Nobelium-titanium alloy is the undisputed leader in the field of low-temperature superconducting materials. Its performance and development trends have a profound impact on high-energy physics, medical diagnosis, energy, and frontier scientific research. The properties of nitinol (typically referred to as Nb-47wt.%Ti, an alloy with a titanium content of approximately 46-50wt%) form the basis for its use as a practical low-temperature superconducting material.
Compared with brittle ceramic superconductors (such as Nb3Sn) with good toughness, the Nb-Ti alloy has excellent ductility. It can be drawn into extremely fine wires (at the micron level) and can withstand huge electromagnetic stress. Excellent compatibility: It can be stably compounded with a large amount of copper (or aluminum) to form multi-core superconducting wire materials. The role of copper is crucial. When the superconducting state becomes unstable (or "superconductivity loss"), it provides a low-resistance bypass for the current to prevent the wire from burning out. Heat conduction helps dissipate local heat. Excellent cost-effectiveness and reliability - the reasons for its market dominance. The mature process includes melting, forging, drawing, and heat treatment, with a mature industrial system spanning over half a century. The cost is relatively low. The raw materials (niobium, titanium) are relatively easy to obtain. Although the processing technology is complex, it can be scaled up. Extremely high reliability: Long-term performance stability, good fatigue and strain resistance.
The tens of thousands of tons of superconducting magnets required for high-energy physics devices such as the Large Hadron Collider (LHC) and the International Thermonuclear Experimental Reactor (ITER) are almost all made of Nb-Ti superconducting wires. Nuclear Magnetic Resonance Imaging (MRI): The main magnets of clinical 1.5T and 3.0T MRI systems are the largest consumer market for Nb-Ti alloys worldwide (accounting for over 90%). Nuclear Magnetic Resonance Spectrometer (NMR) is used for analyzing the structure of substances. Research-grade high-field magnets are combined with Nb₃Sn to manufacture research-grade magnets below 15T.
Improving the critical current density (Jc) at high fields: Through more precise control of the microstructure (such as optimizing the precipitation morphology and distribution of Ti, introducing nanoscale artificial pinning centers, etc.), an attempt is made to approach the theoretical limit of the material. The goal is to enable it to maintain high current-carrying capacity even at higher magnetic fields (such as above 7T), in order to challenge some of the market share of Nb3Sn.
Ultra-fine multi-coreization and optimization of AC loss: To meet the demand for low AC loss in future fusion reactors, high-frequency accelerators, superconducting power transmission and other fields, it is necessary to make the superconducting core wires reach the sub-micron level and optimize their twisting and arrangement. This requires extreme processing and control technologies.
Instead of using traditional Nb-Ti wire with precious metal substrates, high-purity oxygen-free copper is used as the stabilizer. To reduce costs, lighten weight and enhance strength, efforts are being made to actively develop "aluminum-based stabilized Nb-Ti wire" using high-purity aluminum or aluminum alloys as the alternative stabilizer. This is of great significance for future super-large devices (such as fusion power stations).
The higher mechanical properties are necessary to cope with more extreme electromagnetic stresses in the future (such as in compact fusion devices), and thus require the development of Nb-Ti composite wire with high mechanical strength. Quantum computing, as the base material or cavity material for manufacturing high-performance superconducting quantum bits, has put forward unprecedented requirements for the surface purity, consistency, and extremely low loss of it. This is one of the current most cutting-edge research hotspots, and it requires controlling impurities and defects at the material origin.
Compared with the composite integrated development of other superconductors such as Nb-Ti/Nb3Sn or Nb-Ti/high-temperature superconductors (such as REBCO) in mixed structure wires or magnets, they can leverage their respective advantages to achieve a smooth performance transition from low fields to high fields. At higher temperatures: As liquid helium resources become scarce and prices rise, research on the performance of Nb-Ti in the temperature range above 4.2 K (such as 10 K level, which can be cooled by new refrigeration machines or liquid hydrogen/neon) is conducted to adapt to more economical cooling methods. Although its Tc is fixed, the optimized materials may have better performance at slightly higher temperatures than the existing commercial materials.
