Papers by Keyword: Loss Tangent

Abstract: Chemical oxidation reactions were used to create composite materials made of polythiophene (PTh) and reduced graphene oxide with varying compositions. To describe the samples, Fourier transform infrared spectroscopy (FTIR) was used. The hydroxyl (OH) stretching vibrations of the -COOH functional group and adsorbed H₂O molecules are responsible for the intense bands at 3386 cm^-1 and 1302 cm^-1. O-H vibrations can be attributed to absorption at a wavelength of 1610 cm^-1. C-S bending mode of thiophene ring has produced the peak at 666 cm^-1. The dielectric constant, tangent loss, and electric modulus with the applied AC frequency for the polythiophene/reduced graphene oxide composites were studied.

Abstract: The solid polymer electrolyte (SPE) consists of polylactic acid (PLA) with different compositions of lithium perchlorate (LiClO₄) were prepared by using the solution casting method. The conductivity and dielectric properties of the SPE system were studied by using an impedance spectroscopy technique with a frequency ranging from 0.1 Hz to 100 MHz. The optimum composition of the LiClO₄ in the PLA based electrolyte system is 50 %. The highest ionic conductivity value of the PLA-LiClO₄ electrolyte is 2.66 x 10^-5 Scm^-1. The dielectric permittivity, ɛ′ shows high magnitude in the lower frequency due to electrode polarization (EP) effect and become to decrease at high frequency. The magnitude of ɛ′ increases up to 50 % of LiClO₄ in the electrolyte system. The loss tangent was used to measure the relaxation time of the electrolyte system. The shortest relaxation time is PLA- LiClO₄ polymer electrolyte system is 7.98 × 10−6 s. The electric modulus, M′ and M′', increases with frequency, indicating that the force of charge carriers increases in depletion and accumulation regions at room temperature.

Abstract: Experimental studies on the effect of frequency and temperature on the dynamic mechanical properties of filled composites are studied poorly and require further research. The purpose of theresearch is to study the effect of heavy fillerbarite (BaSO₄), on the dynamic characteristics of a highly filled composite based on butyl rubber, and to compare the efficiency of barite in the composite with similar light filler. The conclusions are made on the basis of a comparative analysis of the temperature-frequency dependences of the loss tangent and the storage modulusat various percentages of filler, obtained by the DMA method. It has been established that while increasing barite concentration the elasticity of the composite material decreases, the glass transition temperature shifts upwards, and the reverse occurs in the zone of highly elastic state of the composite: the higher the barite concentration, the higher the damping properties. The authors provided a rationale that the heavy filler shows the effect only in the highly elastic zone if compared with the light one. The article is of practical value for the development of new vibration insulation materials.

Abstract: (Bi₂O₃Fe₂O₃)_0.8(Nb₂O₅)_0.2 was synthesized by solid state reaction method. (Bi₂O₃Fe₂O₃)_0.8(Nb₂O₅)_0.2 was made for the investigation of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Dielectric property. XRD pattern reveals that three phases were obtained with Bismuth Iron Niobium Oxide. SEM elicits that grain size increases with the enhancement of sintering temperature. Dielectric property decreases with the augmentation of frequency.

Abstract: Liquid crystal (LC) polymer, composited with inorganic filler, has a broad application prospect in electronic and electrical industry. In this research, permittivity (ε_r) and dielectric loss tangent (tanδ) of LC composites under different temperatures and frequencies were investigated, and activation energies were calculated and analyzed. At low temperatures and high frequencies, LC composites exhibited well dielectric properties. ε_r changed a little (3.6~4.0) in temperature range of-60°C~160°C when frequency was higher than 10Hz, but increased sharply when temperatures was higher than 100°C and frequency was lower 10Hz. The tanδ increased sharply with increasing temperature when temperatures was higher than 100°C and frequency was lower than 10²Hz, and when frequency was above 10²Hz, the value of tanδ changed gently (10^-3~10^-2). The peak of tanδ would translate to higher frequencies direction with increasing temperature in tanδ-frequency curve, and to higher temperatures direction with increasing frequency in tanδ-temperature curve. Activation energy is calculated by fitting the peak of the imaginary of the electric modulus, and activation energy is 0.43eV in low temperature and 1.59eV in high temperature.

Abstract: Orthorhombic HoMnO₃ films were prepared epitaxially on Nb-doped SrTiO₃ single crystal substrates by using pulsed laser deposition technique. The films showed perfectly a-axis crystallographic orientations. X-ray diffraction and atomic force microscopy were used to characterize the films. The complex dielectric properties were measured as functions of frequency (40 Hz~1 MHz) and temperature (80 K~300 K) with a signal amplitude of 50 mv. The respective dielectric relaxation peaks shifted to higher frequency as the measuring temperature increased, with the same development of real part of the complex permittivity. The cole-cole diagram was obtained according to the Debye model, and the effects of relaxation process were discussed.

Abstract: Surface mount devices (SMDs) such as multilayer ceramic capacitors (MLCCs) have been widely used to reduce the size of electronic circuits as they are mounted directly onto the surface of printed circuit boards (PCBs) and are smaller than their through-hole counterparts because SMDs have shorter internal leads or no leads at all. Another advantage of these components is the lower parasitic inductance, which results in a higher resonant frequency. This work reports on the dielectric characterization of four commercial multilayer ceramic capacitors in a broad frequency range from 0.01 GHz to 2 GHz. The dielectric characterization consists of measuring the reflection coefficient S₁₁ (real and imaginary parts) as function of frequency to calculate the permittivity, impedance and loss tangent of the capacitors tested. In addition, dielectric chemical composition is determined using surface X-ray spectroscopy (EDS). The results show that MLCCs have a resonance frequency higher than 0.3 GHz depending on the value of their capacitance, making them suitable for use in RF equipment, mobile phones, radars, and microwave electronic circuits.

Abstract: This paper presents the results on dielectric properties of pulverized material based on agricultural waste namely oil palm frond and pineapple leaf fiber for microwave absorber application in the X-band frequency range. The investigation is started by identifying the pulverized materials permittivities and loss tangents using coaxial probe technique, followed by density measurement comprising the determination of bulk and solid densities. Then, by using dielectric mixture model, the solid particle dielectric properties were determined. It is observed that the air properties give quite an effect on the permittivity and loss tangent of the pulverized materials. It is also found that the lower the material density the higher material dielectric constant will be. Furthermore, the results show that, both oil palm frond and pineapple leaf fiber are potential to be X-band absorber with average dielectric constant of 4.40 and 3.38 respectively. The loss tangents for both materials were observed to be more than 0.1 which mark them as lossy materials.

Abstract: To evaluate the high temperature properties and rheological behavior of Iranian Rock Asphalt(IRA), convectional test and temperature scanning test over modified asphalt containing A-70 asphalt as base asphalt and IRA as different amount were conducted. The results show 1) an increase in asphalt binder’s capability of deformation resistance under high temperature, decreases both in asphalt binder’s temperature sensitivity and low-temperature performance; 2)an increase in anti-rutting factor, a decrease on loss tangent value, an improvement of dynamic viscosity. Thus the asphalt binder’s high temperature performance is greatly improved and anti-rutting capability strengthened.

Abstract: To develop novel wood preservation technique trimethylborate(TMB) and boric dioxide were used by sol-gel process to modify poplar (Populus euramevicana cv.‘I-214'.) wood. The temperature variations of the storage modulus and the loss tangent along the grain for two kinds of chemically modified poplar woods were measured at 2Hz over a temperature range of -50 to 200°C. The storage modulus of modified woods were observed slight increases over the temperature range tested by introduction of bulky side chains and the tanδ remarkably reduced due to boric acid bridges between the hydroxyl groups which restricted the micro-Brownian motion of the main chains. In TMB treatment, peak width at half height of tanδ broadened significantly, indicating remarked cross-linking effect in polycondensation with wood cellulose.