Niobium foil and Niobium sheets from raw materials to quantum technology

Niobium is an indispensable basic material in modern superconducting technology. As the single-component superconductor with the highest critical temperature (Tc = 9.2K), pure niobium exhibits two superconducting characteristics - zero resistance and complete diamagnetism - at low temperatures, making it the preferred material for manufacturing core components such as superconducting resonators and superconducting magnets. The superconducting niobium foils and sheets, which are made from high-purity metallic niobium (with a purity of ≥ 99.95% or even 99.99%), are processed through precise rolling techniques into thin sheet-like materials. They are widely used in cutting-edge technologies such as particle accelerators, nuclear magnetic resonance imaging (MRI), and controlled nuclear fusion.

From the perspective of the industrial chain, superconducting niobium materials are at the core and upstream position of the entire superconducting industry. The superconducting materials industrial chain consists of three parts: the upstream raw materials, the middle superconducting materials, and the downstream superconducting applications. The upstream raw materials mainly include metal mineral resources such as titanium, niobium, yttrium, and barium. Among them, niobium, due to its unique superconducting properties, holds a dominant position in the low-temperature superconducting field - low-temperature superconducting materials such as niobium-titanium (NbTi) and niobium-trisilicon (Nb₃Sn) occupy the vast majority of the superconducting materials market.

The production of niobium foils and sheets for superconductivity is a complex process that integrates powder metallurgy, vacuum melting, and precise rolling. Due to the extremely high affinity of niobium for gases such as oxygen, nitrogen, and hydrogen, the entire production process must be carried out in a strict vacuum or inert gas protection environment to ensure the high purity of the material and its superconducting properties.

Raw material purification and ingot preparation. This is the fundamental step that determines the superconducting properties of niobium materials. In industry, electron beam melting (EBM) or vacuum self-dissolution arc melting (VAR) technologies are mainly used. Under high-temperature and high-vacuum conditions, volatile impurities can be effectively removed, resulting in niobium ingots with a purity of over 99.95% (Class Nb1) or even over 99.99% (high-purity grade). For superconducting applications, the purity of niobium materials directly affects key performance indicators such as the quality factor (Q value) and acceleration gradient of the superconducting resonator.

Hot processing and cold rolling forming. The high-purity niobium ingot is first subjected to hot rolling for blanking, gradually reducing the thickness of the ingot; then it proceeds to the cold rolling process, where it is gradually thinned to the target thickness through multiple passes of precise rolling. During the cold rolling process, the niobium material undergoes "work hardening", so intermediate annealing treatments need to be interspersed. Annealing is typically carried out at 800–1000°C in a vacuum or protective atmosphere to eliminate internal stress and restore the ductility of the material.

Finished product processing and testing. The final refined niobium foil/niobium sheet after final rolling needs to undergo acid washing to remove the surface oxide layer, or undergo vacuum annealing to improve the surface cleanliness. For high-end applications such as superconducting niobium cavities, surface roughness control (Ra better than 0.5 μm) and defect detection are also required - the defect density of niobium foil for such high-end applications is extremely strict.

Furthermore, with the advancement of superconducting thin film technology, processes such as sputtering film coating have also been employed to fabricate niobium films on substrates, meeting the requirements of microelectronic superconducting devices. In the field of microelectronic superconducting material preparation, there is also a process route that combines powder metallurgy with high-temperature and high-pressure sintering.

The size specifications of superconducting niobium foils and sheets have been established in a complete and standardized system, covering the entire range from ultra-thin foils to thick plates.

Niobium foil (thickness 0.01 - 0.09mm): This is the most notable specification range in the field of superconducting applications. The thickness range covers from 0.01mm to 0.09mm, with a width of 30 - 150mm and a length greater than 200mm. Commonly used commercial thicknesses include 0.025mm, 0.03mm, 0.05mm, 0.076mm, and 0.09mm, etc. This type of ultra-thin Niobium foil is mainly used for the production of superconducting niobium cavities, the base band of superconducting tapes, and the core components of special superconducting devices.

Niobium strip (thickness 0.1 - 0.5mm): Thickness 0.1 - 0.5mm, width 50 - 300mm, length 100 - 2000mm. It is available in both hard state (Y) and soft state (M, i.e. annealed state). Such products are suitable for the winding baseband of superconducting magnet coils, the shielding layer of superconducting cables, etc.

Niobium plates/foils (thickness > 0.5mm): The thickness ranges from 0.5mm to 30mm, with the maximum width reaching up to 1000mm and the maximum length up to 2000mm. Thicker Niobium plates are mainly used as insulation screens in high-temperature furnaces, structural supports for superconducting magnets, and neutron reflection layers in nuclear reactors.

Dimension tolerance control: For superconducting applications, dimensional accuracy is of utmost importance. The thickness tolerance varies depending on the thickness: for niobium foils with a thickness of 0.1 to 0.2 mm, the tolerance is ±0.015 mm, while for thicker plates, the tolerance is relaxed accordingly. Additionally, the supply state of niobium materials is classified as hard state (Y, cold processed state) and soft state (M, annealed state), with the former having higher strength and the latter having better ductility. The choice can be made based on the subsequent processing requirements.

Superconducting radio frequency cavities are one of the most core applications of niobium materials. The core component of particle accelerators (such as free electron lasers and synchrotron radiation sources) - the superconducting radio frequency cavities, are usually made from high-purity niobium sheets through processes such as stamping, welding and chemical polishing. The niobium cavities can generate high-intensity accelerating electric fields with extremely low loss, and are key equipment for high-energy physics research. With the continuous implementation of new-generation integrated research platforms in physics, chemistry, biology and materials at the national level, the demand for superconducting niobium materials and niobium superconducting cavities is constantly increasing.

The base material of low-temperature superconducting wire. The superconducting niobium material can be used to produce alloy materials such as NbTi and Nb₃Sn. These alloy materials are key materials for manufacturing superconducting magnets. In the field of controlled nuclear fusion (such as the ITER international tokamak fusion experiment reactor), superconducting magnets are used to generate strong magnetic fields to confine plasma. Currently, NbTi wire occupies more than 90% of the market share of low-temperature superconducting materials due to its good ductility and ease of shaping.

Medical imaging equipment (MRI). The superconducting magnets of magnetic resonance imaging equipment are an important application field for niobium-titanium wire. As the core component of MRI, the cost of the superconducting magnets accounts for 30%-40% in 1.5T MRI and 50%-60% in 3.0T MRI. The stable supply of high-purity niobium materials directly affects the production cost and technical level of MRI equipment.

The demand for high-field superconducting magnets is increasing. With the rapid development of cutting-edge fields such as controlled nuclear fusion, high-energy physics, and quantum computing, the demand for superconducting magnets with higher magnetic field intensities has soared. This has driven continuous improvements in the processing techniques of superconducting materials like Nb₃Sn (such as powder-in-tube method and optimization of heat treatment processes) to enhance the mechanical strength and operational stability of the magnets.

New application areas are constantly expanding. Besides traditional high-energy physics and medical imaging, superconducting niobium materials are now extending to the field of quantum computing - superconducting qubits, as the core component of a general-purpose quantum computer, require the preparation of high-quality superconducting niobium films and niobium-based devices. Additionally, the demand for magnetically controlled floating-zone single-crystal silicon (MCZ) equipment for superconducting magnets is also increasing day by day.

Chinese Manufacturer - Fortu Tech supplies Niobium foil to multiple countries and regions around the world. Its service coverage includes the United States, Canada, Russia, Germany, France, the United Kingdom, Italy, Sweden, Austria, the Netherlands, Belgium, Switzerland, Spain, Czech Republic, Poland, Japan, South Korea, as well as Chile, Brazil, Argentina, Colombia and other places in Latin America.

Fortu Tech in China can also produce and process Niobium Capillary Tube, Niobium billet, Niobium sheet, Niobium plate, Niobium rod, Niobium wire, Niobium tubes.

If you have any questions or need quote, price, please send email to info@fortu-tech.com.