Difference Between Ceramics And Warm Superconductors
Ceramics are no longer made exclusively from combinations of clays and other raw materials, such as feldspar, bauxite, talc, and silica. Modern or “advanced” ceramics are fashioned from complex chemical compounds fused together in ovens or kilns at temperatures that can exceed 3,000° F (1,600° C). The combinations of these compounds are as endlessly variable as the physical properties they display and the functions they perform.
As new and different ceramic materials were found, so were new and different techniques for shaping ceramics developed. The four most common shaping techniques in use today are extrusion, pressing, slip casting, and jiggering. For all of these techniques, the materials that are to be combined to produce the final ceramic product are first crushed into very fine particles, then mixed together with enough water to make the material elastic enough to be shaped.
Combining alumina, silica, and magnesium produces refractories. These materials are able to withstand witheringly high temperatures. Refractories are used to line industrial furnaces, such as those in which steel is made, or the variety of kilns used to fire pottery and porcelain.
Alumina and porcelain are good electrical insulators; they are used by utility companies to protect their high voltage power lines, as well as in such items as spark plugs. Capacitors for storing electrical charges are made with the addition of barium titanate. Alumina also is used to fashion lasers and heat shields.
Superconductivity refers to a state where all resistance in a metal is lost. Such a material can carry current with no loss of energy. Ordinary metals, because of loosely bound electrons in their structures, can carry an electrical current when voltage is applied—hence the term “conductors.” However, in even the best metal conductors, such as silver and copper, some of the flowing electrons will scatter randomly, colliding with one another and creating a resistance to the current. This resistance generates friction, which causes energy to be lost in the form of heat. For example, copper power lines, although widely used, lose as much as 20 percent of the energy they transmit. The heat generated by resistance in conventional conductors also restricts the size and power of computers and electromagnets.
In a superconductor, the flowing electrons travel in pairs in an orderly column. There are no collisions and, consequently, there is no resistance. Power lines made from a superconductor would lose no energy, no matter how far they carried an electrical current. It is estimated that the use of superconducting power lines would save billions of dollars in electricity costs. Theoretically, a metropolis like New York City or Los Angeles could have all of its electrical energy needs supplied by a mere handful of underground superconductive cables. Also, with no resistance, the material does not heat up, and the present size and power limitations on electronic components and electromagnets would be to a large extent removed.