Introduction to Basic Composition and Microstructure of Sintered NdFeB Magnet

Introduction to Basic Composition and Microstructure of Sintered NdFeB Magnet Sintered neodymium iron boron (NdFeB) magnet or neodymium (Nd) magnet, as its name implies, contains essential rare earth Nd element. Nd atoms, coupling with ferromagnetic element iron (Fe) atoms, help the magnet obtain high remanence (Br) and maximum energy product ((BH)max), which makes it extraordinary compared with other permanent magnets. In commercial sintered NdFeB magnet, Nd element is usually partially substituted by other rare earth elements including praseodymium (Pr), dysprosium (Dy) and terbium (Tb), etc. Because Nd and Pr elements usually coexist in ore and these two elements have similar physical and chemical properties, so it is more economic to… Read More

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What is Maximum Working Temperature of a Permanent Magnet?

What is Maximum Working Temperature of a Permanent Magnet? Permanent magnets are widely applied in various motors, sensors/instruments and electronics, their temperatures almost vary more or less during work. These temperature variations are resulted from eddy current effect and/or ambient temperature variation. Due to thermal fluctuation and magnetic domain evolution, a permanent magnet loses some or all magnetic flux when its temperature elevates. Here comes a question, how high temperature can a permanent magnet withstand to work? For a commercial permanent magnet, the upper temperature limit is called maximum working temperature. In both fields of theory and application, the temperature elevation dependent flux loss is commonly divided into two parts,… Read More

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What are Temperature Coefficients α and β of Permanent Magnets?

What are Temperature Coefficients (α and β) of Permanent Magnets? A permanent magnet’s magnetic properties change as a variation of temperature. For a permanent magnet, remanence (Br) and intrinsic coercivity (Hcj or Hci) are two major parameters, it is important to consider their changes with corresponding temperature variation at work. In order to describe the relative changes, they are calculated according to the following two formulas:             α = [Br(T1)-Br(T2)]/Br(T1)/[ T1-T2]×100                              (1)             β = [Hcj(T1)-Hcj(T2)]/Hcj(T1)/[T1-T2]×100                     … Read More

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What is the Strongest Commercial Permanent Magnet in the World?

What is the Strongest Commercial Permanent Magnet in the World? Researchers and engineers have never stopped their steps to discover and develop novel permanent magnets since 1910s, and several types of permanent magnets had been commercialized and they have been widely used in motion, energy, electronics, medical and other high technologies in our daily life. However, little breakthrough has been taken in the past 18 years of the 21st century. In the current market, almost all types of commercial permanent magnets (ferrite, NdFeB, SmCo and AlNiCo, etc.) were discovered and developed in the 20th century. In the following figure, it depicts the development of some permanent magnets’ maximum energy product… Read More

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How to Magnetize and Demagnetize a Permanent Magnetic Material, respectively?

How to Magnetize and Demagnetize a Permanent Magnetic Material, respectively? Due to random orientation for micro magnetic domains, a permanent magnetic material or magnet usually does not provide any magnetic flux when it is produced. It needs to be magnetized to saturation for use. So how to magnetize a permanent magnetic material? The basic principle is using a coil, i.e. an electromagnet, to generate a magnetic field. The generated magnetic field increases as the charging current increases, it drives micro magnetic domains of a permanent magnetic material rotate to the magnetization direction. When all the micro magnetic domains aligned along the same direction, the permanent magnetic material is magnetized to… Read More

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Do Permanent Magnets ever Lose Their Magnetism or Become Weaker Over Time?

Do Permanent Magnets ever Lose Their Magnetism or Become Weaker Over Time? Actually permanent magnets are not permanent. A Permanent Magnet is a material which has ability to resist demagnetization, including filed demagnetization and thermal demagnetization. The ability is characterized by a physical parameter called coercivity. In regard to field demagnetization, if a demagnetizing field or reverse field is smaller than a permanent magnet’s coercivity, the permanent magnet will keep the same magnetic flux (the demagnetizing process is linear and reversible when the demagnetizing field is lower than a threshold value) or will lose some flux (the demagnetizing process is nonlinear and irreversible when the demagnetizing field is higher than… Read More

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Radially Oriented Neodymium Iron Boron (NdFeB) Ring Magnets

Radially Oriented Neodymium Iron Boron (NdFeB) Ring Magnets Radially oriented NdFeB ring magnets are state-of-the-art ring magnets with diverse magnetization in radial direction. They provide high performance and cost effective alternatives to arc/segment magnets. Radially oriented NdFeB ring magnets include sintered NdFeB magnets, bonded NdFeB magnets and hot-pressed NdFeB magnets. >> Features of Radially Oriented NdFeB Ring Magnets 1. High dimensional accuracy, 2. Optional magnetization patterns including single pole, straight and skew multi-pole types, 3. A single ring magnet makes assembly and installation simple and low cost, 4. Simple and stable structure guarantees excellent dynamic balance performance, and 5. Uniform magnetic properties and magnetization waves distribution contribute to low motor… Read More

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What is the Difference between N35 and N52 Magnets?

What is the Difference between N35 and N52 Magnets? What are N35 and N52 magnets? Seen from their grade strings, both of them are sintered neodymium iron boron (NdFeB) magnets. These two magnets have the same intrinsic coercivity Hcj level higher than 12 kOe (in CGS unit) or 955 kA/m (in SI unit). It is also obviously seen that their maximum energy product (BH)max are around 35 and 52 MGOe, respectively. This huge difference means that the N52 magnets have around 49% more energy than that of the N35 magnets. In other words, a motor or device using N52 magnet(s) would have much higher performance than that using N35 magnet(s),… Read More

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Corrosion Resistance of Rare Earth Permanent Magnets

Corrosion Resistance of Rare Earth Permanent Magnets In the Rare Earth Permanent Magnets family, the 1st generation 1:5 type SmCo magnets and 2nd generation 2:17 type SmCo magnets have high corrosion resistance due to the high cobalt content. Just like ferrite/ceramic magnets and AlNiCo magnets, SmCo magnets usually do not need any treatment for applications. The 3rd generation NdFeB magnets, however, are not the same. Although they have superior magnetic properties, they are more vulnerable to corrosion in humid environments, resulting in the deterioration of magnetic properties and eventual disintegration and failure. So what is the corrosion mechanism of NdFeB magnets? Generally it is an inter-granular corrosion evolution process. When… Read More

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How to Understand the Rare Earth Permanent Magnets’ Grades? Part 1 – Sintered Neodymium Iron Boron Magnets

How to Understand the Rare Earth Permanent Magnets’ Grades? Part 1 – Sintered Neodymium Iron Boron Magnets Generally, the grades of sintered neodymium iron boron (NdFeB) magnets are strings containing three parts, i.e. “N” + “number” + “letter”. The left part “N” is the initial letter of neodymium, meaning it is sintered NdFeB magnet. So it is constant for all the grades. The middle part “number” represents value of maximum energy product (BH)max (in CGS unit). The value varies from 28 to 52. The right part “letter” reflects level of intrinsic coercivity Hcj. The levels include “M” (Hcj ≥ 14 kOe), “H” (Hcj ≥ 17 kOe), “SH” (Hcj ≥ 20… Read More

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