Dielectric Substance Research Articles

Doping Fe and Co Induced Modification in the Structural, Optical and Colossal Permittivity of Nb-doped TiO2 Ceramics

Fe/Nb and Co/Nb co-doped TiO2 ceramics were synthesized by conventional ceramic solid-state reaction process in order to create a high dielectric permittivity substance. Comprehensive structural, optical and dielectric studies were carried out on the samples of formula Nb:TiO2, Fe:(TiO2:Nb) and Co:(TiO2:Nb). The structural and optical characterizations were performed with X-ray diffraction and diffuse reflection spectroscopy, respectively. The dielectric properties including colossal permittivity (CP) were investigated at room temperature in the frequency range of 0.1-100 kHz. The novelty of the present work was to create a CP (ϵ′∼104-105) in host TiO2 by codoping with (Co/Nb) and study the change in the CP by using Fe ions instead of Co ions. The results were explained in the framework of the core/shell model and doping mechanisms.

On Body and Off‐Body Performance Analysis of an Ashoka Tree Shaped Wearable Textile Antenna for Biomedical and Military Applications

AbstractIn this paper an Ashoka tree shaped wearable textile antenna for biomedical and military applications working at 2.4 GHz, 9.04 GHz is investigated and analyzed. The designed antenna has the size of 34 × 40 × 1 mm3. To obtain a wide bandwidth 0.5 × 40 mm2 partial ground plane is used. The lightweight jean material is employed as a non‐conductive dielectric substance with a εr of 1.7 and a substrate height of 1 mm to define the wearable applications. Examining the surface current and actualizing the conductivity of the radiating elements are performed. Full‐wave EM simulation and experimental results are carried out at 30°,60°, and 90° under various bending conditions, both in free space and close to the human body. The suggested antenna performs satisfactorily in terms of gain and specific absorption rate. When worn on the body, the final design offers a peak gain of 7.6 dBi and an efficiency of 94.7%. Findings from simulations using CST Microwave Studio and measurements are quite close. These characteristics show that the suggested antenna is a solid contender for wearable applications that are both off‐ and on‐body. Due to its compatibility, adaptability in structure design and shape, excellent performance at various angles, human safety, miniaturization, power consumption, etc., this Ashoka tree‐shaped antenna can be significantly used in military jackets and in biomedical applications.

EFFICIENCY ENHANCEMENT OF PHOTOVOLTAIC SOLAR CELLS USING METAMATERIALS ABSORBING SCREEN

This paper proposes a novel technique for the efficiency enhancement of photovoltaic (PV) solar cells using metamaterials absorbing screens. This kind of engineered material comprises resonant metallic rings that are printed on a host low-loss dielectric substance and made periodic in a two-dimensional lattice. The absorbing screen has been carefully designed, and its retrieved effective constitutive parameters, effective electric permittivity ϵeff and effective magnetic permeability µeff, are integrated within a numerically modelled amorphous-Silicon-based PV solar cell structure as an impedance matching layer. Such arrangement will greatly achieve matching between the effective impedance of the composite solar cell structure and free-space impedance and will result in higher photons absorption through the metamaterials anti-reflective screen. Numerical full-wave electromagnetic simulations are carried out using CST Microwave Studio for the design of a metamaterial absorbing screen. Due to the large computational resources required, COMSOL Multiphysics was adopted in the design and analysis of the composite structure comprising a two-dimensional PV solar cells layer. Based on the numerical results, both optical and electric characteristics of the PV solar cell structure were enhanced with the use of a metamaterial layer. Moreover, efficiency enhancement by 5% was permissible, in which efficiency reached 12% with the use of metamaterials as compared to the efficiency of the classical PV cells of 7%. The obtained results are very promising, and the potential integration of metamaterials in commercial PV solar cells will show significant advancement in efficiency enhancement of PV cells and realization of smart PV solar cells with the consideration of additional features from metamaterials.

High-performance hybrid graphene-perovskite photodetector based on organic nano carbon source-induced graphene interdigital electrode film on quartz substrate

Hybrid graphene interdigital electrode-perovskite structure has demonstrated high value in the photodetector (PD) due to high absorbance and carrier collection efficiency. However, direct pattern of graphene film on the dielectric substance still faces huge challenges. Especially, the involvement of multi-step transfer and high-energy etching process hamper its development.In this context, we propose an organic nano carbon source (ONCS). Direct pattern of graphene film on the quartz substrate (GFqtz) is attained by the calcination of patterned ONCS film for the first time, which is simply achieved by screen printing technology thanks to the gel state. The transformation mechanism from ONCS to GFqtz has been proposed. In detail, the ONCS in-situ react with the quartz substrate to induce the SiC nanocrystals layer during the calcination. Then, the graphene film composes of the non-ordered graphene crystal layer and the aligned graphene crystals layer. Finally, the perovskite PD are successfully constructed by the GFqtz interdigital electrode. Compared to the PD fabricated by the Au interdigital electrode, the GFqtz-perovskite PD present an ultra-low detective light power density (0.5 μW/cm2) at 1 V bias voltage. The maximum responsivity and defectivity (0.1 A/W) and D* (2.6 × 1011 Jones) of the GFqtz-perovskite PD demonstrate an order of magnitude higher than the Au-perovskite PD's value.

Nonlinear and thermal effects in the absorption of microwaves by random magnets

We study the temperature dependence of the absorption of microwaves by random-anisotropy magnets. It is governed by strong metastability due to the broad distribution of energy barriers separating different spin configurations. At a low microwave power, when the heating is negligible, the spin dynamics is close to linear. It corresponds to the precession of ferromagnetically ordered regions that are in resonance with the microwave field. Previously, we showed [Phys. Rev. B 103, 214414 (2021)] that in this regime a dielectric substance packed with random magnets would be a strong microwave absorber in a broad frequency range. Here we demonstrate that on increasing the power, heating and over-barrier spin transitions come into play, resulting in the nonlinear behavior. At elevated temperatures the absorption of microwave power decreases dramatically, making the dielectric substance with random magnets transparent for the microwaves.

Pulse Laser Deposition of HfO2 Nanoporous-Like Structure, Physical Properties for Device Fabrication

The pulsed laser deposition (PLD) technology was used to effectively create conductive nano and micro hafnium oxide with great purity and transparency for (HfO2) nanofilms. In many optoelectronics devices and their applications, the presence of a high dielectric substance like a nano HfO2, between the metal contacts and the substrates was critical. We used the Pulsed Laser Deposition method to fabricate an Al/HfO2/p-Si Schottky barrier diode where the nanostructured HfO2 films as an intermediate layer and varied substrate temperatures. The optical result reveals a high degree of transparency (93%). The optical bandgap of deposited HfO2 films was observed to vary between 4.9 and 5.3 eV, with a value of roughly 5.3 eV at the optimal preparation condition. The morphology of the surface shows a high homogeneous nano structure with the average values of the roughness about (0.3 nm). With regard to substrate temperature, the produced factor ideality for fabricated diode was determined to be lowering and the associated values of the barrier height rose based on I-V characterization. With regard to substrate temperature, the produced factor ideality for fabricated diode was determined to be lowering and the associated values of the barrier height rose based on I-V characterization. The diode manufactured at 600°C, in particular, had a higher ideality factor value (n = 3.2).

Biostimulation Effects and Temperature Variation in Stimulated Dielectric Substance (Diabetic Blood Comparable to Non-Diabetic Blood) Based on the Specific Absorption Rate (SAR) in Laser Therapy

Human blood exposed to irradiation absorbs electromagnetic energy which consequently effect temperature variation. The evaluation of Specific Absorption Rate (SAR) of human blood helps to ascertain the values for optimum laser power, time, and temperature variation for fair therapy to avoid blood-irradiation pollution but to enhance its rheological properties when using lasers. Prior knowledge of blood SAR evaluating its dielectric properties is significant, but this is under investigation. We investigate the appropriate SAR threshold value as affected by temperature variation using fundamental blood dielectric parameters to optimize the effect of low-level laser therapy based on physiological and morphological changes of the stimulated diabetic blood. Studies were carried out with Agilent 4294A impedance analyser at frequencies (40Hz – 30 MHz) and designed cells (cuvettes) comprises of electrodes were used in the pre- and post-irradiations measurements. At different laser power outputs, blood samples were subjected to various irradiation durations using portable laser diode-pumped solid state of wavelength 532 nm. Results showed laser at low energy is capable of moderating morphologically the proportion of abnormal diabetic red blood cells. Hence, there is a significant effect using a laser at low energy, as non-medicinal therapy in controlling diabetic health conditions. The positive biostimulation effects on the irradiated diabetic blood occurred within absorbance threshold SAR values range of 0.140?0.695 W/kg and average temperatures range of 24.2?28.0 0C before blood saturation absorbance peak. There is morphological stimulation at a laser power of 50 mW for an exposure time of 10–15 minutes and 60 mW for 5–10 minutes of laser therapy that demonstrates better blood rejuvenated conditions. This occurred within the threshold SAR of 0.140?0.695 W/kg and average temperatures range of 24.2?28.0 0C. Therefore, the diabetic blood irradiated using laser output powers of 70 and 80 mW during exposure durations of 5,10, 15 and 20 minutes rather bio-inhibits positive blood stimulation which has resulted to crenation due to excessive irradiation.

A gap-active electrical discharge machining (GA-EDM) to rectify the textural defects of the processed surface

Gap-active electrical discharge machining (GA-EDM) is a novel approach which provides a gap-sensible and auto-adjustable electrode-retraction system. This mechanism is conceptualized from the principle of ‘parallel-plate capacitor having two dielectric mediums’ where the inter-electrode surfaces are acted as the parallel plates. The kerosene is used as a fundamental dielectric substance, and a relatively denser and viscous layer of bio-oil is treated as secondary dielectric material. Besides this, a servo-controlled tool arrangement is employed, which is auto-sensible and synchronized with the flushing system. This multi-dielectric enhances the equivalent capacitance of the plasma-column and can dissipate huge energy during the discharging phase. The extensive heat melts most of the solidification defects and reforms the entire texture, which is far better than the surface developed with normal EDM. Moreover, the viscous layer of the secondary fluid (above the workpiece) provides an adhesive grip and slow heat dissipation procedure, which can check the formation of micro-cracks, develop due to residual effect of rapid quenching. Besides these, the flushing sensible electrode retraction system ensures an adequate passage for flushing, which helps in proper debris-expelling and controlled heat dissipations. Therefore, the adopted gap-active (GA) mechanism can facilitate better textual features with negligible indentation, solidified-agglomerates, and cracks. It is observed that the secondary dielectric enriches the carbon containments in the texture and forms a 10–14 % harder surface than the normal-EDM.

МОДЕЛЬ И АЛГОРИТМ РАБОТЫ ОПТИЧЕСКОГО КОММУТАТОРА 4 × 4

The main objective in improving optical communication systems, which are widely developed nowadays, is a solution of the problem of operation speed of the entire commutation system, which is limited by quick action of the outer elements of the management system. There have been presented the structure and algorithm of a radically new commutation system based on the 4x4 optical switch operation. The specific feature of the switch operation is the lack of external control over switching process. The operation principle of the main element of the 4×4 optical switch - an optical switching element - has been considered. The switching element is a photonic crystal consisting of a layer of metamaterial, a dielectric substance and ferrite films. The results of the numerical simulation of the switch are presented. The analysis of results allows to infer that the proposed switch can be used in modern communication systems.

EM-Wave Biosensors: A Review of RF, Microwave, mm-Wave and Optical Sensing.

This article presents a broad review on optical, radio-frequency (RF), microwave (MW), millimeter wave (mmW) and terahertz (THz) biosensors. Biomatter-wave interaction modalities are considered over a wide range of frequencies and applications such as detection of cancer biomarkers, biotin, neurotransmitters and heart rate are presented in detail. By treating biological tissue as a dielectric substance, having a unique dielectric signature, it can be characterized by frequency dependent parameters such as permittivity and conductivity. By observing the unique permittivity spectrum, cancerous cells can be distinguished from healthy ones or by measuring the changes in permittivity, concentration of medically relevant biomolecules such as glucose, neurotransmitters, vitamins and proteins, ailments and abnormalities can be detected. In case of optical biosensors, any change in permittivity is transduced to a change in optical properties such as photoluminescence, interference pattern, reflection intensity and reflection angle through techniques like quantum dots, interferometry, surface enhanced raman scattering or surface plasmon resonance. Conversely, in case of RF, MW, mmW and THz biosensors, capacitive sensing is most commonly employed where changes in permittivity are reflected as changes in capacitance, through components like interdigitated electrodes, resonators and microstrip structures. In this paper, interactions of EM waves with biomatter are considered, with an emphasis on a clear demarcation of various modalities, their underlying principles and applications.

Long-range coupling between ATP-binding and lever-arm regions in myosin via dielectric allostery.

A protein molecule is a dielectric substance, so the binding of a ligand is expected to induce dielectric response in the protein molecule, considering that ligands are charged or polar in general. We previously reported that binding of adenosine triphosphate (ATP) to molecular motor myosin actually induces such a dielectric response in myosin due to the net negative charge of ATP. By this dielectric response, referred to as "dielectric allostery," spatially separated two regions in myosin, the ATP-binding region and the actin-binding region, are allosterically coupled. In this study, from the statistically stringent analyses of the extensive molecular dynamics simulation data obtained in the ATP-free and the ATP-bound states, we show that there exists the dielectric allostery that transmits the signal of ATP binding toward the distant lever-arm region. The ATP-binding-induced electrostatic potential change observed on the surface of the main domain induced a movement of the converter subdomain from which the lever arm extends. The dielectric response was found to be caused by an underlying large-scale concerted rearrangement of the electrostatic bond network, in which highly conserved charged/polar residues are involved. Our study suggests the importance of the dielectric property for molecular machines in exerting their function.

Study of terahertz spoof surface plasmons on subwavelength gratings with dielectric substance in grooves

Terahertz (THz) plasmonic devises based on periodical corrugated structures are promising for sensing applications in biology and medicine but have not been developed so far because spoof surface plasmons (SSPs) on such structures were studied insufficiently in the THz spectral range. In the paper, the propagation of THz SSPs along one-dimensional subwavelength rectangular plane gratings with a dielectric substance in the grooves was studied and optimal parameters of gratings (period, aspect ratio and groove depth) for sensing of dielectric were found. First grating samples were made and tested using the THz radiation of the Novosibirsk free electron laser.

Microwave resonator method of dynamic measurement of mass of the samples of gasifying solid fuel

The paper describes novel contactless method of determining instantaneous gasification rate of solid materials under intensive blowing the reacting (gasified) surface. Method is based on dynamic measurement of the mass of dielectric substance within specially designed microwave resonator. The attenuation of passing through the resonator signal is proportional to the actual value of the sample mass. Before firing experiments the setup is calibrated using samples of studied material with different channel radius. With the proper choice of data acquisition system one can achieve the web sample thickness resolution around few microns and time resolution higher than 1 kHz. The examples of preliminary tests with paraffin samples blown by air jets with temperatures of 350-1500 K and speeds of 375–700 m/s are presented.

Resistance of a pulsed electrical breakdown channel in ionic crystals

A technique for estimating the resistance of the electrical breakdown channel in ionic crystals is proposed. This technique is based on measuring the channel velocity in a sample when a ballast resistor is connected to the circuit of a needle anode and on using the theoretical dependence of the channel velocity on the channel conductivity. The breakdown channel resistance at a voltage of 140 kV is about 6.5 kΩ in KCl and about 6.1 kΩ in KBr. These resistances are shown to characterize a gas phase. The gas-phase resistance is found to be nonuniform along the breakdown channel. The head part ∼1 mm long has the maximum resistance. This head region is concluded to contain dielectric substance clusters, which then decompose into metal and halogen ions. The cluster lifetime is ∼10−9 s.

지휘소 작전지속성 보장을 위한 도파관의 전자기파 차폐성능 향상방안

The stable fueling and water supply should be prerequisites to guarantee the operational sustainment of military command post. Meanwhile, in terms of the operational sustainment, it is verified that the current wave-guided below cutoff (WBC) system cannot satisfy the requirement of control associated with water supply and fueling within the command post. In this study, as the dielectric substance can block electromagnetic pulse (EMP), it was tried to identify the shielding effectiveness of the multi WBCs filled with water and diesel for attenuating the EMP effect using experiment based on the MIL STD 188-125-1. According to the experimental results, used water in the experiment show the shielding effectiveness from around 640 MHz frequency because of minerals contained in the water. Furthermore, it was noted that EMP attenuating strength of the WBC filled with diesel was enlarged from around 1,680 MHz frequency. Resultingly, it could be concluded that it is enough to supply stable water and diesel through the multi WBC to block EMP within the military command post for guaranteeing the military operations sustainment.

Dielectric anisotropy of oven- and air-dried wood evaluated using a free space millimeter wave

To evaluate the dielectric anisotropy caused by wood structure at a millimeter wave frequency of 100 GHz, the dielectric parameters for flat-sawn specimens of nine wood species at 0 and 11 % moisture content (MC) were measured using a free space method devised for reducing the multiple reflections under an electric field of millimeter waves parallel to longitudinal and tangential directions of wood, and those in radial direction were estimated using a conventional approximation theory. The dielectric parameters in the tangential and radial directions were almost identical and constantly smaller than those in the longitudinal direction. All the dielectric parameters increased with wood density and were larger at 11 than 0 % MC. The dielectric parameters in the longitudinal and transverse directions and the dielectric anisotropy between them were well fitted to the regression lines based on a dielectric mixture model composed of pores and dielectric isotropic wood substance, and a parallel capacitor and Lichtenecker’s exponential formulas were employed to represent the dielectric parameters of the mixture in the longitudinal and transverse directions, respectively. It was concluded that the dielectric anisotropy at 100 GHz is caused by the pore alignment and that the dielectric parameters are almost unaffected by anatomical structures, such as the rays. It was also confirmed that the free space method was effective for the measurement of the dielectric parameters for the flat-sawn specimens.

1/fPermittivity Fluctuation in Fullerene C60

The existence of 1=f fluctuation in an electrical device is a serious problem from the viewpoint of accuracy. Carbon nanotubes (CNTs) are very useful for field-effect transistors, sensors, and microscopes, but their 1=f resistance fluctuation intensity is particularly large. 1–4) Graphene attracts attention as a new material for an electric device, but it also generates a large 1=f fluctuation. 5) Many hypotheses have been proposed about the origin of 1=f fluctuation. 6,7) Regarding the carbon material, some investigations reported that the origin of 1=f fluctuation is the mobility fluctuation in the sample, 1) but some reports insisted that the origin is the trap potential fluctuation at the sample/electrode or sample/ surrounding dielectric interface. 2–4) The potential height fluctuation by the trap and de-trap of electrons modulates the mobility or tunneling probability of the barrier between the sample and the electrode. The studies of the 1=f fluctuation in electrical devices are performed mainly by focusing on the electrical resistance. We have investigated the permittivity fluctuation of a dielectric substance, but it was about the critical fluctuation near Curie temperature. 8) In the present study, fullerene C60 is used as a sample material and the permittivity fluctuations of the real and imaginary parts are measured. Fullerene has the same hexagonal structure of carbon atoms as CNTs and graphene, but it is a dielectric substance. The fluctuation of complex permittivity provides new information. In the present study, the cross-correlation coefficient of the permittivity fluctuations of the real and imaginary parts is calculated. Furthermore, the effect of air adsorption on the surface of fullerene is investigated. A flat board capacitor, whose inside is filled with fullerene, is used to measure the permittivity fluctuation. Fullerene powder of 40 mg is packed between the metal plates with a size of 100 � 100 mm 2 and the distance between the plates is 30m. The real part of the relative permittivity of fullerene C60 is 4–4.5 and it is considered that the imaginary part of it at a low frequency is very small owing to the result of optical measurement. 9) The fluctuation of permittivity is measured by using the bridge circuit and two-phase lock-in amplifier shown in Fig. 1. Part of the bridge circuit is constructed by the fullerene capacitor and the other parts are constructed by low-noise polystyrene capacitors and series resistors. The amplitude and frequency of the applied voltage V0 are 2 V and 5 kHz, respectively. The mean value of V1 is adjusted to V0=2 by the capacitor C and the series resistor R. The value of the capacitance C is 1.7 nF and the value of the equivalent series resistance R is 93 � . The complex capacitance of the fullerene capacitor can be described as

Research on Key Electromagnetic Model for Microwave Hot Recycling of Asphalt Mixtures

For uneven temperature distribution of infrared hot recycling of asphalt mixtures, principle and advantage of microwave hot recycling are introduced. Maxwell's equations are applied to build electromagnetic transmission model of recycled asphalt mixtures. Considering asphalt mixtures as dielectric substance, reflection and refraction of electromagnetic field are researched and model of standing wave ratio is built. Equation of magnetic attenuation is applied to contrast attenuation depths of different pavement materials. The results lay a good theoretical foundation to improve heating efficiency and choose pavement materials.

Study of Hemi-Spherical Dielectric Resonator Antenna with Change in Dielectric Characteristics of Resonator

The paper presents the effect of relative permeability and relative permittivity on the behavior of a miniaturized antenna. The proposed design is combination of hemi-spherical antenna cavity and a hemi-spherical Dielectric Resonator substance; hence this radiating structure is called as hemi-spherical dielectric resonator antenna (HSDRA). Using the DRA, a volumetric source improves the radiation power factor of the radiating slot.[1] The antenna is designed and simulated on HFSS to effectively observe its far-field and near field radiation pattern and different characteristic parameters of antenna system such as gain, VSWR, return loss. The radiation patterns and fields including different characteristics are studied at 3.75 GHz.

Investigation of Material Removal Characteristics in EDM of Nonconductive ZrO2 Ceramic

The use of nonconductive ceramic materials is increasing rapidly in industrial and engineering applications due to its high hardness, low thermal conductivity, and resistance to oxidation. Machining operations for fabricating structures from nonconductive ceramic materials are difficult and most of the traditional machining techniques are not applicable because of its high brittleness. Electro discharge machining (EDM) technique, a noncontact machining process, is applied for processing nonconductive ceramic ZrO2 using assisting electrode. In this technique, pyrolytic carbon layer on the ceramic surface formed by the cracked carbon from the carbonic dielectric, plays the key role for continuous EDM. The formation of pyrolytic carbon and its stability depends upon the input power, workpiece material, tool electrode material, dielectric substance, polarity, and discharge duration. In this study, experiments were done to investigate the effect of input power on the material removal rate (MRR) and to explore the material removal mechanism. The experimental results show that the material is removed in EDM of nonconductive ZrO2 ceramic mostly by spalling and it increases with the increase of input power.