Papers by Keyword: Resistivity

Abstract: A new method is proposed to prepare carbon fiber reinforced concrete (CFRC) and carbon fiber (CF)/carbon black (CB) reinforced concrete in this paper. First, CF is dispersed in 0.4% carboxymethylcellulose sodium (CMC) water solution. Then, resolvable carbon fiber surfacing mat (RCFCM) is manufactured and cut into small patches. Finally, these patches are mixed with cement, sand, gravel, CB and water. During mixing, RCFCM patches are broken up once they meet with water. So, CF is dispersed into concrete. Results show that this method is feasible. CF/CB reinforced concrete possesses low resistivity (<100 Ω•cm), high compressive strength (≥35 MPa) and low contents of CF (0.3 Vol.%) and CB (0.6 Vol.%), so it can be used as a kind of conductive concrete for melting snow and deicing applications on highways. Both the mixing time and the curing period can affect the electrical and mechanical properties of CF/CB reinforced concrete.

Abstract: The Al-doped ZnO (AZO) films were deposited on the glass substrates by RF magnetron sputtering at different substrate temperatures. The effect of substrate temperature on the structural, optical, and electrical properties of AZO films was investigated. The results indicate each of the films has a preferential c-axis orientation. The grain size increases with substrate temperature increasing. All the films exhibit a high transmittance in visible region and have sharp ultraviolet absorption characteristics. The resistivity decreases with substrate temperature increasing up to 250oC, then increases for higher temperature.

Abstract: Cu thin films were prepared by DC magnetron sputtering on Si substrate, and the resistivities change by adjusting its sputtering parameters. It is found that the changes of the sputtering power and substrate temperature and working pressure can affect significantly the Cu film resistivity (ρ). The Cu films resistivity decreases with the increasing of sputtering power. As the substrate temperature “structure zone model” effect, the Cu film resistivity decreases when the substrate temperature was less than 150°C. The resistivities (ρ) begin to increase gradually at various temperatures ranging from 150°C to 300°C, but the rate of increase is not significant. The resistivity abnormal increases when the substrate temperature was 400°C. The Cu films resistivity increases with argon working gas pressure ranging from 0.15 Pa to 2 Pa.

Abstract: Au/NiCr/Ta multi-layered metallic films were deposited on Al2O3 substrate by magnetron sputtering at different substrate temperature. The effect of substrate temperature on magnetron sputtering Au/NiCr/Ta films in crystal orientation, residual stress and resistivity was investigated. The all magnetron sputtering films were highly textured with dominant Au-(111) orientation or a mixture of Au-(111) and Au-(200) orientation. The residual stress in magnetron sputtering films at different substrate temperature was tensile stress with 155MPa-400MPa. A smallest resistivity of 3.6µΩ.cm was obtained for Au/NiCr/Ta multi-layered metallic films at substrate temperature 180°C. The experiment results reveal that the resistivity increased with the increase of the residual stress of metallic films.

Abstract: Due to various reasons, the inherent quality for Weihe River dike remains poor. There are many hidden defects in dikes, such as cracks, holes etc. so that the actual flood protection ability of dikes is low. And it is difficult to resist the impact of the design flood. In order to ascertain the number, distribution and depth of these hidden defects, etc., electrical detecting technique was applied and studied for detection of hidden defects. At the same time, in order to verify the correctness of the detection results of hidden defects, the engineering geological survey for the purpose of verification was carried out on the detection dike sections. Survey results confirmed the reliability of detection conclusions.

Abstract: The value of dielectric constant of paraffin wax doped with different concentrations of lamp black carbon decreases with the increase in the concentration of lamp black carbon in it. It is a case of loss of dielectric property and gain in conducting property and the specimen behaves as a random binary mixture of conductors and insulators, more specifically, a random network of resistors and capacitors. Anderson Bridge is used to investigate the magnetic permeability and susceptibility of different media inside a solenoid. The resistive property of manganin wire is studied using Kelvin double Bridge.

Abstract: This work deals with Al-Cu thin films, deposited onto glass substrates by RF (13.56MHz) magnetron sputtering, and annealed at 773K. The film thickness was approximately the same 3-4µm. They are characterized with respect to microstructure, grain size, microstrain, dislocation density and resistivity versus copper content. Al (Cu) deposits containing 1.8, 7.21, 86.17 and 92.5at%Cu have been investigated. The use of X-ray diffraction analysis and transmission electron microscopy lead to the characterization of different structural features of films deposited at room temperature (< 400K) and after annealing (773K). The resistivity of the films was measured using the four-point probe method. The microstrain profile obtained from XRD thanks to the Williamson-Hall method shows an increase with increasing copper content.

Abstract: Boron-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited by plasma enhanced chemical vapor deposition (PECVD). Microstructures of these films were characterized and analyzed by Raman spectrum and atomic force microscopy (AFM). Thickness and resistivity of these films was measured by high-resolution profilometer and four-point probe respectively. The impact of annealing on boron-doped nc-Si:H thin films’ resistivity and the relationship between resistivity and microstructure were investigated. The results show that annealing and the annealing temperature have great impact on resistivity of nc-Si:H thin films as a result of microstructures changing after annealing. Resistivity of nc-Si:H thin films decreases after annealing, but it rises with the increasing annealing temperature in the range of 250°C to 400°C.

Abstract: WO3 thin film was prepared on glass substrate at room temperature by RF magnetron sputtering deposition with hybrid (Ar+2.5% H2) gas. Effects of RF power on the microstructure, electrical and optical properties of WO3 films are investigated by field emission scanning electron microscopy, X-ray diffraction, Hall measurement and spectrometer. X-ray diffraction analysis reveals that all of the films are amorphous. The minimum resistivity of the WO3 film prepared with RF 70W is 5.74 × 10-3 -cm. The average transmittance in the visible region was decreased with increased RF power from 50W to 150W. The average transmittance was lower than 15% with RF 50W. The electrical and optical mechanisms have been explained in terms of composition and film thickness were changed with RF power.

Abstract: The additive of Al(NO3)3 was doped into ZnO varistors in order to reduce their residual voltages. Some of doped Al3+ enter the ZnO grains and infill into the vacancies of Zn2+ ions in the crystal lattice. Then, the resistances of ZnO grains decrease, which finally results in lower residual voltages of varistor samples. However, when most of Zn2+ vacancies inside the ZnO crystal lattice are filled with Al3+, redundant Al3+ ions inside ZnO grains will increase the grains’ resistances contrarily. In this paper, ZnO and Al(NO3)3 binary ceramics sintered at 1300 °C for 2, 4 and 8 hours were studied. The J-E curves of the investigated samples exhibit weak non-linear characteristics which may be due to the formation of grain boundary. Moreover, The resistivity dependence of ZnO ceramics on Al addition behaves as a U-type curve and the lowest resistivity of ZnO ceramics is obtained with doping 0.25mol% Al3+.