Vocab Flashcards
Diffusion
material transport by atomic motion
isotropic
having identical values of a property in all crystallographic direction
electronegativity
For an atom, having a tendency to accept valence electrons. Also, a term used to describe nonmetallic elements.
covalent bond
type of bond where atoms share electrons between adjacent atoms
vacancy diffusion
the interchange of an atom from a lattice position to an adjacent vacant lattice site
periodic table
The arrangement of the chemical elements with increasing atomic number according to the periodic variation in electron structure. Nonmetallic elements are positioned at the far right-hand side of the table.
carburizing
process where the surface of steel is hardened by increasing the surface concentration of carbon
isotope
Atoms of the same element that have different atomic masses and number of neutrons
anisotrophy
directionality of material properties associated with the variance of atomic or ionic spacing with crystallographic direction
atomic weight
(A) The weighted average of the atomic masses of an atom’s naturally occurring isotopes. It may be expressed in terms of atomic mass units (on an atomic basis), or the mass per mole of atoms.
crystalline
material in which the atoms are situated in a repeating or periodic array over large atomic distances; long range order
diffraction
Constructive interference of x-ray beams that are scattered by atoms of a crystal.
coordination number
number of nearest-neighbor or touching atoms
metallic bond
type of bonding where valence electrons are not bound to any particular atoms in the solid and are more or less free to drift throughout the entire solid
lattice
3-D array of points coinciding with atom positions (or sphere centers)
quantum number
A set of four numbers, the values of which are used to label possible electron states. Three of the quantum numbers are integers, which also specify the size, shape, and spatial orientation of an electron’s probability density; the fourth number designates
spin orientation.
polymorphism
when an element of combination of elements has more than one crystal structure under different conditions
unit cell
small repeating entities within a crystal structure
microscopy
The investigation of microstructural elements using some type of microscope.
point defect
imperfections associated with one or two atomic positions
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.
vacancy
imperfection where a normally occupied lattice site is unoccupied
atomic packing factor
The sum of the sphere volumes of all atoms within a unit cell divided by the unit cell volume; a measure of efficiency
Fick’s first law
The diffusion flux is proportional to the concentration
gradient. This relationship is employed for steady-state diffusion situations.
energy state
the position and energy of an electron described by its quantum numbers
interstitial diffusion
diffusion type where small atoms migrate through the small spaces between larger atoms
bonding energy
represents the energy required to separate two atoms to an infinite separation
diffusion flux
(J) The quantity of mass diffusing through and perpendicular to a unit cross-sectional area of material per unit time.
diffusion coefficient
(D) 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.
amorphous
lacking a systematic and regular arrangement of atoms over a relatively large atomic distance; without form
Fick’s second law
The time rate of change of concentration is proportional to the second derivative of concentration. This relationship is employed in nonsteady-state diffusion situations.
edge dislocation
imperfection where an extra half place of atoms exists where the edge terminates within the crystal
screw dislocation
A linear crystalline defect associated with the lattice distortion created when normally parallel planes are joined together to form a helical ramp. The Burgers vector is parallel to the dislocation line.
grain
Another name for a single crystal; region where crystal planes and directions are continuous
ionic bond
A coulombic interatomic bond that exists between two adjacent and oppositely charged ions.
valence electron
electrons that occupy the outermost shell
