Техническое чтение для энергетиков. Бухарова Г.П. - 51 стр.

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53
SUPERCONDUCTIVITY
According to the prominent scientist in this country V.L. Ginzburg the latest
world achievements in the field of superconductivity mean a revolution in technology
and industry. Recent spectacular breakthroughs in superconductors may be compared
with the physics discoveries that led to electronics and nuclear power. They are likely
to bring the mankind to the threshold of a new technological age. Prestige, economic
and military benefits could well come to the nation that first will master this new field
of physics. Superconductors were once thought to be physically impossible. But in
1911 superconductivity was discovered by a Dutch physicist K. Onnes, who was
awarded the Nobel Prize in 1913 for his low-temperature research. He found the
electrical resistivity of a mercury wire to disappear suddenly when cooled below a
temperature of 4 Kelvin (-269 °C). Absolute zero is known to be О К. This discovery
was a completely unexpected phenomenon. He also discovered that a
superconducting material can be returned to the normal state either by passing a
sufficiently large current through it or by applying a sufficiently strong magnetic field
to it. But at that time there was no theory to explain this.
For almost 50 years after K. Onnes' discovery theorists were unable to develop
a fundamental theory of superconductivity. In 1950 physicists Landau and Ginzburg
made a great contribution to the development of superconductivity theory. They
introduced a model which proved to be useful in understanding electromagnetic
properties of superconductors. Finally, in 1957 a satisfactory theory was presented by
American physicists, which won for them in 1972 the Nobel Prize in physics.
Research in superconductors became especially active since a discovery made in
1986 by IBM scientists in Zurich. They found a metallic ceramic compound to
become a superconductor at a temperature well above the previously achieved record
of 23 K.
It was difficult to believe it. However, in 1987 American physicist Paul Chu
informed about a much more sensational discovery: he and his colleagues produced
superconductivity at an unbelievable before temperature 98 К in a special ceramic
material. At once in all leading laboratories throughout the world superconductors of
critical temperature 100 К and higher (that is, above the boiling temperature of liquid
nitrogen) were obtained. Thus, potential technical uses of high temperature
superconductivity seemed to be possible and practical. Scientists have found a
ceramic material that works at room temperature. But getting superconductors from
the laboratory into production will be no easy task. While the new superconductors
are easily made, their quality is often uneven. Some tend to break when produced,
others lose their superconductivity within minutes or hours. All are extremely
difficult to fabricate into wires. Moreover, scientists lack a full understanding of [low
ceramics become superconductors. This fact makes developing new substances
largely a random process. This is likely to continue until theorists give a fuller
explanation of how superconductivity is produced in new materials.

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