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IntroductionDysprosium is one of a group of elements called Rare Earth. Rare earth elements consist of the Lanthanide series of 15 elements plus yttrium and scandium. Yttrium and scandium are included because of their similar chemical behavior. The rare earths are divided into light and heavy based on atomic weight and the unique chemical and magnetic properties of each of these categories. Dysprosium (Figure 1) is considered a heavy rare earth element (HREE).One of the more important uses for dysprosium is in neodymium‐iron‐boron (Neo)permanent magnets to improve the magnets’ resistance to demagnetization, and by extension, their high-temperature performance.Neo magnets have become essential for a wide range of consumer, transportation, power generation, defense, aerospace, medicalFigure 1: Dysprosium Metalindustrial and other products. Along with terbium (Tb), Dysprosium (Dy) is also used in magnetostrictive devices, but by far the greater usage is in permanent magnets.The demand for Dy has been outstripping its supply. An effect of this continuing shortage is likely to be a slowing of the commercial rollout or a redesigning of a number of Clean Energy applications, including electric traction drives for vehicles and permanent magnet generators for wind turbines. The shortage and associated high prices are also upsetting the market for commercial and industrial motors and products made using them.BackgroundAmong the many figures of merit for permanent magnets, two are of great importance regarding the use of Dy. One key characteristic of a permanent magnet is its resistance to demagnetization, which is quantified by the value of Intrinsic Coercivity (HcJ or Hci). Substituting Dy for a portion of the neodymium (Nd) Neo magnets increase the room temperature value of HcJ and also reduces the rate at which it falls with increasing temperature. Thus Dy‐containing Neo magnets have greater resistance to demagnetization over a wider temperature range. The downside of adding Dy is a drop in Residual Induction (Br). The second key characteristic, Energy Product, is proportional to the square of Br.Therefore, even a small drop in Br results in significantly lower magnet strength.For applications such as motors and generators, resistance to demagnetization is a critical performance objective and the amount of Dy is dictated, not only by demagnetizing stress but also by the expected maximum temperature of the application. Grades of Neo are most often denoted by a suffix indicating the minimum HcJ ( at 20 °C) and a corresponding recommended maximum operating temperature. These notations are shown in Figure 2. At the top of the chart are some typical applications. Letters inovals along the HcJ curve are suffixes denoting the minimum HcJ of Neo magnets. For example, “SH” magnets have a minimum HcJ of 20,000 Oe (1590 kA/m). The Dy percentages shown in Figure 2 are typical for materials where all the Dy is added to the starting alloy. Despite recent improvements in alloying and processing, considerable dysprosium is still required for high-temperature applications. Increased demand for higher Dy grades of Neo magnets is one reason why Dy has been in short supply and why prices have stayed relatively higher even after the pricing bubble collapsed. (Efforts to reduce dysprosium will be discussed later) A list of applications and most likely Dy content (traditional alloying) is shown in Table 1. Two green energy applications are Wind Power, in which designs have used 4 to 5% Dy to resist demagnetization at the operating temperature seen in the generators (up to 150 °C), and hybrid or fully electric vehicle traction drives (EVs), in which demagnetization stress can be severe, especially along the leading and trailing edges of the magnets thus requiring Dy as high as 11%.The recent introduction of dysprosium diffusion ‐ more accurately HRE diffusion since terbium can also be used ‐ is permitting the reduction of HRE content from 4+% Dy for SH grades to ~2% while 8‐11% grades are reduced to 4‐5%.
Neodymium Magnet Material - Powerful & Cost EffectiveNeodymium Iron Boron (NdFeB) magnets were commercially introduced in the early 1980s, and are widely used today for many different applications. The cost of neodymium magnet material (on a dollar-per-energy product basis) is comparable to that of ferrite magnets. * NdFeB magnets are covered by various patents and only licensed materials are allowed into the USA.Integrated Magnetics designs and builds custom neodymium magnets and magnetic assemblies, manufactured to meet your specialty requirements. Send us a request for a quote or contact us today for more information about standard or custom neo magnets. A large inventory of neodymium magnets is also available for online purchase at MagnetShop.com.Key Benefits of Neodymium Magnet MaterialVery high strength.Relatively low cost: by weight, about 20x Ferrite magnets, by "Dollar per BHmax" about 1.5x ferrite magnets.Relatively easy to machine, compared to alnico and samarium cobalt magnets.Key Challenges of Neodymium Magnet MaterialProperties deteriorate rapidly at temperatures in excess of about 150°C depending on the grade and permeance coefficient at which the magnet operates.Most grades of NdFeB magnets need to be protected against oxidation by coating or plating the magnets.Quick Facts about Neodymium Magnet MaterialDensity: 0.275 lbs. per cubic inchSaturation magnetizing field required: about 35kOeManufacturing methods - sintering (most common), injection molding, compression bonding, or calendaring.Available shapes: blocks, bars, discs, rings, arc segments, etc.Available grades: from about 3330 to 5311. (First 2 digits represent BHmax; the second two digits represent intrinsic coercivity or Hci.)Sizes: Off the tool, the largest die-pressed blocks are about 4" x 4", while isostatically pressed blocks can be much longer in the orientation direction (up to 9').Machining: Neodymium magnets should be machined by grinding, using diamond wheels. Of the hard magnet materials, Neo magnets are the easiest to machine. We have successfully machined very small magnets down to 0.012" diameter with a center hole of 0.003" diameter, and a length of 0.040".Surface Treatments for Neodymium Magnet MaterialPainting, coating, or plating is generally recommended for NdFeB, although recently certain grades have been made that exhibit higher resistance to oxidation.Plating NdFeB is a difficult process, and commercial plating houses unfamiliar with the specialized plating techniques required are unlikely to be able to achieve plating with good adhesion on Neo magnets.Nickel, zinc, or tin plating provides good corrosion resistance for NdFeB magnets, though longer lead times or higher volumes may be required for these. Neo magnets can also be plated using ion vacuum deposition (IVD) techniques. This specialty plating is very controllable for thickness and has excellent adhesion to the material.A variety of organic coatings have also been successfully developed for NdFeB, exhibiting good corrosion resistance characteristics. For especially harsh environments, it may be advisable to use a combination of coating techniques or encapsulate the material in a sealed housing.Caution!NdFeB powder is very fine and when dry can ignite spontaneously; special care must be taken when handling NdFeB powder.NdFeB magnets are very powerful; special care must be taken in handling these magnets to avoid injuries.NdFeB magnets are susceptible to corrosion.
Friends who have some knowledge of magnets know that nd-fe-boron magnets are generally recognized as high-performance and cost-effective magnet products in the magnetic material industry at present. Many high-tech fields have designated it to make various parts, such as national defense military, electronic technology, medical equipment, electrical appliances, and other fields involved. More and more problems can be found, among which the demagnetization of ndfeb powerful magnets in high-temperature environments has attracted much attention.Why does ndfeb degenerate at high temperatures?Ndfeb degaussing at high temperatures is determined by its physical structure. The magnetic field can be generated by the magnet, because the electrons carried by the material rotate around the atom in a certain direction, which generates a certain magnetic force, and then has an impact on the related affairs around. But electrons around the atoms in accordance with the established direction also has a certain temperature condition, different magnetic material can withstand temperature is different, in the case of too high temperature, the electronic will deviate from the original track, a chaotic phenomenon, magnetic material at this time the local magnetic field will be upset, and demagnetization.However, the temperature resistance of ndfeb magnets is probably around Baidu, that is, more than Baidu will appear demagnetization phenomenon if the temperature is higher, the demagnetization phenomenon is more serious.Several effective solutions to high-temperature demagnetization of ndfeb magnets are presentedFirst, do not put the NdFeB magnet product at too high a temperature, especially pay attention to its critical temperature, namely Baidu, and timely adjust its working environment temperature, so as to minimize the occurrence of demagnetization.The second is to improve the performance of the products using ndfeb magnets from the technical point of view so that they can have a more temperature structure and are not easily affected by the environment.Third, you can choose high-coercive force materials with the same magnetic energy accumulation. If not, you have to sacrifice a little magnetic energy accumulation and find materials with lower magnetic energy accumulation and higher coercive force, but no more, you can choose samarium cobalt; for reversible demagnetization, only samarium cobalt is available.
Rare earth magnets have become a common feature in the world of power tools. But have you ever wondered what differentiates them from regular, run-of-the-mill magnets? Some of you probably already know the difference, but, for those of us who haven’t been all that concerned about learning any better, the term “rare earth magnets” can sound like fancy marketing jargon that doesn’t have any real importance in how a tool actually functions. The term makes it sound like Klein, for instance, might’ve drilled down to the molten core of the earth to extract the materials to make the magnet for my new tape measure. But, is the mythical-sounding rare earth magnet even all that complex or rare? Well, we got tired of wondering and looked into it ourselves.Some folks have posited that magnetic force is miraculous. While that can be forgiven, as the nature of the magnet does seem mysterious, the explanation for magnetic force has been definitively laid out in most junior high school classes across the country. This is to say that, while magnets are pretty cool, calling them “miraculous” is probably playing a bit too fast and loose with the term.But, for the sake of having a refresher, and without getting too deeply scientific about any of it, here are the basics: matter is made up of atoms. At the center of the atom, we have a nucleus consisting of protons and neutrons. Orbiting the nucleus, much like satellites orbit the earth, we have tinier particles called electrons. The movement of electrons generates a magnetic field.Most electrons travel in pairs that orbit in opposite directions, canceling out any magnetic force that their movement generates. The thing is, in some matter, like iron, atoms may have unpaired electrons which produce net magnetic fields that turn the whole atom into a tiny magnet.Of course, magnetism, as a subject, is far more vast than we’re able to cover on this page. For the time being, however, this action describes why ferromagnetic (“magnetic like iron”) materials attract one another.So, what is a rare earth magnet? Basically, they’re just like your regular ol’ run-of-the-mill magnets, except stronger. Rare earth magnets are the strongest type of permanent magnets available right now. Take your standard ferrite or alnico magnets, for instance. They typically generate a magnetic field of around .5 to 1 Tesla (the unit for measuring magnetic fields). Rare earth magnets punch in at around 1.4 Teslas and can generate even higher magnetic fields.The term “rare earth” is also a bit of a misnomer. Rare earth elements, coming from the lanthanide, scandium, and yttrium families of the periodic table, are actually fairly abundant. They are, however, rarely found in large, concentrated deposits, but dispersed among other elements. From there, magnet manufacturers use these elements in the alloys that form rare earth magnets.We generally see two main types of rare earth magnets in use today, neodymium magnets and samarium cobalt magnets. They both come in different grades and have different properties and applications. Neodymium magnets, the stronger of the two, use an alloy that contains mainly neodymium, iron, boron, and varying degrees of dysprosium and praseodymium. Because these magnets tend toward brittleness and are vulnerable to corrosion, manufacturers typically coat or plate them to protect them from breaking and chipping. Samarium cobalt magnets are the older of the two types. They are made from an alloy containing samarium, cobalt, iron, copper, hafnium, zirconium, and praseodymium. Typically difficult to demagnetize, samarium cobalt magnets have high operating temperatures and high resistance to corrosion.Both of these rare earth magnets find use in a variety of applications these days. Computer hard drives, various engine designs, MRI machines, fishing reel brakes, toys, and even guitar pickups all use rare earth magnets. They’re incorporated into all sorts of other applications as well.Brushless motors seem to make the world go ’round these days, and they have rare earth magnets to thank. Rather than metal brushes making contact with the motor, the brushless motor sort of turns the whole engine inside out. Permanent rare earth magnets are mounted to the rotor, and as electricity runs to the magnets, the polarities of the magnets drive the shaft. Brushless motors tend to be more precise, quieter, more durable, cooler-running, and more powerful than brushed motors. Thanks, rare earth magnets!So, while it’s a little disappointing that rare earth magnets are not actually forged in the fires of Mordor like their name might suggest, they’re actually instrumental in making today’s cordless tool technology possible. Thankfully, the “rare” designation is more like an ironic nickname than anything else, because finding these elements with such regularity helps drive a lot of new innovation.
