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Three-Dimensional Holographic Electromagnetic Imaging for Accessing Brain Stroke
摘要： The authors recently developed a two-dimensional (2D) holographic electromagnetic induction imaging (HEI) for biomedical imaging applications. However, this method was unable to detect small inclusions accurately. For example, only one of two inclusions can be detected in the reconstructed image if the two inclusions were located at the same XY plane but in different Z-directions. This paper provides a theoretical framework of three-dimensional (3D) HEI to accurately and effectively detect inclusions embedded in a biological object. A numerical system, including a realistic head phantom, a 16-element excitation sensor array, a 16-element receiving sensor array, and image processing model has been developed to evaluate the effectiveness of the proposed method for detecting small stroke. The achieved 3D HEI images have been compared with 2D HEI images. Simulation results show that the 3D HEI method can accurately and effectively identify small inclusions even when two inclusions are located at the same XY plane but in different Z-directions. This preliminary study shows that the proposed method has the potential to develop a useful imaging tool for the diagnosis of neurological diseases and injuries in the future.
关键词： brain stroke,sensor array,dielectric properties,electromagnetic induction imaging,magnetic induction tomography
更新于2025-09-09 09:28:46
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Investigation on Structural and Dielectric Properties of Silica Nanoparticles Incorporated Poly(Ethylene Oxide)/Poly(Vinyl Pyrrolidone) Blend Matrix Based Nanocomposites
摘要： Inorganic and organic materials based polymer nanocomposite (PNC) films, comprising silica (SiO2) nanoparticles as inorganic filler and the polymer blend of poly(ethylene oxide) (PEO) and poly(vinyl pyrrolidone) (PVP) as organic matrix (i.e., (PEO–PVP)-x wt% SiO2; x = 0, 1, 3 and 5) have been prepared by the solution-casting method. These PNC films are characterized by employing the scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscopy, and the dielectric relaxation spectroscopy (DRS). The effect of SiO2 nanofiller on the spherulite and porous morphology, miscibility of the polymers, PEO crystallite size, the degree of crystallinity, polymer–polymer and polymer-nanoparticle interactions, and from 20 Hz to 1 MHz range dielectric and electrical dispersion behaviour and also the structural dynamics of these PNC materials have been investigated. The porous morphology, structures of miscible phases, and the PEO crystallite length greatly alter with the incorporation of merely 1 wt% SiO2 in the polymer blend matrix which further changes with the increase of nanofiller concentration up to 5 wt%. The real part of complex permittivity over the radio frequency range (20 kHz–1 MHz) for these PNC films is found about 2 and their dielectric loss tangent values below 0.03, at the room temperature, which are significantly low. The contribution of interfacial polarization effect at lower audio frequencies enhances the complex permittivity of these materials linearly in the range 2 to 4 with the decrease of frequency from 1 kHz to 20 Hz confirming their frequency tunable dielectric behaviour. The dielectric study of 3 wt% SiO2 containing PNC film in the temperature range 30–60 °C reveals its thermally activated dielectric characteristics, and the temperature dependent values of dielectric relaxation time and dc electrical conductivity obey the Arrhenius behaviour with activation energies in the range 0.2–0.3 eV. The dielectric and electrical parameters ascertain the promising applications of these PNC films in the development of novel electroactive functional materials, and also their use as the dielectric substrate and electrical insulating polymeric nanodielectrics for the fabrication of flexible-type naturally degradable organoelectronic devices.
关键词： Electrical conductivity,FTIR,XRD,Dielectric properties,Polymer nanocomposite
更新于2025-09-09 09:28:46
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Influence of Bi Substitution on the Microstructure and Dielectric Properties of Gd3Fe5O12 Ceramics
摘要： The exponential growth in microwave communications in recent years demands innovations and high yield microwave materials. Rare earth iron garnets are well known for their remarkable performance in microwave devices owing to their superior features. In this work we investigate the microstructure and dielectric properties of Bismuth substituted Gd3Fe5O12 ceramics prepared by the conventional solid state reaction route. The variation of lattice parameter, microstructure, permittivity, quality factor and temperature coef?cient of resonant frequency (sf) of Gadolinium Iron Garnet (GIG) with several concentrations of bismuth was investigated. The Bi3+ ion is effectively incorporated into Gadolinium Iron Garnet, due to which the sintering temperature is considerably reduced, and the densi?cation is improved signi?cantly. Moreover, with increase in Bi concentration, the dielectric constant of GIG also increases, while the quality factor is slightly reduced, which is correlated with the higher ionic polarizability of bismuth. At an appreciably low sintering temperature of 1050(cid:2)C, Gd2BiFe5O12 possess a porosity corrected relative permittivity value of 27.3 ± 0.2, unloaded quality factor (Qu 9 f) of 2990 ± 60 GHz (f = 7.3 GHz) and temperature coef?cient of resonant frequency + 60 ± 1 ppm/(cid:2)C.
关键词： microstructure,Low-temperature sintering,microwave dielectric properties,garnet structure
更新于2025-09-09 09:28:46
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Effect of PbO–B2O3–BaO–SiO2 glass additive on dielectric properties of Ba0.5Sr0.5TiO3 ceramics for radio-frequency applications
摘要： In this work, the effects of PbO–B2O3–BaO–SiO2 (PBBS) glass addition (in increasing wt%) into Ba0.5Sr0.5TiO3 (BST0) ceramic on sintering, phase, and dielectric properties of BST0 are studied. The Ba0.5Sr0.5TiO3 (BST0) ceramic was synthesized by the conventional solid-state reaction method, and the PbO–B2O3–BaO–SiO2(PBBS) glass was formed by melting and quenching process. The PBBS glass with different weight percentages (3, 5, 8 and 10 wt%)is added to BST0 ceramic (BST3, BST5, BST8, and BST10, respectively) as a sintering aid to reduce the sintering temperature. Addition of glass helps in better sintering at lower temperatures with the presence of liquid phase at the respective sintering temperatures. The results of liquid phase-sintered ceramics are compared with the BST0 ceramic sintered at 1523 K. The BST10 with 10 wt% glass showed the lowest sintering temperature of 1148 K. Rietveld refinement analysis of BST0 ceramic confirmed the formation of single phase with cubic crystal structure. X-ray diffraction patterns of all liquid phase-sintered ceramics showed that the glass has minimal reaction with the BST0 ceramic and does not affect the crystal structure. Dielectric characterization was performed within the temperature range 20–450 K and frequency range 1 kHz to 1MHz. It is revealed that the transition temperature shifted with different weight percentage of glass addition. All the compositions exhibit the paraelectric phase at room temperature. Dielectric properties were also measured in the microwave frequency range 8.5–11 GHz at room temperature.BST10shows the stable and highest dielectric constant (average value of εr = 27) with lowest dielectric loss (tanδ = ~0.121). Fourier transform infrared (FTIR) and Raman spectroscopy confirmed the formation of desired compositions by detecting molecular vibrations and chemical bonding. The synthesized ceramic is a low-cost candidate and can have potential uses in the radio-frequency applications.
关键词： Dielectric properties,Glass,Sintering,Transition Temperature,Calcination
更新于2025-09-09 09:28:46
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The Role of B-site Substitution on the Structural and Dielectric Properties of Samarium Orthoferrite Polycrystals
摘要： Polycrystalline samples of SmFeO3, SmFe0.5Co0.5O3, and SmFe0.5Cr0.5O3 were prepared by the conventional solid state reaction method. Powder x- ray diffraction pattern confirmed the formation of orthorhombic structure without any impurity phase. Dielectric and impedance properties of the sintered samples were studied as a function of temperature and frequency ranging from 300 K to 550 K and 100 Hz to 50 MHz respectively. The dielectric studies showed interesting properties like dielectric anomaly around spin reorientation temperature suggesting that the magnetic and electric order parameter may be coupled. The behavior of AC conductivity with temperature was explained by hopping mechanisms and the activation energy was found decreased for the doped samples. Nyquist and electric modulus spectra revealed the grain and grain boundary contributions of the sintered samples. The experimental results suggest that the spin reorientation can be tuned in the samarium orthoferrites by changing the B-site ion.
关键词： Dielectric Properties,Orthoferrites,Impedance Spectra,Perovskites,Multiferroic
更新于2025-09-09 09:28:46
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Optical, dielectric properties and thermal analysis on sodium sulfanilate dihydrate nonlinear optical single crystal
摘要： Nonlinear optical sodium sulfanilate dihydrate (SSD) single crystal was grown by slow evaporation solution method at ambient temperature. Unit cell parameters were elucidated with the study of single crystal X-ray diffraction. Fourier transform infrared spectroscopic analyses were performed to indentify a variety of functional groups present in the grown SSD crystal. The level of optical transmittance of the grown SSD crystal was investigated by UV–Vis–NIR spectral analysis. The lower cut off wavelength of the grown crystal was observed at 243 nm and the band gap energy is found to be 5.23 eV. The spectral study of photoluminescence was carried out for the grown crystal which shows a sharp emission peak at 485 nm resulting blue–green emission that is suitable for the optical communication applications. Mechanical strength was measured by utilizing Vickers microhardness test and the value of n is found to be 2.25 asserting that the crystal belongs to soft material category. The dielectric properties were studied as a function of frequency at various temperatures and also the grown SSD crystal has been correlated with electro-optic properties. Thermogravimetric analysis was undertaken by a thermal analyzer with the temperature starting from 30 to 800 °C and TGA/DTA results show that the crystal has good thermal stability and useful for laser applications. Etching analysis also was performed for the grown SSD single crystal proving that it has good crystalline nature with fewer defects.
关键词： Thermal analysis,Sodium sulfanilate dihydrate,Nonlinear optical materials,Dielectric properties,Optical properties,Crystal growth
更新于2025-09-04 15:30:14
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Effect of doping Gd2O3 on dielectric and piezoelectric properties of BaZr0.1Ti0.9O3 ceramics by sol–gel method
摘要： The effects of sintering temperature and doping amount of gadolinium ions on the microstructures and electrical properties of sol gel derived Ba (Zr0.1Ti0.9) O3 + xGd ceramics were investigated in this manuscript. XRD analysis showed that the main crystalline phase of BZT-xGd ceramic samples exhibit a perovskite structure without significantly change. The sample sintered at 1350 °C and doped with gadolinium ions of 0.5 mol% has uniform grain size and compact morphology. And the sample(1350 °C—0.5 mol%) also has a high piezoelectric charge coefficient of 131.33 pC/N, large plane electromechanical coupling coefficient of 0.22, high dielectric constant of 10504, and small dielectric loss of 0.01. The correlation of dielectric and piezoelectric properties of BZT-xGd ceramics with doping amount of Gd3+ ion has been explained by the lattice theory.
关键词： BZT-xGd ceramics,dielectric properties,sol–gel method,gadolinium doping,piezoelectric properties
更新于2025-09-04 15:30:14
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Controllable coating polypyrrole on silicon carbide nanowires as a core-shell nanostructure: a facile method to enhance attenuation characteristics against electromagnetic radiation
摘要： Continuous polypyrrole (PPy) shells were coated on silicon carbide (SiC) nanowires to form core-shell nanostructures and the thicknesses of the shells were efficiently tuned through controlling the rate of polymerization. Compared with the composites loaded with pure SiC nanowires, the values of ε′ and ε′′ for the composites loaded with PPy@SiC nanowires were strengthened remarkably along with the increased thickness of the shells. The electromagnetic absorption (EA) bandwidth lower than ?10 and ?20 dB can be monitored in the area of 3.67-18.00 and 4.13-18.00 GHz, when 5 wt% of PPy@SiC nanowires were loaded in the composite. Meanwhile, the effective EA bandwidth can reach 6.88 GHz and the strongest reflection loss is ?58.6 dB.
关键词： dielectric properties,polypyrrole,silicon carbide nanowires,core-shell nanostructures,electromagnetic absorption
更新于2025-09-04 15:30:14
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The impact of Eu3+ ion substitution on dielectric properties of Y3?xEuxAl5O12 (0.00?≤?x?≤?0.10) ceramics
摘要： This study reported the effect of Eu substitutions on the conductivity and dielectric properties of Y3?xEuxAl5O12 (0.0 ≤ x ≤ 0.1), YAG:xEu3+. All products were fabricated by solid state route. The formation of YAG was approved through X-ray diffraction powder diffraction and high-resolution transmission electron microscope. It was found that the lattice parameters are increasing with increase the substitution content due to the difference in ionic radii between Y3+ and Eu3+. Electrical and dielectric properties of YAG (Y3Al5O12) and YAG:xEu3+ ceramics were investigated extensively for a variety of concentrations (0.00 ≤ x ≤ 0.1) of the substitutional Eu3+ ion from the 4f lanthanide group. The temperature dependence of dielectric loss, dielectric constant, loss tangent and ac/dc conductivity were examined up to 5.0 MHz to understand the electrical and dielectric properties for both doped and undoped YAG ceramics. The experimental results revealed that Eu3+ ion substitutions (especially x = 0.05) in YAG ceramics meaningfully influence the lossy mechanisms, conductivity and dielectric constant which is probably due to the contribution to the conduction mechanism of the 4f–Eu and 3d–Al ions. So, this can be incorporated at the exceptional sites of both Oh (octahedral) and Td (tetrahedral) symmetries in YAG: xEu3+ ceramics.
关键词： conductivity,solid state route,YAG,dielectric properties,Eu3+ ion substitution
更新于2025-09-04 15:30:14
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Enhanced dielectric properties and energy density of flexible KTa0.2Nb0.8O3-BaTiO3/P(VDF-TrFE-CTFE) nanocomposite
摘要： In this work, KTa0.2Nb0.8O3–BaTiO3 (KTN–BT) hybrid nanoparticles were synthesized via a facile one-pot hydrothermal method. Flexible nanocomposite films comprised of poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) P(VDF-TrFE-CTFE) matrix and KTN–BT hybrid fillers of different molar ratio were prepared by solution-casting. It is revealed that the introduction of BT to the KTN causes decreased grain size and homogenous morphology, improving the dielectric constant, breakdown strengthen and energy density of nanocomposite films. Typically, the nanocomposite film containing 40 vol% KTN–BT possesses a dielectric constant of 322 at 100 Hz, which is 8.7 times than that of pure polymer. Also, nanocomposite film with < 10 vol% of filler could achieve high breakdown strength of over 300 MV m?1. The energy density of the film containing 2 vol% KTN–BT filler is 61.4% higher than that of pure P(VDF-TrFE-CTFE) polymer. (7.1 J cm?3 compared to 4.4 J cm?3.) In addition, the nanocomposites also displayed good flexibility and kept excellent dielectric properties after bending and folding. All the improved performance enables these composites to meet the requirements of many flexible electronic devices and energy storage devices.
关键词： KTN–BT,dielectric properties,P(VDF-TrFE-CTFE),nanocomposite,energy density
更新于2025-09-04 15:30:14