Ceramics are known for their electrical insulation characteristics, but they can also exhibit high electrical conductivity. The advent of high temperature ceramic superconductors has made superconductivity a practical technology with meaningful applications in the fields of transportation and medical. For instance, MagLev Trains involve the use of magnetic force or magnets to run or levitate. The mechanism of magnetic field generation and the type of materials used for that purpose vary amongst the different MagLev projects.
Certain materials exhibit superconductivity when their electrical resistance becomes zero. The transition temperature at which zero electrical resistance observed is called the critical temperature, which varies amongst different materials. High purity mercury cooled by liquid helium was the first superconductor discovered in 1911. The extremely low critical temperature of this superconductor and the scarcity and high-cost of liquid helium made the commercial application of superconductivity not feasible.
Simple elements such as aluminum, tine, some heavily-doped semiconductors, and different metallic alloys were used in the early years of superconductor development. To address the problem of cooling the superconductors to extremely low temperatures to enable superconductivity, it became necessary to develop superconductor materials with higher critical temperatures. Yttrium Barium Copper Oxide was the first high temperature superconductor discovered in 1987. As this material allows for liquid nitrogen cooling, it is not only more practical but also more economical. Since then, the world has witnessed a dramatic increase in the critical temperature of ceramic superconductors as well as in the power of the superconductive magnets.
At present, only a few MagLev Systems are commercially operated, including the Shanghai Maglev Train operating between the outskirts of central Pudong and Shanghai Pudong International Airport. With a top operational commercial speed of 431km/h, this train becomes the fastest train in the world being operated in regular commercial service. The Limino Line being operated in Japan is another MagLev System. At present, few other MagLev trains are also available public access. Figure 1 shows a MagLev train operated between Birmingham International Railway Station and Birmingham International Airport. However, expensive repairs forced to close this facility in 1995.
Figure 1. A MagLev train operated between Birmingham International Railway Station and Birmingham International Airport.
In 1990, MagLev transportation achieved another key milestone in Japan with development of the 11-mile long Yamanashi Maglev Test Track (Figure 2), which was used for MLX01 vehicle testing between 1997 and 2011. The track was closed temporarily for upgrading to commercial specifications and line extension to 26 miles. In June 2013, the track used for testing a five- car train at speeds up to 500km/h. Superconducting magnets are used in the Yamanashi System for the basic functions, including propulsion, levitation, braking, and guidance.
Figure 2. The L0 (L-zero) series magnetic-levitation train, developed by Central Japan Railway Company sits parked on a test track at the control center before a trial run in Tsuru, Yamanashi Prefecture.
Liquid helium was used for cooling the magnets in the earlier versions. Rare earth ceramic materials are used as magnets in the later versions. These materials exhibited the property of crossing the supermagnetic threshold at higher temperatures and cooled by liquid nitrogen. Achieving higher speeds is the key advantage of this system, thanks to a larger levitation space enabled by the onboard magnets. One of the latest MagLev developments is the promise of the Japanese government to provide loans to the US to cover 50% expenses of a high-speed MagLev train link between Baltimore and Washington DC that will shorten the journey time to just 15min.
It has to be said that the highly specialist ceramics utilized in the MagLev transportation are vastly different from the technical ceramics offered by Precision Ceramics. Nevertheless, their application is equally significant, which can be obviously witnessed from the ever-expanding field of applications wherein they find specific use.
This information has been sourced, reviewed and adapted from materials provided by Precision Ceramics.
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