Parallel-plate Configuration Research Articles

Field emission properties of nitrogen incorporated DLC films prepared by electrodeposition

Nitrogen incorporated diamond-like carbon (DLC:N) films with different N content were deposited on Si(1 0 0) substrates by electrolysis of urea/methanol organic solution with different mole ratios under a constant voltage of 600 V. Analysis by Raman spectrometry and X-ray photoelectron spectrometry (XPS) shows that N is incorporated into the DLC films by sp 3 C–N and sp 2 C N bonds and induces graphitization of the films. The electronic field emission properties of these films have been studied using a parallel plate configuration, and the dependence on N content investigated. The turn-on field ( E c) is lowered with increasing N content, and there is a simultaneous rise in the field emission current densities under the electric field of 23.5 V/μm. Enhancement in field emission is attributed to the donor activity of nitrogen and the field enhancement effect of sp 2 clusters.

Cell Motion Model for Moving Dielectrophoresis

Moving dielectrophoresis has been recently developed by the authors as an alternative method to achieve simultaneous cell fractionation and transportation. With an array of independently excitable microelectrodes, this method generates a moving electric field to sequentially fractionate and transport cells across a microchannel. Due to the peculiarity of this method, the motion of the cells is unsteady and there are interesting and distinct differences between cells experiencing positive or negative dielectrophoresis. For a proper understanding and design of a microdevice utilizing this methodology, this study presents a model for the equation of motion for a polarized cell and its unsteady motion under moving dielectrophoresis. The model considers the basic module to generate a moving electric field, where there is a finite-width top electrode and an infinite-width bottom electrode, in a parallel-plate configuration. The forces considered include dielectrophoretic force, fluid drag, buoyancy, and gravitational force. These forces are modeled as equivalent point forces acting at the center of mass of the cell. A parallel-plate wall correction factor is employed to account for the effect of the large cell size to microchannel height ratio. Various parameters are examined including the initial position of the cell relative to the electrodes, cell's Clausius-Mossotti factor, cell size, applied voltage, electrode width, interelectrode gap, microchannel height, number of energized electrodes, and types of electrode configurations. Reasonable agreements were obtained between simulated and experimental results. As the solution of the unsteady motion is rather tedious, a MATLAB algorithm, with all the associated files, for the prediction of the cell trajectory, is available on request.

Effect of particle size dispersion on granular lubrication regimes

This article is devoted to the study of granular flow regimes undergoing shear in a parallel-plate configuration with particular interest in granule dispersion. Both experimental and numerical investigations are carried out. Experimental investigations are conducted in a shear cell consisting of two parallel discs that contain the granular media. One disc is fixed, whereas the other rotates to shear the media. A normal force is imposed, and the gap is measured. Numerical investigations are based on simulations that use discrete element method (DEM), which allows local investigation of the flow across the gap. This article focuses on the effect of a mixture of size to the flow regime observed when shear velocity increases. The imposed loads on the granular media are weak, and thus, it is expected that the granular regime will pass from a quasi-static regime to a kinetic one. It is found that the granule mixture has a major influence on the normal displacement (lift) between the discs, whereas the effect on the measured friction coefficient is less pronounced. Numerical investigations are in agreement with experimental measurements, provided that the important parameters such as the local contact condition, i.e. the coefficient of restitution and the local friction coefficient, are properly specified. For the simulations presented, the coefficient of restitution and local coefficient of friction are 0.9 and 0.3, respectively. The results of an extensive set of simulations are presented to study the effect of change in the local friction coefficient and coefficient of restitution. For a low value of restitution coefficient (0.7), it is shown that all the media thickness is sheared when the proportion of large granules tends to 50 per cent, although only one part of the whole thickness is sheared when the proportion of large granules tends to 0. For a higher value of restitution coefficient (0.9), the transition from dense to kinetic regime occurs for a higher shear velocity when the granule sizes are the same. In this case, a high level of vibration is observed at low velocities both experimentally and numerically. Numerical simulations confirm that these vibrations can be analysed as stick—slip phenomena. Results show that the coefficient of restitution has no effect at low speeds (dense regime), but has a pronounced effect at high speeds (kinetic regime). This result is in accordance with the previous studies. The local coefficient of friction has a high effect when it varies from 0 to 0.3 and low effect when it is above 0.3. This also confirms previous studies.

Transient Couette flow in a rotating non-Darcian porous medium parallel plate configuration: network simulation method solutions

The transient, viscous, incompressible, hydrodynamic Couette flow in a rotating porous medium channel is studied in this paper. The channel comprises a pair of infinitely long parallel plates which rotate with uniform angular velocity about an axis normal to the plates. The porous medium is simulated using a Darcy–Forchheimer drag force model which includes both bulk matrix porous drag (dominant at low Reynolds numbers) and second order inertial impedance (dominant at higher Reynolds numbers). The two-dimensional Navier–Stokes equations are reduced to a (z*, t*) coordinate system incorporating Coriolis terms, and appropriate initial and boundary conditions are prescribed. Separate porous drag body force terms are incorporated in both the primary and secondary flow momentum equations. Using a set of transformations, the model is rendered dimensionless and shown to be dictated by the Ekman number, Forchheimer number, Darcy number and Reynolds number in a (z, t) coordinate system. Numerical solutions are obtained for the transformed model using the Network Simulation Method. The influence of the hydrodynamic parameters are computed graphically and also the interaction of parameters on the velocity fields is discussed at length. Excellent agreement is found with earlier non-porous flow studies. The analysis has important applications in geophysics and also chemical engineering systems.

A Biomechanical Comparison of Plate Configuration in Distal Humerus Fractures

Our aim was to test the hypothesis that two plates placed parallel to each other are stronger and stiffer than plates placed perpendicular to each other for fixation of a distal humerus fracture model. We created an artificial distal humeral fracture model by osteotomizing two groups of identical epoxy resin humera. Screw and plate constructs were built to mimic osteosynthesis. In the first group, 3.5-mm reconstruction plates were placed parallel to each other along each of the medial and lateral supracondylar ridges. In the second group, 3.5-mm reconstruction plates were placed perpendicular to each other with a medial supracondylar ridge plate and a posterolateral plate. Stiffness and strength data of the two constructs were obtained by testing to failure with sagittal plane bending forces. The parallel plate group (n = 7) had a mean stiffness of 214.9 +/- 43.3 N/mm and a mean strength of 304.4 +/- 63.5 N. The perpendicular plate group (n = 8) had a mean stiffness of 138.3 +/- 44.6 N/mm and a mean strength of 214.9 +/- 43.3 N. These differences were significant (Student's t test, P < 0.05). As theoretically expected, a parallel plate configuration is significantly stronger and stiffer than a perpendicular plate configuration when subjected to sagittal bending forces in a distal humerus fracture model.

Alignment of Carbon Nanocoils in Polymer Matrix Using Dielectrophoresis

Vertical alignment of carbon nanocoils (CNCs) relative to a substrate in a polymer matrix has been demonstrated using dielectrophoresis under the parallel-plate electrode configuration. The CNCs were aligned toward the electric field with an AC frequency of 100 kHz and form a small aggregation of a CNC chain by the dipolar interaction of CNCs even under parallel-plate electrodes. This phenomenon also induces an increase in optical transmittance in the visible region and the elimination of the wavelength dependence of the transmittance.

Research on a Folded Blumlein Line Using Kapton Film as Dielectrics

In this project, a Blumlein line with a folded parallel-plates configuration using Kapton film as dielectrics was investigated. The characteristic parameters of this Blumlein line were analysed theoretically. The electric field distributions under different inner radii of the folded part were simulated. The output waveforms on the match load were also simulated by means of an equivalent electric circuit. According to the results of the theoretecal analysis and simulation, a Blumlein line with the folded parallel-plates configuration with an output voltage of 500 kV, a pulse duration of 100 ns, and a characteristic impedance of 4.773 ω was designed and manufactured. The experimental results properly demonstrated the wave transmitting process in the Blumlein line, and provided the voltage waveform of 500 kV and the current waveform of 50 kA with a pulse duration of 150 ns. Some engineering problems such as the edge electric breakdown and measuring precision by a resistance divider were revealed, which must be solved in future work to produce a more compact transmission line.

A novel linearly tunable butterfly-shape MEMS capacitor

A new MEMS tunable capacitor with linear capacitance–voltage (C–V) response is introduced. The design is developed based on a parallel-plate configuration and uses the structural lumped flexibility and geometry optimization to obtain a linear response. The moving electrode is divided into two segments connected to one another by a torsional spring. There are extra beams located between the two plates, which constrain the displacement of the moving plate. The resulting nonlinear structural rigidity provides the design with higher tunability than the parallel-plate ones. Furthermore, because the plate's displacement is controlled, the shape of C–V curve changes in such a way that high linearity is achieved. The proposed design can be fabricated by a three-structural-layer process such as PolyMUMPs. The results of analytical solution and experimental measurements verify that the new capacitor can produce tunability of over 100% with high linearity. The introduced design methodology can further be extended to flexible plates and beams to obtain smooth C–V curves.

DIELECTRIC CHARACTERISTICS OF BST/BZT/BST MULTILAYER

Ba 0.6 Sr 0.4 TiO 3 (BST) and Ba 0.6 Sr 0.4 TiO 3/ Ba ( Zr 0.2 Ti 0.8) O 3/ Ba 0.6 Sr 0.4 TiO 3 (BST/BZT/BST) multilayer (ML) films were prepared by pulsed laser deposition on the LaNiO 3-coated LaAlO 3 substrate. X-ray diffraction analysis revealed that the two kinds of films could be epitaxially grown in pure single-oriented perovskite phases and atomic force microscopy showed that the grain size of ML films was similar to BST films in size. The dielectric properties of the BST and ML thin films were measured at 10 kHz and 300 K with a parallel-plate capacitor configuration. The results revealed that the dielectric tunability for ML films slightly decreased, while the loss decreased synchronously. The figure-of-merit factor value increases from 17.32 for BST films to 42.14 for ML films under an applied electric field of 300 kV/cm. The leakage current density of the BST thin films at a positive bias field of 300 kV/cm decreases from 3.76 × 10-6 to 1.25 × 10-7 A/cm2 for ML films. This work clearly reveals the highly promising potential of BST/BZT/BST multilayer films compared with BST films for application in tunable microwave devices.

RuO 2 doped SnO 2 nanobipyramids on Si (100) as a field emitter

Thin films of RuO 2: SnO 2 nanobipyramids have been grown on silicon (100) flat substrates, and their field emission behavior has been investigated. The field emission experiments have been performed in parallel plate configuration. In this experiment, the onset field for 0.1 μA/cm 2 current density has been found to be 0.2 V/μm. The Fowler–Nordheim plot shows non-linear nature typical that of a semiconductor. The field enhancement factor has been estimated to be 35,600 cm − 1 , indicating that the field emission originates from the nanometric features of the emitter. The current stability recorded at a preset value of 1 μA is observed to be good. Our field emission results on RuO 2: SnO 2 nanobipyramids indicate that, RuO 2: SnO 2 nanobipyramids are a potential candidate for futuristic field emission based devices.

電気集じん装置におけるナノ粒子の集じん率向上

Electrostatic precipitators are used in decontaminating polluted gases in expressway tunnels in order to improve both driver safety and the environment around the tunnels. A conventional electrostatic precipitator has high collection efficiency but is still needed to improve collection efficiency for nano-particles smaller than 0.1 μm. The experiments carried out in this study have focused on improving nano-particle collection efficiency without using additional energy. The experimental electrostatic precipitator was a two-stage type consisting of a pre-charger and a collector. The collector had a parallel-plates configuration, including a grounded electrode and a high voltage electrode. A hole-punched stainless plate was used as the high voltage electrode in order to improve nano-particle collection efficiency. The collection efficiency as a function of the particle diameter was studied. As a result, the nano-particle collection efficiency on the ESP with the hole-punched high voltage electrode was significantly improved. In the case of certain number of hole, the nano-particle collection efficiency increases with increasing the punched hole diameter. In the case of the constant of aperture rate, the nano-particle collection efficiency increases with decreasing the punched hole diameter. This effect is probably due to increasing the electric field intensity near the hole edges of the hole punched electrode.

Effect of Electrode Thickness for Reducing Ozone Generation in Electrostatic Precipitator

The influence of electrode thickness on ozone generation in the electrostatic precipitator(ESP) was experimentally investigated. The experimental ESP was two-stage-type which composed of a prechager, followed by the collecting section. The precharger consists of high voltage electrodes and grounded electrodes. The thickness of high voltage electrode was selected as 0.1, 0.2, 0.5 and 0.8 mm and the grounded electrodes was 1.0mm. The collecting electrode section had parallel-plates configuration. The gases emitted from the diesel engine were diluted with air and introduced into ESP in order to measure the particle counts were attributed to saw type electrode. In the present study, the electric field distribution was caluculated using the commercial coad called “Ansys”. The relationship between the ozone generation and collection efficiency was investigated. As a result, the ozone concentration decreased with decreasing the electrode thickness maintaining the same collection efficiency. This result is attributed to decreasing the dissociation area of O2 in the vicinity of the electrodes.

FERROELECTRIC VARACTOR SHUNT SWITCHES FOR BROADBAND PHASE CONTROL APPLICATIONS

ABSTRACT Our research group has recently demonstrated the operation of ferroelectric varactor shunt switches. The device operation is based on the nonlinear dielectric tunability of a barium strontium titanate (BST 60/40) thin-film sandwiched between two metal layers in a parallel plate configuration. A 4:1 change in the varactor capacitance has been achieved with a bias voltage < 10 V, through optimization of the nanostructured BST thin-film fabrication process on high resistivity Si substrates. In this work, we investigated the varactor shunt switches for broadband phase control applications. Varactor shunt switches and cascaded shunt switches were used for phase control circuits, due to the large phase shifts possible as a result of the dc bias dependent tunability of the varactor. The differential phase shift can be defined as the difference between the phase of S21 at a dc bias voltage and zero-bias. The measured differential phase shift for a single varactor shunt switch was 30 ± 2 degrees between 8 and 26 GHz at 8 V dc bias. A cascaded varactor shunt switch resulted in a differential phase shift of 110 degrees ± 10 degrees over the bandwidth of 20 and 31 GHz.

Steady-state polarization measurements of lithium insertion electrodes for high-power lithium-ion batteries

Steady-state polarization measurements of lithium titanium oxide (LTO; Li[Li1/3Ti5/3]O4) were carried out using the 0-V lithium-ion cells consisting of two identical LTO-electrodes with a parallel-plate symmetrical electrode configuration. The sinusoidal voltage with the peak amplitude of 1.0 V was imposed at 0.1 Hz upon the 0-V cells and the current response was measured as a function of time. The steady-state polarization, obtained by plotting the current versus applied voltage, was linear in current up to approximately 60 mA cm−2 or 4 A g−1 based on the LTO weight and suggested the resistance polarization only for the lithium insertion electrode of the LTO. The method was also applied to lithium aluminum manganese oxide (LAMO; Li[Li0.1Al0.1Mn1.8]O4) and the resistance polarization of the LAMO-electrode was determined for currents up to approximately 25 mA cm−2 or 2 A g−1 based on the LAMO weight. The validity of the results was examined for the polarization measurements of the 2.5-V lithium-ion battery consisting of LTO and LAMO, and the significance of the polarization measurements of lithium insertion electrodes for high-power applications was discussed.

Fan-Beam Millimeter-Wave Antenna Design Based on the Cylindrical Luneberg Lens

A new design of two-dimensional cylindrical Luneberg lens is introduced based on TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode propagation between parallel plates, with special focus on ease of manufacturing. The parallel plates are partially filled with low cost polymer material (Rexolite epsiv <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.54) to match Luneberg's law. A planar linear tapered slot antenna (LTSA) is inserted into the air region between the parallel plates at the edge of the Luneberg lens as a feed antenna, with fine positioning to the focal point of the Luneberg lens to optimize the antenna system performance. A combined ray-optics/diffraction method is used to obtain the radiation pattern of the system and results are compared with predictions of a time domain numerical solver. Measurements done on a 10-cm Luneberg lens designed for operation at 30 GHz agree very well with predictions. For this prototype, 3-dB E- and if-plane beamwidths of 6.6deg and 54deg respectively were obtained, and the sidelobe level in the E-plane was -17.7-dB. Although the parallel plate configuration should lead to a narrow band design due to the dispersion characteristics of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode, the measurement results demonstrate broadband characteristics with radiation efficiencies varying between 43% and 72% over the tested frequency band of 26.5-37 GHz. The designed cylindrical Luneberg lens can be used to launch multiple beams by implementing an arc array of planar LTSA elements at the periphery of the lens, and can be easily extended to higher mm-wave frequencies.

Electrical behavior of Y-doped Ba0.6Sr0.4TiO3 thin films

Ba0.6Sr0.4TiO3 (BST) and 1.5 at% Y-doped Ba0.6Sr0.4TiO3 (Y-BST) thin films have been deposited on single-crystal (100) oriented LaAlO3 substrates using pulsed-laser deposition technique (PLD), respectively. X-ray diffraction (XRD) scanning revealed that the two kinds of films could be epitaxially grown in pure single-oriented perovskite phases, but Y-BST thin films showed an enhanced crystallization effect. The dielectric properties of the pure and Y-BST thin films were measured at 10 kHz and 300 K with a parallel-plate capacitor configuration. The results revealed that the addition of Y as an acceptor doping is very effective to increase dielectric tunability, and to reduce leakage current of BST thin films. The figure-of-merit (FOM) factor value increases from 17.32 for BST to 25.84 for Y-BST under an applied electric field of 300 kV/cm. The leakage current density of the BST thin films at a negative bias field of 300 kV/cm decreases from 2.45 × 10−4 A/cm2 to 1.55 × 10−6 A/cm2 by Y doping. The obtained results indicated that the Y-doped BST thin film is a promising candidate material for tunable microwave devices.

The use of camphor-grown carbon nanotube array as an efficient field emitter

Three-dimensional growth of well-aligned high-purity multiwall carbon nanotubes (CNTs) is achieved on silicon, nickel-coated silicon and cobalt-coated silicon substrates by thermal decomposition of a botanical carbon source, camphor, with different catalyst concentrations. Field emission study of as-grown nanotubes in a parallel-plate diode configuration suggests them to be an efficient emitter with a turn-on field of ∼1 V/μm (for 10 μA/cm 2) and a threshold field of ∼4 V/μm (for 10 mA/cm 2). Maximum current density lies in a range of 20–30 mA/cm 2 at 5.6 V/μm with significant reversibility. Prolonged stability test of camphor-grown CNT emitters suggests a life time of ∼5 months under continuous operation. A new feature, metal-assisted electron emission from CNTs, has been addressed. Isolated nanotubes used as a cold cathode in a field emission microscope reveal the pentagonal emission sites and hence the atomic structure of the nanotube tips.

Field electron emission of double walled carbon nanotube film prepared by drop casting method

Thick films of double walled carbon nanotubes (DWCN) were deposited on indium-tin-oxide (ITO) coated glass substrates by drop casting method and were studied for their field electron emission property in a parallel plate configuration using bare ITO coated glass as counter electrode. They show excellent field electron emission property with low turn-on-field of about 0.8 V/μm and threshold field of about 1.8 V/μm. Field enhancement factor calculated from the non-saturated region of the FN plot is about 1715. Field electron emission current was observed to be stable up to 3000 min, indicating thereby that DWCNs are excellent electron emitters with appreciable stable performance.

Multipactor in a Waveguide Iris

Microwave discharge in vacuum in a waveguide iris is analyzed under the approximation of a uniform electric field over the finite width of the iris. The analysis shows that the random electron drift due to the initial velocity of the secondary electrons leads to a significantly increased multipactor threshold as compared to the result predicted by the (infinitely wide) parallel plate configuration. This increase is determined by the value of the iris height-to-length ratio. For each fixed value of this ratio, the multipactor susceptibility charts can be generated in the traditional engineering units. An increase in this ratio results in a similar shrinkage of each of the multipactor resonance zones. Within each particular zone, the effect is more pronounced for the lower RF frequencies due to the longer transit time between the walls of the iris

High dielectric constant polyaniline/epoxy composites via in situ polymerization for embedded capacitor applications

Polyaniline (PANI)/epoxy composites with different polyaniline (PANI) contents were successfully developed by in situ polymerization of aniline salt protonated with camphorsulfonic acid within epoxy matrices and fully characterized. The influence of PANI loading levels on various properties was also explored. Dielectric and electrical properties of PANI/epoxy composites were studied for samples in parallel plate configuration. A PANI/epoxy composite prepared in this fashion reached a high dielectric constant close to 3000, a dielectric loss tangent less than 0.5 at room temperature and 10 kHz. The hardener type was also found as a critical parameter for the dielectric properties of PANI/epoxy composites. The distribution of the conductive element clusters within the polymer matrix was studied by SEM and correlated to the dielectric behavior of the composite films.