Citizendia

Intermetallics or intermetallic compounds is a term that is used in a number of different ways. Most commonly it refers to solid state phases involving metals. There is a "research definition" adhered to generally in scientific publications, and a wider "common use" term. There is also a completely different use in coordination chemistry, where it has been used to refer to complexes containing two or more different metals.

Although the term intermetallic compounds, as it applies to solid phases, has been in use for many years, its introduction was regretted, for example by Hume-Rothery in 1955. [1]

Note that many intermetallic compounds are often simply called alloys, even though strictly speaking they are not. An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has For example, complex metallic alloys are intermetallic compounds with large unit cells. Complex metallic Alloys (CMAs are intermetallic compounds characterized by the following structural features large Unit cells comprising

Contents

Definitions

Research definition

This was stated by Schulze in 1967,[2] and defines intermetallic compounds as solid phases containing two or more metallic elements, with optionally one or more non metallic elements, whose crystal structure is same from that of the other constituents. Under this definition the following are included

The definition of a metal is taken to include:

Alloys, which are a homogeneous mixture of metals, and interstitial compounds such as the carbides and nitrides are excluded under this definition. An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has The term interstitial compound, or interstitial alloy, is used to describe a compound that is formed when an atom of sufficiently small radius sits in an interstitial “hole” For the Software development tool targeting the Symbian OS, see Carbide In chemistry a nitride is a compound of Nitrogen with a less Electronegative element where nitrogen has an Oxidation state of -3 However interstitial intermetallic compounds are included as are alloys of intermetallic compounds with a metal.

Common use

In common use the research definition, including poor metals and metalloids, is extended to include compounds such as cementite, Fe3C. Metalloid is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties nearly every element Cementite or iron carbide is a Chemical compound with the formula Fe3C (or Fe2CFe and an Orthorhombic crystal structure These compounds, sometimes termed interstitial compounds can be stoichiometric, and share similar properties to the intermetallic compounds defined above. The term interstitial compound, or interstitial alloy, is used to describe a compound that is formed when an atom of sufficiently small radius sits in an interstitial “hole”

Complexes

The term intermetallic is used [3] to describe compounds involving two or more metals such as the cyclopentadienyl complex Cp6Ni2Zn4.

Intermetallics involving two or more metallic elements

Intermetallic compounds are generally brittle and high melting. They often offer a compromise between ceramic and metallic properties when hardness and/or resistance to high temperatures is important enough to sacrifice some toughness and ease of processing. The word ceramic is derived from the Greek word κεραμικός ( keramikos) Toughness, in Materials science and Metallurgy, is the resistance to Fracture of a material when stressed. They can also display desirable magnetic, superconducting and chemical properties, due to their strong internal order and mixed (metallic and covalent/ionic) bonding, respectively. In Physics, magnetism is one of the Phenomena by which Materials exert attractive or repulsive Forces on other Materials. Intermetallics have given rise to various novel materials developments. Some examples include alnico and the hydrogen storage materials in nickel metal hydride batteries. Alnico is an acronym referring to alloys which are composed primarily of Aluminium (symbol Al) Nickel (symbol Ni) and Cobalt (symbol Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 A nickel-metal hydride battery, abbreviated NiMH, is a type of Rechargeable battery similar to a nickel-cadmium ( Ni[[Cadmium Cd]] battery Ni3Al, which is the hardening phase in the familiar nickel-base superalloys, and the various titanium aluminides have also attracted interest for turbine blade applications, while the latter is also used in very small quantities for grain refinement of titanium alloys. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 WikipediaNaming A superalloy, or high-performance alloy, is an Alloy that exhibits excellent mechanical strength and creep resistance at high temperatures good surface Titanium (taɪˈteɪniəm is a Chemical element with the symbol Ti and Atomic number 22 Grain boundary strengthening (or Hall-Petch strengthening) is a method of strengthening materials by changing their average Crystallite (grain size Titanium alloys are Metallic Materials which contain a mixture of Titanium and other Chemical elements Such alloys have very high Tensile

Properties and examples

The formation of intermetallics can cause problems, Intermetallics of gold and aluminium are a significant cause of wire bond failures in semiconductor devices and other microelectronics devices. Nickel aluminide (Ni3Al is an Intermetallic material with properties similar to both a ceramic and a metal Gold-aluminium intermetallics are Intermetallic compounds of Gold and Aluminium that occur at contacts between the two metals Wire bonding is a method of making interconnections between a microchip and other electronics as part of semiconductor device fabrication. Semiconductor devices are Electronic components that exploit the electronic properties of Semiconductor materials principally Silicon, Germanium Microelectronics is a subfield of Electronics. Microelectronics as the name suggestsis related to the study and manufacture or Microfabrication, of electronic There are 5 of them. AuAl2 is known as "purple plague". Au5Al2 is known as "white plague".

History

Examples of intermetallics through history include:

German type metal is described as breaking like glass, not bending, softer than copper but more fusible than lead. [4]. The chemical formula does not agree with the one above however the properties match with an intermetallic compound or an alloy of one.

References

  1. ^ Electrons, atoms, metals and alloys W. Hume-Rothery Publisher: The Louis Cassier Co. Ltd 1955
  2. ^ G. E. R. Schulze: Metallphysik, Akademie-Verlag, Berlin 1967
  3. ^ Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A. Frank Albert Cotton ( April 9 1930 – February 20 2007) was the W Sir Geoffrey Wilkinson ( 14 July 1921 &ndash 26 September, 1996) was an English Chemist. ; Bochmann, Manfred (1999). Advanced Inorganic Chemistry (6th Edn. ) New York:Wiley-Interscience. ISBN 0-471-19957-5.
  4. ^ [1] Type-pounding The Penny Cyclopædia of the Society for the Diffusion of Useful Knowledge By Society for the Diffusion of Useful Knowledge (Great Britain), George Long Published 1843

See also

External links

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
 Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic