Rare earth permanent magnet application in information technology
It is well known that magnetic materials such as permanent magnets (also called hard magnet), soft magnetic and gyromagnetic materials in magnetic materials are important functional materials for the information industry. They play a very important role in traditional information departments including telecommunications, telephone, printing, publishing, news, broadcasting, television, and emerging information systems such as electronic computers, lasers, optical fibers, and communications satellites. These important functional materials are used in all aspects of the information industry, including information acquisition, transmission, storage, processing and processing. The collection of information requires a variety of sensors, and a large number of highly sensitive, high-precision magnetic sensors have been fabricated using magnetic effects; microwave ferrite materials with gyromagnetic properties act as one-way during high-power microwave transmission and reception. The circulator or isolator is a necessary device for information transmission such as radio and television, satellite communication, etc. Semi-rigid magnetic or hard magnetic film can be used as a magnetic memory for permanently storing information; in the processing and processing of information, computers and scanners , copiers and other equipment are inseparable from all kinds of permanent magnet motors or other driving devices made of hard magnetic materials; various inductors, chokes and transformers made of soft magnetic materials are indispensable in information processing and processing. . Therefore, the information industry is an industry closely related to the development and utilization of magnetic materials.
Application of rare earth permanent magnet materials for information industry
In magnetic materials, the main function of permanent magnet materials is to provide a magnetic field for various devices or devices, usually as a rotor in energy-converted rotating machinery, and as a device in sensors, traveling wave tubes, acoustic horns, etc. Constant magnetic field source. In the information industry, permanent magnet materials have been widely used. Table 1 lists some of the application fields, components and rare earth permanent magnet materials used in rare earth permanent magnet materials in the information industry. It can be seen that rare earth permanent magnet materials are a very important magnetic functional material for the information industry, and it is related to the modern information industry, especially the “three networks” (telecom network, television network, internet) and smart grid. There is a close relationship between the aspects, and rare earth permanent magnet materials are even indispensable in some fields.
In the hand-held mobile phone, high-performance Nd-Fe-B magnets are used in two places, one is the mobile phone vibration motor, and the other is the mobile phone miniature electro-acoustic component speaker. In 2011, the global mobile phone shipments were about 1.8 billion units, and the average finished product consumption was 2.5g. The demand for Nd-Fe-B magnets for one year was about 4,500 tons. Figure 1 shows two components of a mobile phone using high performance rare earth permanent magnets: a horn and a vibration motor. A flaky rare earth permanent magnet is used in the horn, and a cylindrical rare earth permanent magnet having a center hole is used in the vibration motor.
In both desktop and laptop computers, there is an external storage device, the hard disk drive (HDD). In the hard disk drive, there are two drive components made of rare earth permanent magnets: a voice coil motor (VCM) and a spindle motor. The HDD currently used is 1.8 to 3.5 inches.
The HDD relies on two electromagnetic devices in the search data address to achieve this: the spindle motor performs an angular position search, and the voice coil motor performs a radial position search. Figure 2 shows the structure of the voice coil motor in the hard disk drive. It can be clearly seen that the spindle motor controls the rotation of the hard disk while the voice coil motor controls the magnetic head to search in the radial position. Due to volume limitations, spindle motors typically use sensorless brushless DC motors and high-energy bonded Nd-Fe-B magnets; the preferred magnets for voice coil motors today are high-performance sintered Nd-Fe-B magnets. The reason is that HDD has limited space. Only an anisotropic sintered Nd-Fe-B magnet with high energy product and high coercivity can achieve the required torque with the smallest volume of magnet and make the change of strong armature current. The performance of the magnet is not affected.
In 2011, global hard disk drive shipments were 630 million units, using high-performance sintered Nd-Fe-B magnets and bonded magnets of 6,300t and 1,300t respectively; in 2012, global hard disk shipments fell to 540 million units. The high-performance sintered NdFeB magnet is 5 400t; in 2014, the global hard disk shipments were reduced to 450 million units, and the high-performance sintered NdFeB magnet used was 4500t. With the expansion of the capacity of the solid state hard disk of the flash memory and the decline of the price, the amount of the magnetic hard disk will decrease to some extent, but the magnetic hard disk has much higher reliability than the magnetic information, and is much better than the electrical information used in the solid state hard disk. . Although the demand for magnetic hard drives has recently declined, it will not disappear and will continue to be large enough for long periods of time. To be sure, the magnetic hard drive is still a large user of high performance Nd-Fe-B magnets.
In today’s information society, various computer peripherals and office automation equipment are highly developed, and the key components of their micro-motors are in high demand, and the precision and performance requirements are also increasing. The requirements for such micromotors are miniaturization, thinning, high speed, long life, high reliability, low noise and high precision. Most of the drive motors used in various information related devices such as printers, soft hard disk drives, optical disk drives, facsimile machines, copy machines, etc. are permanent magnet brushless DC motors. These permanent magnet brushless DC motors use high-performance Nd-Fe-B magnets, so the demand for rare earth permanent magnet materials in office automation equipment is also very large.
Optical fiber communication has been extensively used in information transmission, and optical isolators are indispensable. Figure 3 shows an example of an optical isolator. Due to the small size of the fiber and the small size of the optical isolator, the magnet size is required to be small. In order to generate a sufficiently large magnetic field in the magnetic circuit, a high magnetic energy product rare earth permanent magnet must be used, and a high performance Nd-Fe-B magnet is the preferred magnet for the optical isolator.
The microwave tube used in satellite communication and satellite broadcasting cannot be separated from the low temperature coefficient high temperature rare earth permanent magnet material as its magnetic field source. In microwave tubes, such as klystrons, magnetrons, and traveling wave tubes, such magnetic fields are required to control the movement of charged particles in order to achieve high frequency or ultra high frequency oscillation and microwave signal amplification and reception.
In these devices or devices, the magnetic field is typically produced by a focusing magnet that is periodically inverted. The focusing magnet in this period is composed of a plurality of circular rare earth permanent magnets, and the adjacent two magnets have opposite polarities. shows a cross-sectional view of a periodic reverse focusing magnet in a traveling wave tube. In order to achieve effective signal amplification of the traveling wave tube, and to obtain a sufficiently high peak magnetic field and high temperature stability, the Sm-Co magnet is the preferred magnet for the traveling wave tube. Similarly, the magnetic field system of the high-power multi-injection klystron has a similar periodic reverse-focusing magnet. The left side of Figure 4 shows a physical picture of the C-band high-power multi-injection klystron with a pulse power of 120 kW. The average power is 6 kW; and the right side of Figure 5 is the periodic reverse permanent magnet focusing system used in the multi-injection klystron.
Today, people are in the era of rapid development of electronic information technology. Mobile phones, tablets, computers and wireless or wired networks have turned the giant earth into a small global village. People can use the mobile phone or tablet to surf the Internet and send and receive text messages and WeChat with people from anywhere in the world. All of this has benefited from the rapid development of electronic information technology in the past 30 years, including the rapid development of high-performance magnetic materials.
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