Wires: From Chainmail to Superconductors
- PDF / 1,806,381 Bytes
- 2 Pages / 604.8 x 806.4 pts Page_size
- 80 Downloads / 177 Views
Wires: From Chainmail to Superconductors With all the recent excitement about oxide-ceramic superconductors, materials researchers still face the major challenge of how to form these materials into wire. Earlier low-temperature superconducting wires, cooled by liquid helium, were used for giant superconducting magnets and other applications, but the new oxide-ceramic materials offer the possibility of relatively inexpensive applications, from virtually free electricity distribution to levitating trains and to smaller microchips. Unfortunately, most of these experimental superconductors are brittle and fragile, which makes them impossible to draw into wire. A team of scientists at AT&T Bell Laboratories has recently produced a prototype superconducting wire by filling a hollow metal wire with powdered superconducting material. Other researchers at Argonne National Laboratory have created a thin wire of their superconducting material and are working to improve its current density. Of course, wire and its properties are nothing new. Recorded uses of wire go all the way back to the Bible. Archaeological discoveries have shown that wire was made in ancient China and the Middle East, in the tombs of the pharaohs in Egypt, and in the buried ruins of Pompeii. Such early wire was made by hammering and beating thin strips of metal. The most ductile metals include copper, gold, silver, zinc, aluminum, and brass. As described in an English list from 1565, the historical uses of wire range from ornamental to functional—"knitting needles, nayles, pack-needles, chaynes, burde caiges, mouse trappes, buckles, iron rings, and like iron wyre wares." In the Middle Ages, wire was even used for making the rivets and flexible parts of suits of armor. The process of drawing wire by pulling metal—by hand—through a die was in use as early as 1000 A.D. The wire-puller would hammer a section of metal to be drawn into a point, which he then pushed through a hole in the die. The shape of the finished wire depended on the shape of the die-hole through which it was pulled. The earliest wire-pullers used dies made of either iron or stone with holes drilled through them.
Workers could pull only short lengths of wire at a time, and only with extreme effort. Using his own strength, the wirepuller grasped the point with tongs and pulled the metal through the hole, drawing a strand of wire. Presumably, the metal was heated before this operation, though some accounts say wire-pullers grasped the point with their bare hands. It is obvious that no large-diameter wire could be drawn this way unless the metal was very soft; as an alternative, largediameter wire could be fashioned by hammering or rolling metal rods. Some creative inventors developed such contraptions as hanging chairs and foot braces to allow them to pull with their arms while pushing with their feet. With each pull, a worker could draw a length of wire nearly equal to his own height, then grasp the end of the wire near the die and pull again.
With all therecentexcitement about oxide-ceram
Data Loading...
