China
Africa
Explore chapters and articles related to this topic
Magnetic Lenses for Electron Microscopy
Published in Orloff Jon, Handbook of Charged Particle Optics, 2017
Permendur (49% Co–49% Fe–2% V alloy) is usually used as the pole-piece material when high field strength (>2 T) is necessary in the gap. The difference of saturation flux density Bs between pure iron and permendur (Bs = 2.3 T) is only 10%. The significance of permendur is its high permeability and high saturation flux density. Owing to the low technical saturation of pure iron, permendur is widely used as a magnetic lens material. The anisotropy constant decreases with the increase of the cobalt content as shown in Table 4.2. At the concentration near Fe:Co = 1:1, it forms an ordered alloy when it is cooled slowly. At the weight ratio of 1:1 of Fe:Co, which is the concentration of permendur, the anisotropy constant is nearly zero. Vanadium is added to improve the machin-ability of permendur. A nonmagnetic γ-phase appears in Fe–Co–V ternary alloy (Chen, 1961). The content of the γ-phase is different according to the difference in the vanadium concentration and the mechanical and heat treatments. Therefore, Bs depends on the percentage of the nonmagnetic phase. The magnetization curve of permendur is quite different for different production runs, as was indicated by Mulvey and Tahir (1990).
CHAPTER 12 Diversity of Design
Published in Douglas Self, Audio Engineering Explained, 2012
materials, predominantly barium ferrite, which had been developed for deriving the static magnetic fields necessary around cathode ray tubes in television sets. The design of typical Alnico (Aluminium, nickel, cobalt and iron), Ferrite (ceramic), neodymium and Alcomax magnets are shown in Figure 12.15, from which the geometrical differences are obvious (although the Alcomax and Alnico geometries shown are interchangeable). Many modern loudspeakers use neodymium alloys, and an alloy of samarium and cobalt is also finding use in loudspeaker designs. These materials give enormous magnetic strength for their weight, and they have given rise to further changes in magnetic geometry. The ferrite materials are very resistant to loss of magnetism due to time or heat stresses, but they exhibit powerful stray magnetic fields and can pose some difficulties in achieving the desired magnetic field geometries. Alnico is somewhat less durable, but can allow designs enabling very compact and concentrated magnetic fields. Strength for strength, neodymium magnets are much lighter than either ferrite or cobalt alloy magnets, but can be relatively easily demagnetized at relatively low temperatures, and cannot withstand 250°C voice-coil temperatures without permanently losing some of their magnetic strength. The metal magnets are good conductors of electricity, but the ferrite magnets are ceramic materials, and hence are electrically non-conductive. The non-conducting nature of the ferrite materials can be a problem unless careful measures are taken to use other means to avoid unnecessary and undesirable flux modulation effects. Iron of high magnetic permeability is used in the magnetic structures shown in Figure 12.15 to complete the magnetic circuit, and to achieve the correct shape of field and density of magnetic flux in the gap in which the coil is positioned. The type of iron used is normally a mild steel of low carbon content, but when very high flux densities are required, a material known as Permendur is often used, especially in compression drivers. Permendur is an iron-cobalt-vanadium alloy, which is very hard and difficult to work, but its magnetic properties, when required, may demand its use.
Dismantling and Clearance Approach for the Swiss Light Source (SLS)
Published in Nuclear Science and Engineering, 2023
Roman Galeev, Nick Walter, Eike Hohmann, Sabine Mayer
Activation of the reference material samples was performed at the main hot spot area in the vicinity of the vacuum chamber. The following materials were used for this study: reference steel, highly alloyed type 289-1copperpermendur, an alloy of iron (49%), cobalt (49%), and vanadium (2%).