Materials,Parts and Finishes

Aramid (aromatic polyamide)

Aramid fibers are characterized by excellent environmental and thermal stability, static and dynamic fatigue resistance, and impact resistance. These fibers have the highest specific tensile strength (strength/density ratio) of any commercially available continuous-filament yarn. Aramid-reinforced thermoplastic composites have excellent wear resistance and near-isotropic properties — characteristics not available with glass or carbon-reinforced composites. Aramid fiber, […]

Arc discharge

Arc discharge is a type of electrical conduction in gases characterized by high current density and low potential drop. A typical arc runs at a voltage drop of 100 V with a current drain of 10 A. The arc has negative resistance — the voltage drop decreases as the current increases — so a stabilizing […]

Argon

A chemical element (symbol Ar), argon is the third member of the gaseous elements called the noble, inert, or rare gases, although argon is not actually rare. The earth’s atmosphere is the only commercial argon source; however, traces of the gas are found in minerals and meteorites. Argon is colorless, odorless, and tasteless. The element […]

Aromatic hydrocarbon

A hydrocarbon with a chemistry similar to that of benzene. Aromatic hydrocarbons are either benzenoid or nonbenzenoid. Benzenoid aromatic hydrocarbons contain one or more benzene rings and are by far the more common and the more important commercially. Nonbenzenoid aromatic hydrocarbons have carbon rings that are either smaller or larger than the six-membered benzene ring. […]

Arsenic

Arsenic (symbol As) is a soft, brittle, poisonous element of steel-gray color and metallic luster. In atomic structure it is a semimetal, lacking plasticity, and is used only in alloys and in compounds. The bulk of the arsenic used is employed in insecticides, rat poisons, and weed killers, but it has many industrial uses, especially […]

Artificial intelligence

Artificial intelligence is the subfield of computer science concerned with understanding the nature of intelligence and constructing computer systems capable of intelligent action, abbreviated AI. It embodies the dual means of furthering basic scientific understanding and of making computers more sophisticated in the service of humanity. AI is primarily concerned with symbolic representations of knowledge […]

Artificially layered structures

Manufactured, reproducibly layered structures with layer thicknesses approaching interatomic distances. Modern thin-film techniques are at a stage at which it is possible to fabricate these structures, also known as artificial crystals or super lattices, opening up the possibility of engineering new desirable properties into materials. These structures serve as model systems and as a testing […]

Asbestos

Any of six naturally occurring minerals characterized by being extremely fibrous (asbesti-form), strong, and incombustible. They are utilized in commerce for fire protection; as reinforcing material for tiles, plastics, and cements; for friction materials; and for thousands of other uses. Because of a great concern over the health effects of asbestos, many countries have promulgated […]

Asphalt

Asphalt refers to varieties of naturally occurring bitumen. Asphalt is also produced as a petroleum byproduct. Both substances are black and largely soluble in carbon disulfide. Asphalts are of variable consistency, ranging from a highly viscous fluid to a solid. Asphalt is derived from petroleum in commercial quantities by removal of volatile components. It is […]

Babbitt metal

The original name for tin-antimony-copper (Sn-Sb-Cu) white alloys used for machinery bearings, the term now applies to almost any white bearing alloy with either tin or lead (Pb) base. The alloy consists of 88.9% tin, 7.4% antimony, and 3.7% copper. This alloy melts at 239°C. It has a Brinell hardness of 35 at 21°C, and […]

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