Proposals For Superconductors In Maglev Trains Biology Essay


During the investigation it was found that a small number of companies have established a stranglehold on the magnetic levitation train industry. Some of these companies have been researching maglev trains and the subsequent superconductor technology for approximately 50 years. As their research is so far ahead and the intellectual property rights on the technology, means a company diversifying into maglev technology is far behind and impossible to compete at this moment in time. Several years of research would be needed in order to compete. However two ceramics were identified that could be starting points for further research. These are YBCO and BSCCO. These ceramic superconductors can both be cooled by liquid nitrogen which is abundant, inexpensive, easy to store and easy to use. This is a major benefit, in both financially and practically. Out of these two it was decided that BSCCO was the better and is what is recommended to proceed with.

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The methods of processing are more varied and sol-gel processing, high energy powder compaction techniques and seeded infiltration growth technique (SIG) were all analysed. From the research that was conducted the best method to proceed with would be the seeded infiltration growth technique (SIG). This was due to its ability to prevent macro defects and also produce large products with few distortions.


Superconductivity, which occurs in certain materials at very low temperatures, means the material has no electrical resistance and no interior magnetic field when superconductive. In 1911, it was discovered by Heike Kamerlingh Onnes [1] that the electrical resistance of mercury disappeared absolutely when cooled down to 4.2 Kelvin using liquid helium. The phenomenon is then called superconductivity, while the other significant characteristic, diamagnetism, was discovered by Meissner and Ochsenfeld in 1933 [1]. They found if a superconductor was cooled in a magnetic field, the magnetic induction lines were expelled at the same time when the electrical resistance disappeared. Although the problem of magnetoelectricity was overcome, the barrier from the low critical temperatures remained difficult to break.

In the early times, with respect to superconductors, most focuses were on simple elements like tin and aluminium, various metallic alloys and some heavily-doped semiconductors [2]. However, the edge of the long-term lack of progress in superconductor research was broken in 1986, when some cuprate-perovskite ceramic materials were found with critical temperatures of more than 90 Kelvin. From a practical perspective, 90 Kelvin is easy to reach with the readily available liquid nitrogen (boiling point 77 Kelvin). This means more experimentation and more commercial applications are feasible, especially if materials with even higher critical temperatures could be discovered [2].

With the development of superconducting ceramics, more and more attentions were paid to their attractive applications in power generation, power transmission and energy storage. What's the most eye-catching in recent decades; superconducting ceramics are playing an important role in magnetically levitated trains.

Based on the different technologies used, levitation systems can be classified as Electro Magnetic System (EMS) and Electro Dynamic System (DMS) [3]. Due to the diamagnetism of superconductors, they can be used in the DMS. When a superconductor is positioned above a permanent magnet, repulsion will appear between them since no magnetic force is able to go through the superconductor. Hence the levitation brought by the repulsion results in a high speed of about 500 km/h, which the magnetically levitated trains can achieve without any resistance from touching the ground.

As early as 1922, Hermann Kemper, a German engineer, put forward the principle of electro-magnetic levitation, and in 1934 he succeeded in applying for a patent of maglev trains. It was the first beginning of the maglev trains. Since 1970s, with the development of the economic strength of the world's industrialized nations, the developed countries, such as Germany, Japan, the United States, Canada, France, Britain, have begun to formulate plans for magnetic levitation transportation system development to enhance the transportation capacity to meet the needs of their further

economic development.

However, the United States and the former Soviet Union gave up the research in 1970s and 1980s, respectively. Currently, only a few countries, including German, Britain, Japan and China are still studying the maglev system, and fortunately, astonishing progress has been achieved, especially with the use of the superconducting ceramics.

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A maglev train system was laid in Berlin, Germany, in the 1980s. There were three stations in the system, the length of which was 1.6km, using a driverless train. However, due to some political reasons, the line was changed to a general wheel-rail one after running two months, when the Berlin Wall fell.

Another low-speed magnetic levitation train was used in Birmingham International Airport in Britain, from 1984 to 1995. But the reliability problems made the line changed later.

The magnetic levitation train in Shanghai, China, is shown in Figure 1. It is running nowadays, with a length of 30km, and the time required to go through is only 8 minutes. However, due to the very high cost, the train is just a technology product, instead of a means of transportation.

Fig. 1 Maglev levitation train in Shanghai, China

Doubtless, the rapid-developing society calls for high-speed, comfortable and low energy cost transportation like magnetically levitated trains. On the other hand, the development of magnetically levitated trains cannot live without superconducting ceramics for its possibility to carry out high critical temperature, low cost and feasibility.


At the moment there are only a few Maglev systems which are used commercially such as the Shanghai Maglev Train which started construction in April 2001 and finished in 2004[4]. Another is the Limino line in Japan which is a 9 station line in Aichi and opened in 2005. Although this has been very successful few other Maglev trains are currently open to the public. There was a Maglev train which served between Birmingham International Airport and Birmingham International Railway Station but this facility closed in 1995 due to expensive repairs. This was replaced with a bus service and then by an AirRail Link.

There are however a large number of testing facilities which have been heavily invested in to try and get the technology used more worldwide but due to expensive start up costs few countries have decided to proceed with Maglev and instead stay with the traditional Railway systems. The most known of these test facilities is the Transrapid test facility in Emsland, Germany which has a 31.5km length track which opened in 1984. Another well known test facility is the JR-Maglev test facility in Yamanashi Prefecture, Japan where the world record for the fastest Train was recorded at going 581km per hour on December 2nd 2003 [5].

Although the technology proves that the travelling times will be greatly reduced there has been little interest in upgrading to a maglev system. A good example of this would be the UK Ultraspeed project linking London to Glasgow. This project would have cut the time taken on most journeys in half but the project was rejected by the government as it was too costly. Although this was not successful there are other projects planned which are likely to go ahead. There are 2 possible projects in Australia (Melbourne and Sydney), a number in the United States, an extension of the Shanghai Maglev Train, a link between Munich and its airport, a couple of possible projects in India and a line between Tokyo and Nagoya projected to start in 2025. Not all of these are likely to go ahead though as the plans are only just starting for these projects. However it does show that the market size for Maglev is growing although it is uncertain what rate it will increase at. It also has to be said that the size of the current market is very small and there has already been a large amount of research conducted around the development of Maglev.

At the moment there are two main contractors regarding the development of Maglev trains these are Transrapid, a German company based in Emsland which have been developing Maglev trains since the late 1960's. it is a joint venture by Siemens and ThyssenKrupp. Another main developer is a joint venture by Central Japan Railway Company and Railway Technical Research Institute which is based in Japan and has the world record for the fastest train. They have 5 testing facilities located across Japan and have been developing the system longer than Transrapid as they started in 1962, 7 years earlier.


Superconductivity is when zero electrical resistance is observed. The transition temperature at which the resistance becomes zero is known as the critical temperature.

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Different materials reach this critical temperature at different temperatures. The first superconductor to be discovered was high purity mercury cooled by liquid helium. It has an extremely low critical temperature and liquid helium was not readily available and extremely expensive therefore the commercial application of superconductivity was not feasible. The optimum critical temperature is above room temperature, so its optimum working conditions would be room temperature and cooling of the superconductor would be unnecessary.

To overcome the problem of having to cool the superconductors to extremely low temperatures, other superconductors would have to be discovered. These new superconductors must have a high critical temperature.

In 1987 a superconductor was discovered, this new superconductor was Yttrium Barium Copper Oxide. It was a superconductor that could be cooled with liquid nitrogen rather than liquid helium. This was a breakthrough as liquid nitrogen is relatively cheap. This meant superconductivity technology could become more readily available.

Since then the critical temperature of ceramic superconductors have increased dramatically. The world record for critical temperature is now nearly 254 kelvin. The power of the superconductive magnets have also increased dramatically. The world record is now 26.8 tesla.

Figure 2 is a timeline depicting the discovery of early superconductors.

The most effective superconductors for magnetic levitation trains are type II superconductors. They usually conduct at higher temperatures than type I superconductors. This means they conduct high currents and can therefore make more effective electromagnets.

Yttrium Barium Copper Oxide

One high temperature type II superconductor is Yttrium Barium Copper Oxide also known as YBCO (with a chemical formula of YBa₂Cu₃O₇). YBCO was the first material to become a superconductor over 77k, the boiling point of nitrogen. Although it has a high critical temperature, YBCO is not used extensively in maglev technology because although single crystals of YBCO have a high critical current density, polycrystals have a low critical current density. This means only a small current can be transferred while still being superconductive. This problem is due to crystal grain boundaries in the YBCO.

Figure 3 shows the structure of YBa₂Cu₃O₇

Bismuth Strontium Calcium Copper Oxide

Another high temperature superconductor is Bismuth Strontium Calcium Copper Oxide also known as BSCCO. It is a cuprate superconductor that has a critical temperature which is above the boiling point of liquid nitrogen. BSCCO needs to have an excess of oxygen atoms in order to superconduct.

BSCCO was the first superconductor to be used for superconducting wires. It has the same problems with grain boundaries as YBCO, however these can be overcome thanks to Van der Waals coupled BiO layers. BSCCO can also be made into wires by the powder in tube process.

The structure of BSCCO-2212 is shown in Figure 4.

Over the last 20 years ceramic superconductors have become the drastically more effective in their use in magnetic levitation trains, however the identity of specific ceramics is kept secret by the research companies so they keep their competitive advantage. Superconductors such as (Tl₄Ba) Ba₂Ca₂Cu₇O₁₃ in a 9223 structure have a very high critical temperature but are not suitable to be used in the magnetic levitation train industry yet.

Both YBCO and BSCCO could be used as superconductors for maglev trains however if selected they would not be as effective as the superconductors used by companies such as Transrapid. As companies like this have been developing superconductors for many years their technology is very advanced and also secret.


In conventional routes, like other ceramic materials, there are three stages to process a superconducting ceramic used in magnetic levitation trains: powder mixing, shaping and green body firing. However, since superconducting ceramics are a little more complicated, the material should be synthesized before mixing. Moreover, to obtain a produce a product which can be used in magnetic levitation trains, components modeling and manufacturing is essential after all the processing stages mentioned above. The concrete stages are shown in Figure 5.

Synthesis of powders

Powder mixing

Powder compaction

Thermal treatment

Components modeling and manufacturing

Fig. 5 Processing of superconducting ceramic products

Among these stages, powder synthesis and powder compaction are the key issues of manufacturing an ideal superconducting ceramic.

Powder synthesis -sol-gel processing

When considering how to synthesise superconducting ceramic powders, usually a simple mixture of all reagent oxides [6] or a mixture of a precursor phase, a result of pre-reacting, with HgO [7] is produced to react at a high temperature. High degrees of homogenisation of the cations are in need in both cases [8].

Currently, sol-gel processing is often chosen to synthesise superconducting ceramic powders, for an excellent homogenisation at an atomic scale of the elements can be achieved.

The basic idea of sol-gel processing is to start from a cations solution, and then to jellify it by polymerisation [9]. It results in some gel which can be manipulated easily. After that, a xerogel is obtained by heating.

Obviously, the advantages, such as chemical homogeneity and chemical reactivity, have made sol-gel one of the most ideal ways to obtain optimum superconducting ceramics. However, at one time sol-gel processing was only used to synthesise Ba-Ca-Cu-O precursor powders, because the temperature required to transform the gel into the oxide phase is higher than the decomposition temperature of HgO [10].

As a consequence, an improved sol-gel method is developed to synthesise some complex oxides [11] and YBa2Cu3O7 in particular [12]. Unlike the conventional sol-gel, which includes hydrolysis-condensation of inorganic precursors, the new route uses the jellification of a solution by an in-situ polymerisation of acrylamide monomers. It gives possibility to produce a large amount of powder in a much shorter time.

In conclusion, the improved sol-gel method has a clear advantage of quality compared with the solid state reaction, and advantages of processing time and wider applicability compared with the conventional sol-gel route. That is the reason why nowadays sol-gel processing is so widely used in superconductor manufacture.

Powder compaction -high energy powder compaction techniques

The goal of powder compaction is to produce a green body which is as dense and se strong as possible. Nowadays, to fabricate a superconductor product, dynamic compaction is preferred for its very short duration of the process and the development of high pressures compared with the conventional compaction techniques [13].

In the present work, there are two high energy powder compaction techniques usually employed for producing superconducting YBCO ceramics: explosive compaction and electromagnetic compaction.

The explosive compaction and the electromagnetic compaction are shown in Figure 6 (a) and (b), respectively. While the explosive compaction creates high shock pressures and high temperatures to fracture the original grains and sinter, with the shock-waves originated from explosive detonation and propagated through the porous media, the electromagnetic compaction uses the effect of a high strength transient magnetic field.

(a) (b)

Fig. 6 Schematic diagrams of:

explosive compaction;

electromagnetic compaction

(1: silver tube (Φ12/10); 2: YBCO powder; 3: silver powder; 4: plastic disc; 5: steel bolt MS; T: selenoid; C: capacitor; 5: switch.) [13]

In products manufactured with high energy powder compaction techniques, a reduction in porosity is found as a result of the very short duration of the process and the development of high pressures. At the same time during the compaction process, fracture of the initial grains and formation of new grain boundaries lead to an increase in inter-grain current transport in the superconducting state.

A novel processing route -seeded infiltration growth technique (SIG)

As a novel processing route with infinite potential for producing superconducting ceramics in the future, seeded infiltration growth technique (SIG) has been used to process mono-domain YBa2Cu3O7−x (Y123) bulk superconductors. It includes the combination of melt infiltrated liquid source (Ba3Cu5O8) into the Y2BaCuO5 (Y211) pre-form and the nucleation of Y123 domain from SmBa2Cu3O7 crystal seed [14].

The full infiltration of the Y211 pre-form by liquid phase is shown in Figure 7. Generally, the principle is to optimize the amount of liquid phase in order to preferably convert Y211 into Y123 by making the Y211 pre-form absorb more liquid.

Fig. 7 Configuration of SIG process [14]

In the SIG process, the molten liquid phase can infiltrate into the open porous Y211 block, resulting in a large decrease in the macro defects and porosities in the sample, whilst the sample shrinkage can be neglected. With respect to dense textured samples, the SIG process could be taken into account with high Jc values [15].


Materials and processing

From the materials and the processing section a number of different ceramics and processing methods have been identified. In this section we will identify which process and which ceramic the company should proceed with. Firstly the ceramic will be discussed.

The two types of ceramic that are discussed are Yttrium Barium Copper Oxide and Bismuth Strontium Calcium Copper Oxide. From the information in the earlier section we can see that both these ceramics are adequate for a superconductor and are both very similar. However in Yttrium Barium Copper Oxide the polycrystals have a low critical current density meaning there can only be a small current whilst it is superconducting. Although the same problem occurs in Bismuth Strontium Calcium Copper Oxide it can be overcome with Van der Waals coupled BiO layers. Therefore the ceramic top use is Bismuth Strontium Calcium Copper Oxide.

The ways of processing the ceramic are more complex. The methods listed earlier are; sol-gel processing, high energy powder compaction techniques and seeded infiltration growth technique (SIG). Firstly the sol-gel process will be discussed. During this a good chemical homogeneity and chemical reactivity are achieved which are greatly desired in superconductors. This is why this process is currently widely used to produce superconductors.

The second method is high energy powder compaction techniques. During this there is often a reduction in porosity compared with other processes due to the short time it takes to produce the product and the high pressures they are put under. This also leads to a fracture of the original grain boundaries and the formation of which causes an increase in the inter-grain current transport during the superconducting state.  

The final method is SIG. this is a relatively new method of processing ceramics which is currently used to produce bulk superconductors. This process allows the ceramic to have less macro defects and porosities in the sample and reduce the shrinkage of the ceramic. One of the significant advantages of the SIG process that it offers the flexibility to engineer properties, and to produce large specimens of near-net shape without distortions makes it one of the most promising processing route to manufacture a superconducting ceramic used in magnetic levitation trains in the future. 

From the points above it has been decided to proceed with the SIG method as it is seen as a good way to get the best properties out of the ceramic and is a different method to conventional ways of processing superconductors possibly giving us an edge over the competitors.

Recommended course of action

The most prominent problem with Magnetic levitation trains is the huge amount of capital needed to finance such an ambitious venture. There have been several different routes explored trying to pertain the most efficient and cost effective with varying levels of success. Although landmarks have been reached such as the JR-Maglev train, the fastest rail vehicle in the world. This train reached a top speed of 381 km/h (361 mph) using an Electro-dynamic Suspension system. There are several existing maglev systems some of them including the distance have been listing below and where available the cost of the system:

General Atomics, San Diego. 120 meter test track. $90 million in research funding from the federal government, total cost unknown.

Transrapid, Emsland, Germany. 31.5 km track.

JR-Maglev, Yamanashi, Japan. 18.4 km track.

Linimo, Aichi, Japan. 8.9 km track, roughly $100 million per kilometre.

Shanghai Maglev, China. 30.5 km track, $ 1.33 billion.

There have also been maglev systems proposed in Australia, UK, Iran, Japan, Venezuela, China, India, the US, Germany and Indonesia. However several of these planned systems have been abandoned such as the London-Glasgow line.The pecuniary problem is therefore not only linked to technological problems such as having to build new tracks but also a limited potential target market. However the limited target market is linked to the high cost of maglev trains, with research this cost should reduce and therefore the number of potential investors should increase. This is speculative and a high risk venture as technological breakthroughs might not be reached.

Research into maglev train systems have been underway since the 1970s. A small number of companies have established a stranglehold on maglev technology and the constituent superconductor technology and production. Their current technology is very secretive and if Rennib Advanced Ceramics Ltd were to start developing superconductors, the technology would be several years behind market leaders such as Transrapid. Having said this, competition is one of the main factors that defines capitalism, with competition the price of maglev technology would decrease, therefore the market would increase as maglev systems would be more affordable, and with a larger market becomes more potential profit.

One way for the maglev market to expand is to evacuated tunnels. This means the trains would run in a vacuum with a pressurised cabin. As it would be a vacuum there would be no air resistance meaning the theoretical speeds would be faster than an aeroplane. However this system would increase the cost even further and there is significant safety risk concerning the lack of oxygen.

In its current situation maglev rail systems have a limited potential target market, extremely high costs with a small number of companies with a stranglehold on this niche market. As Rennib Advanced Ceramics is a late starter to the maglev market and with the limited potential growth of the market unless huge amounts of capital are invested, superconductors for magnetically levitated trains would not be a wise investment.


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[2] Wikipedia: superconductor.

[3] P.F.Dahl. Superconductivity, AIP, 1992.



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[15] S. Meslin and J.G. Noudem, Supercond. Sci. Technol. 17 (2004), p. 1324.