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Rare Earth Magnets
History– Loadstones (Fe3O4)– Steels– Alnicos (Al, Ni, Co, and Fe)– Ferrites– Rare-Earth
• Samarium-Cobalt• Neodymium-Iron-Boron
What Makes a Magnet• Quantum Level
• Spinning and Orbiting Electrons
• Hysteresis Loop• Crystal Structure
– Tetragonal Symmetry
• Rare-Earth Element– High Curie
Temperature
– High Magnetization
– High Coercivity
– High Remanence
Processing Rare-Earth Magnets• Classifications
– Bonded• Compressing a mixture of NdFeB alloy flakes with a resin
bonding agent
– Sintered• Powdered alloy (3-5 micrometers) is aligned in an
electromagnetic coil, pressed into shape, and then sintered at 1000 degrees Celsius
• High Corrosion Factor– Types of coatings
• Aluminum ion deposition• Nickel plating• Epoxy-resin Painting• Electrolytic Deposition
Applications of Rare-Earth Magnets
• Aerospace– Frictionless Couplings
– Auto Compass
• Automotive
• Medical– Magnetic Resonance Imaging
– Dentures
– Wound Closures
– Optical Implants
• Domestic– Head sets
– Electric Clocks
– Hearing Aids
• Electronic Instrumentation– Sensors
– Servo Motors (robotics)