Friday, February 26, 2010


Have you ever heard about superconductors? Recently, I listened to a lecture by my previous physics professor (Dr. Gene Bickers) about the power and potential of superconductors and became quite interested in it.
Superconductors, which are materials that demonstrate no resistance below transition temperature (Tc), are one of the latest discoveries in the scientific field that proposes wide gamut of possibilities in their applications, ranging from maglev transportation to magnetoencephalography (MEG).

The history of superconductors started in 1911, when a Dutch physicist, Kamerlingh-Onnes, observed an unusual disappearance of resistance when mercury was cooled down to 4 degrees Kelvin. Later, in 1957, American physicist, Bardeen, Cooper, and Schrieffer described theoretical understanding of superconductivity. In 1986, there was a huge step forward in superconductivity when Muller and Bednorz discovered that an alloy of barium, lanthanum, copper, and oxygen compound superconducted at the highest temperature then known which was 30 K. This alloy was a type of ceramics that normally does not conduct electricity well. Expanding from this discovery, researchers soon made combination of alloys that included yttirum which achieved a transition temperature of 90 K. The current world record of highest transition temperature is 164K with mercuric-cuprates (HgBaCaCuO). Also, just recently in 2008, a new class of iron-based superconductors was discovered (LaOFeAs).

Despite the complex and still mysterious behaviors underlying superconductors, making one is not too difficult. The most essential component is copper-oxides or cuprates which are relatively cheap. Next, along with cuprates, add barium, lanthanum or yttrium and bake the mixture at around 900 degree Celsius for about 12-13 hours. Thus, a superconnductor is made by placing rare earth atoms between CuO layers.

Superconductors can be used in wide spectrum of our society. For example, as a strong magnet, superconductors are used in MRI machines. Better the magnetic field, better the resolution of a MRI image. Also, Large Hadron Collider, or LHC, uses many superconductors in order to smash protons in hopes of producing new particles without precedence. A more well-known example comes from maglev trains that use superconductors. In such cases, trains would “float” on strong superconducting magnets and without any friction, will not lose energy through heat which will save incredible amount of energy. A maglev train was constructed in Japan, England, and China, but due to bio-hazard created by strong magnetic fields, wider use of maglev vehicles are being constrained. In addition, the development of a double-relaxation oscillation called SQUID (Superconducting QUantum Interference Device) can be used in magnetoencephalography (MEG) which can pick up magnetic fields in human brain. When SQUID devices are cooled by liquid nitrogen or liquid helium, its superconductivity is capable of sensing a change in a magnetic field and can examine the brain activity without creating too much of a strong magnetic field like the MRI’s.

The history of superconductivity has been relatively short; however, the possibilities of its applications are far-reaching. The fact that superconductors have no resistance means that it has high efficiency which can be used as an alternative energy source, non-invasive biomagnetic and life-saving device, and a high-energy collider. Nevertheless, two of the major obstructions to be overcome is to have a better and fuller understanding of its function and ways to find an economically reasonable way to cool the superconductors. If superconductor’s transition temperature can be raised to the freezing point of liquid nitrogen, the cooling process would be much more affordable.

The lecture ended with my professor’s demonstration of magnetic levitation by a small superconductor which was cooled down with liquid nitrogen. The picture above shows similar demonstration as the one done that day. Although there is much more to be learned about superconductors, perhaps one day, I may be able to transport form city to city with magnetically levitated trains through the power of superconductors.

Reference: & Lecture given by Dr. Gene Bickers of USC on Feb. 1st.

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