Correlation Of Dielectric Properties Research Articles

Correlation of Dielectric Properties and Vibrational Spectra of Composite PVDF/Salt Fibers.

Nitride salts were added to polyvinylidene fluoride fibers and then the fiber mats were prepared by electrospinning. An experimental investigation of the structure was provided by Raman, FTIR, SEM, and XRD. The phase ratio of the polymer was studied both theoretically and experimentally in connection with the addition of the hydrates Mg(NO3)2, Ca(NO3)2, and Zn(NO3)2 salts. The comparison of simulated and experimental data for vibrational spectroscopies is discussed. We provide a comparison of triboelectric, dielectric, and compositional characterization of PVDF fibers doped with three types of nitride hydrates. Doping of PVDF fibers with magnesium nitrate hexahydrate leads to significant improvement of the triboelectric performance.

Correlation of Dielectric Properties with Structure and H-Bonding for Liquids

Correlation of Dielectric Properties with Structure and H-Bonding for Liquids

Modeling the drying kinetics of microwave vacuum drying of concentrated skim milk: correlation of dielectric properties, drying stages, and specific energy demand at pilot scale

This study establishes a correlation between dielectric properties, drying parameters, drying rate and energy demand for microwave vacuum drying (MVD) of concentrated skim milk (CSM). MVD was conducted using a EnWave nutraReV™ unit, at various specific power inputs (0.86, 1.29, 1.72 W g-1), drying pressures (30 to 147 mbar), and CSM layer thickness (1 to 4 mm). The drying rate based on moisture ratio was estimated using the Page model. The specific energy consumption was lowest as CSM dried from 50 to 15% moisture, then rapidly increased as the drying rate decreased due to a low ε” at <15% moisture. The loss factor ε” of CSM at 2.45 GHz increased up to 35% total solids, then steadily decreased up to 95% solids. The specific electrical energy demand of the MVD unit, which accounted for all utility flows at full capacity, was 2.85 kWh kg-1 water evaporated, with the magnetrons accounting for 2.14 kWh kg-1. This study provides valuable data on drying kinetics and energy demand during MVD of CSM, and an approach that can help processors assess the energy efficiency of MVD for various food applications.

Dielectric response of capacitor structures based on PZT annealed at different temperatures

Dielectric response of thin-film capacitor structures of Pt/PZT/Pt deposited by the RF magnetron sputtering method and annealed at temperatures of 540–570 °C was investigated. It was found that dielectric properties of these structures depend on the synthesis temperature. Stability of a polarized state is considered on the basis of the analysis of hysteresis loops and capacitance–voltage (C–V) characteristics. The contribution of the domain mechanism in the dielectric response of the capacitor structure comprising a ferroelectric is discussed. Extreme dependences of electrophysical characteristics of PZT films on their synthesis temperature were observed. Correlation of dielectric properties with microstructure of these films is found out.

A novel strategy for improving radio frequency heating uniformity of dry food products using computational modeling

Abstract This study attempted to quantify effects of dielectric properties (DPs) and densities of a surrounding container and treated food products on heating uniformity in a 6 kW, 27.12 MHz parallel plate radio frequency (RF) system. A computer simulation model was established with finite element-based commercial software, COMSOL Multiphysics®, and experiments with 1.5 kg soybean flour packed in a rectangular polystyrene container were performed to validate the developed model. Surface temperature distributions of soybean flour in three different horizontal layers were obtained with an infrared camera, and temperature–time histories at two representative locations inside the container were monitored with two optical fiber sensors. The uniformity index (UI) was used as a criterion to evaluate the RF heating uniformity within food products. Results showed that the RF heating uniformity in food samples was clearly influenced by DPs and density of the surrounding container. UI was the lowest when the surrounding container dielectric constant was in a comparable range of the sample's, with the loss factor values of surrounding container lying between 0.01–0.1% of the sample's. The optimum RF heating uniformity in food products could be achieved with a smaller density value of the surrounding container. The correlations of DPs and density between surrounding container and food products derived from the validated simulation model could provide valuable information and strategy to improve the RF heating uniformity in low moisture foods for insect or microbial control. Thus, the established strategy can further be used for developing effective industrial-scale RF treatment protocols after optimization of this process by the food industry. Industrial relevance Although the most important characteristic of radio frequency (RF) treatments is fast and volumetric heating generated by dipole rotation and ionic conduction, edge over-heating is still a major problem for foods heated in rectangular containers. The validated model was used to study the effects of dielectric properties and density of sample and surrounding container on sample uniformity index. Simulated results illustrated that the RF heating uniformity could be improved when the dielectric constant and density of surrounding container and sample were in accordance with the established relationships. The established strategy may provide valuable optimized methods to ensure RF heating uniformity in industrial applications.

Correlations of dielectric properties with electronic structure and phonon vibration of low loss tunable Ba0.4Sr0.6Ti1-yMnyO3 ceramics

Correlations of dielectric properties with electronic structure and phonon vibration of Ba0.4Sr0.6Ti1-y MnyO3 (y = 0.00-0.20) ceramics were studied by using spectroscopic techniques. High level of Mn substitution prevented the reduction of Ti4+ and enhanced the charge ordering of Ti3+/Ti4+, leading to materials with high Q values. An increase in the concentration of Mn resulted in hardening of the softest mode, which led to a reduction in relative permittivity, dielectric loss, and tunability with increasing y. Raman spectra revealed that higher vibration frequency of Ti-O bonds was related to lower relative permittivity, and narrower width of Mn-O stretching corresponded to a higher Q × f.

Poly(vinylidene fluoride)-graft-poly(2-hydroxyethyl methacrylate): a novel material for high energy density capacitors

We report the graft copolymerization synthesis of novel high dielectric constant HEMA (2-hydroxyethylmethacrylate)-graft-poly(vinylidene fluoride) (PVDF) copolymers for potential applications in high energy density capacitors. In the present study the graft copolymerization reaction was introduced by irradiation (electron beam) treatment of the PVDF polymer powder. The chemical changes in the PVDF polymers after HEMA grafting were monitored and the results were evaluated by FTIR, DSC, TGA and contact angle measurement. An analysis is presented on the effectiveness of this approach as a function of electron beam operating variables including radiation dose, reaction time, reaction temperature, monomer concentration and effect of solvent. The PHEMA-g-PVDF copolymers demonstrate improved dielectric properties such as high dielectric constant, lower leakage and low dielectric loss as compared to pristine PVDF. Correlation of dielectric properties with the graft copolymerization reaction mechanism was discussed.

Microwave Dielectric Properties of Sr(B′1/2Nb1/2)O3 [B′=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] Ceramics

Sr(B′1/2Nb1/2)O3 [B′=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] ceramics were prepared by the conventional solid‐state ceramic route. The crystal structure and microstructure of the ceramics were characterized by X‐ray diffraction and scanning electron microscopic methods, and the dielectric properties were measured in the microwave range. Addition of a small amount of CeO2 as a sintering aid improved the densification and dielectric properties of the ceramics. The effects of cation substitution and glass addition on the microwave dielectric properties of the ceramics were also investigated. Glass addition resulted in the lowering of the processing temperature of the materials without much affecting the dielectric properties, whereas cation substitution resulted in the variation of the temperature coefficient of resonant frequencies. A correlation of dielectric properties with the tolerance factor and ionic radii of B′‐site elements of the ceramics has been observed.