Relative Dielectric Permittivity Values Research Articles

Primary standard for complex units of permittivity at frequency range 0.1–178.4 GHz GET 110-2023

The article is dedicated to research in the fi eld of measuring the dielectric parameters of materials. The aim of the research is to study promising methods for measuring the complex dielectric permittivity of weakly absorbing materials in the decimeter wavelength range, as well as the non-resonant method for measuring the dielectric parameters of materials with high dielectric losses. In order to achieve the set goal of improving the state primary standard of complex dielectric permittivity in the frequency range from 1 to 178.4 GHz, tasks were set to expand the frequency range to 0.1 GHz and the range of reproducible values of the dielectric loss tangent to 10–1. As a result of the improvement, new equipment was introduced into the composition of the standard, and new measurement methods were developed. To measure the complex dielectric permittivity of weakly absorbing materials in the decimeter wavelength range, a resonant measurement method in a coaxial resonator with a shortening capacitive gap and a measurement method in a bulk H011-resonator with dielectric fi lling were developed. To measure elevated dielectric losses up to 10–2–10–1, a measurement method using a non-resonant measuring transducer based on a shielded dielectric waveguide with a measured dielectric sample as such a waveguide has been developed. The developed methods are applied in the Primary standard of complex dielectric permittivity in the frequency range from 0.1 to 178.4 GHz, GET 110-2023. The frequency range of the standard is 0.1–178.4 GHz, the range of reproducible values of relative dielectric permittivity is 1.2–500, dielectric loss tangent 10–8–10–1. The scope of application of GET 110-2023 is metrological support of dielectric control in production of radio frequency cables, telecommunication equipment, electronic components, etc.

Electron-beam synthesis of thin magneto-dielectric coatings with mixed nickel-iron and upper alumina layers

We have synthesized magneto-dielectric coatings with thicknesses 290, 550, 5460 and 6063 nm with an upper protective and electrically insulating layer of alumina ceramic and a lower magnetic iron-nickel layer. The coatings were formed in a helium atmosphere at forevacuum pressures (from 1.5 to 15 Pa) by electron-beam evaporation of a mixture of iron and nickel fragments, and of a solid alumina ceramic target placed in a separate crucible. Magnetic properties of the coatings have been studied by a ferromagnetic resonance technique with estimation of the effective saturation magnetization together with evaluation of the signal-to-noise ratio and relative broadening of the resonance lines. Owing to the layer of alumina ceramic, the values of relative dielectric permittivity (5.6) and electrical conductivity (0.78–3.00 mS/m) remain typical for thin-film dielectrics.

Magnetically active composites with relatively giant dielectric permittivity

"Magnetically active composites based on silicone rubber, silicone oil, carbonyl microparticles, graphene nanopallets and fabric, as a reinforcing element, are manufactured. For a constant amount of carbonyl iron microparticles and silicone oil, and for different ratios between the amounts of silicone rubber and graphene nanopalets, three composite samples are prepared. Using the plane capacitor method, the relative permittivity of the composites is determined. It is shown that by using graphene nanopallets, composites with giant values of relative dielectric permittivity can be obtained and that the relative dielectric permittivity values are sensitive to the magnetic force induced by the static magnetic field superimposed on the medium-frequency electric field. Using the model of the dipolar magnetic approximation and elements of the theory of dielectrics in medium frequency electric fields, the mechanisms participating in the obtained effects are described."

Assessing concrete strength loss at elevated temperatures as a function of dielectric variation measured by GPR: an empirical study

ABSTRACT Reinforced concrete (RC) parts, which are exposed to high temperatures for a certain period, undergo physical-chemical changes that deteriorate their mechanical properties. To this end, this study investigates the efficiency of using ground-penetrating radar (GPR) as a non-destructive testing (NDT) method in assessing the core compressive strength loss, elastic modulus decrease, and tensile strength loss of concrete under extreme temperatures. RC specimens are fabricated and exposed to elevated temperatures (300°C, 400°C, 500°C, 600°C, and 700°C). GPR measurements are performed to estimate the relative dielectric permittivity (RDP) of the specimens before fire exposure (BFE) and after fire exposure (AFE). The compressive strengths of the cores extracted from the specimens are obtained also for BFE and AFE cases. Attained RDP values are in conformance with the previous research results and contribute additional evidence to the published literature. As the temperature levels are increased, RDP and strength-related values of concrete specimens decrease. The strength-related parameters are more sensitive to elevated temperatures, whereas the change in the RDP values is rather gradual. Through multiple correlations within 95% confidence intervals, core compressive strength loss, elastic modulus decrease, and tensile strength loss are, individually, estimated as a function of relative RDP change and applied temperature levels. Empirical formulas are obtained with high coefficients of correlation. The relative effects of RDP change and temperature are more pronounced in elastic modulus decrease and tensile strength loss compared to compressive strength loss. Overall, the outcomes of this paper confirm the viability of using the GPR technique for concrete dielectric characterisation in estimating the strength-related properties of concrete exposed to high temperatures, which might reduce the need for destructive testing.

Structural elucidation, hydrogen bonding motifs and solid state properties of p-toluenesulfonate salt of β-alaninine for optoelectronic device application

Single crystal of β-alaninium p-toluenesulfonate (BAPT) has been grown by solvent slow evaporation method. Crystal structure of the title compound has been elucidated by single crystal XRD analysis. In structural analysis, chain and ring motifs lead to the hydrophilic layers at z = 0, 1/2 and 1 which is sandwiched between the hydrophobic layers at x = 1/4 and ¾. FTIR and FT-Raman spectra have been recorded to confirm the vibrational modes of the crystal. Optical behavior has been studied by UV–Vis–NIR analysis. Thermal properties of BAPT crystal has been investigated by TG-DTA measurements. Mechanical nature of material was studied through Vicker’s micro hardness studies. From dielectric measurements, relative dielectric permittivity values and theoretical values of polarizability values were determined. The third order NLO responses of BAPT has been analyzed by the Z-scan technique.

Advances in the nondestructive condition assessment of railway ballast: A focus on GPR

This paper addresses the use of nondestructive Ground Penetrating Radar (GPR) methodology in the investigation of railway ballast under a diverse set of fouling and moisture conditions through comprehensive laboratory experiments and field track surveys. Granite ballast and three fouling agents; sand, gravel, and the mixture of these two materials were used in the laboratory tests. Numerous estimation methods were employed to attain the Relative Dielectric Permittivity (RDP) of the ballast using 2 GHz air-coupled antenna for the laboratory tests. Experimentally obtained RDP values were verified by the theory-based mixing model. Field track GPR surveys using miscellaneous frequencies (400, 900, and 2000 MHz) were undertaken, where the same type of granite ballast used in the laboratory tests, were laid along a track section composed of metal, wooden and concrete sleepers. Using the laboratory-measured RDP values, the data from field track surveys and ground-truth data were in good agreement. The results of this paper confirm the efficiency and the eligibility of the GPR technique in condition assessment of railway granite ballast using various frequencies and orientations of antennas.

Physical Parameters and Contrasts of Wooden Objects in Lacustrine Environment: Ground Penetrating Radar and Geoelectrics

We investigate how suitable ground penetrating radar (GPR) and geoelectrics are to prospect the remains of submerged wooden archaeological constructions in the water column. For this purpose, we determined the contrasts of electric resistivity and dielectric permittivity from measurements on present-day wood samples, serving as simplified approximations of water saturated and undegraded archaeological wood. As common substitutes of hard and soft construction wood, we investigated oak and spruce wood. The electric resistivity and dielectric permittivity were determined with increasing moisture content from small-scale electric and GPR measurements using a Wenner alpha array and a 2 GHz Palm antenna in a watering experiment. In a water-saturated state, resistivity values of <270 Ωm and relative dielectric permittivity values of >20 were observed. The anisotropy effects and deviations of the wood species were seen to be up to 30%. On the basis of this, the relative material contrasts of wood with respect to fresh water, sand, and clay were calculatedand compared to values found in the literature for seismic contrasts. Geoelectric, GPR, and seismic measurements show contrasts of 0.3 to 0.8, −0.4 to 0.2, and −0.24 to 0.35, depending on the surrounding material and structural orientation of the wood. The highest contrasts were found for wood in fresh water, followed by clayey and sandy subsoils. On the basis of the determined contrasts, analytical calculations were performed showing that an object of 0.5 m diameter can be detected at depths between 0.5 m and 1.5 m with geoelectrics (Schlumberger) and at depths between 0.5 m and 3 m with ground penetrating radar measurements (400 MHz).

Super Dielectric Materials of Two-Dimensional TiO2 or Ca2Nb3O10 Nanosheet Hybrids with Reduced Graphene Oxide.

High dielectric constants (εr) were observed in two-dimensional composites obtained from stacking of reduced graphene oxide (RGO) with Ca2Nb3O10 and with TiO2 nanosheets. The relative dielectric permittivity values of the composites were found to be higher than 105, an amazingly high value compared to that of similar GO composites and other common dielectric materials. As a consequence, we considered application of the hybrids as super dielectric materials in high capacitance supercapacitors. The route to high capacitance involves the variation of oxygen vacancies within the surface and in the closest bulk interior of the hybrids. The effective charges generated throughout the metal oxide and carbon–oxygen polar bonding systems within the graphene skeleton appear to highly influence dielectric polarization. Moreover, the replenishment of oxygen vacancies at the RGO and metal oxide interface also contributes to polarizability.

In situ characterization of forest litter using ground‐penetrating radar

AbstractDecomposing litter accumulated on the soil surface in forests plays a major role in several ecosystem processes; its detailed characterization is therefore essential for thorough understanding of ecosystem functioning. In addition, litter is known to affect remote sensing radar data over forested areas and their proper processing requires accurate quantification of litter scattering properties. In the present study, ultrawideband (0.8–2.2 GHz) ground‐penetrating radar (GPR) data were collected in situ for a wide range of litter types to investigate the potential of the technique to reconstruct litter horizons in undisturbed natural conditions. Radar data were processed resorting to full‐wave inversion. Good agreement was generally found between estimated and measured litter layer thicknesses, with root‐mean‐square error values around 1 cm for recently fallen litter (OL layer) and around 2 cm for fragmented litter in partial decomposition (OF layer) and total litter (OL + OF). Nevertheless, significant correlations between estimated and measured thicknesses were found for total litter only. Inaccuracies in the reconstruction of the individual litter horizons were mainly attributed to weak dielectric contrasts amongst litter layers, with absolute differences in relative dielectric permittivity values often lower than 2 between humus horizons, and to uncertainties in the ground truth values. Radar signal inversions also provided reliable estimates of litter electromagnetic properties, with average relative dielectric permittivity values around 2.9 and 6.3 for OL and OF litters, respectively. These results are encouraging for the use of GPR for noninvasive characterization and mapping of forest litter. Perspectives for the application of the technique in biogeosciences are discussed.

Formation mechanism and characteristics of lanthanum-doped BaTiO3 powders and ceramics prepared by the sol–gel process

Pure and lanthanum-doped barium titanate nanopowders described by two different formulae, as Ba1−xLaxTiO3, for lower La concentrations (0≤x≤0.005) and Ba1−xLaxTi1−x/4O3 for higher La concentration (x=0.025) were prepared by an alkoxide sol–gel method. Single phase compositions were obtained after annealing at 900°C for 2h, in air. The increase of the lanthanum content causes structural and morphological changes in the oxide powders, including the evolution of the unit cell from tetragonal toward a cubic symmetry, the particle size decrease and a higher aggregation tendency.SEM investigations of the ceramics sintered at 1300°C for 4h indicate significant changes of the microstructural features (strong decrease of the average grain size and increase of the intergranular porosity) with the raise of La amount. Lanthanum addition to barium titanate prepared by sol–gel induces a more significant shift of the Curie temperature toward lower values, than that one reported in literature for ceramics of similar compositions, but processed by the conventional solid state method. The compositions with smaller La amount (x≤0.005) show semiconducting properties at room temperature and high relative dielectric permittivity values, while the undoped ceramics and those doped with higher La content (x=0.025) are good dielectrics. The ceramic with x=0.025 exhibits acceptable low losses, a very diffuse ferroelectric–paraelectric transition and Curie temperature closed to the room temperature, being thus susceptible for high tunability applications.

Non-Invasive Forest Litter Characterization Using Full-Wave Inversion of Microwave Radar Data

Litter is acknowledged to affect microwave remote sensing data over forests, and accurate quantification of litter radiative properties is essential for proper retrieval of forest soil water content and forest canopy biophysical characteristics from satellite or airborne sensors. Furthermore, detailed characterization of forest soil organic horizons is of paramount importance for ecological studies and for carbon cycle and global changerelated studies. Ultrawideband ground-penetrating radar (GPR) data acquired above beech forest litter were used to analyze the effects of litter on the backscattering and investigate the ability of GPR to quantitatively characterize the properties of the forest floor. Radar measurements were performed over different litter configurations (i.e., single layers of recently fallen litter (OL) or of fragmented litter (OF), and combined OL-OF layers) and thicknesses. Radar data were processed through full-wave inversion. Over the considered frequency range (0.8–4.0 GHz), attenuation of the radar signal increased as both frequency and litter thickness increase, due to scattering and dielectric losses. These effects were accounted for in the radar model through frequency dependence of litter apparent electrical conductivity. Good agreement(RMSE = 9.5 × 10−3 m) was observed between estimatedand measured litter thicknesses. Radar data inversions provided reliable estimates of litter electromagnetic properties, with relative dielectric permittivity values around 1.2 and 3.9 for OL and OF litters, respectively, and corresponding values of 0.032 and 0.080 Sm−1 for litter apparent electrical conductivity at 4.0 GHz. These results show great promise for the use of GPR for noninvasive characterization of forest litter.

Dielectric and Microwave Properties of Natural Rubber Based Composites Containing Fullerene Black

It is expected that filling a rubber with a small amount of fullerene could lead to a new set of properties, bringing to the composite advantages over the rubbers in use. In the present work, the dielectric and microwave properties of natural rubber (SMR10) based composites containing various concentration of fullerene black (0-7,5 phr), rich in fullerenes (7,5%) were investigated in the 1-12 GHz frequency range. It has been established that within the range used for the experiments the increasing frequency and fullerene filler amount lead to an increase in the values of relative dielectric permittivity, dielectric loss angle tangent, reflection coefficient and attenuation of electromagnetic waves, while the values for shielding effectiveness get lower. That is due to the fact that under the experimental conditions the change in the reflection coefficient is greater than that in the attenuation of electromagnetic waves. The dielectric properties of the composites (especially the dielectric loss angle tangent) are more affected by fullerene black filler than their microwave properties. Further change in the properties could also occur at higher concentrations of fullerene black but the cost of rubber compound would be much higher

The Passive Generation of Low Frequency Noise Field by MRET-Shield Polymer Compound and Following Amplitude Modulation of RF Carrier Signals

This article is related to the experimental data regarding the ability of polar polymer compound (MRET-Shield polymer) exposed to the external electromagnetic fields of RF range of frequency to generate low frequency composite noise fields. Due to the fractal geometry structure of MRET-Shield polymer compound and the phenomenon of piezoelectricity, this polymer generates subtle, low frequency, non-coherent electromagnetic oscillations (composite noise field) that can modify RF signals as a result of superposition phenomenon. The superposition of composite noise field generated by MRET-Shield polymer compound and RF microwave signals leads to amplitude modulation of RF signals where random low frequency signal generated by MRET-Shield compound is a modulating signal and original microwave signal is a modulated one. To verify the visibility of the proposed hypothesis MRET-Shield polymer compound was tested at MET laboratories, Inc., USA. This test also confirms that the introduction of MRET-Shield polymer to the source of RF signals in the range of 800 MHZ, 900 MHz, 1800 MHz, 1900 MHz, and 2400 MHz does not significantly affect the air measurements of RF signals, and subsequently does not lead to any significant distortion of transmitted RF signals. While many polar polymers are highly flexible and form an amorphous solid upon the process of polymerization, a large number of polymers, such as epoxy, actually form partially crystalline structures. A number of studies show that the external electromagnetic field can affect local ori- entations and phase transitions in polymer crystalline sys- tems of longitudinal chains. The longitudinal polymer crys- talline system is a macromolecule of consecutively co- polymerized liquid crystals and flexible polymer sequences. Polar polymers possess comparatively low values of relative dielectric permittivity (3-15), which means that macro- molecules in the molecular structure of these polymers can be easily displaced by external electromagnetic force. Sub- sequently the external electromagnetic field can seriously modify the local orientation order of the system and affect phase transition parameters and dielectric properties of the polymer compound. A simple molecular mechanism exists since the polar parts of the molecule in epoxy are rigidly attached to the chain backbone. The orientation of the polar groups in the electromagnetic field affects the backbone

Electrical properties of water in clay and silty soils

In order to better understand ground penetrating radar (GPR) results obtained in road surveys and site investigations, the dielectric properties and electrical conductivity of four silt and clay soils were measured at different densities and moisture contents ranging from oven dry material to the plastic state. The real parts K′ and imaginary parts K″ of the relative dielectric permittivity values of the soils were measured with an HP Surface Network Analyzer over a frequency range from 30 MHz to 3.0 GHz. A dielectric and electrical conductivity meter produced by Adek was also used. The results suggest that water in soils can be classified according to its electrical properties as: (1) an adsorption water layer, also known as the hygroscopic water layer; (2) a viscous or capillary water layer; and (3) free water. The measurements also showed that the adsorption water layer can be divided into inner and outer layers in accordance with the electrical double layer theory. The imaginary part of the dielectric value of the material is formed mainly in the outer layer and partly in the viscous (capillary) water layer, which also has two layers with differing electrical properties. The measurements also clearly showed that if the Cation Exchange Capacity (CEC) of a material is low, the water molecules are orderly arranged around the soil particles and the dielectric values of the bound water layers remain almost independent of frequency. If the CEC increases, the molecular structure of the bound water layers is disturbed and the water molecules more easily follow the changing AC field so that the dielectric value is higher. These materials are also highly dielectrically dispersive, especially at GPR frequencies below 400 MHz. Increasing CEC correlates well with increasing imaginary part of the adsorption water layer. Measured ohmic electrical conductivities were low at low moisture content and increased as the outer viscous water layer developed with higher moisture content. A clear jump in electrical conductivity takes place when the free unbound water starts to fill the pores between the mineral grains.

Field dielectric measurements of frozen silt using VHF pulses

Radiowave propagation experiments utilizing short pulses in the VHF band were conducted in the permafrost tunnel at Fox, Alaska. The purpose was to measure dielectric properties of this naturally occurring, perennially frozen organic silt which is common to much of interior Alaska and for which ice content varies between about 54 and 79% by volume. Transmissions across a septum dividing two drifts gave relative dielectric permittivity values between 3.9 and 7.3. The low values resulted when transmission was predominantly through an ice wedge. Propagation along the septum gave values of 3.3 and 5.0 depending on antenna polarization. This propagation was influenced by the dry, surface silts, as was propagation along a ceiling section, which also gave an approximate value of 3.3. The data from attempted transmissions from the ground surface directly above the tunnel to the tunnel ceiling (approximately 12 m distance) are ambiguous, as signals that propagated indirectly along the transmitter cable through a nearby ventilation shaft may or may not have masked direct transmission through the permafrost. The results agree with previous laboratory investigations conducted at temperatures well below that of naturally occurring materials in interior Alaska suggesting that winter refrigeration of the tunnel by circulated outside air greatly affected the natural conditions at this site.