review for exam

Question 1

Explain the equilibrium point in an Energy vs Interatomic Distance curve.

Answer 1

At equilibrium point (Uo, ro), the energy is lowest and therefore most stable

Question 2

what happens at r other than ro for bond length?

Answer 2

force is attractive when r >ro
force is repulsive when r<ro

Question 3

What increases when bond energy increases?

Answer 3

melting point

Question 4

In the one-component phase diagram lab for cyclohexane, a plot of _________ versus ________
yielded a straight line whose slope was equal to △H/R, where △H is the heat of vaporization and R is the gas
constant. P and T are the pressure and temperature for the two co-existing equilibrium phases, respectively.

Answer 4

lnP, 1/T

Question 5

Typically, one would expect to observe a “cup-and-cone” fracture surface (as shown) upon
failure of which of the following samples at room temperature?

Answer 5

ductile steel

Question 6

Which of the following metal(s) could be used as a sacrificial anode in protecting an
underground steel (Fe-C) pipe from corroding?

Answer 6

Zinc and Magnesium

Question 7

The glass transition temperature of a semi-crystalline polymer will

Answer 7

Increase with addition of rigid, bulky side groups

Question 8

Decreasing the average grain size from 1 mm to 0.1 mm in a metal increases which of the
following?

Answer 8

Yield Strength

Question 9

In a FCC metal crystal, edge dislocations are likely to glide most easily in which of the
following directions?

Answer 9

[110]

Question 10

Edge dislocations glide most easily in which directions?

Answer 10

close packed planes/ directions

Question 11

Which of the following statements is true
?
(A) Diffusivity along grain boundaries is higher than within grains.
(B) Substitutional diffusion is slower than interstitial diffusion.
(C)Diffusivity increases linearly with temperature.
(D)A characteristic diffusion length is proportional to the square root of time.

Answer 11

C

Question 12

Ni has a lower electrical conductivity than Cu. Which do you expect to be the result of adding 1
atomic% Cu to Ni?

Answer 12

Higher YS and lower electrical conductivity

Question 13

A composite formed by introducing aligned metal nanowires into an insulating polymer matrix would likely have ___ stiffness and ___ electrical conductivity than the polymer.

Answer 13

Higher, higher

Question 14

what will an electron energy band diagram is correct for extrinsic semiconductors.

Answer 14

--- ◼︎◼︎

line higher on n side

Question 15

Young’s modulus of a typical polymer will
(A) Not change with increasing temperature
(B) Increase with increasing crosslink density
(C) Decrease with increasing molecular weight
(D) All of the above

Answer 15

Increase with increasing crosslink density

Question 16

Forbidden reflections in lattices are due to:

Answer 16

extra symmetrical layers of atoms between hkl planes because of interference

Question 17

What are allowed reflections for SC

Answer 17

SC: All allowed

Question 18

Allowed reflections for BCC

Answer 18

only when h+k+l= even number

Question 19

Allowed reflections for FCC

Answer 19

only if h, k, and l are even

Question 20

In the electrochemical redox reaction Zn2+ + Mg(s) → Mg2+ + Zn(s), which species is
oxidized?

Answer 20

Mg

Question 21

In lab, we showed that LEDs can sometimes act as solar cells when excited by blue, green,
orange, and red LEDs. Which color(s) LEDs (the light sources) should induce a voltage in an orange LED
(acting as the solar cell)?

Answer 21

Green and blue (higher energy)

Question 22

Which of the following planes has the highest atomic density in an FCC crystal?
A (001)
B 011
C 111
D 211

Answer 22

C

Question 23

Ceramics usually have a combination of the following types of bonds

Answer 23

Covalent and ionic

Question 24

in a BCC metal crystal, dislocations are likely to glide most easily in which of the following directions
110
112
111
100

Answer 24

111

Question 25

A polymer melt forms a glassy phase upon cooling. What is true regarding the chain branching in the polymer

Answer 25

The higher the chain branching in the polymer, the higher the glass transition temperature

Question 26

What will decreasing the average grain size from 1mm to .1 mm in a metal increases which of the following?
Yield Strength
Ductility
Toughness
Elastic modulus

Answer 26

YS

Question 27

What is the relationship between diffusivity and temperature

Answer 27

diffusivity increases linearly with temperature

Question 28

Vacancies can exist at equilibrium despite the fact that creating vacancies costs _____

Answer 28

energy

Question 29

What is the trend for resistivity in metal

Answer 29

metal resistivity increases with impurity content

Question 30

The burgers vector of a dislocation in a metal is ____

Answer 30

the unit displacement vector for that dislocation

Question 31

When the dielectric constant of a material is measured at frequencies close to zero, the contributions to polarization come from

Answer 31

ionic, orientation, and electronic polarization

Question 32

a two metal solid solution of eutectic composition is cooled to a temperature below the eutectic temperature. The starting point of the sigmoidal avrami curve describing the percentage of transformation as a function

Answer 32

occurs at longer times for low and high undercoolings, but occurs at shorter times for intermediate undercoolings

Question 33

Cu has a higher conductivity than Ni. Adding 2 atomic% Cu to NI will result in

Answer 33

a higher yield strength and a lower electrical conductivity

Question 34

If the yield strength of polycrytalline Cu is measured before and after a 1.5% tensile strain.

Answer 34

The yield strength after the 1.5% strain will be higher

Question 35

in intrinsic Si, the carrier concentrations n and p of electrons and holes, respectively, are best described by

Answer 35

n=p

Question 36

in steel, it is least likely to find carbon at

Answer 36

substitutional sites