Rare-Earth-Metal Magnet Recycling Made Easy

The recycling process developed by the DOE turns discarded hard disk drive magnets into new magnet material in just a few steps.

We generally imagine the world’s landfills to be piled up with food, paper, and plastic waste. But the reality is that “e-waste,” or electronic devices and components at the end of their useful lives, is also becoming a problem. Discarded computers and their hard drives, portable devices, and other electronics often contain valuable materials like rare earth minerals, but in such minute quantities that the costs to retrieve and recycle them often exceed their value. Better solutions are required to recover materials from e-scrap in a more cost-effective way to help advance the cause of closed loop manufacturing.

Magnet Materials

An example is computer hard disk drives (HDDs), which are a rich source of rare earth magnet materials. The Department of Energy’s Oak Ridge National Laboratory (ORNL) has estimated that about 35 percent of hard drives in the U.S. are shredded for security purposes, but that recycling them could result in the recovery of about 1,000 tons per year (TPA) of magnet material. The challenge has been finding an affordable way to do so that doesn’t create a lot of waste product. There are a lot of ways to go about getting the rare-earth elements out of e-waste, and some of them are very effective. But many create unwanted byproducts, and the recovered elements still need to be incorporated into a new application.

Pictured are hard disk drive magnets that were used in a process to create new alloys. (Image source: Ames Laboratory) 

A new recycling process has been developed at the Department of Energy's Critical Materials Institute (CMI). It turns discarded hard disk drive magnets into new magnet material in just a few steps, helping to solve both the economic and environmental issues typically associated with mining e-waste for valuable materials. The work by the Critical Materials Institute focuses on securing the supply chains of critical materials in the U.S. As part of this, one of its overarching goal is to reduce waste by increasing the efficiency of manufacturing and recycling. Another goal is to eliminate and reduce reliance on often geopolitically fraught rare-earth metals and other materials critical to the success of clean energy technologies.

Ryan Ott, a scientist at Ames Laboratory and a member of the CMI research team, told Design News that the rare-Earth-containing magnets are just one component of potential value in HDDs. They also contain high-quality aluminum along with copper and small amounts of precious metals, such as gold, silver, and palladium. In existing recovery processes, however, the rare earth-containing magnets and materials are often lost to processing waste.

“Our goal is to minimize processing steps and incorporate the recycled material (magnet powder) into a new product that has higher value than if we break it down to individual metals,” said Ott. “These are common challenges to all recycling technologies that we are trying to improve upon.”

The goal of the new process was to eliminate as many recovery steps as possible and go straight from the discarded magnet to a new magnet. It works like this: Discarded HDD magnets are collected, and any protective coatings are removed. The magnets are then crushed into powder, which is deposited on a substrate using plasma spray to synthesize coatings one-half to one millimeter thick. The new material produces a result good enough for many industrial applications.

“The magnets synthesized by this technique will not be as high quality as the starting product,” said Ott. “These magnets, however, would be ideal for applications where ferrite magnets are not sufficient, but more expensive Nd-Fe-B magnets are not necessarily required. This performance and price gap (intermediate performance at reduced cost) is what we are trying to address.”

The research could help to increase manufacturing efficiency by potentially reducing machining waste through the direct synthesis of thin film magnet geometries. This approach eliminates the waste-generating cutting processes as well as the creation of magnet scrap. According to Ames Laboratory, the properties of the end product are customizable, depending on processing controls.

“The magnetic properties can be tailored by both the deposition conditions (e.g., substrate cooling, applied magnetic fields, etc.) as well as post-deposition conditions (e.g., annealing),” Ott told Design News. “The shape of the magnet is also determined by the substrate on which it’s deposited. Right now, sintered magnets are typically formed as blocks and machined into complex shapes and bonded into place. This technology could directly form the complex shape on the substrate, which is part of the system.”

The process is practical and economical in part because it’s quick. According to Ott, the actual thermal spray process is relatively fast (< 30 minutes). The preparation of the powders, which includes thermal annealing and crushing, takes a few hours. The equipment required is widely used in industry and not very specialized, which means the process could be easily adopted for commercial production. The next steps for the research team will be to enhance the magnetic properties in the alloys and then scale up the process.

Tracey Schelmetic graduated from Fairfield University in Fairfield, Conn. and began her long career as a technology and science writer and editor at Appleton & Lange, the now-defunct medical publishing arm of Simon & Schuster. Later, as the editorial director of telecom trade journal Customer Interaction Solutions (today Customer magazine) she became a well-recognized voice in the contact center industry. Today, she is a freelance writer specializing in manufacturing and technology, telecommunications, and enterprise software.

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