Chinese scholars have discovered superconductivity with a transition temperature as high as 32 K in molybdenum diboride (MoB2). This discovery opens up new possibilities for the study of borides as high-temperature superconductors. In addition, magnesium diboride (MgB2) is another boride superconductor that has attracted much attention. MgB2 has a superconducting transition temperature as high as 39 K, which is the highest critical temperature electroacoustic coupling superconductor discovered so far under normal pressure.
The application of boride powder in high-temperature superconductors is mainly based on its unique electronic structure and crystal structure. Through high-voltage technology, scientists can change the structure of the crystal, stabilize some metastable structures, and then adjust the width of the electronic energy band and change the structure of the energy band. These changes help induce the production of high-temperature superconductors and increase the critical temperature of superconductors.
Information system applications include the acquisition, transmission, storage, and processing of information. Superconductors have unique advantages in the acquisition of weak information. This goes back to a major discovery in the 1960s. In 1062, when B.D. J osephson analyzed a sandwich structure with an extremely thin insulating layer sandwiched between two superconductors; he discovered that when a D.C. voltage was applied to this structure When the two ends of a superconductor are connected, a high-frequency current would pass through the structure, so electromagnetic waves of the same frequency must be emitted. This phenomenon was later called the J osephson effect. At that time, J osephson was a graduate student of the British physicist A.B. Pippard, who once proposed the famous phenomenological theory of superconductivity, the "nonlocal superconductivity theory."
From 1961 to 1962, J osephson was greatly inspired after listening to the classes of American scientist P.W. Anderson who was a visiting professor at Cambridge University. Based on the work of his predecessors, he calculated the "superconductor-barrier-superconductor" structure. The results were unexpected, and even his mentor could not figure it out for a while. Finally, he published a paper in the European "Physical Letters" titled "Possible New Effects in Superconducting Tunnels." In his paper, he predicted that in the "superconductor-barrier-superconductor" structure, under a limited D.C. voltage, in addition to D.C. superconducting current, A.C. superconducting current will also appear.
The "superconductor barrier superconductor" structure will produce D.C. superconducting current at zero voltage.
J osephson was still a 22-year-old young man when he made such an important prediction. Later experiments proved that his prediction was correct and had important application prospects. In 1973, he was awarded the Nobel Prize in Physics for this outstanding achievement. At that time, he was only 33 years old and had successfully used the J osephson effect to make a superconducting magnetic field meter. This instrument can detect very weak magnetic fields so that it can detect distant enemy targets, such as submarines, tanks, and other moving targets. The superconductor switch made by the J osephson effect is very sensitive to certain radiations and can detect weak infrared radiation. , provide a direct basis for military command to make correct judgments, and provide a highly sensitive information system for detecting extraterrestrial aircraft, such as artificial satellites or UFOs in the universe. At present, experiments on making transistors using high-temperature superconductors are also in progress. Its successful development will surely provide new support for high-sensitivity information systems.
Experimental results have shown that any high-temperature superconductor material (such as aluminum series, silver series, etc.) can use sputtering technology or evaporation technology to form a thin film on the insulator of the electrode source and make a J osephson device. This device has high-speed switching characteristics and is a rare component for making ultra-high-speed electronic computers. Its use will greatly reduce the size of electronic computers, greatly reduce power consumption, and greatly increase calculation speed. It will combine superconducting data processors with external Memory chips assembled into a J osephson-style electronic computer, which can achieve very high processing power and can perform hundreds of billions of high-speed operations within 1 second, which will greatly exceed the computing speed of existing large-scale electronic computers.
Since the discovery of metal oxide superconductors in 1986, great progress has been made in the research of high-temperature superconductors, which has convinced the defense departments of various countries that a new national defense technology revolution will inevitably occur. In order to adapt to the new situation, countries are taking rapid action and actively carrying out Research on the application of superconductors in military systems. The ultra-light propulsion system for nuclear submarines is a prominent example. This propulsion system can double the speed and weapons load of nuclear submarines while reducing the submarine's gravity by half, killing two birds with one stone. In the early stages of rocket launch, the rocket must slide on the launcher because the faster the mechanical contact speed, the more severe the vibration, which can easily damage the launcher, so the speed must be limited. Suppose the superconducting silent propulsion system is used in a missile warhead. In that case, the warhead can destroy the enemy's ballistic missile during launch at a speed of 20,000km/h, causing the enemy missile to explode in its homeland.
The U.S. aerospace department has always been very concerned about how to improve the success rate of space shuttle launches and reduce costs. It has now proposed a plan to change the vertical launcher into a horizontal launcher. Using superconducting chain levitation technology, when the energized coil of the aircraft makes a linear motion, cutting the magnetic field lines along the orbital launch pad, a strong electromagnetic force will be generated to lift the space shuttle into the air. The key issue here is the need for a large current and strong magnetic field that can make a space shuttle take off. Obviously, these two key problems can only be solved by relying on superconducting D.C. motors and superconducting strong magnetic fields. The space shuttle is placed on a horizontal platform, and the trolley moves linearly along the suspended train track, and the trolley accelerates at an acceleration of 3.234m/s. When the speed rises to 300km/s, the space shuttle engine ignites and starts working. When the space shuttle accelerates to 500km/s at an acceleration of 9.8m/s, the aircraft separates from the horizontal platform by electromagnetic force and automatically takes off. The taxiing distance is 4km. There is also a safety issue here. If the space shuttle A safety issue during a space shuttle launch was resolved when the failure occurred within seconds of ignition, and the engine stopped working while the aircraft remained parked on a horizontal platform.
Superconducting magnetic levitation technology has a wide range of applications. More than 20 years ago, people envisioned using superconducting technology to build levitation trains to achieve high-speed railway transportation. Now, Japan, Germany, Russia, the United Kingdom, France, and China have successfully built the fastest land transportation and superconducting maglev trains. This train is suspended on the superconducting "magnetic pad" roadbed, with speeds as high as 400 to 500km/h. The speed of Japan's J.R. combined maglev train is about five times that of my country's ordinary express trains. It only takes more than 3 hours from Beijing to Shanghai. The track of Japan's J.R. combined maglev train is V-shaped, and coils made of aluminum wire are installed on its side walls. At the corresponding position at its bottom, a superconducting coil made of N.T. alloy is installed. The current passing through the superconducting coil is 686A. When the current density is 2.7×10000/cm, a strong magnetic field is generated, and the magnetic induction intensity is as high as 5.1T. As the D.C. motor starts the train, the aluminum coil on the track generates an induced current, forming a new magnetic field. Because the magnetic lines of the two magnetic fields are in opposite directions, the train levitates under the action of repulsion. By changing the current in the aluminum coil It is very convenient to control the running speed of the train.
Electric vehicles that have been put into use are composed of battery packs and electric motors. Due to the limited storage capacity of the battery, a single trip of this type of car is shorter. The use of high-temperature superconductors can greatly reduce the power loss of batteries, increase storage capacity, and increase power supply capabilities. In this way, electric vehicles will become popular around the world, which will undoubtedly be very beneficial to reducing air pollution and simplifying vehicle structures.
A non-contact power collection system for trams is under research in Canada. Its characteristic is that the power supply line uses superconducting cables and the cables are buried under the surface of the channel. A number of superconducting coils are installed at the bottom of the tram. When the tram travels along the road, the superconducting coil generates an induced current due to electromagnetic induction, thereby pushing the tram forward. This system has neither overhead lines nor tracks and has minimal power consumption, which is very different from the traditional tram concept. It is expected to expand the range of trams available greatly and may be used successfully on motorways in particular.
The electromagnetic propulsion ship designed using superconducting technology has completely changed the propulsion mechanism of existing ships. It has no rotating part and does not need to use a screw propulsion mechanism. It only needs to change the magnetic induction intensity or current intensity of the superconducting magnetic field to change the direction of the ship. Sailing speed. In addition, it also has the advantages of simple structure, convenient operation, and low noise. It is expected to become an important direction for improving ships. Japan has successfully trial-produced an electromagnetic propulsion ship with a length of 30m and a water-pushing capacity of 185t. The success of the trial production with a ship speed of 8nmile/h has greatly promoted the progress of research work in this field.
Transmission cables made of high-temperature superconducting materials have almost zero resistance and extremely small transmission losses. There are many kinds of superconducting cables. The more successful superconducting cables include the four-cylinder type and multi-core type. The cylindrical superconducting cable consists of three tubular superconducting core wires installed in a tube with a heat insulation layer. Cooling liquid nitrogen circulates inside and outside the superconducting core wire at the same time to ensure that the superconducting cable is superconducting. The structure of multi-core superconducting cables is similar to ordinary cables. Superconducting wires with a diameter of less than 100 μm are evenly distributed in the electrical insulation layer and covered with copper tubes with a diameter of 2 mm under the action of internal and external cooling liquid nitrogen. A cable in a superconducting state is a superconducting cable.
Japan is developing a superconducting generator with an excitation coil-rated current capacity of 70MVA and a critical current density of 150A/mm. Superconducting generators have many advantages. Since the coil windings use superconducting wires, they can reduce current losses, improve work efficiency, and expand Motor capacity, reduce motor size. Therefore, superconducting generators have become an important project in technology development.
Traditional transformers have limited performance due to eddy current and hysteresis losses. Using A.C. superconducting wires to make the coil windings of the transformer can greatly reduce the eddy current and hysteresis losses of the transformer and increase the output power of the transformer. In terms of structure, the structure can be simplified to develop small and lightweight transformers. Japan has successfully trial-produced A.C. superconducting wire NbTi alloy with a rated current of 100A. Using this material to make a 500kW A.C. superconducting coil has a power loss of only 0.007%.
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