Copy of `Tulane - Chemical Engineering Glossary`

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Tulane - Chemical Engineering Glossary Category: Sciences > Chemical Engineering Date & country: 13/09/2007, USA Words: 180

Abrasive
A hard and wear-resistant material that is used to wear, grind or cut away other material.

Adhesive
a substance that bonds together the surfaces of two other materials.

Advanced Ceramic
a value-added technical ceramic

Air Set Cement
a that sets through loss of water.

Alloy
a metallic solid or liquid formed from an intimate combination of two or more elements.

Alternating Copolymer
a polymer, composed of two different repeating , in which the different mer units systematically alternate positions along the molecular chain.

Amorphography
the branch of science concerned with the determination of amorphous solid structures and their systemmatic classification (see also crystallography).

Amorphous
having no long-range order.

Anisotropic
exhibiting different values of a property in different crystallographic directions.

Annealing
a generic term used to denote a heat treatment wherein the microstructrure and, consequently, the properties of a material are altered. Frequently, refers to heat treatment whereby a cold-worked metal is softened by allowing it to recrystallize.

Antiferromagnetism
a phenomenon observed in some materials in which complete magnetic moment cancellation occurs as a result of antiparallel coupling of adjacent atoms or ions. The macroscopic solid possesses no net magnetic moment.

Atactic
a type of polymer chain configuration wherein side groups are randomly poitioned on one side of the polymer backbone or the other.

Austenite
face-centered cubic iron; also iron and steel alloys that have the FCC structure.

Bainite
a Fe-C composition consisting of a fine dispersion of cementite in alpha-ferrite. It is an austenitic transformation product that forms at temperatures between those at which pearlite and martensite transformations occur.

Band Gap Energy
for semiconductors and insulators, the energies that lie between the valence and conduction bands.

Bifunctional Monomer
amonomer unit that has two active bonding positions.

Block Copolymer
a linear copolymer in which identical mer units are clustered in blocks along the molecular chain.

Body-centered Cubic (BCC)
a common crystal structure that contains atoms located at the corners of a cubic cell and one atom at the cell center position.

Bonding Energy
the energy required to separate two atoms that are chemically bonded to each other.

Bragg's Law
a relationship that stipulates the condition for diffraction by a set of crystallographic planes.

Branched Polymer
a polymer having a molecular structure of secondary chains that extend from the primary chains.

Brass
a copper-rich copper-zinc alloy.

Brazing
a metal joining technique that uses a molten filler metal alloy having a melting temperature greater than about 425 ° C.

Brittle Fracture
fracture that occur by rapid crack propagation and without appreciable macroscopic deformation.

Bronze
a copper-rich copper-tin alloy.

Burgers Vector
a vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.

Calcination
a high-temperature reaction whereby one solid material dissociates to form a gas and another solid.

Capacitance
the charge-storage ability of a capacitor, defined as the magnitude of charge stored on either plate divided by the applied voltage.

Carburizing
the process by which the surface carbon concentration of a ferrous alloy is increased by diffusion from the surrounding environment.

Cast Iron
a ferrous alloy with carbon content between 2 and 4.5 wt%.

Cathodic Protection
a means of corrosion prevention whereby electrons are supplied to the structure to be protected from an external source such as anoother more reactive metal or a dc power supply.

Cement
a substance that can be used to build together aggregates of sand or stone into a cohesive structure. May be a single compound or a mixture. May be hydraulic set, air set or chemical set.

Cementite
iron carbide (Fe3C).

Ceramic
inorganic, nonmetalllic products for which the interatomic bonding is predominantly ionic.

Chemical Set Cement
a cement that sets through reaction or precipitation. Often subjected to a high temperature during manufacture or use.

Cold Working
the plastic deformation of a metal at a temperature below that at which it recrystallizes.

composite
material consisting of a combination of and metallic materials.

Composite
a material brought about by combining materials differing in composition or form on a macroscale for the purpose of obtaining specific characteristics and properties. The constituents retain their identity such that they can be physically identified and they exhibit an interface between one another.

Concrete
a composite material consisting of aggregate particles bound together in a solid body by a cement.

Condensation Polymerization
the formation of polymers by an intermolecular reaction involving at least two monomer species, usually with the production of a low molecular weight by-product such as water.

Conduction Band
the lowest-lying electron energy band that is not completely filled with electrons.

Congruent Transformation
a transformation of one phase to another that does not involve any change in composition.

Coordination Number
the number of atomic or ionic nearest neighbors.

Copolymer
a polymer that consists of two or more dissimilar mer units in combination along its molecular chains.

Corrosion
Deteriorative loss of a metal as a result of dissolution environmental reactions.

Covalent Bond
a primary interatomic bond that is formed by the sharing electrons between neighboring atoms.

Creep
the time-dependent permanent deformation that occurs under stress; for most materials it is important only at elevated temperatures.

Crosslinked Polymer
A polymer in which adjacent linear molecular chains are joined at various positions by covalent bonds.

Crystal Structure
for crystalline materials, the manner in which atoms or ions are arrayed in space. It is defined in terms of the unit cell geometry and the atom positions within the cell.

Crystal System
a scheme by which crystal structures are classified according to unit cell geometry.

Crystalline
the state of a solid material characterized by a periodic and repeating three-dimensional arrays of atoms, ions, or molecules.

Crystallinity
for polymers, the state wherein a periodic and repeating atomic arrangement is achieved by molecular chain alignment.

Crystallite
a region within a crystalline polymer in which all the molecular chains are ordered and aligned.

Curie Temperature
that temperatue above which a ferromagnetic or ferrimagnetic material becomes paramagnetic.

Devitrification
the process in which a glass (noncrystalline or vitreous solid) transforms to a crystalline solid

Diamagnetism
a weak form of induced or nonpermanent magnetism for which the magnetic susceptibility is negative.

Dielectric
any material that is electrically insulating.

Dielectric Constant
the ratio of the permittivity of a medium to that of a vacuum.

Dielectric Strength
the magnitude of an electric field necessary to cause significant current passage through a dielectric material.

Diffusion
mass transport by atomic motion.

Diffusion Coefficient
the constant of proportionality between diffusion flux and the concentration gradient in Fick's first law.

Dipole (electric)
a pair of equal yet opposite electrical charges that are separated by a small distance

Dislocation
a linear crystalline defect around which there is an atomic misalignment.

Doping
the intentional alloying of semiconducting materials with controlled concentrations of donor or acceptor impurities.

Drawing
a deformation technique used to fabricate metal wire and tubing. Deformation is accomplished by pulling the material through a die by means of a tensile force applied on the exit side.

Ductility
a measure of a material's ability to undergo appreciable plastic deformation before fracture.

Elastic Modulus
see Modulus of Elasticity

Elastomer
a polymeric material that may experience large and reversible elastic deformations.

Electronegativity
for an atom, having a tendency to accept valence electrons.

Engineering Ceramics
technical ceramics for structural applications.

Eutectic Phase
one of the two phases found in the eutectic structure.

Extrinsic Semiconductor
a semi-conducting material for hich the electrical behavior is determined by impurities.

Extrusion
a forming technique whereby a material is forced, by compression, through a die orifice.

Face-centered Cubic (FCC)
a crystal structure found in some of the common elemental metals. Within the cubic unit cell, atoms are located at all corner and face-centered positions.

Fatigue
failure, at relatively low stress levels, of structures that are subjected to fluctuating and cyclic stresses.

Fermi Energy
for a metal, the energy corresponding to the highest filled electron state in the valence bond at 0 K.

Ferrite (iron)
body-centered cubic iron. Also, iron and steel alloys that have the BCC crystal structure.

Ferroelectric
a dielectric material that may exhibit polarization in the absence of an electric field.

Ferromagnetism
permanent and large magnetizations found in some metals (e.g., Fe, Ni, and Co), which result from the parallel alignments of neighboring magnetic moments.

Fiber
any material that has been drawn into a cylinder with a length-to-diameter ratio greater than about ten.

Filler
an inert foreign substance added to a matrix to improve or modify its properties.

Firing
a high-temperature heat treatment that increases the density and strength of a ceramic piece.

Forging
mechanical forming of a metal or alloy by heating and hammering.

Fracture toughness
critical value of the stress intensity factor for which crack extensions occurs.

Free energy
a thermodynamic quantity that is a function of both the internal energy and entropy of a system.

Frenkel Defect
in an ionic solid, a cation-vacancy and cation-interstitial pair.

Glass
an inorganic product of fusion which has cooled to a rigid condition without crystallizing.

Glass-ceramic
a fine-grained crystalline material that was formed as a glass and subsequently devitrified (crystallized).

Hall Effect
the phenomenon whereby a force is brought to bear on a moving electron or hole by a magnetic field that is applied perpendicular to the direction of motion. The force direction is perpendicular to both the magnetic field and the particle motion directions.

Hardenability
a measure of the depth to which a specific ferrous alloy may be hardened by the formation of martensite upon quenching from a temperature above the upper critical temperature.

Hardness
the measure of some materials' resistance to deformation by surface indentation or by abrasion.

Hexagonal Close-Packed (HCP)
a crystal structure found for some metals. The HCP unit cell is of hexagonal geometry and is generated by the stacking of close-packed planes of atoms.

Hole (electron)
for semi-conductors and insulators, a vacant electron state in the valence band that behaves as a positive charge carrier in an electric field.

Homopolymer
a polymer having a chain structure in which all mer units are of the same type.

Hot Working
any metal forming operation that is performed above a metal recrystallization temperature.

Hydraulic Set Cement
a cement that sets through reaction with water.

Hydrogen Bond
a strong secondary interatomic bond which exists between a bound hydrogen atom (its unscreened proton) and the electrons of adjacent atoms.

Hypereutectoid Alloy
for an alloy system displaying a eutectoid, an alloy for which the concentration of solute is greater than the eutectoid composition.

Hypoeutectoid Alloy
for an alloy system displaying a eutectoid, an alloy for which the concentration of solute is less than the eutectoid composition

Hysteresis (magnetic)
the irreversible magnetic flux density-versus-magnetic field strength (B-versus-H) behavior found for ferromagnetic and ferrimagnetic materials.