Dielectric Loss Factor Research Articles

Improvement of Temperature Distribution Uniformity of Ready-to-Eat Rice during Microwave Reheating via Optimizing Packaging Structure.

The taste quality of ready-to-eat rice is influenced by the uniformity of temperature distribution during microwave reheating. The temperature distribution uniformity of ready-to-eat rice loaded in a rectangular lunch box is investigated under microwave reheating. The results show that with a 10-80 °C temperature increase in the ready-to-eat rice, the thermal conductivity increases, dielectric constant, and specific heat increase and then decrease, while the dielectric loss factor decreases and then slightly increases. The microwave-heating process of ready-to-eat rice exhibits a clear 'corner effect', and the observed 'hot spot' results in poor temperature uniformity in ready-to-eat rice. A metalized packaging structure design is subsequently proposed to ameliorate the temperature non-uniformity. According to comparative results of four metalized packaging forms, the spray film volume and film thickness corresponding to film volume are developed as 3.5×10-4 mL/mm2, 0.30 mm, respectively, which levels off the difference in temperature to improve the temperature distribution uniformity of ready-to-eat rice by microwave reheating.

Investigation of the dielectric properties and mechanical stability of lignocellulosic biomass based electrical insulation material for high voltage applications

The laminated insulation pressboards are used in electrical transformers and they are made from pure wood cellulose fibre. It is used in high-voltage transformers for electrical insulation due to its superior electrical and mechanical properties. Many researchers are searching for alternatives to wood raw materials to reduce deforestation. The banana is one of the lignocellulose-based raw materials; the banana fibre contains 48% cellulose. In this work, different frequencies and temperatures are used to investigate the electrical characteristics of epoxy resin composites reinforced with banana leaf fibres, including their dielectric constant, dissipation factor, and loss factor. At frequencies ranging from 1 to 10 kHz and temperatures ranging from 30 to 150 °C, the dielectric properties of several composites containing banana leaf fibre are studied. The composite’s dielectric properties gradually increased with temperature and decreased with frequency. Correspondingly, the mechanical tests involving a banana leaf fibre epoxy composite are conducted for tensile, bending, impact, and water absorption. The banana leaf fibre has been treated with a 5% sodium hydroxide (NaOH) solution to increase its dielectric and mechanical strength. According to this study, the mechanical strength of biocomposites containing up to 60% treated banana leaf fibre epoxy (TBLFE) composites is greater than that of pure epoxy. A thermogravimetric investigation of composites reinforced with banana fibres has revealed remarkable thermal stability up to 220 °C. In a composite made from chemically treated banana fibre pressboard, there is a good bond between the fibres and the matrix. The FESEM surface analysis shows that treated banana leaf fibril insulation boards have a better texture than composites that have not been treated. The testing results depict that banana leaf fibre is one of the good alternatives to wood cellulose for electrical insulation on pressboard for high-voltage applications.

Potential contribution of steel slag fillers to asphalt mastic in terms of microwave heating efficiency, electromagnetic mechanisms and fatigue durability

ABSTRACT This paper investigates the potential contribution mechanisms of steel slag fillers in asphalt mastic, covering asphalt-filler interaction mechanisms, microwave heating efficiency, electromagnetic absorption mechanisms, and fatigue durability. The physico-chemical microscopic mechanisms of the steel slag filler, the limestone filler and the interactions between the fillers and the styrene-butadiene-styrene (SBS)-modified binders were characterized. The microwave-heating efficiency of steel slag-based asphalt mastic (SBS-SS) and limestone-based asphalt mastic (SBS-LS) was quantified. The dielectric behaviour of the fillers and the corresponding mastic was further characterized to reveal the electromagnetic mechanisms associated with the microwave heating technology. The stiffness evolution and the fatigue durability of SBS-based bitumen under the effectiveness of steel slag and limestone fillers were assessed by the viscoelastic continuum damage theory model and dissipative energy approaches. The steel slag fillers exhibited a greater potential to promote microwave heat efficiency than the natural stone fillers due to higher ferric oxide compositions. SBS-SS mastics have an overall greater dielectric constant and loss factor than those of SBS-LS mastics, resulting in superior electric field energy storage and conversion capabilities. The addition of steel slag fillers magnifies the load sensitivity of the bitumen and weakens the fatigue impedance and fatigue life of asphalt mastic composites.

Microwave-assisted CO oxidation over LaNiO3 and Ce-promoted LaNiO3

Microwave-assisted catalytic reactions have been investigated for energy-efficient chemical processes. However, catalysts with comparatively high heating properties, activities, and economics have been developed with limited success. In this study, we investigated the catalytic properties of Ce addition to LaNiO3 catalyst, which has high CO oxidation activity and high microwave heating properties. Ce-added catalysts exhibited high heating properties under microwave heating. Increasing the Ce content in the catalyst enhanced the dielectric loss factor, the ability to absorb microwaves and convert them to heat, and improved the microwave heating properties of the catalyst. The catalytic activity toward CO oxidation over Ce-added catalysts decreased in the order of La0.8Ce0.2NiO3 > La0.9Ce0.1NiO3 > LaNiO3 at all oxygen partial pressures when compared to the same microwave power. To clarify the role of Ce addition, temperature programmed reduction (TPR) by H2, CO, and XAFS measurements were performed. TPR results suggested that Ce promotes oxygen mobility and then affects both CO oxidation and microwave heating properties.

Indium tin oxide nanoparticles induced molecular rearrangement in nematic liquid crystal material

In the present article, we report the influence of indium tin oxide (ITO) nanoparticles (NPs) on the macroscopic molecular arrangement of a nematic liquid crystal (NLC) material namely 4 cyano-4ʹ-pentylbiphenyl (5CB). To achieve the objective, we have adopted various concentrations (0.25, 0.5 and 1 wt%) of ITO NPs in 5CB and filled them in the homogeneously aligned sample cells to observe their influence on the dielectric and optical texture of the NLC under investigation. Firstly, polarizing optical micrographs under crossed polarizers were recorded to observe the uniform dispersion and miscibility of ITO NPs in the nematic phase of 5CB. These micrographs also infer the molecular rearrangement of 5CB material that is occurred under the simultaneous and cumulative anchoring effect induced by ITO NPs and aligning layers. Furthermore, the dielectric parameters (permittivity, loss and dielectric loss factor) of pristine and composites as the function of frequency, temperature and DC biasing have been studied. Surprisingly, dielectric permittivity and relaxation frequency of 0.25 wt% ITO NPs composite was found to be the maximum that is decreased with further increment in the concentration of ITO NPs. We have also confirmed the thermal stability of 0.25 wt% ITO NP-induced changes in 5CB. Apart from it, by virtue of temperature-dependent dielectric anisotropy and optical textures, we have reported a significant decrement (∼14 %) in clearing temperature of 5CB. These results will pave the way to devise a system with ITO NPs as the dopant in order to obtain desired phase transition temperature of liquid crystal materials.

Enhanced Energy Storage Performance and Efficiency in Bi0.5(Na0.8K0.2)0.5TiO3-Bi0.2Sr0.7TiO3 Relaxor Ferroelectric Ceramics via Domain Engineering.

Dielectric materials are highly desired for pulsed power capacitors due to their ultra-fast charge-discharge rate and excellent fatigue behavior. Nevertheless, the low energy storage density caused by the low breakdown strength has been the main challenge for practical applications. Herein, we report the electric energy storage properties of (1 - x) Bi0.5(Na0.8K0.2)0.5TiO3-xBi0.2Sr0.7TiO3 (BNKT-BST; x = 0.15-0.50) relaxor ferroelectric ceramics that are enhanced via a domain engineering method. A rhombohedral-tetragonal phase, the formation of highly dynamic PNRs, and a dense microstructure are confirmed from XRD, Raman vibrational spectra, and microscopic investigations. The relative dielectric permittivity (2664 at 1 kHz) and loss factor (0.058) were gradually improved with BST (x = 0.45). The incorporation of BST into BNKT can disturb the long-range ferroelectric order, lowering the dielectric maximum temperature Tm and inducing the formation of highly dynamic polar nano-regions. In addition, the Tm shifts toward a high temperature with frequency and a diffuse phase transition, indicating relaxor ferroelectric characteristics of BNKT-BST ceramics, which is confirmed by the modified Curie-Weiss law. The rhombohedral-tetragonal phase, fine grain size, and lowered Tm with relaxor properties synergistically contribute to a high Pmax and low Pr, improving the breakdown strength with BST and resulting in a high recoverable energy density Wrec of 0.81 J/cm3 and a high energy efficiency η of 86.95% at 90 kV/cm for x = 0.45.

Microwave-Induced Behavior and Digestive Properties of the Lotus Seed Starch-Chlorogenic Acid Complex.

The effect of chlorogenic acid (CA) on the dielectric response of lotus seed starch (LS) after microwave treatment, the behavior and digestive characteristics of the resulting starch/chlorogenic acid complex (LS-CA) at different degrees of gelatinization and the inhibition of α-amylase by chlorogenic acid were investigated. The variation in dielectric loss factor, ε″, and dielectric loss tangent, tanδε, of the microwave thermal conversion indicated that LS-CA had a more efficient microwave-energy-to-thermal-energy conversion efficiency than LS. This gelatinized LS-CA to a greater extent at any given temperature between 65 and 85 °C than LS, and it accelerated the degradation of the starch crystalline structure. The greater disruption of the crystal structure decreased the bound water content and increased the thermal stability of LS-CA compared to LS. The simulated in vitro digestion found that the presence of the LS-CA complex improved the slow-digestion property of lotus seed starch by increasing its content of resistant and slowly digested starch. In addition, the release of chlorogenic acid during α-amylase hydrolysis further slowed starch digestion by inhibiting α-amylase activity. These findings provide a foundation for understanding the correlation between the complex behavior and digestive properties of naturally polyphenol-rich, starch-based foods, such as LS, under microwave treatment, which will facilitate the development of starch-based foods with tailored digestion rates, lower final degrees of hydrolysis and glycemic indices.

An experimental and computational study for enhancement in optical nonlinearity and dielectric behaviour in thermal annealing induced Ag diffusion at Ag/Sb-S-Se interface

The annealing induced Ag diffusion into Sb40Se30S30 film brings enormous changes in its linear-nonlinear optical along with the structural and dielectric properties which is reported in the current study. The prepared Ag/Sb40Se30S30 film was annealed at different temperatures like 100,150,200 and 250 °C. The structure remained amorphous one as confirmed from XRD while the particle size increased with annealing as observed from FESEM images. The Raman study depicts the microstructural change in terms of shift in vibrational peaks. The optical study was done by UV–Vis-NIR spectrometer from which different optical parameters were evaluated. The decrease in optical bandgap with increase in linear refractive index is accompanied by the increase in optical density, extinction coefficient and decrease in skin depth. The dielectric loss factor increased while the quality factor decreased with annealing. The static dielectric constant increased with the increase in carrier concentration. Both the electrical as well as optical conductivity are found to be increased while optical electronegativity and plasma frequency decreased with annealing. The 3rdorder nonlinear susceptibility and non-linear refractive index are doubled with annealing while there is decrease in nonlinear absorption coefficient. The surface wettability study infers the hydrophilic nature sustains with annealing. The computational analysis using the DFT method was carried out to provide some necessary information about the structure and physical properties of the prepared materials.

Dielectric properties of peaches with and without skin during storage and their relationship to internal quality

This study investigated the variations of the dielectric properties of 80 mature ‘Shahong’ peaches with skin (intact peaches) and without skin (peach pulp) over the frequency range of 200–3000 MHz during storage. The internal qualities and enzyme activities, as well as their correlations, and models to predict the internal qualities based on the dielectric spectra were also analyzed. The results showed that the dielectric constant (ε′) of peaches with or without skin decreased with increasing frequency over the whole frequency range and their dielectric loss factor (ε″) decreased firstly then increased later with the turning point at around 1000 MHz. ε'intact (intact peach's ε'), ε'pulp (pulp's ε'), and ε"pulp (pulp's ε") were positively correlated with SSC and negatively correlated with other internal qualities (|r| ≥ 0.88). The prediction model based on dielectric properties of intact peach for firmness with the highest Riv2 (determination coefficient of internal validation set) of 0.75, while for other internal qualities, the Riv2 was lower than 0.48. Meanwhile, the highest Riv2 of established models based on the pulp's dielectric properties was 0.80, 0.88, and 0.91 for firmness, SSC, and moisture content, respectively. This study provides useful information for understanding the relationship between dielectric properties and fruit internal quality indices, and also offers a research basis for applying dielectric properties in predicting fruit quality in the future.

Synthesis, Macro-Dielectric, Electronic µ-Influx, Voltage Controlling and Computational Studies of Novel Aromatic Cyclic AMPF Crystals

The novel aromatic cyclic compound type of crystals such as AMPF as 2-amino-4-methylpyridinium fumarate are properly grown by slow evaporation method; the grown crystals are analyzed for single crystalline X-ray diffraction study with the lattice constants as a, b, c with 5.0234 Å; 20.0146 Å; 10.8852 Å and β as 95.767° and are grown at room temperature; the crystal is with volume as 1094.41Å3; crystal system is monoclinic and is of P21/n as space group. The computational study portrays and delineates the AMPF with unit cell and the Laue’s pattern of both ways and also with that of the ORTEP – the thermal ellipsoidal plot for proper projection in the atomic scaling. The dielectric behavior of the material is analyzed for pure macro level scaling and is high dielectric constant – εr and Conductivity – σac with less dielectric loss factors prefer the use of AMPF crystals in the field of opto-electronic and µ-electronic engineering usage. The µ-influx of 4.9691 microns properly portrays for electronic filtering application of AMPF and is asserted and implemented as a better candidate in voltage regulation processing.

Determination of Dielectric Models Based on Effective Multi-Exponential Fittings

In high-voltage (HV) transmission and distribution systems, HV apparatuses are subjected to electrical, thermal, and mechanical stresses that deteriorate the insulation performance. The polarization and depolarization current (PDC) measurement is an effective tool used for evaluating insulation performances. The depolarization current represented by the summation of the discharge currents with the different time constants can be utilized for the development of the dielectric model based on the extended Debye’s model (EDM). This paper presents effective techniques for determining the dielectric model. Iterative approaches with predetermination of the time constants and least squares methods (either linear ordinary or percentage ones) were utilized to fit the depolarization current in the form of multi-exponential functions. The fitting parameters determined by the proposed method with the linear ordinary least squares (OLLS) method and provided by commercial software agree very well only in the high current and beginning range. Application of the linear percentage least squares (PLLS) method shows better accuracy than that of the OLLS method, and the deviation from the measured one in the low current range and the late measuring time were reduced significantly. The fitted current by this proposed technique with the PLLS method agrees well with the measured current throughout the whole recording time, even in the low current and late time range. From the accurately fitted currents, the dielectric model and the dielectric loss factors can be determined precisely, and the insulation condition of HV equipment can be evaluated properly.

High performance imide oligomers and thermosets derived from 9,9-bis (3,4-dicarboxyphenyl)fluorene dianhydride

In this work, a new class of imide oligomers and thermosets with improved overall properties was developed by exploiting the steric effects of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). First, a model compound was prepared from BPAF and aniline. This model compound possessed a twisted architecture, with two dihedral angles between fluorene ring and phthalimide segments of around 75°. Then, an array of phenylethynyl-endcapped imide oligomers was synthesized from BPAF, 4-phenylethynyl phthalic anhydride (4-PEPA), and aromatic diamines (4,4′-oxydianiline (4,4′-ODA), 2,2′-bis(trifluoromethyl)benzidine (TFMB), m-phenylenediamine (m-PDA)). The BPAF-derived imide oligomers exhibited improved organic solvents solubility and higher melt viscosity compared to those based on 2,3,3′,4′-biphenyltetracarboxylic dianhydride (3,4′-BPDA), due to their bulky, twisted, and sterically hindered cardo architectures. The imide oligomers under pressure were converted into thermosets by the thermal crosslinking of phenylethynyl at 370 °C for 2 h. The BPAF-derived thermosets exhibited much higher glass transition temperature (Tg) (＞ 404 °C), 5% weight-loss temperature (T5%) (＞ 549 °C) in an air environment, and more excellent high-frequency dielectric properties from 30 to 45 GHz (dielectric constant as low as 2.85 and dielectric loss factor as low as 0.0037) while possessing comparable or even better mechanical properties relative to the 3,4′-BPDA-derived polymers. Therefore, these polymers based on BPAF may have potential applications as matrix resins for heat-resistant, structural and functional composites.

Graphene Implanted Shape Memory Polymers with Dielectric Gene Dominated Highly Efficient Microwave Drive

AbstractMicrowave‐driven strategy shows many advantages including selective energization, uniform heating, and high penetration depth, which is a hot topic in wireless actuators. Understanding microwave stimulus‐response mechanisms is the key to developing universal construction strategies for advanced microwave‐driven actuators. Herein, reduced graphene oxide (rGO) with specified dielectric genes and thermal properties is implanted into the shape memory polymer, liquid crystal elastomer (LCE) as an example, to construct soft, reversible, and sensitive microwave actuators. Based on the analysis of microstructure and dielectric properties, LCE‐rGO composites exhibit excellent polarization relaxation‐dominated dielectric loss and electromagnetic (EM) energy conversion ability. The maximum dielectric loss factor (ε″) and loss tangent (tan δe) of LCE‐rGO are dramatically increased by 216% and 87.5% compared to pure LCE, respectively, and the optimum apparent energy harvest efficiency is 19.4 times higher than that of LCE. In addition, the implantation of rGO significantly lowers the microwave actuation threshold of LCE‐rGO composites and reinforces their stimulus‐response capacity. Response time under 750 W microwave irradiation of LCE‐rGO is shortened to <10s. These findings can provide a solid basis for the design and fabrication of highly efficient microwave stimuli‐responsive polymers and enlighten a new approach to wireless actuated smart devices.

Dielectric Characterization of Heterogeneous Composites Using Time Domain Spectroscopy and Microwave Test Benches in Microwave Frequency

Dielectric composite materials made of polymers and ferroelectric ceramics have recently emerged as one of the important components for applications involving the generation, transformation, and storage of sustainable energy. Because there is a trade-off between dielectric permittivity, dielectric loss, and dissipation factor, the end use is the energy storage capacity. In the present study, epoxy resin (RE)/barium titanate (BaTiO3) composite samples are prepared using the mixture cast method with new molds. The dielectric properties, such as dielectric permittivity, dielectric loss, electrical modulus, static conductivity and dissipation factors due to the concentration of barium titanate and frequency effect on the composites, are examined using two characterization methods. The objective of this study is to determine the dielectric permittivity of the material using two microwave methods, the first is time domain spectroscopy (TDS) and the second is on the X-band microwave test bench (MTB). Additionally, different empirical mixture laws are used to estimate the dielectric permittivity of our composites. It is found that an increase in filler concentration (BaTiO3) increases the effective dielectric permittivity, which is confirmed with different empirical mixture models. The findings of this research can be used for electrical devices, including sensors, wave absorbers, resonators, and antennas.

Tuning of the band gap and dielectric loss factor by Mn doping of Zn1-xMnxO nanoparticles

This study explored the structural, optical, and dielectric properties of Pure and Mn+2 doped ZnO nano-particles (Zn1−xMnxO) with x ≥ 20%, synthesized by co-precipitation method followed by annealing at 4500C. Different characterization techniques were conducted to characterize the as-prepared nano-particles. X-ray Diffraction analysis of the pure and Mn+2 doped presented a hexagonal wurtzite structure and a decreased crystallite size with increasing doping concentration. Morphological analysis from SEM revealed finely dispersed spherical nanoparticles with particle size of 40–50 nm. Compositional analysis from EDX confirmed the incorporation of Mn+2ions in ZnO structure. The Results of UV spectroscopy showed that changing the doping concentration affects the band gap, and a red shift is observed as the doping concentration is increased. The band gap changes from 3.3 to 2.75 eV. Dielectric measurements exhibited decrease in the relative permittivity, dielectric loss factor and ac conductivity by increasing Mn concentration.

Theoretical investigations of optoelectronic and transport properties of halide based K2YAuX6 (X = Cl, Br) double perovskites

Intriguing optoelectronic and transport properties with huge compositional range and structural stability make double perovskites interesting for energy harvesting technologies. Here we theoretically investigate the structural, optical, mechanical, and transport properties of K2YAuX6 (X = Cl, Br) double perovskites using the WIEN2K code. Based on the calculated values of the tolerance factor and enthalpy of production, the thermodynamic and structural stability is affirmed. The ductile nature of these compositions is revealed in the computation of Poisson’s ratio (>0.26) and Pugh’s (1.75) ratio. The involvement of s-states of K, p-states of Cl/Br, and d-states of Y and Au in the formation of valence and conduction band edges is exhibited from the density of state plots. Using the Tran-Blaha mBJ potential and spin-orbital coupling, the energy bandgap value for K2YAuCl6 and K2YAuBr6 is reported as 3.20, and 2.70 eV, respectively, which is suitable for the fabrication of light-emitting diodes. Optical behavior is further explored regarding complex dielectric constant, refractive index, optical conductivity, optical loss, and absorption factor. The small value of thermal conductivity with large value of electrical conductivity, Seebeck coefficient, power factor, and figure of merit revealed the potential of these materials for the fabrication of light-emitting diodes and thermoelectric generators.

Poling above the Curie temperature driven large enhancement in piezoelectric performance of Mn doped PZT-based piezoceramics

The enhancement of piezoelectricity is usually in sacrifice of Curie temperature, which in turn limits its working temperature range. It is well known that there are some trade-off among the various performance parameters of most piezoelectric ceramics, and it is still difficult to achieve synergistic improvement in multiple parameters. Here, it is reported that the piezoelectric coefficient d33 of a 0.6 mol% Mn-doped Pb(Sb0.5Nb0.5)0.02Zr0.51Ti0.47O3 piezoelectric ceramics is increased to 436 pC N−1, and its electro-strain can reach 0.16% (d33* = 800 pm/V) at 2 kV mm− 1 by high-temperature poling, whose Curie temperature can still keep at 347 ℃. The features of "hard" piezoelectric ceramics such as low dielectric loss (tgδ = 0.23%) and high mechanical quality factor (Qm = 546) are also preserved. Through structural characterization, combined with the theoretical results of phase field simulation, it is shown that its excellent piezoelectric performance originates from the highly oriented domain structure and small domain size after high temperature poling. On the other hand, the valence state transition of Mn3+ ions during high-temperature poling increases the defect vacancies and lattice distortion in ceramics, which keeps the acceptor-doped characteristic of the ceramics.

Hydration dominates dielectric spectroscopy-based high accuracy quantification of lactose content in cow's milk.

Lactose is a critical factor in the quality of milk and dairy products. Achieving high accuracy and rapid detection of lactose content in cow's milk remains a challenge. Dielectric spectroscopy has emerged as a promising tool for detecting food components. We explored the effect of lactose content on the dielectric spectra of cow's milk and proposed a rapid analytical method for the quantitative determination of lactose content in cow's milk with high accuracy based on dielectric spectra. We obtained the dielectric spectra of 316 cow's milk samples in the frequency range of 20 to 4500 MHz and noticed a strong negative correlation between the lactose content and the value of the dielectric loss factor (ε'') below 1500 MHz. Lactose doesn't affect cow's milk dielectric properties by excluded volume effect but dominates the effect on the dielectric properties of cow's milk by hydration. The support vector regression (SVR) model based on the variable importance in projection (VIP) has the best prediction performance for lactose content. Its root-mean-square error of prediction set (RMSEP) and residual prediction deviation (RPD) is 0.29 g kg-1 and 6.968, respectively, and its prediction performance is better than that of the currently reported near-infrared (NIR) method and other methods. Despite the weak polarity of lactose molecules, its hydration is a significant factor affecting the dielectric properties of milk. This study provides a basis for high accuracy and rapid quantitative detection of lactose in cow's milk based on dielectric spectra. This article is protected by copyright. All rights reserved.

Preparation of Fe3O4-carbon black/poly(vinylidene fluoride) composites with enhanced properties

In this work, the Fe3O4-carbon black filler was obtained from an in-situ coprecipitation method followed by the modification of the heptadecafluorodecyltrimethoxysilane and the Fe3O4-carbon black/poly(vinylidene fluoride) (PVDF) composites with enhanced properties were prepared by a simple solution blending-water precipitating method. The Fe3O4-carbon black distributed well in the PVDF matrix, which was confirmed by the SEM. According to the results of FTIR and WAXD, a lot of useful polar crystalline phases of PVDF formed in the Fe3O4-carbon black/PVDF composites. The electrically conductive ability, the dielectric permittivity, the dielectric loss factor, and the magnetic saturation value of the Fe3O4-carbon black/PVDF composite increased with the increasing loading amount of Fe3O4-carbon black filler. Especially, when the Fe3O4-carbon black was 5 wt.%, the dielectric permittivity of Fe3O4-carbon black/PVDF composite reached as high as 23.5 at 1000 Hz with a relatively low dielectric loss factor value of 0.38 and a magnetic saturation value of 0.64 emu/g.

Effects of Bi2O3 on the microstructure, mechanical strength, and dielectric properties of CaZnSi2O6 glass ceramics with machinable precursors

Ceramizable silicone rubber composites were prepared using methyl vinyl silicone rubber, kilchoanite, low-melting-point glass frit, nano silica, and Bi2O3. CaZnSi2O6 glass ceramics were sintered at 1000 °C using ceramizable silicone rubber composites as the machinable precursors. The effects of Bi2O3 on the microstructure, mechanical strength, and dielectric properties of CaZnSi2O6 glass ceramics were studied. The results showed that the flexural strength of the ceramic samples first increased and then decreased with an increase in the Bi2O3 content. The maximum value of flexural strength was 110.48 MPa, which improved by 22% compared with that of the ceramic samples without Bi2O3. Bi2O3 provided more liquid phase, and the ceramic samples with Bi2O3 had a denser microstructure. Furthermore, Bi remained in the glass phase and increased the activation energy of relaxation polarization and conduction. The dielectric loss factor (tanδ) of the ceramic samples decreased with increasing Bi2O3 content, and the increase in tanδ with temperature was inhibited. Bi2O3 also improved the breakdown strength of the ceramic samples by 25%, from 22.54 to 28.12 kV/mm.