scholarly journals The Dielectric Properties and Thermal Conductivities of Epoxy Composites Reinforced by Titanium Dioxide

2021 ◽  
Author(s):  
Yuan Jia ◽  
Juxiang Yang ◽  
Weijie Dong ◽  
Beibei Li ◽  
Zhen Liu
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Titanium Dioxide ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Hydrothermal Process ◽  
Sodium Dodecyl ◽  
Sodium Dodecyl Benzene Sulfonate ◽  
Ep Matrix ◽  
Thermal Conductivities

Abstract To improve the dielectric properties and thermal conductivities of epoxy resins (EP), titanium dioxide superfine powders with microspheres structure (S-TiO2) were prepared via a hydrothermal process based on the sodium dodecyl benzene sulfonate and hydroxyl silicate. The different content of S-TiO2 was then employed as modifiers to add into EP resin to prepare the S-TiO2/EP composites. The structure and morphology of the prepared S-TiO2 was observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and influences of different addition of S-TiO2 on the thermal conductivity of S-TiO2/EP composites are researched, while their dielectric constant and dielectric loss are also studied. The results suggested that the reasonable content of S-TiO2 can endow the S-TiO2/EP composites with higher dielectric constant without excessive increase their dielectric loss even under the high frequency. Furthermore, the thermal conductivity of S-TiO2/EP are also be improved, which can be attributed to the good thermal conductivity of S-TiO2 itself and the thermal conductivity path formed by S-TiO2 inside the EP matrix.

scholarly journals Thermal Conductivity of Epoxy Composites Modified by Microspheric Molybdenum Disulfide

2021 ◽  
Author(s):  
Zhen Liu ◽  
Yuan Jia ◽  
Juxiang Yang ◽  
Ruifeng Shi
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Properties ◽  
Molybdenum Disulfide ◽  
Hydrothermal Process ◽  
Sodium Dodecyl ◽  
Sodium Molybdate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Uniform Dispersion ◽  
Ep Matrix

Abstract In order to improve the thermal conductivity of epoxy resins (EP) without reducing their dielectric properties, a kind of molybdenum disulfide with microspheres structure (S-MoS2) was prepared via surfactant promoting hydrothermal process based on the sodium molybdate, thiosemicarbazide, and sodium dodecyl sulfate. The S-MoS2 was then used as modifiers to add into EP matrix to prepare a new kind of S-MoS2/EP composites. The morphology of the prepared S-MoS2 was observed by X-ray diffraction (XRD) scanning electron microscopy (SEM), while the influence of different S-MoS2 loading on the dielectric properties, thermal conductivity and thermal resistance of S-MoS2/EP composites was also researched. The results suggested that the reasonable content of S-MoS2 can highly improve the thermal conductivity of S-MoS2/EP, which can be attributed to the excellent thermal resistant and uniform dispersion of S-MoS2 in EP matrix.

Dielectric Properties of Al2O3 Nanofibers/Epoxy Resin Nanocomposites

2013 ◽  
Vol 873 ◽  
pp. 486-491 ◽  
Author(s):  
Yu Xia Zhang ◽  
Hong Zhou ◽  
Yong Fan
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Epoxy Resin ◽  
Hydrothermal Process ◽  
Epoxy Nanocomposites ◽  
Dielectric Spectra ◽  
Low Level ◽  
Alumina Nanofibers ◽  
Epoxy Resin Nanocomposites

In this article, Al2O3 nanofibers have been successfully synthesized by hydrothermal process and Al2O3 nanofibers/epoxy nanocomposites were fabricated by incorporating the Al2O3 nanofibers modified by 3-aminopropyl trimethoxysilane (APTMOS). Dielectric spectra of the nanocomposites were investigated. The effects of Al2O3 morphology and concerntration on dielectric spectra of nanocomposites were discussed. The results showed that the dielectric constant increased smoothly as the alumina nanofibers concentration increasing, but it decreased with increasing frequency. While the dielectric loss increased slightly with increasing frequency, however, it still remained at a low level.

Dielectric Properties and Thermal Conductivity of Poly(vinylidene fluoride)-Based Composites with Graphite Nanosheet and Nickel Particle

2019 ◽  
Vol 19 (6) ◽  
pp. 3591-3596 ◽  
Author(s):  
Lirong Wu ◽  
Dandan Yang
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Ac Conductivity ◽  
Vinylidene Fluoride ◽  
Filler Loading ◽  
Graphite Nanosheet ◽  
Dielectric Performance ◽  
Poly Vinylidene Fluoride

The nickel (Ni) particles and graphite nanosheet (GNS) filled poly(vinylidene fluoride) (PVDF) composites were prepared by solution blending and hot-press processing in the magnetic field. The influence of Ni particles and GNS fillers for the structure, morphology, AC conductivity, dielectric properties and thermal conductivity of composites was investigated. The results showed that the β-phase crystals of PVDF matrix was increased obviously. The AC conductivity, dielectric constant and dielectric loss of PVDF/Ni/GNS composite reached to 10−9 s/cm, 62 and 0.39 when the filler loading was 11 wt.% at 102 Hz, respectively. At the ratio of 15 wt.% filler, the AC conductivity of PVDF/Ni/GNS composite was vastly improved to 10−6 s/cm, however, the dielectric constant increased to ~80 and dielectric loss was over 600 at 102 Hz. By comparing the dielectric performance of PVDF/Ni/GNS, PVDF/Ni and PVDF/GNS composites, it is found that the parallel arrangement of the filler conduces to improve the dielectric properties of the composites. Furthermore, the thermal conductivity of PVDF/Ni/GNS composites increased with the increase of Ni and GNS contents and the value raised to over 0.5 W/mK when filler loading was 15 wt.%.

Influence of Nanomaterials in Polymer Composites on Thermal Conductivity

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Wonchang Park ◽  
Kyungwho Choi ◽  
Khalid Lafdi ◽  
Choongho Yu
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Polymer Composites ◽  
Effective Medium Theory ◽  
Sodium Dodecyl ◽  
Sodium Dodecyl Benzene Sulfonate ◽  
Drying Methods ◽  
Synthesis Conditions ◽  
Steady State Method ◽  
Thermal Conductivities

Carbon nanotube- or/and graphite-filled polymer composites were synthesized by using simple mixing and drying methods, and their thermal conductivities and structures were characterized by using a steady-state method (ASTM D5470) and scanning and transmission electron microscopies. In order to investigate the influence of synthesis conditions on the thermal conductivity of composites, various concentrations of multiwall carbon nanotubes, graphites, surfactants, and polymer matrix materials as well as two different nanoparticles and solvents were tested. Our composites containing both nanotubes (25 wt. %) and graphites (25 wt. %) with sodium dodecyl benzene sulfonate (SDBS) as a dispersant showed the highest thermal conductivity, ∼1.8 W/m-K at room temperature. The highest conductivity from nanotube/graphite mixtures would be from good adhesion and less voids between nanotubes and polymers as well as excellent thermal conduction from graphite sheets. The thermal conductivities of the composites have been calculated as a function of carbon nanotube concentrations by using a model based on the Maxwell’s effective medium theory, and the most effective method of improving thermal conductivity was suggested.

Plasticizer effect on dielectric properties of poly(methyl methacrylate)/titanium dioxide composites

2021 ◽  
pp. 096739112110147
Author(s):  
Ufuk Abaci ◽  
H Yuksel Guney ◽  
Mesut Yilmazoglu
Keyword(s):  
Dielectric Constant ◽  
Titanium Dioxide ◽  
Dielectric Properties ◽  
Methyl Methacrylate ◽  
Pure Pmma ◽  
Segmental Mobility ◽  
Scanning Calorimetry ◽  
Poly Methyl Methacrylate ◽  
Casting Technique ◽  
Lcr Meter

The effect of plasticizer on dielectric properties of poly(methyl methacrylate) (PMMA)/titanium dioxide (TiO2) composites was investigated. Propylene carbonate (PC) was used as plasticizer in the samples which were prepared with the conventional solvent casting technique. Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (SEM-EDX) and Differential scanning calorimetry (DSC) analyses and LCR Meter measurements (performed between 300 K and 400 K), were conducted to examine the properties of the composites. With the addition of plasticizer, the thermal properties have changed and the dielectric constant of the composite has increased significantly. The glass transition temperature of pure PMMA measured 121.7°C and this value did not change significantly with the addition of TiO2, however, 112°C was measured in the sample with the addition 4 ml of PC. While the dielectric constant of pure PMMA was 3.64, the ε′ value increased to 5.66 with the addition of TiO2 and reached 12.6 with the addition of 4 ml PC. These changes have been attributed to increase in amorphous ratio that facilitates polymer dipolar and segmental mobility.

Microstructure and Microwave Dielectric Properties of BaTi4O9 Ceramics Derived from a Sol-Gel Precursor

2011 ◽  
Vol 326 ◽  
pp. 127-130
Author(s):  
Xian Li Huang ◽  
Fu Ping Wang ◽  
Ying Song
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Sol Gel ◽  
Microwave Dielectric Properties ◽  
Sintering Process ◽  
Temperature Coefficients ◽  
Microwave Dielectric ◽  
Ceramic Samples ◽  
Quality Factor Q

In the present work, the microstructure and microwave dielectric properties of BaTi4O9 ceramics derived from a sol-gel precursor were presented. Density measuring results demonstrated that the largest densities of ceramic sample about 96.7% could be reached by virtue of a cool iso-static press and a sintering process at at 1300 °C for 6 hours. The dielectric constant (εr), quality factor (Q×f) and the temperature coefficients (τf) of the BaTi4O9 ceramic samples were 36.65, 28000 GHz, +20.2 ppm/°C, respectively. XRD, SEM and XPS were used to characterize the microstructure of the ceramics samples. Substantial Ti3+ was proposed to be the cause of dielectric loss.

Preparation and Dielectric Properties of 1-3 La Modified PZT/IPN Piezoelectric Composites

2010 ◽  
Vol 105-106 ◽  
pp. 355-358 ◽  
Author(s):  
Z.L. Zhu ◽  
Dong Yan Tang ◽  
X.H. Zhang ◽  
Y.J. Qiao
Keyword(s):  
Heat Treatment ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Lead Zirconate Titanate ◽  
Polymer Network ◽  
Lead Zirconate ◽  
Interpenetrating Polymer Network ◽  
Ceramic Fibers ◽  
Piezoelectric Composites

To prevent the potential cracking of gel fibers, La modified lead zirconate titanate (PLZT) ceramic fibers with diameter within 50µm were achieved by embedding into PLZT powders during the heat treatment. Then the 1-3 PLZT fiber/interpenetrating polymer network (IPN) piezoelectric composites were prepared by casting the IPN precursors onto the well aligned ceramic fibers. The influences of the heating temperatures and La amounts on the dielectric constant, dielectric loss with frequencies and piezoelectric constant of PLZT were investigated in detail. The morphologies of fibers and composites were observed by biological microscope. And also, the dielectric constant of PLZT fibers and PLZT fiber/IPN piezoelectric composites were detected.

Microwave Nondestructive Sensing of Moisture Content and Water Activity of Almonds

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.

Synthesis and Dielectric Properties of [(K0.5Na0.5)0.935Li0.065]NbO3 Added with Mn for Piezoelectric Ceramic

2016 ◽  
Vol 675-676 ◽  
pp. 635-638
Author(s):  
Jukkrit Kongphimai ◽  
Hassakorn Wattanasarn ◽  
Tosawat Seetawan
Keyword(s):  
Crystal Structure ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Physical Properties ◽  
Crystallite Size ◽  
Piezoelectric Ceramic ◽  
Theoretical Density ◽  
Milling Method ◽  
Xrd Patterns

[(K0.5Na0.5 )0.935Li0.065]NbO3–Mn ceramics (Mn = 0, 1.50 and 3 mol %) (KNNL–Mn) were synthesized and measured dielectric properties. Which the K2CO3, Na2CO3, Li2CO3, Nb2O5 and MnO2 (0, 1.5, 3 mol%) were mixed by ball milling method and calcined powders at 1,073 K for 4 h and the sintered at 1,343 K for 2 h in air. The crystal structure was analyzed by XRD technique, the crystallite size was identified by Scherrer’s equation and calculated the theoretical density. It was found that, the XRD patterns of the KNNL–Mn ceramics added with Mn contents was indicated the tetragonal structure and. the crystallite size of Mn = 0, 1.50 and 3 mol% about 32 nm, 34 nm and 57 nm, respectively. The physical properties of the KNNL–Mn ceramics was found that the maximum theoretical density of 90.79 % for Mn = 1.50 mol%. The dielectric constant was found to be maximum of 909.77 and dielectric loss of 0.48 for Mn = 3 mol%.

Effect of moisture content on dielectric properties of banana leaves and peels in frequency range of 1–20 GHz

Frequenz ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Soumya Sundar Pattanayak ◽  
Soumen Biswas
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Moisture Content ◽  
Measurement Data ◽  
Banana Peel ◽  
Frequency Range ◽  
Proposed Model ◽  
Banana Leaves ◽  
Banana Leaf

Abstract The quality of agricultural products can be remotely sensed and enhanced by determining the dielectric properties. This paper studies the dielectric properties of banana leaf and banana peel over the frequency range 1–20 GHz using the open-ended coaxial probe (OCP) method. A new curve fitting model is proposed to characterize the dielectric properties of banana leaf and banana peel. The different moisture content (MC) levels are considered for both banana leaf and banana peel samples and, their dielectric properties are characterized. Further, the banana leaf and banana peel’s measurement data are compared with the data obtained using the proposed model. In addition, Root Mean Square Error (RMSE) and R-squared (R 2) are calculated to validate the performance of the proposed model. In case of banana leaf at 68.26% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.98 and 0.0648, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.88 and 0.0795, respectively. Further, for banana peel at 80.89% MC, the dielectric constant achieves the value of R 2 and RMSE of 0.99 and 0.2989, respectively. Similarly, dielectric loss achieves the value of R 2 and RMSE of 0.96 and 0.6132, respectively.

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