Vocab

Question 1

Diffusion

Answer 1

material transport by atomic motion

Question 2

isotropic

Answer 2

having identical values of a property in all crystallographic direction

Question 3

electronegativity

Answer 3

For an atom, having a tendency to accept valence electrons. Also, a term used to describe nonmetallic elements.

Question 4

covalent bond

Answer 4

type of bond where atoms share electrons between adjacent atoms

Question 5

vacancy diffusion

Answer 5

the interchange of an atom from a lattice position to an adjacent vacant lattice site

Question 6

periodic table

Answer 6

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.

Question 7

carburizing

Answer 7

process where the surface of steel is hardened by increasing the surface concentration of carbon

Question 8

isotope

Answer 8

Atoms of the same element that have different atomic masses and number of neutrons

Question 9

anisotrophy

Answer 9

directionality of material properties associated with the variance of atomic or ionic spacing with crystallographic direction

Question 10

atomic weight

Answer 10

(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.

Question 11

crystalline

Answer 11

material in which the atoms are situated in a repeating or periodic array over large atomic distances; long range order

Question 12

diffraction

Answer 12

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

Question 13

coordination number

Answer 13

number of nearest-neighbor or touching atoms

Question 14

metallic bond

Answer 14

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

Question 15

lattice

Answer 15

3-D array of points coinciding with atom positions (or sphere centers)

Question 16

quantum number

Answer 16

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.

Question 17

polymorphism

Answer 17

when an element of combination of elements has more than one crystal structure under different conditions

Question 18

unit cell

Answer 18

small repeating entities within a crystal structure

Question 19

microscopy

Answer 19

The investigation of microstructural elements using some type of microscope.

Question 20

point defect

Answer 20

imperfections associated with one or two atomic positions

Question 21

steady state diffusion

Answer 21

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

Question 22

vacancy

Answer 22

imperfection where a normally occupied lattice site is unoccupied

Question 23

atomic packing factor

Answer 23

The sum of the sphere volumes of all atoms within a unit cell divided by the unit cell volume; a measure of efficiency

Question 24

Fick’s first law

Answer 24

The diffusion flux is proportional to the concentration
gradient. This relationship is employed for steady-state diffusion situations.

Question 25

energy state

Answer 25

the position and energy of an electron described by its quantum numbers

Question 26

interstitial diffusion

Answer 26

diffusion type where small atoms migrate through the small spaces between larger atoms

Question 27

bonding energy

Answer 27

represents the energy required to separate two atoms to an infinite separation

Question 28

diffusion flux

Answer 28

(J) The quantity of mass diffusing through and perpendicular to a unit cross-sectional area of material per unit time.

Question 29

diffusion coefficient

Answer 29

(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.

Question 30

amorphous

Answer 30

lacking a systematic and regular arrangement of atoms over a relatively large atomic distance; without form

Question 31

Fick’s second law

Answer 31

The time rate of change of concentration is proportional to the second derivative of concentration. This relationship is employed in nonsteady-state diffusion situations.

Question 32

edge dislocation

Answer 32

imperfection where an extra half place of atoms exists where the edge terminates within the crystal

Question 33

screw dislocation

Answer 33

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.

Question 34

grain

Answer 34

Another name for a single crystal; region where crystal planes and directions are continuous

Question 35

ionic bond

Answer 35

A coulombic interatomic bond that exists between two adjacent and oppositely charged ions.

Question 36

valence electron

Answer 36

electrons that occupy the outermost shell