Quiz 2

Question 1

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

Answer 1

specifying bond types in crystals
specifying important engineering properties

Question 2

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

molecules
neutrons
electrons
Klingons
protons
points
atoms

Answer 2

points

Question 3

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

electrons
neutrons
atoms
Klingons
protons
protons & neutrons
molecules
axes
points

Answer 3

atoms

Question 4

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

Answer 4

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

Question 5

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

Answer 5

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

Question 6

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

2
6
12
5
4
8
3

Answer 6

6

Question 7

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

Answer 7

significant differences in material properties

Question 8

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

Answer 8

True

Question 9

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

Answer 9

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

Question 10

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

Answer 10

body centered cubic structures

Question 11

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

Answer 11

self-centered

Question 12

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

Answer 12

True

Question 13

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

Answer 13

True

Question 14

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

Answer 14

orientations

Question 15

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

Answer 15

less dense

Question 16

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

Answer 16

strength decreases

Question 17

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

Answer 17

dS > 0

Question 18

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

Answer 18

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

Question 19

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

Answer 19

elastic collisions, valence electrons

Question 20

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.

Answer 20

True

Question 21

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 )

Answer 21

( 1 0 0 )

Question 22

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

Answer 22

line or plane of atoms added to a crystal structure

Question 23

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

Answer 23

screw dislocation

Question 24

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

Answer 24

differ in density

Question 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

Answer 25

screw, edge

Question 26

True or false: the Burger’s vector b is useful for describing the magnitude and type (edge or screw) of a crystal dislocation.

Answer 26

True

Question 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

Answer 27

one is crystalline, the other amorphous

Question 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

Answer 28

same phase

Question 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

Answer 29

composition of the crystal

Question 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

Answer 30

Transmission electron microscopy

Question 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

Answer 31

cubic

Question 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

Answer 32

mathematical points

Question 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

Answer 33

metal

Question 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

Answer 34

5

Question 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

Answer 35

when atoms are placed on each lattice point

Question 36

T or F: the terms crystal and lattice are synonymous.

Answer 36

False

Question 37

How many atoms occupy one face centered cubic structure?

4
5
2
1
8
7
3
6

Answer 37

4

Question 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 (r3)
a^3 - 2/3 Pi (r3)
a^2 – 16/3 Pi (r3)
a^3 - 16/3 Pi (r3)
a^3 - 4/3 Pi (r3)
a^2 + 4/3 Pi (r3)
a^3 - 8/3 Pi (r*3)

Answer 38

a^3 - 8/3 Pi (r*3)

Question 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

Answer 39

15

Question 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

Answer 40

same atomic packing factor

Question 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

Answer 41

relationship between material strength and grain size

Question 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

Answer 42

ceramic

Question 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

Answer 43

van der Waals, dry lubricant

Question 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

Answer 44

degree of crystallinity
molecular weight
interactions between polymer chains

Question 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

Answer 45

spacing of atoms

Question 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

Answer 46

apply only to materials with simple cubic unit cells
apply only to crystalline materials
apply only to materials with simple tetragonal unit cells

Question 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

Answer 47

high mobility
high diffusivity
high chemical reactivity

Question 48

True or false: glass, composed primarily of Si and O, is a supercooled liquid.

Answer 48

False

Question 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

Answer 49

crystallinity

Question 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

Answer 50

associated with

Question 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

Answer 51

Hume-Rothery rules

Question 52

True or false: Burger’s vector is a scalar quantity

Answer 52

False

Question 53

True or false: real dislocations are either pure screw type or pure edge type.

Answer 53

False

Question 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

Answer 54

seek information about performance, or lack thereof
examine grain boundaries
measure grain size
observe material structure to assess crystallinity

Question 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

Answer 55

grain size

Question 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

Answer 56

grain size

Question 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

Answer 57

discrepancy between theory and experiment

Question 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

Answer 58

inverse square root

Question 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

Answer 59

raise the temperature of a material above the recrystallization temperature for a short duration

Question 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

Answer 60

rapidly cool a material heated above the recrystallization temperature

Question 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

Answer 61

e. metals with HCP structures are less ductile than metals with FCC structures

Question 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

Answer 62

Scanning Electron microscopy