GLOSSARY OF TERMS

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

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 cement 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 mers, 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.

B

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
a monomer 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.

Bohr Magneton

Boltzmann's Constant
The gas constant per molecule: 1.381x10-23J/atom K; 1.381x10-16 erg/atom K; or 8.63x10-5 eV/atom K.

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.

Bravais Lattice

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.

C

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.

Cermet
a composite material consisting of a combination of ceramic and metallic materials.

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
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.

Configuration

Conformation

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.

Critical Point

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

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.

Crystallography

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.

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

D

Defect

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.

E

Edge Dislocation

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.

Eutectoid Phase

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.

F

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.

Ferrimagnetism

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.

Fracture

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.

G

Gas Constant
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).

H

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.

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

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

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.

I

Impact Energy
a measure of the energy absorbed during the fracture of a specimen of standard dimensions and geometry when subjected to very rapid (impact) loading. Charpy and Izod impact tests are used to measure this parameter, which is important in assessing the ductile-to-brittle transition behavior of a material.

Index of Refraction
see Refractive Index

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.

Interstice

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

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.

J

K

L

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.

Liquidus

M

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.

Magnetization
the total magnetic moment per unit volume of material. Also, a measure of the contribution to the magnetic flux by some material within an H field.

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

Martensitic Transformation

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.

Metastable
nonequilibrium state that may persist for a very long time.

Microstructure
the structural features of an alloy that are subject to observation under a microscope.

Miller Indices
a set of three integers that designate crystallographic planes, as determined from reciprocals of fractional axial intercepts.

Miller-Bravis Indices
a set of four integers that designate crystallographic planes in hexagonal crystals.

Mixed Dislocation
a dislocation that has both edge and screw components.

Modulus of Elasticity
the ratio of stress to strain for a material under perfectly elastic deformation.

Monomer
a molecule consisting of a single mer.

MOSFET
Metal-oxide-silicon field effect transistor, an integrated circuit element.

N

Network Polymer
a polymer composed of trifunctional mer units that form three-dimensional molecules.

Noncrystalline
the solid state wherein there is no long-range atomic order. Sometimes used synonymously with the terms amorphous, glassy and vitreous.

Nucleation
the initial stage in a phase transformation. It is evidenced by the formation of small particles (nuclei) of the new phase, which are capable of growing.

O

Octahedral position
the void space among closed-packed, hard sphere atoms or ions for which there are six nearest neighbors. An octahedron (double pyramid) is curcumscribed by lines constructed from centers of adjacent spheres.

P

Paramagnetism
a relatively weak form of magnetism that results from the independent alignment of atomic dipoles (magnetic) with an applied magnetic field.

Pearlite
a two-phase microstructure found in some steels and cast irons. It results from the transformation of austenite of eutectoid compositions and consists of alternating layers of alpha-ferrite and cementite.

Peritectic

Peritectoid

Permittivity
the proportionality constant between the dielectric displacement D and the electric field E.

Phase
a homogeneous region of matter.

Phase Diagram
a graphical representation of the relationships between environmental constraints, composition, and regions of phase stability, ordinarily under conditions of equilibrium.

Phase Transformation
a change in the number and/or character of the phases that constitute the microstructure of an alloy.

Phonon
a single quantum of vibrational or elastic energy.

Photon
a quantum unit of electromagnetic energy.

Piezoelectric
a dielectric material in which polarization is induced by the application of external forces.

Planck's Constant
a universal constant that has a value of 6.63 x 10-34 J.

Plastic
a solid material in the primary ingredient of which is an organic polymer of high molecular wight.

Plastic Deformation
deformation that is permanent or nonrecoverable after release of the applied load.

Plasticizer
a low molecular weight polymer additive that enhances flexibility and workability and reduces stiffness and brittleness.

Point Defect
a crystalline defect associated with one or, at most, several atomic sites.

Poisson's Ratio
for elastic deformation, the negative ratio of lateral and axial strains that result from an applied axial stress.

Polar Molecule
a molecule in which there exists a permanent electric dipole moment by virtue of the asymmetrical distribution of positively and negatively charged regions.

Polarization (electronic)
for an atom, the displacement of the center of the negatively charged electron cloud relative to the positive nucleus, which is induced by an electric field.

Polarization (ionic)
polarization as a result of the displacement of anions and cations in opposite directions.

Polarization (orientation)
polarization resulting from the alignment (by rotation) of permanent electric dipole moments with an applied electric field.

Polycrystalline
referring to crystalline materials that are composed of more than one crystal or grain.

Polymer
a solid, nonmetallic (normally organic) compound of high molecular weight the structure of which is composed of small repeat (or mer) units.

Polymorphism
the ability of a solid material to exist in more than one form or crystal structure.

Portland Cement

Precipitation Hardening
hardening and strengthening of a metal alloy by extremely small and uniformly dispersed particles that precipitate from a supersaturated solid solution.

Prepreg
continuous fiber reinforcement pre-impregnated with a polymer resin which is then partially cured.

Primary Bond
interatomic bonds that are relatively strong and for which bonding energies are relatively large.

Proportional Limit
the point on a stress-strain curve at which the straight line proportionality between stress and strain ceases.

p-type Semiconductor
a semiconductor for which the predominant charge carriers responsible for electrical conduction are holes. Normally, acceptor impurity atoms give rise to the excess holes.

Q

R

Random Copolymer
a polymer in which two different mer units are randomly distributed along the molecular chain.

Reciprocal Lattice

Recrystallization
the formation of a new set of strain-free grains within a previously cold-worked material; normally an annealing heat treatment is necessary.

Reflection
deflection of a light beam at the interface between two media.

Refraction
bending of a light beam upon passing from one medium into another.

Refractive Index
the ratio of the velocity of light in a vacuum to the velocity of light in some medium.

Refractory
a metal or ceramic that may be exposed to extremely high temperatures without deteriorating rapidly or without melting.

Reinforcement

Relative Magnetic Permeability
the ratio of the magnetic permeability of some medium to that of a vacuum.

Resistivity
the reciprocal of electrical conductivity, and a measure of a material's resistance to the passage of electric current.

Rupture
failure that is accompanied by significant plastic deformation.

S

T

Technical Ceramic
a ceramic that exhibits a high degree of industrial efficiency through carefully designed microstructures and superb dimensional precision.

U

Ultimate Tensile Strength

Unit Cell
the basic structural unit of a crystal structure.

V

Vacancy
a normally occupied lattice site from which an atom or ion is missing.

van der Waals Bond
a secondary interatomic bond between adjacent molecular dipoles, which may be permanent or induced.

Viscoelasticity
a type of deformation exhibiting the mechanical characteristics of viscous flow and elastic deformation.

Viscosity
the ratio of the magnitude of an applied shear stress to the velocity gradient that it produces.

Vulcanization
nonreversible chemical reaction involving sulfur or other suitable agent wherein cross-links are formed between molecular chains in rubber materials.

W

X

Y

Yield Strength
the stress required to produce a very slight yet specified amount of plastic strain.

Young's Modulus
see Modulus of Elasticitythe ratio of stress to strain when deformation is totally elastic.

Z