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Materials Exam 1 > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Material Selection Procedure:

A
  1. For a specific application -> Determine desired properties
  2. From list of properties -> Identify Candidate material
  3. Best candidate material -> Specify processing technique
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2
Q

Properties of Metals

A

Strong, ductile, high thermal & electrical conductivities, opaque (not transparent), reflective

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3
Q

Properties of Plastics

A

Soft, ductile, low strength, low densities, low thermal and electrical conductivities, (opaque, translucent or transparent)

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4
Q

Properties of Ceramics

A

Hard, brittle, low thermal and electrical conductivities, (opaque, translucent, or transparent)

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5
Q

Quantum numbers

A

Comprised of
n = principal (shell); K, L, M, N, O (1,2,3,4, etc.)
l = sub shell; s, p, d, f (0, 1, 2, 3, etc.)
ml = magnetic (from -l to l)
ms = spin; -1/2 or 1/2

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6
Q

Valence electrons determine:

A

Materials chemical, electrical, thermal, and optical properties

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7
Q

Ionization process

A

metal atom donates electrons while nonmetal atoms accept electrons

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8
Q

Electronegativity

A

Defines the tendency of an element to acquire electrons

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9
Q

Ionic Bonding

A

Between metal and non-metal resulting in TRANSFER of electrons from the metal to the nonmetal
(Large difference in electronegativity)

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10
Q

Covalent bonding

A

Between two nonmetals and is characterized by SHARING of electrons

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11
Q

Metallic bonding

A

Between two metals and is associated with DELOCALIZED electron pool (“sea of electrons”)

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12
Q

Force of attraction

A

Fa = -(kZ1Z2)/r^2

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13
Q

Ionic bonds are common in ceramics and result in properties such as

A

Non-directional, relatively high bond energy, hard and brittle, electrically and thermally insulated, conduct electricity if melted or dissolved, high melting and boiling points

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14
Q

The stronger the ionic bond

A

The higher the melting point

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15
Q

Covalent bonds determined by hybridization

A

sp - polyyne
sp2 - graphite, graphene, nanotube, fullerene
sp3 - diamond

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16
Q

Covalent bonds are common in polymers

A

polymers have strong forces within molecules and weak forces between molecules

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17
Q

Due to delocalized electrons in metallic bonding metals…

A

Have moderately high melting and very high boiling points, can be pounded to sheets or drawing into wires, very good electrical and thermal conductors, easily form alloys with other metals

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18
Q

Secondary bonding force ranking

A

Ion-dipole
H bond
dipole-dipole
ion-induced dipole
dipole-induced dipole
dispersion forces

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19
Q

Classification of Solids

A

Crystalline (molecular, metallic, covalent, or ionic solid) or amorphous

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20
Q

edge of sc unit

A

a = 2r

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21
Q

edge of bcc

A

a = 4r/(root 3)

22
Q

edge of hcc

A

a = 2r

23
Q

edge of fcc

A

a = 2r(root 2)

24
Q

Coordination number

A

is the number of nearest neighbors (touching atoms)
scc - coordination #=6
bcc - coordination #=8
fcc - coordination #=12
hcc - coordination #=12

25
Q

atomic packing fraction

A

apf=(volume of atoms in unit cell)/(volume of unit cell)
scc = 52.4%
bcc = 68%
fcc = 74%
hcc = 74%

26
Q

atoms per unit cell

A

scc=1
bcc=2
fcc=4
hcc = 6

27
Q

density of unit cell

A

(# of atoms x atomic weight)/(volume of cell x avagadros #)

28
Q

Examples of simple cubic cell (SCC)

A

Po

29
Q

Example of FCC

A

Cu, Ni, Al, Au, Ag, Pt, Pb

30
Q

Examples of BCC

A

Fe, Mn, Mo, W, Na, Li, K, Rb, Cs

31
Q

Close packing structures

A

FCC and HCP (hexagonal)

32
Q

Example of ceramics

A

NaCl, MgO, Al2O3, SiO2, SrTiO3, SiC, Si3N4

33
Q

Bonds in ceramics

A

can be ionic or covalent

34
Q

Coordination number of material

A

coord # = (r of cation)/(r of anion)

<0.155 = coord #2 = linear
0.155 - 0.225 = coord #3 = triangular
0.225 - 0.414 = coord #4 = tetrahedral
0.414 - 0.732 = coord #6 = octahedral
0.732 - 1 = coord #8 = cubic

35
Q

ceramics density

A

use fancy density equation with formula units (n’)

36
Q

Linear density

A

LD = number of diameters centered on vector/length of vector

37
Q

Planar density

A

number of circular areas on plane/area of plane

38
Q

Crystal structures have anisotropic properties

A

anisotropic properties mean the materials are directional
(isotropic properties are non-directional)

39
Q

allotropy or polymorphism

A

materials having different crystal structures at different temperatures

40
Q

Six common polymers we must know

A

Polyethylene (PE)
Polyvinyl chloride (PVC)
Polytetrafluorethlene (PTFE)
Polypropylene (PP)
Polystyrene (PS)
Polymethyl methacrylate (PMMA)

41
Q

Polyethylene (PE)

A

Mer Unit - C2H4
Mer mass - 28.05g
Linear or branched
Paraffin wax for candles is an example

42
Q

Polyvinyl Chloride (PVC)

A

Mer Unit - C2H3Cl
Mer mass - 62.49g
Linear or branched
Used for pvc pipes…

43
Q

Polytetrafluoroethylene (PTFE)

A

Mer unit - C2F4
Mer Mass - 100.01g
Linear
Used for nonstick coating on pans

44
Q

Polypropylene (PP)

A

Mer Unit - C2H3CH3
Mer mass - 42.08g
Linear or branched
Used for plastic molding like bottles and bottle tops

45
Q

Polystyrene (PS)

A

Mer Unit - C2H3C6H4
C6H4 is aromatic ring attached to the carbon
Mer mass - 103.14
Linear or branched
Used for dads coffee cups

46
Q

Polymethyl methacrylate (PMMA)

A

Mer Unit - C5H8O2 = C2H2CH3C2O2H3
CH3 and C2O2H3 are on opposite sides of one carbon
Mer mass - 100.11g
Linear
Used for acrylate glass and similar clear plastics

47
Q

Polymer structures

A

Linear, branched, cross linked, network

48
Q

Tacticity

A

Spatial arrangement of R units along polymer chain

49
Q

Atactic

A

R groups are randomly positioned on polymer

50
Q

cis polymers

A

H atom and CH3 group are on the same side of chain

51
Q

trans polymers

A

H atom and CH3 group are catycorner on chain

52
Q

spherulite structures

A

spherulite structures have alternating chain-folded crystallites and amorphous regions

Materials Exam 1 (1 decks)

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