A New Paradigm for Improving the Superconducting Upper Critical Magnetic Field of Nanocrystalline Niobium Carbonitride (NbC0.3N0.7) for Fusion Energy and Healthcare

When an electrical current flows through a normal conductor, such as copper, it encounters a resistance that transforms the current’s electrical energy into heat energy. It is therefore necessary to apply a permanent voltage to replenish the energy lost to the resistance and so maintain a steady current flow. There are at least three shortcomings with this situation; firstly, a constant supply of energy is required; secondly, energy is wasted in the form of heat; thirdly, the heating can itself be a problem. If, however, the electrical resistance can be removed from the conductor then these problems disappear.

Below a certain critical temperature (Tc) a superconductor abruptly enters a superconducting state that is devoid of all electrical resistance. This is the primary reason why there has been an avid search for superconducting materials with ever-higher critical temperatures. The hope is that a room temperature superconductor will one day be found. This would remove the need for expensive cooling apparatus and the associated difficulties in maintaining the cooling over long distances. In the case of power transmission lines, for example, lossless transmission of electrical power would increase efficiency, reduce energy costs and reduce the burden on fossil fuels.

The search for high temperature superconductors is therefore an active one that has been augmented by interest from the popular press - though this is by no means the whole story. Superconductivity has immediate applications in electromagnet design. All moving charges produce associated magnetic fields. If a current is made to pass through a coiled wire, called a solenoid, a uniform magnetic field can be setup in its core. If the solenoid is made from superconducting wire and is cooled below its critical temperature, the circuit will remain resistance-free, the supply voltage can be removed, there will be no energy lost from the system and the current and field will remain constant. This lack of energy loss due to the resistance-less state ensures that the only energy cost is in setting up the super-current and in maintaining the required temperature.