Insights from industry

Niobium and Tantalum Superconductor Materials

In this interview, individuals from H.C Starck Solutions talks about how refractory metals like niobium and tantalum can be used in superconducting applications, and how H.C. Starck Solutions apply their expertise in this field.
 

What materials does H.C. Starck Solutions supply for superconductor applications?

H.C. Starck Solutions primarily supplies niobium (Nb) and tantalum (Ta) in sheet and rod forms for Low Temperature Superconductor (LTS) wire manufacturing, and provides extrusion services for the large diameter wire bundles for final redrawing by our customers.

Superconductors can be split into LTS and High Temperature Superconductors (HTS). LTS wire is used today in a variety of applications from medical equipment like MRI and NMR to magnetic levitation, mass spectroscopy, particle accelerators, nuclear fusion research equipment and others.

HTS is still mostly in development stage, with a variety of ceramic based materials reaching higher and higher operation temperatures. LTS wire, which requires cryogenic cooling, remains the workhorse in the industry, however.

The high magnetic fields in MRI scanners are generated using superconducting magnets

The high magnetic fields in MRI scanners are generated using superconducting magnets

How do the superconductor applications for these metals compare to the other areas H.C. Starck Solutions caters to, in terms of market size?

Tantalum’s unique combination of properties make it the primary choice in key electronic applications like capacitors, microchips and others. The chemical processing industry utilizes its high corrosion resistance in heat exchangers, reactors and other equipment for handling hot, concentrated acids. Compared with these two main market segments, the volume of Ta used in superconductors is relatively small.

When compared with the other main applications, including as an alloying element in steel and a variety of other alloys, numismatics, optics or nuclear power generation, Nb usage in superconductors also represents a small percentage of the total market.

Data published in TIC Bulletin No. 160 (Dec 2014) indicates that the main uses of Nb in 2013 were as follows:

  • 88% for High Strength Low Alloy Steel (HSLA) ferro-niobium
  • 4% for niobium chemicals
  • 4% for vacuum-grade niobium master alloys
  • 3% for pure niobium metal
  • 1% for niobium alloys such as NbTi

Are there any particular projects you have supplied superconducting materials for that you can tell us about?

Yes, our materials and extruded products have ended up in a variety of recent well-known international projects. These include research projects into clean fusion energy, and fundamental physics experiments using large-scale particle accelerators.

Superconducting coils are used in particle accelerators like the LHC, to accelerate the particles and control their path.

Superconducting coils are used in particle accelerators like the LHC, to accelerate the particles and control their path. Image Credits: CERN

What are the requirements for niobium for superconducting applications, as opposed to alloying or other uses?

Each Nb application has its own set of criteria and critical properties.

In the manufacturing of superconducting wire, both the sheet, which is typically used as diffusion barrier between copper (Cu) and tin (Sn), and the rod, which is mainly used to generate the Nb3Sn superconducting compound, have strictly controlled mechanical properties, surface roughness and chemical composition.

This is necessary in order to facilitate processing and ensure the realization of a high quality superconductor wire.

In steel making and alloying, the chemical composition remains important, although not as strictly controlled as in superconductors, and the mechanical properties or surface quality are less significant.

In numismatics, the mechanical properties and anodizing properties are important, where other properties are more relaxed.

What are the main ways tantalum is used in superconductor apps?

The main role of tantalum in superconductors is to form a stable and reliable diffusion barrier between the Cu matrix and Sn. This barrier starts as a sheet of Ta whose thickness will be reduced throughout the process of drawing to only a fraction of its initial thickness.

It is paramount that the Ta layer remains intact, preventing direct contact between the Cu and Sn. This is why the initial thickness uniformity, surface quality, microstructure and mechanical properties are of vital importance. Poor control of these properties can result in reduced yields, poor magnetic properties, and a number of other undesirable effects.

Nb properties are equally important for slightly different reasons but with the same goal in mind.

This is where H.C. Starck Solutions excels; not only have we achieved processes allowing us tight control of all critical parameters and properties, but also we constantly strive to make improvements using microstructural or mechanical properties optimization capabilities at our in-house, state-of-the-art R&D facilities.

H. C. Starck supplies Nb and Ta for superconducting applications in both rod and sheet form.

H. C. Starck supplies Nb and Ta for superconducting applications in both rod and sheet form.

How do you think the use of this material will develop?

Although quite mature, there is room for improvement in both Ta and Nb for superconductors, both in terms of property control, and in manufacturing methods.

We believe there are ways to improve Ta and Nb sheet and rod properties through novel manufacturing processes or by finely tuning existing ones.

How do you think the market for superconductor materials will develop over the next few years?

There are immense efforts to bring High Temperature Superconductors to mass production. However, we believe that LTS will continue to represent a large percentage of the superconducting material market. Ultimately, the cost-to-properties ratio will allow LTS, and therefore Ta and Nb, to maintain a significant percentage of the market.

For example, these LTS superconducting materials will certainly continue to be used for the large particle accelerator programs. A very large project on the horizon that is still in the planning stages will require thousands of kilometres of superconducting wire.

About H.C. Starck Solutions

The H.C. Starck Group is a leading global supplier of technology metals and advanced ceramics. The company operates modern manufacturing facilities in Europe, America, and Asia and serves growing industries such as the electronics, chemicals, automotive, medical technology, aerospace, energy technology, and environmental technology industries, as well as engineering companies and tool manufacturers.

On December 31, 2017, the H.C. Starck Group had 2,600 employees in the United States, Canada, Great Britain, Germany, China, Japan, and Thailand.

H.C. Starck’s products are predominantly based on technology metals: Tantalum, Niobium, Tungsten, and Molybdenum.

The Fabricated Products Division converts technology metal powders into customized semi-finished and finished products through pressing, sintering, rolling, melting and thermo-mechanical processing and surface treatment.

The Tungsten Division provides high performance products for the mechanical engineering and tool making, automotive and energy industry, aviation industry, and the chemical industry, for example:

  • tungsten carbides for carbide tools and wear parts
  • tungsten and cast tungsten carbides for oil and gas drilling
  • tungsten metal powders for heavy metal alloys
  • tungsten chemicals as precursors for catalysts

The Advanced Ceramic Components (CER) Division manufactures specialized technical ceramic parts and films. CER produces engineering parts such as sealing rings, functional parts including fuel cells for solid oxide fuel cell (SOFC) systems and products for dental applications as well as for armor and wear protection. Furthermore, CER focuses on technological developments to expand the portfolio toward product applications in the semiconductor industry.

In 2018 H.C. Starck sold the division Surface Technology & Ceramic Powders to the Swedish Höganäs Group, effective March 1st and the division Tantalum and Niobium to the JX Nippon Mining & Metals Group, effective July 1st.

The group is led by a two-member Executive Board: Dr. Jens Knöll (Chairman of the Executive Board), Dr. Jan Lösch (Member of the Executive Board).

H.C. Starck was founded in Berlin in 1920. Since 2007, the company is owned by financial investors Advent International and The Carlyle Group.

H.C. Starck is registered in Goslar (Germany) and the Group’s headquarters is located in Munich (Germany).

H.C. Starck Fabricated Products

This information has been sourced, reviewed and adapted from materials provided by H.C. Starck Solutions.

For more information on this source, please visit H.C. Starck Solutions.

Disclaimer: The views expressed here are those of the interviewee and do not necessarily represent the views of AZoM.com Limited (T/A) AZoNetwork, the owner and operator of this website. This disclaimer forms part of the Terms and Conditions of use of this website.

Will Soutter

Written by

Will Soutter

Will has a B.Sc. in Chemistry from the University of Durham, and a M.Sc. in Green Chemistry from the University of York. Naturally, Will is our resident Chemistry expert but, a love of science and the internet makes Will the all-rounder of the team. In his spare time Will likes to play the drums, cook and brew cider.

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