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Choice of materials and processes
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
The electrical conductivity of copper is adversely affected by the presence of impurities (Figure 27.1). Some impurities like zinc, cadmium and silver have little effect if present in small amounts. Thus, about 1% cadmium is added to copper destined for use in overhead telephone cables in order to strengthen them sufficiently to support their own weight. The conductivity is still of the order of 95%. The presence of only 0.1% phosphorus, however, reduces electrical conductivity by 50% so that phosphorus-deoxidised copper should not be used where high conductivity is required. The electrical conductivity of aluminium is only 60% that of copper, but in terms of conductivity per unit mass, aluminium is a better conductor, for which reason it is used in the power grid network. The electrical conductivities of various grades of copper and other alloys likely to be used in electrical trades are shown in Table 27.7.
Electrokinetic Behavior of Polymer Colloids
Published in Kunio Esumi, Polymer Interfaces and Emulsions, 2020
F. Javier de las Nieves, A. Fernández-Barbero, R. Hildago-Alvarez
According to the value of volume fraction of solid particles in colloidal suspensions, we have concentrated or dilute suspensions of charged particles in a continuous phase (liquid medium). In both cases, the application of an electric field to such a suspension causes the ions and particles to migrate, giving rise to an electric current. Our aim is to determine the relationship between the applied field and the measured electric current. Electrical conductivity may be measured in a steady electric field (static conductivity) or in an alternating electric field (dielectric response measurements). This second possibility has been exhaustively reviewed by O'Brien [186], In our case, we are especially interested in reviewing the conductivity of suspensions as this electrokinetic technique enables us to provide information on the electrical state of polymer colloid-liquid interfaces.
Electrical and Electronic Properties of Expanding Polymers
Published in Rajender K. Sadhir, Russell M. Luck, Expanding Monomers, 2020
In this section, electrical properties of polymers subjected to low stresses are reviewed with emphasis on amorphous or glassy polymers. The inherent properties of insulating polymers having good mechanical and thermal resistance are of interest. Electronic conductivity is observed in metals and semiconductors upon the application of an electric field. In such systems, the current is carried by electrons. In ionic conductivity, charged atoms or groups of atoms are the current carriers. Polymers employed for electrical insulation have very low electrical conductivity. Extremely small currents are, however, often obtained in measuring electrical conductivity of these polymers due to small amounts of foreign (ionic) impurities, which as discussed earlier, are very difficult to keep out during fabrication.
Durability of GGBS based alkali-activated binder treated peat through wetting-drying cycle
Published in Road Materials and Pavement Design, 2023
Suhail Ahmad Khanday, Monowar Hussain, Amit Kumar Das
The ability of a material to carry the current or measure the quantity of current is called electrical conductivity. However, in an electrolytic solution, it is the phenomenon that occurs in an electric field in which there is a movement of ions (Paul & Hussain, 2020a). In peat, ions’ movement occurs through the interconnecting voids filled with moisture (Khanday et al., 2021c). Figure 5 shows the variation of electrical conductivity (in micro-Siemens/cm) with NWD cycles for all peats stabilised by both binders. The result indicates that irrespective of the type of peat, electrical conductivity decreases with NWD cycles for both treated peats. This is attributed to three reasons: firstly, the cementitious gel gets hardened up in the cavities and pores, thus blocking the movement of ions. Secondly, due to the NWD cycle, the ions get leached out; therefore, the availability of ions decreases in pore spaces. Thirdly, pozzolanic reactions occur over time and consume some ions during reactions which also limits the ions present in pore solution (Zheng, 2016). Further, it was seen that fibric peat has a high rate of decrease in electrical conductivity, followed by haemic and sapric peat for both binders. This is because the fibric peat shows low sustainability against NWD cycles, and ions leach out more quickly than other peats.
Electronic structure, magnetic, optical and transport properties of half-Heusler alloys RhFeZ(Z = P, As, Sb, Sn, Si, Ge, Ga, In, Al) – a DFT study
Published in Phase Transitions, 2021
R. Meenakshi, R. Aram Senthil Srinivasan, A. Amudhavalli, R. Rajeswarapalanichamy, K. Iyakutti
Electrical conductivity is a measure of mobility of electrical charges in a material. For a material to be thermo electric (TE), it should possess moderate electrical conductivity. Figure 11 gives the plot between the electrical conductivity per relaxation time and chemical potential at various temperatures of RhFeZ (Z = P, As, Sb, Sn, Si, Ge, Ga, In, Al) alloys. It is observed that the electrical conductivity has the same feature at temperatures 200K, 300K, 400K and 500K for all compounds. At µ = EF, the electrical conductivity of the half-metallic Heusler alloys RhFeGe and RhFeSn exhibits low values for all temperatures. Beyond this region, the electrical conductivity rapidly increases due to the exponential increase of charge carriers. The electrical conductivity exhibits higher values in the positive than in the negative chemical potential region. Thus we infer that the electrical conductivity and temperature have an inverse relationship. For the metallic ferromagnetic half-Heusler alloys RhFeZ (Z = P, As, Sb, Si, Ga, In, Al) the value of electrical conductivity is high when compared to the half metallic half-Heusler alloys such as RhFeGe and RhFeSn.
Mechanical reliability, thermal stability and thermoelectric performance of the transition-metal nitride CrN
Published in Philosophical Magazine Letters, 2020
Jing Jiang, Junfeng Xia, Ting Zhou, Yi Niu, Yide Chen, Jun Luo, Jing Liu, Jiawei Zhou, Jiahao Fan, Chao Wang
In summary, a simple and inexpensive method has been used to synthesise CrN powders with good crystallinity and near-stoichiometry, which is suitable for industrial-scale production. RE TO HERE The thermoelectric and mechanical properties of the bulk CrN samples have been comprehensively investigated. The electrical conductivity decreases with increasing temperature, indicating metal-like transport behaviour. The highest power factor of 3.68 μW cm−1 K−2 and ZT values of 0.12 are obtained at 848 K, with a tendency to further increase at higher temperatures. The hardness, friction test and TGA results demonstrate the good mechanical properties and thermal stability of CrN. These results indicate that CrN is a promising candidate in thermoelectric applications for high temperatures and extreme environments.