Example of Superconducting Materials

Chemistry / by admin / July 04, 2021

protection click fraud

A superconducting material is one that manifests the ability to conduct electrical energy without presenting resistance or energy losses under certain conditions. This quality is called Superconductivity, and It was discovered in 1911 by Heike Kamerlingh Onnes.

It has been concluded that, as the temperature decreases, the electrical resistivity of a metallic conductive material gradually becomes poorer; However, in the conductors usually used, such as Copper Cu and Silver Ag, defects such as impurities generate a ceiling value in the substance. In the case of Copper, even close to absolute zero, a non-zero resistance is shown.

The resistance of a superconductor drops sharply to zero when the material cools below its critical temperature. An electric current flowing in a superconducting wire can persist indefinitely without a power source. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon of quantum mechanics.

Magnetic Character of Superconductors

Although the most outstanding property of superconductors is the absence of resistance, it cannot be said that it is a material of infinite conductivity. In fact, a type I superconducting material is perfectly diamagnetic

instagram story viewer

. Diamagnetism is the quality of a material that allows it to drive away magnetic fields. Contrary to Paramagnetism, which consists of reacting to the attraction of magnetic fields. This means that it does not allow the field to penetrate, which is known as the Meissner effect.

Magnetic fields differentiate two types of superconductors: type I, which do not allow an external magnetic field to penetrate (which entails a high energy effort, and implies the sudden rupture of the superconducting state if the critical temperature is exceeded), and type II, which are imperfect superconductors, in the sense that the field effectively penetrates through small channels called Abrikosov vortices, or fluxons. These two types of superconductors are in fact two different phases that were predicted by Lev Davidovich Landau and Aleksey Alekséyecih Abrikosov.

When a weak external magnetic field is applied to a type II superconductor, it repels it perfectly. If it is increased, the system becomes unstable and begins to introduce vortices to decrease its energy. These vortices are increasing in number, placing themselves in vortex networks that can be observed using appropriate techniques. When the field is large enough, the number of defects is so high that the material is no longer a superconductor. This is the critical field that stops a material from being superconducting, and it is temperature dependent.

Electrical Character of Superconductors

The emergence of superdiamagnetism is due to the material's ability to create supercurrents. Supercurrents are currents of electrons in which no energy is dissipated, so that they can be maintained forever without obeying the Joule Effect of energy loss due to heat generation. The currents create the strong magnetic field necessary to sustain the Meissner effect. These same currents allow energy to be transmitted without energy expenditure, which represents the most outstanding effect of this type of materials.

Because the number of superconducting electrons is finite, the amount of current the material can carry is limited. Therefore, there is a critical current from which the material stops being superconducting and begins to dissipate energy.

In type II superconductors, the appearance of fluxons causes that, even for lower currents Critically, an energy dissipation is detected due to the collision of the vortices with the atoms of the lattice.

High Temperature Superconductors

Due to the low temperatures needed to achieve superconductivity, the most common materials are They are usually cooled with liquid helium (liquid nitrogen is only useful when handling high-speed superconductors). temperature). The required assembly is complex and expensive, being used in few applications, such as the construction of powerful electromagnets for nuclear magnetic resonance (NMR).

In the 80s, they were discovered high-temperature superconductors, which exhibit the phase transition at temperatures above the liquid-vapor transition of liquid nitrogen. This has reduced the costs in the study of such materials, and opened the door to the existence of materials superconductors at room temperature, which would mean a revolution in the industry of the contemporary world.

The biggest disadvantage of high-temperature superconductors is their ceramic composition, which makes them unsuitable for making cables by plastic deformation. However, new techniques have been developed for the production of tapes such as IBAD (Ion Beam Assisted Deposition). Through this technique, cables of lengths greater than 1 kilometer have been achieved.

Examples of Superconductor Applications

A superconductor behaves very differently from normal conductors. It is not a conductor whose resistance is close to zero, but the resistance is exactly equal to zero. This cannot be explained by the conventional models used for common drivers, such as the Drude model.

Superconducting magnets are some of the most powerful electromagnets known. They are used in maglev (magnetic levitation) trains, in nuclear magnetic resonance (NMR) machines in hospitals, and in targeting the beam of a particle accelerator. They can also be used for magnetic separation, where weak magnetic particles are drawn from a background of less or non-magnetic particles, as in pigment industries.

Superconductors have also been used to make digital circuits and radio frequency and microwave filters for mobile phone base stations.

Superconductors are used to build Josephson junctions, which are the building blocks of SQUIDs (Superconducting Quantum Interference Devices), the most widely known magnetometers sensitive.

Depending on the operating mode, a Josephson junction can be used as a photon detector or as a mixer. The large change in resistance to the transition from the normal state to the superconducting state is used to build thermometers in cryogenic photon detectors.

Innovative and forward-looking applications include high performance transformers, energy storage, electric power transmission, electric motors and levitation devices magnetic.

However, superconductivity is sensitive to moving magnetic fields so applications that use alternating current, such as transformers, will be more difficult to make than those that are fed with current keep going.