Electrical Relative Permittivity Research Articles

Microstructural and dielectric properties of civil construction ceramic waste sintered at various temperatures

This study investigates the dielectric properties of ceramic waste derived from roof tiles and bricks commonly used in civil construction. The materials were analyzed by grinding them into a fine powder, followed by producing of cylindrical samples through uniaxial pressing on a steel matrix. The samples were sintered at temperatures of 1000 °C, 1050 °C, and 1100 °C to analyze the effect of temperature on the electrical characteristics of the ceramics. XRD and SEM analyses were performed to evaluate microstructural parameters and coalescence behavior. The dielectric characterization aimed to obtain the real relative electrical permittivity with average values of 2.85, 3.56, and 3.65, correlated with apparent porosity levels of 30.74 %, 20.54 %, and 9.11 %, and the loss tangent of 7.5 × 10−5, 3.9 × 10−5, and 12 × 10−5, respectively. The loss tangent values are lower than those obtained in commercial dielectrics from 1 to 6 GHz frequency range. The dielectric characteristics of samples manufactured from ceramic waste from bricks and tiles can serve as sustainable alternatives to produce dielectric resonator antennas (DRA), applicable to fifth-generation wireless communication devices in the sub-6GHz band.

Determination of dielectric properties of plaster blocks for sealing masonry using non-destructive frequency scanning methods

With the increasing use of traditional and new models of wireless communication systems, the study and determination of the electrical characteristics of materials used in civil construction is an important topic to establish an understanding of how the radio frequency signal behaves inside built environments. This study presents an extensive process of characterization of electrical parameters of plaster blocks used in the construction of walls. Different from the literature where a prior estimation of the data occurs to enable sampling parameters to be obtained, this work proposes an innovative way of obtaining them entirely based on the analysis of the material through frequency measurements, which results in a greater level of precision of the data results. Analyses are made in the frequency range from 0.7 to 5.2 GHz, which has been used for several wireless communication standards. To carry out the electrical characterization of dielectric materials, a non-invasive methodology is proposed based on an innovative combination of the Nicolson–Ross–Weir Method (NRW) and the Ray Tracing Method. Through the proposed methodology and an extensive campaign of measurements using frequency scanning equipment, calculated and experimental data of Shielding Effectiveness (SE), complex relative electrical permittivity, loss tangent, attenuation coefficient and conductivity were obtained for a wide range of frequency, considering different samples of plaster blocks. The obtained results are compared to those available in the related literature, confirming the accuracy of the proposed analysis.

Pine and eucalyptus log moisture determination using the radiofrequency capacitance method

The development of statistical models that correlate the relative electrical permittivity ε’ and the dielectric loss factor ε’’ to the amount of water present in wood, is a key step in the development instantaneous moisture methods. The correlation between those variables is widely applied in the instant moisture measurement for lumber and recently for woodchips, but it is not yet applied for the measurement of logwood. This work consisted in the evaluation of this same method applied also to the logwood. Once approved, the method can be used in the timber trade, in the selection of the logs that feed the pulp production line or that feed the power boiler, until then stored in the patio. The materials used in the present research were pine logs with moisture between 10% and 50% on wet basis and eucalypts logs with moisture between 40% and 60% on wet basis, coming from different plantations, all located in the province Paraná. The evaluation was performed by correlating the primary reading of a capacitive sensor when inserted into the logs and the wood moisture obtained by the gravimetric method. The determination coefficients R² related to the correlation between the capacitive sensor readings and the moisture determination results were 88,3% for the pines logs and 68,1% for the eucalyptus logs. This correlation allowed to affirm that the capacitive method can be applied to estimate the moisture content of the two investigated genera with sufficient accuracy to commercialize and classify the raw material for the pulp production process or for energy production from biomass.

QUALITY EVALUATION OF UHF RFID ANTENNAS AND PASSIVE TAGS ON PAPER SUBSTRATES

The effect of antenna design modification, paper substrates and relative electrical permittivity of background materials on the reflection coefficient of UHF RFID antennas was studied. Simulation software was used to modify the design and calculate the reflection coefficient of the antennas. By modifying the coupling of the dipole with the induction loop of the antennas, areduction of the simulated reflection coefficient was achieved compared to thecommercial antenna. The positive effect of antenna modification was also confirmed by measuring thereflection coefficient of antennas printed on paper by thermal transfer printing, placed on extruded polystyrene and particle board. The reflection coefficient of the modified antennas was lower when placed on extruded polystyrene, whose relative electrical permittivity was lower than particle board. After installing the memory chip to the antennas printed on paper and paperboard, the identification, reading and recording range of passive UHF RFID tags were measured after they were placed on thicker paperboard, extruded polystyrene and particle board. The positive effect of antenna modification on improving the communication quality of passive UHF RFID tags placed on background materials with a relative electrical permittivity of 2.4 to 6.7 wasconfirmed.

Analog interface based on capacitance multiplier for capacitive sensors and application to evaluate the quality of oils

<abstract><p>Currently, interdigital capacitive (IDC) sensors are widely used in science, industry and technology. To measure the changes in capacitance in these sensors, many methods such as differentiation, phase delay between two signals, capacitor charging/discharging, oscillators and switching circuits have been proposed. These techniques often use high frequencies and high complexity to measure small capacitance changes of fF or aF with high sensitivity. An analog interface based on a capacitance multiplier for capacitive sensors is presented. This study includes analysis of the interface error factors, such as the error due to the components of the capacitance multiplier, parasitic capacitances, transient effects and non-ideal parameters of OpAmp. A design approach based on an IDC sensor to measure the quality of edible oils is presented and implemented. The quality relates to the total polar compounds (TPC) and consequently to relative electrical permittivity <inline-formula><tex-math id="M1">\begin{document}$ {\varepsilon }_{r} $\end{document}</tex-math></inline-formula> of the oils. A measurement system has been implemented to measure the capacitance of the IDC sensor, which depended on <inline-formula><tex-math id="M2">\begin{document}$ {\varepsilon }_{r} $\end{document}</tex-math></inline-formula>. The simulation and experimental results showed that, for a capacitance multiplication factor equal to 1000, changes of 3.3 µs/100 fF can be achieved with an acceptable level of noise, which can be easily measured by a microcontroller.</p></abstract>

Stochastic-Deterministic Assessment of Electric Field Radiated by Base Station Antenna above a Two-Layered Ground

The paper deals with stochastic-deterministic modelling of radiated electric field by base station antennas (BSAs) operating in GSM frequency range. Within the framework of deterministic analysis, the total electric field above a two-layered lossy ground is obtained by considering the incident and reflected ray in the far field zone. The influence of nonhomogeneous lower medium is taken into account via two approaches: Fresnel plane wave reflection coefficient (FRM) and simplified reflection coefficient stemming from Modified Image Theory (MIT). Antenna height, relative conductivity, and permittivity of each ground layer, as well as the thickness of the upper ground layer, are considered as input parameters with inherent uncertainty. To quantify the uncertainty of output electric field, deterministic models are treated as black boxes by two stochastic methods, Monte Carlo (MC) and Stochastic Collocation (SC), respectively. Stochastic mean and standard deviation of the output are computed, and sensitivity analysis is carried out in order to analyze the impact of input parameters’ variations on the resulting electric field variance. The presented results expose weakness and strength of the two stochastic methods, particularly identifying the cases when the preferred SC method fails to converge. Furthermore, sensitivity analysis reveals that despite the smallest variation around its respective average value, the antenna height has the highest impact on the output variance at observation points in the vicinity of the antenna. However, as the distance from the antenna increases, the 1st layer depth and its relative electric permittivity become the most significant parameters.

Dependence of the Efficiency of the Nonlinear‐Optical Response of Materials on their Linear Permittivity and Permeability

AbstractThe dependence of the efficiency of various nonlinear‐optical processes on the background linear relative electric permittivity ϵ and magnetic permeability μ of the material is analytically and numerically investigated. The conversion efficiency of low‐order harmonic‐generation processes, as well as the increase rate of Kerr‐effect nonlinear phase shift and nonlinear losses from two‐photon absorption (TPA), are seen to increase with decreasing ϵ and/or increasing μ. The rationale and physical insights behind this nonlinear response are also discussed, particularly its enhancement in ϵ‐near‐zero (ENZ) media. This behavior is consistent with the experimental observation of intriguingly high effective nonlinear refractive indices in degenerate semiconductors such as indium tin oxide and aluminum oxide (where the nonlinearity is attributed to a modification of the energy distribution of conduction‐band electrons due to laser‐induced electron heating) at frequencies with vanishing real part of the linear permittivity. Such strong nonlinear response can pave the way for a new paradigm in nonlinear optics with much higher conversion efficiencies and therefore better miniaturization capabilities and power requirements for next‐generation integrated nanophotonics. It is concluded that the major contribution to the enhanced nonlinear response of ENZ materials arises from propagation effects, that is, the appearance of ϵ and μ in the reduced wave equation describing the interaction.

Experimental apparatus for the determination of thermal conductivity and humidity in building materials by means of electrical permittivity measurements

The on-site measurement of the thermal properties of existing building envelopes is of utmost importance to fairly accurately calculate the thermal loss by transmission to the outside environment and so to define the building overall energy performance. This paper presents a preliminary investigation concerning the use of a new indirect method for measuring the thermal characteristics of building materials throughout the year based on the analysis of the material electrical properties. The main goal is to identify a relationship between thermal transmittance, moisture content and electrical impedance through relative electrical permittivity measurements.

Development and evaluation of hyaluronan nanocomposite conduits for neural tissue regeneration

Hyaluronan-based hydrogels are among the most promising neural tissue engineering materials because of their biocompatibility and the immunomodulation capabilities of their degradation byproducts. Despite these features, the problems related to their handling and mechanical properties have not yet been solved. In the present work it is proposed to address these drawbacks through the development of nanohybrid materials in which different nanometric phases (carbon nanotubes, mesoporous silica nanoparticles) are embedded in a crosslinked hyaluronan matrix. These nanohybrid matrices were next processed in the shape of cylindrical conduits aimed at promoting and improving neural stem cell differentiation and regeneration in neural tracts. These constructs could be of use specifically for peripheral nerve regeneration. Results of the study show that the inclusion of the different phases improved physico-chemical features of the gel such as its relative electrical permittivity, water intake and elastic modulus, giving hints on how the nanometric phase interacts with hyaluronan in the composite as well as for their potential in combined therapeutic approaches. Regarding the in vitro biological behavior of the hybrid tubular scaffolds, an improved early cell adhesion and survival of Schwann cells in their lumen was found, as compared to conduits made of pure hyaluronan gels. Furthermore, the differentiation and survival of neural precursors was not compromised, despite alleged safety concerns.

Designing working diagrams for electrohydrodynamic printing

Cone-jet is an important working mode that is critical to the accuracy of electrohydrodynamic (EHD) printing. This work considers the leaky-dielectric model and firstly proposes five independent dimensionless numbers, viz., the Ohnesorge number Oh, the Weber number We, the electric capillary number CaE, the relaxation parameter α and the relative electrical permittivity of ink εr, to delineate the cone-jet mode. Theoretical and computational analyses on the regime of cone-jet mode depicted by property and operating diagrams are performed. Theoretical analysis suggests that a cone-jet occurs in wide ranges of these dimensionless numbers. Computational analysis based on the finite element method narrows down these ranges. Complete working diagrams for the EHD printing are described in Oh-α and We-CaE spaces, respectively. The theoretical and computational analyses well agree with previous experiments, which provides a general rule to optimize the EHD printing.

Percolation monitoring and water content estimation by Ground Penetrating Radar in a controlled environment

We investigated the percolation of water within a controlled environment in order to recover the EM properties and the internal structure of the materials, and to better understand the drainage processes involved. We implemented an analogue model that accurately replicates a green roof, from the construction materials to the geometry. We acquired several common offset GPR data sets on the entire surface of the model, both before and during different irrigation tests. We separately analyzed variations in the reflected amplitudes and in the EM velocities, the latter of which were calculated by combining the measured thickness of the model with the arrival times of the recorded reflections. The signal amplitudes obtained before and during irrigation are compared in order to estimate the attenuation factor at the different stages of the irrigation process. We use the attenuation factor and the EM velocities to estimate the relative permittivity of the topsoil mixture, from which we then calculate the water content, the porosity, and the relative electrical permittivity of the solid matrix by applying well known empirical formulas. The results were validated by comparing them with independent direct measurements.

Dielectric and Mechanical Properties of Local Commercial Single Walled Carbon Nanotubes for Medical Applications: A Practical Approach

Owing to their exceptional electrical and mechanical properties, low weights and availability of their synthesis and purification carbon nanotubes (CNTs) became the focus of scientists in many medical and electronic applications, and reinforcement of various materials. A close understanding of structure-properties of (CNTs) will be necessary for the development of carbon-nanotube applications. High stiffness and tensile strength of CNTs provide mechanical stability for electric nano-circuits formed by CNTs. Meanwhile, at earlier time of their application, researchers main concern was dedicated for preparation methods of CNTs. Eventually the structural and physical characteristics of CNTs became more attractive for scientist proper applications. Herein the current work introduce a practical approach for screening the dielectric and mechanical properties of local commercial purchased single walled carbon nanotubes for medical applications. Dielectric properties of CNTS were expressed in term of electrical relative permittivity, and electrical conductivity. The dielectric relaxation obeys ordinary alpha and beta relaxation of dielectrics at current frequency range. Besides the mechanical properties in term of dimetral tensile and compression strength that are expressed by Young’s modulus that is closer to graphite. As a results, we highly recommend these commercial (SWCNTs) from our local suppliers for further medical applications.

Pyropermittivity and pyroelectret behavior of graphite

This work reports the pyropermittivity (effect of temperature on the relative electric permittivity κ) and pyroelectret behavior (effect of temperature on the electret’s inherent DC electric field E, with an electret meaning a permanent electric dipole) of graphite, namely isotropic (polycrystalline) graphite with DC resistivity ρ (1.16 ± 0.08) × 10−5 Ω.m, κ 530 ± 18 at 2 kHz, and E 1.30 × 10−5 V/m at room temperature. These effects are to be distinguished from the pyroelectric effect. They pertain to the dielectric behavior, which stems from the carrier-atom interaction. They are relevant to temperature sensing and the conversion of thermal energy to electrical energy. Pyropermittivity allows temperature sensing by capacitance measurement. Pyroelectret allows temperature sensing by electric field measurement. The material is a true electret, i.e., an electret that does not require poling. Upon heating (20–70 °C), κ increases by 32% (positive pyropermittivity), ρ increases by 70% (positive pyroresistivity, reflecting the metallic character), and E increases by 1900% (positive pyroelectret). As a result, the electric power volumetric/gravimetric density due to the electret (important for energy conversion) increases by 24000%. The increase in ρ upon heating promotes the dielectric behavior. All effects are reversible upon cooling. The pyroelectret coefficient is (1.53 ± 0.04) × 10−14 C/(m2.K) – first report for materials in general.

Complex-structured 3D-printed wireframes as asteroid analogues for tomographic microwave radar measurements

This study introduces a fused filament fabrication (FFF) process for manufacturing complex-structured asteroid analogue objects to be applied in tomographic microwave radar measurements and inversion studies. We describe an approach to control the volume fraction of the plastic and, thereby, the effective relative permittivity within a tetrahedral wireframe which serves as metamaterial representing the actual asteroid composition. To determine the effective permittivity of the plastic–air mixture, we use an exponential model. In this study, two analogue objects based on the shape of the asteroids 1998 KY26 and (25143) Itokawa were 3D-printed in a scale suitable for microwave laboratory measurements using ABS filament with a controlled constant relative electric permittivity. The results obtained suggest that the permittivity of solid and powdery asteroid minerals can be modelled with the proposed technique and, in particular, that the numerical structural permittivity models of the earlier numerical studies can be approximated by 3D-printed analogues.

P‐148: Investigation of photoluminescence and birefringence of nanoparticles dispersed nematic liquid crystal and its application towards liquid crystal display and optoelectronic devices

In the present investigation nanoparticles (NPs) have been dispersed into the pure nematic liquid crystal (NLC). NPs have been dispersed into the NLC with two different concentrations. Polarizing optical microscope (POD imnages have been recorded for pure NLC and NP dispersed system in the planar aligned liquid crystal cell. The dispersion of NPs in NLC increases the photoluminescence intensity which is an important finding of this study. Birefringence has also been measured here with the help of transmittance technique and it has been observed that the birefringence got increased after the dispersion of NPs into pure NLC. This is the key finding of the present reported work. Relative electric permittivity has also been measured here and found to be increased for the dispersed system as compared to the pure NLC. It is suggested that the output of the present work may be very useful in liquid crystal display and photonic applications.

A ceramic-based microwave sensor for both permittivity and permeability characterization of materials

In this study, a novel microwave microstrip sensor is proposed for the simultaneous characterization of a material’s permittivity and permeability. The electric permittivity and magnetic permeability of the material under test have similar effects on the frequency and quality factor of the sensor. To solve this problem, the structural characteristics of the proposed sensor make the strongest electric and magnetic fields distributed in different areas of the sensor to avoid the mutual effect of permittivity and permeability measurement. The proposed sensor is implemented using microstrip technology in which ring openings are located on either side of the microstrip line. The sensor is simulated and designed using a high- frequency structure simulator, and a numerical model of the sensor is established to extract the electric permittivity and magnetic permeability of the sample. The sensor is fabricated on high temperature co-fired ceramics (HTCC) substrates by screen printing techniques and it has the advantages of small size, excellent stability and adaptation to severe environments due to the HTCC substrates with high permittivity. In the S-band (2–4 GHz), samples of wood, PET, Fe3O4-PDMS are tested, and the relative electric permittivity and magnetic permeability of the samples obtained were consistent with the values available in the literature.

Electrical properties of cometary dust particles derived from line shapes of TOF-SIMS spectra measured by the ROSETTA/COSIMA instrument

Between Aug. 2014 and Sept. 2016, while ESA’s cornerstone mission Rosetta was operating in the vicinity of the nucleus and in the coma of comet 67P/Churyumov-Gerasimenko, the COSIMA instrument collected a large number of dust particles with diameters up to a millimeter. Positive or negative ions were detected by a time-of-flight secondary ion mass spectrometer (TOF-SIMS) and the composition of selected particles was deduced. Many of the negative ion mass spectra show, besides mass peaks at the correct position, an additional, extended contribution at the lower mass side caused by partial charging of the dust. This effect, usually avoided in SIMS applications, can in our case be used to obtain information on the electrical properties of the collected cometary dust particles, such as the specific resistivity (ρr>1.2⋅1010Ωm) and the real part of the relative electrical permittivity (εr<1.2). From these values a lower limit for the porosity is derived (P>0.8).

Obtaining Directly Quasi-Square Open Ring FSS Constitutive Effective Parameters by Using Coupled WCIP - Retrieval Method

We propose here a method witch analyze the behavior of Quasi-square open ring frequency selective surface (FSS) by using an approach based on the wave iterative concept procedure method (WCIP) coupled to Retrieval from Scattering Parameters method . The scattering parameters calculated by WCIP for a Quasi-square open ring FSS are used, in analytical formulas, to calculate directly observable effective constitutive parameters (relative electric permittivity εreff , magnetic permeability μreff and refractive index n ) of a frequency selective surface. Results of effective constitutive parameters for a Quasi-square open ring FSS structure are presented by Simulation using MATLAB program codes translating the implementation of the proposed approach.

بإستخدام المحلل الشبكي Ca1-xNixFe2O4 دراسة الخصائص الكهربائية والمغناطسية والإمتصاصية لفيرايت السبينل نوع

In this work, the spinal ferrite has been prepared where , used. as radar absorbing materials (RAM). Conventional ceramic techniques method was used to prepare these materials at microwaves with the range of frequencies (8-12) GHz. The absorption for microwaves was examined by the utilized the network analyzer. The relationship between reflectivity, absorption and attenuation coefficient were plotted as a function of frequency, and sintered at a temperature . The results showed the emergence of several resonance peaks at , samples showed high Absorbency in contrast low reflectivity and high values of attenuation coefficient at the same frequencies, this is due to domain rotation as well domain wall motion of the ferrite. The values of the real and imaginary parts of relative magnetic Permeability and relative electric permittivity were measure for all samples. The results revealed the apparent resonance peaks at same frequencies that apparent at absorption and reflectivity curves of the same samples. X-ray diffraction tests were made for one sample and result showed the structure of the sample is polycrystalline. في.هذا البحث تحضير سلسلة من فيرايت السبينل نوع حيث تأخذ القيم بزيادة مقدارها كمواد ماصة للأشعة الرادارية. تم إستخدام الطريقة السيراميكية التقليدية في تحضير العينات والتي تم تلبيدها بدرجة حرارة واحدة درست إم تصاصية العينات ضمن النطاق السيني حيث مدى التردد بإستخدام جهاز المحلل الشبكي. رسمت العلاقة بين ألإمتصاصية، الإنعكاسية، معامل التوهين، النفاذية المغناطيسية و السماحية الكهربائية كدوال للتردد عند النطاق السيني. بينت النتائج ظهور عدة قمم رنينية عند ترددات النطاق السيني, أظهرت العينات إمتصاصية عالية وقيم معامل التوهين عالية في المقابل إنعكاسية قليلة والسبب هو دوران الحقل المغناطيسي نتيجة حركة جدار الحقل المغناطيسي للفيرايت. من قياسات النفاذية المغناطيسية وثابت العزل وضحت النتائج وجود القمم الرنينية عند نفس الترددات التي ظهرت عند منحنيات الإمتصاصية والإنعكاسية. تم فحص حيود الأشعة السينية للعينة حيث أظهرت النتائج أن تركيب العينة هو متعدد التبلور.

Electrical Permittivity and Conductivity of a Graphene Nanoplatelet Contact in the Microwave Range.

This paper investigates the electrical properties in the microwave range of a contact made by graphene nanoplatelets. The final goal is that of estimating the range of values for the equivalent electrical complex permittivity of a contact obtained by integrating low-cost graphene in the form of nanoplatelets (GNPs) into a high-frequency electrical circuit. To this end, a microstrip-like circuit is designed and realized, where the graphene nanoplatelets are self-assembled into a gap between two copper electrodes. An experimental characterization is carried out, both to study the structural properties of the nanomaterials and of the realized devices, and to measure the electromagnetic scattering parameters in the microwave range by means of a microstrip technique. A full-wave electromagnetic model is also derived and used to investigate the relationship between the measured quantities and the physical and geometrical parameters. The combined use of the experimental and simulation results allows for retrieving the values of the equivalent complex permittivity. The equivalent electrical conductivity values are found to be well below the values expected for isolated graphene nanoplatelets. The real part of the electrical relative permittivity attains values comparable to those obtained with GNP nanocomposites.