Material Science

Question 1

Atomic number

Answer 1

number of protons in an atom

Question 2

Isotope

Answer 2

an atom with a different number of neutrons

Question 3

Anion

Answer 3

negatively charged ion

Question 4

Cation

Answer 4

positively charged ion

Question 5

Bonding occurs by three mechanisms:

Answer 5

ionic bonds, covalent bonds, metallic bonds

Question 6

Ionic bonding

Answer 6

coulombic attraction between oppositely charged ions

Question 7

Covalent bonding

Answer 7

sharing of electrons to fill outer shells

Question 8

Metallic bonding

Answer 8

formation of ion cores surrounded by free electrons

Question 9

Ionic bonds form between…

Answer 9

… metallic and nonmetallic atoms

Question 10

Covalent bonds form between…

Answer 10

… atoms that share valence electrons in order to fill their outer shells

Question 11

Metallic bonds form between the elements on the…

Answer 11

… left side of the periodic table

Question 12

The stronger the atomic bonding..

Answer 12

… the higher the melting temperature, hardness, and elastic modulus

Question 13

Ionically bonded materials are usually…

Answer 13

… electrical/thermal insulators

Question 14

Metallically bonded materials usually have…

Answer 14

… high electrical/thermal conductivities

Question 15

Crystal

Answer 15

periodic structure produced by repetition of atomic coordinates in three dimensions

Question 16

Anisotropic

Answer 16

properties differ with direction and orientation

Question 17

Point imperfections

Answer 17

vacancies, interstitials, displaced atoms

Question 18

Diffusion is facilitated by…

Answer 18

… point imperfections

Question 19

Dislocations facilitate…

Answer 19

… plastic deformation by slip

Question 20

As temperature increases, the amplitude of…

Answer 20

… vibrations of atoms within a crystal increases, shaking apart the crystal

Question 21

Flux (J), or rate of diffusion, is proportional to…

Answer 21

… the concentration gradient

Question 22

Two microstructures are produced in a majority of steels:

Answer 22

spheriodite and pearlite

Question 23

Ore

Answer 23

oxides/sulfides that require chemical reduction via a carbon containing gas

Question 24

Refining

Answer 24

dissolved impurities are removed by closely controlled reoxidation and deoxidation (produces steel when iron oxide is refined)

Question 25

Chemicals from which a variety of plastics are produced are refined from..

Answer 25

… petroleum

Question 26

Annealing

Answer 26

reheating a material to make internal adjustments between atoms or molecules

Question 27

Internal stresses are a result of…

Answer 27

… differential expansions between different phases and thermal gradients

Question 28

The strength and hardness of steel increases with…

Answer 28

… carbon content

Question 29

Bending depends on…

Answer 29

… geometry and stress level

Question 30

Cracking depends on….

Answer 30

… geometry, stress level, and loading rate

Question 31

Elastic modulus

Answer 31

ratio of stress to strain

Question 32

Yield strength

Answer 32

threshold level at which initial slip occurs

Question 33

In a tensile test, the area under the stress-strain curve represents…

Answer 33

… energy

Question 34

Breakage always occurs at…

Answer 34

… a location of stress concentration, usually a microscopic flaw

Question 35

Cyclic loading reduces…

Answer 35

… permissible design stresses

Question 36

Endurance limit

Answer 36

unlimited cycling can be tolerated within the endurance limit

Question 37

Creep

Answer 37

a slow dimensional change within a material, commonly seen in plastics (atoms migrate from compressive to tensile regions)

Question 38

Spalling

Answer 38

thermal cracking, results from differential volume changes

Question 39

Embrittlement

Answer 39

abrupt drop in ductility and toughness as temperature lowers (atoms cannot relocate in response to stress)

Question 40

Unlike heat which energizes all of the atoms and molecules in a structure, radiation introduces…

Answer 40

… energy at pinpoints called thermal spikes, causing individual bonds to break and electrons be energizedq

Question 41

All metals expect for gold…

Answer 41

… oxidize in ambient air