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Tulane - Chemical Engineering Glossary
Category: Sciences > Chemical Engineering
Date & country: 13/09/2007, USA
Words: 144


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.

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.

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.

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.

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.

Cementite
iron carbide (Fe3C).

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.

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

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.

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.

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

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.

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.

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.

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

Index of Refraction
see Refractive Index

Instrinsic Semiconductor
a semiconductor material for which the electrical behavior is characteristic of the pure material.

Insulator (electrical)
a nonmetallic material that has filled valence band at 0 K and a relatively wide energy band gap.

Intermetallic
a compound of two metals that has a distinct chemical formula. The bonds in intermetallic compounds are often partly ionic.

Invariant Point
a point on a binary phase diagram at which three phases are in equilibrium.

Isotactic
a type of polymer chain configuration wherein all side groups are positioned on the same side of the chain molecule.

Isotope
atoms of the same element having the different masses.

Izod Impact Test
one of two tests that may be used to measure the impact energy of standard notched specimen.

Laser
an acronym for light amplification by stimulated emission of radiation.

Lattice
the regular geometrical arrangement of points in crystal space.

Lattice Parameter
the combination of unit cell edge lengths and interaxial angles that defines the unit cell geometry.

Lever Rule
mathematical expression whereby the relative phase amounts in a two-phase alloy at equilibrium my be computed.

Macromolecule
a huge molecule made up of thousands of atoms.

Magnetic Field Strength
the intensity of an externally applied magnetic field.

Magnetic Flux Density
the magnetic field produced in a substance by an external magnetic field.

Magnetic Induction
see Magnetic Flux Density

Magnetic Susceptibility
the proportionality constant between the magnetization M and the magnetic field strength H.

Martensite
a metastable Fe-C composition consisting of supersaturated carbon in iron that is the product of a diffusionless (athermal) transformation from austenite.

Matrix
the body constituent of a composite or two-phase alloy that completely surrounds the dispersed phase and gives the body its bulk form.

Melting Point
the temperature at which a solid substance changes to a liquid state.

Mer
the group of atoms that constitutes a polymer chain repeat unit.

Metal
the electroposite elements and alloys based on these elements.