Audio speakers, computer hard drives, and wind turbines all share a common bond. Literally.
They all depend on powerful permanent magnets.
And nearly all of those magnets depend on boron to create a stable, long-lasting, powerful magnetic field.
What is a permanent magnet?
Magnetic fields are essential for the operation of everything from the simplest door closure to complex motors and batteries in electric cars. But not all magnets are permanent magnets.
Electromagnets are created by applying electrical current to a wire wrapped around an iron core. When the current is turned off, the device loses its magnetic properties. The ability to control a magnetic field is useful in applications such as electric locks, induction cooktops, and particle accelerators.
In contrast, permanent magnets:
- Don’t rely on an external electrical source
- Are manufactured in a huge range of sizes and shapes
- Are stable in a wide range of temperatures and environments
These attributes make them useful across a seemingly endless variety of applications, including:
- Earbuds that energize your morning run
- Giant loudspeakers at tonight’s concert
- Fridge doors and other magnetic latches
- Magnetic resonance imaging (MRI) machines
- Computer hard drives
- Actuators that activate valves in industrial pipelines
- Electric meters that measure household energy consumption
- Motors that power EVs, particularly in permanent magnet synchronous motors (PMSMs)
And thousands of other common devices and products that we use every day.
The search for a better permanent magnet
Practical development of permanent magnets began in the early 1900s, and as technologies advanced, so did manufacturing. By the 1960s, the most powerful magnets were samarium cobalt magnets. However, these were costly to make, so researchers began looking for alternatives.
The breakthrough came in 1983, when two completely independent project leaders—Masato Sagawa of Sumitomo Corporation in Japan and John Croat of General Motors in the United States—simultaneously announced the invention of the neodymium-iron-boron permanent magnet. (Both Sumitomo and GM are Rio Tinto materials customers.)
Fun fact: Sagawa and Croat had no idea that they were on the same path. They met at a conference in Pittsburgh in 1983 where they both were presenting papers on their discoveries.
Boron is key to stabilizing permanent magnets
As Croat explained in a 2022 interview with IEEE Spectrum magazine1, the challenge in creating a strong, industrially viable, permanent magnet was stability. Croat’s process involved melting and crystalizing the neodymium and iron to create an alloy with strong magnetic properties. Initially, the process worked well. However, as the materials were heated, they would lose their magnetic properties due to a significant drop in coercivity and thermal stability.
He began to add different materials to improve stability. Boron turned out to be the key.
The addition of a small amount of boron (just 1–1.2% of the total composition) is enough to stabilize the alloy—and produce the most powerful permanent magnets in commercial production today.
How permanent magnets are produced
Although different magnet producers tweak formulations for neodymium-iron-boron magnets depending on the application and strength required, the processes for turning out finished magnets are well established.
First, the three elements are measured and melted to form an alloy. From that point, one of two approaches is used:
- Melt-spinning: The alloy is spun to rapidly cool and solidify it into a ribbon material. The ribbon is then mechanically pulverized into flakes that can be pressed into dies to create the desired magnet shape.
- Sintering: The molten alloy is poured into ingots, and once cooled, ground into a very fine magnet powder. The powder can then be pressed and heated into its final shape.
The source of boron in neodymium-iron-boron magnets is either ferroboron or elemental boron, both of which are produced using boric oxide and boric acid. In this application the purity and particle size of these inputs enables more efficient production of elemental boron and ferroboron.
Because permanent magnets are essential to U.S. national security, building a domestic supply chain for their raw materials is vital. As a U.S.-based supplier of highly pure and consistent boric oxide and boric acid, U.S. Borax plays a crucial role in the boron supply chain for permanent magnets.
A transformative technology
Today, nearly 95% of permanent magnets are neodymium-iron-boron. This rare-earth magnet is considered one of the truly transformative inventions of the 20th century.
During the past 40 years, the permanent magnet’s affordability, power, and flexibility of form has enabled innovations that have shaped our world, including the miniaturization of electronic components, the invention of the read-write hard drive, and the acceleration of sustainable energy solutions that will power our future.
As we continue to push the boundaries of technology, the role of permanent magnets—and the crucial stability provided by boron—will remain at the heart of countless innovations.
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Resources
Reference
1 Zorpette, G. “The Magnet That Made the Modern World.” IEEE Spectrum (June 21, 2022).