Superconductors in bref

دى حاجه بسيطه عن المواد فائقه التوصيل بس التطبيق اللى د/ سلطان طلبه مش موجود عنه معلومات كافيه لو اى زميل عنده معلومه ياريت يبلغنا بالمصدر او اى شى له علاقه بتطبيقاتها على الموتور

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

T h e H i s t o r y o f
S u p e r c o n d u c t o r s

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

Superconductors, materials that have no resistance to the flow of electricity, are one of the last great frontiers of scientific discovery. Not only have the limits of superconductivity not yet been reached, but the theories that explain superconductor behavior seem to be constantly under review. In 1911 superconductivity was first observed in mercury by Dutch physicist Heike Kamerlingh Onnes of [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (shown above). When he cooled it to the temperature of liquid helium, 4 degrees Kelvin (-452F, -269C), its [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] suddenly disappeared. The Kelvin scale represents an "absolute" scale of temperature. Thus, it was necessary for Onnes to come within 4 degrees of the coldest temperature that is theoretically attainable to witness the phenomenon of superconductivity. Later, in 1913, he won a Nobel Prize in physics for his research in this area.
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]
Walter Meissner
The next great milestone in understanding how matter behaves at extreme cold temperatures occurred in 1933. German researchers Walter Meissner (above) and Robert Ochsenfeld discovered that a superconducting material will repel a magnetic field (below graphic). A magnet moving by a conductor induces currents in the conductor. This is the principle on which the electric generator operates. But, in a superconductor the induced currents exactly mirror the field that would have otherwise penetrated the superconducting material - causing the magnet to be repulsed. This phenomenon is known as strong diamagnetism and is today often referred to as the "Meissner effect" (an eponym). The Meissner effect is so strong that a magnet can actually be [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] over a superconductive material.
[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]
In subsequent decades other superconducting metals, alloys and compounds were discovered. In 1941 niobium-nitride was found to superconduct at 16 K. In 1953 vanadium-silicon displayed superconductive properties at 17.5 K. And, in 1962 scientists at Westinghouse developed the first commercial superconducting wire, an alloy of niobium and titanium (NbTi). High-energy, particle-accelerator electromagnets made of copper-clad niobium-titanium were then developed in the 1960s at the Rutherford-Appleton Laboratory in the UK, and were first employed in a superconducting accelerator at the [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] in the US in 1987.


[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] The first widely-accepted theoretical understanding of superconductivity was advanced in 1957 by American physicists John Bardeen, Leon Cooper, and John Schrieffer (above). Their Theories of Superconductivity became know as the [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] - derived from the first letter of each man's last name - and won them a [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]. The mathematically-complex BCS theory explained superconductivity at temperatures close to absolute zero for [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] and [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]. However, at higher temperatures and with different superconductor systems, the BCS theory has subsequently become inadequate to fully explain how superconductivity is occurring.


[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]
Brian Josephson
Another significant theoretical advancement came in 1962 when Brian D. Josephson (above), a graduate student at [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], predicted that electrical current would flow between 2 superconducting materials - even when they are separated by a non-superconductor or insulator. His prediction was later confirmed and won him a share of the 1973 Nobel Prize in Physics. This tunneling phenomenon is today known as the [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] and has been applied to electronic devices such as the [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], an instrument capabable of detecting even the weakest magnetic fields. (Below SQUID graphic courtesy [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط].)


[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

The 1980's were a decade of unrivaled discovery in the field of superconductivity. In 1964 Bill Little of Stanford University had suggested the possibility of organic (carbon-based) superconductors. The first of these theoretical superconductors was successfully synthesized in 1980 by Danish researcher [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] of the University of Copenhagen and 3 French team members. (TMTSF)₂PF₆ had to be cooled to an incredibly cold 1.2K transition temperature (known as Tc) and subjected to [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] to superconduct. But, its mere existence proved the possibility of "designer" molecules - molecules fashioned to perform in a predictable way.

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة] Then, in 1986, a truly breakthrough discovery was made in the field of superconductivity. Alex Müller and Georg Bednorz (above), researchers at the IBM Research Laboratory in Rüschlikon, Switzerland, created a brittle ceramic compound that superconducted at the highest temperature then known: 30 K. What made this discovery so remarkable was that ceramics are normally insulators. They don't conduct electricity well at all. So, researchers had not considered them as possible high-temperature superconductor candidates. The Lanthanum, Barium, Copper and Oxygen compound that Müller and Bednorz synthesized, behaved in a not-as-yet-understood way. [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] The discovery of this first of the superconducting copper-oxides (cuprates) won the 2 men a Nobel Prize the following year. It was later found that tiny amounts of this material were actually superconducting at 58 K, due to a small amount of lead having been added as a calibration standard - making the discovery even more noteworthy.

Müller and Bednorz' discovery triggered a flurry of activity in the field of superconductivity. Researchers around the world began "cooking" up ceramics of every imaginable combination in a quest for higher and higher Tc's. In January of 1987 a research team at the University of Alabama-Huntsville substituted Yttrium for Lanthanum in the Müller and Bednorz molecule and achieved an incredible 92 K Tc. For the first time a material (today referred to as YBCO) had been found that would superconduct at temperatures warmer than liquid nitrogen - a commonly available coolant. Additional milestones have since been achieved using exotic - and often toxic - elements in the base [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] ceramic. The current class (or "system") of ceramic superconductors with the highest transition temperatures are the mercuric-cuprates. The first synthesis of one of these compounds was achieved in 1993 at the University of Colorado and by the team of A. Schilling, M. Cantoni, J. D. Guo, and H. R. Ott of Zurich, Switzerland. The world record Tc of 138 K is now held by a thallium-doped, mercuric-cuprate comprised of the elements Mercury, Thallium, Barium, Calcium, Copper and Oxygen. The Tc of [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] was confirmed by Dr. Ron Goldfarb at the National Institute of Standards and Technology-Colorado in February of 1994. Under extreme pressure its Tc can be coaxed up even higher - approximately 25 to 30 degrees more at 300,000 atmospheres.

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]
The first company to capitalize on high-temperature superconductors was Illinois Superconductor (today known as [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]), formed in 1989. This amalgam of government, private-industry and academic interests introduced a depth sensor for medical equipment that was able to operate at liquid nitrogen temperatures (~ 77K).

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذه الصورة]

In recent years, many discoveries regarding the novel nature of superconductivity have been made. In 1997 researchers found that at a temperature very near absolute zero an alloy of gold and indium was both a superconductor and a natural magnet. Conventional wisdom held that a material with such properties could not exist! Since then, over a [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] have been found. Recent years have also seen the discovery of the first high-temperature superconductor that [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (2000), and the first [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (2001).
[b] Also in 2001 a material that had been sitting on laboratory shelves for decades was found to be an extraordinary new superconductor. Japanese researchers measured the transition temperature of magnesium diboride at 39 Kelvin - far above the highest Tc of any of the [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] or [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] superconductors. While 39 K is still well below the Tc's of the "warm" [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], subsequent refinements in the way MgB₂ is fabricated have paved the way for its use in industrial applications. Laboratory testing has found MgB₂ will [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] NbTi and Nb₃Sn wires in high magnetic field applications like [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط].
Though a theory to explain high-temperature superconductivity still eludes modern science, clues occasionally appear that contribute to our understanding of the exotic nature of this phenomenon. In 2005, for example, Superconductors.ORG discovered that increasing the weight ratios of alternating planes within the layered perovskites can often [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]. This has led to the discovery of more than [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], including a candidate for a [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط].
The most recent "family" of superconductors to be discovered is the "pnictides". These iron-based superconductors were first observed by a group of Japanese researchers in 2006. Like the high-Tc copper-oxides, the exact mechanism that facilitates superconductivity in them is a mystery. However, with Tc's [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], a great deal of excitement has resulted from their discovery[/b]

جزاك الله خيرا انا لقيت التطبيق والموضوع كامل على ويكبيديا بس انا عندى مشكلة فى الاوفيس مش عارفة انزله بس لو حد دخل على الويكبيديا ممكن ينزله كامل والموتور كمان ادعولى المشكلة تتحل بسرعة علشان انزله

الكلام ده من كذا موقع

APPLICATIONS OF SUPERCONDUCTORS


Soon after Kamerlingh Onnes discovered superconductivity, scientists began dreaming up practical applications for this strange new phenomenon. Powerful new superconducting magnets could be made much smaller than a resistive magnet,because the windings could carry large currents with no energy loss. Generators wound with superconductors could generate the same amount of electricity with smaller equipment and less energy. Once the electricity was generated it could be distributed through superconducting wires. Energy could be stored in superconducting coils for long periods of time without significant loss.
The recent discovery of high temperature superconductors brings us a giant step closer to the dream of early scientists. Applications currently being explored are mostly extensions of current technology used with the low temperature superconductors. Current applications of high temperature superconductors include; magnetic shielding devices, medical imaging systems, superconducting quantum interference devices (SQUIDS), infrared sensors, analog signal processing devices, and microwave devices. As our understanding of the properties of superconducting material increases, applications such as; power transmission, superconducting magnets in generators, energy storage devices, particle accelerators, levitated vehicle transportation, rotating machinery, and magnetic separators will become more practical.
The ability of superconductors to conduct electricity with zero resistance can be exploited in the use of electrical transmission lines. Currently, a substantial fraction of electricity is lost as heat through[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] associated with traditional conductors such as copper or aluminum. A large scale shift to superconductivity technology depends on whether wires can be prepared from the brittle ceramics that retain their superconductivity at 77 K while supporting large current densities.
The field of electronics holds great promise for practical applications of superconductors. The miniaturization and increased speed of computer chips are limited by the generation of heat and the charging time of capacitors due to the resistance of the interconnecting metal films. The use of new superconductive films may result in more densely packed chips which could transmit information more rapidly by several orders of magnitude. Superconducting electronics have achieved impressive accomplishments in the field of digital electronics. Logic delays of 13 picoseconds and switching times of 9 picoseconds have been experimentally demonstrated. Through the use of basic [url=http://www.ornl.gov/info/reports/m/ornlm3063r1/app_e.html#Josephson Junction]Josephson junctions[/url] scientists are able to make very sensitive microwave detectors, magnetometers, [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] and very stable voltage sources.
The use of superconductors for transportation has already been established using liquid [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] as a refrigerant. Prototype levitated trains have been constructed in Japan by using superconducting magnets.
Superconducting magnets are already crucial components of several technologies. [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (MRI) is playing an ever increasing role in diagnostic medicine. The intense magnetic fields that are needed for these instruments are a perfect application of superconductors. Similarly, particle accelerators used in high-energy physics studies are very dependant on high-field superconducting magnets. The recent controversy surrounding the continued funding for the Superconducting Super Collider (SSC) illustrates the political ramifications of the applications of new technologies.
New applications of superconductors will increase with critical temperature.Liquid nitrogen based superconductors has provided industry more flexibility to utilize superconductivity as compared to liquid helium superconductors. The possible discovery of room temperature superconductors has the potential to bring superconducting devices into our every-day lives.
High-temperature superconductors are recent innovations from scientific research laboratories. New commercial innovations begin with the existing technological knowledge generated by the research scientist. The work of commercialization centers on the development of new products and the engineering needed to implement the new technology. Superconductivity has had a long history as a specialized field of physics. Through the collaborative efforts of government funded research, independent research groups and commercial industries, applications of new high-temperature superconductors will be in the not so distant future. Time lags however, between new discoveries and practical applications are often great. The discovery of the laser in the early 60's has only recently been appreciated today through applications such as laser surgery, laser optical communication, and compact disc players. The rapid progress in the field of superconductivity leads one to believe that applications of superconductors is limited only by one's imagination and time.

ومن موقع الويكيبديا

applications of superconductivity



Some of the technological applications of superconductivity include

• the production of [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] based on [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط],
  
• [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (including those based on [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] and [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] technology),
  
• powerful electromagnets used in [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (MRI) and [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (NMR) machines and the beam-steering magnets used in [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط],
  
• control magnets in [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] and [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] reactors ([ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]),
  
• power cables,
  
• [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (e.g., for [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] base stations, as well as, [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]), and
  
• [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] and [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] magnets.
  

[[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]] Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR)

The biggest application right now for superconductivity is in producing the large volume, stable magnetic fields required for MRI and NMR. This represents a multi-billion US$ market for companies such as [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] etc. The magnets typically use low temperature superconductors (LTS). These need to be cooled to liquid helium temperatures to superconduct. LTS is also used in high field scientific magnets because copper has a limit to the field strength it can produce.

[[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]] High-temperature superconductivity (HTS)

The commercial applications so far for [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] (HTS) have been limited.

HTS superconduct at temperatures up to that of [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] which makes them cheaper to cool.

The problem with HTS technology is that the currently known high-temperature superconductors are brittle ceramics which are expensive to manufacture and not easily turned into wires or other useful shapes.

Therefore the applications have been where HTS has some other intrinsic advantage i.e. in

• low thermal loss current leads for LTS devices (low thermal conductivity),
  
• RF and microwave filters (low resistance to RF), and
  
• increasingly in specialist scientific magnets, particularly where size and electricity consumption are critical (while HTS wire is much more expensive than LTS in these applications this can be offset by the relative cost and convenience of cooling).
  

[[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]] HTS wire

Commercial quantities of HTS wire based on [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] are now available at around five times the price of the equivalent copper conductor (this wire is referred to as Generation 1 conductor). BSCCO wire requires an expensive batch production process and relatively high quantities of silver (but less than 10% of the cost). Pilot plants have been developed that use [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] to produce coated conductors in a semi-continuous process (Generation 2). Manufacturers are claiming the potential to reduce the price in volume to 50% to 20% of BSCCO. If the latter occurs, HTS wire will be competitive with copper in many large industrial applications, putting aside the cost of cooling.



Promising future industrial and commercial HTS applications include [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط], [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] reactors (see [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]) and [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] devices. (For a relatively technical and US-centric view of state of play of HTS technology in power systems and the development status of Generation 2 conductor see Superconductivity for Electric Systems 2007 US DOE Annual Peer Review [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط].)

HTS also has a future in scientific and industrial magnets, including use in NMR and MRI systems. Also one intrinsic attribute of HTS is that it can withstand much higher magnetic fields than LTS, so HTS at liquid helium temperatures are being explored for very high-field inserts inside LTS magnets.

[[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]] Magnesium diboride

[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] is a much cheaper superconductor than either [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] or [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] in terms of cost per current-carrying capacity per length (cost/(kA*m)), in the same ballpark as LTS, and on this basis many manufactured wires are already cheaper than copper. Furthermore, MgB₂ superconducts at temperatures higher than LTS (its critical temperature is 39 K, compared with less than 10 K for NbTi and 18.3 K for Nb₃Sn), introducing the possibility of using it at 10-20 K in cryogen-free magnets or perhaps eventually in liquid hydrogen. However MgB₂ is limited in the magnetic field it can tolerate at these higher temperatures, so further research is required.

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