Papers by Keyword: Electrical Resistance

Abstract: Diffusion welding is being used in aircraft, optic and electrical industry, where special alloys or combinations of metal or non-metal materials are often used. The alloys and materials come from limited sources and therefore they are expensive as well. These reasons lead to the fact that the destructive testing of diffusion bonded joints is not sufficient for the industry and the used components in operation. The paper discusses about the testing methods suitable for the diffusion bonded joints, which are commonly used in our research of diffusion welding and which are planned to be used afterwards.

Abstract: The penetration of water and chloride ion into the concrete is of factors that cause rust and corrosion in rebars by reaching the existing reinforcement surface in reinforced concrete structures. In this study, effect of using Asphalt Plant Surplus Filler as a partial replacement of cement with replacement values of 0, 5, 10, 15 and 20% on permeability and electrical resistance of cement mortar were investigated with the aim of decreasing cement consumption. In order to determine the penetration of water, 10 cubic specimens with the size of 150 mm were made and tested. In order to determine chloride ion penetration, 20 cylindrical specimens with a length of 50 and a diameter of 100 mm were studied at the ages of 28 and 56 days. To test the electrical resistivity of cement mortar, 30 cubic specimens with the size of 100 mm were tested at the ages of 7, 28 and 56 days. According to the results of the experiments, adding filler to the cement mortar enhances the penetration of water and chloride ion. Electrical resistivity generally increases with the increase of specimen age. Furthermore, the filler increment indicates the reduction of electrical resistivity.

Abstract: The conductive yarn is an essential component of the smart textile making the product light and comfortable to wear. Nevertheless, one of the most common problems is care that limits the use of the product. Application of additional coating to the yarn renders it water-repellent properties and allows reduction of the negative impact of water on its performance. During the research additional coatings were applied to conductive yarns, with the aim of minimizing electrical resistivity changes caused by washing cycles. Two types of coatings were applied to the yarns, they were washed and tested. The article describes changes in the electrical resistance of different conductors depending on the linear density of the yarn, the type of coating applied and the number of washing cycles. The electrical resistance of electrically conductive yarns increases with washing until they become non-conductive. The electrical resistance of non-textured yarns increases more slowly and the smaller increase is observed in thick yarns. The water-repellent silicone coating applied to yarns reduces the electrical resistance increase rate and the yarns retain their conductivity over more washing cycles.

Abstract: Acid-functionalized carbon nanotube (fCNT)-poly (vinylidene fluoride) (PVDF) composite films with different CNT contents (0-0.5wt%) were prepared by melt-blending followed by compression molding. The electrical resistance (R) of the composite films under tensile loading was measured by a two-probe method using a custom made equipment connected to digital multimeter. The films (0.35 and 0.5wt% fCNT composites) showed exponential increases in R with displacement after attaining the elastic strain. Further, the change in resistance divided by resistance (ΔR/R) showed a linear increase with strain (ε). The slope of the linear region is found to be higher for 0.35wt% fCNT composite (5.4) as compared to 0.5wt% fCNT composite (3.4), indicating a better sensitivity in the former case. This may be due to less number of electrical conducting paths in case of 0.35fCNT composite. On account of the results obtained, the composites promise as potential candidates for strain sensing in health monitoring.

Abstract: Electrical resistance is always related to the electronic structure of metallic glass and sensitive to structural changes, which provides a more intuitive approach to investigate structure evolution of metallic glasses upon structural relaxation. Electrical resistance relaxation of the La₅₅Al₂₅Ni₁₀Cu₁₀ bulk metallic glass was studied using the standard four-probe method. The electrical resistance of La₅₅Al₂₅Ni₁₀Cu₁₀ bulk metallic glass decreases significantly with the structural relaxation below the glass transition temperature at 445 K. During the subsequent continuous heating, the relaxed specimen shows a reduction in the resistivity decrease at the glass transition. The relaxed electrical resistance caused by the structural relaxation during the isothermal measurement equals the changes of the electrical resistance reduction in the glass transition region in the subsequent isochronal measurements. The calculated relaxed electrical resistance as a function of the annealing time can be fitted by Kohlrausche-Williams-Watts (KWW) equation. The equilibrium value, time constant and the stretched exponent for the isochronal electrical resistance measurements at 445 K are 0.0384, 2390s and 0.66, respectively. The in-situ electrical resistance data recorded in the isothermal annealing process show the same relaxation behavior with fitting parameters 0.0362, 2033 s, and 0.74, respectively.

Abstract: Metastable β titanium alloy Ti-15Mo was investigated in this study. In-situ electrical resistance and thermal expansion measurements conducted on solution treated material revealed influence of ongoing phase transitions on measured properties. The monotonicity of the dependence of electrical resistance on temperature changes at 225, 365 and 560 °C The thermal expansion deviates from linearity between 305 and 580 °C.

Abstract: We have measured the resistivity and Hall effect of La (Fe_1-хCo_х)Si_y polycrystals in the temperature range 100 K < T < 340 K and applied magnetic fields of up to 5 T. The anomalous Hall effect (AHE) is very large and varies quite linearly with the longitudinal resistivity ρ. AHE in these compounds is determined by the contribution from the external screw scattering mechanism.

Abstract: High hardness, good thermal and electrical conductivity make carbides technologically important materials. The high melting temperature and low coefficients of self-diffusion make it difficult to obtain full dense material. In this paper the results of Spark Plasma Sintering (SPS) of transition metal carbides: NbC, TaC, TiC, ZrC, VC with the addition of graphene 10-20 nm x 14 microns in an amount of 2.5 mass % are presented. Powders were mixed in isopropyl alcohol in a planetary ball mill for 1h. The sintering processes was carried out at 2200°C at two different times: 5 and 30 min. Microstructure of the samples was analyzed using scanning electron microscopy. The measurements of density, Young's modulus hardness and electrical properties were carried out, also. The best properties were obtained for titanium carbide powder, sintered for 30 min. The most significant density increase of the sintered carbide–graphene composite by about 5.3% (depending on increasing sintering duration) was obtained for niobium carbide, while the smallest densities change for zirconium carbide.

Abstract: The isothermal crystallization behavior of the Cu₄₂Zr₄₂Al₈Ag₈ bulk metallic glasse (BMG) was studied by the electrical resistance method. The increasing local activation energy means that the crystallization of the Cu₄₂Zr₄₂Al₈Ag₈ BMG becomes more and more difficult during the isothermal process. In the stage that the crystallized volume fraction falls into the range of 25–85%, the crystallization of the Cu₄₂Zr₄₂Al₈Ag₈ BMG is diffusion-controlled growth with a decreasing nucleation rate.

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.