Loss Factor Values Research Articles

Enhanced Dielectric Properties of Sintered MgFe1.98Nd0.02O4 Nanoparticles

Spinal MgFe1.98Nd0.02O4 was prepared by simplified sol-gel method. To measure the dielectric properties samples were sintered from 700-800 oC in the steps of 50 oC. The sample’s phase purity, crystallographic phase and crystallite size was measured by X-ray diffraction method (XRD). The pellets were analyzed in Scanning Electron Microscope for their surface morphology and grain shape. Dielectric properties were measured from 20 Hz to 3 MHz at room temperature. Samples sintered at 750 oC, showed highest value of AC conductivity which indicated that the material is suitable for use in sensors. However, minimum value of dielectric loss factor was obtained at 800 and#176;C which makes it more suitable for antenna applications.

Enhanced Dielectric Properties of Sintered MgFe1.98Nd0.02O4 Nanoparticles

Spinal MgFe1.98Nd0.02O4 was prepared by simplified sol-gel method. To measure the dielectric properties samples were sintered from 700-800 oC in the steps of 50 oC. The sample’s phase purity, crystallographic phase and crystallite size was measured by X-ray diffraction method (XRD). The pellets were analyzed in Scanning Electron Microscope for their surface morphology and grain shape. Dielectric properties were measured from 20 Hz to 3 MHz at room temperature. Samples sintered at 750 oC, showed highest value of AC conductivity which indicated that the material is suitable for use in sensors. However, minimum value of dielectric loss factor was obtained at 800 and#176;C which makes it more suitable for antenna applications.

Dielectric properties of superparamagnetic titanium doped nanophased Mn–Zn ferrites for high frequency applications

Effect of Ti4+ ions on Structural, Dielectric and Magnetic properties of nanophasedMn0.5Zn0.5TixFe2–4x/3(x = 0.0, 0.01, 0.02,0.03, 0.04 and 0.05) ferrites synthesized by hydrothermal method is studied. XRD peaks reveal pure spinel phase without extra peaks. Lattice parameter (a) is found to vary non-linearly with dopant concentration (x). An overall decrease in Crystallite Size (D) (varying from 78 nm–41 nm) with x is witnessed. Values of dielectric constant () and loss factor (tan δ) of Ti4+ doped Mn–Zn ferrites are lower than that of the undoped sample. Increase of AC resistivity (ρ) by an order of 10 in Ti4+ doped Mn–Zn ferrites is ensued due to locking of Ti4+–Fe2+ pairs. Lowered values of Ms is attributed to spin canting due to growth of nanosized grains, weakening of exchange interactions by non-magnetic Ti4+ doping and lower values of x-ray density. Transition from single to multi- domain region of Mn–Zn–Ti ferrites is clearly evinced from the plot of Coercivity (Hc) with D. Reduced value of coercivity to zero upto a critical size of ∼49 nm indicates the existence of superparamagnetism in these ferrites. Superparamagnetismis first ever reported in the present caseof Ti4+ doped Mn–Zn ferritessynthesized by hydrothermal method. Relatively lowered values of (29–18), tan δ (of the order of 10–2–10–3), higher values of ρ (106 Ω—cm) and lowered values of Hc obtained with Ti4+ doping improve the eddy current losses and direct these materials for high frequency applications.

Dopants Effect on Dielectric Response of (CuTl)0.5Ba2(CaMg)Cu3−xAxO10−δ Superconducting Phase

(CuTl)0.5Ba2(CaMg)Cu3−xAxO10−δ; (x = 0 and 1.5, A = Zn, Ni and Cd) superconducting phase was prepared by a two-step solid-state reaction. X-rays diffraction spectra confirmed the orthorhombic crystal structure of this phase. The ac-conduction mechanism in (CuTl)0.5Ba2(CaMg)Cu3−xAxO10−δ phase was explored via dielectric measurements in the frequency range from 40 Hz to 100 MHz at different temperatures from 77 to 287 K, respectively. The maximum values of the real part of the dielectric constant ($$ \varepsilon_{{r({{\rm Max}} .)}}^{\prime } $$) and imaginary part of the dielectric constant ($$ \varepsilon_{{r({{\rm Max}} .)}}^{\prime \prime } $$) at 40 Hz were increased with Zn and Cd doping, and their values were slightly decreased with Ni doping at Cu sites in CuO2 planes as compared to the undoped pure (CuTl)0.5Ba2(CaMg)Cu3O10−δ sample. But, a decreasing trend was observed in the values of $$ \varepsilon_{{r({{\rm Max}} .)}}^{\prime } $$ in Zn- and Cd-doped samples and an increasing trend was observed in the values of $$ \varepsilon_{{r({{\rm Max}} .)}}^{\prime } $$ in Ni-doped and pure samples with increase in temperature, while the opposite trend was observed with increasing temperature in the values of $$ \varepsilon_{{r({{\rm Max}} .)}}^{\prime \prime } $$ with respective dopants. The overall decrease in the maximum values of the tangent loss (tanδ) factor was observed in all doped samples as compared to the undoped pure sample. The maximum value of tanδ was increased in Zn- and Cd-doped samples and was decreased in pure and Ni-doped samples with increase in temperature. The maximum values of ac-conductivity {σac(Max.) (Ω cm)−1} were increased with Zn and Cd doping, and their values were slightly decreased with Ni doping at Cu sites in CuO2 planes as compared to the undoped pure sample. The values of σac(Max.) (Ω cm)−1 were observed to increase with increase in temperature in all the samples.

Effects of secondary particle size distribution on the magnetic properties of carbonyl iron powder cores

The effects of secondary particle size distribution on the electromagnetic properties of the carbonyl iron powder cores have been investigated in this work. For preparing the cores, the iron powders were firstly undergone insulation treatments including phosphorization and organic coating. After granulation, the secondary particles with different size distributions were molded into the final shape and cured at 200 °C. The results show that for the secondary particles with unimodal size distribution, the real part of the complex magnetic permeability of the powder core is in inverse proportion to the particle size. For the cores prepared from the secondary particles with bimodal size distribution, the effects of the size ratio and volume ratio of the coarse particle/fine particle on the magnetic properties are discussed. It is found that the permeability increases with the increasing volume of fine secondary particles. The minimum magnetic loss factor value is obtained at the coarse/fine secondary particles volume ratio of 7:3. The density and magnetic properties including complex permeability and magnetic loss of the cores prepared with coarse/fine particles size ratio of ~3 and ~7 are both in inverse proportional to the volume fraction of coarse secondary particles. The present work indicates that a reasonable size distribution of the secondary particles is required to improve the magnetic properties of the soft magnetic powder cores.

Estimation of coupling loss factors for rectangular plates with different materials and junctions

In statistical energy analysis, coupling loss factor is the essential parameter for vibro-acoustic analysis of complicated structures. The coupling loss factors have been estimated using energy-level difference method. The tightening torque applied at structural junction has been varied. Higher values of coupling loss factor have been observed for higher tightening torque on bolted junction. The coupling loss factors have been determined for various structural junctions of rectangular composite plates. The riveted and bolted junctions have been examined for composite plates in same plane and size. The coupling loss factors for bolted junction are relatively higher than that for riveted junction of composite plates. The values of coupling loss factors are found to increase with increasing tightening torque applied at structural junctions of composite plates. It is also noted that the experimental results of coupling loss factors for point junctions vary with changes in fiber orientations of composite plates. It is firmly believed that the various findings of the coupling loss factors in this article help for vibro-acoustic analysis of complicated structures.

Effect of blend ratio and compatibilisation on the electrical and dielectric properties of nylon copolymer (6, 66)/EPDM rubber blends

In this work, morphological, electrical, and dielectric performance of nylon copolymer (PA6, 66)/ethylene propylene diene rubber (EPDM) blends were systematically studied with reference to blend ratio and compatibilisation. As the concentration of PA6, 66 and the percentage of compatibiliser in the blend increases the resistivity values decreases. The existence of two phases, PA6, 66 and EPDM with different conductivity and interfacial polarization are responsible for the increase in the dielectric properties of the blends. Compatibilisation of the blends improved the dielectric constant of the blend system. Addition of 2.5% of compatibiliser gave the highest value of dielectric constant. At a high concentration of EPM‐g‐MA, the polarity of the compatibilised blends was found to be increased, which resulted in the substantial increase in the value of loss and dissipation factor. The dielectric values of the blends were correlated with blend phase morphology. Finally the experimental data was compared with various theoretical predications. POLYM. ENG. SCI., 59:2195–2201, 2019. © 2019 Society of Plastics Engineers

The determination of measurement errors in impedance spectroscopy

The paper deals with the methodology, quantification and comparison of measurement deviations for two types of the ceramic shard. The ceramic material has better polarization properties than concrete material. For impedance measurement the ceramic shard is more appropriate. The IS method diagnostics based on processing of measured data which aims evaluating the absolute error and the relative error (deviation) of the loss factor values. Results show the spectrum parts which are useful in the lower frequency range only. When Agilent 33220A and Agilent 54645A are used to carry out the IS, the most important factor from the viewpoint of the tgδ(f) determination accuracy is the accuracy of the phase shift between the excitation signal and that at the measured system output. Other factors are the measurement accuracy of the electric capacity and resistance of the oscilloscope input channel.

Multistable Cosine-Curved Dome System for Elastic Energy Dissipation

This paper presents a new energy dissipation system composed of multistable cosine-curved domes (CCD) connected in series. The system exhibits multiple consecutive snap-through and snap-back buckling behavior with a hysteretic response. The response of the CCDs is within the elastic regime and hence the system's original configuration is fully recoverable. Numerical studies and experimental tests were conducted on the geometric properties of the individual CCD units and their number in the system to examine the force–displacement and energy dissipation characteristics. Finite element analysis (FEA) was performed to simulate the response of the system to develop a multilinear analytical model for the hysteretic response that considers the nonlinear behavior of the system. The model was used to study the energy dissipation characteristics of the system. Experimental tests on 3D printed specimens were conducted to analyze the system and validate numerical results. Results show that the energy dissipation mainly depends on the number and the apex height-to-thickness ratio of the CCD units. The developed multilinear analytical model yields conservative yet accurate values for the dissipated energy of the system. The proposed system offered reliable high energy dissipation with a maximum loss factor value of 0.14 for a monostable (self-recoverable) system and higher for a bistable system.

Facile Fabrication of a Novel PZT@PPy Aerogel/Epoxy Resin Composite with Improved Damping Property.

A novel lead zirconate titanate@polypyrrole (PZT@PPy) aerogel (PPA) was fabricated via in-situ polymerization and subsequent freeze-drying method. The porous PPA was then saturated with epoxy resin to obtain the PPA/epoxy composite (PPAE) by a simple vacuum filling method. In this way, the filler content and dispersion uniformity are well guaranteed, which is in favor of improving the damping and mechanical properties of composites. The morphology and structure of PPAs were investigated using XRD, SEM, EDS and nitrogen absorption and desorption measurements. The results showed that the PPA possessed a three-dimensional porous structure with uniform lead zirconate titanate (PZT) distribution. The influence of PZT content on the damping property of PPAE composite was investigated by dynamic mechanical analysis (DMA). PPAE-75 (i.e., the mass ratio of PZT to PPy is 75 wt %) exhibited the maximum damping loss factor value, 360% higher than that of the epoxy matrix, suggesting good structural damping performance.

Artificial neural network approach for locomotive maintenance by monitoring dielectric properties of engine lubricant

In this paper, we proposed an approach for locomotive maintenance systems by observing engine lube oil. The mechanical particles in lube oil give information about locomotive engine system condition. The engine lubricant is monthly monitored by a spectral analyzer (SA) to detect engine system failure and routine maintenance time. However, this old fashioned technique has many disadvantages such as non-real time measuring, high cost and time consumption. A novel approach is proposed to eliminate these disadvantages. The new method determines the lubricant sample conditions with respect to electrical characteristics by using artificial neural network (ANN). The study focuses on a relationship between mechanical particles (in ppm) and dielectric characteristics of the lube oil samples. Therefore, ANN method is applied to observe linear relation between observed and predicted dielectric constant and loss factor values of the engine oil samples. The electrical characteristics of the samples are observed at four frequency points (2.40 GHz, 5.80 GHz, 7.40 GHz and 9.60 GHz). ANN studies are realized by using data at these frequency points. The regression (R) coefficients are obtained as 0.7239, 0.7951, 0.8513 and 0.7463 for dielectric constant and 0.7627, 0.7196, 0.8015 and 0.7334 for dielectric loss, respectively. Moreover, the mean square error (MSE), mean absolute error (MAE) and mean absolute percentage error (MAPE) are calculated and examined. The obtained results are very sufficient and this approach can be applied to a sensor device having low cost and real time working mechanism in the future.

Stability Study of a Sandwich Beam with Asymmetric and Non-uniform Configuration Supported Viscoelastically Under Variable Temperature Grade

The end conditions, temperature gradient and geometric parameters affect the system stability. This research work concerns with the parametric instability study of a non-uniform asymmetric sandwich beam supported viscoelastically at the ends acted upon by a harmonic axial load and a variable temperature grade which is more appropriate along with a constant temperature grade. Hamilton’s energy principle is used to develop the equations of motion and associated end conditions. Then the non-dimensional form of the equation of motion is obtained. Galerkin’s process is used to find a set of Hill’s equations. The parametric instability regions are acquired by means of Saito-Otomi conditions. The consequences of taper parameter, uniform as well as variable temperature grade, shear parameter, spring parameters and spring loss factors on the instability regions are examined and represented by a number of plots. The results reveal that rise in the values of thermal gradient for bottom layer and shear parameter, make the beam more stable against harmonic load. Increase in the values of taper parameters and thermal gradient for top layer reduce the flexural rigidity of the system, hence worsen the system stability. The dynamic instability of the system reduces with increase in the values of spring loss factors and spring parameters.

Investigation of dielectric properties, total phenolic content and optimum formulation of microwave baked gluten-free cakes.

This study discusses the production of microwave baked gluten-free cakes formulated by mixing buckwheat flour and rice flour at different concentrations. Three different ratios of buckwheat flour to rice flour (20:80%, 30:70%, 40:60%) and two different gum types (xanthan and guar gum) with a white layer cake recipe were employed. The batters were baked in microwave oven at different microwave powers (540W, 450W, 360W) for different baking times (3min, 3.5min, 4min). The effect of microwave power, baking time and buckwheat flour concentration on weight loss, color, specific volume, porosity, total phenolic content and dielectric properties were investigated. The optimum microwave power, baking time and buckwheat flour concentration were found as 432.77W, 3min, 40% for guar gum added cakes and 360W, 3.70min and 29.23% for xanthan gum added ones. It was found that weight loss and color values of the cakes that were baked at the optimal conditions were less than those of control cakes. On the other hand, total phenolic content, specific volume, porosity, dielectric constant and dielectric loss factor values were higher for guar gum added cakes compared to control samples. In addition, it was observed that the cakes prepared with guar gum had similar pore size distribution with control cakes. As a conclusion of the study, it can be declared that surface color and specific volume problems of microwave baking could be solved by addition of guar gum to the formulation which also enables the production of functional, phenolic rich microwave baked cakes.

Detection of Artificially Water-Injected FrozenOctopus minor(Sasaki) Using Dielectric Properties

A few importers of marine products have practiced the fraud of artificially injecting water intoOctopus minorfor increasing their weights prior to the freezing process. These rampant practices have recently become a serious social issue and threaten public health. Therefore, it is necessary to develop the detection method for artificially water-injected frozenOctopus minor. This study was conducted to develop the nondestructive method for verifying adulteratedOctopus minorby measuring dielectric properties using the coaxial probe method. Regardless of weight and measurement locations, a significant difference betweenεvalues from normal octopuses was not observed. Theεvalues ofOctopus minorwere decreased in the microwave frequency range between 500 and 3000 MHz. Theεvalues of water-injected octopuses also showed similar trend with normal octopuses; however, the dielectric loss factor (ε″) values of adulterated octopuses were much lower than normal octopuses. After thawing normal, adulterated, and imported frozenOctopus minor, theεvalues measured at the trunk part from these octopuses were compared and statistically analyzed. Theε″values from normal frozen octopus were significantly different from adulterated and imported frozen octopuses. In addition, theε″values from the adulterated frozen octopus group that weight gain rate was less than 20% was significantly different from other adulterated octopus groups with higher weight gain rate than 20%. Theε″values from adulterated frozen octopus groups with the range of weight gain rate between 20 and 30% were quite similar to imported frozen octopuses. Therefore, it was found that the measurement ofε″values fromOctopus minorhas a great possibility to distinguish normal frozen octopuses and artificially water-injected frozen octopuses.

Chemical durability, electrical and dielectric properties of the ternary system (50-x)K2O–xMnO–50P2O5 phosphate glasses

Abstract K2O–MnO–50P2O5 glasses containing different concentrations of MnO ranging from 20 to 35 mol % have been prepared using conventional melt-quenching technique. The amorphous nature of the samples was asserted by X–ray diffraction. The chemical durability of these glasses increases with rising MnO content. Glasses containing more than 30 mol%MnO had an excellent chemical durability. The electrical and dielectric parameters were measured in the frequency range from 10 KHz to 1 MHz in the temperature range from room temperature to 550°C. It was observed that the values of ac conductivity augment on increasing frequency. The conductivity of all the glasses increases with temperature following the Arrhenius law. Activation energy was found to increase with raise in concentration of manganese oxide and decrease with the increase in the frequency. It was also observed that the values of dielectric constant and loss factor enhance with the increase in temperature and decrease with increase in frequency in all the glasses studied. These results agree with a closer structure and act in a manner that Mn2+ enters the glassy matrix as a network former character

SiO2 nanoparticles doped nematic liquid crystal system: An experimental investigation on optical and dielectric properties

The aim of this work is to investigate the effect of silica (SiO2) nanoparticles (NPs) on optical and dielectric properties of BBEA nematic liquid crystal (NLC). For optical analysis the photoluminescence (PL) and UV-absorbance experiments have been performed. The doped system is showing enhancement in the intensity of photoluminescence with varying concentration of nanoparticles. A red shift is observed in the emission spectra of NLC doped with silica nanoparticles. The PL emission peak of NLC is observed at 377.3 nm which is shifted to 379.7 nm in the presence of silica nanoparticles. We have also observed the enhancement in the value of UV absorption for silica doped systems in comparison to the pure system. Energy band gap of pure and doped systems has been calculated and it is found that the energy band gap is decreasing with concentration which is a promising result of this study. The dielectric parameters of the pure and doped NLC systems were carried out as a function of frequency and temperature. Different dielectric parameters such as relative permittivity, loss factor and dielectric conductivity have been measured. The pure and silica nanoparticles doped systems has shown decreased value of dielectric permittivity and loss factor at lower frequency region and at higher frequency regions these values became constant. The value of relative permittivity also decreases with concentration. The increased value of a.c. conductivity for doped systems can be utilized in device designing. Moreover, the temperature dependence of the birefringence (Δn) was determined from the transmitted intensity of light for pure and doped systems and the improvement in its value for both composites has been observed. Improved value of birefringence has pronounced applications in optical devices.

Effects of carbon fiber modification with multiwall CNT on the electrical conductivity and EMI shielding effectiveness of polycarbonate/carbon fiber/CNT composites

ABSTRACTThe effect of carbon fiber (CF) modification with multiwall carbon nanotube (CNT) on the electrical, mechanical, and rheological properties of the polycarbonate (PC)/CF/CNT composite was investigated. The CF and multiwall CNT (MWCNT) were treated with sulfuric acid and nitric acid (3:1 wt %) mixture, to modify the CF with the CNT. For the PC with acid‐treated CNT (a‐CNT) modified acid‐treated CF (a‐CF) (PC/a‐CF/a‐CNT) composite, the electrical conductivity, and the electromagnetic interference shielding effectiveness (EMI SE) showed the highest values, compared with those of the PC/a‐CF and PC/a‐CF/CNT composites. The EMI SE of the PC/a‐CF (10 wt %)/a‐CNT (0.5 wt %) composite was found to be 26 (dB at the frequency of 10.0 GHz, and the EMI SE was increased by 91.2%, compared to that of the PC/a‐CF composite at the same amount of total filler content. Among the composites studied in this work, the PC/a‐CF/a‐CNT composite also showed the highest values of relative permittivity (εr) and dielectric loss factor. The above results suggest that the CF modification with the a‐CNT significantly affected the electrical conductivity and EMI SE of the composite, and the hybrid fillers of the a‐CNT and a‐CF resulted in good electrical pathways in the PC/a‐CF/a‐CNT composite. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47302.

Loss Factor of Elastomeric Dampers for Rotating Machinery Application

Elastomeric dampers have potential application in rotating machinery vibration control. They are however not widely used due to lack of reliable data on their loss factor. Most available data on these dampers are obtained from testing undertaken during stationary condition of the shaft. When the shaft rotates, the dampers are subjected to rotating load that may affect their loss factor. The effect of shaft rotation on the loss factor is experimentally examined in this work. Impact test was used to determine the frequency response function (FRF) of the dampers. For the dampers subjected to rotating load, the loss factor values derived from the FRF was found to be in good agreement with those determined from the half-power bandwidth method. The results further showed that the loss factor at resonant frequency determined from testing of the dampers under stationary shaft condition underestimates the values of the loss factor when the shaft is rotating. The effect of shaft rotation on the values of the damper’s loss factor was more noticeable for the response in the X-direction as opposed to the Y-direction, indicating that pre-strain plays a more dominant role in influencing the loss factor of the dampers compared to the dynamic amplitude.

Dielectric properties for selected wall material in the development of microwave-encapsulation-drying.

Dielectric properties study is important in understanding the interaction between materials within electromagnetic field. By knowing and understanding the dielectric properties of materials, an efficient and effective microwave heating process and products can be designed. In this study, the dielectric properties of several encapsulation wall materials were measured using open-ended coaxial probe method. This method was selected due to its simplicity and high accuracy. All materials exhibited similar behavior. The result inferred that β-cyclodextrin (BC), starch (S), Arabic (GA) and maltodextrin (M) with various dextrose equivalent exhibited effective encapsulation wall materials in microwave encapsulation-drying technique owing to loss tangent values which were higher than 0.1 at general application frequency of 2.45GHz. Thus, these were found to be suitable as wall material to encapsulate the selected core material in this microwave encapsulation-drying method. On contrary, sodium caseinate showed an ineffective wall material to be used in microwave encapsulation-drying. The differences in the values of dielectric constant, loss factor and loss tangent were found to be contributed by frequency, composition and bulk density.

Digital image processing and thermo-mechanical response of neat epoxy and different laminate orientations of fiber reinforced polymer composites for vibration isolation applications

In this study, tensile tests are performed under quasi-static loading on neat epoxy and for different laminate configurations [(0/90), (0/90/30/–60), (0/90/45/–45) and (30/–60/60/–30)] of glass/epoxy, carbon/epoxy and cross ply interply hybrid (glass/carbon/epoxy) composites. A camera-based advanced image processing technique called as digital image correlation is employed to obtain the full-field strain fields and identify the direction of failure of the matrix and composites as a function of fiber orientation angle. Further, the viscoelastic properties (storage modulus, loss modulus and loss factor) are measured over the temperature range from 20 °C–140 °C for five different frequencies (1, 10, 20, 33 and 50 Hz) using the dynamic mechanical analyzer. The glass transition temperature (Tg) is found out from temperatures corresponding to the loss modulus and loss factor peak values. The results revealed that as the temperature increases, the storage and loss moduli decrease attributed to the softening of the material because of free molecular movements. The cross ply laminates of GFRP and CFRP exhibit higher storage and loss moduli at all frequencies due to strong fiber network as compared to the other laminate configurations. The hybrid composites possess higher storage and loss moduli than GFRP and neat epoxy. The neat epoxy has higher loss factor values than composites. As the frequency increases, the Tg shifts to higher values. Loss modulus Tg values are found to be lower than that of loss factor Tg values.