LCR Bridge Research Articles

Characterization, electrical and optical properties of PVA/MnO2 nanocomposite materials

In this research, various concentrations of manganese dioxide (MnO2) is composed by polyvinyl alcohol (PVA) to forming PVA /MnO2 films. The XRD and SEM are respectively demonstrated the structure and morphological characteristics of the films. The XRD results show that the PVA/MnO2 films is fabricated successfully. The SEM results demonstrate that MnO2 is dispersed evenly along the PVA polymeric chains. The conductivity, impedance and energy density were measured via an LCR bridge with frequency 102 to 106 Hz. There is an increase in dielectric from 64 for PVA to 95 for PVA/0.06MnO2 at 105 Hz, and also the conductivity increases from 3.61x10-3 S/cm for PVA to 5.33x10-3 S/cm for PVA/0.06MnO2. The optical characteristics of PVA and PVA/MnO2 films were recorded by UV/Vis spectroscopy. The band gap reduced from 5.01 eV for PVA to 4.85, 4.71, 4.59 eV respectively for PVA/0.02MnO2, PVA/0.04MnO2, and PVA/0.06MnO2. And the Urbach tail is modified from 1.72 eV for PVA to 3.12, 3.453, and 3.66 eV respectively. The results of the present work open the possibility for applied in different devices as energy storage systems and optoelectronics.

Dielectric properties of unidirectional and biaxial flax/epoxy composites at frequencies up to 1 GHz

The relative permittivity of flax/epoxy composites in unidirectional and biaxial orientations was mapped in the frequency range of 1 kHz to 200 kHz, and for the first time in the range of 1 MHz to 1 GHz. In addition, permittivity was investigated for the first time in the temperature range between − 20 °C and 50 °C. These composites, produced using the vacuum infusion process, are increasingly used for sustainable and lightweight structural components in the automotive industry. The relative permittivity was determined using a self-developed plate capacitor with an LCR bridge and an impedance analyzer. An examination of the microstructure of the flax/epoxy composites shows that the fibers are disordered in the composite, resulting in local variations in fiber volume fraction. Furthermore, it was shown that the matrix also infiltrates into the fiber itself, resulting in an increase of the matrix fraction. It was found that unidirectional fabrics had a higher relative permittivity than biaxial fabrics, due to a higher fiber volume fraction and lower proportion of epoxy. The results suggest that it is the fiber volume fraction, rather than the manufacturing process and fiber orientation, that primarily determines the relative permittivity. It was also found that the permittivity continues to decrease below room temperature and thus behaves in a manner typical of the material in this temperature range as well.

Preparation of Nanocellulose Whisker/Polyacrylamide/Xanthan Gum Double Network Conductive Hydrogels

Hydrogels’ poor mechanical and recovery characteristics inhibited their application as a plastic deformable three-dimensional cross-linked network polymer with electrical properties for intelligent sensing and human motion detection. Cellulose has also been added to the hydrogel to enhance its mechanical properties. The hydrogel has been enhanced this way, and the double-network hydrogel has superior recovery and mechanical capabilities. This study used the traditional free radical polymerization method to prepare double-mesh hydrogels, with polyacrylamide as the backbone network, xanthan gum double-helix structure, and Al3+ complex structure as the second cross-linked network, and endowing the hydrogels with good mechanical recovery and mechanical properties. Adding cellulose nanowafers (CNWs) improved the mechanical properties of the hydrogels. The hydrogel could detect body movements and various postures in the same environment. Moreover, the hydrogel has excellent recovery, mechanical properties, and tensile strain; the maximum fracture stress is 0.14 MPa, and the maximum strain is 707.1%. In addition, Fourier infrared spectroscopy (FTIR) of xanthan gum and Xanthan gum—Al3+ were analyzed, and thermogravimetric analysis (TGA) and LCR bridge were used to analyze the properties of hydrogels. Notably, hydrogel-based wearable sensors have been successfully constructed to detect human movement. Its mechanical properties, sensitivity, and wide range of properties make hydrogel a great potential for various applications in wearable sensors.

Development of a thin high-frequency and high-precision magnetic probe array in Sino-United Spherical Tokamak

Since the major/minor radius of the Sino-United Spherical Tokamak (SUNIST) is 0.3/0.23m, respectively, the space left for magnetic diagnostics in the high field side (HFS) is quite limited. At the same time, a good signal-to-noise ratio and a high-frequency response (up to 1MHz) are required for equilibrium reconstruction (ER) and Alfven eigenmode studies. Such a magnetic probe array must be extremely thin and tightly close to the central column, not exceeding the inner limiter and leaving the aspect ratio of the spherical tokamak unchanged. Therefore, the turn number and the shape of windings should be highly optimized to enable both a high-frequency response and an enough effective area. A 32-channel magnetic probe array fulfilling these requirements on the central column is designed, calibrated, and installed in the SUNIST. The array consists of 16 probes. Each of them consists of two perpendicular windings, which can measure toroidal and poloidal magnetic fields simultaneously. The effective area and frequency response of each probe are calibrated using a Helmholtz coil and an LCR bridge based on an equivalent probe-and-cable circuit model. After that, an expression of the magnetic diagnostic response to the field coil currents is used to calibrate the installation error. With the full coverage of magnetic probes in the poloidal direction, more reliable ER can be obtained, and the features of magnetohydrodynamic activities in the HFS can be studied.

γ-ray effects on PMMA polymeric sheets doped with CdO nano particles

The present work aimed to study the γ-ray irradiation effects on the physical and chemical behavior of poly methyl methacrylate (PMMA) thin polymeric sheets doped with different concentrations of nano CdO (0.3–1.8 wt. %). Co-precipitation technique was used to prepare CdO nanopowder, while casting-solution method was applied to prepare thin sheets of PMMA/CdO. The XRD analysis of CdO, PMMA and their composites confirmed their formation in pure phase. The particle size distribution of the CdO powder was estimated using TEM imaging and found to be 3–20 nm. According to optical microscopy investigation, good homogeneous distribution was obtained for the CdO powder inside the PMMA sheets. Different sets of the prepared samples were irradiated by γ-ray of 60Co source with gradually increasing doses (20–120 kGy). The irradiated samples were analyzed using XRD, FTIR and UV/Vis spectroscopy. Comparative study was done on pristine and irradiated samples at different CdO concentration. The visual appearance of the samples showed chromatic degradation with increasing both CdO concentration and absorbed γ-ray doses. A color map of the irradiated PMMA/CdO samples was presented for monitoring the absorbed dose. The changes in the samples color was attributed to conversion of CdO (reddish brown) to Cd(OH)2 (clear white) as a result of γ-ray irradiation. The unirradiated samples showed slight decrease in their optical band gap with increasing CdO concentration. Furthermore, a linear correlation between the optical band gap and γ-ray dose was deduced for all the irradiated samples. Electrical permittivity and conductivity of pristine and irradiated samples were measured as a function of frequency at room temperature using LCR bridge. A relative increase in the dielectric constant and AC conductivity of the irradiated samples by about 5–25% was observed for the highest CdO concentration. The electrical parameters of the irradiated samples showed significant changes at high γ-ray dose of 120 kGy. The obtained experimental data were discussed in view of γ-ray interaction with the medium using the suitable models and theories of polarization mechanisms. The results are promising for using the prepared samples as γ-ray dosimeters in addition to enhancement of their electrical properties for various applications.

Capacitance sensor for measuring void fraction in small channels

The paper presents a method for the measurement of void fraction in two-phase flow of liquid and gas phases in small channels by means of capacitance sensor. It was assumed arbitrarily that the small channels are those of diameter less than 10 mm. The capacitance sensor investigated in this paper consisted of two electrodes mounted on the outer wall of a glass pipe, and an electronic circuit for signal detection. The capacitance of two electrodes depends on the mean electric permittivity of the medium between them. The mean permittivity is a function of permittivity of the channel material and the percentage of both phases of different dielectric constants: liquid and gas. In this paper, the void fraction in two-phase flow was determined from frequency deviation of a high-frequency oscillator, in which the capacitance sensor was connected to a resonant circuit with an inductance in parallel. The advantage of this method over other methods based on the direct capacitance measurement (for example, LCR bridge) is that the intermediate steps for the determination of void fraction from the capacitance changes are omitted, and the void fraction can be directly determined from the calibration curve. Changes in the capacitance of electrodes for various void fractions have been determined numerically from the distribution of electric field in this geometry.

Assessment and Verification of the Impedance-Frequency Method of Transverse Fault Location in Medium Voltage Cables

The paper presents the results of the assessment and verification of an impedance-frequency method of transverse fault location in medium voltage cables with a local weakening of insulation. A device cooperating with Hameg HM8118 LCR bridge was designed for this purpose. The objective of the method is to measure the input impedances for two different frequencies at one end of the cable with an open state at its other end as well as determining the transverse fault resistance and the distance to the fault location. The proposed method was compared to reflectometry. The effectiveness of the method was confirmed, by numerical and experimental verifications.

Effect of Phosphating and Heat Treatment on Magnetic Properties of Fe-3.3Si-6.5Cr Soft Magnetic Composites

Fe-3.3Si-6.5Cr powders were first treated by phosphoric acid solution and then mixed with epoxy-modified silicone resin uniformly, forming insulation coating. The Fe-3.3Si-6.5Cr soft magnetic composites were prepared by compaction and annealing treatment of the coated Fe-3.3Si-6.5Cr powders. The microstructure and composition of Fe-3.3Si-6.5Cr powders were analyzed by scanning electron microscope coupled with energy-dispersive spectrometer, Fourier-transform infrared spectra, and X-ray photoelectron spectroscopy, respectively. The magnetic properties were determined by the LCR bridge tester and an auto testing system for magnetic materials (MATS-2010SA). Results show that both proper phosphating treatment and annealing at higher temperature can improve the permeability and reduce the core loss of the Fe-3.3Si-6.5Cr SMCs. When the concentration of phosphoric acid was 0.5 wt% and the heat treatment temperature reached 500 °C, the Fe-3.3Si-6.5Cr SMCs showed the optimized magnetic properties, including the permeability (μe) of 44.7 H/cm, the core loss (P) of 521.8 mW/cm3 at the saturated magnetic flux density of 50 mT, and the frequency of 100 kHz. The Fe-3.3Si-6.5Cr SMCs with distinguished magnetic properties provide great application prospect in various fields such as filter inductors, transformers, and sensors.

Physical study of cobalt ferrite and its application in purification of water

The purpose of this work to find the effect of magnetic material on adsorption of heavy metal cations (Cr6+, Cd2+ and Cu2+). Consequently, hexagonal cobalt ferrite (CoFe2O4) was prepared simply by flash method followed by calcination. The prepared sample was characterized using X-ray diffraction and FTIR which revealed the structure of nanoferrite. Field emission scanning electron microscopy and EDX explore the hexagonal-shaped product. The obtained results from surface area analysis (BET) showed that cobalt ferrite has large surface area (71.564 m2/g). The magnetic properties were studied by VSM and Faraday’s method from which the sample acts as ferromagnetic material with large value of saturation magnetization (66.380 emu/g). Electrical properties such as conductivity and activation energy were studied using LCR bridge; the data confirmed semiconductor behavior of sample. The sample under investigation exhibited very good adsorption efficiency for heavy metal cation (Cr6+, Cd2+ and Cu2+) from wastewater. The maximum adsorption appeared for Cd6+ at pH 6 and contact time 8 h.

Preparation, characterization and application of Ni-doped magnetite

Ni-doped magnetite nanoparticles with the formula Ni0.1Fe2.9O4 have been synthesized successfully by co-precipitation method. The prepared sample was characterized using X-ray diffraction, FTIR, field emission scanning electron microscopy, EDX and surface area analysis (BET). The magnetic properties were studied by VSM and faraday’s method; the sample shows ferrimagnetic behavior. Conductivity as well as activation energy was measured and calculated using LCR bridge; the sample shows semiconductor behavior. The prepared sample has a very good efficiency for removing heavy metals (Cr6+, Cd2+, Pb2+ and Cu2+) from wastewater. The maximum adsorption was appeared for Cr6+ at pH 6 and contact time 7 h.

AC electrical properties of geopolymers with carbon black admixture

Geopolymers as competitors to the cement-based construction materials are intensively studied in the present. Their competitiveness mainly arises from their high strength, favourable development of hydration heat at early age, good chemical resistance and thermal stability. Further qualitative improvement of functional properties can be achieved by adding electrically conductive admixtures. In an appropriate amount (called percolation threshold), mechanical properties remain reasonable and electrical properties become sufficient to ensure evolution of heat by acting of an external power source (self-heating), to detect material damage (self-sensing) or to harvest thermoelectric energy (energy harvesting). In this paper three geopolymers with different dosages of carbon black (CB) admixture (0 wt. %, 4 wt. %, 10 wt. %) were studied by means of LCR bridge AC measurements. It was observed significant difference in electrical behavior of the studied geopolymers. 0 wt. % geopolymer exhibited highly capacitive character, 4 wt. % geopolymer was slightly shifted to resistive behavior and 10 wt. % geopolymer behaved like resistor even to high frequencies with reasonable resistance which indicates its possible self-heating ability.

Thermal and electrical characterization of composite metal oxides particles from periwinkle shell for dielectric application

Rather than synthesizing metal oxides through chemical processes as fillers in polymer composites, metal oxides from natural sources (waste) could provide a cheaper and environmentally friendly alternative. In this work, a fine powder prepared from properly cleaned periwinkle shells was examined for its use as filler for polymer composites for high-voltage application. The powder was characterized using scanning electron microscopy (SEM), X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, thermal conductivity set-up and a programmable LCR Bridge. The SEM image of the powder revealed a range of particle sizes that vary from 2 to 34 μm. The chemical analysis shows that CaO is the dominant metal oxide in the powder with 81.8 wt%. The dielectric constant and the electrical conductivity of the powder are 11.08 and 1.5876 × 10−8 S m−1, respectively, at the frequency of 200 Hz. The electrical conductivity of the powder is lower than the conductivity of pure CaO, while the thermal conductivity is slightly higher than that of pure CaO. This could be due to the influence of the other constituent metal oxides. The is an indication that periwinkle shell powder if properly processed to micro- and even nano-sized particles can be a good candidate as a filler in polymer composites to produce polymeric insulation with good insulating and thermal conducting properties.

Influence of rare earth ion substitutions on the structural, optical, transport, dielectric, and magnetic properties of superparamagnetic iron oxide nanoparticles

Superparamgnetic Fe3O4 and RE:Fe3O4 (RE = Dy, Nd, La) nanoparticles with an average crystallite size in the range of 15–24 nm, were synthesized by co-precipitation method. The samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), UV–Vis spectroscopy, LCR bridge, and two-probe technique. X-ray diffraction patterns of all the investigated samples reveal the typical phase of magnetite structure, with a small contribution of orthoferrite (NdFeO3) as a secondary phase in Nd:Fe3O4 sample. The saturation magnetization (Ms) of the samples has values in the range from 41.8 to 52.3 emu/g, and decreases with RE ion doping depending on the ionic radius. Negligible values of the coercivity Hc and remanence Mr, indicate the superparamagnetic nature of the investigated samples. The calculated values of indirect optical band gap of Fe3O4 and RE:Fe3O4 nanoparticles are in the range of 0.9–1.25 eV. The dielectric constant of the samples decreases, while their activation energy increases with the increasing of ionic radii of dopants.

Ceramic Nanoparticle Synthesis at Lower Temperatures for LTCC and MMIC Technologies

Ni1−xMgxFe2O4 (x = 0.2–0.8) nanoparticles are prepared by hydrothermal synthesis followed by microwave processing. The effect of microwave processing in reducing the required heat treatment is discussed. The samples are characterized by powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, and LCR bridge. Microwave processing has enhanced the chemical reaction to form ferrites without any stray ferric oxide phases. Microscopic images have confirmed that the particles still retain nanoscale after microwave processing. An appreciably high magnetic moment is noticed. The experimental magnetic moment is used to estimate the cation distribution in tetrahedral and octahedral sites. Temperature and frequency dependence of initial permeability is discussed in the light of magnetic spin canting.

Frequency Tuned Dielectric and Electrical Properties of a Thermotropic Liquid Crystal Compound 9OBA.

This article presents effect of frequency on the electrical properties of a thermotropic rod like mesogen 4-nonyloxy benzoic acid (9OBA). Frequency dependencies of transverse component of dielectric permittivity (ε⊥) and dielectric loss factor (tanδ) at different temperatures has been studied by using a digital LCR bridge (HIOKI 3532-50 LCR HiTESTER) for the liquid crystal (LC) compounds 9OBA. Influence of frequency on the ac conductivity of this LC compound has been measured. The values of activation energy have also been estimated from the temperature dependent ac and dc conduction process.

Higher dielectric properties of semiconducting biopolymer composites of poly(3-hydroxy butyrate) (PHB) with polyaniline (PANI), carbon black, and plasticizer

Four composites of PHB, with varying amounts of PANI, carbon black (CB), and a tributyl O-acetylcitrate were prepared by solvent casting and then melted to form films by hydraulic hot press. The morphology, thermal properties, and electrical conductivity of PHB were studied by TEM, DSC, four-point probe, LCR bridge, FT-IR, and WAXD. The values of e′ and e″ had a higher values with the addition of PANI/CB compared to pure PHB. The conductivity increased from 10−15 to 10−6 S cm−1 and increased with raised the temperature similar semiconductor. TEM showed good dispersion of PANI and CB and no agglomerations in the PHB matrix. The new PHB composites can be applied in the medical and electronics industries in the near future.

Study of dielectric anisotropy and other related parametersof a liquid crystal compound 7OAOB

ABSTRACTTemperature-dependent dielectric anisotropy has been measured for the compound 4,4′-di-n-heptyloxy-azoxy benzene (7OAOB) by using a digital LCR bridge (HIOKI 3532-50 LCR HiTESTER). The compound 7OAOB is found to exhibit negative dielectric anisotropy in the nematic and smectic-C phase. Frequency-dependent electrical conductivity has been measured for this compound. The dc conductivity has also been obtained from frequency-dependent total conductivity studies by using universal power law equation. The activation energy of the dc conduction process and relaxation time has been determined in different mesophases. The behavior of splay elastic constant (K11) with temperature has been examined for this compound. From the studies of UV-visible spectra, the values of energy band gap have been evaluated.

Studies of temperature and frequency dependence of dielectric permittivities of two Schiff's base liquid crystal compounds

Abstract Effect of temperature and frequency on the dielectric permittivities of two Schiff's base liquid crystal compounds p-ethoxybenzylidine p-heptylaniline(EBHA) and p-butoxybenzylidine p-heptylaniline(BBHA) have been studied by using a digital LCR bridge (HIOKI 3532-50 LCR HiTESTER). Due to the changes of CH 2 groups at the oxygen containing flexible side chain between these two compounds, some changes occur in the behavior of their temperature dependent physical properties such as dielectric anisotropy, splay elastic constant, relaxation time, which has been studied extensively. The frequency dependent electrical conductivity of these two compounds has also been carried out. At the nematic mesophase the values of activation energy have been estimated from the temperature dependent DC and AC conductivity curves. The optical band gap of EBHA and BBHA has been calculated from UV spectra.

Study of Electrical Conductivity in WO3-doped Nonstoichiometric LiTaO3

The results of experimental and analytical studies of the electrical conductivity for different solid solutions synthesized in a vicinity of LiTaO3 in the ternary system Li2O–Ta2O5–(WO3)2 are presented. It is shown that the electrical conductivity increases linearly with the Curie temperature. The experimental conductivity between 200 and 700 ºC was measured using an LCR bridge HP4192A on ceramics sintered at 1250 ºC. Within the theoretical approach to the defect structure analysis combined with our proposed vacancy models, the theoretical results are in a good agreement with the experimental data.

Frequency response of Diamond-like Nanocomposite thin film based MIM capacitor and equivalent circuit modelling

The frequency response of metal-insulator-metal (MI M) based thin film capacitors were studied using LCR bridge where diamond-like nanocomposite ( DLN) film behaves as a dielectric medium. The films were deposited by plasma assisted chemical vapour d eposition (PACVD) method. Fourier transforms infrar ed spectroscopy (FTIR) and Raman spectroscopy give the structure of DLN film. The results show that, equi valent parallel capacitance (EPC) decreases sharply beyond 10 5 Hz for thinner films. But for thicker films, there is no such decrease. This is due to some parasitic series resistance effect in the capacitor circuit. An equ ivalent circuit model for real capacitor has been establish ed. Moreover, there is also a small decrement in EP C with frequency and this effect increases with thickness of film. This may be due to lack of sufficient time for electron transportation through bulk DLN material. The DLN b ased thin film capacitor has a great potential for use in electronic/electrical system.