Abstract: The study of dielectric properties in a binary mixture of liquids is very useful to understand the liquid structure, molecular interaction, dynamics, and kinematics of the mixture. Time-domain reflectometry (TDR) is a powerful tool for studying the cooperation and molecular dynamics of the H-bonded system. Here we discuss the basic calibration and normalization procedure for TDR measurements. Our aim is to explain different types of error occur during TDR measurements and how to minimize it.
Abstract: The study of dielectric relaxation properties of polar liquids in the binary mixture has been carried out at 10, 15, 20 and 25 ºC temperatures for 11 different concentrations using time domain reflectometry technique. The dielectric properties of a solute-solvent mixture of polar liquids in the frequency range of 10 MHz to 30 GHz gives the information regarding formation of monomers and multimers and also an interaction between the molecules of the liquid mixture under study. The dielectric parameters have been obtained by the least squares fit method using the Debye equation characterized by a single relaxation time without relaxation time distribution.
Abstract: Power transformer is a vital element in a power system as it continuously regulates power flow, maintaining good voltage regulation. The working of transformer much depends on the oil insulation, the oil insulation also decides the aging of transformer and hence its reliability. The mineral oil based liquid insulation is globally accepted for power transformer insulation; however it is potentially hazardous due to its non-biodegradability. In this work efficient alternative biodegradable insulating fluid is presented as a replacement to conventional mineral oil. Dielectric tests are performed as distinct alternating fluid to evaluate the suitability for transformer insulation. The selection of the distinct natural esters for an insulation system is carried out by the laboratory investigation of Breakdown voltage, Oxidation stability, Dissipation factor, Permittivity, Viscosity, Flash and Fire point. It is proposed to study and characterize the properties of natural esters to be used in power transformer. Therefore for the investigation of the dielectric behavior rice bran oil, sesame oil, and sunflower oil are considered for the study. The investigated results have been compared with the mineral oil to validate the dielectric behavior of natural esters.
Abstract: The study of static dielectric properties in a binary mixture of 1,2 dichloroethane (DE) and n,n dimethylformamide (DMF) polar liquids has been carried out in the frequency range of 10 MHz to 30 GHz for 11 different concentration using time domain reflectometry technique at 10ºC temperature. The dielectric relaxation study of solute-solvent mixture at microwave frequencies gives information regarding the creation of monomers and multimers as well as interaction between the molecules of the binary mixture. The least squares fit method is used to determine the values of dielectric parameters such as static dielectric constant (ε0), dielectric constant at high frequency (ε∞) and relaxation time (τ).
Abstract: Landmine detection is an important and yet challenging problem remains to be solved. Ground Penetrating Radar (GPR) is a powerful and rapidly maturing technology for subsurface threat identification. The detection methodology of GPR depends mainly on the contrast of the dielectric properties of the searched target and its surrounding soil. This contrast produces a partial reflection of the electromagnetic pulses that are being transmitted into the soil and then being collected by the GPR. One of the most critical hardware components for the performance of GPR is the antenna system. The current paper explores the design and simulation of a pyramidal horn antenna operating at L-band frequencies (1- 2 GHz) to detect a landmine. A prototype model of the GPR system setup is developed to simulate full wave analysis of the electromagnetic fields in different soil types. The contrast in the dielectric permittivity of the landmine and the sandy soil is the most important parameter to be considered for detecting the presence of landmine. L-band horn antenna is proved to be well-versed in the investigation of landmine detection.
Abstract: Alkaline niobate (Na0.5K0.5)NbO3 ceramic system has attracted major attention in view of its potential for replacing the highly toxic but superior lead zirconate titanate (PZT) system for piezoelectric applications. Recently, a more detailed study of this system reveals that the ferroelectric and piezoelectric properties are optimized in the Li- and V-modified system having the composition (K0.485Na0.5Li0.015)(Nb0.98V0.02)O3. In the present work, we further study the pyroelectric behaviour of this composition along with another doped with Mn4+. So, (K0.485Na0.5Li0.015)(Nb0.98V0.02)O3 + x MnO2 (x = 0, and 0.01 wt. %) ceramic compositions were synthesized by conventional ceramic processing route. X-ray diffraction study reveals that both the undoped and Mn4+-doped ceramic samples prepared crystallize into a perovskite structure having orthorhombic symmetry. Dielectric study indicates that Mn4+ doping has little effect on both the Curie temperature (Tc) and tetragonal-orthorhombic phase transition temperature (Tot). The bulk density, room-temperature dielectric constant (εRT), and room-c The room-temperature coercive field (Ec) is observed to be lower in Mn4+ doped sample. The detailed analysis of the P-E hysteresis loops over the range of temperature from about room temperature to Tot points out that enhanced ferroelectric properties exist in this temperature range with better thermal stability for the Mn4+ doped ceramic. The study reveals that small traces of Mn4+ can modify (K0.485Na0.5Li0.015)(Nb0.98V0.02)O3 system so as to improve its ferroelectric properties with good thermal stability over a wide range of temperature.
Abstract: The organic–inorganic hybrid perovskite-like [C6H5C2H4NH3]2ZnCl4 (PEA-ZnCl4) was synthesized by saturated solutions method. X-ray powder diffraction, Raman spectroscopy, UV-visible transmittance, and capacitance meter measurements have been used to characterize the structure, the functional groups, the optical parameters, and the dielectric constants of the material. The material has a layered structure. The optical transmittance (T %) was recorded and applied to deduce the absorption coefficient (α) and optical band gap (Eg). The hybrid shows an insulator character with a direct band gap about 4.46 eV, and presents high dielectric constants up to a frequency of about 105 Hz, which suggests a ferroelectric behavior. The reported optical and dielectric properties can help to understand the fundamental properties of perovskite materials and also to be used for optimizing or designing new devices.
Abstract: To investigate electrical properties of conducting polypyrrole (PPy) and cobalt aluminum oxide (CAO) nanocomposites, impedance analyzer in frequency range of 100 Hz to 5 MHz is used. In this work, PPy/CAO nanocomposites were synthesized by chemical oxidation polymerization method in different weight percent of CAO in PPy. The dielectric properties and AC conductivity studies were carried out for different nanocomposites in temperature range of room temperature to 180 °C. With the increase in frequency, the dielectric constant for all the nanocomposites was observed to decrease. AC conductivity of PPy was improved by addition of CAO nanopowder.
Abstract: Cadmium oxide (CdO) nanoparticles have been
prepared by chemical coprecipitation method. The synthesized
nanoparticles were characterized by X-ray diffraction analysis
(XRD), scanning electron microscopy (SEM), transmission electron
microscopy (TEM), UV analysis, and dielectric studies. The
crystalline nature and particle size of the CdO nanoparticles were
characterized by Powder X-ray diffraction analysis (XRD). The
morphology of prepared CdO nanoparticles was studied by scanning
electron microscopy. The particle size was studied using the
transmission electron microscopy (TEM).The optical properties were
obtained from UV-Vis absorption spectrum. The dielectric properties
of CdO nanoparticles were studied in the frequency range of 50 Hz–5
MHz at different temperatures. The frequency dependence of the
dielectric constant and dielectric loss is found to decrease with an
increase in the frequency at different temperatures. The ac
conductivity of CdO nanoparticle has been studied.
Abstract: Mineral oil is commonly used for high voltage
transformer insulation. The insulation quality of mineral oil is
affecting the operation process of high voltage transformer. There are
many contaminations which could decrease the insulation quality of
mineral oil. One of them is water. This research talks about the effect
of water content on dielectric properties, physic properties, and
partial discharge pattern on mineral oil. Samples were varied with 10
varieties of water content value. And then all samples would be tested
to measure the dielectric properties, physic properties, and partial
discharge pattern. The result of this research showed that an
increment of water content value would decrease the insulation
quality of mineral oil.
Abstract: In order to produce lead free piezoceramics with
optimum piezoelectric and dielectric properties, KNN modified with
Li+ (as an A site dopant) and Sb5+ (as a B site dopant)
(K0.49Na0.49Li0.02) (Nb0.96Sb0.04) O3 (referred as KNLNS in this paper)
have been synthesized using solid state reaction method and
conventional sintering technique. The ceramics were sintered in the
narrow range of 1050°C-1090°C for 2-3 h to get precise information
about sintering parameters. Detailed study of dependence of
microstructural, dielectric and piezoelectric properties on sintering
conditions was then carried out. The study suggests that the volatility
of the highly hygroscopic KNN ceramics is not only sensitive to
sintering temperatures but also to sintering durations. By merely
reducing the sintering duration for a given sintering temperature we
saw an increase in the density of the samples which was supported by
the increase in dielectric constants of the ceramics. And since density
directly or indirectly affects almost all the associated properties, other
dielectric and piezoelectric properties were also enhanced as we
approached towards the most suitable sintering temperature and
duration combination. The detailed results are reported in this paper.
Abstract: In the present work, the dielectric properties of
Epoxy/MWCNT-muscovite HYBRID and MIXED composites based
on a ratio 30:70 were studied. The multi-wall carbon nanotubes
(MWCNT) were prepared using two methods: (a) MWCNTmuscovite
hybrids were synthesised by chemical vapour deposition
(CVD) and (b) physically mixing muscovite with MWCNT. The
effects of different preparation of the composites and filler loading
were evaluated. It was revealed that the dielectric constants of
HYBRID epoxy composites are slightly higher than MIXED epoxy
composites. It was also indicated that the dielectric constant increased
by increasing the MWCNT filler loading.
Abstract: In recent years, the hair building fiber has become
popular, in other words, it is an effective method which helps people
who suffer hair loss or sparse hair since the hair building fiber is
capable to create a natural look of simulated hair rapidly. In the
markets, there are a lot of hair fiber brands that have been designed to
formulate an intense bond with hair strands and make the hair appear
more voluminous instantly. However, those products have their own
set of properties. Thus, in this report, some measurement techniques
are proposed to identify those products. Up to five different brands of
hair fiber are tested. The electrostatic and dielectric properties of the
hair fibers are macroscopically tested using design DC and high
frequency microwave techniques. Besides, the hair fibers are
microscopically analysis by magnifying the structures of the fiber
using scanning electron microscope (SEM). From the SEM photos,
the comparison of the uniformly shaped and broken rate of the hair
fibers in the different bulk samples can be observed respectively.
Abstract: Elastomeric dielectric material has recently become a
new alternative for actuator technology. The characteristics of
dielectric elastomers placed between two electrodes to withstand
large strain when electrodes are charged has attracted the attention of
many researcher to study this material for actuator technology. Thus,
in the past few years Danfoss Ventures A/S has established their own
dielectric electro-active polymer (DEAP), which was called
PolyPower.
The main objective of this work was to investigate the dynamic
characteristics for vibration control of a PolyPower actuator folded in
‘pull’ configuration. A range of experiments was carried out on the
folded actuator including passive (without electrical load) and active
(with electrical load) testing. For both categories static and dynamic
testing have been done to determine the behavior of folded DEAP
actuator.
Voltage-Strain experiments show that the DEAP folded actuator is
a non-linear system. It is also shown that the voltage supplied has no
effect on the natural frequency. Finally, varying AC voltage with
different amplitude and frequency shows the parameters that
influence the performance of DEAP folded actuator. As a result, the
actuator performance dominated by the frequency dependence of the
elastic response and was less influenced by dielectric properties.
Abstract: The dielectric properties and ionic conductivity of
novel "ceramic state" polymer electrolytes for high capacity lithium
battery are characterized by Radio frequency and Microwave
methods in two broad frequency ranges from 50 Hz to 20 KHz and 4
GHz to 40 GHz. This innovative solid polymer electrolyte which is
highly ionic conductive (10-3 S/cm at room temperature) from -40oC
to +150oC can be used in any battery application. Such polymer
exhibits properties more like a ceramic rather than polymer. The
various applied measurement methods produced accurate dielectric
results for comprehensive analysis of electrochemical properties and
ion transportation mechanism of this newly invented polymer
electrolyte. Two techniques and instruments employing air gap
measurement by Capacitance Bridge and in-waveguide measurement
by vector network analyzer are applied to measure the complex
dielectric spectra. The complex dielectric spectra are used to
determine the complex alternating current electrical conductivity and
thus the ionic conductivity.
Abstract: Nanocrystalline powders of the lead-free piezoelectric
material, tantalum-substituted potassium sodium niobate
(K0.5Na0.5)(Nb0.9Ta0.1)O3 (KNNT), were produced using a Retsch
PM100 planetary ball mill by setting the milling time to 15h, 20h,
25h, 30h, 35h and 40h, at a fixed speed of 250rpm. The average
particle size of the milled powders was found to decrease from 12nm
to 3nm as the milling time increases from 15h to 25h, which is in
agreement with the existing theoretical model. An anomalous
increase to 98nm and then a drop to 3nm in the particle size were
observed as the milling time further increases to 30h and 40h
respectively. Various sizes of these starting KNNT powders were
used to investigate the effect of milling time on the microstructure,
dielectric properties, phase transitions and piezoelectric properties of
the resulting KNNT ceramics. The particle size of starting KNNT
was somewhat proportional to the grain size. As the milling time
increases from 15h to 25h, the resulting ceramics exhibit
enhancement in the values of relative density from 94.8% to 95.8%,
room temperature dielectric constant (εRT) from 878 to 1213, and
piezoelectric charge coefficient (d33) from 108pC/N to 128pC/N. For
this range of ceramic samples, grain size refinement suppresses the
maximum dielectric constant (εmax), shifts the Curie temperature (Tc)
to a lower temperature and the orthorhombic-tetragonal phase
transition (Tot) to a higher temperature. Further increase of milling
time from 25h to 40h produces a gradual degradation in the values of
relative density, εRT, and d33 of the resulting ceramics.
Abstract: Microwave dielectric ceramic materials of
(Mg1-xNix)2(Ti0.95Sn0.05)O4 for x = 0.01, 0.03, 0.05, 0.07 and 0.09 were
prepared and sintered at 1250–1400 ºC. The microstructure and
microwave dielectric properties of the ceramic materials were
examined and measured. The observations shows that the content of
Ni2+ ions has little effect on the crystal structure, dielectric constant,
temperature coefficient of resonant frequency (τf) and sintering
temperatures of the ceramics. However, the quality values (Q×f) are
greatly improved due to the addition of Ni2+ ions. The present study
showed that the ceramic material prepared for x = 0.05 and sintered at
1325ºC had the best Q×f value of 392,000 GHz, about 23%
improvement compared with that of Mg2(Ti0.95Sn0.05)O4.
Abstract: (Bi0.5Na0.5)TiO3 doped with 8 mol % BaTiO3 powder
(BNT-BT0.08), prepared by sol-gel method was compacted and
sintered by Spark Plasma Sintering (SPS) process. The influence of
SPS temperature on the densification of BNT-BT0.08 ceramic was
investigated. Starting from sol-gel nanopowder of BNT-BT
containing 8 mol % BaTiO3 with an average particles size of about
30 nm, were obtained ceramics with density around 98 % of the
theoretical density value when the SPS temperature used was about
850 °C. The average grain size of the resulting ceramics was 80 nm.
The BNT-BT0.08 ceramic sample obtained by SPS method has shown
good electric properties at various frequencies.
Abstract: In the present work we investigate both the elastic and
electric properties of a chiral material. We consider a composite
structure made from a polymer matrix and anisotropic inclusions of
GaAs taking into account piezoelectric and dielectric properties of
the composite material. The principal task of the work is the
estimation of the functional properties of the composite material.