Permittivity Values Research Articles

Precursor influence on the raman spectrum of KNNLiTaLa0.01 prepared by two different methods

This work presents a study of ceramics with the (K0.44Na0.52Li0.04)0.97La0.01Nb0.9Ta0.1O3 composition through their Raman spectra. In the previous studies [1], this particular composition has shown good permittivity and piezoelectric parameter values that justify a deeper investigation. Two sets of samples of these ceramic compounds were prepared using different methods. The first set was prepared using a classical solid-state reaction of oxides and carbonates, as described in Ref. 2. The second set was prepared using the NaNbO3 as a precursor. The Raman spectra of the samples obtained by the direct ceramic method consisted of 4 modes. In contrast, the spectra of the samples obtained using the precursor showed a shift of the wavenumber of the A1g(ν1) mode peak towards lower values and consisted of six modes with the appearance of two additional IR modes, F1u(ν3) and F2g(ν4). Notably, the use of the precursor preparation route led to important improvements resulting in a more straightforward method than that of Saito et al. [3].

Microstructures and Dielectric Permittivity Properties of Fe3O4/Cdots Nanocomposites Synthesized by Green Route Utilizing Moringa Oleifera Extract and Watermelon Peel

Dielectric materials are beneficial for storing electrical energy due to their insulating and polarization properties in response to external electric fields. Magnetite has shown promise as a dielectric material among other materials due to its good magnetic properties, low toxicity, and biocompatibility. However, the weakness of Fe3O4, which has low stability and easy agglomeration, requires a modification on its surface by using Carbon dots (Cdots). This research investigates the dielectric properties of Fe3O4/Cdots obtained through the green synthesis method. Fe3O4 nanoparticles were synthesized using the co-precipitation method with Moringa oleifera leaf extract as a reducing and stabilizing agent. In contrast, Cdots were synthesized using the hydrothermal method with watermelon peel waste as a carbon source. The Fe3O4 composite nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), ultraviolet-visible spectroscopy (UV-Vis), and impedance spectroscopy. The XRD spectra revealed the existence of cubic inverse spinel and a reduction in crystal size as the concentration of Cdots increased, measuring 7.8 and 7.1 nm, respectively. SEM-EDX revealed that the sample is composed of Fe, O, and C elements and has a spherical shape with Cdots distributed on the surface of Fe3O4. The UV-Vis spectrum showed the absorption peak of Cdots at 282 nm. The Fe3O4 absorption peak is identical to the Fe3O4/Cdots absorption peak at 193 nm. The increase in band gap energy from 2.96 to 3.33 eV is related to the increase in Cdots concentration. In the 10-900 kHz frequency range, dielectric property tests demonstrated peak dielectric permittivity values (real and imaginary). A substantial decrease was observed between 10 kHz and 200 kHz, followed by a relatively stable pattern up to 900 kHz. The loss tangent value obtained has a tanδ value <0.5, which means that the addition of Cdots affects reducing the energy loss stored in Fe3O4.

A Machine Learning approach for enhancing permittivity mixing rules of binary liquids with a Gaussian modification and a new interaction factor estimation

The microstructure and solvation mechanics of binary liquids are key for predicting mixture permittivity. However, since traditional mixing rules do not consider this complexity, they must be modified to address the mixture characteristics through an interaction factor (kint). This paper evaluates this parameter for several mixing rules, applying Support Vector Regressor models trained with glycerin-water reflective signals acquired with a Dielectric Resonator sensor. The regression error of these models indicates both the optimal interaction factor and the mixing rule that fits the most with experimental permittivity values. Kraszewski and Hashin-Shtrikman mixing rules achieved the best performance with an RMSE of around 1. In addition, this paper suggests that the interaction factor can be estimated through the molar volume and the dielectric contrast between liquids (kint=2.67) without acquiring experimental data. Moreover, after analyzing the physical limitations of a linear modification formula, this paper proposes an alternative based on a Gaussian function that avoids unrealistic volume fractions. Both contributions enhance mixing rule accuracy and improve the flexibility to model mixture dielectric behavior.

Structural, morphological, dielectric, and electrical characteristics of a brownmillerite material for electronic devices: KBiMn2O5

The main objective this communication is to study the structural, morphological, dielectric, and electrical properties of a novel brownmillerite material, KBiMn2O5. Preliminary analysis of the X-ray diffraction (XRD) pattern with N-TREOR09 (trial and error method) with Le-Bail method shows monoclinic symmetry (a = 10.919 Å, b = 5.114 Å, c = 10.453 Å, β = 104.428˚). The examination of scanning electron microscopic spectrum provides the nature of the morphological surface of the sample having an average grain size of 19.89 μm. We have examined Maxwell-Wagner dielectric dispersion, relaxation, and transport mechanisms by analyzing the dielectric, impedance, and conductivity spectra across a wide range of experimental frequencies (1 kHz to 1 MHz) and temperatures (25°C to 500°C). The value of relative permittivity (εr) rapidly increases 200 (room temperature) to 85000 (500°C) with an increase in temperature from room temperature. The high value of εr shows colossal dielectric response (CDR) of the material. The low value of tangent loss (≥ 4.5) can also be applicable to electronic devices. On increasing frequency (1 kHz to 1 MHz), the activation energy of the charged ions from 0.391 eV to 0.328 eV shows a thermally activated relaxation mechanism in the material. The thermistor constant (β), determined as 6317.16, and the temperature coefficient of resistance (TCR) -0.00331 are suitable for high-temperature NTC thermistors, temperature sensors, and other electronic device applications. The study of room temperature non-Ohmic charge conduction and current-voltage charecteristics confirms the suitability of the material for devices.

Design of a Stacked Dual-Patch Antenna with 3D Printed Thick Quasi-Air Substrates and a Cavity Wall for Wideband Applications

In this paper, we propose a stacked dual-patch antenna with 3D printed thick quasi-air substrates and a cavity wall for wideband applications. To achieve the theoretical maximum bandwidth of the patch antenna, the quality factor of the system needs to be minimized. To achieve this, the area of the conductive radiator should be enlarged, while the permittivity of the substrate within the patch must be reduced close to 1. To realize a patch antenna with this maximum bandwidth, the stacked dual-patch configuration is employed to obtain an extended conductive radiator area. In addition, square-pipe resin frames manufactured using a 3D printing method are applied to the proposed antenna to implement a quasi-air substrate structure that has a low permittivity value close to 1. The proposed stacked dual-patch antenna with a quasi-air substrate has a broad bandwidth of 20.7%. The results demonstrate that by using the proposed antenna structure, broadband characteristics close to the fundamental bandwidth limit of the patch antenna can be achieved.

Negative permittivity and permeability behaviour of SrFe12O19/rGO metacomposite for microwave absorption in 2–18 GHz range

Double-negative performance has played a significant role in electronic applications owing to its both permeability and permittivity negative values. Microwave absorption material has a substantial role in electromagnetic shielding, radar absorption, stealth applications, etc. Herein, a novel double-negative metacomposite, SrFe12O19/rGO, was designed by a simple one-pot hydrothermal method, and the microwave absorption properties of the material were studied in the microwave region from 2 to 18 GHz using VNA analysis. The structural and morphological studies were analysed using XRD, FT-IR, and SEM instrumentation techniques and the magnetic property of the material was studied using VSM analysis. Both studies confirmed the hard magnetic nature of the material. The particle sizes of SrFe12O19 and SrFe12O19/rGO measured from XRD are 55.60 nm and 41.55 nm, respectively. Hexagonal plate-like morphology were observed from FESEM images. The coercivity of SrFe12O19/rGO increased, and the magnetocrystalline anisotropy was changed due to the decrease in particle size. The magnetic saturation value decreases due to the presence of non-magnetic rGO. The resultant SrFe12O19/rGO metacomposite shows negative permittivity and permeability values. The minimum reflection loss values observed for pure and rGO-decorated strontium ferrites are −28.49 dB at 7.76 GHz and −23.78 at 11.04 GHz, respectively. In addition to experimental results, simulation studies were also performed to study the reflection loss with matching thickness using a quarter wavelength mechanism. The results show that this composite can be employed as a left-handed metamaterial that finds applications in absorption, antennas, sensors, wireless power transfer systems, etc. The left-handed metamaterial can shift the frequency region from a lower to a higher frequency region. The rGO decorated metacomposite is a promising material for microwave absorption at higher frequency regions.

Dielectric Characterization of Ex-Vivo Breast Tissues: Differentiation of Tumor Types through Permittivity Measurements.

Early analysis and diagnosis of breast tumors is essential for either quickly launching a treatment or for seeing the evolution of patients who, for instance, have already undergone chemotherapy treatment. Once tissues are excised, histological analysis is the most frequent tool used to characterize benign or malignant tumors. Dielectric microwave spectroscopy makes use of an open-ended coaxial probe in the 1-8 GHz frequency range to quickly identify the type of tumor (ductal carcinoma, lobular carcinoma, mucinous carcinoma and fibroadenoma). The experiment was undertaken with data from 70 patients who had already undergone chemotherapy treatment, which helped to electrically map the histological tissues with their electric permittivity. Thus, the variations in the permittivity of different types of tumors reveal distinctive patterns: benign tumors have permittivity values lower than 35, while malignant ones range between 40 and 60. For example, at a frequency of 2 GHz, the measured permittivity was 45.6 for ductal carcinoma, 33.1 for lobular carcinoma, 59.5 for mucinous carcinoma, and 27.6 for benign tumors. This differentiation remains consistent in a frequency range of 1 to 4.5 GHz. These results highlight the effectiveness of these measurements in the classification of breast tumors, providing a valuable tool for quick and accurate diagnosis and effective treatment.

Formic acid stability in different solvents by DFT calculations.

New technologies have been developed toward the use of green energies. The production of formic acid (FA) from carbon dioxide (CO[Formula: see text]) hydrogenation with H[Formula: see text] is a sustainable process for H[Formula: see text] storage. However, the FA adduct stabilization is thermodynamically dependent on the type of solvent and thermodynamic conditions. The results suggest a wide range of dielectric permittivity values between the dimethyl sulfoxide (DMSO) and water solvents to stabilize the FA in the absence of base. The thermodynamics analysis and the infrared and charge density difference results show that the formation of the FA complex with H[Formula: see text]O is temperature dependent and has a major influence on aqueous solvents compared to the FA adduct with amine, in good agreement with the experiment. In these conditions, the stability thermodynamic of the FA molecule may be favorable at non-organic solvents and dielectric permittivity values closer to water. Therefore, a mixture of aqueous solvents with possible ionic composition could be used to increase the thermodynamic stability of H[Formula: see text] storage in CO[Formula: see text] conversion processes. Using the Quantum ESPRESSO package, density functional theory (DFT) calculations were performed with periodic boundary conditions, and the electronic wave functions were expanded in plane waves. For the exchange-correlation functional, we use the vdW-DF functional with the inclusion of van der Waals (vdW) forces. Electron-ion interactions are treated by the projector augmented wave (PAW) method with pseudopotentials available in the PSlibrary repository. The wave functions and the electronic densities were expanded employing accurate cut-off energies of 6.80[Formula: see text]10[Formula: see text] and 5.44[Formula: see text]10[Formula: see text] eV, respectively. The electronic density was computed from the wave functions calculated at the [Formula: see text]-point in the first Brillouin-zone. Each structural optimization was minimized according to the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, with force and energy convergence criteria of 25 meV[Formula: see text]Å[Formula: see text] and 1.36 meV, respectively. The electrostatic solvation effects were performed by the [Formula: see text] package with the Self-Consistent Continuum Solvation (SCCS) approach.

Study on the impact of physical characteristics of soil-rock composite medium on its relative permittivity based on laboratory experiments

The permittivity of soil-rock composite media is crucial for interpreting data originating from geophysical surveys such as ground-penetrating radar (GPR) imaging. At present, relevant theoretical research on the correlation analysis between the electrical and physical parameters of soil-rock composite media has not yet resulted in a complete reference system. This makes it difficult to characterize soil-rock composite media using the electromagnetic characteristic parameters of rock and soil media. In this study, the indoor electromagnetic testing method was used to extract electrical parameters such as the relative permittivity of soil-rock composite, and the influence of water content, density, soil-rock ratio, and other factors on the electrical parameters of soil-rock composite medium was analyzed. Furthermore, an artificial neural network prediction model was established, and the accuracy of the model was evaluated. The results showed that the relative permittivity tends to decrease with an increase in saturation when the moisture content of the mixture is high. The rock has a lower permittivity value than the surrounding soil particles. When the rock content increases, the average permittivity and conductive permittivity of the composite medium decreases. The main factors affecting the electrical properties of soil-rock composite media (in order of their influence, from most to least) are water content, compaction degree, and soil-rock ratio. These results provide a reliable reference for field geophysical exploration.

Polyvinylpyrrolidone – KNNLST lead-free ceramic composites for dielectric applications

Piezoelectric composites offer many advantages compared to piezoelectric ceramics or polymers because of their mechanical flexibility and relatively high stress-induced voltage. In this research, high-molecular weight polyvinylpyrrolidone (PVP) and lead-free piezoelectric (K0.45Na0.51Li0.04) (Nb0.85Ta0.1Sb0.05)O3 (KNNLST) ceramics have been used to produce composites. The possible range of composites from 0 to 100 wt% has been explored. The ceramics were produced using conventional processing methods, while the composites were solution-cast after being mixed with a magnetic stirrer. The composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and dielectric and piezoelectric characterization to determine their properties. The morphology of the composites indicates the homogeneous distribution of the ceramics in the polymer. The XRD patterns show that the dissolved amorphous PVP precipitates and the addition of KNNLST ceramics contributes substantially to the crystalline phase formation. The relative permittivity and loss tangent values increase with an increase in ceramic content. Acceptable polarization and strain hysteresis curves were obtained only for the KNNLST ceramics. The composites produced will be suitable for dielectric applications.

Fabrication of Cellulose Powder Dielectric Composite Material using Pineapple Leaves Fiber

Pineapple, known for its delicious taste and nutritional value, generates substantial waste in the form of cores, leaves, and skin, resulting in significant yearly accumulations. Efficient disposal of pineapple waste has become a critical challenge due to its increasing production and potential environmental pollution. The objective of this paper is to volarize natural fibre derived from pineapple waste by fabricating it into a new dielectric composite material. The fabrication process of dielectric composite material was achieved by using the optimization technique through Design Expert software, resulting in noteworthy findings. Then, the properties of the fabricated materials were analysed in terms of their permittivity value and elemental composition. The permittivity value of the newly fabricated dielectric materials was measured using the vector network analyser (VNA) method, while their elemental composition was characterized using energy-dispersive X-ray (EDX) spectroscopy. The correlation between elemental composition and the permittivity value of newly fabricated composite materials is analysed in this paper. As a result, the dielectric composite material attained its highest permittivity (4.08) when composed of 76.02% carbon and 22.61% oxygen. Conversely, the material exhibited a lower permittivity value (2.87) when its carbon content decreased to 69.32% and its oxygen content increased to 29.81%. This outcome highlights the crucial role of carbon in absorbing and storing electromagnetic signals, influencing the dielectric properties of the material. In conclusion, this paper unveils a ground-breaking use for waste pineapple leaves, showcasing how their carbon content significantly affects the resulting dielectric composite material's permittivity. This innovative eco-friendly material presents a sustainable alternative for non-recyclable dielectric materials in electronic devices such as PCBs, antennas, and sensors, for example.

Investigating the microwave properties of carbon materials from microwave-driven methane pyrolysis

Rising carbon dioxide emissions due to fossil fuel combustion has led to the urgent need to investigate and adopt different energy solutions that can mitigate this problem. Hydrogen has surfaced as a promising alternative in the pursuit for CO2-neutral energy systems. Microwave pyrolysis of methane has recently emerged as an innovative method to accomplish this goal. To enhance our understanding of this technique and its scalability, it is essential to explore the microwave characteristics of the carbon used and generated during this process. This work investigates the microwave properties of two carbon samples (seed carbon; SC and product carbon; PC) from microwave-driven pyrolysis of methane. The cavity perturbation technique was employed from room temperature to 1250 °C for frequencies of 397, 912, 1429, 1948 and 2467 MHz. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis were also performed to elucidate the permittivity results. It was found that SC initially showed a decline in permittivity values up to 200 °C which is attributed to the release of moisture from the sample. These results were correlated to TGA/DSC which showed 5 % mass loss from 100 to 155 °C. The permittivity gradually reached a peak after which it started to fall due to high conductivity. In the case of the PC, the permittivities exhibited undulations but the values remained consistent. Since this form of carbon is formed at elevated temperature, no loss in moisture was seen in TGA/DSC. These findings indicate that the microwaves can penetrate and heat both the samples uniformly across their entire volume, resulting in efficient heating. SC demonstrated higher permittivity magnitudes compared to PC, suggesting its better responsiveness to microwave fields. Nonetheless, the possibility of thermal runaway in SC renders it less favorable for applications involving microwave-driven pyrolysis. XRD analysis showed that the samples SC and PC demonstrated amorphous carbon structures, with PC showing indications of graphitization to some extent. Both SC and PC have the potential to serve as microwave heat carriers in the methane pyrolysis process. This suggests that utilizing the carbon produced can enable a self-sufficient process, eliminating the necessity for costly catalysts.

Influence of Nano-CeO2 and Graphene Nanoplatelets on the Conductivity and Dielectric Properties of Poly(vinylidene fluoride) Nanocomposite Films.

Novel three-phase polymer nanocomposites (PNCs) based on cerium oxide (CeO2) nanoparticles (NPs) and graphene nanoplatelets (GNPs) incorporated in a poly(vinylidene fluoride) (PVDF) matrix were formulated using a solution-casting approach. To understand the structural and morphological features of PVDF/CeO2/GNP nanocomposites (NCs), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analyses were accomplished. The PVDF/CeO2/GNP NCs displayed improved thermal stability which resulted from strong bonding between GNPs and CeO2 NPs and restriction of the polymer chain movement. The introduction of CeO2 NPs and GNPs within the PVDF matrix and good synergy between CeO2 NPs and GNPs led to variable mechanical properties of the prepared NCs. The PVDF/CeO2/GNP NCs portrayed reduced thermal stability, which could be due to the increased mobility of PVDF chains imposed by GNPs leading to the formation of volatile degradation products. Moreover, PVDF/CeO2/GNP NCs exhibited good electrical conductivity and high dielectric permittivity. The obtained dielectric permittivity value for the PVDF/CeO2/GNP NCs was 3-fold greater than PVDF/CeO2 NCs, making these novel tertiary composite materials a probable candidate for energy-storage applications.

Spinel-trirutile microwave dielectric ceramics with high Q and excellent temperature stability based on MgO-Al2O3-Ta2O5 ternary systems

(1-x)MgAl2O4-xMgTa2O6 composite ceramics based on the MgO-Al2O3-Ta2O5 pseudoternary phase diagram were prepared by the solid-state reaction. MgAl2O4 and MgTa2O6 could coexist due to their different crystal structures. MgAl2O4 inhibited the rapid growth of MgTa2O6 grains, and dense microstructures (ρ > 95%) with a uniform grain size distribution was obtained, with an optimal densification temperature of 1550 - 1575 °C. The temperature coefficient of resonant frequency (τf) and quality factor (Q×f) were optimized by introducing MgTa2O6 phases with low dielectric loss and positive τf. In addition, the partial solid solutions of Al3+ into Ta5+ sites resulted in loosening bonds within [Al/TaO6] octahedra and abnormally large polarizabilities, which was confirmed by the decrease in VTa-O and the redshift of A1 g(Ta-O) mode. Consequently, the relative permittivity (εr) and τf values of MgAl2O4-MgTa2O6 composite ceramics were further enhanced, exceeding the predicted ones. The 0.6MgAl2O4-0.4MgTa2O6 composition sintered at 1550 °C achieved excellent performance, with a near-zero τf value of 3.3 ± 1.7 ppm/°C, a low εr of 16.4 ± 0.3 and an ultra-high Q×f of 179,000 ± 6700 GHz @ 8.94 ± 0.04 GHz. These findings hold promising applications in the field of 5 G/6 G high-frequency communication.

Exciton interactions of chlorophyll tetramer in water-soluble chlorophyll-binding protein BoWSCP

The exciton interaction of four chlorophyll a (Chl a) molecules in a symmetrical tetrameric complex of the water-soluble chlorophyll-binding protein BoWSCP was analyzed in the pH range of 3–11. Exciton splitting ΔE = 232 ± 2 cm−1 of the Qy band of Chl a into two subcomponents with relative intensities of 78.1 ± 0.7 % and 21.9 ± 0.7 % was determined by a joint decomposition of the absorption and circular dichroism spectra into Gaussian functions. The exciton coupling parameters were calculated based on the BoWSCP atomic structure in three approximations: the point dipole model, the distributed atomic monopoles, and direct ab initio calculations in the TDDFT/PCM approximation. The Coulomb interactions of monomers were calculated within the continuum model using three values of optical permittivity. The models based on the properties of free Chl a in solution suffer from significant errors both in estimating the absolute value of the exciton interaction and in the relative intensity of exciton transitions. Calculations within the TDDFT/PCM approximation reproduce the experimentally determined parameters of the exciton splitting and the relative intensities of the exciton bands. The following factors of pigment-protein and pigment–pigment interactions were examined: deviation of the macrocycle geometry from the planar conformation of free Chl; the formation of hydrogen bonds between the macrocycle and water molecules; the overlap of wave functions of monomers at close distances. The most significant factor is the geometrical deformation of the porphyrin macrocycle, which leads to an increase in the dipole moment of Chl monomer from 5.5 to 6.9 D and to a rotation of the dipole moment by 15° towards the cyclopentane ring. The contributions of resonant charge-transfer states to the wave functions of the Chl dimer were determined and the transition dipole moments of the symmetric and antisymmetric charge-transfer states were estimated.

Structural studies, dielectric and electrical properties of (1-x) Pb(Zr0.52Ti0.48)O3– xCoFe2O4 multiferroics materials

This work aimed to develop a better combination of PbZr0.52Ti0.48O3 (PZT) and CoFe2O4 (CFO) ceramics with enhanced structural, dielectric, and electric properties. For this aim, (1-x)PZT-xCFO nanocomposites at (0.00, 0.10, 0.20, 0.30, 0.40, 0.50, and 1.00) were synthesized using the combination before calcination of sol–gel (for PZT ceramic) and solid-state (for CFO material) methods. The powder X-ray diffraction analysis reveals that the CFO crystallizes in a spinel cubic structure with the Fd3m space group structure, while the PZT compound crystallizes in two tetragonal and rhombohedral structures with P4mm and R3m space groups respectively, which is confirmed by Raman spectra which also demonstrate that CFO content in (1-x)PZT-xCFO composites affects the vibration types. The scanning electron micrographs (SEM) show that the grains are homogeneous and irregular, with several pores on the surface of ceramics. The dielectric properties of the ceramics were investigated as a function of temperature (from 25 to 500 °C) and frequency (from 100 Hz to 2 MHz) using complex impedance spectroscopy. It shows that with the increase of CFO ratio, the dielectric permittivity values increase in the composites until the composition corresponding to x = 0.3 From 485 to 1620 at 5KHz) and then decreases until 65 for x = 1.00. The dielectric constant a function of frequency at different temperatures of (1-x)CFO-xPZT composites indicated that the dielectric constant increases with the increase of CFO content. The impedance spectrum is characterized by simple semicircular arcs and shows a non-Debye relaxation. The electric conductivity reveals that as CFO increases, conductivity remains constant, and the frequency dependence of conductivity shifts away from high frequencies. Also, the value of the exponent n decreases from 1.44 to 0.26 with an increasing CFO concentration. The activation energy is between 0.32 and 0.16 which confirms that electron hopping is responsible for electrical conduction.

DUAL-BAND BANDSTOP FILTERS BASED ON ULTRA THIN FREQUENCY SELECTIVE SURFACES

In this paper, we present designs for terahertz filters with two independent stopbands based on periodic metallic resonant structures patterned on the dielectric substrate. Two simple and thin structures are proposed to realize required characteristics for single-polarized and dual polarized filter designs. To realize single polarized one, a unit cell of the proposed periodic structure consists of two sets rectangular shape conducting metal patches patterned on the top of the dielectric substrate, and the dual-band response is due the lattice resonances observed in the unit cell. To realize dual polarized filter design, a modified unit cell is considered with additional patches on the bottom of the dielectric substrate. The patches on the bottom layer are the same ones as on the top layer but orthogonally oriented. For this case, polarization-independent frequency response can be obtained after geometric optimization of the unit cell because the top and the bottom layers resonantly interact with only the TE or TM incident plane wave to minimize cross coupling effects between the layers. In order to intensively understand the transmission performance of the proposed filters, a large number of simulations using integral equation method are performed based on the different values for permittivity, period of the unit cell, dielectric thickness, and geometric dimensions. The electric field distributions are analyzed to understand the mechanism of the resonance behavior.

ELECTRON-BEAM SINTERING OF ZIRCONIUM DIOXIDE/TITANIUM CERAMICS FOR MICROELECTRONICS PRODUCTS

Zirconium dioxide (ZrO&lt;sub&gt;2&lt;/sub&gt;) has excellent physical, chemical, and mechanical properties. These properties make it an excellent material for composite ceramics. High values of dielectric permittivity, mechanical resistance, and high radiation resistance allow it to be used to protect integrated circuits (ICs) from external influences. In this study, we fabricated ZrO&lt;sub&gt;2&lt;/sub&gt;/titanium (Ti) ceramic composites by employing electron-beam sintering and a forevacuum-pressure plasma-cathode electron-beam source. We used a scanning electron microscopy method to study the properties of the ceramics after sintering. The results obtained showed that with an increase in the sintering temperature up to 1700&amp;deg;C, the Ti content in the near-surface layer of the composite decreased to almost 0. The depth of the region with low metal component content also increased with an increase in the sintering temperature and reached 2 mm in 3-mm-thick samples. This method can be used in the production of composite materials used in IC packaging.

Numerical modeling of metal-dielectric metasurface as an element of microwave sensors for biomedical applications

This paper reports the results of numerical modeling of wave reflection coefficient behavior of the metal-dielectric metasurface at microwaves that can be used for biomedical applications. The study includes optimization of the working parameters of the metasurface-based structure as a sensitive element of a microwave sensoring systems for determination of proteins concentration in different solutions. In the current research a unit with the geometry, which is similar to the geometry of one well of the standard 96-multiwell laboratory microplate, is used as a resonant metasurface unit cell and liquid-holding structure. Human serum albumin (HSA) is used as a protein specimen in our model study. The present numerical modeling is based on the results of our previous experimental measurements of complex permittivity values of HSA water solutions and its biochemical reaction mixtures using microwave dielectrometry method and the developed setup. The unit cell approach calculations are performed by COMSOL Multiphysics software. The optimization of working parameters of the metal-dielectric metasurface structure with tested solutions allow us to observe the resonance effects of the wave reflection coefficient in the microwave range. We can determine the HSA concentration changes in water solutions and enzymatic reaction mixtures by the resonance frequency shift of the wave reflection coefficient of the metal-dielectric metasurface. Developed metal-dielectric metasurface-based structure demonstrates prospects to be used as a sensitive element of microwave sensors for proteins concentration determination with biomedical purposes.

Synthesis and characterization of cellulose nanocrystal derived from paper as nanofiller for polymer insulation materials

The synthesis and characterization of cellulose nanocrystal by utilizing filter paper as the source of material deserves to be an advanced approach. Nanocellulose has received enormous attention due to its unique properties. Being the most abundant organic polymer on earth, nanocellulose is the most suitable candidate for alternative replacement of petroleum-based products. The cellulose was extracted from filter paper by chemical processes involved alkali treatment, bleaching treatment, and acid hydrolysis. Cellulose nanocrystal has been characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Electrical Impedance Spectroscopy (EIS). The dielectric permittivity of the prepared CNC have been investigated in the different temperatures. The nanofiller CNC exhibits a higher real permittivity value at elevated temperatures (60 °C) in the low-frequency region. At high-frequency region, the real permittivity is independent on temperature. In brief, the studies point to the application potential of CNC for future insulation materials.