What Are Rare Earth Magnets?
What Are Rare Earth Magnets?
Rare earth magnets are strong permanent magnets crafted from alloys of particular earth elements such as neodymium and samarium cobalt, providing powerful permanent magnetic attraction.
Magnets that produce more energy than their weight and size make for ideal products such as electric vehicles and wind turbines that need high energy-to-weight ratios.
Neodymium
Neodymium is a rare earth metal that belongs to the lanthanide family of chemical elements. This group comprises fifteen metal elements with atomic numbers 57 through 71 that are commonly found near the base of the periodic table.
This lanthanide group includes dysprosium, praseodymium and neodymium as well as samarium cobalt which are all used in magnet manufacturing processes. Together these rare earth magnets can be found in devices like motors, generators and spindles used for computer hard drives.
Rare earth elements include 15 different lanthanide atoms that comprise this family and all are essential in creating high-tech devices. They have led to our modern world's development as the seeds of technology have taken root within these 15 elements.
Neodymium is one of the most frequently utilized rare earth metals, mined throughout China, India, Brazil and Australia. As well as being abundant and strong amongst its counterparts it also stands as one of the hardest elements on the market today.
As with other lanthanide metals, neodymium is a highly reactive metal that rapidly oxidizes when exposed to air, leading it to lose strength over time and necessitating storage under an oil layer or within plastic packaging for safekeeping.
Neodymium has many advantageous characteristics beyond its magnetic properties, including coloring glass in delicate hues ranging from violet through wine red and warm grey, as well as helping remove iron contamination on glass surfaces that causes green tinting.
Neodymium iron boron alloy (Nd2Fe14B), though more susceptible than its samarium-cobalt counterparts to corrosion, has long been in production and boasts numerous patents covering its production for over three decades.
This versatile alloy can be purchased in various grades to meet various applications, with N52 being best suited to applications requiring extreme strength while lower grades offer less strength or force for less forceful needs.
Samarium Cobalt
Samarium cobalt magnets were first discovered in the 1970s. This strong and long-term rare earth magnet resists corrosion while offering excellent temperature stability - typically used in motors, pumps, and sensors.
Compare Samarium Cobalt Magnets (SmCo) to Neodymium Magnets - they're not as strong, but offer greater temperature range coverage, greater corrosion resistance, and resistance against demagnetization.
This type of magnet features one atom of rare earth samarium for every five atoms of cobalt - also referred to as SmCo5, SmCo series 1:5, etc.
These SmCo5 magnets have a maximum energy product between 15-24 MGOe, are reversible over a wide temperature range, have a temperature coefficient of -0.05% per degC and are well suited to saturation magnetization at moderate magnetic fields.
Magnets designed specifically for high temperature environments offer increased magnetic strength. Common applications for these magnets are in generators, pump couplings, sensors and motors - as well as wind turbines!
These parts can be very challenging to machine, requiring special techniques and coolant for safe grinding operations. Abrasive grinding methods are possible but require liberal amounts of coolant in order to reduce fire risks caused by oxidized grinding dust.
As with other rare earth magnets, samarium cobalt magnets are anisotropic; that means they preferentially magnetize in one direction over others. Therefore, for optimal performance use magnetizing iron or another metal that has been annealed and does not chip or crack easily as this will allow optimal magnetization results.
Comparable to neodymium magnets, samarium cobalt has a slightly lower BHmax but much stronger magnetic properties and efficiency.
Samarium cobalt can operate at extremely high temperatures; its Curie temperature stands at 1098 K and its density 8.4x103 kg/m3.
Samarium cobalt magnets are widely considered one of the top choices for high-temperature applications such as mining or oil refining, medical equipment or automotive electric drive motors. They're an ideal material choice in these instances and often used across a wide array of industries.
Dysprosium
Dysprosium (element symbol: Dy; atomic number: 66) is one of the lanthanide family of rare earth elements and was first identified by French chemist Paul-Emile Lecoq de Boisbaudran in 1886.
At room temperature, aluminum displays great stability even after it becomes oxidized in air. Furthermore, it dissolves easily in water and can form numerous brightly-colored salts.
Dysprosium, the 66th element in the periodic table, can be found abundantly in various minerals such as gadolinite, xenotime, fergusonite, euxenite polycrase and blomstrandine. Furthermore, dysprosium serves as an important source for both erbium and holmium production.
Dysprosium can be found naturally in monazite sand and bastnaesite and recovered using ion exchange and solvent extraction techniques. Artificial production also occurs via the reduction process between its trifluoride with calcium metal and another process for producing it directly.
Dysprosium, like its counterparts neodymium and samarium cobalt, is another component of rare earth magnets used to increase their high-temperature properties. It is most frequently added to NdFeB magnets in order to improve magnetic moment. This can help them last longer under intense temperatures as well as remain magnetic over longer duration.
Due to its strong magnetic moment, iron is also utilized as a material in nuclear control rods that absorb neutrons to improve reactor operation and help control energy production in nuclear power plants.
Dysprosium shortage has become a serious problem in manufacturing industries across the world. Although still produced primarily in China, demand has steadily grown while supplies remain limited.
One solution to dysprosium shortage is replacing it with terbium, a material with similar magnetic properties; this will reduce the amount of dysprosium necessary to achieve high-temperature characteristics similar to dysprosium.
Improved processing methods may also result in less dysprosium being consumed and, consequently, increasing efficiency when manufacturing magnets.
Another option for producing more dysprosium from existing resources in the form of Dy oxide could help decrease the amount necessary to make rare earth magnets.
Praseodymium
Praseodymium, also referred to as the Lanthanides, is one of the rare earth metals and part of the rare earth group (otherwise known as Lanthanides), and atomic number 59 on the periodic table. It is an attractive soft silvery-yellow malleable and ductile metal found in minerals such as monazite and bastnasite.
Nickel metal hydride batteries found in hybrid cars and wind turbines use rechargeable nickel metal hydride batteries that contain nickel. Nickel-iron metal hydride can also be mixed with magnesium to form highly durable metal alloys used in aircraft engine designs.
Praseodymium takes its name from two Greek words - prasios (green) and didymos (twin). Praseodymium's chemical makeup is similar to neodymium's; however, its oxide coating in air differs. As such, more protection must be taken against air oxidation through storage under oil or plastic coating.
Praseodymium stands out among other lanthanides by only producing one oxide: yellow-green sequioxide Pr2O3, which is stable in water solutions; its +3 oxidation state makes it unique among its fellow lanthanides; additionally, praseodymium can also serve as a doping agent in fiber optic cables.
Praseodymium's magnetic properties enable it to be combined with other lanthanides to produce alloys with strong magnetic properties, used in aircraft engines or the creation of high intensity magnets. Mischmetal, used to make lighter flints, also contains this element, while carbon arc lights are commonly employed by motion picture studios as studio lighting or projector lights.
Praseodymium's color-enhancing abilities extend to glass and enamels as well. Salts of praseodymium are commonly combined with other materials to produce bright yellow shades known as didymium glass, or it can even be used to produce specific types of welder's and glass blower's goggles.
Praseodymium prices have recently seen significant price fluctuations despite its widespread usage due to China's crackdown on illegal rare-earth production, coupled with increasing demand expected through 2020 of 6-12% annually for this metal used extensively by magnets which require high concentrations to function effectively.