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Encyclopedia > Alnico

Alnico is an acronym[1] referring to alloys which are composed primarily of aluminium (symbol Al), nickel (symbol Ni) and cobalt (symbol Co), hence al-ni-co, with the addition of iron, copper, and sometimes titanium, typically 8-12% Al, 15-26% Ni, 5-24% Co, up to 6% Cu, up to 1% Ti, rest is Fe. The primary use of alnico alloys is magnet applications. General Name, symbol, number aluminium, Al, 13 Chemical series poor metals Group, period, block 13, 3, p Appearance silvery Standard atomic weight 26. ... For other uses, see Nickel (disambiguation). ... For other uses, see Cobalt (disambiguation). ... General Name, symbol, number iron, Fe, 26 Chemical series transition metals Group, period, block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... For other uses, see Copper (disambiguation). ... General Name, symbol, number titanium, Ti, 22 Chemical series transition metals Group, period, block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ...


Properties

Alnico alloys make strong permanent magnets, and can be magnetized to produce strong magnetic fields. Of the more commonly available magnets, only rare-earth magnets such as neodymium and samarium-cobalt are stronger. Alnico magnets produce magnetic field strength at their poles as high as 1500 gauss (0.15 tesla), or about 3000 times the strength of Earth's magnetic field. Some types of Alnico are isotropic and can be efficiently magnetized in any direction. Other types, such as Alnico 5 and Alnico 8, are anisotropic, with each having a preferred direction of magnetization, or orientation. Anisotropic alloys generally have greater magnetic capacity in a preferred orientation than isotropic types. Alnico remanence (Br) may exceed 12000 gauss (1.2T), its coercion force (Hc) can be up to 1000 oersted (80kA/m), its energy product ((B*H)max) can be up to 5.5M Gs*Oe (44 T*A/m) - this means Alnico can produce high magnetic flux in closed magnetic circuit, but has relatively small resistance against demagnetization. Magnetic lines of force of a bar magnet shown by iron filings on paper A magnet is an object that has a magnetic field. ... Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges and magnetic dipoles, such as those in electric currents and magnets. ... Ferrofluid on glass, with a rare-earth magnet underneath. ... Neodymium magnet on a bracket from a hard drive A neodymium magnet or NIB magnet (also, but less specifically, called a rare-earth magnet) is a powerful magnet made of a combination of neodymium, iron, and boron — Nd2Fe14B. They have replaced marginally weaker and significantly more heat-resistant samarium-cobalt... Samarium-cobalt magnets (SmCo5) are composed of samarium and cobalt. ... The gauss, abbreviated as G, is the cgs unit of magnetic flux density (B), named after the German mathematician and physicist Carl Friedrich Gauss. ... SI unit. ... Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ...


Alnico is produced by casting or sintering processes. Anisotropic alnico magnets are oriented by heating above a critical temperature, and cooling in the presence of a magnetic field. Both isotropic and anisotropic Alnico require proper heat treatment to get its magnetic properties - without it its coercion is about 10 Oe - comparable to technical iron, which is a soft magnetic material. Ater the heat treatment alnico becomes kind of composite material, named "precipitation material" - it consist of rich-Co precipitate in rich-NiAl matrix. Alnico anisotropy is oriented if it is in external magnetic field during the precipitate particle nucleation, which occur when cooling from 900 to 800 C, near Curie point. Without external field there are local anisotropies of different orientations, due to spontaneous magnetization. The precipitate structure is a "barrier" against magnetization changes, as it prefers few magnetization states requiring high energy to get the material into any intermediate state. Also, small magnetic field change magnetization of matrix phase only, and it is reversible. Casting may be used to create artistic sculptures Casting is a manufacturing process by which a molten material such as metal or plastic is introduced into a mold, allowed to solidify within the mold, and then ejected or broken out to make a fabricated part. ... This article or section does not cite its references or sources. ...


Alnico alloys have some of the highest Curie points of any magnetic material, around 800 °C. This property, as well as its brittleness and high melting point, is the result of the strong tendency toward order due to intermetallic bonding between aluminium and its other constituents. They are also one of the most stable magnets if they are handled properly. The Curie point is a term in physics and materials science, named after Pierre Curie (1859-1906), and refers to a characteristic property of a ferromagnetic material. ... Water and steam are two different forms of the same chemical substance A chemical substance is any material with a definite chemical composition, no matter where it comes from. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... A material is brittle if it is subject to fracture when subjected to stress i. ... Intermetallics is concerned with all aspects of ordered chemical compounds between two or more metals and notably with their applications. ...


Use

Alnico magnets are used in electric motors, electric guitar pickups, microphones, sensors, loudspeakers, and cow magnets. Rotating magnetic field as a sum of magnetic vectors from 3 phase coils An electric motor converts electrical energy into mechanical energy. ... A pickup device acts as a detector and captures mechanical vibrations (usually from suitably equipped stringed instruments such as the electric guitar, electric bass guitar and violin) and converts them to an electronic signal which can be amplified and recorded. ... A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ... Not to be confused with censure, censer, or censor. ... This article or section needs copy editing for grammar, style, cohesion, tone and/or spelling. ... A Cow Magnet is a therapeutic veterinary medical device for cattle. ...


References

  1. ^ Hellweg, Paul (1986). The Insomniac's Dictionary. Facts On File Publications, 115. 0-8160-1364-0. 
  1. Physical Review: 77p839_2, 80p112_2, 80p302_1, 81p478_1;
  2. Review of Modern Physics 17p15, 25p316_1;
  3. Journal of Applied Physics 29p299, 31pS82, 40p1308.

  Results from FactBites:
 
Alnico - Wikipedia, the free encyclopedia (251 words)
Alnico alloys are composed primarily of cobalt, nickel, and aluminium with the addition of iron, copper, and sometimes titanium.
Alnico magnets produce magnetic field strength at their poles as high as 1500 gauss, or about 3000 times the strength of the earth's magnetic field.
Alnico magnets are used in electric motors, sensors, loudspeakers, and cow magnets.
  More results at FactBites »

 
 

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