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experimentally explored by Sun et al. who studied the influence of the interface on the dielectric properties of epoxy/silica composites [ 7 ]. A dielectric material has an arrangement of electric charge carriers that can be displaced by an electric field

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Journal of Thermal Analysis and Calorimetry
Authors: H. W. Starkweather, P. Avakian, J. J. Fontanella, and Mary C. Wintersgill

Dielectric measurements have been made at frequencies from 10 Hz to 100 kHz and temperatures from 4 K to at least 300 K on a number of polymers containing units of hexafluoropropylene (HFP). These included copolymers of tetrafluoroethylene (TFE) and HFP, the homopolymer of HFP, elastomeric copolymers of HFP and vinylidene fluoride, and alternating copolymers of methyl vinyl ether with TFE and HFP. The effect of an ether linkage between the CF3 group and the chain was also considered. Most of these polymers exhibited a main chain local mode relaxation near 228 K and a side group relaxation near 93 K.

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-dependent dielectric properties of honey associated with dielectric heating . Journal of Food Engineering , 102 : 209 – 216 . 10.1016/j.jfoodeng.2010.08.016 Guo , W. , Zhu , X. , Liu , Y. , and Zhuang , H. ( 2010 ). Sugar and water contents of honey with

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Abstract  

This paper describes a new instrument for performing thermal analysis using microwaves both as a form of heating and as a novel means of detecting thermally induced transformations in materials. Results are presented for a selection of processes including decompositions, dehydrations and phase changes. The capability of the instrument to be coupled with ancillary techniques such as EGA is also demonstrated.

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Abstract  

The nature of the β to α phase transition in silver iodide was investigated by conventional and modulated temperature DSC and dielectric property measurements. On cooling, the high temperature phase remained stable 2.5C below its normal transition temperature even at a very slow cooling rate 0.2C h–1. Dielectric property measurements under conventional and microwave heating suggested an anomalous effect of the latter on the β to α phase transition in this material.

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Journal of Thermal Analysis and Calorimetry
Authors: Lisardo Núñez-Regueira, M. Villanueva, I. Fraga, C. A. Gracia-Fernández, and S. Gómez-Barreiro

Abstract  

The thermal degradation of an epoxy system consisting of a diglycidyl ether of bisphenol A (DGEBA, n=0) and m-xylylenediamine (m-XDA) was studied by both thermogravimetric analysis (TG) and dielectric analysis (DEA). It has been checked a deviation of the typical behaviour in the Arrhenius plot expected for this kind of systems, owing to the thermal degradation. Both, structural relaxation time and conductivity values, were represented as a function of the mass loss, that allow a relationship to be obtained between characteristic relaxation time and the degree of degradation at the beginning of the degradation process.

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In the present manuscript, freshly prepared and also pure chemical grade (BDH) antimony trioxide specimens were investigated. Numerous measurements were carried out on these specimens, comprising chemical, spectral and X-ray analyses, pycnometric and X-ray density measurements and observations of the behaviour of the dielectric constant and dielectric loss factor (∈′ and ∈″) as functions of temperature and frequency. The results obtained gave values of 12.4 and 10 for the dielectric constant for the freshly prepared and commercial antimony trioxide specimens, respectively. The results were compared in correlation with the phase constitution and degree of compactness for both specimens. Finally, the data are discussed on the basis of the interactions of the field frequency and temperature with the electric dipoles and electronic polarization of the test specimens.

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Aluminate sodalite ceramics, (Sr8Al12O24)(CrO4)2) — SACR, have been prepared from solution spray-dried precursors. The spray drying of a mixed aqueous nitrate solution gave an anhydrous powder which was thermally decomposed in air at 1350 °C to give a crystalline SACR powder with a median volume diameter of 4–6 μm. The SACR powder was dry pressed and sintered to >90% density. The yellow SACR powder showed two phase transitions between 10 and 45 °C with a 25 ° intermediate phase region indicative of a low defect concentration in the crystalline structure. A colour change observed in the sintered ceramic (changing to a mixed green/yellow) and a narrowing of the phase transition region (15–40 °C) are discussed. Dielectric measurements were consistent with the presence of two extrinsic ferroelectric transitions at 17 and 35 °C.

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amide groups on the properties of partially imidized polyamidic acids as compared with those of the resulting polyimides, during different steps of thermal treatment. Usually, the polarity of the surface influences the dielectric properties and the

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Dielectric properties Dielectric study was performed on pure and KCl-doped TGS crystals at room temperature (30 °C) in the frequency range of 1–500 kHz. The capacitance of these crystals was recorded for the applied frequency and the dielectric

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