Vocabulary Flashcards for Equilibrium, Materials Science, and Polymer Chemistry

A comprehensive set of flashcards covering vocabulary related to equilibrium, materials science, and polymer chemistry.

Gibbs phase rule

For a system at equilibrium, an equation that expresses the relationship between the number of phases present and the number of externally controllable variables.

Dielectric constant

The ratio of the permittivity of a medium to that of a vacuum. Often called the Relative dielectric constant or Relative permittivity.

Materials selection chart

A plot (logarithm-logarithm) of one material property (e.g., strength) versus another property (e.g., density). Materials of a particular type (e.g., metal alloys) cluster together and are enclosed within an envelope that is delineated using a bold line.

Diffraction

Constructive interference of x-ray beams scattered by atoms of a crystal.

Interstitial solid solution

A solid solution in which relatively small solute atoms occupy interstitial positions between the solvent or host atoms.

Unit cell

The basic structural unit of a crystal structure. It is generally defined in terms of atom (or ion) positions within a parallelepiped volume.

Resilience

The capacity of a material to absorb energy when it is elastically deformed.

Atomic vibration

The vibration of an atom about its normal position in a substance.

Congruent transformation

A transformation of one phase to another of the same composition.

Ferroelectric

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

Thermoplastic elastomer

A copolymeric material that exhibits elastomeric behavior yet is thermoplastic in nature. At the ambient temperature, domains of one repeat unit type form at molecular chain ends that crystallize to act as physical crosslinks.

Monomer

A stable molecule from which a polymer is synthesized.

Ferrite

Ceramic oxide materials composed of both divalent and trivalent cations (e.g., Fe2+ and Fe3+), some of which are ferrimagnetic.

Piezoelectric

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

Vacancy

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

Activation polarization

The condition in which the rate of an electrochemical reaction is controlled by the slowest step in a sequence of steps that occur in series.

Self-interstitial

A host atom or ion positioned on an interstitial lattice site.

Diffusion coefficient

The constant of proportionality between the diffusion flux and the concentration gradient in Fick's first law. Its magnitude is indicative of the rate of atomic diffusion.

Equilibrium

The state of a system in which the phase characteristics remain constant over indefinite time periods.

Growth (phase particle)

During a phase transformation and subsequent to nucleation, the increase in size of a particle of a new phase.

Concentration polarization

The condition in which the rate of an electrochemical reaction is limited by the rate of diffusion in the solution.

Imperfection

A deviation from perfection; normally applied to crystalline materials in which there is a deviation from atomic/molecular order and/or continuity.

Peritectic reaction

A reaction in which, upon cooling, a solid and a liquid phase transform isothermally and reversibly to a solid phase having a different composition.

Composition

The relative content of a particular element or constituent (I) within an alloy, usually expressed in weight percent or atom percent.

Amorphous

Having a noncrystalline structure.

Random copolymer

A polymer in which two different repeat units are randomly distributed along the molecular chain.

Addition polymerization

The process by which monomer units are attached one at a time, in chainlike fashion, to form a linear polymer macromolecule.

Photomicrograph

A photograph made with a microscope that records a microstructural image.

Vacancy diffusion

The diffusion mechanism in which net atomic migration is from a lattice site to an adjacent vacancy.

Creep

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

Acceptor state (level)

For a semiconductor or insulator, an energy level lying within yet near the bottom of the energy band gap that may accept electrons from the valence band, leaving behind holes. The level is normally introduced by an impurity atom.

Supercooling

Cooling to below a phase transition temperature without the occurrence of the transformation.

Anion

A negatively charged ion.

Isomerism

The phenomenon by which two or more polymer molecules or repeat units have the same composition but different structural arrangements and properties.

Syndiotactic configuration

A type of polymer chain configuration (stereoisomer) in which side groups regularly alternate positions on opposite sides of the chain.

Permittivity

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

Molecular weight

The sum of the atomic weights of all the atoms in a molecule.

Grain boundary

The interface separating two adjoining grains having different crystallographic orientations.

Scanning electron microscope (SEM)

A microscope that produces an image by using an electron beam that scans the surface of a specimen; an image is produced by reflected electron beams. Examination of surface and/or microstructural features at high magnifications is possible.

Bifunctional

Designates monomers that may react to form two covalent bonds with other monomers to create a two-dimensional chainlike molecular structure.

Modulus of elasticity

The ratio of stress to strain when deformation is totally elastic; also a measure of the stiffness of a material.

Concentration profile

The curve that results when the concentration of a chemical species is plotted versus position in a material.

Plasticizer

A low-molecular-weight polymer additive that enhances flexibility and workability and reduces stiffness and brittleness, resulting in a decrease in the glass transition temperature TG.

Ground state

A normally filled electron energy state from which an electron excitation may occur.

Degree of polymerization

The average number of repeat units per polymer chain molecule.

Corrosion fatigue

A type of failure that results from the simultaneous action of a cyclic stress and chemical attack.

Performance index (P)

A parameter used to quantify the optimization of some aspect of the performance of a component or structure.

Interdiffusion (impurity diffusion)

Diffusion of atoms of one metal into another metal.

Dipole (electric)

A pair of equal and opposite electrical charges separated by a small distance.

Rule of mixtures

The properties of a multiphase alloy or composite material are a weighted average of the properties of the individual constituents.

Saturated

A carbon atom that participates in only single covalent bonds with four other atoms.

Principle of combined action

The supposition, often valid, that new properties, better properties, better property combinations, and/or a higher level of properties can be fashioned by the judicious combination of two or more distinct materials.

Allotropy

The possibility of the existence of two or more different crystal structures for a substance.

Dipole, electric

See Dipole (electric).

Condensation polymerization

The formation of polymer macromolecules by an intermolecular reaction, usually with the production of a by-product of low molecular weight.

Fatigue limit

For fatigue, the maximum stress amplitude level below which a material can endure an essentially infinite number of stress cycles and not fail.

Steady-state diffusion

The diffusion condition for which there is no net accumulation or depletion of diffusing species. The diffusion flux is independent of time.

Van der Waals bond

A secondary interatomic bond between adjacent molecular dipoles that may be permanent or induced.

Bohr atomic model

An early atomic model in which electrons are assumed to revolve around the nucleus in discrete orbitals.

Wave-mechanical model

An atomic model in which electrons are treated as being wavelike.

Polymer-matrix composite

A composite material for which the matrix is a polymer resin and fibers are the dispersed phase.

Shear

A force applied so as to cause or tend to cause two adjacent parts of the same body to slide relative to each other in a direction parallel to their plane of contact.

Metallic bond

A primary interatomic bond involving the nondirectional sharing of nonlocalized valence electrons that are mutually shared by all the atoms in the metallic solid.

True strain

The natural logarithm of the ratio of instantaneous gauge length to original gauge length of a specimen being deformed by a uniaxial force.

Intrinsic semiconductor

A semiconductor material for which the electrical behavior is characteristic of the pure material.

Spinning

The process by which fibers are formed. A multitude of fibers are spun as molten or dissolved material is forced through many small orifices.

Dislocation line

The line that extends along the end of the extra half-plane of atoms for an edge dislocation and along the center of the spiral of a screw dislocation.

Slip

Plastic deformation as the result of dislocation motion. also, the shear displacement of two adjacent planes of atoms.

Trans (structure)

For polymers, a prefix denoting a type of molecular structure. For some unsaturated carbon chain atoms within a repeat unit, a single side atom or group may be situated on one side of the double bond, or directly opposite at a 180° rotation position;  two such side groups within the same repeat unit reside on opposite sides.

Fick's first law

The diffusion flux is proportional to the concentration gradient.

Nanocomposite

A composite composed of nanosize particles embedded in matrix material.

Vulcanization

A nonreversible chemical reaction involving sulfur or another agent that forms crosslinks within rubber materials.  The rubber's modulus of elasticity and strength are enhanced.

Lattice strain

Slight displacements of atoms relative to their normal lattice positions, normally imposed by crystalline defects such as dislocations, and interstitial and impurity atoms.

Stress raiser

A small flaw or structural discontinuity where applied tensile stress is amplified and from which cracks may propagate.

Ductile fracture

A mode of fracture attended by extensive gross plastic deformation.

Miller indices

A set of three integers designating crystallographic planes, as determined from reciprocals of fractional axial intercepts.

Stabilizer

A polymer additive that counteracts deteriorative processes.

Electron energy band

A series of electron energy states that are very closely spaced with respect to energy.

Proeutectoid ferrite

Primary ferrite that exists in addition to pearlite for hypoeutectoid steels.

Junction transistor

A semiconducting device composed of appropriately biased N-P-N or P-N-P junctions, used to amplify an electrical signal.

Galvanic series

A ranking of metals and alloys as to their relative electrochemical reactivity.

Phase transformation

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

Macromolecule

A huge molecule made up of thousands of atoms.

Face-centered cubic (FCC)

A crystal structure found in some elemental metals where atoms are located at all corner and face-centered positions.

Scission

A polymer degradation process by which molecular chain bonds are ruptured.

Electron configuration

For an atom, the manner in which possible electron states are filled with electrons.

Engineering strain

The change in gauge length of a specimen divided by its original gauge length.

Thermosetting polymer

A polymeric material that, once cured (or hardened) by a chemical reaction, will not soften when subsequently heated.

Spheroidite

Microstructure found in steel alloys consisting of spherelike cementite particles within an Α-ferrite matrix. It is produced by an appropriate elevated-temperature heat treatment of pearlite, bainite, or martensite, and is relatively soft.

Hardness

The measure of a material's resistance to deformation by surface indentation or abrasion.

Dielectric displacement

The magnitude of charge per unit area of capacitor plate.

Toughness

A mechanical characteristic that may be expressed in three contexts: (1) the measure of a material's resistance to fracture when a crack (or other stress-concentrating defect) is present; (2) the ability of a material to absorb energy and plastically deform before fracturing; and (3) the total area under the material's tensile engineering stress-strain curve taken to fracture.

Fermi energy

For a metal, the energy corresponding to the highest filled electron state at 0 K.

Foam

A polymer that has been made porous or spongelike by incorporating gas bubbles.

Ultra-high-molecular-weight polyethylene

A polyethylene polymer that has an extremely high molecular weight (approximately 4 × 106 g/mol). Distinctive characteristics of this material include high impact and abrasion resistance and low coefficient of friction.

Hydrogen embrittlement

The loss or reduction of ductility of a metal alloy due to atomic hydrogen diffusion.

Pitting

A form of very localized corrosion where small pits or holes form, usually in a vertical direction.

Isotropic

Having identical values of a property in all crystallographic directions.

Drawing

A forming 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.

Edge dislocation

A linear crystalline defect associated with lattice distortion produced by an extra half-plane of atoms within a crystal.