In-Ceram

Lead ll) oxide, PbO, exists in two forms as orange-red litharge and yellow massicot. Made by oxidation of Pb followed by rapid cooling (to avoid formation of Pb304). Used in accumulators and also in ceramics, pigments and insecticides. A normal hydroxide is not known but hydrolysis of lead(II) oxyacid salts gives polymeric cationic species, e.g. [Pb OfOH) ] and plumbates are formed with excess base. 

Initially in ceramic powder processing, particle surfaces are created tliat increase tlie surface energy of tlie system. During shape fomiing, surface/interface energy and interiiarticle forces are controlled witli surface active additives. 

Ultimately, the surface energy is used to produce a cohesive body during sintering. As such, surface energy, which is also referred to as surface tension, y, is obviously very important in ceramic powder processing. Surface tension causes liquids to fonn spherical drops, and allows solids to preferentially adsorb atoms to lower tire free energy of tire system. Also, surface tension creates pressure differences and chemical potential differences across curved surfaces tlrat cause matter to move. 

The chemical potential of a curved surface is extremely critical in ceramic processing. It detemiines reactivity, tlie solubility of a solid in a liquid, tire rate of liquid evaporation from solid surfaces, and material transport during sintering. 

This chapter will describe some of tire basic unit processes in ceramic manufacturing, and will touch on tire pertinence of tire physical chemistry of surfaces in selected unit processes. For a more comprehensive review of ceramics and ceramic processing, tire reader is referred to otlrer sources [3, 4 and 5]. 

Generally, tlie last step in ceramic component manufacturing is tliennal processing [60, 61, 62 aiid 65]. This is tlie stage where tlie weakly-bound particulate body produced during shape fonning is heat treated to produce a... 

Johnson D W Jr 1987 Innovations in oeramio powder preparation Ceramic Powder Science, Advances in Ceramics vol 21, ed G L Messing ef a/(Westerville, OFI The Amerioan Ceramio Sooiety) pp 3-19... 

Morse T 1979 Handbook of Organic Additives for Use in Ceramic Body Formuiation (Butte, MA Montana Energy and MHD Research and Deveiopment institute)... 

Coble R L and Burke J E 1963 Sintering in oeramios Progress in Ceramic Science vol 3, ed J E Burke (New York MaoMillan) pp 197-251... 

About 80% of the vanadium now produced is used as ferrovanadium or as a steel additive. Vanadium foil is used as a bonding agent in cladding htanium to steel. Vanadium pentoxide is used in ceramics and as a catalyst. 

It also has potential use in ceramic and glass formulas, as the oxide has a high melting point and imparts shock resistance and low expansion characteristics to glass. 

Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and hardness. Tellurium is used as a basic ingredient in blasting caps, and is added to cast iron for chill control. Tellurium is used in ceramics. Bismuth telluride has been used in thermoelectric devices. 

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