scholarly journals Piezoelectric and Dielectric Characterization of MWCNT-Based Nanocomposite Flexible Films

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
S. Banerjee ◽  
W. Du ◽  
U. Sundar ◽  
K. A. Cook-Chennault
Keyword(s):  
Dielectric Properties ◽  
Parallel Plate ◽  
Volume Fraction ◽  
Sol Gel ◽  
Deposition Process ◽  
Contact Method ◽  
Dielectric Polarization ◽  
Multiwalled Carbon ◽  
Dielectric Characterization ◽  
Piezoelectric Strain

PZT-epoxy-multiwalled carbon nanotube (MWCNT) flexible thick film actuators were fabricated using a sol-gel and spin coat and deposition process. Films were characterized in terms of their piezoelectric and dielectric properties as a function of MWCNT volume fraction and polarization process. Correlations between surface treatment of the MWCNTs and composite performance were made. The surface morphology and filler distribution were observed with the aid of SEM and TEM images. The volume fraction of PZT was held constant at 30%, and the volume fraction of MWCNTs varied from 1% to 10%. Two forms of dielectric polarization were compared. Corona discharge polarization induced enhanced piezoelectric and dielectric properties by a factor of 10 in comparison to the parallel-plate contact method (piezoelectric strain coefficient and dielectric constant were 0.59 pC/N and 61.81, respectively, for the parallel-plate contact method and 9.22 pC/N and 103.59 for the corona polarization method, respectively). The percolation threshold range was observed to occur at a MWCNT volume fraction range between 5% and 6%.

scholarly journals Micromorphology and Mechanical and Dielectric Properties of Bismaleimide Composite Modified by Multiwalled Carbon Nanotubes and Polyethersulfone

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Yufei Chen ◽  
Chengbao Geng ◽  
Yang Han ◽  
Mingzhuo Chai ◽  
Hongyuan Guo ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electron Microscope ◽  
Dielectric Properties ◽  
Bisphenol A ◽  
Multiwalled Carbon Nanotubes ◽  
High Performance ◽  
Sol Gel ◽  
Alder Reaction ◽  
Multiwalled Carbon ◽  
The Impact

Multiwalled carbon nanotubes (MWCNTs) were modified by oxidizing agent to obtain O-MWCNTs, and the surface of it was coated with active group. 4,4′-Diaminodiphenylmethane bismaleimide (MBMI) was used as matrix, 3,3′-diallyl bisphenol A (BBA) and bisphenol-A diallyl ether (BBE) were used as reactive diluent, polyethersulfone (PES) as toughening agent, and O-MWCNTs as modifier; OMWCNT/PES-MBAE composite was prepared through in situ sol-gel method. The effect of PES and OMWCNTs on the mechanical and dielectric properties of composite was analyzed, and the microstructure was examined by transmission electron microscope (TEM) and scanning electron microscope (SEM). The mechanism of composite toughened by PES and OMWCNTs was observed and analyzed. The results showed that Diels-Alder reaction between MBMI and allyl compounds occurred completely and unsaturated double bond disappeared. O-MWCNTs and PES resin dispersed smoothly in polymer matrix and were used as reinforcement, and PES resin and O-MWCNTs could synergistically improve the properties of the composite and exhibited a typical ductile fracture. The impact and bending strengths were 16.09 kJ/m2 and 153.57 MPa, which were 74.32% and 53.08% higher than those of the MBAE matrix, respectively, and the dielectric constant and the dielectric loss were 3.76 (100 Hz) and 2.79 × 10−3 (100 Hz), when the content of PES was 2 wt% and O-MWCNTs was 0.02 wt%. The outstanding properties of the material made it play an important role in high-performance insulating material applications.

Relative complex permittivity and its dependence on frequency

2017 ◽  
Vol 14 (6) ◽  
pp. 532-537
Author(s):  
Georgios Giannoukos ◽  
Mart Min ◽  
Toomas Rang
Keyword(s):  
Dielectric Properties ◽  
Complex Permittivity ◽  
Parallel Plate ◽  
Dielectric Material ◽  
Parallel Plates ◽  
Parallel Plate Capacitor ◽  
Content Type ◽  
Dielectric Characterization ◽  
Plate Capacitor ◽  
The Way

Purpose This paper aims to give a brief overview of dielectric properties, relative complex permittivity and its dependence on frequency. The significance of different approaches to complex permittivity is also discussed. Design/methodology/approach The different mechanisms of polarization are then presented. Dielectric measurements are given, and an RC parallel-equivalent circuit is used to simulate a parallel plate capacitor, and the way in which the impedance of the circuits is affected by frequency is illustrated in their respective diagrams. The way in which dielectric properties change with time is also discussed. Findings The goal of this paper is to give an overview of the characteristics of the dielectrics and how frequency affects the relative complex permittivity and to present different approaches to and equations for the relative complex permittivity, such as that of Debye, Cole–Cole, Cole–Davidson and Havriliak–Negami. In addition, three mechanisms of polarization, namely, electronic, atomic and bipolar, are presented. The most common dielectric characterization device, a capacitor with parallel plates between which the dielectric material under study is located, is also discussed. Ohmic and dielectric losses of a non-ideal capacitor are accounted for. Furthermore, this paper studies the equivalent circuits of a non-ideal parallel plate capacitor, those being a resistor and an ideal capacitor connected either in series or in parallel. Originality/value Finally, dielectric responses to both time and to stepwise excitation are given.

Molecular Kinetic Based Dielectric Polarization in Sol-Gel Derived Nanocrystalline CaCu3Ti4O12

2013 ◽  
Vol 699 ◽  
pp. 387-391
Author(s):  
Ranjit Kumar ◽  
M. Zulfequar ◽  
T.D. Senguttuvan
Keyword(s):  
Relaxation Time ◽  
Dielectric Properties ◽  
Grain Boundary ◽  
Dielectric Relaxation ◽  
Sol Gel ◽  
Structural Studies ◽  
Dielectric Polarization ◽  
Reaction Route ◽  
Dipole Relaxation ◽  
Dielectric Relaxations

Nano-sized powders of dielectric CaCu3Ti4O12 was synthesized by sol-gel reaction route. The powders are calcined at 700 °C and sintered at 1000 °C. The calcined powders diameter is in the range of 50 - 150 nm. Structural studies were carried out using the XRD, HRTEM and SEM. Frequency dependent dielectric properties were studied within the range of 20 Hz to 5 MHz. Molecular kinetics associated with dielectric relaxations is analyzed by Havriliak Negami function. It is found that the grain dipoles obey the Debye type of dielectric relaxation, while grain boundary dipoles follow the Cole-Cole type of dielectric relaxation. The observed grain and grain boundary dipole relaxation time are 6.598E-08 sec and 5.755E-04 sec, respectively.

RHEOLOGICAL AND DIELECTRIC CHARACTERIZATION OF ELECTRORHEOLOGICAL FLUIDS COMPOSED OF BOTH DISPERSED PARTICLES AND LIQUID DROPS IN A DIELECTRIC MEDIUM

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2583-2589 ◽  
Author(s):  
L. REJON ◽  
L. GARCIA ◽  
O. MANERO
Keyword(s):  
Dielectric Properties ◽  
Silica Gel ◽  
Electric Fields ◽  
Volume Fraction ◽  
Relative Viscosity ◽  
Dielectric Medium ◽  
Dielectric Behavior ◽  
Oil Emulsion ◽  
Dielectric Characterization ◽  
Oil Emulsions

The rheological and dielectric behavior of novel electrorheological suspensions composed of noncolloidal silica gel particles of irregular shape and oil-in-oil emulsions with different electrical conductivity (and permittivity) are studied in this work. The rheological behavior of the suspensions is examined in systems with various compositions of the oil phase under different intensities of constant DC electric fields. Results reveal that the electrorheological (ER) response of the oil-in-oil emulsion increases with the applied voltage but is affected negatively when the concentration of the oil with higher conductivity is increased. When a small volume fraction of silica gel is added, the ER response increases considerably and its magnitude is strongly dependent on the electric field. In this case, however, larger concentrations of the oil with the higher conductivity, in the presence of silica particles, increase the relative viscosity of the suspensions. The dielectric properties of the suspensions are examined to elucidate the relation between the dielectric relaxation process and the relative composition of liquid drop phases. The mechanisms responsible of the ER response are explained in terms of the relationship between the microstructure changes in the suspensions and their rheological and dielectric properties.

Porous Gel Coatings Obtained by Phase Separation in ORMOSIL System

2000 ◽  
Vol 628 ◽  
Author(s):  
Kazuki Nakanishi ◽  
Souichi Kumon ◽  
Kazuyuki Hirao ◽  
Hiroshi Jinnai
Keyword(s):  
Phase Separation ◽  
Reaction Time ◽  
Volume Fraction ◽  
Sol Gel ◽  
Reaction Times ◽  
Dip Coating ◽  
Coating Solution ◽  
Coating Method ◽  
Gel Phase ◽  
Dip Coating Method

ABSTRACTMacroporous silicate thick films were prepared by a sol-gel dip-coating method accompanied by the phase separation using methyl-trimethoxysilane (MTMS), nitric acid and dimethylformamide (DMF) as starting components. The morphology of the film varied to a large extent depending on the time elapsed after the hydrolysis until the dipping of the coating solution. On a glass substrate, the films prepared by early dipping had inhomogeneous submicrometer-sized pores on the surface of the film. At increased reaction times, relatively narrow sized isolated macropores were observed and their size gradually decreased with the increase of reaction time. On a polyester substrate, in contrast, micrometer-sized isolated spherical gel domains were homogeneously deposited by earlier dippings. With an increase of reaction time, the volume fraction of the gel phase increased, then the morphology of the coating transformed into co-continuous gel domains and macropores, and finally inverted into the continuous gel domains with isolated macropores. The overall morphological variation with the reaction time was explained in terms of the phase separation and the structure freezing by the forced gelation, both of which were induced by the evaporation of methanol during the dipping operation.

scholarly journals Effect of Terminal Groups on Thermomechanical and Dielectric Properties of Silica–Epoxy Composite Modified by Hyperbranched Polyester

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2451
Author(s):  
Jianwen Zhang ◽  
Dongwei Wang ◽  
Lujia Wang ◽  
Wanwan Zuo ◽  
Lijun Zhou ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Binding Energy ◽  
Epoxy Resin ◽  
Volume Fraction ◽  
Epoxy Composite ◽  
Mean Square Displacement ◽  
Mean Square ◽  
Hyperbranched Polyester ◽  
Free Volume Fraction

To study the effect of hyperbranched polyester with different kinds of terminal groups on the thermomechanical and dielectric properties of silica–epoxy resin composite, a molecular dynamics simulation method was utilized. Pure epoxy resin and four groups of silica–epoxy resin composites were established, where the silica surface was hydrogenated, grafted with silane coupling agents, and grafted with hyperbranched polyester with terminal carboxyl and terminal hydroxyl, respectively. Then the thermal conductivity, glass transition temperature, elastic modulus, dielectric constant, free volume fraction, mean square displacement, hydrogen bonds, and binding energy of the five models were calculated. The results showed that the hyperbranched polyester significantly improved the thermomechanical and dielectric properties of the silica–epoxy composites compared with other surface treatments, and the terminal groups had an obvious effect on the enhancement effect. Among them, epoxy composite modified by the hyperbranched polyester with terminal carboxy exhibited the best thermomechanical properties and lowest dielectric constant. Our analysis of the microstructure found that the two systems grafted with hyperbranched polyester had a smaller free volume fraction (FFV) and mean square displacement (MSD), and the larger number of hydrogen bonds and greater binding energy, indicating that weaker strength of molecular segments motion and stronger interfacial bonding between silica and epoxy resin matrix were the reasons for the enhancement of the thermomechanical and dielectric properties.

Influence of Ca-Doping on Structural, Magnetic and Dielectric Properties of Ba3Co2-xCaxFe24O41 Hexaferrite Powders

2015 ◽  
Vol 241 ◽  
pp. 226-236 ◽  
Author(s):  
Neha Solanki ◽  
Rajshree B. Jotania
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Sol Gel ◽  
Calcium Content ◽  
Combustion Method ◽  
Dielectric Behavior ◽  
Dielectric Parameters ◽  
Ca Doping ◽  
Auto Combustion ◽  
Magnetic And Dielectric Properties

Influence of Ca substitution on structural, magnetic and dielectric properties of Ba3Co2-xCaxFe24O41(where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), prepared by Sol-Gel auto-combustion method, has been investigated in present studies. The obtained powder was sintered at 950 oC for 4 hrs. in the static air atmosphere. Structural analysis of Ca-doped Ba3Co2-xCaxFe24O41powders revealed pure Z-type hexaferrite phase at low temperature. The frequency dependent dielectric constant (Єʹ) and magnetic properties such as remanent magnetization (Mr), saturation magnetization (Ms) and coercivity (Hc) were studied. It is observed that coercivity increased gradually with increase in calcium content. The real dielectric constant (Єʹ) and dielectric loss tangent (tan δ) were studied in the frequency range of 20Hz to 2MHz. The dielectric parameters for all samples show normal dielectric behavior as observed in hexaferrites. Contents of Paper

scholarly journals Significantly Improved Dielectric Performance of Poly(1-butene)-Based Composite Films via Filling Polydopamine Modified Ba(Zr0.2Ti0.8)O3-Coated Multiwalled Carbon Nanotubes Nanoparticles

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 285
Author(s):  
Lingfei Li ◽  
Qiu Sun ◽  
Xiangqun Chen ◽  
Zhaohua Jiang ◽  
Yongjun Xu
Keyword(s):  
Carbon Nanotubes ◽  
Dielectric Constant ◽  
Energy Storage ◽  
Composite Film ◽  
Multiwalled Carbon Nanotubes ◽  
Sol Gel ◽  
Composite Films ◽  
Weak Electric Field ◽  
Multiwalled Carbon ◽  
Dielectric Performance

The low dielectric constant of the nonpolar polymer poly(1-butene) (PB-1) limits its application as a diaphragm element in energy storage capacitors. In this work, Ba(Zr0.2Ti0.8)O3-coated multiwalled carbon nanotubes (BZT@MWCNTs) were first prepared by using the sol–gel hydrothermal method and then modified with polydopamine (PDA) via noncovalent polymerization. Finally, PB-1 matrix composite films filled with PDA-modified BZT@MWCNTs nanoparticles were fabricated through a solution-casting method. Results indicated that the PDA-modified BZT@MWCNTs had good dispersion and binding force in the PB-1 matrix. These characteristics improved the dielectric and energy storage performances of the films. Specifically, the PDA-modified 10 vol% BZT@ 0.5 vol% MWCNTs/PB-1 composite film exhibited the best dielectric performance. At 1 kHz, the dielectric constant of this film was 25.43, which was 12.7 times that of pure PB-1 films. Moreover, its dielectric loss was 0.0077. Furthermore, under the weak electric field of 210 MV·m−1, the highest energy density of the PDA-modified 10 vol% BZT@ 0.5 vol% MWCNTs/PB-1 composite film was 4.57 J·cm−3, which was over 3.5 times that of PB-1 film (≈1.3 J·cm−3 at 388 MV·m−1).

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