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Materials Science > Chapters 1, 2, 3 (intro, atomic structure and bonding, crystal structure) > Flashcards

Chapters 1, 2, 3 (intro, atomic structure and bonding, crystal structure) Flashcards

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1
Q

What is a property?

A

the response of a material to an external effect

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2
Q

Examples of properties

A

Mechanical, electrical, deteriorative, optical, magnetic, thermal

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3
Q

what are the classes of materials

A

Metals, ceramics, polymers

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4
Q

what is a metal

A

inorganic metallic elements

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5
Q

name 2 properties of metals

A
  1. Thermal and electrical conductors 2. Strong and ductile
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6
Q

why are metals good conductors

A

because they have free electrons

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7
Q

what is an alloy

A

a combination of 2 or more metals and non-metals

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8
Q

What is a ceramic

A

a compound of metals and non-metals

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9
Q

name 5 properties of ceramics

A
  1. Hard and strong 2. Brittle 3. Resist high temps 4. Low density 5. electrical insulators
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10
Q

common example of a polymer

A

plastic

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11
Q

what is a polymer

A

a long chain molecule and network usually based on carbon

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12
Q

name 3 properties of polymers

A
  1. electrical insulators. 2. low density 3. low operating temperatures
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13
Q

what are composites

A

a mixture of 2 or more materials

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14
Q

what is unique about semi conductors

A

they share properties of both insulators and conductors

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15
Q

what types of materials are used in “Bio-Materials”

A

all

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16
Q

order of density of materials

A

metals
ceramics
polymers & composites

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17
Q

order of stifness

A

metals and ceramics
composites
polymers

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18
Q

order of strength

A

metals
composites
ceramics
polymers

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19
Q

order of electrical conductivity

A

metals
semi conductors
ceramics and polymers

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20
Q

what do properties of materials depend on

A

bonds between atoms

atomic packing

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21
Q

what is an atom comprised of

A

Proton + neutron + electron

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22
Q

where is the mass of the atom located

A

nucleus

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23
Q

where is the volume of the atom located

A

electron cloud

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24
Q

what does the atomic # dictate

A

of protons

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25
Q

what type of electrons determine important properties

A

valence electrons

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26
Q

what are electroPOSITIVE elements

A

metallic elements that GIVE UP outer electrons to become CATIONS

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27
Q

what are electroNEGATIVE elements

A

non metals that ACCEPT electrons to become ANIONS

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28
Q

electronegativity

A

the tendency to attract electrons

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29
Q

essentially, why do atoms bond together?

A

to reduce overall energy

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30
Q

when is equilibrium reached

A

when Fa+Fr=0 OR when the overall energy is at a minimum

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31
Q

what is bonding energy

A

the energy required to break the bonds

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32
Q

what would a higher bonding energy do

A

stronger bonds=higher strength=higher melting temp

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33
Q

types of primary bonds

A
  1. Ionic
  2. Covalent
  3. Metallic
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34
Q

types of secondary bonds

A
  1. Van der Waals

2. Dipole fluctuations

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35
Q

Primary, Secondary; Physical Chemical. MATCH THEM

A

Primary=Chemical, Secondary=physical

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36
Q

between what types of elements are ionic bonds typically found

A

metals and non metals

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37
Q

what type of material are ionic bonds usually found in

A

Ceramics

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38
Q

why do ions pack together

A

to maintain neutrality

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39
Q

materials which are ionically bonded are what? (3 things)

A
  1. very strong
  2. brittle
  3. insulators
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40
Q

Covalent bonds

A

sharing of electrons, they try to attain noble gas configs

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41
Q

degrees between sp^3 orbitals

A

109.5

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42
Q

%Ionic Character formula

A

[1-exp(-0.25(Xa-Xb)^2)]x100

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43
Q

what are ‘ion cores’

A

closely packed metal ions in ordered arrangements

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44
Q

what type of bonding are SEAs of electrons found

A

Metallic

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45
Q

Metallic bonds are insulators or conductors

A

conductors (free electrons)

46
Q

Secondary bonding

A

low energy-weak bonds

47
Q

what are secondary bonds based on

A

dipoles(separation of charge)

48
Q

Where are Van der Waals forces found

A

between 2 adjacent polar molecules

49
Q

What does Amorphous mean?

A

NO REPEATING ORDER or pattern in bonds, aka short range order

50
Q

What are crystals?

A

Atoms bonded together in a REGULAR 3D patter, aka long range

51
Q

what materials are crystalline Patterns found in?

A

Ceramics, Metals, Some polymers

52
Q

What are space lattices

A

the arrangement of atoms

53
Q

What is a unit cell

A

the smallest repetitive unit which is part of the lattice pattern (it must display the minimum # of features but never repeat any)

54
Q

name the 3 types of densely packed structures

A
  1. Body centered cubic(BCC)
  2. Face centered cubic (FCC)
  3. Hexagonal close packed (HCP)
55
Q

formula for atomic packing factor

A

volume of unit cell occupied by atoms/ total unit cell volume

56
Q

where do atoms touch each other in BCC

A

along the cube diagonals

57
Q

where do atoms touch each other in FCC

A

along the FACE diagonals

58
Q

Coordination # of BCC, FCC & HCP respectively

A

8, 12, 12

59
Q

Atoms per unit cell of BCC, FCC, HCP respectively

A

2, 4, 6

60
Q

crystal density formula

A

density=number of atoms in unit cell * Molar Mass/volume of unity cell * Avogadros #

61
Q

what is polymorphism/allotropy

A

elements in which more than 1 crystal form can exist depending on temperature

62
Q

which is the most & least symmetric crystal structure

A

cubic & tricrilic respectively

63
Q

linear desnity formula

A

number of atoms/ unit length of direction vector

64
Q

Planar density formula:

A

(atoms/2D repeat unit)/(area/2D repeat unit)

65
Q

Single crystal

A

when a piece of material is made of 1 single crystal

66
Q

Polycrystals

A

Many different crystals, with varying orienations

67
Q

what is a grain boundary

A

the boundary line at which crystal grains meet

68
Q

If a property varies with direction, it is said to be…

A

Anisotropic

69
Q

If a property doesn’t vary with direction, it is said to be…

A

isotropic

70
Q

describe creep

A

the tendency for a material to lengthen over time under load

71
Q

The degree to which a material will creep is dependant on what?

A

the number of grain boundaries

72
Q

state bragg’s law formula

A

n(lambda)=2d(hkl)sin(theta)

73
Q

what can be said about the position of atoms which are covalently bonded?

A

their elements will be close on the periodic table

74
Q

Basically, why are metals ductile?

A

Non-directional bonding–>fewer restrictions–>can withstand larger forces before bonds break.
ALSO, since metals have free electrons, this allows their structures more freedom, promoting ductility.

75
Q

Which is the only Non-Crystalline ceramic? And what is another word for this category?

A

Glass. Amorphous

76
Q

what are space lattices?

A

the patterns in which atoms prefer structuring themselves in

77
Q

when we refer to lattice constant, which variables are we talking about?

A

a, b, c

78
Q

List the properties of BCC (3)

A
  1. 4R=sqrt3*A
  2. coordination # =8
  3. 2 atoms/unit cell
  4. APF=0.68
79
Q

List the properties of FCC (4)

A
  1. 4R=sqrt2*A
  2. coordination # = 12
  3. 4 atoms/unit cell
  4. APF=0.74
80
Q

List the properties of HCP(2)

A
  1. 6 atoms/ unit cell

2. coordination #=12

81
Q

what crystal SYSTEM is common for all CUBIC crystal STRUCTURES

A

a=b=c and usually, alpha =beta=gamma=90deg

82
Q

how is a crystallographic direction denoted?

A

[xyz]

83
Q

what does the family of directions denote?

A

all edges of a cube

84
Q

what does family denote?

A

all internal diagonals

85
Q

what does the family denote?

A

all face diagonals

86
Q

what can be said about directions and planes with the same indices in cubic systems

A

the direction is perpendicular to the plane

87
Q

if the electronegativity value of an element is high (ie near 4), what will it typically do to electrons

A

acquire/attract them

88
Q

A balance of [these] forces determines the inter-atomic spacing

A

Repulsive and attractive forces

89
Q

H2 would have which type of bonding and why

A

covalent, similar electronegativity, same number of valence electrons require to fill first orbital

90
Q

describe fluctuating dipoles

A

when the atomic nucleus and electron cloud are not symmetrical, secondary bonding occurs between two adjacent molecules due to the charge separation

91
Q

briefly describe why when water freezes, it expands

A

when water freezes, there are 4 hydrogen bonds found between 2 h20 molecules. these 4 bonds are relatively open and spaced apart, causing this expansion

92
Q

chapter 2 question

how and what do alpha, melting temperature and bond length depend on?

A

they depend on Eo(bonding energy). the larger Eo, the large those constants.

93
Q

is energy higher or lower for denser packed structures?

A

lower

94
Q

which materials have the simplest crystal structures

A

metals

95
Q

what happens if you change the sign of all the indices of a direction?

A

it would give the exact opposite direction

96
Q

what can be said about two parallel planes

A

they are equal and will have the same miller indices

97
Q

how do we denote a crystallographic plane?

A

(hkl)

98
Q

how do we denote a family of planes?

A

{hkl}

99
Q

what does the {100} family of planes denote?

A

all faces of a cube

100
Q

In FCC, what are the close packed planes?

A

{111}

101
Q

In HCP, what are the close packed planes?

A

(0001)

102
Q

Although BCC is not as close packed, which is its most densely packed plane?

A

{110}

103
Q

what is the stacking sequence of FCC

A

ABCABCABC

104
Q

what is the stacking sequence of HCP

A

ABABABABABAB

105
Q

give a well-known example of an Anisotropic material

A

wood

106
Q

how might one increase the Creep on a material

A

increase the temperature

107
Q

what effect does increasing the # of grain boundaries have on creep?

A

the material will creep more

108
Q

would properties in metal typically be iso or anisotropic?

A

isotropic

109
Q

why is the diffusion coefficient greater C in alpha-iron BCC rather than C in gamma-iron FCC

A

since the atomic packing factor is less in BCC than it is in FCC, this means there is slightly more interstitial space for the atoms to move about in, making it faster to diffuse

110
Q

are covalent bonds directional

A

yes, they are directional

111
Q

true or false and why? when ro (distance) of 2 atoms is at equilibrium, the binding energy is 0

A

FALSE! the change in binding energy is 0, not the actually value, the binding energy will be at a minimum

Materials Science (13 decks)

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