Combined Effect of Temperature and Oil and Salt Contents on the Variation of Dielectric Properties of a Tomato-Based Homogenate

Tomato-based processed foods are a key component of modern diets, usually combined with salt and olive oil in different ratios. For the design of radiofrequency (RF) and microwave (MW) heating processes of tomato-based products, it is of importance to know how the content of both ingredients will affect their dielectric properties. Three concentrations of olive oil and salt were studied in a tomato homogenate in triplicate. The dielectric properties were measured from 10 to 3000 MHz and from 10 to 90 °C. Interaction effects were studied using a general linear model. At RF frequencies, the dielectric constant decreased with increasing temperature in samples without added salt, but this tendency was reversed in samples with added salt. The addition of salt and oil increased the frequency at which this reversion occurred. At MW frequencies, the dielectric constant decreased with increasing temperature, salt, and oil content. The loss factor increased with increasing salt content and temperature, except in samples without added salt at 2450 MHz. Penetration depth decreased with increasing frequency and loss factor. Salt and oil contents have a significant effect on the dielectric properties of tomato homogenates and must be considered for the design of dielectric heating processes.

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Dielectric and Conductivity Properties of Some Wood Composites

International Journal of Engineering and Technologies ◽

10.18052/www.scipress.com/ijet.8.51 ◽

2016 ◽

Vol 8 ◽

pp. 51-60

Author(s):

K.Ch. Varada Rajulu ◽

B.N. Mohanty

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Dielectric Loss ◽

Low Temperature ◽

Temperature Region ◽

Loss Factor ◽

Wood Composites ◽

Frequency Range ◽

Increasing Temperature ◽

Coaxial Probe

This study presents the dielectric and conductivity properties as function of temperature and frequency of wood based composites. These properties were measured by an open-ended coaxial probe at frequency range between 100 kHz to 100MHz, temperature from 30OC to 200OC which is fully computer interfaced. It has been observed that dielectric constant (ε') and dielectric loss factor (ε") increase with increasing temperature and decrease with increasing frequency. At low temperature region, the conductivity depends significantly on the frequency. However, with the increase in temperature dielectric relaxation takes place and the dependency of the conductivity on frequency get reduced. The patterns of variation were established for the studied specimens and discrepancies were discussed. The study of dielectric properties will help in improving the drying, heating and gluing processes of wood and wood based products.

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Dielectric Properties of Blackberries as Related to Microwave Drying Control

International Journal of Food Engineering ◽

10.1515/ijfe-2017-0198 ◽

2017 ◽

Vol 13 (12) ◽

Cited By ~ 2

Author(s):

Chunfang Song ◽

Tian Sang ◽

Haiying Chen ◽

Li Zhenfeng ◽

Li Jing

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Moisture Content ◽

Penetration Depth ◽

Loss Factor ◽

Large Scale ◽

Coaxial Line ◽

Dielectric Constants ◽

Microwave Drying ◽

Increasing Temperature

AbstractThe dielectric properties of blackberry samples with a 20.0–80.0 % w.b (web basis) moisture content were determined with a network analyzer and an open-ended coaxial-line probe over a frequency range from 5 to 3000 MHz and a temperature range from 20 to 100 °C. The results showed that the dielectric constant decreased with increasing temperature but increased with increasing moisture content; however, the loss factor increased with increasing temperature and moisture content. The dielectric constant and the loss factor decreased with increasing frequency. The penetration depth decreased with increasing temperature, frequency and moisture content. A large penetration depth at 915 MHz may provide practical large-scale dielectric drying for blackberries. The dielectric constants and loss factors for blackberry by combining the above mathematical model and temperature and moisture of the sample in the microwave drying process were used to analyze and control blackberry drying technology.

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Microwave absorption properties of steelmaking dusts: effects of temperature on the dielectric constant (ε′) and loss factor (ε′′) at 1064 MHz and 2423 MHz

RSC Advances ◽

10.1039/c9ra00009g ◽

2019 ◽

Vol 9 (12) ◽

pp. 6859-6870 ◽

Cited By ~ 3

Author(s):

Mamdouh Omran ◽

Timo Fabritius ◽

Guo Chen ◽

Aoxi He

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Microwave Absorption ◽

Loss Factor ◽

Effect Of Temperature ◽

Absorption Properties ◽

Microwave Absorption Properties ◽

Effects Of Temperature

The effect of temperature on the dielectric properties was found to be minor at temperatures below 600 °C. Above this temperature, sharp rises in the values of both the dielectric constant and the loss factor were observed.

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Microwave Nondestructive Sensing of Moisture Content and Water Activity of Almonds

Transactions of the ASABE ◽

10.13031/trans.14338 ◽

2021 ◽

Vol 64 (4) ◽

pp. 1373-1379

Author(s):

Samir Trabelsi

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Dielectric Loss ◽

Moisture Content ◽

Bulk Density ◽

Water Activity ◽

Free Space ◽

Loss Factor ◽

Dielectric Loss Factor ◽

List Type

HighlightsMoisture and water activity were determined nondestructively and in real time from measurement of dielectric properties.Moisture and water activity calibration equations were established in terms of the dielectric properties.Situations in which bulk density was known or unknown were considered.SEC ranged from 0.41% to 0.68% for moisture and from 0.02 to 0.04 for water activity.Abstract. A method for rapid and nondestructive determination of moisture content and water activity of granular and particulate materials was developed. The method relies on measurement of the dielectric constant and dielectric loss factor at a single microwave frequency. For the purpose of illustration, the method was applied to predicting the moisture content and water activity of almond kernels. A free-space transmission technique was used for accurate measurement of the dielectric properties. Samples of Bute Padre almond kernels with moisture content ranging from 4.8% to 16.5%, wet basis (w.b.), and water activity ranging from 0.50 to 0.93 were loaded into a Styrofoam sample holder and placed between two horn-lens antennas connected to a vector network analyzer. The dielectric properties were calculated from measurement of the attenuation and phase shift at 8 GHz and 25°C. The dielectric properties increased linearly with moisture content, while they showed an exponential increase with water activity. Situations in which the bulk density was known and unknown were considered. Linear and exponential growth regressions provided equations correlating the dielectric properties with moisture content and water activity with coefficients of determination (r2) higher than 0.96. Analytical expressions of moisture content and water activity in terms of the dielectric properties measured at 8 GHz and 25°C are provided. The standard error of calibration (SEC) was calculated for each calibration equation. Results show that moisture content can be predicted with SECs ranging from 0.41% to 0.68% (w.b.) and water activity with SECs ranging from 0.02 to 0.04 for almond kernel samples with water activity ranging from 0.5 to 0.9 and moisture contents ranging from 4.8% to 16.5% (w.b.). Keywords: Bulk density, Dielectric constant, Dielectric loss factor, Free-space measurements, Loss tangent, Microwave frequencies, Moisture content, Water activity.

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Phase Development and Dielectric Properties of 0.98BaTiO3-0.02Ba (Mg1/3Nb2/3) O3 Ceramic

Materials Science Forum ◽

10.4028/www.scientific.net/msf.700.58 ◽

2011 ◽

Vol 700 ◽

pp. 58-62

Author(s):

Rachanusorn Roongtao ◽

Supagorn Rugmai ◽

Wanwilai C. Vittayakorn

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Dielectric Constant ◽

Dielectric Properties ◽

Loss Factor ◽

X Ray Diffraction ◽

Phase Purity ◽

X Ray ◽

Phase Development ◽

Scanning Electron

The 0.98BaTiO3-0.02Ba (Mg1/3Nb2/3) O3ceramics has been synthesized through a conventional mixed-oxide by using BT nanopowder and BMN micropowder. The phase purity of the powders and the ceramics was examined using X-ray diffraction (XRD). The 0.98BT-0.02BMN powders were sintered to 92% of the theoretical density at a temperature of 1300 °C for 2 h. The microstructure of the sintered surface was investigated using scanning electron microscopy (SEM). The dielectric constant (εr) and loss factor (tanδ) of the sintered pellets at Curie temperture were 3000 and 0.015, respectively.

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The effects of calcination and doping on structural and dielectric properties of CaCu3-xCoxTi4O12 ceramic

Mediterranean Journal of Chemistry ◽

10.13171/10.13171/mjc8319052011nh ◽

2019 ◽

Vol 8 (3) ◽

pp. 234

Author(s):

Nasr Hadi ◽

Tajdine Lamcharfi ◽

Farid Abdi ◽

Nor-Said Echtoui ◽

Ahmed Harrach ◽

...

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Complex Impedance ◽

Impedance Analysis ◽

Xrd Analysis ◽

Secondary Phases ◽

Solid State Method ◽

Complex Impedance Analysis ◽

Oxide Powders ◽

Increasing Temperature

The influences of calcination temperature and doping with cobalt in A–site on structural and dielectric properties of CaCu3-xCoxTi4O12 (CCCxTO, x = 0.00, 0.02 and 0.10) ceramics sintered at 1050 0C for 8h were investigated. The ceramic samples are prepared by the conventional solid-state method using high purity oxide powders, and they are calcined at 850 °C, 950 °C and 1050 0C for 4h. The X-ray diffraction (XRD) analysis of pure and doped CCTO samples calcined at 950 °C and 1050 0C showed no traces of any other secondary phases, while impurity phases alongside CCTO phase in the x=0.00 sample calcined at 850 0C was observed. Scanning electron microscopy (SEM) investigation showed an increase in grain size with increasing of Co content and calcining temperature. Dielectric measurements indicated that the dielectric constant of the pure CCTO calcined at 1050 0C/4h has a low value in the frequency range of 1kHz up to 1MHz, whereas the substitution of Co up to x = 0.10 into CCTO caused a huge increase in the dielectric constant value of the calcined samples which is equal to 153419 and 18957 at 950 °C and 1050 0C respectively. The complex impedance analysis of all samples shows a decrease in resistance with an increasing temperature, which suggests a semiconductor nature of the samples.

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Effect of Sintering Temperature on Dielectric Properties of CaCu3Ti4O12 Ceramics Prepared by Mechanochemical Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.974.157 ◽

2014 ◽

Vol 974 ◽

pp. 157-161

Author(s):

Masturah Mohamed ◽

Mahesh Talari ◽

Mohd Salleh Mohd Deni ◽

Azlan Zakaria

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Sintering Temperature ◽

Processing Conditions ◽

Dielectric Measurements ◽

Frequency Range ◽

Grain Sizes ◽

Barrier Capacitance ◽

Different Temperatures ◽

Increasing Temperature

CaCu3Ti4O12(CCTO) is well known to have colossal dielectric constant in the range of 105.It is widely accepted that this phenomenon may be attributed to internal layer barrier capacitance (IBLC) model. The dielectric properties of CCTO were reported to be strongly dependent on the processing conditions and grain size. In this work, CCTO samples with different grain sizes were produced by varying sintering temperature in order to investigate IBLC effect on dielectric properties of CCTO. The samples were sintered at four different temperatures, (T=1100°C, 1050°C, 1000°C and 950°C). Dielectric measurements were carried out for the samples in the frequency range of 102– 106Hz using impedance spectrometer. Electron micrographs showed that increasing temperature promoted the grain growth of CCTO while sintering. The internal crystalline defects are seen to play major role by increasing the grain conductivity in dipole formation and increased the dielectric constant of the samples.

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Dielectric properties of dipolar solids

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1946.0027 ◽

1946 ◽

Vol 185 (1003) ◽

pp. 399-414 ◽

Cited By ~ 7

Keyword(s):

Phase Transition ◽

Dielectric Constant ◽

Dielectric Properties ◽

Ground State ◽

Predominant Role ◽

Chain Molecules ◽

Increasing Temperature ◽

Long Chain ◽

Comparison With Experiments ◽

Good Agreement

A quantitative theory of the dielectric properties of crystalline solids consisting of dipolar long-chain molecules is developed (one dipole per molecule). In these solids the dipoles are concentrated in dipolar planes. In the ground state the dipolar planes have a permanent polarization, but usually the polarizations of successive planes have opposite directions. The static dielectric constant rises with increasing temperature up to a critical temperature T 0 and then decreases. At T 0 the substance has a phase transition of the second kind. Comparison with experiments by Muller on a solid ketone lead to good agreement. For chains with an even number of C-atoms metastable states with a permanent polarization are predicted, and a method to reach these states is discussed. The interaction between dipoles plays a predominant role at temperatures below T 0 . It is shown that Lorentz’s or Onsager’s methods are invalid in this temperature range.

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An Experimental Study on the Dielectric Properties of Rubber Materials

Polymers ◽

10.3390/polym13172908 ◽

2021 ◽

Vol 13 (17) ◽

pp. 2908

Author(s):

Hailong Chen ◽

Yudong Xu ◽

Mengqi Liu ◽

Tao Li

Keyword(s):

Experimental Study ◽

Dielectric Constant ◽

Dielectric Properties ◽

Loss Factor ◽

Peak Frequency ◽

Mixing Process ◽

Absorption Properties ◽

Microwave Absorption Properties ◽

Internal Mixing ◽

Dielectric Constant And Loss

According to specific formulas, the mixing of rubber samples occurs by two methods: open mixing and internal mixing. The effects of frequency, mixing process, carbon black (CB) content, zinc oxide (ZnO) content, and stearic acid (SA) content on the dielectric properties of rubber materials were studied. The results showed that the effects of the mixing process on the dielectric properties of the rubber samples cannot be ignored, and the appropriate mixing process should be selected when preparing the required rubber materials. The dielectric constant and loss factor of the rubber samples vary depending on the frequency. The dielectric constant had a peak and valley value, while the loss factor only had a peak. The dielectric constant and loss factor of rubber samples were significantly affected by the content of CB, ZnO, and SA. The peak frequency decreased with the increase in CB content, however, the dielectric constant increased with an increase in CB content. The higher the ZnO content, the lower the peak frequency. In addition, the dielectric constant and loss factor increased with an increase in ZnO content. The higher the SA content, the greater the peak frequency. In addition, the dielectric constant and loss factor decreased with an increase in SA content. It is hoped that the experimental results obtained can provide guidance for the study of the dielectric properties, microwave absorption properties, and microwave heating characteristics of rubber polymers.

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Dielectric properties of zinc sulfide concentrate during the roasting at microwave frequencies

10.20944/preprints201702.0044.v1 ◽

2017 ◽

Author(s):

Guangjun He ◽

Shiwei Li ◽

Kun Yang ◽

Jian Liu ◽

Peng Liu ◽

...

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Dielectric Loss ◽

Zinc Sulfide ◽

Apparent Density ◽

Loss Tangent ◽

Loss Factor ◽

Microwave Energy ◽

Dielectric Loss Factor ◽

Sulfide Concentrate

Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities—1.54 and 1.63 g/cm3—have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 °C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 °C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 °C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively.

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