Papers by Keyword: Electrical Resistivity

Abstract: The Bi₂(Sn_0.95Mn_0.05)₂O₇ compound existing simultaneously in two polymorphic modifications, namely, orthorhombic and cubic has been synthesized for the first time by solid-phase synthesis. The magnetic, dielectric and electrical properties of the compound have been studied. Anomalies in the temperature dependences of the electrical resistance and magnetic propoties have been found. These features are explained as martensitic phase transitions.

Abstract: Monolithic zirconia-molybdenum (m-ZrO₂/Mo) cermets have been prepared by traditional powder metallurgy process with molybdenum volume concentration of 30% and different molybdenum powders with average particle sizes of 80nm, 3μm, 8μm and 13μm. The influence of metal particle size on the morphology and electrical conductivity of the cermet has been investigated. The electrical resistivity of the cermet was measured via 4-probe DC technique from 500 °C to 1600 °C. All the samples showed the positive temperature coefficient of electrical resistivity, but the sample prepared with 80 nm molybdenum powder showed very high resistivity over 0.5 Ω·cm. Hot-press sintering was proved to be helpful to the elongated conductive phase formation, thus the electrical conductivity of cermet increased compared to the pressureless sintering process.

Abstract: The need to insert the durability factor on dimensioning concrete structures has been stimulating the development of new models to predict the service life of those structures. Among those new models, the use of data from Non-Destructive Testing (NDT) is recommended. It is known that electrical resistivity is a parameter related with permeability and, in consequence, with the resistance of the concrete against the intrusion of aggressive agents. Electrical resistivity may be monitored with time by a NDT method, by a low cost and easy execution technique. However, some parameters of this essay need to be further discussed in the literature aiming to standardize this technique. Thus, this study had the goal to verify the influence of test specimen’s shape in measurements of electrical resistivity. In order to that, cylindrical and prismatic test specimens have been molded from a same type of concrete and electrical resistivity was monitored during a period of 120 days. Results show significant differences between the values obtained. Test specimens in cylindrical shape had the higher results. A good correlation between factors was found with R² higher than 0.94.

Abstract: Based on graphic program language LabVIEW and Micro Control Unit MSP430F169, an intelligent electrical resistivity measurement system with four-point probe and four-line was studied in this paper. Structured Query Language of LabVIEW was applied for calibration and management in database. Hardware feedback and software compensation technologies were designed in high-precision current source, whose range was automatic selected in auto-mode. Between the computer program and hardware control unit controlled by MCU, a RS-232 data communication protocol was applied in order to improve the ability of human-machine interaction and automation degree. Experiment results in semiconductor and metal material science indicated that the measurement system measured accurately and automotive, the information database of the tested material was the foundation of data analyzing and data mining.

Abstract: We report that the polycrystalline hexagonal YMn_0.9Ru_0.1O₃ compound can be synthesized by using conventional solid state reaction method at a sintering temperature of 1280⁰0. The reflections/diffraction peaks observed in the XRD measurements matched exactly with standard (JCPDS) data for the hexagonal crystal structure of YMnO₃ without any extra peaks due to impurities. The dc electrical measurements of the as prepared YMn_0.9Ru_0.1O₃ compound have been carried out below room temperature down to the minimum possible. The electrical measurement of the Ru doped YMnO₃ compounds reveal that the resistivity is suppressed with the addition of the ruthenium content and a consistent increase in the resistivity have been witnessed with decreasing temperature. In generalized sense the observed resistivity versus temperature behavior in the studied compounds suggests the induction semiconductor-like character in the material.KeywordsXRD, Electrical resistivity, Manganites

Abstract: This paper presents 4-D high resolution electrical resistivity tomography study for slope monitoring using two optimized (modified) arrays of the Wenner-Schlumberger and Pole-Dipole. These optimized resistivity arrays give a total of 2052 number of datum points from each data acquisition set. These two optimized were used because they have more datum points compared to their original arrays. Perhaps these optimized arrays were able to resolve the subsurface structures from surface areas. Inversion results from the computer (mathematical models) suggested that these optimized arrays were able to give in imaging the Earth’s subsurface structures and characterization at different period of time. Furthermore, in this paper, we are presented merging data levels in order to give high resolution in electrical resistivity tomography. Even though the time taken for data acquisition using this technique is twice, the outcome is compromised and reliable which helpful in the Earth’s subsurface interpretation.

Abstract: sp² rich carbon films were produced by using magnetron sputtering deposition. The hardness, friction coefficient and wear volume were elevated by Knoop micro-hardness and pin-on-disk tester; The composition and microstructure of the carbon films have been characterized in detail by combining the techniques of Rutherford Backscattering Spectrum (RBS), X-Ray Photoelectron Spectrum (XPS) and X-Ray Diffraction (XRD); the electrical resistivity was measured by Four Probe Methods (FPM). It is found that: the films hardness are 11~17GPa (HK0.05), the friction coefficients are 0.1-0.2, the wear rate is 10-15m3/Nm; The maximum intensity position in the C1s indicates the chemical bonds are mainly sp²; the electrical resistivity is 1~2×10^-4Ω·m. XRD proves these carbon films are amorphous.

Abstract: In this work, we present results of synthesis, electric and structural characterization of Ruddlesden- Popper La_n+1Ni_n-xZn_xO_3n+1 (n =1, 0<x<0.4) compounds. The samples were synthesized by combustion reaction method by using citric acid as fuel. The precursors obtained from this reaction were treated for 12 hours at 1100 °C in air. The polycrystalline samples were characterized by X-ray diffraction (XRD) and electric resistivity. The XRD results indicate that samples were obtained with single phase in the orthorhombic symmetry and space group I4/mmm. The preliminary results suggest that the Zn-doping plays an important role on the charge transport and modifies the manner that the holes are arranged in the system.

Abstract: The aim of this research is to improve the electrical performance of the nanometer copper film by laser micro shock processing. The nanometer copper film was prepared by the magnetron sputtering. The mechanism of laser micro shock processing effect on electrical resistivity, hardness and elastic modulus was investigated. The results show that the electrical resistivity of copper film after laser micro shock reduced by 22.5 % on average. And, the hardness and the elastic modulus increased by 38.5 % and 45.2 % on average, respectively. According to our research, we conclude that, the existence of a large number of twin, twin boundary, fault and the grow up grain are the main factor of the improvement of the electrical performance; and the existence of twin, stress concentration holes and fault are the key to improve its mechanical properties.

Abstract: This paper studied the influence of preparation method and electrode on properties of carbon fiber electrically conductive concrete by testing flexural strength and electrical resistance. Carbon fiber electrically conductive concrete is prepared by using dry mix method and wet mix method, the electrodes of which are stainless steel mesh and stainless steel sheet. The results show that the wet mix method of carbon fiber electrically conductive concrete is better than the dry mix method. The stainless steel sheet used as electrode in electrically conductive concrete is better than the stainless steel mesh. The long-term electrical resistivity of carbon fiber electrically conductive concrete is a constant value.