Green and Inexpensive SuperMagnets

The Center for Microwave Magnetic Materials and Integrated Circuits has developed a green, one-step process for creating samarium cobalt permanent magnets that could usher in a new breed of hybrid automobiles using smaller, inexpensive motors.

Rare earth permanent magnets could enable smaller, higher-performance motors and power generators. The rub is that they require an expensive, multi-step process to fabricate.

Now, Northeastern University researchers claim to have invented a cheap, green, one-step process for creating samarium cobalt permanent magnets. Cutting the cost of producing the powerful magnets could usher in a new breed of hybrid automobiles using smaller, cheaper motors. Space and aircraft applications are also possible.

Lead scientist C.N. Chinnasamy of Northeastern University's Center for Microwave Magnetic Materials and Integrated Circuits, said samarium cobalt — the strongest of the rare earth magnetic materials — could be manufactured using recyclable chemicals. The manufacturing process would be scalable for high-volume production, and magnets could be built at a fraction of their current cost, Chinnasamy added.

"Rare earth magnets are essential to NASA and [the Defense Department] for small, high-performance motors and power generators that can operate in high-temperature environments," said Chinnasamy. "With our process, they can be manufactured much more economically."

Chinnassamy worked under the direction of principal investigator Vincent Harris, director of the Center for Microwave Magnetic Materials and Integrated Circuits.

Harris said samarian cobalt magnets are well suited for use in aircraft turbines where temperatures are too high for other types of rare-earth magnets. Chinnassamy's single-step process "is not only less expensive, but the chemicals he uses to make them can be recycled over and over again in a green process that is perfect for high-volume manufacturing," Harris claimed.

The researchers came up with a nanotechnology approach to manufacturing that replaces the expensive, multi-step metallurgic technique currently used to make rare earth magnets. In the current process, the metallurgic approach melts the cobalt and samarium ores in the correct proportions, but must perform the work in a vacuum to prevent oxidation, increasing the cost of the process.

Northeastern's technique instead dissolves cobalt and samarium salts in the correct proportions in a high-temperature solvent. That induces magnet nanoblades — tiny dipoles measuring just 10×100 nanometers — to form and drop to the bottom of the solution. An oxidation-preventing coating of polyvinylpyrrolidone is then applied to the nanoblades, resulting in a black magnetic powder that can be formed into powerful magnets in the presence of a strong magnetic field.

Other techniques for creating supermagnets composed of nanoblade dipoles have succeeded for high operating temperatures, but the rare earth magnets performed poorly at start-up when the magnets operated at room temperature. However, Northeastern University researchers claim their formulation performs well both at room temperature and at very high operating temperatures, thereby permitting applications such as smaller motors with the same performance as larger engines.


Related Faculty: Vincent G. Harris

Related Departments:Mechanical & Industrial Engineering