Calcium electrical resistivity

Piebaked anodes aie produced by molding petroleum coke and coal tar pitch binder into blocks typically 70 cm x 125 cm x 50 cm, and baking to 1000—1200°C. Petroleum coke is used because of its low impurity (ash) content. The more noble impurities, such as iron and siUcon, deposit in the aluminum whereas less noble ones such as calcium and magnesium, accumulate as fluorides in the bath. Coal-based coke could be used, but extensive and expensive prepurification would be required. Steel stubs seated in the anode using cast iron support the anodes (via anode rods) in the electrolyte and conduct electric current into the anodes (Fig. 3). Electrical resistivity of prebaked anodes ranges from 5-6 Hm anode current density ranges from 0.65 to 1.3 A/crn. ... 

As discussed in Chapter 10, a wide variety of additives is used in the polymer industry. Stabilizers, waxes, and processing aids reduce degradation of the polymer during processing and use. Dyes and pigments provide the many hues that we observe in synthetic fabrics and molded articles, such as household containers and toys. Functional additives, such as glass fibers, carbon black, and metakaolins can improve dimensional stability, modulus, conductivity, or electrical resistivity of the polymer. Fillers can reduce the cost of the final part by replacing expensive resins with inexpensive materials such as wood flour and calcium carbonate. The additives chosen will depend on the properties desired. 

Silvery-white metal when freshly cut rapidly turns yellow on exposure to air forming a thin oxide coating face-centered cubic structure malleable, ductile, and somewhat softer than calcium density 2.64 g/cm melts at 777°C vaporizes at 1,382°C vapor pressure 5 torr at 847°C and 20 torr at 953°C electrical resistivity 23 microhm-cm at 20°C thermal neutron absorption cross section 1.21 barns reacts with water soluble in ethanol. Thermochemical Properties... 

The three manganese levels are typical of, respectively. Electric Resistance Welded pipe (ERW) at 1% 0.0 pipe at (a newly developed forming technique for the manufacture of very large pipe out of heavy plate sljieel) and the new I -Mo-Cb steels developed mainly in the U.S. by Amax (Ui). Because of the limited solubility of calcium in steel, the only way these ratios can be achieved, particularly in high steels and for the most critical property levels, is by extreme desulfurization down to 0,00h% max, in the easiest case and 0.001% max. in the most unfavorable situation. 

When the calcium ion concentration is lowered in the fluids bathing nerve axons ifluids which are in very rapid equilibrium with the blood plasma) the electrical resistance ol the axon membrane is lowered, there is increased movement of sodium ions to ihe inside, and the ability ol ihe nerve to return io iis normal siale fallowing a discharge is slowed. Thus, on the one hand, there is hyperexcitabilily. Bui. the ability lor synaptic transmission is inhihited because the rate of acetylcholine liberation is a function ot ihe calcium ion concentration. The neuromuscular junction is... 

Calcium performs a variety of cellular functions in muscle and nerve that ultimately result in muscular contraction. Excellent descriptions of calcium s function in muscle and nerve are to be found in the reviews by Hoyle (37), Cohen (38), and Robertson (39). At the neuromuscular junction, the excitable cells are very sensitive to changes in extracellular concentrations of calcium. Curtis (40) and Luttgau (41) described a fall in the resting action potential and electrical resistance when the extracellular calcium concentration fell below 10 M. The action potential and electrical resistance returned to normal following addition of calcium to this vitro preparation. The magnitude of the Initial muscle membrane action potential, that which regulates the propagation of further muscle contraction, is also mediated by the extracellular calcium concentration. While the inward flow of sodium ions from the extracellular space remains the dominant factor in the mechanism of muscle membrane depolarization, calcium ion flux appears to mediate the cell s permeability to sodium ions. This effect is particularly true in cardiac tissue (W). 

D. M. Shasby and S. S. Shasby. Effects of calcium on transendothelial albumin transfer and electrical resistance. J. Appl. Physiol. 60(l) 7l (1986). 

The electrical resistivity and thermopower of metallic calcium, strontium, and barium have been measured from room temperature to near their melting points. From discontinuities observed in these parameters as functions of temperature, the f.c.c.-b.c.c. phase transition was determined in calcium at 428 2 °C and in strontium at 542 2 C, both at ambient pressure. Four compounds have been identified in the Ca-Ni system by means of X-ray methods. The intermetallic... 

Figure 5.5 Transport properties of a cation exchange membrane having a cationic polyelectrolyte layer formed by electrodeposition. (A) PNaCa ( ) current efficiency (%) ( ) electrical resistance of the membrane during electrodialysis for 1 h. After solutions containing 0.0416N sodium chloride and poly(3-methylene-N, N-dimethylcyclohexylammonium chloride) of various concentrations had been electrodialyzed, for 60 min at a current density of 10 mA cm 2, as anolyte to electrodeposit the polyelectrolyte on the membrane surface (catholyte was 0.0416N sodium chloride), a 1 1 mixed solution of 0.208N calcium chloride and 0.208 N sodium chloride was electrodialyzed at a current density of 10 mA cmr1 for 60 min (cation exchange membrane NEOSEPTA CH-45T).

Lustrous, silver-white surface (when freshly cut) face-centered cubic structure below 300 C. Ignites in air when finely divided, then burns with crimson flame. Much harder than sodium, but softer than aluminum or magnesium. Acquires bluish-gray tarnish on exposure to moist air. dj° 1.54. mp 85C. bp 1440. Electrical resistivity at 20 3.5 ohm cm. Brinell hardness 17. Heat of combustion 15l.9cal/g. sp ht (0-100 ) 0,149 cal/g. Considerably less reactive than sodium. E (aq) CaJ + /Ca —2.87 V. Reacts with water, alcohols, and dd acids with evolution of hydrogen. Reacts with halogens. Dissolves in liquid ammonia to form a blue soln. Contact with alkali hydroxides or carbonates may cause detonation. Bums in air. Calcium salts impart brick red color to a flame. Insol in and inert towards benzene, kerosene. 

Calcium is a silvery white metal with the following main properties density (20°C) 1.55, melting point 838°C, boiling point 1440 °C, specific heat (0-100°C) 0.624 Jg K heat of fusion 217.7 Jg heat of vaporization 4187 J g electrical resistivity (0°C) 3.91x10 Qcm thermal conductivity (20°C) 1.26Wcm K and Mohs-hardness 1.5. Calcium metal is very ductile and can be formed by casting, extrusion, and rolling. The low density and relatively low electrical resistance makes calcium one of the most efficient electrical conductors on a mass basis. 

Reasons for use abrasion resistance, cost reduction, electric conductivity (metal fibers, carbon fibers, carbon black), EMI shielding (metal and carbon fibers), electric resistivity (mica), flame retarding properties (aluminum hydroxide, antimony trioxide, magnesium hydroxide), impact resistance improvement (small particle size calcium carbonate), improvement of radiation stability (zeolite), increase of density, increase of flexural modulus, impact strength, and stiffness (talc), nucleating agent for bubble formation, permeability (mica), smoke suppression (magnesium hydroxide), thermal stabilization (calcium carbonate), wear resistance (aluminum oxide, silica carbide, wollastonite)... 

Until very recently, almost all PVC cables were stabilised with lead salts. These gave good thermal stability and electrical resistance, with low water absorption. When the cable was required to have better flame resistance than inherent in PVC, a small part of the calcium carbonate filler was replaced by antimony trioxide. All such cables perform well and have done for many years. Now, however, the need to focus on ecotoxicity has caused the lead salts to be replaced by a non-heavy metal system, usually a calcium-zinc complex. Likewise, the role of antimony is being questioned and formulators have come up with other solutions. 

---