The history of NDFEB magnets
NDFEB magnets are the most powerful and widely used forms of rare earth magnets. They are made from an alloy consisting of Nickel, iron and Cobalt. They undergo a number of preparatory processes before the final magnet is available to sell in the market.
The motive behind the development of the NDFEB magnets was to find a strong rare earth magnet with properties better than the existing magnetic materials. The companies responsible for the development of the NDFEB were General Motors and another Sumotomo Company. The primary cause for concern was that the materials required for making Samarium Cobalt rare earth magnets were very expensive.
The thrust was towards finding a new material capable of replacing the need for samarium cobalt.
The two companies went about to produce different forms of NDFEB magnets. General Motors developed nanocrystalline NDFEB while Sumitomo Corp.
Developed sintered NDFEB magnets. Sintered NDFEB magnets are a bit susceptible to corrosion.
How are NDFEB magnets manufactured?
There are primarily two techniques for manufacturing NDFEB magnets, each producing a different type of a magnet.
Let us look at the two processes in detail:
Sintered magnet process: This process was developed by the Sumitomo corp. The process involves an ingot being pulverized. Magnetically aligned particles are then sintered in the liquid phase and then are given their desired shape in this process.
China and Japan are the primary producers and exporters of sintered NDFEB magnets.
Bonded magnet process: This method was initially developed by the General Motors and Company of the United States. It involves a method called melt spinning. Melt spinning of a thin ribbon of NDFEB is required.
The method includes pulverization of the ribbon and compression moulding applied to mould it into any desired shape. The NDFEB magnet produced is nanoctystalline.
The bonded magnets may not be as strong as the sintered form, but it is easier to get mould them into desired shapes and do not have eddy current losses. America is the primary producer of bonded NDFEB magnets.
NDFEB magnets, applications and hazards
NDFEB magnets have widespread applications due to their very high coercivity and anisotropy.
The high power of NDFEB magnets make them ideal for a lot of applications.
Some popular applications of the magnets include loudspeakers, headphones, microphones, magnetic resonance imaging, hard drives, motors, jewellery, toys, etc.
However, being extremely powerful, there are some hazards with NDFEB magnets not seen with traditional magnets.
Large pieces of NDFEB magnets are so powerfully attractive that they may cause injury.
Also, NDFEB magnets can harm data on hard drives, compact disks, credit cards etc if they are brought too close to them.
