Electrical Resistance Ratio Research Articles

Magneto-transport study of magnetite (Fe3O4) nanoparticles between Au nanogap electrodes on surface-oxidized Si substrate

We have studied the magneto-transport of magnetite (Fe3O4) nanoparticles (MNPs) between Au nanogap electrodes (ANGEs) on surface-oxidized Si substrate. The MNP sizes are approximately 40nm and the 100nm thick magnetite thin film (which is formed of the MNP aggregation) was prepared between and around the ANGEs by use of the RF reactive magnetron sputtering method. The distance between the ANGEs and the bridge width of the ANGEs are approximately 50nm and 1.5μm, respectively. The ANGEs were produced by the tilted-angle-deposition method. The optical microscope, scanning electron microscope and atomic force microscope were used to observe the sample surface structure and morphology. To investigate the crystal structure and crystallinity of the MNPs, the X-ray diffraction measurement was performed. The electrical resistance and magneto-resistance ratio of the MNPs between the ANGEs were measured as a function of temperature. The magneto-transport mechanism is discussed on the basis of the spin dependent transport.

Phase Angle Measurement in Healthy Human Subjects through Bio-Impedance Analysis.

Bioelectrical impedance is the measure of impedance of the body. Impedance consists of electric resistance and reactance. Phase angle (PA) is the tan value of the ratio of reactance versus electric resistance. PA depends on cell membrane integrity and on body cell mass. There exists a correlation between PA values and body cell mass. The objective of this study was to compare the PA values of normal individuals and their anthropometric measurements. Anthropometric measurements, Bioelectrical impedance analysis and PA measurements were done using Bodystat Quadscan 4000 machine on 42 healthy subjects between the age group of 18 to 50 yrs at a private hospital, Bangalore, Karnataka, India for eight months. Kolmogrov-Smirnov and Pearson's correlation tests were used for data analysis. The PA values were 7.321.17º in healthy subjects. PA values were significantly positively correlated with body mass index (BMI) (r= 0.011, P<0.001). The phase angle values for males and females were 7.43±0.98º and 7.05±1.1.58º, respectively. PA values positively correlated with BMI indicating the nutritional status of the study group. PA values were similar to the values to found in other studies.

Thermoelectric Power Generator Design for Maximum Power: It’s All About ZT

There is a significant amount of literature that discusses thermoelectric power generator (TEG) design, but much of it overly simplifies the design space and therefore the results have limited use in designing real-life systems. This paper develops a more comprehensive model of the thermal and electrical interactions of a TEG in a system with known hot-side and cold-side thermal resistances and corresponding constant system temperature differential. Two design scenarios are investigated for common TEG system applications. In one method, the power from a TEG is maximized for a given electrical load, simulating a case where the TEG is electrically in series with a known load such as a fan. In the second design scenario, the power from a TEG is maximized for a given electrical load resistance ratio, n (the ratio between the external load resistance and the internal TEG resistance), simulating an application where the TEG is electrically in series with a load-matching converter. An interesting conclusion from this work is that, in the first design scenario, the electrical load resistance ratio, n, that maximizes TEG power occurs at \( \sqrt {1 + ZT} \) (where ZT is the thermoelectric figure of merit) instead of 1 as reported previously in literature. Equally interesting is that, if you define an analogous thermal resistance ratio, m′ (representing the ratio between the TEG thermal resistance at open-circuit conditions and the system thermal resistance), the maximum power in both design scenarios occurs at \( \sqrt {1 + ZT} \) instead of the commonly cited value of 1. Furthermore, results are presented for real-life designs that incorporate electrical and thermal losses common to realistic TEG systems such as electrical contact resistance and thermal bypass around the TEG due to sealing.

Polarity-dependent reversible resistance switching in as-deposited AgInSbTe phase change film

Abstract The electrical properties of a nanoscale prototype capacitor-like cell structure using an amorphous Ag8In14Sb55Te23 (AIST) as the active material were investigated. A polarity-dependent reversible switching effect which is different from the amorphous–crystalline phase transformation has been observed. The reversible resistance switching between a high resistance state (HRS) and low resistance state (LRS) was induced by bias amplitude and polarity. The electrical resistance ratio of HRS/LRS was ∼10:1. The AIST phase change material is shown to be very promising for multi-state data storage applications.

Fabrication of Composite Material Using Bagasse Ash and Carbonized Bagasse by Spark Plasma Sintering

Bagasse was obtained after squeezing the sugar cane. In sugar factories, bagasse is burned as fuel for boiler machines. Therefore, there remains lots of bagasse ash every year. Bagasse ash including silica and carbonized bagasse were considered as ceramics material, and mechanical properties of composite using bagasse ash and carbonized bagasse fabricated by spark plasma sintering were investigated. By changing the content ratio between bagasse ash and carbonized bagasse and carbonized bagasse fiber length, the bending strength and flexural modulus were compared with each other. By utilizing the phenomenon that bagasse ash has a melting temperature over 1323K, the sintering temperature of composite was performed at 1423K. The bending strength with content weight ratio of bagasse ash and carbonized bagasse of 1:2 showed the high value of 66MPa. Especially, the composite using carbonized long bagasse fiber showed the highest value for bending strength and flexural modulus. The electrical resistance ratios of composites of 1:2 and 1:3 showed the minimum values and constant trend. Finally, the electrical resistance ratio of composite became about same value as carbonized body only.

Thermal-Treated Pitches as Binders for TiB2/C Composite Cathodes

The effect of thermal treatment on the microstructure and properties of pitches and thermal-treated, pitch-based TiB2/C composite cathodes were investigated. Thermal treatments were performed at 473 K, 523 K, 573 K, 623 K, and 673 K (200 °C, 250 °C, 300 °C, 350 °C, and 400 °C), respectively. The results show that the aromaticity of the treated pitches increases with an increasing thermal treatment temperature, and subsequently, the coking value and quinoline-insoluble (QI) content increase from 60.62 wt pct to 79.09 wt. pct and from 8.97 wt pct to 32.54 wt pct when the treatment temperature increases from 473 K to 623 K (200 °C to 350 °C). The volume fraction of coalesced mesophase in semicoke decreases with an increasing thermal treatment temperature, and after 673 K (400 °C) is reached, the coalesced mesophase is almost invisible. The bulk density and compressive strength of modified pitch-based cathodes increase with an increasing thermal treatment temperature from 2.24 g cm−3 to 2.39 g cm−3 and from 24.21 MPa to 54.85 MPa, whereas open porosity decreases from 34.62 pct to 27.06 pct. Both electrical resistivity and electrolysis expansion ratio first decrease and then increase with an increasing thermal treatment temperature, and the lowest values (45.63 μΩ m and 0.65 pct) are achieved at 573 K (300 °C). Compared with those of the parent pitch-based cathode, the properties of the modified pitch-based cathodes had improved significantly. The mechanisms of the improvements are discussed in the text.

Structural and transport properties of SrRuO3 thin films grown by MOCVD on (001) SrTiO3 substrates: The role of built-in strain and extra phases

Abstract Pure SrRuO3 (SRO) thin films and SRO thin films containing the extra metallic phases Ru, RuO2 and Sr3Ru2O7 were deposited by MOCVD on (0 0 1) SrTiO3 substrates under different conditions (Ru/Sr and Ar/O2 ratio in the gas phase, substrate temperature, supersaturation). The single-phase compressively-strained SRO film is of high structural quality and shows a ferromagnetic transition at a suppressed Curie temperature (Tc) of about 142 K and low electrical resistivity (230 μΩ cm). Under certain deposition conditions Ru and RuO2 extra phases form leading to a reduced room temperature resistivity of 100 μΩ cm. On the other hand, the presence of Sr3Ru2O7 increases the resistivity to 385 μΩ cm. We have observed that the existence of the extra phases caused a slight shift of Tc towards the bulk value, while relaxation of the lattice strain resulted in increase of Tc to 160 K. The deviation from the stoichiometric composition in films with extra phases is also confirmed by the residual electrical resistivity ratio. On the other hand, the pure SRO films, the compressively strained and the plastically relaxed exhibit a stoichiometric ratio.

Crystallization behaviors of an ultra-thin Ga–Sb film

Upon decreasing ultra-thin Ga16Sb84 films from 10 to 3 nm, the exponential increase in crystallization temperature and electrical resistance ratio are attributed to increased specific interface-energies and inhomogeneous interfacial strain at the interfaces. The specific interface-energies and strain also stabilize the Sb(Ga) phase and suppress phase-separation of the GaSb phase.

Electrical breakdown in high‐density polyethylene/graphite nanosheets conductive composites

AbstractThe electrical breakdown is investigated in high‐density polyethylene/graphite nanosheets (HDPE/GNs) conductive composites. A sample suffers electrical breakdown when the applied field exceeds the critical electrical breakdown field below which the sample reaches a stable state. It is found that the ratio of the critical electrical breakdown resistance to the linear resistance assumes a fixed value Y, which is found to be about 1.30 in HDPE/GNs conductive composites. The value Y is independent of GNs' content, sample size, breakdown cycle, but depends on the property of GNs. The critical breakdown field Eb scales with the resistance R0 as $E_{\rm b}\sim R_0^{y_{\rm b}}$ with the exponent yb = 0.46 ± 0.02, which is close to the value predicted in mean‐field theory but higher than the value given by the singly connected bonds networks. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 576–582, 2009

A study of the engineering properties of waste LCD glass applied to controlled low strength materials concrete

The Taiwan production of TFT-LCD front-panels comprises a global share of 39.2%, the highest production rate in the world. Inevitably, a large amount of waste is produced in the fabrication process. The objective of this research is to recycle waste LCD glasses in the production of controlled low strength material (CLSM), which has been used extensively for pipeline refill and pavement foundations world-wide. The glass replaces sand in ratios of 0%, 10%, 20% and 30% in order to produce CLSM specimens with high silicon contents. The specimens are then tested for their compressive strength, supersonic strength, electrical resistivity, and permeability ratio. Results show a slump range up to 200 mm and a slump flow range up to 410 mm. For the general type CLSM, the setting time for the 10% glass–sand replacement is the shortest while that for the 30% replacement is the longest. After a 28-day aging, the compressive strength is 2.87–2.40 MPa. The ultrasonic pulse velocity is between 1267–3200 m/s and is found to be faster for the early strong type. The electrical resistivity after 28 days for the general type is 6.7–8.2 kΩ-cm and doubles for the early strong type. The permeability ratio is 1.03–2.02% for the normal and 0.35–0.75% for the early strong type. It was observed that adding waste LCD glass into CLSM meets engineering property requirements including high fluidity, low strength, high permeability, and low electrical resistivity, ushering in a creative application of waste glass.

A Study on the Application of Ni-Ti Shape Memory Alloy as a Sensor

When the shape memory alloy(SMA) completely consists of austenite phase that shows the super-elastic property, if the external energies, such as stress, crack, propagation and lamination, etc. are increased in this alloy until the austenite phase was transformed into the martensite phase, they are enough to change the mean free path of electrons correlated with the electrical resistivity of materials in the microscopic point of view. On the basis of the above concept, we carried out the feasible study for SMA wire as a strain sensor using the super-elastic property of SMA. The SMA wires of diameter 41 ㎛ were utilized for a sensor material. The relationship between electrical resistivity and tensile properties of the Ni-Ti based SMA wires during tensile loading was investigated. Since the strain is very sensitive to the minute change of electrical resistance of SMA wire, it is possible to use the SMA wire as a sensor of such physical quantities. In the study, the possibility for the application of Ni-Ti SMA wire as a sensor was investigated. The sensing system was able to measure the strain up to 6 % with 0.22 % measuring error. The sensitivity described by the ratio of electrical resistivity showed 0.00005.

Magnetohydrodynamics of trickle bed reactors: Mechanistic model, experimental validation and simulations

An isothermal one-dimensional two-fluid magnetohydrodynamic (MHD) model based on the volume average mass, charge, and momentum balance equations and the Maxwell's equations coupled via the Lorentz force and Ohm's law was developed for the prediction of the two-phase pressure drop and the total liquid holdup in trickle bed reactors experiencing a homogeneous transverse magnetic field. The slit model approximation and the drift flux Kozeny–Carman approach were extended for the derivation of appropriate drag force closures required in the conservation equations, respectively, in the trickle flow regime and in the dispersed bubble flow regime. The expression of liquid–solid drag was adapted to take into account the influence of the magnetic field on the laminar term and the damping of turbulent/inertial term via the Hartman number and the liquid-to-bed electrical resistance ratio. Associating these drag forces with the proposed model resulted in a fully predictive MHD approach for trickle beds. Several model limiting formulations were derived for an electrically conducting fluid flowing downwards with a stagnant gas (pure trickle flow) to yield liquid holdup, as well as for single-phase upward conditions to yield the single-phase pressure drops.

Magnetocrystalline anisotropy in a single crystal ofCeNiGe2

We report measurements on single crystals of orthorhombic CeNiGe2, which is found to exhibit highly anisotropic magnetic and transport properties. The magnetization ratio M(H//b)/M(H^b) at 2 K is observed to be about 18 at 4 T and the electrical resistivity ratio r//b/r^b is about 70 at room temperature. It is confirmed that CeNiGe2 undergoes two-step antiferromagnetic transition at 4 and 3 K, as reported for polycrystalline samples. The application of magnetic field along the b axis (the easy magnetization axis) stabilizes a ferromagnetic correlation between the Ce ions and enhances the hopping of carriers. This results in large negative magnetoresistance along the b axis.

Electrical resistivity and magnetism of Fe/Si multilayers prepared by oblique incidence evaporation

We discussed the origin of the uniaxial magnetic anisotropy of the Fe/Si multilayered films prepared by varying oblique evaporation angle from the view of electric resistance. The tendency in the incidence angle dependence of the uniaxial magnetic anisotropy is in agreement with that of the angle dependence of the electric resistance ratio. The origin of the magnetic anisotropy seems to be due to anisotropic arrangement of atoms in the film.

Electric Resistivity and Magnetoanisotropy in Fe/Si Evaporated Multilayers

Uniaxial magnetic anisotropy of the films can be induced in ferromagnetic thin films evaporated at oblique incidence even in absence of a magnetic field. The induced uniaxial magnetic anisotropy was remarkable in multilayered films formed varying the oblique incidence angle, and the easy axis of the anisotropy is along the perpendicular direction of the incidence of evaporation. In this paper, we have discussed the origin of the uniaxial magnetic anisotropy of Fe/Si multilayered films, prepared by varying the oblique evaporation angle, from the viewpoint of electric resistance. The tendency in the incidence angle dependence of uniaxial magnetic anisotropy is in agreement with that of the angle dependence of the electric resistance ratio. The origin of the uniaxial magnetic anisotropy of thin films induced by oblique angle deposition is due to anisotropic arrangement of atoms in the films.

Electric Properties of Conducting Composite from Poly(ethylene oxide) and Poly(ethylene oxide)-Grafted Carbon Black in Solvent Vapor

A conducting composite from high molecular weight poly(ethylene oxide)(PEO) and low molecular weight PEO-grafted carbon black(CB) was prepared. The electric resistance of the composite in dry air and chloroform vapor was examined. The effects of many factors, such as CB content, CB type and its dispersion in composite, and thickness of the composite film, on the ratio of electric resistance of the composite in dry air (R0) and in chloroform vapor (R), defined as responsiveness (R/R0) of the conducting composite, were investigated. For both CB (Porousblack and Asahi 60H black) used in this study, at CB content of 20—50 wt%, the responsiveness is high over 104 time. In the case of low CB content, the responsiveness is lower than 0.1. To explain the responsiveness of the composite for high and low CB content, two conduction mechanisms were proposed. To clarify the relationship between responsiveness and amount of vapor absorption, a method to simultaneously determine the resistance and vapor absorption amount of the composite was developed.

Magnetic and magneto-resistive properties of Bi-doped (LaCa)MnO3

Bi-doped lanthanum manganites with chemical compositions of BixLa0.67 − xCa0.33MnO3 (x = 0, 0.04, 0.1, 0.2) have been prepared by the standard ceramic process. The crystallinity and microstructures of the samples have been investigated by x-ray diffractometry and optical microscopy, respectively. The magnetic and magneto-resistive properties of the samples have been measured by vibrating sample magnetometery and van der Pauw method, respectively, at the temperatures ranging 100 K–300 K with applied magnetic field of 0.4–0.5 T. Good crystallinity and high Curie temperature (275 K) have been obtained for the Bi-doped samples with small dosage (x = 0.04, 0.1) even they were sintered at 1200°C, which is about 200°C lower than normal sintering temperature of undoped sample. The Bi-doped samples with the small dosage showed lower relative electrical resistivity and higher magneto-resistive ratio compared to the undoped sample in the most temperatures measured. The Bi-doped samples also exhibited large magneto-resistive ratio (maximum of 15% for x = 0.1) at room temperature even under a weak magnetic field of 0.4 T.

Heterophase polydomain structure and metal-semiconductor phase transition in vanadium dioxide thin films deposited on (1010) sapphire

Vanadium dioxide (VO2) thin films deposited on (1010) sapphire are composed of two mixed monoclinic phases, namely M1 and M2. The M1 phase is unstable because of the existence of a larger misfit strain in the (102) VO2 film. The reduction of misfit strain in the film favours the formation of the M2 phase. The X-ray diffraction and pole figure results show that both M1 and M2 phases are well aligned with the substrate and both contain twinned structures. Therefore, the microstructure of the film can be regarded as being a transversely modulated heterophase polydomain. A higher electrical resistivity ratio of the semiconductor phase to the metallic phase (rhos/rhom) can be achieved only in single-phase VO2 thin films, either the M2 or M1 phase. Phase mixing degrades the ratio of rhos/rhom. The film with a single M2 phase exhibits a lower transition temperature of 58 C without any degradation of the rhos/rhom ratio.

Microstructure modification of silver films deposited by ionized magnetron sputter deposition

Silver films have been deposited under controlled ion bombardment by ionized magnetron sputter deposition (IMSD). The technique uses a built-in rf coil to generate an inductively coupled plasma confined close to the substrate. This enables precise control of both the bombarding ion flux (by rf power) and the energy (by substrate bias). By varying the flux and energy of bombarding ions, the film’s structure and properties can be easily modified. Crystallography, grain size, and film texture have been characterized using the x-ray diffraction method, and film stress was measured by a substrate curvature technique. A focused ion beam was used to section the deposited films and to observe the surface morphology and cross-sectional structure. The electrical resistivity ratio (room to liquid nitrogen temperature: R298 K/R77 K) was used to investigate the influence of the film structure on the conductivity. The persistence of bombardment induced film property variation with thickness was studied in terms of the texture variation in bilayers consisting of IMSD and magnetron sputtering deposited films. It is found that the microstructure of deposited films depends predominantly on the ion bombardment during the initial stages of film growth. Using the IMSD technique, the structure and related properties of silver films have been modified by depositing films under precisely controlled ion bombardment.

Analysis of noise in electrically compensated pyranometers

This article analyzes electronic self-generated noise, signal-to-noise ratio and sensitivity for electrically compensated pyranometers. The conclusion from this study is that the source of self-generated noise in this kind of instrument depends mainly on the electrical resistance ratio on its sensors. A sensitivity analysis also demonstrated that the voltage output of these pyranometers is most sensitive to variation in resistance value of the compensation sensor.