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What is the NdFeB infiltration technology?

• 2020-01-03

Since its introduction in the 1980s, NdFeB permanent magnet materials have been widely used in various fields such as automobiles, wind power, aerospace, and military industries with excellent magnetic properties. In recent years, the demand for wind power generation, new energy vehicles, etc. has continued to increase. This puts forward higher requirements for the coercive force and temperature stability of NdFeB permanent magnet materials.

Because the magnetic crystal anisotropy field of the Dy2Fe14B phase is much stronger than that of the Nd2Fe14B phase and the Curie temperature is relatively high, the coercivity and temperature stability of the material can be greatly improved. In sintered NdFeB materials, the content of rhenium is very high, and some can reach more than 10%. Everyone knows that the price of heavy rare-earth element europium is high, and a large amount of addition will increase the production cost of neodymium iron boron. Therefore, how to reduce the amount of europium under the premise of ensuring high coercivity and temperature stability has become an important issue.

The traditional element addition method is to add in the melting process, that is, Dy, Tb and Nd, Fe, B and other elements are smelted together, Dy distribution in the grain boundary and the main phase of the grain in the magnet. However, research shows that Dy at the grain boundary has the most significant effect on improving the coercive force, and the traditional method of adding elements is a “waste of resources”.

Japanese researchers first proposed the concept of “grain boundary diffusion”. They used a special process to make Dy exist only at the grain boundary and not enter the crystal by diffusion. This not only improved the performance of NdFeB materials, but also greatly reduced Dy. The total amount of elements reduces the cost of materials. They deposited Dy vapor on the surface of the particles during the milling process, and Dy atoms diffused along the grain boundaries during subsequent sintering. Dy and Fe located at the grain boundary are antiferromagnetically coupled, and the coercive force of the material increases from 800 kA / m to 1800 kA / m with almost no reduction in remanence.

Damage to the surface of the magnet after machining will weaken the magnetic properties, especially for small-size samples, the coercivity is significantly reduced, and grain boundary diffusion technology can be used to repair and increase the magnetic surface magnetic properties. At present, the grain boundary diffusion technology has received widespread attention, and its preparation processes mainly include evaporation diffusion, magnetron sputtering, surface coating, and the like.

Evaporation diffusion

The Dy / Tb evaporation process on the surface of the neodymium-iron-boron magnet is to place the heavy rare earth element or its compound and the original sample to be processed in a steaming furnace, and use high temperature heating to evaporate the heavy rare earth element at high temperature. It is deposited on the surface of the original magnet and diffuses into the magnet along the grain boundary.

The evaporation diffusion method can simultaneously perform sublimation of Dy evaporation source, deposition on the surface of neodymium-iron-boron, and diffusion in the magnet under the condition of high temperature heating. The advantage of using the evaporation diffusion method is to diffuse heavy rare-earth elements. It is more sufficient to reduce the amount of heavy rare-earth elements and reduce the cost, thereby successfully preparing a high coercivity and low rare-earth content neodymium-iron-boron magnet.

Magnetron sputtering

Unlike the evaporation diffusion method described above, magnetron sputtering separates the Dy deposition process from the diffusion process. It deposits Dy on the surface of the original magnet by physical sputtering, and then performs high temperature diffusion. Magnetron sputtering has the advantages of uniform film thickness and obvious coercive force enhancement effect.

Some research experiments have shown that after sintered and tempered N35 magnets are treated with sputtering Dy, the coercive force is greatly improved when the remanence is reduced by only 0.009T and 0.03T, which are increased by 708.44kA / m and 665.46, respectively. kA / m, the increase rate is as high as 73.5% and 64.8%, and the average mass fraction of Dy element of the magnet after Dy infiltration does not increase by more than 0.4%. After infiltrating the Dy-treated magnet, Dy is enriched in a continuous band at the Nd-rich phase, which makes the Nd-rich phase more continuous and smooth. The improvement of the Nd-rich phase structure and morphology is one of the reasons for the increase in coercive force. The (Nd, Dy) 2Fe14B epitaxial layer formed has a large magnetic crystal anisotropy field, and the hardening of the grain epitaxial layer can better suppress the reverse domain nucleation, which is also the main reason for the increase of coercive force.

Surface coating

The surface coating method refers to coating a rare earth compound directly on the surface of the original magnet sample, and performing a high-temperature heat treatment diffusion in a rare gas atmosphere after drying treatment. Using this method can significantly improve the coercive force of the magnet, the advantage is that the process is simple and convenient, the disadvantage is that it is easy to cause uneven coating and insufficient diffusion.

What is Laminated Magnet or Lamination Magnet？

• 2019-10-31

Eddy current is one of the biggest difficulties in the motor industry which will give rise to the temperature of permanent magnets and caused demagnetization, then affected the working efficiency of the motor. We named it “Eddy Current Loss of Permanent Magnets”

In most cases, the eddy current loss of permanent magnets is much lower than iron loss and copper loss of the motor, but it will generate a large temperature rise in the high-speed motor and the high power density motor.

Ideally, rotor magnetic field and stator magnetic field of PMSM are rotating synchronously, or relatively static, thus permanent magnets without eddy current loss in such case. In fact, there are a series of space and time harmonics are existing in the air gap magnetic field, and these harmonic components are stemming from cogging effect, non-sinusoidal distribution of magnetomotive force and phase current. The harmonic magnetic field will link with rotor magnetic field and hence generated eddy current and caused relevant eddy current loss. It should be also noted that the harmonic magnetic field and eddy current loss will rise with increasing motor speed.

Laminated magnets are regarded as a wise solution to solve the eddy current loss in the surge of high-speed rotating machinery development.

Laminated magnets are made by bonding several pieces of thin magnets together via special isolation glue which also be called magnet segmentation technology, and thus dramatically reduce the eddy flux loss of the magnets without changing the structure and performance of the motors. Actually, puzzles existing in the development of laminated magnets are the assembly process and consequently high costs. U-Polemag has collected much experience via some axial flux motor projects.

Welcome to inquiry us for more information,and we will try our best to offer you the best service.

U-POLEMAG Corrosion-proof Coating Solution (Over 500 Hrs on SAT)

• 2019-09-05

“High density polymer resin coating” is new solution for protecting neodymium magnets which are easy to be oxidized from the rust. It resist over 500 hours on salty spray testing (SST), and we can supply different colors as your request. It’s not only a good solution for the rust proof, also passed the allergy patch test by Japanese medical company, used in their medical solutions and also such as medical accessories which will always touch to the human skins

Industrial vitamins, “industrial gold” and “new mother” materials.

• 2019-05-28

President Xi Jinping’s visit earlier this week to a rare earth firm in east China’s Jiangxi province has triggered sharp speculation whether the strategic sector will be included in the escalating Sino-US trade war.

China is one of the world’s major suppliers of rare earth metals, a group of 17 elements that are widely used in high-tech products ranging from flat-screen TVs to lasers and military equipment.

According to some estimates, China is sitting on 90 percent of the world’s rare earth reserves.

China’s rare earths exports, a Reuters report said, have been spared from recent tariffs by the US, which has decided not to impose import duties on those and some other critical minerals from China as part of the trade war.

“Beijing, however, has raised tariffs on imports of U.S. rare earth metal ores from 10 percent to 25 percent from June 1, making it less economical to process the material in China,” the report said.

Xi’s visit to the JL MAG Rare-Earth company as well as the development of the rare earth industry in the city of Ganzhou could be an indication that Beijing is well aware of the power of the element of rare earth in the ongoing tit-for-tat trade war – and could be ready to deploy it.

Xi was accompanied by vice-premier Liu He, the top negotiator with Washington amid the ongoing dispute.

Brief reports on the visit didn’t give details or mention the trade war but the official news agency, Xinhua’s report in Chinese pointed out the importance of rare earth to China, calling it “industrial vitamin, “industrial gold” and “mother of new materials”.

It also said that rare earth is an important element that cannot be regenerated.

In March, China announced that the first batch of quota for rare earths totals 60,000 tonnes, about half the quota set for 2018, according to a circular jointly issued by the Ministry of Natural Resources and Ministry of Industry and Information Technology.

Of the total, 50,425 tonnes were allocated for light rare earths, with 9,575 tonnes for medium and heavy rare earth metals, the Xinhua reported.

“China has by far been the largest source of imported rare earths into the US for a number of years, totalling almost US$92 million in 2018, according to the US International Trade Commission. Japan, the US’ second largest source, contributed US$23 million worth of imports in the same year,” the Hong Kong-based South China Morning Post reported.

Interestingly, Xi visited a monument in Yudu, in the same province, which marked the start of the Communist Party’s Long March 85 years ago. It could be interpreted as the Communist party’s general secretary’s message of unity and endurance to the Chinese amid trade war.

The ministry of foreign affairs, however, advised against “over interpreting” Xi’s visits.

“It’s only normal for the Chinese leader to pay a domestic field trip and do research on relevant industrial policies. I hope you will not over-interpret that.

To the China-US economic and trade relations, just like I said earlier, they must be based on mutual respect, equality and mutual benefit,” spokesperson, Lu Kang said.

What’s Behind the Recent Surge in Rare Earth ETF?

• 2019-05-23

The world is closely watching the exchanges between China president Xi Jinping and America’s Trump. Jinping’s latest trip to a major rare earth minerals company in Jiangxi province has stirred speculations and reactions.

VanEck Vectors Rare Earth/Strategic Metals ETF’s REMX gain ofaround 5% to close at $15.25 on May 21 can also be the result of this visit. Per Reuters, MVIS Global Rare Earth/Strategic Minerals Index recorded the highest one-day gain of 6.4% since October 2011 on the day.

Rare Earth Elements & US Connection

According to The Rare Earth Technology Alliance, there are 17 elements that are deemed rare. Found in Earth’s crust, these elements are integral for the making of modern technologies, including consumer electronics, computers and networks, communications, clean energy, advanced transportation, health care, environmental mitigation, national defense, to name a few. Available in plenty in different regions, processing rare earth elements into materials is often extremely polluting. China has created well-developed production set-ups for the same.

United States once happened to be a major producer of rare earth elements. However, over the last decade, China’s aggressive pricing schemes helped it develop almost a monopoly in rare earth materials with United States and other miners in the world exiting the segment. In fact, per a Wall Street Journal article, the only mine in the United States producing rare earth minerals, Mountain Pass, is itself dependent on China for processing. Resultantly, the United States had imported around $160 million worth of rare earth elements in 2018, with majority imports from China. The figure excludes the price of finished goods and intermediate products made using rare earths.

However, United States understands its over-dependence on foreign resources for essential minerals. Thus, in March 2019, Congress introduced a bipartisan bill to ramp up mining of U.S. rare earth elements and other critical minerals.

Can Rare Earth be China’s ‘Trump Card’ in Trade War?

China is considered the largest producer of rare earth elements as it accounts for 90% of the global production with only one-third of the world’s rare earth deposits. In fact, it accounted for 80% of the rare earths imported by the United States from 2014 to 2017.

It is believed that if China targets the rare earths exports to the United States, the effects can be catastrophic for the latter with its manufacturers in major industries like defense, oil refineries and technology struggling with supply shortages, delay and soaring raw materials prices. China can also go to the extent of targeting U.S. firms manufacturing machinery and electronics within the Chinese regions from easily accessing rare earths.

However, America might have alternative sources for some of the rare earth elements, like Australia for permanent magnets. Per Reuters, China’s move might end its so-called-monopoly and speed up the process of developing alternative sources with Brazil, Vietnam, Russia, India and Australia gaining the most.

Definition of permanent magnet material

• 2019-04-22

Common permanent magnet materials are AlNiCo, ferrite permanent magnet materials and rare earth permanent magnet materials. Alnico-cobalt alloys have been developed from Al-Ni-Fe alloys. At present, the types of Al-N-cobalt alloys that can be manufactured in China are mainly LNG34, LNG52, LNGJ32, LNGJ56 and so on. Since the main characteristic of AlNiCo is high Br (residual magnetic induction) and low coercive permanent magnet materials, the relative magnetic permeability is above 3, so in the specific application, the magnetic pole must be a growth cylinder or a long rod. to minimize the effect of effect.

The AlNiCo magnet has a low coercive force. Therefore, any iron device should be strictly prohibited from contacting the AlNiCo permanent magnet material during use to avoid local demagnetization of the permanent magnet and distortion of the magnetic flux distribution in the magnetic circuit. The advantage of the AlNiCo magnet is that the temperature coefficient is small, and the deterioration of the permanent magnet characteristics due to temperature changes is small, but the material is hard and brittle, and processing is difficult. The main applications of AlNiCo are in electronic ignition systems, watt-hour meters, voltammeters, medical instruments, industrial motors, magnetic reed switches, generators, hand tools, vending machines, etc.

Ferrite permanent magnet material is one of the most widely used permanent magnet materials, and its main component is MoFe2O3. It has the advantages of large coercive force, light weight, abundant raw material source, low price, oxidation resistance, corrosion resistance, large anisotropy constant of magnetic crystal, and approximate demagnetization curve as straight line. The disadvantage is that the residual magnetism is low, the temperature coefficient is large, and it is brittle. The coercive force of the ferrite permanent magnet material is between the AlNiCo material and the rare earth cobalt permanent magnet material. Because of its low remanence, it is generally suitable for design into a flat shape. Due to its low cost, ferrite magnetic materials have a wide range of applications, from motors and speakers to toys and handicrafts, making them the most widely used permanent magnet materials. The rare earth permanent magnet material has the advantages of high coercive force, large maximum magnetic energy product, and reversible magnetic permeability equal to one. Therefore, its magnetic properties far exceed that of other magnetic materials such as ferrite and aluminum nickel cobalt.