review for exam Flashcards
Explain the equilibrium point in an Energy vs Interatomic Distance curve.
At equilibrium point (Uo, ro), the energy is lowest and therefore most stable
what happens at r other than ro for bond length?
force is attractive when r >ro
force is repulsive when r<ro
What increases when bond energy increases?
melting point
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.
lnP, 1/T
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?
ductile steel
Which of the following metal(s) could be used as a sacrificial anode in protecting an
underground steel (Fe-C) pipe from corroding?
Zinc and Magnesium
The glass transition temperature of a semi-crystalline polymer will
Increase with addition of rigid, bulky side groups
Decreasing the average grain size from 1 mm to 0.1 mm in a metal increases which of the
following?
Yield Strength
In a FCC metal crystal, edge dislocations are likely to glide most easily in which of the
following directions?
[110]
Edge dislocations glide most easily in which directions?
close packed planes/ directions
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.
C
Ni has a lower electrical conductivity than Cu. Which do you expect to be the result of adding 1
atomic% Cu to Ni?
Higher YS and lower electrical conductivity
A composite formed by introducing aligned metal nanowires into an insulating polymer matrix would likely have ___ stiffness and ___ electrical conductivity than the polymer.
Higher, higher
what will an electron energy band diagram is correct for extrinsic semiconductors.
--- ◼︎◼︎
line higher on n side
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
Increase with increasing crosslink density
Forbidden reflections in lattices are due to:
extra symmetrical layers of atoms between hkl planes because of interference
What are allowed reflections for SC
SC: All allowed
Allowed reflections for BCC
only when h+k+l= even number
Allowed reflections for FCC
only if h, k, and l are even
In the electrochemical redox reaction Zn2+ + Mg(s) → Mg2+ + Zn(s), which species is
oxidized?
Mg
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)?
Green and blue (higher energy)
Which of the following planes has the highest atomic density in an FCC crystal?
A (001)
B 011
C 111
D 211
C
Ceramics usually have a combination of the following types of bonds
Covalent and ionic
in a BCC metal crystal, dislocations are likely to glide most easily in which of the following directions
110
112
111
100
111
A polymer melt forms a glassy phase upon cooling. What is true regarding the chain branching in the polymer
The higher the chain branching in the polymer, the higher the glass transition temperature
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
YS
What is the relationship between diffusivity and temperature
diffusivity increases linearly with temperature
Vacancies can exist at equilibrium despite the fact that creating vacancies costs _____
energy
What is the trend for resistivity in metal
metal resistivity increases with impurity content
The burgers vector of a dislocation in a metal is ____
the unit displacement vector for that dislocation
When the dielectric constant of a material is measured at frequencies close to zero, the contributions to polarization come from
ionic, orientation, and electronic polarization
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
occurs at longer times for low and high undercoolings, but occurs at shorter times for intermediate undercoolings
Cu has a higher conductivity than Ni. Adding 2 atomic% Cu to NI will result in
a higher yield strength and a lower electrical conductivity
If the yield strength of polycrytalline Cu is measured before and after a 1.5% tensile strain.
The yield strength after the 1.5% strain will be higher
in intrinsic Si, the carrier concentrations n and p of electrons and holes, respectively, are best described by
n=p
in steel, it is least likely to find carbon at
substitutional sites
