Superconductor applications: Immense promise for the future
Superconductors, which offer no resistance to electrical current and can repel magnetic fields, hold immense promise for future applications.
Heat from resistance
The electricity that powers many devices, from street lights to sewing machines to laptop computers, nearly always encounters resistance that converts some of its energy to heat. This heat is a major cause of deterioration and breakdown. Expect in a few machines, such as stoves, toasters, and arc furnaces, the heat is unwanted and wastes energy and dollars.
The materials known as superconductors offer no resistance to electrical current — but only at extremely low temperatures. At the same temperatures, superconductors also repel external magnetic fields. Superconductivity was discovered by the Dutch scientist Heike Kamerlingh Onnes in 1911, three years after he liquefied helium. He used the cooling effect of helium’s change from liquid to gas to reach temperatures close to absolute zero — zero degrees Kelvin. The first superconductor was mercury cooled to a temperatures of 4°K.
Superconductors already have practical applications, since refrigeration of materials down to the boiling point of liquid helium or hydrogen is feasible, though very expensive. Superconducting materials have been used experimentally to speed up connections between computer chips, and superconducting coils make possible the very powerful electromagnets at work in some of the magnetic resonance imaging (MRI) machines used by doctors to examine soft tissue inside their patients. In Japan and German, superconducting magnets lift experimental magnetic levitation (maglev) trains above the rails, almost eliminating friction. Some high-energy particle accelerators that physicists use to study atomic structures also use these magnets.
More exciting is the prospect of finding materials in which superconductivity occurs at higher, more usable temperatures. If long-distance power lines could be made of superconducting materials, for example, electric bills would plummet.
Superconductivity at higher temperatures
Progress in reaching the goal of superconductivity at room temperature has been slow. in 1986 Johann Georg Bednorz and Karl Alex Müller at IBM used a ceramic made of lanthanum, barium, copper, and oxygen (LBCO) to achieve superconductivity at 30°K. A year later Paul Chu of the University of Huston and Maw-Kuen Wu of the University of Alabama substituted yttrium for lanthanum (YBCO) and achieved superconductivity at approximately 90°K. At that temperature, liquid nitrogen, a relatively inexpensive refrigerant, can be used.
LBCO, YBCO, and relatives are the so-called high temperature superconductors that seem to offer much promise for the future.
Still a mystery
Superconductors have already been put to a number of uses and have enormous potential impact on everyday life. Still, explaining superconductivity has proved difficult. No comprehensive theoretical explanation was offered until 1957, almost fifty years after Onnes’ discovery. And while industry is developing all kinds of practical applications for the latest superconductors, the theory behind them remains a mystery.