An electric motor (left) as used in millions of car‘s gearboxes, was chosen by the Fraunhofer team as one of their benchmark. The permanent magnets (rotor with quarter ring magnet, centre; rotor as flux collector, right) built into them contain rare earths. The Fraunhofer researchers significantly reduced the need of rare earths using a combination of different approaches.
Rare earths are among the most strategically important raw materials for German industry, as they are crucial parts of many high-tech products. For a more efficient use of these valuable elements, eight Fraunhofer Institutes have developed new solutions in a now completed joint project. These include optimized manufacturing processes, approaches to recycling and the development of new materials that can replace rare earths. The Fraunhofer experts showed that the demand for rare earths can be reduced to up to one fifth of today’s value in benchmark electric motors.
In the Fraunhofer flagship project “Criticality of rare earths”, launched in 2013, eight Fraunhofer Institutes bundled their expertise to enable a more efficient use of these raw materials. The trigger for the project was a price shock: China, where about 90 percent of the world’s rare earths are produced, then imposed an export stop, the prices skyrocketed and the vulnerability of German industry in terms of security of supply of these raw materials became obvious.
Therefore, the researchers aimed to use the available rare earths more wisely and to look for substitute materials, especially for the elements dysprosium and neodymium. These are needed, for example, for magnets, such as those used in electric motors. As a reference, the Fraunhofer team therefore chose two electric motors. Combining all the options developed in the project to reduce or replace rare earths, the demand for dysprosium and neodymium in these engines can be reduced to up to 20 percent of the originally required quantities.
“Our goal was to halve the need for rare earths on these benchmark engines. We have clearly outperformed by combining different technical approaches,” says Prof. Ralf B. Wehrspohn, head of the Fraunhofer Institute for Microstructure of Materials and Systems IMWS and spokesman of the flagship project. He emphasizes the relevance of the chosen examples: “In an average car today, there are dozens of such engines moving windows, wipers or oil pumps. Many of these motors work with permanent magnets that contain rare earths. With new assistance systems and, last but not least, the trend towards electromobility, their numbers will increase significantly in the future. All this shows how important an efficient use of these valuable raw materials is.«
The Fraunhofer researchers have analyzed the global markets for rare earths, and at the same time developed concepts on how the future reuse or recycling of rare earths can be considered in the design of electric motors. They also targeted magnet manufacturing processes to find ways to reduce waste. This was made possible for example by injection molding, in which the magnetic material is brought directly into the desired shape together with a plastic binder and then sintered. This also eliminates time elaborate reworking.
In another subproject, a method was developed to recycle permanent magnets, for example, from electronic devices no longer in use, wind turbines or cars. They disintegrate by treatment with pure hydrogen and the resulting particles are then re-poured or sintered. The recycled magnets reach 96 percent of the capacity of new magnets. Unique in the world is the method developed in the flagship project to introduce dysprosium into grain boundary phases by a combination of spark plasma sintering (SPS) and hot pressing, thus producing anisotropic magnets for a wide range of applications in electric motors.
The design of the benchmark electric motors has also been optimized: If the motors do not get so hot during operation, magnets with lower temperature stability and thus a lower portion of dysprosium can be used. Last but not least, materials were searched for and found that can also serve as magnets but do not contain rare earths. In high-throughput procedures, the researchers have tested numerous combinations of materials and have demonstrated new alloys that, in place of rare earths, contain, among other things, cerium. As flakes, the new compounds already have a very good magnetic performance. All identified substitution materials were also analyzed for their current and expected security of supply.
Involved in the flagship project “Criticality of rare earths” were the Fraunhofer Institute for Silicate Research ISC with the project group IWKS, the Fraunhofer Institute for Machine Tools and Forming Technology IWU, the Fraunhofer Institute for Mechanics of Materials IWM, the Fraunhofer Institute for Microstructure of Materials and Systems IMWS, the Fraunhofer Institute for Structural Durability and System Reliability LBF, the Fraunhofer Institute for Systems and Innovation Research ISI, the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM and the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB.
“We tackled the topic from the quantum physical computer simulation of magnetic materials, to near-net-shape magnet production, to the recovery and recycling of rare-earth metals at the end of a product’s life cycle. Thanks to the breadth and depth of competences, which are also unique on an international scale, we have made very concrete progress and identified further starting points for the more efficient use and substitution of rare earths. We now want to bring these results to the market with partners from industry,” says Wehrspohn.
Prof. Dr. Ralf B. Wehrspohn
Fraunhofer Institute for Microstructure of Materials and Systems IMWS
06120 Halle (Saale)
Phone +49 345 5589-100
Fax +49 345 5589-101