spheroidal graphite iron

metallurgy

Also known as: SG iron, ductile iron

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aqueduct construction

In aqueduct
Ductile iron, a stronger and more elastic type of cast iron, is one of the most common materials now used for smaller underground pipes (secondary feeders), which supply water to local communities.
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cast iron

In iron processing: White iron
…irons, which are also called ductile irons, are strong and malleable; they are also easy to cast and are sometimes preferred to steel castings and forgings.
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microstructure

In metallurgy: Grain size
…casting, the result is a “spheroidal graphite” iron, in which graphite appears as spherical nodules and ductility is greatly increased. If the molten iron is chill cast (i.e., rapidly cooled), it will form a “white” iron containing about 60 percent cementite, or iron carbide. This material is hard and wear-resistant,…
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water supply system pipelines

In water supply system: Materials
Ductile iron, a stronger and more elastic type of cast iron, is used in newer installations. Iron pipes are provided in diameters up to 122 cm (48 inches) and are usually coated to prevent corrosion. Underground sections are connected with bell-and-spigot joints, the spigot end…
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condensed-matter physics

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A high-resolution electron microscope image of quasicrystalline aluminum-manganese-silicon, revealing a fivefold symmetry of atomic positions.

condensed-matter physics

Written by Richard Tilghman Weidner, Laurie M. Brown•All

Fact-checked by The Editors of Encyclopaedia Britannica

Article History

Key People:: Lev Davidovich Landau; Louis-Eugène-Félix Néel; Allan MacDonald; Ivar Giaever; Leo Esaki

Related Topics:: metallurgy; crystal; physics; crystallography; condensed matter

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condensed-matter physics, discipline that treats the thermal, elastic, electrical, magnetic, and optical properties of solid and liquid substances. Condensed-matter physics grew at an explosive rate during the second half of the 20th century, and it has scored numerous important scientific and technical achievements, including the transistor.

Among solid materials, the greatest theoretical advances have been in the study of crystalline materials whose simple repetitive geometric arrays of atoms are multiple-particle systems that allow treatment by quantum mechanics. Because the atoms in a solid are coordinated with each other over large distances, the theory must go beyond that appropriate for atoms and molecules. Thus conductors, such as metals, contain some so-called free (or conduction) electrons, which are responsible for the electrical and most of the thermal conductivity of the material and which belong collectively to the whole solid rather than to individual atoms. Semiconductors and insulators, either crystalline or amorphous, are other materials studied in this field of physics.

Other aspects of condensed matter involve the properties of the ordinary liquid state, of liquid crystals, and, at temperatures near absolute zero (−273.15 °C, or −459.67 °F), of the so-called quantum liquids. The latter exhibit a property known as superfluidity (completely frictionless flow), which is an example of macroscopic quantum phenomena. Such phenomena are also exemplified by superconductivity (completely resistance-less flow of electricity), a low-temperature property of certain metallic and ceramic materials. Besides their significance to technology, macroscopic liquid and solid quantum states are important in astrophysical theories of stellar structure in, for example, neutron stars.