Low-temperature electric resistivity

Low Temperature Electrical Resistance of Fifteen Commercial Conductors (1 156 REVERSIBLE PROCESSES The Reversible Separation of Multicomponent Mixtures (2) 27 The Reversible Separation of Multicomponent Mixtures (3) 47 Hydrogen Separation—A Compromise with Reversibility (4) 319 SEPARATION [see also DISTILLATION]... 

Some of the most interesting and esoteric recent research is on low-temperature electrical resistivity. Measurements are frequently coupled with NMR, EPR and other newer experimental techniques. In combination with the phase, structural, surface and electronic results discussed earlier, results of these studies should give the reader a more clearly defined picture of hydride properties and their temperature dependence in the MHj-MHj composition range. 

Fig. 28. Low-temperature electrical-resistivity data for DyHj+j, at several compositions. At x = 0.13, results for both rapid-cooled (curve Q) and slow-cooled (curve R) samples are shown. Magnetic contributions seen at low compositions are smeared out for X 0.10 a new magnetic feature characteristic of longer-range ordering is seen at x = 0.13 (curve R). After Vajda and Daou (1992).

CY Allison, CB Finch, MD Foegelle, FA Modine. Low-temperature electrical resistivity of transition-metal carbides. Solid State Commun 68 387, 1988. 

Electrical Properties at Low Temperatures The eleciiical resistivity of most pure metalhc elements at ambient and moderately low temperatures is approximately proportional to the absolute temperature. At very low temperatures, however, the resistivity (with the exception of superconductors) approaches a residual value almost independent of temperature. Alloys, on the other hand, have resistivities much higher than those of their constituent elements and resistance-temperature coefficients that are quite low. The electrical resistivity of alloys as a consequence is largely independent of temperature and may often be of the same magnitude as the room temperature value. 

Low-voltage electric resistance heater cables fixed to the structural floor slab and then protected within a 50 mm thickness of cement and sand to give a suitable surface on which the floor vapour barrier can be laid. The heating is thermostatically controlled, and it is usual to include a distance reading or recording thermometer to give visual indication of the temperature of the floor at several locations below the insulation. 

In recent years, many poly(phosphazenes), [RoPN]n, with a variety of substituents at phosphorus have been prepared and they often exhibit useful properties including low temperature flexibility, resistance to chemical attack, flame retardancy, stability to UV radiation, and reasonably high thermal stability. (1,2) Compounds containing biologically, catalytically, or electrically active side groups are also being investigated. (3,4)... 

Flexible PVC is appreciated for the versatility of its characteristics according to the formulation. Significant quantities of fillers and plasticizers are used to optimize some of the characteristics such as behaviour at low temperatures, fire resistance, flexibility and hardness in the elastomer range, low price, electric insulation, easy welding and joining, possibility of transparency, food contact, fireproofing. 

PPEs are used in technical parts because of the good price/performance ratios for mechanical and electrical properties creep behaviour, low moisture uptake, heat and low-temperature behaviour, resistance to moisture and hot water good dimensional stability. 

Aircraft Electrical Potting Compound - Low temperature flexibility, resistance to corona, resistance to hydraulic fluids and aircraft fuels. 

The electrical resistivity, measured in single crystals along the chain axis by a lock-in technique (88 Hz) shows a metallic behavior (dp / dT > 0) in a wide range of temperature (see Fig. 1), with high values of electrical conductivity at room temperature (aRj lO S/cm). At low temperature, the resistivity rises with decreasing temperature. It is not yet clear if there is a structural transition, or only a gradual loss of electronic degrees of freedom. 

ATS FAAR also supplies guided universal impact resistance testers and a low-temperature impact resistance tester for electrical cable (Table 18.2). The application of dynamic mechanical analysis (DMA) to the determination of impact resistance is discussed in Section 15.1. 

PTFE has excellent properties, including chemical inertness, heat resistance (at both high and low temperatures), electrical insulation, and low coefficient of friction (static 0.08 and dynamic 0.01), and it is nonstick over a wide temperature range (-260°C to... 

Superconductivity. The metallic range is also classified into classes of (i) J = 0(2) and (ii) J E 1(2), In the first kind the joint space (that is of J degrees) consists of 2-dimensional units which can be electrons, while the second kind needs to involve a 1-dimensional or 3-dimensional unit at least. The electrons are most rigidly tied in the first kind, Wlien the 3- and/or 4-dimensional u-nits are compelled to be inactive, such as at an extremely low temperature, electricity by virtue of mod(2) could be the sole activity. The elements of the first kind will obtain a certain electrical inertness that no resistance to electric currents is exhibited so that superconductivity is materialized. 

This localization gives rise to non-classical effects which are manifested both in the temperature and the magnetic-field dependences of the electrical resistivity at low temperature. The resistivity value goes through a minimum, then increases logarithmically, while the magnetoresistance is negative [478],... 

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