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Abstract
Superconductivity is the phenomenon in which a material losses all its electrical resistance and allowing electric current to flow without dissipation or loss of energy. The atoms in materials vibrate due to thermal energy contained in the materials: the higher the temperature, the more the atoms vibrate. An ordinary conductor's electrical resistance is caused by these atomic vibrations, which obstruct the movement of the electrons forming the current. If an ordinary conductor were to be cooled to a temperature of absolute zero, atomic vibrations would cease, electrons would flow without obstruction, and electrical resistance would fall to zero. A temperature of absolute zero cannot be achieved in practice, but some materials exhibit superconducting characteristics at higher temperatures.
Super conductors
A superconductoris a material that can conduct electricity or transport electrons through conductor with no resistance ,at very low temperature conditions. It conducts electricity based on the phenomenon of superconductivity.
In 1911, the Dutch physicist Heike Kamerlingh Onnes discovered superconductivity in mercury at a temperature of approximately 4 K (-269o C). Many other superconducting metals and alloys were subsequently discovered but, until 1986, the highest temperature at which superconducting properties were achieved was around 23 K (-250o C) with the niobium-germanium alloy (Nb3Ge)
In 1986 George Bednorz and Alex Muller discovered a metal oxide that exhibited superconductivity at the relatively high temperature of 30 K (-243o C). This led to the discovery of ceramic oxides that super conduct at even higher temperatures. In 1988, and oxide of thallium, calcium, barium and copper (Ti2Ca2Ba2Cu3O10) displayed superconductivity at 125 K (-148o C), and, in 1993 a family based on copper oxide and mercury attained superconductivity at 160 K (-113o C). These "high-temperature" superconductors are all the more noteworthy because ceramics are usually extremely good insulators.
Like ceramics, most organic compounds are strong insulators; however, some organic materials known as organic synthetic metals do display both conductivity and superconductivity. In the early 1990's, one such compound was shown to super conduct at approximately 33 K (-240o C). Although this is well below the temperatures achieved for ceramic oxides, organic superconductors are considered to have great potential for the future.
Properties of Superconductors
Zero Resistivity
The fact that the resistance is zero has been demonstrated by sustaining currents in superconducting lead rings for many years with no measurable reduction. An induced current in an ordinary metal ring would decay rapidly from the dissipation of ordinary resistance, but superconducting rings had exhibited a decay constant of over a billion years!
Critical Magnetic Field
The superconducting state cannot exist in the presence of a magnetic field greater than a critical value, even at absolute zero. This critical magnetic field is strongly correlated with the critical temperature for the superconductor, which is in turn correlated with the bandgap. Type II superconductors show two critical magnetic field values, one at the onset of a mixed superconducting and normal state and one where superconductivity ceases.
It is the nature of superconductors to exclude magnetic fields (Meissner effect) so long as the applied field does not exceed their critical magnetic field. This critical magnetic field is tabulated for 0K and decreases from that magnitude with increasing temperature, reaching zero at the critical temperature for superconductivity. The critical magnetic field at any temperature below the critical temperature is given by the relationship
Critical Current
If a current is generated in a superconducting lead ring, it will persist because of the zero resistivity. Above a certain current, the magnetic field created by the current drives the material into a normal resistive state. Because it is a known fact that a current carrying conductor induces magnetic field. If the current is above a certain value, Ic, whereby the induced magnetic field is above the critical magnetic field, then there is a transition from a superconducting to a normal state. This Icis known as the critical current
Ultra conductors
Ultra conductors are the materials exhibit a characteristic set of properties including conductivity and current carrying capacity equivalent to superconductors, but without the need for cryogenic support.
New superconducting materials are being discovered on a regular basis, and the search is on for room temperature superconductors, which, if discovered, are expected to revolutionize electronics. Room temperature superconductors (ultraconductors) are being developed for commercial applications by Room Temperature Superconductors Inc.(ROOTS).Ultraconductors are the result of more than 16 years of scientific research ,independent laboratory testing and eight years of engineering development. From an engineering perspective, ultraconductors are a fundamentally new and enabling technology. These materials are claimed to conduct electricity at least 100,000 times better than gold, silver or copper.
Technical introduction
Ultraconductors are patented1 polymers being developed for commercial applications by Room Temperature Superconductors Inc (ROOTS).
The Ultraconductor properties appear in thin (5 - 100 micron) films of certain dielectric polymers following an induced, non-reversible transition at zero field and at ambient temperatures >> 300 K. This transition resembles a formal insulator to conductor (I-C) transition.
The base polymers used are certain viscous polar elastomers, obtained by polymerization in the laboratory or as purchased from industrial suppliers. Seven chemically distinct polymers have been demonstrated to date.
Properties of Ultraconductors
Ultraconductors are the electrical conductors which have certain properties similar to present day superconductors. They are best considered as a novel state of matter. They are made by the sequential processing of amorphous polar dielectric elastomers. They exhibit a set of anomalous magnetic and electric properties including very high electrical conductivity very high electrical conductivity (> 1011 S/cm -1) and current densities (> 5 x 108 A/cm2) over a wide temperature range (1.8 to 700 K). Additional properties established by experimental measurements include: the absence of measurable heat generation under high current; thermal versus electrical conductivity orders of magnitude in violation of the Wiedemann-Franz law; a jump-like transition to a resistive state at a critical current; a nearly zero Seebeck coefficient over the temperature range 87 - 233 K; no measurable resistance when Ultraconductor films are placed between superconducting tin electrodes at cryogenic temperatures.
From an engineering point of view, we expect the polymer to replace copper wire and HTS in many applications. It will be considerably lighter than copper, and have less electric resistance.
MATERIALS
The chemically distinct polymers used to create Ultraconductors to date includeolefin, acrylate, urethane and silicone based plastics. Based on experiment and theory, the total list of candidate polymers suited to the process is believed to number in the hundreds.
A successful candidate polymer must be polar without significant crystalline or glass phase at the time of processing. (Intrinsically conducting [conjugated] polymers cannot be used.)
Ultraconductor films are prepared on metal, glass, Teflon or semiconductor substrates. The polymer is initially viscose (during processing). For practical application the channels are subsequently “locked” in the polymer, by cross linking, or glass transition. The channel’s characteristics are not affected by either mode.
Due to the connection between the ferromagnetic signature and electric conductivity, Ultraconductor samples are routinely tested for ferromagnetic response, as a process control. Higher values of ferromagnetism are related to the density of structures, and so to the number of conducting regions at the film surface. The magnetic responses typical of the processed Ultraconductor samples are entirely absent in the unprocessed base polymers, as tested and in the literature.
CONCLUSION
Superconductors are a topic of extensive worldwide research. They are the underlying science behind many new technologies like the carbon nanotubes.The sheer brilliance of this
object is yet to be applied to full use. If ultraconductors are fully commercialized it would
enhance the contribution of its predecessor. Energy is endangered and any technology that
strives for a better handlement of electrical power and energy strives for the betterment of mankind as a whole.