Electrical properties of interdigitated partially bent like shaped liquid crystalline compound

This article represents the electrical studies of an interdigitated highly skewed N(4-n-pentyloxybenzylidene) 4-n-alkylaniline (5O.16) compound. Interestingly the compound is partially bent like and unsymmetrical in alkyl chain length. Dielectric and impedance spectroscopy studies indicate the coupling between the liquid crystal and the electrical field. Studies were carried out as a function of temperature as well as frequency. Semicircular nature of the Cole–Cole plots indicates the reorientation of the molecule with the applied field. Using the experimental data and the theoretically fitted results the effective equivalent model circuit was designed. Which used to explain the behavior of the compound under the external electric effect and the influence of the electrodes with different variable represent the resistor circuit. However, the effect of the conductivity of temperature and frequency are also reported.     

Synthesis,characterization, and phase transition of an inorganic-organic hybrid compound,[(3-nitroanilinium+) (18-crown-6)] [IO4-](CH3OH)

A novel inorganic-organic hybrid supramolecular compound,[(3-nitroanilinium~+)(18-crown-6)][IO_4](CH_3OH)(1),was discovered as phase-transition materials displaying dielectric anomalous behaviors.The yellow block crystal formed by N-H…O hydrogen bonding that made contact through the cavity of 18-crown-6 was characterized by single-crystal X-ray diffraction,elemental analysis,infrared analysis,thermogravimetric analysis,differential scanning calorimetry,and potential-energy calculations.Differential scanning calorimetry measurements indicate that the compound experiences a reversible phase transition at around 220 K.Temperature-dependent dielectric measurements further confirm the phase transitions.Potential-energy calculations demonstrate that the phase transition occurs due to the molecular order-disorder rotation of CH_3OH,whereas the space grouping of the crystal remains unchanged.     

Structural,dielectric and magnetic properties of cobalt based spinel ferrites

CoYb_xFe_2-xO₄ (x = 0.00, 0.025, 0.05, 0.075, 0.10) spinel ferrites were synthesized by co-precipitation technique. Structural, dielectric and magnetic properties were measured. X-ray diffraction analysis showed that all the prepared spinel ferrites possessed cubic spinel structure. Dielectric constant, AC conductivity and dielectric loss decreased with the addition of rare earth ions. The impedance analysis explained the role of grains and grain boundaries with in prepared samples. Cole-Cole plots helped to measure the values of grains and grain boundary's resistance. The magnetic properties proved the soft nature of these ferrites. Saturation magnetization and remanence decreased while coercivity was enhanced with the addition of ytterbium concentration. All these parameters suggested that these prepared samples might be suitable for high frequency applications.     

Dielectric barrier discharge in needle-to-plane configuration: Model of surface charge relaxation

Relaxation process of surface charge owing to dielectric barrier discharge (DBD) in “needle – air gap – polyethylene terephthalate film – plane” configuration is considered. Experimental data of the surface charge relaxation (SCR) are obtained by means of the rotating capacitive probe. Taking into account Gaussian radial distribution of accumulated charge density, effective surface and volume electrical conductivities of a barrier dielectric, phenomenological model of SCR for any dielectric thickness is proposed and exact solutions are obtained. The adequacy of the model is confirmed by the numerical computation. There is a good agreement between the experimental results and the model calculations.     

Macrokinetic study on ozone boundary concentration. Effect of temperature

The process of ozone production in pure oxygen using the tubular, high voltage pulse supplied ozonizer was studied. The unusual methodology of conducting kinetics measurements of the ozone synthesis process was presented. It was shown how the process rate changes along the discharge gap. The effect of power density and gas residence time in the discharge gap on the process rate was analysed. The temperature influence on the course of the process, particularly on the ozone boundary concentration and ozone decomposition rate constant, was discussed.     

Enhanced depolarization temperature in 0.90NBT–0.05KBT–0.05BT ceramics induced by BT nanowires

The depolarization temperature (T_d) of piezoelectric materials is an important figure of merit for their application at elevated temperatures. This study focuses on the effect of BaTiO₃ (BT) nanowires on T_d and piezoelectric properties of morphotropic-phase-boundary 0.90NBT–0.05KBT–0.05BT ceramics. The results reveal that BaTiO₃ nanowires can pin the domain wall, leading to the increase of coercive field (E_c) from 21.06 kV/cm to 34.99 kV/cm. The T_d value of 0.90NBT–0.05KBT–0.05BT ceramics can be enhanced approximately 20 °C when using BT nanowires instead of BT solution as the raw material. Meanwhile, at the same polarization conditions, the piezoelectric constant of the ceramic added BT nanowires (172 pC/N) is decreased but still remains a larger value compared with those of other lead-free ceramics. The results imply that the addition of BT nanowires into NBT–KBT is a very effective route to improve T_d.     

Dielectric Properties of Polymer Composites Filled with Different Metals

Electrically conductive composite systems based on polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) filled with metal powders of Al and Cu have been studied. The composite preparation conditions allow the formation of a random distribution of metallic particles in the polymer matrix. Dependence of the dielectric and conductivity properties of the PVC and PMMA/fillers was studied over a broad range of frequency and volume fraction of metal fillers. The experimental results could be explained by means of the conductivity of fillers and the interface polarization between polymers and fillers. Percolation was also seen in this study when the volume fraction of conducting fillers was close to critical value, in which the composites undergo an insulator‐conductor transition. The relation among the dielectric property and the fillers with different conductivity was proposed.