Investigation of frequency dependent electrical and dielectric properties of maple wood (acer trautvetteri medw.) with different surface treatments

In present study, we investigated frequency and voltage dependence of electrical and dielectric properties of Ag/nGO doped poly(vinyl alcohol) (PVA)/ p-Si structures. The nGO-PVA films were prepared by using improved Hummers method and this thin film layers were analyzed with SEM and EDX. The main parameters as ideality factor (n), barrier height (Φbo) and saturation current (I0) were obtained from current–voltage (I-V) measurements. The frequency dependent electrical characteristics of structure investigated using capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements in the frequency range of 10 kHz to 1000 kHz in 300 K absolute temperature. The capacitance, conductance and series resistance (RS) values decreased with increasing frequency. These decreases at higher frequencies are attributed to existence of interface state densities. The presence of the interface state densities (NSS) are also evidenced as a peak in the capacitance, conductance and series resistance–frequency characteristics. After, the dielectric properties of Ag/GO-PVA/ p-Si structures were obtained using C–V and G/ω–V measurements in the same frequency ranges. The values of dielectric constant (ε′), dielectric loss (ε″), and loss tangent (tanδ) decreases with increasing frequency while ac electrical conductivity (σac) increase with increasing frequency. Our results showed that frequency dependent electrical and dielectric properties were strongly frequency and voltage dependent.

Dielectric properties of rambutan wood (Nephelium Lappaceum) were investigated in three anisotropic directions, namely miters-cut, cross-cut, and rib-cut. Dielectric constants and dielectric loss factors were measured at ambient temperatures by using an impedance analyzer. The dielectric constant decreased as frequency increased from 4 to 1 MHz. Among the wood specimens, the rib-cut direction has the lowest dielectric constant, while the cross-cut direction has the highest value. A dielectric dispersion occurred within frequencies 100 Hz to 10 kHz, which corresponding to a relaxation peak as observed on dielectric loss factor spectra. The relaxation peak value of the dielectric loss factors shifted towards higher frequencies in the sequence of rib-cut, miters-cut, and cross-cut specimen. Above 500 Hz, the cross-cut specimen has the highest value conductivity than others. Generally, these variations were subjected to the anatomical structure in the wood, such as parenchyma, ray cell, vessel cell, and fiber cell.

BiFeO3-based multiferroic ceramics if prepared in phase pure form possess wide range of applications based on their charming and switchable polarization, piezoelectric, magnetoelectric and spintronic properties. In this regard, we investigate the influence of Mn substitution at Fe-site in BiFe0.99Cu0.01O3 samples, synthesized by sol–gel-based self-assisted combustion technique. Crystal structure was determined using X-ray diffraction which revealed a rhombohedrally distorted cubic perovskite structure of all the samples. The lattice constant increased, while crystallite size decreased with increased concentration of Mn. A systematic analysis of frequency-dependent dielectric constant, loss factor, tangent loss and impedance has been presented using an impedance analyzer. It is observed that the trend of dielectric constant, loss factor, tangent loss and impedance is decreasing with increasing frequency. It was also observed that electrical properties were mainly influenced by dominance of grain boundaries effect in 20 Hz–20 MHz range. Effect of increased concentration of Mn on frequency-dependent dielectric properties has also been discussed, and it is found that dielectric properties decreased with increasing concentration of Mn mainly attributed to the suppression of oxygen vacancies.

Novel mesoporous SiO2 conjugated graphene oxide 2D layers: Frequency and temperature dependent dielectric properties

Dielectric properties of rubber wood have been studied at low and microwave frequencies with different moisture content and grain direction. The ultrasonic properties were studied with pulsed longitudinal waves of frequency 45 kHz, Two anisotropic directions have been considered for this study — parallel and perpendicular to grain. The low frequencies were of 0.01, 0.1, L0, 10 and 100 Hz and microwave frequencies were of 1, 2.45, 6, 8, 10, 14 and 17 GHz. The moisture content affected the dielectric constant and dielectric loss factor both at low and microwave frequencies? The moisture content above 30% showed little influence on dielectric properties whereas it increases linearly from 0 to 30% in both the grain directions at low frequencies. A continuous increase of dielectric properties was obtained with the increase of moisture content at microwave frequencies and the trend becomes concave upward. Dielectric properties increase as the frequencies increase except dielectric loss factor at microwave frequencies where reverse trends were observed. Little change of dielectric loss factor was obtained at frequencies above 6 GHz. The parallel to grain direction showed higher dielectric constant and dielectric loss factor compared to perpendicular to grain direction. This dielectric anisotropy of wood may be attributed due to the microscopic, macroscopic molecular as well as chemical constituents of wood. Ultrasonic properties were also affected considerably by the moisture content and grain direction. The dried wood showed higher ultrasonic velocity and elastic stiffness constant compared to green wood. The parallel to grain direction exhibits higher ultrasonic velocity and elastic stiffness constant than perpendicular to grain.

The dielectric properties of piezoelectric materials are important in many applications of piezoelectric materials, such as active structural control, underwater sonar, dielectric insulator, etc. The experimental measurement of dielectric properties of materials is usually done using commercial electrical impedance analyzer, LCR meter, or network analyzer, such as an HP 4194 impedance analyzer. The excitation voltage of these commercial analyzers is generally very low, e.g., 1.5 volts rms or under. However, the dielectric properties of piezoelectric materials (both dielectric constant and dielectric loss factor) can be very sensitive to the level of applied electric voltage (field). Since virtually all the applications of piezoelectric materials are under high field, it is important to develop measurement techniques to determine the voltage dependent dielectric material properties. This paper introduces a high- voltage/high-power electromechanical impedance analyzer developed based on a commercial electrical power analyzer/phase angle multimeter. The developed analyzer is then used to determine the dielectric constant and dielectric loss factor of G1195 PZT. The measurement results, dielectric constant and loss factor as a function of applied electric field, frequency, and ambient temperatures, are presented in the paper.

Today, the wood of the oriental beech (Fagus orientalis Lipsky.) is widely used in various applications, including furniture, musical instruments, carvings, and veneer. In this study, the dielectric properties of oriental beech were investigated at AC signal frequencies of 100 Hz–1 MHz in the voltage range of 0–100 V DC, and the effects of different surface conditions on these properties were investigated. The dielectric, thermal and surface free energy behaviors of control wood (CW) and wood soaked in water for two weeks (SW) were analyzed comprehensively. Basic parameters such as specific heat capacity (Cp), real (ε′) and imaginary (ε″) dielectric constants, alternating current electrical conductivity (σac), free energy component (G/ω), dielectric loss factor (tanδ) were evaluated in detail within the scope of experimental measurements. SW samples exhibited approximately 1,000-fold higher (ε″) values and a two-to three-fold increase in (tanδ) compared to CW samples. Furthermore, (σac) increased from ~10⁻⁹ S/m in CW to ~10⁻⁴ S/m in SW, indicating a significant increase in ionic conductivity due to the higher moisture content. CV samples maintain their insulation properties by showing consistent dielectric properties across the entire frequency range. All measurements were repeated three times (n=3) and the standard deviation was found to be less than 5%. These results show that whereas dry wood retains consistent dielectric performance with low losses, moisture dramatically increases conductivity and dielectric losses.

Drying is a complex heat and mass transfer process which is affected by operating parameters environment and thermophysical properties of wood. Basis for classification of methods of drying is a method of transmission of heat to material. The basic method of drying is convective, but it is accompanied by a conductivity of wood (from the material surface to its center) and thermal radiation. The research investigates the processes of initial heating and steaming of beech wood in the form of profile pieces, which describes the dynamics of change in temperature of wood in general and particularly of surface and inner layers of wood, as well as changing the thermal properties (coefficients of heat-conducting, diffusivity and specific heat capacity) of wood. The change of thermal properties of wood causes the change of heat-exchange criteria of Fourier and Nusselt. So the use of differential equalization of heat-conducting of Fourier is possible only for the certain period of process of heating. Firstly, experimental studies of process of drying of profile workpiece (firewoods) are undertaken with a previous steaming and without a previous steaming; the corresponding sizes of speed of drying, coefficients of moisture conductivity and output of moisture are found. Consequently, taking into account the criterion of Reynolds the coefficient of drying and mass transfer coefficient of Fourier and Nusselt it is possible to synthesize the physical-mathematical model of process of drying. In the course of the study we have elaborated the structure of technological process of drying of firewoods. It is proved to include such successive technological operations as the initial heating, steaming, drying, that allows considerably to intensify mass transfer processes and, to the eventual result, shorten duration of process of drying on 25 % and accordingly to economize the charges of thermal energy. As a conclusion the author proposes structure of the technological process of drying wood that involves the use of environmentally-friendly drying agent for heating and steaming, and drying process steam-air mixture received from the combustion of waste wood. In general, the structure provides an energy saving of realization of technological process and reduces its overall duration.

The dielectric properties (components of the complex permittivity relative to free space) of ground hard red winter wheat of 11–25% moisture content were determined by dielectric spectroscopy measurements with an open-ended coaxial-line probe and impedance analyser over the frequency range from 10 MHz to 1.8 GHz at temperatures from 5 to 95 °C. Both the dielectric constant and dielectric loss factor, over the stated range of variables, decreased with increasing frequency and increased with increasing moisture content and temperature. Plots of the dielectric constant and loss factor in the complex permittivity plane revealed a linear relationship between the two permittivity components at frequencies above 1 GHz, but they showed nonlinearity at lower frequencies due to the increasing influence of ionic conduction as confirmed by Cole–Cole plots of the permittivity data.

To provide necessary information for further pasteurization experiments and computer simulations based on radio frequency (RF) and microwave (MW) energy, dielectric and thermal properties of walnut components were measured at frequencies between 10 and 3000 MHz, temperatures between 20 and 80 °C, and moisture contents of whole walnuts between 8.04% and 20.01% on a dry basis (d.b.). Results demonstrated that dielectric constants and loss factors of walnut kernels and shells decreased dramatically with raised frequency within the RF range from 10 to 300 MHz, but then reduced slightly within the MW range from 300 to 3000 MHz. Dielectric constant, loss factor, specific heat capacity, and thermal conductivity increased with raised temperature and moisture content. Dielectric loss factors of kernels were greater than those of shells, leading to a higher RF or MW heating rate. Penetration depth of electromagnetic waves in walnut components was found to be greater at lower frequencies, temperatures, and moisture contents. The established regression models with experimental results could predict both dielectric and thermal properties with large coefficients of determination (R2 > 0.966). Therefore, this study offered essential data and effective guidance in developing and optimizing RF and MW pasteurization techniques for walnuts using both experiments and mathematical simulations.

Rubber compounds with high friction coefficients are widely used in safety shoes, functional shoes, etc. However, in the presence of a liquid lubrication layer, friction coefficients between rubber compounds and the opposing surface are generally very low. In this work, friction coefficients of rubber compounds are improved by a two‐pronged method. First, micron silicon carbides (SiC) with irregular shape and knife‐edge are selected as fillers to improve the plowing friction in dry state, and to improve the adhesive friction in wet state via piercing the liquid lubrication layer. Second, tackifying phenolic resin is added to increase the damping performance of rubber compounds, so as to improve the hysteresis friction in both dry and wet states. The results show that the comprehensive static and dynamic friction properties of rubber compounds are the best in both dry and wet states (0.5 wt% sodium dodecyl sulfate solution or 90 wt% glycerol solution), when SiC size is 7–14 μm and SiC content is 75–90 phr. Phenolic resin can increase the loss factor (tanδ) and loss modulus (E") of rubber compounds, and improve the static and dynamic friction coefficients in wet state (90 wt% glycerol solution). At the same time, it can improve the hardness of rubber compounds and reduce the relative content of SiC, thus reducing the static and dynamic friction coefficients of rubber compounds in dry and wet states (0.5 wt% sodium lauryl sulfate aqueous solution). In general, the optimal content of phenolic resin is 10–15 phr. Highlights Rubber friction coefficients improved via both adhesion and hysteresis friction. Irregular silicon carbides pierce liquid layer to improve adhesive friction of rubber. Phenolic resin increases hysteresis friction of rubber via damping property.

Yttrium substituted strontium hexaferrite, SrAl4YxFe8−xO19 with x = 0.0, 0.05, 0.10, 0.20, and 0.30, are prepared by the auto combustion method. The ferrites have been examined using XRD, SEM, FTIR, and VSM. The structural study confirms that the Y3+ ions reorganize themselves without troubling the parent lattice. In FTIR, the low wavenumber absorption bands confirm the hexagonal ferrites. Saturation (Ms) and remanence (Mr) magnetization is observed to decrease whereas, coercivity (Hc) and Curie temperature (Tc) is improved with Y3+ content. The variation in the dielectric constant $$( \in )$$ and dielectric loss factor (tanδ) is discussed in the frequency range of 20Hz–20 MHz. The value of dielectric constant $$( \in )$$ and dielectric loss factor (tanδ) is decreased with Y3+ content. The optimized magnetic properties are obtained from x = 0.20 compositions having Ms ~ 4.45 emu/g, Mr ~ 1.91 emu/g, Hc ~ 36 kOe, (BH)max ~ 36.64 MGOe and Tc ~ 614 °C. This material is very suitable for longitudinal recording media.

Synthesis, structural, magnetic and electrical properties of Co1−xZnxFe2O4 (x = 0.0, 0.2) nanoparticles

Synthesis and electrical properties of the (PVA) 0.7(KI) 0.3· xH 2SO 4 (0 ≤ x ≤ 5) polymer electrolytes and their performance in a primary Zn/MnO 2 battery

Tailoring the structure-morphology-vibrational-optical-dielectric and electrical characteristics of Ce@NiO NPs produced by facile combustion route for optoelectronics