tanδ) was below 0.003. Also, the x = 0.6 composition had the optimum microwave dielectric properties (εr = 45.7, Qf = 24,930 GHz, τf = + 3.1 ppm/°C). The results reveal that CSTAN0.6 ceramics can be used for communication devices such as resonators and filters.

Modelling of changes in the internal insulation parameters of high-voltage bushing to analyze the reliability of control under operating voltage

The article considers the modelling of changes in the parameters of the internal insulation of high-voltage bushings for the analysis of the reliability of control under operating voltage. The data of the actually installed input at the substation were used to model the parameters of the internal insulation of the high-voltage input. To assess the relationship between the dielectric losses of the capacitor-type input insulation and its condition, a substitution scheme was used, in which the active power is equal to the power dissipated in the input insulation, and the current is shifted relative to the voltage by the same angle as in this input. The modelled parameters are the capacity of the internal insulation of the input, the active resistance of the input and the resistance that simulates a change in the parameters of the internal insulation. The numerical value of the capacitive current through the insulation of the high-voltage input, the numerical value of the active current, the numerical value of the resistance, and the numerical value of the power loss for this input are calculated. A simplified high-voltage input insulation scheme has been developed. Losses were calculated and evaluated when the tangent of the dielectric loss angle was changed by 2%. The replacement scheme for isolating the high-voltage input without taking into account the possibility of changing the parameters is given. A model was built that allows you to take into account the change in input parameters, to which an additional resistance is connected in parallel. A resistive divider circuit was chosen as the circuit simulating the parameters because it provides sufficient accuracy, stability, and power. The method that was used to simulate the change in the parameters of the internal insulation of the capacitor-type high-voltage inputs can be recommended as an aid to the analysis of the sensitivity of the control device under the operating voltage of the inputs of power transformers.

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.

Effect of doping ratio and amount of polyaniline, cobalt ferrite, and carbon fiber powder on the electromagnetic properties of coated polyester-cotton fabrics

In this project, polyaniline powder was firstly prepared by in situ polymerization using aniline as the monomer, ammonium persulfate as the oxidant, and camphor sulfonic acid as the dopant. Next, polyester-cotton fabrics were used as the base fabrics, polyaniline, cobalt ferrite, and carbon fiber powder as the functional particles, and PU-2540 type polyurethane as the base, and single-layer coated polyester-cotton fabrics were prepared by the textile coating process. Finally, the effects of the polyaniline, cobalt ferrite, and carbon fiber powder doping ratio and functional particle content on the shielding effectiveness, reflection loss, real and imaginary parts of the dielectric constant, and loss angle tangent of single-layer coated polyester-cotton fabrics were focused on using the controlled variable method. The results show that in the frequency range of 0.01–3 GHz, when the doping ratio of polyaniline, cobalt ferrite, and carbon fiber powder is 1:0:3, and when the content of functional particles is 40%, the minimum reflection loss of single-layer coated polyester-cotton fabrics is –22.1 dB at 1.6 GHz, and the effective absorption bandwidth is 1.14 GHz.

Diagnostics on the Basis of the Frequency-Temperature Dependences of the Loss Angle Tangent of Heavily Moistured Oil-Impregnated Pressboard

The aim of this study was to perform precision measurements of the frequency-temperature dependences of the loss angle tangent of the liquid-solid composite with the FDS Dirana meter. The composite consisted of heavily moistered oil-impregnated pressboard. The moisturization of the pressboard occurred in a manner as close as possible to the process of wetting the insulation in power transformers to a moisture content of (5.0 ± 0.2) wt. %. This value of moisture content was chosen because exceeding this value can lead to transformer failure. The measuring temperature range was from 293.15 K (20 °C) to 333.15 K (60 °C), with a step of 8 K. The measuring frequency range was 0.0001 Hz to 5000 Hz. It was observed that the shape of the frequency dependence of the loss angle tangent for a moisture content of 5.0 wt. % does not depend on the value of the measuring temperature. An increase in temperature leads to a shift of the waveforms into the higher frequency region. This is associated with a decrease in the relaxation time, and its value depends on the activation energy. It was found that a good fit of the waveforms, simulated by Dirana, to the actual tgδ waveforms obtained at temperatures between 293.15 K (20 °C) and 333.15 K (60 °C) requires the introduction of temperatures, higher than the actual insulation temperatures, into the program. It was found that estimating the moisture content for different temperatures using Dirana soft-ware for insulating an oil-impregnated pressboard produced large discrepancies from the actual content. Better results were obtained after an adjustment requiring manual temperature correction towards higher, compared to measured, temperatures. The moisture content estimated after correction by the Dirana meter ranges from of 4.5 wt. % to 5.7 wt. % and increases almost linearly with increasing measuring temperature. The average moisture content estimated by the Dirana meter for all measuring temperatures is 5.1 wt. % and is close to the actual content (5.0 ± 0.2) wt. %. The uncertainty of the estimate is ±0.43 wt. % and is more than twice as high as the true value.

Моделирование диэлектрических характеристик синтактных материалов

Syntactic materials (spheroplastics) having low density due to structural features, depending on the material of the microsphere walls can have a sufficiently high strength and low thermal conductivity, which makes them promising for use as heat insulation materials. By selecting the material of the microsphere walls and the concentration of the components of the spheroplastics, their dielectric characteristics can be significantly changed. In this work, the task of modeling the effective dielectric characteristics of a syntactic material with a polymer binder and filler in the form of hollow glass microspheres is considered, taking into account the presence of technological impurities in the material. A model for calculating the effective permittivity of a sample of a syntactic material was proposed, based on a model of a matrix composite with several types of inhomogeneous or homogeneous inclusions. To calculate, a generalized effective-field approximation for a heterogeneous medium with coated inclusions was used. Model calculations were carried out for syntactic foam with an organosilicon binder polydime-thylsiloxane and hollow microspheres with E-glass shell with some moisture presence in the material. Frequency dielectric characteristics of this material were obtained in the range of 102–1010 Hz. It has been shown that an increase in the volume fraction of hollow microspheres leads to a decrease in the dielectric constant and the tangent of the dielectric loss angle. It has also been shown that the calculated values are in satisfactory accordance with the experimental data obtained at an electromagnetic field frequency of 9.8 GHz.

Flotator Oxal as the plasticizer for suspension PVC

Flotator Oxal, a mixture of dioxane ethers and alcohols, was studied as a plasticizer for suspension PVC in comparison with the well-known dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DOP). The rheological parameters and gelation ability of the plasticizers were determined, and the values of the storage modulus and tangent of mechanical loss angle in the glassy and rubbery states were measured by the DMA method, and the glass transition temperatures were determined. The deformation-strength properties and rigidity of polymer films were tested before and after light-thermal aging. Oxal was shown to reveal a fairly low viscosity and high gelation properties in relation to PVC. At the same time, its ability to reduce the glass transition temperature and elasticize the polymer in the glassy and rubbery state is somewhat lower than that of phthalate plasticizers. PVC samples plasticized with DBP have the highest resistance to light-thermal aging.

Поляризационные процессы в пленках йодида серебра вблизи температуры суперионного фазового перехода

The article reports the results of dielectric spectroscopy analysis exploring polarization processes in silver iodide nanocrystalline films in the region of thermal superionic phase transition. It also provides calculations of the system’s relaxation and energy parameters. The abrupt change of parameters at the transition point is demonstrated by activation energy of semiconductor conduction and commit phases, indicator of the degree of frequency dependence of conductivity, and the maximum value of the function of the tangent of the dielectric loss angle. The article proposes a model of the micro-mechanism of the thermal phase transition from a semiconductor to a superionic state. It is shown that, along with the superionic phase transition, films undergo a percolation phase transition with the formation of a two-dimensional percolation cluster.

IMPROVEMENT OF METHODS FOR DIAGNOSING AN OIL-FILLED HIGH-VOLTAGE COUPLING CAPACITOR

Oil-filled high-voltage capacitors are used in high-frequency electrical communication systems, the reliability of which is highly demanding. The article is devoted to the improvement of procedures for diagnosing an oil-filled high-voltage coupling capacitor by using methods of gas chromatographic determination of the content of dissolved diagnostic gases in mineral condenser oils. The aim of the work is to increase the reliability of the technical diagnostics results of electric capacitor communication type SMA-166V3- 14UHL1 to monitor its technical condition, determine the location and causes of failure, predict technical condition and clarify the possibility of maintenance and repair. The following studies were performed: electrical characteristics and thermal field characteristics of the communication capacitor; properties of condenser oil after disassembly of the condenser. The following parameters are determined: for the coupling capacitor - the tangent of the dielectric loss angle, electric capacitance and its changes, electrical resistance; for condenser oil - electric breakdown voltage, dielectric loss tangent, flash point in a closed crucible, density, moisture content, acid number, presence of mechanical impurities, hydrogen solubility, dissolved diagnostic gases content, antioxidant additive and furan compounds. The obtained results allow to increase the reliability of the results of diagnosing the technical condition of oil-filled electric capacitors in connection with the use of traditional and additional methods of diagnosing high-voltage electrical equipment filled with mineral oils.

Crystal structure, microstructure, piezoelectric and dielectric properties of high-temperature piezoceramics Bi-=SUB=-3-x-=/SUB=-Nd-=SUB=-x-=/SUB=-Ti-=SUB=-1.5-=/SUB=-W-=SUB=-0.5-=/SUB=-O-=SUB=-9-=/SUB=- (x=0, 0.1, 0.2)

A new series of perovskite-like oxides Bi3-xNdxTi1.5W0.5O9 (x=0, 0.1, 0.2) has been synthesized by the method of high-temperature solid-state reaction. The X-ray diffraction study showed that the compounds are single-phase and have the structure of the family of Aurivillius phases with parameters close to the orthorhombic unit cell corresponding to the space group A21am. The relative permittivity ε/ε0 and loss angle tangent tgsigma are measured as functions of temperature at different frequencies. The piezoelectric modulus d33 was measured for the synthesized compounds. The microstructure of Bi3-xNdxTi1.5W0.5O9 (x=0, 0.1, 0.2) was obtained. The study of the microstructure shows that the crystallites have a shape characteristic of Aurivillius phases. Keywords: Aurivillius phases, Bi2.8Nd0.2Ti1.5W0.5O9, activation energy Ea, Curie temperature TC.

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.

НИЗЬКОТЕМПЕРАТУРНА ІОННО-ПЛАЗМОВА ТЕХНОЛОГІЯ ОСАДЖЕННЯ НАНОСТРУКТУРОВАНИХ ПЛІВОК НІТРИДУ АЛЮМІНІЮ ТА БОРУ

A low-temperature (substrate heating temperature up to 400 °C) ion-plasma technology for the formation of nanostructured AlN and BN films by the method of high-frequency reactive magnetron sputtering of the corresponding targets has been developed (the modernized installation "Cathode-1M"), which has in its technological cycle the means of physical and chemical modification, which allow to purposefully control the phase composition, surface morphology, size and texture of nanocrystalline films. The possibility of using the method of high-frequency magnetron sputtering for deposition of transparent hexagonal BN films in the nanoscale state on quartz and silicon substrates is shown. Atomic force microscopy (AFM) has shown that AlN films can have an amorphous or polycrystalline surface with grain sizes of approximately 20-100 nm, with the height of the nanoparticles varying from 3 to 10 nm and the degree of surface roughness from 1 to 10 nm. It was found that the dielectric penetration of polycrystalline AlN films decreases from 10 to 3.5 at increased frequencies from 25 Hz to 1 MHz, and the peak tangent of the dielectric loss angle reaches 0.2 at 10 kHz. Such features indicate the existence of spontaneous polarization of dipoles in the obtained AlN films. Interest in dielectric properties in AlN / Si structures it is also due to the fact that there are point defects, such as nitrogen vacancies and silicon atoms, which diffuse from the silicon substrate during synthesis and play an important role in the dielectric properties of AlN during the formation of dipoles. The technology makes it possible, in a single technological cycle, to produce multilayer structures modified for specific functional tasks with specified characteristics necessary for the manufacture of modern electronics, optoelectronics and sensorics devices. It should also be noted that the technology of magnetron sputtering (installation "Cathode-1M") is highly productive, energetically efficient and environmentally friendly in comparison with other known technologies for creating semiconductor structures and allows them to be obtained with minimal changes in the technological cycle.