Quiz 2 Flashcards

1
Q

Materials engineers need to understand the structure of materials. To help understand the structure of materials with high order on the atomic level, crystal systems and lattices were developed. These systems and lattices serve all purposes listed as follows except (choose all that apply, if any):

specifying planes in crystals
specifying directions in crystals
specifying bond types in crystals
none, all choices listed are applicable
specifying positions of atoms in crystals
specifying important engineering properties

A

specifying bond types in crystals
specifying important engineering properties

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2
Q

A crystal lattice is made of (fill in the blank).

molecules
neutrons
electrons
Klingons
protons
points
atoms

A

points

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3
Q

A crystal structure is composed of (fill in the blank).

electrons
neutrons
atoms
Klingons
protons
protons & neutrons
molecules
axes
points

A

atoms

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4
Q

Which of the following is (are) not among the Hume-Rothery rules that specify the relative degree of solubility of a solute atom in a solid solvent?

similar electronegativity
< 15% atomic radius mismatch
similar stacking layers
same unit cell
same row on the periodic table
same valence
same number of protons
same atomic packing factor

A

similar stacking layers
same row on the periodic table
same number of protons
same atomic packing factor

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5
Q

Crystal systems and Bravais lattices are used by materials scientists to do which of the following. Choose all that apply.

describe various descriptions
describe the type of atoms in crystals
describe the bonding of atoms in crystals
describe the indescribable
describe planes in crystals
describe the positions of atoms in crystals
describe directions in crystals

A

describe planes in crystals
describe the positions of atoms in crystals
describe directions in crystals

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6
Q

How many parameters are available to crystallographers to quantify the general 3D unit cell of a crystal?

2
6
12
5
4
8
3

A

6

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7
Q

A key theme throughout the course is that material structure affects material properties. Analysis of material structure begins by consideration of the crystalline structure of materials (if such materials are crystalline). In your text it was noted that FCC and HCP have similarities as well as differences. A major difference between FCC and HCP unit cells of crystalline materials is that they have:

significant differences in packing factors
significant differences in material properties
none of the choices listed
significant differences in atomic species
similarities of material properties

A

significant differences in material properties

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8
Q

True or false: lattice points do not refer to specific atoms in crystals.

A

True

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9
Q

Why are X-rays useful for studying materials? Choose all that apply.

X-rays are X-rated
X-rays have sufficiently low energy that do not perturb material structure and thus alter what is being sought due to the measurement
wavelength of X-rays is comparable to the distance between atoms
X-rays are easy to generate
X-rays are essential for electron microscopy (an invaluable tool for structural analysis)
none of the choices listed
X-rays can reveal quantitative material structural information

A

wavelength of X-rays is comparable to the distance between atoms
X-rays can reveal quantitative material structural information

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10
Q

Assuming no variation in atomic dimensions among the considered structures, which of the following crystal structures have the most empty space in a unit cell? Choose all that apply (if more than one).

hexagonal structures
body centered cubic structures
face centered cubic structures
corundum structure
quartzite structure

A

body centered cubic structures

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11
Q

Which of the following is not one of the types of Bravais lattices noted in your textbook?

self-centered
face-centered
volume - centered
primitive
base-centered

A

self-centered

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12
Q

True or false: more than one atom can be associated with a lattice point.

A

True

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13
Q

True or false: while most metals are 99+% crystalline, they are generally not composed of a perfect single crystal.

A

True

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14
Q

At 573 degrees C, silica (SiO2) did not alter its fundamental HCP crystal structure, but the (fill in the blank) of the crystal tetrahedra comprising this structure did change.

angles
dimensions
orientations
bonding
shape

A

orientations

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15
Q

Phase changes in ceramic structures may occur suddenly at specific temperatures, as was noted in your textbook and the lectures regarding silica (SiO2). Specifically, this material undergoes a sudden and rapid phase change from alpha-quartz to beta-quartz at 573 degrees C. This phase change is important because the crystal structure changes at this temperature and becomes (fill in the blank) when it assumes the beta-quartz structure.

less hard
less dense
harder
stiffer
less stiff
denser

A

less dense

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16
Q

For metals in general, as grain size increases (fill in the blank)

strength increases
strength decreases
crystallinity decreases
reflectivity decreases
crystallinity increases
another effect occurs not included in this list

A

strength decreases

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17
Q

Which of the follow expressions are most relevant to materials engineers who study atomic order in materials?

PV = nRT
T sub a = T sub b = T sub c
Fa = -k/r^2
A^2 + B^2 + C^2 = 0
dS > 0
dU = dQ - dW
e - mc^2

A

dS > 0

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18
Q

The Miller - Bravais indices ( h k i l ) are used to denote planes in the hexagonal close packed system. These indices differ from the Miller indices ( h k i ) used to denote planes for BCC and FCC systems. The relationship h + k = -i can be used to relate the Miller - Bravais indices to the Miller indices. What is the fundamental basis for the last cited mathematical relationship? Choose all that apply.

3 points define a plane
none of the choices listed
crystallographers are unable to do simple math, and that’s why there are 4 indices in the Miller - Bravais system
the 4th index of the Miller - Bravais system is redundant in 3D and crystallographers always prefer simplicity
HCP crystals are actually 4 dimensional
HCP unit cells are actually a formm of triclinic unit cells

A

3 points define a plane
the 4th index of the Miller - Bravais system is redundant in 3D and crystallographers always prefer simplicity

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19
Q

X-ray diffraction involves (fill in the blank) between the X-ray photons and the (fill in the blank) of the target atoms

elastic collisions, nuclear protons & neutrons
plastic collisions, inner shell electrons
plastic collisions, valence electrons
elastic collisions, valence electrons
elastic collisions, inner shell electrons

A

elastic collisions, valence electrons

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20
Q

True or false: Bragg’s Law of diffraction, while useful for determining crystal dimensions, applies only for primitive unit cells like simple cubic and tetragonal systems having lattice points at corners only.

A

True

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21
Q

Using Miller indices and assuming: a) the x-direction is into/out of the plane of your screen, the y-direction goes left & right, and the z-direction goes up & down, and b) the origin is at the back lower left corner, and c) the circles along each axis represents one unit dimension; which of the following correctly describes the shaded plane shown below?

image 15

( 1 1 1 )
( 0 1 1 )
none of the above
( 0 0 1 )
(1 1 0 )
( 1 0 0 )
(0 1 0 )

A

( 1 0 0 )

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22
Q

Regarding crystal structures, a dislocation can be described as a:

a line of area centered atoms
line of face centered atoms
a line of atoms arranged at corners of crystal lattices
line or plane of atoms added to a crystal structure
none of the choices listed
a curved path in a crystal structure due to added atoms that follow neither a linear, planar or screw dislocation type pattern

A

line or plane of atoms added to a crystal structure

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23
Q

What type of crystal imperfection is shown in the accompanying illustration:

image 16

wedge dislocation
one half of a cubic system missing
Bravais displacement
crystal fault
screw dislocation
Harmon-Kardon crystal defect
rhombohedral system defect
Tolouse - Lautrec dislocation
linear dislocation
Hume - Rothery dislocation

A

screw dislocation

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24
Q

What is the key material property difference between two crystals with point defects: one with a Schottky defect, the other with a Frenkel defect?

differ in ways not listed among these choices
differ in density
differ in unit cell dimensions
differ in charge
differ in crystal structure
differ in atomic placement

A

differ in density

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25
Which of the following is a type of "line" defect in a crystal? Choose all that apply Schottky occupied screw lever vacancy edge Frenkel
screw, edge
26
True or false: the Burger's vector b is useful for describing the magnitude and type (edge or screw) of a crystal dislocation.
True
27
Both quartz and glass have the same basic chemical composition (SiO2), except the difference is: one is orthorhombic, the other is tetragonal one is crystalline, the other amorphous one is BCC, the other is FCC one is alpha-quartz, the other is beta-quartz one is one quartz, the other is two pints
one is crystalline, the other amorphous
28
Which of the following is NOT one of the Hume - Rothery rules: similar electronegativity same phase same crystal structure same valence < 15% size mismatch
same phase
29
Imperfections in crystals include not only imperfections in the structural arrangement of atoms, but also imperfections in the (fill in the blank). phase of the crystal unit cell lengths of the crystal system ability to predict properties of the crystal angles of the unit cell of the crystal composition of the crystal
composition of the crystal
30
The attached image shows the arrangement of atoms in a single silicon crystal. Experimentally derived images such as this assist materials engineers to understand material structure and this materials engineering has a decidedly empirical nature. What experimental technology was used to obtain this (see below) image? image 18 gamma-irradiation microscopy transmission electron microscopy light microscopy microwave microscopy X-radiography electron microscopy scanning electron microscopy
Transmission electron microscopy
31
What crystal structure has equal axes lengths and equal shared angles? rhombohedral triclinic (hence the term "tri") orthorhombic (hence the term "ortho") monoclinic (hence the term "mono") tetragonal (hence the term "tetra") cubic hexagonal
cubic
32
Lattice points are (fill in the blank) regularly arranged in 3D space. atoms or molecules lattice points mathematical points individual atoms none of the above atoms
mathematical points
33
You are given a material to determine what it is. The only information provided to you is that this material is 99% crystal in nature and that the crystal structure is relatively simple. Based on this information alone, it's most likely that this material is a (fill in the blank): polymer metal iron-based alloy glass liquid metal ceramic
metal
34
The number of "slip systems" in a metal structure is one of the keys to understanding the macroscopic properties of that material. How many slip systems form the threshold for ductile material behavior? 12 3 6 5 8 9 2 4 10
5
35
When does a lattice become a crystal structure? when atoms are placed on each lattice point when it grows up and goes away to college none of the choices listed when all angles of the unit cell axes are known when all axes of the unit cell are known when it assumes a FCC, BCC or HCP crystal structure
when atoms are placed on each lattice point
36
T or F: the terms crystal and lattice are synonymous.
False
37
How many atoms occupy one face centered cubic structure? 4 5 2 1 8 7 3 6
4
38
Assuming r is the radius of an atom and a is the unit cell axis length, then the "empty space" inside a BCC crystal is given by which of the following expressions: a^2 - 4/3 Pi (r*3) a^3 - 2/3 Pi (r*3) a^2 -- 16/3 Pi (r*3) a^3 - 16/3 Pi (r*3) a^3 - 4/3 Pi (r*3) a^2 + 4/3 Pi (r*3) a^3 - 8/3 Pi (r*3)
a^3 - 8/3 Pi (r*3)
39
The general rule for adding interstitial atoms inside FCC and HCP unit cells is that the added atoms must have a radius that is less than approximately (fill in the blank) percent of the atoms comprising the FCC and HCP unit cells. 45 15 25 50 5 20 10 30
15
40
A key theme throughout the course is that material structure affects material properties. Analysis of material structure begins by consideration of the crystalline structure of materials (if such materials are crystalline). In your text it was noted that FCC and HCP have similarities as well as differences. A major similarity between FCC and HCP unit cells of crystalline materials are that they have: same basic unit cell same indices used to denote specific planes of atoms same atomic packing factor same layering of atoms same arrangement of atoms
same atomic packing factor
41
What does the Hall-Petch equation show? relationship between atomic radius and ductility relationship between material strength and crystallinity relationship between ductility and crystal size relationship between ductility and grain size relationship between material strength and grain size relationship between atomic radius and material strength relationship between crystal structure and volume
relationship between material strength and grain size
42
You are told that each unit cell of a material is of the composition MX where M is a metal and X is a non-metal. Based on this description, you assume that the material is a: supercooled liquid metal polymer ceramic glass
ceramic
43
Graphite is an interesting material because it has (fill in the blank) bonding between layers of covalently bonded hexagonal C rings. This bonding type allows graphite to display properties as a (fill in the blank). van der Waals, adhesive van der Waals, dry lubricant hydrogen, adhesive hydrogen, dry lubricant
van der Waals, dry lubricant
44
Polymers are important engineering materials that have wide applications in healthcare technology. Which of the following structural considerations affect the properties of polymers (choose all that apply). degree of crystallinity creep behavior molecular weight stress relaxation characteristics interactions between polymer chains
degree of crystallinity molecular weight interactions between polymer chains
45
Diffraction is a useful tool for determination of crystalline material structure. The fundamental relationship derived by Bragg is known as Bragg's Law. What information does the materials engineer obtain from application of Bragg's Law? number of atoms other information not included among the choices provided wavelengths of atoms type of atoms spacing of atoms
spacing of atoms
46
Like every other experimental technique used to evaluate material structure, diffraction experiments have limitations. What are the limitations of diffraction studies of materials (choose all that apply). apply only to polymers with 50% crystallinity apply only to ceramics apply only to materials with simple orthorhombic unit cells apply only to materials with simple cubic unit cells apply only to crystalline materials apply only to metals apply only to materials with simple tetragonal unit cells
apply only to materials with simple cubic unit cells apply only to crystalline materials apply only to materials with simple tetragonal unit cells
47
Materials engineers are interested in grain boundaries in polycrystalline materials. The reason for this is that such grain boundaries are regions with (choose all that apply) high life high mobility high chemical reactivity high volume high diffusivity high crystallinity high GPA
high mobility high diffusivity high chemical reactivity
48
True or false: glass, composed primarily of Si and O, is a supercooled liquid.
False
49
Glass and quartz have identical chemical constituents, their primary difference is in the degree of (fill in the blank) crystallinity cost hardness utility transparency
crystallinity
50
One of the simplest ceramics considered in your text was NaCl. The text notes that the unit cell of this ceramic material had 2 ions, Na and Cl are (fill in the blank) each lattice point. instead of at none of the choices listed in addition to associated with
associated with
51
Disorder in crystalline materials not only pertains to crystal structure, but also to chemical constituents. As such, impurity atoms can substitute in crystals and disrupt structure. Which set of rules determines the degree of solubility of a solute in a solid solvent? Hume-Rothery rules Bang-Olufsen Rules Hirth-Pound rules Heisenberg Rules Hall-Petch rules
Hume-Rothery rules
52
True or false: Burger's vector is a scalar quantity
False
53
True or false: real dislocations are either pure screw type or pure edge type.
False
54
Why do materials engineers perform metallographic examination of material surfaces (choose all that apply) seek information about performance, or lack thereof examine grain boundaries make use of expensive optical instrumentation and justify laboratory operating budgets measure grain size observe material structure to assess crystallinity make pretty pictures with novel etching agents
seek information about performance, or lack thereof examine grain boundaries measure grain size observe material structure to assess crystallinity
55
The ASTM published relationship N = 2 ^ (G-1) is used by metallographers to estimate: grain size material hardness material beauty unit cell dimensions material tensile strength material unit cell structure atomic radius number of slip planes grain number
grain size
56
The relationship d = 1 / n sub L times M is used by metallographers to estimate: grain size material tensile strength grain number material hardness number of slip planes material unit cell structure material beauty atomic radius
grain size
57
A "creeping caterpillar" is a simple example offered by a graduate student to explain (fill in the blank) movement in perfect crystals movement of atoms in glasses discrepancy between theory and experiment movement of glasses in atoms structure of perfect crystals movement of atoms in polymers
discrepancy between theory and experiment
58
The empirical relationship that links grain size with material strength is: strength increases as the (fill in the blank) of grain size. square root square inverse square inverse of the reversed converse cube inverse square root 4th power inverse cube root
inverse square root
59
How can a materials engineer increase the grain size of a material? raise the temperature of a material above the recrystallization temperature for a short duration slowly cool a material heated above the recrystallization temperature raise the temperature of a material below the recrystallization temperature for a short duration rapidly cool a material heated above the recrystallization temperature raise the temperature of a material above the recrystallization temperature for a short duration
raise the temperature of a material above the recrystallization temperature for a short duration
60
How can a materials engineer decrease the grain size of a material? raise the temperature of a material above the recrystallization temperature for a short duration slowly cool a material heated above the recrystallization temperature rapidly cool a material heated above the recrystallization temperature raise the temperature of a material above the recrystallization temperature for a short duration raise the temperature of a material below the recrystallization temperature for a short duration
rapidly cool a material heated above the recrystallization temperature
61
A key theme throughout the course is that material structure affects material properties. Analysis of material structure begins by consideration of the crystalline structure of materials (if such materials are crystalline). Metals with FCC crystal structures have 12 independent means of allowing atomic "slip" whereas metals with HCP structures have 3 independent means of allowing atomic "slip". What is the material property implication of this microscopic structural difference? a. metals with HCP or FCC structures have equal mechanical properties because their atomic packing factors are equivalent b. metals with HCP structures are more ductile than metals with FCC structures c. metals with HCP structures are less strong compared to metals with FCC structures d. metals with HCP structures are stronger than metals with FCC structures e. metals with HCP structures are less ductile than metals with FCC structures
e. metals with HCP structures are less ductile than metals with FCC structures
62
A biomaterials engineer wishes to study the surface of a failed metallic implant. The surface of this failed implant is important. Which imaging technique is most useful to this engineer? Transmission Electron Microscopy X-ray diffraction X-ray crystallography Scanning Electron Microscopy none of the choices listed
Scanning Electron microscopy