In 1980, neodymium magnets were invented by General Motors and Sumitomo Special Metals. When they combined neodymium with a small amount of iron and boron, a strong magnet was obtained.
Neodymium magnets are composed of neodymium, boron, iron and a few transition metals. These magnets are referred to as NdFeB or Neo magnets. The composition of the magnet can be varied as per the requirement of the strength and what that magnet is being used for. Corrosion is the biggest threat for the neodymium magnets; they become hard and become brittle. Hence, they are surface treated.
Even though magnets offer high strength, they are extremely light weighted. Neodymium magnets are one of the prime factors for the technological advances happening today.
Depending on the manufacturing process, neodymium magnets are classified into two types:
- Sintered NdFeB magnets
- Bonded NdFeB magnets
Sintered NdFeB magnets are produced by melting the raw materials in a furnace. Later casted into a mold and cooled to form ingots. The ingots are pulverized and powdered by milling. Later, it is sintered into dense blocks. The blocks are then heat-treated and cut into shape, surface treated to prevent corrosion and then magnetized.
Bonded NdFeB magnets are prepared by melting and spinning a thin ribbon of the NdFeB alloy. The ribbon features randomly oriented Nd2Fe14B nano-scale grains. This ribbon is then pulverized into particles and mixed with a polymer. They are compression-or injection-moulded into bonded magnets.
Applications
- Hard disk drives – A hard disk contains tracks and sectors that feature magnetic cells. These cells are magnetized when data is written to the drive.
- These magnets are used in loudspeakers, microphones, and headphones – Current-carrying coils present in these devices are used in combination with permanent magnets to convert electricity into mechanical energy.
- Dentures – small sized neodymium magnets are used to place dentures safely in place.
- Door catches – residential and Commercial buildings use neodymium magnetic catches for the doors for safety and security.
- Magnetic jewelry – To make magnetic therapy jewelry, bracelet and necklace clasps neodymium magnets are used.
- Anti-lock brake sensors – anti-lock brakes installed in cars use neodymium magnets wrapped inside copper coils in their sensors.