The neodymium magnet (also known as NdFeB NIB or Neo magnet), the most commonly used rare type -magnet magnets, are permanent magnets made of neodymium, iron and boron alloys to form tetragonal crystals Nd 2 Fe 14 B. Developed independently in 1982 by General Motors and Sumitomo Special Metals, neodymium magnets are the most commercially available permanent magnet available. They have replaced other types of magnets in many applications in modern products that require strong permanent magnets, such as motors in wireless equipment, hard disk drives and magnetic fasteners.
Video Neodymium magnet
Description
Neodymium is a ferromagnetic metal (more specifically indicative of antiferromagnetic properties), which means that as iron can be a magnet to be a magnet, but the Curie temperature (above the ferromagnetic temperature disappears) is 19 Â ° K (-254 ° C) , so that in its pure form its magnetism only appears at very low temperatures. However, neodymium compounds with transition metals such as iron can have Curie temperatures well above room temperature, and these are used to make neodymium magnets.
The strength of neodymium magnets is caused by several factors. The most important is that the tetragonal crystal structure Nd 2 Fe 14 B has a very uniaxial uniaxial uniform anisotropy ( H A ~ 7 T - the strength of the magnetic field H in units A/m rather than the magnetic moment in AÃ, Â · m 2 ). This means a crystalline material that magnets magnetically along a certain crystal axis, but is very difficult to pull in the other direction. Like other magnets, neodymium magnetic alloys are composed of microcrystalline grains that are harmonized in a strong magnetic field during manufacture so that their magnetic axes all point in the same direction. The resistance of the crystal lattice to change the direction of magnetization gives a very high coercivity compound, or resistance to magnetic damage.
Neodymium atoms can also have large magnetic dipole moments because they have 4 unpaired electrons in their electron structure as opposed to (average) 3 in iron. In the magnet it is an unpaired electron, aligned so that they rotate in the same direction, which produces a magnetic field. It gives Nd 2 Fe 14 B high saturation magnetization compound ( J s ~ 1.6 T or 16 kG ) and usually 1.3 teslas. Therefore, since the maximum energy density is proportional to J s 2 , this magnetic phase has the potential to store large amounts of magnetic energy ( BH max Ã, ~ 512Ã, kJ/m 3 or 64Ã, MGÃ,  · Oe). This magnetic energy value is about 18 times larger than a "regular" magnet by volume. This property is higher in NdFeB alloys compared to the cobalt samarium magnet (SmCo), which is the first type of rare-earth magnet to be commercialized. In practice, the neodymium magnet properties depend on the alloy composition, microstructure, and manufacturing techniques used.
The crystal structure Nd 2 Fe 14 B can be described as an alternating layer of iron atoms and a neodymium-boron compound. The diamonic boron atoms do not contribute directly to the magnets, but increase cohesion with strong covalent bonds. The relatively low rare earth content (12% volume) and the relative abundance of neodymium and iron compared with samarium and cobalt make the price of neodymium magnets lower than the samarium-cobalt magnet.
Maps Neodymium magnet
History
General Motors (GM) and Sumitomo Special Metals independently found the compound Nd 2 Fe 14 B almost simultaneously in 1984. This research was initially driven by the high cost of SmCo raw materials. permanent magnets, which have been developed previously. GM focuses on the development of nanotritilin magnets Nd 2 Fe 14 B, while Sumitomo develops full-density sintered Nd 2 Fe 14 B magnet.
GM commercialized the discovery of Neo isotropic powder, Neo bonded magnet, and associated production processes by establishing Magnequench in 1986 (Magnequench has since become part of Neo Materials Technology, Inc., which later merged into Molycorp). The company supplies the Nd 2 Fe 14 B powder for the bonded magnet producers.
The Sumitomo facility is a part of Hitachi Corporation, and currently produces and licenses other companies to produce sintered sub-magnets 2 14 B. Hitachi has more than 600 patents covering magnets neodymium.
Chinese manufacturers have become the dominant force in the production of neodymium magnets, based on their control over many of the world's rare stone mine sources.
The US Department of Energy has identified the need to find a replacement for rare earth metals in permanent magnet technology, and has begun funding such research. The Agency for Advanced-Energy Research Projects has sponsored a Rare Earth Alternative in Critical Technology program (REACT), to develop alternative materials. In 2011, ARPA-E secured a total of 31.6 million dollars to fund the Land-Rare Replacement project.
Production
There are two main neodymium magnet manufacturing methods:
- Classic powder metallurgy or sintered magnetic process
- Quick hold or bonded magnet process
Nd-magnet Sinter is prepared by the raw material which is melted in the furnace, thrown into mold and cooled to form ingots. Crushed and milled ingots; The powder is then sintered into a solid block. The blocks are then treated with heat, cut into shapes, treated and magnetized surfaces.
In 2015, Nitto Denko Corporation of Japan announced the development of a new method of neodymium sintering magnetic material. This method utilizes "organic/inorganic hybrid technology" to form mixtures such as clays that can be shaped into various shapes for sintering. Most importantly, it is said that it is possible to control the orientation of a non-uniform magnetic field in a sintered material to locally focus the terrain on, for example, improving the performance of the electric motor. Mass production is planned for 2017.
In 2012, 50,000 tonnes of neodymium magnets are produced officially each year in China, and 80,000 tonnes in a "company-by-company" build-up conducted in 2013. China produces more than 95% rare earth elements, and generates about 76% of the world's rare-earth magnets.
Nd-magnet bound is prepared by melting the thin ribbon of NdFeB alloy. The ribbon contains a randomly oriented nano-scale grain Nd 2 Fe 14 B. The ribbon is then smoothed into particles, mixed with polymers, and either a compression mold or injection into a bonded magnet. The bonded magnet offers less flux intensity than a sintered magnet, but can form a net formed into intricate sections, as is typical of the Halbach, trapezoidal, and other forms and assemblies (eg Pot Magnet, Separate Grid , etc.). There are about 5,500 tonnes of Neo bonded magnets produced each year. Additionally, it is possible to suppress the heat of nanoococstalline particles that are melted onto a dense isotropic magnet, and then falsify or reverse it back to a high-energy anisotropic magnet.
Properties
Value
Neodymium magnets are rated according to their maximum energy product, which corresponds to the output of magnetic flux per unit volume. Higher values ​​indicate a stronger magnet and range from N35 to N52. Letters that follow the class show the maximum operating temperature (often Curie temperature), which ranges from M (up to 100 ° C) to EH (200 ° C).
Nilai magnet Neodymium:
- N35-N52
- N33M-N48M
- N30H-N45H
- N30SH-N42SH
- N30UH-N35UH
- N28EH-N35EH
Sifat magnetik
Some important properties used to compare permanent magnets are:
- Remanence (B r )
- which measures the strength of the magnetic field
- Coercivity ( H ci )
- material endurance to become magnetic damage
- Energy products ( BH max )
- magnetic energy density
- Curie Temperature ( T C )
- the temperature at which the material loses its magnet
Neodymium magnets have higher remanent, coercivity and much higher energy products, but Curie's temperatures are lower than other types. Special neodymium magnetized alloys that include TB and dysprosium have been developed that have higher Curie temperatures, allowing them to tolerate higher temperatures. The table below compares the magnetic performance of neodymium magnets with other types of permanent magnets.
Physical and mechanical properties
Corrosion problem
Sintered Nd 2 Fe 14 B tends to be susceptible to corrosion, especially along the sintered grain of the magnet. This type of corrosion can cause serious damage, including the collapse of a magnet into a small magnetic particle powder, or a peeled surface layer.
This vulnerability is handled in many commercial products by adding a protective coating to prevent atmospheric exposure. Nickel plating or two-layer copper-nickel coating is the standard method, although coating with other metals, or polymer protective coatings and shellacs is also used.
Dangers
The greater force provided by rare earth magnets creates hazards that may not occur with other types of magnets. Neodymium magnets larger than a few cubic centimeters strong enough to cause injuries to the body parts squeezed between two magnets, or magnets and metal surfaces of iron, even causing fractures.
Magnets that are too close to each other can attack each other with enough force to destroy and destroy fragile materials, and flying chips can cause various injuries, especially eye injuries. There are even cases where young children who have swallowed some of the magnets have had parts of the gastrointestinal tract sandwiched between two magnets, causing injury or death. Stronger magnetic fields can be harmful to mechanical and electronic devices, because they can remove magnetic media such as floppy disks and credit cards, and draw watches and shadow masks from CRT type monitors at a greater distance than other types of magnets.
Apps
Existing magnetic applications
Neodymium magnets have replaced alnico and ferrite magnets in many applications in modern technology where powerful permanent magnets are required, since their greater strength allows the use of smaller and lighter magnets for given applications. Some examples are:
- Head actuator for computer hard disk
- Clear head for cheap cassette recorder
- Mechanical e-cigarette trigger switch
- Lock for door
- Loudspeaker and headphones
- Phone speakers, taptik feedback, and auto focus actuator
- Magnetic bearings and clutch
- Benchtop NMR Spectrometer
- Electric motors:
- The cordless device
- Servomotor
- Motorcycle lift and compressor
- Synchronous motors
- Spindle and stepper motors
- Electric steering wheel
- Moving motor for hybrid and electric vehicles. The electric motor of each Toyota Prius requires 1 kilogram (2.2 pounds) of neodymium.
- Actuator
- Electrical generators for wind turbines (only those with permanent magnet excitation)
- Direct-drive wind turbines require c. 600 kg of PM material per megawatt
- turbines using gears require less PM per megawatt material
- Determination of Nanocellulose chiral nematic suspension to make cellulosic nanocrystals films with specular and off-specular tuneable optical responses
- Voice Coil
Neodymium content is estimated at 31% of magnetic weights
New app
In addition, the strength of larger neodymium magnets has inspired new applications in areas where magnets were not previously used, such as magnetic jewelry clips, children's magnetic clip sets (and other neodymium magnetic toys) and as part of the modern sport parachute closure mechanism. They are also the main metal in the famous table-toy magnet, "Buckyballs", although some US retailers choose not to sell it because of child safety issues.
The strength and homogeneity of the magnetic field in neodymium magnets has also opened up new medical applications with the introduction of an open magnetic resonance scanner (MRI) used to describe the body in the radiology department as an alternative superconducting magnet that uses a superconducting wire coil to produce a magnetic field.
Neodymium magnets are used as a surgically placed anti-reflux system which is a magnet band that is planted around the lower esophageal sphincter to treat gastroesophageal reflux (GERD) disease.
See also
- Lanthanide Metal
- Fishing with magnets
- Neodymium magnetic toys
- Rare earth magnet
- Samarium-cobalt magnet
- Transition metal replacement such as NdCoB
References
Further reading
- MMPA 0100-00, Standard Specification for Permanent Magnetic Materials
- K.H.J. Buschow (1998) Permanent Magnetic Materials and Their Applications , Trans Tech Publications Ltd., Switzerland, ISBNÃ, 0-87849-796-X
- Campbell, Peter (1994). Permanent Magnetic Material and its Applications . New York: Cambridge University Press. ISBN: 0-521-24996-1.
- Furlani, Edward P. (2001). Permanent Magnet and Electromechanical Devices: Materials, Analysis, and Applications . London: Academic Press. ISBN: 0-12-269951-3.
- Brown, D; Ma, Bao-Min; Chen, Zhongmin (2002). "Development in processing and permanent magnetism of type NdFeB". Magnetic Journal and Magnet Materials . 248 (3): 432-440. Bibcode: 2002JMMM..248..432B. doi: 10.1016/S0304-8853 (02) 00334-7.
- Magnetic Properties and Geothermal Magnetism of Earth-Iron-Borida Rare Earth At Composition.
External links
- Magnet Man A cool experiment with a magnet
- Geeky Rare-Earth Magnet Refuses Shark, Genevieve Rajewski, 05.15.07, wired.com
- Caution as China clamps down rare goods exports, Cahal Milmo, 01.02.10, independent.co.uk
- Bowley, Roger. "More with Magnets". Sixty Symbols . Brady Haran for the University of Nottingham.
Source of the article : Wikipedia
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