Effects of Moisture Absorption on the Dielectric Properties of Nanoclay-Reinforced Epoxy for Radome Applications

The relative permittivity and loss tangent at 10 GHz of a nanoclay-reinforced epoxy is investigated as a function of nanoclay loading percentage and moisture content. The energy dissipation associated with frictional and inertial losses during the reorientation of absorbed dipole water molecules exposed to an oscillating electromagnetic field has a significant impact on the relative permittivity and loss tangent of moisture-contaminated polymer materials. This can damage the performance of polymer-based radar-protecting structures (radomes) designed to protect sensitive radar equipment. Thus, prevention or minimization of water absorption in these materials is critical to mitigating this effect. The moisture barrier properties of nanoclay reinforcement are well known, and are targeted in this study as a potential method to reduce the moisture absorption rate and therefore improve the performance of polymer-based radomes exposed to precipitation and humid air. The ability of a water molecule to rotate freely in the presence of an EM field is dependent on its physical and chemical state; whether it be bound and unable to rotate, or unbound and able to dissipate energy through unrestricted rotation. Therefore, any potential dielectric property changes associated with the physical and chemical interaction of water and nanoclay must be quantified prior to exploiting prospective moisture-barrier benefits. In this study, the relative permittivity and loss tangent of an epoxy system reinforced with nanoclay up to 5% content by weight are assessed using a resonant cavity technique at 10 GHz during moisture uptake due to immersion in distilled water at 25°C. Variations in moisture diffusion behavior are observed due to the nanoclay loading percentage. Although deviations in the dielectric properties due solely to nanoclay loading percentage are minimal, effects due to moisture absorption are much more prominent. In the most extreme case, a nearly 15% increase in relative permittivity is observed at 5% moisture content by weight, with a direct correlation between diffusion behavior and degradation of relative permittivity observed for all samples. Likewise, an increase in the loss tangent of approximately 220% is observed at 5% moisture content by weight.

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Dielectric properties of hops – an effect of bulk density

Research in Agricultural Engineering ◽

10.17221/34/2017-rae ◽

2017 ◽

Vol 63 (Special Issue) ◽

pp. S18-S23

Author(s):

Lev Jakub ◽

Kumhála František

Keyword(s):

Dielectric Properties ◽

Moisture Content ◽

Bulk Density ◽

Relative Permittivity ◽

Loss Factor ◽

Drying Process ◽

Material Loss ◽

Measuring Device ◽

Temperature Changes ◽

Strong Linear Correlation

Continuous detection of basic physical properties of freshly picked and cleaned wet hop cones would be very helpful for better control and automation of harvesting processes. That is why the main aim of this article was to determine the effects of bulk density changes on dielectric properties of freshly picked hop cones. Relative permittivity and loss factor were measured using a newly developed capacitance measuring device. A strong linear correlation between fresh hops relative permittivity and bulk density was found. This finding could be used e.g. for consequent hop drying process control. Significant differences between tested hop varieties were observed for both relative permittivity and loss factor measurements. These differences cannot be explained only by a slightly different moisture content of the measured varieties and ambient temperature changes. Measured material loss factor was only slightly affected by bulk density changes. However, relative permittivity was affected by bulk density changes significantly. These facts could be used for other properties of wet hop cones estimation.

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Dielectric Properties and Microwave Heating Characteristics of Sodium Chloride at 2.45 GHz

High Temperature Materials and Processes ◽

10.1515/htmp-2013-0008 ◽

2013 ◽

Vol 32 (6) ◽

pp. 587-596 ◽

Cited By ~ 12

Author(s):

Chenhui Liu ◽

Libo Zhang ◽

Jinhui Peng ◽

Wenwen Qu ◽

Bingguo Liu ◽

...

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Sodium Chloride ◽

Moisture Content ◽

Penetration Depth ◽

Loss Tangent ◽

Loss Factor ◽

Dielectric Measurement ◽

Linear Functions ◽

Microwave Drying

AbstractThe effects of moisture content and temperature on the dielectric property of sodium chloride were investigated by using open-ended senor dielectric measurement system at the frequency of 2.45 GHz. Moisture content is a major influencing factor in the variation of dielectric properties. Dielectric constant, loss factor and loss tangent all increase linearly with moisture content increasing. Three predictive models were developed to obtain dielectric constant, loss factor, loss tangent and of sodium chloride as linear functions of moisture content. Temperature between 20 °C and 100 °C has a positive effect on dielectric constant and loss factor. Penetration depth decreased nonlinearly with moisture and temperature increasing. A predictive model was developed to calculate penetration depth for sodium chloride as a fifth function of moisture content. In addition, the measurements indicate that the particles temperature increases linearly with microwaving heating time at different power levels. The knowledge gained from these results is useful in developing more effective applications of microwave drying and designing better sensors for measuring moisture content of sodium chloride.

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AC CONDUCTIVITY AND DIELECTRIC PROPERTIES OF MANGANESE DOPED LAYERED Na1.89Li0.10K0.01Ti3O7 CERAMICS

International Journal of Modern Physics B ◽

10.1142/s0217979213502007 ◽

2013 ◽

Vol 28 (01) ◽

pp. 1350200

Author(s):

SHRIPAL SHARMA ◽

RAKESH SINGH ◽

GEETIKA

Keyword(s):

Electrical Conductivity ◽

Dielectric Properties ◽

Chemical Synthesis ◽

Loss Tangent ◽

Relative Permittivity ◽

Ac Electrical Conductivity ◽

Conduction Mechanisms ◽

Tan Δ ◽

Electron Clouds ◽

Derivatives Of

Manganese doped derivatives of polycrystalline Na 1.89 Li 0.10 K 0.01 Ti 3 O 7 bearing 0.01, 0.05 and 1.0 molar % of manganese have been prepared by chemical synthesis. The results of ac electrical conductivity studies in form of log (σT) versus 1000/T plots are reported in the frequency and temperature range of 10 kHz–1 MHz and 350–775 K, respectively. The corresponding plots have been divided into five temperature regions, I, II, III, IV and V. The various conduction mechanisms in different regions have been discussed. The nature of conductivity has been explained by proposing a model about the obtained conductivity σ(ω) which is the sum of three terms arising from three different mechanisms. Moreover, various Na–K–Li–O–Ti–O linkages in Na 2-x-y Li x K y Ti 3 O 7 materials may result special forms of electron clouds. Experimental results of the loss tangent ( tan δ) and relative permittivity (εr) versus temperature at different frequencies have been described. The results of tan δ and εr versus frequency plots at different temperature have also been given for these doped derivatives.

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ELECTRICAL PROPERTIES OF MUNG BEANS (Vigna Radiata L.)

Journal on Processing and Energy in Agriculture ◽

10.5937/jpea25-34115 ◽

2021 ◽

Vol 25 (3) ◽

pp. 101-105

Author(s):

Ján Novák

Keyword(s):

Electrical Properties ◽

Moisture Content ◽

Electric Field ◽

Loss Tangent ◽

Vigna Radiata ◽

Relative Permittivity ◽

Dielectric Material ◽

Variable Moisture Content

This paper contains the results of measuring the electrical properties of mung beans (Vigna radiata L.) set. The conductivity and relative permittivity are the main parameters of dielectric material electrical properties. The electrical properties of mung beans samples had not been sufficiently measured, and the aim of this work was to perform the measurements of these properties. Measurements were performed under variable moisture content and the frequency of electric field from 0.1 kHz till 200 kHz for conductivity and in the range from 1 MHz to 16 MHz for relative permittivity, using RLC meter and Q meter, respectively. It was concluded that relative permittivity, and conductivity increased with increase of moisture content, resistivity, impedance, loss tangent, and relative permittivity decreased as the frequency of electric field increased, respectively.

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Comparison of Dielectric Properties of Traditional and High-Oleic Runner-Type Peanuts at Microwave Frequencies

Transactions of the ASABE ◽

10.13031/trans.14323 ◽

2021 ◽

Vol 64 (6) ◽

pp. 1817-1822

Author(s):

Micah A. Lewis ◽

Samir Trabelsi

Keyword(s):

Dielectric Constant ◽

Oleic Acid ◽

Linoleic Acid ◽

Dielectric Properties ◽

Moisture Content ◽

Loss Tangent ◽

Loss Factor ◽

Microwave Frequencies ◽

High Oleic ◽

Transmission Measurements

HighlightsPermittivity measurements were taken for traditional and high-oleic runner-type peanut pods and kernels at microwave frequencies.The dielectric constant, loss factor, loss tangent, and complex plane were compared between the two cultivars to observe any effect caused by the high-oleic trait.Despite differences in composition, minimal to no differences were observed in permittivity between the two cultivars.Abstract. Different cultivars of peanuts containing higher amounts of oleic acid have been developed to improve oxidative stability and overall peanut quality. Increasing oleic acid levels and decreasing linoleic acid levels in peanuts deter lipid oxidation, preventing the creation of off-flavors and increasing the shelf life. Since their conception, high-oleic peanuts have been tested from chemical and sensory perspectives to observe differences between them and traditional peanuts. Such tests have shown minimal differences, if any. However, tests to observe the effect of changing the levels of oleic and linoleic acid on permittivity, which is often used for nondestructive determination of the moisture content and bulk density of foods and agricultural products, have not been reported. Thus, a vector network analyzer (VNA) was used to take free-space transmission measurements of the complex permittivities of high-oleic and traditional runner-type peanut pods and kernels. Measurements were taken at 23°C between 5 and 9 GHz. Measurements yielded the dielectric constant and loss factor, which are often correlated to moisture content. Analysis was performed to compare the changes in the dielectric constant, loss factor, and loss tangent with moisture content for high-oleic and traditional peanuts. Linear trends were observed for each parameter with increasing moisture content for both cultivars. Results from the complex plane showed coefficient of determination (r2) values greater than 0.9 for pods and kernels. Therefore, at microwave frequencies, changing the levels of oleic and linoleic acid within the peanuts was observed to have minimal to no effect on their permittivity. Thus, moisture calibrations based on correlations between dielectric properties and moisture content for traditional runner-type peanuts can be applied to high-oleic cultivars. Keywords: Dielectric properties, Free-space transmission measurements, Microwave measurements, Oleic acid, Peanut kernels, Peanut pods.

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Synthesis and Pressure-Assisted Sintering of CaCu3Ti4O12 Dielectrics

Ceramics ◽

10.3390/ceramics4030033 ◽

2021 ◽

Vol 4 (3) ◽

pp. 447-466

Author(s):

Jan Pertášek ◽

Pavel Ctibor ◽

Josef Sedláček ◽

Frantisek Lukáč

Keyword(s):

High Pressure ◽

Phase Composition ◽

Dielectric Properties ◽

Loss Tangent ◽

Relative Permittivity ◽

Sintering Temperature ◽

Dielectric Behavior ◽

Feedstock Powder ◽

Dielectric Characteristics ◽

Conventional Sintering

In this paper, we examined the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics fabricated by various routes and discussed the most important conditions affecting their dielectric behavior. We prepared feedstock powder using a molten salt route and compared it with a commercial powder. Both powders were sintered using SPS. For some samples, annealing was applied after sintering. Other samples were obtained by high-pressure forming and conventional sintering, using both powders. Phase composition, porosity and microhardness were evaluated in comparison with the literature. The results showed that a sintering temperature just below or equal to 1000 °C should be set for the SPS process. However, the best dielectric characteristics were obtained in samples prepared by high-pressure forming and conventional sintering, which showed a relative permittivity of 22,000 and a loss tangent of 0.13 at 1 MHz.

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PENGARUH VIRGIN COCONUT OIL (VCO) TERHADAP KARAKTERISTIK DAN UMUR SIMPAN ROTI MANIS

JURNAL TEKNOLOGI DAN INDUSTRI PANGAN ◽

10.33061/jitipari.v5i1.3643 ◽

2020 ◽

Vol 5 (1) ◽

Author(s):

Aulia Alfi

Keyword(s):

Moisture Content ◽

Shelf Life ◽

Coconut Oil ◽

Temperature Treatment ◽

Ash Content ◽

Virgin Coconut Oil ◽

Food Ingredients ◽

Life Analysis ◽

Antibacterial And Antifungal ◽

Physical And Chemical

Virgin Coconut Oil (VCO) adalah bahan alami yang memiliki sifat antimikroba (antivirus, antibakteri, dan antijamur). Sehingga VCO dapat memberikan efek pengawet pada bahan makanan, salah satunya adalah roti manis. Penelitian ini dilakukan untuk mengevaluasi pengaruh VCO terhadap karakteristik (fisik dan kimia) dan umur simpan roti manis. Roti manis dianalisis secara fisik (tekstur dan porositas) dan kimia (kadar air, kadar abu, kadar lemak, kadar protein, dan kandungan karbohidrat), dan analisis umur simpan dengan FFA, uji organoleptik dan jamur setiap dua hari selama delapan hari penyimpanan di suhu ruang. Variasi perlakuan roti manis adalah dari rasio konsentrasi VCO: margarin: mentega, K (0%: 8%: 8%); A (4%: 6%: 6%); B (8%: 4%: 4%), C (12%: 2%: 2%); D (16%: 0%: 0%). Hasil penelitian menunjukkan bahwa VCO tidak memiliki pengaruh yang signifikan terhadap karakteristik fisik dan karakteristik kimia roti manis. Namun, VCO berpengaruh signifikan terhadap kadar air roti manis yang dihasilkan, roti manis K memiliki kadar air tertinggi (22,36%) dan berbeda dengan sampel roti manis lainnya. VCO secara efektif menghambat pertumbuhan jamur di roti manis pada konsentrasi 8%, 12%, dan 16%. Roti manis K dan A memiliki masa simpan 4 hari, sedangkan roti manis B, C, dan D memiliki masa simpan 6 hari.Kata kunci: VCO, roti manis, karakteristik, umur simpanABSTRACTVirgin Coconut Oil (VCO) is a natural ingredient that has antimicrobial (antiviral, antibacterial, and antifungal) properties. So that VCO can provide a preservative effect on food ingredients, one of which is sweet bread. This research was conducted to evaluate the effect of VCO on characteristics (physical and chemical) and shelf life of sweet bread. Sweet bread was analyzed physically (texture and porosity) and chemistry (moisture content, ash content, fat content, protein content, and carbohydrate content), and shelf life analysis with FFA, organoleptic and mold tests every two days for eight days of storage at ambient temperature. Treatment variations of sweet breads is from the ratio of the concentration of VCO: margarine: butter, K (0%: 8%: 8%); A (4%: 6%: 6%); B (8%: 4%: 4%), C (12%: 2%: 2%); D (16%: 0%: 0%). The results showed that VCO did not have a significant effect on the physical characteristics and chemical characteristics of sweet bread. However, the VCO has a significant effect on the water content of the sweet bread produced, sweet bread K has the highest moisture content (22,36%) and it is different from other sweet bread samples. VCO effectively inhibits the growth of sweet bread mold at concentrations of 8%, 12%, and 16%. K and A sweet bread has a shelf life of 4 days, while sweet breads B, C, and D have a shelf life of 6 days.Keywords: VCO, sweet bread, characteristics, shelf life

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The Primary Origin of Excellent Dielectric Properties of (Co, Nb) Co-Doped TiO2 Ceramics: Electron-Pinned Defect Dipoles vs. Internal Barrier Layer Capacitor Effect

Molecules ◽

10.3390/molecules26113230 ◽

2021 ◽

Vol 26 (11) ◽

pp. 3230

Author(s):

Theeranuch Nachaithong ◽

Narong Chanlek ◽

Pairot Moontragoon ◽

Prasit Thongbai

Keyword(s):

Dielectric Properties ◽

Loss Tangent ◽

Barrier Layer ◽

Dielectric Response ◽

High Resistivity ◽

Low Loss ◽

Rutile Tio2 ◽

Complex Defect ◽

Very High ◽

Co Doped

(Co, Nb) co-doped rutile TiO2 (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO2 phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO2 with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ » 36,105 and a low loss tangent of tanδ » 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoVoTi complex defect. On the other hand, the substitution of TiO2 with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.

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Moisture Measurement in Paper and Cardboard Packaging Waste Bales for Recycling

Applied Sciences ◽

10.3390/app11104586 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4586

Author(s):

Ana Silveira ◽

João Cardoso ◽

Maria José Correia ◽

Graça Martinho

Keyword(s):

Quality Control ◽

Dielectric Properties ◽

Moisture Content ◽

Reliable Method ◽

Drying Method ◽

Waste Streams ◽

Oven Drying ◽

Quality Issue ◽

Commercial Device ◽

Non Destructive

Moisture content is a quality issue raised by recycling plants in the acceptance of paper and cardboard coming from waste streams. The current way to measure this parameter is by the oven drying method, which is a slow and invasive process, costing time and resources for the recyclers to do this type of quality control. An alternative to such a measurement technique is the use of plate-form devices which indirectly measure the moisture content using the dielectric properties of water and paper. This study has tested this method and developed a representative equation for the use of devices with these properties in the Portuguese market. For that, 48 wastepaper and cardboard bales were tested with both the traditional (oven drying) method and a commercial device equipped with dielectric technology. An equation that fits the studied reality (R2 = 0.76) was achieved, and possible problems regarding the use of this device were tested. The results showed that this type of device could be used as a time- and cost-saving, non-destructive and reliable method in the quality control of wastepaper and cardboard bales.

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Study on the Moisture Absorption and Thermal Properties of Hygroscopic Exothermic Fibers and Related Interactions with Water Molecules

Polymers ◽

10.3390/polym12010098 ◽

2020 ◽

Vol 12 (1) ◽

pp. 98 ◽

Cited By ~ 1

Author(s):

Yi Cui ◽

Shuyi Gao ◽

Ruiyun Zhang ◽

Longdi Cheng ◽

Jianyong Yu

Keyword(s):

Moisture Content ◽

Thermal Performance ◽

Water Sorption ◽

Moisture Absorption ◽

Bound Water ◽

Absorption Process ◽

Heating Performance ◽

Hygroscopic Behavior ◽

Water Sorption Capacity ◽

Main Factor

The aim of this paper is to study the hygroscopic behavior of hygroscopic exothermic fiber-based materials and to obtain a better understanding of the thermal performance of these fibers during the moisture absorption process. The temperature distribution of different kinds of hygroscopic exothermic fibers in the process of moisture absorption, observed by infrared camera, demonstrated two types of heating performance of these fibers, which might be related to its hygroscopic behavior. Based on the sorption isotherms, a Guggenheim-Anderson-de Boer (GAB) multi-layer adsorption model was selected as the optimal moisture absorption fitting model to describe the moisture absorption process of these fibers, which illustrated that water sorption capacity and the water–fiber/water–water interaction had a significant influence on its heating performance. The net isosteric heats of sorption decreased with an increase of moisture content, which further explained the main factor affecting the heat dissipation of fibers under different moisture contents. The state of adsorbed water and water vapor interaction on the fiber surface were studied by simultaneous thermal analysis (TGA-DSC) measurement. The percentage of bound and unbound water formation at low and high humidity had a profound effect on the thermal performance of fibers. It can therefore be concluded that the content of tightly bound water a strong water–fiber interaction was the main factor affecting the heating performance of fibers at low moisture content, and the content of loosely bound water reflected that water sorption capacity was the main factor affecting the heating performance of fibers at high moisture content. This was further proven by the heat of desorption.

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