Calcium alloys

Rea.ctivity ofLea.d—Ca.lcium Alloys. Precise control of the calcium content is required to control the grain stmcture, corrosion resistance, and mechanical properties of lead—calcium alloys. Calcium reacts readily with air and other elements such as antimony, arsenic, and sulfur to produce oxides or intermetaUic compounds (see Calciumand calciumalloys). In these reactions, calcium is lost and suspended soHds reduce fluidity and castibiUty. The very thin grids that are required for automotive batteries are difficult to cast from lead—calcium alloys. 

Barium is a member of the aLkaline-earth group of elements in Group 2 (IIA) of the period table. Calcium [7440-70-2], Ca, strontium [7440-24-6], Sr, and barium form a closely aUied series in which the chemical and physical properties of the elements and thek compounds vary systematically with increa sing size, the ionic and electropositive nature being greatest for barium (see Calcium AND CALCIUM ALLOYS Calcium compounds Strontium and STRONTIUM compounds). As size increases, hydration tendencies of the crystalline salts increase solubiUties of sulfates, nitrates, chlorides, etc, decrease (except duorides) solubiUties of haUdes in ethanol decrease thermal stabiUties of carbonates, nitrates, and peroxides increase and the rates of reaction of the metals with hydrogen increase. 

Nowadays, most battery manufacturers prefer to use lead-calcium alloys. Calcium acts as a grid-hardening agent. There is also some tin (up to 1%, sometimes more) in the alloy. This improves the casting process and helps to avoid problems at the grid/active-material interface of the positive plate (see Chapter 2). 

As sodium can be used to eliminate impurities contained in metals, one could consider it as a means for producing wanted compounds and alloys. This field of application is rather large and the following cases of alloy production, mainly based on the strong halogen affinity of this metal, may be examined alkaline earth metal alloys, calcium sodium alloys and calcium metal derived from them, and sodium alloys, especially those with potassium, when calcium, magnesium, cerium, aluminum, uranium, thorium, and titanium, for instance, are introduced into a base metal. 

Magnesium deoxidizer, alloys Calcium Lithium deoxidizer, aluminum Sodium gluconate... 

Sodium phosphate dibasic dihydrate purification, Cu Calcium phosphide purification, Cu alloys Calcium phosphide purification, enzymes Polystyrene purification, gasoline Potassium phosphate tribasic purification, glucose Sodium acetate anhydrous purification, glycerin Polystyrene purification, hydrogen Copper oxide (ic)... 

Beryllium is added to copper to produce an alloy with greatly increased wear resistance it is used for current-carrying springs and non-sparking safety tools. It is also used as a neutron moderator and reflector in nuclear reactors. Much magnesium is used to prepare light nieial allo>s. other uses include the extraction of titanium (p. 370) and in the removal of oxygen and sulphur from steels calcium finds a similar use. 

Rubidium can be liquid at room temperature. It is a soft, silvery-white metallic element of the alkali group and is the second most electropositive and alkaline element. It ignites spontaneously in air and reacts violently in water, setting fire to the liberated hydrogen. As with other alkali metals, it forms amalgams with mercury and it alloys with gold, cesium, sodium, and potassium. It colors a flame yellowish violet. Rubidium metal can be prepared by reducing rubidium chloride with calcium, and by a number of other methods. It must be kept under a dry mineral oil or in a vacuum or inert atmosphere. 

Silicon Alkali carbonates, calcium, chlorine, cobalt(II) fluoride, manganese trifluoride, oxidants, silver fluoride, sodium-potassium alloy... 

FLAVORCHARACTERIZATION] (Volll) -lead-calcium alloys in READ ALOYS] (Vol 15)... 

Goldbeater Gold-beryUium Gold bronzes Gold-cadmium alloys Gold-calcium alloy... 

Alloys suitable for castings that ate to be bonded to porcelain must have expansion coefficients matching those of porcelain as well as soHdus temperatures above that at which the ceramic is fired. These ate composed of gold and palladium and small quantities of other constituents silver, calcium, iron, indium, tin, iridium, rhenium, and rhodium. The readily oxidi2able components increase the bond strength with the porcelain by chemical interaction of the oxidi2ed species with the oxide system of the enamel (see Dental materials). 

Calcium hydride is prepared on a commercial scale by heating calcium metal to about 300°C in a high alloy steel, covered cmcible under 101 kPa (1 atm) of hydrogen gas. Hydrogen is rapidly absorbed at this temperature and the reaction is exothermic. 

FoUowing the removal of the enriched dross, the required quantities of calcium, as a lead—calcium alloy and magnesium in the form of metal ingots, are added. The bath is stirred about 30 min to incorporate the reagents and hasten the reaction. The molten lead is cooled gradually to 380°C to permit the precipitate to grow and soHdify. The dross is skimmed for use with the next lot of lead to be treated. 

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